Contour evolution and sliding behavior of molten Sn-Ag-Cu on tilting Cu and Al₂O₃ substrates

The contour evolution and sliding behavior of molten Sn-3.0 wt.%Ag-0.5 wt.%Cu on tilting Cu and Al₂O₃ substrates were investigated. Experiments were performed to determine how the upper and lower contact angles and the sliding behavior changed with tilted angle of surface, kind of substrates and temperature. When the molten drop, as a whole, slid down the tilting solid surface, the upper and lower contact angles measured were defined as the advancing angle and receding angle, respectively. In general, the contour evolution of sample on Cu substrate experienced three periods and each period had different steps with the increase of the temperature compared to the only two periods on Al₂O₃, which could explain articulately the spreading and wetting behavior for sample on tilting Cu substrate. The reactive layer near receding contact point was thicker than that near advancing contact point as the molten drop slid, because that the former had longer contact time with substrate than the latter. The sliding behavior on Al₂O₃ was not the same as that on Cu accompanied which the base profile deformed.