FPC board with grounding structure

Abstract

The utility model discloses an FPC board with a grounding structure. The FPC board comprises a shielding layer, a first circuit layer, a base material layer and a grounding layer which are stacked in sequence. The shielding layer is connected with the first circuit layer through insulating glue; the first circuit layer comprises a signal line and a first ground wire, the first ground wire is arranged close to the signal line, a first grounding bonding pad is formed on the first ground wire, a first via hole is correspondingly formed through laser cutting after the grounding layer and the base material layer are laminated, and the first via hole and the first grounding bonding pad are coaxially arranged; after the shielding layer, the first circuit layer, the base material layer and the grounding layer are connected in a press fit mode, secondary laser drilling is carried out on the position of the first via hole to form a first through hole, and the first through hole is filled with a flexible conductive material so that the first circuit layer can be conductively communicated with the grounding layer. The technical scheme of the utility model aims to solve the technical problems of poor grounding signal connection reliability and weak anti-interference capability.

Description

Technical Field

[0001] This utility model relates to the field of flexible circuit board technology, and in particular to an FPC board with a grounding structure. Background Technology

[0002] Flexible printed circuit boards (FPCs) are highly reliable and highly flexible printed circuit boards made with polyimide or polyester film as the substrate. FPCs are lightweight, thin, bendable, and heat-resistant, and are widely used in electronic products such as consumer electronics, automotive electronics, medical devices, industrial control, and aerospace.

[0003] In existing technologies, to achieve grounding design for FPC boards, a common approach is to stack ground layers on the FPC board and connect the ground wires of each layer to the ground layer via vias. However, this grounding design has several drawbacks. For example, the connection between the vias and the ground layer is usually achieved through copper plating, which is unreliable and prone to disconnection due to mechanical or thermal stress during use. These problems severely affect the stability and lifespan of the FPC board. Furthermore, this grounding setup has poor anti-interference capabilities, which is detrimental to the transmission of high-frequency signals. Utility Model Content

[0004] The purpose of this invention is to provide an FPC board with a grounding structure, which aims to solve the technical problems of poor reliability of grounding signal connection and weak anti-interference ability.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] An FPC board with a grounding structure includes a shielding layer, a first circuit layer, a substrate layer, and a grounding layer stacked sequentially. The shielding layer and the first circuit layer are connected by an insulating adhesive. The first circuit layer includes a signal line and a first ground line. The first ground line is disposed close to the signal line and has a first grounding pad. After the grounding layer and the substrate layer are laminated, a first via is formed by laser cutting, and the first via is coaxially disposed with the first grounding pad.

[0007] After the first circuit layer, the substrate layer, and the ground layer are laminated together, a second laser drilling is performed at the location of the first via to form a first through hole. Flexible conductive material is filled into the first through hole to make the first circuit layer and the ground layer electrically connected.

[0008] In one embodiment, the flexible conductive material is a conductive epoxy resin or a conductive adhesive containing silver powder.

[0009] In one embodiment, the shielding layer is made of conductive carbon black, and a protective coating is also provided on the outer surface of the shielding layer.

[0010] In one embodiment, the grounding layer is made of copper foil, and the grounding layer is connected to a flexible grounding finger, which is used to contact the inner shell of the product using the FPC board.

[0011] In one embodiment, a second circuit layer is further included, which is disposed between the first circuit layer and the shielding layer, and the second circuit layer is connected to the first circuit by an insulating adhesive.

[0012] The first circuit layer is provided with a second ground pad, and the second circuit layer is provided with a third ground pad. After the ground layer and the substrate layer are laminated, a second via is formed by laser cutting. The third ground pad, the second ground pad, and the second via are coaxially arranged. After the second circuit layer, the first circuit layer, the substrate layer, and the ground layer are laminated and connected, a second laser drilling is performed on the position of the second via to form a second through hole. The second through hole is filled with a flexible conductive material to make the second circuit layer and the ground layer electrically connected.

