Odyssian Technology
CONTRACTOR: ODYSSIAN TECHNOLOGY, LLC
CONTRACT NO.: HQ0006-05-C-7191
PHASE I FINAL REPORTOUTLINE AND SYNOPSIS REPORT
February August23rd, 2005 – APRIL 23rd, 2005
SBIR phase i
“Improved Reliability and Producibility of Ballistic Missile Defense Systems through Highly Controlled Deposition of Critical Battery Components”
Prepared Submitted by:
Barton Bennett
Odyssian Technology, LLC
(574) 257-7555 - Office
(574) 850-4060 - Mobile
Submitted to:
Samuel Stuart, COR/ NavSea Crane
Dale McNabb, MDA/CTV
DISCLAIMER STATEMENT
The views, opinions, and findings contained in this report are those of the author(s) and should not be construed as an official Department of Defense position, policy, or decision.
EXPORT CONTROL WARNING
This document contains technical data whose export is restricted by the Arms Export Control Act (Title 22, U.S.C. Sec. 2751, et seq.) or the Export Administrator Act of 1979, as amended, Title 50 U.S.C. app. 2401 et seq. Violations of these export laws are subject to severe criminal penalties. Disseminate IAW the provisions of the DOD Directive 5230.25.
DISTRIBUTION
Distribution authorized to US Government agencies only. Other requests for this document must be referred to (applicable MDA/2LTR)
|REPORT DOCUMENTATION PAGE |Form Approved |
| |OMB No. 0704-0188 |
|Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing|
|data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or |
|any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, |
|Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that |
|notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a |
|currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. |
|1. REPORT DATE (DD-MM-YYYY) |2. REPORT TYPE |3. DATES COVERED (From - To) |
|23-08-2005 |Final Technical Report |02-23-2005 to 08-23-2005 |
|4. TITLE AND SUBTITLE |5a. CONTRACT NUMBER |
| |HQ0006-05-C-7191 |
| | |
| | |
| | |
| | |
| | |
| | |
| | |
|Improved Reliability and Producibility of Ballistic Missile Defense Systems through Highly Controlled Deposition of|5b. GRANT NUMBER |
|Critical Battery Components | |
| |5c. PROGRAM ELEMENT NUMBER |
|6. AUTHOR(S) |5d. PROJECT NUMBER |
| | |
| | |
| | |
|Barton Bennett, President & Sr. Program Manager |5e. TASK NUMBER |
| | |
| | |
| | |
| | |
| | |
| |5f. WORK UNIT NUMBER |
|7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) |8. PERFORMING ORGANIZATION REPORT |
| |NUMBER |
|AND ADDRESS(ES) | |
|Odyssian Technology, LLC | | |
|3740 Edison Lakes Pwy, Suite 201 | | |
|Mishawaka, Indiana 46545 | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
| | | |
|9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) |10. SPONSOR/MONITOR’S ACRONYM(S) |
|Sponsoring Agency: |Monitoring Agency: | |
|Missile Defense Agency |NavSea Crane | |
|7100 Defense Pentagon |B3235, Code 6093 |11. SPONSOR/MONITOR’S REPORT |
|Washington, D.C. 20301-7100 |300 Highway 361 | NUMBER(S) |
| |Crane, IN 47522 | |
|12. DISTRIBUTION / AVAILABILITY STATEMENT |
|Distribution authorized to U.S. Government Agencies only, Proprietary Information, 04 April, 2004. Other requests for this document shall be referred to the Missile |
|Defense Agency/MP, 3550 7100 Defense Pentagon, Washington, D.C. 20301-7100. |
|Data rights IAW DFAR 252.227-7018. SBIR Data Rights. |
| |
|13. SUPPLEMENTARY NOTES |
|This document contains technical data whose export is restricted by the Arms Export Control Act (Title 22, U.S.C. Sec. 2751, et seq.) or the Export Administrator Act of |
|1979, as amended, Title 50 U.S.C. app. 2401 et seq. Violators are subject to severe criminal penalties. |
|14. ABSTRACT |
|This phase I SBIR program developed and demonstrated thin film igniter technology for use in improving the reliability and producibility of thermal batteries that are |
|used in U.S. missile systems. Thin film thermal igniter designs were developed and evaluated and processing methods were explored and optimized. Thin film was applied |
|using three different physical vapor deposition (PVD) processes which included; thermal evaporation, electron beam evaporation, and sputtering deposition. These |
|processes were evaluated for optimum igniter performance. A thermal analysis model was developed that offers utility in predicting the ignition performance of new or |
|modified thermal batteries. The thin film igniter design will significantly reduce the cost of missile systems by improving reliability and producibility over existing|
|bridge wire igniter designs. The analysis tool will significantly reduce thermal battery development and modification cost by reducing the need for iterative testing |
|and design alteration. |
|15. SUBJECT TERMS |
|thermal, battery, igniter, PVD, thin film, thermal battery, analysis |
|16. SECURITY CLASSIFICATION OF: |17. LIMITATION |18. NUMBER OF |19a. NAME OF RESPONSIBLE PERSON |
|Not classified |OF ABSTRACT |PAGES |Samuel Stuart |
|a. REPORT |b. ABSTRACT |c. THIS PAGE | | |19b. TELEPHONE NUMBER (include area code) |
| | | |SAR |54 |(812) 854-5958 |
|Unclas |Unclas |Unclas | | | |
| |Standard Form 298 (Rev. 8-98) |
| |Prescribed by ANSI Std. 239.18 |
DATA RIGHTS
| |
|The technology reported herein is subject to SBIR Data Rights IAW DFAR 252.227-7018. |
| |
SBIR DATA RIGHTS
| |
| |Contract No. | HQ0006-05-C-7191 | |
| |Contractor Name | Odyssian Technology | |
| |Contractor Address |3740 Edison Lakes Parkway, Suite 201 | |
| Mishawaka, Indiana 46545 |
| |Expiration of SBIR Data Rights Period |23 August, 2010 | |
| | | | | | | |
The Government's rights to use, modify, reproduce, release, perform, display, or disclose technical data or computer software marked with this legend are restricted during the period shown as provided in paragraph (b)(4) of the Rights in Noncommercial Technical Data and Computer Software--Small Business Innovative Research (SBIR) Program clause contained in the above identified contract. No restrictions apply after the expiration date shown above. Any reproduction of technical data, computer software, or portions thereof marked with this legend must also reproduce the markings.
The following language is added to this report at the request of our subcontractor Rose-Hulman Institute of Technology (RHIT). The following applies to RHIT.
Technical data rights developed during SBIR: none
Prior technical data rights used during Phase I SBIR: Rose-Hulman used a previous technical data right developed prior to the phase I SBIR proposal. The Technical data right involves the deposition of thin film material directly onto the igniter posts and insulating material. The prior technical data right further includes a shadow mask having either a line, arced line or a circle where the mask may also act as a holder for the igniters during deposition. This technical data right was developed by a group of students during a senior design project led by Nicole Hartkemeyer and supervised by Research Fellow Scott Kirkpatrick and Director of MEMS Lab Dr. Azad Siahmakoun. This design was developed out of a design concept for a heater element that may be deposited and possibly patterned to produce a reliable ignition source for the igniter material. This was suggested by RHIT professor Dr. Tom Adams in a meeting with Crane for possible collaboration projects.
TABLE OF CONTENTS
1.0 PROGRAM INTRODUCTION..................................................................................................................1
2. PROGRAM OBJECTIVES……………………………………………………………………....2
3. PROGRAM ACCOMPLISHMENTS AND RESULTS………………………………………….2
1. SCHEDULE AND BUDGET PERFORMANCE………………………………..….....2
2. TECHNICAL ACCOMPLISHMENTS……..……................................................................3
TASK I – METHODS AND REQUIRMENTS DEFINITION…………..………...…3
TASK II – DESIGN STUDY……………….…………………………………....…….4
TASK III – PROCESS DEVELOPMENT AND FABRICATION……………….…..18
TASK IV – TESTING AND EVALUATION............................................................. …....22
4. SUMMARY OF PHASE I DEMONSTRATED FEASABILITY AND BENEFIT……….……38
5.0 SYNOPSIS OF PROPOSED PHASE II PROGRAM………………..................................…....…39
APPENDIX A – REQUIREMENTS AND GOALS ……………………………………………A1 thru A-5
.
LIST OF FIGURES
Figure 1: Updated Program Schedule……………………………………………………………………….3
Figure 2: Solid Model of Igniter Base……………………………………………………………………….4
Figure 3: Thermal Modeling No Powder No Convection Line-shape Time = 5s ....………………………...7
Figure 4: Thermal Modeling No Powder No Convection Line-Shape Time = 150s ………………………..7
Figure 5: Thermal Modeling No Powder No Convection Line-Shape Time = 300s ………………………..8
Figure 6: Transient Temperature Curve No-Fire Load No Convection No Powder Line-Shape …………...9
Figure 7: Transient Temperature Curve All-Fire Load No Convection No Powder Line-Shape ……...…....9
Figure 8: Thermal Modeling No Powder No Convection Circle-Shape Time = 5s ………………………..10
Figure 9: Thermal Modeling No Powder No Convection Inverted-Dog Bone Time = 5s ………………...11
Figure 10: Thermal Modeling With Powder No Convection Line-Shape ………………………………...…12
Figure 11: Transient Temperature Curve No-Fire Load No Convection With Powder Line-Shape…….........13
Figure 12: Transient Temperature Curve No-Fire Load With Convection With Powder Line-Shape….….....13
Figure 13: Thermal Modeling No-Fire Load With Powder With Convection Line-Shape .........................…...14
Figure 14: Thermal Modeling All-Fire Load With Powder With Convection Line-Shape ……………….….15
Figure 15: Thermal Modeling No-Fire Load With Powder With Convection Circle-Shape ……………..…..15
Figure 16: Thermal Modeling All-Fire Load With Powder With Convection Circle-Shape…….…….........…16
Figure 17: Sensitivity Study for Igniter Thermal Modeling ………………………………………….….…...17
Figure 18: Fabricated Line-Shape Mask ……………………………………………………………….…....18
Figure 19: Peeling of Nichrome on Oxidized Si Wafer ………………………………………………..……19
Figure 20: E-beam and Sputtered Nichrome on Si Wafers ………………………………………….……...20
Figure 21: Data Run Sheet for Igniter Depositions…………………………………………………..……...21
Figure 22: 2D Contour Surface Plot of Nichrome Deposited Si Wafer via Sputtering………………..……..22
Figure 23: 2D Contour Surface Plot of Nichrome Deposited Si Wafer via E-beam …………………..…….23
Figure 24: 2D contour surface plot of an oxidized Si wafer coated with NiCr via thermal evaporation...…..24
Figure 25: Thin film average resistivity per run showing deposition rate is a major factor.. ………….......….25
Figure 26: Average resistivity of the various depositions with respect to thickness. …………………...….....27
Figure 27: E-beam deposition runs showing large variation and large standard deviation.……………...…....27
Figure 28: Sputtering deposition runs showing less variation…………………………………………..…...28
Figure 29: SEM picture of entire igniter head. …………………………………………………….…...…...29
Figure 30: SEM picture of igniter head showing peeling of porous Nichrome. and pitting…..……..…..…...29
Figure 31: SEM picture of epoxy/pole (electrical lead) interface………..…………………………..……....30
Figure 32: SEM close-up (×5) of figure 31. Peeling chip at epoxy/pole interface………..……….…....…...30
Figure 33A&B: Invention of Shutter System used to control PVD on each igniter………..……….…....…...31
Figure 34: Schematic diagram of the shutter control system………..………………………………..……....34
Figure 35: Ignition times with respect to resistivity showing 1.3 to 1.6 ohms required for Sputtered Film.......37
Figure 36: Photograph of an example application - the Tomahawk cruise missile………..……….………....39
Figure 37: Basic conceptual design for the proposed phase II igniter deposition system.………..….….…....40
Figure 38: A Close-up design similar to a Vac-Coupling to provide a vacuum sealing surface. .……… …....41
Figure 39: A top down conceptual view of an igniter holder/mask..…………………………………...…...42
Figure 40: A cross section view of an igniter holder/mask..……………..……………………...…………...42
LIST OF TABLES
Table 1: No-Fire and All-Fire Line-Shaped Thickness Requirements ………………………………………6
Table 2: Table 2: Positional Igniter Bridge Wire Resistivities for Each PVD Run……...……………………26
Table 3: All-Fire and No-Fire Testing Results……...............................................................……………………36
THIS PAGE IS INTENTIONALLY LEFT BLANK
Phase I Outline and Synopsis ReportFinal Report – AugustApril 23, 2005
SBIR phase i
1.0 Program introduction
This phase I SBIR program is developeding a new design and process for manufacturing thermal battery igniter components. The missiles used by the military today are electronics intensive: control systems, navigation systems, and targeting systems all have components on-board the missile. These systems require a power source that is capable of delivering large amounts of power over the period of time the missile is in flight. Thermal batteries are used extensively in military missile systems because of their superior performance in meeting the arduous demands of missile power supplies. One of the major advantages of thermal batteries over other power sources is that thermal batteries are stored with the electrolyte in a solid state to prevent passive power leakage over time. Igniters are used to initiates a combustive exothermic reaction that heats and activates the electrolyte. Conventional igniters have a thermal element called a Bridge Wire that is a small filament wire that provides resistant heat to initiate the combustive reaction. Under this SBIR program, physical vapor deposition (PVD) technology was used to develop a more reliable thin film heating elementis b. Improving the reliability of this vital battery component improves the dependability of the military missile systems that use thermal batteries. Odyssian Technology, as well as, NavSea Crane and EaglePicher foresee cost savings and significant reliability improvements from the use of thin film (PVD) thermal battery igniters. Thin film processing using PVD minimizes cost by significantly lowering touch-labor of the manufacturing process and by allowing for batch processing.
