A thermal interface material (TIM) is used in areas with high thermal loads in order to optimize the heat dissipation between two solid bodies. The TIM displaces the air trapped in the cavities between these bodies and lowers the temperature of the solid body to be cooled by dissipating the heat loss. On the one hand, this prevents thermal failures. On the other hand, the life of the body is extended if it is a power electronic component.

A temperature that is 10 K higher halves the service life of a chip. Thermal interface material reliably reduces heat loss if used correctly and if the thermal situation is correctly assessed.

The selection of the TIM plays a decisive role in the thermal design of electronics. Ideally, the TIM can be completely dispensed with. There are manufacturing tolerances in every manufacturing process; there is a deviation from the construction. In addition, there are deviations in shape such as roughness, waviness, concave and convex deformations as well as scratches, burrs and dirt that arise, for example, during assembly.

Air is a poor conductor of heat. At 80 ° C, its thermal conductivity is only 0.03 W / (mK). Therefore, even with the smallest layer thickness in the range of 1 µm, a critical and above all uncontrollable thermal resistance occurs. In the statistical tolerance calculation, the geometric errors of the individual parts add up to a lower and an upper limit value. This results in variations in the thermal contact resistance, which are decisive for the quality and service life of the electronics.

The aim must be to make this contact resistance controllable and reproducible. The statistical tolerance calculation provides the gap dimension requirements for the TIM. From the thermal requirements for the semiconductor temperature, we get the specification for the maximum thermal resistance in the heat path. This is determined, for example, with the help of thermal simulation calculations. Further selection parameters are the electrical insulation properties and the installation conditions. For assembly purposes, the TIM is divided into two classes: preformed and dispensable materials. Preformed TIMs are hard and soft pads, phase change material (PCM), gap pads or graphite foils. These can be designed with an adhered or adhesive coating. This coating inevitably increases the thermal resistance compared to the non-coated variant. The dispensable TIMs include pastes, gap fillers, gels and adhesives.