Microcomputer electroacoustic emission sensor and preparation method thereof

Abstract

The invention belongs to the technical field of communication, and provides a microcomputer electroacoustic emission sensor and a preparation method thereof.The microcomputer electroacoustic emission sensor comprises a substrate device and a cantilever device partially attached to the substrate device, and a gas cavity is formed in the attached position and the non-attached position; a through hole is etched in the cantilever device, and the cantilever device and the substrate device penetrate through the gas cavity through a through hole gap to form a liquid-gas cantilever bridge structure based on surface tension; and the space of one side, close to the through hole, of the gas cavity is gradually increased. By utilizing the surface tension of a liquid medium, a gas cavity is formed below the cantilever structure, a liquid-cantilever-gas structure is formed, and liquid cannot enter the cavity structure under the action of the surface tension by controlling the width of a gap between the piezoelectric cantilever structure and the surrounding wall structure; direct detection of acoustic emission signals propagated in liquid in the storage tank is realized, and the sensitivity of the sensor is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of communication, and particularly relates to a micro-electromechanical acoustic emission sensor and a preparation method thereof. BACKGROUND

[0002] In the petrochemical industry, the bottom plate of atmospheric storage tanks often has safety hazards such as corrosion perforation due to the influence of various factors during long-term service. The main influencing factors include the chemical corrosion effect of the storage medium, the cyclic load caused by liquid level fluctuation, and the uneven settlement of the foundation, etc. In view of this problem, acoustic emission detection technology has become an effective means for evaluating the integrity of the tank bottom plate due to its unique advantages. Acoustic emission technology can realize non-destructive evaluation of the defect position and severity by monitoring the elastic wave signals generated by the corrosion or stress change of the bottom plate material under normal operating conditions of the tank. Compared with traditional detection methods, acoustic emission detection has the characteristics of strong real-time performance and simple operation, and is widely used in online monitoring of storage tanks.

[0003] However, the traditional external acoustic emission tank detection technology still has certain limitations. The acoustic emission signals generated by the corrosion or leakage of the bottom plate usually have low amplitude, and significant attenuation occurs during propagation to the tank wall. In particular, when the defect is located in the central region of the bottom plate, the sensors installed on the outer wall often cannot effectively capture these weak signals. This phenomenon leads to insufficient defect recognition ability of the traditional acoustic emission detection method in the central region of the bottom plate, thereby affecting the reliability of the overall evaluation result. SUMMARY

[0004] In view of the above problems, the present application provides a micro-electromechanical acoustic emission sensor, which comprises: a base device and a cantilever device attached to the base device, wherein the attached part and the unattached part form a gas cavity; a through hole etched through the cantilever device, and the cantilever device and the base device pass through the gas cavity through the through hole gap to form a liquid-gas cantilever bridge structure based on surface tension; The space of the gas cavity near the through hole side gradually increases.

[0005] Further, the cantilever device and the base device are attached on one side of the cantilever device and the base device, and an arc-shaped section is recessed in the opposite direction along the surface, and a stepped structure is formed between the end of the arc-shaped section and the surface of the cantilever device; The through hole is arranged at the end of the arc-shaped section.

[0006] Further, the base device comprises a first substrate, and a metal circuit layer, a first resin layer and an adhesive layer are sequentially arranged on the first substrate, the metal circuit layer, the first resin layer and the adhesive layer are arranged at intervals, and the adhesive layer covers the first substrate. The adhesive layer on which the cantilever device is attached to the metal circuit layer forms a gas cavity.

[0007] Further, the cantilever device comprises a second resin layer, a piezoelectric material layer and a third resin layer covering the piezoelectric material layer are sequentially arranged on the second resin layer, wherein the arc-shaped section is arranged on the third resin layer, and the thickness of the third resin layer close to the through hole is smaller than the thickness of the third resin layer away from the through hole.

[0008] Further, the piezoelectric material layer around the through hole is provided with a notch, and the notch width is greater than the gap width of the through hole.

[0009] Further, a through circuit connection hole is formed along the second resin layer, the piezoelectric material layer, the third resin layer, the adhesive layer and the first resin layer, and the circuit connection hole is in contact with the metal circuit layer. A circuit connection layer is arranged at the circuit connection hole, and the circuit connection layer is electrically connected with the metal circuit layer and the piezoelectric material layer. A protective layer is arranged at the exposed part of the circuit connection layer.

