Ultrasonic measurements of surface defects on flexible circuits using high-frequency focused polymer transducers

Abstract

High frequency transducers made from a layer-by-layer deposition method are investigated as transducers for ultrasonic imaging. Prototypes of adhesive-free transducers with four active elements were made on a high performance PEI (Polyetherimide) substrate with precision milled spherical cavities used to produce focused ultrasonic beams. The transducer prototypes were characterized using a pulse - echo experimental setup in water tank using glass plate as a reflector. Then, it was used in a 3D ultrasonic scanning tank, to produce high - resolution ultrasonic images of flexible electronic circuits with the aim to detect defects in the outermost cover layer.