Thermal grease (also called CPU grease, heat paste, heat sink compound, heat sink paste, thermal compound, thermal gel, thermal interface material, or thermal paste) is a kind of thermally conductive (but usually electrically insulating) compound, which is commonly used as an interface between heat sinks and heat sources (e.g., high-power semiconductor devices). The main role of thermal grease is to eliminate air gaps or spaces (which act as thermal insulator) from the interface area so as to maximize heat transfer. Thermal grease is an example of a Thermal interface material.
As opposed to thermal adhesive, thermal grease does not add mechanical strength to the bond between heat source and heat sink. It will have to be coupled with a mechanical fixation mechanism such as screws, allowing for pressure between the two, spreading the thermal grease onto the heat source.
Composition
Thermal grease consists of a polymerizable liquid matrix and large volume fractions of electrically insulating, but thermally conductive filler. Typical matrix materials are epoxies, silicones, urethanes, and acrylates, solvent-based systems, hot-melt adhesives, and pressure-sensitive adhesive tapes are also available. Aluminum oxide, boron nitride, zinc oxide, and increasingly aluminum nitride are used as fillers for these types of adhesives. The filler loading can be as high as 70â€"80 wt %, and the fillers raise the thermal conductivity of the base matrix from 0.17â€"0.3 watts per meter Kelvin or W/(m·K), up to about 2 W/(m·K).
Silver thermal compounds may have a conductivity of 3 to 8 W/(m·K) or more. However, metal-based thermal grease can be electrically conductive and capacitive; if some flows onto the circuits it can cause malfunctioning and damage.
Filler properties
Utilizing thermal grease
Intel, aftermarket recommendation
Intel, crit.tv, Arctic GmbH recommend to squeeze a pea-sized amount of thermal grease onto the center of the CPU. The Heat sink is then installed on top of the thermal grease. Intel uses Dow Corning TC-1996 thermal grease.
AMD recommendation
AMD recommends to squeeze a pea-sized amount onto the center of the CPU. This should be evenly spread over the entire processor surface area, and you can use a credit card as a tool to help accomplish this task. Keep in mind that the purpose of thermal compound is to compensate for imperfections between the CPU and cooling block, not to add a barrier between them. A proper application should result in a very thin layer without any visible streaks or clumps.
See also
- Computer cooling
- Hot-melt adhesive
- Phase-change material
- Thermally conductive pad
- Thermal adhesive
- List of thermal conductivities
References
External links
- Barros, Daniel (2006-01-12). "How To Correctly Apply Thermal Paste".Â