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The truth about copper heatsinks and aluminum ones

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February 3, 2001 5:57:35 AM

This is just a FYI post.

I've written this before, but I think that it may help someone if I post this info in it's own thread. So here you go...

Just a little helpful info on copper heatsinks.

Making the base plate out of copper offers a few advantages over aluminum with the main reason being that <b>copper transfers heat faster</b> than aluminum. However, <b>copper retains heat longer</b>. Aluminum does everything the opposite way. It transfers heat more slowly, but retains it for a much shorter period of time.

So the best design is to have a copper baseplate on the bottom of your aluminum heatsink to transfer the heat away from your CPU quickly. Then the aluminum transfers the heat a little more slowly from the copper to itself. Then, finally, the aluminum releases the heat to the air more quickly than the copper, thus forming the optimum heatsink system.

This is probably the reason why the Hedgehog (all-copper heatsink) works poorly with a stock fan. Because it retains heat really bad and cools poorly if it doesn't have a mammoth CFM fan to assist it in releasing that heat. If it has a great fan -one that is big enough to suck the heat away fast enough for the high transfer speed of copper to perform at it's best- then the headgehog will work great (you would also need some good case fans to keep the ambient air inside the case cool enough to keep up the heat transfer efficiency).

If you ask me, you are better off with a smaller copper/aluminum heatsink. Because it's more effective for it's size, less noisy (since you don't need as many fans or as big), it doesn't stress your motherboard with it's weight, and costs less.

To sum it all up:

Copper= Transfer fast, release slow
Aluminum= Transfer slow, release fast



<font color=blue><b>-------------------Update-----------------------</font color=blue></b>

After more research, I have found that the above information is mostly incorrect. Please read my correction at the end of this thread.



:wink: :cool: :wink: :cool: :wink: :cool: :wink: :cool:
:smile: <b><font color=green> Have a day </font color=green></b> :smile: <P ID="edit"><FONT SIZE=-1><EM>Edited by Fa1c0n on 02/14/01 00:55 AM.</EM></FONT></P>
February 3, 2001 8:49:22 AM

Thats some great information.

Thanks

<font color=red>Sumadin</font color=red>


<font color=blue>"A mind is a terrible thing"</font color=blue>
February 3, 2001 9:07:47 AM

how about the contact between copper and aluminium?
i think i can make myself one but how to stick those 2 together?

Misu
__'_
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Anonymous
a b K Overclocking
February 3, 2001 12:59:20 PM

how is this so? if copper transfers heat better, wouldn't that mean it transfers heat to the air faster than aluminum? or maybe aluminum shows more temperature increase for the same amount of energy as does copper, so even though it trasfers heat more slowly, that heat transfer shows a freater efect in temperature?

I'm not saying you're wrong, i'm just not understanding how better heat transfer from the core implies poorer heat transfer to the air.
February 3, 2001 2:11:00 PM

It is very sinple if you explain it properly copper absorbs heat much better than aluminum and higher absorbtion equal more retention also so you have a delema you get the heat into copper but need to get rid of it fast so that it can continue to obsorb from the cpu and it is known that copper will transfer to aluminum better than to air and aluminum will transfer to air very easaly. It all boils down to the meatals in question and their properties.

SANDMAN
Anonymous
a b K Overclocking
February 3, 2001 8:20:14 PM

Quote:
...(copper) retains heat really bad and cools poorly if it doesn't have a mammoth CFM fan to assist it in releasing that heat.

Something like this pops up in just about every cooling forum every now and then. It has a grain of truth in it. Just a grain, though, cause most of it is a plain misunderstanding.

A HSF releases the heat to ambient air by forced convection. The efficiency of forced convection depends on the surface temperature of the heatsink and on air velocity. It does not depend on the heatsink material. So, in this sense, to say aluminium releases heat better than copper is wrong.

