Ultrasonic welding utilizes high-frequency vibration waves transmitted to the surfaces of two objects to be welded. Under pressure, the surfaces rub against each other, forming a fusion between molecular layers.
The main components of an ultrasonic welding system include an ultrasonic generator, transducer, amplitude transformer, welding head triplet, mold, and frame. Ultrasonic waves can be used not only to weld metals and hard thermoplastics, but also to process fabrics and films.
1. Ultrasonic Metal Welding Principle
Ultrasonic metal welding utilizes the mechanical vibration energy of ultrasonic frequencies (above 16kHz) to join similar or dissimilar metals. During ultrasonic welding, no current or high-temperature heat source is applied to the workpiece; instead, under static pressure, the frame's vibration energy is converted into frictional work, deformation energy, and a limited temperature rise between the workpieces. The metallurgical bond between the joints is a solid-state weld achieved without melting the base materials. Therefore, it effectively overcomes the spatter and oxidation phenomena produced during resistance welding. Ultrasonic metal welding machines can perform single-point welding, multi-point welding, and short strip welding on fine wires or thin sheets of non-ferrous metals such as copper, silver, aluminum, and nickel. They are widely used for welding thyristor leads, fuse elements, electrical leads, lithium battery electrodes, and tabs.
In lithium battery technology, there are three types of metal welding methods: copper/aluminum foil to tab, tab to tab, and tab to bus. Welding copper/aluminum foil to tabs is the most challenging because the two ends of the weld use metals of different thicknesses and materials; one end (tab) is relatively thick (e.g., 0.2mm), while the other end consists of multiple layers of extremely thin metal sheets.
ACEY-USW-1 Ultrasonic spot welding machine is designed for joining nickel and aluminum materials in the context of battery manufacturing or other applications.
Welding foil to tabs connects all the anode and cathode foils inside the battery to their corresponding tabs, thereby transferring energy from the battery's internal components to the external components. Hundreds of lithium battery cells constitute a typical lithium battery pack. The battery cells are connected in series or parallel. If one connection fails, the entire battery pack will fail. Therefore, robust and secure connections are crucial.
The connection between the multi-layer foil and the tabs is achieved using Ultrasonic Metal Welding (UMW), as shown in the diagram below. UMW is ideal for welding dissimilar metal materials such as copper, aluminum, and nickel. Two metal parts are pressed together and vibrated relative to each other at high ultrasonic frequencies (typically 20-40kHz). The heat generated by friction removes oxides and contaminants from the metal surfaces, creating a smooth surface. Under appropriate pressure and heat, a weld is formed between the two.
2. Advantages of Ultrasonic Metal Welding
a. The welding material does not melt, preserving the metal's properties.
b. Excellent electrical conductivity after welding, with extremely low or near-zero resistivity.
c. Low requirements for the weld metal surface; oxidation or electroplating is acceptable.
d. Short welding time; no flux, gas, or solder is required.
e. Spark-free welding; environmentally friendly and safe.
3. Applicable Products
1) Nickel-metal hydride batteries: Nickel mesh and nickel sheet are fused together.
2) Lithium-ion batteries and polymer batteries: Copper foil and nickel sheet are fused together; aluminum foil and aluminum sheet are fused together.
3) Wire fusion: Fusion of single or multiple wires bonded together.
4) Wire fusion with various electronic components, contacts, and connectors.
5) Fusion of dissimilar metal sheets for high-current contacts such as electromagnetic switches and fuseless switches.
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Acey Intelligent also provides Laser Welding Machine and Ultrasonic Wire Bonding Machine. If you have any questions, please feel free to contact us.