[0013] In one embodiment, the first line layer is a signal line layer; the second line layer is a power line layer.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] This invention solves the problem of unreliable connection between the grounding pad and the grounding layer in existing technologies by performing secondary laser drilling on the first via after the shielding layer, the first circuit layer, the substrate layer, and the grounding layer are laminated together. This creates a through-hole, which is then filled with a flexible conductive material, ensuring reliable connection between the first ground wire and the grounding layer and the shielding layer. Furthermore, the shielding layer in this invention is insulated from the first circuit layer, improving electromagnetic shielding effectiveness, reducing electromagnetic interference, and optimizing high-frequency signal transmission performance. This significantly enhances the stability and anti-interference capability of the FPC board, ensuring the long-term stability of the grounding structure and the quality of signal transmission. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this utility model 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 this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] The structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the implementation conditions of this utility model. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and purposes that this utility model can produce, should still fall within the scope of the technical content disclosed in this utility model.

[0018] Figure 1 This is a schematic diagram of an embodiment of the FPC board with a grounding structure according to the present invention;

[0019] Illustration: 100, FPC board with grounding structure; 110, shielding layer; 120, first circuit layer; 121, first grounding pad; 122, second grounding pad;

[0020] 130, Substrate layer; 140, Ground layer; 141, First via; 142, Second via;

[0021] 150. Second line layer; 151. Third grounding pad; 160. Flexible conductive material. Detailed Implementation

[0022] To make the technical objectives, features, and advantages of this utility model more apparent and understandable, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0023] In the description of this utility model, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be a component centrally located at the same time.

[0024] The technical solution of this utility model will be further described below with reference to the accompanying drawings and specific embodiments.

[0025] This utility model embodiment provides an FPC board 100 with a grounding structure.

[0026] Please see Figure 1 In one embodiment of this utility model, the FPC board 100 with a grounding structure includes a shielding layer 110, a first circuit layer 120, a substrate layer 130, and a grounding layer 140 stacked sequentially. The shielding layer 110 and the first circuit layer 120 are connected by insulating adhesive. The first circuit layer 120 includes a signal line and a first ground line. The first ground line is disposed close to the signal line and has a first grounding pad 121. After the grounding layer 140 is laminated with the substrate layer 130, a first via 141 is formed by laser cutting, and the first via 141 is coaxially disposed with the first grounding pad 121.

[0027] After the first circuit layer 120, the substrate layer 130 and the ground layer 140 are pressed together, a second laser drilling is performed on the position of the first via 141 to form a first through hole. Flexible conductive material 160 is filled in the first through hole so that the first circuit layer 120 and the ground layer 140 are electrically connected.

[0028] Specifically, shielding layer 110 refers to a conductive layer used to isolate external electromagnetic interference. Optionally, the material of shielding layer 110 is conductive carbon black, copper foil, aluminum foil, etc. First circuit layer 120 is the main circuit layer on the FPC board, containing signal lines and a first ground line; the signal lines are used to transmit signals, and the first ground line is positioned close to the signal lines to provide a grounding path to reduce signal noise interference. Substrate layer 130 is the base layer of the FPC board. Substrate layer 130 is made of polyimide or polyester film, possessing good flexibility and high-temperature resistance. It provides support and insulation for each conductive layer. Further, ground layer 140 is a layer used to provide overall grounding, typically made of copper foil, but also aluminum foil. A first via 141 is formed together in ground layer 140 and substrate layer 130, and the first via 141 is coaxially arranged with the first ground pad 121. After the first circuit layer 120, the substrate layer 130, and the ground layer 140 are laminated together, the first via 141 is subjected to secondary laser drilling to form the first through hole. It is understood that the secondary laser drilling technology can ensure that the substrate layer 130 melts to form the first through hole, and the first through hole is filled with flexible conductive material 160 to connect the first ground wire with the ground layer 140.

[0029] Furthermore, the flexible conductive material 160 can be a conductive epoxy resin or a conductive adhesive containing silver powder. This ensures that the grounding layer 140 and the first line have good conductivity and anti-interference capabilities, and due to the flexibility of the flexible conductive material 160, it can withstand the bending deformation of the FPC board without damaging the electrical connection.

[0030] Furthermore, a shielding layer 110 is provided above the first line layer 120, which can reduce external signal interference, thereby improving the reliability of the FPC board and the signal transmission quality.

[0031] Specifically, after the first through hole is formed, filling the first through hole with flexible conductive material 160 helps to improve the reliability of the conductive connection compared to a blind hole.

