Flexible ultrasonic sensor and packaging method

Abstract

According to the flexible ultrasonic sensor and the packaging method, in the flexible ultrasonic sensor, a sensor shell is of a flexible structure; the thin film electrode is arranged in the sensor shell, the plurality of top electrodes are arranged on the PZT piezoelectric thin film and form a parallel electrode structure through a flexible copper foil adhesive tape and conductive silver paste, the bottom electrode is located on the lower side of the PZT piezoelectric thin film and is insulated from the top electrodes, and an internal lead is connected with the thin film electrode; the single-core lead is connected with the internal lead; and the output end lead comprises a BNC wire connected with the single-core lead.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible ultrasonic sensors, in particular to a flexible ultrasonic sensor and a packaging method. Background Art

[0002] In recent years, with the continuous progress and development of science and technology, people have put forward new requirements for various sensing devices in daily life and production monitoring. In the field of modern science and technology, flexible sensors have many advantages such as strong flexibility, good adaptability, light weight, low cost, easy integration, versatility, low power consumption and real-time monitoring, making them gradually become an important part of various applications. Compared with traditional rigid sensors, flexible pressure sensors have good elasticity and flexibility, can conform to the application surface, can capture high-quality pressure signals on curved surfaces, and have good sensing performance.

[0003] Although different types of flexible sensors have different working principles, they are all composed of a flexible substrate, sensitive materials, and conductive electrodes. Among them, the elastic substrate gives the flexible sensor a certain degree of flexibility and strain capacity, so that it can fully fit the irregular surface and obtain the excitation signal. The conductive network constructed by the sensitive material gives the sensing structure a certain degree of conductivity and sensitivity. It is the most important component of the flexible sensor and determines the performance of the sensor.

[0004] Piezoelectric materials can convert tiny mechanical deformations into electrical signals, thereby realizing the conversion between force signals and electrical signals, and have received extensive attention in the fields of materials science and engineering. When the sensor is stimulated by external stimuli, the piezoelectric material generates an electrical signal through the piezoelectric effect and transmits the electrical signal through the connection, giving it sensing performance.

[0005] Among them, flexible ultrasonic sensors have very broad prospects in the field of partial discharge detection in power systems.

[0006] Partial discharge is the main precursor of insulation failure in electrical equipment. When partial discharge occurs, it is often accompanied by physical characteristics such as pulse current, electromagnetic waves, ultrasound, optical signals, and gas. By detecting these physical quantities and promptly discovering the partial discharge defects inside the equipment, fault warning can be achieved to ensure equipment safety and power supply reliability. As a non-invasive partial discharge detection method, the ultrasonic method is portable and non-destructive. However, the ultrasonic signal generated by the partial discharge inside the electrical equipment is weak in itself, and the acoustic signal is significantly attenuated after propagating to the surface of the equipment. There are electromagnetic signals and noise signals in the environment where the electrical equipment is located, which may affect the normal operation of the electrical equipment in the detection system. Therefore, it is necessary to improve the sensitivity of the sensor and increase the detectable range and stability of the sensor. In addition, the sensor needs to be well designed with electromagnetic shielding to reduce or eliminate the interference of complex electromagnetic signals and noise signals in the environment.

[0007] The detection range and sensitivity of a single top electrode sensor are limited. In order to improve the performance of flexible sensors and increase the stability of sensors, a sensor parallel structure can be designed. The parallel structure is based on the sensing of a single top electrode, and multiple top electrodes are integrated to form a diversified structure to achieve the purpose of improving monitoring sensitivity and stability. However, sensor parallel connection is not just about sticking multiple monolithic sensors on the detection surface, but requires connecting multiple sensing units in a simpler way through specific circuit design, and using simpler circuit design sensors to achieve large-area or multiple signal perception. Compared with a single sensor, the advantage of the sensor is that the array adds more signal detection sources to the measurement of data, thereby being able to collect more signals.

