Dynamic resistance monitoring of aging process of pressureless sintered nano-silver joints

Nano-Ag paste is a promising lead-free chip bonding material used in the field of electronic packaging because of its low sintering temperature and high service temperature. The long-term reliability of pressure-assisted sintered nano-Ag joints has been extensively studied, but the knowledge on the performance of pressureless nano-Ag joints during long-term stressing is limited. In this paper, we studied the changes of the porosity, particle size and diffusion layer during the 9 day aging process at 150 °C. At the same time, the dynamic resistance monitoring system was used to monitor the resistance change of the solder joint in real time, and the resistance change curve during aging was drawn. During heating from room temperature to 150 °C the resistance increased. During thermal aging, the resistance value dropped by ≈25 % and finally stabilized after 4 to 5 days. By microscopic morphology analysis of the solder joints aged for different times, we found that porosity reduction was the reason for the resistance drop.