Fabrication of 2-2 piezoelectric composites by interdigital pair bonding

This paper presents a method called Interdigital Pair Bonding (IPB) for the fabrication of 2-2 and 1-3 piezoelectric composites used in ultrasound transducers, especially for transducers for high frequency medical imaging. The principle of the IPB process is explained. The example of a 2-2 piezoelectric composite fabricated using a 40 μm thickness dicing saw blade is examined in detail. After the IPB processing, the resultant composite had a ceramic phase with a width of 36 μm and an epoxy phase with a width of 4 μm. Spurious modes were shifted to frequencies above 50 MHz. An effective electromechanical coupling coefficient k_t of 0.66 was achieved at 40 MHz. As a result of high volume fraction of the ceramic phase (90 % for this composite), composites exhibited a high effective sound velocity of 4400 m/s and a high clamped dielectric constant of 1237 ε₀. The extension of IPB to the fabrication of 1-3 composites is discussed