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

Abstract

The invention relates to the technical field of electromagnetic shielding devices, and discloses an electromagnetic shielding structure for a keyboard chip, a manufacturing method of the electromagnetic shielding structure and a wireless keyboard applying the electromagnetic shielding structure, and the method comprises the following steps: a first circuit layer is provided with a signal wire and a grounding wire, and is connected to a second circuit layer provided with a welding pad and a false welding pad through a via hole; the chip is welded on the welding pad, and the false welding pad is electrically connected with the grounding wire; an insulating layer and a third circuit layer are formed outside the chip, and a coverage area is connected with the false welding pad through a via hole; the electromagnetic shielding layer is arranged on the solder mask layer, and the electromagnetic shielding layer is electrically connected with the grounding wire through the conductive adhesive layer, so that the chip is wrapped and shielded in all directions. The structure can effectively reduce electromagnetic interference and improve the stability of wireless keyboard signals, and is suitable for thin keyboard circuit design.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic shielding device technology, and in particular to an electromagnetic shielding structure for a keyboard chip, its manufacturing method, and a wireless keyboard. Background Technology

[0002] With the increasing popularity of wireless keyboards, their internal circuit components are becoming more highly integrated and thinner to fully leverage their portability. The keyboard chip, as the control core, needs to process multiple signals simultaneously, including keyboard input, wireless communication, and backlight driving. However, since wireless keyboards typically operate in the 2.4GHz or Bluetooth bands, the keyboard chip is highly susceptible to electromagnetic interference (EMI), leading to unstable signal transmission, manifesting as input delays, code loss, or communication interruptions.

[0003] In existing technologies, chips are typically soldered onto printed circuit boards (PCBs) using surface-mount technology (SMT). This mounting method is simple in structure and facilitates mass production, but it often lacks effective electromagnetic shielding around the chip, making it susceptible to high-frequency signal leakage or external interference. To suppress electromagnetic interference, existing technologies often add a metal shielding cover above the chip or form an overall shielding layer on the PCB surface. However, these traditional solutions have the following drawbacks: First, the shielding cover is bulky. Placing the chip on the PCB surface using surface mounting and then covering it with the shielding cover results in a complex assembly structure, with the chip and shielding cover thicknesses progressively increasing from the PCB thickness. This not only complicates assembly but also hinders the design of thin keyboards. Second, the contact between the shielding layer and ground is unstable, making it difficult to form a continuous conductive path and affecting the shielding effect. Third, some solutions only cover the upper surface of the keyboard chip, failing to achieve full coverage and thus limiting shielding performance.

[0004] Therefore, how to achieve a stable and reliable electromagnetic shielding structure in a thin keyboard circuit board while maintaining compatibility with keyboard chip assembly processes, so as to ensure the working stability of the keyboard chip, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies, such as severe electromagnetic interference of wireless keyboard chips, limited shielding effect, and the fact that traditional shielding covers are not conducive to thinness. This invention proposes an electromagnetic shielding scheme suitable for thin wireless keyboards, thereby achieving all-round coverage and shielding of the keyboard chip and improving the stability of wireless signals.

[0006] To achieve the above objectives, the present invention proposes the following technical solution: I. Fabrication method of electromagnetic shielding structure for keyboard chip The method includes: providing a copper-clad substrate, the copper-clad substrate including a substrate layer and a copper foil layer, and etching the copper foil layer to form a first circuit layer, the first circuit layer including signal traces for transmitting keyboard chip signals and ground traces for electrical grounding; forming a plurality of first vias and at least one second via in the substrate layer, the first vias corresponding to signal traces and the second vias corresponding to ground traces; forming a second circuit layer on the substrate layer, the second circuit layer including a plurality of solder pads, dummy solder pads surrounding the solder pads, a first via filled in the first via and a second via filled in the second via, the solder pads being electrically connected to the signal traces, the dummy solder pads being electrically connected to the ground trace, the first circuit layer and the second circuit layer being respectively disposed on opposite sides of the substrate layer; mounting a keyboard chip on the solder pads of the second circuit layer and achieving electrical connection by solder; forming an insulating layer on the substrate layer to cover the keyboard chip, solder pads and dummy solder pads, and forming a plurality of third vias in the insulating layer. Multiple fourth vias are provided, with the third vias corresponding to dummy solder pads, and the fourth vias extending to the first circuit layer. A third circuit layer is formed on the insulating layer, including at least one electrically independent coverage area, a third via formed within the third via, and a fourth via formed within the fourth via. The coverage area is electrically connected to the dummy solder pads through the third via, and the third circuit layer is electrically connected to the first circuit layer through the fourth via. The coverage area remains electrically independent and does not participate in signal transmission; instead, it is specifically used to form a shielding effect and a grounding barrier. Solder resist layers are formed on the first and third circuit layers to cover the signal traces and the coverage area, while openings in the solder resist layer are formed at the grounding trace locations. An electromagnetic shielding layer is formed on the solder resist layer, including a protective layer, a metal layer, and a conductive adhesive layer. The conductive adhesive layer fills the openings, allowing the metal layer to be electrically connected to the grounding trace, thereby constituting an electromagnetic shielding structure that can fully cover the keyboard chip.

