Hi Steve!
Now you're getting into some really nasty stuff.

Potting epoxy reacts well with mildly heated Red Fuming Nitric Acid,
(which also reacts well with your hands, skin and bones. It is NASTY
stuff, and should be used only with training and the proper
facilities/protective
gear). I'm not much of a worry-wart, but RFNA is some powerful stuff
and deserves serious caution.

A good failure analyist will show you how to drill a small well with a
dremel
tool into the top of the chip (.005 or so deep) to contain a small amount
of RFNA... let react, and before gummy, flush away suspended goop
with acetone from a squeeze bottle. Repeat until at die surface.

There's a fair amount of technique to do this well...I'd not recommend
trying it without a mentor.

Alternatives are plasma etch, and some machine controlled versions
of the RFNA approach.

Get your employere to pop for a Failure Analysis course taught by
Bud Trapp (Technology Associates, Portola CA, I believe) and you'll
not regret it.

Best
John

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