Aging-time-resolved in situ microstructural investigation of tin films electroplated on copper substrates, applying two-dimensional-detector X-ray diffraction

Pure thin tin films, electroplated on copper substrates, were investigated by in situ X-ray diffraction analysis during room-temperature aging, using a laboratory diffractometer equipped with a two-dimensional detector. Diffraction spots of single Sn grains in the Sn film could be observed and traced over time by using the diffraction method adopted. For the as-deposited specimens, striking changes of the Sn reflection spots, concerning their position and intensity, as well as sudden appearances and disappearances of additional diffraction spots, were observed. This could be ascribed to local microstructural changes in the films such as grain rotation, grain growth and grain dissolution. In contrast to the as-deposited specimens, so-called post-baked specimens (i.e. annealed at 423 K for 1 h after layer deposition) exhibited a stable microstructure. The results obtained are discussed with respect to their relevance for the Sn whisker-growth phenomenon.