Abnormal swelling behavior of sintering nano-Ag joint during high-temperature ageing

Nano-Ag paste is a kind of potential candidate for die bonding materials for power electronics due to its low processing temperature, superior electrical and thermal conductivity as well as thermo-mechanical performance. In this paper, the reliability of pressure-assisted sintering nano-Ag joints during high temperature storage (HTS) test at 300 °C in air was evaluated. The copper sheets with nickel and silver plating were used as dummy chips and substrates. It was found that the strengths of the sintered silver joints would sharply drop during the initial aging stage at 300 °C in air , and at the same time, the thickness of the sintered layer increased. In order to further explore the relationship between the sudden drop of nano-Ag joints’ shear strengths and the increased thickness of the sintered Ag layer, the sintered silver joints were storage at 100 °C in air and at 300 °C in vacuum. Finally it was found that the abnormal swelling behavior of the nano-Ag joints were attributed to the high temperature ageing and oxygen, which was the main cause for the sharp drop of the sintered joints’ shear strengths.