Hi Amol,
High Sn solders do have lower creep rates, higher strengths, and higher
modulii of ductility relative to SnPb—this clearly contributes to the problems you
observe. what you can do is slow down the cooling rates from reflow to no more
than 1.5C/sec to avoid the thermal shock causing pad cratering and to some
extent brittle interfacial failures.
The PCb material may also contribute—some of the LF-soldering capable PCB
base materials are more brittle.
Werner Engelmaier
Future workshops:
Reliability Issues with Lead-Free Soldering Processes, June 17, London
Interconnect Failures and Design for Reliability for PCB PTHs, June 17,
London
Solder Joint Reliability: Parts 1 through 4, July 17/18, Thal, Switzerland
Pb-Free Soldering Processes—Survival, Quality, Reliability, August 18,
Orlando
Reliability Issues with Lead-Free Soldering Processes, September 22,
Schaumburg
Failure Mode and Root Cause Analyses Reliability (Fatigue, Brittle Fracture,
ENIG), September 22, Schaumburg
**************
Gas prices getting you down? Search AOL Autos for
fuel-efficient used cars.
(http://autos.aol.com/used?ncid=aolaut00050000000007)
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