Effect of wraparound electrodes on ultrasonic array performance

In many ultrasonic transducer array structures, it is convenient to make electrical connection to the top and bottom electrodes of thickness driven array elements by wrapping one or both electrodes around the elevational edges of the element. This is called a “wraparound electrode”. The high, non-uniform electric fields at the corner(s) of the element where the opposite polarity electrodes are in close proximity result in a significant degradation of the electromechanical coupling constant and a large down-shift in acoustic velocity. Incorporating isolation cuts along the azimuthal edges of the array elements provides an air or polymer filled gap that greatly reduces the electric fields in the corner. As a result, the coupling constant and acoustic velocity are restored to the values expected from the structure without wraparound electrodes