[0007] II. Electromagnetic shielding structure for keyboard chips The structure includes: a copper-clad substrate, comprising a substrate layer and an etched first circuit layer, the first circuit layer including signal traces for transmitting keyboard chip signals and ground traces for electrical grounding; a second circuit layer disposed on the substrate layer, the second circuit layer including multiple solder pads, multiple dummy solder pads, multiple first vias and at least one second via, the solder pads being electrically connected to the signal traces through the first vias, and the dummy solder pads being electrically connected to the ground traces through the second vias, the first circuit layer and the second circuit layer being disposed on opposite sides of the substrate layer; a keyboard chip mounted on the solder pads and electrically connected by solder; an insulating layer covering the keyboard chip, the solder pads and the dummy solder pads; and a third circuit layer. The first circuit layer is formed on the insulating layer. The third circuit layer includes at least one electrically independent coverage area, which is electrically connected to the dummy solder pad through a third via. The third circuit layer is electrically connected to the first circuit layer through a fourth via. The coverage area is electrically independent and does not participate in signal transmission. Instead, it is used to form a shielding effect and a grounding barrier. The solder resist layer covers the signal traces and the coverage area and has an opening at the grounding trace location. The electromagnetic shielding layer is formed on the solder resist layer. The electromagnetic shielding layer includes a protective layer, a metal layer, and a conductive adhesive layer. The conductive adhesive layer fills the opening, so that the metal layer is electrically connected to the grounding trace, thereby forming a continuous and reliable grounding path and achieving all-round shielding of the keyboard chip.

[0008] III. A wireless keyboard The wireless keyboard includes a keyboard body and a printed circuit board. The printed circuit board is provided with the aforementioned electromagnetic shielding structure. The electromagnetic shielding structure covers the keyboard chip and is connected to the grounding trace through the electromagnetic shielding layer, thereby reducing electromagnetic interference of the keyboard chip during operation and ensuring the stability of wireless signal transmission.

[0009] Beneficial effects: This invention embeds the keyboard chip within an electromagnetic shielding structure and introduces dummy solder pads, a covering area, and openings in the solder resist layer around the keyboard chip's solder pads. After the electromagnetic shielding layer is attached, a stable grounding path is formed, enabling the electromagnetic shielding layer, the third via, and the covering area to provide comprehensive shielding for the keyboard chip. Compared to existing technologies, this solution avoids the problems of large size and difficulty in achieving thinner designs associated with traditional metal shielding covers. It also improves the continuity and reliability of shielding, effectively reduces electromagnetic interference, and ensures the stability and user experience of the wireless keyboard. Attached Figure Description

[0010] 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.

[0011] in: Figure 1 This is a flowchart of the electromagnetic shielding structure manufacturing method provided in this embodiment of the technical solution; Figure 2 This is a cross-sectional view of the copper-clad substrate provided in this embodiment of the technical solution; Figure 3 Yes Figure 2 A cross-sectional view of the copper foil layer of a copper-clad substrate after etching to form the first circuit layer; Figure 4 Is Figure 3 A cross-sectional view of the substrate layer after the first through hole and the second through hole are formed; Figure 5 Is Figure 4 A cross-sectional view after the second circuit layer is formed on the substrate layer; Figure 6 yes Figure 5 A partial top view of the solder pads and dummy solder pads of the second circuit layer; Figure 7 Is Figure 5 A cross-sectional view of the keyboard chip installed on the second circuit layer; Figure 8 Is Figure 7 A cross-sectional view after an insulating layer is formed on the substrate layer; Figure 9 Is Figure 8 A cross-sectional view of the insulating layer after the third and fourth through holes are formed; Figure 10 Is Figure 9 A cross-sectional view after the third circuit layer is formed on the insulating layer; Figure 11 yes Figure 10 A top view of the third via of the third circuit layer surrounding the keyboard chip; Figure 12 Is Figure 10 A cross-sectional view after the solder resist layer is formed on the first and third circuit layers; Figure 13 Is Figure 12 A cross-sectional view after an electromagnetic shielding layer is formed on the solder resist layer; Figure 14 This is a top view of the metal layer of the electromagnetic shielding layer in a variation example.

