Pressure sensing circuit board, preparation method thereof and flexible pressure sensing element

Abstract

The invention provides a pressure-sensitive circuit board and a preparation method thereof, and a flexible pressure-sensitive element, the pressure-sensitive circuit board comprises a circuit substrate and a stress-strain layer, and the circuit substrate comprises an insulating layer and a first circuit layer; the stress-strain layer comprises two electrodes and a sensitive structure located between the two electrodes, the sensitive structure comprises a plurality of linear resistors arranged side by side and connecting parts connecting two adjacent linear resistors, the linear resistors and the connecting parts form a bent shape, the connecting parts are located at the bent parts, and the resistivity of the connecting parts is smaller than that of the linear resistors. According to the pressure-sensitive circuit board provided by the embodiment of the invention, the linear resistors with relatively high resistivity are connected in series through the connecting parts with relatively low resistivity, so that the sensitivity of the sensitive structure cannot be reduced due to the difference between the stress of the bending parts and the stress of the linear resistors, and the sensitivity of the stress-strain layer is improved.

Description

Technical Field

[0001] The present application relates to the technical field of flexible sensors, and in particular to a pressure-sensitive circuit board and a preparation method thereof, and a flexible pressure-sensitive element. Background Art

[0002] Flexible sensors, typically composed of a flexible substrate combined with a conductive material, can convert specific external signals, such as force or heat, into electrical signals, which are then transmitted to computers for processing. Due to their excellent flexibility and ductility, flexible sensors can be arranged arbitrarily to meet measurement requirements. Therefore, they hold great potential for application in medical electronics, environmental monitoring, and wearable electronics.

[0003] However, the sensitivity of existing flexible sensors is low and needs to be improved urgently. Summary of the Invention

[0004] In view of this, in order to solve at least one of the above problems, it is necessary for the present application to provide a pressure-sensitive circuit board.

[0005] In addition, the present application also needs to provide a method for preparing the aforementioned pressure-sensitive circuit board and a flexible pressure-sensitive element using the aforementioned pressure-sensitive circuit board.

[0006] An embodiment of the present application provides a pressure-sensitive circuit board, comprising: a circuit substrate and a stress-strain layer, wherein the circuit substrate comprises an insulating layer and a first circuit layer disposed on the insulating layer; the stress-strain layer comprises two electrodes spaced apart and a sensitive structure located between the two electrodes, wherein the electrodes are electrically connected to the first circuit layer; and the sensitive structure comprises a plurality of linear resistors arranged side by side and a connecting portion connecting two adjacent linear resistors, wherein the linear resistors and the connecting portion form a bent shape, the connecting portion being located at the bent portion, and the resistivity of the connecting portion being less than the resistivity of the linear resistors.

[0007] In some possible embodiments, the stress strain layer includes: a resistance layer and a second circuit layer, the resistance layer is arranged on the surface of the insulating layer away from the first circuit layer, the resistance layer includes the straight resistor and a bending portion connecting two adjacent straight resistors, and the two straight resistors located on the outermost sides each have an output end; the second circuit layer is arranged on the surface of the resistance layer away from the insulating layer, the second circuit layer includes two electrodes and the connecting portion, the two electrodes are respectively located on the surface of the two output ends, and the connecting portion is located on the surface of the bending portion.

[0008] In some possible embodiments, the linear resistor is arranged perpendicular to the connecting portion.

[0009] In some possible embodiments, the material of the connecting portion includes copper; the material of the linear resistor includes at least one of constantan, NiCr alloy, NiMo alloy, iron-based alloy, and platinum-based alloy.

[0010] In some possible embodiments, after being heated, a potential difference is formed between the linear resistor and the connecting portion.

[0011] In some possible embodiments, the line spacing between two adjacent linear resistors is 25μm to 1000μm, and the line width of the linear resistors is 25μm to 100μm; the minimum line width of the connecting portion is 25μm, and along the arrangement direction of the multiple linear resistors, the minimum length of the connecting portion is 115μm.

[0012] In some possible embodiments, the pressure-sensitive circuit board further includes a first covering film and a second covering film, wherein the first covering film is located on a side of the circuit substrate close to the stress strain layer and covers the stress strain, and the second covering film is located on a side of the circuit substrate away from the stress strain and covers the first circuit layer.

[0013] In some possible embodiments, the pressure-sensitive circuit board further includes a bracket, and the bracket is disposed on a side of the second covering film away from the circuit substrate.

