MISRI, BASED ON MY EXPERIENCE, YOU CAN USE 5:1 ETCH. 5 PARTS FUMING NITRIC ACID
AND 1 PART CONCENTRATED SULFURIC ACID.
           ------------

NOTE, I UNDERLINE CONCENTRATED TO EMPHASIZE THIS TYPE AND NOT FUMING SULFURIC
ACID. MIXING BOTH FUMING HNO3 AND H2SO4 CAN CAUSE SEVERE EXPLOSION.

TO BE SAFE, WHEN YOU DECAP, DECAP ALSO CONTROLLED STRIPS W/ KNOWN SILVER TO BE
ON THE STRIPS. HEAT UP THE ACID ON HOT PLATE, LET IT BOILS AND DIP THE UNITS/
STRIPS FOR 1-2 MINUTES TILL MOLD DISAPPEARS.

BR,
NIK
X1614

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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