The grain of truth is this: suppose you have two sinks, one of copper, the other of aluminium, with identical dimensions, and you deposit the same amount of heat energy in both, then the aluminium sink <b>will</b> indeed release the energy to the air faster. This is because aluminium is both lighter and has a lower specific heat, so the temperature of the Al sink shoots up much faster than that of the Cu sink. The higher temperature helps forced convection to dissipate heat faster.

However, in terms of the cooling effect, all that is irrelevant. The CPU couldn't care less which sink releases energy faster. The only thing it cares about is the temperature of the sink it's touching. And the fact is that all the while when the Al sink is busy getting hot and releasing its heat in the air, the Cu sink just absorbs the energy and <b>stays cooler</b>. Cool sink = happy CPU.

Of course, in actual use the CPU produces heat continuously so the capacity of any sink to absorb energy is quickly exhausted. In order to dissipate, say, a steady 50W of heat, both (identically dimensioned) sinks have to reach the same (average) pin temperature. At this steady state, all that matters to the CPU temperature is the thermal conductivity of the sink material. Cu has much better thermal conductivity, so the temperature delta within the sink is smaller -> the CPU is cooler.

So, in terms of its cooling ability, copper is clearly superior to aluminium, end of story. However, it is softer, heavier and more difficult to machine tool than aluminium. As a result, it is just very expensive to make good heatsinks out of copper. I've never held a Hedgehog in my hand, but according to the information I've seen, its Achilles' heel may be the poor bonding between the pins and the base. It may not be the best heatsink around, but if it were made of aluminium, it would be way worse still.
February 4, 2001 3:46:48 AM

Hmmm...

I do understand how you are arriving at your conclusion (I read it about 5 times carefully), and I do completely understand what you are saying, but I'm still not completely convinced that there isn't a little more to it than that.

But I may very well be mistaken. Far be it from me to claim to know it all! I will look more deeply into this subject, and try to confirm your information. If I come up with a different conclusion, I will post it here. If not, I am glad that my post has generated such informed responses, and has therefore helped people either way.

If what I have posted is indeed in error, I apologize.

And if it is in error, and that error is a common one as you say, then having my original post and your rebuttal will be helpful for everyone to read. So thank you! It is also very possible that I, at least, oversimplified my original post.

I am curious, T_Random. What are your qualifications?

Either way, it appears that our posts are in agreement on everything except the cooling potential of copper.

:wink: :cool: :wink: :cool: :wink: :cool: :wink: :cool:
:smile: <b><font color=green> Have a day </font color=green></b> :smile:
February 4, 2001 4:12:54 AM

Nevin,

You appear to be an engineer who works for Arctic Silver (The thermal solution provider) so I will check out your information with great interest.

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:smile: <b><font color=green> Have a day </font color=green></b> :smile:
February 4, 2001 4:31:47 AM

I found this post very interesting and wanted to add my experience with the copper hedgehog.
I have bought 3 heat sinks for my 900 @ 1 gig tbird.
I can’t rely on the temp readings because I moved the location of my temp probe each time (I have an A7V). On the hedge hog I stuck it right next to the CPU and thus got the highest readings of all at 50c.
So I am basing the performance on how well my 900 would overclock.


1st one was a fop38 with the load ass delta fan.
It seemed to work well and was able to hit 1 gig with 105 fsb x 9.5 but would not run at 100 x 10.

The 2nd was a coolmaster, it was quiet but my computer would only boot into windows at stock (900mhz),zero overclockability.

3rd was the copper hedgehog with a quiet fan (sanyo denki I think) and it would run 105 x 9.5 or 100 x 10 and I was able to drop the voltage to 1.75. I would have to say the hedgehog was the clear winner for me. It allowed me the reach the same speed with a fan that moves much less air.


Also I found out that 105 x 9.5 gives better SETI times then 100 x 10.

Thx & Cya
Anonymous
a b K Overclocking
February 4, 2001 6:34:43 AM

Nevin,

an excellent article. I could have saved my effort and just linked to it.

There is one slight inaccuracy, though:

Quote:
In the case of aluminum vs. copper, assuming identical geometries, copper will more effectively move the heat away from the point of contact with the CPU and into the extremities of the heat sink. This will give the heatsink a higher average temperature overall.

