Electromagnetic shielding structure for keyboard chip, manufacturing method thereof and wireless keyboard

Abstract

The application 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 using the electromagnetic shielding structure. The method comprises the following steps: a first circuit layer is formed with signal wires and ground wires, and is connected to a second circuit layer provided with solder pads and dummy solder pads through through holes; a chip is welded to the solder pads, and the dummy solder pads are electrically connected to the ground wires; an insulating layer and a third circuit layer are formed outside the chip, and a covering area is connected to the dummy solder pads through the through holes; an electromagnetic shielding layer is arranged on a solder mask layer, and the electromagnetic shielding layer is electrically connected to the ground wires through a conductive adhesive layer, so that the chip is comprehensively coated and shielded. The structure can effectively reduce electromagnetic interference, improve the stability of a wireless keyboard signal, and is suitable for thin keyboard circuit design.

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 chip, a manufacturing method thereof and a wireless keyboard. BACKGROUND

[0002] With the popularity of wireless keyboards, the internal circuit elements thereof are increasingly developing towards high integration and thinness to fully exert the portability thereof. Among them, the keyboard chip needs to process multiple signals such as keyboard input, wireless communication and backlight driving as a control core. However, since the wireless keyboard usually works at 2.4GHz or Bluetooth frequency band, the keyboard chip is easily affected by electromagnetic interference (EMI) during work, resulting in unstable signal transmission, which is manifested as input delay, code loss or communication interruption.

[0003] In the prior art, the chip is usually welded on a printed circuit board (PCB) in a surface-mount technology (SMT) manner. This mounting method is simple in structure and facilitates mass production, but the periphery of the chip often lacks effective electromagnetic shielding design, which is easy to cause high-frequency signal leakage or external interference. At the same time, in order to suppress electromagnetic interference, the prior art usually adds a metal shielding cover above the chip or forms an overall shielding layer on the surface of the circuit board. However, these traditional schemes have the following disadvantages: first, the shielding cover is large in size, the chip is arranged on the surface of the printed circuit board in a surface-mount technology, and then the shielding cover is covered, so the overall thickness is based on the printed circuit board, and gradually adds the thickness of the chip and the shielding cover, which not only is complex in assembly, but also is not conducive to the thin design of the keyboard; second, the contact between the shielding layer and the ground is unstable, and it is difficult to form a continuous conduction path, which affects the shielding effect; third, some schemes only cover the upper surface of the keyboard chip, and cannot realize omnidirectional covering of the keyboard chip, so the shielding performance is limited.

[0004] Therefore, how to realize a stable and reliable electromagnetic shielding structure in a thin keyboard circuit board while maintaining the compatibility of the keyboard chip assembly process, so as to ensure the working stability of the keyboard chip, has become a technical problem to be solved in the field. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art that the electromagnetic interference of the wireless keyboard chip is serious, the shielding effect is limited, and the traditional shielding cover is not conducive to thin design, and proposes an electromagnetic shielding scheme suitable for a thin wireless keyboard, so as to realize omnidirectional covering and shielding of the keyboard chip and improve the stability of the wireless signal.

[0006] To achieve the above-mentioned purpose, the present application proposes the following technical scheme:

[0007] I. Method for manufacturing electromagnetic shielding structure for keyboard chip

[0008] The method comprises: providing a copper-clad substrate, the copper-clad substrate comprising a substrate layer and a copper foil layer, and etching the copper foil layer to form a first circuit layer, the first circuit layer comprising signal traces for transmitting signals of a keyboard chip and ground traces for electrical grounding; forming a plurality of first through holes corresponding to the signal traces and at least one second through hole corresponding to the ground traces on the substrate layer; forming a second circuit layer on the substrate layer, the second circuit layer comprising a plurality of pads, dummy pads around the pads, first vias filled in the first through holes, and second vias filled in the second through holes, the pads being electrically connected to the signal traces, the dummy pads being electrically connected to the ground traces, the first circuit layer and the second circuit layer being respectively arranged on opposite sides of the substrate layer; mounting the keyboard chip on the pads of the second circuit layer and realizing electrical connection through solder; forming an insulating layer on the substrate layer to cover the keyboard chip, the pads, and the dummy pads, and forming a plurality of third through holes corresponding to the dummy pads and a plurality of fourth through holes penetrating the first circuit layer on the insulating layer; forming a third circuit layer on the insulating layer, the third circuit layer comprising at least one electrically independent covering area, third vias formed in the third through holes, and fourth vias formed in the fourth through holes, the covering area being electrically connected to the dummy pads through the third vias, the third circuit layer being electrically connected to the first circuit layer through the fourth vias, the covering area being electrically independent and not participating in signal transmission, but being specially used for forming a shielding effect and a grounding barrier; forming a solder resist layer on the first circuit layer and the third circuit layer to cover the signal traces and the covering area, while forming an opening of the solder resist layer at the position of the ground traces; and forming an electromagnetic shielding layer on the solder resist layer, the electromagnetic shielding layer comprising a protective layer, a metal layer, and a conductive adhesive layer, the conductive adhesive layer being filled into the opening to electrically connect the metal layer to the ground traces, thereby constituting an electromagnetic shielding structure that can comprehensively cover the keyboard chip.

