Different thermal compounds
ArcticSilver II, AOS “HTC” Compound, standard silicone compound
The most commonly used interface material in the electronics cooling area is thermal compound, a sticky paste applied directly on the heatsink or CPU.
A good-quality thermal compound will provide the best possible performance. However, the disadvantage of thermal compound is that it is quite messy to
handle, and therefore not suitable for mass production.
For this reason, most heatsink manufacturers ship their heatsinks with a “thermal pad”, which is supposed to replace thermal compound. The cheapest heatsinks
usually come with silver/grey graphite pads. Graphite pads are inexpensive, but provide poor performance (unless a high pressure is applied to the pad,
which is not the case when the CPU and heatsink are installed in a regular way). A graphite pad is better than no interface material at all, but if you have the choice, stay away from them.
Today, there are far more advanced thermal pads available, made by companies such as Power Devices, Bergquist or Chomerics, to name only a few. For links to
the web sites of these companies, check out the links page. The performance of these pads can be roughly equal to standard thermal compound.
Chomerics pad, with its protective foil
The foil must be removed before installation
Newer thermal pads are usually made of a phase-change material, which melts to fill all the fine gaps between CPU and heatsink the first time the CPU is
heated up. These pads are typically only suitable for one-time installation; if you uninstall the heatsink, e.g. in case of a CPU upgrade, the pad must be
removed from the heatsink and replaced by thermal compound. In no case, a thermal pad and thermal compound should be used together.