Thermal grease

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From left to right: Arctic Cooling MX-2 and MX-3, Tuniq TX-3, Cool Laboratory Liquid Metal Pro( Liquid Metal based), Shin-Etsu MicroSi G751, Arctic Silver 5, Powdered Diamond. In background Arctic Silver grease remover
Silicone thermal compound
Metal (silver) thermal compound
Metal thermal grease applied to a chip
Surface imperfections

Thermal grease (also called thermal gel, thermal compound, thermal paste, heat paste, heat sink paste, thermal interface material, or heat sink compound) is a kind of thermally conductive (but usually electrically insulating) adhesive, which is commonly used as an interface between heat sinks and heat sources (e.g., high-power semiconductor devices). The grease gives a mechanical strength to the bond between the heat sink and heat source, but more importantly, it eliminates air (which is a thermal insulator) from the interface area.

Composition[edit]

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, although 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 70–80 wt %, and the fillers raise the thermal conductivity of the base matrix from 0.17–0.3 watts per metre Kelvin or W/(mK), up to about 2 W/(mK).[1]

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[edit]

Compound Thermal conductivity (ca. 300 K)
(W m-1 K-1)
Electrical resistivity (ca. 300 K)
(Ω cm)
Thermal expansion coefficient
(10-6 K-1)
Reference
Diamond 20 ‒ 2000 1016 ‒ 1020 0.8 (15 – 150 °C) [2]
Silver 418 1.465 (0 °C) [3]
Aluminum nitride 100 ‒ 170 > 1011 3.5 (300 – 600 K) [4]
β-Boron nitride 100 > 1010 4.9 [4]
Zinc oxide 25.2 [5]

See also[edit]

External links[edit]

  • How To Correctly Apply Thermal Paste [1], Hardwaresecrets.com.

References[edit]

  1. ^ Werner Haller et al. (2007), "Adhesives", Ullmann's Encyclopedia of Industrial Chemistry (7th ed.), Wiley, pp. 58–59 
  2. ^ Otto Vohler et al. (2007), "Carbon", Ullmann's Encyclopedia of Industrial Chemistry (7th ed.), Wiley 
  3. ^ Hermann Renner et al. (2007), "Silver", Ullmann's Encyclopedia of Industrial Chemistry (7th ed.), Wiley, p. 7 
  4. ^ a b Peter Ettmayer; Walter Lengauer (2007), "Nitrides", Ullmann's Encyclopedia of Industrial Chemistry (7th ed.), Wiley, p. 5 
  5. ^ Hans G. Völz et al. (2007), "Pigments, Inorganic", Ullmann's Encyclopedia of Industrial Chemistry (7th ed.), Wiley