IEEE Transactions on Components and Packaging Technologies, Vol. 24, No. 4, pp. 721-728, December 2001

Junction Temperature Considerations in Evaluating Electronic Parts for Use Outside Manufacturers-Specified Temperature Ranges

Lloyd Condra
Boeing Commercial Airplane Group
Seattle, WA

Neeraj Pendse
National Semiconductor Corporation
Santa Clara, CA

Diganta Das, and Michael Pecht
University of Maryland
College Park, MD


When assessing the suitability of active electronic parts for use over a temperature range outside the manufacturer specified range, some manufacturers use a limiting value of junction temperature to define the maximum allowable thermal stress applied to the die. This process of thermal uprating based on junction temperature includes the following steps:

  1. the maximum junction temperature limit is defined (obtained directly from the part data sheet, is calculated from other parameters listed on the part data sheet, or is decided by the equipment manufacturers design practices);
  2. a margin is subtracted from the maximum junction temperature limit thus defining the maximum design value;
  3. the maximum operating part junction temperature is computed for the given application;
  4. the maximum operating part junction temperature is compared with the maximum design value.

This approach to junction temperature based thermal uprating is appealing, because it offers the opportunity to avoid expensive and time-consuming part level electrical tests; however, the process may be more complicated than it appears.

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