The oxidation of pure Sn and eutectic 63Sn-37Pb solder was investigated at 85 degrees Celsius in either dry air or a humid environment at 85% relative humidity (R.H.). Both the chemical nature of oxide and its thickness were characterized using the Sequential Electrochemical Reduction Analysis (SERA) technique by measuring the electrolytic reduction potential and total transferred electrical charges for each alloy composition and oxidizing condition. For pure Sn, SnO is shown to grow faster under humid condition than in dry air, while a very thin (<10 A) layer of SnO2 is always formed on the top surface of both alloys. For eutectic 63Sn-37Pb, a mixture layer of SnO and SnO2 is formed and SnO2 is shown to grow thick when aged under the humid condition.
By: Sung-il Cho, Jin Yu, Sung K. Kang, Da-Yuan Shih
Published in: RC23141 in 2004
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