Journal of the Microelectronics and Packaging Society

This study developed a Sn58Bi-0.1TiC composite solder paste by mechanically mixing of Sn58Bi solder paste with 0.1 wt% TiC nanopowder. Sn58Bi-xTiC (x = 0, 0.1) solder paste was printed onto OSP-treated Cu pads of a PCB, and 350 µm SAC305 solder balls were placed on the top of the printed solder paste. Reflow soldering was performed at 190°C, and the joints were analyzed for their microstructures and mechanical properties. The addition of TiC nanoparticles refined the Bi phase and inhibited its diffusion toward the top of the SAC305 solder balls. At the hybrid solder joint interface, intermetallic compounds such as Cu₆Sn₅ and Ag₃Sn were observed, which tended to coarsen with an increasing number of reflow cycles. Fracture surface analysis showed that after a single reflow cycle, the fractures occurred within the Sn58Bi solder in the Sn58Bi/SAC305 hybrid joints, whereas the fractures in the Sn58Bi-0.1TiC/SAC305 hybrid joints occurred within the SAC305 solder balls. Moreover, the brittle fracture area expanded with additional reflow cycles. Shear test revealed that while the addition of TiC nanoparticles did not significantly affect the shear strength, the Sn58Bi-0.1TiC/SAC305 hybrid joints demonstrated higher fracture energy compared to the Sn58Bi/SAC305 hybrid joints.

Keywords Sn58Bi, Sn3.0Ag0.5Cu (SAC305), Ceramic nanoparticles, Organic solderability preservative (OSP), Solder joint