The influence of bonding layer on the characteristics of piezoelectric polymer transducer

摘要

Piezoelectric polymer film poly(vinylidene fluoride) (PVDF) is increasingly used to make the high-frequency ultrasound transducer. This film is usually bonded with backing substrate by an adhesive material, such as epoxy, for the transducers. The adhesive layer, called bonding layer in this paper, influences the electromechanical characteristics of the transducer. In this study, the effects of the bonding layer on the characteristics of piezoelectric polymer transducer were investigated intensively. EPO-TEK 301epoxy was used to bond a PVDF film (52 μm thickness) with backing substrate of copper(Cu) together. The resonance characteristics of the films themselves and of the transducers made of the films with different active area were measured by an impedance analyzer, and the pulse-echo responses of the transducers with different thickness of the bonding layer were measured by a pulsar/receiver system. The measured results were compared with those of simulation by KLM equivalent circuit model. As the results, it was shown that the bonding layer changes the waveform of pulse-echo response dramatically and reduces the resonance frequency of the transducer. Consequently, it was noted that the influence of bonding layer should be carefully considered in polymer transducer design.