The last sentence is not generally true. In the steady state, to dissipate energy at the same rate, the Al and Cu sinks will need to have same average pin temperature. The temperature inside both sinks increases towards the CPU, but due to the higher thermal conductivity (=lower temperature gradient) of Cu, it increases less in the Cu sink. So, the average temperature of the Cu sink is lower, not higher.

But as I said, an excellent read in general.

Fa1c0n:

No particular formal qualifications. Just reading and figuring out. I'm an economist by trade, but I have a university degree in mathematics as well. That makes thermodynamics a bit easier to grasp.

Cheers.
February 4, 2001 11:40:12 AM

how does this sound, a bit pricey, silver baseplate which is like copper only a lot more effective with silver rods rising up from it plated in gold which is like aluminium (aluminum for you US people) only a lot better with 2 fans and air directing fins one fan to push air between one to suck it out and a pci slot exhaust to get rid of the warm internal air
:)  nice but a bit on the expnsive side, also might be a bit heavy which isnt the best of things
Anonymous
a b K Overclocking
February 4, 2001 6:24:50 PM

I have been reseaching this topic, and so for I have found that how this post was started is mostly correct. Copper will definitely draw the heat from a source quicker, and spread the heat thoughout the copper heatsink faster, as aluminum resists the transfer of heat a little slower that copper. The drawback to copper is that is wants to retain its energy, this is why AMD, IBM, and Intel are either working with or on Copper designs for CPU's, as it can transfer energy quicker and better, therefore allowing for .13 micron and smaller designs without the loss of current. So recap, Copper retains and transfers energy quicker, Aluminum transfers energy quickly, but does not store energy as Copper does.

Another thing, even in Intels own documentation on heatsink, processor design, etc... is that a combination of these materials yields the best results. Several non-active cooling methods, no fans, are done with Copper bases and Aluminum fins. This is probably the best current cost effective solution, such as Alpha heatsinks, Copper bases surrounded by Aluminum. They also found that smaller Aluminum fins, tightly packed radiate heat faster than larger fins, due to energy retention of the larger fins. The only stipulation for a heatsink design is that it must be able to cool a CPU with a certain wattage dissapation and keep it within temperature specs.

I also ran across a few hybrid mixtures of Ceramic, Copper, Aluminum, and Silicone meterials to provide the best of both worlds. The silicone to reduce oxidation of the metal. The Copper, Aluminum, and Ceramic to provide good cooling properties without the weight of a solid Ceramic heatsink or Copper heatsink.

Lastly, this is only what I have found on the internet. I am not a scientest, nor an engineer of any kind. So in other words, don't slam me here, as these are just my conclusions from all the information I have read thus far.
a b K Overclocking
February 4, 2001 10:55:12 PM

Let me see if as a designer I can rationalize this. Since copper has a higher specific heat than aluminum, it tends to retain heat longer, but it also transfers heat better. Since aluminum does a lesser job of tranfering heat, the cooling fins should have a thickness that allows heat to be transefered as fast as it is dissapated (no aluminum foil heatsinks). But since copper has a higher latencey, the fins should be designed thinner so that they have less mass to retain the heat. I think that copper would work better than aluminum if the fins were thinner than those of an other wise identical heatsink. But this would also creat a lager airgap between the fins, allowing better airflow and giving copper even more advantages. In fact, copper and aluminum heatsinks should be designed differently to take advantage of their properties. If they are, copper becaomes a clear winner. But if copper heatsinks follow the traditional aluminum design with thick fins, it looses it's advantage. I have seen sheet aluminum designs before-I think the sheet design would be ideal for copper, because of its higher conductivity.
We must also remember that surface texture affects these things. A rough surface not only has more surface area, which helps, but also creats eddies of air as it passes over the small bumps. I have seen flow test showing that surface imperfections can work as "liquid ball bearings" if designed properly. But the biggest advantvantage for heatsink design is that these eddies stir the air as it flows across the surface, allowing the hot air on the surface to mix with cooler air above the surface. Because copper is soft, most copper products are relatively smooth. I think that roughing the surface through bead blasting my provide a finish similar to that found on extruded sinks on a sheet sink, giving it all the advantages of both designs.