[0009] II. Electromagnetic shielding structure for keyboard chip

[0010] The structure comprises: a copper-clad substrate, the copper-clad substrate comprising a substrate layer and a first circuit layer etched thereon, the first circuit layer comprising 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 comprising 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 being electrically connected to the signal traces through the first vias, 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, respectively; 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; a third circuit layer formed on the insulating layer, the third circuit layer comprising at least one electrically independent covering area, the covering area being electrically connected to the dummy solder pads through third vias, the third circuit layer being electrically connected to the first circuit layer through fourth vias, the covering area being electrically independent and not participating in signal transmission, but being specially used for forming a shielding effect and a grounding barrier; a solder resist layer covering the signal traces and the covering area, and having an opening at the position of the ground traces; and an electromagnetic shielding layer formed on the solder resist layer, the electromagnetic shielding layer comprising a protective layer, a metal layer, and a conductive adhesive layer, the conductive adhesive layer being filled into the opening to electrically connect the metal layer to the ground traces, thereby forming a continuous and reliable grounding path and realizing all-around shielding of the keyboard chip.

[0011] Three, a wireless keyboard

[0012] The wireless keyboard comprises a keyboard body and a printed circuit board, the printed circuit board being provided with the above-mentioned electromagnetic shielding structure, the electromagnetic shielding structure covering the keyboard chip and being in electrical communication with the ground traces through the electromagnetic shielding layer, thereby reducing electromagnetic interference of the keyboard chip during operation and ensuring transmission stability of wireless signals.

[0013] Advantages:

[0014] The keyboard chip is embedded in the electromagnetic shielding structure, and the dummy solder pads, the covering area, and the solder resist layer opening are introduced around the keyboard chip solder pads, after the electromagnetic shielding layer is attached, a stable grounding communication path is formed, so that the electromagnetic shielding layer, the third vias, and the covering area realize all-around covering and shielding of the keyboard chip. Compared with the prior art, the scheme avoids the problem of large volume of traditional metal shielding covers which is not conducive to thinning, and at the same time improves the continuity and reliability of shielding, effectively reduces electromagnetic interference, and ensures the use stability and user experience of the wireless keyboard. BRIEF DESCRIPTION OF DRAWINGS

[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:

[0017] Figure 1 This is a flowchart of the electromagnetic shielding structure manufacturing method provided in this embodiment of the technical solution;

[0018] Figure 2 This is a cross-sectional view of the copper-clad substrate provided in this embodiment of the technical solution;

[0019] 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;

[0020] 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;

[0021] Figure 5 Is Figure 4 A cross-sectional view after the second circuit layer is formed on the substrate layer;

[0022] Figure 6 yes Figure 5 A partial top view of the solder pads and dummy solder pads of the second circuit layer;

[0023] Figure 7 Is Figure 5 A cross-sectional view of the keyboard chip installed on the second circuit layer;

[0024] Figure 8 Is Figure 7 A cross-sectional view after an insulating layer is formed on the substrate layer;

[0025] Figure 9 Is Figure 8 A cross-sectional view of the insulating layer after the third and fourth through holes are formed;

[0026] Figure 10 Is Figure 9 A cross-sectional view after the third circuit layer is formed on the insulating layer;

[0027] Figure 11 yes Figure 10 A top view of the third via of the third circuit layer surrounding the keyboard chip;

[0028] Figure 12 Is Figure 10a sectional view of the first circuit layer and the third circuit layer after forming the anti-solder layer on the anti-solder layer;

[0029] Figure 13 is a sectional view of the first circuit layer and the third circuit layer after forming the anti-solder layer on the anti-solder layer; Figure 12 is a sectional view of the first circuit layer and the third circuit layer after forming the anti-solder layer on the anti-solder layer;

[0030] Figure 14 is a top view of the metal layer of the electromagnetic shielding layer in a variant.

