A XANES Study of Natural Oxide Films on Plated Tin

Like the oxide films that form on several metals, the natural oxide film that forms on tin is very thin, approximately 20 nm at most and it may less than 10 nm in the newly plated surface. Basically, obtaining the properties of oxide films is a prerequisite for calculating the electrical contact resistance. However, in most actual connectors, the initial film structure is broken during connecting action. Thus, knowledge of the precise properties of oxide films has not been considered necessary for designing connectors. The authors of previous reports attempted to calculate the electrical contact resistance of tin-plated terminals using analytical models. The construction of such computational analytical models requires knowledge of the precise properties of oxides. That is one of the motivations of the present study. The electronic structure of natural oxide films was investigated in this work by soft X-ray absorption near-edge structure (XANES) spectroscopy. The O K-edge and Sn M
_4,5
-edge were selected for XANES analysis in this case. The X-rays were provided by synchrotron radiation. One-month-old (new) and 10-year-old (old) specimens were prepared for the analysis, and their spectra were compared with the spectra of SnO
₂
and SnO sintered standard samples. Both SnO
₂
and SnO constituents are detected from all the specimens.