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November 2000

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Subject:
From:
Werner Engelmaier <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 22 Nov 2000 10:29:34 EST
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Hi David,
(1) You do not say what the cyclicenvironment for product life is.
(2) Even though -55 to 125 degC cycling is widely used because it produces
results FAST, this cyclic temperature range confounds at least 2 different
damage mechanisms of solder. As a consequence, there can be no valid
translation to other cyclic environments that are more characteristic of
product use.
You can assume a non-confounding scenario, ignoring the impact of the damage
mechanism(s) not present in the product cyclic environment and obtain a
conservative low-ball limit.
For a better understandingy you should read IPC-SM-785, Guidelines for
Accelerated Reliability Testing of Surface Mount Solder Attachments, and
IPC-D-279, Design Guidelines for Reliable Surface Mount Technology Printed
Board Assemblies, Appendix A.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com

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