[0012] 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.

[0013] Please see Figure 1 The flowchart provided here illustrates a method for fabricating an electromagnetic shielding structure for a keyboard chip, which mainly includes the following steps: Step S1, please refer to Figure 2 and Figure 3 .like Figure 2 As shown, a copper-clad substrate 110 is provided, comprising a substrate layer 111 and a copper foil layer 112. In this embodiment, the substrate layer 111 may be made of epoxy glass fiber reinforced material (FR-4), polyimide, or bismaleimide triazine resin (BT) to balance mechanical strength, insulation performance, and heat resistance. The thickness of the copper foil layer 112 can be selected between 9 micrometers and 35 micrometers, determined based on shielding effect and thinning requirements. For example... Figure 3 As shown, the copper foil layer 112 is etched to form a first circuit layer 120. The first circuit layer 120 includes signal traces 121 for transmitting keyboard chip signals and ground traces 122 for electrical grounding. The first circuit layer 120 is formed by etching the copper foil layer 112 to create a predetermined circuit pattern. This etching process can be implemented using either a wet or dry process. Optionally, the linewidth and spacing of the signal traces 121 can be between 50 micrometers and 150 micrometers to ensure the integrity of high-speed signal transmission. The ground traces 122 can be wider than the signal traces 121 to reduce impedance and improve shielding. Specifically, the ground traces 122 provide a uniform reference potential for the circuit board, ensuring the stability of the keyboard chip and related keyboard circuits during operation. Furthermore, the ground traces 122 provide a current loop for the signal traces 121, forming a closed path, thereby reducing impedance discontinuities during high-speed signal transmission and improving signal integrity. Furthermore, the grounding trace 122 also acts as a shielding strip in the circuit board layout, reducing the risk of crosstalk between signal lines and suppressing the propagation of electromagnetic noise within the keyboard circuit board. Therefore, the grounding trace 122 not only achieves the conventional grounding function but also plays a crucial role in the stable operation and anti-interference capability of the circuit. The first circuit layer 120 formed through this step provides a stable electrical path for the subsequent installation of the keyboard chip and the grounding of the shielding layer, thus structurally reserving the conditions for the conduction of the electromagnetic shielding structure.

[0014] For step S2, please refer to... Figure 4 A plurality of first through-holes 111a and at least one second through-hole 111b are formed in the substrate layer 111. The first through-hole 111a corresponds to the signal trace 121 and is used to establish a signal transmission channel between different circuit layers. The second through-hole 111b corresponds to the ground trace 122 and is used to provide a longitudinal connection for electrical grounding. In this embodiment, the first through-holes 111a and the second through-hole 111b can be formed by laser drilling or laser ablation. Laser drilling has the advantages of high processing accuracy and controllable hole diameter, and is suitable for thin circuit boards. The hole diameter of the first through-hole 111a is preferably 50 micrometers to 150 micrometers to meet the low impedance transmission of high-speed signals. The hole diameter of the second through-hole 111b can be appropriately increased, for example, it can be designed to be 100 micrometers to 200 micrometers to reduce the impedance of the grounding loop and improve the current carrying capacity. If it is necessary to form a second through-hole 111b with a larger diameter, mechanical drilling can also be used. Specifically, the first through-hole 111a can be arranged in a matrix according to the distribution pattern of the keyboard chip pins, thereby ensuring stable conduction of the circuit between the signal trace 121 and the keyboard chip pins; the second through-hole 111b can be distributed in key positions according to the grounding requirements of the circuit board to form a continuous and low-impedance grounding network.

