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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: Leroy Meyers (meyers@generalatronics.com )
Organization:GAC
Date posted: Wed Apr 12 8:57:03 US/Eastern 2000
Subject: 217 Quality Factors
Message:
For a microcircuit purchased to a Standard Military Drawing (SMD), what is the most accurate Quality Factor to use for these 2 device classes: Device class M: Vendor self-certification to the requirements for MIL-STD-883 compliant, non-JAN Class Level B microcircuits in accordance with MIL-PRF-38535, Appendix A. Device class Q or V: Certification and qualification to MIL-PRF-38535. Would class M be considered B-1 with a quality factor of 2 and class Q or V be considered B with a quality factor of 1?


Reply:

Subject: Quality Factors
Reply Posted by: Bruce Dudley (bdudley@alionscience.com )
Organization: Reliability Analysis Center
Date Posted: Wed Apr 12 14:27:58 US/Eastern 2000
Message:
Both of the classes shown in your question could be considered as "B" level as the information that we are seeing indicates that screening of microcircuits is adding very little to the overall quality of industrial high reliability grade devices. In the last ten years, the quality levels of microcircuits has risen without the need for any extra testing, in fact some extra testing actually decreases the reliability by adding unneeded stresses. In our new PRISM model for microcircuits, we are using a process grading function that evaluates the device manufacturer's process along with the assembler processes. Extra testing does not factor very high in this assessment. Consideration of use of ISO-9000 proceedures and Statistical Process Control methodology have been found to be more important in developing overall part quality.


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