Comparison of copper fin Heat Sink and aluminum fin Heat Sink performance

Copper Fin Heat Sink performance vs. Aluminum has always been debated and never stopped. Do copper fins perform better, or do aluminum fins perform better? Copper or Aluminum? It's a real question!

Some people say that copper conducts heat faster and aluminum dissipates heat faster. Is this statement correct? Others say, Copper is better than aluminum in any case in PCHeat Sinks made by CPUHeat Sink manufacturers. Is there a scientific basis for this? To understand these questions, we must start with thermal conductivity and heat dissipation.

Thermal conductivity and heat dissipation.

In the working process of a Heat Sink, heat transfer is divided into two main parts: heat conduction and heat dissipation. As the name suggests, the so-called heat conduction can be understood as heat conduction in a solid. For the heat sink, we can roughly consider the heat conduction process from the CPU to the fins as heat conduction.

The term heat dissipation is even more succinct and naturally refers to the process of heat transfer from a solid to a gas as the heat radiates from the fins into the air.

The two processes of heat conduction and heat dissipation are at the heart of Heat Sink's work, and they go hand in hand.

Copper vs. Aluminum

After clarifying the concepts of thermal conductivity and heat dissipation, let's analyze the material characteristics of copper and Aluminum.

As we all know, the most prominent advantage of copper is high thermal conductivity. The thermal conductivity of pure copper (copper violet) is as high as 401W/m*K, which is second only to silver (429W/m*K) among common metals and much higher than that of Aluminum (240W/m*K.) Therefore, in the direct thermal conductivity of the base, heat pipes, and other components, copper, which has a higher thermal conductivity, is far superior to Aluminum. In front of Aluminum, there is no doubt that copper conducts heat faster.

Pure copper radiator base

The most prominent feature of Aluminum is large specific heat capacity. The specific heat capacity of pure Aluminum is as high as 8.8×10^2J/(kg-°C), which is 2.25 times higher than copper's. However, does a larger specific heat capacity necessarily mean a larger heat capacity?

Heat Sinks are not products that can scale infinitely in volume, and in real-world comparisons, it's often not the weight of the Heat Sink that remains constant but its volume—and in terms of density, copper has a huge advantage. As mentioned earlier, Aluminum has 2.25 times the specific heat capacity of copper. However, pure copper is up to 3.3 times denser than Aluminum!

1m^3 × 2700kg/m^3 × 0.88 × 10^3J/(kg-°C) = 2376000J = heat absorbed by 1m^3 of aluminum

1m^3 × 8900kg/m^3 × 0.39 × 10^3J/(kg-°C) = 3471000J - heat absorbed by 1 cubic meter of copper

After some conversions, we can see that the same volume of copper absorbs about 30-40% more heat. Although the specific heat capacity is smaller, the copper Heat Sink has a greater heat capacity thanks to its density.

But this doesn't necessarily seem to be a good thing, and it's in the absorption of heat that the disagreement arises. The process of heat dissipation in a Heat Sink requires the convection of a fluid (i.e., air), according to the formula used to estimate heat convection:

Heat flow = convective heat transfer coefficient x object surface area x (temperature difference between object surface and fluid ΔT)

It can be learned that, in the case of the same convective heat transfer coefficient (which can be understood as wind force), the greater the temperature difference ΔT between the object's surface and the air, the greater the heat flow and the better the heat dissipation.

The aluminum dissipates heat faster argument suggests that although aluminum Heat Sinks have a smaller heat capacity, they have an advantage in dissipating heat faster because they heat up quicker, and the larger temperature gradient results in greater heat flow.

However, is this the case?

Remember what we said before? Heat conductivity and Heat Sink go hand in hand; you can't have one without the other. The key is that Heat Sink is a whole, and Heat Dissipation can't be discussed independently of Heat Conduction!

Let's set the CPU's temperature to T1, the fins' temperature to T2, and the air's temperature to T3, with the temperature difference between the fins and the air still being ΔT.

We all want the CPU temperature T1 to be lower, so we want more heat to be transferred to the Heat Sink, causing the fin temperature T2 to rise. The smaller the difference between the CPU temperature T1 and the fin temperature T2, the more evenly the heat is distributed across the Heat Sink. This is the process of heat conduction.

As mentioned earlier, the greater the temperature difference between the surface of an object and the air, the better the heat dissipation. So, the larger the temperature difference ΔT between the fin temperature T2 and the air temperature T3, the faster the heat dissipation. This is the process of heat dissipation.

I don't know if you've noticed, but according to the order of heat transfer, a small difference between CPU temperature T1 and fin temperature T2 is a prerequisite for a large difference between fin temperature T2 and air temperature T3. That is to say, under the premise of constant air temperature, only when the heat is sufficiently transferred to the fins will the temperature difference between the fins and the air be bigger.

The higher the thermal conductivity of the material, the faster it conducts heat, all other conditions being equal. According to the heat conduction formula, the higher the thermal conductivity of copper fins, the smaller the temperature gap with the CPU and the larger the temperature difference ΔT with the air; thus, the heat dissipation efficiency is stronger.

T1-T2 = Thermal Resistance × Heat Flow

Thermal resistance = conductor length ÷ (thermal conductivity × cross-sectional area)

This means that, in practice, other conditions are constant, Aluminum's thermal conductiviAluminumot strong, and it is impossible to create a larger ΔT temperature difference than copper. The claim that aluminum dissipates heat faster ignores Aluminum's weakneAluminumhermal conductivity and forces copper and aluminAluminumport the same amount of heat in the same amount of time, which naturally leads to the wrong conclusion.

So, copper is suitable for components responsible for heat conduction, such as heat pipes and bases, and aluminAluminumeal for parts accountable for heat dissipation, such as fins. Yes, but no.

It's right because while Heat Sinks can't be infinitely large, they can't be infinitely heavy. If all the fins were made of pure copper for the growing tower Heat Sinks, the Heat Sink would become too heavy for the motherboard.

Therefore, pure copper is a more performant solution than copper-aluminum hybrid, as conditions permit.

Reach a verdict

Thermal conductivity and heat dissipation go hand in hand and are indispensable. They are the core of the cooling system and can not be discussed separately. Copper thermal conductivity point of view is not a problem, and the aluminum heat dissipation fast statement, which ignores the link between the two, will be thermal independent of the thermal conductivity discussion, which led to the wrong. Thermal conductivity is discussed independently of thermal conductivity, thus arriving at the wrong results.