Flexible thin film piezoelectric sensor, fastener and processing technology

Abstract

The present invention belongs to the technical field of thin film piezoelectric sensors, and in particular relates to a flexible thin film piezoelectric sensor, a fastener and a processing technology. The flexible thin film piezoelectric sensor includes a flexible substrate, on which a piezoelectric layer, a protective layer and an electrode layer are formed in sequence from the inside to the outside, and the flexible substrate is a metal foil. The material of the flexible substrate includes but is not limited to stainless steel, Ti, Al and its alloys, and the thickness of the flexible substrate is 10um to 1mm. The flexible thin film piezoelectric sensor of the present invention has the advantages of using existing thin film piezoelectric sensors. It can be quickly fitted with fasteners using coupling agent glue, which is simple to operate, and can be connected to the fastener base by metal welding, which is highly firm and reliable. In addition, the flexible substrate of the metal foil can produce a larger product in a single batch, which can effectively reduce the production cost of a single sensor.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin film piezoelectric sensors, and in particular relates to a flexible thin film piezoelectric sensor, a fastener and a processing technology. Background Art

[0002] At present, one of the ways to combine piezoelectric sensors and fasteners is to directly stick the piezoelectric ceramic sheet to the fastener with a coupling agent glue. The disadvantage of this method is that the test data of the piezoelectric ceramic sheet will cause measurement errors due to differences in the thickness of the glue, the measurement accuracy is insufficient, and the environmental weather resistance of the glue will shorten the service life of the sensor. Another combination method is to directly grow a thin film piezoelectric sensor in situ on the end face of the fastener. The disadvantage of this method is that it requires the design of sample tooling and equipment space according to fasteners of different sizes, and it is difficult to integrate thin film piezoelectric sensors by in situ growth on large and long bolts, which greatly increases the equipment cost.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a flexible thin film piezoelectric sensor, fastener and processing technology, which solves the technical problems of insufficient measurement accuracy of existing piezoelectric ceramic sheets and low production efficiency and high process cost of thin film piezoelectric sensors.

[0005] To solve the above technical problems, the first aspect of the present invention proposes a flexible thin film piezoelectric sensor, comprising a flexible substrate, on which a piezoelectric layer, a protective layer and an electrode layer are formed in sequence from the inside to the outside, and the flexible substrate is a metal foil.

[0006] The piezoelectric layer in the present invention is used to convert external electrical signals into ultrasonic signals, and then receive ultrasonic echo signals and convert them into electrical signals; the protective layer is used to protect the piezoelectric layer material, reduce the impact of the external environment on the performance of the piezoelectric material, and achieve electrical insulation isolation; the electrode layer is used to receive and output electrical signals. The electrode layer can be a single layer or a composite layer structure. An annular mask is provided on the electrode layer for electrical isolation. The electrode layer is divided into an inner electrode and an outer electrode so that two electrode leads can be realized on one side. The piezoelectric layer and the flexible substrate, the piezoelectric layer and the protective layer, and the protective layer and the transition layer are all bonded at the atomic level. The atomic level bonding is achieved by any one of physical vapor deposition technology, chemical vapor deposition technology, and pulsed laser deposition technology. The shape of the flexible substrate is not fixed and is mainly determined by the fasteners used. The flexible substrate of the present invention can be flexibly bent and is preferably a metal foil.

[0007] Further optionally, the material of the flexible substrate includes but is not limited to stainless steel, Ti, Al and alloys thereof, and the thickness of the flexible substrate is 10 um to 1 mm.

[0008] Furthermore, the piezoelectric layer can optionally be made of materials including, but not limited to, zinc oxide, aluminum nitride, cadmium sulfide, zinc sulfide, tantalum oxide, lithium niobate, lead titanate, and polyvinylidene fluoride. The piezoelectric layer can also be a multilayer composite structure, such as a ZnO / AlN composite piezoelectric layer. The thickness of the piezoelectric layer varies depending on the frequency of the acoustic wave and is generally between 0 and 30 μm, with a preferred thickness of 0.5 μm to 20 μm.

