Effect of Ga on the Oxidation Properties of Sn–8.5Zn–0.5Ag–0.1Al–xGa Solders
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The oxidation properties of Sn–8.5Zn–0.5Ag–0.1Al–xGa lead-free solders in the liquid state (250 °C) under O2 atmosphere were investigated using a thermal gravimetric analyzer. The Ga content of the investigated solders was 0.05–2 wt%. The results indicate that Ga enhances the oxidation resistance of Sn–Zn–Ag–Al solder. Cross-sections of the solder surfaces were examined using focus ion beam milling. The thickness of the oxidation layer, which was about 30–100 nm, increased with increasing Ga content. The oxidation layer was found to be nonuniform at low Ga content. The oxide layers on the surface of solders were investigated using Auger electron spectroscopy and thin-film XRD. The results showed that the oxide layer formed was ZnO. Al and Ga tended to segregate on the surface of the solder.
KeywordsSn–Zn Pb-free solder Oxidation resistance ZnO
The financial support of this work by the National Science Council of the Republic of China under grant NSC-93-2216-E006-011 is gratefully acknowledged.
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