Ultrasonic transduction module, ultrasonic transducer and electronic equipment

Abstract

The embodiment of the invention provides an ultrasonic transduction module, an ultrasonic transducer and electronic equipment, and relates to the field of ultrasonic devices. The invention aims to improve the performance of the ultrasonic transduction module. According to the specific scheme, a second electrode layer and a piezoelectric layer of the ultrasonic transduction module serve as a resonator. Or the second electrode layer, the piezoelectric layer and the first electrode layer form a resonator together. Alternatively, the piezoelectric layer, the first electrode layer and the substrate together form a resonator. Therefore, the resonator can improve the penetrating power of the ultrasound generated by the piezoelectric layer and improve the sensitivity of the ultrasonic transduction module. The second electrode layer has an electrode and functions as a part of a resonator. The second electrode layer is fully utilized to reduce the thickness of the ultrasonic transduction module, the two layers can form a resonator, and the size of the ultrasonic transducer and the miniaturization of electronic equipment can be reduced.

Description

Technical Field

[0001] This application relates to the field of ultrasonic devices, and more particularly to an ultrasonic transducer module, an ultrasonic transducer, and an electronic device. Background Technology

[0002] Ultrasonic fingerprint recognition technology utilizes a piezoelectric layer to transmit and receive ultrasonic waves, thereby acquiring and identifying fingerprint image information. The ultrasonic transducer is a crucial component of this technology; typically, a resonant structure is incorporated into the transducer to address the issue of insufficient ultrasonic wave penetration.

[0003] Currently, the performance of ultrasonic transducers directly affects the user experience. Summary of the Invention

[0004] This application provides an ultrasonic transducer module, an ultrasonic transducer, and an electronic device, with the aim of improving the performance of the ultrasonic transducer.

[0005] To achieve the above objectives, this application adopts the following technical solution.

[0006] In a first aspect, embodiments of this application provide an ultrasonic transducer module. The ultrasonic transducer module includes a substrate, a first electrode layer, a piezoelectric layer, and a second electrode layer stacked sequentially. The acoustic impedance of the substrate and the acoustic impedance of the piezoelectric layer are not equal; the ratio of the acoustic impedance of the piezoelectric layer to the acoustic impedance of the second electrode layer is 0.5-2. The sum of the thickness-to-wavelength ratio of the second electrode layer and the thickness-to-wavelength ratio of the piezoelectric layer is a / 4; where a is a positive integer.

[0007] Thus, the second electrode layer and the piezoelectric layer can function as a resonator, which can enhance the penetration capability of ultrasound generated by the piezoelectric layer. Alternatively, the resonator can enhance the penetration capability of mechanical waves transmitted to the piezoelectric layer. The ratio of the acoustic impedance of the piezoelectric layer to that of the second electrode layer is 0.5-2, improving the sensitivity and performance of the ultrasonic transducer module. Furthermore, the second electrode layer and the piezoelectric layer can form a resonator, eliminating the need for other layer structures and facilitating the miniaturization of electronic devices.

[0008] In conjunction with the first aspect, in some feasible ways, the acoustic impedance of the piezoelectric layer is equal to that of the second electrode layer. Thus, during the propagation of sound waves in the piezoelectric layer and the second electrode layer, the loss of sound waves by the piezoelectric layer and the second electrode layer is smaller, which can further improve the sensitivity of the ultrasonic transducer module.

[0009] In conjunction with the first aspect, in some feasible embodiments, the ratio of the acoustic impedance of the substrate to the acoustic impedance of the piezoelectric layer is less than 0.5 or greater than 2. Thus, the acoustic impedance of the substrate and the acoustic impedance of the piezoelectric layer differ significantly, which can reduce the influence of the substrate on the resonant function of the resonator composed of the piezoelectric layer and the second electrode layer.

[0010] In conjunction with the first aspect, in some feasible ways, the ratio of the acoustic impedance of the first electrode layer to the acoustic impedance of the piezoelectric layer is less than 0.5 or greater than 2. This reduces the influence of the first electrode layer on the resonant function of the resonator composed of the piezoelectric and second electrode layers.

[0011] In conjunction with the first aspect, in some feasible implementations, the sum of the thickness-to-wavelength ratio of the second electrode layer, the thickness-to-wavelength ratio of the piezoelectric layer, the thickness-to-wavelength ratio of the first electrode layer, and the thickness-to-wavelength ratio of the substrate is b / 4; where b is a positive integer greater than a. Thus, the substrate and the first electrode layer can be considered as a resonator, or the second electrode layer, the piezoelectric layer, the first electrode layer, and the substrate can be considered as a resonator. Combining the aforementioned resonator formed by the second electrode layer and the piezoelectric layer, the ultrasonic transducer module has two resonators, which can further improve the sensitivity of the ultrasonic transducer module.

[0012] In conjunction with the first aspect, in some feasible implementations, the ultrasonic transducer module further includes a protective layer, with the second electrode layer located between the piezoelectric layer and the protective layer, and the thickness-to-wavelength ratio of the protective layer being less than or equal to 0.1. Thus, the protective layer can be considered an acoustically transparent layer, which does not affect the resonance of the resonator, thus benefiting the sensitivity of the ultrasonic transducer module. Furthermore, the protective layer also protects the second electrode layer, preventing it from direct contact with air or dust, effectively ensuring the performance of the second electrode layer.

[0013] In conjunction with the first aspect, in some feasible ways, the propagation speed of sound waves in the second electrode layer is less than or equal to 3000 m / s. This allows for a further reduction in the thickness of the second electrode layer, which is beneficial for thinning the ultrasonic transducer module.

[0014] In conjunction with the first aspect, in some feasible embodiments, the material of the second electrode layer includes at least one selected from aluminum, copper, silver, gold, graphite, nickel, tungsten, or conductive particles, said conductive particles comprising a core and a conductive layer encapsulating the core. The aforementioned materials possess electrical conductivity. The aforementioned materials can also improve the oxidation resistance of the second electrode layer.

[0015] In conjunction with the first aspect, in some feasible ways, the substrate material includes silicon, glass, or polymer. Thus, the ultrasonic transducer module of this application embodiment can be adapted to substrates made of a variety of materials.

[0016] Secondly, embodiments of this application provide an ultrasonic transducer module. The ultrasonic transducer module includes a substrate, a first electrode layer, a piezoelectric layer, and a second electrode layer stacked sequentially; the ratio of the acoustic impedance of the substrate to the acoustic impedance of the piezoelectric layer is 0.5-2; the ratio of the acoustic impedance of the piezoelectric layer to the acoustic impedance of the second electrode layer is 0.5-2; and the sum of the thickness-to-wavelength ratio of the second electrode layer, the thickness-to-wavelength ratio of the piezoelectric layer, the thickness-to-wavelength ratio of the first electrode layer, and the thickness-to-wavelength ratio of the substrate is c / 4; where c is a positive integer.

[0017] Thus, the second electrode layer, piezoelectric layer, and substrate, with relatively small differences in acoustic impedance, together form a resonator. The resonator can improve the sensitivity of the ultrasonic transducer module. Similarly, the second electrode layer serves both as a conductor and as part of the resonator. This is beneficial for the miniaturization of electronic devices and effectively improves the performance of the ultrasonic transducer module.

[0018] In conjunction with the second aspect, in some feasible implementations, the ultrasonic transducer module further includes a protective layer, with the second electrode layer located between the piezoelectric layer and the protective layer. The thickness-to-wavelength ratio of the protective layer is less than or equal to 0.1. Thus, the protective layer can be considered an acoustically transparent layer, which does not affect the resonance of the resonator, thereby improving the sensitivity of the ultrasonic transducer module. Furthermore, the protective layer also protects the second electrode layer, preventing it from direct contact with air or dust, effectively ensuring the performance of the second electrode layer.

[0019] In conjunction with the second aspect, in some feasible ways, the acoustic impedance of the substrate and the acoustic impedance of the piezoelectric layer are equal. Thus, during the propagation of sound waves through the piezoelectric layer and the substrate, the loss of sound waves by the piezoelectric layer and the substrate is less, which can further improve the sensitivity of the ultrasonic transducer module.

[0020] In conjunction with the second aspect, in some feasible ways, the acoustic impedance of the piezoelectric layer is equal to that of the second electrode layer. Thus, during the propagation of sound waves through the piezoelectric layer and the second electrode layer, the loss of sound waves by the piezoelectric layer and the second electrode layer is less, which can further improve the sensitivity of the ultrasonic transducer module.

[0021] In conjunction with the second aspect, in some feasible ways, the propagation speed of sound waves in the second electrode layer is less than or equal to 3000 m / s. This allows for a further reduction in the thickness of the second electrode layer, thereby thinning the ultrasonic transducer module.

