Forum: Reliability & Maintainability Questions and Answers

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Posted by: Mok Yin Liong (myinlion@dso.org.sg )
Organization:Defence Science Organization National Laboratories
Date posted: Mon Feb 22 21:03:50 US/Eastern 1999
Subject: PEM Reliability Modelling
Message:
I have some questions regarding the PEM reliability model given in the RAC publication "Reliable Application of PEM" :
i. When we divide the failure rate obtained from this model (in failures per million calendar hrs) by the duty cycle (power on time over total time), we get the equivalent operating failure rate (in failures per million operating hrs). This PEM operating failure can then be combined (=added?) with that obtained through Mil-Hbk-217 for other components. By doing so, are we assuming that PEM has a much higher non-operating failure rate than other components (since we are ignoring the non-operating failure rate of the other components)? ii. If we assume a duty cycle of 100% (i.e. the PEM is powered up all the time), can we treat the failure rate obtained from the RAC reliability model as the operating failure rate? Does this violate any underlying assumptions of the RAC PEM reliability model? iii. Based on the limited information given for the RAC PEM model, it appeared that ESD/EOS failures are omitted. Should an additional term be added to this model to take care of ESD/EOS failures? iv. Should there be a different base failure rate for microprocessors and memory devices? Data from some publications indicate that microprocessors have a much higher failure rate than memory devices (up to ten times). Thank you.

Replies:
RAC PEM Reliability Model
Bill Denson Mon Apr 19 11:22:43 US/Eastern 1999

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Posted by: Joel Mandel (Mendel@teledata.co.il )
Organization:ADC Teledata
Date posted: Sun Feb 14 2:14:33 US/Eastern 1999
Subject: Commercial components vrs industrial
Message:
Recently I have been hearing there is no difference between commercial component production lines and industrial
component production the only difference is the testing at the end of the line. Is thia true ?if so what risk is it to use a commercial componet for industrial temperatures?

Replies: (list all replies)
Commercial Components
Bruce Dudley Tue Feb 16 14:38:45 US/Eastern 1999
Com. Vs. Industrial Components
Mark Mobley Tue Mar 23 11:33:33 US/Eastern 1999

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Posted by: Bob Moore (bobbybase@darley.freeserve.co.uk )
Date posted: Wed Feb 10 16:53:45 US/Eastern 1999
Subject: Non approved components
Message:
How do I go about identifying a list of component types that are non approved for Air Force or Naval use, eg wet tantalum capacitors or aluminium electrolytic capacitors?
Are there any websites that have this information?

Replies:
Non-Approve Parts List
Bruce Dudley Thu Feb 11 12:50:55 US/Eastern 1999

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Posted by: Christophe Crocombette (christophe.crocombette@edf.fr )
Organization:Electricite de France
Date posted: Tue Feb 9 7:42:22 US/Eastern 1999
Subject: Reliability of electronic parts and long time storage
Message:
My company is being storing some obsolete parts for maintenance activities.
I am looking for any information about the subject of electronic parts and long time storage : - failure mecanisms, - state of art of long time storage conditions in the industry - etc. If you cope with the same problem, please let me know what your approach is... I have also some specific questions : Is dry nitrogen with regulated temperature (systematically) used for long time storage ? Are there specific recommandations about long time storage of electronic parts ? Is there a predictive method to calculate the reliability during long time storage ? Thank you ! Chris

Replies: (list all replies)
Storage Reliability
Bruce Dudley Mon Feb 15 13:47:37 US/Eastern 1999
Storage
Mark Mobley Tue Mar 23 11:48:45 US/Eastern 1999

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Posted by: Bob Bouvier (bbouvier@csc.com )
Organization:BMPCOE (CSC)
Date posted: Mon Feb 8 12:48:58 US/Eastern 1999
Subject: Parts Derating in NAVSEA TE000-AB-GTP-010
Message:
I'm interested in your opinions on the NAVSEA Parts Requirements document and, in particular, on what it has on parts derating. I am not familiar with RAC materials on the subject so I'd like to know how the NAVSEA info. compares with what RAC puts out in terms of scope, details, etc. but in a general way, please. Is there redundancy? Is there anything in it that could be removed? What's missing? Any and all opinions are welcome. Thanks very much.

Replies:
Derating Criteria
Bruce Dudley Thu Feb 11 15:42:17 US/Eastern 1999

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