Thermal principles and improvement strategies of thermal interface materials
With the development of modern electronic devices towards miniaturization, high power density, and high integration, the heat dissipation problem of electronic devices has become a key factor affecting the service life and performance of devices, especially in the 5G field. Therefore, better thermal management solutions are needed to solve this problem. Generally speaking, the heat generated by electronic devices needs to be transferred to the surface of the heat sink, and filling thermal interface materials (TIMs) between the electronic device and the heat sink can maximize the heat transfer capacity.
TIMs are mainly composed of organic matrices and inorganic fillers. Therefore, the overall thermal conductivity of TIMs will be determined by the thermal conductivity of polymers and inorganic fillers, the interfacial thermal resistance of polymers and inorganic fillers, and the interfacial thermal resistance between the contact surfaces of inorganic fillers. The thermal conductivity is mainly determined by electrons or/and phonons, and the heat generated by the chip is transferred to the heat sink through Tims, thereby achieving the circulation of the heat dissipation system and cooling electronic devices.
Electronic heat conduction mainly occurs in conductive thermal conductive materials. When these materials are in an imbalanced environment, electrons will diffuse from high to low temperatures, generating corresponding currents and heat flows, resulting in electronic heat conduction. In media and non-conductive polymers, heat conduction is usually phonon heat conduction. When one side of this type of material is heated, the lattice of the material vibrates, and the corresponding vibration is transmitted to adjacent atoms, resulting in the transfer of heat flow in the material. Typically, TIMs we encounter are of this type. As a component of TIMs, inorganic non-metallic fillers have a relatively regular lattice distribution, and phonons can propagate along the lattice direction, often exhibiting excellent thermal conductivity; In another important component of polymer, polymer chains are intertwined and do not conduct high-speed phonons. These phonons are highly dispersed at the polymer chain interface, resulting in a significant reduction in phonon flow and a decrease in thermal conductivity. Therefore, reducing the scattering of phonons is particularly important for improving thermal conductivity.
The conventional method for constructing TIMs is to use inorganic fillers with high thermal conductivity. However, due to the low thermal conductivity of polymer polymers, the overall thermal conductivity of TIMs constructed in this way is often not ideal due to their interface thermal resistance with inorganic fillers. Therefore, reducing the interfacial thermal resistance between inorganic fillers and polymer, inorganic fillers and inorganic fillers, and constructing thermal conductivity pathways, or taking into account both, have become the direction for improving the thermal conductivity of TIMs.
The miniaturization and high power of electronic products and equipment require that the thermal conductivity of thermal conductive materials should also be constantly improved. Therefore, high thermal conductivity, excellent thixotropy, and good storage stability are the most important research and development direction of thermal conductive materials.