[0022] In conjunction with the second aspect, in some feasible embodiments, the material of the second electrode layer includes at least one of aluminum, copper, silver, gold, graphite, nickel, tungsten, silver, gold, or conductive particles, said conductive particles comprising a core and a conductive layer enclosing the core.

[0023] In conjunction with the second aspect, in some feasible ways, the substrate material includes silicon, glass, or a polymer.

[0024] Thirdly, embodiments of this application provide an ultrasonic transducer module. The ultrasonic transducer module includes a substrate, a first electrode layer, a piezoelectric layer, and a second electrode layer stacked sequentially. The ratio of the acoustic impedance of the substrate to that of the piezoelectric layer is 0.5-2; the ratio of the acoustic impedance of the second electrode layer to that of the piezoelectric layer is less than 0.5 or greater than 2. The sum of the thickness-to-wavelength ratio of the piezoelectric layer, the thickness-to-wavelength ratio of the first electrode layer, and the thickness-to-wavelength ratio of the substrate is d / 4, where d is a positive integer.

[0025] In this way, the piezoelectric layer and the substrate together form a resonator. The acoustic impedance of the piezoelectric layer differs significantly from that of the second electrode layer, and the second electrode layer has a relatively small impact on the resonance effect of the resonator. The resonance effect of this resonator can improve the sensitivity of the ultrasonic transducer module. The second electrode layer serves both as a conductor and as part of the resonator. This is beneficial for reducing the thickness of the ultrasonic transducer module.

[0026] In conjunction with the third aspect, in some feasible ways, the acoustic impedance of the substrate and the acoustic impedance of the piezoelectric layer are equal. Thus, during the propagation of sound waves through the piezoelectric layer and the substrate, the loss of sound waves by the piezoelectric layer and the substrate is less, which can further improve the sensitivity of the ultrasonic transducer module.

[0027] In conjunction with the third aspect, in some feasible implementations, the thickness-to-wavelength ratio of the second electrode layer is e / 4, where e is a positive integer. Thus, the second electrode layer can be considered a resonator. Combining the aforementioned resonator formed by the piezoelectric layer and the substrate, the ultrasonic transducer module has two resonators, which can further improve the sensitivity of the ultrasonic transducer module and optimize its performance.

[0028] In conjunction with the third aspect, in some feasible embodiments, the ultrasonic transducer module further includes a protective layer, wherein the second electrode layer is located between the piezoelectric layer and the protective layer, and the thickness-to-wavelength ratio of the protective layer is less than or equal to 0.1.

[0029] In conjunction with the third aspect, in some feasible ways, the propagation speed of sound waves in the second electrode layer is less than or equal to 3000 m / s.

[0030] In conjunction with the third aspect, in some feasible embodiments, the material of the second electrode layer includes at least one of aluminum, copper, silver, gold, graphite, nickel, tungsten, silver, gold, or conductive particles, said conductive particles comprising a core and a conductive layer enclosing the core.

[0031] In conjunction with the third aspect, in some feasible ways, the substrate material includes silicon, glass, or polymer. Thus, for substrates made of various materials, the sensitivity of the ultrasonic transducer module can be improved while reducing its thickness.

[0032] Fourthly, embodiments of this application provide an ultrasonic transducer. The ultrasonic transducer includes a control module and any one of the ultrasonic transducer modules provided in the first, second, and third aspects described above, wherein both the first electrode layer and the second electrode layer are electrically connected to the control module. Because ultrasonic transducer modules have the advantages of low thickness and high sensitivity, this ultrasonic transducer is small in size and highly sensitive.

[0033] Fifthly, embodiments of this application provide an electronic device. The electronic device includes: an acoustic wave penetrating layer and any of the ultrasonic transducers provided in the fourth aspect above, wherein the acoustic wave penetrating layer covers the ultrasonic transducer module. Because the ultrasonic transducer is small in size and has high sensitivity, it is beneficial for the miniaturization of the electronic device.

[0034] In conjunction with the fifth aspect, in some feasible embodiments, the difference between the acoustic impedance of the acoustic wave penetrating layer and the acoustic impedance of the substrate is greater than the difference between the acoustic impedance of the acoustic wave penetrating layer and the acoustic impedance of the second electrode layer; and the distance between the acoustic wave penetrating layer and the substrate is less than the distance between the acoustic wave penetrating layer and the second electrode layer. Alternatively, the difference between the acoustic impedance of the acoustic wave penetrating layer and the acoustic impedance of the substrate is less than the difference between the acoustic impedance of the acoustic wave penetrating layer and the acoustic impedance of the second electrode layer; and the distance between the acoustic wave penetrating layer and the substrate is greater than the distance between the acoustic wave penetrating layer and the second electrode layer.

[0035] In this way, good acoustic decoupling can be achieved between the acoustic wave penetrating layer and the ultrasonic transducer module.

[0036] In conjunction with the fifth aspect, in some feasible embodiments, the electronic device further includes an adhesive layer located between the acoustic wave-penetrating layer and the ultrasonic transducer module. Thus, the adhesive layer can improve the connection performance between the acoustic wave-penetrating layer and the ultrasonic transducer module.

[0037] In conjunction with the fifth aspect, in some feasible embodiments, the second electrode layer is bonded to the bonding layer, and the acoustic impedance of the acoustic wave penetrating layer, the acoustic impedance of the bonding layer, and the acoustic impedance of the second electrode layer sequentially increase or decrease. Alternatively, the substrate is bonded to the bonding layer, and the acoustic impedance of the acoustic wave penetrating layer, the acoustic impedance of the bonding layer, and the acoustic impedance of the substrate sequentially increase or decrease. This facilitates the effective penetration of sound waves from the ultrasonic transducer module to the acoustic wave penetrating layer.

[0038] In conjunction with the fifth aspect, in some feasible embodiments, the electronic device further includes: an acoustic damping layer; the ultrasonic transducer module is located between the acoustic damping layer and the acoustic wave penetrating layer. The substrate is closer to the acoustic damping layer relative to the second electrode layer, and the ratio of the acoustic impedance of the substrate to the acoustic impedance of the acoustic damping layer is less than 0.5 or greater than 2. Alternatively, the second electrode layer is closer to the acoustic damping layer relative to the substrate, and the ratio of the acoustic impedance of the second electrode layer to the acoustic impedance of the acoustic damping layer is less than 0.5 or greater than 2.

[0039] In conjunction with the fifth aspect, in some feasible ways, the acoustic damping layer is a porous structure.

[0040] Regarding the beneficial effects of the fourth and fifth aspects, please refer to the description of any of the optional implementations of the first, second, third, and fourth aspects, which will not be repeated here. Based on the implementations provided in the above aspects, this application can be further combined to provide more implementations. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application.

[0042] Figure 2 A cross-sectional view of an electronic device provided in an embodiment of this application.

[0043] Figure 3 This is a schematic diagram of the structure of the ultrasonic transducer provided in the embodiment of this application.

[0044] Figure 4 This is a schematic diagram of the structure of an ultrasonic transducer module provided in an embodiment of this application.

[0045] Figure 5 This is a schematic diagram of another ultrasonic transducer module provided in an embodiment of this application.

[0046] Figure 6 This is a schematic diagram of the structure of an ultrasonic transducer module and an acoustic wave penetrating layer provided in an embodiment of this application.

[0047] Figure 7 This is a schematic diagram of another ultrasonic transducer module and acoustic wave penetrating layer provided in an embodiment of this application.

[0048] Figure 8 This is a schematic diagram of an ultrasonic transducer module and acoustic damping layer provided in an embodiment of this application.

[0049] Figure 9 This is another structural schematic diagram of the ultrasonic transducer module and acoustic damping layer provided in the embodiments of this application.

[0050] In the diagram: 10 - Electronic device; 1 - Cover plate; 2 - Display screen; 3 - Middle frame; 4 - Back cover; 20 - Ultrasonic transducer; 23 - Flexible circuit board; 100 - Ultrasonic transducer module; 21 - Control module; 22 - Acoustic wave penetration layer; 110 - Substrate; 120 - First electrode layer; 130 - Piezoelectric layer; 140 - Second electrode layer; 30 - Adhesive layer; 40 - Acoustic damping layer. Detailed Implementation

[0051] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0052] Hereinafter, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature.

[0053] Furthermore, in the embodiments of this application, directional terms such as "up," "down," "left," "right," "horizontal," and "vertical" are defined relative to the orientation of the components shown in the accompanying drawings. It should be understood that these directional terms are relative concepts, used for relative description and clarification, and can change accordingly depending on the orientation of the components in the accompanying drawings.

