Study on conductive mechanism of silver coated copper powders for conductive adhesives

The conductive mechanism of the nano-silver-copper powder conductive adhesive was analyzed by discussing the influencing factors of the concentrated resistance and the breakdown resistance. The effects of curing process of conductive adhesive on electrical properties were systematically investigated from theoretical calculations and experimental verification. The electrical properties of the prepared conductive paste on copper plates were investigated. The influence of nano fillers on the conductive mechanism of conductive adhesives was analyzed. The results show that as the volume fraction of the filler increases,the smaller the distance between the fillers,the greater the probability of contact with each other. The more contact points between the fillers,the smaller the concentration resistance,and the tunneling electrons or field emission electrons can pass through the resin matrix when the distance between the fillers is sufficiently small. Therefore,the filler volume fraction has excellent conductivity only after reaching the percolation threshold. The morphology of the conductive filler mainly affects the size of the concentrated resistance. The dendritic nano-silver-copper powder has a large branch length and many branches,and the probability of overlapping each other is greatly increased,thereby reducing the concentrated resistance. The nano silver particles mainly affect the size of the tunneling resistance. The surface energy of the nano-silver particles is high,and melting occurs at 170-200 ℃,which provides sufficient energy for electrons to cross the barrier and form tunneling electrons. Finally the field emission phenomenon also affects the tunneling resistance. This is because after the conductive paste is solidified and the copper plate is applied,when a voltage is applied across the copper plate,a strong uniform electric field is generated in the conductive paste between the lap joints,and a field emission phenomenon is generated,thereby enhancing the electrical properties of the conductive paste.