Ultrasonic-enhanced silver‑indium transient liquid phase bonding in advancing rapid and low-temperature packaging

Transient liquid phase (TLP) bonding technique is one of the promising solutions to third-generation wide-bandgap semiconductor power packaging. However, its prolonged heating process of the components restricts its application to some extent. To address this issue, the singular impact of acoustic cavitation induced by ultrasound emerges as a promising solution. For the first time, this study proposes the incorporation of ultrasound into the silver‑indium (Ag-In) TLP bonding process, enabling rapid and efficient bonding with 50 μm interlayers within seconds, while achieving a maximum shear strength of 60 MPa. A comprehensive comparative and analytical investigation of the interfacial microstructure, mechanical properties, and grain distribution has been carried out, in comparison to that of the conventional Ag-In TLP joint. The overall temperature profile was monitored utilizing a non-contact infrared camera and subsequently corroborated with finite element simulation outcomes. The phase analysis unveiled a predominant composition of the solid solution phase (Ag)-In within the bonding region, which contributes to a pronounced enhancement of the mechanical properties of the joints. Transmission electron microscopy (TEM) confirmed the complete degradation of the initial bonding interface, resulting in a bond with a bulk-like appearance. Finally, this work has elucidated the underlying mechanisms for the ultrasonic-enhanced transient liquid phase bonding (U-TLP) joint formation, where the influence of acoustic cavitation on element diffusion and the metallurgical bonding process has been discussed.