Piezoelectric ultrasonic transducer and preparation method thereof

Abstract

The invention provides a piezoelectric ultrasonic transducer and a preparation method thereof. The piezoelectric ultrasonic transducer comprises a base, a vibrating membrane fixed to the base, and a piezoelectric membrane connected with the vibrating membrane; a cavity is formed in the center of the base; and the piezoelectric membrane comprises a first surface close to the vibrating membrane anda second surface far from the vibrating membrane. The piezoelectric ultrasonic transducer further comprises a first electrode arranged at the first surface and a second electrode arranged at the second surface; and a mass block is arranged on the surface of one side, close to the base, of the vibrating membrane and is placed in the cavity of the base. The piezoelectric ultrasonic transducer can improve sound pressure of a product.

Description

technical field [0001] The invention relates to the field of ultrasonic sensors, in particular to a piezoelectric ultrasonic transducer and a preparation method thereof. Background technique [0002] Ultrasonic sensors have a wide range of applications in social production and life, including ultrasonic processing, ultrasonic positioning, ultrasonic detection, ultrasonic imaging and other aspects. As a device that converts electrical energy and mechanical energy, the ultrasonic transducer is an important component of the ultrasonic sensor. Traditional ultrasonic transducers are usually manufactured based on mechanical processing, so they have disadvantages such as large volume, low processing accuracy, high processing cost, and difficulty in forming an array structure. Ultrasonic transducers based on MEMS (Microelectromechanical Systems, microelectromechanical systems) technology are processed by microelectronics technology, the diameter size can be reduced to the micron le...

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Problems solved by technology

[0003] The current MEMS ultrasonic transducers are mainly capacitive and piezoelectric. Among them, the MEMS capacitive ultrasonic transducer is composed of two upper and lower electrode plates, driven by the electrostatic force between the electrode plates, and has a large electromechanical coupling coefficient. , high resonant frequency, but there are also disadvantages such as high driving voltage, greater influence by parasitic capacitance, large electrical output impedance, difficult to match, difficult to balance receiving efficiency and transmitting efficiency; compared with capacitive ultrasonic transducers , the piezoelectric ultrasonic transducer is composed of a piezoelectric film, a vibrating layer, and upper and lower metal electrodes. It has the advantages of low driving voltage, low output impedance, and both transmission and reception efficiency, so it has been applied in many occasions.

However, since the transducer first relies on the piezoelectric layer to generate lateral strain when it works, and then converts it into a longitudinal deformation perpendicular to the substrate direction with the assistance of the vibration layer, the electromechanical coupling coefficient of the whole process is low, and the conversion efficiency of electrical energy and mechanical energy is low. , which limits the sound pressure output of the ultrasonic sensor

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