Hi folks! Some additional data - we (e.g. the industry technoweinees) are
much too quick to jump to the conclusion that we have a galvanic
compatibility problem when using either immersion gold or immersion silver
pwb finishes. Rockwell Collins published a paper at the 2003 IPC Fall
meeting which demonstrated that the galvanic impact was secondary to a
standard corrosion reaction in a salt fog test - i.e. our tin/lead test
samples which were in a galvanically happy couple situation underwent
healthy corrosion. The galvanic compatibility tables are very important and
should not be ignored but they also can be misleading depending on the
environment/configuration. Collins has a follow up immersion silver,
immersion gold, immersion tin, and tin/lead galvanic corrosion study in
progress and will report the results sometime in early 2005.

Dave



                      Vladimir Igoshev
                      <[log in to unmask]        To:       [log in to unmask]
                      >                        cc:
                      Sent by: TechNet         Subject:  Re: [TN] Corrosion resistance of Ni/Au plating
                      <[log in to unmask]>


                      05/04/2004 09:19
                      AM
                      Please respond to
                      "TechNet E-Mail
                      Forum."; Please
                      respond to
                      Vladimir Igoshev







Rudy,

It's not supposed to be any Au layer left after re-flow. It desolves in
solder.

Vladimir
Sent from my Blackberry Wireless
Vladimir Igoshev, 519-888-7465 ext.5283


-----Original Message-----
From: Rudy Sedlak <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Tue May 04 10:05:27 2004
Subject: Re: [TN] Corrosion resistance of Ni/Au plating

Central to this issue is the question of whether the Gold was completely
covered by the Tin/Lead solder.

I suspect it was not, and if it was not, this would set up a galvanic cell,
which would accelerate the attack on the Tin Lead dramatically.

Rudy Sedlak
RD Chemical Company

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