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November 2000

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Subject:
From:
David Fish <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 29 Nov 2000 04:10:24 -0800
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Guenter:  Should the rate of temperature decrease be the same as the rate of temperature increase that you quote?  Dave Fish

Guenter Grossmann wrote:

> David
>
> This translates to nothing because:
> - We don't know the temperature swing in your application.
> - 5 min. dwell time at -55 degC is as much as nothing, thus no strain is induced.
> - 10 degC / min is very fast below 20 degC and you are very likely to activate degradation mechanisms that do not occur in reality.
>
> Running a test
> - 0 / 120 degC
> - 4 degC / min up to 20 degC
> - 10 degC / min above 20 degC
> - dwell time of 5 min at 120 degC
> - dwell time 30 min at 0 degC
>
> would give in my opinion the possibility for a rough estimate of the lifetime in a realtime environment by
>
> Nfr = Nft ( dTt  / dTr )exp1.7
>
> Nfr = Number of cycles to failure reality
> Nft = Number of cycles to failure test
> dTr = Temperature swing reality
> dTt = Temperature swing test
>
> Best regards
>
> Guenter
>
> Guenter Grossmann
> Swiss Federal Institute for Materials Testing and Research EMPA
> Centre for Reliability
> 8600 Duebendorf
> Switzerland
>
> Phone: xx41 1 823 4279
> Fax :      xx41 1823 4054
> mail:     [log in to unmask]
>
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