Tesla has applied Wire Bonding, a specific application of ultrasonic welding technology, in its battery system, which makes the application of ultrasonic welding technology in the field of power battery group connection more and more discussed. The application of ultrasonic welding in power battery can be seen that the application examples mainly focus on pole lug welding and fuse welding.

Characteristics of ultrasonic welding

Welding material type, can be used for the same metal materials, especially high conductivity, high thermal conductivity materials (such as gold, silver, copper, aluminum, etc.) and some of the refractory metal welding, also can be used for the performance difference of dissimilar metal materials (such as thermal conductivity, hardness, melting point, etc.), the material such as metal and nonmetal, plastic welding, It can also complete the welding of materials with different thickness and the welding of multilayer foil;

• The welding parts are not energized, do not need external heat source, the joint does not present microscopic pores and other defects, do not generate brittle intermetallic compounds, such as resistance welding easy to appear molten metal spatter and other questions;

• The physical and mechanical properties of the weld metal do not change microscopic, and the static load strength and fatigue strength of the welded joint are higher than that of the resistance welding joint, and the stability is good;

• The oxide film or coating on the surface of the welded metal has little influence on the welding quality, and the preparation work on the surface of the welded parts is relatively simple before welding;

• Less power required for welding; Small deformation of weldment;

• No need to increase any binder, filler or solvent, with simple operation, fast welding speed, high joint strength, high production power advantages;

• Disadvantages: The main defect of ultrasonic welding is that it is restricted by the power of existing equipment, so the thickness of welding parts touching the upper sound pole cannot be too thick; Joints can only be used lap joints, butt joints are not available.

Principle of ultrasonic welding

Ultrasonic welding is a solid phase welding method. The connection between welds is realized by high-frequency elastic vibration of acoustic system and static pressure between workpiece. Under the joint action of static pressure and elastic vibration energy, the elastic vibration energy is converted into friction energy, deformation energy and heat energy between the workpiece, resulting in the formation of pure metal bonding and atomic diffusion on the surface of the two workpiece, thus achieving friction welding.