Eric:

We just went over this discussion on Technet, and most folks agreed that it
is not a particular brand of ammoniacal etchant, it is the nature of the
beast.  The free ammonia is what is doing your stripping.  And while there is
very little free ammonia in the etch chamber (at pH 8.4, or so), but even
with very little there, if you are etching 3 oz Copper, that film is exposed
for a long time....then you go through the replenisher...which has a pH of of
at least 9.5, and probably over 10.0.  (Free ammonia is consumed by
complexing the Copper in the etch chamber, and the pH falls dramatically)

At these high pH values in the replenisher, more than 50% of the ammonia is
free, and if the dryfilm was weakened before, it is "bye-bye" in the
replenisher chamber...and there is no ammoniacal etchant out there that is
any different.

As I suggested before, you might want to consider making that first etch
chamber water (and stop it cascading back into the etcher) and add your
replenisher directly into the etch chamber, as we all did 20 years ago, this
might help your situation out a lot.

Other than that, maybe maybe putting double dryfilm on might assist?

Rudy Sedlak
RD Chemical Company

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