[0014] The present application also provides a method for preparing a pressure-sensitive circuit board, including:

[0015] forming a first circuit layer on one surface of the insulating layer to form a circuit substrate; and

[0016] A stress strain layer is formed on a surface of the insulating layer facing away from the first circuit layer. The stress strain layer includes two electrodes arranged at intervals and a sensitive structure located between the two electrodes. The electrodes are electrically connected to the first circuit layer. The sensitive structure includes a plurality of linear resistors arranged side by side and a connecting portion connecting two adjacent linear resistors. The linear resistors and the connecting portion form a bent shape. The connecting portion is located at the bent portion, and the resistivity of the connecting portion is less than the resistivity of the linear resistors.

[0017] In some possible embodiments, the method for preparing the stress-strain layer includes:

[0018] forming a resistance layer on a surface of the insulating layer facing away from the first circuit layer, the resistance layer including the linear resistors and a bending portion connecting two adjacent linear resistors, wherein the two outermost linear resistors each have an output end; and

[0019] A second circuit layer is formed on the surface of the resistance layer, wherein the second circuit layer includes the two electrodes and the connecting portion. The two electrodes are respectively located on the surfaces of the two output ends, and the connecting portion is located on the surface of the bending portion.

[0020] An embodiment of the present application also provides a flexible pressure-sensitive element, which includes multiple pressure-sensitive circuit boards as described above, multiple circuit substrates constitute a base, multiple stress-strain layers are arranged at intervals and surround a pressure-sensitive area, and all the electrodes are electrically connected.

[0021] Compared with the prior art, the pressure-sensitive circuit board provided in the embodiment of the present application connects linear resistors with higher resistivity in series through connecting parts with lower resistivity, so that the sensitivity of the sensitive structure will not be reduced due to the difference in force between the bending part and the linear resistor part, thereby effectively improving the overall sensitivity of the stress strain layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of a strain gauge subjected to axial force.

[0023] Figure 2 for Figure 1 Enlarged view of part A.

[0024] Figure 3 This is a cross-sectional structural diagram of a pressure-sensitive circuit board provided in one embodiment of the present application.

[0025] Figure 4 In the pressure-sensitive circuit board provided in one embodiment of the present application, only a top view of the stress-strain layer is shown.

[0026] Figure 5 This is a schematic structural diagram of a flexible pressure-sensitive element provided in one embodiment of the present application.

[0027] Figure 6 For Figure 5 Schematic diagram of the flexible pressure-sensing element applying force downward.

[0028] Figure 7 This is a flow chart of a method for preparing a pressure-sensitive circuit board provided in one embodiment of the present application.

[0029] Figures 8A to 8J A structural schematic diagram of a pressure-sensitive circuit board manufacturing process provided in one embodiment of the present application.

[0030] Description of main component symbols

[0031] Pressure sensitive circuit board 100

[0032] Circuit board 10

[0033] Insulation layer 1

[0034] First circuit layer 2

[0035] Stress strain layer 20

[0036] Electrode 3

[0037] Sensitive structure 4

[0038] Linear resistor 41

[0039] Connecting portion 42

[0040] Bending portion 43

[0041] Output 44

[0042] Resistor layer 5

[0043] Second circuit layer 6

[0044] Through hole 7

[0045] Via 8

[0046] Opening 9

[0047] First cover film 30

[0048] Second cover film 40

[0049] Bracket 50

[0050] Metal substrate 1a

[0051] First metal layer 2a

[0052] Second metal layer 3a

[0053] The third metal layer 4a

[0054] Intermediate metal layer 5a

[0055] Dry film 6a

[0056] Flexible pressure-sensitive element 200

[0057] Substrate 201

[0058] Pressure-sensitive area 202

[0059] Arrangement direction a

[0060] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0061] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0062] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. When an element is referred to as being "disposed on" another element, it may be directly disposed on the other element or there may be an intermediate element.

[0063] like Figure 1 The figure shows the axial stress diagram of a strain gauge. When the strain gauge is subjected to unidirectional stress, the sensitive grid on the strain gauge encounters longitudinal stress stretching (ε x ) and transverse stress shrinkage (ε y ), so its resistance change is: ΔR / R=S x ε x +S y ε y , (longitudinal GF = S x ; Horizontal GF = S y GF is the gauge factor of the varistor). Figure 2 As shown in the figure, the core part of the strain gauge is the sensitive grid. Although the length of the sensitive grid remains unchanged after the resistor is wound into it, the stress and strain states of the straight section and the bent section are different. The GF value of the bent section will be smaller than that of the straight section. This is the lateral effect. The existence of this lateral effect will lead to a decrease in the sensitivity of the sensitive grid.

