A heatsink thermal pad is a small, usually square pad that is typically used with a central processing unit (CPU) and heatsink to create a better system of thermal conductivity. This is often used instead of thermal paste since it is less messy than the paste and is sometimes included with a newly purchased heatsink rather than thermal paste. A heatsink thermal pad is typically less effective than thermal paste, however, so any computer user looking to overclock his or her CPU should consider using the paste rather than a pad.
Inside of a computer tower, or case, the CPU is connected directly to the motherboard. As the computer functions, the CPU can very quickly heat up, and without proper cooling, the computer may shut down or not start up properly and the CPU can actually melt inside the computer. This cooling is typically achieved by using a heatsink, a device connected to the CPU that transfers heat away from the CPU and disperses the heat throughout the computer, where it passes out of the tower by the fans on the case.
For the heat transfer to properly occur between the CPU and the heatsink, they must come in contact as perfectly as possible. Microscopic flaws in the surface of the CPU and heatsink, however, reduce this contact and lessen the effectiveness of a heatsink. A heatsink thermal pad or thermal paste is used to fill in any of the gaps from these flaws and create more effective heat transfer. The heatsink thermal pad is placed between the CPU and heatsink and creates more flawless connectivity.
One of the main reasons that a heatsink thermal pad is typically less effective than thermal paste is that the pads are often made from graphite or a similar substance that does not provide the heat transfer that other materials do. Thermal paste is a very sticky compound about the consistency of a gel, usually made with silicone and zinc oxide. Other materials such as ground metals or even silver can also be used to increase the heat transference of thermal paste. These materials are not typically used in making a heatsink thermal pad, and cheaper pads are often made from less effective materials.
Newer or more expensive types of heatsink thermal pads can be made using phase change materials that will actually melt the first time the computer is used and the CPU begins to heat up. This creates a connection similar to that achieved using thermal paste and can quite effectively improve the heat transfer between the CPU and heatsink. For computer users running a high end machine or an overclocked CPU, thermal paste is still typically preferable to a heatsink thermal pad. Only one or the other should be used, however, as both can reduce the effectiveness of the system. A pad should only be used once.