Mechanical properties and electromigration reliability of Fe304 nanoparticle-modified Sn58Bi solder joints

In recent years, Artificial Intelligence (AI) and fifth-generation mobile communications technology (5G) have driven the rapid development of 2.5D/3D advanced-package integrated circuits for applications in mobile electronics, high-performance computers, self-driving devices, the Internet of things and big data. Sn58Bi eutectic solder has become a promising low-temperature solder for 2.5D/3D packaged multi-level interconnect structures because it has the characteristics of low melting point, low cost and excellent mechanical properties. In this study, Fe3O4 nanoparticles with a size of about 10 nm and good particle dispersion were prepared by chemical synthesis, and Fe3O4 nanoparticles with different content gradients were added to regulate the organization and mechanical properties of Sn58Bi solder. The results showed that Sn58Bi solder with 1% Fe3O4 nanoparticles showed the best overall performance. The tensile strength, shear strength and plasticity were improved. At the same time, the nanoparticle modification significantly enhanced the wetting performance of the solder. Moreover, in order to investigate the atomic migration and microstructural evolution of the modified interconnects under current, the EM testing at 1×10⁴A/cm²were carried out and the cross sections were observed. The results show that the addition of Fe3O4 nanoparticles significantly inhibited the growth rate of Bi rich phase, resulting in an improvement of the anti-electromigration performance of the interconnects. The study of its microstructure reveals that the addition of Fe3O4 nanoparticles destroyed the eutectic precipitation of the Sn-Bi two phases and promoted the generation of many micron-sized small particles of Bi within Sn phase, so these properties of the solders were affected.