On 09/28/2015 10:36 AM, Shoppa, Tim wrote:
These are the small 0.01uF or smaller capacitors with
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.