Dave,
Unfortunately, there is no 'acceptable number of cycles' either in
 air-to-air and
one liquid-liquid thermocycling nor IST. There can be a 'minimum threshold'
that would assure no failures as the result of the assembly processes, but
there is further loading (less severe but more cycles) that during
operational use in the field. Many applications are benign, but severe uses,
e.g. automotive and military, could experience field failures on boards that
would have no problems in benign uses e.g. computer, telecom. 
Thus, we do need the capability to numerically correlate IST results to
equivalent air-to-air and liquid-liquid cycles, and more importantly to
cycles at a given use environment. Therefore, any data that would allow
arriving at such a correlation would be very welcome.

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]

regards
Dave

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