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Copper vs. Aluminum - Thermal Conductivity & Radiation

DanishDevil

DanishDevil

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First of all, I want to lay some ground rules, because I have seen this go way out of bounds on many other forums.

If you're going to make a claim, please voice your opinion and state WHY.

The question we are focusing on related to processor cooling, specifically with air cooling, not water cooling. We can start a discussion for water cooling as well, but keep them separate and your comments specified and whether or not it makes a difference.

In a CPU heatsink, what is the best combination of copper and aluminum to extract heat away from the processor effectively, without having cost be a factor?

A few claims:

Copper has a higher thermal conductivity, and therefore is superior to aluminum in processor cooling.
Click to expand...

Copper is better at conducting heat than aluminum, but aluminum is able to radiate the heat into the air better than copper because of its lower density.
Click to expand...

Links to other topics discussing the issue:

http://episteme.arstechnica.com/6/ubb.x?q=Y&a=tpc&s=50009562&f=77909585&m=8490955581
 
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Does this mean copper coolers will work better with higher flow fans,and aluminium lower power fans?-

Copper is better at conducting heat than aluminum, but aluminum is able to radiate the heat into the air better than copper because of its lower density.
Click to expand...
 
What about lapping of copper coolers?

I've always lapped my CPU/GPU coolers as a habit.

Mostly been using Thermal takes heatsink compound aswell.

Seems to work a charm for me.
 
Not sure what this means about fan power. The whole thermodynamics of cooling a processor has a lot of factors built into it.

As far as lapping, that doesn't really play into this discussion...
 
Indeed,

I must say that I started playing with Alu heatsinks in the beginning, but I have a marked preference for copper heatsinks with high speed/high volume fans attached to them.

Even the passive heatsinks I fit to my customers RAM and G-card RAM is copper if I can find them. A mixture of Thermaltake and Coolermaster products.

I just find that in my experience copper offers better cooling.

Here in South Africa it isn't unusual for the daily ambient temps to reach 35'C - 40'C.

So when you're running a high end machine and then OC'ing it, Copper Heatsinks suddenly become very important pieces of kit.
 
The best practical coolers have a copper base, usually heatpipes, and aluminum fins. Copper is better at heat transfer and aluminum is better at heat dissipation, so good heatsinks have a copper base that quickly/efficeintly gets the heat away from whatever is being cooled, heatpipes that quickly take the heat away from the base, and the heatpipes are attatched to aluminum fins that quickly dissipate heat. Some coolers are just a block with a copper base and aluminum fins. The aluminum absorbs heat away from the base and dissipates it at the fins. The heatpipe coolers are better though.

If coolers were just blocks temps would be much higher metal sandwiches with holes for tubing, they generally have some kind of pins inside the sandwich that gives much greater surface area for the water to make contact with the metal and dissipate the heat that way.

Silver is the best practical heat conductor, but it's too expensive to use in the place of copper. That's why we have arctic silver thermal paste. It's not a whole chunk of silver that's been put through metalworking processes, it's just silver dust mixed with some kind of thermal paste. Gold would be better but it's too expensive so it's not made. Diamond is the best, but they don't make that either, however I have seen a thread here on tpu about mixing diamond dust with other thermal paste for the absolute best stuff that can be made but I don't know where to start looking to dig that one up.
 
hat said:
The best practical coolers have a copper base, usually heatpipes, and aluminum fins. Copper is better at heat transfer and aluminum is better at heat dissipation, so good heatsinks have a copper base that quickly/efficeintly gets the heat away from whatever is being cooled, heatpipes that quickly take the heat away from the base, and the heatpipes are attatched to aluminum fins that quickly dissipate heat. Some coolers are just a block with a copper base and aluminum fins. The aluminum absorbs heat away from the base and dissipates it at the fins. The heatpipe coolers are better though.

If coolers were just blocks temps would be much higher metal sandwiches with holes for tubing, they generally have some kind of pins inside the sandwich that gives much greater surface area for the water to make contact with the metal and dissipate the heat that way.
Click to expand...

Myths About Materials/Coolants

Myth: Aluminum absorbs/dissipates heat faster than copper.

Reality: All thermal properties of copper are better than aluminum. Aluminum's advantage is that it is lighter and easier to machine. So, if one were given a pound of copper and a pound of aluminum, you might make a better performing heatsink with aluminum, as it might have more surface area to dissipate heat than copper for a given weight. Considering footprint limitations for air cooled CPU heatsinks, however, copper is definitely favored.
Click to expand...

Shortly said, copper dissipates and conducts heat better at all times. Aluminum is just cost- and weightsaving (especially weight). See the first link in my previous post.
 
good compromise cooler is copper plate with copper pipes going to aluminum fins,

cheapest solution is all aluminum

highest performing solution is copper (more dense material is the quicker stuff is conducted)

http://en.wikipedia.org/wiki/Heat_sink
 
Copper, because it can store more heat -> gets hotter -> is higher above ambient (than aluminium) -> thus radiates heat better.

Or something like that I read that finally made sense to me on the matter.
 
So what about the copper HS with the high volume/speed fan attached.

Would that be the ideal combination?
 
The best cooler would be:
High thermal conductivity
High surface area
Lots of coolant (air, water, whatever) touching the surface area.
 
As many have said copper is better. Full copper is better for cooling, but less practical (price, WEIGHT). A mixture of copper/aluminium can work as well as full copper in most practical situations though, because the cooler acts as a "capacitor" retaining the heat far from the CPU and dissipating it "slowly" (in comparison to full copper) doesn't matter too much. It also has the advantage of price and weight, specially weight, so with Al you can make more and bigger fins increasing surface area, mitigating the diference between Cu and Al.
 
