Heat Sink Compound / Paste

Heat sinks operate by conducting heat from the processor to the heat sink and then radiating it to the air. The better the transfer of heat between the two surfaces (the CPU and the heat sink metal) the better the cooling. Some processors come with heat sinks glued to them directly, ensuring a good transfer of heat between the processor and the heat sink.

Heat sinks that are attached using clips normally sit rather loosely on top of the processor. It may feel like it is attached securely, but there will be a gap between the CPU and the heat sink, and that gap of air them makes for poor heat transfer, even if it is very small. Air is a poor conductor of heat compared to most liquids or solids. To improve the thermal connection between the processor and heat sink, a special chemical called heat sink compound should be used. A thin layer of this is spread between the two, which greatly improves heat transfer and the cooling of the processor.

Heat sink compound is typically a white paste made from zinc oxide in a silicone base. Very little of the substance is needed, just enough to fill the gap between the CPU and heat sink. Using more will not make it work better, it will just make a big mess when you press the heat sink down onto the CPU, much like putting too much strawberry jam in your PB&J sandwich. :^) The use of this compound is strongly recommended for those who want to cool their processors properly. See the Heat Sink Installation Procedure for instructions on how to use it properly.

Tip: The easiest place to get this compound in North America is at Radio Shack, which sells it for about $3 a tube. A single tube is enough for a good dozen processor treatments.

Note: Some processors come from the manufacturer with the heat sink glued or similarly permanently attached to the chip already. These heat sinks do not require heat sink compound. (This does not always apply to chips you get from a systems vendor.)

Warning: Do not put strawberry jam on your processor. :^)