Microstructure And Properties Of Ultrasonic Assisted Soldering Al₂O₃ Ceramic And Aluminum Alloy Joints

The soldering structure of Al₂O₃ ceramic and 2024 aluminum alloy has a broad application prospect in electronic packaging,aerospace and other fields.The soldering process of Al₂O₃ ceramic and 2024aluminum alloy is a current research hot spot for the joining of dissimilar materials.The following problems exist in the soldering of Al₂O₃ ceramic and 2024 aluminum alloy:Al₂O₃ ceramic are chemically stable and difficult to form a bond with metals;the coefficient of thermal expansion of Al₂O₃ ceramic is small and does not match the coefficient of thermal expansion of the solder and 2024 aluminum alloy.Therefore,there is a large residual stress in the joint after high-temperature welding,which affects the joint performance;the melting point of 2024 aluminum alloy is low.Traditional soldering process temperature is high,it is difficult to achieve the joining with Al₂O₃ ceramic through the conventional soldering process,which seriously limits the engineering application of Al₂O₃ceramic/2024 aluminum alloy joints.Therefore,how to realize the low-temperature soldering of Al₂O₃ ceramic and 2024 aluminum alloy is the key problem that needs to be solved.The use of ultrasonic-assisted soldering to join Al₂O₃ ceramic and2024 aluminum alloy can effectively reduce the soldering temperature and achieve rapid wetting of the solder to Al₂O₃ ceramic and 2024 aluminum alloy after the solder melts.Since the melting point of 2024 aluminum alloy is low,an alloy with a lower melting point than 2024 aluminum alloy should be selected as the solder.Zn5Al alloy and Sn9Zn2Al alloy were selected as solder,and the spreading behavior of the solder on the surface of the base material under different ultrasonic times was investigated.The interfacial structure of the Al₂O₃ ceramic/2024 aluminum alloy ultrasonic soldered joints was analyzed under different ultrasonic time.The interfacial reaction products were obtained by the analysis of element distribution and element diffusion in Al₂O₃ ceramic/2024aluminum alloy joints.By testing the mechanical properties of the joints,the effect law of ultrasonic precoating time of Al₂O₃ ceramic on the joint strength was obtained,and the fracture morphology,fracture mode and fracture path of Al₂O₃ ceramic/2024 aluminum alloy joints under ultrasonic action were further investigated.In order to relieve the joint stress and improve the joint strength,a composite soldering material was prepared by mixing Zn5Al solder with Si C particles with lower thermal expansion coefficient,which increased the joint strength from 39 MPa to 66 MPa.The effect law of the mass fraction of Si C particles on the joint strength was investigated by shear test on the joint,and the enhancement mechanism of Si C particles on the joint strength was revealed.The joint strength was increased from 64 MPa to 84MPa by mixing glass powder particles with Sn9Zn2Al solder to prepare a composite brazing material,and the effect of the mass fraction of glass powder particles on the joint strength was investigated by conducting shear tests on the joint,revealing the enhancement mechanism of glass powder particles on the joint strength.