Homebrew PCBs

Thanks for the information.  

I tried a couple more boards and this time skipped the rubbing
alchohol wipedown after the lemon juice scrub. It may have helped and
certainly didn't hurt. I changed a few other things and went back to
the MultiProject paper, so I don't know which change was most
important. But I'm fairly pleased with the result, it's the best toner
to copper transfer I've gotten yet. Only problem is the pinholes left
by the printer, but touchup with a sharpie isn't too hard.    


--- In Homebrew_PCBs@yahoogroups.com, "Earl T. Hackett, Jr."
<hacketet@c...> wrote:
> Not lemon juice, but citric acid was a common antitarnish when
stripping print and etch innerlayers in caustic.  Amines work better
as an antitarnish, but they form complexes with dissolved copper and
makes waste treatment very expensive.  It reacts with the copper and
forms a layer that resists oxidation reasonably well.  After stripping
these boards went through a black or red oxide treatment to enhance
adhesion in multilayer boards.  I seem to remember one or two shops
that used citric acid in a chem clean line and I don't remember any
adhesion problems with the photoresist.