Flexible circuit board adopting aluminum as conducting circuit

Abstract

The utility model discloses a flexible circuit board adopting aluminum as a conducting circuit, and relates to the technical field of flexible circuit boards. Comprising an aluminum foil layer which forms a conduction circuit through an etching process and plays a role in electrical conduction; the bottom polyimide film is located at the bottom layer of the flexible circuit board and plays a role in insulation and welding resistance; the bottom layer epoxy resin glue covers the bottom layer polyimide film and is used for bonding the bottom layer polyimide film and the aluminum foil layer; the top polyimide film is located on the top layer of the flexible circuit board and plays a role in insulation and welding resistance; and the top epoxy resin adhesive covers the lower surface of the top polyimide film and is used for bonding the top polyimide film and the aluminum foil layer. On the basis of a conventional flexible circuit board processing technology, aluminum is used for replacing copper to serve as a conducting circuit. According to the circuit board, the cost and the weight are remarkably reduced while the good conductive performance is guaranteed, and the circuit board has good corrosion resistance and is suitable for various severe environments.

Description

Technical Field

[0001] This utility model relates to the field of flexible circuit board technology, specifically to a flexible circuit board that uses aluminum as the conductive line. Background Technology

[0002] Conductive circuitry is crucial for the electrical connections and signal transmission in flexible printed circuit boards (FPCs), ensuring effective communication and power transfer between electronic components. Conductive materials form the basis of these circuits, and their performance directly impacts the electrical performance, reliability, and application range of the FPC. Selecting a suitable conductive material requires comprehensive consideration of factors such as conductivity, flexibility, corrosion resistance, cost, and process compatibility. With the development of new materials and technologies, the role of conductive materials in FPCs will become even more important.

[0003] Currently, most of the conductive lines in flexible printed circuit boards (FPCBs) are made of copper, which has the following disadvantages: copper is expensive, increasing production costs; copper is easily damaged in corrosive environments, affecting conductivity and solderability, requiring a protective coating; the thermal expansion coefficients of copper and the substrate differ greatly, easily generating stress when the temperature changes, leading to circuit damage; copper has a high density, increasing the overall weight, making it unsuitable for weight-sensitive applications. Utility Model Content

[0004] The purpose of this invention is to provide a flexible circuit board that uses aluminum as the conductive line, which significantly reduces cost and weight while maintaining good conductivity, has good corrosion resistance, and is suitable for various harsh environments.

[0005] To achieve the above objectives, this application proposes a flexible circuit board using aluminum as the conductive line, comprising:

[0006] The aluminum foil layer is etched to form conductive lines, thus providing electrical conductivity.

[0007] The bottom polyimide film, located at the bottom of the flexible circuit board, serves as an insulating and solder resist agent.

[0008] The bottom epoxy resin adhesive covers the bottom polyimide film and is used to bond the bottom polyimide film to the aluminum foil layer;

[0009] The top polyimide film, located on the top layer of the flexible circuit board, serves as an insulating and solder resist agent.

[0010] The top layer epoxy resin adhesive, covering the bottom of the top layer polyimide film, is used to bond the top layer polyimide film to the aluminum foil layer.

[0011] In one embodiment, the top polyimide film and the top epoxy resin adhesive have a top opening at the same location, exposing the aluminum foil layer at that location.

[0012] In one embodiment, the bottom polyimide film and the bottom epoxy resin adhesive have a bottom opening at the same location, exposing the aluminum foil layer at that location.

[0013] In one embodiment, a zinc-plated layer is provided on the aluminum foil layer at the top window location to increase the adhesion of the coating.

[0014] In one embodiment, a zinc-plated layer is provided on the aluminum foil layer at the bottom window location to increase the adhesion of the coating.

[0015] In one embodiment, the zinc plating layer is covered with a nickel plating layer to prevent the aluminum foil layer at the top window location or the aluminum foil layer at the bottom window location from being corroded and oxidized.

[0016] In one embodiment, the nickel plating layer is covered with a gold plating layer to further prevent the aluminum foil layer at the top window location or the aluminum foil layer at the bottom window location from being corroded and oxidized.

[0017] In one embodiment, at the location where there is no aluminum foil layer after the conductive line is formed, the top epoxy resin adhesive is bonded to the bottom epoxy resin adhesive.

[0018] In one embodiment, the aluminum foil layer is less than 0.5 mm thick.

[0019] Compared with the prior art, the above technical solution adopted by this utility model has the following advantages: ① Using aluminum as the conductive material significantly reduces the cost of raw materials compared with traditional copper circuit boards.

[0020] ② Aluminum has a much lower density than copper, so the flexible circuit board of the present invention significantly reduces weight while maintaining good conductivity, which is beneficial to the lightweight design of electronic products.

[0021] ③ Aluminum materials easily form a dense oxide film on their surface, which has good corrosion resistance, is suitable for various harsh environments, and can extend the service life of circuit boards.

[0022] ④ The flexible circuit board can be assembled using solder, which improves production efficiency and applicability. Attached Figure Description

[0023] Figure 1 A side view illustrating the principle of a flexible circuit board using aluminum as the conductive trace;

[0024] Figure 2 A top view illustrating the principle of a flexible circuit board using aluminum as the conductive conductor.

