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Date: | Wed, 17 Apr 1996 14:13:22 +0400 (EDT) |
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Gary, it has been a while since I worked on capacitors, but here are my
comments.
I have not heard of tantalum capacitors failing as a result of current
surges. An aluminized paper capacitor supplier once showed me films of
plastic film capacitors coming apart during surges (of course, his paper
components did not fail under such stress). Tantalums do not self clear
if an internal short develops. The part is destroyed. They can't
toerate any reverse voltage, so have to be installed with proper polarity.
Are aluminum electrolytics less stable with temperature? I have not
heard anyone express such a concern before. They do have a tendency to
dry out and become open circuit under temperature stress. Long-lived Al
electrolytics have low-loss electrolytes and superior paper, as compared
with the more pedestrian variety. By less stable, do you mean their
capacitance value changes with temperature over a short time, or that
they dry out, over a relatively long time?
Lou Hart
.
On Tue, 16 Apr 1996, Gary Peterson wrote:
> Does anyone have an opinion, comments or data to support a rumor I heard?
>
> I'm told that tantalum caps can fail shorted if required to supply a current
> surge. To prevent this failure aluminum electrolytics are preferred on digital
> boards.
>
> I thought Aluminum electrolytics weren't very stable in capacitance over temp
> and were not preferred to tantalum for that reason as well as size (more
> Capacitance per volume in Ta than Al).
>
> Gary P.
> ---
> Gary D. Peterson
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