Capacitive flexible pressure sensor and method of making the same

Abstract

This application provides a capacitive flexible pressure sensor, including a first electrode plate, a second electrode plate, and an insulating layer. The first electrode plate includes a first substrate layer, a first electrode layer, and a first dielectric layer stacked together. The first electrode layer includes a plurality of spaced-apart first electrodes. The first substrate layer has a thickness direction. The first electrodes include sidewalls that are inclined to the thickness direction. The second electrode plate includes a second substrate layer, a second electrode layer, and a second dielectric layer stacked together. The second electrode layer includes a plurality of spaced-apart second electrodes. Each second electrode has a groove corresponding to a first electrode, and the second electrode has an inner wall surrounding the groove. An insulating layer is disposed between the first and second electrode plates and has a through hole. The first and second electrodes are disposed in the through hole, and the depth of the through hole is greater than the height of the first electrode and also greater than the depth of the groove, so that an air cavity is formed between the sidewall and the inner wall. This application also provides a method for manufacturing the capacitive flexible pressure sensor.

Description

Technical Field

[0001] This application relates to the field of sensor technology, and in particular to a capacitive flexible pressure sensor and its manufacturing method. Background Technology

[0002] Capacitive flexible pressure sensors have advantages such as high sensitivity, short response time, and low power consumption, and have been widely used in wearable electronic devices, medical devices, human-computer interaction, and smart homes.

[0003] Traditional capacitive flexible pressure sensors generally consist of an upper electrode plate and a lower electrode plate, which are parallel to each other and form an air cavity in the middle. By applying pressure to the upper electrode plate, the distance between the upper and lower electrode plates decreases, and the capacitance increases, thus converting the pressure signal into an electrical signal for identification. This type of capacitive flexible pressure sensor has the following disadvantages: (1) The relative area of ​​the electrodes remains unchanged, only the distance changes, the capacitance value and its rate of change are relatively small, the sensitivity is not high and the pressure detection range is very small, which limits the wide application of the sensor; (2) When pressure is applied, the linear correlation between the pressure value and the capacitance value is poor. Summary of the Invention

[0004] In view of the above, it is necessary to provide a capacitive flexible pressure sensor to solve at least one of the above problems.

[0005] In addition, it is necessary to provide a method for manufacturing a capacitive flexible pressure sensor.

[0006] This application provides a capacitive flexible pressure sensor with a first electrode plate. The first electrode plate includes a first substrate layer, a first electrode layer, and a first dielectric layer stacked together. The first electrode layer includes a plurality of first electrodes spaced apart. The first substrate layer has a thickness direction. The first electrode includes a sidewall, which is inclined to the thickness direction.

[0007] The second electrode plate is disposed at a distance from the first electrode plate. Along the thickness direction, the second electrode plate includes a second substrate layer, a second electrode layer and a second dielectric layer stacked together. The second electrode layer includes a plurality of second electrodes disposed at a distance. Each second electrode is provided with a groove. Each groove corresponds to a first electrode. The first electrode is movably disposed in the groove. The second electrode has an inner wall formed around the groove.

[0008] An insulating layer is disposed between the first electrode plate and the second electrode plate. The insulating layer has a through hole. The first electrode and the second electrode are disposed in the through hole. Along the thickness direction, the depth of the through hole is greater than the height of the first electrode. At the same time, the depth of the through hole is greater than the depth of the groove, so that an air cavity is formed between the side wall and the inner wall. The side wall, the inner wall, and the air cavity constitute a capacitor.

[0009] In some embodiments, the first electrode has a first axis of symmetry, the second electrode has a second axis of symmetry, and the first electrode and the second electrode are coaxially arranged.

[0010] In some embodiments, the sidewall of the first electrode is parallel to the inner wall of the second electrode.

[0011] In some embodiments, the first electrode is frustum-shaped, and the diameter d1 of the surface of the first electrode facing the groove is smaller than the diameter d2 of the surface of the first electrode away from the groove; the groove matches the shape of the first electrode, and the opening diameter d3 of the groove facing the first electrode is larger than the opening diameter d4 of the groove away from the first electrode.

