Ultrasonic-assisted nano Ag-Al alloy sintering to enable high-temperature electronic interconnections

Advanced interconnect materials are demanded with the rapid development of wide band gap (WBG) devices, which operate at higher temperatures (above 250°C) compared to the current Si devices. The most common Sn-based solders are not adequate because of its low melting temperature. With the advantage of sintering at relatively low temperatures and serving at high temperatures, metal powder sintering technology such as nano Ag becomes highly attractive. However, high cost and element emigration properties limit the application of nano Ag. Developing new metal powder sintering technology should be a promising solution for high-temperature integration. This paper investigates the combination of Al with nano Ag binary sintering assisted by ultrasonic vibration, this can offer an attractive solution for high temperature applications, such as WBG device packaging. Nano Ag-Al paste was prepared by adding 10 weight percent (wt%) nano Al powders into commercial nano Ag paste, this can reduce cost and offer good thermal and electrical conductivity. With the help of ultrasonic vibration during the sintering process, the adhesion between nano paste and chip metallization has been improved. The microstructures of thermal aged joints show that there is less void growth in nano Ag-Al systems compare to nano Ag joints. Current results suggest that the developed ultrasonically assisted nano Ag-Al sintering process has potential advantages in maintaining mechanical stability.