Electromagnetic shielding structure for keyboard, manufacturing method of electromagnetic shielding structure and keyboard

Abstract

The invention relates to the technical field of electromagnetic shielding devices, and provides an electromagnetic shielding structure for a keyboard, a manufacturing method of the electromagnetic shielding structure and the keyboard. The structure is arranged on the inner surface of an upper cover / lower cover of a keyboard or covers the surface of an insulating covering layer on a printed circuit board, and mainly comprises an electrically continuous reflecting layer which extends along a target area and is conducted with a keyboard ground wire through a peripheral grounding wire; the absorbing layer is arranged on the reflecting layer, a patterned opening is formed in the absorbing layer and the reflecting layer, and the depth of the patterned opening is limited between the two layers, so that the reflecting layer is kept electrically continuous below the patterned opening; and a protective layer covering the absorbing layer, filling the patterned opening and contacting the reflective layer. Therefore, transmission and re-radiation can be reduced in the target frequency band, resonance of the cavity and the gap is suppressed, and backlight channel avoidance and thinning are both considered.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electromagnetic shielding devices, in particular to an electromagnetic shielding structure for a keyboard, a manufacturing method thereof and a keyboard. BACKGROUND

[0002] A notebook keyboard integrates a microcontroller unit (MCU), a matrix scanning circuit, a backlight driving circuit and a power management circuit in a limited cavity. During operation, electromagnetic radiation such as clock, PWM (pulse width modulation), switching power supply harmonic and the like is easily generated. At the same time, the upper cover / lower cover of the keyboard is usually made of plastic, the cavity is thin, the opening is large, and the gap is long, which is easy to form cavity and gap resonance, resulting in problems of peak exceeding the standard or poor consistency in regulatory testing. The keyboard usually also has a backlight module, and the light guide and diffusion path of the backlight module are sensitive to metal layers and strong absorption materials. If not handled properly, bright spots, dark bands or moire patterns may appear, affecting the optical quality.

[0003] In the prior art, common shielding solutions include: (1) A whole piece of metal shielding cover (welded to a printed circuit board): a relatively complete Faraday cavity can be formed, and the shielding effect is stable, but there are generally problems of increased volume and weight, thermal deformation and stress risk, and difficult repair; at the same time, the space occupation is large, and it is difficult to achieve fine shielding of only specific circuit areas.

[0004] (2) Whole surface metallization (conductive coating spraying / vacuum plating) inside the keyboard shell: a large area of reflection shielding can be provided, but the regionalization and patterning flexibility are insufficient, and the grounding path is often discontinuous due to structural limitations; close to the backlight module, optical defects are easily generated.

[0005] (3) Absorbing material patch (ferrite sheet, composite absorbing sheet, conductive foam / gasket): local peaks can be reduced, and assembly tolerances and near-field coupling have a certain tolerance, but the thickness and weight occupation are obvious, the consistency of manual attachment is poor, and the adhesion and compression stress decay in the service life can easily cause performance fluctuations.

[0006] In summary, the existing solutions cannot simultaneously consider: (i) thin and light weight and cost control; (ii) local fine shielding of specific circuit areas and zoning deployment; (iii) coexistence with the backlight module and maintaining optical uniformity; (iv) stable, continuous and mass producible consistent grounding path. Therefore, there is an urgent need for an electromagnetic shielding structure that can be arranged on the bearing surface of the keyboard, a manufacturing method thereof and a keyboard device, which can realize patterning control only in the upper layer while maintaining the electrical continuity of the reflection layer and reliable grounding, and can consider target frequency band suppression and backlight module avoidance, and can adapt to the existing mass production process route. SUMMARY

[0007] The present application relates to the technical field of electromagnetic shielding devices, and aims to solve the technical problems of large volume and weight, difficulty in realizing local fine shielding, difficulty in coexisting with a backlight channel, and cavity and gap resonance easily leading to excessive peak value of a traditional whole-piece metal shielding cover in a notebook keyboard scenario, and provides an electromagnetic shielding structure for a keyboard, a manufacturing method thereof, and a keyboard.

[0008] To achieve the above-mentioned object, the present application provides the following technical solutions. I. Electromagnetic shielding structure The electromagnetic shielding structure sequentially comprises, from inside to outside: a reflection layer, provided on a bearing surface, the reflection layer being an electrically continuous conductive layer and extending to cover a corresponding target area; wherein the bearing surface is an inner surface of a keyboard upper cover and / or lower cover, or a surface of an insulating cover layer covering above a keyboard printed circuit board; the reflection layer is electrically connected to a grounding trace provided at the periphery of the electromagnetic shielding structure to be connected to the keyboard ground; an absorption layer is provided on the reflection layer, the absorption layer and the reflection layer are formed with a patterned opening, and the depth of the patterned opening along the normal direction of the bearing surface is limited between the absorption layer and the reflection layer, so that the reflection layer remains electrically continuous below the patterned opening area; and a protective layer covers the outer surface of the absorption layer, the protective layer fills the patterned opening and further contacts the reflection layer. Therefore, the reflection layer can be reliably grounded through the grounding trace at the periphery of the structure, forming an effective shielding loop.

