Effects of rare earth Ce addition on the microstructure and shear property of Cu/In-50Ag/Cu composite solder joint

The microstructure and shear property of Cu/In-50Ag- x Ce/Cu ( x = 0, 0.3, 0.6, 1.2, 2 wt%) composite solder joints fabricated by transient liquid phase (TLP) bonding were investigated. The results showed that the appropriate amount of Ce particles refined the microstructure in the Cu/In-50Ag/Cu solder joint, and inhibited Cu 2 In phase formation at the Cu/solder interface. The refined Ag 2 In phases contribute to suppressing the formation of microstructural defects. The Ce particles can improve the microstructure uniformity of composite solder joint, the porosity of Cu/In-50Ag-0.6Ce/Cu solder joint is only 1.05%, and the excessive (1.2–2 wt%) Ce particles are harmful to the composite solder joints. Doping 0.3–0.6 wt% Ce particles can improve the shear strength of composite solder joints by reducing microstructural defects, refining Ag 2 In phases and improving the phase boundaries strength. The maximum shear strength value of the Cu/In-50Ag-0.6Ce/Cu composite solder joint reaches 17.58 MPa. The fracture mechanism is mainly brittle fracture, which occurs near the in-situ reaction zone. The Cu/In-50Ag-0.6Ce/Cu composite solder joint fabricated by TLP bonding with finer microstructure and higher mechanical properties is acceptable. • Appropriate amount Ce can refine Ag 2 In and inhibit Cu 2 In layer in the solder joint. • The porosity relates to Ce content, and 0.6 wt% Ce leads to porosity of 1.05%. • The shear strength relates to joint defects, Ag 2 In size and phase boundaries strength. • Doping 0.6 wt% Ce particles into In 50Ag for TLP bonding is acceptable.