Piezoelectric sensor preparation method and piezoelectric sensor

Abstract

The invention discloses a preparation method of a piezoelectric sensor and the piezoelectric sensor, and relates to the technical field of piezoelectric sensors. The preparation method of the piezoelectric sensor comprises the following steps: arranging a piezoelectric ceramic piece subjected to cutting and surface pretreatment in a forming mold, pouring UHPC (Ultra High Performance Concrete) slurry subjected to vacuum degassing, and forming a piezoelectric composite functional element after vibration compaction and maintenance treatment; precisely cutting the piezoelectric composite functional element and preparing an electrode, and then bonding a conductive electrode plate on the surface of the electrode and welding a shielding lead; and fixing the piezoelectric composite functional element connected with the lead in a packaging mold, pouring an epoxy packaging material subjected to degassing treatment, and carrying out curing and demolding treatment to obtain the piezoelectric sensor. UHPC serves as a base material of a piezoelectric composite functional element, the acoustic impedance and the thermal expansion coefficient of the UHPC are highly matched with those of a common concrete structure, and the problems of interface debonding, stress transfer distortion and the like existing between a traditional metal packaging sensor and concrete are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of piezoelectric sensors, in particular to a preparation method of a piezoelectric sensor and the piezoelectric sensor. BACKGROUND

[0002] With the development of civil engineering structures towards intelligence and digitization, intelligent sensing materials with self-sensing capability play a key role in real-time monitoring of structural state. Piezoelectric materials are widely used in the detection of physical quantities such as stress, strain, vibration and damage evolution due to their fast response speed, high sensitivity and excellent dynamic performance.

[0003] In the prior art, piezoelectric ceramics are often used as sensing functional bodies, but they are usually embedded in concrete structures after being packaged with metal shells. Such traditional piezoelectric sensors have the following outstanding problems:

[0004] Poor interface compatibility: there is a significant acoustic impedance difference and mismatch in thermal expansion coefficient between the metal packaging material and the concrete matrix, which leads to distortion of stress transmission and affects signal accuracy;

[0005] Insufficient durability: corrosion and debonding easily occur at the interface between metal and concrete, especially in long-term service or harsh environments, which reduces the stability of the sensor;

[0006] Low assembly precision: the parallelism of the functional element and the loading surface cannot be guaranteed by traditional packaging methods, which leads to uneven stress and introduces measurement errors;

[0007] Severe signal interference: external electromagnetic environment causes interference during lead transmission, reducing the signal-to-noise ratio.

[0008] In recent years, researchers have attempted to embed piezoelectric ceramics directly into cement matrix to form piezoelectric composites in order to improve the material compatibility with concrete structures; however, ordinary cement matrix has low strength, high brittleness and high porosity, which limits the mechanical performance and long-term stability of the sensor. SUMMARY

[0009] To solve the above problems, the present application provides a preparation method of a piezoelectric sensor and a piezoelectric sensor, which embeds a piezoelectric ceramic sheet into an ultra-high performance concrete matrix to form a piezoelectric composite functional element, and then prepares electrodes, connects leads and encapsulates with epoxy to finally obtain a piezoelectric sensor that is highly compatible with concrete structures, has excellent mechanical performance, stable signal output and long-term durability. A piezoelectric sensor is provided, which can be obtained based on different preparation methods under different conditions.

[0010] The first technical solution adopted by the present application is to provide a preparation method of a piezoelectric sensor, comprising the following steps:

[0011] The cut and surface pretreated piezoelectric ceramic piece is arranged in a forming mold, a UHPC (Ultra-High Performance Concrete, ultra-high performance concrete) slurry subjected to vacuum degassing is cast, and after vibration compaction and curing treatment, a piezoelectric composite functional element is formed.

[0012] The piezoelectric composite functional element is precisely cut and electrodes are prepared, and then conductive electrode pieces are bonded on the electrode surface and shielding leads are welded.

[0013] The piezoelectric composite functional element connected with the leads is fixed in a packaging mold, a degassed epoxy-based packaging material is cast, and after curing and demolding treatment, the piezoelectric sensor is obtained.