[0009] II. Manufacturing method The method is used for manufacturing an electromagnetic shielding structure, which sequentially comprises, from inside to outside: a reflection layer, an absorption layer, and a protective layer. First, a bearing surface is provided; conductive ink is printed on the target area of the bearing surface to form a reflection layer, and the reflection layer is solidified, the reflection layer being an electrically continuous conductive layer and extending to cover a corresponding target area; absorption ink is printed on the target area above the reflection layer to form an absorption layer, and the absorption layer is solidified, so that the reflection layer is electrically connected to a grounding trace provided at the periphery of the electromagnetic shielding structure to be connected to the keyboard ground; laser ablation processing is performed on the absorption layer and the reflection layer to form a patterned opening, the ablation depth of the patterned opening being limited between the absorption layer and the reflection layer, so that the reflection layer remains electrically continuous below the patterned opening area; and a protective layer is provided on the outer surface of the absorption layer, so that the protective layer fills the patterned opening and further contacts the reflection layer.

[0010] III. Keyboard device The keyboard device comprises an upper cover, a lower cover, a printed circuit board arranged between the upper cover and the lower cover, and a micro control unit mounted on the printed circuit board; the electromagnetic shielding structure is arranged on the inner surface of the upper cover / lower cover or the surface of an insulating cover layer covering above the printed circuit board, covering a corresponding micro control unit and a specific circuit area associated with the micro control unit and / or a backlight driving circuit area; the reflection layer is connected to the ground of the keyboard through the grounding trace, realizing consistency and stability with the grounding system of the whole machine.

[0011] In summary, compared with the prior art, the present invention has the following positive effects: (1) The reflective layer provides the main reflection and discharge path, and the absorption layer dissipates the remaining energy entering the structure. The two work together to reduce transmission and re-radiation, and effectively suppress the resonance peak of the cavity and gap.

[0012] (2) The patterned openings in the absorption and reflection layers do not disrupt the electrical continuity of the reflection layer and can perform directional attenuation of the target frequency band, adapting to the interference characteristics of microcontroller harmonics / matrix scanning / backlight driving, etc. Furthermore, shielding units corresponding to different areas can be set as needed, and multi-band collaborative shielding can be achieved by combining different patterns or material ratios, making it suitable for keyboard products of different models and layouts.

[0013] (3) By using the backlight channel avoidance and the gradual change of opening density design, the backlight brightness and uniformity can be taken into account, avoiding bright spots, shadows and moiré patterns; the overall structure is thin and lightweight, which is superior to the traditional metal cover solution.

[0014] (4) The reflective and absorbent layers are printed and cured at low temperature, which makes them compatible with keyboard materials and assembly processes, improving consistency and yield. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0016] in: Figure 1 This is a cross-sectional view of the electromagnetic shielding structure for a keyboard provided in this embodiment of the technical solution; Figure 2 This is a top view showing the relative positional relationship between the electromagnetic shielding structure and the keyboard backlight module provided in this embodiment of the technical solution; Figure 3 Yes Figure 2 A magnified top view of the absorption layer of the electromagnetic shielding structure and a portion of the keyboard backlight module; Figure 4 This is a cross-sectional view of the electromagnetic shielding structure in a variation example; Figure 5 This is a cross-sectional view of the bearing surface provided in this embodiment of the technical solution; Figure 6 Is Figure 5 A cross-sectional view of the reflective layer formed on the bearing surface; Figure 7 Is Figure 6A cross-sectional view of an absorption layer formed on a reflective layer; Figure 8 Yes Figure 7 The reflective layer is laser-exfoliated to form a cross-sectional view of patterned openings; Figure 9 This is a flowchart illustrating the method for fabricating an electromagnetic shielding structure for a keyboard, as provided in this embodiment of the technical solution. Figure 10 This is a cross-sectional view of the keyboard device provided in this embodiment of the technical solution.

[0017] Explanation of main component symbols Detailed Implementation 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, not all, of the embodiments of the present invention. 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.

[0018] Please see Figure 1 This embodiment of the technical solution provides an electromagnetic shielding structure 100 for a keyboard. The electromagnetic shielding structure 100 is disposed on the bearing surface of the keyboard. The electromagnetic shielding structure 100 includes, from the inside to the outside: a reflective layer 110 disposed on the bearing surface, the reflective layer 110 being an electrically continuous conductive layer that extends to cover a corresponding target area; an absorption layer 120 disposed on the reflective layer 110, the absorption layer 120 having a patterned opening 121, and the depth of the patterned opening 121 along the normal direction of the bearing surface being limited between the absorption layer 120 and the reflective layer 110, so that the reflective layer 110 remains electrically continuous below the area of ​​the patterned opening 121; and a protective layer 130 covering the outer surface of the absorption layer 120, the protective layer 130 filling the patterned opening 121 and further contacting the reflective layer 110.