[0031] Main element symbol explanation

[0032] DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of, rather than all of, the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without any creative effort fall within the scope of protection of the present application.

[0034] Please refer to Figure 1 which is a flow chart of a method for manufacturing an electromagnetic shielding structure for a keyboard chip, and mainly includes the following steps:

[0035] First step S1, please refer to Figure 2 and Figure 3 . As shown in Figure 2 , a copper-clad substrate 110 is provided, which includes a base material layer 111 and a copper foil layer 112. In the present embodiment, the base material layer 111 can 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 microns and 35 microns, which is determined according to the shielding effect and thinning requirements. Further as Figure 3As shown, the copper foil layer 112 is etched to form a first circuit layer 120, which 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 form a predetermined circuit pattern, which can be achieved by wet or dry process. Optionally, the line width and line spacing of the signal traces 121 can be between 50 and 150 microns to ensure the integrity of high-speed signal transmission; the ground traces 122 can be designed to be wider than the signal traces 121 to reduce impedance and improve shielding effect. Specifically, the ground traces 122 provide a uniform reference potential for the circuit board, ensuring the stability of the keyboard chip and related circuits of the keyboard during operation. Secondly, the ground traces 122 can provide a current loop for the signal traces 121, forming a closed path to reduce impedance discontinuity problems of high-speed signals during transmission and improve signal integrity. In addition, the ground traces 122 can also act as a shielding band in the circuit board layout, reducing the risk of crosstalk between signal lines and suppressing the propagation of electromagnetic noise in the circuit board of the keyboard. Therefore, the ground traces 122 not only realize the conventional grounding function, but also play an important role in the stable operation and anti-interference ability of the circuit. The first circuit layer 120 formed by this step can provide a stable electrical path for the subsequent installation of the keyboard chip and the grounding of the shielding layer, thereby reserving the conduction conditions of the electromagnetic shielding structure in structure.

[0036] In the second step S2, please refer to Figure 4In the substrate layer 111, a plurality of first through holes 111a corresponding to the signal traces 121 are formed for establishing signal transmission channels between different circuit layers, and at least one second through hole 111b corresponding to the ground traces 122 is formed for providing longitudinal connection of electrical ground. In this embodiment, the first through holes 111a and the second through hole 111b can be formed by laser drilling or laser ablation, which has the advantages of high machining precision and controllable hole diameter, and is suitable for thin circuit boards. The diameter of the first through holes 111a is preferably 50-150 microns to meet the low impedance transmission requirement of high-speed signals, and the diameter of the second through holes 111b can be appropriately increased, for example, to 100-200 microns to reduce the impedance of the ground loop and improve the current carrying capacity. If a second through hole 111b with a larger diameter is needed, a mechanical drilling method can also be used. Specifically, the first through holes 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 traces 121 and the keyboard chip pins; the second through holes 111b can be distributed at key positions according to the grounding requirements of the circuit board to form a continuous and low-impedance ground network.

