PowerPCB Training Manual, Your First Design



CADPRO LIBRARY CONSTRUCTION STANDARDS

MANUFACTURING

PAD-STACKS

1. ANNULAR RINGS:

a. Pin one on thru-hole components have a square pads on top & bottom layers only.

b. As a general rule component pins have a minimum of 20 mil larger than finished hole size.

c. The general rule for Vias is a minimum of 10 mil larger than finished hole size

d. Pad size for mounting holes should be the same size of washer of the screw.

e. To meet a 3 mil annular ring specification for Thru-Hole Pins:

Example: .037 Finished Hole (PADS Software Thru-Hole Pad default)

+.004 For Drill Bit (Fab. notes specify .001” min hole wall plating thickness)

(.002 For Drill Drift (Caused by stacking of boards) (Consider Tear-dropping)

(.003 For Layer Slippage (Caused by pressure from lamination press)

+.006 For .003 minimum guaranteed finished Annular Ring

= .057 Pad (.020 Larger than finished hole size)

Note: Tolerance on finished hole should be (.003, The finished hole size could be between .034 and .040

f. To meet a 3 mil annular ring specification for STANDARDVIA:

Example: .020 Finished Hole (PADS Software VIA default)

+.004 For Drill Bit (Fab. notes specify .001” min. hole wall plating thickness)

(.002 For Drill Drift (Caused by stacking of boards)

(.003 For Layer Slippage (Caused by pressure from lamination press)

+.006 For .003 minimum guaranteed finished Annular Ring

= .040 Pad (.020 Larger than finished hole size)

Note: Tolerance on finished hole should be ( .003 The finished hole size could be between .017 and .023

g. To meet a 3 mil annular ring specification for MICROVIA:

Example: .014 Finished Hole (PADS Software VIA default)

+.000 For Drill Bit (Drill Bit can even be smaller than .014”)

(.002 For Drill Drift (Caused by stacking of boards)

(.003 For Layer Slippage caused by pressure & temperature of lamination press

+.006 For .003 minimum guaranteed finished Annular Ring

= .025 Pad (.011 Larger than finished hole size)

Note: Tolerance on finished hole should be +.000 -.014, which will produce a plugged hole.

2. NON-PLATED HOLE PADS:

a. For non-plated holes smaller than .060 - Pad size should be .015.

b. For non-plated holes larger than .060 - Pad size should be .050.

c. Solder Mask for non-plated holes is .005 larger than hole size, add both Layers 21 & 28 to pad-stack.

3. DETERMINING PLANE THERMALS & PLANE CLEARANCES FOR CAM PLANES:

a. Measurement A is the drill size. This is defined in Setup/Pads Stack at Drill Size.

b. Measurement B is the ID (Inner Diameter) of the thermal. This is not defined in PowerPCB. In the Readme.fab file it is defined as 80% of the OD. (Outer Diameter) the measurement C.

c. Measurement C is the OD of the thermal or it is the clearance diameter for a non thermal hole on a plane layer. This is defined in the Setup/Pads Stack at Parameters/Diameter: when layer_25 is highlighted in the ‘Sh: Sz: Layer:’ window.

For a Via use the Drill Size plus 30 mil Then round up to the nearest 5 mil increment.

For a Plated Part Hole use the Drill Size plus 40 mil Then round up to the nearest 5 mil increment.

For a Plated Mounting Hole use the Drill Size plus 50 mil Then round up to the nearest 5 mil increment.

For a Non Plated Hole use the Drill Size plus 50 mil Then round up to the nearest 5 mil increment.

d. Measurement D is the Spoke of the thermal. This is defined in the Readme.fab file. This Spoke width is usually defined as 15 mil.

e. Measurement E is the angle of the spokes. This is defined in the Readme.fab file as 45 degrees four way entry.

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4. SOLDER MASK CLEARANCES:

a. For Thru-hole designs use .010 over the Pad Size. SMOBC Mask is OK

b. For Fine Pitch Surface Mount designs use .005 over the Pad Size. Should use Liquid Photo-Imagable Mask.

c. For Non-Plated holes use .005 larger than drill size. This value must be added to Pad-stack Layers 21 & 28.