[0012] In some embodiments, the capacitive flexible pressure sensor includes at least one sensing unit, each sensing unit including an n*n array of electrode units arranged in a matrix, each electrode unit including a first electrode and a second electrode; wherein n≥3, and n is an odd number.

[0013] In some embodiments, starting from the electrode unit at the center of the sensing unit, the diameters d3 and d4 of the second electrode remain constant, while the diameters d1 and d2 of the first electrode gradually increase synchronously outwards; or

[0014] Starting from the electrode unit at the center of the sensing unit, the diameters d1 and d2 of the first electrode remain unchanged, while the diameters d3 and d4 of the second electrode gradually decrease synchronously in all directions.

[0015] In some embodiments, along the thickness direction, the relationship between the distance h between the first dielectric layer and the second dielectric layer and the height H of the second electrode is: 0.5H < h < H.

[0016] This application also provides a method for manufacturing a capacitive flexible pressure sensor, comprising the following steps:

[0017] A first electrode plate is provided, the first electrode plate including a first substrate layer, a first electrode layer and a first dielectric layer stacked together, the first electrode layer including a plurality of first electrodes spaced apart, the first substrate layer having a thickness direction; the first electrode includes a sidewall, the sidewall being inclined to the thickness direction.

[0018] A second electrode plate is provided, the second electrode plate including a second substrate layer, a second electrode layer and a second dielectric layer stacked together, the second electrode layer including a plurality of second electrodes spaced apart, each second electrode having a groove, and the second electrode having an inner wall surrounding the groove;

[0019] An insulating layer is provided, and the first electrode plate, the insulating layer, and the second electrode plate are stacked and pressed together to obtain the capacitive flexible pressure sensor.

[0020] Each groove corresponds to a first electrode, and the first electrode is movably disposed in the groove; the insulating layer is provided with a through hole, and the first electrode and the second electrode are disposed in the through hole. Along the thickness direction, the depth of the through hole is greater than the height of the first electrode, and the depth of the through hole is greater than the depth of the groove, so that an air cavity is formed between the side wall and the inner wall.

[0021] In some embodiments, the first electrode has a first axis of symmetry, the second electrode has a second axis of symmetry, and in the pressing step, the first electrode and the second electrode are coaxially arranged, and the sidewall is parallel to the inner wall.

[0022] In some embodiments, prior to the pressing step, an insulating layer having the through-hole is pre-punched.

[0023] The capacitive flexible pressure sensor provided in this application designs a first electrode and a corresponding groove in the second electrode. Within the same surface space, the effective overlap area between the first and second electrodes is larger, saving space and allowing for the arrangement of more capacitors. During pressure application, the effective overlap area between the first and second electrodes gradually increases, resulting in a greater rate of change in capacitance under the same pressure. This leads to higher sensitivity within a small pressure range, which is beneficial for signal detection, and it is also suitable for monitoring a relatively large pressure range.

[0024] In addition, by setting the first electrode and the second electrode coaxially, and setting the sidewall of the first electrode parallel to the inner wall of the second electrode, the distance between the two electrodes gradually decreases during the compression process, which can further increase the rate of change of capacitance value.

[0025] In addition, by designing the sensing units arranged in a matrix and making the diameter of the first electrode or the second electrode change in an orderly manner, the capacitance value changes uniformly during the pressure process, which is beneficial to improving the linear correlation between the pressure value and the capacitance value.

[0026] The capacitive flexible pressure sensor provided in this application can be widely used in touch screens, styluses, electronic pressure valves, electronic skin and other fields of consumer electronics products. Attached Figure Description

[0027] Figure 1 This is a cross-sectional schematic diagram of a capacitive flexible pressure sensor provided in an embodiment of this application.

[0028] Figure 2 for Figure 1 The diagram shows the arrangement of electrode units to form a sensing unit.