[0014] In an optional embodiment, the vibration compaction operation specifically comprises: after the UHPC slurry is cast into the forming mold, the forming mold is subjected to vibration treatment to expel air bubbles inside the slurry and improve the compactness and uniformity of the functional element.

[0015] In an optional embodiment, the curing treatment comprises the following steps:

[0016] The cast and compacted test piece is subjected to static curing; the duration of the static curing is a first preset duration.

[0017] The test piece subjected to static curing is subjected to program-controlled temperature steam curing, which comprises heating to a target temperature at a first controllable rate and maintaining the temperature for a second preset duration, and then cooling to room temperature at a second controllable rate.

[0018] In an optional embodiment, the UHPC slurry is prepared by mixing and stirring cement-based binder, water and high-efficiency water reducing agent, and then subjected to the vacuum degassing treatment.

[0019] In an optional embodiment, the conductive electrode piece is a metal foil coated with conductive adhesive on one side, and the conductive adhesive layer is bonded and electrically connected to the electrode surface of the functional element.

[0020] In an optional embodiment, the shielding lead is a shielding coaxial cable, and the core wire is electrically connected to the conductive electrode piece by welding.

[0021] In an optional embodiment, the packaging mold is a mold prepared by additive manufacturing technology, and a guide positioning structure is arranged inside the cavity of the mold to ensure that the functional element and the mold side wall maintain a predetermined relative position and parallelism when the packaging material is cast.

[0022] In an alternative embodiment, the epoxy-based encapsulation material is prepared by mixing epoxy resin, curing agent, cement-based inorganic filler and functional additives in a predetermined ratio.

[0023] In an alternative embodiment, the degassing process of the epoxy-based encapsulation material before pouring is performed by vacuum extraction to remove the air bubbles introduced during the mixing process.

[0024] The second technical solution adopted by the present application is to provide a piezoelectric sensor prepared by the preparation method of any one of the preceding embodiments.

[0025] Compared with the prior art, the present application has at least one of the following beneficial effects:

[0026] 1. By using ultra-high performance concrete (UHPC) as the matrix material of the piezoelectric composite functional element, the acoustic impedance and thermal expansion coefficient are highly matched with ordinary concrete structures, effectively solving the problems of interface debonding and stress transmission distortion between traditional metal packaged sensors and concrete.

[0027] 2. The UHPC matrix has ultra-high strength, high density and excellent crack resistance, which can effectively protect the internal piezoelectric ceramic element and improve the structural stability and service life of the sensor under complex load, humid environment and long-term service conditions.

[0028] 3. The packaging mold is prepared by using additive manufacturing technology, and a guide positioning structure is arranged in the mold, which can accurately control the position and attitude of the piezoelectric composite functional element during the packaging process, ensure that it is highly parallel to the loading surface, and reduce the assembly error.

[0029] 4. The metal foil coated with conductive adhesive on one side is used as the conductive electrode sheet to realize firm bonding and good electrical connection with the electrode surface of the functional element; in combination with the shielded coaxial cable as the lead wire, external electromagnetic interference is effectively suppressed, and signal noise is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0031] Among them:

[0032] Figure 1 The flowchart of the preparation method of the piezoelectric sensor provided by an embodiment of the present application is shown in the figure.

[0033] Figure 2 A model schematic diagram of a piezoelectric composite functional element provided by an embodiment of the present application;

[0034] Figure 3 A model schematic diagram of a piezoelectric composite functional element provided by an embodiment of the present application; Figure 2 A model schematic diagram of a piezoelectric composite functional element provided by an embodiment of the present application;

[0035] Figure 4 A model schematic diagram of a piezoelectric composite functional element provided by an embodiment of the present application;

[0036] Figure 5 A model schematic diagram of a piezoelectric composite functional element provided by an embodiment of the present application;

[0037] Figure 6 A model schematic diagram of a piezoelectric composite functional element provided by an embodiment of the present application;

[0038] Figure 7 A model schematic diagram of a piezoelectric composite functional element provided by an embodiment of the present application; DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the drawings in the embodiments of the present application. It can be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application. In addition, it should be noted that, for the convenience of description, only the parts related to the present application are shown in the drawings, but not all the structures. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0040] The terms "first", "second", and the like in the present application are used to distinguish different objects, but not to describe a specific order. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units is not limited to the listed steps or units, but optionally includes other steps or units not listed or optionally includes other steps or units inherent to the process, method, product or device.

