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From: Winfield Hill
Subject: Re: Electronic News story: Leaky capacitors shorting circuits; problem spreads
Date: 31 Oct 2002 17:43:35 -0800
Organization: Rowland Institute
References: <email@example.com> <firstname.lastname@example.org>
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>Winfield Hill wrote ...
>> For me the lesson is to be very careful when selecting low-esr
>> electrolytics for use in high-current switching supplies. The
>> mobo manufacturers used capacitors that pushed the envelope too
>> far and were smaller than was wise, 8mm dia instead of the more
>> common 10mm size.
> Win, I can't argue with you on design criteria (it would be blatantly
> presumtous of me to even attempt to do so) but I have found the rotten
> little buggers failing all over the place irrespective of what and
> where they are used - they are in the "good idea at the time"
> They first started surfacing (no pun intented) about 8 years ago in
> video camcorders - which makes sense considering the need for
> miniatureisation(sp) and was probably exacerbated by our climatic
> conditions (ie hot summers) - as the boards are invariably multilayer
> thru hole plated the corrosive effects usually totalled the board
> rendering it uneconomical to repair.
Can you detail what you mean by "they"? There's been a steady increase
in the capacitance/volume ratio for decades. Most of the new-design
small high-value capacitors I select these days are 12.5mm (0.5-inch)
dia, rather than the even-smaller 10mm caps the news story says are OK
(they condemn the 8mm parts). What is a guiding characteristic of the
parts in which you've seen failures over the last 8 years? If it's all
"smaller" parts, how could we to use that as a point for judgement?
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