Re: Printed circuit caps ; G10 vs FR-4


How does one clearly distinguish between G10 epoxy PCB and FR-4 PCB ?
Where can high voltage G10 PCB be purchased from ?

While a databook mentions G10 as having a dielectric strength of 15 KV/mil,
Richard Quick's capacitor info mentions epoxy circuit board as having a
dielectric strength of the much lower value of only 700 V/mil. Perhaps one
could suck it and see if there might have been some oversight which gave
rise to very disparate figures, but i believe that the G10 & FR-4 grades
must in fact be very different in their dielectric strengths; so will need
to be sure of purchasing the correct grade if at all possible. 

I expect G10 will be a more expensive grade, so that the NZD$85 (USD$40)
cost of FR-4 300mmx300mm x8 plates, for a 10nF cap, will become more like
twice or three times that figure for G10 plates. Anyone have actual prices
and a source for 300mmx300mm G10 double sided PCB ?


On 25 Sep 99, at 13:09,
Tesla List wrote:
> Original Poster: "Steve Cook" <Steve-at-g8cyerichmond.freeserve.co.uk> 
> has anyone thought of using printed circuit board for making pulse caps? I
> recently came across some surplus double sided G10 board. My data books give
> the dielectric constant as 4.5, and the electrical strength as 15kV/mil. I/ve
> made a small one (0.0005mfd). I ran it at 15kV for an hour, no noticeable
> heating and no break down. The copper was removed for about 1/2" all
round the
> edge. I ran a bead of hot glue over the edge of the copper. Capacity
works out
> at 16pF per sq in. That means that a piece with plates 6.25x10" will give
> 1nF!!