P2O-10 The Effect of PZT8 Piezoelectric Crystal Aging on Mechanical and Electrical Resonances in Ultrasonic Transducers

Modern resonant ultrasonic transducers utilizing piezoelectric crystals typically employ phase-lock-loop control schemes. This system "locks" on the electrical resonance as dictated by the equivalent RLC circuit, which is close to, but not the actual mechanical resonant frequency. As the piezoelectric crystals age after assembly and preload, some characteristics of the transducer change such as displacement to current gain, resonant frequency, and impedance, which can cause portability problems in industrial production applications. This research investigates the effects of piezoelectric crystal aging (via heat-treatment) on the mechanical and electrical resonances for the common PZT8 material used in ultrasonic transducers for semiconductor wire bonding. The motivation for the study is to minimize these aging effects by compensating the electrical control system so that the electrical resonance coincides with the mechanical resonance