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). At each interface, a thermal boundary resistance exists to impede heat dissipation. In addition, the electronic performance and device lifetime can degrade dramatically under continuous overheating and large thermal stress at the interfaces. Therefore, for the last several decades, there have been intensive efforts in developing various TIMs with the aim of minimizing the thermal boundary resistance between layers and enhancing thermal management performance, as well as tackling application requirements such as low thermal stress between materials of different thermal expansion coefficients, low elastic modulus or viscosity, flexibility, and reusability: *

Thermal paste Thermal paste (also called thermal compound, thermal grease, thermal interface material (TIM), thermal gel, heat paste, heat sink compound, heat sink paste or CPU grease) is a thermally conductive (but usually electrically insulating) chemi ...

: Mostly used in the electronics industry, it provides a very thin bond line and therefore a very small

thermal resistance Thermal resistance is a heat property and a measurement of a temperature difference by which an object or material resists a heat flow. Thermal resistance is the reciprocal of thermal conductance. * (Absolute) thermal resistance ''R'' in kelvi ...

. It has no mechanical strength (other than the surface tension of the paste 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 The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the inter ...

of the paste will allow it to stay in position during use. *

Thermal adhesive Thermal adhesive is a type of thermally conductive glue used for electronic components and heat sinks. It can be available as a paste (similar to thermal paste) or as a double-sided tape. It is commonly used to bond integrated circuits to heatsi ...

: As with the thermal paste, 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 paste, as it cures. * Thermal gap filler: This could be described as "curing thermal paste" or "non-adhesive thermal glue". It provides thicker bond lines than the thermal paste as it cures while still allowing an easy disassembly thanks to limited adhesiveness. *

Thermally conductive pad In computing and electronics, thermal pads (also called thermally conductive pad or thermal interface pad) are pre-formed rectangles of solid material (often paraffin wax or silicone based) commonly found on the underside of heatsinks to aid the ...

: As opposed to previous TIM, a thermal pad comes not in liquid or paste form, but in a solid state (albeit often soft). Mostly made of

silicone A silicone or polysiloxane is a polymer made up of siloxane (−R2Si−O−SiR2−, where R = organic group). They are typically colorless oils or rubber-like substances. Silicones are used in sealants, adhesives, lubricants, medicine, cooking ...

or silicone-like material, it has the advantage of being easy to apply. It provides thicker bond lines, but will usually need higher force to press the heat sink onto the heat source so that the thermal pad conforms to the bonded surfaces. *

Thermal tape A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example ...

: This adheres to the bonded surfaces, requires no curing time and is easy to apply. It is essentially a thermal pad with adhesive properties. *

Phase-change materials A phase change material (PCM) is a substance which releases/absorbs sufficient energy at phase transition to provide useful heat or cooling. Generally the transition will be from one of the first two fundamental states of matter - solid and liq ...

(PCM): Naturally sticky materials, used in place of

thermal pastes Thermal paste (also called thermal compound, thermal grease, thermal interface material (TIM), thermal gel, heat paste, heat sink compound, heat sink paste or CPU grease) is a thermally conductive (but usually electrically insulating) chemi ...

. 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 A heat sink (also commonly spelled heatsink) is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant, where it is dissipated away from the device, t ...

. *Metal thermal interface materials (metal TIMs): Metallic materials offer substantially higher

thermal conductivity The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal ...

as well as the lowest thermal interface resistance. This high conductivity translates to less sensitivity to bondline thicknesses and coplanarity issues than polymeric TIMs.

References

{{Reflist Computer hardware cooling Heat exchangers Heat transfer Materials science

See also

References