so if been tring to decide what cooler to get for my proc and i was looking at the zalman 9700 LED and NT. I noticed that one was all copper and the other was copper and alu. so the question popped into my head, which is better?

While that statement is correct it suggests (given the context of the OP) that copper heatsinks are generally better than those composed of copper and aluminium which isn´t necessarily so.
CPU coolers are limited by their weight and since aluminum tends to be a lot lighter than copper, you can have a larger aluminium cooler, which should have a larger surface (and fins that don´t dent like butter) and dissipate heat quite well. Basically it boils down to a function of weight and heat disspipation. I´m not sure how large the aluminum component has to be to be equal to copper though.

Given its the same cooler just difference construction, the CU one is better.

This is typical of Zalman, one is a pure copper cooler (the more expensive one usually) and the more budget minded one has a copper core but everything else is aluminum.

Go with the CU one.

the performance of CU is better
the weight of a AL-CU is lower
but AL-CU will do perfect, even if you overclock, a little.
the extra money isn't much, but doesn't give you a price/performance wise extra.

Copper pulls more heat from the source than aluminum, but aluminum dissipates heat faster than copper.

Look at the Tuniq tower 120, do you really want a heatsink that weighs in at 2kilograms? I dont think so. Dont only look at the material used but the design as well.

I've recently had to choose myself and I laid out the cash for the 9700 (after some advice and a few benchmarks from various sites). I've still got to get my e6600 (should be within the next week or two) but I've always prefered to use a copper unit where possible.

Aluminum actually dissipates heat better. Copper conducts heat better.

This is the reason most heat sinks use a copper slug and copper heat pipes up to aluminum fins, and not the other way around.

Do you have a source for this info?

-Brad

I'm hoping this post will look proper, but I'm not a posting expert. But I do have some expertise to add outside of adding emoticons...

The Cp (heat transfer coeff) of copper is higher than that of aluminum. Copper is superior in all aspects of conducting heat from a high-temp reservoir (your CPU) to your low-temp reservoir (the air).

But, in the real world, the "shape" of your cooler will have a lot to do with how efficiently the heat is moved. For example, you will kill an old-fashioned copper-brass plate-fin radiator with new-fangled aluminum serpentine fin radiator. The heat transfer surface (regardless) of material is fantastically more efficient because of the geometry.

Frankly, I do not know whether the all-copper model will do much better, or not. But my gut says it will be a minimal improvement over aluminum. In 6 months after the dust bunnies have collected, the least of your worries will be the base material of the H.T. surface. I would go for the aluminum myself.

Though copper fins are easier to straighten than aluminum. Aluminum IS brittle, and if you handle the cooler excessively, perhaps copper is the best choice.

FWIW

Do you have a source for this info?

-Brad

At some point I did. But as am am looking for it I'm finding things that are contridicting what i have read.

So at this point I will retract my statement that Aluminum dissapates better until further notice.

But it IS a fact the copper conducts better.

Don't be so hard on yourself -

You can sort of make the argument that aluminum is more efficient beause the ability to make a very efficient shape (notice that many factory heat sinks are made of an aluminum extrusion) allows aluminum to trump copper.

But people will pay $$ more for overclockable memory even if they never overclock and other such things. So why not heat sinks?

Just thought of something else. The aluminum is generally a shiny silver color, whereas the copper cooler may look dull in comparison. The aesthetic vote goes to aluminum!

Im still waiting for a pure silver Tuniq tower

Actually the silver 9700 LED is a copper base plate and fins. It's nickel coated to make it look silver and that's why it's expensive. But no difference on the all copper one.

Ok, lets apply some science:

It is true that copper conducts heat better, higher Cp value (as mentioned by someone else) but no-one has mentioned the specific heat capacities (SHC).

The SHC is how much energy one kilogram of substance can absorb to raise it by 1 degree.

Copper has a SHC of 0.31 KJ/Kg/K
Aluminium has a SHC of 0.91KJ/Kg/K (more than double!)

This means that for the same weight of metal Aluminium contains twice as much energy which means it can transfer more energy to the air that passes over it thus keep the processor cooler.

An ideal heatsink i would think is one that has copper nearest to the cpu to transfer the heat away quickly (copper heat pipes) but then changes to aluminium to gain highest transfer of heat to the air (big aluminium fins).

Aluminium is also less dense which means that it can have the same surface area as copper and will weigh less. Higher surface area=more heat transfer.

I think this should clarify the issue.

(I am a chemistry student at oxford university btw)

A key thing you have to remember is that this is all in STEADY-STATE:

1) One material absorbing heat into itself better than another means the cpu will stay colder when you first start up but in general operation the temperature in a given spot on the heat sink remains the same over time. i.e. don't count on copper's specific heat capacity to absorb your cpu's heat while you use it, the copper instead has to transport the heat to the fins where it is dissipated by the cooler air.

2) The heat drawn away from the cpu is at the exact same rate as the heat drawn away from the fins by the air (conservation of energy for steady-state systems means conservation of power).

I calculated this for a friend a few years ago and it is very design-dependent, but generally copper will be 5-10% better than aluminum for the same design. So CU is better, just not that much. If you want to get into a real sciencish discussion of how aheatsink should be designed, PM hotfoot.

Jo

Edit: I should also say that the transfer to air is the hardest part since both Cu & Al have very high conductivity, so even though Cu's conductivity is better than Al's by a decent amount (~69%), it does not translate into much extra heat dissipation. Designing a better shape, larger heatsink, thinner fins, better airflow though it are much much more important than Cu vs Al.

Finally someone that knows what specific heat is. Also this is why water cooling works so well. The specific heat of water is 1, and an advantage it has over aluminum is that it has a larger mass that also plays a large roll in how much heat can be dissipated

(BTW aluminum has one i not two just kidding)

Copper heatsinks are heavy (1.5-2 lbs!). That will put significant strain on the motherboard. One thing is for sure, you don't need all that weight bouncing around. So if you intend on transporting/moving the PC a lot, consider getting a lighter aluminum heatsink.

A note about the spelling of aluminIUM, which is the correct spelling. Heres something I found

"Aluminium is the IUPAC spelling and therefore the international standard"

So you annoying americans, please spell aluminium correctly in this UK (not america for those of you who dont know) forum.

Nope. Thermal conductivity of a material doesn't depend on transfer direction. Also, copper is way better than aluminium for thermal conductivity.