Enhancement of solderability of Cu₆₀Zr₃₀Ti ₁₀ bulk metallic glass by dealloying in hydrofluoric acid solution

To extend the engineering applications of bulk metallic glasses (BMGs), it is necessary to create process to form appropriate BMG/BMG and BMG/crystalline metal joint. In this study, hydrofluoric acid (HF) solution treatment and a laser soldering process were employed to enhance the solderability of Cu ₆₀Zr₃₀Ti₁₀ BMG. The surface treatment in HF solution successfully dissolved surface Zr and Ti, resulting in concentration of Cu at the surface. A reflow soldering process using Sn-3.0 mass% Ag-0.5 mass% Cu (SAC) solder on this surface showed obvious dewetting because the thin Cu-rich layer dissolved into the molten solder. Laser soldering with a 0.01 s irradiation time, which produces rapid heating and cooling rates, offered good wettability of SAC solder and Sn-57 mass% Bi (SB) solder. At the interface between the SB solder and the HF-treated BMG foil, an intermetallic compound (IMC) layer was observed by scanning electron microscopy (SEM).