5. SMT PAD-STACK

a. Never use Plane Clearance Layer 25 in a SMT Pad-stack. (Perform did not default to layer 25 in pad-stack)

b. If layer 21, Top Mask, is used in a pad-stack, when the part is placed on the flip side, it will move to layer 28

c. If layer 22, Top Paste, is used in a pad-stack, when the part is placed on the flip side, it will move to layer 23.

d. Values for Inner Layer and Opposite Side should always be 0.

e. Value for Drill should always be 0.

f. Use chart below for IC pad size.

6. DETERMININING HOLE SIZES:

a. Size of lead plus 11 mil then round up to the next available drill size in chart below.

SMT IC PAD SIZE CHART

|SHAPE TYPE |PITCH |PAD LENGTH |PAD WIDTH |

|SOIC |.050” |.075” |.025” |

|SOPIC |.050” |.075” |.025” |

|SOJ |.050” |.075” |.025” |

|PLCC |.050” |.075” |.025” |

|LCC |.050” |.100” |.025” |

|CFP |.050” |.086” |.025” |

|SSOIC |.025” |.070” |.015” |

|QSOP |.025” |.070” |.015” |

|VSOP |.030” |.100” |.018” |

|PSOP |.800mm |.070” |.020” |

|SSOP |.650mm |.070” |.015” |

|PSSOP |.650mm |.070” |.015” |

|TSOP |.300mm |.063” |.006” |

|TSOP |.400mm |.063” |.010” |

|TSOP |.500mm |.063” |.013” |

|TSOP |.550mm |.063” |.013” |

|TSOP |.650mm |.063” |.018” |

|TSOP |.800mm |.063” |.018” |

|SQFP |.300mm |.063” |.006” |

|SQFP |.400mm |.063” |.009” |

|SQFP |.500mm |.063” |.012” |

|QFP |.635mm |.075” |.015” |

|QFP |.650mm |.075” |.015” |

|QFP |.800mm |.075” |.018” |

|QFP |1.00mm |.075” |.020” |

|VIA NAME |ROUTE GRID |TRACE WIDTH |CLEARANCE |BD. THICKNESS |

|VIA055X028 |.025 & .0125 |.012 |.012 |.125, .093, .062 |

|VIA040X020 |.0125 & .008333 |.012 & .008 |.012 & .007 |.125, .093, .062 |

|VIA028X015 |.00625 |.006 |.006 |.093, .062, .031 |

|VIA025X014 |.005 & .008333 |.005 & .008 |.005 & .007 |.093, .062, .031 |

|VIA020X010 |.005 |.005 |.005 |.062, .031, .018 |

|VIA019X010 |.00625 |.006 |.006 |.062, .031. .018 |

PLATED THROUGH HOLE CHART

|PAD |PLANE |DRILL |DRILL |USE |

|SIZE |CLEARANCE |SIZE |TOLERANCE | |

|.019 |.040 |.010 |+.000 -.010 |VIA019X010 |

|.020 |.040 |.010 |+.000 -.010 |VIA020X010 |

|.025 |.045 |.014 |+.001 -.014 |VIA025X014 |

|.028 |.045 |.015 |+.002 -.015 |VIA028X015 |

|.040 |.050 |.020 |+.003 -.003 |VIA040X020 |

|.040 |.055 |.024 |+.003 -.003 |HIGH DEN. CONN’S |

|.055 |.060 |.028 |+.003 -.003 |VIA055X028 |

|.055 |.065 |.032 |+.003 -.003 |HIGH DEN. CONN’S |

|.055 |.070 |.035 |+.003 -.003 |IC’s W/.005 GRID |

|.057 |.080 |.037 |+.003 -.003 |IC’s W/.00625 GRID |

|.060 |.080 |.037 |+.003 -.003 |IC’s W/.008333 GRID |

|.060 |.080 |.040 |+.003 -.003 |CONNECTORS |

|.065 |.085 |.042 |+.003 -.003 |CONNECTORS |

|.070 |.090 |.047 |+.003 -.003 |CONNECTORS |

|.080 |.095 |.052 |+.003 -.003 |CONNECTORS |

|.090 |.100 |.057 |+.003 -.003 |MISC |

|.100 |.105 |.062 |+.003 -.003 |CONNECTORS |

|.110 |.110 |.067 |+.003 -.003 |CONNECTORS |

|.120 |.115 |.072 |+.003 -.003 |CONNECTORS |

|.130 |.120 |.078 |+.003 -.003 |MISC |