[0009] The protective layer is typically made of a material with stable physical and chemical properties, durability, and high resistance, including but not limited to chromium oxide, aluminum oxide, aluminum nitride, silicon oxide, silicon nitride, silicon carbide, diamond, and doped diamond. The thickness of the protective layer is generally 0-10 μm, preferably 0-3 μm. A protective layer is not required. If the piezoelectric layer is physically and chemically stable and has high resistance (such as AlN and Ta2O5), a separate protective layer between the piezoelectric layer and the electrode layer is not necessary.

[0010] Materials for the electrode layer include, but are not limited to, indium, tin, aluminum, titanium, nickel, copper, silver, gold, platinum, tungsten, and their alloys. The electrode layer can be a single layer or a composite layer structure, such as Ni / Al, Ti / Sn, etc. The electrode layer can be a single metal or an alloy, such as various tin alloys and aluminum alloys. The thickness of the electrode layer is generally 0 to 50 μm, but not 0, and preferably 1 to 15 μm.

[0011] Further optionally, a transition layer is provided between the flexible substrate and the piezoelectric layer, and the material of the transition layer includes but is not limited to titanium, nickel, and chromium. The transition layer is mainly used for the firm connection between the core structure of the thin film piezoelectric sensor and the bolt base. The material of the transition layer is generally metal, including but not limited to titanium, nickel, chromium, etc., and the thickness of the transition layer is generally 0 to 3um, preferably 0 to 1um. The transition layer is not a necessary structure, and it mainly depends on whether the bonding strength between the piezoelectric layer material and the base material meets the requirements. If the bonding strength between the piezoelectric layer material and the base material is good, no transition layer is required. There is also atomic-level bonding between the transition layer and the flexible substrate, and between the transition layer and the piezoelectric layer. The atomic-level bonding is achieved by using any one of physical vapor deposition technology, chemical vapor deposition technology, and pulsed laser deposition technology.

[0012] A second aspect of the present invention provides a fastener, comprising a fastener base, wherein an end surface of the fastener base is provided with the flexible thin film piezoelectric sensor provided by the first aspect of the present invention.

[0013] Further optionally, the flexible thin film piezoelectric sensor is bonded to the fastener base by using coupling agent glue, or the flexible thin film piezoelectric sensor is bonded to the fastener base by using metal welding.

[0014] The shape of the flexible substrate of the present invention is determined by the fastener substrate. The fastener substrate is preferably a bolt comprising a screw and a bolt head connected to the bolt shank. The flexible thin film piezoelectric sensor is disposed on the bolt head. The flexible substrate is preferably a metal foil. The flexible thin film piezoelectric sensor can be securely bonded to the fastener substrate via metal welding. This minimizes the acoustic impedance difference between the metals, reducing losses during ultrasonic signal transmission and reception. The flexible thin film piezoelectric sensor can also be securely bonded to the fastener and substrate using a coupling agent or glue, allowing for rapid bonding to the fastener substrate.

[0015] The flexible thin film piezoelectric sensor of the present invention has a higher single batch output, and the equipment cost and growth cost can be greatly reduced. The cost of a single sensor unit is reduced by more than 3 / 4 compared with the thin film piezoelectric sensor directly grown on the end face of the fastener.

[0016] A third aspect of the present invention provides a process for manufacturing a thin film piezoelectric sensor, comprising the following steps:

[0017] Step 1: Generate a piezoelectric layer, a protective layer, and an electrode layer on a metal foil from the inside out to produce a flexible thin film piezoelectric sensor.

[0018] Step 2: The flexible thin film piezoelectric sensor obtained in step 1 is attached to the end surface of the fastener base by using coupling agent glue or metal welding.