To improve the likelihood of successful Phase III technology transition, Odyssian Technology has partnered will be workingwith EaglePicher which is a major supplier of thermal batteries and igniters for the U.S. Department of Defense, Department of Energy, and NASA. During Phase I EaglePicher will be providing provided definition of application requirements, critiqued design concepts, and suppliedy igniter components needed for fabrication and testing of the new bridge wire design. The University of Notre Dame, Rose-Hulman Institute of Technology, and K&D Design and Development Corporation also participated as subcontractors to provide equipment access and services required for processing and testing multiple proof-of-concept demonstration articles. Odyssian Technology hads overall program responsibility and is developeding conceptual designs using 3D solid modeling, and finite element analysis, and.
Odyssian Technology and its team successfully demonstrated the feasibility of a PVD bridge wire for thermal battery igniters. Odyssian first worked with EaglePicher and Rose-Hulman Institute of Technology to develop phase I performance and processing specifications. Items that were considered during this task included cost, ease of use, and reliability of bridge wires produced. A finite element analysis model of the igniters was created to determine which design variables would have the greatest effect on the reliability of the igniters. The major design variables considered during phase I included thickness and geometry of the bridge wire deposition. Several process and igniter fabrication trials were conducted at the University of Notre Dame and Rose-Hulman Institute of Technology using various PVD methods and several different design configurations.
During Phase II the thin film PVD Igniter design will be optimized, the thermal modeling tool will be further developed, and a production pilot system will be constructed and characterized.
with equipment and assistance from the University of Notre Dame and Rose-Hulman Institute of Technology is fabricating and evaluating multiple proof-of-concept demonstration articles.
2.0 status summaryProgram objectives
This Phase I SBIR program was designed to demonstrate the feasibility of a Thin Film PVD heating element (bridge wire) for use in thermal battery igniters. The phase I program focused on developing and assessing production worthy methods for design and processing of these thin film elements. The scope of phase I was established to accomplish the following objectives.
i) Identify optimal processing equipment and designs for manufacturing lowest cost most reliable bridge wires for thermal battery igniters.
ii) Experimentally correlate design variables with reliability in bridge wires to ensure optimal design of thermal battery igniter bridge wires.
iii) Develop electrical – mechanical coupled models for predicting most viable device variables for experimental setup.
3.0 program ACCOMPLISHMENTS and results
The program performance and technical accomplishments of phase I are discussed and summarized in this section of the final report. The original phase I work plan called for the design and fabrication of PVD bridge wire igniters for initial performance testing and design optimization. After completing this task for the line-shaped bridge wire design further testing and optimization steps were taken for a circle-shaped PVD bridge wire. Additional process variability testing was also conducted at Rose-Hulman Institute of Technology and the University of Notre Dame above the original scope of the program. Odyssian Technology also worked beyond the scope of the project by developing a more complete and complex thermal model of the igniter system than originally proposed.
3.1 – Schedule and budget performance
This program was successfully executed to schedule with all technical tasks completed by the scheduled end date of August 23rd, 2005. Expenditures charged to this program were within limits of the original proposed budget.
The work plan of this program includes the following five tasks;
Task 1 – Methods and Requirements Definition
Task 2 – Design Study
Task 3 – Process Development and Fabrication
Task 4 – Testing and Evaluation
Task 5 – Program Management and Reporting
A copy of the updated program schedule is shown in Figure 1. This schedule shows completion of all technical tasks. Task 2 (Design Study) start date was moved up from its original start date to provide additional time for creating an optimized design of the PVD bridge wire before start of the fabrication and testing tasks. Task 4 (Testing and Evaluation) start date was also moved up so that testing results from the fabrication of igniters could be used to further optimize the fabrication of later igniters.
[pic]
Figure 1: Program Schedule – All Technical Tasks have been completed.
3.2 – Technical Accomplishments
Due to the limited funding available in Phase I and the desire to keep within current military specifications, the scope of Phase I was restricted to the development of a PVD bridge wire design using 8020 Nichrome. This is the material used in the currently implemented hot-wire bridge design. A summary of the technical progress made during this SBIR program is provided in the following subparagraphs.
Task 1 – Methods and Requirements Definition
Odyssian Technology discussed the definition of the methods and requirements with EaglePicher as well as Rose-Hulman Institute of Technology. These requirements were reviewed by both groups and are shown in Appendix A. This document lists the various igniter tests required by the appropriate military specification (MIL-DTL-23659D) for the EP250-1 igniter. Shown are the specifications used to test the reliability of existing igniters. A standard test matrix is also shown. The new bridge wire design will have to meet these same testing requirements before they are used on an existing military system. Also shown in Appendix A is a breakdown of the requirements and goals that were expected to be reached during each phase of this SBIR program and the final status of each of these requirements. Input from EaglePicher and Rose-Hulman indicated that the scope of each phase’s requirements and goals was well accepted.
Task 2 – Design Study
This program is on schedule with technical tasks expected to be complete by August 24th, 2005. During this reporting period, input from EaglePicher under the Task I – Methods and Requirements Definition was received, and the Task II – Design Study was begun. A solid model of the igniter was created for use in a finite element analysis thermal model. Initial work has been done on this thermal model and will be continued throughout the next reporting period. Initial work has also been done by subcontractor Scott Kirkpatrick of Rose-Hulman Institute of Technology on design concepts for masking equipment in the phase II pilot production system. All contracts are currently in place except for Rose-Hulman. The contract with Rose-Hulman is under review without any current or expected problems.
3.0 milestone/ task status
The work plan of this program includes the following five tasks;
Task 1 – Methods and Requirements Definition
Task 2 – Design Study
Task 3 – Process Development and Fabrication
Task 4 – Testing and Evaluation
Task 5 – Program Management and Reporting
Tasks 1 and 2 were active during this reporting period. A majority of the technical activity involved the creation of a solid model of the thermal battery igniter (model number EP-250-1) and generation of a thermal model using the finite element analysis program NE/NASTRAN. This thermal model will be used throughout the Task II – Design Study to help optimize the bridge wire design for maximum reliability.
3.1 – Schedule status
A copy of the updated program schedule is shown in Figure 1. As shown, Task 2 (Design Study) start date has been moved up to provide additional time for creating an optimized design of the bridge wire before the fabrication and testing stages. Currently, it is anticipated that the technical tasks will be completed by the original program end date.
Figure 1: Updated Program Schedule – Task 2 has been moved up another week to provide Odyssian Technology with additional time to work on the design study, particularly the development of a thermal model for the igniter and bridge wire.
3.2 – Technical Accomplishments
During this reporting period, technical progress was made primarily under Task 1, and 2. A summary of this progress is provided in the following subparagraphs.
Task 1 – Methods and Requirements Definition
Odyssian Technology discussed the definition of the methods and requirements with EaglePicher as well as Rose-Hulman Institute of Technology. These requirements were reviewed by both groups and are shown in Appendix A. The document lists the various igniter tests required by the appropriate military specification (MIL-DTL-23659D) for the EP250-1 igniter. These are current tests used to determine the reliability of current bridge wire processing. A standard test matrix is also shown. The new bridge wire design will have to meet these same testing requirements before they are used on an existing military system. Also shown in Appendix A is a breakdown of which requirements and goals are expected to be reached during each phase of this SBIR program. Input from EaglePicher and Rose-Hulman indicated that the scope of each phase’s requirements and goals was well accepted.
Task 2 – Design Study
A solid model drawing of the igniter was created and used to make a thermal model with the finite element analysis program NE/NASTRAN. Figure 2 below shows the 3D solid model created using Solid Works along with the materials that make up each igniter component. Not shown is the pyrotechnic powder which sits on top of the bridge wire, and the metal cap that contains the powder and wraps around the outer metallic seal. The physical dimensions needed to construct the model of the igniter were provided by EaglePicher.
[pic]During this reporting period progress was made under this task in creating a solid model of the EP250-1 model igniters. Figure 2 below shows the solid modeling created using SolidWorks. Not shown is the pyrotechnic powder which sits on top of the bridge wire, and the metal cap that contains the powder and wraps around the outer metallic seal. Definition of dimensions and material properties were provided by EaglePicher. Appendix B contains the 2-D CAD drawing supplied by EaglePicher for this task. The 3-D solid model of the igniter is used to create a thermal model of the system using the finite element analysis program NE/NASTRAN.
AThe n estimated required thickness of the line-shaped thin film bridge wire wasis first calculated so the model couldan be physically constructed. The following section details how the thickness of bridge wires was theoretically determined.
List of Terms:
[pic] = current (Amps)
[pic] = firing time (sec)
[pic] = length of bridgewire (m)
[pic]= bridge wire thickness (m)
[pic] = bridge wire width (m)
[pic] = area of wire cross-section (m2)
[pic] = specific heat of material (J / (Kg °C))
[pic] = resistivity of material (Ω m)
[pic] = density of material (Kg / m3)
[pic]= initial bridgewire temperature (°C)
[pic]= final bridgewire temperature (°C)
[pic] = heat flow of bridge wire
[pic]= work flow of bridge wire
[pic]= total energy in wire
Equations begin with the basic conservation of energy in order to calculate the conversion of electrical energy to the needed change in temperature:
[pic] (Eq. 1)
The wire is assumed to be adiabatic and the electrical form of work was substituted yielding:
[pic] (Eq. 2)
The change in energy was then substituted for the change in temperature for the given mass and specific heat:
[pic] (Eq. 3)
This equation was then solved for the Ac:
[pic] (Eq. 4)
The equation is then solved for thickness:
[pic] (Eq. 5)
This is done using the following equation:
[pic]
Where:
[pic] = current (Amps)
[pic] = firing time (sec)
[pic]= bridge wire thickness (m)
[pic] = bridge wire width (m)
[pic] = specific heat of material (J / (Kg °C))
[pic] = resistivity of material (Ω m)
[pic] = density of material (Kg / m3)
[pic]= initial bridge wire temperature (°C)
[pic]= final bridge wire temperature (°C)
The equation above originates with the conservation of energy and can be used to theoretically determine the required thickness of the thin film bridge wire. The current, [pic], takes the value of either the no-fire current or the all-fire current. The no-fire test places a 1 amp current across the two lead wires for five minutes. The igniter must not detonate (must not reach 300 (C, the ignition temperature of the igniter pyrotechnic powder) in this amount of time. The all-fire test places a 3 amp current across the two lead wires and within a 20ms time, the pyrotechnic powder must reach the required 300(C and detonate the igniter. Table 1 contains the data used to calculate the required thickness of the bridge wire line-shaped design to meet both the no-fire and all-fire requirements.
[pic]The actual thickness used in the design will be determined through the thermal model of the igniter and by fabrication and testing of the PVD bridge wire design.
[pic]
One issue with the theoretical results of these calculations is the excessive thickness required to meet the all-fire and no-fire tests. A target thickness of about 1 micron is desired for the PVD process. This data indicates that 750 microns of Nichrome must be deposited in order to prevent the bridge wire from reaching 300(C within 5 minutes using a 1A current source. Any less material will result in a bridge wire with less cross-sectional area, thus making its resistance and resulting temperature increase. The relationship between resistance and geometry can be seen in the following equation:
Relectric = presist*(l/Ac) (Eq. 6)
The method above assumes that all of the energy generated by the current,[pic], is converted into resistive heating and this energy remains inside the bridge wire. The amount of current was therefore used to determine the final temperature of the bridge wire as shown in Eq. 5. However, the assumption that all the energy stays inside the bridge wire is incorrect as the bridge wire, being in contact with its surroundings, looses heat energy via conduction and convection into adjacent materials and air. Some energy is also lost via electromagnetic radiation. The thermal model developed takes into account the fact that the bridge wire is loosing energy to its surroundings, giving a more accurate prediction of the required thickness.
Initially, the model included conduction through all the materials that contacted the bridge wire except the igniter powder. Because this model did not include the igniter powder or convection losses, it predicted a need for higher thickness of material than is comparable for the PVD process based on past fabricated test articles. A bridge wire thickness of 23 microns was derived from the model in order to meet the specification for No-Fire current load (1A over 300s). Figures 3 through 5 illustrate this thermal model at several time intervals.
