Waterproof capacitive touch screen based on PCB bonding pad and transparent conductive film

Abstract

The invention discloses a waterproof capacitive touch screen based on a PCB (printed circuit board) bonding pad and a transparent conductive film, which belongs to the technical field of touch screens and comprises a cover plate, a transparent conductive film sensor, a printed circuit board, an integrated connecting structure and a main sealing structure. The transparent conducting film sensor comprises a transparent base material, a capacitive sensing electrode pattern formed on the transparent base material, and a transparent conducting film bonding pad array which is electrically connected with the capacitive sensing electrode pattern and located in a non-visual area. And all electrical connection points are firmly packaged by the anisotropic conductive material and the main sealing structure, so that water vapor and electrolyte are fundamentally prevented from eroding channels, and the protection grade of IP67 and above is easily realized.

Description

Technical Field

[0001] This invention relates to the field of touch screen technology, specifically to a waterproof capacitive touch screen based on PCB pads and a transparent conductive film. Background Technology

[0002] Capacitive touchscreens are widely used in consumer electronics, industrial control, automotive electronics, and outdoor equipment. Traditional capacitive touchscreens typically use transparent sensing electrodes (ITO patterns) fabricated on glass or thin-film substrates, and then use silver paste traces at the edges to collect signals to a flexible printed circuit board (FPC), which is then connected to the main control circuit via connectors or thermoforming.

[0003] This structure has obvious reliability defects: the silver paste traces are susceptible to environmental influences. The main components of silver paste are silver particles and organic binders. Its texture is porous and it is easy to absorb moisture in humid environments, which leads to increased impedance and signal attenuation. Under long-term exposure, silver ions are prone to migration or sulfidation / chlorination corrosion, which can lead to circuit breaks or leakage between adjacent traces, causing touch failure or accidental touch.

[0004] To address waterproofing issues, existing technologies often employ methods such as overall adhesive sealing after assembly, adding waterproof foam, or using waterproof and breathable membranes (ePTFE). These are "back-end remedial" measures that fail to fundamentally solve the inherent corrosion susceptibility of the silver paste traces and increase structural complexity and thickness.

[0005] Based on this, the present invention designs a waterproof capacitive touch screen based on PCB pads and a transparent conductive film to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a waterproof capacitive touchscreen based on PCB pads and a transparent conductive film to solve the above-mentioned technical problems.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a waterproof capacitive touch screen based on PCB pads and a transparent conductive film, comprising: a cover plate, a transparent conductive film sensor, a printed circuit board, an integrated connection structure, and a main sealing structure; A transparent conductive film sensor includes a transparent substrate, a capacitive sensing electrode pattern formed on the transparent substrate, and a transparent conductive film pad array electrically connected to the capacitive sensing electrode pattern and located in a non-visible area. A printed circuit board, which is provided with a touch control circuit and a PCB pad array corresponding to the transparent conductive film pad array; An integrated connection structure, composed of anisotropic conductive materials, allows the transparent conductive film sensor to be electrically interconnected and mechanically bonded to the PCB pad array of the printed circuit board in the Z-axis direction via the integrated connection structure through its transparent conductive film pad array. The above is only one connection method. A second method involves printing 0.04-0.08mm thick raised UV ink + conductive ink on the surface of the conductive adhesive film. The PCB circuit board and the transparent conductive film + cover plate are assembled in an overlapping structure to achieve contact between the transparent conductive film and the PCB pads. A third method involves using a mold hot pressing process to locally raise the transparent conductive film by 0.2-0.3mm in height to achieve contact between the transparent conductive film and the PCB pads. In addition, a main sealing structure is provided around the integrated connection structure and seals the connection area between the transparent conductive film pad array and the PCB pad array.

[0008] Preferably, the integrated connection structure is an anisotropic conductive film or anisotropic conductive adhesive.

[0009] Preferably, the transparent conductive film pad and the capacitive sensing electrode pattern are made from the same transparent conductive layer using the same patterning process.

[0010] Preferably, the material of the capacitive sensing electrode pattern is indium tin oxide, metal mesh, or silver nanowires.

[0011] Preferably, the printed circuit board is a rigid printed circuit board, a flexible printed circuit board, or a rigid-flex board.

[0012] Preferably, it further includes a peripheral potting layer disposed on the component side of the printed circuit board and covering its electronic components.

[0013] Preferably, the main sealing structure is a sealing frame formed of silicone, epoxy resin or polyurethane material.

[0014] Preferably, the cover plate is fully bonded to the visible area of ​​the transparent conductive film sensor through an optically transparent adhesive layer, and the edge of the cover plate is bonded and sealed to the printed circuit board or intermediate support structure through edge sealant.