[0037] In the third step S3, referring to Figure 5 In the substrate layer 111, a plurality of first through holes 111a corresponding to the signal traces 121 are formed for establishing signal transmission channels between different circuit layers, and at least one second through hole 111b corresponding to the ground traces 122 is formed for providing longitudinal connection of electrical ground. In this embodiment, the first through holes 111a and the second through hole 111b can be formed by laser drilling or laser ablation, which has the advantages of high machining precision and controllable hole diameter, and is suitable for thin circuit boards. The diameter of the first through holes 111a is preferably 50-150 microns to meet the low impedance transmission requirement of high-speed signals, and the diameter of the second through holes 111b can be appropriately increased, for example, to 100-200 microns to reduce the impedance of the ground loop and improve the current carrying capacity. If a second through hole 111b with a larger diameter is needed, a mechanical drilling method can also be used. Specifically, the first through holes 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 traces 121 and the keyboard chip pins; the second through holes 111b can be distributed at key positions according to the grounding requirements of the circuit board to form a continuous and low-impedance ground network. Figure 6As shown, the dummy solder pad 132 is arranged around the solder pad 131 to surround the setting area of the solder pad 131 and is electrically connected with the ground trace 122 through the second via hole 134. In detail, the dummy solder pad 132 is not directly connected with the keyboard chip pins of the keyboard chip itself, and its main function is to form a surrounding structure to provide a grounding point for the subsequent shielding layer, and to build a shielding boundary around the keyboard chip to reduce the coupling path of electromagnetic interference. In other words, the dummy solder pad 132 is not used for chip electrical connection, but only for providing a solder pad for grounding shielding. In an embodiment, the solder pad 131 and the dummy solder pad 132 can be formed by electroplating or chemical plating process, and the surface of the solder pad 131 and the dummy solder pad 132 can be further covered with a surface treatment layer with good weldability, such as a nickel / gold layer, an organic solderability preservative film, etc., to improve the welding reliability and prevent oxidation. The surface treatment layer can effectively isolate water vapor and temperature and humidity changes in the external environment, avoid oxidation, corrosion or performance degradation of the solder pad 131 and the dummy solder pad 132 during the process or storage process, to ensure the reliability of the keyboard chip welding and the conductive stability of the dummy solder pad 132. Through this step, the second circuit layer 130 is constructed on the substrate layer 111, not only realizing the reliable connection of the keyboard chip signal pins and the signal trace 121, but also laying the foundation for the establishment of the ground network and the realization of the subsequent shielding effect.

[0038] In the fourth step S4, please refer to Figure 7The keyboard chip 140 is mounted on the solder pad 131 of the second circuit layer 130 and is 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 pads of the keyboard chip 140 correspond to the solder pad 131, and the keyboard chip 140 is reliably combined with the solder pad 131 after the solder 141 is heated and melted. The solder 141 can be a tin-lead alloy or a lead-free solder 141, such as a 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 installed in a flip-chip manner, i.e., the pins or pads of the keyboard chip 140 are directly aligned and installed in a flip-chip manner. This installation method eliminates the traditional wire bonding structure, making the electrical path between the keyboard chip 140 and the circuit layer shorter, thereby reducing parasitic inductance and signal delay, which is suitable for high-speed signal transmission. This installation method can also reduce the overall package height (without wire bonding arc height), meeting the demand for thinness of wireless keyboards. After the installation of the keyboard chip 140 is completed, underfill 190 can be further filled at the bottom of the keyboard chip 140, so that the underfill 190 covers the area of the solder 141 and the solder pad 131. The underfill 190 can be injected along the edge of the keyboard chip 140 and solidified under heating conditions, thereby filling the gap at the bottom of the keyboard chip 140. Optionally, the underfill 190 can be an epoxy resin-based composite material, and inorganic fillers can be added to adjust the coefficient of thermal expansion. The flowability needs to be sufficient to penetrate into the gap between the keyboard chip and the solder pad. After solidification, the underfill 190 can significantly disperse the mechanical stress generated during the operation of the keyboard chip, improve the fatigue resistance of the solder joint, and prevent cracking of the solder joint due to thermal cycling or mechanical impact. In addition, the underfill 190 can also prevent external moisture and ionic substances from penetrating into the solder joint area, enhancing the environmental reliability of the overall package. For wireless keyboards, which are long-term high-frequency input and portable application electronic products, this design helps to prolong the service life of the keyboard chip and ensure the electrical stability during long-term operation.

[0039] In the fifth step S5, please refer to Figure 8 and Figure 9 . As Figure 8As shown, an insulating layer 150 is formed on the substrate layer 111 to cover the keyboard chip 140, the solder pad 131 and the dummy solder pad 132, so as to achieve electrical isolation and mechanical protection. In a variant, if the underfill adhesive 190 is not filled after the keyboard chip 140 is mounted, the insulating layer 150 can also be filled to the bottom of the keyboard chip 140 by spraying in the step of forming the insulating layer 150. The insulating layer 150 can be formed by polyimide, epoxy resin or other heat-resistant polymer materials, and the thickness of the insulating layer 150 can be determined according to the requirement of completely covering 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 formed by spin coating, printing, lamination or spraying, etc., and after curing, a uniform dielectric layer is formed. Moreover, as shown in Figure 9 As shown, a plurality of third through holes 150a and a plurality of fourth through holes 150b are formed in the insulating layer 150, the third through holes 150a correspond to the dummy solder pad 132, so as to establish an electrical connection channel between the dummy solder pad 132 and the upper layer circuit. The fourth through holes 150b extend through the insulating layer 150 and reach the first circuit layer 120, so that the subsequent circuit layer can be directly connected to the first circuit layer 120. Similarly, the third through holes 150a and the fourth through holes 150b can be formed by laser drilling or laser ablation, and the aperture range is preferably between 50 microns and 150 microns. Through this step, the insulating layer 150 not only realizes the packaging protection of the keyboard chip 140 and the surrounding circuit area, but also reserves the through hole structure for the construction of the upper layer circuit, so as to ensure the reliable interconnection between different circuit layers.

