Currently Googling for Breakdown V of PTFE and Kapton

Found

dielectric strength tests for Kapton thickness.

0.3um is 3000 AC V/mil 0.5um is 3000 AC V/mil 1.0um is 6000 AC V/mil 2.0um is 5000 AC V/mil

Not quite the thickness you need but regarding Kapton I bet you could obtain more info from Dupont:

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Regards, Joerg

http://www.analogconsultants.com/

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Textbook value for PTFE aka TFE aka Teflon is 480 volts per milli- inch, and for polyimide/Kapton is 560 volts per milli-inch.

That assumes pure material, clean surfaces, and no conduction enhancement from ambient light... This data, from _The_Practicing_Scientist's_Handbook_, Moses, Alfred J.,

1978 edition...

Huh.. That's wayyyy different than what's on the link that Joerg provided.

Table 2 Kapton Type 150 FCR Polyimide film 1.5 mil : 4400V/mil

Table 1 Kapton Type 100 CR Polyimide Film 1mil: 7400V/mil

I supppose it depends on the type of polyimide. Perhaps the withstand test is differant.

According to (blows dust off book :O === ***) Reference Data for Engineers 1993 Polyimide: 570 V/mil

It depends on what you're measuring, or require.

For FEP (Kapton), Dupont book breakdown is over 4KV/mil (170KV/mm), but life test data to IEC343 (that includes corona resistance) at

10,000 hrs is measured in the 100s of volts/mil.

RL

Ahhh.. Ok for example...

Kapton CR

1.pdf Corona resistance >100 000 hours @ 20KV/mm

Kapton.

DO NOT confuse nor conflate breakdown ratings with operational ratings.

Breakdown ratings are typically 8 to 10 (or more) times higher than=20 operating ratings. This applies to most dielectrics whether used for=20 insulation or to build capacitors.

True dat. Also true that plain old silicone caulk (aka RTV for room temperature vulcanizing) has impressive insulating abilities for a common material, so it would not be surprising if a tape adhesive using silicone rubber did as well. But confusing breakdown and operational will lead to getting bitten. For one thing, geometry matters a lot, and any actual test will have a specific geometry which may or may not look like your application.

In ASCII art >| is much harder to insulate than )| or ||, for instance.

On a purely "quick test to destruction" (hipot - crank up voltage until current flows) basis while working on some lab equipment, I got 30KV from ordinary (well, probably 3M ordinary, but not the high-voltage version, for sure) heat shrink tubing. Doesn't mean you should design for that...nor did I measure what thickness it had shrunk to.

There may also be some sort of surface effect with the different unit breakdown for different thicknesses of kapton. As such, two wraps of thinner material may be better than one wrap of thicker material (and that's even more true in the real world where defects and dirt may happen.)

Generally, anything designed to the hairy edge of breakdown will eventually blow up, short out, etc. As such, outside of a lab environment where you need to push the hairy edge and have designed things to fail gracefully (or at least without killing anyone) when they do fail, it's best to avoid that.

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That's what happened. I went for the short term spec (V breakdown). When I should be looking at the long term spec (hours to insulator deterioration by corona).

The text books list operational.

If you are building something that needs to pass muster at an agency (pretty much anything does) there are only two things that count:

a. The standard

b. A formal statement by the manufacturer and this has to be in writing. A book doesn't count. BTDT, many many times.

--
Regards, Joerg

http://www.analogconsultants.com/

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