Inductive pressure sensor and preparation method thereof

Abstract

The invention discloses an inductive pressure sensor and a preparation method thereof, and belongs to the technical field of sensors. The structure of the inductive pressure sensor comprises a 5 * 5 coil array for generating induced current, a circuit for outputting electric signals, an insulating layer between the circuit and a coil, a supporting wall between the coil and a permanent magnet, a PDMS film and the permanent magnet embedded in the film. According to the inductive pressure sensor, the electromagnetic induction principle is utilized, the inductive pressure sensor has the rapid and obvious electrical response characteristic to dynamic pressure signals, the PDMS thin film has good compressive deformation resistance and excellent thermal stability and cohesiveness, the position of the permanent magnet is driven to change through the position change of the PDMS thin film when the inductive pressure sensor is under pressure, and the dynamic pressure signals are detected. The cavity gap between the PDMS film and the coil array is large, so that the sensor has a wide pressure detection range; meanwhile, the coil array is arranged in a 5 * 5 array mode, the output current is increased, and the sensitivity is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and in particular to an inductive pressure sensor and a preparation method thereof. Background Art

[0002] The pressure sensor is a device or apparatus that can sense pressure signals and convert them into usable output electrical signals according to certain rules. The principle of electromagnetic induction means that a conductor placed in a changing magnetic flux will generate an electromotive force, which is called an induced electromotive force or an induced electromotive force. If the conductor is closed into a loop, the electromotive force will drive the electrons in the closed loop to flow, forming an induced current.

[0003] An inductive pressure sensor is a sensor that converts the pressure change to be measured into the change of its own inductance value based on electromagnetic induction. When subjected to external pressure, the magnet of the pressure sensor is displaced, and the magnetic flux passing through the closed circuit changes, thereby generating an induced electromotive force and forming an induced current. By measuring the change in current, the information of the external pressure change can be accurately obtained.

[0004] At present, most of the existing inductive sensors have a slow response speed and are not suitable for occasions with fast dynamic response. In addition, they have problems such as low resolution and poor stability. In order to solve the above problems, it is necessary to study an inductive pressure sensor that has both high sensitivity and a wide detection range and can quickly respond to dynamic pressure, and can be used in various occasions that require fast pressure detection. Summary of the invention

[0005] The problem to be solved by the present invention is to provide an inductive pressure sensor and a preparation method thereof, which has high sensitivity and wide detection range and is used for fast response dynamic pressure detection.

[0006] The present invention adopts the following technical solution: an inductive pressure sensor, comprising: a substrate, a coil array, an insulating layer, an output circuit, a supporting wall, and a PDMS film arranged in sequence from bottom to top;

[0007] A support cavity is formed between the substrate and the PDMS film via a support wall;

[0008] Several permanent magnets are embedded in the grooves inside the PDMS film. When the PDMS film is subjected to pressure, the PDMS film drives the permanent magnets to change their positions.

[0009] The coil array is arranged at the lower part of the supporting cavity, the coil array and the output circuit are connected through the connecting holes arranged in the insulating layer, and a pressure transmission cavity gap is formed between the coil array and the PDMS film to expand the pressure detection range.

[0010] Specifically, the substrate is Si, the coil array is arranged above the substrate, the insulating layer is used to isolate the coil array from the output circuit, the coil array and the output circuit are Cu, and the insulating layer is Al2O3.

[0011] Specifically, the thickness of the coil array and the output circuit is 200 nm respectively, the thickness of the insulating layer is 100 nm, the thickness of the supporting wall is 40 μm, and the thickness of the PDMS film is 450 μm.

[0012] Furthermore, the coil array is neatly arranged in a 5*5 array to increase the output current, and each coil rotates 10 times in an equidistant spiral.

[0013] Specifically, the connection holes in the insulating layer connecting the coil array and the output circuit include several large circular holes and small circular holes, the large circular holes have a diameter of 140 μm, and the small circular holes have a diameter of 80 μm. The output circuit mask connects each large circular hole together and connects each small circular hole individually.

