Heatsink, just don't drop it on concrete

Sure, why not I guess...

They make power resistors out of the stuff

And hey, they filed a patent for a laundry clip :-)

Come to think of it, one should be able to clip wet socks underneath there and then dry them.

Eight bucks for a 1x2 inch heatsink "isn't spendy"? Aluminum ones run maybe 80 cents in onesies on Digikey.

Cheers

Phil Hobbs

But it does have its bling factor. Just imagine the unfettered flow of electrons in a class D stage, using space-age ceramic technology for the ultimate sound experience :-)

I'm skeptical about the cooling, but it would be nice for high voltage.

Real bling and real cooling would be solid diamond.

I struggle with the high heatsink capacitance of power transistor tabs. $7 is cheap at the price for s solution. Wanna make a 500V/us fast-slewing HV amplifier stage? Find a low-C power part, and a low-C heatsink. :-) Read all about it in the soon-to-be-out AoE x-Chapters.

No offense Phil, but I somehow doubt even you can bootstrap the capacitance of a heatsink in a sufficiently high frequency switcher. ;-)

Cheap compared to the outright infeasibility of something, or compared to more exotic materials (AlN, BeO).

Tim

Y'know, I'll bet it's transparent to long IR as well. Not that there's much to see on the metal backside of a transistor or what have you, but it may be useful sometimes. A sil-pad would definitely be emissive, grease may be as well.

Tim

An AlN insulator over a water-cooled aluminum or copper block is pretty good for cooling vs capacitance. Flowing water directly onto the fet tab would be a lot better.

I'm buying Chinese custom-fabbed AlN insulators, for TO247 SiC fets, for a dollar or so.

It's TO220 size roughly, but I'm cooling a TO247. Smaller insulator makes less capacitance.

I really want diamond.

On a sunny day (Mon, 17 Jun 2019 19:29:35 -0400) it happened Phil Hobbs wrote in :

Dunno. mostly profit. a quick search for ceramic heatsink on ebay finds many for Raspberry 3B+ at 99 cents. OK, smaller, no pins, but material cost?

Could have some advantages.

On a sunny day (Mon, 17 Jun 2019 16:37:21 -0700) it happened Joerg wrote in :

Would be a real brick wall filter :-)

I think it is similar compounds with other metals than Aluminum. I seem to recall this stuff is also very temperature stable, but has to be a lot more pure,

Probably thermally useless.

On a sunny day (Mon, 17 Jun 2019 21:02:38 -0700) it happened John Larkin wrote in :

I do not think so, that particular raspi had a big thermal problem later fixed IIRC. Those thing must really work?

What's the thermal resistance of this kind of stuff ?

Ceramic resistors come to mind. If it really works OK but not as good as aluminum, then it might have an advantage like Win says about the capacitance and could help common mode noise issues that happen with aluminum heat sinks.

Can't make aluminim castings out of the stuff. Or can you ?

Yep, I'd have much less struggle with my thermal problems, if my whole circuit was in an oil bath.

About 30 W/m.K. Not great, but comparable to a lot of metals, and still way better than air.

My guess is they're HIPing it with a very carefully shaped die. I wonder if it can be extruded perfectly prismatic, or if the die needs to be shaped in such a way that the powder compacts and shrinks as it moves through.

Apparently sapphire can be extruded as well, from a crucible with a carefully shaped lid (Czochralski process). That would be a little too fancy for a heatsink, though...

Casting is much less impressive for ceramics. You make a slip with water, suspension agents (deflocculant) and gum. Pour into a porous mold, the water gets sucked out from the surface, then either let it continue or pour out the excess to make a hollow form. Open mold and let dry, then fire. The powder has no stiction by itself (unlike clay), which is where the gum comes in: a binder is used, that is soluble in water, that doesn't form a skin as it dries, and which pyrolyzes to substances that are still sticky, without also expanding in the process. That way, the green ceramic body can go straight into the kiln without crumbling to dust.

Pressed shapes are more common I think, other than HIP extruded shapes. Ceramic powder and a bit of binder, no water needed. Make mold 10% or so oversized, since it shrinks about that much on firing.

Tim

Not that it really matters, but do you have a price point for the X-chapters? (Seems like less sales volume than AoE3, so more $.) And will it be reading for beach reading this summer? (before July 4th say.)

George H.