XPS/Auger will do the trick... you can get composition (and plus IR scan
in the same region) to (hopefully) pin point the source of defect (you
have to know enough about the chemistry and process of the Au in order
to do the FA...The problem is, most of FAB don't even know the detail
chemistry and process)...
                                           my 1.35 cents...jk

-----Original Message-----
From: Mike Di Giacomo [mailto:[log in to unmask]]
Sent: July 12, 2001 7:12 PM
To: [log in to unmask]
Subject: Re: [TN] Staining on Gold


Hi Bev,

        If you want to determine the composition of the stain, I've
found
doing an SEM/EDXA (Scanning Electron Microscope /X-Ray Diffraction) of
the
stain and background should tell all you need to know. In my past life
we
had discoloration on gold pads that were to have die attach/wire bonding
done to it and in that case we had some problems, soldering to SMT pads
wasn't an issue.

Hope this helps,

Mike Di Giacomo
Process Development Engineer
WorldHeart Corp.

-----Original Message-----
From: Bev Christian [mailto:[log in to unmask]]
Sent: Thursday, July 12, 2001 6:37 PM
To: [log in to unmask]
Subject: [TN] Staining on Gold


TechNetters,
I have checked the archives and have not been successful in finding
sufficient info on the titled subject.  Either I have not done a
diligent
enough search or the info is not there.  So, here are my questions.
1) If you were presented with varying amounts of what looks like water
stains on immersion gold pads how would you determine its composition?
No
guesses now, I can do that.  I want to know how people have actually
done
it!  Also, I am not referring to "purple plague" but just slightly off
color
gold.
2) Has anyone ever been able to correlate amount of staining to
solderability issues?  Or is it a non-issue?
3) Has anyone seen staining cause problems with respect to keypad
electrical
continuity?

regards,
Bev Christian
Research in Motion

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