Alternatively, it may suggest that the electrochemical oxide influences the rate at the whiskers grow once the whisker has penetrated the oxide layer. It might be expected that when a whisker penetrates through the oxide film, the whisker would have a similar rate of growth to the untreated samples; therefore, the electrochemical oxide also appears to be having an influence on the driving force for whisker growth as well as inhibiting whisker initiation. It was shown previously that for Sn-Cu on Cu, IMC growth didn’t appear to be influenced by the presence of the electrochemical oxide [1]. In the absence of an oxide film, the surface of the tin serves as a source for vacancies to facilitate tin diffusion through the coating, to support the growth of whiskers [2]. However, the presence of a sufficiently thick oxide may impede diffusion of tin atoms by reducing the number of available surface vacancies [3], therefore slowing the rate at which whiskers may grow. This may suggest that whisker growth on the electrochemically oxidised samples is diffusion limited.