[pic]
Figure 3: 23 micron thick Nichrome bridge wire at time = 5s and maximum temperature = 144.9C
[pic]
Figure 4: 23 micron thick Nichrome bridge wire at time = 150s and maximum temperature = 225.2C
[pic]
Figure 5: 23 micron thick Nichrome bridge wire at time = 300s and maximum temperature = 290C
Although a 23 micron thickness keeps the bridge wire under 300(C with the No-Fire loading condition, a thickness of no more than 6.5 microns is required for the model to reach 300(C with an All-Fire loading condition of 3A over 20 ms. These findings are an obvious decrease from the 750 for No-Fire verses 19.28 micron thickness for All-Fire predicted by the conservation of energy equation alone. By including the fact that the bridge wire is loosing energy to its surroundings, the thickness becomes much lower.
The temperature distribution illustrated in Figures 3 through 5 provides some insightful observations about the thermal behavior of the entire igniter system. The most notable is that the center of the bridge wire is maintained at a higher temperature than its ends. Conduction through two different materials is the reasoning behind this temperature distribution. The center of the bridge wire is in contact with the glass potting material while the two ends are in contact with the highly thermal conductive nickel lead wires. While the potting material is a comparibly lower thermal conductor, the two lead wires act as heat sinks keeping the bridge wire much cooler in that area of contact. This distribution in temperature will in turn effect how uniformly the pyrotechnic powder is heated, and therefore represents a potential source of variability in ignition performance. The information presented was considered in the design study for chosing the shape and thickness of the phase I bridge wire design.
Figure 6 and 7 shows the maximum temperature vs. time graph for this model at the bridge wire thicknesses of 23 microns and 6.5 microns for the no-fire and all-fire conditions respectively.
[pic]
Figure 7: 6.5 micron thick Nichrome bridge wire Maximum Temperature vs. Time graph for All-Fire loading condition
The need for more uniform temperature distribution over the heating element caused the investigation of different bridge wire shapes with this model. Circle and inverted dog-bone shapes were considered for their possible improvement in uniform temperature distribution. Figures 8 and 9 demonstrate the variation in temperature after 5 seconds of the No-Fire loading condition (1 Amp) using modeling analysis for both of these shapes. As with the previous model, this model does not factor in convection or conduction into the cap.
When comparing the line shape in Figure 3 to the circle shape in Figure 8, the circle shape has a uniform temperature that is of a much wider area than the line shape at the 5 second loading point. A potential disadvantage of the circle’s large surface area, however, is that the needed thickness of the deposited material is much thinner to pass the all-fire and no-fire tests. If the thickness of the bridge wire becomes too thin, the surface roughness of the substrate may cause physical breaks in the bridge wire resulting in an open circuit. This potential difficulty can be resolved by modifying the shape of the bridge wire until a minimum needed thickness is reached. The inverted dog-bone shape in Figure 9 is one example of this modification. The inverted dog-bone does not have as much of a total effective cross-sectional area as the circle design, which therefore leads to a thicker required bridge wire deposition. The inverted dog bone shows an improvement in uniform temperature distribution over the line design, therefore offering an option for increasing overall thickness of the bridge wire deposition.
[pic]
Figure 8: Circle Nichrome bridge wire at time = 5s
[pic]
Figure 9: Inverted Dog-Bone Nichrome bridge wire at time = 5s
Odyssian Technology worked with Eagle Picher to model the powder, resulting in improved accuracy of the thermal model. Odyssian created a model that includes a solid component that represents the powder material in contact with the bridge wire. Due to the lack of available powder data, a model of the powder was constructed by estimating material properties. These properties were then varied to assess the effect on the resulting bridge wire deposition thickness. Initial material estimates included; thermal conductivity of 50 W/m-(C, a density of roughly 2600 kg/m^3, a specific heat of approximately 500 J/kg-(C.
The estimated material properties in the model were used to simulate the effect of the powder and to perform sensitivity assessment. A low density, for example, is expected for the powder due to its porous nature. Therefore, a low density material was used as a first estimate. The powder’s thermal conductivity was initially assigned be relatively high to have the effect of increasing thickness of the bridge wire deposition. The higher thermal conductivity, the greater the required thickness due to the powder acting less as a thermal insulator and more like a heat sink or thermal conductor that distributes heat and prevents localized high temperatures. The final material property to identify for the powder for thermal analysis was specific heat. This parameter is the amount of heat required to change a unit mass of substance by one degree in temperature. The higher this value, the more thermal energy the powder can hold at a given temperature and the more it behaves as a heat sink. All the materials in the system model hold a specific heat of approximately 500 J/kg-(C. This value was used as a first estimate for modeling the powder’s specific heat. This material property also has the largest impact on the maximum temperature of the system. Allowing the specific heat, for example, to increase to 4000 J/kg-(C reduces the required bridge wire thickness to about 5 microns. Increasing the specific heat beyond this point has a progressively less of an effect on reducing the required bridge wire thickness. Figure 10 illustrates this new model for the no-fire load condition and with an 11 micron bridge wire thickness that was determined via simulation of this model.
The addition of a convection load on the igniter system was later added to the model to produce a higher level of accuracy to the steady state condition. The steady state response was simulated by initially loading the bridge wire with either the no fire or all fire condition (1A or 3A current input) with the removal of the load after the condition’s specified time. After a long period of time under no load, the igniter system should return to room temperature via heat convection through the surrounding air. Without the addition of a small convection load in the model, the energy generated by the current load will remain in the system and not dissipate after the current load is removed. The resulting steady state response was a uniform temperature much higher than room temperature. This condition is shown in Figure 11. The 11 micron thick bridge wire system (including the powder) having no convection load applied to the outer surfaces and placed under the no-fire loading condition retained the energy added to the system long after the removal of the load. Steady state uniform temperature occurred at about 260(C. By placing a small convection load (6 W/m2 -(C) on this same system as in Figure 12, the steady state temperature returns to room temperature as expected. Adding this feature to the model improves the accuracy of the transient response curve for the igniter system.
[pic]
Figure 11: 11 micron thick Nichrome bridge wire and igniter powder system with no convection loads Maximum Temperature vs.
Time graph for No-Fire loading condition – steady state system temperature approximately 260(C
[pic]
Figure 12: 11 micron thick Nichrome bridge wire and igniter powder system with convection loading Maximum Temperature vs.
Time graph for No-Fire loading condition – steady state system temperature approximately 20(C
Additional modeling work was completed recently to better represent the powder material. Research has been conducted by both Odyssian Technology and Eagle Picher to identify existing data and analysis on related pyrotechnic powders or igniters. A few papers were located including those entitled, “Calculations of Effective Thermal Properties in a Highly Compressed Pyrotechnic Mixture,” which contained thermal conductivity and density data for an unspecified pyrotechnic powder material. This paper was the result of a 1982 seminar and authored by C.E. Hermance of the University of Waterloo. After discussions with Eagle Picher about this finding, a decision was made to use the data from this paper as a best guess on the material properties of the powders contained within the EaglePicher igniters. This data will also be used for any EaglePicher purposes until material data can be found by the original manufacturer or the powders can be tested for the appropriate material properties.
Specific heat property data was still lacking from the research. To approximate this needed information, specific heat was estimated from calcium since the pyrotechnic powder, boron calcium chromate, is based on the calcium element. The specific heat of calcium is 653 J/kg - (C which will be used for the value of specific heat of the powder until more pertinent data is obtained. Thermal conductivity values from the described papers were 2 W/m - (C, and density was averaged at 1815 kg/m3. Figures 13 and 14 illustrate the final modeling conducted for the line-shape bridge wire using these new material property estimates for the powder material. Figure 13 shows the no-fire loading condition (1A) with the powder material (hidden) and convection loading. Figure 14 shows the all-fire (5A) loading condition for the same model. A Five amp source was used as the all-fire condition here to represent the military specifications for the igniter. Eagle Picher currently implements the all-fire test at 3.5 amps. This model was optimized to find the minimum amount of convection needed in the modeling to make the all-fire and no-fire obtainable by the same required thickness. For this case, a convection coefficient of 6 W/m2 - (C was discovered to meet this objective. The required thickness found was 10.89 microns. If more convection is added to this model, the all-fire and no-fire test requirements will both be met with either an increasingly larger time overlap or with an allowed reduction in the minimum required thickness.
[pic]
Figure 13: No-Fire Load 10.89 micron thick Nichrome bridge wire at time = 300s and maximum temperature = 299.8C
[pic]
Figure 14: All-Fire Load 10.89 micron thick Nichrome bridge wire at time = 0.05s and maximum temperature = 301.1C
This optimization procedure was repeated for the circle-shaped thin film bridge wire. The new material properties previously described were also used in this model. Figure 15 shows the No-Fire (1A) loading condition with a minimum required convection coefficient of 13 W/m2 - (C. The required thickness for this model to pass both no-fire and all-fire (5A) loading conditions was 1.7 microns. Figure 16 shows the all-fire (5A) loading condition for this same model at worst case.
[pic]
Figure 15: No-Fire Load 1.7 micron thick Nichrome bridge wire at time = 300s and maximum temperature = 298.1C
[pic]
Figure 16: All-Fire Load 1.7 micron thick Nichrome bridge wire at time = 0.05s and maximum temperature = 303.2C
A sensitivity study was also conducted by Odyssian Technology to determine how responsive the igniter model is to the major unknown variables. These variables include convection coefficient, thermal conductivity of the powder, density of the powder, and specific heat of the powder. Figure 17 shows a graph comparing how large a temperature change was observed in the model after the identified variable was run at best guess and then reduced by 90% of its original value. For example a model was run for the line shaped bridge wire with a convection coefficient of 6 W/m2 - (C. The resulting maximum temperature of this model was then compared to the same model with a convection coefficient of 0.6 W/m2 - (C, a 90% reduction. The change in temperature was seen to be about 400 (C, showing that the modeling is very sensitive to the value of convection coefficient placed on the system. The material properties of the powder, however, presented a much lower sensitivity.
[pic]
Figure 17: Sensitivity Study for Igniter Thermal Model shows high sensitivity towards the convection coefficient.
Several factors have been identified for improving the igniter thermal modeling that was developed during this phase I SBIR program. Obtaining a better definition of the igniter powder material properties, as well as a better definition for the ignition temperature of the powder would help to make the thermal modeling more accurate. The model also needs to be completed with the addition of the final component of the igniter set-up, namely, the outer metal cap which houses the powder. Adding this component will result in an increase of heat drawn away from the igniter bridge-wire, thus requiring a thinner bridge wire to meet the all-fire temperature requirement. Another component that is not included in the current model is the interaction of the igniter with the rest of the battery assembly. A heat sink may be added to the end of the lead wires to simulate the power source leads that will be supplying the needed current to the bridge wire. The battery also holds the igniter through contact with the header, resulting in an additional source of heat conduction away from the bridge wire. Because the battery is not present during the testing of the bridge wire, there may be a desire to create a model of the igniter during testing (no battery materials present) and a model during actual application. A better understanding of the convection coefficients on the igniter during testing and application is vital due to the model’s high sensitivity towards the convection coefficient’s value. Radiation may be another form of heat transfer that could be added to the model for enhanced accuracy.
Task 3 – Process Development and Fabrication
Odyssian, through the use of a local machine shop (K&L Machine and Mfg), was responsible for fabricating the line-shaped and circle-shaped bridge wire masks. Masking is used in the PVD process to act as a stencil for controlling the Nichrome deposition. Figure 18 is the resulting line-shaped mask made from a rigid plastic material. The line-shaped and circle-shaped thermal models were used to derive the dimensions of the masks that were needed to achieve a thin film bridge wire thickness of only a couple microns. The actual thickness was determined during the testing and optimization tasks conducted at Rose-Hulman Institute of Technology.
Three separate PVD processes were attempted for this project: e-beam evaporation, sputtering and thermal evaporation. Challenges and sources of variability were alloy concentration variation, affects of deposition base pressure, deposition rates, cracking and peeling of the thin film, uniformity of deposition, and resistivity changes over time (aging).
Evaporated and sputtered nichrome have been used in specific systems requiring a well known, unchanging resistivity with respect to temperature (thermal coefficient of resistivity “TCR”). A number of papers were discovered regarding both sputtering and evaporation of this material. Aging of NiCr thin films after depositions has led to the annealing of thin films in oxygen to “stabilize” the resistivity. The oxidized film is expected to change very little over time after annealing. Adding an annealing step would increase handling and cost of the procedure. An alternative material such as TaN may be a suitable replacement in future research.
As depositions increase in thickness, the film begins to act more like a bulk material. This bulk material is highly stressed, and instead of adhering tightly to the substrate, the film will begin to peel away. The peeling results from the shear stress overcoming the bonding forces between the film and the substrate. Adhesion is better at smaller thicknesses.
Deposition of alloyed thin films from single sources is a difficult task for evaporation processes. Chrome has a much higher partial pressure at its melting temperature in comparison to Nickel. This results in higher concentrations of chrome in the film in comparison to the original material concentration in the crucible. Process drift occurs as the concentration of the material changes in the melt concentration and is deposited on the devices over time. For these reasons, e-beam and thermal evaporation is not suggested for process development beyond phase I, but is reasonable to consider in phase I for comparison.
