Hi All,

I have a slight problem that I want to avoid turning into a major costly
issue.  I have a few plating racks that are starting to be overrun with
wild plating ( copper and tin) up the rack away from the contacts in areas
that are not supposed to be plating.  There are even areas of isolated
plated metal surrounded by plastic.  Upon inspection, I was able to peel
off the plated tin and copper and noticed several layers.  I think this is
most likely due to multiple plating cycles.

The racks are solid copper core with a plastic shrouding.  The manufacturer
claims that "no rack stripping" is needed.  In the universe where I am
from, most plastics aren't conductive and don't plate.  I understand that
once initiated, the plating will propagate in the path of least resistance,
but what is causing it?

My suspicions include poor rinsing of the racks (conductive salts
remaining?) after a plating cycle or conductive carbon (from our Shadow
process) getting into scratches in the plastic shrouds and eventually
arcing causing this plating, but I haven't been able to confirm or disprove
either theory yet.  It's not affecting quality, but I don't want to wait
until it does.  Is there some preventative measure to eliminate the problem
that anyone has tried?

Thanks,
Sean Clinton

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