Effect of Different Proportions and Powder Sizes of Sn on The Performance of Cu-Sn TLPB Joints

As power devices supported by wide bandgap (WBG) semiconductor materials such as silicon carbide (SiC) and gallium nitride (GaN) are widely used in home appliances, new energy vehicles, and aerospace. At the same time, power devices are gradually becoming miniaturized and their operating temperature is up to 300°C, which is a challenge to the traditional die-attach technologies and materials. So far, the Transient Liquid Phase Bonding (TLPB) has been considered as a promising technology due to its low-temperature bonding ability and high-temperature application. In this paper, we mixed Cu powder with different types of Sn-based solders and used low-temperature TLPB technology to improve the performance of Cu-Sn TLPB joints bonded with it. Scanning electron microscopy (SEM) and X-ray diffractometry (XRD) were used to analyze the different types of intermetallic compounds (IMCs) and elemental distribution within the TLPB joints. We found that under the experimental prerequisites of this paper, the Cu-Sn TLPB paste obtained by mixing the Sn-based solder containing 88% Sn had the best mechanical properties (39.38 MPa), and the Cu particles within the TLPB joints reacted completely. The IMC basically transformed from Cu
6
Sn
5
into Cu
3
Sn. The mechanical properties of the TLPB joints derived from Cu-based pastes with smaller sizes of Sn powder were relatively better (27.85 MPa) for the Sn-based solder with Sn content of 42%, and the higher bismuth content resulted in a relatively lower thermal conductivity of the TLPB joints. These results provide an experimental basis for improving the TLPB process.