[0054] In the embodiments of this application, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a fixed connection, an electrical connection, a detachable connection, or an integral part; it can be a direct connection or an indirect connection through an intermediate medium.

[0055] Biometric identification (such as fingerprint recognition) is widely used in mobile phones for user identification, unlocking, and secure payments, and has become an indispensable function of modern mobile phones. Laptops, door locks, and smart cars can also use fingerprint recognition to verify user identity. For example, users can unlock car doors by authenticating their identity with fingerprints, eliminating the hassle of using car keys.

[0056] This application provides an electronic device with biometric detection capabilities for objects being pressed. For example, it can detect fingerprints, palm prints, or handprints. This electronic device can be, for example, a device with biometric detection capabilities, such as a mobile phone, tablet, laptop, e-reader, personal computer (PC), personal digital assistant (PDA), desktop monitor, gaming device, smart wearable products (e.g., smartwatches, smart bracelets, smart jewelry), virtual reality (VR) terminal devices, augmented reality (AR) terminal devices, drones, electronic databases, bank ATMs, etc. Alternatively, the electronic device can be a smart door lock, television, remote control, refrigerator, or rechargeable small household appliances (e.g., soymilk maker, robot vacuum cleaner), etc. Alternatively, the electronic device can be a car navigation system, a car-mounted high-density digital video disc (DVD), car door handles, engine ignition, etc. The electronic device can be an electronic device with a display function or an electronic device without a display function; this application does not limit the scope of the application.

[0057] This application uses a mobile phone as an example to illustrate the embodiments. Figure 1 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Figure 1 As shown, the electronic device 10 may include a cover plate 1, a display screen 2, a middle frame 3, and a rear shell 4. The rear shell 4 and the display screen 2 are located on opposite sides of the middle frame 3, and the middle frame 3 and the display screen 2 are disposed inside the rear shell 4. The cover plate 1 is disposed on the side of the display screen 2 away from the middle frame 3, and the display surface of the display screen 2 faces the cover plate 1.

[0058] For example, the display screen 2 can be a low-temperature poly-silicon (LTPS) display screen, an active-matrix organic light-emitting diode (AMOLED) display screen, a low-temperature polycrystalline oxide (LTPO) display screen, or a micro light-emitting diode (micro LED) display screen. Of course, this application embodiment does not limit the type of display screen 2; any display screen with display function is applicable to this application embodiment, and the above example is merely illustrative.

[0059] In embodiments of this application, the electronic device 10 further includes an ultrasonic transducer 20.

[0060] For example, the ultrasonic transducer 20 can be an ultrasonic fingerprint sensor, see [reference]. Figure 2 The ultrasonic transducer 20 is disposed on one side of the display screen 2. The ultrasonic transducer 20 is used to provide biometric identification function for the electronic device 10.

[0061] It is understood that the structure of the electronic device 10 shown in the above figures does not constitute a limitation on the electronic device 10. The electronic device 10 may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0062] For example, see Figure 1 The electronic device 10 may also include a circuit board 200. Figure 2 A cross-sectional view of an electronic device provided in an embodiment of this application. See also... Figure 2 The circuit board 200 is coupled to the ultrasonic transducer 20, for example, the two are directly electrically connected, or they can be indirectly coupled.

[0063] The circuit board 200 can be a printed circuit board (PCB). Of course, the circuit board 200 can also be a flexible circuit board, a rigid-flex circuit board, etc. Optionally, the circuit board 200 can be fixed between the middle frame 3 and the rear shell 4 by means of threaded connection, snap-fit, adhesive, etc.

[0064] In some embodiments, the electronic device may further include an acoustic wave penetrating layer 22, an ultrasonic transducer 20, and the acoustic wave penetrating layer 22 being connected. The acoustic wave penetrating layer 22 covers the ultrasonic transducer 20.

[0065] For example, the ultrasonic transducer 20 includes a control module 21 and an ultrasonic transducer module 100, which are electrically connected. The ultrasonic transducer module 100 is connected via an adhesive layer 30 and a sound wave penetrating layer 22.

[0066] For example, the ultrasonic transducer module 100 is electrically connected to the control module 21 via a flexible printed circuit (FPC) 23.

[0067] In some embodiments, the electronic device 10 may also include components such as a battery, camera, microphone, speaker, radio frequency circuit, input unit, sensor, audio circuit, wireless fidelity (WiFi) module, power supply, and Bluetooth module, which will not be described in detail here.

[0068] The thickness of the ultrasonic transducer 20 directly affects the volume of the electronic device 10. The embodiments of this application can reduce the thickness of the ultrasonic transducer 20, which is beneficial to the miniaturization of the electronic device 10.

[0069] Figure 3 This is a schematic diagram of the ultrasonic transducer 20 provided in an embodiment of this application. Please refer to... Figure 3 The control module 21 can control the ultrasonic transducer 20 to perform analysis and identification of the object to be detected (such as fingerprints).

[0070] Figure 3 In this module, control module 21 includes a transceiver circuit module and a signal processing module. The transceiver circuit module and signal processing module are electrically connected. The transceiver circuit module includes a transceiver switch, a control unit, a pulse generator, and an echo channel. The transceiver switch, pulse generator, and echo channel are all electrically connected to the control unit. The echo channel includes amplification and filtering, sample-and-hold, and analog-to-digital (ADC) conversion; amplification and filtering are connected to sample-and-hold, and sample-and-hold and ADC are connected. The signal processing module includes signal processing and plotting; signal processing and plotting are connected.

[0071] In some embodiments of this application, some lines in the transceiver circuit module and the signal processing module may be disposed within the ultrasonic transducer module 100. For example, some lines in the echo channel may be integrated on the substrate of the ultrasonic transducer module 100 (see below).

[0072] Figure 3 The ultrasonic transducer 20 can be applied in a variety of scenarios.

[0073] In some embodiments, the ultrasonic transducer 20 is used in ultrasonic fingerprint imaging. The working principle of ultrasonic fingerprint imaging is as follows:

[0074] The control unit controls the pulse transmitter to generate an excitation voltage signal at the working frequency, which is applied to the ultrasonic transducer module 100 via a transceiver switch and emits sound waves. The emitted sound waves pass through the sound wave penetration layer 22 and reach the finger surface. The valley and ridge parts of the finger surface generate echo reflection signals of different intensities. The echo reflection signals pass through the sound wave penetration layer 22 and are received by the ultrasonic transducer module 100 and converted into electrical signals. The echo reflection signals are switched from the transmission channel to the echo channel via the transceiver switch. After amplification, filtering, sampling and holding, and analog-to-digital conversion, they are converted into digital signals. Finally, the digital signals are processed, features are extracted, and compared with the stored fingerprint information to complete fingerprint recognition.

[0075] In some embodiments, the ultrasonic transducer 20 is used in medical ultrasound imaging or industrial ultrasound imaging. The working principle of medical ultrasound imaging or industrial ultrasound imaging is as follows:

[0076] The control unit controls the pulse transmitter to generate an excitation voltage signal at the working frequency, which is applied to the ultrasonic transducer module 100 via a transceiver switch and emits sound waves. The emitted sound waves pass through the acoustic wave penetration layer 22 and reach the inside of the imaging tissue. When the signal reaches the target defect location (if any), due to the difference in acoustic impedance between the defect and the surrounding medium, an echo signal is generated. The echo reflection signal passes through the acoustic wave penetration layer 22 and is received by the ultrasonic transducer module 100 and converted into an electrical signal. The echo reflection signal is switched from the transmission channel to the echo channel via the transceiver switch. After amplification, filtering, sample-and-hold, and analog-to-digital conversion (ADC), it is converted into a digital signal. Finally, the digital signal is processed to achieve imaging.

[0077] It is understandable that the ultrasonic transducer 20 is not limited to the above-mentioned scenarios. For example, it can also be applied to ultrasonic detection, such as ultrasonic ranging and ultrasonic flow meters. The principle of ultrasonic detection scenarios includes: detecting by emitting ultrasonic waves and detecting the flight time, phase, or intensity of the echo.

[0078] This application does not limit the structure of the sound wave penetrating layer 22 described above. The sound wave penetrating layer 22 may include a single layer structure or a multi-layer structure. In embodiments where the electronic device is a mobile phone, the mobile phone's display screen can be considered as the sound wave penetrating layer 22. The sound wave penetrating layer 22 may be a flexible display screen, or it may be a non-flexible display screen. In embodiments where the electronic device is a smart door lock, the glass cover or resin cover of the smart door lock can be considered as the sound wave penetrating layer 22. The sound wave penetrating layer 22 may be a metal layer, a glass layer, or an adhesive layer.

