Albert:

Your thinking is ahead of its time.

We have developed something that is in the direction of what you ask for, if
not there.

We developed a process that allows you to electroplate/electrowin the metals,
Copper, Tin, and Lead, if present out of spent stripper.  The stripper cannot
be reused at that point, as we must neutralize the stripper in order to
electrowin the metals from the solution.

The other potential life enhancer for Tin Strip is to consider replenishing
the stripper with straight nitric acid.  It turns out that the speed of the
Tin stripper falls off dramatically as the Nitric is consumed, and less than
50% of the Nitric in the incoming stripper is consumed before it is
considered spent.  So small, say 2-5% additions of Nitric can extend the life
of the stripper.
There are two limitations to this idea.  There is a limit to how much Tin you
can get into the system before it simply becomes too much for the pumps to
spray.

The other is that the dissolved Copper level, and thus the Copper attack go
up as the  stripper becomes more and more used, and unless you are using a
very well designed stripper, with very good anti-tarnish system, you could
have excessive Copper attack on the PCB.

If you want more information, please contact me directly.

Rudy Sedlak
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