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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: RS Moore ( )
Organization:BAE SYSTEMS
Date posted: Wed Feb 9 5:04:46 US/Eastern 2000
Subject: Tantalum Capacitors
Does anyone have any experience of whether SMT tantalum capacitors need series resistance to increase the circuit impedance thereby reducing the probability of the capacitor failing short circuit? If so, what is the likely improvement? I have experienced 2 failure incidents in endurance testing on a PEC where the capacitors are use as decouplers on a 5V and 15V rail. They are 40% voltage derated. Any thoughts? Bob Moore


Subject: Tantalum SMT Capacitors
Reply Posted by: Bruce Dudley ( )
Organization: Reliability Analysis Center
Date Posted: Wed Feb 16 15:34:23 US/Eastern 2000
In general, we recommend a greater derating margin than 40% for tantalum capacitors. Derating of 50% for tantalums capacitors should inprove the reliability of the device and circuit. If one adds a series resistor, the decoupling capacitor has no useful function and you might as well remove it. Since you have been experiencing capacitor failures, at some unknown rate, the entire circuit design should be evaluated from beginning to end to find any other design faults.

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