[0079] Figure 4 This is a schematic diagram of the structure of an ultrasonic transducer module 100 provided in an embodiment of this application. Please refer to... Figure 4 The ultrasonic transducer module 100 includes a substrate 110, a first electrode layer 120, a piezoelectric layer 130, and a second electrode layer 140. The substrate 110, the first electrode layer 120, the piezoelectric layer 130, and the second electrode layer 140 are stacked sequentially.

[0080] The acoustic impedance of the substrate 110 is not equal to that of the piezoelectric layer 130. The ratio of the acoustic impedance of the piezoelectric layer 130 to that of the second electrode layer 140 is 0.5-2. The sum of the thickness-to-wavelength ratio of the second electrode layer 140 and the thickness-to-wavelength ratio of the piezoelectric layer 130 is a / 4; where a is a positive integer. For example, a can be 1, 2, 3, 4, 5, 6, 7, or 8, etc.

[0081] Thus, the second electrode layer 140 and the piezoelectric layer 130 form a resonator, which can improve the penetration capability of the ultrasound generated by the piezoelectric layer 130. Alternatively, the resonator can improve the penetration capability of mechanical waves transmitted to the piezoelectric layer 130, thereby increasing the sensitivity of the ultrasonic transducer module 100 and improving its performance. The second electrode layer 140 serves as both an electrode and part of the resonator. The resonator can consist only of the aforementioned second electrode layer 140 and piezoelectric layer 130, without the need for other layer structures, which is beneficial for reducing the size of the ultrasonic transducer 20 and miniaturizing the electronic device.

[0082] Acoustic impedance is the product of the velocity of sound and the density of the medium through which sound waves travel.

[0083] The thickness-to-wavelength ratio of the aforementioned second electrode layer 140 is: the thickness of the second electrode layer 140 and the wavelength of the sound wave propagating within the second electrode layer 140. Here, the wavelength is the ratio of the speed of sound and the frequency of the sound wave propagating within the second electrode layer 140. The speed of sound propagating within the second electrode layer 140 is typically related to the material of the second electrode layer 140. The frequency of the sound wave is either the frequency of the electrical signal excited by the second electrode layer 140 or the frequency of the sound wave received by the second electrode layer 140. The speed of sound can be the longitudinal wave speed, the transverse wave speed, or the guided wave speed, selected according to the propagation mode of the sound wave within the second electrode layer 140. The other thickness-to-wavelength ratios are similar and will not be elaborated further.

[0084] The thickness of the aforementioned second electrode layer 140 is defined as the dimension of the second electrode layer 140 along the stacking direction of the substrate 110, the first electrode layer 120, the piezoelectric layer 130, and the second electrode layer 140. In embodiments where the second electrode layer 140 has a non-uniform thickness, the thickness of the second electrode layer 140 is the average value of the aforementioned dimensions.

[0085] This application does not limit the operating frequency of the ultrasonic transducer module 100; the operating frequency is set according to the operating scenario and penetration thickness of the ultrasonic transducer 20. For example, in an embodiment where the ultrasonic transducer 20 is used for fingerprint imaging, a higher frequency results in higher resolution in order to distinguish fingerprint ridges and valleys. Furthermore, the frequency is set according to the acoustic wave penetration thickness of the ultrasonic transducer module 100. Since higher acoustic frequencies experience greater attenuation, the highest resonant frequency is typically limited to ensure sufficient echo intensity. Therefore, for fingerprint recognition scenarios, the target frequency can be 5MHz (megahertz) to 20MHz, for example, the target frequency can be 5MHz, 8MHz, 10MHz, 12MHz, 15MHz, 18MHz, or 20MHz, etc.

[0086] The aforementioned "the sum of the thickness-to-wavelength ratio of the second electrode layer 140 and the thickness-to-wavelength ratio of the piezoelectric layer 130 is a / 4" is a standard thickness-to-wavelength resonance theory applicable to single-layer resonators, meaning that resonance can be achieved with a thickness-to-wavelength ratio of a / 4. For resonators composed of multiple layers, due to acoustic reflection within the resonator, the actual thickness-to-wavelength ratio deviates from the theoretical value of a / 4. For example, the sum of the thickness-to-wavelength ratio of the second electrode layer 140 and the thickness-to-wavelength ratio of the piezoelectric layer 130 is a / 4 ± 0.1. The same logic applies to multiples of one-quarter, and will not be elaborated further below.

[0087] For example, the ratio of the acoustic impedance of the piezoelectric layer 130 to the acoustic impedance of the second electrode layer 140 can be 0.6, 0.7, 0.8, 0.9, 0.92, 0.95, 0.98, 1, 1.02, 1.05, 1.1, 1.2, 1.4, 1.6, 1.9, or 2, etc. The examples of acoustic impedance ratios between 0.5 and 2 in the following text are similar and will not be repeated here.

[0088] In the embodiments of this application, the acoustic impedance of the piezoelectric layer 130 is equal to that of the second electrode layer 140. Thus, the acoustic impedance difference between the piezoelectric layer 130 and the second electrode layer 140 is small, resulting in low sound wave loss propagating within the piezoelectric layer 130 and the second electrode layer 140, which can further improve the sensitivity of the ultrasonic transducer module 100.

[0089] In the embodiments of this application, the acoustic impedance of the piezoelectric layer 130 being equal to that of the second electrode layer 140 means that the ratio of the acoustic impedance of the piezoelectric layer 130 to that of the second electrode layer 140 is 0.8-1.2. For example, the ratio of the acoustic impedance of the piezoelectric layer 130 to that of the second electrode layer 140 may be 0.8, 0.9, 0.92, 0.95, 0.98, 1, 1.02, 1.05, 1.1, or 1.2, etc. The description of equal acoustic impedance in the following text is similar and will not be repeated hereafter.

[0090] In some embodiments of this application, the unequal acoustic impedance of the substrate 110 and the piezoelectric layer 130 means that the ratio of the acoustic impedance of the substrate 110 to the acoustic impedance of the piezoelectric layer 130 is greater than 2 or less than 0.5; for example, the ratio of the acoustic impedance of the substrate 110 to the acoustic impedance of the piezoelectric layer 130 is 0.2, 0.3, 0.4, 0.5, 2, 2.1, 2.2, 2.5, or 3, etc. A larger difference between the acoustic impedance of the substrate 110 and the acoustic impedance of the piezoelectric layer 130 can avoid the influence of the substrate 110 on the resonator composed of the piezoelectric layer 130 and the second electrode layer 140.

[0091] For example, if the sum of the thickness-to-wavelength ratio of the second electrode layer 140 and the thickness-to-wavelength ratio of the piezoelectric layer 130 is 1 / 4, then the sum of the thickness of the second electrode layer 140 and the thickness of the piezoelectric layer 130 is minimized, which is beneficial for miniaturization of electronic devices.

[0092] Typically, the thickness of an electrode layer that only has conductive properties is less than 1 μm. This thickness of electrode layer can be considered an acoustically transparent layer, which does not have a resonant effect. In other words, the thickness-to-wavelength ratio of an electrode layer that only has conductive properties is close to 0.

[0093] In the embodiments of this application, the second electrode layer 140 has the functions of both conducting electricity and serving as a resonator component. Making full use of the thickness of the second electrode layer 140 is beneficial for the miniaturization of electronic devices.

[0094] Exemplarily, the material of the second electrode layer 140 includes conductive materials and polymers. Exemplarily, it includes at least one of aluminum, copper, silver, gold, graphite, nickel, tungsten, or conductive particles.

[0095] The conductive particles comprise a copper core and a conductive layer encapsulating the core. Alternatively, the conductive particles may comprise an aluminum core and a conductive layer encapsulating the aluminum core; or, the conductive particles may comprise a graphite core and a conductive layer encapsulating the graphite core; or, the conductive particles may comprise a glass core and a conductive layer encapsulating the glass core. The aforementioned conductive materials possess electrical conductivity. In some embodiments, the conductive particles comprise a core and an antioxidant conductive layer encapsulating the core, thereby improving the oxidation resistance of the second electrode layer.

[0096] In some embodiments of this application, the conductive material may include other conductive materials such as copper, aluminum, and iron.

[0097] In some embodiments of this application, the propagation speed of the sound wave in the second electrode layer 140 is less than or equal to 3000 m / s. The thickness of the second electrode layer 140 can be further reduced, thereby thinning the ultrasonic transducer module. For example, the propagation speed of the sound wave in the second electrode layer 140 can be 3000 m / s, 2500 m / s, 2400 m / s, 2300 m / s, 2200 m / s, 2000 m / s, 1900 m / s, 1500 m / s, 1000 m / s, 500 m / s, etc.

[0098] For example, the aforementioned antioxidant conductive layer can be made of antioxidant metal materials such as gold, nickel, or tungsten.

