Bon jour Jean-François,
You do not give any details of your CCs--size, thermal history and a 
cross-section would be helpful. If the CCs are not defective 'as received' 
and are not damaged during placement, you mostlikely have larger size CCs 
with rather large solder joints--fillets to the top--which are killing you 
CCs during rapid temperature transients.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com 

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