Dave Tweed wrote:
>
> Roman Black <fastvid@EZY.NET.AU> wrote:
> > Thanks for the response, but you didn't cover the
> > basic issue. :o) We are using zinc oxide, which I have
> > always believed is DENSER than aluminium, ie will sink
> > better than machined alloy no matter how flat.
>
> Actually, density has very little to do with the two parameters that
> are critical to thermal managment: thermal conductivity and specific
> heat.
>
> Lead is the densest metal, but it falls short of other metals in both
> areas.
>
> Aluminum scores fairly high in both areas, plus it has the advantage
> of being relatively easy to shape.
>
> Zinc oxide powder suspended in silicone grease is not a better
> conductor than the aluminum, so you really do want a very thin
> layer. A bead of it on the edges of a device is probably
> counterproductive (wasteful, and messy besides).


Thanks Dave, yes I stand corrected. I looked up thermal
conductivity on google and got a list of metals and
insulators values. Heatsink compound was a lot worse
than aluminium, quite surprising the amount that it
was worse. Also surprising was just how badly water
scored on that list too, but I don't think it takes
into account any convection.
-Roman

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