A flexible capacitive pressure sensor and a method for preparing the same

Abstract

The invention relates to a flexible capacitive pressure sensor and a preparation method thereof, and relates to the field of sensors. The sensor comprises a base layer, a first electrode layer, a dielectric layer, a second electrode layer and a packaging layer which are stacked in sequence; a plurality of rectangular through holes are distributed on the base layer, the first electrode layer, the dielectric layer, the second electrode layer and the packaging layer, and the rectangular through holes on the base layer, the first electrode layer, the dielectric layer, the second electrode layer and the packaging layer are arranged correspondingly; a plurality of metal disks are distributed on the first electrode layer and the second electrode layer, and the metal disks on the first electrode layer and the metal disks on the second electrode layer are arranged overlappingly; a plurality of rectangular through holes are arranged around each metal disk; the metal disks on the first electrode layer are connected in series through metal wavy lines, and the metal disks on the second electrode layer are connected in series through metal wavy lines, and the accuracy of sensor measurement is improved through a stress reduction structure.

Description

Technical Field

[0001] The present invention relates to the field of sensor technology, and in particular to a flexible capacitive pressure sensor and a preparation method thereof. Background Art

[0002] Most of the existing flexible capacitive pressure sensors are composed of upper and lower electrode plates and a flexible dielectric layer. When subjected to a certain force in a non-target sensing direction, the sensor will deform. Due to the existence of Poisson's ratio, the sensor will also deform in the target sensing direction, causing the capacitance value to change, affecting the accuracy of the measurement. Summary of the invention

[0003] The purpose of the present invention is to provide a flexible capacitive pressure sensor and a preparation method thereof, which improves the measurement accuracy of the sensor through a stress-reducing structure.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] A flexible capacitive pressure sensor comprises a base layer, a first electrode layer, a dielectric layer, a second electrode layer and a packaging layer stacked in sequence; a plurality of rectangular through holes are distributed on the base layer, the first electrode layer, the dielectric layer, the second electrode layer and the packaging layer, and the rectangular through holes on the base layer, the first electrode layer, the dielectric layer, the second electrode layer and the packaging layer are arranged correspondingly; a plurality of metal disks are distributed on the first electrode layer and the second electrode layer, and the metal disks on the first electrode layer and the metal disks on the second electrode layer are arranged overlappingly; a plurality of rectangular through holes are arranged around each metal disk; the metal disks on the first electrode layer are connected in series by a metal wavy line, and the metal disks on the second electrode layer are connected in series by a metal wavy line.

[0006] Optionally, the metal wavy lines on the first electrode layer and the metal wavy lines on the second electrode layer do not cross or overlap.

[0007] Optionally, a plurality of rectangular through holes are distributed on the base layer, the first electrode layer, the dielectric layer, the second electrode layer and the packaging layer, specifically including:

[0008] A plurality of rectangular through holes are randomly distributed on the base layer, the first electrode layer, the dielectric layer, the second electrode layer and the packaging layer.

[0009] Optionally, the diameter of the metal disc ranges from 3 to 6 mm.

[0010] Optionally, the width of the rectangular through hole ranges from 1 to 3 mm.

[0011] Optionally, the inner diameter of the arc segments of the metal wave line is greater than or equal to 0.1 mm, and the distance between adjacent crests and troughs on the metal wave line is greater than or equal to 0.15 mm.

[0012] Optionally, the base layer, the dielectric layer and the packaging layer are all made of polydimethylsiloxane.

[0013] The present invention also discloses a method for preparing a flexible capacitive pressure sensor, wherein the method for preparing the flexible capacitive pressure sensor is used to prepare the flexible capacitive pressure sensor, and the method for preparing the flexible capacitive pressure sensor comprises:

[0014] Spin-coat photoresist on the surface of the silicon wafer to generate a sacrificial layer;

[0015] Spin-coating polydimethylsiloxane on the surface of the sacrificial layer to form a base layer;

[0016] A first flexible circuit board is attached to the base layer, and the first flexible circuit board is etched by using a reactive ion etching technique to obtain a first electrode layer;

[0017] Spin-coating polydimethylsiloxane on the surface of the first electrode layer to form a dielectric layer;

[0018] A second flexible circuit board is attached to the dielectric layer, and the second flexible circuit board is etched by using a reactive ion etching technique to obtain a second electrode layer;

[0019] Spin-coating polydimethylsiloxane on the surface of the second electrode layer to form an encapsulation layer and obtain an overall thin film structure;

[0020] The overall film structure is fixed on the surface of the processing platform, and the overall film structure is laser cut or mold stamped according to the preset positions and sizes of the multiple rectangular through holes to obtain a flexible capacitive pressure sensor.

