Dynamic current characteristic of ultrasonic transducer for wire bonding

Ultrasonic transducer, as an important part of thermosonic wire bonding system, converts the electrical energy into mechanical vibration energy, results in an oscillatory motion parallel to the bonding interface. This paper studies the dynamic current characteristic of the ultrasonic transducer during thermosonic wire bonding process. The equivalent circuit model of ultrasonic transducer is set up based on Butterworth-Van Dyke (BVD) model. The input impedance and dynamic current characteristic are calculated by MATLAB. The electrical parameters are measured by an impedance analyzer, and the dynamic current characteristic was measured with a new ultrasonic generator developed based on FPGA. The simulation result agrees well with the experiment result. It is shown that keeping stimulation frequency offset to the resonance frequency of transducer can reduce transient state process and improve the bonding speed.