As the name suggests, TIMs are Thermal Interface Materials that the electronic industry typically uses between two mating surfaces. They help to conduct heat from one metal surface to another. TIMs are a great help in thermal management, especially when removing heat from a semiconductor device to a heat sink. By acting as a filler material between the two mating surfaces, TIMs improve the efficiency of the thermal management system.
There are various types of material that can act as TIMs, and there are important factors that designers must consider when selecting a specific material to act as a TIM for a unique application.
Every conductor has its own resistance which impedes the flow of electrical current through it. Impressing a voltage across a conductor starts the free electrons moving inside it. Moving electrons collide against other atomic particles within the conductor, giving rise to friction and thereby generating thermal energy or heat.
In electronic circuits, active devices or processing units like CPUs, TPUs, GPUs, and light-emitting diodes or LEDs generate copious amounts of heat when operating. Other passive devices like resistors and transformers also release high amounts of thermal energy. Increasing amounts of heat in components can lead to thermal runaway, ultimately leading to their failure or destruction.
Therefore, it is desirable to keep electronic components cool when operating, thereby ensuring better performance and reliability. This calls for thermal management to maintain the temperature of the device within its specified limits.
It is possible to use both passive and active cooling techniques for electronic components. It is typical for passive cooling methods to use natural conduction, convection, or radiation techniques for cooling down electronic devices. Active cooling methods, on the other hand, typically require the use of external energy for cooling down components or electronic devices.
Although active cooling can be more effective in comparison to passive cooling, it is more expensive to deploy. Using TIMs is an intermediate method to enhance the efficiency of passive cooling techniques, but without excessive expense.
Although the mating surfaces of the component and its heat sink may appear flat, in reality, they are not. They typically have tool marks and other imperfections such as pits and scratches. The presence of these imperfections prevents the two surfaces from forming close physical contact, leading to air filling the space between the two non-mating surfaces. Air, being a poor conductor of heat, introduces higher thermal resistance between the interfacing surfaces.
TIMs, being a soft material, fills a majority of the gaps between the mating surfaces, expelling the air from between them. In addition, TIMs have better thermal conductivity than air does, typically, 100 times better, and their use considerably improves the thermal management system. As such, many industrial and consumer electronic systems use TIMs widely for ensuring efficient heat dissipation and preventing electronic components from getting too hot.
The electronic industry uses different forms of TIMs. These can be thermal tapes, greases, gels, thermal adhesives, dielectric pads, or PCMs that change their phase. The industry also uses more advanced materials such as pyrolytic graphite, as these are thermally anisotropic.