Fabrication of a miniaturized 64-element high-frequency phased array

We have developed a 40 MHz, 64-element phased array transducer packaged into a 2.5mm by 3.1mm endoscopic form factor. The array is a forward looking kerfless design based on PMN-32%PT with an element-to-element pitch of 38 microns. In order to achieve such a miniaturized form factor, a novel technique of wire bonding the array elements to a miniature flex circuit oriented in line with the forward looking ultrasound beam was developed. A technique of scratch dicing the back of the array was also implemented in order to improve directivity of the array elements The array was fabricated with a single P(DVF-TrFE) matching layer and a TPX lens for passive elevation focussing to a depth of 7mm. The two-way-6dB pulse bandwidth was measured to be 55% and the average electromechanical coupling (k_T) for the individual elements was measured to be 0.62. The one-way directivity pattern from single elements was measured to be +/-25 degrees, which was shown to be a large improvement compared to an identical kerfless array. The-3dB elevation focus resulting from a TPX lens was measured to be 152 microns at the focal depth (∼7mm).