Heredity of preferred orientation of β-Sn grains in Cu/SAC305/Cu micro solder joints

Abstract

The microstructure heredity of Cu/Sn-3.0Ag-0.5Cu(wt%)/Cu micro solder joints between sequential reflows was investigated. The solder joints that were isothermally reflowed for the first time all presented a mixed structure of large and interlaced grains after the second isothermal reflow. However, the joints that were reflowed under temperature gradient for the first time maintained the strong oriented textures with θ angles larger than 50° after isothermally reflowed for the second and even third time, clearly showing the heredity of preferred orientation of β-Sn grains. The unique cluster model of Sn embryos and cavity geometry among interfacial Cu6Sn5 grains formed under temperature gradient were supposed to contribute to the microstructure heredity of β-Sn grains between sequential reflows.