Hi Pascal,
Acceleration factors for LF-soldrs do not as yet exist--the necessary data
simply have not been generated. Your cycle time of 40 minutes is much too short
for any significant creep to have taken place and thus you do not get the
necessary creep-fatigue. For IPC-9701A, we are discussing 30 minute hold times at
each temperature extreme, fully realizing that even this is inadequate
relative to the 10 minte hold times prescribed for SnPb-solders. This is because the
creep rates for LF-solders are almost a factor of 100 slower than for SnPb
solders. While this is a good thing for the reliability of product   that
experiences short period cycles, it makes accelerated testing for prodcut that sees
something like one cycle/day essentially impossible without the existance of
acceleration models.

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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