High density interconnect for polymer based ultrasound transducers

Electrical interconnect strategy is an essential part of ultrasound transducer array development. Methods available include soldering, conductive adhesive bonding, fine wire welding (wire bond), Z-axis conductive films and, presented for the first time in an ultrasonic transducer, anisotropic conductive adhesive (ACA) pastes and films (ACF). ACA pastes work by trapping a metal coated polymer sphere between conductors. The spheres are then held in place by the supporting heat cured epoxy matrix. Images of the component parts are presented, as is an image from a PVdF transducer array with ACA interconnects and a centre frequency of 25 MHz. This work is of particular use in high frequency ultrasound arrays where interconnect density is high and for 2D array where large element counts are prevalent.