スズめっき皮膜/銅基板界面の微視的不均一性評価

概要

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Three-dimensional visualization by serial sectioning and deformation analysis by EBSD were performed for detailed microscopic evaluation of the interface between an electroplated film of tin and a copper substrate. Three-dimensional morphology revealed that the intermetallic compound of Cu6Sn5 developed nonuniformly from the tin grain boundaries, which are thought to be preferred nucleation sites of Cu6Sn5. Results further showed that the whisker root grain coarsened in the plated plane because of incoming tin atoms and consequent grain boundary movement. Scanning ion microscopy and a kernel average misorientation map showed that copper deforms locally as Cu6Sn5 develops at the interface between the electroplated film and substrate. The mode of the local deformation of copper adjacent to Cu6Sn5 was evaluated using pattern analysis of EBSD. The tensor, which describes the local deformation, showed that rotation and shear strain were introduced because of the volume change in the Cu6Sn5 formation. The nonuniform morphology of Cu6Sn5 and resultant local deformation of copper suggest nonuniform deformation in the tin film, which might induce tin atom diffusion and promote whisker growth.
社団法人表面技術協会の論文
2008-12-01