Thermosonic

Thermosonic refers to a process or method that combines heat and ultrasonic energy to achieve a result, most commonly in the field of wire bonding for semiconductor packaging. In thermosonic bonding, a bonding tool applies mechanical force while delivering ultrasonic vibrations and controlled heat to a wire and a bond pad. The cooperative effect of vibration and warmth promotes plastic deformation, clean metal-to-metal contact, and diffusion bonding to form a metallurgical joint.

The underlying principle is that ultrasonic energy loosens the surface films and facilitates interfacial material flow, while elevated temperature reduces flow stress and enhances bonding at lower pressures and shorter times than purely ultrasonic or thermocompression bonding. The result is a reliable electrical interconnection with good fatigue and pull-test performance when process parameters are properly tuned.

Typical materials used include gold wires and gold or aluminum pads, with copper wires increasingly common in some applications. Wire diameters commonly range from about 15 to 25 micrometers for microelectronics. Equipment consists of a bonding machine with a capillary tip, an ultrasonic generator, and a heating element that maintains the desired bond temperature. Process parameters such as ultrasonic power, bond force, temperature, and bonding time are carefully controlled to optimize bond quality and minimize damage to delicate devices.

Applications are primarily in semiconductor device packaging and microelectronics, where low bonding temperatures and reliable interconnects are important. Thermosonic bonding is sometimes preferred over purely ultrasonic or thermocompression methods for its balance of low thermal stress and robust joint strength. Education and industry standards guide its proper use and safety considerations.