[0015] Step 3, S3, please refer to Figure 5 A second circuit layer 130 is formed on the substrate layer 111. The second circuit layer 130 includes a plurality of solder pads 131, dummy pads 132 surrounding the solder pads 131, a first via 133 filling the first via 111a, and a second via 134 filling the second via 111b. The solder pads 131 are electrically connected to the signal traces 121, and the dummy pads 132 are electrically connected to the ground traces 122. Optionally, the thickness of the second circuit layer 130 can be from 10 micrometers to 25 micrometers. The solder pads 131 are disposed at predetermined positions on the second circuit layer 130 for mounting and soldering the keyboard chip. An electrical channel is established between the keyboard chip and the first circuit layer 120 through the first via 133, the solder pads 131, and the signal traces 121. Figure 6As shown, the dummy solder pad 132 is arranged around the solder pad 131 to surround the area where the solder pad 131 is located, and is electrically connected to the ground trace 122 through the second via 134. Specifically, the dummy solder pad 132 itself is not directly connected to the keyboard chip pins; its main function is to form a surrounding structure, providing a grounding point for the subsequent shielding layer, and simultaneously constructing a shielding boundary around the keyboard chip to reduce electromagnetic interference coupling paths. In other words, the dummy solder pad 132 is not used for chip electrical connections, but only as a grounding shielding pad. In one embodiment, the solder pad 131 and the dummy solder pad 132 can be formed using electroplating or chemical plating processes. A surface treatment layer with good solderability, such as a nickel / gold layer or an organic solder resist film, can be applied to the surfaces of the solder pad 131 and the dummy solder pad 132 to improve soldering reliability and prevent oxidation. The surface treatment layer effectively isolates the surface from moisture and temperature / humidity changes in the external environment, preventing oxidation, corrosion, or performance degradation of the solder pads 131 and dummy solder pads 132 during manufacturing or storage, thus ensuring the reliability of keyboard chip soldering and the conductivity stability of the dummy solder pads 132. Through this step, the second circuit layer 130 is constructed on the substrate layer 111, not only achieving a reliable connection between the keyboard chip signal pins and the signal traces 121, but also laying the foundation for establishing a grounding network and achieving subsequent shielding effects.

[0016] Step 4, S4, please refer to Figure 7The keyboard chip 140 is mounted on the pad 131 of the second circuit layer 130 and electrically connected by solder 141. In this embodiment, the keyboard chip 140 can be a microcontroller unit (MCU) or an integrated circuit with keyboard control and wireless communication functions. The pins or solder joints of the keyboard chip 140 correspond to the pad 131, and a reliable connection between the keyboard chip 140 and the pad 131 is achieved by heating and melting the solder 141. The solder 141 can be a tin-lead alloy or a lead-free solder 141, such as Sn-Ag-Cu alloy, to ensure the mechanical strength and electrical conductivity of the solder joint. In a preferred embodiment, the keyboard chip 140 can be mounted using a flip-chip method, that is, the pins or solder joints of the keyboard chip 140 are directly aligned with the pad 131 and flipped for mounting. This mounting method eliminates the traditional wire bonding structure, shortening the electrical path between the keyboard chip 140 and the circuit layer, thereby reducing parasitic inductance and signal delay, making it suitable for high-speed signal transmission. This mounting method also reduces the overall package height (eliminating wire bonding arc height), meeting the thinness requirements of wireless keyboards. After installing the keyboard chip 140, an underfill 190 can be applied to the bottom of the keyboard chip 140, covering the area between the solder 141 and the pads 131. The underfill 190 can be injected along the edge of the keyboard chip 140 and cured under heat, filling the gaps at the bottom of the keyboard chip 140. Optionally, the underfill 190 can be made of epoxy resin-based composite material, and inorganic fillers can be added to adjust the coefficient of thermal expansion; its fluidity must ensure sufficient penetration into the gap between the keyboard chip and the pads. After curing, the underfill adhesive 190 significantly disperses the mechanical stress generated during keyboard chip operation, improves the fatigue resistance of solder joints, and prevents solder joint cracking caused by thermal cycling or mechanical impact. Furthermore, the underfill adhesive 190 also prevents external moisture and ionic substances from penetrating into the solder joint area, enhancing the environmental reliability of the overall package. For electronic products like wireless keyboards that operate in high-frequency input and portable environments, this design helps extend the lifespan of the keyboard chip and ensures electrical stability during long-term operation.

[0017] Step 5, S5, please refer to Figure 8 and Figure 9 .like Figure 8As shown, an insulating layer 150 is formed on the substrate layer 111 to cover the keyboard chip 140, the solder pads 131, and the dummy solder pads 132, thereby achieving electrical isolation and mechanical protection. In a variation, if the underfill adhesive 190 is not filled after the keyboard chip 140 is installed, the insulating layer 150 can be filled to the bottom of the keyboard chip 140 by spraying during the step of forming the insulating layer 150. The insulating layer 150 can be formed of polyimide, epoxy resin, or other heat-resistant polymer materials. The thickness of the insulating layer 150 is sufficient to completely cover the keyboard chip 140, so as to ensure coverage while avoiding increasing the overall thickness of the circuit board. Specifically, the insulating layer 150 can be achieved by processes such as spin coating, printing, lamination, or spraying, and forms a uniform dielectric layer after curing. Furthermore, as... Figure 9 As shown, a plurality of third vias 150a and a plurality of fourth vias 150b are formed in the insulating layer 150. The third vias 150a correspond to the dummy solder pads 132 to establish an electrical connection channel between the dummy solder pads 132 and the upper layer circuitry. The fourth vias 150b penetrate the insulating layer 150 and extend to the first circuit layer 120, allowing subsequent circuit layers to directly communicate with the first circuit layer 120. Similarly, the third vias 150a and the fourth vias 150b can be formed by laser drilling or laser ablation, with the aperture preferably ranging from 50 micrometers to 150 micrometers. Through this step, the insulating layer 150 not only provides encapsulation protection for the keyboard chip 140 and its surrounding circuitry area but also reserves via structures for the construction of upper layer circuitry, thereby ensuring reliable interconnection between different circuitry layers.

