Improvement in high-temperature degradation by isotropic conductive adhesives including Ag-Sn alloy fillers

摘要

The reliability evaluation of Cu and Sn/Ni joined with isotropic conductive adhesives (ICAs) including Ag-Sn alloy fillers with or without Ag plating instead of Ag fillers was examined using tensile tests, electrical resistivity tests and microstructural observations. For an ICA, including Ag-Sn alloy fillers added to Sn-58wt%Bi fillers, the tensile strength was found to improve, but the electrical resistivity worsened with 150℃ heat exposure. An ICA, including, Ag-Sn alloy fillers with Ag plating, was able to maintain electrical resistivity after being subjected to 150℃ heat exposure. The Ag plating on the Ag-Sn fillers reacted with the Sn in the Ag-Sn fillers, leading to the joining of the fillers with each other though metallurgical connections, and the transformation of Ag into Ag_3Sn within a 1-h curing time at 150℃, since the Ag plating was microscopic and active. After heat exposure, the Sn distributed itself along the sub-strate/ICA interface by the diffusion of Sn though the connected fillers, and Cu_3Sn formed at the Cu/ICA interface, in contrast with the Ag-Sn alloy fillers without Ag plating.