As a key part in the manufacturing process of lithium batteries, the welding process is applied to the connection of multiple positions of lithium battery aluminum/copper anode and cathode current collectors, electrodes, and battery packaging. Any welding joint defects will significantly affect the performance of lithium batteries. consistency. Therefore, it is necessary to understand the ultrasonic welding process.

The principle of ultrasonic welding

In the ultrasonic welding process, the transducer converts high-frequency electrical signals into ultrasonic vibration signals. High-frequency vibration is transmitted to the surface of the metal to be welded through the welding tool head. The interface metal oxide film is broken under a certain pressure and the intense friction of ultrasonic vibration, clean interface metal contacts and under the combined action of friction and ultrasonic softening, further plastic flow and diffusion will gradually increase the connection area and eventually form a reliable connection.

Effect of welding pressure on welding

The strength of the welded joint increases with pressure and then decreases. Welding pressure will change the sliding resistance of the welding interface. A small welding pressure will cause a small sliding resistance of the interface, so that the energy generated by the friction is not enough to form an effective connection at the interface; too much welding pressure causes the tool head to be pressed down too deep, welding the interface Metals bite each other, which affects the relative motion of the interface, hinders the further connection of the interface metals, and results in poor mechanical properties of the welded joint. Therefore, proper welding pressure parameters are decisive for welding quality.

Effect of time on welding

The welding time directly affects the energy input during the welding process and has a direct effect on the welding effect. The welding time is too short and the input energy is insufficient. It is difficult to form an effective solder joint due to insufficient friction; as the welding time increases, the temperature increases due to mutual friction, the workpiece material begins to soften, and the oxide film at the interface of the welding area is damaged and plastically deformed , Can form a better connection; when the welding time is further extended, the welding head is easy to form deep marks on the surface of the workpiece, which will adversely affect the welding effect. In addition, too long welding time will easily cause the welding head and the workpiece to be welded Bonding

Effect of amplitude on welding

In the ultrasonic welding process, the vibration system formed by the workpiece and the workpiece directly affects the instantaneous velocity of the vibration at the interface of the workpiece, which ultimately affects the friction heat generation and plastic deformation, which affects the welding quality.

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