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January 2003

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Subject:
From:
Werner Engelmaier <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Sun, 26 Jan 2003 19:36:51 EST
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Hi David,
When you get intermittents, that means you have a full crack not a
micro-crack. Fractured solder joints are notorious for this, and cannot be
found by X-ray or visual innspection. Your description makes me suspect not
so much solder joint cracking, but interfacial separation due to 'black pad'
or a similar problem causing an absence of a metallurgical bond.
Cross-section some of these joints to see what you have, an effective
screening procedure is vibration.

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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