Capacitive gate sensor and manufacturing method thereof

Abstract

The invention aims to provide a capacitive gate sensor and a manufacturing method thereof, the capacitive gate sensor comprises a fixed gate and a movable gate in sliding connection with the fixed gate, the fixed gate comprises a substrate, a main circuit layer, an insulating film, a branch circuit layer and an insulating layer, the substrate is made of ceramic or glass, the main circuit layer is arranged on one side surface of the substrate, and the insulating film is arranged on the other side surface of the substrate. The insulating film is arranged on the side face, away from the substrate, of the main circuit layer, the branch circuit layer is arranged on the side face, away from the main circuit layer, of the insulating film, the branch circuit layer penetrates through the insulating film to be electrically connected with the main circuit layer, and the insulating layer is arranged on the side face, away from the insulating film, of the branch circuit layer.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and particularly to a capacitive grating sensor and a manufacturing method thereof. Background Art

[0002] The capacitive grating sensor is a new type of sensor developed on the basis of the variable area capacitive sensor.

[0003] The capacitive grating sensor works based on the basic principle of capacitance. The size of the capacitance is related to the facing area of the two electrodes, the distance between the electrodes, and the dielectric constant of the medium between the electrodes. The formula is where C is the capacitance, ∈ is the dielectric constant, s is the facing area, and d is the distance between the electrodes.

[0004] The capacitive grating sensor is widely used in measuring tools such as digital calipers, micrometers, and dial indicators, and is widely used in industrial production. The principle of the capacitive grating sensor is that the differential capacitance generated by the moving grating scale and the fixed grating scale during movement changes periodically, and the chip calculates the corresponding displacement by calculating the cycle period.

[0005] Due to the high density of the emitters of the capacitive grating sensor, at present, the emitters need to be punched through the flying wire process to transfer the circuit to the back of the PCB. The PCB is mainly FR4 (glass fiber reinforced epoxy copper clad laminate), and this substrate has poor thermal conductivity and a large thermal expansion coefficient, which seriously restricts the high-precision manufacturing requirements of the capacitive grating sensor; moreover, it is difficult to miniaturize the design of the capacitive grating sensor by using the flying wire method. Therefore, in order to solve the above problems, the capacitive grating sensor and its manufacturing method of the present application are proposed. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies in the prior art, and provide a capacitive grating sensor and a manufacturing method thereof with high stability, high precision, and miniaturizable design.

[0007] The purpose of the present invention is achieved by the following technical solutions:

[0008] A capacitive grating sensor includes a fixed grating and a moving grating slidably connected to the fixed grating. The fixed grating includes:

[0009] A substrate, the material of the substrate being ceramic or glass;

[0010] A main circuit layer, the main circuit layer being disposed on one side surface of the substrate;

[0011] An insulating film, the insulating film being disposed on the side surface of the main circuit layer away from the substrate;

[0012] A branch circuit layer is disposed on a side of the insulating film away from the main circuit layer, and the branch circuit layer penetrates through the insulating film to be electrically connected to the main circuit layer;

[0013] An insulating layer is disposed on a side of the branch circuit layer away from the insulating film.

[0014] Optionally, the branch circuit layer includes an independent receiving electrode and a plurality of transmitting electrodes.

[0015] Optionally, the transmitting electrodes are equally spaced apart, and the transmitting electrodes are equally divided into several groups in sequence with eight in each group, and the transmitting electrodes with the same order in each group are electrically connected to each other.

[0016] Optionally, the main circuit layer includes a plurality of on-board circuits, and the receiving electrode and the transmitting electrodes with the same order in each group are electrically connected to one of the on-board circuits.

[0017] Optionally, the fixed grating further includes a flexible circuit board, which includes a base film and a plurality of external connection circuits spaced on the base film, and the base film is disposed on the substrate so that each external connection circuit is electrically connected to each on-board circuit.

[0018] A capacitive grating sensor manufacturing method includes the following steps:

[0019] Step S10: Obtain a substrate made of ceramic or glass, and sequentially form a main circuit layer on one side of the substrate by using a copper plating process and an etching process;

[0020] Step S20: Obtain an insulating film with a plurality of vias, apply glue to the insulating film and thermally press it onto a side of the main circuit layer away from the substrate;

[0021] Step S30: Sequentially form a branch circuit layer on a side of the insulating film away from the main circuit layer by using a copper plating process and an etching process, and a plurality of emitters are provided on the branch circuit layer;

[0022] Step S40: Form an insulating layer on a side of the branch circuit layer away from the insulating film by using a spraying process.