[0029] Figure 3 for Figure 2 The sensing unit shown is in Figure 1 The diagram shows the arrangement of a capacitive flexible pressure sensor.

[0030] Figure 4 for Figure 1 The diagram shows the manufacturing process of the first electrode plate.

[0031] Figure 5 To form after pressing together the first electrode plate, the insulating layer and the second electrode plate Figure 1 The diagram shows the fabrication process of a capacitive flexible pressure sensor.

[0032] Explanation of main component symbols

[0033]

[0034]

[0035] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0036] To better understand the above-mentioned objectives, features, and advantages of this application, the application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. Many specific details are set forth in the following description to provide a thorough understanding of this application; the described embodiments are merely some, not all, of the embodiments described in this application.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The term "and / or" as used herein includes all and any combination of one or more of the associated listed items.

[0038] In the various embodiments of this application, for ease of description and not limitation, the term "connection" used in the patent application specification and claims is not limited to physical or mechanical connections, whether direct or indirect. Terms such as "upper," "lower," "above," "below," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship also changes accordingly.

[0039] Please see Figure 1 This application provides a capacitive flexible pressure sensor 100, which includes a first electrode plate 10, a second electrode plate 20, and an insulating layer 30. The first electrode plate 10 and the second electrode plate 20 are disposed at a distance from each other. The insulating layer 30 is located between the first electrode plate 10 and the second electrode plate 20. The first electrode plate 10 and the second electrode plate 20 are insulated from each other, that is, the circuit control of the first electrode plate 10 and the second electrode plate 20 is independent of each other.

[0040] The first electrode plate 10 includes a first substrate layer 11, a first electrode layer 13, and a first dielectric layer 15 stacked together. The first substrate layer 11 has a thickness direction L, and the first dielectric layer 15 covers the first electrode layer 13. The first electrode layer 13 includes a plurality of insulated first electrodes 131, which are arranged at intervals. Each first electrode 131 includes a sidewall 132.

[0041] Along the thickness direction L, the second electrode plate 20 includes a second substrate layer 21, a second electrode layer 23, and a second dielectric layer 25 stacked together, with the second dielectric layer 25 covering the second electrode layer 23. The second dielectric layer 25 is disposed facing the first dielectric layer 15, and the first substrate layer 11 and the second substrate layer 21 are located outside the capacitive flexible pressure sensor 100. The second electrode layer 23 includes a plurality of insulated second electrodes 231, which are arranged at intervals. Each second electrode 231 has a groove 232, through which a portion of the second substrate layer 21 is exposed. The second electrode 231 has an inner wall 233 surrounding the groove 232. Each groove 232 corresponds to a first electrode 131, and the shape of the groove 232 matches that of the first electrode 131. The first electrode 131 is movably disposed in the groove 232.

[0042] The insulating layer 30 has a through hole 31, and the first electrode 131 and the second electrode 231 are disposed in the through hole 31. Along the thickness direction L, the depth of the through hole 31 is greater than the height of the first electrode and the depth of the groove 232, so that an air cavity 40 is formed between the side wall 132 and the inner wall 233. The side wall 132, the inner wall 233 and the air cavity 40 constitute a capacitor.

[0043] In this embodiment, the first electrode 131 has a first axis of symmetry I1, and the second electrode 231 has a second axis of symmetry I2. The first axis of symmetry I1 and the second axis of symmetry I2 are coaxial, meaning the first electrode 131 and the second electrode 231 are coaxially arranged. The first electrode 131 is approximately frustum-shaped, meaning its cross-section is approximately trapezoidal. The surface diameter d1 of the first electrode 131 facing the groove 232 is smaller than the surface diameter d2 of the first electrode 131 facing away from the groove 232. The second electrode 231 is approximately annular, and the longitudinal section of the groove 232 is approximately trapezoidal. The opening diameter d3 of the groove 232 facing the first electrode 131 is larger than the opening diameter d4 of the groove 232 facing away from the first electrode 131. The distance h between the first dielectric layer 15 and the second dielectric layer 25 is smaller than the height H of the second electrode 231, and 0.5H < h < H.

