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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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Original Message:

Posted by: Ray Moran ( )
Date posted: Fri Feb 23 10:38:57 US/Eastern 2001
Subject: Capacitor Reliability
Hi, I have heard that aluminum electrolytics can outgas if subjected to high temperatures. Have any studies been done to quantify this effect as a fuction of temperature? I am using a miniature aluminum electrolytic rated at 105 C, and the max temp it will ever see is 80 C. Is it safe to assume that since I am operating well within the temperature range, any outgassing would be be negligible? Any advice or leads would be much appreciated. Thanks! Ray Moran


Subject: Al Electrolytic Capacitors
Reply Posted by: Bruce Dudley ( )
Organization: Reliability Analysis Center
Date Posted: Thu Mar 1 13:23:45 US/Eastern 2001
All aluminum electrolytic capacitors outgas to some degree. Temperature is a factor in the rate of out gassing along with external pressure (altitude). In 1985, Mr. J.Andrew Lauber issued a technical paper called "Aluminum Electrolytic Capacitors--Reliability, Expected Life and Shelf Capabilities" which indicates that temperature and vapor pressure are related to weight loss of the electrolyte. This means that the reliability of the aluminum electrolytic capacitors is impacted by temperature and outgassing due to the loss of weight. The equation used is: W = (A)exp^(-B/T) where W is the weight loss in mg/hour, A is a magnitude constant, B is a slope constant and T is temperature in degrees Kelvin. Specific figures of weight loss and temperature for several styles of capacitors are included in this paper.

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