[0099] For example, the surface resistivity of the second electrode layer 140 is less than 10 Ω / sq (ohms per square meter), which gives the second electrode layer 140 excellent conductivity.

[0100] Since the ratio of the acoustic impedance of the second electrode layer 140 to the acoustic impedance of the piezoelectric layer 130 is 0.5-2, and the acoustic impedance is related to the material, the material ratio of the second electrode layer 140 is set according to the material of the piezoelectric layer 130.

[0101] The piezoelectric layer 130 includes a piezoelectric material, which achieves the mutual conversion of electrical energy and acoustic energy (mechanical energy) through the inverse piezoelectric or direct piezoelectric effect.

[0102] In some embodiments of this application, the piezoelectric material is a piezoelectric polymer material, such as polyvinylidene fluoride (PVDF) and its copolymers poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) and poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)). The acoustic impedance of the piezoelectric layer 130 formed by the aforementioned piezoelectric material is approximately 5 MRayle. In these embodiments, the acoustic impedance of the second electrode layer 140 is, for example, 2.5 MRayle to 10 MRayle. Exemplarily, the mass ratio of the conductive material to the polymer in the second electrode layer 140 can be (60%-90%):(40%-10%); for example, the mass ratio of the conductive material to the polymer can be 60%:40%, 70%:30%, 80%:30%, or 90%:10%, etc.

[0103] In embodiments where the piezoelectric material is a piezoelectric polymer, the substrate 110 may be made of materials such as glass or silicon, and the acoustic impedance of the substrate 110 differs significantly from that of the piezoelectric layer 130. In embodiments where the substrate 110 is made of glass or silicon, the substrate 110 may also be referred to as a substrate.

[0104] In some embodiments of this application, the piezoelectric material is a piezoelectric ceramic material. Examples of piezoelectric ceramic materials include lead zirconate titanate (PZT) and its alloys, and KNN (K x Na 1-x NbO3), PMN-PT; or aluminum nitride (AlN), aluminum nitride alloy materials (Sc x Al 1-x N), zinc oxide (ZnO) and its alloys (V) x Zn 1-x O), etc. The acoustic impedance of the piezoelectric layer 130 formed by the aforementioned piezoelectric material is approximately 30 MRaly. In these embodiments, the acoustic impedance of the second electrode layer 140 is, for example, 15 MRaly to 60 MRaly. Exemplarily, a high-density conductive material can be selected, for example, the conductive material in the second electrode layer 140 can be, for example, tungsten or nickel.

[0105] In embodiments where the piezoelectric material is a piezoelectric ceramic material, the substrate 110 is made of a flexible material, such as a polymer material like polyimide (PI) or polyethylene terephthalate (PET). In embodiments where the substrate 110 is made of a flexible material, the substrate 110 can also be referred to as a flexible substrate.

[0106] In the embodiments of this application, the material of the first electrode layer 120 is not limited. The material of the first electrode layer 120 may be, for example, a metallic material such as Al, Au, Ag, Pt, Cu, Mo, or Ti. In some embodiments, the material of the first electrode layer 120 includes indium tin oxide (ITO).

[0107] The embodiments of this application do not limit the thickness of the first electrode layer 120. For example, the thickness of the first electrode layer 120 is on the nanometer scale. The nanometer-thickness of the first electrode layer 120 has little impact on the thickness of the ultrasonic transducer module 100, and the nanometer-thickness of the first electrode layer 120 has little impact on the flatness of the ultrasonic transducer module 100. In addition, the nanometer-thickness of the first electrode layer 120 can be regarded as an acoustically transparent layer, and the thickness-to-wavelength ratio of the first electrode layer 120 is close to 0, which can be denoted as 0.

[0108] It is understood that in some embodiments, the thickness of the first electrode layer 120 can be relatively large. In embodiments where the thickness of the first electrode layer 120 is relatively large, the ratio of the acoustic impedance of the first electrode layer 120 to the acoustic impedance of the substrate 110 is 0.5-2. For example, the acoustic impedance of the first electrode layer 120 is equal to the acoustic impedance of the substrate 110.

[0109] The shape of the first electrode layer 120 is not limited in this embodiment. For example, the shape of the first electrode layer 120 can be rectangular, circular, or other shapes. In addition, the first electrode layer 120 may include multiple independent electrode portions; or, the first electrode layer 120 can be a complete one-piece electrode structure.

[0110] The electrode layer is typically very thin, on the nanometer scale, to minimize its impact on the flatness of the piezoelectric layer deposited on its surface. The electrode material can be a variety of conductive materials, including metallic materials such as Al, Au, Ag, Pt, Cu, Mo, and Ti, or some conductive polymer materials such as indium tin oxide (ITO).

[0111] In some embodiments of this application, the ultrasonic transducer module 100 further includes a circuit layer located between the first electrode layer 120 and the substrate 110.

[0112] For example, the circuit layer has a thickness on the micrometer scale and can also be considered acoustically transparent. In some scenarios, the circuit layer can be considered part of the substrate 110. For instance, the circuit layer can be a thin film transistor (TFT) structure, which can be formed using complementary metal-oxide-semiconductor (CMOS) technology.

[0113] In some embodiments of this application, an adhesive layer may also be disposed between the first electrode layer 120 and the piezoelectric layer 130, the adhesive layer being used to increase the bonding force between the first electrode layer 120 and the piezoelectric layer 130. The thickness of the adhesive layer may be, for example, at the submicron level, such as several hundred nanometers.

[0114] In embodiments where the material of substrate 110 includes silicon, pixel circuitry and a first electrode layer 120 are integrated on substrate 110 using a CMOS process.

[0115] In some embodiments of this application, the ultrasonic transducer module 100 further includes leads ( Figure 4 (Not shown in the diagram), the leads transmit the circuit signals from the first electrode layer 120 and the second electrode layer 140 to the control module. For example, the leads can be led out on the side of the substrate 110 near the piezoelectric layer 130 using anisotropic conductive film (ACF) lead technology, or the circuit signals can be led to the side of the substrate 110 away from the piezoelectric layer 130 using through silicon via (TSV) or through glass via (TGV) technology, and then led out using anisotropic conductive film lead technology.

[0116] In an embodiment where the piezoelectric material of the piezoelectric layer 130 is a piezoelectric polymer and the substrate layer 110 is glass, the acoustic pressure reflection coefficient at the interface between the piezoelectric layer 130 and the substrate layer 110 is 50%. The acoustic pressure reflection coefficient is equal to (R2-R1) / (R2+R1). R1 ​​is the acoustic impedance of the piezoelectric layer 130, and R2 is the acoustic impedance of the substrate layer 110. 50% of the sound waves emitted from the piezoelectric layer 130 are reflected back, and the boundary between the piezoelectric layer 130 and the substrate layer 110 is a strongly reflective boundary.

[0117] In these embodiments, the side of the second electrode layer 140 away from the piezoelectric layer 130 can be an air layer. The acoustic impedance of the air layer is close to 0, and 100% of the sound waves emitted from the second electrode layer 140 are reflected back. The boundary of the second electrode layer 140 away from the piezoelectric layer 130 is a strong reflection boundary. The ratio of the acoustic impedance of the second electrode layer 140 to the piezoelectric layer 130 is 0.5-2, and the second electrode layer 140 and the piezoelectric layer 130 together constitute a resonant stack. The sum of the thickness-to-wavelength ratio of the second electrode layer 140 and the thickness-to-wavelength ratio of the piezoelectric layer 130 is an odd multiple of one-quarter, such as one-quarter, three-quarters, five-quarters, seven-quarters, etc.

[0118] The aforementioned strong reflection boundaries include strong hard reflection boundaries and strong soft reflection boundaries; strong hard reflection boundaries are also called hard boundaries; strong soft reflection boundaries are also called soft boundaries. If the acoustic impedance of layer one is greater than that of layer two, then the boundary from layer one to layer two is called a soft boundary. Conversely, if the acoustic impedance of layer one is less than that of layer two, then the boundary from layer one to layer two is called a hard boundary.

[0119] In some embodiments of this application, the sum of the thickness-to-wavelength ratio of the second electrode layer 140, the thickness-to-wavelength ratio of the piezoelectric layer 130, the thickness-to-wavelength ratio of the first electrode layer 120, and the thickness-to-wavelength ratio of the substrate 110 is b / 4; where b is a positive integer greater than a. Thus, the substrate 110 and the first electrode layer 120 can be considered as a resonator, or the second electrode layer 140, the piezoelectric layer 130, the first electrode layer 120, and the substrate 110 can be considered as a resonator. Combining the resonator formed by the aforementioned second electrode layer 140 and the piezoelectric layer 130, the ultrasonic transducer module 100 has two resonators, which can further improve the sensitivity of the ultrasonic transducer module 100.

