In the past two years, due to the rapid development of new energy electric vehicles, the demand for lithium-ion batteries has also continued to increase, and the application of ultrasonic welding of copper foil and aluminum foil has increased significantly. Ultrasonic welding of non-ferrous metals such as copper and aluminum is a mature connection process and is widely used in automotive and consumer electronics and other fields.
1. Ultrasonic Welding Workflow
The ultrasonic generator (ultrasonic power supply) converts 220V/50Hz electrical energy into 20kHz high-frequency voltage. This electrical signal is transmitted to the transducer through a high-frequency line. There is a piezoelectric ceramic piece inside the transducer, which uses the inverse piezoelectric effect to convert mechanical vibration energy (that is, ultrasonic energy). The generated mechanical vibration acts on the welding surface through the amplitude modulator and welding horn, and the welding is completed under pressure.
The mold and welding horn provide the rigid support needed when welding. The parts to be welded are fixed on the base and do not move. Under the action of pressure and vibration, the movement of metal molecules is accelerated, and shared electrons are recombined to form metallic bonds.
2. Ultrasonic Metal Welding Mechanism-Recrystallization Process below Melting Point
Both the upper welding head and the lower base surface are knurled, so the upper material moves laterally during welding, while the lower material is fixed, resulting in relative movement between the upper and lower layers. Under pressure, the rough protrusions on the connecting surface are constantly rubbing against each other.
The three main stages of ultrasonic metal welding to form molecular bonds are:
- Relative movement causes shear and plastic deformation of the rough raised features on the joint surface — initial plastic deformation;
- Ultrasonic vibrations cause dispersion of the oxide layer on the joint surface and further plastic deformation of the raised features. This results in the increased metal-to-metal contact area and the formation of weld zones, a feature also called microwelds.
- Further ultrasonic vibration will cause the contact surface to continue to increase, thereby increasing the welding area.
The decisive advantage of ultrasonic welding is “cold” welding, that is, the connection is formed at a temperature well below the melting point of the metal. It is a solid-state and solid-state pressure welding process.
3. Welding Application Categories
Metal foil welding: Typical cases include tab welding of square case batteries, soft packages, and cylindrical batteries.
Terminals and terminals welding: In terminal ultrasonic welding, the thickness of the metal plates welded to each other can be up to 3mm. The weld strength requirements for this application are much higher. Soldering of terminals and terminals is used for connections carrying large load currents.
Wiring harness & terminal welding: In modern vehicles, cables and terminal connectors assembled with ultrasonic welding have become essential parts. Materials are copper and aluminum.
4. Welding Process Parameters
The main advantages of the ultrasonic metal welding process are the detailed welding data, the ability to fine-tune the welding process, and the quality control of the welding. For different applications, the optimal parameters need to be adjusted to meet the customer’s needs.
The main parameters of ultrasonic metal welding are working frequency, amplitude, welding pressure, welding time, welding power, welding energy, and welding depth.
If you have questions about ultrasonic welding, please contact us at dastechsz@outlook.com
