Fractography analysis of Sn-58Bi solder joint after addition of cobalt nanoparticles

Miniaturization of electronic devices causes reliability issues in solder joints such as a reduction in mechanical, structural, and electrical properties. This work focuses on studying the effects of cobalt nanoparticle (NP) addition on the structural and mechanical properties of the Sn-58Bi solder joint. 0, 0.5, 1, and 2% Co NP added samples were prepared. The reflow process was done at 180 °C for 1 min. After the reflow process, all samples were aged at 70 °C for different periods of 0 h, 126 h, and 504 h. After the tensile test, the fractography was done using scanning electron microscopy (SEM). The result showed that after the addition of Co-nanoparticles, the grain size of Sn-58Bi was refined and significantly reduced for as reflowed samples. After thermal aging, the grain size was increased for all types of samples, while the increment in Sn-58Bi-0.5Co/1Co/2Co was controlled as compared to the Sn-58Bi solder joint.