[0019] Specifically, the bearing surface may be: (1) the inner surface of the keyboard top cover; (2) the inner surface of the keyboard bottom cover; (3) the surface of the insulating cover layer (such as solder resist, cover film or protective film) covering the keyboard printed circuit board 13, and the bearing surface is used to bear the reflective layer 110, the absorbent layer 120 and the protective layer 130.

[0020] Example 1: The inner surface of the top cover serves as the bearing surface. The top cover is typically made of polycarbonate (PC), acrylonitrile-butadiene-styrene copolymer (ABS), or polycarbonate / acrylonitrile-butadiene-styrene copolymer (PC / ABS) injection molding. To improve the adhesion and printing uniformity of the conductive ink, surface pretreatment can be performed on the inner surface of the top cover, such as plasma treatment, fine sanding, or primer coating. Taking plasma treatment as an example, the plasma treatment power is 100~500W, and the treatment time is 10~60 seconds. Subsequently, a continuous conductive reflective layer 110 is formed on the bearing surface according to the target area, and then an absorption layer 120 is formed on it. The absorption layer 120 is then laser-peeled to obtain patterned openings 121. To ensure the correspondence between the electromagnetic shielding area and the circuit area, the positioning posts / ribs of the top cover can be used in conjunction with the reference holes of the printed circuit board 13 for alignment. A clearance strip is provided in the area near the backlight module (such as light guide plate, diffuser, light-emitting diode, etc.), that is, the boundary of the reflective layer 110 is kept at a safe distance from the nearest edge of the backlight module, thereby avoiding the area where the backlight module is located; the absorption layer 120 can be provided with a gradient opening density strip on the side facing the backlight channel to take into account both electromagnetic shielding and optical uniformity. A crimping position or contact step can be reserved around the perimeter of the top cover, and the reflective layer 110 is connected to the ground line 15 of the keyboard through the grounding line 14 via conductive foam or metal spring.

[0021] Example 2: The inner surface of the lower cover serves as the bearing surface. When the inner surface of the lower cover is used as a load-bearing surface, it can typically cover the area below the microcontroller unit (MCU) and the projection area of ​​the high-speed / matrix traces. The lower cover is usually adjacent to components such as metal hinges and heat sinks, and preferably has multiple grounding traces 14 distributed at multiple points around the perimeter of the electromagnetic shielding structure 100 to reduce cavity mode excitation.

[0022] Example 3: The surface of the insulating covering layer serves as the bearing surface. When the bearing surface is an insulating cover layer covering the printed circuit board 13, the reflective layer 110 and the absorption layer 120 can be formed directly on the surface in sequence. To ensure reliable grounding, windowed solder joints or metallized vias can be designed around the perimeter of the reflective layer 110, and connected to the keyboard ground line 15 through the grounding trace 14. If there are printing height differences or surface mount protrusions in this area, a leveling primer / intermediate coat can be pre-applied to improve the continuity of the reflective layer 110 and the accuracy of subsequent patterns. For structures related to the backlight module (such as light guide plates, diffusers, light-emitting diodes, etc.), a clearance strip is provided on the bearing surface.

[0023] Example 4: Bearing surface of metal casing When the upper or lower cover is made of metal (such as aluminum-magnesium alloy), an insulating primer can be applied to the inner surface of the metal to form a bearing surface. Then, a reflective layer 110 and an absorption layer 120 can be formed on it to avoid direct short circuit between the reflective layer 110 and the metal casing, which could lead to uncontrollable grounding. Grounding is still reliably connected to the keyboard ground wire 15 through the grounding traces 14 distributed around the perimeter.

[0024] The above embodiments can be used individually or in combination with each other. Unless otherwise stated, the selection of materials, structures, and processes described herein are exemplary descriptions and do not constitute a limitation on the scope of protection of this invention.

