Porosity Dependence of Thermal and Electrical Properties in Nano-Silver Paste

Nano-silver paste is considered one of the most promising die-attach materials for high-temperature applications contributing to its excellent thermal and electrical properties and low bonding temperature. However, it is difficult to measure the thermal conductivity and electrical resistivity of nano-silver in practical applications. In this work, we proposed a finite element modeling method to predict the thermal conductivity and electrical resistivity of nano-silver. Nano-silver flake and film with different porosity were prepared by adjusting the sintering temperature, and the thermal and electrical properties were measured. The simulated results are in good agreement with the experimental results under all porosity. The error values between the experimental and simulated temperatures are less than 10%. With the increase of porosity, the thermal conductivity of nano-silver decreases and the electrical resistivity increases. Pores will cause heat flow and current concentration, and increase the possibility of failure of nano-silver in practical applications. The results indicate that the porosity plays a more important role in the thermal and electrical properties of the nano-silver compared with pores location.