[0008] The information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0009] In view of the shortcomings or defects of the prior art, a flexible ultrasonic sensor and a packaging method are provided to achieve the perception of a large area or multiple signals, improve the detection range and stability of the flexible ultrasonic sensor, and make it safer and more reliable.

[0010] The purpose of the present invention is achieved through the following technical solutions.

[0011] A flexible ultrasonic sensor comprises: A sensor housing, which is a flexible structure; A thin film electrode is disposed in the sensor housing, and the thin film electrode comprises: PZT piezoelectric film, A plurality of top electrodes are arranged on the PZT piezoelectric film, and the plurality of top electrodes form a parallel electrode structure through a flexible copper foil tape and a conductive silver paste. a bottom electrode, which is located at the lower side of the PZT piezoelectric film and is insulated from the top electrode, Internal leads connecting the thin film electrodes; A single-core wire connected to the inner lead wire; The output terminal lead includes a BNC line connected to the single-core wire.

[0012] In the flexible ultrasonic sensor, the sensor housing comprises a pair of flexible film materials which are conductive on the outside and insulated and sticky on the inside.

[0013] In the flexible ultrasonic sensor, the flexible film material is a PET film.

[0014] In the flexible ultrasonic sensor, an insulating shielding structure is provided between the top electrode and the bottom electrode to prevent conduction.

[0015] In the flexible ultrasonic sensor, one end of the flexible copper foil tape is attached to the top electrode or the bottom electrode to complete the connection, and the other end is connected to the single-core wire by welding.

[0016] In the flexible ultrasonic sensor, one end of the single-core wire is connected to the flexible copper foil tape, and the other end is connected to the signal wire and the shielding wire of the BNC wire.

[0017] In the flexible ultrasonic sensor, the single-core wire and the sensor housing have an electromagnetic shielding layer, and the sensor housing is connected to the BNC ground wire at the connection point between the single-core wire and the BNC wire to complete grounding.

[0018] The packaging method of the flexible ultrasonic sensor comprises the following steps: Place the mask with the opening array on the PZT piezoelectric film to obtain different top electrode parallel arrays, use tape to fix the PZT piezoelectric film and the mask on the back, so that the PZT piezoelectric film is close to the mask, and ensure that the sputtered electrode shape is consistent with the mask opening shape. At the bottom electrode, use tweezers to make a few scratches to expose the bottom electrode under the PZT piezoelectric film, and place the mask and PZT piezoelectric film in the gold spraying instrument and take them out after sputtering the electrode; Place the PZT piezoelectric film with the electrodes sprayed on the insulating and sticky side of the PET film, and cover the PZT film with polyimide to ensure that the top and bottom electrodes are exposed through the openings of the polyimide film; A plurality of top electrodes are connected together using a flexible copper foil tape to form a parallel electrode structure. Conductive silver paste is used between the top electrode and the flexible copper foil tape. Two flexible copper foil tapes are used to connect the top electrode and the bottom electrode respectively. Cover the PET film with another piece of PET film to ensure there are no bubbles between the two pieces of PET film; Take two single-core wires to connect the top electrode and the bottom electrode respectively, take a single-ended BNC wire, and weld the two single-core wires to the signal wire and the outer shielding wire of the single-ended BNC wire respectively.

[0019] In the packaging method, a layer of polyimide film is attached to the connection between the single-core wire connecting the top electrode and the signal wire of the BNC wire to prevent the signal wire from being connected to the ground wire.

[0020] In the packaging method, a layer of flexible copper foil tape is wrapped around the connection between the two single-core wires and the BNC wire and the outer sides of the two single-core wires.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a stable flexible ultrasonic sensor packaging preparation process, which can give full play to the piezoelectric properties of the flexible piezoelectric film. The top electrode parallel arrangement structure can realize large-area signal detection and multiple signal detection, and can stably improve the detection sensitivity and use stability of the sensor. The parallel structure packaging shielding method can prevent the internal circuit of the sensor from being turned on and realize the external electromagnetic interference and noise shielding of the sensor. Thereby improving the stability and reliability of the flexible piezoelectric ultrasonic sensor in complex environments. The sensitivity shown in the lead breaking experiment is higher, and more ultrasonic signal information can be detected.

