Current Research in Transient Liquid Phase Bonding Materials and Joint Reliability for Power Chip Packaging

Power semiconductors have gradually developed towards miniaturization and high densification due to their high working voltage, large current and large heat dissipation. The new generation of wide bandgap semiconductor devices can increase the operating temperature and power density, showing a good application prospect, which puts forward higher requirements for matching power packaging materials. With the continuous increase of operating temperature, the safety issues such as instability and unstable operating environment under high temperature need to be solved, which puts forward higher requirements for the high temperature reliability of power chip packaging. The research of lead-free solder and the corresponding joining technology is the focus of current research because high-lead solder is not environmentally friendly. Transient liquid phase bonding (TLP bonding) technology can meet the requirements of "low-temperature bonding and high-temperature ser-vice" by forming high-melting-resistant intermetallic compounds joints at low temperatures, and has good application prospects in high-temperature packaging of the new generation of power semiconductors. The high temperature resistant packaging materials for TLP bonding include Sn-based, In-based and Bi-based, etc. At present, TLP bonding materials mainly have the form of lamination, solder paste and preform. Among them, laminated solder was first applied to TLP bonding, and there have been relatively mature researches on bonding mechanism and joint performance and reliability. In recent years, solder paste and preform based on the composite powder have relatively high reaction efficiency. However, sufficient theoretical and experimental studies are needed to verify its industrial application prospects. The characteristics of Sn-based and In-based solder for TLP bonding are reviewed. The status and progress of TLP bonding mechanism, the microstructure of joints, mechanical properties and structural reliability of different solders are presented. The study for inhibition of defects in the joint, the phase transformation mechanism and failure mechanism of the joint under different service conditions will be significant in the preparation of high-reliability joints. © 2021, Materials Review Magazine. All right reserved.