[0064] To this end, embodiments of the present application provide a pressure-sensitive circuit board. Exemplarily, the pressure-sensitive circuit board can be a strain gauge in a flexible pressure sensor, but is not limited thereto. A flexible pressure sensor employing the pressure-sensitive circuit board can reduce the aforementioned lateral effect and improve overall sensitivity.

[0065] See also Figure 3 and Figure 4The pressure-sensitive circuit board 100 provided in the embodiment of the present application includes: a circuit substrate 10 and a stress-strain layer 20. The circuit substrate 10 includes an insulating layer 1 and a first circuit layer 2 provided on the insulating layer 1. The stress-strain layer 20 includes two electrodes 3 arranged at intervals and a sensitive structure 4 located between the two electrodes 3. The electrodes 3 are electrically connected to the first circuit layer 2. The sensitive structure 4 includes a plurality of linear resistors 41 arranged side by side and a connecting portion 42 connecting two adjacent linear resistors 41, wherein the linear resistors 41 extend approximately along a straight line, so that the linear resistors 41 can form a bent shape with the connecting portion 42. The connecting portion 42 is located at the bent portion, and the resistivity of the connecting portion 42 is less than the resistivity of the linear resistor 41. Specifically, when the pressure-sensitive circuit board 100 is used as a stress gauge in a flexible pressure sensor, the sensitive structure 4 can be a sensitive grid in a strain gauge. The pressure-sensitive circuit board 100 of the embodiment of the present application provides a connecting portion 42 with a lower resistivity at the bending portion of the sensitive structure 4, thereby connecting the linear resistors 41 with a larger resistivity in series. This can prevent the sensitivity of the entire sensitive structure 4 from being reduced due to the different forces applied to the straight line segments at the bending portion, thereby improving the sensitivity of the entire sensitive structure 4.

[0066] From a stacked perspective, the stress-strain layer 20 comprises a resistor layer 5 and a second circuit layer 6. The resistor layer 5 is disposed on the surface of the insulating layer 1 facing away from the first circuit layer 2, and the second circuit layer 6 is disposed on the surface of the resistor layer 5 facing away from the insulating layer 1. The resistor layer 5 comprises linear resistors 41 and a bend 43 connecting two adjacent linear resistors 41. In other words, the linear resistors 41 and the bend 43 form a bend resistor structure. The two outermost linear resistors 41 each have an output terminal 44. The second circuit layer 6 comprises two electrodes 3 and a connecting portion 42. The two electrodes 3 are located on the surfaces of the two output terminals 44, respectively, and the connecting portion 42 is located on the surface of the bend 43. Forming the second circuit layer 6 on the resistor layer 5 facilitates the formation of the electrodes 3 and the connecting portion 42, facilitating electrical connection between the electrodes 3 and the first circuit layer 2. It also ensures sufficient connection between the connecting portion 42 and the linear resistors 41, preventing the risk of short circuits.

[0067] In some embodiments, the linear resistor 41 and the connecting portion 42 are arranged approximately perpendicularly. By arranging the linear resistor 41 of the sensitive structure 4 and the connecting portion 42 at the bending portion at a right angle, the lateral effect of the sensitive structure 4 can be further reduced, thereby further improving the sensitivity of the sensitive structure 4.

[0068] In some embodiments, the material of the connecting portion 42 may include copper. The material of the linear resistor 41 may include at least one of alloys with high resistivity such as constantan, NiCr alloy, NiMo alloy, iron-based alloy, and platinum-based alloy.

[0069] In addition, since two different metals are connected in series, a potential difference can be generated between the linear resistor 41 and the connecting portion 42 after being heated. Therefore, the pressure-sensitive circuit board 100 can also serve as a thermocouple to simultaneously detect the stress and temperature changes of the object to be measured.

[0070] In some embodiments, the line spacing between two adjacent linear resistors 41 can be 25 μm to 1000 μm, and the line width of the linear resistors 41 can be 25 μm to 100 μm. By controlling the minimum line spacing and minimum line width between the linear resistors 41 within the above ranges, the size of the sensitive structure 4 can be reduced, thereby reducing the size of the pressure-sensitive circuit board 100.

