Substrate-Dependent Sintering Mechanism of Ag Nanostructures Derived from Ag-Based Complex

The sintering of Ag nanostructures is a promising bonding technique for wide-bandgap semiconductor power devices. This study aimed to investigate the substrate-dependent sintering mechanisms of Ag nanostructures sintered on Ag, Al, and Cu substrates via the thermal decomposition of an Ag-based complex at 180 °C. A specific mechanism based on the reaction between the Ag-based complex and substrate can be elucidated for the sintering of Ag nanostructures. The sintering of Ag nanostructures on Ag and Al substrates involved the sintering of polydispersed Ag particles. The smaller Ag particles enhanced the stacking density by filling the interspaces between the larger Ag particles and acted as diffusion pathways, facilitating the sintering process and leading to superior low-temperature bonding performance. Notably, a shear strength of 21.8 MPa was achieved for the sintered Ag on the Ag substrate at 160 °C, indicating a well-bonded interface. However, the presence of an Al oxide layer on the Al substrate hindered the formation of a robust interface with sintered Ag, resulting in diminished shear strength. In contrast, the sintering of Ag nanostructures on the Cu substrate involved a displacement reaction between the Ag-based complex and Cu substrate. This reaction led to Cu compounds with a high decomposition temperature of 211 °C and formation of intermediate organic products and CuO in Ag joints, which deteriorated the joint properties. These findings provide valuable insights into selecting appropriate substrates for the sintering of Ag nanostructures using Ag-based complexes, thereby highlighting the critical role of substrate materials in optimizing bonding performance.