Associate Professor, School of Materials Science and Engineering, Tsinghua University, Beijing, China.

Speech Title: Thermal properties and reliability of polymer and metal-based thermal interface materials
Abstract: With rapid development of electronic devices, heat dissipation has become a critical problem that affects the device performance and reliability, especially in high power devices such as LED, IGBT, and Laser. Thermal interface materials (TIMs) are used to conduct the heat generated by power devices to the heat sink and then to ambient environment. Polymer and metal-based TIMs are widely-used. In this presentation, we studied the thermal properties and reliability of several kinds of TIMs. For the polymer-based TIMs, they have an advantage of electrical insulating, but their disadvantage is that the intrinsic thermal conductivity is low. In order to enhance the thermal conductivity, we synthesized several kinds of polymer-based TIMs containing irregular AlN or spherical Al₂O₃ powders. The thermal conductivity was increased by ~13 times with proper surface treatment of ceramic powders and reached 2.7 W/(mK). In addition, the thermal and insulating properties of the polymer-based composite TIM did not degrade after thermal cycling testing, indicating a good reliability for use in power devices. For the metal-based TIMs, they generally have a high thermal conductivity, but their processing temperature is usually high. We synthesized Ag nanoparticles with different sizes, sintered them at 250°C to form a TIM, and achieved an ultra-low thermal resistance of less than 2.0 mm²K/W. We also used low-cost Sn-Bi solder paste as TIM and achieved a low thermal resistance of less than 5.0 mm²K/W with a processing temperature of 180°C. The thermal resistance of both Ag nanoparticle-based TIM and Sn-Bi TIM did not degrade after several hundreds of thermal cycles.