Rigid-flex board laminated structure

Abstract

The embodiment of the utility model provides a rigid-flex board laminated structure, and relates to the field of rigid-flex boards. Comprising at least one layer of soft board, a covering film, a shielding film, a prepreg and a hard board, and each layer of soft board comprises a core board and copper foils arranged on the upper surface and the lower surface of the core board; the upper surface and the lower surface of the part, needing to be bent, of the soft board are respectively coated with a covering film; a shielding film is attached to one side, far away from the soft plate, of the covering film; the upper surface and the lower surface of the flexible board are respectively coated with prepregs, and the prepregs are connected with the covering film and the shielding film. A hard board is attached to one side, far away from the soft board, of the prepreg, and a through hole for exposing the shielding film is formed in the hard board; a transition layer is embedded in the prepreg, and the transition layer is used for relieving stress concentration at the joint of the hard board and the soft board or / and the joint of the soft boards. The structure is simple, production is easy, the occurrence risks of layering cracking, bubbles, holes and the like can be reduced, and the stability and reliability of the overall structure are improved.

Description

Technical Field

[0001] This utility model relates to the field of rigid-flex PCBs, and in particular to a rigid-flex PCB laminate structure. Background Technology

[0002] Nowadays, with the birth and development of FPC (Flexible Printed Circuit) and PCB (Printed Circuit Board), a new product called rigid-flex PCB has emerged. This means that flexible circuit boards and rigid circuit boards are combined together through processes such as lamination, according to relevant process requirements, to form a circuit board with the characteristics of both FPC and PCB.

[0003] During the lamination process, existing rigid-flex PCBs are prone to problems such as air bubbles and voids due to stress concentration. Furthermore, during use, thermal expansion and contraction or environmental changes can affect the bond strength of the joints, leading to compromised structural stability. The presence of air bubbles or voids, along with decreased bond strength, can cause delamination and cracking in rigid-flex PCBs over long-term use, ultimately affecting their electrical performance and mechanical strength. Utility Model Content

[0004] In view of the above problems, the present invention provides a rigid-flex plate laminate structure that overcomes or at least partially solves the above problems.

[0005] A rigid-flex PCB laminate structure includes a flexible PCB, a cover film, a shielding film, a prepreg, and a rigid PCB.

[0006] The flexible circuit board has at least one layer, and each layer of the flexible circuit board includes a core board and copper foil disposed on the upper and lower surfaces of the core board; the upper and lower surfaces of the flexible circuit board where bending is required are respectively covered with the cover film; the shielding film is attached to the side of the cover film away from the flexible circuit board;

[0007] The upper and lower surfaces of the flexible board are respectively covered with the prepreg, and the prepreg is in contact with the cover film and the shielding film; the rigid board is attached to the side of the prepreg away from the flexible board.

[0008] The prepreg has a transition layer embedded in it, which is used to alleviate stress concentration at the junction of the rigid board and the flexible board or / and at the junction of the flexible board and the flexible board.

[0009] Preferably, the transition layer includes a wedge-shaped structure, with the thinner end of the wedge-shaped structure close to the flexible plate and the thicker end of the wedge-shaped structure close to the rigid plate.

[0010] Preferably, multiple wedge structures are provided, and the multiple wedge structures are spaced apart on the horizontal plane.

[0011] Preferably, the transition layer includes a serrated structure, which is distributed in strip-like intervals or in a planar overall distribution on the prepreg.

[0012] Preferably, the transition layer includes a wavy structure, which is distributed in strip-like intervals or in a planar overall distribution on the prepreg.

[0013] Preferably, when multiple flexible boards are provided, the multiple flexible boards are stacked sequentially, and a cover film, a shielding film and a prepreg are provided between adjacent flexible boards; and the rigid board is provided on the outermost prepreg.

[0014] Preferably, the flexible boards of different layers have different bending points; multiple through holes are provided, each corresponding to a different bending point.

[0015] Preferably, the thickness of the covering film and the shielding film is the same as the thickness of the cured sheet.

[0016] Preferably, the rigid board is an FR4 copper-clad laminate; the core board is a polyimide film.

[0017] Preferably, the thickness of the rigid plate is 27μm to 33μm, the thickness of the polyimide film is 23μm to 27μm, and the thickness of the copper foil is 10μm to 14μm.