[0014] Specifically, the permanent magnet is made of N52 type NdFeB material, and is cylindrical in shape, with a diameter of 500 μm and a height of 200 μm.

[0015] Specifically, the support wall is photoresist, and the support wall is connected to the PDMS film through epoxy resin.

[0016] The technical solution of the present invention also provides a method for preparing an inductive pressure sensor, which is used to prepare any of the above-mentioned inductive pressure sensors, comprising the following steps:

[0017] S1, depositing a coil array on the substrate using a coil array mask and magnetron sputtering;

[0018] S2, using an insulating layer mask and magnetron sputtering to deposit an insulating layer on the coil array, so as to isolate the coil array and the output circuit, and connect them only through the connection holes penetrating the insulating layer;

[0019] S3, depositing an output circuit on the insulating layer by using an output circuit mask and magnetron sputtering;

[0020] S4, using a support wall mask to photoetch a support wall pattern on the output circuit;

[0021] S5, taking another substrate, and photolithography a groove pattern on the substrate using a groove mask;

[0022] S6, coating the surface of the groove pattern with a mixture of PDMS substrate and curing agent, and peeling it off after curing;

[0023] S7, embedding the permanent magnet into the groove of the PDMS film;

[0024] S8, coating the surface of the PDMS film embedded with the permanent magnet with a mixture of the PDMS substrate and the curing agent again, and then curing;

[0025] S9, connecting the PDMS film to the supporting wall to form an inductive pressure sensor.

[0026] In particular, before depositing the coil array on the substrate in step S1, a layer of Cr film is deposited on the substrate by magnetron sputtering to improve the adhesion between the substrate and the coil array.

[0027] Furthermore, the magnetron sputtering has a DC power of 150 W, a pressure of 5 mTorr, a flow rate of 50 sccm, and a rotation speed of 10 rpm.

[0028] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0029] The inductive pressure sensor of the present invention has a fast and obvious electrical response characteristic to dynamic pressure, and has both high sensitivity and a wide detection range. When the PDMS film is subjected to pressure, the position of the permanent magnet is changed by the change in the position of the PDMS film. Since the cavity gap between the PDMS film and the coil array is large, it has a wide pressure detection range. In addition, the coil array is arranged in a 5*5 array, which increases the output current and improves the sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the structure of the inductive pressure sensor of the present invention;

[0031] Figure 2 This is a structural diagram of a coil array mask of an inductive pressure sensor of the present invention;

[0032] Figure 3 This is a structural diagram of the insulating layer mask of the inductive pressure sensor of the present invention;

[0033] Figure 4 This is a structural diagram of a mask plate for an output circuit of an inductive pressure sensor of the present invention;

[0034] Figure 5 This is a structural diagram of a mask plate for a supporting wall of an inductive pressure sensor of the present invention;

[0035] Figure 6 This is a structural diagram of a groove mask of an inductive pressure sensor of the present invention;

[0036] Explanation of symbols in the figure: 1-PDMS film; 2-permanent magnet; 3-support wall; 4-output circuit; 5-insulating layer; 6-coil array; 7-substrate. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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 should fall within the scope of protection of the present invention.

[0038] Meanwhile, the step numbers in the embodiments of the present invention are only provided for the convenience of explanation and description, and no limitation is imposed on the order of the steps. The execution order of the steps in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0039] In one embodiment of the present invention, an inductive pressure sensor, such as Figure 1 As shown, arranged from bottom to top are: substrate 7, coil array 6, insulating layer 5, output circuit 4, supporting wall 3, PDMS film 1; and a plurality of permanent magnets 2 are embedded in the PDMS film 1.

[0040] The coil array 6 is neatly arranged in a 5*5 array, such as Figure 2 As shown, in the coil array mask, each coil rotates 10 times in the form of an equidistant spiral.

[0041] The circles in the insulating layer mask are used as connection holes to connect the coil to the output circuit, such as Figure 3 As shown, the diameter of the large circular hole is 140 μm and the diameter of the small circular hole is 80 μm.

