Manufacturing and experimental investigation of 2-2 piezocomposite transducer arrays

Since the experimental data relative to 2-2 piezocomposites manufactured in their actual size is scarce, an experimental investigation of the vibration behaviour of 2-2 PZT-polymer composite array transducers for clinical ultrasound equipments was carried out with several prototypes having the same dicing pitch of 0.11 mm, and various volume fractions (VF) and thickness values. Furthermore, with the 2-2 plates, many array transducers were manufactured with subsequent deposition of the electrodes and a second dice-and-fill procedure with pitch of 0.245 mm. In these latter conditions, the 2-2 plate become an “asymmetric” 1-3 composite and thus a more complex vibration pattern of the structure should be expected. Several volume fractions (VF) of the 2-2 plate were investigated (70, 65 ,60 ,50 and 40 percent) and for each VF several arrays having the thickness mode within the range from 2,5 MHz to 8 MHz were manufactured and analyzed. Thus, on the basis of both Electrical Impedance and by Laser Doppler Vibrometer (LDV) measurements, we obtained dispersion curves corresponding to each VF. With LDV, maps of both amplitude and phase of the surface displacement at various frequencies are presented where thickness mode, first lateral mode of the composite plate and cross-coupling through adjacent array elements are clearly visible. The performances of the manufactured transducers were finally presented as the pulse length, peak-to-peak pulse amplitude and pulse bandwidth.