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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: Dianne Keating (keatingd@engr.mun.ca )
Date posted: Wed Jul 4 12:25:03 US/Eastern 2001
Subject: Quality Level
Message:
I am using RELEX to preform some reliability analysis and I was just wondering if someone could tell me how to determine the quality level for capacitors, resistors and diodes. For example for a ceramic chip capacitor you can select from D, C, S, R, P, M, L. What do these letters stand for? And how do I determine which one to use? Thanks!


Reply:

Subject: Quality Level
Reply Posted by: Vaishali Hegde (vaishali.hegde@relexsoftware.com )
Organization: Relex Software Corporation
Date Posted: Thu Jul 5 11:16:28 US/Eastern 2001
Message:
D, C, S, R, P, M, L are quality levels from MIL-HDBK-217FN2. You can go to http://www.dscc.dla.mil/Downloads/MilSpec/Docs/MIL-PRF-55681/prf55681.pdf to get information on definitions of these quality levels. Page 14-17 has the information you are looking for.


Reply:

Subject: Quality Level
Reply Posted by: Paul Jaworski (pjaworski@alionscience.com )
Organization: Reliability Analysis Center
Date Posted: Thu Jul 5 12:31:52 US/Eastern 2001
Message:
These letters are quality levels with an associated quality factors from MIL-HDBK-217 rev F n. 2, pg. 10.1 and are based on known quality levels for capacitors. For military approved parts the quality level is stated within the part number. Refer to the appropriate military standard for part marking descriptions. If you are using a commercial part, use the 1.0 factor or non-established reliability 3.0. There other quality levels for resistors and diodes. Enclosed is the quality table from MIL-HDBK-217 Quality Factor Established Reliability Styles D…………………………………………0.001 C…………………………………………0.01 S,B……………………………………0.03 R…………………………………………0.1 P…………………………………………0.3 M…………………………………………1.0 L…………………………………………1.5 Non-Established Reliability…………………….3.0 Commercial or Unknown Screening Level……10.0 NOTE: Established reliability styles are failure rate graded (D, C, S, etc.) based on life testing defined in the applicable military device Specification. This category usually applies only to three-letter styles with an "R" suffix. You can attain a copy of MIL-HDBK-217 at: http://stinet.dtic.mil/str/dodiss4_fields.html For future reference on RELEX you can go to RELEX at http://www.relexsoftware.com/feedback.asp or call (724) 836-8800.


Reply:

Subject: Quality factors fro Chip Capacitors
Reply Posted by: Art Stone (Arthur.Stone@L-3Com.com )
Organization: L-3 Communications
Date Posted: Thu Sep 12 16:07:46 US/Eastern 2002
Message:
In reading the response to this question, I notice that you state, "If you are using a commercial part, use 1.0 factor or non-established reliability 3.0" But the table you enclose, the PiQ Table for Capacitors from MIL-HDBK-217FN2, indicates that for commercial capacitors or capacitors with an unknown level screening level of screening, the PiQ factor should be 10. Which PiQ is appropriate for a capacitor bought to a vendor's part number but where the part number is not tied to an MIL-PRF or MIL-C document (not a QML or QPL part).


Reply:

Subject: Capacitpor Quality
Reply Posted by: b.w.dudley (bdudley@alionscience.com )
Organization: RAC
Date Posted: Mon Sep 16 9:41:49 US/Eastern 2002
Message:
Using MIL-HDBK-217 as the reference source, the quality level for commercial capacitors bought to a vendor part number would be 10. The response that you are referencing from Paul Jaworski has a typographical error. The commercial reliability factor referenced should be 10 not 1.0 as shown.


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