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Date: | Wed, 16 Oct 96 13:14:58 cst |
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Hi Richard-
I have not had any problems with the components you describe provided
the plating was done correctly to begin with. There have been some
discussions within the IPC solderability committees about the need to
have "clean" packaging materials to avoid some of the problems you
described (sulfur contamination/corrosion of a finish due to packaging
is an industry documented phenomena, especially for silver finishes).
Your packaging thoughts are an idea that many people would endorse but
I don't think the refrigeration theory would be supported. Again -
good plating should solve you problem. Good Luck.
Dave Hillman
Rockwell Collins
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______________________________ Reply Separator _________________________________
Subject: ASSY: Solderability - Storage of Tin Plated Parts
Author: [log in to unmask] at ccmgw1
Date: 10/14/96 1:58 PM
I have been told by others with this experience that
electro-tin plated or tin-dipped parts, such as RF
screens or 'cans', may become unsolderable after a
month or less on the stockroom shelf. Apparently, the
tarnishing of the tin results from the parts being
improperly packaged in materials such as paper,
cardboard or plastic which were made with sulfur- or
acid- compounds. These parts are typically made from
copper or aluminum, with a nickel overplating, then
tinned.
Thus, I am tempted to instruct my vendor to assure
that parts of this nature must be packaged in
acid-free, sulfur-free packaging. When the parts
arrive, I would instruct the stockroom to store them
at low temperatures (refrigerated) to also reduce
electromigration.
Does anyone have information that these assumptions
are correct, and is there published material that
might add validity to these assumptions?
----------------------
Richard Huziak
Manufacturing Engineering
SED Systems
Saskatoon, SK, Canada
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