Hi Bev,
It sort of dependents. First there is no such thing as intermittent
micro-cracks in SJs. If they are micro-cracks, they can be present starting about 40%
into the life of the SJs, but they do not impact electrical signals,
intermittent or otherwise. If you have a full solder joint fracture, electrical signal
interruption will be intermittent, because the fracture surfaces are in at
least some slight compression and make very good 'connector surfaces.'
If you have fully fractures SJs, they will only show intermittent opens if
they are disturbed by either temperature changes or mechanical shock/vibration.
The best way to find them is to do functional tests during vibration loading.

Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com


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