A multilayer flexible wiring board having a multilayer region which is freely bendable
By using a multi-layer flexible circuit board design that allows for free bending of multiple layers, the problem of insufficient flexibility in traditional circuit boards with fewer than 4 layers is solved. This results in a multi-layer circuit board with high flexibility and stable signal, suitable for high integration and high-speed signal transmission requirements in fields such as smartphones, wearable devices, 5G communications, automotive electronics, aerospace, and medical electronics.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- DALIAN JIXING ELECTRONICS
- Filing Date
- 2025-07-29
- Publication Date
- 2026-06-23
AI Technical Summary
Traditional multilayer circuit boards lack flexibility when designed with fewer than four layers, making it difficult to meet the needs of complex application scenarios, especially in the fields of smartphones, wearable devices, 5G communications, automotive electronics, aerospace, and medical electronics, where high integration, high-speed signal transmission, and lightweight requirements are necessary.
The circuit board adopts a multi-layer flexible circuit board design that can be freely bent, including a stacked structure of bottom polyimide film, epoxy resin, copper plating layer and copper foil layer. Through-holes are used to achieve interlayer conductivity, and the conductive lines are formed by etching process. The layers are fixed by thermosetting adhesive layer to ensure the reliability and signal stability of the circuit board.
It achieves high flexibility and reliability of multi-layer circuit boards, which can be repeatedly bent in multiple areas while maintaining stable electrical and mechanical properties, saving space, ensuring the stability of signal transmission, and is suitable for miniaturization and thinning of equipment.
Smart Images
Figure CN224401745U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of electronic information technology, specifically to a multi-layer flexible circuit board that can be freely bent in multiple layers. Background Technology
[0002] With the rapid development of electronic information technology, multilayer circuit boards, as core components of high-end electronic products, are experiencing rapid growth in market demand. In fields such as smartphones, wearable devices, 5G communications, automotive electronics, aerospace, and medical electronics, the requirements for circuit board integration, signal transmission speed, bend resistance, and lightweighting are increasing. Traditional single and multilayer circuit boards are often designed with fewer than four layers, otherwise they will not be flexible, which is no longer sufficient to meet the needs of complex application scenarios.
[0003] Therefore, multilayer circuit boards, with their unique structural advantages—combining high-density wiring with the flexibility of flexible circuit boards—can be freely bent in areas with four or more layers, making them a new favorite in the market. It is expected that in the next few years, with the continued expansion of the smart terminal market and the emergence of new technologies, the market demand for multilayer circuit boards will continue to rise, bringing broad development space and opportunities to the industry. Utility Model Content
[0004] The purpose of this invention is to provide a multi-layer flexible circuit board with multiple layers that can be freely bent, so as to solve the problems mentioned in the background art.
[0005] To achieve the above objectives, the present invention provides the following technical solution: a multi-layer flexible circuit board with a multi-layer area that can be freely bent, comprising a bottom polyimide film, a bottom epoxy resin adhesive disposed on the top of the bottom polyimide film, and the bottom epoxy resin adhesive and the bottom polyimide film forming a bottom cover film, a bottom copper plating layer disposed on the top of the bottom epoxy resin adhesive, a bottom copper foil layer disposed on the top of the bottom copper plating layer, and a bottom base film disposed on the top of the bottom copper foil layer;
[0006] The bottom substrate film has multiple inner FPC layers on top, the inner FPC layers have a top substrate film on top, the top substrate film has a top copper foil layer on top, the top copper foil layer has a top copper plating layer on top, and the top copper plating layer has a top polyimide film bonded to the top of the top polyimide film with a top epoxy resin adhesive.
[0007] Preferably, the bottom copper plating layer and the top copper plating layer achieve interconnection between the copper foil layers through copper plating on the walls of the vias.
[0008] Preferably, the bottom copper foil layer and the top copper foil layer are formed into conductive lines through an etching process.
[0009] Preferably, the underlying substrate film and the underlying copper foil layer constitute the underlying single-sided substrate.
[0010] Preferably, multiple inner FPC layers are bonded and fixed together by a thermosetting adhesive layer.
[0011] Preferably, the top epoxy resin adhesive and the top polyimide film constitute the top cover film.
[0012] Preferably, the bottom cover film has a bottom cover film window.