[0025] In this embodiment, the reflective layer 110 is disposed on the carrier surface (taking the surface of the insulating cover layer covering the printed circuit board 13 as an example), and the reflective layer 110 is an electrically continuous conductive layer that extends to cover the corresponding target area. Specifically, the target area includes at least the projection range corresponding to the microcontroller unit 16 and its associated high-speed / matrix scanning traces. If necessary, it can be appropriately extended outwards according to the distribution of interference sources to form a continuous shielding perimeter and coordinate with the grounding trace 14. The material of the reflective layer 110 can be selected from one or more of silver, copper, silver-plated copper, or nickel. Preferably, a conductive ink system compatible with the carrier surface material is used, which has a low curing temperature, low shrinkage, high adhesion, and also ensures the adhesion of the subsequent absorption layer 120 and the stability of laser processing. If necessary, an adhesion promoter can be added to improve the bonding strength with the carrier surface. Specifically, the thickness of the cured reflective layer 110 is preferably 2 micrometers to 20 micrometers to obtain low sheet resistance and good flatness within a limited cavity, and the reflective layer 110 maintains electrical continuity within the target area. The reflective layer 110 is preferably formed by conductive ink printing. The following methods can be selected according to the equipment and production line: (1) screen printing, (2) inkjet printing, (3) gravure printing. The curing process is selected according to the ink system and the low temperature curing curve is selected to ensure that the solvent evaporation and conductive network formation are completed within the temperature resistance range of the bearing surface material. For thick film or multiple overprinting, a segmented curing method can be adopted.

[0026] like Figure 2As shown, taking the light-emitting diode (LED) of the keyboard backlight module as an example, the reflective layer 110 is arranged to avoid interference with the LED in the area close to it. The minimum distance between the reflective layer 110 and the nearest edge of the LED in the backlight module is not less than 1.0 mm to reduce the impact on the light guiding and diffusion path and avoid bright spots, shadows, or moiré patterns. In other words, a minimum distance needs to be reserved between the reflective layer 110 and the components of the backlight module (such as LEDs) to ensure that the reflective layer 110 will not interfere with the surrounding components after the accumulation of process tolerances. In addition, in a preferred embodiment, the boundary of the reflective layer 110 is aligned with the reference of the bearing surface; for cross-layer steps or curved surfaces, local thickening / overprinting can be used to ensure that the boundary of the reflective layer 110 is continuous and unbroken.

[0027] like Figure 1As shown, the absorption layer 120 is sequentially disposed on the reflective layer 110. Patterned openings 121 are formed in both the absorption layer 120 and the reflective layer 110, and the depth of the patterned openings 121 along the normal direction of the bearing surface is limited between the absorption layer 120 and the reflective layer 110, so that the reflective layer 110 maintains electrical continuity below the region of the patterned openings 121. That is, the patterned openings 121 may stop at the absorption layer 120 without reaching the reflective layer 110, or the patterned openings 121 may penetrate the absorption layer 120 and enter the reflective layer 110. In detail, the depth of the patterned openings 121 is controlled by laser ablation. When the patterned openings 121 extend to the reflective layer 110, only a portion of the surface material of the reflective layer 110 is removed without breaking the conductive network of the reflective layer 110, thereby maintaining electrical continuity. The absorber layer 120 can be a low-temperature curing lossy composite coating with a cured thickness of 5 micrometers to 50 micrometers. Its material includes at least one of nickel cobalt oxide particles (NiCo2O4) and a carbon-based conductive component. Specifically, the nickel cobalt oxide particles primarily provide dielectric / magnetic loss, while the carbon-based conductive component, such as reduced graphene oxide (rGO) and / or carbon nanotubes (CNTs), is used to establish the conductive network and adjust sheet resistance and bandwidth. Furthermore, the absorber layer 120 employs a low-temperature curing resin system (such as an acrylic or epoxy-modified system) compatible with the reflective layer 110 and the carrier surface, and dispersants and solvents can be added to achieve stable printing rheology and uniform dispersion. Moreover, the material ratio of the absorber layer 120 can be adjusted according to the target frequency band and required loss level to achieve a balance between absorption capacity, mechanical strength, and subsequent pattern processingability. Similarly, the absorption layer 120 can be formed on the reflective layer 110 by screen printing, inkjet printing, or gravure printing. After printing, it is cured at a low temperature (not higher than 120°C) to form a dense and well-adhesive absorption layer 120 film. In this embodiment, laser lift-off processing is preferably used to form patterned openings 121 in the absorption layer 120. The opening type can be any one or a combination of slits, slots, or hole arrays. The minimum linewidth is preferably 20 micrometers to 150 micrometers. The lift-off depth can be controlled by energy density and scanning strategy to limit the distance between the absorption layer 120 and the reflective layer 110. For example, an ultraviolet laser with an energy density of 1-5 J / cm² can be used. 2 The scanning speed is 100-500 mm / s. Specifically, since the patterned opening 121 is formed by laser lift-off, it has a trapezoidal cross-section with a wider upper opening and a narrower lower opening along the film thickness direction (i.e., the end away from the bearing surface is wider, and the end closer to the bearing surface is narrower), thereby controlling the patterned opening 121 to penetrate the absorption layer 120 and form a groove or slot in the reflective layer 110. In a variation, such as... Figure 3As shown, the absorption layer 120 has a gradient aperture density band near the boundary of the backlight module, and the aperture density of the gradient aperture density band gradually decreases from the center of the absorption layer 120 towards the backlight module. That is, the absorption layer 120 closer to the backlight module has a less dense aperture distribution, and the farther away from the backlight module, the denser it can be. In detail, a step-by-step (gradually decreasing in zone) or continuous (adjusting the aperture diameter / pitch / duty cycle or using digital dithering) implementation method can be used to smooth the electromagnetic boundary and reduce the risk of eddy current skin and bright spots / moiré patterns. Therefore, by the gradient band design of the absorption layer 120 and the avoidance arrangement of the reflective layer 110 (i.e., the distance between the nearest edge of the reflective layer 110 and the backlight module is not less than 1.0 mm), both shielding effectiveness and backlight uniformity are taken into account.

