RMQSI Answers ForumCategory: Handbooks and StandardsQuality factor for Resistors
Guest Forum User asked 20 years ago

Can some body help me out please? I am working for resistor Reliability prediction methods. I am following MIL-HDBK 217F. In the Reliabiltiy Prediction Calculation it is mentioned that Quality Factors for resistor as S,R,P,M. Can you please give some idea about these abbreviations.

Thanks in advance.

9 Answers
Guest Forum User answered 20 years ago

You should review MIL-PRF 199 the resistor military specification for specific definitions. In general the letters apply to the screening or life tests that are performed on the military designated parts. S is the best and M is the least. These quality factors only apply to military devices with three letter designations. For commercial parts, MIL-HDBK-217 says that you must apply a factor of 10 to the analysis. Since MIL-HDBK-217 is obsolete, you should consider the use of a more up to date analysis technique such as PRISM, as you will find that the resistor and capacitor analysis is going to dominate the end result and give you a false or pessimistic picture of the hardware.

ajaykumar answered 15 years ago

Dear Sir,
I would like to know about the Screening or life test.
Can you please expain about Screening and how to do ?

I am doing reliability prediction using MIL-HDBK-217FN2. For Commercial components the Quality factor is 10. if we use the value of 10 for resistors the failure rate will be high. is there any other chance to improve the quality factor for commercial parts?

is it possible to convert commercial to screening?

Please help me.


smorris answered 15 years ago

The failure rate designation (M, P, R, S) identifies the failure rate level for which the resistor is qualified (at 50 percent rated wattage).

Failure-rate level Failure rate
designation percent/1,000 hours
M……….. 1.0
P……….. 0.1
R……….. 0.01
S……….. 0.001

Since commercial devices are not qualified to these levels, you should not use them unless you have other experience data to base your “adjustments” on.

ajaykumar answered 15 years ago

Thank you very much.


williamsmith answered 14 years ago

its sounds good