John,

I will mimic what Steve says to the letter. I also agree with Ingemar and
will add that while you can Al wire bond to nickel plate successfully the
immersion Au provides a reasonable barrier to minimize Ni oxide growth
which, while slow growing, is quite tough to dissipate, even with
ultrasonics, hence Ingemar not recommending it. Therefore the Au provides
good preservation of the Nickel surface, especially if there is a solder
reflow operation where the elevated temperature will dramatically speed Ni
oxide growth.

Regards,
Bruce Misner

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of John Parsons
Sent: Wednesday, January 12, 2005 6:32 PM
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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