Design, manufacturing and packaging of high frequency micro ultrasonic transducers for medical applications

The challenges for the realization of a miniaturized high frequency ultrasonic transducer linear array lie in the interconnections on the fine pitch piezoceramic elements. Within the footprint the size of a needle, only peripheral interconnections can be allowed on the transducer array such that the acoustic operations on both faces of the vibrating piezoelectric elements are not obstructed. The very low maximum processing temperature allowed also poses difficulty for conventional bonding techniques. This article presents 3-dimensional packaging using spirally rolled flexible circuits, room-temperature anisotropic conductive bonding and stencil printing for the setup of a wafer-level production process flow.