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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

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

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Posted by: Robert Webb ( )
Organization:Ultra Electronics, Controls Division, UK
Date posted: Thu May 9 13:01:50 US/Eastern 2002
Subject: Dormancy factors
I am seeking advice on reliability of electronics taking into account dormant periods. Can credit be taken for periods of non-operation to improve the reliabilty prediction of equipment that is only operational for a certain percentage of an overall mission? In my particular example, the equipment would be powered in a 'sleeping' state and not driving any loads for the majority of the mission. I have a copy of your 'Reliability Toolkit' which contains factors obtained from RADC-TR-85-91, but is this still applicable in current thinking? Your advice would be much appreciated. Regards Robert Webb


Subject: Sleeping Failure Rates
Reply Posted by: Nathan Holzhauer ( )
Organization: IITRI
Date Posted: Tue May 21 12:46:51 US/Eastern 2002
An article in the RAC library, “Coping with Compliance” from the September/October 1996 issue of Advanced Packaging magazine, addresses the issue of ‘sleeping’ standby modes. The key issue raised is that there is “no free lunch”. By using a ‘sleeping’ standby mode one trades off failure of components due to being continuously powered to increased failure of soldier joints due to increased thermal cycling. The author, David Sangster suggests modeling the system with thermal ‘mini cycles’ in addition to the traditional power-up/power-down cycles.

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