EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: made2hack on July 14, 2014, 05:21:41 pm
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Hello all,
It is my understanding that the majority of heat sinks are extruded aluminum. Does anyone know if heat sinks are also cast? As in, hot molten aluminum in a shape?
If yes, no, why the extruded? Cost consideration? Standardization? Is an extruded aluminum any better than a cast model? (Assuming 0 porosity of the final mold)
Also, how is the aluminum attached to the copper (in a copper/aluminum) combination? Simply "glued" together? Or soldered?
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i have never seen cast heatsinks, only extruded.
you cant take the mold appart after the alu settles with casting. or it is difficult at least.
extruding can be done in pieces of 6 meter or much long and saw off at length. so easy.
other methods are soldering the copper vins to a copper base, much used in cpu heatsinks.
fisher elektronik pressfits extra fins into the base to create a more efficient cooling design.
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I could be wrong, but I believe the heatsinks on HP's E36xx series power supplies are cast alu.
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I've sen cast heatsinks, but only when a specific shape is required.
If you're making enough, then extruding is much much cheaper.
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I imagine extrusion will be cheaper, since I guess if you have a giant press + die, it goes faster.
However, I want to prototype a heat sink, and, whilst I can cast aluminum at home (with some effort), I don't have a multi-ton press + die.
Any idea what AL alloys are used? Or do i just pick the one with the highest conductivity?
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Most castable alloys will do for this casting, as they are generally quite conductive. You do need to take care of surface finish to get all the sand off, and you will have to mill the actual device mounting areas to get them flat.
The copper plugs are generally added by a press into a machined hole, and then the whole assembly is surface finished in the area to get the smooth flat surface required.
The reason most use an extruded heatsink is because you just cut to length, and the as extruded surface is generally smooth enough to use without further machining if used with a thermal pad or heatsink compound. As well you can get a very complex high surface area in the one dimension from the die, using a minimum of material, and can easily have slots for mounting hardware. A casting can do this, but the moulding will be complex and prone to cracking during casting as it cools faster with large surfaces compared to the thicker areas.