[0041] In this document, the term "embodiment" means that the specific features, structures or characteristics described in connection with the embodiment can be included in at least one embodiment of the present application. The phrase appears in various places in the specification does not necessarily refer to the same embodiment, nor is it mutually exclusive or alternative to other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0042] The piezoelectric sensor in the prior art is packaged with a metal shell, which causes significant acoustic impedance mismatch between the sensor and the concrete structure, large difference in thermal expansion coefficient, and poor interface bonding performance, etc., which easily causes stress transmission distortion, high signal noise, interface debonding or corrosion during long-term service, etc., seriously affecting the sensing accuracy and durability. In addition, the traditional manufacturing process cannot accurately control the relative position and parallelism of the functional element and the loading surface, further aggravating the measurement deviation. The piezoelectric sensor provided by the embodiment of the application is directly embedded in the concrete slurry which is vacuum degassed and vibrationally compacted to form a composite functional element, which fundamentally improves the material compatibility of the sensor and the concrete matrix. In combination with the overall packaging process of the epoxy-based material, the disadvantages of poor interface matching, signal distortion and insufficient durability are effectively solved, and the measurement accuracy and long-term stability of the sensor are significantly improved.

[0043] As shown in Figures 1-7 , the flowchart of the preparation method of the piezoelectric sensor provided by the embodiment of the application comprises the following steps: Figure 1 The piezoelectric sensor provided by the embodiment of the application comprises the following steps:

[0044] The piezoelectric ceramic sheet cut and surface pretreated is arranged in a forming mold, and the UHPC slurry vacuum degassed is poured and vibrationally compacted, cured and treated to form a piezoelectric composite functional element. In this embodiment, a PZT-5 type piezoelectric ceramic block with a size of 10mmx10mmx10mm is selected, which is fixed on a tempered glass slide by epoxy resin bonding, and is precisely positioned in the scribe machine by using a vacuum chuck.

[0045] A diamond blade with a thickness of 1.2mm is used to cut 4 times in the vertical direction to form an array of piezoelectric ceramic columns, with a cutting depth of 8mm and a ceramic base of 2mm thick at the bottom to enhance the structural stability. After cutting, the ceramic assembly is immersed in anhydrous ethanol for ultrasonic cleaning for 5 minutes to remove surface debris and organic contaminants, and then dried in a 60°C oven for 2 hours to complete the surface pretreatment.

[0046] A mold cavity with a size of 12mmx12mmx10mm is prepared by using a light-cured 3D printing technology, which is provided with a positioning groove inside for accurately fixing the position of the piezoelectric ceramic sheet. The pretreated piezoelectric ceramic sheet is arranged at the central position of the bottom of the mold to ensure that the polarization direction is perpendicular to the upper and lower surfaces of the mold.

[0047] The concrete slurry is prepared by mixing and stirring cement-based binder, water and high-efficiency water reducing agent, and then vacuum degassing. The degassing treatment of the epoxy-based packaging material before pouring is performed by vacuum pumping to remove the air bubbles introduced during the mixing process.

[0048] In the present embodiment, the cement-based powder (containing ordinary Portland cement, silica fume, fine quartz sand) 150 parts, deionized water 18 parts, polycarboxylic acid superplasticizer 1.55 parts are weighed by mass ratio, added into the mixer and mixed uniformly, the stirring time is 5 minutes. Then the slurry is transferred to a sealed container and placed in a vacuum degassing machine for 3 minutes of vacuum treatment to completely remove the air bubbles introduced during stirring and improve the density and fluidity of the slurry.

[0049] In other embodiments, the ratio of cement-based cementitious material, water and superplasticizer can be adjusted additionally, and no limitation is made thereto.

[0050] The degassed UHPC slurry is slowly poured into the forming mold where the piezoelectric ceramic sheet has been placed, completely covering the ceramic sheet and being slightly higher than the upper surface of the mold; after the concrete slurry is poured into the forming mold, the forming mold is vibrated to remove the air bubbles in the slurry and improve the density and uniformity of the functional element.

