Ultrasonic welding also known as bonding, which makes use of mechanical vibration energy of ultrasonic frequency(16～120 kHz) , which is a special way to connecting the same or different metal, semiconductor, plastic, ceramic, etc. Ultrasonic welding is widely used in the fields of integrated circuit, capacitor, EHV transformer shield structures, micromotor, electronic components and battery, encapsulation of plastic parts and some other productions. Compared with traditional welding technology, ultrasonic welding technology has advantages like high speed, efficient, high degree of automation, etc. It has become the basic technology in the field of semiconductor encapsulation.
The principle of ultrasonic welding
Ultrasonic energy is the vibration energy of machinery, working frequency more than sound wave. Semiconductor encapsulation uses the frequency of ultrasonic from 40 kHz to 120 kHz. Ultrasonic welding is a way of phase bonding process, the special method can be described as when starting welding, the metal materials will produce strong plastic flow under the effect of friction, which creates the condition for the contact between pure metal surfaces. The temperature rise of joint zone and high frequency vibration further affect the activation status of metal lattice atom. Therefore, when covalence metal atoms close to each other till nanometer, it will be possible to through the public electron to form the electron bridge among atoms.
Through the study of welding process, it proves that friction, plastic flow and temperature are the three main factors to realize ultrasonic welding. Friction plays the leading role in the process, it’s not only the primary heat source, but also create condition for the contact of metal surfaces by excluding oxidation film.
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