A manufacturing method of an ultrasonic transducer that includes;
- a supporting plate provided with a plurality of concave portions that are opened to a first surface on one side in a thickness direction, and a plurality of waveguides having first end portions on one side that are respectively opened to bottom surfaces of the plurality of concave portions and that have opening widths smaller than those of the plurality of concave portions and second end portions on another side that are opened to a second surface on another side in the thickness direction to form sound wave radiation openings;
- a flexible resin film that is fixed to the first surface of the supporting plate so as to cover the plurality of concave portions;
- and the same number of piezoelectric elements as the plurality of concave portions that are fixed to a first surface of the flexible resin film so that their center regions overlap, in a plan view, with the corresponding plurality of concave portions and their peripheral regions overlap, in a plan view, with the first surface of the supporting plate, wherein a vibrating body formed by the piezoelectric element and the flexible resin film has a resonance frequency of the lowest flexural vibration mode higher than a driving frequency of the piezoelectric element, and wherein the supporting plate is configured so that a resonance frequency of the lowest flexural vibration mode of the entire of the ultrasonic transducer is higher than the driving frequency of the piezoelectric element, the method comprising:
- a supporting plate forming step of forming the supporting plate;
- a flexible resin film fixing step of fixing the flexible resin film to the supporting plate by an adhesive or thermocompression bonding to cover the plurality of concave portions;
- a piezoelectric element fixing step of fixing the plurality of piezoelectric elements to the flexible resin film by an insulative adhesive in such a manner that the center regions overlap in the plan view with the corresponding plurality of concave portions and the peripheral regions overlap in the plan view with the supporting plate;
- a lower sealing plate arranging step of preparing a lower sealing plate that has a plurality of piezoelectric-element-directed openings having sizes surrounding the plurality of piezoelectric elements, respectively, and that is thicker than the piezoelectric element, and then fixing the lower sealing plate to the flexible resin film by an adhesive so that the plurality of piezoelectric elements are arranged within the plurality of piezoelectric-element-directed openings in the plan view;
- a wiring assembly preparation step of preparing a wiring assembly that includes an insulating base layer, a conductor layer including first and second wirings that are arranged on the base layer and that are electrically connected to a pair of first and second application electrodes, respectively, of the piezoelectric element, and an insulative cover layer enclosing the conductive layer, the base layer being provided with first and second wiring/piezoelectric element connection openings that respectively expose parts of the first and second wirings;
- a wiring assembly fixing step of fixing the base layer to the lower sealing plate by an adhesive;
- and
- an electric connection step of electrically connecting the portion of the first wiring that is exposed through the first wiring/piezoelectric element connection opening and the portion of the second wiring that is exposed through the second wiring/piezoelectric element connection opening to the first and second electrodes of the piezoelectric element, respectively.