Hello Werner,
To my limited knowledge, I have not seen thermal cycling acceleration  models
for LF assemblies using SnCu(x), SnAgCuBi, SnBi based solders, or  mixed
assemblies.  I am also unaware of vibration models (as of yet) for LF  assemblies
but there is work in progress on that aswell.

However,  I have seen a dozen+ thermal cycling reliability models for  SAC
assemblies.   In my SMTAI'05 paper (which I sent you an early copy  of in July),
I gave a list of 11 different models that have been developed by  various
organizations for SAC assemblies.  Authors from IMEC also  presented a SAC
crack-propagation model during SMTAI'05, based on detailed crack  growth measurements
 in SAC soldered assemblies.  Many of those models are  strain-energy based,
i.e.:

Cycles to failure or dN/DA (inverse of crack propagation rates)  go as 1 /
[Strain Energy]^m

with exponents m all close to 1 for thermal cycling data.  The latter  fact
is based on correlations of empirical data but agrees with theoretical  /
physics based models for soft Sn-based solders.

All the best,
Jean-Paul


In a message dated 10/13/2005 2:09:30 PM Eastern Standard Time,
[log in to unmask] writes:

Because  of the
quite different behavior of SnPb and LF-solders under accelerated  test
conditions, no valid product reliability conclusions can be drawn  from
such tests until we have accelaration models for  LF-solders.



Quote of the month:
"It is the weight, not numbers  of experiments that is to be regarded", Isaac
 Newton.
_______________________________________________
Jean-Paul  Clech

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

_http://www.jpclech.com_ (http://www.jpclech.com/)

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