[0051] In the present embodiment, after pouring, the mold is placed on a small vibration table for vibration and compaction treatment, the vibration time is controlled to be 10 seconds and the frequency is 50 Hz, to further remove the residual air bubbles in the slurry, promote the UHPC slurry to fully fill the gap between the ceramic columns, and improve the uniformity and density of the composite material; immediately after pouring and compacting, the surface of the mold is sealed with plastic film to prevent water evaporation.

[0052] The curing process includes the following steps:

[0053] The poured and compacted test piece is placed for curing; the duration of the standing curing is a first preset duration;

[0054] The test piece after standing curing is subjected to program-controlled temperature steam curing, which includes heating to a target temperature at a first controllable rate and maintaining the temperature for a second preset duration, and then cooling to room temperature at a second controllable rate.

[0055] In the present embodiment, the test piece is first cured in a standard curing box at 20±0.5℃ for 24 hours; then transferred to a steam curing box, heated to 90±1℃ at a rate not exceeding 15℃ / h, and maintained at a constant temperature for 48 hours, and then slowly cooled to room temperature at a rate not greater than 15℃ / h, to complete the program-controlled temperature curing. After cooling, the piezoelectric composite functional element blank with a size of about 11.5mm×11.5mm×9mm is obtained.

[0056] The blank is then precisely cut and trimmed to ensure that the upper and lower surfaces are flat and the parallelism is less than 0.01mm, and silver electrode preparation is performed, to finally obtain a high-performance UHPC-based piezoelectric composite functional element.

[0057] The piezoelectric composite functional element is precisely cut and electrodes are prepared, and then conductive electrode sheets are bonded to the surface of the electrodes and shielded lead wires are welded; first, the piezoelectric composite functional element blank after demoulding is precisely cut; a high-precision diamond scribe machine is used to cut and trim along the preset size on both sides under the protection of cooling water, and finally the element is processed to the target size of 10mm×10mm×7mm; the feed speed and spindle speed are controlled during cutting to ensure that the flatness of the upper and lower surfaces is better than 0.01mm, and the non-parallelism between the two main stress surfaces is less than 0.01mm, so as to ensure uniform stress transmission during subsequent loading and avoid measurement errors caused by eccentric compression.

[0058] After cutting, the upper and lower surfaces of the element are ultrasonically cleaned with anhydrous ethanol for 5 minutes to remove surface residual particles and dust, and then placed in a 60°C oven for drying for 2 hours; after the element cools to room temperature, a magnetron sputtering device is used to uniformly spray silver on the upper and lower surfaces to form a conductive metal layer with a thickness of about 3-5μm as the base electrode; the silver spraying process is carried out in a clean environment to ensure that the electrode layer is dense, continuous, and free of open circuit or pinhole defects. After silver spraying, the element is again placed in a 60°C oven for 24 hours to eliminate moisture and enhance the adhesion of the silver layer to the UHPC substrate.

[0059] The conductive electrode sheet is a metal foil sheet coated with conductive adhesive on one side, which is bonded and electrically connected to the electrode surface of the functional element through the conductive adhesive layer coated thereon; in this embodiment, a copper foil with a thickness of 0.1mm coated with conductive adhesive (such as silver adhesive or epoxy conductive adhesive) on one side is selected as the conductive electrode sheet.

[0060] The conductive adhesive surface of the copper foil is precisely aligned with the silver-sprayed electrode surface of the piezoelectric composite element, gently pressed together, and then slowly scraped flat from the center to the edge with a scraper to exclude air bubbles, ensuring firm bonding and low contact resistance. To avoid short circuiting of the upper and lower electrodes, two pieces of copper foil are bent and extended outward from the opposite sides of the element, forming a lead connection area.

[0061] The shielded lead wire is a shielded coaxial cable, and the core wire is electrically connected to the conductive electrode sheet by welding; an ultra-flexible and high-density shielded coaxial cable is selected as the lead wire, with a tinned copper wire as the core wire and a copper mesh shielding layer on the outer layer, which can effectively suppress electromagnetic interference. A low-temperature soldering station (temperature controlled within 280°C) is used to weld the core wire of the shielded cable to the bent end of the upper and lower electrode sheets, with small and firm welding points to avoid overheating damage to the UHPC substrate or piezoelectric ceramic. After welding, the welding points are locally wrapped with an insulating heat-shrinkable tube to prevent short circuiting. The other end of the lead wire is connected to a BNC signal connector to form a complete signal output path.