[0023] Optionally, the insulating film is made of PET or PP.

[0024] Optionally, the insulating layer is made of UV glue.

[0025] Optionally, after the step S40, it further includes:

[0026] Step S50: Obtain a flexible printed circuit board, apply glue to the flexible printed circuit board and thermally press it onto the substrate so that the flexible printed circuit board is electrically connected to the main circuit layer.

[0027] Compared with the prior art, the present invention has at least the following advantages:

[0028] 1. The substrate is made of ceramic or glass. Compared with the existing capacitive grid sensors using FR4 material, due to the small coefficient of thermal expansion, the deformation caused by temperature change is reduced, and the stability is higher.

[0029] 2. Compared with the existing method of using flying wires for connection, in the present application, after the insulating film is laminated on the main circuit layer by a thermal pressing process, a copper layer is plated on the insulating film and etched to form a branch circuit layer. The branch circuit layer is connected to the main circuit layer through the vias of the insulating film. In this way, the multi-layer structure effectively reduces the circuit between the branch circuit layer and the main circuit layer. This multi-layer structure can effectively reduce the thickness of the fixed grid, thereby reducing the overall thickness of the capacitive grid sensor and realizing miniaturized design. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0031] Figure 1 Structural schematic diagram of a capacitive grid sensor according to an embodiment of the present invention;

[0032] Figure 2 For Figure 1 Partial structural schematic diagram of the capacitive grid sensor shown;

[0033] Figure 3 For Figure 1 Partial structural schematic diagram of the capacitive grid sensor from another angle shown;

[0034] Figure 4 For Figure 1 Partial structural schematic diagram of the capacitive grid sensor from yet another angle shown;

[0035] Figure 5 Structural schematic diagram of a branch circuit layer according to an embodiment of the present invention;

[0036] Figure 6 Flowchart of a manufacturing method of a capacitive grid sensor according to an embodiment of the present invention.

[0037] Explanation of the reference numerals:

[0038] 10. Fixed grating; 100. Substrate; 200. Main circuit layer; 300. Insulating film; 400. Branch circuit layer; 500. Insulating layer; 410. Receiving electrode; 420. Transmitting electrode; 210. On-board circuit; 600. Flexible printed circuit board; 610. Base film; 620. External circuit; 310. Via hole. Detailed implementation mode

[0039] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings.

[0040] As Figures 1 to 5 shown, a capacitive grating sensor includes a fixed grating 10 and a moving grating slidably connected to the fixed grating 10. The fixed grating 10 includes a substrate 100, a main circuit layer 200, an insulating film 300, a branch circuit layer 400 and an insulating layer 500. The material of the substrate 100 is ceramic or glass. The main circuit layer 200 is disposed on one side surface of the substrate 100. The insulating film 300 is disposed on the side surface of the main circuit layer 200 away from the substrate 100. The branch circuit layer 400 is disposed on the side surface of the insulating film 300 away from the main circuit layer 200, and the branch circuit layer 400 passes through the insulating film 300 to be electrically connected to the main circuit layer 200. The insulating layer 500 is disposed on the side surface of the branch circuit layer 400 away from the insulating film 300.

[0041] It should be noted that the substrate 100, as the basic support structure of the entire fixed grating 10, is made of ceramic or glass. These two materials have a small coefficient of expansion, can provide a stable support platform for the subsequent layer structures, and reduce the deformation caused by temperature changes. Compared with using FR4 as the base material in the prior art, the substrate 100 in the present application is ceramic or glass, which has higher stability. Further, the insulating film 300 and the insulating layer 500 respectively play the roles of electrical isolation and protection for the main circuit layer 200 and the branch circuit layer 400. The substrate 100, the main circuit layer 20, the insulating film 300, the branch circuit layer 400 and the insulating layer 500 are formed into a five-layer composite structure by a hot pressing process. Among them, the branch circuit layer 400 and the main circuit layer 200 are electrically connected through the vertical interconnection holes of the insulating film 300, which can effectively shorten the distance between the branch circuit layer 400 and the main circuit layer 200. Compared with the connection method using flying wires in the prior art, the thickness dimension of the fixed grating 10 can be further reduced, thereby reducing the thickness dimension of the capacitive grating sensor to achieve a miniaturized design.

[0042] As Figure 1 shown, in an embodiment, the branch circuit layer 400 includes an independent receiving electrode 410 and a plurality of transmitting electrodes 420.

