A method for manufacturing a low-frequency flexible industrial array ultrasonic probe and its application

Abstract

This invention relates to a manufacturing method for a low-frequency flexible industrial array ultrasonic probe and its application. The manufacturing method includes the following steps in sequence: (1) wafer pretreatment; (2) rigid backing layer assembly: bonding a high-impedance rigid backing layer to the negative electrode surface of each low-frequency piezoelectric wafer; (3) flexible FPC board assembly; (4) ground wire connection; (5) low-impedance flexible backing layer forming: injecting a low-impedance flexible material into the entire negative electrode surface of the wafer, and after the low-impedance flexible material cures, a low-impedance flexible backing layer is formed. The low-impedance flexible backing layer covers the high-impedance rigid backing layer, the low-frequency piezoelectric wafer, and the common ground electrode. The method is reasonably designed, assembling the rigid backing layer first, followed by the assembly of the flexible FPC board, ground wire connection, and low-impedance flexible backing layer forming in sequence, avoiding the complexity of simultaneously processing the interface of two materials. This allows the manufactured low-frequency flexible industrial array ultrasonic probe to have a composite backing structure, achieving high acoustic performance and high flexibility, and improving the acoustic and mechanical functions of the ultrasonic probe.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic testing, specifically to a method for manufacturing a low-frequency flexible industrial array ultrasonic probe and its application. Background Technology

[0002] Currently, low-frequency flexible industrial array ultrasonic probes are mainly used for efficient and highly coupled contact ultrasonic imaging and thickness measurement of large industrial components with complex curved shapes, such as pipe bends, pressure vessel heads, and the main shafts and blades of wind turbine generators. Their design goal is to ensure sufficient detection depth and signal-to-noise ratio while effectively conforming to irregular surfaces to obtain stable and reliable detection signals.

[0003] There are two main methods for manufacturing low-frequency flexible industrial array ultrasonic probes: one is to use a flexible material with low acoustic impedance and low attenuation coefficient as a backing layer to cover the crystal array elements. These materials have excellent flexibility, making the probe easy to bend. However, the disadvantage is that the soft backing has poor acoustic performance. Flexible backing materials such as silicone have low density and sound velocity, resulting in a serious mismatch between their acoustic impedance and that of piezoelectric ceramics. At the same time, their sound wave attenuation coefficient is insufficient, which causes most of the energy generated by the thick crystal to be reflected back to the crystal, resulting in a wide pulse, low resolution, and poor sensitivity. The second method is to use a hard backing material with high acoustic impedance and high attenuation coefficient as a backing layer to cover the crystal array elements. These materials can effectively dampen crystal vibration and obtain narrow pulses and high sensitivity. However, the disadvantage is that they have a high Young's modulus and are brittle. After curing, they form a rigid whole and completely lose the flexibility of the probe, making it impossible to fit curved surfaces.

[0004] Regardless of the method used, the backing layer formed is a single material, making it difficult to simultaneously meet the two core requirements of "good acoustic performance" and "excellent flexibility" under the challenge of thick wafers at low frequencies. Thick wafers at low frequencies exacerbate system rigidity and make bending difficult: According to the frequency formula for piezoelectric wafers, the lower the operating frequency, the greater the wafer thickness (e.g., a 0.5MHz wafer is approximately 2.8mm thick). These thick and rigid ceramic units are themselves "rigid points." In existing processes, whether fully immersed in a soft or hard backing, the overall bending stiffness of the probe is significantly increased, making it difficult to achieve uniform bending at small radii. In practical applications, this easily leads to poor coupling and detection blind spots. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, the technical problem this invention aims to solve is how to manufacture a low-frequency flexible industrial array ultrasonic probe that can synergize the advantages of different materials. The specific technical solution is as follows:

[0006] A method for manufacturing a low-frequency flexible industrial array ultrasonic probe includes the following steps in sequence.

[0007] (1) Wafer pretreatment: Clean the positive and negative electrode surfaces of multiple low-frequency piezoelectric wafers;

[0008] (2) Rigid backing layer assembly: Select an appropriate number of low-frequency piezoelectric chips, and then bond a high-impedance rigid backing layer to the negative electrode surface of each low-frequency piezoelectric chip. One low-frequency piezoelectric chip and one high-impedance rigid backing layer constitute one assembly. A high-impedance rigid backing layer is also bonded above the ground common electrode.

