Hello Yves,
Like you mentioned it truly depends on the storage conditions of
temperature, humidity and time.  Without getting into risk management
(i.e. reducing the probability of non-solderable/poor-solderability
parts), MIL-STD-2000 did provide some good guidelines that were widely
accepted for years.  Regardless of the storage conditions (assume some
control), parts were considered acceptable for use within 120 days of
passing the solderability test.  In other words, the parts that you
tested 1 month ago should still exhibit acceptable solderability for
another 3 months without any great concern.
Although this is just a guideline, I would suggest tracking and
documenting the soldering process yields of these suspect parts and
revise your operation plans accordingly (there's nothing better than your
own data).  Hope this helps.
NOTE:  You may want to visit the requirements contained in J-STD-002.

Steve Sauer
Sr. Mfg. Engineer
Xetron Corporation
[log in to unmask]

 ----------
From:  Yves Trudell[SMTP:[log in to unmask]]
Sent:  Monday, July 27, 1998 2:31 PM
To:  [log in to unmask]
Subject:  [TN] Solderability test - period of validation

Technetters, the following question is vague, and I'm sure that I'll get
a
lot of "it depends" type of answers, but that's fine as long as the
responses contain some examples of guidelines that are followed.
 -   The solderability on many devices must be verified prior to assembly
if
the devices have surpassed a certain date code limit.
So, here's the question:
 -   Once the solderability has been tested on one of these "old" lots,
for
how long do you consider the test results valid?  i.e. I may have some
devices with date codes that are 24 months old where I verified their
solderability 1 month (or choose any time period for the example) ago.
Should I re-verify solderability again prior to releasing them for
assembly?

I'm looking for any guidelines that are used or considered in such
situations. I understand that storage conditions are likely the main
variable and that a general guideline is not likely.  Any case-specific
examples would be greatly appreciated.

Yves Trudell
Nortel, Wireless Networks Calgary
Quality System Engineering

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