[0042] Furthermore, if Figure 4 As shown, all the large circles in the output circuit mask are connected together, and each small circle is connected individually.

[0043] Support wall mask Figure 5 As shown, the thickness of the wall is 150 μm, and the area of ​​the cavity in the middle of the supporting wall is 850*850 μm.

[0044] The diameter of the circle in the groove mask is 700μm. Figure 6 As shown, the groove is used to place the permanent magnet therein.

[0045] Furthermore, the detailed preparation method of the inductive pressure sensor described in this embodiment includes the following steps:

[0046] Step 1: Coat a layer of positive photoresist on the surface of the substrate, pre-bake, expose with a UV photolithography machine and develop with a developer, leaving a coil array pattern at last;

[0047] Step 2: Deposit a 20 nm Cr film by magnetron sputtering (DC power 150 W, pressure 5 mTorr, flow rate 50 sccm, rotation speed 10 rpm, time 3 min) to improve adhesion, and then deposit a 200 nm Cu film (DC power 150 W, pressure 5 mTorr, flow rate 50 sccm, rotation speed 10 rpm, time 30 min);

[0048] Step 3: Use a stripping solution to strip off the excess photoresist and the Cu on the glue, leaving only the coil array;

[0049] Step 4: coating a layer of positive photoresist on the surface of the coil array, pre-baking, exposing by UV photolithography and developing by developer, and finally leaving an insulating layer pattern;

[0050] Step 5: Deposit a 100 nm Al2O3 film by magnetron sputtering (DC power 150 W, pressure 5 mTorr, flow rate 50 sccm, rotation speed 10 rpm, time 15 min);

[0051] Step 6: Use a stripping solution to strip off the excess photoresist and Al2O3 on the glue, leaving only the insulating layer;

[0052] Step 7: Coat a layer of positive photoresist on the surface of the above-mentioned insulating layer, and after pre-baking, expose it through a UV photolithography machine and develop it with a developer, and finally leave an output circuit pattern;

[0053] Step 8: Deposit a 200 nm Cu film by magnetron sputtering (DC power 150 W, pressure 5 mTorr, flow rate 50 sccm, rotation speed 10 rpm, time 30 min);

[0054] Step 9: Use a stripping solution to remove the excess photoresist and Cu on the glue, leaving only the output circuit;

[0055] Step 10: Coat a layer of positive photoresist on the surface of the output circuit, pre-bake, expose with a UV photolithography machine and develop with a developer, and finally leave a supporting wall pattern;

[0056] Step 11: Take another substrate, coat a layer of negative photoresist on the surface of the substrate, pre-bake, and then expose it through a UV photolithography machine;

[0057] Step 12: Coat a layer of positive photoresist on the surface of the negative photoresist, and after pre-baking, expose it with a UV photolithography machine and develop it with a developer, leaving a groove pattern for embedding the magnets;

[0058] Step 13: Coat the surface of the above pattern with a mixture of PDMS substrate and curing agent (PDMS substrate: curing agent = 10:1, stir for 10 minutes), and then dry and cure (temperature 80°C, time 1 hour);

[0059] Step 14: Use a stripping solution to completely strip off the positive and negative photoresists and remove the PDMS film with the grooves printed on it;

[0060] Step 15: embed the permanent magnet into the groove of the PDMS film;

[0061] Step 16: Coat the surface of the embedded magnet with a mixture of PDMS substrate and curing agent (PDMS substrate: curing agent = 10:1, stir for 10 minutes), and then dry and cure (temperature 80°C, time 1 hour);

[0062] Step 17: Drop an appropriate amount of epoxy resin on the supporting wall as an adhesive, connect the PDMS film to the supporting wall, and form a complete inductive pressure sensor.

[0063] When in use, after the PDMS film is subjected to pressure, the above-mentioned inductive pressure sensor drives the position of the permanent magnet to change through the change of the position of the PDMS film. Since the cavity gap between the PDMS film and the coil array is large, it has a wider pressure detection range. In addition, the sensor coil array is arranged in a 5*5 array, which increases the output current, improves the sensitivity, and has a fast and obvious electrical response characteristic to dynamic pressure.

