Hi Graham,
The SMD geometry produces a stress concentration in the solder joint which
causes crack initiation earlier than otherwise. Once initiated, the crack will
propagate due to cyclic creep-fatigue of the solder caused by the global
thermal expansion mismatch between component and PCB.
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, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com
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