Sintering Behavior and Effect of Silver Nanowires on the Electrical Conductivity of Electrically Conductive Adhesives

In this paper, two kinds of silver nanowires with a 160 nm average diameter ranging from 30 to 90 µm length and a 450 nm average diameter up to 100 µm length were successfully synthesized by a polyol process with FeCl3 and Na₂S as reaction inhibitor, respectively. The experimental results indicate that the morphologies and sintering behaviors of both of silver nanowires are impacted by glutaric acid and sintering temperature. The isotropically conductive adhesives (ICAs) filled with micro-sized silver flakes and silver nanowires as hybrid fillers were fabricated and the electrical properties were investigated based on the fraction of the silver nanowires of the total of silver fillers and the curing temperature, etc. The in situ monitoring the variation in electrical resistance of the ICAs explores that silver nanowires have influence on the curing behavior of the ICAs. Silver nanowires synthesized with Na2S as reaction inhibitor and treated with glutaric acid can significantly improve the electrical conductivity of the ICAs in the case of the low loading of silver fillers in the appropriate proportion range of the weight ratio of micro-sized silver flakes and silver nanowires, primarily as a result of connecting effect. When the loading of silver fillers in the ICAs is high, the electrical conductivity is also enhanced slightly in the case of the proper fraction of silver nanowires of the total of silver fillers. The effect of the curing temperature on the electrical conductivity relates to the fraction of silver nanowires and the total loading of silver fillers. The electrical conductivity of the ICAs filled with micro-sized silver flakes and silver nanowires synthesized with FeCl₃ as reaction inhibitor is greatly damaged, indicating that the size of silver nanowires also is one of main factor to impact the electrical conductivity of the ICAs doped with silver nanowires. The electrical property of the ICAs filled with micro-sized silver flakes and silver nanowires results mainly from the synergy of silver flakes and nanowires, forming the conductive pathways.