|.135 |.125 |.082 |+.003 -.003 |MISC |

|.140 |.130 |.087 |+.003 -.003 |MISC |

|.150 |.135 |.093 |+.003 -.003 |MISC |

|.150 |.140 |.098 |+.003 -.003 |MISC |

|.160 |.150 |.102 |+.003 -.003 |NO. 2-56 SCREW |

|.170 |.160 |.110 |+.003 -.003 |NO. 2-56 SCREW |

|.200 |.175 |.125 |+.003 -.003 |NO. 4-40 SCREW |

|.200 |.175 |.128 |+.003 -.003 |NO. 4-40 SCREW |

|.225 |.200 |.144 |+.003 -.003 |NO. 6-32 SCREW |

|.250 |.210 |.156 |+.003 -.003 |NO. 6-32 SCREW |

|.300 |.250 |.187 |+.003 -.003 |NO. 8-32 SCREW |

|.300 |.275 |.225 |+.004 -.004 |NO. 10-32 SCREW |

|.350 |.325 |.265 |+.005 -.005 | ¼” SCREW Loose Fit |

NON-PLATED HOLE CHART

|PAD |PLANE |SOLDER |DRILL |DRILL |USE |

|SIZE |CLEARANCE |MASK |SIZE |TOLERANCE | |

|.015 |.050 |.025 |.020 |+.003 -.003 |Break Away Tabs |

|.015 |.065 |.040 |.032 |+.003 -.003 |Break Away Tabs |

|.050 |.105 |.070 |.062 |+.003 -.003 |Break Away Tabs |

|.050 |.135 |.100 |.093 |+.003 -.003 |SIMM Sockets |

|.050 |.145 |.105 |.098 |+.003 -.003 |NO. 2-56 SCREW |

|.050 |.160 |.115 |.110 |+.002 -.002 |NO. 2-56 SCREW |

|.050 |.175 |.130 |.125 |+.002 -.002 |NO. 4-40 SCREW |

|.050 |.175 |.135 |.128 |+.002 -.002 |NO. 4-40 SCREW |

|.050 |.200 |.150 |.144 |+.002 -.002 |NO. 6-32 SCREW |

|.050 |.210 |.160 |.156 |+.002 -.002 |NO. 6-32 SCREW |

|.050 |.250 |.195 |.187 |+.002 -.002 |NO. 8-32 SCREW |

|.050 |.275 |.230 |.225 |+.002 -.002 |NO. 10-32 SCRW |

|.050 |.325 |.275 |.265 |+.002 -.002 | ¼” SCREW |

ASSEMBLY

SILKSCREEN

1. Silkscreen outline should closely resemble the actual component.

2. Silkscreen outline should be at least .010” away from all exposed copper.

3. Silkscreen outline should always be put on Layer 0.

4. Use .010” line width for outlines.

5. Reference Designator should be placed exactly in the center of component.

6. Multiple polarity marks on the same decal should be avoided. Example: SMT Diodes.

7 Post assembly inspection dot, .020”, should be used on all IC’s, located by pin 1.

8. Use a Minimum .050” circle to represent polarity of IC’s.

9. Use chamfered outline to represent polarity of capacitors. Plus signs “+” cannot be relocated.

10. Use .100” chamfer in PGA outlines.

11. Build all parts in the same family with the same rotation.

Example: Build your IC’s long in X direction. Reason, Paper sizes are long in X, Board Lengths should be long in length and IC’s should flow with the length of the board.

PLACEMENT COURTYARDS

1. Placement courtyard on all SMT decals, Layer 20 - Width .005

2. Find out from assembly shop how close each part can be placed to each other.

COMPONENT ORIGINS

1. SMT - CENTER

2. Thru-hole - PIN 1

3. SMT - Put a .025” + 2D line on layer 20, width .005 on origin.

ROUTING

PAD GEOMETRY

1. Pad size should be optimized for maximum routing channels.

2. Pad placement should be optimized for maximum routing channels, but always stay within the tolerance range of solderability.

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