Comparative study of solder wettability on aluminum substrate and microstructure-properties of Cu-based component/aluminum laser soldering joint

[Display omitted] •The thickness of Al2O3 oxide film (18.45 nm) on the surface of the aluminum substrate is determined by XPS depth profiling.•After surface modification (tin plating), the contact angle between the tin solder joint and the aluminum substrate is significantly decreased (110°→14°).•The Cu-based component/aluminum laser soldering joint without defects is obtained, and the maximum linear load increases from 0 to 95.2 N/mm after tin plating. Cu-based component/aluminum substrate solder joint is achieved through laser soldering technology in this paper. The solder wettability on aluminum substrate and microstructure-properties of Cu-based component/aluminum substrate laser soldering joint are studied. The results show that the presence of the high melting point Al2O3 oxide film (∼18.45 nm thickness) isolates the contact between the molten Sn-based solder and the aluminum substrate, which results in the poor wetting properties of aluminum substrate. The surface modification of aluminum substrate can significantly improve wettability (110°→14°). Anisotropic Sn dendrites appear in the brazing area of laser soldering joints, and Ag3Sn is precipitated in the β-Sn matrix. The (Cu, Ni)6Sn5 IMC is formed near the Ni layer side. Due to the extremely fast cooling rate, the IMC thickness is less than 5 μm, and a continuous (Cu, Ni)6Sn5 region with a thickness of less than 1 μm appears at the interface near the Ni layer side. The average maximum linear load of the laser soldering joints is 95.2 N/mm. The laser soldering joint fracture occurs along the brittle (Cu, Ni)6Sn5 IMC formed at the Ni layer interface, and the fracture mode is mainly ductile fracture.