[0032] Understandably, this solution, after the shielding layer 110, the first circuit layer 120, the substrate layer 130, and the grounding layer 140 are pressed together, performs secondary laser drilling on the first via 141 to form a first through hole, and fills the first through hole with flexible conductive material 160, so that the first ground wire is reliably connected to the grounding layer 140 and the shielding layer 110, thereby effectively solving the problem of unreliable connection between the grounding pad and the grounding layer 140 in the prior art. In traditional technology, the conductive connection between the grounding pad and the via may lead to poor contact or breakage due to thermal stress or mechanical stress. However, this solution, through secondary laser drilling and filling with flexible conductive material 160, utilizes the adhesion and flexibility of the through hole and the flexible conductive material 160 to improve the stability and conductivity of the connection, enhance the reliability of the grounding effect, and ensure the long-term stability of the grounding structure. In addition, the shielding layer 110 of this solution, through its insulated connection with the first circuit layer 120, effectively isolates external electromagnetic interference, improves the signal transmission quality, and reduces noise interference, especially in the process of high-frequency signal transmission. Compared to other traditional grounding designs, this solution improves the reliability and signal transmission quality of the FPC board through innovative structural and material combinations, making the FPC board perform better in high-frequency, high-reliability applications.

[0033] In one specific embodiment, the material of the shielding layer 110 is conductive carbon black, and the outer surface of the shielding layer 110 is also provided with a protective coating.

[0034] Understandably, conductive carbon black possesses excellent electrical conductivity, chemical stability, and high-temperature resistance, enabling it to block and reduce external electromagnetic interference and improve signal transmission quality. Furthermore, the protective coating is primarily designed to protect the shielding layer 110 from external environmental influences and enhance its wear resistance and corrosion resistance.

[0035] Furthermore, the grounding layer 140 is made of copper foil, and the grounding layer 140 is connected to a flexible grounding finger (not shown in the figure), which is used to contact the inner shell of the product using the FPC board.

[0036] Understandably, using copper foil as the material for ground layer 140 ensures excellent conductivity and stability, reduces signal interference, and improves circuit stability. It also guarantees the strength of the FPC board. Furthermore, the design of the flexible grounding finger allows the FPC board to maintain a good grounding connection with the product's inner casing, reducing static electricity buildup.

[0037] Based on any of the above embodiments, the FPC board 100 with a grounding structure of the present invention further includes a second circuit layer 150, which is disposed between the first circuit layer 120 and the shielding layer 110, and the second circuit layer 150 is connected to the first circuit by an insulating adhesive.

[0038] The first circuit layer 120 is provided with a second grounding pad 122, and the second circuit layer 150 is provided with a third grounding pad 151. After the grounding layer 140 and the substrate layer 130 are laminated, a second via 142 is formed by laser cutting. The third grounding pad 151, the second grounding pad 122 and the second via 142 are coaxially arranged. After the shielding layer 110, the second circuit layer 150, the first circuit layer 120, the substrate layer 130 and the grounding layer 140 are laminated and connected, a second laser drilling is performed on the position of the second via 142 to form a second through hole. The second through hole is filled with a flexible conductive material 160 so that the second circuit layer 150 and the grounding layer 140 are electrically connected.

[0039] It is understood that when the FPC board 100 with the grounding structure is a multilayer circuit board, in order to ensure the reliability of the connection between each circuit layer and the grounding layer 140, a grounding pad is provided in each circuit board at a corresponding position to ensure that the circuit layer far away from the grounding layer 140 can be reliably connected to the grounding layer 140.

[0040] It should also be explained that in this embodiment of the invention, the grounding pad is a circular copper foil with a via in the center. Specifically, the grounding pads in the first and second circuit boards are obtained through an etching process. The first via 141 and the second via 142 in the ground layer 140 are typically obtained by initial laser drilling.

[0041] It should also be explained that, in the technical solution of this utility model, the second drilling is mainly to increase the aperture size of the substrate layer 130 on the grounding layer 140, remove the insulating layer on the first circuit layer 120 and / or the second circuit layer 150, as well as the shielding layer 110, thereby improving the reliability of the connection between the flexible conductive material 160 and the grounding layer; and the setting of the first via 141 and the second via 142 can be used to observe and verify the reliability of the connection between the flexible conductive material 160 and the grounding layer, as well as for cleaning impurities after the second laser cutting. Therefore, the technical solution of this utility model has good beneficial effects.

[0042] Furthermore, in a specific embodiment, the first line layer 120 is a signal line layer; the second line layer 150 is a power line layer.