[0021] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0022] The present invention discloses a flexible capacitive pressure sensor and a preparation method thereof. A plurality of rectangular through holes are distributed on a base layer, a first electrode layer, a dielectric layer, a second electrode layer and a packaging layer, and the rectangular through holes on the base layer, the first electrode layer, the dielectric layer, the second electrode layer and the packaging layer are arranged correspondingly; a plurality of metal disks are distributed on the first electrode layer and the second electrode layer, and the metal disks on the first electrode layer and the metal disks on the second electrode layer are arranged overlappingly; a plurality of rectangular through holes are arranged around each metal disk; the metal disks on the first electrode layer are connected in series through metal wavy lines, and the metal disks on the second electrode layer are connected in series through metal wavy lines, wherein the wavy lines on the first electrode layer and the second electrode layer and the rectangular through holes on the sensor constitute a stress reduction structure, thereby reducing the influence of external forces in non-sensing directions and improving the measurement accuracy of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A top view schematic diagram of a flexible capacitive pressure sensor of the present invention;

[0025] Figure 2 This is a schematic diagram of the structure of a flexible capacitive pressure sensor of the present invention;

[0026] Figure 3 A schematic diagram showing a comparison of strain finite element simulations in a non-sensing direction between a flexible capacitive pressure sensor of the present invention and a traditional pressure sensor;

[0027] Figure 4 A schematic diagram showing the comparison of the application effects of a flexible capacitive pressure sensor of the present invention and a traditional pressure sensor;

[0028] Figure 5 The present invention is a schematic flow chart of a method for preparing a flexible capacitive pressure sensor. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The purpose of the present invention is to provide a flexible capacitive pressure sensor and a preparation method thereof, which improves the measurement accuracy of the sensor through a stress-reducing structure.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Figure 1 FIG. 1 is a top view schematic diagram of a flexible capacitive pressure sensor of the present invention, as shown in FIG. Figure 1 As shown, a flexible capacitive pressure sensor comprises a substrate layer, a first electrode layer (lower electrode layer), a dielectric layer, a second electrode layer (upper electrode layer) and a packaging layer which are stacked in sequence; a plurality of rectangular through holes 2 are randomly distributed on the substrate layer, the first electrode layer, the dielectric layer, the second electrode layer and the packaging layer, and the rectangular through holes 2 on the substrate layer, the first electrode layer, the dielectric layer, the second electrode layer and the packaging layer are arranged correspondingly; a plurality of metal disks 1 are distributed on the first electrode layer and the second electrode layer, and the metal disks 1 on the first electrode layer and the metal disks 1 on the second electrode layer are arranged overlappingly; a plurality of rectangular through holes 2 are arranged around each metal disk 1; the metal disks 1 on the first electrode layer are connected in series through metal wavy lines 3, and the metal disks 1 on the second electrode layer are connected in series through metal wavy lines 3.

[0033] A plurality of rectangular through holes are randomly distributed on the base layer, the first electrode layer, the dielectric layer, the second electrode layer and the packaging layer. Specifically, the rectangular through holes do not need to be distributed regularly. The positions of the rectangular through holes are adaptively adjusted according to the distribution of the first electrode layer and the second electrode layer on the plane.

[0034] The metal wavy wire 3 is a metal wire in a wavy shape.

[0035] The base layer, the first electrode layer, the dielectric layer, the second electrode layer and the packaging layer of the present invention are arranged in sequence from bottom to top. For a flexible capacitive pressure sensor of the present invention, each metal disk 1 is provided with a rectangular through hole 2 in the four directions of top, bottom, left and right.

[0036] Figure 2 Here, S1 represents a substrate layer and a first electrode layer, S2 represents a dielectric layer and a second electrode layer, and S3 represents a packaging layer.

