Tin whisker growth on immiscible Al–Sn alloy

Abstract

Spontaneous growth of Sn whiskers has seriously affected the reliability of electronic systems and caused many major accidents. Its growth mechanism and mitigation strategy have been the focus of research in the past decades. In this paper, a large number of Sn whiskers were found to grow quickly on Al–Sn alloys prepared by mechanical alloying when treated at 300 °C. Different from the large randomness of the whisker growth on metallic coatings and platings as in major research work of this topic, the Sn whisker growth from ball-milled Al–Sn substrate shows good repeatability. To demonstrate the compressive stress in the samples, X-ray diffraction residual stress analysis was detected. An average compressive stresses in Al phase after heat treatment was 81.2 MPa, which may have been responsible for the whiskers growing directly on the surface. Meanwhile, the interfacial energy caused by high-energy ball milling may have played a positive role in the growth of whiskers. Sn whiskers formed on Al–Sn alloy samples have shorter incubation period and faster growth rate, which makes it much more convenient to research the mechanism.