[0013] Compared with the prior art, the beneficial effects of this utility model are:
[0014] 1. High flexibility and reliability: The multi-layer flexible circuit board with multiple bendable areas can be repeatedly bent in multiple areas and maintain stable electrical and mechanical properties during the bending process. This greatly improves the service life and reliability of the circuit board and reduces failures and maintenance costs caused by bending.
[0015] 2. Space saving: Due to its multi-layered structure and bendable characteristics, the circuit board can achieve complex circuit layouts within a limited space, effectively saving internal space of electronic devices and making miniaturization and thinner design possible.
[0016] 3. Stable signal transmission: Through optimized circuit design and interlayer connection technology, this circuit board can ensure stable signal transmission and reduce signal interference and attenuation, which is especially important for electronic devices with high-speed data transmission and high-frequency applications.
[0017] Based on conventional flexible circuit board processing technology, this utility model achieves free bending of multiple layers through a stacked design, realizing complex circuit layouts within a limited space, effectively saving internal space of electronic devices, and providing possibilities for miniaturization and thinning of devices. Attached Figure Description
[0018] Figure 1 This is a cross-sectional view of the multilayer FPC of this utility model;
[0019] Figure 2 This is a cross-sectional view of the single-layer FPC of this utility model.
[0020] In the diagram: 1. Bottom polyimide film; 2. Bottom epoxy resin adhesive; 3. Bottom copper plating layer; 4. Bottom copper foil layer; 5. Bottom base film; 6. Thermosetting adhesive layer; 7. Bottom cover film window; 8. Through hole; 9. Inner FPC layer; 10. Top base film; 11. Top copper foil layer; 12. Top copper plating layer; 13. Top epoxy resin adhesive; 14. Top polyimide film; 15. Inner FPC bottom polyimide film; 16. Inner FPC bottom epoxy resin adhesive; 17. Inner FPC bottom copper foil layer; 18. Inner FPC base film; 19. Inner FPC top copper foil layer; 20. Inner FPC top epoxy resin adhesive; 21. Inner FPC top polyimide film. Detailed Implementation
[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0022] Example 1
[0023] Please see Figure 1 This utility model provides a technical solution: a multi-layer flexible circuit board that can be freely bent in multiple layers, including a bottom polyimide film 1, located at the bottom layer of the product, which serves as an insulating solder resist. A bottom epoxy resin adhesive 2 is disposed on the top of the bottom polyimide film 1, and the bottom epoxy resin adhesive 2 and the bottom polyimide film 1 form a bottom cover film for bonding the bottom polyimide film to copper foil. A bottom copper plating layer 3 is disposed on the top of the bottom epoxy resin adhesive 2, a bottom copper foil layer 4 is disposed on the top of the bottom copper plating layer 3, and a bottom base film 5 is disposed on the top of the bottom copper foil layer 4.
[0024] Multiple inner FPCs 9 are disposed on the top of the bottom substrate film 5, a top substrate film 10 is disposed on the top of the inner FPCs 9, a top copper foil layer 11 is disposed on the top of the top substrate film 10, a top copper plating layer 12 is disposed on the top of the top copper foil layer 11, and a top polyimide film 14 is bonded to the top of the top copper plating layer 12 by a top epoxy resin adhesive 13, which serves as an insulating solder resist.
[0025] In this invention, the bottom copper plating layer 3 and the top copper plating layer 12 achieve interconnection between the copper foil layers through copper plating on the walls of the through holes 8.
[0026] In this invention, the bottom copper foil layer 4 and the top copper foil layer 11 are formed by etching to form conductive lines, which serve as electrical conductors.
[0027] In this invention, the bottom substrate film 5 and the bottom copper foil layer 4 constitute the bottom single-sided substrate.
[0028] In this invention, multiple inner FPC9 layers are bonded and fixed by a thermosetting adhesive layer 6.
[0029] In this invention, the top epoxy resin adhesive 13 and the top polyimide film 14 form the top cover film for bonding the top polyimide film to the copper foil.
[0030] In this invention, a bottom cover film opening 7 is provided on the bottom cover film to expose the copper foil layer for electrical connection with other equipment.
