dieletric strength question

[jmonty-at-flash-dot-net (by way of Terry Fritz <twftesla-at-uswest-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