Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum (src_forum@alionscience.com )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Original Message:

Posted by: Mok Yin Liong (myinlion@dso.org.sg )
Organization:Defence Science Organization National Laboratories
Date posted: Mon Feb 22 21:03:50 US/Eastern 1999
Subject: PEM Reliability Modelling
Message:
I have some questions regarding the PEM reliability model given in the RAC publication "Reliable Application of PEM" : i. When we divide the failure rate obtained from this model (in failures per million calendar hrs) by the duty cycle (power on time over total time), we get the equivalent operating failure rate (in failures per million operating hrs). This PEM operating failure can then be combined (=added?) with that obtained through Mil-Hbk-217 for other components. By doing so, are we assuming that PEM has a much higher non-operating failure rate than other components (since we are ignoring the non-operating failure rate of the other components)? ii. If we assume a duty cycle of 100% (i.e. the PEM is powered up all the time), can we treat the failure rate obtained from the RAC reliability model as the operating failure rate? Does this violate any underlying assumptions of the RAC PEM reliability model? iii. Based on the limited information given for the RAC PEM model, it appeared that ESD/EOS failures are omitted. Should an additional term be added to this model to take care of ESD/EOS failures? iv. Should there be a different base failure rate for microprocessors and memory devices? Data from some publications indicate that microprocessors have a much higher failure rate than memory devices (up to ten times). Thank you.

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