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: Jon Ilseng (ilseng@austin.apc.slb.com )
Organization:Schlumberger Oilfield Services
Date posted: Mon Aug 9 15:54:12 US/Eastern 1999
Subject: MIl-HDBK-217F Stress Analysis Predictions
Message:
I have a question concerning the MIL-HDBK-217F Stress Analysis Predictions for Commercial Fixed Film Resistors (Style RN) vs. Commercial Resistor Networks containg Fixed Film Resistors. The PCB I am doing a MIL-HDBK-217F stress analysis prediction contains these parts. The PCB operates in a Ground Mobile environment at 40 Degrees C ambient temperature. For a 0.125W Fixed Film Resistor operating at 2% of its rated power, the predicted failure rate is 0.0984. For a resistor network containing 9 Fixed Film Resistors, the predicted failure rate is 0.037. Why does a resistor network containing 9 Fixed Film Resistors have a smaller failure rate than one Fixed Film Resistor? My only guess is because of the difference in quality factor values. For a resistor network with commercial resistors, the quality factor value is 3.0. For a commercial Fixed Film Resistor, the quality factor value is 15.0. I would appreciate anyone's help.

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