[0009] (3) Flexible FPC board assembly: The various assemblies obtained in step (2) are bonded to the flexible FPC board, and the ground common electrode is also bonded to the flexible FPC board. The flexible FPC board is located at the bottom of the low-frequency piezoelectric chip and the ground common electrode.

[0010] (4) Ground connection: Connect the negative electrode surface of each low-frequency piezoelectric chip in step (3) to the common ground electrode through a wire, and the multiple low-frequency piezoelectric chips form a discrete low-frequency piezoelectric chip array.

[0011] (5) Low-impedance flexible backing layer molding: Low-impedance flexible material is poured into the entire negative electrode surface of the wafer. After the low-impedance flexible material is cured, a low-impedance flexible backing layer is formed. The low-impedance flexible backing layer covers the high-impedance rigid backing layer, the low-frequency piezoelectric wafer, and the ground common electrode. A flexible FPC board is bonded to the bottom surface of the low-impedance flexible backing layer.

[0012] As a preferred embodiment of the manufacturing method of the present invention, in step (2), the central axis of each low-frequency piezoelectric wafer coincides with the central axis of the high-impedance hard backing layer, the secondary axis width W1 of the low-frequency piezoelectric wafer is greater than the secondary axis width W2 of the high-impedance hard backing layer, and the high-impedance hard backing layer covers the central region of the low-frequency piezoelectric wafer.

[0013] As a preferred embodiment of the manufacturing method of the present invention, in step (4), the areas on both sides of the low-frequency piezoelectric wafer that are not covered by the high-impedance hard backing layer form a reserved area, the welding node is set in the reserved area, the wire is a single-core coaxial wire with stretching allowance, the wire is connected to the negative electrode surface of the low-frequency piezoelectric wafer through the welding node and then connected to the ground common electrode.

[0014] As a preferred embodiment of the manufacturing method of the present invention, a low-impedance flexible backing layer covers the reserved area, thereby encapsulating the welding nodes and wires.

[0015] As a preferred embodiment of the manufacturing method of the present invention, the low-impedance flexible backing layer separates the adjacent low-frequency piezoelectric wafer and the high-impedance rigid backing layer, and the low-impedance flexible backing layer contacts the left and right sides and the top surface of the low-frequency piezoelectric wafer, as well as the left and right sides and the top surface of the high-impedance rigid backing layer.

[0016] As a preferred embodiment of the manufacturing method of the present invention, in step (3), the thickness of the flexible FPC board needs to be ≤0.1mm. The flexible FPC board is equipped with signal gold fingers, ground gold fingers, and connectors. The positive electrode path of the low-frequency flexible industrial array ultrasonic probe is, in sequence, connector, signal gold fingers, and positive electrode of the low-frequency piezoelectric crystal. An external pulse generator is electrically connected to the positive electrode surface of the low-frequency piezoelectric crystal through the positive electrode path to excite sound waves. The negative electrode path of the flexible industrial array ultrasonic probe is, in sequence, ground gold fingers, ground common electrode, single-core coaxial wire, and welding node. The external grounding terminal is electrically connected to the negative electrode surface of the low-frequency piezoelectric crystal through the negative electrode path.

[0017] As a preferred embodiment of the manufacturing method of the present invention, the low-frequency piezoelectric wafer is made of PZT piezoelectric ceramic material, the high-impedance hard backing layer is made of a material with high acoustic impedance and high acoustic attenuation performance, and the low-impedance flexible backing layer is made of a material with low Young's modulus and high elastic deformation capability.

[0018] As a preferred embodiment of the manufacturing method of the present invention, the high-resistivity rigid backing layer is made of a composite material of epoxy resin and tungsten powder, and the low-resistivity flexible backing layer is made of a blend of silicone rubber or polyurethane.

[0019] As a preferred embodiment of the manufacturing method of the present invention, the low-frequency piezoelectric wafer and the ground common electrode are respectively bonded to the high-impedance rigid backing layer and the flexible FPC board by acoustic adhesive.

[0020] An application of an ultrasonic probe manufactured using the above-described method: When the ultrasonic probe is used for testing, the surface of the wafer directly emits sound waves that pass through the flexible FPC layer to the object being tested. At the same time, the negative electrode surface of the wafer generates a back wave. The high-impedance rigid backing layer absorbs more than 90% of the back wave energy, and the remaining back wave and the vibrations of the welding nodes and single-core coaxial wires are absorbed by the low-impedance flexible backing layer.