[0062] The piezoelectric composite functional element with the connected lead wire is fixed in a packaging mold, and a degassed epoxy-based packaging material is poured, and after curing and demoulding, a piezoelectric sensor is obtained.

[0063] The encapsulation mold is a mold prepared by an additive manufacturing technique, and a guide positioning structure is arranged inside a cavity of the mold, which is used to ensure that a functional element and a side wall of the mold maintain a preset relative position and parallelism when pouring an encapsulation material.

[0064] In the embodiment, a cuboid-shaped plastic mold is prepared by using a light-curing 3D printing technology, the overall size of the mold is 20 mm x 18 mm x 13 mm, the size of the internal cavity is 17 mm x 15 mm x 11 mm, and the internal cavity is used to form the final sensor shape. A guide rail clamping groove structure is symmetrically arranged inside the cavity on both sides, the width of the clamping groove is slightly larger than the thickness (7.1 mm) of the piezoelectric composite functional element, the depth is 8 mm, and the clamping groove is connected with the side wall of the mold through a simple fulcrum, so that the clamping groove has a certain elastic positioning capacity. The guide rail structure can realize accurate embedding and positioning of the functional element, and ensure that the upper and lower surfaces of the functional element are parallel to the loading surface of the mold.

[0065] The piezoelectric composite functional element connected with the BNC lead wire is slowly inserted into the mold cavity along the guide rail, so that the element is placed in the middle, the upper and lower surfaces are parallel to the top and bottom surfaces of the mold, the lead wire is led out through the lead wire outlet reserved on the side of the mold, and excessive bending is avoided to cause the welding point to break. After being fixed, the posture of the element is checked to ensure that there is no inclination or deviation.

[0066] The epoxy-based encapsulation material is mixed by epoxy resin, curing agent, cement-based inorganic filler and functional additives in a predetermined ratio. 3 parts of 42.5 grade ordinary portland cement, 18 parts of epoxy resin E-5, and 1 part of aluminum oxide powder (as inorganic filler) are weighed according to the mass ratio, and a polyamide curing agent with a mass ratio of 5:1 to the epoxy resin is additionally taken. First, the epoxy resin is heated to 60°C to reduce the viscosity, and the curing agent is stirred uniformly; then the cement and aluminum oxide powder are pre-mixed uniformly, slowly added to the epoxy mixture, and continuously stirred for 5 minutes to form a uniform slurry. The mixed encapsulation material is transferred into a vacuum degassing machine for vacuum treatment for 3 minutes to completely remove the air bubbles introduced during stirring, and to improve the material density and insulation performance.

[0067] The degassed epoxy encapsulation material is slowly poured along one side of the mold to avoid impacting the functional element. During the pouring process, the mold is kept horizontal to allow the material to flow naturally and fill the cavity, completely covering the piezoelectric composite element and filling the entire cavity. After pouring is completed, the mold is placed in a static environment and cured at 20°C for 48 hours to allow the epoxy material to fully crosslink and cure.

[0068] After curing, the precision scriber is used to cut along the outer edge of the mold to remove the excess mold material, and a complete piezoelectric sensor with a size of 17mmx15mmx11mm is obtained. The cutting speed is controlled to avoid vibration damage to the internal components. After demolding, the sensor is placed in an electric heating constant temperature drying oven and dried at 60°C for 4 hours to further remove trace moisture and improve insulation performance, so as to obtain a UHPC-based piezoelectric sensor with complete structure, reliable lead, and dense packaging, which can be used for embedded stress and strain monitoring in concrete structures.