[0037] The present invention uses a hollow structure of a flexible capacitive pressure sensor formed by a rectangular through hole 2 to reduce the influence of non-target direction external forces on sensor deformation, thereby improving the measurement accuracy. This solves the problem that a thin or flexible capacitive sensor with a thickness of only a few hundred microns is affected by a non-sensing direction external force.

[0038] The metal wavy lines 3 on the first electrode layer and the metal wavy lines 3 on the second electrode layer do not cross or overlap, so as to reduce the influence of external parasitic capacitance.

[0039] The diameter of the metal disc 1 ranges from 3 to 6 mm.

[0040] The width of the rectangular through hole 2 ranges from 1 to 3 mm, and the spacing between each two adjacent rectangular through holes 2 is 2 to 4 mm.

[0041] The inner diameter of the arc segments of the metal wave line 3 is greater than or equal to 0.1 mm, and the distance from adjacent wave crests to wave troughs on the metal wave line 3 is greater than or equal to 0.15 mm.

[0042] The materials of the base layer, the dielectric layer and the packaging layer are all polydimethylsiloxane (PDMS).

[0043] The rectangular hollow structure (rectangular through hole 2) of the present invention does not need to be evenly and regularly distributed in the plane, and adaptive adjustments can be made according to the distribution of the capacitor plates and the remaining space in the space, thereby improving practicality.

[0044] As a specific embodiment, a flexible capacitive pressure sensor has 16 rectangular through holes 2, and the first electrode layer and the second electrode layer each include 9 metal disks 1. Figure 1 shown.

[0045] The sensitivity simulation of the flexible capacitive sensor with stress relief structure of the present invention is carried out using COMSOL software, deformation is applied to the horizontal direction (non-sensing direction) of the flexible capacitive sensor, and the capacitance change is recorded, such as Figure 3 As shown, it can be concluded that the sensor without stress relief structure is more sensitive to the strain in the non-sensing direction.

[0046] In addition, a sensitivity test is performed on a flexible capacitive sensor imitating human skin of the present invention. A tensile force is applied to the plane direction (non-sensing direction) of the flexible capacitive sensor of the present invention using a stretching machine, and a capacitance tester is used to measure the capacitance change of the sensor. Figure 4 As shown, it can be concluded that the sensor without stress relief structure is more sensitive to the strain in the non-sensing direction.

[0047] Figure 3 and Figure 4 The vertical axis is the capacitance change rate.

[0048] Figure 5 FIG. 1 is a flow chart of a method for preparing a flexible capacitive pressure sensor according to the present invention, as shown in FIG. Figure 5As shown, a method for preparing a flexible capacitive pressure sensor is used to prepare the above-mentioned flexible capacitive pressure sensor. A method for preparing a flexible capacitive pressure sensor includes:

[0049] Step 101: Spin-coat photoresist on the surface of a silicon wafer to generate a sacrificial layer.

[0050] Wherein, step 101 specifically includes: spin coating AZ4620 photoresist on the surface of the silicon wafer to generate a sacrificial layer.

[0051] Step 102: Spin-coat polydimethylsiloxane on the surface of the sacrificial layer to generate a base layer.

[0052] Step 103: attaching a first flexible circuit board to the base layer, and etching the first flexible circuit board using reactive ion etching technology to obtain a first electrode layer.

[0053] Step 103 specifically includes attaching a commercially processed first flexible circuit board on the base layer, and removing the remaining polyimide without metal circuits by reactive ion etching (RIE) technology to obtain the lower circuit structure (first electrode layer) of the capacitive sensor after etching.

[0054] Step 104: Spin-coat polydimethylsiloxane on the surface of the first electrode layer to form a dielectric layer.

[0055] Wherein, step 104 specifically includes spin coating polydimethylsiloxane on the surface of the first electrode layer, and forming a dielectric layer after the polydimethylsiloxane is cured.

[0056] Step 105: attaching a second flexible circuit board to the dielectric layer, and etching the second flexible circuit board using reactive ion etching technology to obtain a second electrode layer.

[0057] Step 105 specifically includes attaching a commercially processed second flexible circuit board on the dielectric layer, and removing the remaining polyimide without metal circuits by reactive ion etching (RIE) technology to obtain the upper circuit structure (second electrode layer) of the capacitive sensor after etching.

