Mechanical property of the epoxy-contained Sn-58Bi solder with OSP surface finish

In the electronic packaging technology, lead-free solders have been widely used to replace lead-based solders because of the toxicity of lead. Among the investigated lead-free solders, the Sn-58Bi solder has been considered as a highly promising candidate because of its low-melting temperature, high tensile strength and good creep resistance. However, the Sn-58Bi solder has poor ductility and shock absorbance. To enhance the mechanical properties of the Sn-58Bi solder, epoxy resin is mixed with the Sn-58Bi solder. The advantages of the Sn-58Bi solder with epoxy are good reliability and no need of a cleaning process. This study elucidated not only the mechanical properties of the Sn-58Bi epoxy solder but also the effects of the epoxy during the reflow process by conducting a shear test and a board-level drop test. The shear strength of the Sn-58Bi epoxy solder was about 2 times higher than that of the Sn-58Bi solder. In result of the drop test, the Sn-58Bi solder specimen failed under the 10th drop. However, the number of drops of the Sn-58Bi epoxy solder was over 100 drops without failure.