Oxidation study of pure tin and its alloys via electrochemical reduction analysis

Abstract

The oxidation of pure Sn and high Pb-Sn alloys was investigated under different oxidizing conditions of temperature and humidity. Both the chemical nature and the amount of oxides were characterized using electrochemical reduction analysis, by measuring the electrolytic reduction potential and total transferred electrical charges. For pure tin, SnO grew faster under humid conditions than in dry, air. A very thin (< 10 angstrom) layer of SnO2 was formed on the top surface under humid conditions. The mixture of SnO and SnO2 was found for oxidation at 150 degrees C. For oxidation of high Pb-Sn alloys, tin was preferentially oxidized on the surface, and tin content over the solubility limit suppressed the formation of lead oxide. For the evaporated Pb-3Sn alloy reflowed two times at 370 degrees C under H-2 atmosphere, tin was enriched on the surface as tin dendrites and lead oxide was formed in the tin-depleted region that surrounds tin dendrites.