[0043] It should be noted that the receiving electrode 410 and the transmitting electrode 420 are physically isolated within the branch circuit layer 400. The receiving electrode 410 is in a strip structure, and the transmitting electrode 420 is arranged in an array. The receiving electrode 410 and the transmitting electrode 420 are respectively connected to the main circuit layer 200 through the vertical interconnection holes of the insulating film 300. In this way, a periodically varying excitation signal is provided from the main circuit layer 200 to the transmitting electrode 420. There is an electric field between the transmitting electrode 420 and the reflecting electrode of the moving grating, and between the reflecting electrode of the moving grating and the receiving electrode 410. Due to the capacitance coupling and charge transfer effects of the reflecting electrode of the moving grating, the output signal on the receiving electrode 410 changes with the position change between the transmitting electrode 420 and the reflecting electrode of the moving grating. When the moving grating moves relative to the fixed grating (the moving grating is connected to the object to be measured for displacement), the relative area between the transmitting electrode 420 and the reflecting electrode of the moving grating changes, the amount of charge on the reflecting electrode of the moving grating changes, and the charge is induced onto the receiving electrode 410. The charge Q accumulated on the receiving electrode 410 is proportional to the displacement of the moving grating. The receiving electrode 410 sends out the measurement signal through the main circuit layer 200. In this embodiment, through the physical separation, array layout and isolation structure design of the receiving electrode 410 and the transmitting electrode 420, the capacitive grating sensor meets the requirements of high sensitivity and high precision.

[0044] As Figure 5 shown, in one embodiment, the transmitting electrodes 420 are respectively equidistantly distributed, and each of the transmitting electrodes 420 is equally divided into several groups in sequence with every eight as a group, and the transmitting electrodes 420 with the same order within each group are electrically connected to each other.

[0045] It should be noted that the transmitting electrodes 420 are arranged at equal intervals, and every eight electrodes form a driving unit A to form a periodically repeated modular array. Within each driving unit A, the electrodes numbered 1 to 8 are numbered in sequence in the detection direction, and the electrodes with the same number are interconnected across groups (for example, the first transmitting electrodes 420 of all driving units A are interconnected, and the second transmitting electrodes 420 of all driving units A are interconnected). Further, the transmitting electrodes 420 with the same number are vertically and electrically connected to the corresponding driving points on the main circuit layer 200 through the vertical interconnection holes of the insulating film 300. Further, the eight transmitting electrodes 420 within the same driving unit A are arranged in a trapezoidal tooth-like structure, so that the transmitting electrodes 420 with the same number within each driving unit A are linearly electrically connected to avoid signal interference between the transmitting electrodes 420 within the same driving unit A.

[0046] As Figure 1 shown, in one embodiment, the main circuit layer 200 includes several on-board circuits 210, and the receiving electrode 410 and the transmitting electrodes 420 with the same order within each group are electrically connected to one of the on-board circuits 210.

[0047] It should be noted that the main circuit layer 200 is a collection of multiple on-board circuits 210, and each of the on-board circuits 210 is independent of each other. One of the on-board circuits 210 is electrically connected to the receiving electrode 410 through a vertical interconnection hole of the insulating film 300. Eight of the on-board circuits 210 are respectively connected to the emitting electrodes 420 with corresponding serial numbers in each driving unit A through a vertical interconnection hole of the insulating film 300. In this way, these eight on-board circuits 210 are connected to alternating signals with a phase difference of 45°. When the moving grating slides relative to the fixed grating, the electrical signal of the receiving electrode 410 is proportional to the displacement of the moving grating, and this electrical signal is led out through the on-board circuit 210 connected to the receiving electrode 410. It should be noted that since the substrate 100 is made of ceramic or glass, it has a smaller coefficient of thermal expansion and less thermal deformation, so it has good stability, and the structure between the on-board circuits 210 is more stable, thereby improving the stability and accuracy of the moving grating.

[0048] As Figure 1 shown, in one embodiment, the fixed grating 10 further includes a flexible printed circuit board 600. The flexible printed circuit board 600 includes a base film 610 and a plurality of external circuits 620 spaced apart on the base film 610. The base film 610 is disposed on the substrate 100 so that the external circuits 620 are respectively electrically connected to the on-board circuits 210.

[0049] It should be noted that the base film 610 is made of polyimide. In this way, each on-board circuit 210 on the substrate 100 can be externally connected through the flexible printed circuit board 600, making it convenient for the capacitive grating sensor to be signal-connected to external devices. Moreover, the flexible printed circuit board 600 has a certain flexibility, which can avoid stress transfer to the substrate 100 during actual use.

