Heatsink Insulators?

Alumina ?

Graham

Well, for the time being, a layer of self adhesive tape would do.

Rene

AlN.

John

If thin enough, and wide enough, and cheap enough, and drillable enough.

I seem to recall a post that noted the usual thickness of AlN almost outweighs the conductivity.

Tim

Depends on how thick. The OP specified a kilovolt, so some thickness is reasonable. AlN conducts heat something like 10x as well as alumina, and is close to BeO.

John

When I need something like that I consider bringing out my 100 ft. roll of mica tape.

greg

If you only want to insulate some..... then fone up Mrs Berquist and ask them for a sample of of their whatever does the job..... Ummm ST-1500.

Tell them that Genome suggested that they should produce some sheets of just less than magazine size for people just like ourselves and have an ordering system with a selection of 'quality' magazines to slip the sample in before putting it in the brown paper envelope for $15 delivered.

The wife/boyfreud will think your journey down the garden shed has nothing at all to do with mounting high powered semiconductors on metallic things. Ooooooh,I feel quite dizzy.

DNA DNA

Check out

With an .008" thick Sil-Pad you'd need thermal conductivity of 0.7 watt/m*K. All of these materials are better than that.

In message , dated Fri, 1 Sep

Friendian slip?

-- OOO - Own Opinions Only. Try

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

That stuff is thermally crap. If you compress it a couple of hundred PSI, it might get close to half the thermal conductivity they claim, and even that's not all that good.

John

I think they claim it gets down to thrumble blob at 50PSI according to ASTM5570 as defined by them because they have a machine that does it.

Are you saying they are a lying bunch of f****rs?

DNA

You've measured it?

Yes. I've never seen a sil-pad conduct heat anywhere close to the advertized value.

John

OK. I have no data or relevant experience to refute your assertion, but I'm still inclined to believe that they can and do deliver performance they advertise. They've been around quite a while.

I'd be inclined to bet that I could demonstrate their claimed performance in my lab to within 20% or better. YMMV.

If you've got a 7805 that's dissipating a couple of watts, they're fine. But if you are pushing semiconductors hard, which you have to do to get real performance, sil-pads are going to be a major roadblock.

And I doubt the 20% claim. This thermal stuff is notoriously difficult to get repeatable measurements from. Just check a few references for the thermal conductivities of various materials: you'll see numbers all over the place.

John

no

I don't have any trouble getting repeatable thermal measurements, but I don't have any Sil-pad material to play with. I usually use mica, seems to work OK. But then, I never push semiconductors very hard. Don't have to -- I'm not designing to cost or for production anymore. Example: dirt-simple 600-watt PWM voltage reducer for a boatlift motor