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June 1999

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Subject:
From:
Werner Engelmaier <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 24 Jun 1999 20:15:16 EDT
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Hi Bernhard,
To my knowledge, an I am the chair of the IPC Reliability Committee, there is
no document that addresses the reliability of embedded/potted electronics,
either THT or SMT. Certainly, the recommendations made in IPC-SM-785 for
accelerated testing are useful in your situation; you just will not be able
to use the acceleration factors.
The possible problems posed by potting compounds have to do with their CTE,
their cure temperature [which sets the initial stress conditions (you want
compressive on the solder joints and a cure temperature higher than the
highest operating temperature)], and the operational temperature excursions
(severity and number). These parameters will determine what accelerated test
conditions should be used and if there is an acceleration factor that can be
applied.

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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