Hi Kenneth,
The half-cycle dwell time is the time available for stress relaxation/creep
at each cycle temperature extreme. Therefore of you have sine-wave shaped
temperature cycles the td in SM-785 is about one quarter of the cyclic
period; it becomes an effective dwell time, because in a sine-wave there is
no true dwell.
Most cycles, however, are trapezoidal; that is there heat-up and cool-down
ramps which are not included in td.

Werner Engelmaier
Engelmaier Associates, Inc.
Electronic Packaging, Interconnection and Reliability Consulting
23 Gunther Street
Mendham, NJ  07945  USA
Phone & Fax: 201-543-2747
E-mail: [log in to unmask]

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