[0010] Further, the protective layer is a silicon dioxide protective layer; or, The first resin layer / second resin layer / third resin layer is a positive photoresist or a negative photoresist.

[0011] The application also provides a preparation method of a micro-electromechanical acoustic emission sensor, and the method comprises the following steps: A cantilever device is formed, and a through hole is etched in the cantilever device; One side of the cantilever device is attached to a part of a base device, and a gas cavity is formed between the attached part and the unattached part; The cantilever device and the base device pass through the gas cavity through a through hole gap to form a liquid-gas cantilever bridge structure based on surface tension; The space close to the through hole of the gas cavity gradually increases.

[0012] Further, the preparation of the cantilever device comprises the following steps: An arc-shaped section recessed in opposite directions along the surface is coated on the surface of the cantilever device, and a stepped structure is formed between the end of the arc-shaped section and the surface of the cantilever device; A through hole is etched at the end of the arc-shaped section of the cantilever device; One side of the cantilever device with the arc-shaped section is attached to a part of a base device, and a gas cavity is formed between the attached part and the unattached part.

[0013] Further, the gap width of the through hole etched is W, and 0.2 µm < W < 0.5 µm.

[0014] The micro-electromechanical acoustic emission sensor and the preparation method thereof of the present application install the micro-electromechanical acoustic emission sensor at a position below the liquid level on the inner surface of the storage tank, expose the piezoelectric cantilever structure in the liquid medium, directly detect the acoustic emission signal in the liquid medium, avoid the reflection and dispersion problems of the acoustic emission signal in the conduction from the liquid medium to the tank wall, that is, avoid the attenuation in the propagation of the acoustic emission signal liquid medium-tank wall, improve the identification ability of the signal, form a gas cavity below the cantilever structure by the surface tension of the liquid medium, form a liquid-cantilever-gas structure, control the width of the gap between the piezoelectric cantilever structure and the surrounding wall structure, so that the liquid cannot enter the cavity structure under the action of the surface tension, so that the liquid in the storage tank can only partially fill the gap between the cantilever structure and the surrounding wall structure, and the liquid does not leak into the air cavity below the cantilever structure through the micro-scale gap, realize the direct detection of the acoustic emission signal propagating in the liquid in the storage tank, and improve the sensitivity of the sensor, and the piezoelectric material is packaged by adopting a double-resin layer structure, which not only ensures the elasticity of the cantilever structure, but also avoids the corrosion of the gas and liquid environment in the storage tank to the piezoelectric material.

[0015] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. The objects and other advantages of the present application can be realized and achieved by the structures indicated in the specification, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0017] Figure 1 A micro-electromechanical acoustic emission sensor structure schematic diagram in the embodiment of the present application is shown; Figure 2 A second substrate deposition metal sacrificial layer schematic diagram in the embodiment of the present application is shown; Figure 3 A second resin layer structure schematic diagram in the embodiment of the present application is shown; Figure 4 A piezoelectric material layer structure schematic diagram in the embodiment of the present application is shown; Figure 5 A third resin layer structure schematic diagram in the embodiment of the present application is shown; Figure 6 A via hole structure schematic diagram in the embodiment of the present application is shown; Figure 7A metal circuit layer and a first resin layer structure schematic diagram in the embodiment of the present application is shown. Figure 8 A glue layer coating schematic diagram in the embodiment of the present application is shown. Figure 9 A base device and a cantilever device alignment schematic diagram in the embodiment of the present application is shown. Figure 10 A metal sacrificial layer removal schematic diagram in the embodiment of the present application is shown. Figure 11 A circuit connection hole structure schematic diagram in the embodiment of the present application is shown. Figure 12 A circuit connection layer structure schematic diagram in the embodiment of the present application is shown. Figure 13 A protective layer structure schematic diagram in the embodiment of the present application is shown. Figure 14 A micro-electro-mechanical acoustic emission sensor structure schematic diagram in the embodiment of the present application is shown.