[0015] A method for manufacturing a waterproof capacitive touchscreen includes the following steps: S1. Provides a transparent conductive film sensor with a transparent conductive film pad array, and a printed circuit board with a corresponding PCB pad array and touch control circuit; S2. An anisotropic conductive material is disposed on the transparent conductive film pad array or the PCB pad array; S3. Align and bring the transparent conductive film pad array into contact with the PCB pad array through the anisotropic conductive material, perform thermo-press bonding, and form an integrated connection structure; S4. Apply a sealing material to the outer periphery of the integrated connection structure and cure it to form a main sealing structure; S5. The cover plate is fully bonded to the visible area of ​​the transparent conductive film sensor through an optically transparent adhesive layer, and the edges are sealed.

[0016] Preferably, after step S4, the method further includes the step of: potting encapsulating adhesive onto the component side of the printed circuit board to form an outer encapsulating layer covering the electronic components.

[0017] In summary, this application has the following beneficial technical effects: 1. Intrinsic Waterproofing: Completely eliminates porous and easily corroded silver paste wiring. All electrical connection points are firmly encapsulated by anisotropic conductive materials and a main sealing structure, fundamentally eliminating channels for water vapor and electrolyte corrosion, easily achieving IP67 and above protection levels.

[0018] II. High reliability and long lifespan: The PCB+ACF connection method is a mature industrial standard, with high connection strength, stable impedance, and excellent resistance to vibration and thermal cycling, which greatly improves the service life of the product in harsh environments.

[0019] III. Performance Improvement: Low and consistent PCB trace impedance is beneficial for improving signal transmission quality, signal-to-noise ratio and touch response speed. The more compact structure is conducive to making devices thinner and lighter.

[0020] IV. Process simplification and cost optimization: The reduction of materials such as FPC and connectors simplifies the supply chain and assembly steps (eliminating multiple processes such as silver paste printing, curing, and FPC bonding), potentially improving production yield and long-term cost-effectiveness. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the overall disassembled structure of this embodiment; Figure 2 This is a schematic diagram of the transparent conductive film sensing structure in this embodiment; Figure 3 This is a schematic diagram of the printed circuit board structure in this embodiment.

[0023] The attached diagram lists the components represented by each number as follows: 1. Cover plate; 2. Optical transparent adhesive layer; 3. Transparent conductive film sensor; 31. Transparent substrate; 32. Capacitive sensing electrode; 33. Transparent conductive film pad; 4. Integrated connection structure; 5. Printed circuit board; 51. PCB substrate; 52. PCB pad; 53. Touch control chip; 54. Electronic component; 6. Main sealing structure; 7. Peripheral potting layer; 8. Edge sealant. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The following is in conjunction with the appendix Figure 1-3 This application will be described in further detail.

[0026] A waterproof capacitive touchscreen based on PCB pads and a transparent conductive film includes, from top to bottom, the following: a cover plate 1, typically made of tempered glass or a transparent polymer sheet; an optically transparent adhesive layer 2, such as solid or liquid optical adhesive; a transparent conductive film sensor 3; an integrated connection structure 4; a printed circuit board 5; and a sealing structure (main sealing structure 6 and edge sealant 8).

[0027] Transparent conductive film sensor 3: On a transparent PET film (as a transparent substrate 31), an ITO capacitive sensing electrode 32 (e.g., a mutual capacitance Tx emitter electrode and Rx receiver electrode pattern) is formed by magnetron sputtering and photolithography. In the non-visible area of ​​the sensor (usually located on one side edge), the lead ends of the sensing electrode are designed and processed into a series of regular, precisely sized transparent conductive film pads 33. These pads 33 are integrally formed with the sensing electrode 32, are made of the same material (ITO), and are connected by widened and reinforced leads.

[0028] Fabrication of Printed Circuit Board 5: A rigid PCB substrate 51 is used. On one surface of the PCB, a touch control chip 53 (such as a microcontroller or a dedicated touch controller) and other necessary electronic components 54 (such as resistors, capacitors, and ESD protection devices) are integrated and soldered. On the same surface or a specific area of ​​the edge of the PCB, an array of PCB pads 52 is fabricated using standard PCB processes (such as gold plating). The number, position, and spacing of the PCB pads 52 correspond one-to-one with the transparent conductive film pads 33 on the transparent conductive film sensor 3. The PCB is also equipped with an external connector for connecting to the host device.

[0029] Core connection process: The pre-cut anisotropic conductive film (as an integrated connection structure 4) is pre-attached to the pad 52 area of ​​the PCB. Then, using a high-precision vision alignment system, the pad 33 of the transparent conductive film sensor 3 is placed face down, so that the pad 33 and the pad 52 on the PCB are precisely positioned and bonded through ACF. Subsequently, a hot press head is used to perform hot pressing bonding at a certain temperature (e.g., 180°C), pressure (e.g., 3-5 MPa), and time (e.g., 5-10 seconds). During the hot pressing process, the thermosetting resin in the ACF melts and solidifies to form a strong adhesive layer. At the same time, the dispersed conductive microspheres are flattened in the Z-axis direction, forming independent conductive channels between the corresponding pads 33 and 52, realizing electrical connection. In the XY plane, the conductive microspheres are isolated from each other to maintain insulation. Thus, the sensor signal enters the control circuit on the PCB through the direct path of ITO pad 33 → conductive microsphere → PCB pad 52, completely eliminating any silver paste traces.

