Is copper really a better heatsink?

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saxile

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Let me know what you think as well, this is my thoughts:

No, I think copper is a very bad heatsink. Yes it does transfer heat faster, but at the same time it holds it longer therefore not letting the heat escape. Now that some places have finally relized this they have started making copper alloy and sometime mixed with Aluminum Alloy. But I believe the best for cooling purposes is still Aluminum or Aluminum alloy.
 
Here is how I understand it.

It is easiest for me to think in terms of electrical circuits since I have more experience with them. Fortunately, thermal circuits are completely analogous to electrical ones, at least on the level I deal with them.

The source of heat, the CPU chip, can be thought of as the + terminal of a DC voltage source. The ambient air surrounding the heatsink can be thought of as the - terminal of a DC voltage source. The heat sink itself can be thought of as the resisatance connecting the + to the - terminal of the source, just like a wire and resistor in an electrical circuit. This is the analogy.

Now as in an electrical circuit, the lower the amount of resistance in the circuit the lower the amount of heat dissapated in that resistance. It's just that for a thermal circuit we refer to thermal resistance, or resistance to heat flow, instead of a resistance to current flow.

Now from the analogy it is easy to see that heatsinks with the lowest thermal resistance will run coolest.

Materials scientists say that copper has lower thermal resistance. This means that for a given physical configuration copper outperforms aluminum.

Obviously I have not gone into great depth, in fact this is about as in depth as I go on this subject. It helped me to see the analogy, maybe it will clear things up for you too.

I really wouldn't know what the purpose of the alloy is. It wouldn't suprise me to learn that the alloy has better thermal properties though since in general most of materials science engineering seems like a lot of voodoo to me.
 
Copper absorbs the heat faster but it holds heat inside it. (example put a Aluminum in the fridge and a can the same size made of copper. The Aluminum can will cool off faster and will warm up faster, where as copper takes longer to cool off and heat up.)
 
Aluminum has a higher specific heat capacity, which means it takes more input energy to raise it's temperature per degree than it does to raise the temperature of an equal amount of copper. This means that an aluminum heatsink has the capacity to hold more thermal energy in it than a copper heatsink. It also means that the temperature difference between the heatsink and core will be as greater than a copper heatsink initially, resulting in possibly better cooling. However, once given a chance to reach thermal equilibrium, the copper heatsink will be able to "pump" more heat from the core into the surrounding air, thereby being more effective.

Think of a heatsink as being a faucet, and the thermal conductivity being how big the nozzle in your faucet is. The temperature of the core is like the pressure of the pumping station. It's easy to see that a larger opening in your nozzle, the more water you'll be able to get out. Same with heat. The better the thermal conductivity of you heatsink, the more heat you'll be able to transfer from your core to the air.

Specific heat capacity is only relevant for fluids in dynamic cooling situations.

Lyrics. Wasted time between solos.
 
I know copper is a better conductor than AL (I think its electrical conductivity is something like 2:1 over AL). Is it true that copper 'holds' heat longer than AL? Empirically, it seems to be the case since from the kitchen, I know that AL pans cool much quicker than Cu pans. But this could be due to that fact that Cu can hold much more heat due to being denser. If it is the case, which physical measure describes this phenomenon?

As for heat sinks, I think it has been shown many times that the biggest factor in cooling is how much air is forced over the hsf (which is also a function of the HS surface area). The difference due to Cu and Al difrrential conductivity is negligible. If you have good ventilation, it al/cu doesn't matter at all.

Al has advantages since it is cheaper and lighter. Cu is better because it is more malleable and so can be formed into shapes with greater surface area. Also, it doesn't have to be treated as with anodized Al. So for HSF, get the one with the greatest surface area.

Those zalman flower fan hs look like a good idea. they maximize surface area, plus you place a 92 mm fan above it giving you quieter and better air flow. ANyone tried one of those?
 
