Measurements have been made of the diffusivity and electromigration of195Au in lead‐tin solders in the composition range 0–12 at. % tin. A marked decrease in the diffusivity is attributed to tin trapping of gold with a binding energy of about 0.21±0.03 eV. The addition of the tin has no perceptible effect on the electromigration of the gold. A curious minimum in theDx/Dvs concentrationxappears in the concentration range, 1–5 at. % tin, for specimens that have been prepared by a slow quench from the melt. This effect disappears when the specimens are heated above 180 °C. The origin of this behavior is still a topic of open speculation.