[0021] Beneficial effects: The manufacturing process of the low-frequency flexible industrial array ultrasonic probe of this invention is reasonably designed. It first assembles a rigid backing layer, then assembles a flexible FPC board, connects the ground wire, and forms a low-impedance flexible backing layer. This process of pre-positioning the rigid backing layer and then integrally injecting and encapsulating the low-impedance flexible backing layer avoids the complexity of simultaneously dealing with the interface of two materials. It can make the manufactured low-frequency flexible industrial array ultrasonic probe have a composite backing structure, and at the same time obtain high acoustic performance and high flexibility. It breaks through the physical limitations of a single material and improves the acoustic and mechanical functions of the ultrasonic probe. Attached Figure Description

[0022] Figure 1 This is a flowchart of the present invention;

[0023] Figure 2 This is a front view of the ultrasonic probe of the present invention;

[0024] Figure 3 This is a right view of the ultrasonic probe of the present invention;

[0025] Figure 4 This is a top view of the ultrasonic probe of the present invention;

[0026] Figure 5 This is a diagram showing the application status of the ultrasonic probe of the present invention. Detailed Implementation

[0027] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0028] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the position or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0029] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0030] like Figure 1-4 As shown, 1. A method for manufacturing a low-frequency flexible industrial array ultrasonic probe, comprising the following steps in sequence:

[0031] (1) Wafer pretreatment: Clean the positive and negative electrode surfaces of multiple low-frequency piezoelectric wafers 1;

[0032] (2) Assembling the rigid backing layer: Select an appropriate number of low-frequency piezoelectric wafers 1, and then attach a high-impedance rigid backing layer 2 to the negative electrode surface of each low-frequency piezoelectric wafer 1. One low-frequency piezoelectric wafer 1 and one high-impedance rigid backing layer 2 form a combination. A high-impedance rigid backing layer 2 is also attached above the ground common electrode 3. This step of assembling the rigid backing layer first can ensure that the low-frequency piezoelectric wafer 1 and the high-impedance rigid backing layer 2 can be tightly wrapped together during the subsequent flexible backing layer potting.

[0033] (3) Flexible FPC board assembly: Align and bond the various components obtained in step (2) to the flexible FPC board 4. The ground common electrode 3 is also bonded to the flexible FPC board 4. The flexible FPC board 4 is located at the bottom of the low-frequency piezoelectric chip 1 and the ground common electrode 3 to ensure alignment.

[0034] (4) Ground connection: Connect the negative electrode surface of each low-frequency piezoelectric chip 1 in step (3) to the common ground electrode 3 through wire 5, and the multiple low-frequency piezoelectric chips 1 form a discrete low-frequency piezoelectric chip array.

[0035] (5) Low-impedance flexible backing layer molding: Low-impedance flexible material is poured into the entire negative electrode surface of the wafer. After the low-impedance flexible material is cured, a low-impedance flexible backing layer 6 is formed. The low-impedance flexible backing layer 6 covers the high-impedance rigid backing layer 2, the low-frequency piezoelectric wafer 1, and the ground common electrode 3. The bottom surface of the low-impedance flexible backing layer 6 is bonded with a flexible FPC board 4. The low-impedance flexible backing layer is located on the outermost layer and provides the probe with an overall low Young's modulus and elastic deformation capability. This allows the probe to maintain good flexibility even when a thick and rigid wafer and a high-impedance backing are embedded.

[0036] Specifically, in step (2), the central axis of each low-frequency piezoelectric crystal coincides with the central axis of the high-impedance rigid backing layer. The secondary axis width W1 of the low-frequency piezoelectric crystal is greater than the secondary axis width W2 of the high-impedance rigid backing layer. The high-impedance rigid backing layer covers the central area of ​​the low-frequency piezoelectric crystal. This ensures that when the probe bends, the most rigid part is limited to the center of the crystal, allowing the probe to have better bending deformation and to fit closely to complex curved surfaces such as pipe bends and wind turbine main shafts. In step (4), the areas on both sides of the low-frequency piezoelectric crystal that are not covered by the high-impedance rigid backing layer form a reserved area. The welding node 7 is set in the reserved area. The conductor 5 is a single-core coaxial conductor with tensile allowance. The single-core coaxial conductor has a reserved tensile deformation length. When the probe bends, the conductor can release stress through deformation instead of directly bearing tensile force. The wire 5 connects the negative electrode surfaces of multiple low-frequency piezoelectric crystals through welding nodes and then connects them to the ground common electrode 3. By welding in areas other than the pre-set hard layer on the negative electrode surface of the crystal, the difficulty of precision operation on the hard backing material is avoided, the manufacturing cost is reduced, and the product consistency is improved.