[0018] Step S6, please refer to Figure 10A third circuit layer 160 is formed on the insulating layer 150. The third circuit layer 160 includes at least one electrically independent coverage area 161, a third through-hole 162 formed in the third through-hole 150a, and a fourth through-hole 163 formed in the fourth through-hole 150b. The coverage area 161 is electrically connected to the dummy solder pad 132 through the third through-hole 162, and the third circuit layer 160 is electrically connected to the first circuit layer 120 through the fourth through-hole 163. In this embodiment, the coverage area 161 is preferably plate-shaped, with an area larger than the vertical projection range of the keyboard chip 140, to ensure effective coverage over the keyboard chip 140. The coverage area 161 not only has electrical connection function but also serves as a grounding point for subsequent electromagnetic shielding, thereby enhancing the overall shielding effect. In this embodiment, the so-called "electrically independent coverage area" refers to at least one conductive metal pattern formed in the third circuit layer 160, which is not connected to the signal trace 121 or other functional circuits, but is electrically connected to the grounding network (e.g., the dummy solder pad 132 and the ground trace 122) only through the third via 162. The coverage area 161 is electrically independent and does not participate in signal transmission, but is specifically used to form a shielding effect and grounding barrier. With this design, the coverage area can act as a "floating ground plane", effectively covering and surrounding the keyboard chip 140, forming a closed loop with the dummy solder pad 132 below, thereby forming a local grounding plane. This not only blocks the outward coupling of electromagnetic radiation generated by the keyboard chip, but also shields external electromagnetic noise from entering the keyboard chip area. Therefore, the coverage area 161 is actually a dedicated grounding shielding pattern located above the keyboard chip 140, isolated from the signal circuit, and only performs shielding and grounding functions, which is a key design for achieving a thin shielding structure.

[0019] Specifically, such as Figure 11 As shown, the third via 162 is distributed around the keyboard chip 140, forming a ring or rectangular array structure. This arrangement allows the coverage area 161 and the dummy solder pads 132 to form a closed loop, thereby establishing a uniform grounding barrier around the keyboard chip 140 and reducing electromagnetic interference leakage from the edges of the keyboard chip 140 or coupling to surrounding circuits. The third circuit layer 160 can be formed on the surface of the insulating layer 150 by electroplating or chemical plating, with a thickness preferably between 10 and 25 micrometers to ensure conductivity while also meeting the thinning requirements of the keyboard circuitry. Through this step, the third circuit layer 160 achieves reliable interconnection with the underlying signal network and grounding points, and forms the coverage area 161 above the keyboard chip 140, providing the electrical and structural foundation for the final shielding structure.

[0020] Step 7, S7, please refer to Figure 12 A solder resist layer 170 is formed on the first circuit layer 120 and the third circuit layer 160 to cover the signal trace 121 and the coverage area 161, providing insulation protection, preventing solder 141 from flowing during the soldering process, and improving the wear resistance and oxidation resistance of the circuit layers. The solder resist layer 170 can be made of photosensitive epoxy resin, polyimide, or other insulating coating materials suitable for printed circuit board processes, and can be formed by screen printing, spraying, or coating, followed by photocuring or thermocuring for final shaping. During the patterning process of the solder resist layer 170, openings 171 are reserved at specific locations to form channels for external electrical connections. In particular, openings 171 are formed at the location of the ground trace 122, allowing the ground trace 122 to be exposed to the external environment. Specifically, the so-called "specific locations" may also include the circuit areas of the first circuit layer 120 and the third circuit layer 160 where the key units of the keyboard will be installed. Through this step, the signal trace 121 and the coverage area 161 are effectively insulated and protected, avoiding the influence of external solder 141 or environmental factors on the line. At the same time, the opening 171 formed at the grounding trace 122 creates the necessary conditions for the introduction of the electromagnetic shielding layer 180.

