Microstructure, shear properties and corrosion resistance of Cu/Cu-In/Cu solder joints

Transient liquid phase sintering can successfully fabricate reliable high-temperature solder joints at a relatively low joining temperature by forming intermetallic compounds. In this work, microstructure, shear properties and corrosion resistance of Cu/Cu-In/Cu solder joints prepared by TLPS process were investigated. The shear strength of the Cu-In solder joints significantly increased during the initial aging period and then slightly decreased due to the increase of pores after continuous 24 h aging. The corresponding microstructure is that part of the Cu₂In in the Cu-In solder joints transforms to Cu₇In₃ in the meanwhile. After continuous aging, the interfacial microstructure remained stable and contributed to good shear strength that exceeds 20 MPa after 96 h aging at 250 °C and 350 °C, which was 20.8 MPa and 23.4 MPa, respectively. Regarding corrosion resistance, the Cu-In interfacial layer (−0.24 V) has similar corrosion resistance to Cu substrate (−0.22 V) and shows superior to the commonly used Sn63Pb37 solder (-0.40 V) and Sn95.5Ag3.8Cu0.7 solder (−0.42 V).