[0071] In some embodiments, the minimum line width of the connecting portion 42 is 25 μm, and along the arrangement direction a of the plurality of linear resistors 41 , the minimum length of the connecting portion 42 is 115 μm.

[0072] In some embodiments, the insulating layer 1 may be made of a resin such as epoxy resin, prepreg (PP), BT resin, polyphenylene oxide (PPO), polyimide (PI), polyethylene terephthalate (PET), or polyethylene naphthalate (PEN). For example, in this embodiment, the insulating layer 1 may be made of polyimide. In some embodiments, the insulating layer 1 may have a thickness of 12 μm to 125 μm.

[0073] Please refer again Figure 3 The pressure-sensitive circuit board 100 also includes a first covering film 30 and a second covering film 40. The first covering film 30 is located on the side of the circuit substrate 10 close to the stress strain layer 20 and covers the stress strain layer 20. The second covering film 40 is located on the side of the circuit substrate 10 away from the stress strain layer 20 and covers the first circuit layer 2.

[0074] Please refer again Figure 3The pressure-sensitive circuit board 100 further includes a bracket 50, which is disposed on the side of the second cover film 40 away from the circuit substrate 10. The addition of the bracket 50 provides support for the circuit substrate 10 and the stress-strain layer 20 when subjected to vertical or planar forces. In some embodiments, the bracket 50 can be made of a material such as SUS that provides good support and has an elastic modulus that matches that of the pressure-sensitive circuit board 100.

[0075] The pressure-sensitive circuit board 100 provided in this embodiment of the present application utilizes a relatively high-resistivity linear resistor 41 connected in series via a relatively low-resistivity connecting portion 42. This prevents the sensitivity of the sensitive structure 4 from being reduced by the difference in force between the bend and the linear resistor 41, thereby effectively improving the overall sensitivity of the stress-strain layer 20. Furthermore, by utilizing two different metals in series, the sensitive structure 4 generates a potential difference between the linear resistor 41 and the connecting portion 42 upon heating. Therefore, the pressure-sensitive circuit board 100 can also function as a thermocouple, simultaneously detecting changes in force and temperature of the object under test.

[0076] That is, the stress strain layer 20 in the embodiment of the present application has the dual functions of a strain-type pressure sensor and a thermocouple, and the stress strain layer 20 is embedded in the flexible circuit board through circuit board manufacturing technology, which is conducive to expanding application scenarios.

[0077] See also Figure 5 The present embodiment further provides a flexible pressure-sensitive element 200 using the aforementioned pressure-sensitive circuit board 100. Specifically, the flexible pressure-sensitive element 200 can be a flexible pressure sensor. The flexible pressure-sensitive element 200 can include multiple pressure-sensitive circuit boards 100. In the flexible pressure-sensitive element 200, the multiple pressure-sensitive circuit boards 100 are spaced apart on a substrate 201, so that the multiple stress-strain layers 20 are spaced apart and enclose a pressure-sensitive area 202. All electrodes 3 are electrically connected, for example, by wires.

[0078] In some embodiments, the flexible pressure-sensitive element 200 includes four pressure-sensitive circuit boards 100 , which are located on four sides of a substrate 201 to form a substantially rectangular structure. The approximate middle of the substrate 201 is a pressure-sensitive area 202 .

[0079] Understandable, please refer to Figure 4 The bracket 50 in the pressure-sensitive circuit board 100 can also be used as the substrate 201 to support and transmit pressure.

[0080] like Figure 6 As shown, when pressure is applied to the pressure-sensitive area 202 , the four resistance changes generated by the four pressure-sensitive circuit boards 100 due to different force directions are used to output signals based on the Wheatstone bridge principle and transmitted to the chip, which gives corresponding feedback.

[0081] See also Figure 7 , and refer to Figure 3 The present application also provides a method for preparing the aforementioned pressure-sensitive circuit board 100, which specifically includes the following steps:

[0082] In step S1 , a first circuit layer 2 is formed on one surface of the insulating layer 1 to form a circuit substrate 10 .

