Transducer fabrication using a 355nm pulsed picosecond laser - Rapid prototyping of 40 Mhz composites, custom electrode patterns, and circularly symmetric curvable composite patterns

In this work, a 355 nm pulsed picosecond laser dicing system is used to cut a 40 MHz 1-3 composite, an 11.6 MHz circularly symmetric 1-3 composite, and create custom electrode fanouts and element sub-dices for a 40 MHz phased array. The kerfs for the 40 MHz, composite, measuring 42 mumathrm{m} thick, were measured to be 3.2 mumathrm{m} and the pillars 15.8 mumathrm{m} square. kt was found to be 0.43 under no bias and 0.47 with a DC bias. The circularly symmetric composite shows a kt of 0.62 but contains spurious acoustic modes within the operating band which could be accounted for in the future by adjusting pillar spacing or changing epoxy filler. The circular composite has pillars designed to be 50 mumathrm{m} square, with kerfs of 30 mumathrm{m}. Total thickness is 148 mumathrm{m} which results in an 11.68 MHz resonance. A phased array electrode pattern was defined on a piezoelectric substrate with a fan-out geometry for electrical interconnect. This pattern contained features measuring less than 3 um in width. This array was subsequently kerfed fully through the piezoelectric substrate as well as sub-diced starting from within the array element.