Manufacturing and electrical interconnection of piezoelectric 1-3 composite materials for phased array ultrasonic transducers

Piezoelectric 1-3 composite material sensors are used in phased array ultrasonic testing systems. The Dice-and-Fill technique is a very flexible method to fabricate these materials for frequencies up to 10 MHz. A polarized PZT plate is cut in two directions with a dicing saw to separate the PZT pillars. The pitch of the microstructure has to be finer with increasing center frequency to suppress spurious modes. Square shaped pillars with a width of 55 mum, a distance of 30 mum and a height of more than 500 mum are realized. The required times for the dicing process and the number of defects afterwards are compared for various materials. Additionally the usability of ceramic materials for mechanical dicing is evaluated. After the dicing process the structure is filled with a passive polymer, grinded and metalized by physical vapor deposition. The different mechanical and thermal properties of the PZT ceramic and the epoxy filling result in high demands on the electrical interconnection of the composite material. Different methods are investigated. It shows that hot bar soldering is most suitable. A soldering process based on SnBi solder is optimized.