One possible solution would be to use a very small dab of silver conductive
epoxy after bonding.  Epotek makes such an epoxy, although it is also
available from a variety of other sources.


David Nemeth
Senior Engineer
Sophia Wireless, Inc.
14225-C Sullyfield Circle
Chantilly, VA 20151


-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Stanley R. Shanfield
Sent: Monday, February 27, 2006 2:50 PM
To: [email protected]; [email protected]
Subject: [mems-talk] Wire bonding problems


We are trying to manually wire bond to thin (~.2 micron) Pt/Au on glass.
Although we get good bonds on test wafers at the time the metal is
deposited, the bonding is very unreliable after it has gone through more
processing (i.e. at wire pull test, the wire falls off, leaving the pad
intact,& undamaged; or the pull strength is low). The wafer sees anodic
bonding conditions at one point in our process sequence, and the sawing
process can leave scratches on the pads (the scratches do not penetrate the
metal).

Going up in bonding energy, time and force is a concern, since the glass
sometimes forms fissures under the bonding area at more extreme bonding
conditions, and a subsequent wire pull creates a pull-out from the glass. It
does not seem to help anyway. These bonds have to survive a ~350C
temperature excursion, so a pull-out is a concern.

Has anyone ever dealt with a problem like this? Any advice or observations?
You input would be much appreciated!