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why are heatspreaders in alu?

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flixotide

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Joined
Oct 29, 2002
Location
Denmark
I've thought of this so many times, and never found a reasonable explanation. But seing as heatspreaders seem to be on their way back for AMD again with A64, and Intel too, my curiosity kills me.

Why don't the chip producers make those heatspreaders in copper? For heat spreading its a far superior material.

The only reasonable explanation I can find is that copper might be too soft when fairly thin... but apart from that I find it ridiculous that they use aluminium.

Cheers, Flix
 

Korndog

Member
Joined
Nov 30, 2002
Location
California
yea, think its mostly because alum. (alloy version atleast) is pretty strong, heard my friend say its comparible with med. grade steel.
plus for the same reason why u don't find copper connectors and stuff, oxidizing.
 

joikd

Registered
Joined
Apr 24, 2002
That's news to me. I always thought they were nickel-plated copper.
 

mccoyn

Senior Member
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Nov 17, 2003
Location
Michigan, USA
I know Intel uses nickel over copper. The problem can't be cost as both companies provide heatsinks in their retail processors that have a copper slug that is bigger than the whole IHS.
 

cstarritt

Member
Joined
Nov 7, 2003
i thought they were a plated copper too, is the p4 IHS alu or is it copper thats plated and LOOKS like alu. a plated coper would solve the oxidation problem. cost is not the issue for a chip that retails for a few hundred or more.
 

deathman20

High Speed Premium Senior
Joined
Aug 5, 2002
From my understanding intel heatsinks are Copper thats Nickel Plated to prevent oxidation. Besides that it still transfers heat pretty well anyways, if not just start lapping the heatspreader and you'll solve your problem then :)
 

I.M.O.G.

Glorious Leader
Joined
Nov 12, 2002
Location
Rootstown, OH
The benefit of aluminum over copper that I see is cost. Aluminum would involve less cost to obtain, less cost to move around the warehouse, less cost to machine.

Remember that the chip makers aren't concerned with maximum heat transfer, and that heat spreaders aren't really there to improve heat transfer - they are no better at spreading heat than the base of a heatsink would be and they add another layer for heat to conduct through.

The chip makers use IHS's to protect the chips, make them less likely to be damaged and perhaps lower support/RMA costs.

So the material that is chosen for the IHS is not very important, just so long as it is good enough.

Aluminum is good enough, so the question I ask is why do they ever use Copper?

cstarritt said:
cost is not the issue for a chip that retails for a few hundred or more.

Cost and price are two seperate things. Lower cost with the same price means higher profit margin. Just because price is high does not mean cost is immaterial.

If copper costs 1.25 times as much as aluminum to obtain, and they are buying in huge quantities, this cost difference is VERY considerable. And then you have to consider handling costs - copper weighs a lot more than aluminum. And then manufacturing costs - aluminum is easier to machine than copper.
 

mccoyn

Senior Member
Joined
Nov 17, 2003
Location
Michigan, USA
Its nickel not aluminum. The purpose of a heat spreader is to spread heat. See, engineers have a funny way to name things. If it were all copper, or even all copper and aluminum the heat wouldn't spread. It would radiate in a spherical pattern meaning the edges of the heat spreader would not transfer less heat and the center would have to transfer more. By adding a layer that doesn't transmit heat as well, the heat follows a path of less resistance, which is across the heat spreader and then through the nickel. Well, thats my theory.
 

felinusz

Senior Overclocking Magus
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Feb 26, 2003
Location
Taiwan
I have always wondered why they even started using these things anyways - and always thought that it was to prevent accidental processor core cracks. Isn't everything cooler with the IHS removed?
 

Silversinksam

Moderator/ Silver Paste Taster©
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Aug 8, 2001
Location
Sunshine State, USA
mccoyn said:
Its nickel not aluminum. The purpose of a heat spreader is to spread heat. See, engineers have a funny way to name things. If it were all copper, or even all copper and aluminum the heat wouldn't spread. It would radiate in a spherical pattern meaning the edges of the heat spreader would not transfer less heat and the center would have to transfer more. By adding a layer that doesn't transmit heat as well, the heat follows a path of less resistance, which is across the heat spreader and then through the nickel. Well, thats my theory.

Yes it's nickel over copper, as you mentioned nickel is .906 W/cm-K and copper is Copper 3.937 W/cm-K, But even with the nickel plating the majority of the heat is still in a spherical pattern. Nickel is harder than copper and the nickel protects the soft copper imho

The IHS is there to protect the chip, not to spread the heat, anyone will tell you that the chip will run cooler without the heatspreader. Now with the MO intel steppings fused, you cant remove the IHS. But as IMOG mentioned the cost factors, this would rule out why Silver isn't used :( Silver 4.173 W/cm-K (But I am working on a silver IHS project :)

Also the IHS isn't perfectly flat for a reason. the reason is to account for thermal fluctuations of the metal. As far as the radiating in a spherical pattern, thats why Arctic Silver instructions(step #10) recommend a dab of thermal paste in the center of the IHS as the paste spreads out in a spherical pattern and is less apt to allow air bubbles if this method is used/.
 

I.M.O.G.

Glorious Leader
Joined
Nov 12, 2002
Location
Rootstown, OH
mccoyn said:
Its nickel not aluminum. The purpose of a heat spreader is to spread heat. See, engineers have a funny way to name things. If it were all copper, or even all copper and aluminum the heat wouldn't spread. It would radiate in a spherical pattern meaning the edges of the heat spreader would not transfer less heat and the center would have to transfer more. By adding a layer that doesn't transmit heat as well, the heat follows a path of less resistance, which is across the heat spreader and then through the nickel. Well, thats my theory.

Not quite. The heat radiates in a somewhat spherical pattern no matter what. Adding a layer that doesn't transmit heat as well only slows down the overall thermal transfer... Why would letting the heat spread out in the heatspreader be better than letting the heat spread out in the HS base? It wouldn't.

The heatspreader is only an obstacle to heat transfer, it does not help. If it were made out of diamond (or perhaps silver ;) ), then perhaps it would help, but even then it might not because the heat still has to interface between "CPU DIE -> thermal goop-> heatspreader -> thermal goop -> HS -> air".

"CPU DIE -> thermal goop -> HS -> air" is better as far as I can see.