[0044] Furthermore, the sidewall 132 is arranged parallel to the inner wall 233. As the first electrode 10 moves toward the second electrode 20 under pressure, the distance W between the first electrode 131 and the second electrode 231 gradually decreases, thereby improving the linear correlation between the pressure value and the capacitance value in the capacitive flexible pressure sensor 100.

[0045] Specifically, when pressure is applied to the first electrode 10, due to the presence of the air cavity 40, the first electrode 131 gradually moves closer to the second electrode 231, and the effective overlapping area S of the first electrode 131 and the second electrode 231 gradually increases, the distance W gradually decreases, and the capacitance value C gradually increases. When the pressure decreases or disappears, the first electrode 131 returns to its initial position, and the corresponding capacitance value C gradually decreases to the initial value C0. The capacitance value C between the two electrodes of the capacitive flexible pressure sensor 100 satisfies the following formula:

[0046]

[0047] Among them, 𝜀 r The dielectric constants of the first dielectric layer 15 and the second dielectric layer 25 are represented, and φ0 represents the vacuum dielectric constant of the air cavity 40. Compared to a planar capacitor, the capacitive flexible pressure sensor 100, by designing a first electrode 131 and a corresponding groove 232 in the second electrode 231, has a larger effective overlap area S between the first electrode 131 and the second electrode 231 within the same surface space, saving space and allowing for the arrangement of more capacitors. Furthermore, combined with the gradually decreasing distance W between the first electrode 131 and the second electrode 231, the rate of change of the capacitance value C is greater, resulting in higher sensitivity of the capacitive flexible pressure sensor 100, which is beneficial for signal detection and applicable to a wider pressure detection range. The capacitive flexible pressure sensor 100 can be widely used in touch screens, styluses, electronic pressure valves, electronic skin, and other fields of consumer electronics products.

[0048] Both the first substrate layer 11 and the second substrate layer 21 can be selected from flexible film materials such as polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), polydimethyl oxyalkylene (PDMS), and polyimide (PI). Furthermore, the first substrate layer 11 needs to possess a certain degree of resilience so that it can return to its initial position after deformation. Therefore, in practical applications, a more rigid material layer, such as a steel sheet (not shown), can be attached to the side of the first substrate layer 11 facing away from the first electrode layer 13.

[0049] The first dielectric layer 15 and the second dielectric layer 25 primarily serve to protect the first electrode 131 and the second electrode 231, while also functioning as capacitor dielectrics. Both the first dielectric layer 15 and the second dielectric layer 25 can be made of a polymer such as polypropylene (PP), polystyrene (PS), or polyethylene terephthalate (PET). To improve sensitivity and prevent relative displacement between the first electrode 10 and the second electrode 20 during pressure application, the elastic modulus of the insulating layer 30 can be greater than 0.1 GPa, for example, made of epoxy resin.

[0050] In this embodiment, the first electrode 131 and the second electrode 231 are made of copper. In other embodiments, they may also be made of chromium or gold.

[0051] In addition, when the capacitive flexible pressure sensor 100 is used in practice, due to the presence of the air cavity 40, the first electrode plate 10 will inevitably form a phenomenon where the bending moment is large in the middle position and small at the edge position when it is under pressure. That is, the deformation at the middle position is greater than the deformation at the surrounding positions, which leads to uneven change in capacitance value.

[0052] Please see Figure 1 , Figure 2 and Figure 3 In this application, a first electrode 131 and its corresponding second electrode 231 are considered as one electrode unit 50. Several electrode units 50 are arranged in an array to form a group of sensing units 60. The capacitive flexible pressure sensor 100 includes multiple groups of sensing units 60 arranged in an array. Each sensing unit 60 includes a 5*5 array of electrode units 50 arranged in a matrix. Starting from the electrode unit 50 at the center of the sensing unit 60, the diameters d3 and d4 of the second electrode 231 remain unchanged, while the diameter of the first electrode 131 gradually increases along the first direction A1, the second direction A2, and the third direction A3.

