LAUSR

A transient liquid phase sintering (TLPS) bonding process, Ni-Sn TLPS bonding was developed for the new generation of power semiconductor packaging. A model Ni/Ni-Sn/Ni sandwiched structure was assembled by using 30Ni-70Sn mixed powder as the reactive system. The results show that the bonding layer is composed of Ni3Sn4 and residual fine Ni particles with a small amount of Ni3Sn2 at 340°C for 240 min, which has a heat-resistant temperature higher than 790°C. The microstructural evolution and thermal characteristic of the bonding layer for various times at 300°C and 340°C were also studied, respectively. This reveals that, after isothermally holding for 240 min at 300°C and for 180 min at 340°C, Sn has been completely transformed into Ni-Sn intermetallic compounds (IMCs) and the bonding layer is mainly composed of Ni3Sn4 and residual Ni particles. The analysis result for the mechanical properties of the joint shows that the hardness of the bonding layer at 340°C for 240 min is uniform and that the average value reaches 3.66 GPa, which is close to that of the Ni3Sn4 block material. The shear test shows that, as the holding time increases from 60 min to 180 min at 340°C, because of the existence of Sn, the disparity of shear strength between room temperature and 350°C is large. But when the holding time is 180 min or longer, Sn has been completely transformed into Ni-Sn IMCs. Their performances are very similar whether at room temperature or 350°C.