A new vibratory response-based method for determining the optimal assembly tightening torque of the high-frequency piezoelectric ultrasonic transducer

Pre-tightening torque has a significant impact on the performance of a bolt-clamped high-frequency piezoelectric ultrasonic transducer widely used in wire bonding. To develop a vibratory response-based method for the determination of optimal pre-tightening torque, the vibration amplitude signals of the transducer under different excitation conditions were monitored, and the characteristic parameters of the response, involving the resonance frequency, settling time within the initial transient response, and vibration amplitude of the steady-state stage, were extracted. Based on a series of in-depth tests, analyses, and discussions, the influences that the pre-tightening torque has on the vibratory response properties were investigated. Then, the experimental measurement and the random forest method were combined to determine the optimal pre-tightening torque. The performance test results show that the developed method can give the optimal pre-tightening torque according to the desired vibrational response properties, and it is feasible, effective, and reliable as well as improves the adaptability and flexibility of the high-frequency ultrasonic transducer in the application.