Monday, December 27, 2010

PCB design lessons learned

I've learned a few lessons after printing out my first board.
  1. Be patient! In all aspects, designing a PCB takes patience.
    • Take your time doing the toner transfer with the iron. Firm, even pressure, and at least 5 minutes under the iron.
    • When soaking the board after ironing, be patient and let the warm water disintegrate the paper, or else you risk tearing the toner off of the board.
    • When etching, don't rush -- etching a 6x6 board took me over half an hour, and as evidenced by the shorted pads, I could have probably let it etch for another few minutes.
  2. 10mil traces are OK -- but be careful! they have a tendency to smear if ground on too hard during the transfer.
  3. Touch-up before etching -- carefully inspect every trace and touch up anything that looks remotely like a gap with an etch resist pen.
  4. Invest in a circuit pen -- would have saved me a lot of time repairing traces if I could have just dabbed some conductive ink in the gap.
  5. Trust and utilize the design constraints feature of your PCB utility. Maintain at least 10mil between all components -- any closer and the error from toner smearing and/or etching errors tends to cause shorts. I think I was lucky -- I had some components as little as 5mil apart and ignored the DRC whining at me. I should have listened.
The next board I build I'll try to follow all of these rules. And of course I'll keep you posted!

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