Fabrication and thermo-mechanical properties of Ag9In4 intermetallic compound

Abstract

To ensure optimal working conditions for the next-generation power modules, a comprehensive understanding of the thermo-mechanical properties of the joint layer between the chip and substrate is essential. The Ag9In4 intermetallic compound is a promising candidate for the joint layer; however, related material data are not available. This study proposes a straightforward method to fabricate densified and pure Ag9In4 bulk samples. Bulk Ag9In4 with less than 0.1% porosity was fabricated by pouring molten alloy into the water-cooled mold, followed by a two-step heat treatment at 520 °C and 250 °C for 40 h each. Properties, including Young's modulus, hardness, creep behavior, and coefficient of thermal expansion, were measured from 30 °C to 250 °C. As the temperature increased, the Young's modulus of Ag9In4 decreased linearly from approximately 117.9 GPa–95.9 GPa. Correspondingly, the coefficient of thermal expansion increased linearly from 19.2 μm/m/°C to 22.69 μm/m/°C, with an average value of 20.58 μm/m/°C. Moreover, the hardness decreased from 4.1 GPa to 1.7 GPa following an exponential relationship with temperature. At 250 °C, a significant creep phenomenon was detected in Ag9In4. The creep mechanism changed from dislocation climb to dislocation diffusion, with creep stress exponents of 33.1 and 10.6 at 30 °C and 250 °C, respectively.