[0018] This application specifically includes the following advantages:

[0019] In the embodiments of this application, a flexible circuit board (FPCB), a cover film, a shielding film, a prepreg, and a rigid board are used. The FPCB has at least one layer, and each layer includes a core board and copper foil disposed on the upper and lower surfaces of the core board. The cover film is attached to the upper and lower surfaces of the FPCB where bending is required. The shielding film is attached to the side of the cover film away from the FPCB. The prepreg is also attached to the upper and lower surfaces of the FPCB, and the prepreg is in contact with the cover film and the shielding film. The rigid board is attached to the side of the prepreg away from the FPCB, and the rigid board has through holes exposing the shielding film. A transition layer is embedded within the prepreg, which is used to alleviate stress concentration at the junction of the rigid board and the FPCB, and / or at the junction of the FPCB and the FPCB. By designing a sandwich-like structure with two rigid boards on both sides of the flexible board, the rigid-flex board structure is simplified and easy to manufacture, reducing the risk of delamination and cracking during production. At least one flexible board is placed between the two rigid boards, allowing for the addition of more flexible boards as needed, and enabling arbitrary bending and assembly. A transition layer is placed between the prepreg sheets of the rigid and flexible boards to alleviate stress concentration at the joint, thereby improving the overall structural stability and reducing delamination, cracking, bubbles, and voids. Attached Figure Description

[0020] To more clearly illustrate the technical solution of this application, the drawings used in the description of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of a rigid-flexible laminated plate according to an embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of the structure of a rigid-flexible laminated plate according to an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram of the structure of a rigid-flexible laminated plate according to an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the structure of a rigid-flexible laminated plate according to an embodiment of the present invention;

[0025] Figure 5 This is a schematic diagram of the structure of a rigid-flexible laminated plate according to an embodiment of the present invention;

[0026] Reference numerals: 10, flexible board; 20, cover film; 30, shielding film; 40, prepreg; 50, rigid board; 11, core board; 12, copper foil; 41, wedge structure; 42, serrated structure; 43, wavy structure. Detailed Implementation

[0027] To make the objectives, features, and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0028] Reference Figure 1-5 This diagram illustrates a structural schematic of a rigid-flex PCB laminate according to the present invention, which specifically includes the following structure: a flexible PCB 10, a cover film 20, a shielding film 30, a prepreg 40, and a rigid PCB 50.

[0029] The flexible circuit board 10 has at least one layer, and each layer of the flexible circuit board 10 includes a core board 11 and copper foil 12 disposed on the upper and lower surfaces of the core board 11; the upper and lower surfaces of the flexible circuit board 10 that need to be bent are respectively covered with the cover film 20; the shielding film 30 is attached to the side of the cover film 20 away from the flexible circuit board 10.

[0030] The upper and lower surfaces of the flexible board 10 are respectively covered with the prepreg 40, and the prepreg 40 is in contact with the cover film 20 and the shielding film 30; the side of the prepreg 40 away from the flexible board 10 is covered with the rigid board 50, and the rigid board 50 has through holes that expose the shielding film 30.

[0031] The prepreg 40 is embedded with a transition layer, which is used to alleviate stress concentration at the junction of the rigid plate 50 and the flexible plate 10 or / and at the junction of the flexible plate 10 and the flexible plate 10.

[0032] In the embodiments of this application, a flexible circuit board 10, a cover film 20, a shielding film 30, a prepreg 40, and a rigid board 50 are used. The flexible circuit board 10 has at least one layer, and each layer includes a core board 11 and copper foil 12 disposed on the upper and lower surfaces of the core board 11. The cover film 20 is respectively attached to the upper and lower surfaces of the flexible circuit board 10 where bending is required. The shielding film 30 is attached to the side of the cover film 20 away from the flexible circuit board 10. The upper surface of the flexible circuit board 10... The prepreg sheet 40 is also attached to the upper and lower surfaces respectively, and the prepreg sheet 40 is in contact with the cover film 20 and the shielding film 30; the rigid board 50 is attached to the side of the prepreg sheet 40 away from the flexible board 10, and the rigid board 50 has through holes that expose the shielding film 30; a transition layer is embedded in the prepreg sheet 40, and the transition layer is used to alleviate stress concentration at the junction of the rigid board 50 and the flexible board 10 or / and the junction of the flexible board 10 and the flexible board 10. By designing a sandwich-like structure with two rigid boards 50 on both sides of the flexible board 10, the rigid-flex board structure is simplified, production is easy, and the risk of delamination and cracking is reduced. At least one layer of flexible board 10 is placed between the two rigid boards 50, and the number of flexible boards 10 can be increased as needed, allowing for arbitrary bending and assembly. By placing a transition layer between the semi-cured sheet 40 between the rigid board 50 and the flexible board 10, the stress concentration at the junction of the rigid board 50 and the flexible board 10 is alleviated, thereby improving the stability of the overall structure and reducing the occurrence of delamination, cracking, bubbles, and voids.