[0037] The low-impedance flexible backing layer 6 covers the reserved area, thus encasing the welding node 7 and the wire 5. While protecting the welding points, the flexible layer also prevents external forces from directly acting on them, greatly reducing the risk of wire breakage and detachment due to bending fatigue, extending the probe's lifespan when frequently changing testing positions, and eliminating the mechanical vibration transmission path caused by metal components (wires, welding points). Specifically, the low-impedance flexible backing layer 6 separates the adjacent low-frequency piezoelectric wafer 1 and the high-impedance rigid backing layer 2. The low-impedance flexible backing layer 6 contacts the left and right sides and the top surface of the low-frequency piezoelectric wafer, as well as the left and right sides and the top surface of the high-impedance rigid backing layer. The space between adjacent wafers is completely filled with low-modulus flexible backing material, preventing rigid connections between thick wafers through rigid materials. Furthermore, the high-impedance rigid backing layer dampens the vibration of the wafer itself, while the fully covered flexible layer acts as a soft boundary, effectively absorbing and isolating shear waves and stray vibrations propagating through the structure.

[0038] Specifically, in step (3), the thickness of the flexible FPC board must be ≤0.1mm to avoid obstructing the transmission of sound waves. The flexible FPC board 4 is equipped with signal gold fingers 8, grounding gold fingers 9, and connectors 10. The positive electrode path of the low-frequency flexible industrial array ultrasonic probe is, in sequence, connector 10, signal gold fingers 8, and the positive electrode of the low-frequency piezoelectric crystal. The external pulse generator is electrically connected to the positive electrode surface of the low-frequency piezoelectric crystal through the positive electrode path to excite sound waves. The negative electrode path of the flexible industrial array ultrasonic probe is, in sequence, grounding gold fingers 9, ground common electrode 3, wire 5, and welding node 7. The external grounding terminal is electrically connected to the negative electrode surface of the low-frequency piezoelectric crystal through the negative electrode path.

[0039] Specifically, the low-frequency piezoelectric crystal is made of PZT piezoelectric ceramic material, and the high-impedance rigid backing layer is made of a material with high acoustic impedance and high acoustic attenuation performance, preferably a composite material of epoxy resin and tungsten powder. The high acoustic impedance characteristics of the high-impedance rigid backing layer effectively match the high mechanical energy output of the thick crystal, and its high attenuation coefficient can quickly absorb more than 90% of the energy radiated backward from the crystal. This fundamentally solves the defects of pulse width and low sensitivity in the "soft backing" scheme, achieving narrow pulse (≤2 cycles) and high signal-to-noise ratio, ensuring the accuracy of thickness measurement and imaging. The low-impedance flexible backing layer is made of a material with low Young's modulus and high elastic deformation capability, preferably a silicone rubber or polyurethane blend, providing the probe with overall low Young's modulus and elastic deformation capability. This allows the probe to maintain good flexibility even when a thick and rigid crystal and high-impedance backing are embedded, enabling it to closely fit complex curved surfaces such as pipe bends and wind turbine main shafts, solving the problems of inflexibility and poor coupling in the "hard backing" scheme.

[0040] Specifically, the low-frequency piezoelectric chip and the ground common electrode are bonded to the high-impedance rigid backing layer and the flexible FPC board respectively using acoustic adhesive. That is, in step 2, the negative electrode surface of the low-frequency piezoelectric chip is bonded to the high-impedance rigid backing layer using acoustic adhesive, and the upper surface of the ground common electrode is bonded to the high-impedance rigid backing layer using acoustic adhesive. In step 3, the bottom surface of the low-frequency piezoelectric chip and the bottom surface of the ground common electrode are bonded to the flexible FPC board using acoustic adhesive.

[0041] The ultrasonic probes prepared using the above method, such as Figure 2-4 As shown, the array includes a discrete low-frequency piezoelectric chip array, a high-impedance rigid backing layer 2, a ground common electrode 3, a wire 5, a low-impedance flexible backing layer 6, and a flexible FPC board 4. The discrete low-frequency piezoelectric chip array is composed of multiple independent low-frequency piezoelectric chips 1. The high-impedance rigid backing layer 2 is bonded to the negative electrode surface of each low-frequency piezoelectric chip 6. The negative electrode surface of each low-frequency piezoelectric chip is connected to the ground common electrode 3 through the wire 5. The peripheral low-impedance flexible backing layer 6 covers the discrete low-frequency piezoelectric chip array 1, the high-impedance rigid backing layer 2, the ground common electrode 3, and the wire 5. The flexible FPC board 4 is installed at the bottom of the discrete low-frequency piezoelectric chip array and at the bottom of the low-impedance flexible backing layer 6.