[0028] The outer surface of the absorption layer 120 is covered with a protective layer 130, which fills the patterned opening 121 and further contacts the reflective layer 110. That is, the protective layer 130 further fills the patterned opening 121 extending into the groove or slot area of ​​the reflective layer 110, without affecting the existing conductive bridges and / or perimeter connecting bands of the reflective layer 110, thus maintaining electrical continuity and a low-resistance circuit. Specifically, since the patterned opening 121 formed by laser ablation can have a trapezoidal cross-section with a wider upper opening and a narrower lower opening along the thickness direction, the protective layer 130, after filling, can form a "wedge-type" mechanical lock at the narrower lower opening, thereby strengthening the stacking strength of the absorption layer 120 and the reflective layer 110 and reducing defects such as delamination and peeling. In this embodiment, the protective layer 130 is an electrically insulating, non-magnetic, low-temperature curing transparent / semi-transparent varnish system. Its film-forming substrate can be selected from one or a combination of UV-curable acrylics (such as polyurethane acrylates, epoxy acrylates), organosilicon / siloxanes (polysiloxanes or organic-inorganic hybrid siloxanes), and low-temperature thermosetting modified acrylic / epoxy varnishes. To improve the interfacial bonding force between the absorber layer 120 and the reflector layer 110, aminosilanes, epoxy / acrylic grafted compatibility promoters, or plasma activation followed by coating can be used. The protective layer 130 is mainly used for: (1) improving wear resistance and scratch resistance, reducing wear caused by assembly friction, vibration, and long-term use; (2) blocking environmental media such as sweat, salt spray, and humid heat, inhibiting material migration or powdering of the absorber layer 120; and (3) stabilizing the surface morphology of the absorber layer 120, maintaining the geometric dimensions and edge quality of the patterned openings 121, thereby ensuring the consistency of shielding performance. The protective layer 130 is an electrically insulating and non-magnetic coating that will not form conductive bridges between the patterned openings 121 and will not change the electrical continuity of the reflective layer 110. Furthermore, the thickness of the protective layer 130 can be 2 micrometers to 20 micrometers, satisfying both wear resistance and barrier properties while avoiding excessive backflow into the boundary microstructures.

[0029] Specifically, the reflective layer 110, as an electrically continuous conductive layer, is reliably connected to the keyboard ground wire 15 via the grounding trace 14 disposed around the electromagnetic shielding structure 100, forming a stable shielding loop. Preferably, multiple grounding points are formed at the perimeter of the shielding area to constitute a stable shielding loop and reduce gap leakage and boundary current concentration. Figure 1 As shown, when the bearing surface is the surface covering the insulating cover layer on the printed circuit board 13, the reflective layer 110 can be directly electrically connected to the grounding trace 14, making the reflective layer 110 conductive with the keyboard ground line 15. Preferably, the grounding trace 14 is distributed at least four times along the perimeter of the electromagnetic shielding structure 100 at different edges or corners. The grounding point density can be appropriately increased when near interference sources or the boundaries of long gaps. Furthermore, the absorption layer 120 dissipates residual electromagnetic energy entering the structure, reducing transmission and re-radiation. The absorption layer 120 effectively introduces damping at the boundary between the reflective layer 110 and the cavity, which helps suppress resonance peaks caused by the shell, gaps, or openings, thereby improving the stability of the shielding effect within the target frequency band.