[0053] Since the first electrode 131 is frustum-shaped, the diameter mentioned here includes the surface diameter d1 of the first electrode 131 facing the groove 232 and the surface diameter d2 of the first electrode 131 away from the groove 232. During the change, the diameter d1 and the diameter d2 increase synchronously, that is, the sidewall 132 of the first electrode 131 and the inner wall 233 of the second electrode are always kept parallel.

[0054] Understandably, in other embodiments, the diameter of the first electrode 131 may be kept constant, and the diameter of the second electrode 231 may gradually decrease along the first direction A1, the second direction A2, and the third direction A3.

[0055] In this embodiment, the first direction A1 and the second direction A2 are perpendicular to each other, and the third direction A3 makes an angle of 45° with both the first direction A1 and the second direction A2.

[0056] The capacitive flexible pressure sensor 100 provided in this application designs a first electrode 131 and a corresponding matching groove 232 on the second electrode 231. The sidewall 132 of the first electrode 131 and the inner wall 233 of the second electrode 231 are arranged parallel to each other. This makes the effective overlapping area of ​​the first electrode 131 and the second electrode 231 gradually increase and the distance gradually decrease during the pressure process. Under the same pressure, the rate of change of capacitance value is greater, and it has higher sensitivity in a small pressure range, which is beneficial for signal detection and can be applied to monitoring a relatively large pressure range.

[0057] In addition, by designing the sensing units 60 arranged in a matrix and making the diameters of the first electrode 131 or the second electrode 231 change in an orderly manner, the capacitance value changes uniformly during the pressure process, which is beneficial to improving the linear correlation between the pressure value and the capacitance value.

[0058] Please see Figure 4 and Figure 5 This application also provides Figure 1 The method for manufacturing the capacitive flexible pressure sensor 100 shown includes the following steps:

[0059] Step S1: Please refer to Figure 4 The first electrode plate 10 is formed.

[0060] The first electrode plate 10 can be formed by the following steps.

[0061] Step S11: Please refer again Figure 4 A single-sided copper-clad laminate 10a is provided, including a first substrate layer 11 and a copper foil layer 13a stacked thereon.

[0062] Step S12: A photosensitive dry film 17 is disposed on the surface of the copper foil layer 13a opposite to the first substrate layer 11.

[0063] Step S13: Expose and develop the photosensitive dry film 17 to form a photosensitive pattern layer 17a.

[0064] Step S13: Etch the copper foil layer 13a to form the first electrode layer 13, and remove the photosensitive pattern layer 17a.

[0065] The first electrode layer 13 includes a plurality of first electrodes 131 spaced apart, and the longitudinal section of the first electrode 131 is trapezoidal.

[0066] Step S14: A first dielectric layer 15 is provided on the single-sided copper clad laminate 10a. The first dielectric layer 15 covers the first electrode layer 13, fills the gaps between the plurality of first electrodes 131, and is bonded to the surface of the first substrate layer 11.

[0067] Step S2: Fabricate the second electrode plate 20.

[0068] The steps for forming the second electrode plate 20 are the same as those for the first electrode plate 10, and will not be repeated here.

[0069] Step S3: Please refer to Figure 5 An insulating layer 30 with through holes 31 is pre-stamped and stacked in the order of first electrode plate 10, insulating layer 30 and second electrode plate 20 and then pressed together to form the capacitive flexible pressure sensor 100 with air cavity 40.

