A new automatic resonance frequency tracking method for piezoelectric ultrasonic transducers used in thermosonic wire bonding

• A new RFT method for piezoelectric ultrasonic transducer is discussed.
• Binary search algorithm and fuzzy controller are combined for RFT.
• A self-developed driving and control system for transducer is developed.
• The proposed method for RFT is feasible, reliable and efficient.

This paper presents a new resonance tracking method for the piezoelectric ultrasonic transducer used in thermosonic wire bonding. Based on the relationships among the dynamic resistance, impedance phase and resonant frequency of the transducer, the binary search algorithm had been used to automatically track the transducer resonance frequency. To improve the tracking algorithm performance, fuzzy logic method was used to ensure the optimal search range where the resonance frequency was included. A self-developed driving and control system based on an advanced ARM microprocessor was designed. The digital lock-in amplifier was used to measure and calculate the transducer impedance. Several typical piezoelectric ultrasonic transducers were utilized to examine the system performance. The test results show that it is feasible, efficient and reliable to use the binary research algorithm to track the transducer resonance frequency. Especially, the software-based resonance tracking algorithm has greatly improved the system flexibility and adaptability, and it also can be used in other ultrasonic applications through software modifications.