Re: dieletric strength question

["Steve" <Steve-at-g8cyerichmond.freeserve.co.uk> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Sorry about my error, of course you are correct, I missed the decimal point
out!!!
Two tables I have give 1.5kV for standard epoxy-glass board, I believe that
this is actually too high, and err towards about 1/3 of this. Of course the
test conditions are dc, and for our purposes we need to de-rate.
----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, September 09, 2000 1:16 AM
Subject: Re: dieletric strength question


> Original poster: "Jim Lux" <jimlux-at-jpl.nasa.gov>
>
> 15 kV/mil????  I'd go for 1.5 kV, perhaps, with no design margin.  15
kV/mil
> = 15 MV/inch = 590 kV/mm, which is somewhat more than the breakdown
strength
> for  mica(50 kV/mm in 1mm thick, 100-200 for 0.1 mm), polyethylene (40
> kV/mm), PTFE(Teflon)(25 kV/mm).
>
> Any composite is going to have a lower breakdown strength than a pure
> material, because of the field concentrations caused by the differing
> dielectric constants (epsilon) of the component materials.
>
>
> 30 kV in .0625 inch PCB is only 500V/mil, which is probably about the max
> that you'd feel safe at, and you'd want to make real sure that there
weren't
> any voids in the substrate, rough edges or corners on the traces, etc.
>
> Perhaps 15 kV/mm would be a more believable puncture voltage spec for
> glass/epoxy?  (1 mm = ca 39.4 mil)
>
> -----Original Message-----
> From: Tesla list <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
> Date: Friday, September 08, 2000 11:44 AM
> Subject: Re: dieletric strength question
>
>
> >Original poster: "Steve" <Steve-at-g8cyerichmond.freeserve.co.uk>
> >
> >No problems here, epoxy pcb has a puncture voltage of 15kV per mil or
> >thereabouts. I have made caps for tank circuits running at 10kV, and have
> >tested them to 30kV, using 1/16th board. Details are on my website
> >http://www.teslauk-dot-com
> >Steve
> >----- Original Message -----
> >From: Tesla list <tesla-at-pupman-dot-com>
> >To: <tesla-at-pupman-dot-com>
> >Sent: Friday, September 08, 2000 1:17 AM
> >Subject: dieletric strength question
> >
> >
> >> Original poster: jmonty-at-flash-dot-net
> >>
> >> I had a friend pose me the following question that someone on the
> >> list probably can answer off the top of his or her head.
> >> Here's the question.
> >>
> >> "I've made a capacitor out of double sided epoxy circuit board for
> >> the cold end of the resonator in the two meter cavity amp. It needs
> >> to take 3KV and just by looks I'd say it does. Guess as a last
> >> resort I could hook it up to HV but my heart won't take many more
> >> shotgun explosions going off in the shack.
> >> It measures .050, including the copper, which is a few mils."
> >>
> >>
> >> Any help in determining a ball park puncture voltage would be most
> >> appreciated.
> >>
> >> Jeff Montgomery
> >> Palestine, Texas
> >>
> >>
> >>
> >>
> >
> >
> >
> >
>
>
>
>