Effect of Gamma Radiation on Micromechanical Behaviour of SAC305 Solder

Electronic packaging is the technology concerning to the establishment of electrical interconnections and it is a major discipline within the field of electronics engineering. Packaging of an electronics system should considered the protection from mechanical damage, cooling, radio frequency noise emission and protection from electrostatic charge. Solder alloys have been extensively used as interconnection materials for microelectronic package. Solder joint in radiation environment requires higher reliability and resistance to any damage caused by ionizing radiation. The electrical failure during radiation has proved that the reliability of solder joint is importance and sensitive to the service condition. In this study, a lead-free solder alloy, SAC305 (96.5Sn3.0Ag0.5Cu wt.%) were prepared into two batches, which are unirradiated and irradiated batches with the various doses 5, 50, 500 Gy of gamma radiation. Nanoindentation was used in order to investigate the effect of the radiation to micromechanical properties such as hardness, H and reduced modulus, E of the solder. The results showed that the SAC solder changed when exposed to gamma rays. The hardness of the specimens calculated from the nanoindentation were decreased to 195.4 from 279.6 MPa with the increasing of radiation dose. These values of hardness are also lower than the hardness of non-irradiated sample indicating possible radiation damage and needs further related atomic dislocation study. The reduced modulus for irradiated specimens significantly increased as well, with values from 25.6 to 123.9 GPa after exposure. The increment of the reduced modulus occurred as a result of strain hardening or softening of the solder.