[0019] In the present invention, the protective layer in step one is not a necessary structure. If the physical and chemical properties of the piezoelectric layer are stable and the resistance is high (such as AlN and Ta2O5), there is no need to prepare an insulating protective layer separately between the piezoelectric layer and the electrode layer. In addition, a transition layer can be provided between the piezoelectric layer and the flexible substrate. The transition layer is not a necessary structure. It depends on whether the bonding strength between the piezoelectric layer material and the base material meets the requirements. If the bonding strength between the piezoelectric layer material and the base material is good, no transition layer is required. Preferably, an in-situ growth method is adopted to sequentially generate a transition layer (which can be omitted according to the piezoelectric layer material), a piezoelectric layer, a protective layer (which can be omitted according to the piezoelectric layer material) and an electrode layer on the flexible substrate. Preferably, any one of physical vapor deposition technology, chemical vapor deposition technology and pulsed laser deposition technology is used to sequentially generate each layer structure. In step one, an annular mask is also provided on the electrode layer. The annular mask is used to electrically isolate the electrode layer and divide the electrode layer into an inner electrode and an outer electrode so that two electrode leads can be realized on one side.

[0020] In step 2, the coupling agent glue is used to achieve rapid bonding between the flexible substrate and the fastener substrate, and the operation is simple; the metal welding method is used to achieve high firmness and reliability of the connection between the flexible substrate and the fastener substrate.

[0021] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0022] The flexible thin-film piezoelectric sensor of this invention combines the advantages of both existing sensors. It can be quickly attached to fasteners using a coupling agent or glue, offering simple operation, while also being able to be connected to the fastener base using metal welding, providing high strength and reliability. Furthermore, the flexible metal foil base can be produced in larger batches, effectively reducing the production cost of individual sensors.

[0023] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an undue limitation of the present invention. Obviously, the drawings described below are only some embodiments. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without inventive effort. In the accompanying drawings:

[0025] Figure 1 : This is a structural diagram of the flexible thin film piezoelectric sensor of Example 1 of the present invention.

[0026] Figure 2 : A structural diagram of a screen printing structure according to one embodiment of the present invention.

[0027] Figure 3 : This is a base structure diagram of embodiment 1 of the present invention.

[0028] Figure 4 : This is a diagram showing the coordination between the screen printing structure and the base during screen printing of the screen printing device according to embodiment 1 of the present invention.

[0029] Figure 5 : This is a structural diagram of the imprint mold according to embodiment 1 of the present invention.

[0030] Figure 6 : A diagram showing the preparation process of a thin film piezoelectric sensor using the imprinting mold of Example 1 of the present invention.

[0031] Figure 7 : This is a process flow chart of the processing technology of embodiment three of the present invention.

[0032] Figure 8 : This is an ultrasonic echo signal intensity spectrum of the flexible thin film piezoelectric sensor prepared on the metal Ti foil in Example 3 of the present invention.

[0033] Figure 9 : This is an ultrasonic echo signal intensity spectrum of the flexible thin film piezoelectric sensor prepared on the stainless steel foil in Example 3 of the present invention.

[0034] Figure 10 : This is the ultrasonic echo signal intensity spectrum of the thin film sensor directly generated on the stainless steel metal substrate in the comparative example.

[0035] Among them: 1-flexible substrate; 2-transition layer; 3-piezoelectric layer; 4-protective layer; 5-electrode layer.

[0036] 21-frame; 22-screen plate; 23-hollow pattern; 24-scraper; 25-base; 26-metal base; 27-positioning part; 211-sunken step; 31-embossing mold; 311-mold body; 312-embossing part; 122-annular embossing groove; 123-first embossing surface; 124-second embossing surface.

[0037] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but rather to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0038] In the description of the present invention, it should be noted that the terms "inside" and "outside" etc. indicating orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0039] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connected," "in contact," and "connected" should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; and direct or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0040] In order to solve the technical problems of insufficient measurement accuracy, low production efficiency and high process cost of thin film piezoelectric sensors prepared by the existing technology, this embodiment proposes a flexible thin film piezoelectric sensor, a fastener and a processing technology.

[0041] Example 1

[0042] This embodiment proposes a flexible thin film piezoelectric sensor, such as Figure 1 As shown, the flexible substrate 1 includes a piezoelectric layer 3, a protective layer 4, and an electrode layer 5 formed on the flexible substrate 1 from the inside out. The flexible substrate 1 is a metal foil. The material of the flexible substrate 1 includes but is not limited to stainless steel, Ti, Al, and their alloys. The thickness of the flexible substrate 1 ranges from 10 μm to 1 mm.

