SRC Forum - Message Replies
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
Posted by: JJC
Date posted: Fri Nov 17 10:57:34 US/Eastern 2000
What is the significance of increased atmosheric pressure when performing HAST testing at accelerated temperature and humidities.
Subject: HAST Testing
Reply Posted by: Bruce Dudley
Organization: Reliability Analysis Center
Date Posted: Mon Nov 20 10:15:08 US/Eastern 2000
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.