Darrel,
We think IAg is different that the thick silver plating that is used on
components.  The IAg thickness on our boards is about 6 microinches thick.
It will tarnish extensively (i.e., turn back in color) if exposed to sulfur
so we don't expose it to S and if it does get exposed we don't use the
boards.

Most people miss the reason we use IAg.  We are not using it as a solderable
surface!.  We are using it as a visual inspection to know that the copper
features should be solderable  (i.e., if the copper features change from a
copper color to a silver color during IAg plating than the copper wasn't
contaminated with solder mask residue or tin-strip residue from the board
fabrication process.

Regards,

George
George M. Wenger DMTS
Bell Laboratories Princeton, Supply Network Solutions
Engineering Research Center FMA / AQA / RCA Lab
(609) 639-2769 (Office); 3210 (Lab); 2343 (Fax)
[log in to unmask]


-----Original Message-----
From: Darrel Therriault [mailto:[log in to unmask]]
Sent: Wednesday, June 07, 2000 10:16 AM
To: [log in to unmask]
Subject: Re: [TN] Immersion White Tin


At 10:39 AM 6/7/00 -0400, you wrote:
>[log in to unmask]



George,

Thanks for a very insightful synopsis of IWT.  I recall many years back
that silver plated ICs caused solder problems
due to tarnishing.  Is IAg different from that problem?

Thanks again for the info.  Very helpful.

Regards.....DT

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