[0043] Materials for the piezoelectric layer 3 include, but are not limited to, zinc oxide, aluminum nitride, cadmium sulfide, zinc sulfide, tantalum oxide, lithium niobate, lead titanate, and polyvinylidene fluoride; materials for the protective layer 4 include, but are not limited to, chromium oxide, aluminum oxide, aluminum nitride, silicon oxide, silicon nitride, silicon carbide, diamond, and doped diamond; and materials for the electrode layer 5 include, but are not limited to, indium, tin, aluminum, titanium, nickel, copper, silver, gold, platinum, tungsten, and their alloys. The thickness of the piezoelectric layer 3 is 0 to 30 μm, not 0; the thickness of the protective layer 4 is 0 to 10 μm; and the thickness of the electrode layer 5 is 0 to 50 μm, not 0. An annular mask is also provided on the electrode layer 5 for electrical isolation, dividing the electrode layer 5 into an inner electrode and an outer electrode. The protective layer 4 is not a required structure. If the piezoelectric layer 3 has stable physical and chemical properties and high resistance (such as AlN and Ta2O5), there is no need to separately prepare a protective layer 4 between the piezoelectric layer 3 and the electrode layer 5.

[0044] A transition layer 2 is provided between the flexible substrate 1 and the piezoelectric layer 3. Materials for this layer include, but are not limited to, titanium, nickel, and chromium. The thickness of this layer ranges from 0 to 3 μm. This layer is optional and depends primarily on the required bonding strength between the piezoelectric layer 3 and the substrate. If the bonding strength between the piezoelectric layer 3 and the substrate is good, no transition layer 2 is required.

[0045] In one achievable method of this embodiment, a transition layer 2 (which may be omitted depending on the material of the piezoelectric layer 3), a piezoelectric layer 3, a protective layer 4 (which may be omitted depending on the material of the piezoelectric layer 3), and an electrode layer 5 are sequentially formed on a flexible substrate 1 by in-situ growth. Preferably, each layer structure is sequentially formed by using any one of physical vapor deposition, chemical vapor deposition, and pulsed laser deposition techniques.

[0046] In another possible implementation of this embodiment, the piezoelectric layer 3 and the protective layer 4 are sequentially formed on the flexible film using physical vapor deposition technology, and the electrode layer 5 structure of the thin film piezoelectric sensor is prepared using screen printing technology. Figure 2-Figure 4The screen printing device base 25 and screen printing structure for screen-printing the electrode layer 5 are provided with at least one positioning portion 27 on the base 25, which is used to position the flexible substrate 1. Preferably, multiple positioning portions 27 are provided on the base 25, allowing the electrode layer 5 structure to be screen-printed simultaneously on the end surfaces of multiple flexible substrates 1. The positioning portion 27 is configured as a positioning groove adapted to the shape of the flexible substrate 1. When the flexible substrate 1 is placed in the positioning groove, the protective layer 4 is aligned with the water inlet substrate. The screen printing structure includes a screen plate 22, which is pre-determined with a hollow pattern 23 adapted to the structure of the electrode layer 5. The hollow pattern 23 corresponds to the position of the positioning portion 27, allowing the slurry flowing through the gaps in the hollow pattern 23 to fall directly onto the protective layer 4. The hollow pattern includes a first hollow portion and a second hollow portion located within the first hollow portion. The first hollow portions are separated by a barrier ring. The first hollow portion is used to prepare the outer electrode of the electrode layer 5, and the second hollow portion is used to prepare the inner electrode of the electrode layer 5. The barrier ring between the first hollow portion and the second hollow portion forms a gap between the inner electrode and the outer electrode, which facilitates the preparation of a mask ring between the inner electrode and the outer electrode.

[0047] To prevent the slurry from falling outside the flexible substrate 1 due to displacement between the screen plate 22 and the base 25 during the screen printing process, preferably, sunken steps 211 are provided on the four edges of the base 25. The screen printing structure includes a frame 21 provided around the screen plate 22. During the screen printing process, the lower end of the frame 21 is snapped onto the sunken steps 211. Alternatively, a snap-fit structure can be provided between the frame 21 and the four edges of the base 25 so that the frame 21 can be directly snapped onto the base 25 during screen printing.