[0021] Step 8, S8, please refer to Figure 13An electromagnetic shielding layer 180 is formed on the solder resist layer 170. The electromagnetic shielding layer 180 includes a protective layer 181, a metal layer 182, and a conductive adhesive layer 183. The conductive adhesive layer 183 fills the opening 171, allowing the metal layer 182 to be electrically connected to the grounding trace 122, thereby forming an electromagnetic shielding structure 100 covering the keyboard chip 140. The protective layer 181 can be made of polyimide, epoxy resin, or other wear-resistant and heat-resistant insulating materials, mainly used to improve the overall mechanical strength and environmental stability of the electromagnetic shielding layer 180. The metal layer 182 is the main part providing electromagnetic shielding and can be formed using highly conductive metals such as copper or nickel. Its thickness is preferably between 5 and 10 micrometers to ensure good conductivity and shielding effect. The metal layer 182 can be deposited on the protective layer 181 by sputtering, electroplating, or chemical deposition processes to obtain a continuous and dense conductive coverage surface. The conductive adhesive layer 183 is used to adhere the metal layer 182 to the solder resist layer 170, and simultaneously fills the opening 171, enabling the metal layer 182 to achieve an electrical connection with the previously exposed grounding trace 122. In a preferred embodiment, the conductive adhesive layer 183 contains conductive particles, such as silver powder or nickel powder, which can form a stable conductive path after curing. With this design, the metal layer 182 is no longer suspended on the surface of the solder resist layer 170, but forms a low-impedance electrical connection with the grounding trace 122 through the conductive adhesive layer 183. Finally, the electromagnetic shielding layer 180 completely covers the keyboard chip 140 and the corresponding circuit area, and forms a complete shielding space through the grounding trace 122, the third via 162, and the covered area 161. In other words, in this embodiment, the electromagnetic shielding structure 100 mainly includes the electromagnetic shielding layer 180, the coverage area 161, the third through-hole 162, and the grounding trace 122, and surrounds the keyboard chip 140 from all sides, thereby constructing an all-around electromagnetic shielding structure 100 around the keyboard chip 140. The electromagnetic shielding structure 100 not only effectively suppresses electromagnetic interference radiated outwards by the keyboard chip 140 during operation, but also resists external interference from entering the area of ​​the keyboard chip 140, significantly improving the signal stability of the wireless keyboard during high-speed communication.

[0022] It is understood that the electromagnetic shielding layer 180, as part of the electromagnetic shielding structure 100 of this application, is formed above and below the keyboard chip 140, respectively, along with the coverage area 161, to form electromagnetic protection on both the top and bottom surfaces.

[0023] Please see Figure 13The present invention also provides an electromagnetic shielding structure 100 for a keyboard, mainly comprising a copper-clad substrate 110, a second circuit layer 130, a keyboard chip 140, an insulating layer 150, a third circuit layer 160, a solder resist layer 170, and an electromagnetic shielding layer 180. In this embodiment, the keyboard chip 140 may be a microcontroller unit (MCU) or an integrated circuit with keyboard control and wireless communication functions. The pins or solder joints of the keyboard chip 140 correspond to the solder pads 131 of the second circuit layer 130, and are reliably bonded by heating and melting the solder 141.

[0024] Specifically, the copper-clad substrate 110 includes a substrate layer 111 and a first circuit layer 120 formed by etching. The first circuit layer 120 includes signal traces 121 for transmitting keyboard chip signals and ground traces 122 for electrical grounding. A second circuit layer 130 is disposed on the substrate layer 111. The second circuit layer 130 includes multiple solder pads 131, multiple dummy solder pads 132, multiple first vias 133, and at least one second via 134. The solder pads 131 are electrically connected to the signal traces 121 through the first vias 133, and the dummy solder pads 132 are electrically connected to the ground traces 122 through the second vias 134. The first circuit layer 120 and the second circuit layer 130 are respectively disposed on opposite sides of the substrate layer 111. The keyboard chip 140 is mounted on the solder pads 131 and electrically connected by solder 141, thereby achieving stable conduction between the keyboard chip 140 and the signal traces 121.

[0025] The insulating layer 150 covers the keyboard chip 140, the solder pads 131, and the dummy solder pads 132, providing insulation protection and overall encapsulation. A third circuit layer 160 is formed on the insulating layer 150. The third circuit layer 160 includes at least one electrically independent coverage area 161. The coverage area 161 is electrically connected to the dummy solder pads 132 through a third via 162. The third circuit layer 160 is electrically connected to the first circuit layer 120 through a fourth via 163. The coverage area 161 is electrically independent and does not participate in signal transmission; it is specifically used to form a shielding effect and a grounding barrier. To enhance the shielding effect, the third vias 162 can be distributed around the keyboard chip 140, forming a ring or rectangular array structure, so that the coverage area 161 and the dummy solder pads 132 constitute a uniform grounding barrier.

