[kevin gilmore]

quote
What is considered the ultimate dielectric for a capacitor ?

There is only one real answer. A pure vacuum glass cap.
Nothing else comes close, not even teflon.

I use teflon boards for some of the very high frequency
work i do.

teflon is non hygroscopic. That means it will not retain or
attract water. Also because of the way it is made, the thickness
can be very accurately controlled. For microwave striplines
this is of supreme importance.

Just about every epoxy based circuit board out there attracts
and retains water. The board capacitance can therefore change
due to humidity and temperature.


For audio use, (like the d/a board inside a theta gen V) teflon
it is a disaster. Unless secured to a very flat surface it bends
and rolls up, twisting and turning with the heat. For an RF
board with 20 screws holding a 2 x 3 inch board to a piece
of brass, great.

The cyanate ester that levinson uses is among the best
material available. Expensive however.

 

[rickcr42]

the master has spoken

'bout time you weighed in Kevin

 

[tangent]

What about the branded substrates, like Rogers 4000 and Arlon 25N?

 

[ppl]

IMHO Teflon is the Best. I understand that it is flexible but i have made plenty of circuits on this stuff and some 15 years old and not mounted all that well at all it has stayed in the same posistion that it was installed in.

MARK LEVINSON used to offer Teflon as an option But it was so spendy that it became unpopular. A $4,000 USD option on a $10,000 USD preamp is not what you would call cost effective. ML in realizing that the FR4 is like Kevin pointed out hygroscopic(Retains Water) and also has Higher DC than desired went with the cyanate ester, This material is sold as a cost effictive alternative to Teflon. the material also can be processed like FR4 since it is not flexible as teflon is. The manufactures of Teflon Boards do not recomend them for SMT use due to the flexibility of the material. I have used 8 pin SMT op Amps on this stuff witth no problem but i think the large DAC chips might be a problem.

Borbely uses teflon in the EB-2000 http://www.borbelyaudio.com/index22.htm

 

[ppl]

Attached is a photo of my Pocket Headphone amp this is on teflon and is only supported in the front and rear of the Board no screws what so ever.

 

[aos]

I've never seen any PCB manufacturer even offer teflon as an option. I have seen Rogers 4000 and Arlon and a few more, but never teflon.

 

[ppl]

aos> i hear your cry for help so please see the below link from stereophile on the ML-20.5 http://www.stereophile.com/showarchives.cgi?606:9