Mechanical Properties of Sn58Bi–Cu Composite Solder Filled with Copper Particles

Sn58Bi–Cu composite solder, in which copper (Cu) particles were applied as a reinforcement material, was synthesized to address the material limitations and improve the bonding properties of Sn–58Bi eutectic solder. To evaluate the impact of Cu particle concentration on the solderability and mechanical properties of Sn58Bi–Cu composite solder, five variants with different Cu particle concentrations (0, 3, 5, 10, and 15 vol%) were synthesized. Wetting, ball shear, and microhardness tests were then performed. The wetting test revealed that the Sn58Bi–Cu composite solder containing Cu particles up to 10 vol% exhibited satisfactory wetting morphology and a wetting angle of approximately 30°, indicating appropriate wetting behavior. In contrast, the Sn58Bi–Cu composite solder containing excessive amounts of Cu particles (15 vol%) demonstrated weak wetting angle and solderability due to increased viscosity from the intensified chemical reaction between the molten solder and Cu particles. The solder ball shear and microhardness test results for the Sn58Bi–Cu composite solder containing Cu particles up to 10 vol% showed that the mechanical properties of the solder joint improved with increasing Cu particle concentrations. This improvement in mechanical properties was attributed to the grain refinement of the joint and the reinforcement effect of Cu particles.