[0120] As can be seen from the above, Figure 4 The acoustic impedance and thickness of each layer in the ultrasonic transducer module 100 have various examples, and some examples are described below.

[0121] For example, the substrate 110 is made of glass and has a thickness of 90 μm (micrometers); the first electrode layer 120 has a submicrometer thickness. The piezoelectric layer 130 is made of polyvinylidene fluoride (PVDF) and has a thickness of 9 μm. The second electrode layer 140 is made of copper and polymer and has a thickness of 25 μm. Simulation of this example ultrasonic transducer module 100 shows that the overall resonant frequency of the resonator is 12 MHz, allowing the determination of the wavelengths of each layer. Dividing the thickness by the wavelength yields the thickness-to-wavelength ratio. The sum of the thickness-to-wavelength ratio of the piezoelectric layer 130 and the second electrode layer 140 is 0.24, close to the theoretical value of 0.25. The thickness-to-wavelength ratio of substrate 110, the thickness-to-wavelength ratio of the first electrode layer 120, the thickness-to-wavelength ratio of piezoelectric layer 130, and the sum of the thickness-to-wavelength ratio of the second electrode layer 140 are 0.42, which deviates from the theoretical value of 0.5. This deviation is mainly due to acoustic reflection at the boundary between substrate 110 and piezoelectric layer 130.

[0122] Furthermore, in order to utilize 50% of the energy transmitted from the piezoelectric layer 130 to the first electrode layer 120, in some embodiments, the second electrode layer 140, the piezoelectric layer 130, the first electrode layer 120, and the substrate 110 can be considered as a resonator. The thickness of the substrate 110 can be 90 μm-130 μm, for example, the thickness of the substrate 110 can be 90 μm, 110 μm, 120 μm, 130 μm, etc. In some embodiments, the substrate 110 acts as a separate resonator, and the thickness of the substrate 110 can be 200 μm-300 μm, for example, the thickness of the substrate 110 can be 240 μm, 250 μm, or 260 μm, etc.

[0123] As described above, in some embodiments of this application, the side of the second electrode layer 140 away from the piezoelectric layer 130 can be an air layer. In some embodiments of this application, the side of the second electrode layer 140 away from the piezoelectric layer 130 can be other layer structures.

[0124] Figure 5 This is a schematic diagram of another ultrasonic transducer module 100 provided in an embodiment of this application. Figure 5 and Figure 4 The differences include: the ultrasonic transducer module 100 may further include a protective layer 160, which is located on the side of the second electrode layer 140 away from the piezoelectric layer 130. In other words, the second electrode layer 140 is located between the protective layer 160 and the piezoelectric layer 130, and the thickness-to-wavelength ratio of the protective layer 160 is less than or equal to 0.1.

[0125] Thus, the protective layer 160 can be considered an acoustically transparent layer. The protective layer 160 does not affect the resonance of the resonator, which is beneficial to the sensitivity of the ultrasonic transducer module 100. In addition, the protective layer 160 also protects the second electrode layer 140, preventing it from directly contacting air or dust, effectively ensuring the performance of the second electrode layer 160.

[0126] For example, the protective layer 160 has a thickness of submicron level. The protective layer 160 can achieve the function of electrical isolation. Since its thickness wavelength is relatively small, the protective layer 160 does not affect the resonance function of the ultrasonic transducer module 100.

[0127] The foregoing described embodiments in which the acoustic impedance of the substrate 110 and the piezoelectric layer 130 are unequal. In some embodiments of this application, the ratio of the acoustic impedance of the substrate 110 to the acoustic impedance of the piezoelectric layer 130 can be 0.5-2, which will be exemplarily described below.

[0128] In some embodiments of this application, the ratio of the acoustic impedance of the substrate 110 to the acoustic impedance of the piezoelectric layer 130 is 0.5-2, the ratio of the acoustic impedance of the piezoelectric layer 130 to the second electrode layer 140 is 0.5-2, and the sum of the thickness-to-wavelength ratio of the second electrode layer 140, the thickness-to-wavelength ratio of the piezoelectric layer 130, the thickness-to-wavelength ratio of the first electrode layer 120, and the thickness-to-wavelength ratio of the substrate 110 is c / 4; where c is a positive integer. Exemplarily, c can be 1, 2, 3, 4, 5, 6, or 7, etc.

[0129] Similarly, the second electrode layer 140, piezoelectric layer 130, and substrate 110, all with equal acoustic impedance, are considered as resonators, enhancing the sensitivity of the ultrasonic transducer module 100. Likewise, the second electrode layer 140 functions as both a conductor and a resonator component. Utilizing the thickness of the second electrode layer 140 and substrate 110 to form a resonator facilitates the reduction in thickness of the ultrasonic transducer module 100 and the miniaturization of electronic devices.

[0130] In some embodiments, the acoustic impedance of the substrate 110 is equal to that of the piezoelectric layer 130, and the acoustic impedance of the piezoelectric layer 130 and the second electrode layer 140 is equal. This improves the sensitivity of the resonator composed of the second electrode layer 140, the piezoelectric layer 130, and the substrate 110.

[0131] As described above, in embodiments where the thickness of the first electrode layer 120 is small (e.g., less than 10 μm), the first electrode layer 120 can be regarded as an acoustically transparent layer, and the thickness-to-wavelength ratio of the first electrode layer 120 can be denoted as 0.

[0132] In embodiments where the first electrode layer 120 is relatively thick, the acoustic impedance of the substrate 110 is equal to that of the first electrode layer 120, and the second electrode layer 140, piezoelectric layer 130, first electrode layer 120, and substrate 110 are collectively considered as a resonator. In such embodiments, the first electrode layer 120 serves both as a conductor and as a component of the resonator.

[0133] It is understood that the acoustic impedance of the substrate 110, the acoustic impedance of the piezoelectric layer 130, and the acoustic impedance of the second electrode layer 140 are equal. Based on this, the materials of the substrate 110, the piezoelectric layer 130, and the second electrode layer 140 can be selected in various ways.

[0134] In some embodiments, the substrate 110 is made of polyimide or polyethylene terephthalate resin. The piezoelectric layer 130 is made of the aforementioned piezoelectric polymer material. The second electrode layer 140 is made of a conductive material and a polymer.

[0135] In some embodiments of this application, the ratio of the acoustic impedance of the substrate 110 to the acoustic impedance of the piezoelectric layer 130 is 0.5-2, and the ratio of the acoustic impedance of the piezoelectric layer 130 to the acoustic impedance of the second electrode layer 140 is less than 0.5 or greater than 2; the sum of the thickness-to-wavelength ratio of the piezoelectric layer 130, the thickness-to-wavelength ratio of the first electrode layer 120, and the thickness-to-wavelength ratio of the substrate 110 is d / 4, where d is a positive integer. Exemplarily, d can be 1, 2, 3, 4, 5, 6, or 7, etc.

[0136] Thus, the piezoelectric layer 130 and the substrate 110 together form a resonator. The acoustic impedance of the piezoelectric layer 130 differs greatly from that of the second electrode layer 140. The second electrode layer 140 has little impact on the resonance effect of the resonator. The resonance effect of this resonator can improve the sensitivity of the ultrasonic transducer module.

[0137] In some embodiments, the acoustic impedance of the substrate 110 and the acoustic impedance of the piezoelectric layer 130 are equal, and the ratio of the acoustic impedance of the piezoelectric layer 130 to the acoustic impedance of the second electrode layer 140 is less than 0.5 or greater than 2. Similarly, the sensitivity of the resonator composed of the piezoelectric layer 130 and the substrate 110 can be improved.

[0138] Similarly, in embodiments where the first electrode layer 120 is thicker, the first electrode layer 120 serves both as a conductor and as a resonator component. This facilitates the reduction of the thickness of the ultrasonic transducer module 100.

[0139] It is understood that the second electrode layer 140, piezoelectric layer 130, first electrode layer 120, and substrate 110, which satisfy the aforementioned acoustic impedance relationship, can have various combinations. For example, the substrate 110 may be made of polyimide or polyethylene terephthalate resin. The piezoelectric layer 130 may be made of the aforementioned piezoelectric polymer material. The second electrode layer 140 may be made of a conductive material and a polymer. The first electrode layer 120 may be made of a conductive material and a polymer.

[0140] In some embodiments of this application, the thickness-to-wavelength ratio of the second electrode layer 140 is e / 4, where e is a positive integer. For example, e can be 1, 2, 3, 4, 5, 6, or 7, etc. Thus, the second electrode layer 140 can serve as a resonator, which, together with the resonator formed by the piezoelectric layer 130 and the substrate 110, complements each other to enhance the sensitivity of the ultrasonic transducer module 100.