[0022] The above description is only an overview of the technical solution of the present invention. In order to make the technical means of the present invention clearer and to achieve the extent that those skilled in the art can implement it according to the contents of the specification, and in order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are exemplified below. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used to represent the same components throughout the drawings.

[0024] In the attached picture: Figure 1 This is a schematic diagram of the preliminary packaging and solder joint wiring method of the flexible ultrasonic sensor; Figure 2 This is a schematic diagram of BNC wiring and shielding methods; Figure 3 Design a schematic diagram for the parallel structure; Figure 4 This is a schematic diagram of the packaged finished sensor; Figure 5 Schematic diagram of the decomposed structure of the flexible ultrasonic sensor.

[0025] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0026] The specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0027] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0028] To facilitate understanding of the embodiments of the present invention, several specific embodiments will be further explained below with reference to the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0029] For a better understanding, Figures 1 to 5 As shown, a flexible ultrasonic sensor comprises: A sensor housing, which is a flexible structure; A thin film electrode is disposed in the sensor housing, and the thin film electrode comprises: PZT piezoelectric film, A plurality of top electrodes are arranged on the PZT piezoelectric film, and the plurality of top electrodes form a parallel electrode structure through a flexible copper foil tape and a conductive silver paste. a bottom electrode, which is located at the lower side of the PZT piezoelectric film and is insulated from the top electrode, Internal leads connecting the thin film electrodes; A single-core wire connected to the inner lead wire; The output terminal lead includes a BNC line connected to the single-core wire.

[0030] In a preferred embodiment of the flexible ultrasonic sensor, the sensor housing includes a pair of flexible film materials with conductive outer sides and insulating and adhesive inner sides.

[0031] In a preferred embodiment of the flexible ultrasonic sensor, the flexible film material is a PET film.

[0032] In a preferred embodiment of the flexible ultrasonic sensor, an insulating shielding structure is provided between the top electrode and the bottom electrode to prevent conduction.

[0033] In a preferred embodiment of the flexible ultrasonic sensor, one end of the flexible copper foil tape is attached to the top electrode or the bottom electrode to complete the connection, and the other end is connected to the single-core wire by welding.

[0034] In a preferred embodiment of the flexible ultrasonic sensor, one end of the single-core wire is connected to the flexible copper foil tape, and the other end is connected to the signal wire and the shielding wire of the BNC wire.

[0035] In a preferred embodiment of the flexible ultrasonic sensor, an electromagnetic shielding layer is present between the single-core wire and the sensor housing, and the sensor housing is connected to a BNC ground wire at the connection point between the single-core wire and the BNC wire to complete grounding.

[0036] The packaging method of the flexible ultrasonic sensor comprises the following steps: Place the mask with the opening array on the PZT piezoelectric film to obtain different top electrode parallel arrays, use tape to fix the PZT piezoelectric film and the mask on the back, so that the PZT piezoelectric film is close to the mask, and ensure that the sputtered electrode shape is consistent with the mask opening shape. At the bottom electrode, use tweezers to make a few scratches to expose the bottom electrode under the PZT piezoelectric film, and place the mask and PZT piezoelectric film in the gold spraying instrument and take them out after sputtering the electrode; Place the PZT piezoelectric film with the electrodes sprayed on the insulating and sticky side of the PET film, and cover the PZT film with polyimide to ensure that the top and bottom electrodes are exposed through the openings of the polyimide film; A plurality of top electrodes are connected together using a flexible copper foil tape to form a parallel electrode structure. Conductive silver paste is used between the top electrode and the flexible copper foil tape. Two flexible copper foil tapes are used to connect the top electrode and the bottom electrode respectively. Cover the PET film with another piece of PET film to ensure there are no bubbles between the two pieces of PET film; Take two single-core wires to connect the top electrode and the bottom electrode respectively, take a single-ended BNC wire, and weld the two single-core wires to the signal wire and the outer shielding wire of the single-ended BNC wire respectively.

