Hi All,
While it has been evident from the results published by various sources, that 
LF-solders creep slower than Sn/Pb solders, I did not realize that the creep 
rates can be as much as 100 times slower. You may want to look at a paper by 
Günter Grossmann et. al. at <
www.weichloeten.de/eureka-leadfree/04gg-comp-rel.pdf>. The consequence of this is, that the results of accelerated temperature 
cycling tests with short or no dwells at the cyclic temperature extremes are 
meaningless in comparing the reliability of LF-solder joints to Sn/Pb-solder 
joints. Thus, the claims that one sees about the equivalent or superior 
reliability of LF-solders cannot be drawn from any of the test results I have seen so 
far.
While LF-solders are o.k. for consumer goods such as cell phones, I would 
urge caution in using them for high-reliabillity applications.

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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