[0083] Step S2: forming a stress strain layer 20 on the surface of the insulating layer 1 facing away from the first circuit layer 2. The stress strain layer 20 includes two electrodes 3 spaced apart and a sensitive structure 4 located between the two electrodes 3. The electrodes 3 are electrically connected to the first circuit layer 2. The sensitive structure 4 includes a plurality of linear resistors 41 arranged side by side and a connecting portion 42 connecting two adjacent linear resistors 41. The linear resistors 41 and the connecting portion 42 form a bent shape. The connecting portion 42 is located at the bent portion, and the resistivity of the connecting portion 42 is less than the resistivity of the linear resistors 41.

[0084] Step S2 specifically includes the following steps:

[0085] In step S21 , a resistor layer 5 is formed on the surface of the insulating layer 1 facing away from the first circuit layer 2 . The resistor layer 5 includes the linear resistors 41 and a bending portion 43 connecting two adjacent linear resistors 41 . The two outermost linear resistors 41 each have an output terminal 44 .

[0086] In step S22 , a second circuit layer 6 is formed on the surface of the resistor layer 5 . The second circuit layer 6 includes two electrodes 3 and a connecting portion 42 . The two electrodes 3 are respectively located on the surfaces of the two output ends 44 , and the connecting portion 42 is located on the surface of the bending portion 43 .

[0087] See also Figures 8A to 8J , and refer to Figure 3 The method for preparing the pressure-sensitive circuit board 100 specifically includes the following steps:

[0088] Step S101, as Figure 8A As shown, a metal substrate 1a is provided, which includes an insulating layer 1, a first metal layer 2a arranged on a surface of the insulating layer 1, a second metal layer 3a arranged on the insulating layer 1 away from the first metal layer 2a, and a third metal layer 4a arranged on the surface of the second metal layer 3a.

[0089] In some embodiments, the first metal layer 2a and the third metal layer 4a may be made of a metal with a low resistivity, such as copper. The second metal layer 3a may be made of a metal with a high resistivity, such as constantan, NiCr alloy, NiMo alloy, iron-based alloy, or platinum-based alloy, and may be used to form a resistor.

[0090] Step S102, as Figure 8B and Figure 8C As shown, the first metal layer 2a is patterned to form the first circuit layer 2, and the second metal layer 3a and the third metal layer 4a are patterned to form the resistance layer 5 and the intermediate metal layer 5a. The specific structure of the resistance layer 5 is mentioned above and will not be described in detail here.

[0091] Specifically, the first metal layer 2a, the second metal layer 3a, and the third metal layer 4a may be patterned by acid etching.

[0092] Step S103, as Figure 8D and Figure 8E As shown, a through hole 7 is formed through the first circuit layer 2 , the insulating layer 1 and the resistor layer 5 , so that the intermediate metal layer 5 a is exposed through the through hole 7 .

[0093] Specifically, the through hole 7 can be formed by laser drilling.

[0094] Step S104, as Figure 8F As shown, electroplating is performed in the through hole 7 to form a conductive hole 8 , and the intermediate metal layer 5 a is electrically connected to the first circuit layer 2 through the conductive hole 8 .

[0095] Step S105, as Figures 8G to 8I As shown, the middle metal layer 5 a is patterned to form a second circuit layer 6 . The specific structure of the second circuit layer 6 is described above and will not be described in detail here. The resistance layer 5 and the second circuit layer 6 constitute a stress strain layer 20 .

[0096] Step S106, as Figure 8J As shown, a first covering film 30 is provided on the side of the insulating layer 1 close to the stress strain layer 20 , and the first covering film 30 covers the stress strain layer 20 . A second covering film 30 is provided on the side of the insulating layer 1 close to the first circuit layer 2 , and the second covering film 30 covers the first circuit layer 2 .

[0097] Specifically, openings 9 are formed in the first covering film 30 corresponding to the two electrodes 3 , so that the electrodes 3 can be exposed through the openings 9 , facilitating subsequent wire connection processing.

[0098] Step S107, refer to Figure 3 As shown, the bracket 50 is formed on the surface of the second cover film 40 by heat pressing.

[0099] The method for preparing a pressure-sensitive circuit board 100 provided in an embodiment of the present application forms a second circuit layer 6 on the surface of a resistor layer 5. The connectors 42 in the second circuit layer 6 connect multiple linear resistors 41 in series, effectively reducing the lateral effect of the pressure-sensitive circuit board 100 and improving its overall sensitivity. Furthermore, this method can form linear resistors 41 with a line width of 25μm to 1000μm and a line spacing of 25μm to 100μm, thereby increasing the density of the sensitive structure 4 and reducing the size of the sensitive structure 4, thereby reducing the size of the pressure-sensitive circuit board 100. Furthermore, the above-described method for preparing the stress-strain layer 20 facilitates the structural design of the resistor layer 5, improves the layout flexibility of the resistor layer 5, and simplifies the preparation method.

