Characterization of indium doped Sn1Ag0.7Cu3Bi1.5Sb solder/solder joints

In this study, the Calculation of Phase Diagrams (CALPHAD) method was employed to predict the phase constitution of Sn1Ag.7Cu3Bi x In1.5Sb solder joints with different contents, which also guided the composition ratio of In in the system. Therefore, Sn1Ag.7Cu3Bi x In1.5Sb ( x = 4, 7, 12, 14, 17) solder joints were fabricated and investigated. According to experimental results, In addition could effectively lower the solidus and liquidus temperature supercooling degree of the alloy while increasing its melting range. In could substitute Sn atoms in the Cu6Sn5 phase to form a Cu 6 (Sn, In) 5 phase, and could induce the formation of Ag 2 (Sn, In), Ag 9 In 4 . When the In content exceeds 12 wt.%, the matrix phase γ-InSn 4 phase was formed. Based on the mechanical properties and post-mortem characterization, doping In could significantly ductile the solder joint with limited strength sacrifice, thanks to the increase in the phase volume fraction of the γ-InSn 4 phase. This study provides a viable method to relieve the brittleness of Sn1Ag.7Cu3Bi1.5Sb solder alloy while achieving a lower soldering temperature, which could serve as a guideline for future solder alloy design.