Suicide is painless...........
Anonymous
a b K Overclocking
February 5, 2001 5:34:56 PM

Thanks for the thoughtful response. Let's see if I can clarify this a bit further.

Quote:
The drawback to copper is that is wants to retain its energy, this is why AMD, IBM, and Intel are either working with or on Copper designs for CPU's,...

Frankly, I don't see what this has to do with the material of the CPU interconnects, but let's concentrate on the first part of the sentence: "copper...wants to retain its energy".

Strictly taken copper does not have a will so it does not want this nor that. But what you mean is that for some reason it does not dissipate the heat energy it stores as quickly as aluminum. In order to respond to this, it would be useful to know what physical phenomenon you are talking about. Could you link the Intel documentation you are referring to?

Anyway, in this thread, a few possible interpretations have popped up already:

1. <b>Higher specific heat</b>. As I explained in my first post, when equal amount of heat (say 50 Joules) is deposited in a copper sink, its temperature increases less than that of Al sink, so force convection works slower. For the reason I also explained in my first post, this is irrelevant for cooling.

2. <b>Radiation</b>. Heat sinks dissipate energy not only by convection but also by radiation. Unlike convection, radiation <b>does</b> depend on material. Al radiates heat better than Cu, so in this way your statement is true. However, radiation plays such a minuscule role in the total heat dissipation of a HSF that it can for all practical purposes be ignored (which is why I did not mention it in my first post).

3. <b>Surface texture</b>. I must confess that I have never heard this argument until Crashman pointed out. If it is true, as he says, that Al sinks tend to have rougher surface than Cu sinks (and I suppose it is true), then this could be important. In a heatsink, a smooth, laminar flow would mean that the same, increasingly warm air molecules sweep the surface of the sink which understandably degrades cooling. So you want turbulent flow, and uneven surface helps to create that. In a way, I excluded this possibility in my first post by assuming physically identical Cu and Al sinks. Anyway I concede the point here.

All in all, to the extent your statement relates to either of the first two interpretations, it is a misconception, although a widespread one. As to the third interpretation, I cannot estimate how important it is in practice.

Quote:
They also found that smaller Aluminum fins, tightly packed radiate heat faster than larger fins, due to energy retention of the larger fins.

I have trouble making sense of this. I cannot gather what you mean by "energy retention". Further, radiation has very little relevance here. First, the number or surface area of fins, which matter a lot for convection, are almost irrelevant for radiation: most of the radiation emitted by tightly packed fins is absorbed by the neighbouring fins. A rectangular block of metal radiates probably better than a fin heatsink. Second, and more to the point, because convection is so much more efficient means of heat dissipation, radiation does not matter.

I agree that a combination of a copper heat spreader and aluminum sink is probably the best practical compromise. (It does introduce an additional junction that has a thermal resistance, but the benefits probably outweight this.) But my claim is that this is due to manufacturing considerations, not to any superior property of Al in releasing heat.

Cheers.
February 5, 2001 11:45:28 PM

In response to surface texture.
If the aluminium or copper is cast then it would have a rough texture(surface finish).
If it is machined, then the surface finish COULD be quite smooth. Especially if it is polished.
On some of the heat sinks with the pins,(swifttech) these may even be polished. As for which surface finish is better for convection, wouldnt know.

<font color=red>Sumadin</font color=red>


<font color=blue>"A mind is a terrible thing"</font color=blue>
a b K Overclocking
February 6, 2001 2:43:26 AM

Ah, now the subject of pins-seems like flow between the pins would creat more turbulance and better mixing-you no loger have a flat surface to deal with, so little laminar flow. So perhaps a rougher finish would have less affect on a pin design-I won't be sleeping tonight!

