Effect of ZnO nanoparticle addition on the wettability, microstructure and mechanical properties of In-45.6Sn-5Bi low temperature solder

The ZnO nanoparticles were added to improve the wettability and mechanical properties of In-45.6Sn-5Bi (ISB) solder alloy. The wetting angle decreased from 48.9 ° to 38.6 ° with 0.05 wt% ZnO addition. The microstructure of ISB-xZnO composite solder alloys was significantly refined via the mechanism of heterogeneous nucleation and the pinning effect at the grain boundary, which contribute to the increase in hardness of the composite solder. The ISB-0.075 wt% ZnO composite solder alloy has the highest hardness of 7.8 HV_0.2, which increased by 25.8 % compared with that of plain solder. The shear test revealed that ZnO nanoparticles has obviously inhibited the intermetallic compounds (IMCs) growth, promoting the shear strength of the solder joint. The formation mechanism of the distinctive acicular Cu-In-Sn IMCs generated by the reaction between Cu substrate and InSn-based solder was discussed. The ISB-0.075 wt% ZnO composite solder joint showed an excellent shear strength of 6.87 MPa, which is 1.28 times that of the plain solder joint.