Effect of reflow temperatures on the interfacial behavior and shear properties of the In–15Pb–5Ag/Au/Ni solder joint

During the reflow soldering process of system-level packing, the soldering temperature must be carefully regulated. This can effectively control the phase composition, interfacial reaction, and shear properties of In–15Pb–5Ag/Au/Ni solder joints. This study aims to explore the influence of soldering temperature on the microstructure evolution and mechanical properties of In–15Pb–5Ag/Au/Ni solder joints. The findings show that as the soldering temperature rises, AgIn₂ inside the solder joint transforms into a mixture with Ag₉In₄. At the same time, Au₃In, Au₇In₃, and Au₃In₂ interfacial phases are formed at the interface with the average grain size and total thickness gradually increases. At 170 ℃, the crystal direction of all phases is concentrated in the highest shear modulus, and the average particle size and thickness of the interfacial phases are 0.9 μm and 1.248 μm, respectively. The shear strength of the solder joint reaches the highest of 19.67 MPa. The fracture pattern of the solder joint changes from interfacial phases/solder composite fracture to internal solder fracture when the soldering temperature rises from 160 to 170 to 180 ℃. The findings about In–15Pb–5Ag solder joints could pave the way for optimizing system-level packing processes and quality, as well as for advancing system-level packing toward high performance.