Small glass capacitors polarized?

Chuck Guzis cclist at
Mon Sep 28 13:03:59 CDT 2015

On 09/28/2015 10:36 AM, Shoppa, Tim wrote:
> These are the small 0.01uF or smaller capacitors with transparent
> edges and you can see foil in the innards? If so, I think you are
> talking about "polystyrene capacitors". Yes, they were extremely
> popular in UK/EU for at-chip decoupling capacitors in the 1970's and
> 80's. They are not polarized.
> I'm not sure why polystyrenes were so popular for bypass/decoupling
> in EU and not so popular on this side of the pond.  Here in the US we
> were more likely to see polystyrene in audio filtering/coupling
> locations where the cheapest ceramics had odd piezo properties and
> low leakage of polystyrenes were desirable. I do remember seeing
> polystyrene bypass capacitors on at least a few DEC boards of the
> 70's so they did make some inroads.
> There are real glass capacitors used where zero leakage and zero
> soakage are uber-concerns.

Ah, now I understand what's being talked about.  "Bypass"  or even 
"decoupling" in the query would have sent me down the right path.  Were 
not for "small", I might have looked at some vacuum capacitors also.

Yeah, I've got a bunch of boards with those small glass ones in that 
application. My suspicion was that they were preferred in applications 
were soldering temps were likely to be very high.

Then there were the exploding Rifa caps used for AC line filters.


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