[0064] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An inductive pressure sensor, characterized in that: It comprises a substrate (7), a coil array (6), an insulating layer (5), an output circuit (4), a supporting wall (3), and a PDMS film (1) which are arranged in sequence from bottom to top; A support cavity is formed between the substrate (7) and the PDMS film (1) via a support wall (3); A plurality of permanent magnets (2) are embedded in the inner grooves of the PDMS film (1). When the PDMS film (1) is subjected to pressure, the PDMS film (1) drives the permanent magnets (2) to change their positions; The coil array (6) is arranged at the bottom of the support cavity, the coil array (6) and the output circuit (4) are connected via a connection hole arranged in the insulating layer (5), and a pressure transmission cavity gap is formed between the coil array (6) and the PDMS film (1) to expand the pressure detection range.

2. The inductive pressure sensor according to claim 1, characterized in that: The substrate (7) is Si, the coil array (6) is arranged above the substrate, the insulating layer (5) is used to isolate the coil array (6) and the output circuit (4), the coil array (6) and the output circuit (4) are Cu, and the insulating layer (5) is Al2O3.

3. The inductive pressure sensor according to claim 2, characterized in that: The thickness of the coil array (6) and the output circuit (4) is 200 nm respectively, the thickness of the insulating layer (5) is 100 nm, the thickness of the supporting wall (3) is 40 μm, and the thickness of the PDMS film (1) is 450 μm.

4. The inductive pressure sensor according to claim 3, characterized in that: The coil array (6) is neatly arranged in a 5*5 array to increase the output current, and each coil rotates 10 times in an equidistant spiral.

5. The inductive pressure sensor according to claim 4, characterized in that: The connection holes in the insulating layer (5) connecting the coil array (6) and the output circuit (4) include a plurality of large circular holes and small circular holes, wherein the diameter of the large circular holes is 140 μm, and the diameter of the small circular holes is 80 μm. The output circuit connects each large circular hole together and connects each small circular hole individually.

6. The inductive pressure sensor according to claim 1, characterized in that: The permanent magnet (2) is made of N52 type neodymium iron boron material and is cylindrical in shape with a diameter of 500 μm and a height of 200 μm.

7. The inductive pressure sensor according to claim 1, characterized in that: The supporting wall (3) is photoresist, and the supporting wall (3) is connected to the PDMS film (1) via epoxy resin.

8. A method for preparing an inductive pressure sensor, used for preparing the inductive pressure sensor as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: S1, depositing a coil array (6) on the substrate (7) using a coil array mask and magnetron sputtering; S2, using an insulating layer mask and magnetron sputtering to deposit an insulating layer (5) on the coil array (6) to isolate the coil array (6) and the output circuit (4), and only connect them through the connection holes penetrating the insulating layer (6); S3, depositing an output circuit (4) on the insulating layer (6) by using an output circuit mask and magnetron sputtering; S4, using a support wall mask to photoetch a support wall (3) pattern on the output circuit (4); S5, taking another substrate, and photolithography a groove pattern on the substrate using a groove mask; S6, coating the surface of the groove pattern with a mixture of PDMS substrate and curing agent, and peeling it off after curing; S7, embedding the permanent magnet (2) into the groove of the PDMS film (1); S8, coating the surface of the PDMS film (1) embedded with the permanent magnet (2) with a mixture of the PDMS substrate and the curing agent again, and then curing; S9, connecting the PDMS film (1) and the supporting wall (3) together to form an inductive pressure sensor.

9. The method for preparing an inductive pressure sensor according to claim 8, characterized in that: In step 1, before depositing the coil array (6) on the substrate (7), a layer of Cr film is deposited on the substrate (7) by magnetron sputtering to improve the adhesion between the substrate and the coil array.

10. The method for preparing an inductive pressure sensor according to claim 8, characterized in that: The magnetron sputtering has a DC power of 150 W, a pressure of 5 mTorr, a flow rate of 50 sccm, and a rotation speed of 10 rpm.

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