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

Abstract

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.