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From [log in to unmask] Tue Jun 17 10: |
35:48 1997 |
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>From willli Mon Jun 9 21: |
29:41 1997 |
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Hi Steve,
This has been a very common problem with ceramic LCCs on FR-4 PCBs, because
of the large difference in CTE (coefficient of thermal expansion) between
ceramic and FR-4 causes large thermal expansion mismatches during thermal
cycling. If the LCCs are small (24 I/O or less) increasing the standoff
height may be an adequate solution. For larger components you are likely need
to go to leaded attachments with leads that are not too stiff.
There are a number of analytical tools available (see IPC-D-279, 'Design
Guidelines for Reliable Surface Mount Technology Printed Board Assemblies')
to assure the reliability of your design. I provide this analysis for my
clients.
Werner Engelmaier
Engelmaier Associates, Inc.
Electronic Packaging, Interconnection and Reliability Consulting
23 Gunther Street
Mendham, NJ 07945 USA
Phone & Fax: 973-543-2747
E-mail: [log in to unmask]
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