Research On Process And Mechanism Of Ultrasonic Assisted Soldering Of SiC Ceramics

Silicon carbide(SiC)ceramics have small thermal expansion coefficient,strong oxidation resistance,high thermal conductivity and wear resistance,good thermal stability and other excellent features,it is important material of packaging substrate.SiC ceramics have a strong covalent bond,therefore it is difficult to be wetted by liquid metal.In this study,low-temperature soldering of SiC ceramics in the air was realized,using low-temperature solders that is Sn-3.5Ag-4Ti and Sn-3.5Ag-4Al by ultrasonic soldering the soldering process,the interface microstructure and the bonding mechanism of the two kinds of active solders were studied.On this basis,the ultrasonic coating and brazing process was explored.The shear strength of the joints are increased with the time of ultrasonic irradiation,brazed with Sn-Ag-Ti at 250 ?.There are not significant differences in the microstructure of the joints at different time of ultrasound.the interface is straight,no cracks,no holes or impurities as the defects and joint connection is good.Under the effect of ultrasound,the active element Ti diffuses into the interface and generates enrichment.With Ultrasound time prolonged,Ti reacts with amorphous SiO2,and the interface reaction is not sufficient to full.In the initial stage,Ti reacts with amorphous SiO2 to form discontinuous TiO.Reaction of amorphous SiO2 with Ti is complete at 6s of Ultrasonic time.The shear strength of the joints are increased with the time of ultrasonic irradiation,brazed with Sn-Ag-Al at 250?.There are not significant difference in the microstructure of the joints at different time of ultrasound.the interface is straight,no cracks,holes or impurities as the defects and joint connection is good.Under the action of ultrasound,the active element Al diffuses into the solid-liquid interface and generates enrichment.Ultrasound time is prolonged,the interface reaction is not sufficient to full.The amorphous SiO2 upper layer first reacts with Al.Reaction of amorphous SiO2 with Al is complete at 20 s of Ultrasonic timeThe strength of the SiC ceramic joint are found to be related to the progress of the interface reaction.The activity of the Ti element is higher than Al element.With the increase of coating time,the production of TiO increase on the surface of SiC ceramics and the joint strength increase.