Hi Lance,
I would venture to say, that the CTE of these diodes is significantly
different than the PCB. I would further hazard the guess,  that the diodes with
disturbed SJs are predominantly those oriented in the conveyor belt direction. What
I think is happening is that the leading edge SJ solidifies, the trailing
edge one is still pasty, and the differential contraction on cooling causes the
trailing SJ to be disturbed.

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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