In order to promote the maximum amount of thermal conductivity, aluminum heatsinks are used in a wide variety of applications with high-level thermal requirements. This is in part due to the fact that aluminum is highly conductive of heat energy, transmitting at about five times the conductivity of steel. Yet in addition to their high conductivity, aluminum heatsinks are advantageous due to their high level of malleability; it is a soft metal, and can be refined quite rapidly. In addition, there is a wide variety of methods by which aluminum heat sinks can be produced, including forging, die-casting and other options for this highly inexpensive material. On top of these beneficial features, however, aluminum also has an extremely light weight, making it a desirable type of heatsink - especially for portable appliances - due to the low level of mounting stress involved.
Copper - a metal with a much higher rate of thermal conductivity - is also used to construct heatsinks, and can actually be used in conjunction with aluminum to optimize the effectiveness of the heatsink. Many heatsinks that join copper and aluminum together will include a base that is made out of copper while the fins are constructed as thin slivers of aluminum connected strongly to the base and extruded out into the air. The advantage to this type of extrusion system is that the copper is able to more effectively carry heat from its source to the lighter cooling fins.
An alternative to bonding two metals together is found in the process of creating a heatsink made entirely out of aluminum. This can be done with Skived Fin Technology, or the cutting out of the whole heatsink from the same block of metal. Aluminum heatsinks built in this way have the conductive advantage of no possible interruptions in thermal flow between the base of the heatsink and its fins. While not make use of the higher conductivity of copper, skived aluminum is nonetheless very effective as a heatsink.