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  #1  
Old May 19th, 2011, 01:02 AM
Corono Corono is offline
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Default IEC TR 62380 Reliability Prediction: Overstress

Hi

I need some help for a reliability prediction with IEC TR 62380 (or RDF 2000, that's the same). In the reliability calculation of some devices like diodes and ICs, there is a factor "lambda_{overstress}". Can somebody explain me what this factor means in detail and for which devices I should use it and for which not? This factor is quite large compared to the rest of the FIT-rate, so it is important to know how to use it. I think it has something to do with protection, but I'm not sure.

Best

Corono
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  #2  
Old May 24th, 2011, 04:50 PM
David David is offline
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Default Re: IEC TR 62380 Reliability Prediction: Overstress

Hi Corono,

Welcome to the forum!

According to IEC 62380, lambda_overstress is “a failure rate considered to be constant, due to external electrical influences. This failure rate depends on the electrical environment of the equipment, given that the equipment does have primary or secondary protections, depending on the state of the art of the period observed.” The failure rate is used for active components, i.e., integrated circuits, low power and power diodes, low power and power transistors, and optocouplers. Typical values of lambda_overstress range from 10 to 100 FIT for interface circuits. Lambda_overstress is zero for non-interface circuits. IEC 62380 defines interface circuits as “circuits or devices connecting the equipment to the outside environment.”

I hope this helps.
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David
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  #3  
Old May 25th, 2011, 12:46 AM
Corono Corono is offline
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Default Re: IEC TR 62380 Reliability Prediction: Overstress

Hi David

Thank you for the answer.
So for example, I need this value for surge protection diodes or for Varistors at the input, is this correct?

And if I have a normal AC-DC-Converter without any protection, should I use this lambda for each device in the current path, e.g. MOSFETs, because all parts are then connected to the environment?

Best wishes

Corono
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