[0069] In summary, the preparation method of the piezoelectric sensor includes the following steps: arranging the piezoelectric ceramic sheet cut and surface pretreated in the forming mold, pouring the UHPC slurry degassed by vacuum, and forming the piezoelectric composite functional element after vibration compaction and curing treatment; the piezoelectric composite functional element is precisely cut and electrodes are prepared, then conductive electrode sheets are bonded on the surface of the electrodes and shielding leads are welded; the piezoelectric composite functional element connected with the leads is fixed in the packaging mold, the epoxy-based packaging material is poured after degassing treatment, and the piezoelectric sensor is obtained after curing and demolding treatment. By using UHPC as the matrix material of the piezoelectric composite functional element, its acoustic impedance and thermal expansion coefficient are highly matched with ordinary concrete structures, solving the problems of interface debonding and stress transmission distortion between traditional metal packaged sensors and concrete.

[0070] As shown in Figure 6 , a model schematic diagram of the piezoelectric sensor provided by an embodiment of the present application is shown. Figure 6 The piezoelectric sensor is prepared by the preparation method of any one of the piezoelectric sensors described above.

[0071] The performance of the piezoelectric sensor can also be verified by frequency response analysis. Specifically, the corresponding frequency response curve of the prepared piezoelectric sensor is obtained under different amplitudes; as shown in Figure 7 , a frequency response curve schematic diagram of the piezoelectric sensor under different amplitudes provided by an embodiment of the present application is shown. Figure 7

[0072] In the several embodiments provided by the present application, it should be understood that the disclosed method and device can be implemented in other ways. For example, the device embodiments described above are only schematic. The division of the modules or units is only a logical function division, and there can be another division manner in actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0073] ​The units described as separate components may or may not be physically separate, and the components displayed as units may or may not be physical units, that is, may be located in one place, or may be distributed to multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the present embodiment scheme.

[0074] In addition, each functional unit in each embodiment of the present application can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0075] The above is only an embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent flow transformation using the content of the present application specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method of preparing a piezoelectric sensor, characterized by, The method comprises the following steps: arranging the cut and surface pretreated piezoelectric ceramic sheet in a forming mold, pouring a vacuum degassed UHPC slurry, and after vibration compaction and curing treatment, forming a piezoelectric composite functional element; precisely cutting the piezoelectric composite functional element and preparing electrodes, then bonding conductive electrode sheets on the electrode surface and welding shielding leads; fixing the piezoelectric composite functional element with leads in a packaging mold, pouring a degassed epoxy-based packaging material, and after curing and demolding treatment, obtaining the piezoelectric sensor.

2. The production method according to claim 1, characterized by, The vibration compaction operation specifically comprises: after the UHPC slurry is poured into the forming mold, vibration treatment is performed on the forming mold to expel the air bubbles inside the slurry and improve the compactness and uniformity of the functional element.

3. The production method according to claim 1, characterized by, The curing treatment comprises the following steps: After the compacted test piece is placed for curing, the duration of the static curing is a first preset duration; After the test piece is cured, it is subjected to program-controlled temperature steam curing, which comprises heating to a target temperature at a first controllable rate and maintaining the temperature for a second preset duration, and then cooling to room temperature at a second controllable rate.

4. The method of claim 1, wherein, The UHPC slurry is prepared by mixing and stirring cement-based binder, water and high-efficiency water reducing agent, and then performing vacuum degassing treatment.

5. The preparation method according to claim 1, characterized in that, The conductive electrode sheet is a metal foil coated with conductive adhesive on one side, which is bonded and electrically connected to the electrode surface of the functional element through the conductive adhesive layer.

6. The production method according to claim 5, wherein The shielding lead is a shielded coaxial cable, and the core wire is electrically connected to the conductive electrode sheet by welding.

7. The preparation method according to claim 1, characterized in that, The packaging mold is a mold prepared by additive manufacturing technology, and a guide positioning structure is arranged inside the cavity of the mold to ensure that the functional element and the mold side wall maintain a predetermined relative position and parallelism when pouring the packaging material.

8. The method of claim 1, wherein, The epoxy-based packaging material is prepared by mixing epoxy resin, curing agent, cement-based inorganic filler and functional additives in a predetermined ratio.

9. The preparation method according to claim 8, characterized in that, Before pouring the epoxy-based packaging material, the degassing treatment is performed by vacuum pumping to remove the air bubbles introduced during the material mixing process.

10. A piezoelectric sensor, characterized by, The piezoelectric sensor is prepared by the preparation method of any one of claims 1 to 9.

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