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]

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To subscribe/unsubscribe send a message <to: [log in to unmask]>   *
* with <subject: subscribe/unsubscribe> and no text in the body.          *
***************************************************************************
* If you are having a problem with the IPC TechNet forum please contact   *
* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask]      *
***************************************************************************