Difference between revisions of "PCB Design"
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** Signal width: 12-16 mils / 0.254-0.4064 mm - avoid bridging of traces | ** Signal width: 12-16 mils / 0.254-0.4064 mm - avoid bridging of traces | ||
** Power width: 16-20 mils / 0.4064-0.508 mm - allow vcc and ground to flow current | ** Power width: 16-20 mils / 0.4064-0.508 mm - allow vcc and ground to flow current | ||
* Clearance | * Clearance and spacing between trace, pad, via: | ||
** Width: 10 mils / 0.254 mm | ** Width: 10 mils / 0.254 mm | ||
* Via drill size: | * Via drill size: | ||
Revision as of 22:01, 29 January 2011
The the prototyping is done, putting the design proper PCB board makes it more rigid and possible to offer unassembled kits. The process is mostly straight forward but the design process to lay out the board requires some time to get right.
Eagle will be used here, it's cross platform and great part libraries.
Setup
- CAM, Computer Aided Manufacturing, processing files
- SparkFun CAM
- Creates the proper gerber files for manufacturing:
- glt - Top copper layer, main traces
- gbl - Bottom copper layer, same bottom
- gto - Top silkscreen, all text, lines, illustrations can be painted on top of the soldermask
- gbo - Bottom silkscreen, same bottom
- gts - Top soldermask, where to put tin/gold plated pads and mask all other green/other color
- gbs - Bottom soldermask, same bottom
- gtp - Top solder paste stensil, only needed for assembly of parts to the board
- txt - Drill coordinates, for vias and mounting holes
- Eagle parts libraries:
- SparkFun Eagle Library
- Includes most of the parts SparkFun offer ont their website
- Adafruit Eagle Library
- Ladyada has made a library for most of the parts used in their tutorials
- SparkFun Eagle Library
Good practices
Some of these guidelines can be used in the Design Rules property window in Eagle. The PCB manufacturer normally provide a list of minimum requirements for their equipment/method.
- Traces:
- Signal width: 12-16 mils / 0.254-0.4064 mm - avoid bridging of traces
- Power width: 16-20 mils / 0.4064-0.508 mm - allow vcc and ground to flow current
- Clearance and spacing between trace, pad, via:
- Width: 10 mils / 0.254 mm
- Via drill size:
- Diameter: 30 mils / 0.762 mm - proper connection between layers
- Distance to board edge:
- Isolation: 12 mils / 0.3048 mm - for clean cut or v-score of the boards
PCB Manufacturers
A great place to start is Ladyada's PCB cost calculator.
- BatchPCB - Easy and cheap for small boards
Board config
- FR4 - Stands for Flame Retardant and 4 means woven glass reinforced epoxy resin
- Standard 1.5 mm thickness
Tools
- Eagle - Connect schematic and design PCB board layout
- Viewplot - View the files coming out of Eagle for verification