Deposition base pressure has been reported to affect the resistivity of the deposited film. In order to prevent effects from base pressure, the deposition processes should all be operated at the same base pressure. Most depositions were in the range of 4 to 6 x10^-6 Torr.
Using the E-beam and Sputtering equipment at Rose-Hulman Institute of Technology, as well as thermal evaporator equipment at the University of Notre Dame, Nichrome was initially deposited onto silicon wafers for the purpose of evaluating the variance in thickness due to the deposition process. The suface roughness of a silicon wafer is much less significant than the surface roughness of the igniter substrates. By noting the uniformity in the deposition on a silicon wafer, a comparison was made of geometry variance due to inconsistancies in the deposition process. Any additional variances seen after depositing onto the igniters can then be attributed to surface roughness effects and not processing variations.
A couple of challenges emmerged when depositing Nichrome onto a silicon wafer. The first deposition of NiCr, with a target of 2 microns, failed to adhere to the oxidized silicon wafer as seen in Figure 19. This failure was attributed to several factors. Two likely factors are cleanliness and excessive heating. First, no cleaning step was performed before the deposition of NiCr on the oxidized wafer. Second, there is a significant difference in the coefficient of thermal expansion (CTE) between NiCr and silicon causing high stresses to manifest along the PVD edges and contact surface. A third probable cause is the thickness of the deposited layer. Deposited films have maximum attainable thicknesses. These thicknesses are determined by numerous variables, but are most affected by surface adhesion vs. internal stress of the film. As films get thicker, they increase in volume. The larger volume provides a greater shear stress at the interface caused by the internal stresses of the film. During this reporting period, several wafers were deposited with a target of 300nm Nichrome in both the E-beam and sputtering equipment at Rose-Hulman and thermal evaporator equipment at the University of Notre Dame. No peeling was evident at this thickness. Example wafers run through the Rose-Hulman equipment are shown in Figure 20.
Several different batches of igniters were subjected to Nichrome deposition, in which the Nichrome was laid down between the poles (electrical leads) to create a bridge. The process was run enough times to produce 18 batches of igniters. Each batch contained 5, 6 or 9 igniters, depending on the mask used or the orientation that was desired for the batch. After the deposition, the igniters were documented to record their position and orientation on the mask. The run sheet in Figure 21 was created and modified during phase I depositions. A 50 mA current was then applied to the igniter, and the precise current and voltage was measured across the igniter using multimeters. The resistance of the igniter was then determined using Ohm’s Law. The igniters with a resistance under 5 Ω were assembled in preparation for testing. Igniters which had a resistance above 5 Ω were set aside to either be resurfaced or annealed. Those which were resurfaced also underwent another deposition. The process above was repeated for these igniters.
Some igniters were polished before deposition using a Buehler Ecomet 3 – Variable Speed Grinder/Polisher with 600 grit sandpaper. The igniters were then brought into the MEMS lab at the Rose-Hulman Institute of Technology where the Nichrome was deposited onto the surface of the igniters. The resistance of the igniters was measured using a breadboard wired so that two Fluke 8050A Digital Multimeters can measure the current and voltage across the igniter. The power was supplied by an Agilent E3611A DC Power Supply.
|Run | | | | | | |
| | | | | | | |
|Base Pressure: | |Running Pressure: |Start Time: |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
|Final Temperature of Chuck: |Date: | |End Time: | |
| |(˚C) | | | | | |
|F: | | | | | | |
|B: | | | | | | |
| | | | | | | |
|Type of Run: | |Deposition Rate: |Time from |
| | | | | |Pump down to |
| | | | | |Deposition: |
| | | | | | | |
| | | | | | | |
|Thickness: | |Orientation Guide: | | |
| | | | | | | |
| | | | |↑ | | |
| | | |1 |2 |3 |
| | | |Surface Prep: | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
Figure 21: Data Run Sheet for Igniter Nichrome Deposition Runs
The igniters which were under 5 Ω were assembled by packing the pyrotechnics together with the chosen igniter head. The process for packing the igniters closely follows the process flow determined by EaglePicher. The process that was used specifically for these igniters started with pouring 65 mg of the output mix into the cup and compacted at 55 pounds force. After pressing the output mix, the ignition mix was poured into the top of the cup, and the mix was pressed to 126 pounds force. Next, the igniter head was pressed into the cup using 310 pounds force. When the process had completed, the igniter cup was crimped around the head piece using enough force to provide uniform crimp.
The force was applied using an MTS 858 Table Top System with a computer program running the input for the process. The process allowed for a 1 pound force per second ramp input to the desired force, followed by a 6 second dwell at the end, if necessary. This process was repeated for each of the different amounts of force needed for the igniter. Tooling was supplied by Eagle Picher, and all connecting pieces were fashioned in the Rose-Hulman Institute of Technology machine shop. An electronic balance with a tolerance of +/- 1 mg was used to measure out the mass of the powders used.
Task 4 – Testing and Evaluation
Nichrome Depositions
Using the 300nm Nichrome on silicon wafer deposits discussed in the previous section, several resistivity variation measurements were conducted at Rose-Hulman. Four-point probe measurements were used to map out the resistance variation across the wafers. The sputtered wafers demonstrated the most consististcy in resistivity across the wafer surfaces. Figure 22 shows a sputtered NiCr wafer. As seen in the legend to the right in the figure, each successive color represents a change of only 2 mV drop. Still withstanding, little color variation existed across the wafer. The variance is essentially 46-50 mV across the interior of the wafer (as the edges vary greatly). Only a few areas displayed deviation.
[pic]
Figure 22: 2D contour surface plot of an oxidized Si wafer coated with NiCr via sputtering, no tape in the center
Figure 23 is a 2D contour surface plot of an oxidized Si wafer coated with NiCr using e-beam evaporation. The legend at the right in the figure breaks the color increments by 5 mV. The stripe across the middle is where no NiCr was deposited. This graph has less uniformity or otherwise large resistivity variations across the wafer.
[pic]
Figure 23: 2D contour surface plot of an oxidized Si wafer coated with NiCr via E-beam evaporation
Figure 24 is a contour plot of a thermal evaporation run conducted at the University of Notre Dame. The color scale is broken in 2mV increments. This graph shows the least uniformity of the three PVD systems tested.
[pic]
Figure 24: 2D contour surface plot of an oxidized Si wafer coated with NiCr via thermal evaporation
Several deposition variables were allowed to change to monitor their effect on thin film resistivities. These variables were thickness, deposition technique, and deposition rate. Deposition thicknesses were varied based upon data acquired from previous depositions. The goal of the project was to produce thin films with a resistivity in proximity to 1 Ohm. After a series of all fire testing of igniters having values less than 4 Ohms, the target resistivity was shifted to 1.3-1.6 ohm range.
Deposition processes were also drastically affected by other variables beyond thickness. Figure 25 shows the first 15 depositions and their resistivities. The resistivity at 10 microns from depositions at a very low rate (8 Ang/s middle dot) and a very high rate (100 Ang/s, highest dot) produce higher resistivities than an average deposition rate controlled by hand (lower dot at 10 microns)
[pic]
Figure 25 Thin film average resistivities per run are shown for the first 15 depositions. Three depositions at 10 microns of thickness and varied deposition rates have a larger change in resistivity than any thickness effect.
Table 2 shows the 18 deposition runs made by RHIT and the resistivity at each position within the holder. Highlighted positions were selected for testing in an “All-Fire” and “No-Fire” test. The most notable observation was that depositions were beginning to become more predictable and have a much smaller variation and standard deviation in resistivity within each successive run. The final run indicates a standard deviation down to .15 ohms.
Table 2: Positional Igniter Bridge Wire Resistivities for Each PVD Run
|1 |2 |3 |4 |5 |6 |7 |8 |9 |average |standard dev | |1 (evap - 1.5 microns - unpolished) |5.30 |17.16 |5.48 |x |4.65 |6.51 |5.30 |6.54 |5.64 |5.30 |4.126204 | |2 (sputter - 1 micron polished) |x |x |12.89 |11.92 |12.40 |11.52 |16.16 |13.53 |19.41 |13.97 |2.84152 | |3 (sputter - 2 microns - mixed polishing) |16.12 |36.66 |29.80 |16.59 |15.41 |15.65 |14.27 |12.12 |17.51 |19.58 |8.198449 | |4 (sputter - 4 microns - mixed polishing) |7.70 |3.62 |5.66 |4.17 |4.65 |3.14 |5.68 |5.92 |4.93 |5.05 |1.379661 | |5 (sputter - 10 microns - unpolished) |2.19 |1.50 |1.52 |1.77 |1.56 |1.31 |1.56 |0.89 |1.71 |1.56 |0.35 | |6 Line (evap - 3 microns - unpolished) |11.14 |x |x |7.33 |x |x |6.15 |x |x |8.21 |2.607956 | |6 Circle (evap - 3 microns - unpolished) |x |2.60 |x |x |2.68 |x |x |1.76 |x |2.35 |0.50964 | |7 (evap - 8 microns - unpolished) |4.13 |3.27 |4.45 |18.84 |3.16 |x |2.32 |4.71 |4.09 |5.62 |5.398287 | |8 (evap - 8 microns - unpolished) |2.68 |9.52 |x |x |2.23 |x |1.42 |7.94 |3.18 |4.49 |3.368762 | |9 (sputter - 12 microns - unpolished) |1.67 |0.96 |0.81 |0.62 |0.90 |0.86 |1.44 |1.12 |0.80 |1.02 |0.336341 | |10 (evap - 1 micron - polished) |5.55 |8.63 |5.29 |5.51 |12.03 |7.21 |x |5.75 |6.01 |7.00 |2.323518 | |11 (evap - 1 micron - polished) |8.24 |5.52 |9.05 |29.30 |5.70 |20.25 |13.01 |7.61 |7.12 |11.76 |8.026844 | |12 (sputter - 11 micron - mixed) |0.81 |0.71 |0.66 |0.89 |2.04 |0.75 |0.77 |0.85 |0.71 |0.91 |0.429913 | |13 (evap - 10 microns) |40.05 |x |43.81 |x |39.01 |x |16403.23 |x |934.81 |3492.18 |7227.865 | |14 (evap - 10 microns) |7704.55 |x |619.87 |x |8.77 |x |7052.78 |x |1284.20 |3334.03 |3726.805 | |15 (evap - 10 microns) |1.60 |x |2.54 |x |4.08 |x |17.82 |x |2543000.00 |508605.21 |1137261 | |Circle Mask | | | | | | | | | | | | |16 (sputtered - 2.5 microns) |1.31 |1.16 |1.31 |1.82 |1.25 |1.22 |x |x |x |1.35 |0.239562 | |17 (evap - 3 microns) |0.74 |0.92 |2.63 |0.86 |1.57 |1.53 |x |x |x |1.38 |0.708879 | |18 sputter - 2.3 microns) |1.40 |1.47 |1.61 |1.43 |1.80 |1.61 |x |x |x |1.55 |0.150289 | |
Figure 26 appears to show a large amount of variation in the data collected for resistivity. This variation is due to the number of variables that may be altered beyond thickness. One of these variables is shown in Figure 25 where the deposition rate drastically affects the resistivity of e-beam deposited films. Another variable is that the E-beam depositions have a large variation in their resistivity over sputtered samples as seen in Figure 27. A third variable is the shape and thickness of the bridge wire. Figure 26 shows two regions of improved film variation; one at large thicknesses (10-12 microns) and one at lower thicknesses (2-4 microns). The higher region is sputtered thin films and the lower region is the result of circular masking.
[pic]
Figure 26 Shows the average resistivity of the various depositions respect to thickness. This graph cuts off at 20 Ohms thus ignoring the large variation seen in Table 2. Error bars shown are one standard deviation. The cluster of small standard deviations points between 2 and 4 microns and 2 ohms are circle deposited film patterns.
A wide variation in both resistivity and standard deviation occurred throughout the e-beam deposition thickness profile resulting in no discernible decrease in resistivity with increasing thickness.
[pic]
Figure 27. E-beam deposition runs showing large variation and large standard deviation. The small standard deviation deposition was a circular mask.
Figure 28 shows a clear decrease in resistivity and standard deviation with increasing thickness for the sputtering deposition of line-shaped bridge wire. The data provided in this figure and Figure 27 indicates thicker films and circular masks are advantageous to lowering the variation between devices within the same run.
[pic]
Figure 28 - Sputtering deposition of line-shaped bridge wire shows more controlled standard deviation with increasing thickness.
In conclusion, reliable and predictable thin film igniters can be produced using a circular pattern and relatively thicker film with the use of PVD sputter equipment. In order to increase the thickness further, a new material search is suggested with a higher resistivity (although the film is more likely to not adhere with increased thickness).
