Mechanism of Ni 3 Sn 4 rapid formation of Sn-Ni mixed particles paste in ultrasound-assisted TLP for power electronic chip attachment

In the field of semiconductors, the rapid development of third-generation semiconductors represented by SiC and GaN makes it possible for IC chips to work properly in harsh environments at high temperatures. Currently the solder used for packaging IC chips is mostly Sn- based lead-free solder, and its working temperature is generally lower than 300°C. So, it is very important to study the solder and packaging technology that can be used for high temperature service. In this study, we have successfully prepared a solder paste by mixing 30μm big Ni particles and 2μm small Ni particles with Sn particles. High-melting-point joint structure consisting of Ni3Sn4 compound and Ni can be obtained at low ultrasonic power of 200 W and in 10s using these kind of solder pastes. Meanwhile, our research found that, in the process of ultrasound-assisted TLP, Ni 3 Sn 4 compound growth is a nucleation-growth-stripping cycle mechanism. During this process, the solid Ni and liquid Sn can be in continuous contact, which is the main reason why Ni 3 Sn 4 is quickly formed in such a short time.