XC. On tin whiskers

Abstract

Summary The growth of tin whiskers is explained as a process in which oxidation of the whisker surface develops a stress which draws out a continuing thread of metal from the main mass. A mechanism is provided by a dislocation in the main mass which travels continuously around the root of the whisker. It then follows that the whisker axis should be parallel to the Burgers vector of the dislocation, i.e. a slip direction in the crystal. All that is needed to start the process is an oxidizing or other reactive atmosphere, a small knob on the surface, and a dislocation. The order of magnitude of the growth rate can be satisfactorily accounted for. The substantially uniform thickness of whiskers is explained because the growth rate increases rapidly with diminution of radius, but below a certain radius the process fails because the tensile stress at the root fractures the whisker. The angular bends produced in whiskers subjected to a very high bending stress is attributed to an unusual kind of deformation twinning.