[0048] The method of screen printing the electrode layer 5 is as follows:

[0049] Positioning: Place the flexible substrate 1 on which the piezoelectric layer 3 and the protective layer 4 are grown using physical vapor deposition into the positioning portion 27 of the base 25. Fasten the base 25 around the frame 21 so that the preset electrode hollow pattern 23 is aligned with the surface of the insulating protective layer 4.

[0050] Scraping: Sintered metal slurry is applied to the surface of the screen plate 22. A scraper 24 is used to force the silver slurry through the preset electrode hollow pattern 23 and onto the protective layer 4 to form the electrode layer 5 pattern. The sintered metal slurry used to prepare the electrode layer 5 includes, but is not limited to, one of aluminum, silver, nickel, and alloys thereof.

[0051] Curing: Place the thin film piezoelectric sensor with the printed electrode layer 5 in a vacuum drying oven for curing at a curing temperature of 120° C. to 150° C. for 10 to 20 minutes.

[0052] Making a mask: A mask for separating the inner electrode and the outer electrode is prepared in the space between the inner electrode and the outer electrode of the printed electrode layer 5 .

[0053] This embodiment uses screen printing technology to prepare the electrode layer 5, which greatly improves the processing efficiency of the electrode layer 5. At the same time, efficient production can be achieved without a large vacuum chamber, thereby reducing production costs to a certain extent.

[0054] In another possible implementation of this embodiment, a piezoelectric layer 3 is formed on a flexible substrate 1 using a physical vapor deposition technique, a protective layer 4 is formed on the piezoelectric layer 3 using an imprinting technique, and then an electrode layer 5 is formed on the protective layer 4. The imprinting mold 31 for preparing the protective layer 4 using the imprinting technique includes a mold body 311, Figure 5 and Figure 6 The mold body 311 is provided with an imprinting portion 312, which includes an imprinting surface and an annular imprinting groove 122 formed on the imprinting surface. The imprinting surface is used to imprint the protective layer 4 of the thin film piezoelectric sensor, and the annular imprinting groove 122 is used to imprint the mask ring of the thin film piezoelectric sensor. The annular imprinting groove 122 is formed in the middle of the imprinting surface. When the imprinting mold 31 of this embodiment is used to imprint the thin film piezoelectric sensor, the layer structure of the thin film piezoelectric sensor and the mask ring are integrally formed, thereby improving the production efficiency of the thin film piezoelectric sensor. The imprinting mold 31 of this embodiment is preferably used to imprint the protective layer 4 with the mask ring. The stamping surface includes a first stamping surface 123 and a second stamping surface 124. The first stamping surface 123 is located within the inner ring of the annular stamping groove 122, and the second stamping surface 124 is located outside the outer ring of the annular stamping groove 122. The second stamping surface 124 is an inclined surface, and the side of the second stamping surface 124 away from the annular stamping groove 122 is sunken deeper into the mold body 311 than the side of the second stamping surface 124 closer to the annular stamping groove 122. In this embodiment, by setting the second stamping surface 124 as an inclined surface, the protective layer 4 produced by stamping has a layer structure that is thick around the edges and thin in the middle. This layer structure can provide better protection for the piezoelectric layer 3. The second stamping surface 124 is an inclined plane, or the second stamping surface 124 is a first arc surface protruding to the outside of the mold body 311, and the first stamping surface 123 is a plane, or the first stamping surface 123 is a second arc surface protruding to the outside of the mold body 311. The protective layer 4 stamped in this way is a downwardly concave arc surface, which on the one hand increases the connection area between the protective layer 4 and the electrode layer 5, ensuring the connection reliability between the outer electrode and the protective layer 4, and on the other hand also plays a certain protective role for the electrode layer 5 during service.

[0055] The method for preparing the protective layer 4 by embossing in this embodiment is as follows:

[0056] The piezoelectric layer 3 is formed on the end surface of the flexible substrate 1 by using a physical vapor deposition method.