[0026] The solder resist layer 170 covers the signal trace 121 and the coverage area 161, protecting the signal trace 121 and the coverage area 161. An opening 171 is provided at the location of the ground trace 122, allowing the electromagnetic shielding layer 180 to conduct. Furthermore, the electromagnetic shielding layer 180 is formed on the solder resist layer 170 and includes a protective layer 181, a metal layer 182, and a conductive adhesive layer 183. The conductive adhesive layer 183 fills the opening 171, electrically connecting the metal layer 182 to the ground trace 122, thereby completing the electromagnetic shielding circuit.

[0027] In this embodiment, the dummy solder pad 132 can surround the area where the solder pad 131 is set, and the covering area 161 is plate-shaped, with an area not less than the projected area of ​​the keyboard chip 140 in the vertical direction, to ensure complete coverage of the keyboard chip 140. The metal layer 182 can be a copper layer or a nickel layer, and in a variation, such as... Figure 14 As shown, the metal layer 182 can be etched to form a micropore array with a pore size of 30 to 80 micrometers and a corresponding array pitch of 100 to 250 micrometers. The aperture ratio is 10%–30%, where the "aperture ratio" is defined as the ratio of the total area of ​​the pores to the total area of ​​the metal layer. This design ensures electromagnetic shielding performance while also addressing heat dissipation and thinness requirements. Through the above structural design, this invention can achieve all-around shielding of the keyboard chip, forming a stable grounding path, while maintaining shielding performance, heat dissipation requirements, and overall lightweight design, thus improving the thermal management performance of the wireless keyboard during long-term operation.

[0028] In one embodiment of the present invention, a wireless keyboard is also provided, comprising a keyboard body and an electromagnetic shielding structure 100 disposed within a printed circuit board of the keyboard body, wherein the electromagnetic shielding structure 100 covers a keyboard chip. The printed circuit board is equipped with a keyboard chip and circuit modules that cooperate with the keyboard chip, and the electromagnetic shielding structure 100 is disposed in the area of ​​the keyboard chip.

[0029] Specifically, the electromagnetic shielding structure 100 includes a copper-clad substrate 110, a second circuit layer 130, an insulating layer 150, a third circuit layer 160, a solder resist layer 170, and an electromagnetic shielding layer 180, which are stacked sequentially to form a comprehensive shield for the keyboard chip. In the wireless keyboard, the keyboard chip can be a microcontroller (MCU) or an integrated circuit that simultaneously performs keyboard input processing and wireless communication functions. The keyboard chip is electrically connected to the signal trace 121 via solder pads 131, and a grounding network is formed by dummy solder pads 132 and ground trace 122. The coverage area 161 and the dummy solder pads 132 are connected through a third via 162, forming a shielding boundary surrounding the keyboard chip; the solder resist layer 170 has an opening 171 at the location of the ground trace 122, and the conductive adhesive layer 183 fills the opening 171 and makes the metal layer 182 connected to the ground trace 122, thereby completing the electromagnetic shielding loop. In one embodiment, the keyboard body adopts an ultra-thin shell design, reducing the overall thickness of the printed circuit board, while still achieving effective shielding within a limited space through the aforementioned electromagnetic shielding structure 100. By employing a structure combining a surrounding pseudo-solder pad 132, a coverage area 161, and a metal layer 182 on the printed circuit board, the electromagnetic shielding structure 100 not only suppresses electromagnetic radiation from the keyboard chip during operation but also effectively resists external electromagnetic interference, ensuring the signal transmission stability of the wireless keyboard in the 2.4GHz or Bluetooth bands. In summary, by introducing the electromagnetic shielding structure of this invention into the printed circuit board of the wireless keyboard, electromagnetic interference can be effectively reduced while maintaining the overall thinness and lightness of the device, thereby improving the reliability and user experience of the wireless keyboard.

