Degradation mechanism of ag-epoxy conductive adhesive/Sn-Pb plating interface by heat exposure
The compatibility between Ag fillers and Sn-Pb plating at elevated temperature was examined by mechanical test, electrical test, and microstructure observation. The degradation at 150°C is caused by the preferential diffusion of Sn from the plating layer into Ag in the conductive adhesive. By this diffusion, Ag-Sn intermetallic compounds formed in the Ag fillers adjacent to the plating layer, and many large Kirkendall voids are formed in the Sn-Pb plating layer. Furthermore, an interfacial debonding occurred between the conductive adhesive, and the Sn-Pb plating layer is also observed near the free surface after heat exposure.