Effect of Si3N4 nanowires doping on microstructure and properties of Sn58Bi solder for Cu bonding

Purpose - The purpose of this study is to delve into the mechanism of Si3N4 nanowires (NWs) in Sn-based solder, thereby furnishing a theoretical foundation for the expeditious design and practical implementation of innovative lead-free solder materials in the electronic packaging industry. Design/methodology/approach - This study investigates the effect of adding Si3N4 NWs to Sn58Bi solder in various mass fractions (0, 0.1, 0.2, 0.4, 0.6 and 0.8 Wt.%) for modifying the solder and joining the Cu substrate. Meanwhile, the melting characteristics and wettability of solder, as well as the microstructure, interfacial intermetallic compound (IMC) and mechanical properties of joint were evaluated. Findings - The crystal plane spacing and lattice constant of Sn and Bi phase increase slightly. A minor variation in the Sn58Bi solder melting point was caused, while it does not impact its functionality. An appropriate Si3N4 NWs content (0.2 similar to 0.4 Wt.%) significantly improves its wettability, and modifies the microstructure and interfacial IMC layer. The shear strength increases by up to 10.74% when adding 0.4 Wt.% Si3N4 NWs, and the failure mode observed is brittle fracture mainly. However, excessive Si3N4 will cause aggregation at the junction between the solder matrix and IMC layer, this will be detrimental to the joint. Originality/value - The Si3N4 NWs were first used for the modification of lead-free solder materials. The relative properties of composite solder and joints were evaluated from different aspects, and the optimal ratio was obtained.