As a key part of the lithium battery manufacturing process, the ultrasonic welding process is applied to the lithium battery; aluminum foil/copper foil positive and negative current collectors, electrodes, and battery packaging are connected at multiple locations. Any defect in the welded joint will affect the consistency of the performance of the lithium battery. So it is necessary to understand the ultrasonic welding process.

In the ultrasonic welding process, the sensor converts high-frequency electrical signals into ultrasonic vibration signals. The high-frequency vibration is transmitted to the surface of the welded metal through the welding joint, and the interface metal oxide film is broken under a certain pressure and strength. Ultrasonic vibration and friction, under the combined action of friction and ultrasound, further soften the flow and diffusion of plastic, gradually increase the connection area and finally realize the connection.

The strength of the welded joint decreases as the pressure increases. The welding pressure changes the sliding resistance. A small welding pressure will cause the sliding resistance of the interface to be small, so that the energy generated by friction is not enough to form an effective connection at the interface, and the welding pressure will cause the tool head to be pressed too deeply. Therefore, the advancing welding pressure parameter plays a decisive role in welding quality.

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. Due to insufficient friction, it is difficult to form an effective solder joint; if the welding time is too long, the temperature rises and mutual friction causes the workpiece material to soften. The oxide film at the interface of the welding zone is destroyed and plastic deformation, which can form more Good connection, when the welding time is further extended, the welding head is likely to form deeper marks on the surface of the workpiece, which will affect the welding effect. If the welding time is too long, it will easily cause the welding head and the workpiece to be welded.

In the ultrasonic welding process, the vibration system formed by the workpiece and the workpiece directly affects the instantaneous speed of vibration at the interface of the workpiece, and ultimately affects the frictional heating and plastic deformation, thereby affecting the welding quality.