Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

I will second David's comments on the photo process.

I too have been making boards, both 1 and 2 sided, since
about 1980 using the photo process; and like David, I highly
recommend it.

You can -easily- achieve 6-8 mil traces/spaces; unlike the
toner-transfer method where you must use the greatest
care to achieve a -clean and solid- 10 mils, let alone anything
finer than that.

In fact, with some careful attention, you can achieve -2 mils-
with a dryfilm/photo process; which you simply -cannot- do
with toner transfer, no matter what.

I used an old hot-roll laminator found surplus; a surplus box
of Dupont Riston dry-film; and made my own exposure frame
using "germicidal" UV flourescent tubes (about 6-8 of them,
as I recall). These lamps WILL hurt your eyes; as they are
entirely UNfiltered; unlike so-called "blacklight" tubes, which
ARE still filtering out the shortest and strongest UV.

Exposure times with 6-8 of these 18" long tubes is in the range
of just 1-2 minutes.

I used regular washing-soda for developer and regular sodium
hydroxide for stripper. I would pre-laminate half a dozen
12" square sheets of board; and store them in a cool place.

When I needed to make a board or two, I'd simple shear these
pre-laminated sheets to size; and within 10 minutes I'd have
a fully developed board, with razor-sharp and 100% complete
traces EVERY time; ready to drop into the spray-etcher.

Artwork was generally laser-print on transparency film; unless
I was doing a chem-milling job or something, where I needed
the ultimate resolution; in which case I'd have my Gerber files
photoplotted for 7 bucks at the local plotting-service.

Again, this method gives HIGH quality results EVERY time,
with EASE. To me, this -consistent- quality was WELL worth
the few hundred bucks in parts and surplus equipment to set it
up.

Richard
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