Electronic power devices are widely used in high-speed railways, new energy vehicles, aerospace, solar energy and wind power generation.
In recent years, electronic and power devices have developed in the direction of high power, high density, integration, etc., and higher requirements have been placed on ceramic heat dissipation substrates in the devices. At present, the commonly used alumina substrates have low thermal conductivity and poor reliability of aluminum nitride substrates, which limit its application in high-end power semiconductor devices. Silicon nitride ceramic substrate has the advantages of high strength, high toughness, high insulation, high thermal conductivity, high reliability, and thermal expansion coefficient matching the chip. It is a substrate material with comprehensive performance and broad application prospects.
The team of Zeng Yuping, a researcher at the Shanghai Institute of Ceramics, Chinese Academy of Sciences, conducted research on high-performance silicon nitride ceramic materials. In view of the high oxygen content on the surface of α-Si3N4 raw material powders, methods such as carbothermic reduction, silicon thermal reduction, and metal thermal reduction are proposed to consume or convert surface oxygen; new non-oxide additives such as metal hydrides, silicides, and borides have been developed To replace the traditional oxide sintering aid; use the "dissolution-precipitation" mechanism to adjust the microstructure, grain boundary phase composition, and lattice oxygen content of silicon nitride ceramics by adjusting the liquid phase composition. Studies have found that the removal of surface oxygen and the use of non-oxide additives are conducive to the formation of an "anoxic-nitrogen-rich" liquid phase. The high N/O ratio in the liquid phase is conducive to the α→β phase transition and grain growth; the low SiO2 activity hinders the formation of lattice oxygen, thereby achieving simultaneous improvement of thermal and mechanical properties. The thermal conductivity of the prepared silicon nitride ceramics can reach 136.9 W/(m·K) after the third-party inspection. This research provides design ideas for the regulation of grain boundary phase and lattice oxygen during liquid phase sintering of high thermal conductivity silicon nitride ceramics.