Development of a Long-Focal-Range Annular Array Ultrasonic Transducer

Abstract

Conventional annular array transducers designed with Fresnel divided elements have a limited maximum size of the aperture of the transducer. In this study, we designed and fabricated a prototype of a large-aperture annular array transducer to inspect next-generation semiconductors. A new annular array pattern was designed with a wide focal range and a large focal length using equal areas for the inner elements and equal stroke widths for the outer elements. The prototype was fabricated by epoxy bonding with a patterned metal electrode on a flexible printed circuit and a piezoelectric copolymer. As a result of evaluation, we obtained a fine spatial resolution below 100 µm and a narrow relative sensitivity variation of 6.5 dB for a large focal length and a wide focal range from 10 to 30 mm.