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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: Sadat ( )
Organization:Nortel Networks
Date posted: Wed Nov 6 14:53:10 US/Eastern 2002
Subject: Tantalum Caps
We have been examing the failure rates of tantalum capacitors and have concerns about them. Is it possible to answer the following question with regards to translating the capacitors expected reliability into FITS? "1% at 1000 hours at 85C at 60% confidence" translates into X FITs at 50C?"


Subject: Capacitor Reliability
Reply Posted by: B.W.Dudley ( )
Organization: RAC
Date Posted: Thu Nov 21 9:08:14 US/Eastern 2002
Your question deals with the data from initial testing for defect rates of capacitors, specifically 1% defects for tantalum capacitors. Using the acceleration parameters from the old MIL-HDBK-217 for tantalum capacitors and 1000 devices for the 1000 hour test hours, I computed that the failure rate at 50 degrees and 60% confidence is 3,300 FITS. This of course is extremely high but that is what happens one uses the "defect" rates from early life. Using the RAC PRISM model for tantalum capacitors, I calculated that the life reliability is 0.8 fits at 50 degrees C. Of course this value has no confidence level associated as it is NOT TEST DATA. Life time information can be using the following equations as cited in this web site This link was provided by Mr. Poltz (, see the question on capacitor life

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