In the past, I have observed problems with PbSn solder and Ag filled epoxy.
 The symptoms were high resistance readings between the soldered end
terminations and the silver filled epoxy.  Sometimes the resistance
readings were intermittent.

Our supplier indicated that soldered end terminations should not be used
with silver filled epoxy.  Reasons for the incompatibility were:

1.  The conductive epoxy has poor adhesion to solder.

2.  The curing process (or other elevated temperature conditions) may
result in an oxide formation on the solder surface, resulting in increased
contact resistance.

I suggest you contact your supplier.  I believe that the problem is epoxy
dependent.  Some epoxies seemed to exhibit the failure mode, and some did
not.

Dave Anderson

>>> Sheila Smith <[log in to unmask]> 08/07/97 07:20am >>>
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



At 11:10 AM 8/7/97 +0200, you wrote:
>*****  Unclassified  *****
>>
>>I have been told that gold and silver are incompatible materials for
>>bonding together, and that, therefore, gold finishes and silver-filled,
>>electrically conductive adhesives will not work well together.  Does
>>anyone have any data to corroborate or contradict this information?
>>
>>Steve Murphy
>>
>-------------------------------------------------------------------------------
>
>Steve,
>
>We have a very long experience with silver-filled, electrically conductive
adhesives on gold. We use it, among others, for die bonding. We have never
experienced problems due to incompatibility between gold and silver. We
have
seen problems with both materials in combination with PbSn solders, maybe
thats where this 'rumour' comes from.
>Hope this helped.......
>Jan Bokhove
>Dep. CQM
>Hollandse Signaalapparaten
>tel. +31 74 2482949
>e-mail [log in to unmask]
>