Hi Sheila,
Because of the creeping behavior of solders in the temperature ranges of
interest (above -20C), there can be no S-N curves. S-N curves are for elastic
strains only. Solder fatigue is strain, not stress, driven. What you really
need are Manson-Coffin diagrams (log strain vs. log fatigue life).

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]

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