[0018] In the figure, 1, a piezoelectric cantilever structure; 2, a surrounding wall; 3, a base device; 4, a cantilever device; 5, a gas cavity; 6, a through hole; 7, an arc segment; 8, a first substrate; 9, a metal circuit layer; 10, a first resin layer; 11, a glue layer; 12, a second substrate; 13, a metal sacrificial layer; 14, a second resin layer; 15, a piezoelectric material layer; 16, a third resin layer; 17, a notch; 18, a circuit connection hole; 19, a circuit connection layer; 20, a protective layer; 21, a third substrate; 22, a first noble metal layer; 23, a second noble metal layer; 24, a polymer protective layer. DETAILED DESCRIPTION

[0019] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0020] The present application provides a micro-electro-mechanical acoustic emission sensor and a preparation method thereof. In view of the problem of corrosion acoustic emission signal attenuation in external installation detection of a traditional acoustic emission sensor, a liquid bridge piezoresistive cantilever structure based in-tank acoustic emission sensor is designed by using micro-electro-mechanical system principle and microelectronic manufacturing process. Surface tension is used to fill the gap between the cantilever structure and the surrounding wall structure with liquid in the tank, and the liquid does not leak into the air cavity under the cantilever structure through the micro-scale gap, so as to realize direct detection of the acoustic emission signal propagating in the liquid in the tank.

[0021] Figure 1 A micro-electro-mechanical acoustic emission sensor structure in the embodiment of the present application is shown, Figure 1 In the embodiment of the present application, a hydrophone acoustic emission sensor is provided, a piezoelectric structure is exposed outside and directly contacts with liquid, acoustic emission signals conducted in the liquid can be directly monitored, the micro-electro-mechanical acoustic emission sensor comprises a base device 3 and a cantilever device 4 partially attached to the base device 3, wherein the attachment and the non-attachment form a gas cavity 5; a through hole 6 is etched through the cantilever device, and the cantilever device 4 and the base device 3 form a liquid-gas cantilever bridge structure based on surface tension through the through hole 6 gap passing through the gas cavity 5; the space near one side of the gas cavity 5 gradually increases. In the embodiment of the present application, the through hole 6 divides the cantilever device 4 into a piezoelectric cantilever structure 1 and a surrounding wall 2, the piezoelectric cantilever structure 1 and the gas cavity 5 form a liquid-gas cantilever bridge structure based on surface tension, and by controlling the width of the gap between the piezoelectric cantilever structure 1 and the surrounding wall 2 structure, the liquid cannot enter the cavity structure under the action of surface tension, and the sensitivity of the sensor is improved.

[0022] It should be noted that, in the embodiment of the present application, unlike the traditional acoustic emission sensor which fixes the piezoelectric material on the outer surface of the storage tank by magnetic attraction or adhesion, detects the acoustic emission signals propagated from the tank bottom to the liquid medium to the tank wall, and the novel micro-electro-mechanical acoustic emission sensor proposed in the present application is installed on the inner surface of the storage tank below the liquid level, the piezoelectric cantilever structure 1 is exposed in the liquid medium, and the acoustic emission signals in the liquid medium are directly detected, avoiding the attenuation of the acoustic emission signals in the liquid medium to the tank wall.

[0023] In the embodiment of the present application, the width of the gap between the piezoelectric cantilever structure 1 and the surrounding wall 2 structure through the through hole 6 is W, and the value of W is less than 50 microns.

[0024] In the embodiment of the present application, the gas cavity 5 is also specifically limited, an arc-shaped section 7 recessed in the opposite direction along the surface is arranged on the side where the cantilever device 4 and the base device 3 are attached, a step-shaped structure is formed between the end of the arc-shaped section 7 and the surface of the cantilever device 4; the through hole 6 is arranged at the end of the arc-shaped section 7. The novel micro-electro-mechanical acoustic emission sensor proposed is different from the liquid-cantilever-liquid structure adopted by the traditional underwater vibration sensor, utilizes the surface tension of the liquid medium to form a gas cavity below the cantilever structure, forms a liquid-cantilever-gas structure, and is more sensitive to acoustic emission signals.

[0025] In the embodiment of the present application, in order to ensure the elasticity of the cantilever structure and avoid the corrosion of the gas and liquid environment in the storage tank to the piezoelectric material, the piezoelectric material is packaged by adopting a double-resin layer structure. Specifically, the cantilever device includes a second resin layer 14, a piezoelectric material layer 15 and a third resin layer 16 covering the piezoelectric material layer are sequentially arranged on the second resin layer 14, wherein the arc-shaped section 7 is arranged on the third resin layer 16, and the thickness of the third resin layer 16 close to one side of the through hole 6 is smaller than the thickness of the third resin layer 16 away from the other side of the through hole 6.