[0030] In a variation example, such as Figure 4As shown, the electromagnetic shielding structure 100 may include an electrically isolated gap 150, dividing the electromagnetic shielding structure 100 into two or more electrically independent shielding units 140. The electrically isolated gap 150 divides the reflective layer 110 into multiple electrically independent shielding units 140, with the reflective layer 110 within each shielding unit 140 maintaining electrical continuity. In this case, the reflective layer 110 within a single shielding unit 140 is electrically independent and uninterrupted, without being electrically connected to the reflective layer 110 of adjacent shielding units 140. Each shielding unit 140 has different patterned openings and / or different absorption layer ratios to correspond to different target frequency bands. The so-called "absorption layer ratio" refers to the mass ratio of nickel cobalt oxide particles to carbon-based conductive components (such as rGO / CNT), ranging from 1:1 to 1:5, indicating a material composition ratio. For example, the absorption layer 120 may include different ratios of nickel cobalt oxide particles to carbon-based conductive components. In detail, each shielding unit 140 includes its own reflective layer 110 and an absorbent layer 120 thereon. Electrical isolation gaps 150 are provided between adjacent shielding units 140, and each shielding unit 140 is electrically connected to a grounding trace 14 at its perimeter, but there is no direct conductivity between shielding units 140. Through zoned arrangement and differentiated parameter configurations, such as different patterned opening parameters (pitch / aperture ratio / type) and / or different material ratios (NiCo2O4 to rGO / CNT ratio), targeted control of different target frequency bands or different interference sources is achieved. One shielding unit 140 covers the projection area of ​​the microcontroller unit 16 and its high-speed / matrix scan traces, while another shielding unit 140 covers the projection area of ​​another microcontroller unit 16 and its high-speed / matrix scan traces. Each shielding unit 140 can be annular, strip-shaped, L-shaped, or an irregular polygon to adapt to the actual component and trace distribution. Furthermore, as... Figure 4 As shown, since the absorption layer 120 in different shielding units 140 can adopt different types and densities of second patterned openings 141 and third patterned openings 142, for example: the second patterned opening 141 adopts a smaller pitch / higher aperture ratio to suppress the master clock and harmonics; the third patterned opening 142 adopts a larger pitch / lower aperture ratio to suppress low-frequency PWM radiation.

[0031] Please see Figure 9 This document provides a flowchart of a method for fabricating an electromagnetic shielding structure for a keyboard, as described in this embodiment of the technical solution. The method is used to fabricate an electromagnetic shielding structure, which, from the inside out, sequentially includes: a reflective layer 110, an absorption layer 120, and a protective layer 130. The method mainly includes steps A to E: A) Provide a bearing surface; B) Print conductive ink in the target area of ​​the bearing surface to form a reflective layer 110, and cure the reflective layer 110, wherein the reflective layer 110 is an electrically continuous conductive layer and extends to cover the corresponding target area; C) Print absorbent ink in the target area above the reflective layer 110 to form an absorbent layer 120, and cure the absorbent layer 120 so that the reflective layer 110 is electrically connected to the grounding trace 14 located around the electromagnetic shielding structure 100, so as to conduct to the keyboard ground line 15. D) Laser-assisted ablation of the absorption layer 120 and the reflective layer 110 to form a patterned opening 121, wherein the ablation depth is limited between the absorption layer 120 and the reflective layer 110, thereby maintaining electrical continuity of the reflective layer 110 below the patterned opening 121 region; and E) Cover the outer surface of the absorption layer 120 with a protective layer 130, such that the protective layer 130 fills the patterned opening 121 and further contacts the reflective layer 110.

[0032] Regarding step A, as follows Figure 5 As shown, the bearing surface is selected and defined. The bearing surface can be the inner surface of the upper cover, the inner surface of the lower cover, or the surface of an insulating covering layer (such as a solder resist, cover film, or protective film) covering the PCB. Then, the bearing surface is subjected to dust removal, degreasing, and surface activation (such as plasma or primer treatment) to improve the adhesion of subsequent inks and the continuity of the film surface. Furthermore, alignment references (such as positioning posts / reference holes) are established on the bearing surface, and masking films are applied to the corresponding areas of the keyboard backlight module, grounding contacts / press-fit positions, studs, and other functional positions to form clearance zones and opening areas.

[0033] Regarding step B, as follows: Figure 6 As shown, a continuous conductive reflective layer 110 is formed in the target area of ​​the bearing surface using conductive ink through screen printing, inkjet printing, or gravure printing, extending along the perimeter of the target area to form a closed boundary. The reflective layer 110 is then cured according to the ink system, preferably at a low-temperature curing temperature not exceeding approximately 150°C; alternatively, it can be cured in stages according to different formulations. The thickness of the cured reflective layer 110 is preferably 2 micrometers to 20 micrometers; electrical continuity is confirmed by a four-probe or cross-regional continuity test. For areas crossing ribs or steps, secondary overprinting or a leveling primer can be used to ensure no breaks or pinholes.

[0034] Regarding step C, as follows Figure 7As shown, the absorption layer 120 is formed in the target area above the reflective layer 110 using screen printing, inkjet printing, or gravure printing. The absorption layer 120 is a low-temperature curing lossy composite coating, and the material includes at least one of nickel cobalt oxide particles and a carbon-based conductive component. The absorption layer 120 is then cured, for example, at a low-temperature curing temperature not exceeding approximately 120°C. The thickness of the cured absorption layer 120 is preferably 5 micrometers to 50 micrometers. Furthermore, the grounding trace 14 around the reflective layer 110 is kept clean and free of residue, allowing the reflective layer 110 to be connected to the keyboard ground wire 15 via the grounding trace 14.