DrPepper said:
http://www.xbitlabs.com/articles/coolers/display/thermalright-true-copper-u120x_8.html#sect0

Note that the all copper design is not that much better but it is better than the aluminium one.
Click to expand...

Thing is, it all comes down to about a square inch of contact between proc and cooler, and theres a max amount of heat that can be pulled away from that contact area.

Even the best cooler can only pull heat from that square inch and spread it throughout the cooler, which means that the "TRUE pure copper" is probably very near the maximum capacity you can pull away there.

The only thing that can increase your cooling capacity then is increase the difference in temp between CPU and ambient. Say with liquid nitrogen :D
 
Actually the current technology is hitting it dead on. Use copper and copper heat pipes to remove the heat from the cpu, then use Al to dissipate that heat into the air, not only that but you have to consider the weight of the cooler. If some of these massive heatsinks we see today were made entirely out of copper it would weight like 3 lbs and would be way to much stress on the motherboard and socket. Especially for tower mounted motherboards, everyone would have to have desktop cases so the heatsink was directly down on the socket.

The best is a combo of Copper Core/Heat Pipes channeling that heat to Al Fins. AL is lighter and dissipates heat faster into the air.

So in short. Copper is able to soak up heat faster due to its mass, but also because it has more mass it takes longer to cool down.
 
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The best cooler is running your chip in mineral oil.

:)
 
hat said:
The best practical coolers have a copper base, usually heatpipes, and aluminum fins. Copper is better at heat transfer and aluminum is better at heat dissipation, so good heatsinks have a copper base that quickly/efficeintly gets the heat away from whatever is being cooled, heatpipes that quickly take the heat away from the base, and the heatpipes are attatched to aluminum fins that quickly dissipate heat. Some coolers are just a block with a copper base and aluminum fins. The aluminum absorbs heat away from the base and dissipates it at the fins. The heatpipe coolers are better though.

If coolers were just blocks temps would be much higher metal sandwiches with holes for tubing, they generally have some kind of pins inside the sandwich that gives much greater surface area for the water to make contact with the metal and dissipate the heat that way.

Silver is the best practical heat conductor, but it's too expensive to use in the place of copper. That's why we have arctic silver thermal paste. It's not a whole chunk of silver that's been put through metalworking processes, it's just silver dust mixed with some kind of thermal paste. Gold would be better but it's too expensive so it's not made. Diamond is the best, but they don't make that either, however I have seen a thread here on tpu about mixing diamond dust with other thermal paste for the absolute best stuff that can be made but I don't know where to start looking to dig that one up.
Click to expand...

think this is what you were talking about.

http://www.heatsinkfactory.com/ic-diamond-7-carat-thermal-compound-15-gram-p-16605.html
 
Copper is better at conducting heat than aluminum, but aluminum is able to radiate the heat into the air better than copper because of its lower density.
Click to expand...
Now that, my friend, is bullsharks. It is ONLY TRUE if your comparison is the same WEIGHT of fin... 100g of aluminium has more surface area than 100g of copper, assuming same "thinness" of the fin. But suggesting that lower density itself is the reason for higher cooling rates is so wrong the author of that statement is due a Darwin award.
 
lemonadesoda said:
Now that, my friend, is bullsharks. It is ONLY TRUE if your comparison is the same WEIGHT of fin... 100g of aluminium has more surface area than 100g of copper, assuming same "thinness" of the fin. But suggesting that lower density itself is the reason for higher cooling rates is so wrong the author of that statement is due a Darwin award.
Click to expand...

Exactly. If the same volume and shape is made out of both materials, copper will win hands down.

Furthermore, lower density would mean there's a relative lot of air in the aluminum, which would actually make it perform worse, like air pockets under your cooler base instead of TIM.
 
Diamond (2300 W/mK)
Pyrolytic Graphite (1950 W/mK)
Silver (429 W/mK),
Pure Copper (401 W/mK), and
Pure Aluminum (237 W/mK)

The physical action of conduction/convection relies solely on the two material's individual thermal conductivities, their proximity to each other, and their time in contact with each other. Thus, a pure copper heatsink will always outperform a heatsink of the exact same geometry of a pure aluminum heatsink assuming that both have the same contact with the heat source and the same rate of airflow over the surface.

That is as basic as it gets...

The difficult problem is we are restricted. The heatsink can only have so much mass before it hurts the motherboard or cracks the IHS or just goes beyond load specs. We are also limited to the physical size of the heatsink. This is why we are seeing all these really cool heatpipes and copper/AL mixed blocks. So you have to run hybrid heatsinks to get the largest surface area in a small space and the most mass it can have without going over specs.
 
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DanishDevil said:
First of all, I want to lay some ground rules, because I have seen this go way out of bounds on many other forums.

If you're going to make a claim, please voice your opinion and state WHY.

The question we are focusing on related to processor cooling, specifically with air cooling, not water cooling. We can start a discussion for water cooling as well, but keep them separate and your comments specified and whether or not it makes a difference.

In a CPU heatsink, what is the best combination of copper and aluminum to extract heat away from the processor effectively, without having cost be a factor?

A few claims:





Links to other topics discussing the issue:

http://episteme.arstechnica.com/6/ubb.x?q=Y&a=tpc&s=50009562&f=77909585&m=8490955581
Click to expand...


All I know is Cooking with a copper vessel tastes far better than aluminum vessel:D
 
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