[0042] An application of an ultrasonic probe manufactured using the above method, such as... Figure 5 As shown, the ultrasonic probe fits tightly against the object being tested during the testing application. Because the low-impedance flexible backing layer 6 covers the high-impedance rigid backing layer 2, the low-frequency piezoelectric chip 1, and the ground common electrode 3 on the outermost side, the probe as a whole can still maintain good flexibility and fit tightly against the curved surface of the object being tested. The surface of the chip directly emits sound waves through the flexible FPC layer 4 to the object being tested. At the same time, the negative electrode surface of the chip generates back sound waves. The high-impedance rigid backing layer 2 absorbs more than 90% of the back wave energy. The remaining back waves and the vibrations of the welding node 7 and the single-core coaxial wire 5 are absorbed by the low-impedance flexible backing layer 6, which also provides overall flexibility and blocks crosstalk between array elements.

[0043] In summary, the advantages of the method of the present invention are as follows:

[0044] (i) The rigid backing layer is assembled first, followed by the assembly of the flexible FPC board, grounding connection, and low-impedance flexible backing layer molding. This rigid backing layer pre-positioning and finally low-impedance flexible backing layer overall potting and encapsulation process avoids the complexity of simultaneously dealing with the interface of two materials, and can make the manufactured low-frequency flexible industrial array ultrasonic probe have a composite backing structure.

[0045] (ii) The secondary axis width W1 of the low-frequency piezoelectric chip is greater than the secondary axis width W2 of the high-impedance rigid backing layer, leaving enough space for arranging welding nodes and single-core coaxial wires, thus avoiding the difficulty of precision operation on the rigid backing material.

[0046] (iii) Active damping of wafer vibration is achieved through a high-impedance hard layer, while a soft boundary condition is constructed using a fully covered flexible layer, forming a multi-level vibration suppression mechanism. The high-impedance hard layer absorbs most of the back wave energy of the vibration source through its material properties; the flexible layer, through its low stiffness, acts as a soft boundary to absorb and isolate shear waves propagating from the structure, and also completely blocks the vibration transmission path caused by metal components, thus achieving high acoustic performance and high flexibility. This technical solution breaks through the physical limitations of a single material and realizes the decoupling and synergy of acoustic and mechanical functions.

[0047] (iv) The flexible layer completely encapsulates both the welding joint and the single-core coaxial conductor. The conductor can release stress through deformation instead of directly bearing tensile force. All welding joints are infused within the flexible backing layer. While protecting the welding joints, the flexible layer also prevents external forces from acting directly on them, greatly reducing the risk of wire breakage and desoldering caused by bending fatigue. This extends the service life of the probe when frequently changing testing positions and solves the problem of traditional rigid conductors easily breaking when the flexible probe is bent. It forms a dual protection of electromagnetic shielding and mechanical isolation, completely blocking the vibration transmission path caused by metal components. (v) The single-core coaxial conductor has a specific tensile deformation length reserved in the section connecting to the negative electrode of the chip. Stress buffering is achieved through an elastic deformation mechanism. When the probe bends, the conductor absorbs strain energy through geometric deformation, preventing the conductor body from directly bearing tensile loads and further solving the problem of conductor breakage.

[0048] The above description is a further detailed explanation of the present invention in conjunction with specific preferred embodiments. It should not be considered that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the protection scope of the present invention.

Claims

1. A method for manufacturing a low-frequency flexible industrial array ultrasonic probe, characterized in that, The steps are as follows: (1) Wafer pretreatment: Clean the positive and negative electrode surfaces of multiple low-frequency piezoelectric wafers; (2) Rigid backing layer assembly: Select an appropriate number of low-frequency piezoelectric chips, and then bond a high-impedance rigid backing layer to the negative electrode surface of each low-frequency piezoelectric chip. One low-frequency piezoelectric chip and one high-impedance rigid backing layer constitute one assembly. A high-impedance rigid backing layer is also bonded above the ground common electrode. (3) Flexible FPC board assembly: The various assemblies obtained in step (2) are bonded to the flexible FPC board, and the ground common electrode is also bonded to the flexible FPC board. The flexible FPC board is located at the bottom of the low-frequency piezoelectric chip and the ground common electrode. (4) Ground connection: Connect the negative electrode surface of each low-frequency piezoelectric chip in step (3) to the common ground electrode through wires, and multiple low-frequency piezoelectric chips form a discrete low-frequency piezoelectric chip array. (5) Low-impedance flexible backing layer molding: Low-impedance flexible material is poured into the entire negative electrode surface of the wafer. After the low-impedance flexible material is cured, a low-impedance flexible backing layer is formed. The low-impedance flexible backing layer covers the high-impedance rigid backing layer, the low-frequency piezoelectric wafer, and the ground common electrode. A flexible FPC board is bonded to the bottom surface of the low-impedance flexible backing layer.

