Soldering is a potential technique for joining metallic glasses. It can be performed at far below the crystallization temperature of various metallic glasses; thus, there is no possibility of crystallization. However, Cu-Zr-based metallic glass displays poor wettability to Pb-free solder, because a strong native oxide film prevents direct contact between the solder and the glass. To overcome this problem, Cu-Zr-based metallic glass clad with a thin film of Cu has been developed. This was produced by casting the melt of a Cu36Zr48Al8Ag8 pre-alloy into a Cu mold cavity, inside which a thin film of Cu with a thickness of 2 μm was placed. Cu36Zr48Al8Ag8 metallic glass was successfully formed and welded to the Cu thin film. From microstructure analysis, it was found that a reaction layer was formed at the interface between the Cu and the Cu36Zr48Al8Ag8 metallic glass. However, no oxide layer was observed in the Cu-clad layer. It was found that the Cu cladding played an important role in preventing the formation of the surface oxide film. Consequently, solderability to the Cu-Zr-based metallic glass was drastically improved.
Devitrification of thin film Cu-Zr metallic glass via ultrashort pulsed laser annealing