Effect of Fe particles on the structure and properties of SnBi/Cu joint during aging

To solve the problem of poor tissue stability of SnBi alloys during servicing, the microstructure of Sn35Bi-1Fe/Cu joints before and after aging was observed by scanning electron microscope (SEM), combined with energy spectrum analysis (EDS) and XRD, to analyzed the tissue changes of joint, and the mechanical properties of joints were analyzed by universal testing machine. The influence of Fe particles on SnBi/Cu joint structure and properties during aging was studied. The results show that with the increasing of contents of Fe particles, the shear strength of Sn35Bi-xFe/Cu (x = 0%, 0.3%, 0.7%, 1.0% and 1.5%) joints increases first and then decreases. When the Fe particle content is 1% (wt.%), the maximum value is 50.23 MPa, and the mechanical properties of Sn35Bi-1.5Fe/Cu joints are always better than those of Sn35Bi/Cu joints; during the constant temperature aging stage, Fe particles in the Sn35Bi-1Fe/Cu joint through pinning the Bi phase, and grain boundary energy was consumed by reacting with Sn to form FeSn₂ compound to decreased Bi phase migration rate, lead to Bi phase coarsening was inhibited, at the same time, growth rate of interface IMC layer was decreased, the generation of interface Cu₃Sn was suppressed, the mechanical properties of the joints in the aging stage was improved.