Ultrasonic sensing device and the manufacturing method thereof

1. An ultrasonic sensing device, comprising:

a housing, comprising a bottom wall, a top wall and a surrounding side wall connected between the top wall and the bottom wall, wherein the top wall has an opening formed at the position where the top wall is connected with the surrounding side wall, and the opening is opposite to the bottom wall;

a piezoelectric assembly, comprising an encapsulating body and a piezoelectric sheet, wherein at least a portion of the piezoelectric sheet is enclosed by the encapsulating body, the encapsulating body is disposed on the bottom wall and surrounded by the surrounding side wall, and the piezoelectric sheet has a sensing surface exposed to the encapsulating body and facing the bottom wall;

a board, disposed on the top wall of the housing and has a pressing surface facing the encapsulating body and the top wall; and

a plurality of fixing members, configured to fix the board on the top wall of the housing to press the board to the encapsulating body of the piezoelectric assembly, thereby pressing the sensing surface of the piezoelectric sheet to the bottom wall.

2. The ultrasonic sensing device according to claim 1 , wherein the board is bent or flat.

3. The ultrasonic sensing device according to claim 1 , wherein the board is a circuit board.

4. The ultrasonic sensing device according to claim 1 , wherein the board has a single material or a composite material.

5. The ultrasonic sensing device according to claim 1 , wherein the piezoelectric assembly further comprises a positive guide pin having an end connected to the piezoelectric sheet and a negative guide pin having an end connected to the piezoelectric sheet, the positive guide pin and the negative guide pin pass through the encapsulating body, and the board has two openings allowing the positive guide pin and the negative guide pin to pass therethrough.

6. The ultrasonic sensing device according to claim 1 , wherein the encapsulating body is adhered to the surrounding side wall.

7. The ultrasonic sensing device according to claim 1 , wherein the encapsulating body has a surrounding shape conformed to the surrounding side wall.

8. The ultrasonic sensing device according to claim 1 , wherein the piezoelectric assembly further comprises a matching layer or a conducting layer disposed on the sensing layer of the piezoelectric sheet and corresponding to vibration energy of the piezoelectric sheet.

9. The ultrasonic sensing device according to claim 1 , wherein each of the plurality of fixing members is a screw, the board has a plurality of through holes, and the top wall has a plurality of screw holes.

10. The ultrasonic sensing device according to claim 1 , further comprising an outer frame and a cover, wherein the outer frame surrounds and connects to the top wall and the surrounding side wall of the housing and extends in a direction away from the bottom wall, the outer frame has an opening at an end away from the bottom wall, and the cover closes the opening.

11. The ultrasonic sensing device according to claim 10 , further comprising a reflective board and a plurality of connecting rods, wherein the reflective board is disposed opposite to the housing and the outer frame, and each of the plurality of connecting rods is connected between the reflective board and the outer frame.

12. The ultrasonic sensing device according to claim 1 , wherein the encapsulating body comprises a matching layer and/or an absorbing layer corresponding to vibration energy of the piezoelectric sheet.

13. A manufacturing method of an ultrasonic sensing device, comprising steps of:

providing a housing, wherein the housing comprises bottom wall, a top wall and a surrounding side wall connected between the top wall and the bottom wall, wherein the top wall has an opening where the surrounding side wall is connected with, and the opening is opposite to the bottom wall;

providing a piezoelectric sheet and disposing the piezoelectric sheet on the bottom wall through the opening of the top wall;

injecting a liquid colloid into the opening;

covering a board on the top wall of the housing; and

fixing the board to the top wall by a plurality of fixing members to press the board to the colloid, thereby pressing the piezoelectric sheet to the bottom wall.

14. A manufacturing method of an ultrasonic sensing device, comprising steps of:

providing a housing, wherein the housing comprises bottom wall, a top wall and a surrounding side wall connected between the top wall and the bottom wall, wherein the top wall has an opening where the surrounding side wall is connected with, and the opening is opposite to the bottom wall;

providing a piezoelectric assembly, wherein the piezoelectric assembly comprises an encapsulating body and a piezoelectric sheet, wherein at least a portion of the piezoelectric sheet is enclosed by the encapsulating body, the encapsulating body is disposed on the bottom wall and surrounded by the surrounding side wall, and the piezoelectric sheet has a sensing surface exposed to the encapsulating body and facing the bottom wall;

disposing the piezoelectric assembly on the bottom wall with a direction that sensing surface facing the bottom wall;

covering a board on the top wall of the housing; and

fixing the board to the top wall by a plurality of fixing members to press the board to the encapsulating body of the piezoelectric assembly, thereby pressing the sensing surface of the piezoelectric sheet to the bottom wall.