Heatsinks, baseplates, Aluminium vs other metals

[db3306]

i found some 5mm alu as well so im all good now
But just out of curiosity, if i would have mixed copper and alu and bolted it. Would one metal expand faster than the other if heated and result in a crackde baseplate?

[-bart-]

Al expands 35% better than Cu

http://www.youtube.com/watch?v=DwDEbCi4SM4

[steve-o]

Al expands 35% better than Cu

Better as in more? Wouldn't that make copper superior (less expansion) .. Or do I have it bass-ackwards ..?

[-bart-]

I meant Al expands 35% more than Cu, lenght-wise.

[Stoney3K]

Better as in more? Wouldn't that make copper superior (less expansion) .. Or do I have it bass-ackwards ..?

Copper is more thermally conductive and expands less, so in that respect it IS superior.

However, as already noted, it is less stiff than Al, so it's more difficult to machine and more prone to warping or damage on impact, e.g. when the projector is not handled "gently" by a few roadies.

[planters]

Copper is so expensive, and heavy and is really quite difficult to machine. Other than the micro-scale and heat loaded components such as the diode mount these negatives far outweigh its 60% better thermal conductivity. You'll be floored if you try to price out a large machinable slab of this stuff. Years ago the US government phased almost all the Cu out of Pennys (they are almost entirely zinc now) because people were melting them for the copper and the price has risen a lot since then.