Effects of Cobalt Nanoparticle on Reliability of Tin-Bismuth Solder Joint

Abstract

Eutectic Sn–Bi alloy is acquiring significant observation in the electronic packaging industry because of its advantageous properties such as ductility, low melting temperature, and mechanical strength. Miniaturization of electronic devices causes reliability issues in solder joints. To solve these issues, a cobalt nanoparticle was added to the Sn-58Bi solder joint. This work focuses to find out the effects of cobalt nanoparticle (NP) addition on the structural and mechanical properties of the Sn-58Bi solder joint. The reflow process of 0%, 0.5%, 1% and 2% of cobalt addition was done at 180 °C and reflow time of 1 minute. After reflow process, cobalt additions of 0%, 0.5%, 1%, and 2% were aged at 70 °C for different periods of 0 h, 126 h, and 504 h. To characterize the specimen, scanning electron microscopy (SEM) was used. The tensile test was carried out for the Sn-58Bi and Sn-58BixCo (x = 0.5, 1 and 2) solder joints. The tensile test was run before and after aging time. After the addition of Co-nanoparticles, the microstructure of Sn-58Bi was refined and grain size was reduced. The grain size was increased when the aging time was increased for all samples, while the increment in Sn-58Bi-0.5Co/1Co/2Co was controlled as compared to the Sn-58Bi solder joint. The tensile strength was significantly increased after the addition of Co NP. As the aging time increased, the ultimate tensile strength of all samples decreased.