[0026] It should be noted that in the embodiment of the present application, the base device 3 includes a first substrate 8, a metal circuit layer 9, a first resin layer 10 and an adhesive layer 11 covering the first substrate 8 are sequentially arranged on the first substrate 8; the cantilever device 4 is attached to the adhesive layer 11 on the metal circuit layer 9 to form a gas cavity 5.

[0027] In order to prevent the liquid environment from corroding the piezoelectric material layer 15, a notch 17 is arranged on the piezoelectric material layer around the through hole, the width of the notch 17 is greater than the gap width of the through hole 6, and the through hole 6 should not contact the piezoelectric material layer 15.

[0028] In the embodiment of the present application, the method for preparing a micro-electromechanical acoustic emission sensor is also described, which includes forming a cantilever device 4, etching a through hole 6 in the cantilever device 4; attaching one side of the cantilever device 4 to part of the base device 3, and forming a gas cavity 5 between the attached part and the unattached part; the cantilever device 4 and the base device 3 are connected through the gap of the through hole 6 to form a liquid-gas cantilever bridge structure based on surface tension, and the space close to one side of the through hole 6 of the gas cavity 5 gradually increases.

[0029] Specifically, the preparation of the cantilever device 4 includes: coating the surface of the cantilever device 4 with arc-shaped sections 7 recessed in opposite directions along the surface, and forming a stepped structure between the end of the arc-shaped section 7 and the surface of the cantilever device 4; etching a through hole 6 in the end of the arc-shaped section 7 of the cantilever device 4; attaching one side of the cantilever device 4 with the arc-shaped section to part of the base device 3, and forming a gas cavity 5 between the attached part and the unattached part.

[0030] The following describes the specific steps of the method for preparing a micro-electromechanical acoustic emission sensor in detail: Step S1: depositing a metal sacrificial layer A metal sacrificial layer 13 is deposited on a second substrate 12 by a physical vapor deposition method, Figure 2 A schematic diagram of depositing a metal sacrificial layer on a second substrate in the embodiment of the present application is shown; Figure 2In the embodiment, the metal sacrificial layer 13 can be aluminum, copper or other metal or alloy material, and the second substrate 12 can be single crystal silicon, polycrystalline silicon or silicon dioxide or other non-metal material. It should be noted that the embodiment does not limit the selection of the material of the second substrate 12, the selection of the material of the metal sacrificial layer 13, and the deposition method of the metal sacrificial layer 13.

[0031] Step S2: preparing a second resin layer In the embodiment, the second resin layer 14 is prepared on the metal sacrificial layer 13 by using the gluing, photolithography and developing process, Figure 3 FIG. 2 shows a structure diagram of the second resin layer in the embodiment, Figure 3 In the embodiment, the material of the second resin layer 14 can be positive photoresist or negative photoresist.

[0032] It should be noted that the embodiment does not limit the specific components of the positive photoresist or the negative photoresist.

[0033] Optionally, the process for preparing the second resin layer 14 is only exemplary, and the specific preparation process is not limited in actual application.

[0034] Step S3: preparing a piezoelectric material layer In the embodiment, the piezoelectric material layer 15 is prepared on the first resin layer by using the physical vapor deposition, photolithography and wet etching process, Figure 4 FIG. 3 shows a structure diagram of the piezoelectric material layer in the embodiment, Figure 4 In the embodiment, the piezoelectric material layer 15 can be one or more of lithium gallate, lithium germanate, titanium germanate, lithium niobate and lithium tantalate, and the embodiment does not limit the method for preparing the piezoelectric material layer 15 and the selection of the material of the piezoelectric material layer 15.

[0035] Optionally, in the embodiment, the piezoelectric material layer 15 is prevented from being corroded by the liquid environment, and the notch 17 of the piezoelectric material layer 15 is arranged on the side of the through hole 5, and the width is significantly greater than the gap width of the through hole 5.

