Specifically, this part is the most relevant:
Quote:
Fact 1: Aluminum has a higher specific heat and lower density than Copper. Specific heat is a measure of how densely a material can store thermal energy. If you add thermal energy to a specific mass of material, it will increase in temperature.
The specific heat of aluminum is 903 joules/kg*K at 300K while copper is only 385. The density of aluminum is 2702 kg/m^3 at 300K while copper’s is 8933. The product of specific heat and density determines how much energy may be stored in a given volume. For a given volume of material, copper will store more energy at a given temperature change than aluminum.
False Perception: Since aluminum stores less energy per volume, it must be more efficient at getting rid of heat.
Truth: During steady-state operation, there is no net energy storage in the heat sink or fins/pins; hence, specific heat plays no part in steady-state performance.
Fact 2: Aluminum has lower density than Copper. Volume for volume, aluminum is much lighter than copper.
False Perception: Weight acts as a “sink” for heat. Since copper is more dense, it absorbs heat well from the die. Since aluminum is light, it gets rid of heat more effectively than copper.
Truth: Density has no direct relationship with steady-state heat transfer.
Fact 3: A small volume of aluminum will cool more quickly than an equal volume of copper once the heat source is gone. This is due to the same reason as fact #1, namely there is less energy stored per unit volume is aluminum than copper. This is, however, a transient condition. Heat transfer from a computer is a steady-state condition where the temperature of the heat sink remains relatively constant. The specific heat of a material partially determines how a material responds to transient conditions but has no effect at all on steady-state operation.
False Perception: Since aluminum cools more quickly once a heat source is removed, it must be more efficient at convection.
Truth: The heat source driving energy into the heat sink remains in effect until you turn off your computer. If you have aluminum pins or fins, congratulations, they will cool off more quickly than copper ones after you shutdown your PC.
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Aluminium is better at radiating heat that copper is, but that is not very relevant unless you are planning to have your computer operating in a vacuum.