[0057] The potting glue used to make the protective layer 4 is coated on the surface of the piezoelectric layer 3 to form a film to be printed; the potting glue to be printed is coated on the surface of the piezoelectric layer 3 to form a film to be printed, and the thickness of the film is preferably 1μm-50μm.

[0058] The imprinting mold 31 pre-coated with a release agent is pressed onto the film to be imprinted, and then heated to a set temperature and kept warm for a first set time; a layer of coupling agent is pre-coated on the imprinting portion 312 of the imprinting mold 31 to facilitate demoulding, and a hot stamping machine is used to press the potting adhesive layer to a thickness of 1-40μm, and then heated to 100°C and kept warm for 10-20 minutes.

[0059] The imprinting mold 31 is demolded and taken out, and after continuing to keep warm at the set temperature for a second set time, an insulating protective layer 4 with a mask ring is formed on the surface of the piezoelectric layer 3; the metal substrate is demolded and taken out, and placed in an oven for further curing. The oven temperature is maintained at 100°C and kept warm for 2 hours to allow the imprinting layer to adhere to or cover the surface of the piezoelectric layer 3.

[0060] The electrode layer 5 is prepared on the protective layer 4 located inside the mask ring and the protective layer 4 located outside the mask ring. The cured bolts are cleaned with alcohol to remove surface residues, etc., and then the electrode layer 5 is prepared on the protective layer 4. The electrode layer 5 is prepared by physical vapor deposition and then brazing. The electrode layer 5 is preferably prepared by brazing, specifically: a low-temperature tin-based solder for preparing the electrode layer 5 is placed inside and outside the mask ring; the solder is heated to a molten state and then kept warm for 5-10 minutes to allow the solder to fully wet and diffuse, and then cooled to 100-150°C with the furnace and taken out for air cooling.

[0061] This embodiment uses an imprint mold 31 to directly imprint the protective layer 4 and mask ring onto the potting compound used to prepare the protective layer 4. This reduces the number of steps required to add the mask ring, reduces machinery costs, and improves production efficiency. The use of brazing technology to prepare the electrode layer 5 on the protective layer 4 improves the efficiency of preparing the electrode layer 5.

[0062] In the thin film piezoelectric sensor of this embodiment, the protective layer 4 adopts a layer structure that is thick around the edges and thin in the middle, which can provide better protection for the piezoelectric layer 3.

[0063] Example 2

[0064] This embodiment provides a fastener comprising a fastener base, with the flexible thin film piezoelectric sensor of Example 1 disposed on an end surface of the fastener base. The flexible thin film piezoelectric sensor is bonded to the fastener base using a coupling agent or adhesive, or by metal welding.

[0065] Example 3

[0066] This embodiment proposes a processing technology for a flexible thin film piezoelectric sensor, such as Figure 7 The flowchart shown includes the following steps:

[0067] Step 1: Generate a piezoelectric layer, a protective layer, and an electrode layer on a metal foil from the inside out to produce a flexible thin film piezoelectric sensor.

[0068] Step 2: The flexible thin film piezoelectric sensor obtained in step 1 is attached to the end face of the fastener base by using coupling agent glue or metal welding.

[0069] In one achievable method of this embodiment, a flexible thin film piezoelectric sensor is prepared on a metal Ti foil. Specifically, the flexible thin film piezoelectric sensor is prepared by sequentially generating each layer structure on a 200 μm thick metal Ti foil using physical vapor deposition, and then the sensor is fixed to the end of an M8-30 hexagonal carbon steel bolt using Loctite 680 glue. The ultrasonic echo signal of the sensor is collected using ultrasound. The ultrasonic echo signal intensity spectrum is shown in FIG. Figure 8 As shown by Figure 8 It can be seen that the signal intensity of the flexible thin film piezoelectric sensor prepared on the metal Ti foil reaches △100 when the signal gain is 50db.