[0031] Example 2
[0032] Please see Figure 2 A single-layer flexible circuit board includes an inner FPC bottom polyimide film 15, an inner FPC bottom copper foil layer 17 bonded to the top of the inner FPC bottom polyimide film 15 via an inner FPC bottom epoxy resin adhesive 16, an inner FPC base film 18 disposed on the top of the inner FPC base film 17, an inner FPC top copper foil layer 19 disposed on the top of the inner FPC base film 18, and an inner FPC top polyimide film 21 bonded to the top of the inner FPC top copper foil layer 19 via an inner FPC top epoxy resin adhesive 20; the inner FPC bottom polyimide film 15 is located at the bottom of the product and serves as an insulating solder resist; the inner FPC bottom epoxy resin adhesive 16 and the inner FPC bottom polyimide film 17 are bonded together via an inner FPC bottom epoxy resin adhesive 20. The inner FPC bottom layer cover film, composed of a polyimide film at the bottom of the PC layer, is used to bond the inner FPC bottom layer polyimide film to the inner FPC bottom layer copper foil. The inner FPC bottom layer copper foil layer 17 forms conductive lines through an etching process to achieve electrical conductivity. The inner FPC base film 18 is made of polyimide film. The inner FPC top layer copper foil layer 19 forms conductive lines through an etching process to achieve electrical conductivity. The inner FPC top layer epoxy resin adhesive 20 and the inner FPC top layer polyimide film together form the inner FPC top layer cover film, used to bond the inner FPC top layer polyimide film to the inner FPC top layer copper foil. The inner FPC top layer polyimide film 21 is located on the top layer of the product and serves as an insulating solder resist.
[0033] This invention involves the following steps: First, the inner layer FPC is processed according to the FPC processing technology. The process flow includes material cutting / drilling / drying film pressing / exposure / development / etching / film removal / cover film application / lamination / curing / targeting / plasma cleaning. After these steps, the inner layer FPC is processed, forming copper foil circuits and attaching a cover film. The top and bottom single-sided substrates are then bonded to the inner layer FPC using thermosetting adhesive (there is no thermosetting adhesive in the bending area), and lamination is performed using a vacuum conventional press. After lamination, the multilayer board undergoes targeting / drilling / hole drilling / copper plating / drying film pressing / exposure / development / etching / film removal / cover film application / lamination / curing / surface treatment / shape shaping to complete the multilayer FPC processing. At this point, the areas of the multilayer FPC without thermosetting adhesive are layered and can be freely bent.
[0034] The contents not described in detail in this specification are prior art known to those skilled in the art. Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A multi-layer flexible circuit board with freely bendable multi-layer areas, characterized in that: The film includes a bottom polyimide film (1), on the top of which is a bottom epoxy resin adhesive (2), and the bottom epoxy resin adhesive (2) and the bottom polyimide film (1) form a bottom cover film. On the top of the bottom epoxy resin adhesive (2) is a bottom copper plating layer (3), on the top of the bottom copper plating layer (3) is a bottom copper foil layer (4), and on the top of the bottom copper foil layer (4) is a bottom base film (5). The bottom substrate film (5) is provided with a plurality of inner FPCs (9), the top of the inner FPCs (9) is provided with a top substrate film (10), the top of the top substrate film (10) is provided with a top copper foil layer (11), the top of the top copper foil layer (11) is provided with a top copper plating layer (12), and the top of the top copper plating layer (12) is bonded with a top polyimide film (14) by a top epoxy resin adhesive (13).
2. The multi-layer flexible circuit board with freely bendable multi-layer areas according to claim 1, characterized in that: The bottom copper plating layer (3) and the top copper plating layer (12) are connected to each other through copper plating on the wall of the through hole (8).
3. The multi-layer flexible circuit board with freely bendable multi-layer areas according to claim 1, characterized in that: The bottom copper foil layer (4) and the top copper foil layer (11) are formed into conductive lines through an etching process.
4. The multi-layer flexible circuit board with freely bendable multi-layer areas according to claim 1, characterized in that: The underlying substrate film (5) and the underlying copper foil layer (4) together form the underlying single-sided substrate.
5. A multi-layer flexible circuit board with freely bendable multi-layer areas according to claim 1, characterized in that: Multiple inner FPC layers (9) are bonded and fixed by a thermosetting adhesive layer (6).
6. A multi-layer flexible circuit board with freely bendable multi-layer areas according to claim 1, characterized in that: The top epoxy resin adhesive (13) and the top polyimide film (14) together form the top cover film.
7. A multi-layer flexible circuit board with freely bendable multi-layer areas according to claim 1, characterized in that: The bottom cover film is provided with a bottom cover film window (7).