[0030] 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. A method for fabricating an electromagnetic shielding structure for a keyboard chip, characterized in that, include: A copper-clad substrate is provided, the copper-clad substrate including a substrate layer and a copper foil layer, and the copper foil layer is etched to form a first circuit layer, the first circuit layer including signal traces for transmitting keyboard chip signals and ground traces for electrical grounding; A plurality of first vias and at least one second via are formed in the substrate layer, wherein the first vias correspond to the signal traces and the second vias correspond to the ground traces; A second circuit layer is formed on the substrate layer. The second circuit layer includes a plurality of solder pads, dummy solder pads located around the solder pads, a first via filled in the first via and a second via filled in the second via. The solder pads are electrically connected to the signal traces, and the dummy solder pads are electrically connected to the ground traces. The first circuit layer and the second circuit layer are respectively disposed on opposite sides of the substrate layer. The keyboard chip is mounted on the pads of the second circuit layer and electrically connected by solder. An insulating layer is formed on the substrate layer to cover the keyboard chip, the solder pads and the dummy solder pads, and a plurality of third through holes and a plurality of fourth through holes are formed in the insulating layer. The third through holes correspond to the dummy solder pads, and the fourth through holes penetrate to the first circuit layer. A third circuit layer is formed on the insulating layer. The third circuit layer includes at least one electrically independent coverage area, a third via formed in the third via, and a fourth via formed in the fourth via. The coverage area is electrically connected to the dummy solder pad through the third via, and the third circuit layer is electrically connected to the first circuit layer through the fourth via. The coverage area is electrically independent and does not participate in signal transmission, but is specifically used to form a shielding effect and grounding barrier. Solder resist layers are formed on the first line layer and the third line layer to cover the signal traces and the coverage area, and an opening of the solder resist layer is formed at the ground trace location; as well as An electromagnetic shielding layer is formed on the solder resist layer. The electromagnetic shielding layer includes a protective layer, a metal layer, and a conductive adhesive layer. The conductive adhesive layer fills the opening, so that the metal layer is electrically connected to the grounding trace, thereby forming an electromagnetic shielding structure that covers the keyboard chip.

2. The method for fabricating an electromagnetic shielding structure for a keyboard chip as described in claim 1, characterized in that, The dummy solder pads surround the area where the solder pads are positioned.

3. The method for fabricating an electromagnetic shielding structure for a keyboard chip as described in claim 2, characterized in that, The third via surrounds the keyboard chip.

4. The method for fabricating an electromagnetic shielding structure for a keyboard chip as described in claim 1, characterized in that, The chip is mounted using a flip-chip method.

5. The method for fabricating an electromagnetic shielding structure for a keyboard chip as described in claim 1, characterized in that, The first through hole, the second through hole, the third through hole and the fourth through hole are formed by laser drilling or laser ablation.

6. An electromagnetic shielding structure for a keyboard chip, characterized in that, include: A copper-clad substrate, the copper-clad substrate comprising a substrate layer and a first circuit layer formed by etching, the first circuit layer comprising signal traces for transmitting keyboard chip signals and ground traces for electrical grounding; A second circuit layer is disposed on the substrate layer. The second circuit layer includes a plurality of solder pads, a plurality of dummy solder pads, a plurality of first vias and at least one second via. The solder pads are electrically connected to the signal traces through the first vias, and the dummy solder pads are electrically connected to the ground traces through the second vias. The first circuit layer and the second circuit layer are respectively disposed on opposite sides of the substrate layer. A keyboard chip is mounted on the solder pad and electrically connected via solder. An insulating layer covers the keyboard chip, the solder pads, and the dummy solder pads; A third circuit layer is formed on the insulating layer. The third circuit layer includes at least one electrically independent coverage area. The coverage area is electrically connected to the dummy solder pad through a third via. The third circuit layer is electrically connected to the first circuit layer through a fourth via. The coverage area is electrically independent and does not participate in signal transmission. Instead, it is specifically used to form a shielding effect and a grounding barrier. A solder resist layer covers the signal traces and the coverage area, and has an opening at the ground trace location; as well as An electromagnetic shielding layer is formed on the solder resist layer. The electromagnetic shielding layer includes a protective layer, a metal layer, and a conductive adhesive layer. The conductive adhesive layer fills the opening, so that the metal layer is electrically connected to the grounding trace.

7. The electromagnetic shielding structure for a keyboard chip as described in claim 6, characterized in that, The dummy solder pads surround the area where the solder pads are positioned.

8. The electromagnetic shielding structure for a keyboard chip as described in claim 7, characterized in that, The third via surrounds the keyboard chip; and / or, The coverage area is plate-shaped, and its area is not less than the projected area of ​​the keyboard chip.

9. The electromagnetic shielding structure for a keyboard chip as described in claim 6, characterized in that, The metal layer is a copper or nickel layer, and a micropore array is formed by etching, with a pore size of 30-80 micrometers and an open area of ​​10%-30%.

10. A wireless keyboard, characterized in that, The keyboard includes a keyboard body and an electromagnetic shielding structure for a keyboard chip as described in any one of claims 6 to 9 disposed within a printed circuit board of the keyboard body, wherein the electromagnetic shielding structure covers the keyboard chip.

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