James

The results you will achieve will be totally different and specific to
the test.
In thermal shock deformation and  degradation mechanisms will be
activated that are irrelevant in thermal cycling and vice versa.
- Degradation in solder joints depends on the strain rate
- The degradation path in solder joints can be influenced by the stress
applied. And, the higher the strain rate the higher the stress.
- Thermal shock can lead to the destruction of the components something
that will not occur in thermal cycling
- Due to thermal shock the substrate will bend or warp and bring in
additional stress into the component and the joints not occurring in
thermal cycling

If your application includes thermal shock you must test the specimen
accordingly if the stress is thermal cycling, thermal cycling is the
test you have to do otherwise it is impossible to make any connection
between the test results and the real application. I do have even doubts
about the validity of comparative tests done with thermal shock if no
thermal shock occurs in the application (see above).

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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