Harmonic excitation response performance and active regulation of the high-frequency piezoelectric ultrasonic transducer used in the thermosonic bonding for microelectronics

High-frequency piezoelectric ultrasonic transducer is one of the most important components in the modern thermosonic bonding for microelectronics and its harmonic excitation response performance can vary due to many reasons, often leading to a mutable bonding quality. In this research, an in-depth understanding of the harmonic excitation response performance of the transducer was provided. Relying on the electromechanical equivalent method and a series of experimental investigations, the main influential factors of the response performance, and the relevant rules were explored and analyzed. Then, the percentage peak overshoot and settling time were extracted from the exciting response signal and viewed as two basic morphological feature parameters to characterize the response performance. To regulate the exciting response performance actively and get the desired ultrasonic energy delivery efficiency, a new method based on radial basis function neural network was developed and it could predict the resonant frequency and the settling time accurately when the excitation condition of the transducer was changed. Test results manifest the newly proposed method is feasible and efficient, and it also can be used to the ultrasonic transducers in other applications. (C) 2020 Published by Elsevier B.V.