Heat sink material refers to the specific material used by heatsink. As for the heat sink material, the thermal conductivity of each material is different. The thermal conductivity is arranged from high to low, namely silver, copper, aluminum and steel. But silver would be too expensive to use as a heatsink, so copper materail is the best solution. Although aluminum is much cheaper, it clearly does not conduct heat as well as copper (about 50% as well). At present, the most commonly used heat sink material is mainly copper and aluminum , both have their advantages and disadvantages. Copper has good thermal conductivity, but it is very expensive and difficult to process, too heavy (many full copper heat sink exceed the weight limit of the CPU), small in heat capacity, and easy to oxidize. While pure aluminum is too soft to be used directly, only the aluminum alloy used can provide enough hardness. The advantage of aluminum alloy is low price, light weight, but the thermal conductivity is much worse than copper. Some of the heat sink make good use of each strength, in the aluminum heat sink base embedded a copper plate. 

Comprehensive consideration of price, heat dissipation performance, processing difficulty, and so on, the best heat sink material is aluminum.

1. Aluminum heat sink 

2. Copper heat sink