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Re: [Amps] heat sinks

Subject: Re: [Amps] heat sinks
From: Manfred Mornhinweg <>
Date: Mon, 19 Nov 2018 14:45:10 +0000
List-post: <>

   With the high cost aluminum I can't help but wonder if something like
copper sheeting could be used instead.   (1/4" thick or so)

Copper is nearly twice as good a thermal conductor as pure aluminium, per volume, and the usual aluminium alloy used for extrusions is worse than pure aluminium. That makes copper roughly 3 times better than extruded aluminium. But copper is also 3.3 times heavier than aluminum, so that its thermal conductivity per weight is slightly worse than a typical aluminium alloy, and much worse than pure aluminium. So technically copper is the better material for high density heatsinks and for hot spots (like heat spreaders), while aluminium is better for the outer parts of normal heatsinks, and for complete low density heatsinks, which are more limited by metal-air thermal resistance than by the bulk material thermal resistance.

The cost of metals varies all the time. Right now copper is 3.23 times as expensive as aluminium, per weight. So a copper heatsink having the exact same shape and size as an aluminium heatsink would cost 10.66 times as much! That's prohibitive, except in applications where the better conductivity of copper is a deciding advantage.

And if you were to make a copper heatsink with thinner structures, so as to emulate the thermal resistance of an aluminium heatsink, that copper heatsink would end up costing about 3 times as much as the aluminium heatsink, weighing almost the same, but being far more fragile due to the thin fins.

That's why copper heatsinks are rare.

Instead of 1/4" thick copper, 1/2" thick pure aluminium conducts heat slightly better, weighs only 61% as much, and costs only one fifth as much!

Copper is convenient only for small pieces where thermal flow crowds, like right under a high power transistor, or from a high power transistor to highly turbulent cooling water.


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