Thermal paste is an essential component of all electronic devices that develop heat during operation. It allows the heat to be dissipated through a metal heatsink and away from the circuit board, preventing overheating and potential permanent damage or abnormal operating conditions. Despite today’s highly efficient circuitry, even small computers can generate significant amounts of heat. Consequently, proper thermal transfer is crucial to system performance and reliability.
Thermal compounds consist of a base matrix and a thermally-conductive filler. Base matrices are typically epoxies, silicones, or urethanes; fillers may be made of metals, ceramic materials, carbon micro-particles, aluminum oxide, or boron nitride. The optimal formulation is one that is easy to apply, fills gaps well, conducts heat efficiently, and stays stable for thousands of hours without losing adhesion or discoloration.
In addition, the ideal thermal paste should not interfere with nearby components or cause short-circuiting during normal operation. Many modern pastes are based on a mix of oxidized metals (such as aluminum oxide) and other ceramic materials with a silicone binding agent. Others, such as ARCTIC MX-4, contain suspended particles of silver, which is much more thermally conductive than copper. However, silver is electrically conductive and should only be used on dies with heatspreaders or areas that do not have exposed components nearby.
To maximize the effectiveness of thermal pastes, they must be applied to a flat, even surface on both surfaces of the processor. In the case of CPUs, this is usually the IHS (Integrated Heat Sink). The use of a spreader ensures that there are no air pockets between the IHS and the CPU core. This is important because a gap between the two can significantly reduce the effective contact area and, therefore, improve the performance of the system. Thermal paste application