Thermal interface material

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The term thermal interface material (shortened to TIM) describes any material that is inserted between two parts in order to enhance the thermal coupling between these two components. A large portion of those application are related to the heat dissipation and the TIM is inserted between the heat producing device (e.g. the heat source) and the heat dissipation device (e.g. the heat sink).

There are several kind of TIM with different target applications:

  • Thermal grease: Mostly used in the electronics industry, it allows 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 for the thermal grease, it allows a very thin bond line but will additionally provide some 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 allows 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, Thermal pad does not come in liquid or paste form but in solid state (albeit often soft). Mostly made of silicone or silicone-like material, it has the advantage to be easy to apply, it can allow 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 are easy to apply. It is essentially a thermal pad with adhesive properties.
  • Phase-change materials (PCM): Naturally sticky materials, used as replacement of thermal greases. Application is similar to solid pads. After achieving melting point - 55-60 degrees change to half liquid status and fill all gaps between heat source and heat sink.

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