[0030] Waterproof sealing process: After bonding, an automatic dispensing device is used to apply a ring of polyurethane sealant around the integrated connection structure 4 (i.e., the bonding area). After curing, it forms the main sealing structure 6. This structure completely covers and seals the entire electrical connection interface (pads, ACF), isolating moisture and contaminants. Next, epoxy resin potting compound can be applied to the component side of the PCB to form an outer potting layer 7, which covers and protects components such as the touch control chip 53. Finally, the cover plate 1 is fully bonded to the transparent conductive film sensor 3 through the optically transparent adhesive layer 2, and waterproof foam adhesive or liquid sealant is used as the edge sealant 8 to bond and seal the edge of the cover plate 1 to the side of the PCB 5 or the specially designed step, forming a complete waterproof barrier.

[0031] The traditional signal path is: ITO electrode → silver paste trace → FPC → connector → main PCB. The path is long, there are many interfaces, and the weakness (silver paste) is obvious. The signal path of the present invention is: ITO electrode → ITO pad 33 → ACF → PCB pad 52 → PCB trace → chip 53. The path is extremely short, the interface is robust, and intrinsic safety is achieved.

[0032] In the description of this invention, it should be understood that the terms "coaxial," "bottom," "one end," "top," "middle," "other end," "upper," "side," "top," "inner," "front," "center," "both ends," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0033] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "setting," "connection," "fixing," "screw connection," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0034] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A waterproof capacitive touchscreen based on PCB pads and a transparent conductive film, characterized in that, include: Cover plate, transparent conductive film sensor, printed circuit board, integrated connection structure and main sealing structure; A transparent conductive film sensor includes a transparent substrate, a capacitive sensing electrode pattern formed on the transparent substrate, and a transparent conductive film pad array electrically connected to the capacitive sensing electrode pattern and located in a non-visible area. A printed circuit board, which is provided with a touch control circuit and a PCB pad array corresponding to the transparent conductive film pad array; An integrated connection structure is made of anisotropic conductive material. The transparent conductive film sensor is electrically interconnected and mechanically bonded to the PCB pad array of the printed circuit board in the Z-axis direction through the integrated connection structure with its transparent conductive film pad array. In addition, a main sealing structure is provided around the integrated connection structure and seals the connection area between the transparent conductive film pad array and the PCB pad array.

2. A waterproof capacitive touchscreen based on PCB pads and a transparent conductive film according to claim 1, characterized in that: The integrated connection structure is an anisotropic conductive film or anisotropic conductive adhesive.

3. A waterproof capacitive touchscreen based on PCB pads and a transparent conductive film according to claim 1, characterized in that: The transparent conductive film pads and the capacitive sensing electrode patterns are made from the same transparent conductive layer using the same patterning process.

4. A waterproof capacitive touchscreen based on PCB pads and a transparent conductive film according to claim 1, characterized in that: The material of the capacitive sensing electrode pattern is indium tin oxide, metal mesh, or silver nanowires.

5. A waterproof capacitive touchscreen based on PCB pads and a transparent conductive film according to claim 1, characterized in that: The printed circuit board is a rigid printed circuit board, a flexible printed circuit board, or a rigid-flex board.

6. A waterproof capacitive touchscreen based on PCB pads and a transparent conductive film according to claim 1, characterized in that: It also includes an outer potting layer disposed on the component side of the printed circuit board and covering its electronic components.

7. A waterproof capacitive touchscreen based on PCB pads and a transparent conductive film according to claim 1, characterized in that: The main sealing structure is a sealing frame made of silicone, epoxy resin or polyurethane material.

8. A waterproof capacitive touchscreen based on PCB pads and a transparent conductive film according to claim 1, characterized in that: The cover plate is fully bonded to the visible area of ​​the transparent conductive film sensor through an optically transparent adhesive layer, and the edge of the cover plate is bonded and sealed to the printed circuit board or intermediate support structure through edge sealant.

9. A method for manufacturing a waterproof capacitive touchscreen as described in any one of claims 1-8, characterized in that, Including the following steps: S1. Provides a transparent conductive film sensor with a transparent conductive film pad array, and a printed circuit board with a corresponding PCB pad array and touch control circuit; S2. An anisotropic conductive material is disposed on the transparent conductive film pad array or the PCB pad array; S3. Align and bring the transparent conductive film pad array into contact with the PCB pad array through the anisotropic conductive material, perform thermo-press bonding, and form an integrated connection structure; S4. Apply a sealing material to the outer periphery of the integrated connection structure and cure it to form a main sealing structure; S5. The cover plate is fully bonded to the visible area of ​​the transparent conductive film sensor through an optically transparent adhesive layer, and the edges are sealed.

10. The manufacturing method according to claim 9, characterized in that, After step S4, the method further includes the step of: potting encapsulating adhesive onto the component side of the printed circuit board to form an outer encapsulating layer covering the electronic components.

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