Effect of contact interface on transducer system on thermosonic bonding

The effect of contact interface on ultrasonic energy propagation and vibration properties and vibration properties is the common problem of all kinds of ultrasonic transducer. In thermosonic bonding, contact interfaces between different parts are nonlinear factors, which affect directly the ultrasonic energy propagation and bonding quality. By using finite element method and laser Doppler vibrometer, the effect of contact interface on the ultrasonic energy and vibration are investigated. It is found that incorrect contact interfaces cause multiple vibration modals and mix certain resonance frequencies, inducing non-stable output of the ultrasonic energy, and leading to hysteresis response. All these would cause some bonding shortcomings such as lower bonding strengths and chip tilting. The researches result help to understand the bonding process and transducer design.