[0040] In the sixth 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.

[0041] 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.

[0042] 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 traces 121 and the covering area 161, for providing insulation protection, preventing solder 141 from flowing during soldering process, and improving wear resistance and oxidation resistance of the circuit layer. The material of the solder resist layer 170 can be selected from photosensitive epoxy resin, polyimide or other suitable insulating coating materials for printed circuit board process, and can be formed by screen printing, spraying or coating, and then be cured by light or heat to complete the shaping. During the patterning of the solder resist layer 170, openings 171 are reserved at specific positions to form channels for external electrical connection. In particular, openings 171 are formed at the positions of the ground traces 122 to expose the ground traces 122 to the external environment. Specifically, the so-called "specific positions" can also include the circuit areas of the first circuit layer 120 and the third circuit layer 160 that are to be used for mounting the key units of the keyboard. Through this step, the signal traces 121 and the covering area 161 are effectively insulated and protected, avoiding the influence of external solder 141 or environmental factors on the circuit, and at the same time, the openings 171 formed at the positions of the ground traces 122 create necessary conditions for the introduction of the electromagnetic shielding layer 180.

[0043] Step 8 S8, please refer to Figure 13An electromagnetic shielding layer 180 is formed on the anti-welding layer 170, which includes a protective layer 181, a metal layer 182 and a conductive adhesive layer 183. The conductive adhesive layer 183 fills into the opening 171, so that the metal layer 182 is electrically connected to the ground 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, which is mainly used to improve the mechanical strength and environmental stability of the electromagnetic shielding layer 180 as a whole. The metal layer 182 is the main part for providing electromagnetic shielding effect, which can be made of copper or nickel and other highly conductive metals, and its thickness is preferably between 5 microns and 10 microns 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 process, thereby obtaining a continuous and dense conductive coverage. The conductive adhesive layer 183 is used to fit the metal layer 182 and the anti-welding layer 170, and at the same time fills into the opening 171, so that the metal layer 182 can be electrically connected to the previously exposed ground 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. Through this design, the metal layer 182 is no longer suspended on the surface of the anti-welding layer 170, but forms a low-impedance electrical connection with the ground trace 122 through the conductive adhesive layer 183. Finally, the electromagnetic shielding layer 180 covers the keyboard chip 140 and the corresponding circuit area as a whole, and forms a complete shielding space through the ground trace 122, the third via hole 162 and the coverage area 161. That is, in this embodiment, the electromagnetic shielding structure 100 mainly includes the electromagnetic shielding layer 180, the coverage area 161, the third via hole 162 and the ground trace 122, which surrounds the keyboard chip 140 from top to bottom and left to right, thereby building a full-range electromagnetic shielding structure 100 around the keyboard chip 140. The electromagnetic shielding structure 100 not only effectively suppresses the electromagnetic interference radiated outward by the keyboard chip 140 during operation, but also resists external interference from entering the keyboard chip 140 area, thereby significantly improving the signal stability of the wireless keyboard during high-speed communication.

[0044] It can be understood that the electromagnetic shielding layer 180 as part of the electromagnetic shielding structure 100 of the present application is formed above and below the keyboard chip 140 with the coverage area 161 respectively, to form electromagnetic protection on the top and bottom surfaces.

[0045] Please refer to Figure 13The application 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 mask layer 170 and an electromagnetic shielding layer 180. In the 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 soldering points of the keyboard chip 140 correspond to the solder pads 131 of the second circuit layer 130 and are reliably combined after being heated and melted by solder 141.

