Micromachined high frequency PMN-PT/Epoxy 1-3 composite ultrasonic annular arrays

Micromachined high-frequency PMN-PT 1-3 composite ultrasonic annular arrays have been developed. The design, fabrication, and performance of the miniature transducers are described in this paper. PMN-PT single crystal 1-3 composite was produced using micromachining techniques. The area of the single crystal pillar is 9 μm × 9 μm. The space between each pillar was ~5 μm; this region was filled with a polymer. A six-element annular transducer with equal area for each element and 16 μm kerfs between annuli was produced. The composite thickness employed in these tests was 24 μm. A novel electric interconnection strategy for high density array elements is presented. After the transducer was attached to the electrical connection board and packaged, the array transducer was tested in a pulse/echo arrangement, whereby the center frequency, bandwidth, two-way insertion loss (IL), and cross talk between adjacent elements were measured for each annulus. The center frequency is about 50 MHz and the -6 dB bandwidth is about 90%. The minimum insertion loss is -19.5 dB at 50 MHz and the crosstalk between adjacent elements is about -35 dB. The micromachining techniques developed in this paper can be applied in fabrication of other array transducers.