[0141] Please return Figure 3 The acoustic wave penetrating layer 22 covers the ultrasonic transducer module 100. In the embodiments of this application, the layer structure closest to the acoustic wave penetrating layer 22 in the ultrasonic transducer module 100 and the acoustic impedance of the acoustic wave penetrating layer 22 are relatively large.

[0142] In some embodiments, the difference between the acoustic impedance of the acoustic wave penetrating layer 22 and the acoustic impedance of the substrate 110 is greater than the difference between the acoustic impedance of the acoustic wave penetrating layer 22 and the acoustic impedance of the second electrode layer 140. The distance between the acoustic wave penetrating layer 22 and the substrate 110 is less than the distance between the acoustic wave penetrating layer 22 and the second electrode layer 140. In other words, the acoustic impedance of the substrate 110 is greater than that of the acoustic wave penetrating layer 22 compared to the acoustic impedance of the second electrode layer 140, and the substrate 110 is closest to the acoustic wave penetrating layer 22. For example, the substrate 110 is in contact with the acoustic wave penetrating layer 22. This facilitates acoustic decoupling between the acoustic wave penetrating layer 22 and the ultrasonic transducer module 100.

[0143] The aforementioned "acoustic decoupling between acoustic wave penetrating layer 22 and ultrasonic transducer module 100" means that the acoustic wave penetrating layer 22 and ultrasonic transducer module 100 are not coupled. If the acoustic wave penetrating layer 22 and ultrasonic transducer module 100 are coupled, the acoustic wave penetrating layer 22 will affect the resonant frequency of ultrasonic transducer module 100 as part of the resonant stack.

[0144] For example, in an embodiment where the acoustic wave penetrating layer 22 is a display screen and the substrate 110 is made of silicon or glass, the material closest to the ultrasonic transducer module 100 in the display screen is a polymer with an acoustic impedance of approximately 3 MRay. The significant difference between the acoustic impedance of the polymer and the substrate 110 creates a strong acoustic reflection boundary, facilitating acoustic decoupling between the polymer and the silicon or glass, and reducing the impact of the acoustic wave penetrating layer 22 on the resonant frequency of the resonators in the ultrasonic transducer module 100. This effectively prevents the formation of new resonators through coupling between the acoustic wave penetrating layer 22 and the ultrasonic transducer module 100, and avoids significant drift in the resonant frequency generated by the resonators inside the ultrasonic transducer module 100 caused by the acoustic wave penetrating layer 22.

[0145] In some embodiments, the difference between the acoustic impedance of the acoustic wave penetrating layer 22 and the acoustic impedance of the substrate 110 is smaller than the difference between the acoustic impedance of the acoustic wave penetrating layer 22 and the acoustic impedance of the second electrode layer 140. The distance between the acoustic wave penetrating layer 22 and the substrate 110 is greater than the distance between the acoustic wave penetrating layer 22 and the second electrode layer 140. In other words, compared with the acoustic impedance of the second electrode layer 140, the acoustic impedance of the substrate 110 is smaller than that of the acoustic wave penetrating layer 22, and the substrate 110 is farther away from the acoustic wave penetrating layer 22. For example, the acoustic wave penetrating layer 22 is attached to the second electrode layer 140. This also facilitates acoustic decoupling between the acoustic wave penetrating layer 22 and the ultrasonic transducer module 100.

[0146] For example, in embodiments where the acoustic impedance of the acoustic wave penetrating layer 22 and the substrate 110 is close, the acoustic wave penetrating layer 22 is a polymer and the substrate 110 is PI or PET. The acoustic wave penetrating layer 22 is bonded to the second electrode layer 140, which achieves acoustic decoupling between the acoustic wave penetrating layer 22 and the ultrasonic transducer module 100.

[0147] In embodiments where the acoustic wave penetrating layer 22 is made of metal or glass and the substrate 110 is made of glass or silicon, the acoustic impedances of the acoustic wave penetrating layer 22 and the substrate 110 are close. The acoustic wave penetrating layer 22 is bonded to the second electrode layer 140, and the acoustic impedance of the second electrode layer 140 is set to be much greater than or much less than the acoustic impedance of the acoustic wave penetrating layer 22, thereby achieving acoustic decoupling between the acoustic wave penetrating layer 22 and the substrate 110.

[0148] In some embodiments of this application, the acoustic wave penetrating layer 22 can be bonded to the second electrode layer 140 or the substrate 110. For example, the acoustic impedance of the second electrode layer 140 is equal to the acoustic impedance of the piezoelectric layer 130, and the acoustic wave penetrating layer 22 can be bonded to either the second electrode layer 140 or the substrate 110. For example, in an embodiment where the acoustic wave penetrating layer 22 is a foldable screen, the material closest to the foldable screen and the ultrasonic transducer module 100 is stainless steel or carbon fiber. The acoustic impedance of the second electrode layer 140 is equal to the acoustic impedance of the piezoelectric layer 130; for example, the acoustic impedance of the substrate 110, the second electrode layer 140, and the piezoelectric layer 130 are all approximately 5 MRaly, and the acoustic wave penetrating layer 22 can be bonded to either the second electrode layer 140 or the substrate 110.

[0149] In some embodiments of this application, the acoustic wave penetrating layer 22 and the ultrasonic transducer module 100 are connected by an adhesive layer.

[0150] Figure 6 This is a schematic diagram of the structure of an ultrasonic transducer module 100 and an acoustic wave penetration layer 22 provided in an embodiment of this application. Please refer to... Figure 6 The electronic device may also include an adhesive layer 30, which is located between the acoustic wave transmission layer 22 and the ultrasonic transducer module 100. The acoustic wave transmission layer 22 and the ultrasonic transducer module 100 are connected through the adhesive layer 30.

[0151] In some embodiments of this application, the bonding layer 30 includes an adhesive, and the acoustic wave penetrating layer 22 and the ultrasonic transducer module 100 are connected through the bonding layer 30.

[0152] This application does not limit the structure of the adhesive layer 30; the adhesive layer 30 may include one, two, three, or multiple layers. In embodiments where the adhesive layer 30 includes a multiple layer structure, the materials of the multiple layers may be the same or different. For example, in some embodiments, the adhesive layer 30 may include a polymer layer, a metal layer, etc. For example, the adhesive layer 30 may include one or more polymer layers, and the adhesive layer 30 may include one or more metal layers. Exemplarily, the aforementioned polymer layer may be an adhesive layer.

[0153] In some embodiments of this application, the equivalent acoustic impedance of the bonding layer 30 can be set by setting the material and thickness of the bonding layer 30, which is beneficial to the effective penetration of sound waves from the ultrasonic transducer module 100 to the sound wave penetrating layer 22.

[0154] In embodiments where the bonding layer 30 comprises a metal layer and a polymer, the acoustic impedance of the bonding layer 30 is the equivalent acoustic impedance of the metal layer and the polymer, which is calculated using the following equations (1)-(3):

[0155] M1=ρ h1 t h1 (1)

[0156]

[0157] Rm 2 =M l K l (3)

[0158] In the formula: ρ h1 -Metal layer density; t h1 -Metal layer thickness; ρ p1 -Polymer layer density; t p1 -Polymer layer thickness; v p1 -Sound velocity of the polymer layer.

[0159] For example, in the ultrasonic transducer module 100, the acoustic impedance of the layer structure closest to the sound wave penetrating layer 22, the acoustic impedance of the bonding layer 30, and the acoustic impedance of the sound wave penetrating layer 22 increase or decrease sequentially. In this way, by setting the acoustic impedance of the bonding layer 30, effective sound wave penetration can be achieved while reducing the thickness of the bonding layer 30.

[0160] In some embodiments of this application, such as Figure 6 As shown, the second electrode layer 140 is bonded to the adhesive layer 30, and the acoustic impedance of the acoustic wave penetrating layer 22, the acoustic impedance of the adhesive layer 30, and the acoustic impedance of the second electrode layer 140 increase or decrease sequentially. In this way, sound waves can penetrate the adhesive layer 30 and transmit to the acoustic wave penetrating layer 22 more effectively.

[0161] Figure 7 This is a schematic diagram of another ultrasonic transducer module 100 and acoustic wave penetrating layer 22 provided in an embodiment of this application. Figure 7 and Figure 6 The differences include the different positional relationships of the bonding layer 30. Please refer to [link / reference]. Figure 7 The substrate 110 is bonded to the bonding layer 30, and the acoustic impedance of the acoustic wave penetrating layer 22, the acoustic impedance of the bonding layer 30, and the acoustic impedance of the substrate 110 increase or decrease sequentially. Similarly, sound waves can penetrate the bonding layer 30 and be transmitted to the acoustic wave penetrating layer 22 in a good manner.