[0070] In another achievable method of this embodiment, a flexible thin film piezoelectric sensor is prepared on a stainless steel foil. Specifically, the flexible thin film piezoelectric sensor is prepared by sequentially generating each layer structure on a 20 μm thick stainless steel foil using physical vapor deposition, and then the sensor is fixed to the end of an M8-30 hexagonal carbon steel bolt by metal welding. The ultrasonic echo signal of the sensor is collected by ultrasonic wave. The ultrasonic echo signal intensity spectrum is shown as follows: Figure 9 As shown by Figure 9 It can be seen that the signal intensity of the flexible thin film piezoelectric sensor prepared on the stainless steel foil reaches △140 when the signal gain is 50db.

[0071] Comparative Example

[0072] The thin film piezoelectric sensor is prepared by directly generating each layer structure in sequence on the end of 8.8-grade carbon steel bolt M8-30 by physical vapor deposition method. The ultrasonic echo signal of the sensor is collected by ultrasonic wave. The ultrasonic echo signal intensity spectrum is shown in the figure below. Figure 10 As shown by Figure 10 It can be seen that the signal intensity of the flexible thin film piezoelectric sensor prepared on the metal Ti foil is △160 when the signal gain is 50db.

[0073] Generally speaking, the surface roughness of the flexible substrate is higher than that of the fastener substrate, and the crystal quality of the piezoelectric film is reduced, which affects the ultrasonic signal strength of the sensor. Figure 8 and Figure 9 It can be seen that the signal strength of the thin film sensor based on the flexible substrate produced by this embodiment is not much different from the signal strength of the sensor grown directly on the fastener, but the production process of the thin film sensor based on the flexible substrate of this embodiment is much simpler than the production process of the sensor grown directly on the fastener. This also shows that the thin film sensor based on the flexible substrate of this embodiment can basically maintain the same signal strength as the sensor grown directly on the fastener, and can also achieve single-time large-scale production.

[0074] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with this patent can make slight changes or modifications to equivalent embodiments using the above technical content without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the solution of the present invention.

Claims

1. A fastener, characterized in that: The fastener includes a fastener base, an end surface of which is provided with a flexible thin film piezoelectric sensor, the flexible thin film piezoelectric sensor including a flexible base, a piezoelectric layer, a protective layer and an electrode layer being formed on the flexible base in sequence from the inside to the outside, and the flexible base is a metal foil; The flexible thin film piezoelectric sensor is bonded to the fastener base by metal welding. 2 . The fastener according to claim 1 , wherein the material of the flexible substrate includes but is not limited to stainless steel, Ti, Al and alloys thereof.

3. The fastener according to claim 1, wherein: The thickness of the flexible substrate is 10 μm to 1 mm.

4. The fastener according to any one of claims 1 to 3, characterized in that: The material of the piezoelectric layer includes but is not limited to zinc oxide, aluminum nitride, cadmium sulfide, zinc sulfide, tantalum oxide, lithium niobate, lead titanate and polyvinylidene fluoride; The material of the protective layer includes but is not limited to chromium oxide, aluminum oxide, aluminum nitride, silicon oxide, silicon nitride, silicon carbide, diamond and doped diamond; The material of the electrode layer includes, but is not limited to, indium, tin, aluminum, titanium, nickel, copper, silver, gold, platinum, tungsten and alloys thereof.

5. The fastener according to claim 4, characterized in that The thickness of the piezoelectric layer is 0-30 μm, not 0; The thickness of the protective layer is 0~10um; The thickness of the electrode layer is 0-50 μm, not 0.

6. The fastener according to claim 1, wherein: A transition layer is further provided between the flexible substrate and the piezoelectric layer. The material of the transition layer includes but is not limited to titanium, nickel, and chromium.

7. The fastener according to claim 6, wherein: The thickness of the transition layer is 0-3 μm.

8. A processing technology for a flexible thin film piezoelectric sensor, characterized in that: The processing technology is used to prepare the fastener according to any one of claims 1 to 7, comprising the following steps: Step 1: Generating a piezoelectric layer, a protective layer, and an electrode layer on a metal foil from the inside out to produce a flexible thin film piezoelectric sensor; Step 2: The flexible thin film piezoelectric sensor obtained in step 1 is attached to the end surface of the fastener base by metal welding.

Images