[0035] Regarding step D, as follows Figure 8 As shown, patterned openings 121 (such as slits, slots, or arrays of holes) are formed in the absorption layer 120 and the reflective layer 110 using laser lift-off processing, with a minimum linewidth of 20 micrometers to 150 micrometers. The lift-off is confined between the absorption layer 120 and the reflective layer 110 by adjusting energy density and scanning strategy, ensuring electrical continuity of the reflective layer 110 below the patterned opening 121 region. Furthermore, as... Figure 3 As shown, near the boundary of the backlight module, the patterned opening 121 employs a gradient opening density band (which can be stepped or continuous: adjusting the aperture / pitch / duty cycle or using digital dithering) to smooth the electromagnetic boundary and reduce the risk of bright spots / moiré patterns. For example, the opening density gradually decreases from 50% in the central region of the patterned opening 121 to 10% at the edge of the backlight module.

[0036] Regarding step E, for example... Figure 1 As shown, a protective layer 130 is applied to the outer surface of the absorption layer 120, filling the patterned opening 121 and further contacting the reflective layer 110. The protective layer 130 can be formed by spraying, screen printing, dip coating, or spin coating, using processes such as "thin spraying—baking—curing" to control thickness and edge reflow. The thickness of the protective layer 130 is preferably 2 micrometers to 20 micrometers. The protective layer 130 is an electrically insulating, non-magnetic coating that does not form conductive bridges between the patterned openings 121 and does not cover functional areas such as grounding windows, crimping positions, and mounting studs. Specifically, since the patterned opening 121 formed by laser ablation can have a trapezoidal cross-section with a wider upper opening and a narrower lower opening along the thickness direction, when the protective layer 130 fills the patterned opening 121, it forms a "wedge-type" mechanical lock, thereby strengthening the bond strength between the absorption layer 120 and the reflective layer 110 and reducing delamination, peeling, and other defects.

[0037] Using the above method, a low-resistance shielding loop of reflective layer 110—grounding trace 14—keyboard ground wire 15 can be formed without affecting the light-emitting path of the backlight module and the keyboard assembly space. By means of absorption layer 120—patterned opening 121—gradient band, the frequency band can be adjusted and the boundary can be smoothed. This can stably reduce transmission and re-radiation in the target frequency band, suppress cavity / gap resonance peaks, and meet the requirements of keyboard product thinness and mass production consistency.

[0038] Please see Figure 9 The keyboard device 10 provided in this embodiment includes an upper cover 11, a lower cover 12, a printed circuit board 13 disposed between the upper cover 11 and the lower cover 12, and a microcontroller unit 16 mounted on the printed circuit board 13. An electromagnetic shielding structure 100 is disposed on the inner surface of the upper cover 11 and / or the lower cover 12, or on the surface of an insulating covering layer over the printed circuit board 13. The electromagnetic shielding structure 100 covers the microcontroller unit 16 and specific circuit areas and / or backlight driving circuit areas associated with the microcontroller unit 16; and the reflective layer 110 of the electromagnetic shielding structure 100 is connected to the keyboard ground line 15 via a grounding trace 14. In this embodiment, the electromagnetic shielding structure 100 is disposed on the inner surface of the lower cover 12, and also covers the area of ​​the printed circuit board 13 where the microcontroller unit 16 is located. Both electromagnetic shielding regions sequentially include a continuous conductive reflective layer 110 formed by conductive ink printing, an absorption layer 120 located on the reflective layer 110, and a protective layer 130. Patterned openings 121 are provided in the absorption layer 120 and the reflective layer 110 to maintain electrical continuity of the reflective layer 110 below the corresponding region. A protective layer 130 is formed on the outer surface of the absorption layer 120, filling the patterned openings 121 and further contacting the reflective layer 110. The reflective layers 110 are connected along the perimeter of their respective shielding regions via grounding traces 14 and ground wires 15 (preferably distributed at multiple points) to form a stable shielding loop and reduce gap leakage. Therefore, by simultaneously implementing the electromagnetic shielding structure 100 of the present invention on the inner surface of the lower cover 12 and in the region where the microcontroller unit 16 is located on the printed circuit board 13, the source region near-field coupling and cavity / gap resonance can be synergistically suppressed without changing the appearance and assembly interface, achieving reduced transmission, reduced re-radiation, and a stable improvement in shielding effect within the target frequency band.

[0039] It is understood that the scope descriptions in this application all include the endpoints. For example, 5 micrometers to 50 micrometers, this scope description includes the endpoint of 5 micrometers and the endpoint of 50 micrometers, that is, 5 micrometers, 50 micrometers, and values ​​in between 5 micrometers and 50 micrometers all fall within this range.

