Study On Mechanism Of Solder Droplets Spreading On SiC Ceramic Surface Under

Conventional brazing generally requires fluxing to achieve the connection between the brazing filler metal and the parent metal during welding in an atmospheric environment.Ultrasonic-assisted brazing can achieve the connection between the brazing filler metal and the parent metal(same,dissimilar metals and non-metals)without the use of flux in the atmosphere.However,there are few studies on the conduction and distribution of ultrasonic vibration on the base metal and the dynamic spreading process of solder droplets on the surface of the base metal,which affects the wide application of ultrasonic assisted brazing technology.Therefore,this paper focuses on revealing the mechanism of non-wetting and spreading behavior of solder droplets during ultrasonic assisted brazing.It is revealed that the mechanism of non-wetting and spreading behavior of solder droplets during ultrasonic assisted brazing is the main research goal.The experimental verification was carried out,and the vibration intensity of SiC ceramic surface and the spreading process of solder droplets on the surface of the base metal under the action of ultrasonic by high-speed camera were recorded by laser vibrometer.The vibration distribution of the surface of SiC ceramic with a size of 40 mm×20 mm×3mm after ultrasonic application was analyzed by ANSYS software.The results show that the vibration response of the surface of the base metal under the action of ultrasonic is non-uniform,but has a certain distribution law: the vibration intensity distribution of the SiC ceramic surface under the same ultrasonic amplitude appears to gradually increase along the ultrasonic tool head to the other end of the base metal,along the horizontal central axis.The situation is gradually increased to both sides of the base material;and as the ultrasonic amplitude increases,the surface vibration intensity of the base material increases.The spreading behavior of solder droplets under ultrasonic waves was simulated using Fluent fluid software.Under the ultrasound,the solder droplets on the SiC ceramic surface spread rapidly.As the amplitude of the ultrasound increases,the droplet spreading rate increases,and at the same time,the final spreading area of the droplet increases.Ultrasound affects the internal pressure of the solder droplets.When no ultrasonic waves are applied,the internal pressure of the solder droplets is small and the pressure value is below 420 Pa.After applying ultrasonic wave,the internal pressure of the solder droplets exhibits periodic positive and negative pressure continuous transformation with time in one ultrasonic cycle,and the absolute value of the internal pressure of the solder droplets increases remarkably,and as the ultrasonic amplitude increases,the inside of the droplets increases.The pressure change amplitude increases,and the internal pressure changes the most when the ultrasonic amplitude is 8 ?m.When the ultrasonic amplitude is 4 ?m,the absolute internal pressure of the dropletis 650 kPa,and the absolute value of the pressure increases with the increase of the ultrasonic amplitude.The absolute value of the pressure at 8 ?m is 1400 kPa.The dynamic spreading process of the solder droplets on the surface of the base metal under the action of ultrasonic was recorded by a high-speed camera.After applying ultrasonic wave,the solder droplets exhibit different shapes during the spreading process,such as atomization and ripple of the spreading front;during the same time,as the ultrasonic amplitude increases,the droplet spreading rate increases;at the same amplitude,with time extension,The droplet spreading rate is gradually reduced.The mechanism of non-wetting spreading of solder droplets on the surface of the base metal was analyzed.The main driving force was derived from ultrasonic action.The larger the ultrasonic amplitude,the larger the offset and the sound pressure amplitude.Ultrasonic action causes the solder droplets to be subjected to a sound pressure offset of a different sinusoidal distribution down the direction,causing the solder droplets to flow in the direction of the offset gradient,thereby causing the droplets to spread outward.