I'm using  Copper Lead frame (plated copper over Alloy 42) and Silver strip
layer for die and wire bonding area. This is for SOT 23/ SC 59 packages.

We just notice that the incomming leadframe is having intermittant 'missing
silver' problem. Unfortunately about 20K products have been molded
(incapsulated).

Now i want to Decapsulate (remove the mold compound) some sample to identify 
how serious the problem is. 

What chemical/solution is best to do this work. The solution should NOT attack
the Copper and silver layer. Thus I can identify the missing silver area
products.

Fuming Nitric Acid?, Fuming Sulfuric acid?, Mix 50-50 ?

Appreciate yr inputs.

Regards
Mohd Misri
Seremban BIM

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