Larry:
This is beginning to be fun, but thank god I do not have to deal with the
real life situation.

Rob is right, it is the free Ammonia that is your enemy, and after consulting
my Handbook of Chemistry and Physics, we find that at pH 9.25, half the
ammonia present is free, the other half is present as the ammonium ion, or
effectively neutralized.  And the higher the pH, the greater the fraction of
the ammonia present that is free.

The real problem you are going to have is that etch replenisher is buffered
so strongly, and it is so concentrated, that nothing you can do, that will
still keep it functional as a replenisher is going to change the pH, or the
free ammonia content.  See, if you actually could change the replenisher pH
enough so that it did not give you a problem (not likely, without massive
additons of Hydrochloric Acid), it would no longer function as an etch
replenisher, which needs lots of free Ammonia to function.  (I could go into
why, but then you would fall asleep.  If you are interested go to
www.pcbfab.com)

In my mind, you have two choices, one of which is bad, the other is worse.
1. Shorten first rinse
2. Change first rinse to tap water.

Damn, I hate to be the bearer of such bad news...

Rudy Sedlak
RD Chemical Company

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