Method for reducing crosstalk of array ultrasonic transducer based on double flexible circuit board

Abstract

The application discloses a method for reducing crosstalk of an array ultrasonic transducer based on double flexible circuit boards. The array ultrasonic transducer based on double flexible circuit boards comprises a matching layer, an upper flexible circuit board, a piezoelectric material layer, a lower flexible circuit board and a backing layer; the upper flexible circuit board, the lower flexible circuit board and the piezoelectric material layer are bonded through thin insulating adhesives with a thickness of not more than 5 microns respectively; and the piezoelectric material layer is cut to form a plurality of separated independent vibration elements. The application considers the electric excitation and potential measurement of the common electrode, so that the configured array only needs 2n interconnections to drive the full series of n 2 vibration elements. In addition, due to the polarization state of the piezoelectric material, each vibration element exhibits a bias-sensitive activity. The application applies a forced voltage bias to the electrically coupled element through the column electrode to minimize the net polarization and piezoelectric activity, thereby reducing the electrical crosstalk.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic transducer technology, and in particular to a method for reducing crosstalk in array ultrasonic transducers using dual flexible circuit boards. Background Technology

[0002] Currently, the most common ultrasonic transducers are single-element transducers. Single-element transducers are typically used to generate ultrasound waves with a fixed focus, thus processing only one target at a time. A single-element transducer must mechanically move to the next target position to continue processing, meaning a single-element ultrasound imaging system needs to include an electromagnetic motor that drives a flexible shaft to mechanically rotate the transducer, achieving 360-degree rotation within the endoscope to form a 2D image. Due to the relatively complex and bulky structure of the electromagnetic motor, it is usually located far from the ultrasonic transducer. Therefore, for single-element endoscopic ultrasound imaging systems, the imaging speed largely depends on the rotational speed of the electromagnetic motor and the characteristics of the flexible shaft. Consequently, the imaging frame rate of current endoscopic ultrasound imaging systems is usually limited by the mechanical rotation scanning method, and imaging is very time-consuming. Furthermore, to achieve real-time 3D ultrasound imaging, linear actuation components are even required, making the entire 3D ultrasound imaging system extremely complex and unsuitable for integration into an endoscope capsule for ultrasound imaging.

[0003] These shortcomings of single-element transducers can be overcome by linear or area array ultrasonic transducers. However, with the increasing demand for miniaturization and integration of transducers, there is a growing desire to integrate more elements into a smaller size, leading to increasingly smaller element spacing. As the number of array elements increases and the element spacing decreases, the excitation difficulty of the elements increases exponentially.

[0004] Therefore, current array ultrasonic transducers urgently need to solve the problem of accurate excitation of multiple elements. To address the element excitation issue in array ultrasonic transducers, those skilled in the art have proposed connecting the elements by designing corresponding island bridge electrodes. However, this method is only suitable for ultrasonic transducers with sparse elements. For independent elements formed by cutting a single piece of piezoelectric material, the small element spacing makes island bridge electrical connections impractical. Researchers have also designed specific circuit boards to connect the elements to the board pads, but the traditional PCB manufacturing process limits the element spacing and size of array ultrasonic transducers and makes miniaturization difficult. For high-frequency ultrasonic transducers with small element sizes and a large number of elements, this connection method not only makes alignment and bonding between the circuit pads and the elements extremely difficult, leading to element failure, but also exacerbates crosstalk between elements, reducing imaging resolution. Summary of the Invention

[0005] The main objective of this invention is to overcome the shortcomings and deficiencies of the prior art and provide an array ultrasonic transducer based on dual flexible circuit boards and a method for reducing crosstalk in the array ultrasonic transducer using dual flexible circuit boards. This invention can reduce the crosstalk level between elements, improve imaging resolution, and promote its application in fields such as endoscopy and industrial detection that require ultrasonic transducers to achieve precision imaging and detection.

[0006] The technical solution of the present invention is described in detail below.

[0007] This invention provides an array ultrasonic transducer based on dual flexible circuit boards, which comprises, from top to bottom, a matching layer, an upper flexible circuit board, a piezoelectric material layer, a lower flexible circuit board, an insulating structure, and a backing layer; the upper flexible circuit board, the lower flexible circuit board, and the piezoelectric material layer are bonded together by insulating adhesive; the piezoelectric material layer is cut to form several separate independent vibration elements.