2. The method for manufacturing a low-frequency flexible industrial array ultrasonic probe according to claim 1, characterized in that, In step (2), the central axis of each low-frequency piezoelectric wafer coincides with the central axis of the high-impedance hard backing layer. The secondary axis width W1 of the low-frequency piezoelectric wafer is greater than the secondary axis width W2 of the high-impedance hard backing layer. The high-impedance hard backing layer covers the central region of the low-frequency piezoelectric wafer.

3. The method for manufacturing a low-frequency flexible industrial array ultrasonic probe according to claim 2, characterized in that, In step (4), the areas on both sides of the low-frequency piezoelectric chip that are not covered by the high-impedance hard backing layer form a reserved area. The welding node is set in the reserved area. The wire is a single-core coaxial wire with stretching allowance. The wire is connected to the negative electrode surface of the low-frequency piezoelectric chip through the welding node and then connected to the ground common electrode.

4. The method for manufacturing a low-frequency flexible industrial array ultrasonic probe according to claim 3, characterized in that, A low-impedance flexible backing layer covers the reserved area, thereby encapsulating the welding joints and conductors.

5. The method for manufacturing a low-frequency flexible industrial array ultrasonic probe according to claim 4, characterized in that, The low-impedance flexible backing layer separates the adjacent low-frequency piezoelectric wafer and the high-impedance rigid backing layer. The low-impedance flexible backing layer contacts the left and right sides and the top surface of the low-frequency piezoelectric wafer, as well as the left and right sides and the top surface of the high-impedance rigid backing layer.

6. The method for manufacturing a low-frequency flexible industrial array ultrasonic probe according to claim 3, characterized in that, In step (3), the thickness of the flexible FPC board must be ≤0.1mm. The flexible FPC board is equipped with signal gold fingers, ground gold fingers, and connectors. The positive path of the low-frequency flexible industrial array ultrasonic probe is, in sequence, connector, signal gold fingers, and the positive electrode of the low-frequency piezoelectric crystal. The external pulse generator is electrically connected to the positive electrode surface of the low-frequency piezoelectric crystal through the positive path to excite sound waves. The negative path of the flexible industrial array ultrasonic probe is, in sequence, connector, ground gold fingers, ground common electrode, single-core coaxial wire, and welding node. The external grounding terminal is electrically connected to the negative electrode surface of the low-frequency piezoelectric crystal through the negative path.

7. The method for manufacturing a low-frequency flexible industrial array ultrasonic probe according to claim 1, characterized in that, The low-frequency piezoelectric wafer is made of PZT piezoelectric ceramic material, the high-impedance hard backing layer is made of a material with high acoustic impedance and high acoustic attenuation performance, and the low-impedance flexible backing layer is made of a material with low Young's modulus and high elastic deformation capability.

8. A method for manufacturing a low-frequency flexible industrial array ultrasonic probe according to claim 7, characterized in that, The high-resistivity rigid backing layer is made of a composite material of epoxy resin and tungsten powder, while the low-resistivity flexible backing layer is made of a blend of silicone rubber or polyurethane.

9. A method for manufacturing a low-frequency flexible industrial array ultrasonic probe according to claim 1, characterized in that, The low-frequency piezoelectric crystal and the ground common electrode are bonded to the high-impedance rigid backing layer and the flexible FPC board respectively by acoustic adhesive.

10. An application of an ultrasonic probe manufactured using the method of claims 1-9, characterized in that, When the ultrasonic probe is used for testing, the surface of the chip directly emits sound waves that pass through the flexible FPC layer to the object being tested. At the same time, the negative electrode surface of the chip generates back sound waves. The high-impedance rigid backing layer absorbs more than 90% of the back wave energy, and the remaining back waves and the vibrations of the welded joints and single-core coaxial wires are absorbed by the low-impedance flexible backing layer.

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