[0043] It is understandable that setting the signal line layer away from the shielding layer 110 can reduce the interference of reflected signals in the signal layer itself on the data signal, and help reduce the internal electromagnetic interference of the signal line layer.

[0044] Specifically, the processing steps of one embodiment of the FPC board 100 with a grounding structure of this utility model are as follows:

[0045] First, a suitable polyimide film is selected as the substrate layer 130 of the FPC board. The ground layer 140 is a copper foil layer, which is pressed onto the substrate layer 130 to form the ground layer 140 of the FPC.

[0046] Secondly, laser drilling is performed on the laminated ground layer 140 to form multiple first vias 141 and second vias 142 for subsequent interlayer electrical connections.

[0047] Next, a first circuit layer 120 and a second circuit layer 150 are fabricated using a double-sided copper-clad laminate. A photoresist is coated onto the surface of the copper foil, and then the circuit pattern of the signal layer is transferred onto the copper foil through exposure and development processes. Further, unprotected copper foil is removed using a chemical etching method to form the first circuit layer 120 and the second circuit layer 150, respectively. Corresponding ground pads are formed in both the first circuit layer 120 and the second circuit layer 150.

[0048] Next, the shielding layer 110, the first circuit layer 120, and the second circuit layer 150 are sequentially laminated onto the substrate layer 130, and insulating adhesive is used to ensure interlayer insulation and interlayer adhesion between the shielding layer 110 and the first circuit layer 120 and the second circuit layer 150.

[0049] Furthermore, secondary laser drilling is performed on the positions of the first via 141 and the second via 142 of the grounding layer 140. After removing impurities and insulating adhesive layers from the holes, the first via 141 and the second via 142 after secondary laser treatment are filled with flexible conductive material 160 so that the first circuit layer 120 and the second circuit layer 150 are electrically connected to the grounding layer 140 and the shielding layer 110, respectively.

[0050] Next, after completing the above steps, a protective coating or cover film is applied to the shielding layer 110 to protect the shielding layer 110 from the influence of the external environment.

[0051] The above-described embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model 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 this utility model.

Claims

1. An FPC board having a ground structure, characterized by, The FPC board comprises a shielding layer, a first circuit layer, a substrate layer and a grounding layer which are sequentially stacked; the shielding layer and the first circuit layer are connected by insulating glue; the first circuit layer comprises a signal line and a first ground line, the first ground line is arranged close to the signal line, the first ground line is formed with a first grounding pad, the grounding layer and the substrate layer are laminated, a first via hole is formed by laser cutting, and the first via hole is coaxially arranged with the first grounding pad; After the shielding layer, the first circuit layer, the substrate layer and the grounding layer are laminated and connected, the position of the first via hole is secondarily laser punched to form a first through hole, the first through hole is filled with flexible conductive material to enable the first circuit layer and the grounding layer to conductively communicate.

2. The FPC board with a ground structure according to claim 1, characterized by, The flexible conductive material is conductive epoxy resin or conductive glue containing silver powder.

3. The FPC board with a ground structure according to claim 1, characterized by, The material of the shielding layer is conductive carbon black, and the outer surface of the shielding layer is further provided with a protective coating.

4. The FPC board with a ground structure according to claim 1, characterized by, The material of the grounding layer is copper foil, and the grounding layer is connected with an elastic grounding finger, which is used to contact the inner shell of a product to which the FPC board is applied.

5. The FPC board having a ground structure according to any one of claims 1 to 4, characterized by, The FPC board further comprises a second circuit layer, which is arranged between the first circuit layer and the shielding layer, and the second circuit layer and the first circuit layer are connected by insulating glue; The first circuit layer is provided with a second grounding pad, the second circuit layer is provided with a third grounding pad, the grounding layer and the substrate layer are laminated, a second via hole is formed by laser cutting, the third grounding pad, the second grounding pad and the second via hole are coaxially arranged, after the second circuit layer, the first circuit layer, the substrate layer and the grounding layer are laminated and connected, the position of the second via hole is secondarily laser punched to form a second through hole, the second through hole is filled with flexible conductive material to enable the second circuit layer and the grounding layer to conductively communicate.

6. The FPC board with a ground structure according to claim 5, characterized by, The first circuit layer is a signal line layer, and the second circuit layer is a power line layer.

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