3D large deformation and nonlinear stress analyses of tin whisker initiation and growth on lead-free components

In this study, a 3D nonlinear stress and large deflection analysis of the tin whisker initiation and growth on a pure matte Sn-plated copper substrate is investigated. The structure is subjected to compressive stress acting at the Sn-layer, which is generated by the spontaneous chemical reaction of the diffusion of Cu into Sn and the formation of Cu6Sn5. The Sn-layer is assumed to be an elasto-perfectly-plastic material. The results presented herein is useful in understanding why the compressive stress in the Sn-layer can initiate and grow a tin whisker at the weak spot of a SnOx-layer. Also, a set of useful methods is suggested to reduce (or even prevent) the reliability risk of Sn whiskers.