4 to 6 years is not normal or typical. I recommend a solderability test at
at least a 95% confidence level sample size. This should be conducted after
the bake out necessary to safely use the parts in reflow. If the devices
are leaded, the type of lead finish may be significant. If the finish was
NiPdAu, the solderability should be OK. Regardless of the MSL level
guaranteed by the manufacturer and regardless of the 'guaranteed' storage
conditions, after 4 to 6 years I would not trust the rating even on
unopened/factory sealed bags. Otherwise, 16 weeks does not sound too long
to me to eliminate any concerns.
Best regards,
Leo
Leo M. Higgins III, Ph.D.
Vice President, Technical Support Operations
ASAT, Inc.
3755 Capital of Texas Highway, Suite 100
Austin, Texas 78704
office phone 512-383-4593
mobile 512-423-2002
[log in to unmask]
www.asat.com
The information contained in this electronic message is CUSTOMER/SUPPLIER
PRIVILEGED AND CONFIDENTIAL INFORMATION intended only for the use of the
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of David Britton
Sent: Tuesday, April 11, 2006 2:32 PM
To: [log in to unmask]
Subject: [TN] Shelf Life Policy Inquiry
Recently, our Contract Manufacturer has been asking for approval to use
parts that are 4-6 years old. Due to the lifespan of some of our
products, it appears that the frequency of requests is increasing.
For the recent request, my choice is to approve the use of 6 yr. old
parts, or wait up to 16 weeks for new parts. I am concerned about
possible solderability issues and the potential for damage/degradation if
the parts were not stored properly over that time.
We currently do not have a shelf life policy but it seems like we need to
have some position. I can only find a couple of references to an "accepted
practice" of a 2-year shelf life used by manufacturers. One other
Engineering Bulletin from EIA about Tantalum Caps, states:
"Solid tantalum capacitors have no known wear-out mechanism or shelf-life
limitations. However, solderability and cover-tape peel strength may be
affected by storage conditions. Consult individual manufacturers' data
sheets for recommended storage."
Suggestions or recommendations welcome.
Regards,
David Britton
Quality Engineering Manager
Danaher Motion - Santa Barbara, CA
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