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June 2004

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From:
Dave Chapman <[log in to unmask]>
Date:
Thu, 17 Jun 2004 09:43:42 -0500
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We require from our board suppliers that a slip sheet (non sulfur bearing)
must be at the least on the top board and the bottom board. There is a
special anti-tarnish paper most of our board houses use.
(Since the silver finish is actually below the board surface we don't have a
scratch concern for the internal boards in the stack) The boards must be
wrapped and vacuum sealed. We conducted a supplier audit and asked their
capabilities to meet our new requirements for packaging and storage.
Dave Chapman
CSI

-----Original Message-----
From: David D. Hillman [mailto:[log in to unmask]]
Sent: Wednesday, June 16, 2004 5:49 PM
To: [log in to unmask]
Subject: Re: [TN] Yellow Discoloration of Immersion Silver Boards


Hi Rich! I recommend getting a copy of Lenora Tuscano/Don Cullen's paper
given at the IPC 2003 Fall meeting titled "The Study, Measurement, and
Prevention of Tarnish on Immersion Silver Board Finishes". The paper
documents that the "yellow" tarnish found on immersion silver pwbs used in
the study, using SERA and ESCA analytical techniques, can be silver
sulfide, is in the thickness range of 200-500 angstroms, and is still quite
solderable (lots of info in the paper - this is the reader's digest
version). As others in our TechNet community have discussed, the yellowing
can be a typical visual appearance. Good Luck.

Dave Hillman
Rockwell Collins
[log in to unmask]




                      Richard
                      Kraszewski               To:       [log in to unmask]
                      <[log in to unmask]        cc:
                      COM>                     Subject:  [TN] Yellow
Discoloration of Immersion Silver Boards
                      Sent by: TechNet
                      <[log in to unmask]>


                      06/16/2004 09:13
                      AM
                      Please respond to
                      "TechNet E-Mail
                      Forum."; Please
                      respond to
                      Richard
                      Kraszewski







We are seeing yellow discoloration of Immersion Silver Boards right out
of the package from our board house.  They seem to solder fine, however
this is causing some concern with our customer.  I suspect that it could
be a thin film of  silver bromide or silver carbonate both which are
yellow powders.

Any one seen this before?

What is it?

How does the board house remedy this situation?

Any associated concerns or other bits of wisdom?

I would truly appreciate any input.


Rich Kraszewski

Advanced Manufacturing Engineer - KEDS

Phone:  260.925.8919









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