*****  Unclassified  *****
>Jan,
>
> What sort of problems have you seen with Ag filled adhesives & PbSn
>solders??  We are experiencing a mystery anamoly after elevated temp burn-in
>and suspect the Ag filled epoxy is doing something unexpected ... could you
>elaborate?
>
> Thanks, Sheila Smith, TRACOR AES
>
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Sheila,

It has been a long time ago that we have seen these problems. Nowadays we don't  combine silver filled epoxy's with PbSn solders. But back to your question,what happens is that the silver forms a intermetallic with Sn. Due to this, voids evolve on the interface between the silver filled epoxy and the solder. This eventually causes the bond to crack. This will be accelerated at high temperatures.
I hope my memory served me well because the last time we stumbled over this phenomenon has been about ten years ago....
If you want to know more about this, let me know. But i have to see if there is still some documentation left, somewhere.


Jan Bokhove
Dep. CQM
Hollandse Signaalapparaten
tel. +31 74 2482949
e-mail [log in to unmask]