Re: Cap C-V test

On 04/05/2025 16:40, john larkin wrote:

On Sun, 4 May 2025 15:11:26 +0100, John R Walliker
<jrwalliker@gmail.com> wrote:
 

On 04/05/2025 03:17, john larkin wrote:

On Sun, 4 May 2025 02:11:47 +0200, Lasse Langwadt <llc@fonz.dk> wrote:
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On 5/1/25 22:09, john larkin wrote:

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https://www.dropbox.com/scl/fi/a7425c69k3w8wx8tqjpq5/X110_CV_Test.jpg?rlkey=pc3c0b12ncswv6ajrn148stdk&raw=1
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The DUT is a Venkel 2.2 uF 100v 1812-size ceramic cap. I need to run
it at 48 volts. 0.8 uF is probably OK. I have room on my board so I
guess I'll add another cap in parallel.

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or in series, I believe there are some automotive standards that call
for that on high current lines because ceramics tend to fail short with
mechanical stress
>

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Two of those caps in series would make about half the capacitance of
two in parallel, but ESR and ESL would suffer by 4:1.
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We don't see many ceramic cap failures. Our worst parts are "sealed"
relays that actually aren't. Some switches, too.
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We don't use surface-mount film caps. They are awful.

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Even the PPS type?
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John

 I haven't tried all the dielectrics, but the surface-mount film caps
that we have used tend to delaminate and trap wash water. I use the
radial leaded epoxy-glopped parts. We actually don't use many film
caps lately.
 

I have found them to be better than any of the alternatives. In
particular, they don't melt during soldering and are quite
stable.  Have a look.
John