Thermomechanical Properties of Zeta (Ag3In) Phase

The thermomechanical properties of materials within die-attach joints play an essential role in assessing the reliability of high-power modules. Ag-In transient liquid phase (TLP) bonding serves as an alternative method for die attachment. However, relevant material data for the ζ (Ag3In) phase, one of the Ag-In intermetallic compound (IMC) products of TLP bonding, are limited. This paper proposes an approach to fabricate a densified and pure bulk sample of the ζ (Ag3In) phase. The thermomechanical properties of the ζ (Ag3In) phase were subsequently investigated at elevated temperatures and compared to those of other IMCs frequently observed in die-attach joints. As the temperature increased from 30 °C to 200 °C, the hardness of the ζ (Ag3In) phase decreased linearly from 1.78 GPa to 1.46 GPa. Similarly, the Young’s modulus also decreased linearly from 82.3 GPa to 66.5 GPa. These properties rank among the lowest levels compared to those of other IMCs. The average coefficient of thermal expansion within the temperature range of 70 °C to 250 °C was approximately 18.63 ± 0.61 μm/m/°C, placing the ζ (Ag3In) phase at a moderate level. When considering its potential for mitigating thermal stress, these combined properties render the ζ (Ag3In) phase an appropriate material choice for die-attach joints compared to other IMCs.