The effects of displacement rate on fracture behaviors of 100Sn solder and 63Sn37Pb solder alloys have been investigated by SEM in-situ testing. It was found that for the 100Sn solder, grain boundary sliding was the dominant deformation mechanism at lower tensile rate regime, while a large area of slip lines crossing grains were detected at the surface of specimens at higher tensile rate regime. For the 63Sn37Pb eutectic alloy, however, because of existence of the second phase, fracture behavior depended on the growth and linkage of cavities ahead of crack tip, and the crack paths changed from intergranular to transgranular with the increasing of loading rate. (C) 2005 Springer Science + Business Media, Inc.