[0008] In this invention, the piezoelectric material layer is cut to form an n×n element array, where n is an integer greater than or equal to 2. The length and width of the elements are equal, the width of the elements is 3-10 times the spacing between adjacent elements, and the distance between the centers of two elements is less than or equal to the propagation wavelength λ of the ultrasonic transducer in water.

[0009] In this invention, both the upper and lower flexible circuit boards are single-layer boards. The upper flexible circuit board has horizontal wiring and is connected to n oscillator pads. Simultaneously, the pads corresponding to each row of oscillators are connected via wiring. The lower flexible circuit board has vertical wiring and is connected to n lower flexible circuit board pads. Simultaneously, the pads corresponding to each column of oscillators are connected via wiring. Pads are respectively provided on the corresponding oscillators of the upper and lower flexible circuit boards, and are connected to the upper and lower surfaces of the piezoelectric material layer via these pads. Any oscillator in the oscillator array is used as the excitation oscillator. The oscillator pads in the row corresponding to the excitation oscillator are connected to drive electrical signals. The oscillator pads in the column corresponding to the lower flexible circuit board pads are grounded. The lower flexible circuit board pads in the remaining columns are connected to column electrodes for applying bias voltage.

[0010] In this invention, the piezoelectric material layer is a 1-3 composite material composed of piezoelectric ceramic PZT-5H and epoxy resin; the insulating adhesive is epoxy resin Epotek301, and the thickness of the insulating adhesive layer does not exceed 5μm; the backing layer is Esolder3022 obtained by high-temperature curing; the matching layer is a parylene coating; and the insulating structure is prepared by mixing and curing epoxy resin Epotek301.

[0011] In this invention, the dimensions of the oscillating element lead-out pad, the upper flexible circuit board pad, and the lower flexible circuit board pad are equal to the length and width of the oscillating element.

[0012] In this invention, when the number of oscillators exceeds 64, the oscillator lead-out pads on the upper and lower flexible circuit boards are directly set as connectors to achieve connection with the Verasonics Vantage ultrasonic experimental platform.

[0013] In this invention, the array ultrasonic transducer is planar or cylindrical, consisting of a matching layer, an upper flexible circuit board, a piezoelectric material layer, a lower flexible circuit board, an insulating structure, and a backing layer arranged radially outward from the center.

[0014] The present invention also provides a method for fabricating the above-mentioned array ultrasonic transducer based on dual flexible circuit boards, as detailed below:

[0015] When the array ultrasonic transducer is planar, the following steps are included:

[0016] (1) The lower flexible circuit board and the block piezoelectric material are bonded by insulating adhesive to ensure that the adhesive layer is evenly distributed on the entire surface of the flexible circuit board and the ultrasonic transducer; the central area of ​​the lower flexible circuit board corresponding to the ultrasonic transducer contains an n×n pad array, n≥2; the lower flexible circuit board is wired vertically, and the oscillator lead-out pads are located on the upper side of the flexible circuit board, and the pads corresponding to each column of oscillators on the lower flexible circuit board are connected by wiring.

[0017] (2) Cut the bulk piezoelectric material to form separate n×n arrays, n≥2, and the cutting thickness is the thickness of the bulk piezoelectric material;

[0018] (3) Using epoxy resin adhesive Epotek301, an insulating structure with the same length and width as the bulk piezoelectric material is prepared by mixing and curing. The thickness of the insulating structure is the same as the thickness of the bulk piezoelectric material. The structure is then bonded and fixed to the bottom of the flexible circuit board. (4) The backing layer is bonded using insulating adhesive.

[0019] (5) The flexible circuit board is attached using insulating adhesive; the central area of ​​the ultrasonic transducer attached to the flexible circuit board also contains an n×n pad array, where n≥2;

[0020] (6) Apply a layer of p-phenylenediene on the upper flexible circuit board as a matching layer;

[0021] (7) Weld wires to the lead-out pads of the upper and lower flexible circuit boards to connect the ultrasonic transducer drive system.