[0070] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A capacitive flexible pressure sensor, characterized by, include: The first electrode plate includes a first substrate layer, a first electrode layer and a first dielectric layer stacked together. The first electrode layer includes a plurality of first electrodes spaced apart. The first substrate layer has a thickness direction. The first electrode includes a sidewall that is inclined to the thickness direction. The second electrode plate is disposed at a distance from the first electrode plate. Along the thickness direction, the second electrode plate includes a second substrate layer, a second electrode layer and a second dielectric layer stacked together. The second electrode layer includes a plurality of second electrodes disposed at a distance. Each second electrode is provided with a groove. Each groove corresponds to a first electrode. The first electrode is movably disposed in the groove. The second electrode has an inner wall formed around the groove. An insulating layer is disposed between the first electrode plate and the second electrode plate. The insulating layer has a through hole. The first electrode and the second electrode are disposed in the through hole. Along the thickness direction, the depth of the through hole is greater than the height of the first electrode. At the same time, the depth of the through hole is greater than the depth of the groove, so that an air cavity is formed between the side wall and the inner wall. The side wall, the inner wall and the air cavity constitute a capacitor.

2. The capacitive flexible pressure sensor according to claim 1, characterized in that, The first electrode has a first axis of symmetry, the second electrode has a second axis of symmetry, and the first electrode and the second electrode are coaxially arranged.

3. The capacitive flexible pressure sensor according to claim 1, wherein, The sidewall of the first electrode is parallel to the inner wall of the second electrode.

4. The capacitive flexible pressure sensor of claim 1, wherein, The first electrode is frustum shaped, and the diameter d1 of the surface of the first electrode facing the groove is smaller than the diameter d2 of the surface of the first electrode away from the groove; the groove matches the shape of the first electrode, and the opening diameter d3 of the groove facing the first electrode is larger than the opening diameter d4 of the groove away from the first electrode.

5. The capacitive flexible pressure sensor according to claim 4, characterized in that, The capacitive flexible pressure sensor includes at least one sensing unit, each sensing unit including an n*n array of electrode units arranged in a matrix, each electrode unit including a first electrode and a second electrode; wherein, n≥3, and n is an odd number.

6. The capacitive flexible pressure sensor according to claim 5, wherein, Starting from the electrode unit at the center of the sensing unit, the diameters d3 and d4 of the second electrode remain constant, while the diameters d1 and d2 of the first electrode gradually increase synchronously outwards; or Starting from the electrode unit at the center of the sensing unit, the diameters d1 and d2 of the first electrode remain unchanged, while the diameters d3 and d4 of the second electrode gradually decrease synchronously in all directions.

7. The capacitive flexible pressure sensor of claim 1, wherein, Along the thickness direction, the relationship between the distance h between the first dielectric layer and the second dielectric layer and the height H of the second electrode is: 0.5H < h < H.

8. A method of fabricating a capacitive flexible pressure sensor, characterized by, include: A first electrode plate is provided, the first electrode plate including a first substrate layer, a first electrode layer and a first dielectric layer stacked together, the first electrode layer including a plurality of first electrodes spaced apart, the first substrate layer having a thickness direction; the first electrode includes a sidewall, the sidewall being inclined to the thickness direction. A second electrode plate is provided, the second electrode plate including a second substrate layer, a second electrode layer and a second dielectric layer stacked together, the second electrode layer including a plurality of second electrodes spaced apart, each second electrode having a groove, and the second electrode having an inner wall surrounding the groove; An insulating layer is provided, and the first electrode plate, the insulating layer, and the second electrode plate are stacked and pressed together to obtain the capacitive flexible pressure sensor. Each groove corresponds to a first electrode, and the first electrode is movably disposed in the groove; the insulating layer is provided with a through hole, and the first electrode and the second electrode are disposed in the through hole. Along the thickness direction, the depth of the through hole is greater than the height of the first electrode, and the depth of the through hole is greater than the depth of the groove, so that an air cavity is formed between the side wall and the inner wall.

9. The method for manufacturing a capacitive flexible pressure sensor according to claim 8, characterized in that, The first electrode has a first axis of symmetry, and the second electrode has a second axis of symmetry. In the pressing step, the first electrode and the second electrode are coaxially arranged, and the sidewall is parallel to the inner wall.

10. The method for manufacturing a capacitive flexible pressure sensor according to claim 8, characterized in that, Prior to the pressing step, an insulating layer with the through holes is pre-punched.

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