In message
<[email protected]>, dated
Mon, 20 Oct 2014, Gary McInturff <[email protected]> writes:
John you?re going to be wrong no matter what you do ? depending on who
you are talking to.
Very likely.
The 10 degree rise = twice the failure estimation is based on the
Arrhenius model ? which is actually a chemical model, but widely
applied to electronicsÂ
It's applicable if the failure mechanism is in fact chemical - thermal
degradation, ion migration, chemical reaction....
So as a rule of thumb you can state you acceleration factor is based on
that ? assuming that you product is displaying a normal (Gaussian)
random mode failure mechanism and not infant or wear-out modes.
Arrhenius is really a wear-out mode, and there have been cases (loss of
vac in tubes due to lead-outs, purple plague?) where the 'wear out' was
so swift as to cause infant failures. I think those distinctions are
valid only 'after the event', when you can count the failures by type in
the early and late sections of the failure history curve.
Testing at low (if necessary), normal and high temperature is the only
way to get dependable results for a given product. Especially if it
contains elastomers that can cause failure.
--
OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk
Quid faciamus nisi sit?
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
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