Tin whisker growth from titanium-tin intermetallic and the mechanism

Abstract

• Tin (Sn) whiskers were observed to grow out of Ti 6 Sn 5 intermetallic particles. • The critical role (as tin atom source) of Ti 6 Sn 5 intermetallic compound in Sn whisker growth is identified. • An atomic diffusion-based whisker growth model is proposed, and a new preparation method of metal nanowires is expected. Spontaneous growth of metal whiskers, represented by tin whiskers, has haunted tin-based platings and solder joints for decades and caused huge losses to the electronics industry. Despite numerous efforts, the underlying growth mechanism has been resisting interpretation, and the whiskering phenomenon even continues to expand its territory. Here, we report the growth of tin whiskers from a Ti 6 Sn 5 intermetallic. These tin whiskers share similar characteristics with those found on the platings or solder joints, but grow more and faster, with finer diameters. After tin whisker growth, Ti 6 Sn 5 retains its crystal structure, implying a dealloying process. Combining experimental and first-principles calculation results, we analyzed the growth mechanism of tin whiskers in detail, and proposed a diffusion-based growth model. The strain energy stored in Ti 6 Sn 5 during deformation provides a driving force for whisker growth, and the short-circuit diffusion paths generated by such deformation accelerate whisker growth. These findings identify the critical role of intermetallic substrate in the whiskering phenomenon, shedding new light for comprehensively understanding the whisker growth mechanisms. Furthermore, the plenty and rapid growth of tin whiskers also means a new method for the preparation of one-dimensional metallic materials.