Claims

1. A pressure-sensitive circuit board, characterized in that: include: A circuit substrate comprising an insulating layer and a first circuit layer provided on the insulating layer; and a stress strain layer, the stress strain layer including two electrodes spaced apart and a sensitive structure located between the two electrodes, the electrodes being electrically connected to the first circuit layer, the sensitive structure including a plurality of linear resistors arranged side by side and a connecting portion connecting two adjacent linear resistors, the linear resistors and the connecting portion forming a bent shape, the connecting portion being located at the bent portion, and the resistivity of the connecting portion being less than the resistivity of the linear resistors.

2. The pressure-sensitive circuit board according to claim 1, wherein: The stress-strain layer comprises: a resistor layer disposed on a surface of the insulating layer facing away from the first circuit layer, the resistor layer comprising the linear resistors and a bending portion connecting two adjacent linear resistors, wherein the two outermost linear resistors each have an output end; and The second circuit layer is arranged on the surface of the resistance layer away from the insulating layer. The second circuit layer includes two electrodes and the connecting portion. The two electrodes are respectively located on the surfaces of the two output ends, and the connecting portion is located on the surface of the bending portion.

3. The pressure-sensitive circuit board according to claim 1, wherein: The linear resistor is arranged perpendicular to the connecting portion.

4. The pressure-sensitive circuit board according to claim 1, wherein: The material of the connecting portion includes copper; The material of the linear resistor includes at least one of constantan, NiCr alloy, NiMo alloy, iron-based alloy and platinum-based alloy.

5. The pressure-sensitive circuit board according to claim 4, wherein: After being heated, a potential difference is formed between the linear resistor and the connecting portion.

6. The pressure-sensitive circuit board according to claim 1, wherein: The line distance between two adjacent linear resistors is 25 μm to 1000 μm, and the line width of the linear resistor is 25 μm to 100 μm; The minimum line width of the connecting portion is 25 μm, and along the arrangement direction of the plurality of linear resistors, the minimum length of the connecting portion is 115 μm.

7. The pressure-sensitive circuit board according to claim 1, wherein: The pressure-sensitive circuit board also includes a first covering film and a second covering film. The first covering film is located on a side of the circuit substrate close to the stress and strain layer and covers the stress and strain. The second covering film is located on a side of the circuit substrate away from the stress and strain and covers the first circuit layer.

8. The pressure-sensitive circuit board according to claim 7, wherein: The pressure-sensitive circuit board further includes a bracket, which is arranged on a side of the second covering film away from the circuit substrate.

9. A method for preparing a pressure-sensitive circuit board, characterized in that: include: forming a first circuit layer on one surface of the insulating layer to form a circuit substrate; as well as A stress strain layer is formed on a surface of the insulating layer facing away from the first circuit layer. The stress strain layer includes two electrodes arranged at intervals and a sensitive structure located between the two electrodes. The electrodes are electrically connected to the first circuit layer. The sensitive structure includes a plurality of linear resistors arranged side by side and a connecting portion connecting two adjacent linear resistors. The linear resistors and the connecting portion form a bent shape. The connecting portion is located at the bent portion, and the resistivity of the connecting portion is less than the resistivity of the linear resistors.

10. The method for preparing a pressure-sensitive circuit board according to claim 9, wherein: The preparation method of the stress strain layer comprises: forming a resistance layer on a surface of the insulating layer facing away from the first circuit layer, the resistance layer including the linear resistors and a bending portion connecting two adjacent linear resistors, wherein the two outermost linear resistors each have an output end; and A second circuit layer is formed on the surface of the resistance layer, wherein the second circuit layer includes the two electrodes and the connecting portion. The two electrodes are respectively located on the surfaces of the two output ends, and the connecting portion is located on the surface of the bending portion.

11. A flexible pressure-sensitive element, characterized in that: It comprises a plurality of pressure-sensitive circuit boards according to any one of claims 1 to 8, wherein the plurality of circuit substrates constitute a base, the plurality of stress-strain layers are spaced apart and enclose a pressure-sensitive area, and all the electrodes are electrically connected.

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