For the tiny small uF caps, why do they use electrolytics?

[PCBONEZ]

For the tiny 0.1uF-15uF range caps, why do they use electrolytics at all?
- Why don't they just use ceramics? [Which don't dry out.]

Brought up by larrymoencurly here:
https://www.badcaps.net/forum/showpo...2&postcount=13
I've been wondering the same thing and don't have a solid answer.
-
A good enough question to deserve it's own thread so I moved it here.
.

[Per Hansson]

Re: For the tiny small uF caps, why do they use electrolytics?

Could it be cost related?
I'm not thinking of prices for a couple hundred caps

But say you want 10 million caps for a production run, could you get a better price on electrolytics than ceramics?

[PCBONEZ]

Re: For the tiny small uF caps, why do they use electrolytics?

I think you probably nailed it.
- I've always thought of ceramics as being cheaper but when the uF is the same as the lytic they just aren't.

Looking at 1.0uF, Radial, 50v, +/-20% I found this:
[Ceramics don't seem to have a 105c so I looked at 85c and 125c.]
-
Cheap end of scale Ceramic [85c] -> $0.17360 each in qty 5000.
http://search.digikey.com/scripts/Dk...me=478-2479-ND
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Cheap end of scale Ceramic [125c] -> around $0.60 each in 1000's quanities.
-
Nuther note is the 1.0uF Ceramics leads are spaced 5mm or more, though with their shape they probably don't take much more PCB space.

To compare, 1.0uF Panny FC - $0.04600 in qty 5000.
http://search.digikey.com/scripts/Dk...name=P10312-ND

So Ceramics are at least 3x more expensive even in bulk.
I checked at 0.33uF too and it was the same.
.

[PCBONEZ]

Re: For the tiny small uF caps, why do they use electrolytics?

So NOW the questions are:

Since they presumably only use lytics in those apps to save $$$$,,,,
,,,, are, and if so when are, ceramics a better choice for repairs?

I probably knew this years ago, but my bung leaks.
.

[Toasty]

Re: For the tiny small uF caps, why do they use electrolytics?

Maybe this will help?:

http://my.execpc.com/~endlr/

Or maybe it muddies the waters...?

[Harvey]

Re: For the tiny small uF caps, why do they use electrolytics?

I always thought that

High-K ceramics (Class 2 and higher) have poor electrical properties, which are highly dependent on temperature, voltage, and frequency, plus a significant aging rate.

was the main reason.

[Wizard]

Re: For the tiny small uF caps, why do they use electrolytics?

Correct. Ceramics is regarded as loose capacitance and varies in tolerance and temp, humidity as well.

If you want precision and more stable, poly is way to go but bulk precludes these for need for space reasons.

And bit of resistance in the electrolytic/polymer capacitors is desireable in many applications as well.

Cheers, Wizard

[larrymoencurly]

Re: For the tiny small uF caps, why do they use electrolytics?

Maybe this will help?:

http://my.execpc.com/~endlr/

Or maybe it muddies the waters...?

The FAQ there says: "I have no idea why someone would use a 0.1 uF electrolytic capacitor however."

Of course in my Antec SmartPower IIs, those caps just happen to be Fuhjyyus.

[everell]

Re: For the tiny small uF caps, why do they use electrolytics?

The FAQ there says: "I have no idea why someone would use a 0.1 uF electrolytic capacitor however."

Of course in my Antec SmartPower IIs, those caps just happen to be Fuhjyyus.

My Antec SmartPower SP350 and SP400 also have Fuhjyyu .1 uF (and .22 uF) capacitors. So what did you do about this problem in your SmartPower II?

[PCBONEZ]

Re: For the tiny small uF caps, why do they use electrolytics?

Those are usually on the fan board and from unit to unit I sometimes see ceramic disc caps there.

For under 10uF I usually just get these in 50v.
http://www.panasonic.com/industrial/...a_kg_02_02.pdf
They are mostly 4mm so fit anywhere and [under 10uF] they have better ripple than LXZ, FC, PW and all of those.

Digikey carries them.