[0037] In a preferred embodiment of the packaging method, a layer of polyimide film is attached to the connection between the single-core wire connecting the top electrode and the signal wire of the BNC wire to prevent the signal wire from being connected to the ground wire.

[0038] In a preferred implementation of the packaging method, a layer of flexible copper foil tape is wrapped around the connection between the two single-core wires and the BNC wire and the outer sides of the two single-core wires.

[0039] In one embodiment, a flexible ultrasonic sensor includes, Sensor housing, PET (polyethylene terephthalate) film, The thin film electrode includes a top electrode and a bottom electrode. The top electrode is a parallel electrode structure and is insulated from the bottom electrode. The internal leads of the sensor include flexible copper foil tape and conductive silver paste.

[0040] The sensor output lead includes a single-core wire and a single-ended BNC wire.

[0041] Sensor electromagnetic shielding structure design.

[0042] Furthermore, the sensor housing is made of a flexible film material, which is conductive on the outside and insulated and has a certain viscosity on the inside. The two pieces are attached together to form a flexible housing of the sensor. The top electrode uses magnetron sputtering to sputter a platinum target onto the film surface, and a plurality of top electrodes of different shapes and sizes can be obtained by using different mask plates. The bottom electrode is located on the lower side of the PZT piezoelectric film, and the bottom electrode is exposed by cutting the PZT film, and then the bottom electrode is formed on the film surface by magnetron sputtering. The mask plate can be used to design different types and numbers of top electrode parallel structures, and the top electrodes are connected in parallel to form a whole through copper foil tape and conductive silver paste. During the process of connecting the top electrode in parallel with the lead wire, an insulating shielding design is used to prevent the top electrode from being conductive with the bottom electrode. The flexible copper foil tape is cut into a specific shape, one end of which is connected to the top electrode / bottom electrode, and the other end is connected to the single-core wire. The copper foil tape is attached to the top electrode / bottom electrode to complete the connection, and the other end of the copper foil tape is connected to the single-core wire by welding. One end of the single-core wire is connected to the copper foil tape, and the other end is connected to the signal wire and shield wire of the single-ended BNC wire. At the connection between the wire and the BNC wire, the single-core wire part and the sensor housing have an electromagnetic shielding design. And the sensor housing is connected to the BNC ground wire at the connection between the wire and the BNC wire to complete the grounding. In one embodiment, the position of the bottom electrode is determined by the gold-spraying mask, and the bottom electrodes obtained by gold-spraying with different masks are different. Generally, when making parallel connections, in order to facilitate wiring, the bottom electrode and the top electrode are on the same horizontal line, such as Figure 5 As shown, the bottom electrode is located to the left of the two top electrodes.

[0043] Example

[0044] The packaging method of the flexible ultrasonic sensor comprises the following steps: (1) Take a piece of PZT (lead zirconate titanate) flexible piezoelectric film and place the mask with an opening array on the piezoelectric film. Different mask plates can be customized to obtain different top electrode parallel arrays. Use tape to fix the film and the mask on the back to make the film close to the mask and ensure that the shape of the sputtered electrode is consistent with the shape of the mask opening. Use tweezers to make a few scratches on the bottom electrode of the film to expose the bottom electrode of the PZT layer. Place the mask and film in the gold spraying instrument and take them out after sputtering the electrode.

[0045] (2) Remove the film from the mask and use a multimeter to measure the capacitance of each top electrode to ensure that each top electrode and bottom electrode are in a non-conductive state.

[0046] (3) Cut a piece of PET conductive film with a width of 2.5 cm and a length of 5 cm. Remove the protective film on the surface of the PET and place the PZT film with the electrode sprayed on the insulating and sticky side of the PET film, slightly above it for easy wiring. A layer of silicone grease can be applied between the PZT film and the PET film to ensure a tight connection between the two.

[0047] (4) Take a piece of polyimide film and use a puncher to make a hole in the polyimide film according to the shape of the top electrode sprayed on the mask. Make sure that the position of the hole in the polyimide film is consistent with the position of the top electrode on the film. Cover the polyimide on top of the PZT film. Make sure that the top electrode and the bottom electrode can be exposed through the hole in the polyimide film. The purpose here is to prevent the top electrode and the bottom electrode from being conductive during the subsequent wiring process.

