Time-dependent fracture of copper-cored lead-free solder ball and nickel rod joints in air, distilled water, and NaCl solution

Solder joints have been used for electric connections in many electronic devices, and the joints are subjected to mechanical loadings such as static or cyclic tension/compression and shearing under various environments. Since the melting point of solder is very low comparing with the other normal metals, the time-dependent damage accumulation and fracture are often found in the solders even at the room temperature. In this paper, tensile tests of copper-cored lead-free solder ball and nickel rod joints were carried out in air, distilled water, and salt water environments using a unique testing device with permanent magnet. The time-dependent fracture of the joints was investigated from the viewpoint of damage accumulation.