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

Etched another board tonight, this is a 4 layer 6/6 board. After
etching, I noticed that the copper was undercut about a mil or so.
Since the 0.5oz copper is 0.7mil thick, this seems a little high, but
I suppose some undercutting is going to happen. However, 1 mil per
side on 6/6 gives me 4/8! Yes, there were some broken traces - I
attribute this to defects in the film lamination, since there were
some. I ran it anyway, it was my third attempt to laminate film on
the really thin clad.

Do those of you with spray tanks get much undercutting?

Anyway, my observations from this batch:

Agitate during development. There were some spots that had the flimsy
strands of mask between traces still, I suppose more development might
have helped. Other spots the mask was fine.

Keep rotating the board during etching so it etches evenly - uneven
etching means some spots get overetched and undercut.

Perhaps I'll bloat the film by a few pixels to try to compensate for
undercutting.