Forum: Reliability & Maintainability Questions and Answers
Posted by: Rob (firstname.lastname@example.org )
Date posted: Thu Jul 27 15:10:25 US/Eastern 2000
Subject: IR Soldering
I'm looking for information on IR (Infrared) Soldering, both process and reliability data (failure rates, or failure modes/mechanisms).
Posted by: S. White (email@example.com )
Organization:Zellweger Analytics Ltd
Date posted: Thu Jul 27 7:30:35 US/Eastern 2000
Subject: Ceramic chip capacitors generic failure rate
How come ceramic chip capacitors have a generic failure rate that has become worse in the Notice 2 re-edition of MIL-HDBK-217?
Data from MIL-HDBK-217 Appendix A-8 shows that in a Gf environment failure rate = 0.0022 for the first edition and Notice 1 but Notice 2 shows a rise to 0.053. Aluminium Oxide capacitors have also changed 0.061 fpmh in the first and Notice 1 editions but a radical improvement to 0.019 in Notice 2. Is this a mistake in Notice 2? I would have expected Ceramic Chip capacitors to be far more reliable than more complicated to make Aluminium Oxides.
Posted by:Rob (firstname.lastname@example.org )
Organization:Design Analytx Int'l.
Date posted: Wed Jul 26 17:04:27 US/Eastern 2000
Subject: Availability Calculations
Problem: In modeling for Operational Availability (Ao) in a single redundant system, when a failure occurs the redundant spare switches in after fifteen seconds. I want to model for the probability of a second failure while the first is being switched/active maintenance begins. The latter begins after the system is restored by the redundant spare.
What happens to my availability during the period of active repair? It is my contention that the Availability equation should be replaced by System Reliability equation once the failed unit is replaced by the redundant spare, thereby removing any further redundancy for any future event until a working spare is put in place. Where should I go to research further. I have most texts and they don't treat this subject in enough detail to satisfy my need for in-depth details.
Posted by: Bob
Date posted: Fri Jul 14 6:56:42 US/Eastern 2000
Subject: Component reliability calculation
If a supplier claims that the number of failures observed for his product is 0.009% testing for 1000 hours at 125 deg C and then claims this results in an MTBF of over 11 million hours, how do I determine (i) the confidence limits on this figure, (ii) the calculated MTBF for (my) specified confidence limits and (iii) approximate reliability at specified temperatures?
Or is there insuffucient data here to proceed? Could someone point me to a useful source of information on how to perform the above type of calculations.
Posted by: Julien Nico (JNico@zodiac-group.com )
Organization:Aérazur - Zodiac Group
Date posted: Fri Jul 7 12:31:46 US/Eastern 2000
Subject: Reliability data for zip fastener
I'm trying to find some reliability data for a zip fastener (a zipper). Unfortunately, nothing is included in the NPRD 95.
I will really appreciate if someone can give me some data or a means to estimate MTBF for this kind of applications Many thanks