Mechanism of oxide film removal by KF-AlF3 and CsF-AlF3 mixed fluxes on Cu and Al base metals and their effect on wettability

Abstract

CsF-AlF3 was added in different mass percentages to KF-AlF3 flux, and CsF-AlF3/KF-AlF3 mixed fluxes with different components were prepared by ball milling. The melting curves of four kinds of fluxes were measured using differential scanning calorimetry (DSC). The properties of the fluxes were studied by flowing and wetting experiments. The intermetallic compounds (IMCs) at the interface of the filler metal/copper (Cu) base metal were studied by field emission scanning electron microscope (SEM-EDS), electron backscattering diffraction (EBSD). The results showed that as the mass of CsF-AlF3 increased, the solidus and liquidus temperatures of the flux gradually decreased. The flux has better flowability on the Cu and Al surfaces. In the presence of the fluxes, the wettability of the filler metal on the Al is better compared to the wettability on the Cu. Three kinds of IMCs, namely Cu9Al4, CuAl and CuAl2, were found at the interface between filler metal and Cu. The texture strength and deformation degree of CuAl2 with preferred orientation are the largest. The order of formation of IMCs is Cu9Al4, CuAl, CuAl2.

Keywords

• Flux
• Flow test
• Wettability
• Growth of IMCs
• EBSD