Good morning,

I'm experiencing a problem that appears each time I dump and remake the
resist stripper chemistry. Resist is Morton 5050 series. Stripper chemistry
is the recommended for this resist.

The problem is excess copper after etch, massive excess copper. Electrolytic
tin(acid tin)is used as the etch resist. Resist/stripper chemistry vendor
and tin vendor are pointing at each other.

It appears as if the re-made chemistry is attacking the tin, somehow, and is
being re-deposited onto the foil copper surface. The tin then protects the
copper during etch in ammoniacal etch solution.

There are 2 chemistry sumps on the stripper. When this problem appears it is
generally 'solved' by mixing the new sump with the used sump and processing
as normal. Also, we have on occasion not mixed the sumps and the problem
goes away in a few hectic hair graying days.

There are several theories floating around here at our shop but I would like
to hold them in reserve so as not to prejudice anyone's opinions.

All help is greatly appreciated.

Russell

ps- I know this is considered the easiest process to operate in the entire
shop, but it is eluding all of our efforts to date. Perhaps I/we are too
close to it to recognize a basic flaw in the current process.



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