[0025] The layers are: 1. Bottom layer polyimide film, 2. Bottom layer epoxy resin adhesive, 3. Aluminum foil layer, 4. Top layer epoxy resin adhesive, 5. Top layer polyimide film, 6. Zinc plating layer, 7. Nickel plating layer, 8. Gold plating layer, 9. Top layer window. Detailed Implementation

[0026] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0027] In the description of this application, it should be understood that the terms "center", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0028] Please see Figure 1-2 This embodiment provides a flexible circuit board using aluminum as the conductive line, comprising:

[0029] Bottom polyimide film 1: Located on the bottom layer of the flexible circuit board, it serves as insulation and solder resist;

[0030] Bottom epoxy resin adhesive 2: Covers the bottom polyimide film and is used to bond the bottom polyimide film to the aluminum foil layer;

[0031] Aluminum foil layer 3: Conductive circuits are formed through an etching process to provide electrical conductivity; preferably, the thickness is less than 0.5 mm.

[0032] Top layer epoxy resin adhesive 4: Covers the bottom of the top layer polyimide film and is used to bond the top layer polyimide film to the aluminum foil layer;

[0033] Top layer polyimide film 5: Located on the top layer of the flexible circuit board, it serves as insulation and solder resist;

[0034] Zinc plating layer 6: A coating formed on the aluminum surface, serving as a medium for nickel plating on the aluminum surface and used to increase the adhesion of the coating;

[0035] Nickel plating layer 7: A plating layer formed on the zinc surface to prevent pad erosion and oxidation, thereby enhancing overall corrosion resistance;

[0036] Gold plating layer 8: A plating layer formed on the nickel surface, which further prevents oxidation and corrosion, while providing good conductivity and solderability;

[0037] Top-level window 9: Open a window in the top polyimide film and top epoxy resin adhesive to expose the aluminum pads to be used.

[0038] In a preferred embodiment provided in this example, the top polyimide film and the top epoxy resin adhesive have a top opening at the same location, exposing the aluminum foil layer at that location; the bottom polyimide film and the bottom epoxy resin adhesive have a bottom opening at the same location, exposing the aluminum foil layer at that location. The top opening and the bottom opening can be set at the same location on the aluminum foil layer, or they can be staggered.

[0039] The above-mentioned method for manufacturing flexible circuit boards using aluminum as the conductive line is as follows:

[0040] First, the top or bottom layer of polyimide film is bonded to the aluminum foil layer using a high-pressure press with a top or bottom layer epoxy resin adhesive. Preferred bonding parameters are: temperature 180°C, pressure 120 kgf, and time 120 s. Subsequently, curing is performed using a hot air oven, with preferred curing parameters: temperature 180°C and time 60 min. Next, the surface of the aluminum foil layer is sanded to remove the oxide layer and foreign matter.

[0041] Next, the aluminum foil layer is subjected to a series of processes including descaling, exposure, development, and etching to obtain the desired circuit pattern. Then, on the etched aluminum foil layer, a bottom or top layer polyimide film (with pre-reserved solder joint openings) is bonded to the aluminum foil layer using a high-speed press press. Preferred bonding parameters are: temperature 180°C, pressure 120 kgf, and time 120 s. Subsequently, curing is performed using a hot air oven, with preferred curing parameters of: temperature 180°C and time 60 min.

[0042] The exposed aluminum foil layer at the window opening is polished again to remove the oxide layer and foreign matter. Then, a zinc replacement solution is used to replace a layer of zinc on the aluminum surface at the window opening, with a zinc thickness preferably of 0.1-1 μm. Next, nickel is plated on the zinc surface using a nickel plating solution, and then gold is plated on the nickel surface using a gold plating solution. Finally, the required shape is punched out using a die to obtain a flexible circuit board with aluminum as the conductive wire that can be directly soldered and assembled.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 application.

Claims

1. A flexible circuit board using aluminum as the conductive line, characterized in that, include: The aluminum foil layer is etched to form conductive lines, thus providing electrical conductivity. The bottom polyimide film, located at the bottom of the flexible circuit board, serves as an insulating and solder resist agent. The bottom epoxy resin adhesive covers the bottom polyimide film and is used to bond the bottom polyimide film to the aluminum foil layer; The top polyimide film, located on the top layer of the flexible circuit board, serves as an insulating and solder resist agent. The top layer epoxy resin adhesive, covering the bottom of the top layer polyimide film, is used to bond the top layer polyimide film to the aluminum foil layer.

2. The flexible circuit board using aluminum as the conductive line according to claim 1, characterized in that, The top polyimide film and the top epoxy resin adhesive have a top opening at the same location, exposing the aluminum foil layer at that location.

3. The flexible circuit board using aluminum as the conductive line according to claim 1, characterized in that, The bottom polyimide film and the bottom epoxy resin adhesive have a bottom opening at the same position, exposing the aluminum foil layer at that position.

4. A flexible circuit board using aluminum as the conductive line according to claim 2, characterized in that, A galvanized layer is provided on the aluminum foil layer at the top window location to increase the adhesion of the coating.

5. A flexible circuit board using aluminum as the conductive line according to claim 3, characterized in that, A zinc-plated layer is provided on the aluminum foil layer at the bottom window position to increase the adhesion of the coating.

6. A flexible circuit board using aluminum as the conductive line according to claim 4 or 5, characterized in that, The zinc plating layer is covered with a nickel plating layer to prevent the aluminum foil layer at the top window position or the aluminum foil layer at the bottom window position from being corroded and oxidized.

7. A flexible circuit board using aluminum as the conductive line according to claim 6, characterized in that, The nickel plating layer is covered with a gold plating layer to further prevent the aluminum foil layer at the top window position or the aluminum foil layer at the bottom window position from being corroded and oxidized.

8. A flexible circuit board using aluminum as the conductive line according to claim 1, characterized in that, In the area where there is no aluminum foil layer after the conductive line is formed, the top epoxy resin adhesive is bonded to the bottom epoxy resin adhesive.

9. A flexible circuit board using aluminum as the conductive line according to claim 1, characterized in that, The thickness of the aluminum foil layer is less than 0.5 mm.

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