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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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Posted by: Katell Cadoret
Date posted: Fri Sep 21 9:01:39 US/Eastern 2001
Subject: Aging factor / electronic ship
Message:
I'd like to have some informations about aging tests on electronic ship as ASIC. In fact I want to know if it's better to consider an aging with temperature or with frequency. With temperature as aging parameter, it's difficult for me to solve the arrhénius equation because i have no idea of the ship energy activation. where can i find such an information. My problem is in fact to determine the aging factor in order to be able later to correlate the test results with reality. Can frequency that pilots the ship be a good aging parameter ? if frequency is multiplied by two, is that meaning that the ship lifetime is divided by 2? if somebody has some informations about this, thank you very much ! Bye, Katell


Reply:

Subject: Aging Factor
Reply Posted by: B. W. Dudley (bdudley@alionscience.com )
Organization: Reliability Analysis Center
Date Posted: Thu Oct 4 13:48:35 US/Eastern 2001
Message:
In the Reliability Analysis Center library there are numerous articles on accelerated testing and activation energy parameters. Most of the activation energy parameters are for specific failure mechanisms such as corrosion, or oxide defects, or metal migration and vary by significant amount. For example, the assembly inter-metallic has a test proven activation energy of 1.4 electron volts where metal corrosion is only 0.3 electron volts. Combining all the possible factors for a given item is a difficult process. The much disputed, MIL-HDBK-217 does have average activation values for microcircuits. The value for CMOS is 0.35 electron volts. There are no magic analytical models that accurately estimate the life of complex assemblies. Each life analytical model describes physical change mechanisms associated with specific material characteristics. The first step in constructing accelerated tests is to define the failure mechanisms in terms of the materials used in the product to be tested. The next step is to determine the environmental parameters the product will be exposed when operating and when not operating or stored. Based on the failure mechanisms most likely to limit the life of the product, one can choose a test or tests that will accelerate that failure mechanism. In summary, the only tried and true method is to perform multiple high stress experimental tests to determine the real activation energy for the product using plots of the data.


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