[0036] Step S4: preparing a third resin layer In the embodiment, the third resin layer 16 is prepared on the piezoelectric material layer 15 by using the gluing, photolithography and developing process, Figure 5 FIG. 4 shows a structure diagram of the third resin layer in the embodiment, Figure 5In order to ensure that the third resin layer 16 is solidified with the second resin layer 14 after the subsequent baking process, to realize the protection of the piezoelectric material layer 15, and to prevent the liquid environment from corroding the piezoelectric material layer 15, the third resin layer 16 completely wraps the piezoelectric material layer 15, and the edge of the third resin layer 16 is in direct contact with the second resin layer 14.

[0037] Optionally, the third resin layer 16 can be a positive photoresist or a negative photoresist. It should be noted that the specific composition of the positive photoresist or the negative photoresist is not limited in the embodiment of the present application.

[0038] The arc-shaped section 7 is arranged on the third resin layer 16, and the arc-shaped section 7 is recessed in the opposite direction of the surface of the third resin layer 16, and a stepped structure is formed between the end of the arc-shaped section 7 and the surface of the third resin layer 16.

[0039] Step S5: preparing a gap seam In the embodiment of the present application, the gap seam is prepared by the following steps: Figure 5 The gap seam is prepared by the following steps: performing photoetching and dry anisotropic etching on the pattern structure in the third resin layer 16 and the second resin layer 14, Figure 6 Fig. 2 shows a schematic diagram of the through-hole structure in the embodiment of the present application, Figure 6 In the embodiment of the present application, the opening penetrates the third resin layer 16 and the second resin layer 14 to reach the metal sacrificial layer 13.

[0040] It should be noted that in order to prevent the liquid environment from corroding the piezoelectric material layer 15, the opening does not contact the piezoelectric material layer 15.

[0041] Step S6: preparing a metal circuit layer and a first resin layer In the embodiment of the present application, the metal circuit layer 9 is prepared on the first substrate 8 by adopting physical vapor deposition, photoetching and wet etching processes, and the first resin layer 10 is prepared on the metal circuit layer 9 by adopting gluing, photoetching and developing processes, Figure 7 Fig. 3 shows a schematic diagram of the metal circuit layer and the first resin layer structure in the embodiment of the present application, Figure 7 In the embodiment of the present application, the material of the metal circuit layer 9 can be metal or alloy material such as aluminum or copper, the material of the first resin layer 10 can be positive photoresist or negative photoresist, and the first substrate 8 can be non-metallic material such as single crystal silicon, polycrystalline silicon or silicon dioxide. It should be noted that the preparation process of the metal circuit layer 9 and the first resin layer 10 in the embodiment of the present application is only exemplary. The selection of the material of the metal circuit layer 9, the selection of the material of the first resin layer 10 and the selection of the material of the first substrate 8 are not specifically limited in the embodiment of the present application.

[0042] Step S7: preparing an adhesive layer The adhesive layer 11 is coated on the first resin layer 10 by using a coating process to cover the whole first substrate 8, Figure 8 An adhesive layer coating schematic diagram in the embodiment of the present application is shown, Figure 8 In the embodiment, the adhesive layer 11 is arranged in the lamination process of the base device 3 and the cantilever device 4 to ensure the bonding strength of the first resin layer 10 and the third resin layer 16.

[0043] It should be noted that the material of the adhesive layer 11 is a thermosetting resin material, and the selection of the material of the adhesive layer 11 is not specifically limited in the embodiment of the present application.

[0044] Step S8: laminating the base device and the cantilever device The base device 3 and the cantilever device 4 are aligned and laminated by using a lamination process, Figure 9 An alignment schematic diagram of the base device and the cantilever device in the embodiment of the present application is shown, Figure 9 In the embodiment, the third resin layer 16 is partially laminated with the adhesive layer 11, and a gas cavity 5 is formed at the non-laminated position.

[0045] Step S9: removing the metal sacrificial layer In the embodiment of the present application, a wet isotropic etching process is used to remove the metal sacrificial layer 13, Figure 10 A schematic diagram of removing the metal sacrificial layer in the embodiment of the present application is shown, Figure 10 In the embodiment, the metal sacrificial layer 13 is removed to separate the second substrate 12.

[0046] Step S10: preparing a circuit connection hole In the embodiment of the present application, the second substrate 12 is removed, Figure 9 In the embodiment, a photoetching and dry anisotropic etching process is performed on the pattern structure of the removed second substrate 12 to open the circuit connection hole 18, Figure 11 A schematic diagram of the circuit connection hole structure in the embodiment of the present application is shown, Figure 11 In the embodiment, the circuit connection hole 18 penetrates the second resin layer 14, the piezoelectric material layer 15, the third resin layer 16, the adhesive layer 11 and the first resin layer 10 to reach the metal circuit layer 9.

