Question: "What would you recommend as "accelerated life test" if not a 
thermal cycling
? Power cycling ? Mechanical test ? Any combination ?
Merci beaucoup, Pascal Guihéneuf"

Answer:
Hello Pascal,
Answering those questions in a general context could be a very long story! 
So, just a few short comments:

1) For thermal cycling of SAC assemblies, I presently use stress/strain 
(hysteresis loop) simulations to optimize test conditions (the goal being to 
accumulate damage in an effective manner).  Optimum profile is actually component 
dependent but there are general trends.

2) Power cycling has, in general, been expensive and of long duration 
(although the cycles can be rapid, which does not allow for efficient damage 
accumulation without optimization of cycling conditions).  Werner can probably comment 
more on running a long power cycling test, a couple of years back.

3) There has been claims that mechanical cycling can be correlated to thermal 
cycling. That may be true if you have a large, global CTE mismatch situation, 
although I have never seen an established correlation of wide enough scope 
that bridges thermal and mechanical cycling results.  One thing that is not 
captured by mechanical cycling is stresses in the joints due to local CTE 
mismatches (between solder itself and the interconnected parts).

With best regards,
Jean-Paul.

__________________________
Jean-Paul Clech
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http://jpclech.com/ 

EPSI Inc.
P.O. Box 1522, Montclair, NJ 07042, USA
tel: +1 (973)746-3796
fax: +1 (973)655-0815

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