Microstructure and Bonding Strength of Low-Temperature Sintered Ag/Nano-Ag Films/Ag Joints

Nano-Ag paste is one of the most widely used die-attachment materials in modern electronic devices, which are gaining continuously increasing application in transportation industries. The nano-Ag film in a pre-formed dimension and free from the use of chemical dispersing agents has been proposed to be a promising alternative to nano-Ag paste for the die-attachment application. Although the bonding mechanisms of Nano-Ag paste have been extensively studied, little is known about the relationship between the microstructure and mechanical properties of low-temperature-sintered Ag/nano-Ag film/Ag joints. In this work, the influences of temperature, pressure, and dwell time at peak temperature on the microstructure and the shear strength of low-temperature-sintered Ag/nano-Ag film/Ag joints were systematically investigated. Mechanical properties tests indicate that both temperature and pressure have pronounced effects on the bonding strength of sintered Ag/nano-Ag film/Ag joints. TEM and hot nanoindentation characterizations further reveal that the sintering temperature plays the most determinant role in the coarsening of nano-Ag film and, hence, the bonding and fracture behaviors of Ag/nano-Ag film/Ag joints sintered at 210–290 °C. The diffusion-induced coarsening of nano-Ag particles can be activated, but remains sluggish at 250 °C, and the mechanical integrity of sintered joints is circumscribed by the interfacial bonding between nano-Ag film and Ag substrate after sintering at 290 °C.