Good point - we actually use a silver saver paper in conjunction with
vac/pack. Daubert VCI Inc. www.daubertvci.com
Little pricy but they do help in inhibiting corrosion.
Jeffrey Bush
Director, Quality Assurance and Technical Support
76 Technology Drive - POB 1890
Brattleboro, Vermont 05302-1890
Tel. 802.257.4571.21 Fax. 802.257.0011
[log in to unmask]
http://www.vtcircuits.com
-----Original Message-----
From: Dave Chapman [mailto:[log in to unmask]]
Sent: Thursday, June 17, 2004 10:44 AM
To: [log in to unmask]
Subject: Re: [TN] Yellow Discoloration of Immersion Silver Boards
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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