[0047] Step S11: preparing a circuit connection layer In the embodiment of the present application, a physical vapor deposition method is used to deposit, Figure 11 On the pattern structure of the circuit connection hole 18, a photoetching and wet etching process is performed to prepare a circuit connection layer 19 at the circuit connection hole 18, Figure 12 A schematic diagram of the circuit connection layer structure in the embodiment of the present application is shown, Figure 12 In the embodiment, the circuit connection layer 19 connects the piezoelectric material layer 15 and the metal circuit layer 9.

[0048] Step S12: preparing a protective layer In Figure 12 The protective layer 20 is formed by using a chemical vapor deposition method, photolithography and dry etching process, Figure 13 The protective layer structure in the embodiment of the present application is shown, Figure 13 In the embodiment of the present application, the liquid environment is prevented from corroding the circuit connection layer 19 by setting the protective layer 20.

[0049] It should be noted that the protective layer 20 is a silicon dioxide protective layer, and the present application does not limit the selection of the material of the protective layer 20.

[0050] After the protective layer is formed, the micro-electro-mechanical acoustic emission sensor of the present application is prepared.

[0051] In the embodiment of the present application, in addition to the micro-electro-mechanical acoustic emission sensor structure described above, the second resin layer 14 and the third resin layer 16 can be replaced by a second noble metal layer 23 and a first noble metal layer 22 to protect the piezoelectric material layer 15, and the noble metal can be gold, silver, platinum, etc. Accordingly, the first resin layer 10 is deleted, the first noble metal layer 22 is not used in the variable thickness process, and a polymer protective layer 24 is added above the second noble metal layer 23 to cover the entire structure of the device except the gap seam.

[0052] If the noble metal corrosion protective layer is used instead of the resin corrosion protective layer, the opening operation is not performed, and the superfluid carbon dioxide is used to dissolve the resin sacrificial layer to form a cantilever structure, Figure 14 The micro-electro-mechanical acoustic emission sensor structure in the embodiment of the present application is shown, Figure 14 In the embodiment of the present application, the second noble metal layer 23 is used to replace the second resin layer 14, Figure 1 The micro-electro-mechanical acoustic emission sensor structure is shown, and the polymer protective layer 24 is arranged on the second noble metal layer 23, the polymer protective layer 24 covers the entire area of the third substrate 21 except the gap seam, and the circuit connection hole 18, the circuit connection layer 19 and the silicon dioxide protective layer 20 are deleted. The superfluid carbon dioxide is used to dissolve the resin sacrificial layer to form a cantilever structure.

[0053] It should be noted that compared with the shell, protective film, piezoelectric element, damping block, connecting wire and high-frequency socket of the conventional acoustic emission sensor, the present application is a micro-electro-mechanical system acoustic emission sensor based on a silicon electronic manufacturing process. After mass production, the production cost is much lower than that of the existing conventional acoustic emission sensor, and the prediction of a single sensor can be reduced by more than 90%, which is suitable for the demand of the tank state online monitoring system.

[0054] The micro-electromechanical acoustic emission sensor and the preparation method thereof are characterized in that the micro-electromechanical acoustic emission sensor is installed at a position below the liquid level on the inner surface of the storage tank, the piezoelectric cantilever structure is exposed to the liquid medium, and the acoustic emission signal in the liquid medium is directly detected, thereby avoiding the reflection and dispersion problems of the acoustic emission signal in the conduction from the liquid medium to the tank wall, i.e., avoiding the attenuation of the acoustic emission signal in the propagation from the liquid medium to the tank wall, improving the signal recognition capability, forming a gas cavity below the cantilever structure by using the surface tension of the liquid medium, forming a liquid-cantilever-gas structure, controlling the width of the gap between the piezoelectric cantilever structure and the surrounding wall structure, and making the liquid unable to enter the cavity structure under the action of the surface tension, so that the liquid fills the gap between the cantilever structure and the surrounding wall structure in the storage tank, and does not leak into the air cavity below the cantilever structure through the micro-scale gap, thereby realizing the direct detection of the acoustic emission signal propagating in the liquid in the storage tank and improving the sensitivity of the sensor, and the piezoelectric material is packaged by using a double-resin layer structure, which ensures the elasticity of the cantilever structure and avoids the corrosion of the piezoelectric material by the gas and liquid environment in the storage tank.