[0050] As Figures 1 to 6 shown, a manufacturing method of a capacitive grating sensor includes the following steps:

[0051] Step S10: Obtain a substrate 100 made of ceramic or glass, and sequentially form a main circuit layer 200 on one side surface of the substrate 100 by using a copper plating process and an etching process;

[0052] Step S20: Obtain an insulating film 300. A plurality of through holes 310 are formed in the insulating film 300, and the insulating film 300 is glued and hot-pressed onto the side surface of the main circuit layer 200 away from the substrate 100;

[0053] Step S30: Sequentially form a branch circuit layer 400 on the side surface of the insulating film 300 away from the main circuit layer 200 by using a copper plating process and an etching process;

[0054] Step S40: Form an insulating layer 500 on the side surface of the branch circuit layer 400 away from the insulating film 300 by using a spraying process.

[0055] It should be noted that the substrate 100 is made of ceramic or glass. Through the copper plating process, for example, the electroless copper plating process is used to plate a copper layer with a thickness of 0.03 mm to 0.07 mm on the substrate 100. In particular, the thickness of the copper layer can be 0.05 mm. Then, through the etching process, the redundant parts of the copper layer are removed, and the part of the copper layer remaining on the substrate 100 forms the main circuit layer 200. Then, an insulating film 300 is obtained, where the material of the insulating film 300 is PET or PP, and a number of vias 310 are provided at predetermined positions on the insulating film 300. After applying glue on the insulating film 300, the insulating film 300 is thermocompression bonded to the main circuit layer 200 by the thermocompression process.

[0056] Furthermore, through the copper plating process, for example, the electroless copper plating process is used to form a copper layer again on the surface of the insulating film 300. It should be noted that this copper layer is electrically connected to the main circuit layer 200 through the vias 310 reserved on the insulating film 300. Then, through the etching process, the redundant parts of this copper layer are removed, and the part of the copper layer remaining on the side of the insulating film 300 away from the substrate 100 forms the branch circuit layer 400. The branch circuit layer 400 is electrically connected to the main circuit layer 200 through the vias 310 of the insulating film 300.

[0057] Finally, a spraying process is used to form an insulating layer 500 on the surface of the branch circuit layer 400, where the material of the insulating layer 500 is UV glue. In this way, the branch circuit layer 400 is insulated and protected by the insulating layer 500.

[0058] Furthermore, after step S40, step S50 is further included. A flexible printed circuit board 600 is obtained and glued and thermocompressed onto the substrate 100 so that the flexible printed circuit board 600 is electrically connected to the main circuit layer 200.

[0059] It should be noted that in order to facilitate the signal connection between the capacitive grating sensor and external devices, a flexible printed circuit board 600 is installed on the substrate 100 as an intermediate connection structure. Specifically, after applying glue on the flexible printed circuit board 600, the flexible printed circuit board 600 is pressed onto the substrate 100 by the thermocompression process, and the wires of the flexible printed circuit board 600 are electrically connected to the main circuit layer 200 on the substrate 100. In this way, when the capacitive grating sensor is used subsequently, external devices only need to be plugged and unplugged with the flexible printed circuit board 600. In this way, the moving grating of the capacitive grating sensor is manufactured.

[0060] Furthermore, after step S50, step S60 is further included. The moving grating is slidably mounted on the fixed grating.

[0061] It should be noted that in the existing capacitive grating sensor structure, the moving grating is slidably mounted on the fixed grating. Since the sliding mounting structure of the moving grating and the fixed grating is an existing technology, it will not be elaborated here. The existing moving grating structure can be directly adopted, and the existing method of slidably mounting the moving grating on the fixed grating can be used.

[0062] Further, in one embodiment, in step S10, the main circuit layer 200 includes a plurality of on-board circuits 210.

[0063] Specifically, after forming a copper layer on the substrate 100 through a copper plating process, the predetermined positions on the copper layer are retained, and the other positions are etched away, so as to form the main circuit layer 200 composed of a plurality of on-board circuits 210 on the substrate 100. Among them, the on-board circuits 210 are independent of each other, and one end of each on-board circuit 210 is evenly distributed at the edge of the substrate 100.

[0064] Further, in one embodiment, in step S20, each via 310 is connected to at least one of the on-board circuits 210. In this way, it is ensured that in the subsequent step S30, when copper is plated on the insulating film 300, the copper can be connected to the on-board circuit 210 through the via 310.