[0022] When the array ultrasonic transducer is cylindrical, the following steps are included:

[0023] (1) Cut the rectangular block piezoelectric material into 4 identical material bodies with equal length and width;

[0024] (2) The lower flexible circuit board and the material body are bonded together using insulating adhesive, ensuring that the adhesive layer is evenly distributed across the entire flexible circuit board and 1 / 4 of the ultrasonic transducer surface; at this point, the lower flexible circuit board corresponds to the central area of ​​the ultrasonic transducer to which it is bonded, including... There are 4 pad arrays, n≥4; the lower flexible circuit board is vertically wired, the pads of the oscillating elements are located on the upper side of the flexible circuit board, and the pads corresponding to each column of oscillating elements on the lower flexible circuit board are connected by wiring.

[0025] (3) Cut the material volume element to form There are 4 independent vibrational elements, and the cutting thickness is the thickness of the material body.

[0026] (4) Use insulating adhesive to attach the upper flexible circuit board and the material body with the lower flexible circuit board attached, and use a clamp to bend the material body to 90°; the upper flexible circuit board is wired horizontally, and the pads corresponding to each row of oscillating elements on the upper flexible circuit board are connected by wiring.

[0027] (5) Prepare the ring-shaped insulating structure and backing layer, and bond them together with insulating adhesive. After curing and placing at room temperature, structure B is obtained.

[0028] (6) Using insulating adhesive and clamps, four 90° bent material bodies are attached to the pre-prepared structure B to form a radial array transducer;

[0029] (7) Apply a layer of p-phenylenediene on the upper flexible circuit board as a matching layer;

[0030] (8) Weld wires to the lead-out pads of the upper and lower flexible circuit boards to connect the ultrasonic transducer drive system.

[0031] In this invention, the thickness of the adhesive layer formed by bonding with insulating adhesive does not exceed 5 μm.

[0032] Furthermore, the present invention provides a method for reducing crosstalk in the array ultrasonic transducer based on dual flexible circuit boards. During excitation, an orthogonal bias addressing method is used to apply an excitation signal to the upper flexible circuit board pad corresponding to the activated element, ground the lower flexible circuit board pad corresponding to the column, and apply a bias voltage to the remaining lower flexible circuit board pads connected to the column electrodes. The bias voltage is a negative voltage of the coercive voltage. Crosstalk in the ultrasonic transducer is reduced by the forced bias voltage method.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] This invention proposes a method for reducing crosstalk in array ultrasonic transducers based on dual flexible circuit boards. Compared to traditional array ultrasonic transducers that require n×n interconnects to access all elements in an n×n array, the proposed method, by considering the electrical excitation and potential measurement of the shared electrode, allows the configured array to drive the entire series of n elements with only 2n interconnects. 2 Each element exhibits bias-sensitive activity due to the polarization state of the piezoelectric material. This invention reduces electrical crosstalk by applying a forced voltage bias to the electrically coupled element through column electrodes to minimize net polarization and piezoelectric activity. Additionally, the structure bonded under the flexible circuit board also contributes to reducing crosstalk. Attached Figure Description

[0035] Figure 1 A top view of a 3×3 array ultrasonic transducer formed by repeatedly cutting a single piezoelectric material on its upper surface.

[0036] Figure 2 This is a simplified diagram of the flexible circuit board on the upper part of the separated 3×3 array ultrasonic transducer.

[0037] Figure 3 This is a simplified diagram of the lower flexible circuit board of a 3×3 array ultrasonic transducer.

[0038] Figure 4 This is a schematic diagram of the first clamp structure in Example 2.

[0039] Figure 5 This is a schematic diagram of the second clamp structure in Example 2. Detailed Implementation

[0040] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0041] Example 1

[0042] This invention discloses an array ultrasonic transducer based on dual flexible circuit boards, comprising, from top to bottom, a matching layer, an upper flexible circuit board, a piezoelectric material, a lower flexible circuit board, a structure, and a backing layer. The upper and lower flexible circuit boards and the piezoelectric material are bonded together with Epotek 301 epoxy resin adhesive. During bonding, a threaded clamp is used to tighten the threads at room temperature and cure at 40°C for 2 hours, ensuring that the adhesive layer is uniformly distributed across the entire surface of the flexible circuit board and the piezoelectric material, and that the thickness of the adhesive layer does not exceed 5 μm.