A Scanning Electron Microscope (SEM) was used to observe the deposited Nichrome. Pictures revealed that a very porous structure is being deposited across the epoxy surface, while the Nichrome on the surface of the Stainless Steel leads retains the same surface integrity as the underlying material. The composition of the deposited Nichrome was also measured at various positions of a sputtered igniter. The Nichrome over epoxy was measured to have 79.99 wt% Ni and 20.01 wt% Cr, as was expected with this deposition. Over the leads, the composition was 78.04 wt% Ni, 19.48 wt% Cr and 2.49 wt% Fe. The porous Nichrome over the epoxy also appears to experience pitting or some form of deformation in surface structure. With this observation, the quality of the metal was also surveyed within a 5 μm diameter pit. The pit contained 83.92 wt% Ni and 16.08 wt% Cr. Photos of the SEM are appended as Figures 29-32. Figures 29 and 30 show the interface of the pole on the igniter head along with the 1 micron thin line-shape bridge wire on the Epoxy surface. The Nichrome covering this area experienced a problem with peeling off of the poles, while the epoxy produced a series of pits in the Nichrome film. The peeling caused an inconsistent film as the Nichrome transitioned from pole to epoxy. The resulting step can be seen in Figures 31 and 32. A chip which peeled off from the film covering the epoxy did show good columnar growth of the Nichrome grains. This evidence is easily visible in Figure 32.
[pic]
Figure 29: SEM picture of entire igniter head. Epoxy shines bright white, while the porous Nichrome, 1micron thick film, can be seen across the surface between the two distinctly smooth poles.
[pic]
Figure 30: SEM picture of igniter head. Peeling of porous Nichrome, 1micron thick film, is seen over the contacts, with visible pitting on bridge over epoxy.
[pic]
Figure 31: SEM picture of epoxy / pole interface. Epoxy exists in upper left, with pole in lower right corner covered with 10 micron thick Nichrome film.
[pic]
Figure 32: SEM close-up (×5) of figure 31. Peeling chip at epoxy / pole interface shows columnar grains of 10 (m thick NiCr film forming over epoxy.
Several sources of variability associated with the new physical vapor deposition process still currently exist. The most significant of these is the surface roughness of igniter base and the variability in the equipment to deposit a uniform layer of material onto the igniter base substrate. These uncertainties can be further magnified when trying to manufacture multiple igniters at the same time. Odyssian has conceptualized a processing technique to circumvent these sources of variability resulting in a well-defined and accurately controlled deposition of material on each igniter base.
The proposed processing technique uses a feedback controlled Multi-shutter System during the PVD process to monitor each igniter or group of igniters’ deposition thickness (via resistance measurements) and individually or by groups block the deposition of additional material when the desired thickness is reached. Due to the variability in surface roughness and equipment non-uniformity, not all the igniters being processed will reach their desired thickness at the same time. The benefit of the feedback controlled shutter system will be to allow many igniters to be processed in a single PVD run without sacrificing quality to these uncertainties.
The proposed system would include a mechanism to monitor the resistance across each igniter in the PVD system, and automatically controlled mechanical shutters to block the deposition of additional material onto the igniter or group of igniters. The mechanical shutters may be built directly into the mask/holder (as shown in Figure 33) for the igniters or institute a separate stand/device. The mechanism to monitor the resistance could take on different forms such as a series of multimeters or a single data acquisition system. This monitoring system would then communicate with the mechanical shutters to notify the shutters when the desired thickness is reach and to block all further deposition onto its associated igniter(s).
Currently there are several methods that exist to monitor deposition thickness during a PVD process. The most common of these is through the use of a quartz crystal present in the system. As material is being deposited on the desired target, depositing of the material on the crystal is also occurring with an assumed equal amount of material. The electrical properties of the crystal due to the deposition are monitored and displayed as a thickness reading throughout the PVD run. The assumption that the crystal sees the same thickness as the target is, however, incorrect. Because the target is located in a different position from the crystal, it will see a different deposited thickness. The magnitude of this difference is dependent on several factors including the crystal’s distance away from the target and the uniformity to which the equipment can deposit material inside that distance. The benefit of the proposed feedback control system is that resistance measurements are taken from each igniter and the exact status of the igniter is displayed and controlled. With this system the equipment no longer needs to carry a perfectly uniform deposition for each of the igniters in the system to reach their desired thickness. Also the igniters themselves do not need to maintain the same surface roughness from one igniter to the next in order to reach their desired electrical resistance and thermal characteristics.
Figure 34 illustrates a schematic diagram of the shutter control system for a single igniter and shutter. The electronic circuitry consists of three major parts. These parts include a current source, a monitoring circuit, and an actuator driver. The current source consists of an LM317 variable voltage regulator and 24 ohm resistor seen at the top of the schematic diagram. The LM317 is design to output a constant voltage of 1.2V between the Output (OUT) and the Adjust (ADJ) pins. By placing a 24 ohm resistor between these pins, the constant voltage drop across the fixed resistor produces a fixed current through the resistor. This current level can be calculated based on Ohm’s Law as:
[pic]
This condition sets up a 50mA current source as no current can actually flow through the Adjust pin due to its high input impedance. This current source is fed directly to the igniter being monitored. A 50mA current level was chosen based on the military specification of the maximum amount of current that can be placed through a bridge wire for non-destructive resistance measurements. This circuit comprises of half of a classic four wire resistance measurement device.
The other half of the resistance measurement also terminates two wires at the igniter. This circuit is the monitoring portion of the system. These wires feed back to a differential-to-single-ended amplifier. The amplifier has a unity gain and is used for common mode rejection so that any noise that appears on both of the long lead wires gets rejected through the amplifier. The output of this amplifier feeds into the inverting end of an LM339 comparator circuit. An adjustable voltage divider on the non-inverting end of the comparator sets up the reference voltage. The goal of the monitoring system is to change the output of the comparator when a resistance of one ohm is seen across the bridge wire. With 50mA energizing the bridge wire, a one ohm resistance across the bridge wire will result in a 50mV signal differential being fed back to the amplifier. During monitoring, the current source will continue to try to supply 50mA to the squib using as high as a voltage level as needed but limited by the 12V supply voltage. As the Nichrome is deposited, the electrical resistance across the bridge wire decreases allowing less voltage to be required to supply the 50mA current. With the non-inverting input of the comparator setup as a 50mV reference, the comparator will keep its output at a ground potential while the voltage from the amplifier is above the 50mV. When this voltage drops below 50mV, the comparator floats its output.
The shutter actuation portion of the circuit activates when the comparator output is floating and no longer grounded. The MP2222 transistor switch becomes saturated causing the activation of the relay coil. The double-pole double-through relay contacts switch position causing a reversal of the polarity across a rotary actuator. The polarity reversal causes the actuator to move in a direction to close the shutter.
Using the polarity reversal scheme with the relay, an actuation voltage is always present across the actuator leads. The actuator is a simple electromechanical movement that is designed to withstand a permanent stalled condition with a limited amount of current. The resistor on one terminal of the actuator limits the current allowed to travel through the actuator. With this current limiting, the actuator can safely stall against a physical hard stop to hold the shutter open prior to the relay activation. When the relay is activated, the actuator moves is the opposite direction to meet another hard stop that will hold the shutter in a closed position.
The use of this circuit requires some careful observations. The circuit must not be activated for some time after the PVD process is started. Otherwise, the current source could cause the burning and removal of Nichrome as it is trying for form on the substrate. Enough of the material must be deposited to handle the electrical power energizing the bridge wire prior to its introduction.
[pic]
No-Fire / All-Fire Tests
The No-Fire test is a 5 minute test in which 1 amp of current is applied to the igniter. During this test, the igniter is to remain inert and avoid detonation. The igniter should then be tested under the All-Fire test, in which 3.1 amperes of current is applied to the igniter and it is expected to detonate within 20 ms of the event. At the end of this project, the EaglePicher current ignition testing was discovered to be at 3.5 amps as opposed to 3.1 amps. This is difference is quite significant. The power drop across the igniter “wire” is a result of the formula power formula (I2 * R). For a nominally 1 Ohm igniter operating at 3.5 amps, the power created would be 12.25 Watts. The same igniter would only create 9.61 Watts at 3.1 Amps. The resistivity required to produce 12.25 Watts at 3.1 Amps shifts upward to about 1.27 Ohms.
A DC power source was used to supply the input current. The power source would be set to a constant current of either 1 or 3.1 Amps (with a few runs at 3.5 Amps) and a maximum voltage of 6 volts. The output was toggled on the device using an output on/off switch. The response of this toggle method was recorded using a 1 Ω resistor so that the time response of the current source and toggle switch could be determined. An oscilloscope was used in parallel to record the voltage across the igniter head. This measurement was performed over a large period of time (5 seconds), so that the time of the detonation could be determined. If the detonation occurred in that 5 second range, the detonation point could be seen as the bridge would be destroyed and the voltage would spike to the maximum voltage output from the current source.
Several different data points were measured during the fire tests in order to get a better understanding of the differences in the results. A grid containing all of the recorded data can be found in Table 3. The five minute No-Fire test were documented by recording the starting voltage output from the power source (Vs1) and the voltage recorded by the oscilloscope (Vo1) along with the accompanied image of the response. The voltage on the power source was observed closely with the final voltage (Vs2) being recorded as to whether the igniter passed or failed the 5 minute test. The duration of the No-Fire test was recorded (TimeNF) as well with a successful test recording the full five minutes. The grid also contains a column denoting igniters which failed the No-Fire test for ease of reading.
The All-Fire test was performed immediately following the No-Fire test. For the first 50 igniters, there was no cool down time between the two tests. However, the method has now been revised to allow the igniter to cool down to ambient temperature before performing the All-Fire test. When the All-Fire test was performed, the oscilloscope was set to trigger and record the necessary data for the event. The voltage across the igniter was read (Vo2) from the captured trace and the time that it took to break the bridge (TimeAF) was determined as the point at which the voltage spiked to reach the total potential allowed by the current source. The trace was then saved (File) for later reference. A problem with this method was that some igniters carried current even after detonation, giving no readable sign of detonation with just an oscilloscope. In addition, the oscilloscope was not always able to read on a long enough time scale to catch the detonation point for any igniters which fired five or more seconds late.
Table 3 also contains the initially measured resistance (Rinit), as determined by the methods described above in the Nichrome deposition section. A column denoting the method of deposition (E-beam/Sputter) is also included for easy reference. The time the igniter was allowed to cool (TimeC) between tests is also included, although the method was not carried out until the final six igniters were tested.
A total of 56 igniters have been assembled and tested under the No-Fire / All-Fire tests. Of these 56 igniters, 35 passed the No-Fire test successfully. The igniters that failed the test tended to have a higher resistance, as they averaged 3.08 Ω. Igniters that passed the No-Fire test had lower resistances as they averaged 1.46 Ω. Only 3 igniters passed both of the fire tests with captured data. Some igniters that fired did not cause the oscilloscope to trigger in order for the scope to capture the time until detonation. The three igniters that passed both tests had resistances measuring 1.31, 1.6 and 0.81 Ω. All the igniters in the range of 1.0 - 1.8 Ω portrayed better responses for the All-Fire time portion of the test.
The test equipment used included an Agilent 54622D Mixed Signal Oscilloscope to record the voltage change across the igniter. An Agilent E3631A DC Power Source was used for most of the fire tests, as the 0-6V, 5A capabilities of the source fit the needs of this test extremely well. The response of the power source shows negligible ringing and is capable of ramping the voltage level to meet the current source set point in approximately 4.00 ms. A Fluke 8050A Digital Multimeter was also used to gauge the voltage drop across the igniter in a more reliable fashion than the oscilloscope could provide.
[pic]Table 3: All-Fire and No-Fire Testing Results
Figure 35 displays the “All-fire” and “no-fire” window created by the deposited films using 3.1 Amps “All-fire” current. The first passing igniter had a measured resistance of 1.3 Ohms. By changing the “All-Fire” current to 3.5 amps, a dramatic increase in the size of the operating window between All-fire and No-Fire can be expected in the range of 1 to 1.6 ohms.
[pic]
Figure 35 Shows the ignition time in seconds with respect to resistivity for "All-Fire" at 3.1 Amps; and time in minutes with respect to resistivity for "no-fire" at 1 Amp.. These tests show a window between 1.3 and 1.6 ohms for successful igniters (first failure of “no fire” at 1.71 Ohms). All data shown is for sputtered depositions.
Once an idea of the required thickness is theoretically determined, a solid model drawing can be created and then imported into NE/NASTRAN. Work was started under this reporting period on a thermal model of the bridge wire and will be continued into the next reporting period. Figure 3 shows some initial temperature profile results though at this time are only a good qualitative representation. Work will continue in order to provide accurate quantitative data of the bridge wire under the all-fire and no-fire conditions.
[pic]
The temperature profile illustrated in Figure 3 provides some insightful knowledge about the thermal behavior of the entire igniter system. The most notable information comes from the fact that the center of the bridge wire is maintained at a higher temperature than its ends. Conduction through two different materials is the reasoning behind this temperature distribution. The center of the bridge wire is in contact with the glass potting material while the two ends are in contact with the highly conductive (thermal) nickel lead wires. Since the potting material is a comparibly lower thermal conductor, the two lead wires act as a heat sink keeping the bridge wire much cooler in that area of contact. This distribution in temperature will in turn effect how uniformly the pyrotechnic powder is heated, and therefore represents a potential problem. The information presented will be considered in the design study when chosing the shape and thickness of the phase I bridge wire design.
