Genny,
You have to go with the flow. Sometimes localized hand soldering will
give you a false positive. If you want to know whether to use them or
not, sacrifice a few and run them though all the subsequent processes 
(especially thermal excursions) they would be exposed to in order to
establish an expected level of success. If you have to have an official
reason; test them per IPC J-STD-003 for solderability.
Dewey 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Genny Gibbard
Sent: Wednesday, June 24, 2009 9:16 AM
To: [log in to unmask]
Subject: [TN] Immersion Tin solderability eval

We have some Immersion Tin boards that are several years old.  From
everything I have read here or elsewhere, ImmSn is supposed to have a
short shelf life.  6 mos to a year.  No one wants to scrap the boards
without testing them, though.  
How would you verify whether they are still good?  We hand-soldered some
pads and actually had no problems which surprised me, considering the
age of the boards, but I don't know if that is a valid test.

Genny 

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