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November 1997

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Date:
Fri, 28 Nov 1997 08:32:05 -0500
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Hi Sven-Eric,
It is interesting how information can get corrupted and twisted. There is
nothing wrong with thin plastic packages per se. However, if the package
thickness drives people to rigid die attaches for large die--and perhaps to
Alloy 42 lead frames-you can have a serious solder joint reliability problem.
The reason: TSOPs with Alloy 42 leadframes have shown measured CTEs that are
lower than if the package were made of ceramic. For Alloy-42-TSOPs: large
delta CTE with FR-4 plus very stubby, stiff leads=short life (TQFPs are much
more forgiving because of the significantly more compliant leads).

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]

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