[0043] The piezoelectric material of the array ultrasonic transducer is formed by repeatedly cutting a single block of piezoelectric material on its upper surface to create separate vibration elements. The piezoelectric material is a 1-3 composite material consisting of piezoelectric ceramic PZT-5H and epoxy resin. The cutting depth is the thickness of the entire material.

[0044] Figure 1 To form a separate 3×3 array by repeatedly cutting a single block of piezoelectric material on its surface, we will only use a 3×3 array for the following explanation. In practical applications, the array can be n×n (n≥2). Here, 11 represents the element spacing, and 12 represents the element itself. The length and width of each element are equal. The width of element 12 is 3-10 times the element spacing 11. The distance between the centers of two elements is less than or equal to the propagation wavelength λ of the ultrasonic transducer in water.

[0045] Both the upper and lower flexible circuit boards are single-layer boards. The upper flexible circuit board has horizontal wiring. The simplified wiring diagram for the separate 3×3 array is shown below. Figure 2 As shown, 21 is the pad used in the upper flexible circuit board to bond the ultrasonic transducer separation element, and 22 is the element lead-out pad.

[0046] The bonding pad 22 of the vibrating element is located on the right side of the flexible circuit board and is used for external wire connection to the ultrasonic transducer drive system. The bonding pads corresponding to each row of vibrating elements on the upper flexible circuit board are connected by wiring. The bonding pads on the upper flexible circuit board used to bond the ultrasonic transducer separation vibrating elements are all of equal size.

[0047] The lower flexible circuit board, as shown Figure 3 As shown, the pads at positions 31 and Figure 1 The length and width of the ultrasonic transducer element are equal. The pads shown at positions 32-34 are used for external leads to connect to the ultrasonic transducer drive system.

[0048] When the number of elements exceeds 64, the lead-out pads of the elements on the upper and lower flexible circuit boards can also be directly set as connectors to achieve connection with the Verasonics Vantage ultrasonic experimental platform.

[0049] In this embodiment, a planar radial array transducer is provided, and its specific fabrication steps are as follows:

[0050] 1. The flexible circuit board and the bulk piezoelectric material are bonded together using Epotek 301 epoxy resin adhesive. During bonding, a threaded clamp is used to tighten the threads at room temperature and cure at 40°C for 2 hours to ensure that the adhesive layer is evenly distributed across the entire surface of the flexible circuit board and the ultrasonic transducer, and that the thickness of the adhesive layer does not exceed 5μm. The clamp is made of polytetrafluoroethylene (PTFE), and its length and width are 2-3 times that of the bulk piezoelectric material. Subsequently, the material is left at room temperature for 24 hours in the tightened state before being removed from the clamp. At this point, the central area of ​​the flexible circuit board corresponding to the bonded ultrasonic transducer contains an n×n (n≥2) pad array, and the length and width of the pads are equal to the length and width of the individual elements of the ultrasonic transducer after subsequent cutting and separation. Furthermore, the flexible circuit board has vertical wiring, and the element lead-out pads are located on the upper side of the flexible circuit board. The pads corresponding to each row of elements on the flexible circuit board are connected by wiring.

[0051] 2. Cut the bulk piezoelectric material to form separate n×n (n≥2) arrays, and the cutting thickness is the same as the thickness of the bulk piezoelectric material.

[0052] 3. An insulating structure with the same length and width as the bulk piezoelectric material and the same thickness as the bulk piezoelectric material was prepared by mixing and curing Epotek 301 epoxy resin. Then, the cured insulating structure was adhered to the corresponding piezoelectric material area of ​​the ultrasonic transducer on the bottom surface of the lower flexible circuit board using Epotek 301 epoxy resin. During bonding, a threaded clamp was designed to tighten the threads at room temperature and cure at 40°C for 2 hours, ensuring that the adhesive layer was evenly distributed across the entire lower surface of the lower flexible circuit board and that the thickness of the adhesive layer did not exceed 5 μm. Finally, it was left at room temperature for 24 hours in the tightened state before being removed from the clamp.

