Modern Central Processing Units (CPUs) consume a lot of power, which is converted to heat in the process. However, one of a computer’s worst enemies is heat. Heat can cause severe damage to any electronic component, especially integrated circuits (ICs).
Heat damage is not an issue for smaller electronic components, which do not generate enough heat to cause problems. However, CPUs, northbridge chips, and graphics cards all produce enough heat to destroy themselves if overheated. Early Pentium 1 computers had a serious problem with overheating, especially when used in a warm environment. This led to the installation of heatsinks and fans as standard items on computer CPUs.
The purpose of a heatsink or fan is to remove the heat from the CPU (or other chip) and dissipate it into the air. To do this, the heat first must be transmitted from the CPU to the heatsink. While this might seem like a simple enough proposition, it is not. Air makes a very effective heat insulator, so for the heat to get from the CPU to the heatsink, the heatsink must be installed without any air gaps whatsoever. Even an air gap of a few microns can slow down heat transfer.
Since it is virtually impossible to make a CPU and heatsink that fit together perfectly, a thermal paste or grease is sandwiched between the two. This non-conductive material is designed to fill any air gaps, ensuring the best possible mechanical connection between the two. The better air gaps are eliminated, the better heat flows out of the CPU and into the heatsink.