Al fine wire, signal only, isn't very demanding, but heavy Al wire (50um and up) combined with high currents can be schrecklich, as Werner would say. Too thick gold and impurities can cause bond lifting after some time of operating at high temperature. If you are uncertain, I'd recommend a night or two in bed reading Harman's wire bonding Bible.

I anticipate that you aim at wedge bonding. In fact we've found that you can bond successfully on nickel without any gold at all (don't take it as a recommendation, but just as information). We let the autobonder make thousands of fine wire Al bonds on nickelplated aluminium plates, not one single missing, and wire pull test statistics looked just fine.

Asked Steve to hang some typical pics on the wall FYI. Not best quality images, but give you an idea. Two pics 37um and the others 125 um Si-doped Al wire. Interesting to see what other's think about bonding directly on nickel like this....

Ingemar Hernefjord
Ericsson Microwave Systems

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of John Parsons
Sent: den 13 januari 2005 00:32
To: [log in to unmask]
Subject: [TN] FAB - Al Wire Bonding


Greetings all,
I am trying to learn something about the wire bonding process.  Our customer
has a part on which they spec the finish of some edge connector fingers as
"Gold Plated for Wire Bonding Al Wire".  As we do not provide a wire
bondable gold finish in-house we have subcontracted the service.  The
plating service tells me that typically for Al wire bonding all that is
required is a typical ENIG process (5-10u" Au over 200u" Ni).  I believe
that in past verbal communications with the customer they have said that an
ENIG finish would not suffice and that they require 15u" of bondable gold
(electroless gold or electroplated??) .

What say you? Or does "it depend" :-)

Regards
John Parsons

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