SRC Forum - Message Replies

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

Original Message:

Posted by: asphil
Organization:IEGS
Date posted: Fri Apr 16 1:51:19 US/Eastern 2004
Subject: Thermal factor estimation
Message:
When using MIL-217, we have to enter thermal parameter. Although I calculate temperature rising for IC, I can't calculate it for passive components. How should I do for this?

Reply:

Subject: Thermal Analysis
Reply Posted by: BWD (bdudley@alionscience.com )
Organization: RAC
Date Posted: Thu May 6 15:09:47 US/Eastern 2004
Message:
The failure rate models in MIL-HDBK-217 are based on ambient surrounding temperature except for microcircuits and hybrid devices. Therefore, you only need to estimate the temperature rise near each device. A measurement is the best way, but engineering judgement is usually sufficient. A 5 or 10 degree C rise is often more than sufficient for an analysis. If you cannot measure and the estimate is not sufficient, then one needs to perform a detail thermal analysis.