[0046] Specifically, the copper-clad substrate 110 comprises a substrate layer 111 and a first circuit layer 120 formed by etching. The first circuit layer 120 comprises signal wires 121 for transmitting keyboard chip signals and ground wires 122 for electrical grounding. The second circuit layer 130 is arranged on the substrate layer 111. The second circuit layer 130 comprises a plurality of solder pads 131, a plurality of dummy solder pads 132, a plurality of first through holes 133 and at least one second through hole 134. The solder pads 131 are electrically connected to the signal wires 121 through the first through holes 133. The dummy solder pads 132 are electrically connected to the ground wires 122 through the second through hole 134. The first circuit layer 120 and the second circuit layer 130 are respectively arranged on opposite sides of the substrate layer 111. The keyboard chip 140 is mounted on the solder pads 131 and electrically connected through the solder 141, thereby realizing stable conduction between the keyboard chip 140 and the signal wires 121.

[0047] The insulating layer 150 covers the keyboard chip 140, the solder pads 131 and the dummy solder pads 132 for insulation protection and overall packaging. The third circuit layer 160 is formed on the insulating layer 150. The third circuit layer 160 comprises at least one electrically independent covering area 161. The covering area 161 is electrically connected to the dummy solder pads 132 through third through holes 162. The third circuit layer 160 is electrically connected to the first circuit layer 120 through fourth through holes 163. The covering area 161 remains electrically independent and does not participate in signal transmission, but is specially used for forming shielding effect and grounding barrier. In order to enhance the shielding effect, the third through holes 162 can be distributed around the keyboard chip 140 to form a ring or a rectangular array structure, so that the covering area 161 and the dummy solder pads 132 form a uniform grounding barrier.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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 sequentially stacked to form a full-range shielding for the keyboard chip. In the wireless keyboard, the keyboard chip can be a microcontroller (MCU) or an integrated circuit with both keyboard input processing and wireless communication functions. The keyboard chip is electrically connected to the signal trace 121 through the solder pad 131 and forms a ground network together with the ground trace 122 through the dummy solder pad 132. The coverage area 161 and the dummy solder pad 132 are connected through the third via hole 162 to form a shielding boundary around the keyboard chip; the solder resist layer 170 has an opening 171 at the position of the ground trace 122, the conductive adhesive layer 183 fills the opening 171 and makes the metal layer 182 conductive with the ground trace 122, thereby completing the electromagnetic shielding loop. In an embodiment, the keyboard body adopts an ultra-thin shell design, and the overall thickness of the printed circuit board is reduced, while the electromagnetic shielding structure 100 described above can still achieve effective shielding in a limited space. By using the combination of the surrounding dummy solder pad 132, the coverage area 161, and the metal layer 182 on the printed circuit board, the electromagnetic shielding structure 100 formed thereby not only suppresses the electromagnetic radiation of the keyboard chip during operation, but also effectively resists external electromagnetic interference, ensuring the stability of signal transmission of the wireless keyboard at 2.4 GHz or Bluetooth frequency band. In summary, by introducing the electromagnetic shielding structure of the present application to the printed circuit board of the wireless keyboard, the electromagnetic interference can be effectively reduced while maintaining the thinness of the whole machine, thereby improving the reliability and user experience of the wireless keyboard.