Work was also conducted during this reporting period by the subcontractor Scott Kirkpatrick under the design of of the phaseII pilot production system. Below is a describtion of the progress made under this phase I task.
Deposition system design
Regardless of the final selection for the PVD process, one obstacle for the system to overcome is deposition process time. A suggested solution for rapid device deposition is to use the mask/device holder as a vacuum sealable surface. The holder would be set on an o-ring, and a small chamber containing the deposition method of choice, currently depicted as a sputter cathode as shown in Figure 4.
[pic]
Figure4: Basic conceptual design for an igniter deposition system.
The igniter which would protrude through the mask will need an o-ring to seal against. This o-ring may be placed on the mask sealing to the face of the igniter, or it may be place on the sides of the igniter sandwiched between plates to form a tight seal as shown in Figure 5.
[pic]
Figure 5: A Closeup design similar to a Vac-Coupling to provide a vacuum sealing surface.
Screws would hold the top plate in place to the holder about the perimeter as depicted in Figure 6 and Figure 7. This would also provide the force required to seal the o-rings to the devices. The mask may be attached in a similar manner as the top plate, or machined out of the same block of material as the holder.
[pic]
Figure 6: A top down conceptual view of an igniter holder/mask.
[pic]
Figure 7: A cross section view of an igniter holder/mask.
Device design concepts
One important consideration in the current design is how the surface will define the end product. Upon looking at an igniter, the surface appears to be flat. Assuming the grinding operation on the igniter was 120 grit, the surface is only flat however down to the range of 50 micrometers, and for 600 grit the bumps should be on the order of 10 micrometers. This surface has several effects on the resulting thin films. First, since the deposition processes are PVD, the deposited films are not conformal, and may be shadowed from forming a complete circuit. Second, the undulations may cause the path length of the current to change, depending on the thickness of the film and the orientation of the last facing operation. Figure 8 (a)shows a thin film that has an increased path length; and in (b) a film is shown that does not have its path length increased due to surface affects. An increased path length is not necessarily a bad idea on this design. Heaters are often a wire setup in an oscillating path meant to increase the path length. Our surface may simply have this built in.
[pic]
Figure 8: A thin (a) and thick (b) film operating regimes for a deposited thin film bridge wire, showing how the path of the electron will change depending on the thickness of the film.
Even though the surface is not perfectly smooth, the greatest effect will occur when the sanding of the devices ends with the direction of sanding perpendicular to the direction defined by the posts. This is illustrated in Figure 9. Figure (a) would be expected to have a lower resistance than (b).
[pic]
Figure 9: Illustration indicating direction of last facing operation on the igniter. In (a) the last facing operation was vertical, while in (b) the last facing operation was horizontal.
Suggested set of experiments
Calibration runs
Each process needs a calibration run performed on an oxidized silicon wafer with a 0.5 micron film thickness to test thickness uniformity and resistivity.
Igniter depositions
A series of runs may be initially to provide a set of data to work from. Given 3 runs initially a curve may be fit based off of the all fire/no fire tests to make a best guess at the optimal thickness. Also it would be suggested to attempt to make a device that does have surface effects and another device that clearly is not altered due to surface effects. For 600 grit sandpaper, the thickness should be on the order of 10-15 microns thick to remove most of the effect.
Suggested thicknesses for runs would be 400, 800, 1200 and 10000 nanometers. The 10000 nanometer run would be to check a device not altered by surface effects as discussed above.
4.0 future plansSummary of phase i demonstrated feasibility and benefit
Phase I demonstrated the feasibility of using physical vapor deposition (PVD) to create thin film thermal igniters. During phase I, over 20 PVD runs were made using three different types of PVD processes to assess the benefit and feasibility of manufacturing thin film thermal igniter elements (bridge wires). Thin films from Thermal Evaporation PVD, E-beam Evaporation PVD, and Sputtering PVD were evaluated and tested. Scanning electron microscopy (SEM) and surface resistivity measurements were used to characterize the thin film depositions. Thermal model analysis and test data were used to evaluate the relative merits of three different igniter bridge wire designs. These included line-shaped, inverted-dog-bone-shaped, and circular-shaped designs. All of this work resulted in an understanding of the primary relationships and attributes that influence thin film igniter performance. These relationships include,
1. Sputtering deposition has less variation in surface resistivity over e-beam and thermal evaporation PVD.
2. As sputtered PVD film thickness increased, variation in resistivity decreased.
3. As surface area increased (circle .vs. line shape), the variation decreased due to increased conduction paths.
4. Surface roughness (pitting, cracking, etc.) of the substrate significantly influences electrical continuity and bulk resistance when film depositions are reduced to about 4 microns or less.
5. Thicker depositions result in peeling due to increased residual stresses and peeling moments.
6. Thicker depositions result in cracking due to thermal expansion mismatch between the film and substrate.
In Summary, feasibility of a thin film igniter was shown to exist when using Sputtering PVD and a circular-shape bridge wire configuration. The circular-shape allows for thinner deposition which significantly reduces variation due to film peeling and cracking. The larger surface area of the circular-shaped configuration provides a greater electrical conduction path which overcomes the obstructions associated with surface roughness. The controlled feedback Shutter System, previously described, overcomes the variation of deposition that is inherent is larger deposition areas. In addition, the thermal model was shown to be a feasible means for predicting the performance of the thin film igniter.
It is generally understood that Thin film Igniters offer improved reliability over conventional bridge wire designs that rely on the use of fine wire filaments. These existing bridge wires are manually welded to the igniter leads which can cause kinking or deformation of the filaments. These localized deformations are believed to be the cause localized heating and non-uniform thermal distribution within the bridge wire. Such localized heating can cause localized over-heating and burn out or fusing of the bridge wire filaments.
Many military systems would directly benefit from Odyssian’s proposed bridge wire technology. Examples include the Tomahawk and Tactical Tomahawk missile systems. Shown in Figure 4, the Tomahawk Land Attack Missile (TLAM) is a long range, subsonic cruise missile used for land attack warfare, launched from U. S. Navy surface ships and U.S. Navy and Royal Navy submarines. Tomahawk cruise missiles are designed to fly at extremely low altitudes and high subsonic speeds. They are piloted by several mission tailored guidance systems. The first operational use was in Operation Desert Storm, 1991, with immense success. This missile has since been used successfully in several other conflicts as well.
The Tomahawk missile uses an internal navigation system with digital scene matching area correlation and global positioning satellite systems. The Tactical Tomahawk missile adds the capability to reprogram the missile while in-flight to strike any of 15 pre-programmed alternate targets or redirect the missile to any Global Positioning System (GPS) target coordinates. It is also able to loiter over a target area, and with its on-board camera, allows war fighting commanders to assess target battle damage. Because of its long range, lethality, and extreme accuracy the Tomahawk has become the weapon of choice for the U.S. Department of Defense. Odyssian Technology’s proposed thin film bridge wire technology would ultimately offer improved reliability to the operation of onboard electronics and increase the level of mission success.
A number of other military systems would have benefited from Odyssian’s proposed bridge wire technology including the Paveway III, Sparrow/ESSM, RAM AOTD, JSOW, Standard Missile III, Aegis Ballistic Missile Defense Program, Javelin, JASSM, HELLFIRE, ATACMS, ISB, and THAAD.Future plans for the upcoming month includes continuation with work started on the thermal model, and begin the design and construction of the mask to be used on the phase I test articles In addition, Odyssian will brief appropriate EaglePicher and Rose-Hulman personnel on the accomplishments of phase I and the proposed plans for phase II.
Figure 36 – The Tomahawk cruise missile depends on its onboard navigation system for accurate, exact targeting and attacks. The incorporation of Odyssian’s proposed bridge wires into the Tomahawk’s onboard thermal battery will further ensure the success of the vital navigation system onboard the missile
5.0 program synopsis SYNOPSIS of proposed phase II program
Program Synopsis – Odyssian Technology
Tasks for Odyssian Technology, prime contractor
1. Identify igniter and processing requirements
2. Complete solid modeling and simple thermal modeling of the igniter
3. Oversee phase I mask design and construction
4. Conduct initial processing trials of mask equipment at the University of Notre Dame
5. Oversee fabrication and testing of thin film bridge wire igniters at Rose-Hulman
6. Evaluate data obtained from test articles
7. Be responsible for report materials and act as a communication link between all parties involved
Program Synopsis – Eagle Picher
Tasks for EaglePicher
1. Provide assistance in identifying igniter and processing requirements
2. Supply needed igniter materials and testing equipment
3. Provide input for the bridge wire design and processing method
Program Synopsis – Subcontractor Scott Kirkpatrick
Tasks for K& D Design and Development Corporation outline
1. Identifying deposition methods for bridge wires
2. Consider deposition processes with
a. Cost
b. Ease of Use
c. Bridge wire reliability
3. Review and provide feedback for experimental setup
4. Enumerate variables among deposition processes to optimize the Design of Experiments
5. Identify optimal production equipment
6. Provide oversight for deposition processes
Program Synopsis – Rose-Hulman Institute of Technology
Tasks for RHIT Fabrication and Testing of Bridge Wires
1. Five deposition runs on both a sputter system and an e-beam evaporation system
2. Determination of the optimal thickness of the igniter metal based on the One mapping run of thickness variation between igniters using the igniter metal
3. The deposited igniters will be tagged and shipped to Odyssian Technology
4. Analysis of thickness tolerances for “no fire/all fire” testing
5. Phase I Midterm, Progress, and Final Reports will be sent to Odyssian Technology
Program Synopsis – University of Notre Dame
Tasks for the University of Notre Dame Fabrication Mask Testing
1. Make thermal evaporation equipment available for initial deposition testing
2. Provide oversight for deposition process
6.0 Final Report Outline
Title Page
Table of Contents
List of Figures
List of Tables
1.0 Program Introduction
This section of the report will overview the reason for the SBIR program. The problem will be reviewed, and the purpose for a new design explained.
2.0 Program Objectives
The project goals will be stated in this section of the report. A breakdown of what tasks will be accomplished in each of the programs phases will be discussed.
3.0 Program Accomplishments and Results
This section will overview the tasks accomplished during phase I. The original scope for phase I will be compared to the actual outcome.
3.1 Schedule and Budget Performance
This section will focus on comparing the original planned schedule and budget to the actual
Technical Accomplishments
This section will detail all the technical tasks accomplished during the phase I task. The phase I design study results will be laid out, the final modeling results will be revisited, the phase I test article fabrication will be discussed, and the final results of testing will be presented.
4.0 Feasibility and Benefit
This section of the report will discuss the design’s feasibility and benefit to continue work in phase II. Commercial applications as well as current customer needs will be presented.
Phase II Production Pilot System
The Phase II program will develop a reliable pilot production system capable of low cost, high rate, and accurate deposition of thin film igniter bridge wires (thermal elements). This system will deposit thin film directly onto the squib igniter posts. Approximately 300,000 igniters are expected to be made per year which is approximately 1200 igniters daily or 3 igniters each minute. The Phase II Production Pilot System will be designed to exceed this capacity with a high yield of igniters that conform to stringent resistivity distributions. The system will be designed with multiple user levels from operator to maintenance and process engineer. The goal of the deposition system will be to reliably produce a batch of 60 igniters in less than five minutes with a thickness in the range of 2-4 microns.
During phase II, several new concepts will be explored for incorporation into the final system design. These include in-situ annealing and bias. Typical thin film processes (especially evaporated films) anneal the thin film after deposition to make a more reliable film at about 300° C for 30 minutes. This would add significant time to the process. Deposition at elevated temperatures however, can alleviate some of these issues producing a more predicable thin film. Substrate bias is another method to affect the growth of thin films and is suggested that the system developed be capable of bias as well. These and other process optimization concepts will be used to develop the Phase II Production Pilot System.
EaglePicher will provide oversight and requirements to assure that the Phase II Production Pilot System satisfies associated production and performance specifications. System specifications will be defined and approved by EaglePicher and our MDA customer prior to system development. The following high level system attributes are listed to describe the capability and configuration of the phase II system.
System Description
Rapid thin film deposition process of less than five minutes per 60 igniters
Feedback controlled Shutter System to control electrical/thermal performance of igniters
Automated igniter loading/unloading
In-situ annealing.
Substrate Bias.
High conformal part yields (approaching six sigma)
Power supply of 30KW or less
Target system cost of less than $250,000
During design of the phase II system consideration will be give to developing a masking device/holder with a vacuum sealable surface for rapid change-out and system robustness. The holder would be set on an o-ring, within a small chamber containing the deposition method of choice, currently depicted as a sputter cathode as shown in Figure 37.
[pic]
Figure 37: Basic conceptual design for an igniter deposition system.
