Re: gEDA-user: electrolytic capacitors

[Peter Clifton <pcjc2@xxxxxxxxx>]

On Fri, 2008-12-26 at 21:00 -0500, gene wrote:
> What does it mean when manufactures specify 'Endurance @ temp' or 'life 
> time @ temp'?  For example, one company claims:
> Endurance : 105 C 1000 h to 5000h
> Then they further state that after testing at 105C with maximum ripple 
> current applied, that when the part is cooled to 20C, it will then meet 
> original specs.

It will still have had its life-time shortened.

The spec you quote above, AIUI, means that after somewhere between 1000
and 5000 hours of operation at 105 degrees centigrade, the cap (as
measured at 20 degrees) will be outside of its quoted specifications.

I can't remember the exact numbers, but derating to lower temperatures
has a stupid factor of lifetime increase. It might even be as much as
double the life-time for every 10 degrees drop in working temperature.

I guess that merely being at elevated temperature is also lifetime
degrading. You circuit wouldn't need to be on for the electrolyte to be
degrading.

-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)



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