Characteristics And Mechanism Of The Ultrasonic Cavitation With In The Filling Under Ultrasonic Of Liquid Sn

On the process of ultrasonic soldering, the cavitation would be occurred in the liquid solder under ultrasonic. The bonding of the base metal and solder would be promoted and improved by the ultrasonic cavitation, so ultrasonic cavitation directly affects the joints of ultrasonic soldering. In this paper, the characteristics and distribution of the cavitation within the process of the solder of pure Sn filling under ultrasonic, and analyzing the reason of it through the fluid simulation software; explore the mechanism of the removal of oxide film by ultrasonic cavitation and analyzes the influencing factors of it.The study found that the structure of the cavitation within the filling under ultrasonic main transient cavitation bubble and steady bubbles. As the filling process, the cavitation structure within the gap mainly large steady bubbles changed to mainly a small volume of transient cavitation bubbles. On the same base metal surface, the cavitation is influenced by the amplitude and the size of gap; the greater the amplitude, the smaller the gap, the greater the cavitation bubble density, more uniform distribution, the stronger the cavitation.The amplitude of the sound pressure in the gap increases with the process of filling under ultrasonic by simulation through fluid simulation software. So steady state cavitation bubbles collapsing to create more smaller transient cavitation bubbles with the process of filling, result in the structure of the cavitation changed. The distribution of sound pressure within the gap is consistency with the vibrating of base metal, the maximum sound pressure amplitude is influenced by the amplitude and the size of the gap, the greater of the amplitude, the smaller of the gap, the greater the maximum sound pressure amplitude, with the corresponding cavitation effect is stronger.The mechanism of cavitation is to impact the base metal by microjets and shock wave generated by the collapsing of bubbles, resulting in the fatigue damage of the surface of base metal. Cavitation effects directly related to the cavitation strength, fatigue strength of the base material surface also affects the cavitation effect.