| Summary: | 碩士 === 國立雲林科技大學 === 材料科技研究所 === 99 === This study investigated the corrosion and oxidation effects on different contents of rare-earth elements (Mm) in lead-free solders Sn-3Ag-0.5Cu-XMm and Sn-3Ag-0.5Cu-4Ti-XMm alloys. The composition and structure of the oxidation layers in the high temperature atmospheric environment or corrosive environment of 3.5 wt.% NaCl solution were analyzed.
In high temperature atmospheric environment, the growth rate of oxidation layer of Sn-3Ag-0.5Cu-XMm and Sn-3Ag-0.5Cu-4Ti-XMm alloys with 0.05 wt.% and 0.1 wt.% of rare-earth elements was lower than the alloys with 0 wt.%、0.2 wt.% and 0.5 wt.% of rare-earth elements. The addition of a trace amount of rare-earth elements into solders caused heterogeneous nucleation and grain size reduction of the matrix β-Sn and improved the oxidation and corrosion resistance of solders.The high concentration of rare-earth element in Sn-3Ag-0.5Cu-XMm and Sn-3Ag-0.5Cu-4Ti-XMm alloys caused the formation of LaSn3 intermetallic compound, on which Sn-whisker grew up easily. Thus, it reduced the oxidation and corrosion resistance of solders
In high temperature atmospheric environment, while adding 4wt.% of titanium in Sn-3Ag-0.5Cu-4Ti-XMm alloy, a thin and uniform oxidation layer of TiO or TiO1+X formed on the alloy surface. The thin and uniform oxidation film of TiO or TiO1+X hindered the diffusion of oxygen into the matrix β-Sn of alloy, prevented tin-oxide forming, and reduced the oxidation rate of Sn-3Ag-0.5Cu-4Ti-XMm alloy.
In 3.5wt.% NaCl solution, the corrosion potential (Ecorr) of Sn-3Ag-0.5Cu-XMm and Sn-3Ag-0.5Cu-4Ti-XMm lead-free solders with 0.05 wt.% and 0.1 wt.% of rare-earth elements was higher than the solders with other concentrations of rare-earth elements. In comparison with the Sn-3Ag-0.5Cu-XMm alloy without Ti containing, the Sn-3Ag-0.5Cu-4Ti-XMm alloy with 4 wt.% Ti has a higher corrosion potential (Ecorr) and a lower corrosion current density (Icorr). The results revealed that the addition of 4 wt.% Ti and rare-earth elements between 0.05 wt.% to 0.1 wt.% in Sn-3Ag-0.5Cu reduced the corrosion rate and improved the corrosion resistance of lead-free solders. Similar results were found in oxidation tests.
|
|---|
