Thermal compound is a liquid or gel used to fill the gaps between two surfaces for better heat transfer. It is commonly used between the microprocessor and a mechanical heat sink in electronic devices like computers, tablets and laptops to improve performance by lowering temperatures. High-quality thermal pastes will offer low bond line and good thermal resistance and conductivity to ensure that the CPU and heat sink have a solid contact. This is important as air, which is a poor conductor of heat, can fill the gap between the processor and the heat sink and prevent efficient transfer of heat between them.
Most mainstream thermal compounds consist of a bonding material and a filler material. The bonding material is often a type of silicone, while the filler could be silver, aluminum or other materials ground into a fine powder and mixed with the bonding material. The final mixture is usually kept as a secret recipe and can be different for each manufacturer.
The most important property of a thermal paste is its conductivity, indicated on the label in W/mK. The higher the number, the better the thermal conductivity. The other properties of a thermal paste to look out for are the viscosity (also indicated on the label as “spreadability”) and the chemical stability.
Gelid GC-Extreme is a liquid metal thermal compound with a moderate viscosity that allows it to spread easily over the surface of the CPU integrated heat sink. It also has excellent stability during application and requires only modest pressure to achieve an even coating. Phobya LM is another liquid metal thermal compound that has a moderate viscosity and requires little effort to apply to the CPU IHS.