Glob tops are not supposed to fall off under slight mechanical
pressure, so clearly there is a fault. You have to assume that basics
are correct - clean dry and grease free surfaces etc- so could it be
its simple finger trouble, or the wrong material:

Typically this sort of thing happens when people are making in batches
and uncured devices are left in an uncontrolled environment whilst the
batch is being made up leading to moisture ingress, The later ones
won't have the defect making fault finding difficult. Or something
similar.
Alternatively an inappropriate material was used, e.g. a TEC or
hardness/rigidity mismatch would do this - something designed for
alumina as opposed to FR4 maybe.
Sounds to me as though a complete plod through analysis of the actual
history (as opposed to what is written in the S.O.P ) would be
rewarding.

Mike

----- Original Message -----
From: "Stephen R. Gregory" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, May 08, 2001 10:39 PM
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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