[0162] In some embodiments of this application, the electronic device may also include an acoustic damping layer.

[0163] Figure 8 This is a schematic diagram of a structure of the ultrasonic transducer module 100 and the acoustic damping layer 40 provided in an embodiment of this application. Please refer to... Figure 8 The electronic device may also include an acoustic damping layer 40. The ultrasonic transducer module 100 is located between the acoustic damping layer 40 and the acoustic wave penetration layer 22.

[0164] For example, the substrate 110 is closer to the acoustic damping layer 40 than the second electrode layer 140, and the ratio of the acoustic impedance of the substrate 110 to that of the acoustic damping layer 40 is less than 0.5 or greater than 2. In other words, compared to the second electrode layer 140, the substrate 110 is closer to the acoustic damping layer 40, and the difference between the acoustic impedance of the substrate 110 and the acoustic impedance of the acoustic damping layer 40 is greater. The acoustic damping layer 40 has a smaller impact on the thickness of the ultrasonic transducer module 100. The acoustic damping layer 40 has a smaller impact on the resonance of the resonators in the ultrasonic transducer module 100, ensuring excellent sensitivity of the ultrasonic transducer module 100. The acoustic damping layer 40 can optimize the bandwidth characteristics of the ultrasonic transducer module 100 and improve imaging resolution.

[0165] In some embodiments of this application, the acoustic propagation loss of the acoustic damping layer 40 is greater than 30 dB / cm. The acoustic damping layer 40 exhibits high acoustic wave transmission loss characteristics, thereby reducing sound wave loss within the acoustic damping layer 40.

[0166] This application does not limit the structure of the acoustic damping layer 40. For example, the acoustic damping layer 40 has a porous structure. This application also does not limit the pore size and porosity of the acoustic damping layer 40. The size and porosity can be set according to the acoustic impedance requirements of the acoustic damping layer 40.

[0167] Figure 9 This is another structural schematic diagram of the ultrasonic transducer module 100 and the acoustic damping layer 40 provided in the embodiments of this application. Figure 9 and Figure 8 The differences include: the second electrode layer 140 is closer to the acoustic damping layer 40 relative to the substrate 110; and the ratio of the acoustic impedance of the second electrode layer 140 to that of the acoustic damping layer 40 is less than 0.5 or greater than 2. Similarly, the acoustic damping layer 40 has a smaller impact on the resonance of the resonator in the ultrasonic transducer module 100, ensuring excellent sensitivity of the ultrasonic transducer module 100. The acoustic damping layer 40 can optimize the bandwidth characteristics of the ultrasonic transducer module 100 and improve imaging resolution.

[0168] In the embodiments of this application, the acoustic damping layer 40 is not necessary and may be omitted.

[0169] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0170] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. An ultrasonic transducer module, comprising: The ultrasonic transducing module comprises a substrate, a first electrode layer, a piezoelectric layer and a second electrode layer which are sequentially stacked; The acoustic impedance of the substrate and the acoustic impedance of the piezoelectric layer are not equal; the ratio of the acoustic impedance of the piezoelectric layer to the acoustic impedance of the second electrode layer is 0.5-2; The sum of the thickness-wavelength ratio of the second electrode layer and the thickness-wavelength ratio of the piezoelectric layer is a / 4; a is a positive integer.

2. The ultrasonic transduction module of claim 1, wherein, The ratio of the acoustic impedance of the substrate to the acoustic impedance of the piezoelectric layer is less than 0.5 or greater than 2.

3. The ultrasonic transduction module of claim 1, wherein, The acoustic impedance of the piezoelectric layer is equal to the acoustic impedance of the second electrode layer.

4. The ultrasonic transduction module of any one of claims 1-3, wherein, The sum of the thickness-wavelength ratio of the second electrode layer, the thickness-wavelength ratio of the piezoelectric layer, the thickness-wavelength ratio of the first electrode layer and the thickness-wavelength ratio of the substrate is b / 4; b is a positive integer greater than a.

5. The ultrasonic transduction module of any one of claims 1-4, wherein, The ultrasonic transducing module further comprises a protective layer, the second electrode layer is located between the piezoelectric layer and the protective layer, and the thickness-wavelength ratio of the protective layer is less than or equal to 0.

1.

6. The ultrasonic transduction module of any one of claims 1-5, wherein, The transmission speed of the acoustic wave in the second electrode layer is less than or equal to 3000m / s.

7. The ultrasonic transduction module of any one of claims 1-6, wherein, The material of the second electrode layer comprises at least one of graphite, nickel, tungsten, aluminum, copper, silver, gold or conductive particles; the conductive particles comprise a core and a conductive layer wrapping the core.

8. The ultrasonic transduction module of any one of claims 1-7, wherein, The material of the substrate comprises silicon, glass or polymer.

9. An ultrasonic transducer module, characterized by The ultrasonic transducing module comprises a substrate, a first electrode layer, a piezoelectric layer and a second electrode layer which are sequentially stacked; the ratio of the acoustic impedance of the substrate to the acoustic impedance of the piezoelectric layer is 0.5-2, and the ratio of the acoustic impedance of the piezoelectric layer to the acoustic impedance of the second electrode layer is 0.5-2; The sum of the thickness-wavelength ratio of the second electrode layer, the thickness-wavelength ratio of the piezoelectric layer, the thickness-wavelength ratio of the first electrode layer and the thickness-wavelength ratio of the substrate is c / 4; c is a positive integer.

10. An ultrasonic transducer module, comprising: The ultrasonic transducing module comprises a substrate, a first electrode layer, a piezoelectric layer and a second electrode layer which are sequentially stacked; the ratio of the acoustic impedance of the substrate to the acoustic impedance of the piezoelectric layer is 0.5-2; the ratio of the acoustic impedance of the piezoelectric layer to the acoustic impedance of the second electrode layer is less than 0.5 or greater than 2; The sum of the thickness-wavelength ratio of the piezoelectric layer, the thickness-wavelength ratio of the first electrode layer and the thickness-wavelength ratio of the substrate is d / 4, and d is a positive integer.

11. The ultrasonic transduction module of claim 10, wherein, The thickness-wavelength ratio of the second electrode layer is e / 4, and e is a positive integer.

12. An ultrasonic transducer, characterized by The ultrasonic transducer comprises a control module and the ultrasonic transducing module according to any one of claims 1-11, and the first electrode layer and the second electrode layer are both electrically connected to the control module.

13. An electronic device, comprising: The electronic device comprises an acoustic wave penetrating layer and the ultrasonic transducer according to claim 12, and the acoustic wave penetrating layer covers the ultrasonic transducing module.

14. The electronic device of claim 13, wherein, The difference between the acoustic impedance of the acoustic wave penetrating layer and the acoustic impedance of the substrate is greater than the difference between the acoustic impedance of the acoustic wave penetrating layer and the acoustic impedance of the second electrode layer; the distance between the acoustic wave penetrating layer and the substrate is less than the distance between the acoustic wave penetrating layer and the second electrode layer. Alternatively, a difference between an acoustic impedance of the acoustic wave penetrating layer and an acoustic impedance of the substrate is less than a difference between the acoustic impedance of the acoustic wave penetrating layer and an acoustic impedance of the second electrode layer; a distance between the acoustic wave penetrating layer and the substrate is greater than a distance between the acoustic wave penetrating layer and the second electrode layer.

15. The electronic device of claim 13 or 14, wherein, The electronic device further includes a bonding layer between the acoustic wave penetrating layer and the ultrasonic transducing module.

16. The electronic device of claim 15, wherein, The second electrode layer is bonded to the bonding layer, and the acoustic impedance of the acoustic wave penetrating layer, the acoustic impedance of the bonding layer, and the acoustic impedance of the second electrode layer are sequentially increased or sequentially decreased. Alternatively, the substrate is bonded to the bonding layer, and the acoustic impedance of the acoustic wave penetrating layer, the acoustic impedance of the bonding layer, and the acoustic impedance of the substrate are sequentially increased or sequentially decreased.

17. The electronic device of any of claims 13-16, wherein, The electronic device further includes an acoustic damping layer; the ultrasonic transducing module is between the acoustic damping layer and the acoustic wave penetrating layer. The substrate is closer to the acoustic damping layer than the second electrode layer, and a ratio between the acoustic impedance of the substrate and the acoustic impedance of the acoustic damping layer is less than 0.5 or greater than 2. Alternatively, the second electrode layer is closer to the acoustic damping layer than the substrate, and a ratio between the acoustic impedance of the second electrode layer and the acoustic impedance of the acoustic damping layer is less than 0.5 or greater than 2.

18. The electronic device of claim 17, wherein, The acoustic damping layer is a porous structure.

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