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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: Per Jonsson (per.jonsson@boforsdefence.se )
Organization:Bofors Defence
Date posted: Mon Aug 16 8:31:11 US/Eastern 2004
Subject: Long term storage of electronics
Message:
I have a question about electronics in general and circuit boards in particular. Is there research done about how long it is possible to store electronic devices? Does anything happen if you store a cicuit for more than 20 years or is there a good chanse that everything works allright even after so many years. Is there any actions to take during storage to decrease the risk of failure? Thanks for any help on the subject! /Per


Reply:

Subject: Long Term Sorage of Electronics
Reply Posted by: Ken
Date Posted: Thu Aug 19 8:52:48 US/Eastern 2004
Message:
Check in the RAC Toolbox, there are two references for dormant/storage of devices. One is for failure rate conversion and the other is for dormant failure mechanisms. The later shows that temperature and humidity are the predominate accelerators for items in a dormant state. Thus temperature and humidity control are key. After 20 years, obsolescence may be as big a concern as dormant failures. A good reference for degradation is “Electromigration and Electronic Device Degradation” authored by Christou and published by John Wiley & Sons.


Reply:

Subject: one more question
Reply Posted by: Per Jonsson (per.jonsson@boforsdefence.se )
Date Posted: Fri Aug 27 3:18:40 US/Eastern 2004
Message:
Thanks Ken, especially the conversion factors was interesting for me. I have also been reading in the "Reliability Toolkit: Commercial Practices Edition" but I still can´t figure out some details about the conversion factors. I don´t understand if ground active to ground passive means that the stuff simply is not used or if it is put in a store with controlled environment? /Per


Reply:

Subject: Storage Reliability
Reply Posted by: BWD (bdudley@alionscience.com )
Organization: RAC
Date Posted: Tue Aug 31 10:06:45 US/Eastern 2004
Message:
The Reliability Toolkit translation factors for dormancy were developed for short term situations. The failure rates were based on data collected many years ago and covers short storage times. The purpose of the translation was to enable an analyst to make a rapid check based on active failure rates to see if the proposed design could meet the needs for short off cycles such as power off for the weekend. Long term assessments need to be analyzed part by part as corrosion is the main problem area. The best assessment for long term is to perform accelerated testing to see if problem areas exist.


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