Fast formation of Ni–Sn intermetallic joints using Ni–Sn paste for high-temperature bonding applications

The suitability of Ni–Sn combination paste as a transient liquid phase sintering (TLPS) bonding material for applications in high-temperature power electronic technologies was investigated. The microstructure and mechanical properties of joints bonded through TLPS with a Sn-30 wt% Ni paste were investigated at varying bonding temperatures (250, 270, 300, and 350 °C) and times using field-emission scanning electron microscopy, field-emission transmission electron microscopy, electron probe micro-analyzer, differential scanning calorimetry, and X-ray diffraction analyses. The results indicated that Ni and Sn reacted and bonded quickly to form Ni–Sn intermetallic compounds, which primarily consisted of Ni₃Sn₄ and residual Ni particles. The mechanical strength analysis results show that the shear strength values of the joints tended to increase as the bonding temperature increased. As Ni₃Sn₄ reacted with Ni particles, the joints achieved a stable and dense microstructure. The shear strength values were determined to be 47.9 MPa (300 °C) and 41.4 MPa (350 °C) for 15 and 5 min, respectively. Furthermore, the shear strength value saturated at a bonding temperature of 350 °C for a bonding duration of 5 min.