[0053] 4. The backing layer is bonded using Epotek 301 epoxy resin adhesive. During bonding, the threads are tightened at 40°C using a threaded clamp, and the mixture is cured at high temperature for 2 hours to ensure that the adhesive layer is evenly distributed on the lower surface of the entire insulating structure and the upper surface of the backing layer, and that the thickness of the adhesive layer does not exceed 5μm. Subsequently, it is left at room temperature for 24 hours in the tightened state before being removed from the clamp. The backing layer is obtained by high-temperature curing of Esolder 3022, and its length and width are equal to the length and width of the bulk piezoelectric material, with a thickness of 3mm.

[0054] 5. The flexible circuit board is bonded using Epotek 301 epoxy resin adhesive. During bonding, the threads are tightened at room temperature using a threaded clamp, and the board is cured at 40°C for 2 hours to ensure the adhesive layer is evenly distributed across the entire flexible circuit board and ultrasonic transducer surface, with a thickness not exceeding 5μm. Subsequently, it is left at room temperature for 24 hours in the tightened state before being removed from the clamp. At this point, the central area of ​​the upper flexible circuit board corresponding to the bonded ultrasonic transducer also contains an n×n (n≥2) pad array, and the length and width of the pads are equal to the length and width of a single element of the ultrasonic transducer after cutting and separation.

[0055] 6. Apply a 1μm thick layer of para-xylene using the Diener PARYLENE coating system as a matching layer. Connect the ultrasonic transducer drive system by soldering wires to the oscillator lead-out pads of the upper and lower flexible circuits.

[0056] In this invention, during excitation, an orthogonal bias addressing method is adopted to reduce crosstalk between oscillators and allow the activation of the target element. Specifically, an excitation signal is applied to the upper flexible circuit board pad 22 corresponding to the activated oscillator 21, the corresponding lower flexible circuit board pad 32 is grounded, and bias voltages are applied to the lower flexible circuit board pads 33 and 34, wherein the bias voltage is the negative of the coercive voltage.

[0057] In a specific embodiment, the block piezoelectric material is cut to form a separate 16×16 element array. The width of the element 12 is three times the spacing between the elements 11. When the distance between the centers of two elements is equal to the propagation wavelength λ of the ultrasonic transducer in water, the crosstalk between the elements can be reduced by 7.25dB by using a forced voltage bias method.

[0058] Example 2

[0059] This embodiment provides a cylindrical radial array transducer, the specific fabrication steps of which are as follows:

[0060] 1. Cut the rectangular block piezoelectric material into 4 identical material bodies with equal length and width.

[0061] 2. The lower flexible circuit board and the 1 / 4 block piezoelectric material (material body) are bonded together using Epotek 301 epoxy resin adhesive. During bonding, a threaded clamp is used to tighten the threads at room temperature and cure at 40°C for 2 hours to ensure that the adhesive layer is evenly distributed across the entire surface of the flexible circuit board and the 1 / 4 ultrasonic transducer, and that the thickness of the adhesive layer does not exceed 5μm. The clamp is made of polytetrafluoroethylene, and its length and width are 2-3 times that of the 1 / 4 block piezoelectric material (material body). Afterwards, it is left at room temperature in the tightened state for 24 hours before being removed from the clamp. At this point, the lower flexible circuit board corresponds to the central area of ​​the bonded ultrasonic transducer, containing... The circuit consists of an array of pads, with the length and width of the pads equal to the length and width of the individual elements of the ultrasonic transducer after subsequent cutting and separation. Furthermore, the lower flexible circuit board has vertical wiring, and the element lead-out pads are located on the upper side of the flexible circuit board. The pads corresponding to each column of elements on the lower flexible circuit board are connected by wiring.

[0062] 3. Cut a 1 / 4 block of piezoelectric material (material volume) into a vibrating element to form... Each independent vibrational element is cut to a thickness equal to that of the material body.

[0063] 4. Place the upper flexible circuit board and the material body with the lower flexible circuit board attached into the container. Figure 4 The first fixture shown is made of polytetrafluoroethylene (PTFE). The central angle corresponding to the arc portion in the middle of the fixture is 90°, and the arc length is equal to 1 / 4 of the length of the piezoelectric material (material body). An upper flexible circuit board and the material body with the lower flexible circuit board attached are bonded together using Epotek 301 epoxy resin adhesive, and the threads are tightened at 80°C, causing the material body to bend at 90°. Furthermore, the upper flexible circuit board has horizontal wiring, and the pads corresponding to each row of elements on the upper flexible circuit board are connected by wiring.

