New ultrasonic-assisted soldering technology was adopted to weld four sets of Cu/Sn-Bi-1.5Al2O3/Cu micro-butt butt joints by adjusting the ultrasonic power.Through wetting testing

microstructure observation

micro-hardness experiment

tensile testing

fracture morphology analysis

effects of ultrasonic power on microstructure and properties of the Sn-Bi-1.5Al2O3/Cu solder joint were evaluated comprehensively.The results show that the filling ability of the composite solder is enhanced

and the largest spreading area is increased by 51.7% based on utilizing the secondary effects of ultrasonic cavitation and acoustic streaming of the ultrasound in liquid solder.After ultrasonic treatment

with the increase of ultrasonic power

fine grain strengthening is generated

and microstructure is improved with the decrease of defect.When the ultrasonic power is 800 W

the Bi phase content is decreased by 4.7%compared with ones in un-ultrasonic treatment.Meanwhile

hardness of the central brazing seam and IMC layer on boundary is increased by 40.7%and 89.9%

respectively

in addition

the tensile strength and elongation are increased by 40.7%and 89.9%

respectively

and the fracture position is transferred from the brazing seam boundary gradually to the central joint.