Thermal interface material

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A thermal interface material (shortened to TIM) is any material that is inserted between two components in order to enhance the thermal coupling between them. A common use is heat dissipation, in which the TIM is inserted between a heat-producing device (e.g. an integrated circuit) and a heat-dissipating device (e.g. a heat sink).

There are several kind of TIM with different target applications:

  • Thermal grease: Mostly used in the electronics industry, it provides a very thin bond line and therefore a very small thermal resistance. It has no mechanical strength (other than the surface tension of the grease and the resulting adhesive effect) and will need an external mechanical fixation mechanism. Because it does not cure, it is used only where the material can be contained or in thin application where the viscosity of the grease will allow it to stay in position during use.
  • Thermal adhesive: As with the thermal grease, it provides a very thin bond line, but provides some additional mechanical strength to the bond after curing. Thermal glue allows thicker bond line than the thermal grease as it cures.
  • Thermal gap filler: It could be described as "Curing Thermal Grease" or "Non-adhesive Thermal Glue". It provides thicker bond lines than the thermal grease as it cures while still allowing an easy disassembly thanks to limited adhesiveness.
  • Thermally conductive pad: As opposed to previous TIM, a thermal pad does not come in liquid or paste form, but in a solid state (albeit often soft). Mostly made of silicone or silicone-like material, it has the advantage to be easy to apply. It provides thicker bond lines, but will usually need higher force to press the heat sink on the heat source so that the thermal pad conform to the bonded surfaces
  • Thermal tape: It adheres to surface, requires no curing time and is easy to apply. It is essentially a thermal pad with adhesive properties.
  • Phase-change materials (PCM): Naturally sticky materials, used in place of thermal greases. Its application is similar to solid pads. After achieving a melting point of - 55-60 degrees, it changes to a half liquid status and fills all gaps between the heat source and the heat sink.
  • Metal thermal interface materials (metal TIMs): Metallic materials offer substantially higher thermal conductivity as well as the lowest thermal interface resistance. This high conductivity translates to less sensitivity to bondline thicknesses and coplanarity issues than polymeric TIMs. (Full Metal TIMs, authored by Robert N. Jarrtett, Jordan P. Ross, and Ross Berntson, published in Power Systems Design Europe, September 2007)

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