Simply put, ultrasonic wire harness terminal welding is a precision joining technique that uses high-frequency ultrasonic vibrations to fuse a wire harness (conductor) and a terminal (connector) into a single unit in the solid state. It is a solid-state welding process that requires no solder or flux and does not rely on high temperatures to melt the metal. Compared to the general "ultrasonic wire harness welding" discussed previously, "terminal welding" specifically refers to the connection between a wire harness and a terminal, whereas the former encompasses a broader scope, including direct wire-to-wire welding.

Its physical mechanism involves the combined action of high-frequency mechanical energy and pressure, occurring in roughly three steps:
1. High-frequency vibration: The equipment converts electrical energy into mechanical vibrations at frequencies of 20–40 kHz (inaudible to the human ear), with amplitudes typically ranging from 10 to 50 micrometers.

2. Interface cleaning: The welding tool applies vibration and pressure to the terminal and conductor; high-speed friction at the contact interface instantly removes surface oxide layers, oil, and impurities, exposing the pure metal lattice.

3. Molecular bonding: Under the combined influence of pressure and mild heat (reaching approximately 40%–60% of the melting point), clean metal atoms diffuse across the interface, forming a strong solid-state metallurgical bond. No melting occurs during the process, and the material properties remain unchanged.

This process has become a standard manufacturing method in sectors such as new energy vehicles and energy storage systems:
High-voltage connections: Copper/aluminum busbars within power battery packs, motor lead wires, and thick wire harnesses for charging piles.
Safety components: Vehicle body grounding straps, airbag wire harnesses, etc.

Precision connections: Welding of precision terminals for sensors, actuators, and other components—applications where traditional thermal welding processes struggle to perform effectively.