The igniter would protrude through the mask and seal with an o-ring. This o-ring may be placed on the mask sealing to the face of the igniter, or placed on the sides of the igniter sandwiched between plates to form a tight seal as shown in Figure 38
[pic]
Figure 38: A Closeup design similar to a Vac-Coupling to provide a vacuum sealing surface.
Screws would hold the top plate in place to the holder about the perimeter as depicted in Figure 39 and 40. This would also provide the force required to seal the o-rings to the devices. The mask may be attached in a similar manner as the top plate, or machined out of the same block of material as the holder.
[pic]
Figure 39: A top down conceptual view of an igniter holder/mask.
[pic]
Figure 40: A cross section view of an igniter holder/mask.
The most appropriate process for the Phase II Pilot Production System has been identified as a sputtering system. Sputter systems are frequently used in industrial applications from semiconductors to mirror coatings and have proven cost effective. Sputtering systems are typically easier to use than evaporation systems for the end user as well. Sputtering also displays better reliability within and between runs than evaporation. Existing sputtering technology will be used in conjunction with novel feedback controlled deposition, automated load/unload, and rapid processing features to achieve a pilot production system capable of low cost manufacture of highly reliable thin film igniters.
Phase II Igniter Model – Performance Prediction Tool
The thermal analysis model developed during phase I of this SBIR program proved to correlate relatively close to empirical results, even without substantiated material properties and convection data. The sensitivity analysis that this model allowed showed non-intuitive results; such as the significant impact that material convection coefficients have on the required thin film bridge wire thickness. Phase I modeling results clearly illustrated the value of having a tool that can predict the performance of a thermal igniter. Such a tool would have multiple uses including; predicting the performance of new igniter designs, assessing the impact of changing material sources (i.e., pyrotechnic powder), quantifying the effect of processing drift on igniter performance to determine or substantiate non-conformance specifications, and identifying probable cause of non-conforming / non-functioning igniter production batches.
EaglePicher has expressed an interest in having a robust and accurate Predictive Model that accurately simulates the performance of any igniter configuration. Such a tool would offer great value in reducing the cost of developing new igniter systems, controlling the manufacture of existing igniter systems, and trouble shooting problem igniter systems. Consequently, phase II will continue the modeling effort initiated during phase I. The phase II modeling effort will further develop the phase I model and will correlate it to test data. This modeling effort will focus on simulating thin film igniters and surrounding devices.
It should be noted that Odyssian Technology and EaglePicher are interested in developing a highly versatile Predictive Model that accurately predicts the performance of a wide range of possible igniter configurations. Such an effort would require significant resources and time and will be considered for future collaborative efforts and other research opportunities. The Predictive Model developed under this phase II program will be focused on thin film igniters and surrounding interactions (powder, cap, leads, etc.).
Phase II Program Scope and Work Plan
The proposed Phase II program will focus on optimizing the Phase I thin film igniter design and developing a Phase II Pilot Production system capable of economically manufacturing reliable thin film igniters. The Phase II program will focus on demonstrating the following objectives,
1. Demonstrate reliable performance of an optimized circular-shaped thin film igniter fabricated using the Sputtering PVD process.
2. Develop and demonstrate a robust automated Thin Film Pilot Production System that is capable of manufacturing low cost thin film igniters.
3. Demonstrate the manufacture of thin film igniters that satisfy existing Military Specifications.
Phase II will achieve these objectives through the successful execution of the following technical tasks,
Task I – Optimization of the Circular-shaped Thin Film Igniter Design
Task II – Completion of the Phase I Predictive Igniter Model
Task III – Testing of the Thin Film Igniter to Established Military Specifications
Task IV – Development and Demonstration of the Phase II Pilot Production System
Appendix A
PHASE I Requirements and Goals
• Igniters must be shown to pass no-fire tests as outlined in the military specifications for the EP-250 igniter (Goal of 30 igniters passing this test)
• Igniters must be shown to pass all-fire tests as outlined in the military specifications for the EP-250 igniter (Goal of 30 igniters passing this test)
• Goal to easily manufacture multiple igniters at a time
PHASE II Requirements and Goals
• Goal to reduce no fire / all fire current range
• Must be storable a minimum of 10 years (Goal of 40+ years) [Address if time and money allow]
• Igniters pass initial testing as required by the military specifications for the EP-250 igniter (this includes all tests, using a smaller test matrix than required to determine reliability)
PHASE III Requirements and Goals
• Igniters must pass all tests required by military specifications with a minimum reliability of 99% at a confidence level of 95% (Goal 99% confidence level)
• Must be storable a minimum of 10 years (Goal of 40+ years) [If not already addressed in Phase II]
• Igniters must pass all testing as required by the military specifications for the EP-250 igniter using the current full scale test matrix
• Must meet all other Military Specified (MIL-DTL-23659D) safety requirements, documentation requirements, and approval requirements
EP-250-1 Military Specified Tests (MIL-DTL-23659D)
• Visual inspection will be conducted for all igniters ensuring no defects are present, no incompatibility or inferior quality is evident, the igniter meets the requirements with respect to workmanship, marking, conformance to drawings, and each part of a new igniter shall be 100 percent dimensionally inspected for conformance to the applicable drawing.
• Radiographic Inspection: All igniters shall be inspected by radiographic means such as X-ray, neutron bombardment, gamma rays etc. and plates examined for defects.
• A leak test shall be conducted with a dry gas leak detector of sufficient sensitivity to ascertain if igniters meet the leak rate requirement. Igniters which exhibit a leak rate in excess of 10-5 cc per second of air at a pressure differential of 1 ± 0.1 atmospheres shall be considered defective.
• A dielectric withstanding voltage of 500 ± 25 volts DC shall be applied for 60 seconds between pairs of pins or leads in all combinations prior to assembly of the bridge and between the shorted pins or leads (all pins or leads shorted to each other external to the igniter) and the case after complete assembly of the igniter. The leakage current shall not exceed 0.1 mA. In each test, the leakage current shall be measured with an accuracy of 5 percent. Igniters which exhibit a leakage current in excess of that stated above shall be considered defective and discarded.
• Circuit Resistance: The resistance of each bridge circuit shall be measured with an accuracy of one percent using a test which subjects the bridge circuit to a current of less than 50 milliamperes.
• No-Fire Test: The igniter shall not fire within 5 minutes when subjected to a current of 1 ampere minimum per bridge with an associated power of 1 watt minimum per bridge. The igniter shall meet this requirement at 70° ± 5°F. and 220° ± 5°F. For an igniter having more than one bridge, the current shall be applied to all bridge circuits. The test current shall be regulated throughout the period of application to within 2 percent. If a rectified current is used, the ripple content shall not exceed 5 percent rms of the test current. The igniter shall be conditioned at 70 ± 5°F or 225 ± 5°F. as appropriate for a period of 12 hours.
• Static Discharge: The igniter shall not fire or dud when subjected to the 25000 volt simulated human electrostatic discharge. The igniter shall meet this requirement at 70° ± 5°F and a relative humidity of 50 per cent or less. A 500 ± 5 percent picofarad capacitor charged to 25000 ± 500 volts and 5000 ± 5 percent ohm resistor shall be connected in a 5 microhenry total inductance series circuit between pairs of pins or leads in all combinations and between the shorted pins or leads (all pins or leads shorted to each other external to the igniter) and the case of the igniter. The series connection shall be maintained for 60 seconds. Switching in this circuit shall be accomplished by bringing together two 0.5 ± 0.05 inch spherical metal electrodes from an initial separation of 3 inches in air. Each series test shall constitute a separate test. Igniter used for this test shall be temperature conditioned for a minimum time of 12 hours at 70° ± 5°F.
• Stray Voltage: The igniter shall be capable of withstanding the effects of a stray voltage environment without pre-igniting (firing). The igniter shall meet this requirement at 70° ± 5°F. Each igniter shall be subjected to 2000 pulses of direct current. Each pulse shall be of 300 milliseconds duration and pulse rate shall be 2 per second. Each pulse shall have a minimum amplitude of 100 ± 5 milliamperes. The igniter shall be temperature conditioned at 70° ± 5°F for a period of 12 hours.
• Drop Tests: The igniter shall not fire when dropped from a height of 6 Feet and 40 Feet. After being subjected to the drop test, the igniters shall meet the design performance requirements when test fired and shall be safe for handling and disposal. Six unprotected igniters are to be dropped and impacted onto a 2 inch thick steel plate imbedded in concrete, in each of the following orientations where possible: 2 unprotected initiators nose up, 2 unprotected initiators nose down, and 2 unprotected initiators horizontal.
• Shock Test: The test is conducted using a suitable test vehicle, where the degree of support shall be the same as that afforded by the device of intended application. The shock pulse shall be applied to the igniter's mounting points in both directions along each of three mutually perpendicular axes. The shape of each shock pulse shall approximate as nearly as possible a half sine wave. The amplitude of each shock pulse shall exceed 200 g's for 1.5 ± 0.4 milliseconds and it shall exceed 65 g's for 9 ± 0.9 milliseconds. Igniters shall be free from visible damage or leaks (if applicable), and shall perform satisfactorily in function tests subsequent to this test.
• Vibration Test: The igniters shall be tested to the vibration test of Table 514-1 aircraft category, procedure 1, parts 1, and 2, with curve H of MIL STD 810 except that each resonant and cycling period shall be divided equally among - 65° F., 70°F., and 200°F. The time of vibration shall be continuous and not accumulative at each temperature. After being subject to the vibration test, the igniter shall meet the design performance requirements when test fired.
• Temperature-Shock/Humidity/Altitude Test: The igniter shall be capable of withstanding temperature-shock/humidity/altitude cycling conditions as outlined by section 4.6.5 in MIL-DTL-23659D and shall meet the design performance requirements when test fired.
• Cook Off Test: The maximum temperature to which an igniter can be exposed for a period of one hour without cook off shall be established (within 25° F). Four igniters shall be placed in an oven preheated to the highest temperature which it is estimated that the igniters will withstand for 1 hour. If no igniter cooks off during 1 hour, the temperature shall be increased 25°F and the test repeated with four new igniters. The test shall be repeated in 25° increments until cook off of at least one igniter occurs within a 1 hour period. If cook-off occurs in the first group tested, the temperature shall be decreased 25°F and the test repeated with four new igniters. The test shall be repeated in 25° decrements until cook-off does not occur within a 1 hour period.
• High Temperature Exposure: The maximum temperature (within 25°F) to which an igniter may be exposed for 12 hours and perform satisfactorily at 225°F shall be determined. Igniters shall be placed in an oven preheated to a temperature 25°F less than the maximum determined for exposure without cook-off. The temperature shall be maintained for 12 hours. If no igniter cooks off, the 10 igniters shall be cooled to 70°F and functionally tested. If any igniter cooks off, or fails to meet design performance requirements after cooling, the test shall be repeated with additional groups of igniters, decreasing the temperature in increments of 25°F until design performance requirements are met.
• Salt Fog Test: The igniter shall meet the salt fog test requirements and after being subject to the salt fog test, the igniter shall meet the design performance requirements when test fired. The salt fog test shall be conducted according to Method 509.2 Procedure 1 of MIL-STD-810.
• All-Fire Test: A direct current pulse of 3 amperes shall be applied to the bridge circuit. The igniter must detonate within a 20 millisecond timeframe. For an igniter having more than one bridge, the current pulse shall be applied to one bridge circuit only. The test current shall be a DC current pulse, regulated throughout the period of application, to within 2 percent of the desired value. If a rectified current is used, the ripple content shall not exceed 5 percent rms of the test current. The igniters shall be preconditioned at 70 ± 5°F., -80° ± 5°F., or at 225° ± 5°F. as appropriate, for a period of 12 hours.
The number of igniters required to meet the reliability and confidence level of this specification for go-no-go testing is 298. An engineering design test schedule for qualifying these igniters is outlined in the proceeding Table from MIL-DTL-23659D.
Failure of any igniter to conform to the applicable requirements of this specification shall be cause for rejection of the design of the igniter. However, if it can be determined that the igniter failed to meet the requirements as a result of previous firing of the igniter, the failure and reason for failure shall be noted and the firing repeated using another igniter. If the failure can be attributed to design or other defect, the igniters to be used in engineering design testing may be reworked, have parts replaced or redesigned to correct the defects, and all the tests shall be repeated. Before the tests are repeated, full particulars concerning the failure and action taken to correct the defects shall be submitted to the cognizant Safety Authority.
