Effect of contact interface in transducer system in ultrasonic bonding

The effect of contact interface on ultrasonic energy propagation is the common problem of all kinds of ultrasonic transducer. In Ultrasonic bonding, contact interfaces between different parts are nonlinear factors, so they 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, induce non-stable output of the ultrasonic energy, and lead to hysteresis response. All these would cause some bonding shortcomings such as lower bonding strengths and chip tilting.