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

Randy:

I'm no chemist, and I use Ferric Chloride, but I THINK the "other stuff" is
AMMONIUM persulfate! BUT... For all I know, perhaps sodium- or
potassium-persulfate would work, too. I just do NOT know.

I bought some ammonium persulfate solids from Kepro about 20 years ago, and,
either I didn't read all the instructions well, or "goofed", somehow, as it
didn't work very well, at all. (I only tried it once). Then, not knowing
it, the Ammonium persulfate is deliquescent, and it's HUMID here, so, the
solids turned "gooey" all alone, THROUGH the plastic container they came in,
and that ate THROUGH the plastic container, the bottom of my cabinet, onto a
carpet, and, well... I guess the Chinese are wondering what kind of
kidney-trouble the American living below them has!

And, though FeCl³ has a nasty staining color, it takes much less "Husbandry"
to use with relative ease. Which is too bad, as the former A-S stuff was
CLEAR, if caustic!

Adding stuff "for speed" will get you in trouble, as that means HEAT, and
heat will mess up the edges of even the BEST resist-patterns!

Once, I was amazed to learn that, in professional etching, the holes are
drilled FIRST, and then plating-through, if any, and then etching. Logical,
but I had never thought about it until I had reason to get a few boards done
by a "professional PCB house". The hole-pattern makes locating the
negatives, if you are using photo-etch method, much more accurate, of course,
and my "old idea" of using the etched pattern also as the "drilling pattern"
was silly in several respects. One learns as he ferments... Uh, "ages"...