[0055] Although the present application is described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalent features, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A microelectro-acoustic emission sensor, characterized in that, The microelectroacoustic emission sensor includes: A base device (3) and a cantilever device (4) partially attached to the base device (3), wherein the attached portion and the unattached portion form a gas cavity (5). Through-holes (6) are etched through the cantilever device, and the cantilever device (4) and the substrate device (3) are connected through the gap of the through-holes (6) to form a liquid-gas cantilever bridge structure based on surface tension. The space of the gas cavity (5) gradually increases on the side near the through hole (6).

2. The microelectroacoustic emission sensor according to claim 1, characterized in that, The cantilever device (4) is provided with an arc-shaped segment (7) that is recessed in the opposite direction of the surface on the side where it is attached to the base device (3). The end of the arc-shaped segment (7) forms a step-like structure between the end of the arc-shaped segment (7) and the surface of the cantilever device (4). The through hole (6) is opened at the end of the arc segment (7).

3. The microelectroacoustic emission sensor according to claim 1 or 2, characterized in that, The substrate device (3) includes a first substrate (8), on which a metal circuit layer (9), a first resin layer (10), and an adhesive layer (11) located on the first resin layer (10) and covering the first substrate (8) are sequentially disposed. The cantilever device (4) forms a gas cavity (5) by attaching the adhesive layer (11) to the metal circuit layer (9).

4. The microelectroacoustic emission sensor according to claim 3, characterized in that, The cantilever device includes a second resin layer (14), on which a piezoelectric material layer (15) and a third resin layer (16) covering the piezoelectric material layer are sequentially disposed. The arc segment (7) is disposed on the third resin layer (16), and the thickness of the third resin layer (16) near the through hole (6) is less than the thickness of the side away from the through hole (6).

5. The microelectroacoustic emission sensor according to claim 4, characterized in that, A notch (17) is provided in the piezoelectric material layer around the through hole, and the width of the notch (17) is greater than the gap width of the through hole (6).

6. The microelectroacoustic emission sensor according to claim 4, characterized in that, A through circuit connection hole (18) is provided along the second resin layer (14), the piezoelectric material layer (15), the third resin layer (16), the adhesive layer (11) and the first resin layer (10), and the circuit connection hole (18) is in contact with the metal circuit layer (9). A circuit connection layer (19) is provided at the circuit connection hole (18), and the circuit connection layer (19) is electrically connected to the metal circuit layer (9) and the piezoelectric material layer (15). The exposed portion of the circuit connection layer (19) is provided with a protective layer (20).

7. The microelectroacoustic emission sensor according to claim 6, characterized in that, The protective layer (20) is a silicon dioxide protective layer; or, The first resin layer (10) / the second resin layer (14) / the third resin layer (16) are positive photoresists or negative photoresists.

8. A method for fabricating a microelectro-acoustic emission sensor, characterized in that, The method includes: A cantilever device (4) is formed, and a through hole (6) is etched in the cantilever device (4). One side of the cantilever device (4) is partially attached to the base device (3), and the attached part and the unattached part form a gas cavity (5). The cantilever device (4) and the base device (3) are connected by a gas cavity (5) through a through hole (6) to form a liquid-gas cantilever bridge structure based on surface tension. The space of the gas cavity (5) gradually increases on the side near the through hole (6).

9. The method for fabricating a microelectroacoustic emission sensor according to claim 8, characterized in that, The fabrication of the cantilever device (4) includes: An arc-shaped segment (7) with a concave shape in the opposite direction of the surface is coated on the surface of the cantilever device (4), and a step-like structure is formed between the end of the arc-shaped segment (7) and the surface of the cantilever device (4); A through hole (6) is etched at the end of the arc segment (7) of the cantilever device (4). One side of the cantilever device with an arc segment is partially attached to the base device (3), and the attached part and the unattached part form a gas cavity (5).

10. The method for fabricating a microelectroacoustic emission sensor according to claim 8 or 9, characterized in that, The width of the through hole (6) formed by etching is W, where 0.2µm < W < 0.5µm.

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