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

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 °C heat exposure. An ICA, including, Ag–Sn alloy fillers with Ag plating, was able to maintain electrical resistivity after being subjected to 150 °C 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 Ag3Sn within a 1-h curing time at 150 °C, since the Ag plating was microscopic and active. After heat exposure, the Sn distributed itself along the substrate/ICA interface by the diffusion of Sn though the connected fillers, and Cu3Sn formed at the Cu/ICA interface, in contrast with the Ag–Sn alloy fillers without Ag plating.