Physical Mechanism And Dynamics Of Ultrasonic Induced Spreading Of Liquid Solder

As a new darling in the field of soldering,ultrasonic soldering received much attention by scholars. Most scholars paid more attention to the practical application of ultrasonic soldering,but ignored its basic spreading process. In this paper,the spreading of liquid solder which occur on a 50 mm × 30 mm × 3mm base metal by ultrasonic-assisted was as an example to summarized the process of spreading and simulated,at the same time we explored the mechanical of interface during spreading.The dynamic spreading process by different base metal,the amplitude of ultrasonic and frequency and other conditions were summarized through the high-speed video of spreading,and the ripples and atomization during spreading were also summarized. The basic physical process of spreading by ultrasonic-assisted was proposed,and we established an integrated physical model. We designed an experiments to analysis the of oxide film in the front of the solder,and found that after blocking the frontier of solder,the oxide film under the solder can be removed.By using ANSYS software to calculate the amplitude and vibration modes on the surface of base metal under different conditions,we found that both the characteristics of base metal and the conditions of vibration can alter the amplitude and its distribution. The amplitude on the surface of base metal increased with the increasing of ultrasonic amplitude and the elastic modulus of the base material,but the vibration modes constant. If the ultrasonic frequency and the size of base metal changed,both the amplitude and the vibration modes would change. And one path which pass through the center of solder differed from others under the same condition.The spreading process under different conditions was simulated using the CFD software,and the results were validated by the experiment. The result of relationships between spreading rate and time from calculated fit with the result of experiments well.We found the critical amplitude and frequency of ultrasonic which lead to spreading of solder by simulating,and solved the force state at the forefront of the three-face interface when the amplitude of ultrasonic was 6μm and the frequency was 21.9k Hz. Finally we worked out the critical force when the spreading occur was 782 Pa. After calculated the pressure of the interface between solder and base metal,we found that the amplitude of ultrasonic additional pressure gradient decreased from the center of the liquid solder to the edge of it,while the cavitation won’t exist if the amplitude of ultrasonic additional pressure gradient is too small,therefore this paper considered the reason of the phenomenon that the oxide film is still exist was due to the smaller amplitude of ultrasonic additional pressure gradient.