[0058] Step 106: Spin-coat polydimethylsiloxane on the surface of the second electrode layer to generate an encapsulation layer and obtain an overall thin film structure.

[0059] Step 107: fix the whole film structure on the surface of the processing platform, and perform laser cutting or mold stamping on the whole film structure according to the preset positions and sizes of the plurality of rectangular through holes to obtain a flexible capacitive pressure sensor.

[0060] The precision of laser cutting or die stamping is greater than or equal to 0.05 mm.

[0061] The present invention discloses a method for preparing a flexible capacitive pressure sensor. The prepared planar stress-reducing metal interconnect structure has the characteristics of smooth edges, small stress and large envelope size, is easy to be integrated and packaged or integrally bonded, and is very suitable for electrical interconnection and reliability packaging of thin devices.

[0062] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0063] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A flexible capacitive pressure sensor, It is characterized in that It comprises a base layer, a first electrode layer, a dielectric layer, a second electrode layer and a packaging layer which are stacked in sequence; a plurality of rectangular through holes are distributed on the base layer, the first electrode layer, the dielectric layer, the second electrode layer and the packaging layer, and the rectangular through holes on the base layer, the first electrode layer, the dielectric layer, the second electrode layer and the packaging layer are arranged correspondingly; a plurality of metal disks are distributed on the first electrode layer and the second electrode layer, and the metal disks on the first electrode layer and the metal disks on the second electrode layer are arranged overlappingly; a plurality of rectangular through holes are arranged around each metal disk; the metal disks on the first electrode layer are connected in series via a first metal wavy line, and the metal disks on the second electrode layer are connected in series via a second metal wavy line.

2. The flexible capacitive pressure sensor according to claim 1, It is characterized in that The first metal wavy lines on the first electrode layer and the second metal wavy lines on the second electrode layer do not cross or overlap.

3. The flexible capacitive pressure sensor according to claim 1, It is characterized in that A plurality of rectangular through holes are distributed on the base layer, the first electrode layer, the dielectric layer, the second electrode layer and the packaging layer, specifically including: A plurality of rectangular through holes are randomly distributed on the base layer, the first electrode layer, the dielectric layer, the second electrode layer and the packaging layer.

4. The flexible capacitive pressure sensor according to claim 1, It is characterized in that The diameter of the metal disc ranges from 3 to 6 mm.

5. The flexible capacitive pressure sensor according to claim 1, It is characterized in that The width of the rectangular through hole ranges from 1 to 3 mm.

6. The flexible capacitive pressure sensor according to claim 1, It is characterized in that The inner diameters of the arc segments of the first metal wave line and the second metal wave line are both greater than or equal to 0.1 mm, and the distances between adjacent crests and troughs on the first metal wave line and the second metal wave line are greater than or equal to 0.15 mm.

7. The flexible capacitive pressure sensor according to claim 1, It is characterized in that The materials of the base layer, the dielectric layer and the packaging layer are all polydimethylsiloxane.

8. A method for preparing a flexible capacitive pressure sensor, It is characterized in that The method for preparing the flexible capacitive pressure sensor is used to prepare the flexible capacitive pressure sensor according to any one of claims 1 to 7, and the method for preparing the flexible capacitive pressure sensor comprises: Spin-coat photoresist on the surface of the silicon wafer to generate a sacrificial layer; Spin-coating polydimethylsiloxane on the surface of the sacrificial layer to form a base layer; A first flexible circuit board is attached to the base layer, and the first flexible circuit board is etched by using a reactive ion etching technique to obtain a first electrode layer; Spin-coating polydimethylsiloxane on the surface of the first electrode layer to form a dielectric layer; A second flexible circuit board is attached to the dielectric layer, and the second flexible circuit board is etched by using a reactive ion etching technique to obtain a second electrode layer; Spin-coating polydimethylsiloxane on the surface of the second electrode layer to form an encapsulation layer and obtain an overall thin film structure; The overall film structure is fixed on the surface of the processing platform, and the overall film structure is laser cut or mold stamped according to the preset positions and sizes of the multiple rectangular through holes to obtain a flexible capacitive pressure sensor.

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