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May 2007

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Subject:
From:
Werner Engelmaier <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 29 May 2007 18:09:12 EDT
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text/plain
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text/plain (31 lines)
Hi Inge,
Unfortunately, for solder joints the MTBF-concept makes little sense because 
they fail as the result of wear-out.
If you look at the wear-out of solder joints of a large population, you see 
almost a 2-order of magnitude between first failure and last failures, since 
the Weibull shape factor is about 3.
For some laptops rhyming as the one previously mentioned, out-of-the-box 
failures have been reported with most failure having occurred in ghe 12 to 24 
months range--depending on usage, of course.
The problem is a design issue with large component, large delta-CTE, large 
on/off T-difference, little lead compliancy—a textbook case of how not to do it.



Werner



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