[SI-LIST] Re: Reset problem with power supply

weirsi@xxxxxxxxxx said:
> Electrolytic caps come along with some engineering requirements.  The
> first is long term product life:  electrolytics have a typical shelf
> life of 5-10 years for cheap to very high quality.  This is a function
>  primarily of the seals.  However it is not that unusual to find a box
>  with large body computer grade electrolytics going for more than 20
> years.  The big issues: are  initial conditioning, adequate
> temperature,  voltage derating, and absolutely : NO EXPOSURE TO
> HALOGENS.  A 10 year  life is readily attainable, and with a lot of
> derating 20 years can be  had in large body parts.  Miniatures are
> really constrained to about 10  years no matter what is done.
> Consumer products contain only miniatures  these days, and are so
> fiercely price sensitive that no one pays for the  kind of derating
> needed to see long service lives.  As a result, the  electrolytics
> rank #1 to #2 for failure rates in consumer electronics  ahead or
> behind of the power semiconductors.

Thanks.

I assume the halogens mostly come from cleaning.  Has that been solved by the 
save-the-ozone efforts?  Do assembly houses know about that?  Is it in the 
data sheets?

I don't remember hearing it before, but I could easily have not paid 
attention.  I just scanned one handy data sheet.  I didn't see anything about 
cleaning.  It's probably buried off in an app note or such.

I did see that they are only rated for 2000 hours.  I hadn't paid much 
attention to that before.  That's under 3 months at 24/7.  Ouch.  Thanks for 
the heads up.  I'll have to find the temperature re-rating specs.  Sigh.


What do military or other high reliability folks do?

I expect a lot of military gear is still in service after 10 years.  (B-52s 
are still flying.)  Does the electronics turn over fast enough to avoid this 
problem?




-- 
These are my opinions, not necessarily my employer's.  I hate spam.



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