[Soekris] Solid state capacitors

[Mats Lundqvist]

Thanks for the info, it'll be very useful when I have low-power low-temp
project.

Any suggestions to hardware similar to the soekris to use? With through-hole
components.

Then again, where on earth are you supposed to get a hold of a mini-pci wlan
card that can take the cold as well? I can imagine that to be a lot harder,
and more expensive.

">ahaa....I did not know that, I always figured the caps to burst from the
>electrolyte expanding when frozen.

I've never seen that."

Have you seen them work in that kind of environment? I mean -10 to -25C or
similar.
They must've degraded or break when exposed to that...?


2007/1/11, Poul-Henning Kamp <phk at phk.freebsd.dk>:
>
> In message <45d561bc0701110843h7cfed9a5l71b5a735c413b7f7 at mail.gmail.com>,
> "Mats
> Lundqvist" writes:
>
> >ahaa....I did not know that, I always figured the caps to burst from the
> >electrolyte expanding when frozen.
>
> I've never seen that.
>
> >But isn't thermal stress only an issue when it's in rapid concession?
>
> No.
>
> Silicon has a thermal expansion of approx 4.7e-6/K, so a silicon
> chip 5 mm square, will be 23.5 nanometer shorter for each degree
> the temperature drops.
>
> Epoxy is generally in the 40 to 50e-6/K range, so the 5mm epoxy the
> silicon chip is bonded to on the other hand will be 235 nanometer
> shorter per degree.
>
> Drop the temperature 40C and the differential is 8.5 micrometer
> and the resulting stress is quite sizeable.
>
> It's much less of an issue when you raise the temperature, because
> most plastics get softer with rising temperature.
>
> Surface mounted devices suffer from the same problem relative to
> the PCB (this is belived to be a major factor in the decreased
> reliability in temperature-stress environments).
>
> So if you want cold-water electronics, you want through-hole
> components (because the leads can bend and absorb the stresses
> and you want ceramic chips.
>
>
>
> --
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by
> incompetence.
>



-- 
Vänliga Hälsningar
Mats Lundqvist
Office Data Dalarna
+4670-513 73 87 (privat)
+4670-606 66 11 (jobb)
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