Suicide is painless...........
February 7, 2001 10:33:20 PM

That's a long ass post.

-MP Jesse
a b K Overclocking
February 8, 2001 2:53:43 AM

Post padding jesse?

Suicide is painless...........
February 8, 2001 11:52:30 PM

Post padding?! What does that mean?

-MP JEsse
a b K Overclocking
February 9, 2001 2:53:32 AM

Post padding is putting up a post for no other reason than to raise your post count.

Suicide is painless...........
February 9, 2001 11:19:06 PM

Well, if i'm post padding so are you by bothering to even accuse me of post padding.

If you really wanted to accuse me of and not try to post pad yourself- you'd of sent me a private message.

-MP Jesse
February 14, 2001 7:04:07 AM

After doing more research on this topic, I have come to the conclusion that most of what I said about these 2 metals was incorrect. I am not a thermodynamics or materials expert, and gathered most of my original info from the Internet. I am disgusted with the low quality of my info sources, and my own lack of research on this topic before making my original post. I like to post, and pride myself on posting, accurate information and I try very hard to get my facts strait before posting anything (usually). So, to make things right, here are my corrections (most of which have been already stated by others):

First of all:

There is no such physical phenomenon as how well a material "gives up heat" convection-wise (from what I have read).

2. Aluminum <b><i>radiates</i></b> heat better than copper, but this is almost completely irrelivent to cooling your CPU (from the best information I can gather).

3. Copper is far better as a heatsink material (thermodynamically).

4. Copper heatsinks are not as easy to manufacture as aluminum ones, are more expensive, and heavier (possibly causing tiny air gaps between the CPU and heatsink. Thus causing worse performance if not properly attached, and possible motherboard damage depending on the heatsink/fan weight).

5. If all these problems are overcome, then copper is the best choice.

Hopefully I have all my facts strait now! If not, please feel free to correct me again. :smile: I can only learn!



:wink: :cool: :wink: :cool: :wink: :cool: :wink: :cool:
:smile: <b><font color=green> Have a day </font color=green></b> :smile:
February 14, 2001 2:05:04 PM

Cool, makes me feel better for spending the money on my copper hedgehog.
Anonymous
a b K Overclocking
February 15, 2001 11:43:55 PM

very interesting thoghts here but unfortunately only of a theoretical nature. however, just today I read the test on 24 CPU coolers on the german page of Tomshardware(I am a german so I have no trouble understanding it).
the one that kept the CPU at the lowest temperature was a massive (I mean really massive at over 700 gramm) combination of copper plate and aluminium pins with huge fast rotating fan (damn noisy), the Swiftech MC462. however, there is also a way more innovative construction with silver connection plate to the CPU and low speed radial twin-fan (very quite) that was very effective and would be the one I would go for, the NoiseControl Silverado.

to check it out see the article at http://www.tomshardware.de/cpu/01q1/010215/index.html .
and don't worry about the german language the graphs can be read by anyone.
February 16, 2001 10:40:34 PM

Actually my final post was not theoretical (to the best of my knowledge). So I'm not sure what you mean't by that. Please clarify specifically what you believe to be "theoretical" about what I posted. What I wrote in my last post was what I had learned from several engineers and materials experts. So I believe that it states <i>facts</i> that are quite accurate as to the properties of aluminum and copper. If you think that some of what has been said in this thread is not accurate, or is theoretical (not confirmed), and can state specifically what your reasons are, I would definitely like to hear them.

Yes, silver is a better conductor of heat than aluminum <i>or</i> copper. However I was not including silver in the debate (the thread is about aluminum vrs. copper heat sinks). A larger aluminum heat sink has more surface area, yes. The only comparison that would be of value would be to have indentical dimensions for all heatsinks.

Here are the thermal conductivity ratings of the materials in question (from Tomshardware <A HREF="http://www4.tomshardware.com/cpu/00q4/001211/cpu_cooler..." target="_new">review of 17 heatsink/fans</A>).