[0065] Further, in one embodiment, in step S30, the branch circuit layer 400 includes an independent receiving electrode 410 and a plurality of transmitting electrodes 420.

[0066] It should be noted that after forming a copper layer on the insulating film 300 through a copper plating process, when etching the copper layer, the reserved part of the copper layer at the predetermined position forms a receiving electrode 410 and a plurality of transmitting electrodes 420, and the receiving electrode 410 and each transmitting electrode 420 are located on the via 310. In this way, the receiving electrode 410 and each transmitting electrode 420 can be connected to one of the on-board circuits 210 through the via 310. The receiving electrode 410 and the transmitting electrode 420 are independent structures.

[0067] Thus, through the method for manufacturing a capacitive grating sensor of the present application, in the stage of manufacturing the fixed grating, compared with the existing method of using flying wires for connection, after the insulating film 300 is laminated on the main circuit layer 200 through a hot pressing process in the present application, a copper layer is plated on the insulating film 300 and etched to form a branch circuit layer 400, wherein the branch circuit layer 400 is communicated with the main circuit layer 200 through the via hole 310 of the insulating film 300. In this way, the multi-layer structure effectively reduces the circuit between the branch circuit layer 400 and the main circuit layer 200. This multi-layer structure can effectively reduce the thickness dimension of the fixed grating, thereby reducing the overall thickness dimension of the capacitive grating sensor and realizing miniaturized design. The substrate 100 is made of ceramic or glass. Compared with the existing capacitive grating sensor using FR4 material, due to the small coefficient of thermal expansion, the deformation caused by temperature change is reduced and the stability is higher.

[0068] The above-described embodiments merely represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the invention patent. Among them, the installation / fixing / setting mentioned in the present invention can be understood as including but not limited to being locked and fixed by using screws unless otherwise specifically defined. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent shall be subject to the appended claims.

Claims

1. A capacitive grating sensor, comprising a fixed grating and a moving grating slidably connected to the fixed grating, characterized in that, The fixed grating includes: a substrate made of ceramic or glass; a main circuit layer disposed on one side surface of the substrate; an insulating film disposed on the side surface of the main circuit layer away from the substrate; a branch circuit layer disposed on the side surface of the insulating film away from the main circuit layer, and the branch circuit layer passes through the insulating film to be electrically connected to the main circuit layer; an insulating layer disposed on the side surface of the branch circuit layer away from the insulating film.

2. The capacitive grating sensor according to claim 1, wherein The branch circuit layer includes an independent receiving electrode and a plurality of emitting electrodes.

3. The capacitive grating sensor according to claim 2, wherein Each of the emitting electrodes is equidistantly distributed, and each of the emitting electrodes is equally divided into several groups in sequence with every eight as a group, and the emitting electrodes with the same order in each group are electrically connected to each other.

4. The capacitive grating sensor according to claim 3, characterized in that, The main circuit layer includes a plurality of on-board circuits, and the receiving electrode and the emitting electrodes with the same order in each group are electrically connected to one of the on-board circuits.

5. The capacitive grating sensor according to claim 4, wherein, The fixed grating further includes a flexible printed circuit board, which includes a base film and a plurality of external circuits spaced on the base film, and the base film is disposed on the substrate so that each of the external circuits is electrically connected to each of the on-board circuits.

6. A manufacturing method of a capacitive grating sensor, characterized in that, It includes the following steps: Step S10: Obtain a substrate made of ceramic or glass, and sequentially form a main circuit layer on one side surface of the substrate by using a copper plating process and an etching process; Step S20: Obtain an insulating film with a plurality of vias formed thereon, apply glue to the insulating film and hot-press it to the side surface of the main circuit layer away from the substrate; Step S30: Sequentially form a branch circuit layer on the side surface of the insulating film away from the main circuit layer by using a copper plating process and an etching process, and a plurality of emitters are provided on the branch circuit layer; Step S40: Form an insulating layer on the side surface of the branch circuit layer away from the insulating film by using a spraying process.

7. The manufacturing method of the capacitive grid sensor according to claim 6, characterized in that, The material of the insulating film is PET or PP.

8. The manufacturing method of the capacitive grating sensor according to claim 6, characterized in that The material of the insulating layer is UV glue.

9. The capacitive grid sensor manufacturing method according to claim 6, characterized in that, After the step S40, it further includes: Step S50: Obtain a flexible printed circuit board, apply glue to the flexible printed circuit board and hot-press it to the substrate so that the flexible printed circuit board is electrically connected to the main circuit layer.

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