Jim

Well the soak time has mainly the effect of the strain brought into the
solder joint.
Regarding the strain rate during the soak time:
Yes, the stresses will be relieved. This means that during the soak the
strain rate is continuously become smaller until the theoretically
possible strain is induced into the solder joint. The influence of this
strain-rate / time behaviour is in my opinion rather difficult to
quantify. However, the strain rate in the dwell is factors smaller than
in the ramp and thus the influence on the degradation should be
negligible or at least the failure caused by the assumption that there
is no influence is within the spread of failures occurring in reality
and in tests.


Best regards

Guenter

EMPA
Swiss Federal Laboratories  for Materials Testing and Research
Centre for Reliability
Guenter Grossmann,  Senior Engineer

8600 Duebendorf
Switzerland

Phone: xx41 1 823 4279
Fax :     xx41 1 823 4054
mail:     [log in to unmask]

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