One main consideration for thermosonic bondable gold in addition to
purity and thickness is hardness.  IMHO you should be using 90 Knoop
maximum in order to achieve a good Au/Au weld.  Also do you know the
specs on the wire your customer is using ?  % Elongation as well as the
doping is critical in forming a reliable thermosonic gold bond.  Stage
temperature during bonding needs to be below Tg of material being bonded
otherwise you will loose US coupling. I would not recommend cold stage
bonding unless the process is qualified using ball shear aged adhesion
tests. 

Bill Christoffel
Advanced Manufacturing Engineer
NorLux Corp.

-----Original Message-----
From: Steve Kelly [mailto:[log in to unmask]]
Sent: Saturday, June 22, 2002 10:22 AM
To: [log in to unmask]
Subject: [TN] Wire bondable gold


We made some flex circuits for a customer and wound up putting too much
gold on - approx. 75 microinches. The nickel is averaging 153. The gold
meets all the purity specs. Under the wire bond area is a large heat
sink. My customer is having difficulties wire bonding. Is too much gold
a problem or can the heat sink cause issues. Regards Steve Kelly
--------------------------
Sent from my BlackBerry Wireless Handheld (www.BlackBerry.net)

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