Appendix A
PHASE I Requirements and Goals
Igniters must be shown to pass no-fire tests as outlined in the military specifications for the EP-250 igniter (Goal of 30 igniters passing this test)
Igniters must be shown to pass all-fire tests as outlined in the military specifications for the EP-250 igniter (Goal of 30 igniters passing this test)
Goal to easily manufacture multiple igniters at a time
PHASE II Requirements and Goals
Goal to reduce no fire / all fire current range
Must be storable a minimum of 10 years (Goal of 40+ years) [Address if time and money allow]
Igniters pass initial testing as required by the military specifications for the EP-250 igniter (this includes all tests, using a smaller test matrix than required to determine reliability)
PHASE III Requirements and Goals
Igniters must pass all tests required by military specifications with a minimum reliability of 99% at a confidence level of 95% (Goal 99% confidence level)
Must be storable a minimum of 10 years (Goal of 40+ years) [If not already addressed in Phase II]
Igniters must pass all testing as required by the military specifications for the EP-250 igniter using the current full scale test matrix
Must meet all other Military Specified (MIL-DTL-23659D) safety requirements, documentation requirements, and approval requirements
EP-250-1 Military Specified Tests (MIL-DTL-23659D)
Visual inspection will be conducted for all igniters ensuring no defects are present, no incompatibility or inferior quality is evident, the igniter meets the requirements with respect to workmanship, marking, conformance to drawings, and each part of a new igniter shall be 100 percent dimensionally inspected for conformance to the applicable drawing.
Radiographic Inspection: All igniters shall be inspected by radiographic means such as X-ray, neutron bombardment, gamma rays etc. and plates examined for defects.
A leak test shall be conducted with a dry gas leak detector of sufficient sensitivity to ascertain if igniters meet the leak rate requirement. Igniters which exhibit a leak rate in excess of 10-5 cc per second of air at a pressure differential of 1 ± 0.1 atmospheres shall be considered defective.
A dielectric withstanding voltage of 500 ± 25 volts DC shall be applied for 60 seconds between pairs of pins or leads in all combinations prior to assembly of the bridge and between the shorted pins or leads (all pins or leads shorted to each other external to the igniter) and the case after complete assembly of the igniter. The leakage current shall not exceed 0.1 mA. In each test, the leakage current shall be measured with an accuracy of 5 percent. Igniters which exhibit a leakage current in excess of that stated above shall be considered defective and discarded.
Circuit Resistance: The resistance of each bridge circuit shall be measured with an accuracy of one percent using a test which subjects the bridge circuit to a current of less than 50 milliamperes.
No-Fire Test: The igniter shall not fire within 5 minutes when subjected to a current of 1 ampere minimum per bridge with an associated power of 1 watt minimum per bridge. The igniter shall meet this requirement at 70° ± 5°F. and 220° ± 5°F. For an igniter having more than one bridge, the current shall be applied to all bridge circuits. The test current shall be regulated throughout the period of application to within 2 percent. If a rectified current is used, the ripple content shall not exceed 5 percent rms of the test current. The igniter shall be conditioned at 70 ± 5°F or 225 ± 5°F. as appropriate for a period of 12 hours.
Static Discharge: The igniter shall not fire or dud when subjected to the 25000 volt simulated human electrostatic discharge. The igniter shall meet this requirement at 70° ± 5°F and a relative humidity of 50 per cent or less. A 500 ± 5 percent picofarad capacitor charged to 25000 ± 500 volts and 5000 ± 5 percent ohm resistor shall be connected in a 5 microhenry total inductance series circuit between pairs of pins or leads in all combinations and between the shorted pins or leads (all pins or leads shorted to each other external to the igniter) and the case of the igniter. The series connection shall be maintained for 60 seconds. Switching in this circuit shall be accomplished by bringing together two 0.5 ± 0.05 inch spherical metal electrodes from an initial separation of 3 inches in air. Each series test shall constitute a separate test. Igniter used for this test shall be temperature conditioned for a minimum time of 12 hours at 70° ± 5°F.
Stray Voltage: The igniter shall be capable of withstanding the effects of a stray voltage environment without pre-igniting (firing). The igniter shall meet this requirement at 70° ± 5°F. Each igniter shall be subjected to 2000 pulses of direct current. Each pulse shall be of 300 milliseconds duration and pulse rate shall be 2 per second. Each pulse shall have a minimum amplitude of 100 ± 5 milliamperes. The igniter shall be temperature conditioned at 70° ± 5°F for a period of 12 hours.
Drop Tests: The igniter shall not fire when dropped from a height of 6 Feet and 40 Feet. After being subjected to the drop test, the igniters shall meet the design performance requirements when test fired and shall be safe for handling and disposal. Six unprotected igniters are to be dropped and impacted onto a 2 inch thick steel plate imbedded in concrete, in each of the following orientations where possible: 2 unprotected initiators nose up, 2 unprotected initiators nose down, and 2 unprotected initiators horizontal.
Shock Test: The test is conducted using a suitable test vehicle, where the degree of support shall be the same as that afforded by the device of intended application. The shock pulse shall be applied to the igniter's mounting points in both directions along each of three mutually perpendicular axes. The shape of each shock pulse shall approximate as nearly as possible a half sine wave. The amplitude of each shock pulse shall exceed 200 g's for 1.5 ± 0.4 milliseconds and it shall exceed 65 g's for 9 ± 0.9 milliseconds. Igniters shall be free from visible damage or leaks (if applicable), and shall perform satisfactorily in function tests subsequent to this test.
Vibration Test: The igniters shall be tested to the vibration test of Table 514-1 aircraft category, procedure 1, parts 1, and 2, with curve H of MIL STD 810 except that each resonant and cycling period shall be divided equally among - 65° F., 70°F., and 200°F. The time of vibration shall be continuous and not accumulative at each temperature. After being subject to the vibration test, the igniter shall meet the design performance requirements when test fired.
Temperature-Shock/Humidity/Altitude Test: The igniter shall be capable of withstanding temperature-shock/humidity/altitude cycling conditions as outlined by section 4.6.5 in MIL-DTL-23659D and shall meet the design performance requirements when test fired.
Cook Off Test: The maximum temperature to which an igniter can be exposed for a period of one hour without cook off shall be established (within 25° F). Four igniters shall be placed in an oven preheated to the highest temperature which it is estimated that the igniters will withstand for 1 hour. If no igniter cooks off during 1 hour, the temperature shall be increased 25°F and the test repeated with four new igniters. The test shall be repeated in 25° increments until cook off of at least one igniter occurs within a 1 hour period. If cook-off occurs in the first group tested, the temperature shall be decreased 25°F and the test repeated with four new igniters. The test shall be repeated in 25° decrements until cook-off does not occur within a 1 hour period.
High Temperature Exposure: The maximum temperature (within 25°F) to which an igniter may be exposed for 12 hours and perform satisfactorily at 225°F shall be determined. Igniters shall be placed in an oven preheated to a temperature 25°F less than the maximum determined for exposure without cook-off. The temperature shall be maintained for 12 hours. If no igniter cooks off, the 10 igniters shall be cooled to 70°F and functionally tested. If any igniter cooks off, or fails to meet design performance requirements after cooling, the test shall be repeated with additional groups of igniters, decreasing the temperature in increments of 25°F until design performance requirements are met.
Salt Fog Test: The igniter shall meet the salt fog test and after being subject to the salt fog test, the igniter shall meet the design performance requirements when test fired. The salt fog test shall be conducted according to Method 509.2 Procedure 1 of MIL-STD-810.
All-Fire Test: A direct current pulse of 3 amperes shall be applied to the bridge circuit. The igniter must detonate within a 20 millisecond timeframe. For an igniter having more than one bridge, the current pulse shall be applied to one bridge circuit only. The test current shall be a DC current pulse, regulated throughout the period of application, to within 2 percent of the desired value. If a rectified current is used, the ripple content shall not exceed 5 percent rms of the test current. The igniters shall be preconditioned at 70 ± 5°F., -80° ± 5°F., or at 225° ± 5°F. as appropriate, for a period of 12 hours.
The number of igniters required to meet the reliability and confidence level of this specification for go-no-go testing is 298. An engineering design test schedule for qualifying these igniters is outlined in the proceeding Table from MIL-DTL-23659D.
Failure of any igniter to conform to the applicable requirements of this specification shall be cause for rejection of the design of the igniter. However, if it can be determined that the igniter failed to meet the requirements as a result of previous firing of the igniter, the failure and reason for failure shall be noted and the firing repeated using another igniter. If the failure can be attributed to design or other defect, the igniters to be used in engineering design testing may be reworked, have parts replaced or redesigned to correct the defects, and all the tests shall be repeated. Before the tests are repeated, full particulars concerning the failure and action taken to correct the defects shall be submitted to the cognizant Safety Authority.
Appendix B
EP 250-1 CAD drawing provided by EaglePicher
[pic][pic]
-----------------------
A Technology Service and Solutions
Company
[pic]
Figure 19: Nichrome deposited on an oxidize silicon wafer failed to adhere to the surface with a 2 micron thick layer
Chlorine Sensor (Tin Fuse)
[pic][pic]
Figure10: 11 micron thick Nichrome bridge wire with powder Time= 300s Maximum temperature = 298.2(C
o-ring
igniter hole
holder/mask
top plate
screw
Igniter
Screw
Mask
Holder
Igniter hole/
Sputter direction
O-ring
Top Plate
Sputter cathode
chamber
O-ring
Igniter mask/holder
Figure 34X: The igniter shutter circuit triggers from an analog signal generated by measuring a voltage drop across the squib that is excided by a constant current source.
[pic][pic]
Figure 10: 300nm Nichrome deposited on an oxidize silicon wafer using E-beam (LEFT) and sputtering [pic]
=BCNOWcx~ëÚºÚ³©œ’ˆ’œ€r[A6h€|ýh`_çCJ aJ 3?h€|ýh`_çh/V{CJ aJ cH[pic]dhdhdhJ‹•F-?h`_çh/V{CJ aJ cH[pic]dh(RIGHT) equipment at Rose-Hulman Institute of Technology
[pic]
scratches
Igniter posts
(b)
(a)
(b)
(a)
o-ring
igniter hole
holder/mask
top plate
[pic]
[pic] [pic]
Figure 33A: Line Mask Top Side – Igniters are placed in the top side of the mask/holder and Nichrome is deposited from underneath
[pic][pic]
Figure 33B: Line Mask Bottom Side – Shutters open and close to accurately control the deposition of nichrome on to individual igniter heads
Figure 2: Phase I Demo Igniter Component (With line shaped thin film bridge wire) – Solid model drawings of the phase I bridge wire design with PVD thin film wire are shown. Materials of each component are given and their properties are used to create a thermal model of the igniter using finite element analysis.
[pic][pic]
Two lead wires (52 Nickel Alloy ASTM F30)
Glass potting material (glass corning 9013)
Outer metallic seal / eyelet (1215 or 12L14 mild steel)
Line shape thin film Bridge wire (8020 Nichrome deposited through PVD)
Chlorine Sensor (Tin Fuse)
Eq. 1
screw
Figure3: Initial Results from the Igniter Thermal Model – The solid model was used to create a thermal model of the bridge wire system. A thermal load is placed across the bridge wire to show a qualitative representation of the expected temperature profile.
Igniter
Screw
Mask
Holder
Igniter hole/
Sputter direction
O-ring
Top Plate
Sputter cathode
chamber
O-ring
Igniter mask/holder
[pic]
[pic]
[pic] [pic]
Figure5: 11 micron thick Nichrome bridge wire with powder Time= 300s Maximum temperature = 298.2(C
[pic]
[pic]
[pic]
Figure 6: 23 micron thick Nichrome bridge wire Maximum Temperature vs. Time graph for No-Fire loading condition
[pic]
Figure 9: Nichrome deposited on an oxidize silicon wafer failed to adhere to the surface with a 2 micron thick layer
[pic]
Figure 7: Inverted Dog-Bone Nichrome bridge wire at time = 5s
Figure 6: Circle Nichrome bridge wire at time = 5s
[pic]
Figure 3: 23 micron thick Nichrome bridge wire at time = 300s and maximum temperature = 290C
Figure 4: 23 micron thick Nichrome bridge wire at time = 150s and maximum temperature = 225.2C
Figure 3: 23 micron thick Nichrome bridge wire at time = 5s and maximum temperature = 144.9C
[pic][pic]
Figure 20: 300nm Nichrome deposited on an oxidize silicon wafer using E-beam (LEFT) and sputtering (RIGHT) equipment at Rose-Hulman Institute of Technology
[pic][pic]Figure 18: Phase I Demo Igniter Mask (For line shaped thin film bridge wire) – The igniters are placed in the routed holes and the line-shaped slots at the bottom of the mask act as a stencil preventing Nichrome from being deposited everywhere except where there is an opening through the mask. The result is a line-shaped thin film Nichrome bridge wire on the igniter base.
................
................
In order to avoid copyright disputes, this page is only a partial summary.
To fulfill the demand for quickly locating and searching documents.
It is intelligent file search solution for home and business.
Related download
- ballistic missile basics
- statement of work
- system design specification appendix a ship
- odyssian technology
- we are highly confident that we will field an effective
- stratcom posture statement
- a cruise missile system for europe
- graduate school of public and international affairs
- smdc history
- navsup naval supply systems command
Related searches
- how does technology affect education
- how has technology improved society
- why technology is good in education
- technology in education journal articles
- technology in elementary classrooms arti
- technology articles for students
- technology in the classroom articles
- articles about technology in schools
- scholarly article on technology in the classroom
- technology articles for kids
- technology articles for middle schoolers
- using technology in the classroom