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March 2002

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Subject:
From:
Gerard O'Brien <[log in to unmask]>
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Date:
Wed, 20 Mar 2002 16:41:21 -0500
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Suzanne - as part of a long term real time shelf, I have tested quite a few
of the white tins out there. In all cases the solderability has easily
passed the six months shelf life - in one case the test group is over 700
days on a shelf in my lab with no protection and still soldering. It should
be noted that these samples when manufactured did not have any Stannic Oxide
present (as measured by SERA)in the deposit, one of the major causes for
solderability problems with this type of surface finish, similarly the
presence of sulfur from the catalyst breakdown was also not present.  So to
cut to the chase - you will have no problems with 6 months shelf life for
immersion tin (under normal board storage conditions) if the deposit is
"clean".If you have stannic oxide present or sulfur then its all over.

Regards

Gerard O'Brien
Photocircuits Corporation

-----Original Message-----
From: Lupita Roberts [mailto:[log in to unmask]]
Sent: Wednesday, March 20, 2002 11:34 AM
To: [log in to unmask]
Subject: [TN] FW: shelve life of pwb's


I am wondering if anyone can help me with the shelve life of raw
PWB's. I was experiencing solderability issues and oxidation issues
with some boards. I was told by several suppliers that White Tin only
has a shelve life of 6 months and they were not warrantied beyond that
point. I have been unsuccessful in trying to find data in regards to
this issue.

Suzanne Foulkes
QC Supervisor
Inservco Inc.
LaGrange, Ohio 44050

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