[0048] (5) Use copper foil tape to connect multiple top electrodes together to form a large top electrode. Silver paste can be used between the electrode and the copper foil tape to make the connection between the electrodes tighter and stronger. Cut two pieces of copper foil tape and connect the copper foil to the top electrode and the bottom electrode respectively. Silver paste can be used to ensure a tight connection.

[0049] (6) Cover the sensor with another piece of PET film of the same size, making sure there are no bubbles between the two pieces of PET to protect the piezoelectric sensitive material.

[0050] (7) Take two single-core wires, one red and one black. Connect the red wire to the top electrode and the black wire to the bottom electrode. Use wire strippers to strip the inner core of the wire. Use solder to connect the single-core wire to the copper foil. Be careful to prevent the top and bottom electrodes from conducting. Apply a layer of polyimide film to the solder joint of the top electrode lead.

[0051] (8) Take a single-ended BNC cable and solder the two single-core wires to the signal wire and outer shield wire of the single-ended BNC cable. Connect the red wire to the BNC signal wire, and the black wire to the BNC shield wire. Stick a layer of polyimide film at the connection between the red wire and the BNC signal wire to prevent the signal wire from being connected to the ground wire.

[0052] (9) Wrap a layer of copper foil tape around the connection between the two wires and the BNC wire and the outside of the two wires to prevent external electromagnetic interference from coupling into the signal here. Wrap a layer of copper foil around the outside of the sensor to connect the sensor housing to the BNC shielding wire to complete the grounding and prevent the introduction of power frequency interference signals.

[0053] The basic principles of the present application are described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, effects, etc. mentioned in the present application are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. are required by each embodiment of the present application. In addition, the specific details disclosed above are only for the purpose of illustration and ease of understanding, not for limitation, and the above details do not limit the present application to being implemented by adopting the above specific details.

[0054] The above description has been given for the purpose of illustration and description. In addition, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although multiple example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, changes, additions and sub-combinations thereof.

Claims

1. A flexible ultrasonic sensor, characterized in that: These include, A sensor housing, which is a flexible structure; A thin film electrode is arranged in the sensor housing, and the thin film electrode comprises: PZT piezoelectric film, A plurality of top electrodes are arranged on the PZT piezoelectric film, and the plurality of top electrodes form a parallel electrode structure through a flexible copper foil tape and a conductive silver paste. a bottom electrode, which is located at the lower side of the PZT piezoelectric film and is insulated from the top electrode, Internal leads connecting the thin film electrodes; A single-core wire connected to the inner lead wire; The output terminal lead includes a BNC line connected to the single-core wire.

2. The flexible ultrasonic sensor according to claim 1, characterized in that: Preferably, the sensor housing comprises a pair of flexible film materials which are conductive on the outside and insulated and adhesive on the inside.

3. The flexible ultrasonic sensor according to claim 2, characterized in that: The flexible film material is a PET film.

4. The flexible ultrasonic sensor according to claim 1, characterized in that: An insulating shielding structure is provided between the top electrode and the bottom electrode to prevent conduction.

5. The flexible ultrasonic sensor according to claim 1, characterized in that: One end of the flexible copper foil tape is attached to the top electrode or the bottom electrode to complete the connection, and the other end is connected to the single-core wire by welding.

6. The flexible ultrasonic sensor according to claim 1, characterized in that: One end of the single-core wire is connected to the flexible copper foil tape, and the other end is connected to the signal wire and the shielding wire of the BNC wire.

7. The flexible ultrasonic sensor according to claim 1, characterized in that: The single-core wire and the sensor housing have an electromagnetic shielding layer, and the sensor housing is connected to the BNC ground wire at the connection point between the single-core wire and the BNC wire to complete grounding.

8. The packaging method of the flexible ultrasonic sensor according to any one of claims 1 to 7.

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