Effects of magnetic field on microstructure and mechanical properties of lead-free solder joint

Magnetic field is believed to have a significant impact on the evolution of microstructure during solidification or service condition. Many researches apply magnetic field to obtain a material with textures or special microstructure, such as turbine blade. The magnetic field is able to influence the crystal growth process, constrain crystal arrangement direction; and effectively inhibit the conductive fluid in thermo solute convection. However, the effect of magnetic field on the reliability of solder joint or related research is rarely reported. The purpose of this research is to investigate how magnetic field impact on the microstructure and mechanical performance of Sn-based lead-free solder joint. This research contains two possible aspects. Firstly, magnetic field with different intensities was posed on Sn0.3Ag0.7Cu to analyze the solidification microstructure. The roles of the second phase particles, such as Ni, were also considered. Intensity of magnetic field ranged from 0T-7T. Secondly, the solder joint was subjected to current density with magnetic field. The coupling effect of magnetic and electric fields was studied. The result indicated that, magnetic field influenced migration rate and migration direction of atoms. Consequently, the thicknesses of the intermetallic compounds (IMCs) at two interfaces were different. The appearance of interfacial IMCs changed. The couple of magnetic and electric made the solder joint failure more quickly. This study contributes to understand the reliability of solder joint under multi-field condition.