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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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Original Message:

Posted by: JJC
Date posted: Fri Nov 17 10:57:34 US/Eastern 2000
Subject: HAST
Message:
What is the significance of increased atmosheric pressure when performing HAST testing at accelerated temperature and humidities. Thanks


Reply:

Subject: HAST Testing
Reply Posted by: Bruce Dudley (bdudley@alionscience.com )
Organization: Reliability Analysis Center
Date Posted: Mon Nov 20 10:15:08 US/Eastern 2000
Message:
Increasing the pressure in a HAST(Highly Accelerated Stress Test) test may causes moisture to penetrate the package of the circuit under test resulting in possible corrosion failure. The problem with this test is the difficulty in extrapolating the data to operating life times. Each of the variables by themselves can be modeled, but together the interactions are not known and therefore the accuracy of the extrapolation using the available algorithms is questionable as most models assume independence of the variables. In the JEDEC Standard for testing microcircuits, the HAST test (Test Method-A110) says the purpose of the test is to evaluate the reliability of non-hermitic packaged microcircuits. The pressure component is to accelerate moisture through the external protective material or along the interface between the external protective material and the metallic conductors which pass through it.


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