[0040] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. An electromagnetic shielding structure for a keyboard, disposed on the keyboard's bearing surface, characterized in that, The electromagnetic shielding structure, from the inside out, includes: A reflective layer is disposed on the bearing surface. The reflective layer is an electrically continuous conductive layer and extends to cover the corresponding target area. The bearing surface is the inner surface of the keyboard upper cover and / or lower cover, or the surface of an insulating cover layer covering the keyboard printed circuit board. The reflective layer is electrically connected to a grounding trace disposed around the electromagnetic shielding structure to conduct to the keyboard ground. An absorption layer is disposed on the reflective layer, and patterned openings are formed in both the absorption layer and the reflective layer. The depth of the patterned openings along the normal direction of the bearing surface is limited between the absorption layer and the reflective layer, thereby maintaining electrical continuity of the reflective layer below the patterned opening region. A protective layer covers the outer surface of the absorbent layer, the protective layer fills the patterned openings and further contacts the reflective layer.

2. The electromagnetic shielding structure for a keyboard according to claim 1, characterized in that: The material of the reflective layer is one or more of silver, copper, silver-plated copper, or nickel, and the thickness after curing is 2 micrometers to 20 micrometers.

3. The electromagnetic shielding structure according to claim 1, characterized in that: The absorption layer is a low-temperature curing loss composite coating with a thickness of 5 micrometers to 50 micrometers after curing. Its material includes at least one of nickel cobalt oxide particles and carbon-based conductive components.

4. The electromagnetic shielding structure for a keyboard according to claim 1, characterized in that: The electromagnetic shielding structure also includes an electrical isolation gap, which divides the electromagnetic shielding structure into two or more electrically independent shielding units, wherein the electrical isolation gap divides the reflective layer into multiple electrically independent shielding units, and the reflective layer within each shielding unit remains electrically continuous.

5. The electromagnetic shielding structure for a keyboard according to claim 1, characterized in that: The reflective layer is formed by printing with conductive ink, and the printing method is any one of screen printing, inkjet printing or gravure printing.

6. The electromagnetic shielding structure for a keyboard according to claim 1, characterized in that: The electromagnetic shielding structure is arranged to avoid the area near the keyboard backlight module, and the minimum distance between the reflective layer and the nearest edge of the keyboard backlight module is not less than 1.0 mm.

7. The electromagnetic shielding structure for a keyboard according to claim 6, characterized in that: The absorption layer has a gradient aperture density band near the boundary of the backlight module, and the aperture density of the gradient aperture density band gradually decreases from the center of the absorption layer toward the backlight module.

8. A method for manufacturing an electromagnetic shielding structure for a keyboard, characterized in that, The method is used to fabricate an electromagnetic shielding structure, which, from the inside out, comprises: a reflective layer, an absorbing layer, and a protective layer. The method includes: A) Provide a bearing surface; B) Print conductive ink in the target area of ​​the bearing surface to form a reflective layer, and cure the reflective layer, wherein the reflective layer is an electrically continuous conductive layer and extends to cover the corresponding target area; C) Print absorbent ink in the target area above the reflective layer to form an absorbent layer, and cure the absorbent layer so that the reflective layer is electrically connected to the grounding traces located around the electromagnetic shielding structure to conduct to the keyboard ground line; D) Laser-laden ablation of the absorber layer and the reflector layer to form patterned openings, wherein the ablation depth of the patterned openings is limited between the absorber layer and the reflector layer, thereby maintaining electrical continuity of the reflector layer below the patterned opening region; and E) Cover the outer surface of the absorption layer with a protective layer, such that the protective layer fills the patterned opening and further contacts the reflective layer.

9. The method for manufacturing the electromagnetic shielding structure for a keyboard according to claim 8, characterized in that: a) The printing method for steps B and C is any one of screen printing, inkjet printing or gravure printing; b) The minimum linewidth of the patterned opening formed in step D is 20 micrometers to 150 micrometers; c) The electromagnetic shielding structure is arranged in a way that avoids the area near the keyboard backlight module, such that the minimum distance between the reflective layer and the nearest edge of the keyboard backlight module is not less than 1.0 mm.

10. A keyboard device comprising an upper cover, a lower cover, a printed circuit board disposed between the upper cover and the lower cover, and a microcontroller unit mounted on the printed circuit board, characterized in that: An electromagnetic shielding structure for a keyboard as described in any one of claims 1-7 is provided on the inner surface of the upper cover and / or the lower cover, or on the surface of an insulating cover layer covering the printed circuit board, the electromagnetic shielding structure covering a specific circuit area and / or backlight driving circuit area corresponding to the microcontroller and the microcontroller associated with it. as well as The reflective layer of the electromagnetic shielding structure is connected to the keyboard ground wire via a grounding trace.

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