[0052] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions described in the foregoing embodiments, or make equivalent replacements for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A method for fabricating an electromagnetic shield structure for a keyboard chip, characterized by, The application relates to a manufacturing method of a keyboard chip, which comprises the following steps: providing a copper-clad substrate, which comprises a substrate layer and a copper foil layer, and etching the copper foil layer to form a first circuit layer, wherein the first circuit layer comprises signal lines for transmitting keyboard chip signals and ground lines for electrical grounding; forming a plurality of first through holes and at least one second through hole on the substrate layer, wherein the first through holes correspond to the signal lines and the second through hole corresponds to the ground lines; forming a second circuit layer on the substrate layer, wherein the second circuit layer comprises a plurality of pads, dummy pads around the pads, first via holes filled in the first through holes and second via holes filled in the second through holes, the pads are electrically connected to the signal lines, the dummy pads are electrically connected to the ground lines, and the first circuit layer and the second circuit layer are arranged on opposite sides of the substrate layer respectively; mounting a keyboard chip on the pads of the second circuit layer and realizing electrical connection through soldering; forming an insulating layer on the substrate layer to cover the keyboard chip, the pads and the dummy pads, and forming a plurality of third through holes and a plurality of fourth through holes in the insulating layer, wherein the third through holes correspond to the dummy pads and the fourth through holes penetrate the first circuit layer; forming a third circuit layer on the insulating layer, wherein the third circuit layer comprises at least one electrically independent covering area, third via holes formed in the third through holes and fourth via holes formed in the fourth through holes, the covering area is electrically connected to the dummy pads through the third via holes, the third circuit layer is electrically connected to the first circuit layer through the fourth via holes, the covering area is electrically independent and does not participate in signal transmission, but is specially used for forming a shielding effect and a grounding barrier; forming a solder mask layer on the first circuit layer and the third circuit layer to cover the signal lines and the covering area, and forming an opening of the solder mask layer at the position of the ground lines; forming an electromagnetic shielding layer on the solder mask layer, wherein the electromagnetic shielding layer comprises a protective layer, a metal layer and a conductive adhesive layer, the conductive adhesive layer is filled into the opening, the metal layer is electrically connected to the ground lines, and thus an electromagnetic shielding structure covering the keyboard chip is formed. The dummy pads surround the arrangement area of the pads.

2. The method of claim 1, wherein the method further comprises: forming a first conductive layer on the first substrate; forming a second conductive layer on the second substrate; and forming a third conductive layer on the third substrate. The third via holes surround the keyboard chip.

3. The method of claim 2, wherein the method further comprises: forming a first conductive layer on the first substrate; forming a second conductive layer on the second substrate; and forming a third conductive layer on the third substrate. The chip is mounted in a flip chip mounting mode.

4. The method of claim 1, wherein the method further comprises: forming a first electromagnetic shield layer on the first substrate; and forming a second electromagnetic shield layer on the second substrate. The first through holes, the second through holes, the third through holes and the fourth through holes are formed by laser drilling or laser ablation.

5. The method of claim 1, wherein the method further comprises: forming a first electromagnetic shield layer on the first substrate; and forming a second electromagnetic shield layer on the second substrate. The application relates to a manufacturing method of a keyboard chip, which comprises the following steps:

6. An electromagnetic shielding structure for a keyboard chip, characterized by providing a copper-clad substrate, which comprises a substrate layer and a copper foil layer, and etching the copper foil layer to form a first circuit layer, wherein the first circuit layer comprises signal lines for transmitting keyboard chip signals and ground lines for electrical grounding; ​ A second circuit layer is disposed on the substrate layer, and includes a plurality of pads, a plurality of dummy pads, a plurality of first vias, and at least one second via. The pads are electrically connected to the signal traces through the first vias. The dummy pads are electrically connected to the ground traces through the second vias. The first and second circuit layers are disposed on opposite sides of the substrate layer, respectively. A keyboard chip is mounted on the pads and electrically connected through solder. An insulating layer covers the keyboard chip, the pads, and the dummy pads. A third circuit layer is formed on the insulating layer, and includes at least one electrically independent covering area. The covering area is electrically connected to the dummy pads through third vias. The third circuit layer is electrically connected to the first circuit layer through fourth vias. The covering area is electrically independent and does not participate in signal transmission, but is used to form a shielding effect and a ground barrier. A solder mask layer covers the signal traces and the covering area, and has an opening at the position of the ground traces. An electromagnetic shielding layer is formed on the solder mask layer, and includes a protective layer, a metal layer, and a conductive adhesive layer. The conductive adhesive layer is filled into the opening, so that the metal layer is electrically connected to the ground traces. The dummy pads surround the pads.

7. The electromagnetic shield structure for a keyboard chip according to claim 6, wherein The third vias surround the keyboard chip; and / or 8. The electromagnetic shield structure for a keyboard chip according to claim 7, wherein, The covering area is a plate-shaped area, and its area is not less than the projection area of the keyboard chip. The metal layer is a copper layer or a nickel layer, and forms a micropore array through etching. The pore diameter of the micropore array is 30-80 microns, and the opening rate is 10%-30%.

9. The electromagnetic shield structure for a keyboard chip according to claim 6, wherein, A keyboard body and an electromagnetic shielding structure for a keyboard chip according to any one of claims 6-9 are disposed in a printed circuit board of the keyboard body, and the electromagnetic shielding structure covers the keyboard chip.

10. A wireless keyboard, characterized by ​

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