A Study on the Thermal Oxidation and Wettability of Lead-free Solders of Sn-Ag-Cu and Sn-Ag-Cu-In

초록

The surface oxidation mechanism of lead-free solder alloys has been investigated withmultiple reflow using X-ray photoelectron spectroscopy. It was found that the solder surfaceof Sn-Ag-Cu-In solder alloy is surrounded by a thin InOx layer after reflow process; thiscoating protects the metallic surface from thermal oxidation. Based on this result, we haveperformed a wetting balance test at various temperatures. The Sn-Ag-Cu-In solder alloy showscharacteristics of both thermal oxidation and wetting balance better than those of Sn-Ag-Cusolder alloy. Therefore, Sn-Ag-Cu-In solder alloy is a good candidate to solve the twoproblems of easy oxidation and low wettability, which are the most critical problems of Pb-freesolders.

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