Re: Printed circuits caps

To: tesla-at-pupman-dot-com
Subject: Re: Printed circuits caps
From: "Malcolm Watts" <malcolm.watts-at-wnp.ac.nz> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Mon, 27 Sep 1999 03:38:55 -0600
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Hi Steve,

> 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!!

I've tried it. Despite various wisdoms suggesting it wasn't a good 
idea it worked quite well. I ran into trouble with arcing around the 
edge of the board so getting sufficient creepage distance between 
the plates is important.  I think one piece punctured through at a foil 
edge but otherwise it was a nice cheap way to get started.

Regards,
Malcolm