Reference
- uCAMco archive -- the home of the Gerber spec
- Local archive (EDF password) of Gerber documents
Grids / Traces
- Use English measurements (mils, not mm)
- (for metric components of course, define the footprint in mm)
- Place all components on .050 grid to start, .025 if required
- Trace width spacing minimum .006 / .006 (wider for power)
- Route on .025 grid to start, .0125 if required
- For metric / off-grid pads, route nearby then short off-angle segment to pad
ALWAYS WORK WITH GRID SNAP ON and set to a sensible value. "Sensible" means normally .025 for placement, no smaller than .0125 for routing. Use smaller only for special requirements or silkscreen text placement.
Holes / Pads
- Hole sizes specified are finished which are typically .003-.004 smaller than the drill size.
- A good minimum via size is .015 pad with .005 hole.
- For thru-hole component leads, specify a hole size at least .005 largerthan the lead diameter.
- CAVEAT In vsn 4.0.7, KiCad?'s gerber generating code will convert slots to circular drills.
Silkscreen
- Minimum text height .040 and minimum line width .006
- Silkscreen text cannot overlap other silkscreen graphics, pads or holes
- Start with all text right-side up, rotate 90 degrees in one direction if needed
Useful Writeups on Footprint Design
Selected PCB capabilities from mid-range houses as of June 2016
Feature | Advanced | Sunstone | Sierra | JLCPCB | OshPark? |
Outer Layer Trace Width (1 oz) | .005 | .006 | .003 | .0035 | .006 |
Outer Layer Trace Spacing | .005 | .006 | .003 | .0035 | .006 |
Innner Layer Trace width (1 oz) | .004 | ||||
Inner Layer Trace Spacing | .005 | ||||
Pad size over drill (dia) | .010 | .006 | .006 | .010 | |
Pad size over finish hole | .018 | ||||
Via size over drill (dia) | .008 | ||||
Minimum drill (full spec) | .006 | .008 | .010 | ||
Minimum drill (quick proto) | .010 | .010 | .008 | ||
Soldermask minimum web | .004 | .005 | .004 | ||
Soldermask clearance (std) | .002 | .002 | |||
Manufacturer Notes
Sierra (aka protoexpress.com) have "No Touch" service (guidelines). Around $100 for 3 pcs 2.5x5.5 for example.
Advanced (aka 4pcb.com) has "$33 special" (min 3pcs) up to 50 in2. Could batch these.
Sunstone ValueProto? service is around $115 plus shipping for a 2.5x3.5 board.
Last modified 5 years ago
Last modified on Feb 24, 2020, 6:32:12 PM