[0064] 5. Subsequently, it is cured at 40°C for 2 hours, and then left at room temperature in a tightened state for 24 hours before being removed from the fixture. This process is repeated 4 times to form 4 material bodies with 90° bends, and upper and lower flexible circuit boards are attached to the material bodies.

[0065] 6. Prepare the annular insulating structure and backing layer in advance, attach them with epoxy resin adhesive Epotek 301, cure at 40°C for 2 hours, and leave at room temperature for 24 hours in a tight state before removing them from the fixture to form structure B.

[0066] 7. Using Epotek 301 and such Figure 5 The second fixture shown attaches four 90° bent material bodies to a pre-prepared structure B, forming a radial array transducer. Similarly, it is cured at 40°C for 2 hours and then left at room temperature in a tightened state for 24 hours before being removed from the fixture. Four 90° alignment lines are present on the top surface of the fixture to ensure precise connection of the four independent units. Furthermore, transparent glass is chosen as the material for the fixture to observe the alignment of the four 90° bent material bodies. Structure B is cylindrical, with its outer diameter equal to the inner diameter of the fixture.

[0067] 8. Apply a 1 μm thick layer of para-xylene using the Diener PARYLENE coating system as a matching layer. Connect the ultrasonic transducer drive system by soldering wires to the oscillator lead-out pads of the upper and lower flexible circuits.

[0068] When the number of elements exceeds 64, the lead-out pads of the elements on the upper and lower flexible circuit boards can also be directly set as connectors to achieve connection with the Verasonics Vantage ultrasonic experimental platform.

[0069] The present invention proposes a method for reducing crosstalk in array ultrasonic transducers based on dual flexible circuit boards. Compared to traditional array ultrasonic transducers that require n×n interconnects to access all elements in an n×n array ultrasonic transducer, the method proposed in this invention, by considering the electrical excitation and potential measurement of the shared electrode, allows the configured array to drive the entire series of n elements with only 2n interconnects. 2 Each element exhibits bias-sensitive activity due to the polarization state of the piezoelectric material. A forced voltage bias is applied to the electrically coupled element via the column electrodes to minimize net polarization and piezoelectric activity, thereby reducing electrical crosstalk. Furthermore, the structure bonded under the flexible circuit board also contributes to reducing crosstalk.

Claims

1. An array ultrasonic transducer based on dual flexible circuit boards, characterized in that, It comprises, from top to bottom, a matching layer, an upper flexible circuit board, a piezoelectric material layer, a lower flexible circuit board, an insulating structure, and a backing layer; the upper flexible circuit board, the lower flexible circuit board, and the piezoelectric material layer are bonded together with insulating adhesive; the piezoelectric material layer is cut to form several separate independent vibration elements; wherein: The piezoelectric material layer is cut to form an n×n element array, where n is an integer greater than or equal to 2. The length and width of the elements are equal, and the width of the elements is 3-10 times the spacing between adjacent elements. The distance between the centers of two elements is less than or equal to the propagation wavelength λ of the ultrasonic transducer in water. Both the upper and lower flexible circuit boards are single-layer boards. The upper flexible circuit board has horizontal wiring, which is connected to the pads of n oscillating elements. At the same time, the pads corresponding to the oscillating elements in each row are connected by wiring. The lower flexible circuit board has vertical wiring, which is connected to the pads of n lower flexible circuit boards. At the same time, the pads corresponding to the oscillating elements in each column are connected by wiring. Pads are set on the corresponding oscillating elements of the upper and lower flexible circuit boards, and are connected to the upper and lower surfaces of the piezoelectric material layer through the pads. Taking any oscillating element in the oscillating element array as the excitation oscillating element, the pads of the oscillating elements in the row of the upper flexible circuit board corresponding to the excitation oscillating element are connected to the drive electrical signal. The pads of the oscillating elements in the column of the lower flexible circuit board are grounded. The pads of the lower flexible circuit boards in all remaining columns are connected to the column electrodes for applying bias voltage.

