Microstructural evolution and performance of high-tin-content Cu40Sn60 (wt. %) core/shell powder TLPS bonding joints

Abstract

This paper investigated the microstructure evolution and performance of high tin content Cu@Sn core/shell (60 wt% Sn) powder transient liquid phase sintering bonding. The formation and evolution mechanism of voids were analyzed. Results showed that, after consuming Sn, the joint was mainly composed of Cu6Sn5, Cu3Sn, and Cu, raising the remelting temperature of the joint to 400 °C. The porosity in the joint was decreased firstly, then increased, and finally decreased with bonding time. The maximum porosity was 0.876% and 1.052% at 300 °C for 150 min and 340 °C for 120 min. With the bonding time increased, the room temperature (RT) shear strength was increased first, then decreased, and finally remained stable. In contrast, the high-temperature (350 °C) shear strength was increased first, then remained stable with bonding time. The joint was possessed excellent RT (20.79 MPa) and high-temperature (18.46 MPa) shear strength. The electrical resistivity of joints was increased first, then remained stable with bonding time. The electrical resistivity was reached its maximum value of 1.83 × 10−5 Ω·cm at 300 °C for 150 min. The thermal conductivity of the joint was 28.72 W/(m·K), 26.83 W/(m·K), and 25.99 W/(m·K) at 30 °C, 250 °C, and 350 °C, respectively.