PCB Design

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:
    • GTL - 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

Good practices

• Signal traces width: 12-16 mils / 0.254-0.4064 mm
• Power traces width: 16-20 mils / 0.4064-0.508 mm

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