2. The array ultrasonic transducer based on dual flexible circuit boards according to claim 1, characterized in that, The piezoelectric material layer is a composite material composed of piezoelectric ceramic PZT-5H and epoxy resin. The insulating adhesive is epoxy resin Epotek301, and the thickness of the insulating adhesive layer does not exceed 5µm. The backing layer is Esolder3022, which is cured at high temperature. The matching layer is a parylene coating; the insulating structure is prepared by mixing and curing epoxy resin Epotek301.

3. The array ultrasonic transducer based on dual flexible circuit boards according to claim 1, characterized in that, The array ultrasonic transducer is planar, or cylindrical, with a matching layer, upper flexible circuit board, piezoelectric material layer, lower flexible circuit board, insulating structure and backing layer arranged radially outward from the center.

4. A method for fabricating an array ultrasonic transducer based on dual flexible circuit boards according to claim 3, characterized in that, When the array ultrasonic transducer is planar, the following steps are included: (1) The lower flexible circuit board and the block piezoelectric material are bonded by insulating adhesive to ensure that the adhesive layer is evenly distributed on the entire surface of the flexible circuit board and the ultrasonic transducer; the central area of ​​the lower flexible circuit board corresponding to the ultrasonic transducer contains an n×n pad array, n≥2; the lower flexible circuit board is wired vertically, and the oscillator lead-out pad is located on the upper side of the flexible circuit board. The pads corresponding to each column of oscillators on the lower flexible circuit board are connected by wiring. (2) Cut the bulk piezoelectric material to form separate n×n arrays, n≥2, and the cutting thickness is the thickness of the bulk piezoelectric material; (3) Using epoxy resin adhesive Epotek301, an insulating structure with the same length and width as the bulk piezoelectric material is prepared by mixing and curing. The thickness of the insulating structure is the same as the thickness of the bulk piezoelectric material. The structure is then bonded and fixed to the bottom of the lower flexible circuit board. (4) Use insulating adhesive to bond the backing layer; (5) The flexible circuit board is attached by means of insulating adhesive; the central area of ​​the ultrasonic transducer attached to the flexible circuit board also contains an n×n pad array, n≥2; (6) Apply a layer of p-phenylene xylene on the upper flexible circuit board as a matching layer; (7) The ultrasonic transducer drive system is connected by welding wires to the lead-out pads of the upper and lower flexible circuit boards.

5. A method for fabricating an array ultrasonic transducer based on dual flexible circuit boards according to claim 3, characterized in that, When the array ultrasonic transducer is cylindrical, the following steps are included: (1) Cut the rectangular block piezoelectric material into 4 identical material bodies with equal length and width; (2) The lower flexible circuit board and the material body are bonded together with insulating adhesive, ensuring that the adhesive layer is evenly distributed across the entire flexible circuit board and 1 / 4 of the ultrasonic transducer surface; at this time, the lower flexible circuit board corresponds to the central area of ​​the ultrasonic transducer to which it is bonded, including There are 4 pad arrays, n≥4; the lower flexible circuit board is vertically wired, the pads of the oscillating elements are located on the upper side of the flexible circuit board, and the pads corresponding to each column of oscillating elements on the lower flexible circuit board are connected by wiring. (3) Cut the material volume element to form There are 4 independent vibrational elements, and the cutting thickness is the thickness of the material body. (4) Use insulating adhesive to attach the upper flexible circuit board and the material body with the lower flexible circuit board attached, and use a clamp to bend the material body to 90°; the upper flexible circuit board is wired horizontally, and the pads corresponding to each row of oscillating elements on the upper flexible circuit board are connected by wiring. (5) Prepare the ring-shaped insulating structure and backing layer, bond them with insulating adhesive, cure and place at room temperature to obtain structure B; (6) Using insulating adhesive and clamps, four 90° bent material bodies are attached to the pre-prepared structure B to form a radial array transducer; (7) Apply a layer of p-xylene on top of the upper flexible circuit board as a matching layer; (8) The ultrasonic transducer drive system is connected by welding wires to the lead-out pads of the upper and lower flexible circuit boards.

6. The method for fabricating an array ultrasonic transducer based on dual flexible circuit boards according to claim 4 or 5, characterized in that, The thickness of the adhesive layer formed by bonding with insulating adhesive shall not exceed 5μm.

Images