Forum: Reliability & Maintainability Questions and Answers

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Posted by: Per Jonsson
Date posted: Fri Apr 22 5:21:28 US/Eastern 2005
Subject: prediction - books, software or what..
Message:
What is the best way of predicting failure rate of a component? I know there are some different kinds of software but are those sufficient or do I need more tools?
When it comes to software there are also an economical matter to consider before an investment. How much do one have to pay for a good tool by the way? Thanks for any help on the matter! P.S. This forum is a great thing.

Replies:
Credible reliability prediction
Larry George Sun Apr 24 13:26:33 US/Eastern 2005

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Posted by: IC
Date posted: Wed Apr 20 5:13:06 US/Eastern 2005
Subject: Software reliability
Message:
Can anybody point me in the direction of any good sources of information in relation to undertaking the reliability analysis for software.
Thanks In advance.

Replies:
Software Reliability
bwd Wed Apr 20 9:23:06 US/Eastern 2005

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Posted by: Rushabh J (rushabh.jariwala@gmail.com )
Date posted: Wed Mar 30 8:26:11 US/Eastern 2005
Subject: How to estimate IC Failure Rate in IDLE Mode
Message:
I am trying to predict the reliability of electronics control. The control is programmed such a way that 5 ICs would be active every 0.5 Sec. for 0.0012 Sec. and then it would go to it's sleep mode or idle mode. Main point is we are not switching it off but just keeping it in IDLE / SLEEP mode. For all this ICs I got the failure rate data in the working condition of IC. We got the Reliability Test Report conducted for 1000 Hrs.
I tried in RELEX as well as PRISM to find any option which takes care of standby/IDLE/Sleep mode failure rates, but it gives option to enter the mission profile time against different temperature. But I believe entering different temperature is not the solution . Because Ideally in stand by more failrue rate would change. My question is how to calculate the total Reliability. In the IDLE/Sleep mode time what should we consider the failure rate. Thanking in Anticipation.

Replies:
Quiescent or Sleep Failure Modes
bwd Thu Mar 31 10:39:48 US/Eastern 2005

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Posted by: Ankur (ankur@indogroup.net )
Organization:Indo
Date posted: Fri Mar 25 11:13:20 US/Eastern 2005
Subject: Failure Rates
Message:
I am doing FMEA analysise of a benchmark power supply as for trial. For this I have to calculate RPN which is (RPN= SEVERITY x PROBABILITY OF FAILURE X DETECTION). I have found out the failure rates of each components using prism. That gives me failures/million hr. How can relate this failure rate with the severity or prbability of occurence. Can you suggest on this. I'll be really kind
if you can help,

Replies:
Risk Priority Numbers
bwd Wed Mar 30 11:58:37 US/Eastern 2005

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Posted by: Ümit BÜLBÜL (ubulbul@aselsan.com.tr )
Organization:aselsan inc.
Date posted: Mon Mar 14 5:02:00 US/Eastern 2005
Subject: MIL-STD-217F
Message:
Dear Sirs,
I am an hardware design engineer in a firm called Aselsan Inc, mostly serving in military areas. I have a general question related to the applicability and validity of MIL-STD-217F as regards the new technological progress taken in electronic/electrical components. Could you share your thoughts about my comments(or questions) given below and suggest alternative methods if possible : Question_1) We design many products consisting mostly MOSFETs, ceramic capacitors, opto-couplers etc. But according to MIL-STD-217F BJT transistors seem to be superior than MOSFETs. But as you know MOSFET technology has improved for the past years and I think MOSFETSs now are more rugged than BJTs (if you take necessary consideration against ESD disadvantage of MOSFETs). Also according to MIL-STD-217F chip ceramic capacitors seem to be worse than chip tantalum capacitors. Apart from the cracking problems observed in ceramic capacitor I think that ceramics are better than tantalum. Question_2) If MIL-STD-217F standard is a good approximation to component failure rates what is the reason of the big difference between MIL-STD-217F Notice1 and Notice2 regarding failure rate equations and different coefficients suggested in these revisions? Question_3) According to MIL-STD-217F to get a good MTBF data for a complex system (e.g. tanks, gun systems etc.) we should use at least JANXXX type components which are becoming more difficult to find and even in case we find, it is nearly impossible to satisfy the other system criteria if we use JANXXX (because JANXXX type components are somehow old and not competetive regarding packet size, efficiency and other advantages of todays' high technology components. What is your suggestion on this ? Question_4) For the MTBF data of mechanical components which standard should we use for military projects? In summary in our military designs we have some difficulty to satisfy the MIL-STD-217F Notice2 specifications coming from customer side. Therefore your comments are valuable for us to reevaluate these requirements and provide alternative but reasonable solutions to MTBF requirements of our customers? best regards, Ümit BÜLBÜL Electronics Eng.

Replies:
MIL-HDBK-217
bwd Tue Mar 15 14:59:33 US/Eastern 2005

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