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

Hi all, It's me again. I've been busy for a couple of months now, but
I accidentally have perfected the cheap photo etching method I posted
a few months ago.

So here we go:
The emulsion is way past expiration date. And that's a good thing! For
some reason, it becomes less viscous when it expires. It's thick as
cooking oil now, before that it was as thick as good latex-based wall
paint. This allows for two things: a thin layer and quicker drying.

The thin layer allows for thinner tracks too. I went down to 0.01" and
had minimal trouble. I'm working with 0805 SMDs with no problem at all.

Also I now expose to sunlight. I asked the pros about how they do this
and they all said you need either 2 - 3kW special lamps with special
timers, or the cheap (and more efficient) sunlight for "about 3 or 4
minutes". It works GREAT. not even the finest line cuts when
developing (that was my problem before).

But, the expired emulsion leaves a nasty residue, as if it's still
stuck to copper. No problem. Fine steel wool makes it go away. Even
pushing (relatively) hard to the thin tracks, the artwork stays.

I'm really happy with the results.