Yes, but a larger nozzle means less water pressure at the same time, where as a smaller moves the water through faster
 
Your right my model is incomplete. The specific heat capacity can be viewed as a thermal capacitor in parrallel with the thermal resistance. The reason I didn't mention it the first time is that for computer cooling it is more or less a negligible affect, due to he fact that computers are either normally being used for xtended on periods, or extended off periods.

As in an electrical circuit the capacitance is charged at the beginning for DC, but the rest of the time only performs a waveform smoothing function. In our case, we use a temp vs time waveform, for the electrical circuit case this is analogous to the voltage vs time waveform. For example a material with a greater specific heat capacity, would be more resistant to changing it's temperature during local temporary temperature fluctuations, due to the fact that it has this heat well (capacitance?) from which it can draw and add heat to and from. So the net effect will be a smoothing of the temperature vs time curve, not some biasing of the curve.
 
the copper spreads the heat to all its parts but the aluminum keeps it around the core. if you have a low heat prducing prossecor its best with aluminium but when you want to move alot of heat its best with the copper.

<font color=blue>there are <font color=red>penguins</font color=red> living on my north bridge in my computer case</font color=blue>
 
yes, but which has a faster flow, the pinhole does, the more pressure behind something the faster it moves. Yes the bigger hole has more coming through it, but look at how slow it moves.
 
Yes, copper makes a better heatsink. In order from lowest to highest it is Al > Cu > Ag > diamond.

Yes Al will dissipate its heat quicker than Cu, but Cu will pick up more than Al (a gross oversimplication). So when you first turn on the PC, an Al heatsink will heat up quicker and start moving heat away sooner, but as the system approaches its thermal equalibrium (roughly about the time that Windows starts booting) the Cu heatsink will be moving more heat.

That's why some manufacturers make heat sinks with a Cu core and Al fins. In theory the Cu core will pick up the heat better and then the Al fins will disperse it quicker. In pratice it doesn't work this way, but I won't go into details here.

Silver (Ag) is even better than Cu. Diamond is the best of all. It is many times more efficient than Ag. Problem is that both of these materials cost alot, and Ag isn't that much more efficient that the extra cost is worth it.

Past diamond, there's graphite, but that will only conduct heat along one plane, plus it's too soft to use in a heatsink. After that its a certain form of liquid helium that only exists within a few degrees of absolute 0. After that there's nothing.

So realistically the best is silver. Pratically the best is copper. Al, Cu and Ag aren't that far apart though. When you start getting empirical, other factors greatly outweigh the construction material. It's better to have more/thinner fins, a greater surface area and a faster fan that it is to chose Cu over Al. If everything else is the same, you might see a 1 or possibly 2 degree difference between Al and Ag.

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Knowan likes you. Knowan is your friend. Knowan thinks you're great.
 
Sure the water will move faster, but you're moving much less in a given time. Copper is better than Aluminum, that's about it.

Silver is better, but it's expensive, and pure silver is much too soft to use (you can scratch it with your fingernails).

Lyrics. Wasted time between solos.
 
Might want to read <A HREF="http://www.amdmb.com/article-display.php?ArticleID=105&PageID=4" target="_new"> This </A>

:smile: <font color=blue>You get what you pay for.... All advice here is free.</font color=blue> :smile:
 
Well I went from A Fop38 to A CakII38..It is way better than the Fop38..Im down 9c from my original 39c.Well case cooling has a lot to do with it..But none the less,Their new copper HSF Is better than a lot of them..
Athlon1.2@1.3


"GlobalWin Fan Forever"
 
thinking about this, with the graphite transferring heat® in one plane...and being too soft...®
maybe graphite can be used to direct heat in a heatsink.®
like put it INSIDE aluminum, or copper.®
maybe it could work inside something like the zalman® flower design.®
i dunno how the hell that would work...®
and NO ONE STEAL MY IDEA IF IT WORKS!®
hehe®


-DAvid

-Live, Learn, then build your own computer!-

**now it is all ® hehe­­ :smile: <P ID="edit"><FONT SIZE=-1><EM>Edited by HonestJhon on 02/19/02 11:57 PM.</EM></FONT></P>
 
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