Homebrew PCBs

Larry,

How do you create the negative?

Bertho

 

 

From: Larry Battraw   Sent: Wednesday, October 12, 2011 01:44



Hi Tom,

I used to live in AZ and actually visited Circuit Specialists frequently. I
don't have a problem with presensitized boards per se except for the fact
that I tend to make complex boards with lots of mistakes-- I'll admit to
also having a habit of frequent tweaks as well. Presensitized boards just
don't make sense for me, especially when I purchased 20 _pounds_ of blank
PCB boards in many handy shapes, specifically for use with applied
photoresists. They were very cheap per board (A few cents each) in that
form, and when you use a hydrochloric-acid-based etchant and bulk materials
for photoresist/artwork/ink the cost is very low. I've also enjoyed the
challenge of rolling my own process from end-to-end without the need to buy
extra stuff per job. That, and I'm always assured of the freshness of my
resists since I'm the one applying them and I know the age of the materials.

My typical work flow will be to use gEDA to create a schematic/PCB layout,
then to print and image the artwork onto a sensitized board, followed by
developing. At that point I'll check the results for minimum trace
width/spacing, fit and location of components to make sure things aren't too
close together, or if I haven't goofed up a footprint. If everything looks
good I etch, otherwise I strip and recoat the board and by the time I'm
ready for another run it's dry/fixated and ready for anothering imaging
step. I may also find a mistake in the schematic and so the layout will
change accordingly. I may run through 5 strip-reimage steps before I
finally etch with that "perfect" result where all the features are clear,
it's not over/under-exposed, etc.

Regards,
Larry





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