Material Thermal Conductivity

silver 422 W/mK
copper 402 W/mK
gold 298 W/mK
aluminium 226 W/mK
steel 73.3 W/mK
lead 34.8 W/mK

Thank you for the info about silver though, it was quite interesting. It's nice to see some real innovation in heatsink design.

:wink: :cool: :wink: :cool: :wink: :cool: :wink: :cool:
:smile: <b><font color=green> Have a day </font color=green></b> :smile:
Anonymous
a b K Overclocking
February 17, 2001 12:55:50 PM

first of all I didn't mean to offend you, if you feel so I appologize.
the term 'theoretical' was used because you wrote about the property of the different materials and not of an actual cooler. but I think the most people (like me) want to know which CPU-cooler they actually can buy that does a good cooling job. I doubt that there are many who build a CPU-cooler themselves.
I totally agree that CPU-cooler design is a field that gives still a wide opportunity to develope and I sincerly hope that some gifted people will do so. for those you're posting is definitly a good point to start from.
I respect your posting very much and hope that you will continue to do such proper research in everything that you find interest in.

respect
February 19, 2001 9:14:58 PM

Thank you for your clarification. I was not offended. Thank you also for your input. :smile:

I was just being direct. Sorry if I came across too severely. It's just that many times people disagree with something without giving any facts to back up their reason. It is obvious that you are not one of them. I hope to hear much more from the people on this forum, such as yourself, who genuinely are interested in the exchange of accurate information. This thread has been very educational for me.

Take care.

:wink: :cool: :wink: :cool: :wink: :cool: :wink: :cool:
:smile: <b><font color=green> Have a day </font color=green></b> :smile:
February 19, 2001 9:52:39 PM

Quote:
how about the contact between copper and aluminium?
i think i can make myself one but how to stick those 2 together?

Sorry it took so long for me to answer this.

As far as I know, for those interested in making their own copper spreader/aluminum heatsink, there is no easy way for the home user to create the low thermal resistance contact between copper and aluminum.

<A HREF="http://www.micforg.co.jp" target="_new">Alpha</A> uses a very <A HREF="http://www.micforg.co.jp/alcu_embed.html" target="_new">high pressure process</A> to bond both materials simultaneously at the time of forging that leaves very little thermal resistance between the two materials.

If a person were to stick the two together themselves (I haven't tried it) I would suspect that it might work more poorly than a plain aluminum sink. Possibly not though. It would be an interesting (though somewhat unnecessary if you can buy them) experiment to try sometime. But only if you are ready to live dangerously! :) 



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:smile: <b><font color=green> Have a day </font color=green></b> :smile:
February 20, 2001 10:29:30 PM

i don't know if this would work but you could try using artic silver epoxy to glue the the copper and the alunium togther
February 23, 2001 11:11:08 AM

I just posted an other thread about my modification of an FOP32, in a newsgroupe we had more or less the same discution about copper and aluminium.
Well to make a long story short i tried it bought a cold plate and just put some arctic sliver between CPU and coldpate and between the coldplate and the FOP32 and my temp droped about 5C.

My thread's name is:
I just shaved 5C of my load temp on a aluminium HS
December 2, 2011 7:18:13 AM

Can somebody heat up 2 block of identical size, 1 copper and 1 aluminum, to 200C then let them air cooled to see which will cool faster? We all know copper absorbs heat almost twice better. The only reason they're making copper base aluminum fin heatsink because aluminum is cheaper and lighter. The contacts between the copper and aluminum in those HSFs squash all your theories about mixed metal will create a better heatsink. Go for the one which absorbs better and leave dissipation problem to the engineers. Look at Zalman 9500 for example. If its heatpipes have better contact with the base, or direct heatpipes contact with the CPU, it definitely will be the best HSF out there.
a c 183 K Overclocking
December 2, 2011 4:48:08 PM

^ 10yr old post guy!
Braaaains!
a c 324 K Overclocking
December 2, 2011 5:44:49 PM

Yeah, let's go ahead and close this one out... :/ 
!