[SI-LIST] Re: Reset problem with power supply
- From: Hal Murray <hmurray@xxxxxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Sun, 07 Dec 2008 02:19:34 -0800
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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