Steve,

I have seen that before with conventional glob-topped assemblies if:  They
had been subjected to thermal cycling; solder reflow (a thermal cycle); had
poor adhesion to the substrate for one reason or another; selected a poor
choice of encapsulant material (TCE mis-match); were improperly cured
(allowed to sit at room humidity for a long time before heat cure); or a
combination of all of the above.

PS - the parts that I built, did not exhibit this anomaly, but Brand-X's
did!

Another Steve

-----Original Message-----
From: Stephen R. Gregory [mailto:[log in to unmask]]
Sent: Tuesday, May 08, 2001 5:39 PM
To: [log in to unmask]
Subject: [TN] Removing Epoxy Encapsulation...


Hi ya'll!!

Thanks for all the suggestions for chemicals to remove epoxy encapsulation
material.
I had some Uresolve 411 here, but that won't work. Our customer has sent
some
parts to a failure analysis lab, and the vendor is doing some work on their
end too.

I was looking at the parts under a microscope holding it with tweezers, and
was gently scraping it with an x-acto knife, when the whole encapsulation
just popped off! It wasn't any force at all!

I got a few more parts and found that I could very easily separate the whole
glob off with hardly any force at all...like the encapsulation material
wasn't bonded well to the substrate. I took a picture, go to:

http://stevezeva.homestead.com/index.html

You see the wire in the epoxy, and the silver epoxy for the die...but as you
can see, the whole deal popped of very cleanly...are you supposed to be able
to do that? Any ideas?

-Steve Gregory-   <----Flak jacket is on in case he slips and makes a
joke...hehehe

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