[0033] The following will further describe a rigid-flex plate laminate structure in this exemplary embodiment.

[0034] In the embodiments of this application, reference is made to Figure 1 The flexible circuit board 10 has at least one layer. Each layer of the flexible circuit board 10 includes a core board 11 and copper foil 12 disposed on the upper and lower surfaces of the core board 11. The copper foil 12 on the upper and lower surfaces of the core board 11 serves to conduct electricity. The upper and lower surfaces of the flexible circuit board 10 that need to be bent are respectively covered with the cover film 20 to isolate the copper foil 12 from the outside world and thus serve as surface insulation. The side of the cover film 20 away from the flexible circuit board 10 is covered with the shielding film 30. The shielding film 30 can be an electromagnetic shielding film 30 to protect the inner layer circuit of the final rigid-flex board from external interference (strong electromagnetic areas or areas susceptible to interference).

[0035] The upper and lower surfaces of the flexible board 10 are respectively covered with the prepreg sheet 40, and the prepreg sheet 40 is in contact with the cover film 20 and the shielding film 30. The thickness of the cover film 20 and the shielding film 30 is the same as the thickness of the prepreg sheet, that is, the prepreg sheet 40 is arranged in the same layer as the cover film 20 and the shielding film 30 and is connected to each other. The side of the prepreg sheet 40 away from the flexible board 10 is covered with the rigid board 50. The prepreg sheet 40 firmly binds the flexible board 10 and the rigid board 50 together, playing a role in bonding and supporting. The rigid board 50 has a through hole that exposes the shielding film 30, so that the flexible board 10 has a window at this point, which facilitates bending.

[0036] Through the above structural design, a sandwich structure of rigid-soft composite board is formed. The structure is simple, the production difficulty is low, and it avoids too many layers or too complex structure, which can reduce the occurrence of delamination and cracking during the production process.

[0037] In this embodiment, a transition layer is embedded within the prepreg 40. This transition layer alleviates stress concentration at the junction of the rigid board 50 and the flexible board 10, and / or at the junction of the flexible boards 10 with each other, thereby improving structural stability and further reducing the occurrence of delamination, cracking, bubbles, or voids caused by environmental factors or uneven stress distribution during the production process. Placing the transition layer inside the prepreg 40 ensures a good connection between it and both the flexible board 10 and the rigid board 50. Furthermore, the resin and reinforcing materials within the prepreg 40 provide support and protection for the transition layer, contributing to improved stability and durability.

[0038] As an example, such as Figure 1 As shown, the transition layer includes a wedge-shaped structure 41, with the thinner end of the wedge-shaped structure 41 close to the flexible plate 10 and the thicker end close to the rigid plate 50. The thickness of the wedge-shaped structure 41 is thinner on the flexible plate 10 side and then gradually transitions to a thicker thickness on the rigid plate 50 side. This gradual design can effectively guide stress flow and disperse stress, thereby reducing stress concentration and avoiding excessive stress concentration at the junction of the flexible and rigid plates 50. This reduces the occurrence of delamination, cracking, and other problems, and improves the stability and reliability of the flexible-rigid bonded plate structure.

[0039] When rigid and flexible plates 50 are directly bonded, large shear stress and peel stress are easily generated at the interface due to the abrupt change in material rigidity. The introduction of the wedge structure 41, through the gradual change in thickness, allows the interface stress to transition smoothly, reducing the adverse effects of stress abrupt changes.

[0040] As an example, multiple wedge structures 41 can be provided, with the multiple wedge structures 41 spaced apart on the horizontal plane. Specifically, depending on the application requirements and manufacturing process of the rigid-flex PCB, in practical applications, the number, shape, size, and thickness of the wedge structures 41 can be optimized to achieve the best performance and reliability.

[0041] As an example, such as Figure 2 As shown, the transition layer includes a sawtooth structure 42, which is distributed in strip-like intervals or in a planar overall distribution.

[0042] As an example, such as Figure 3 As shown, the transition layer includes a wave-shaped structure 43, which is distributed in strip-like intervals or in a planar overall distribution.

[0043] The aforementioned transition layer can also be designed as a sawtooth structure 42 or a wave-shaped structure 43 to increase the complexity of the transition area and significantly improve the flexibility and stress dispersion of the structure.

[0044] As an example, refer to Figure 4 When multiple layers of the flexible boards 10 are provided, the multiple layers of flexible boards 10 are stacked sequentially to form a layered structure of flexible boards 10. The specific number depends on actual needs, and the number of stacks should not be too large to avoid instability of the overall structure. A cover film 20, a shielding film 30, and a prepreg 40 are provided between adjacent flexible boards 10 to reduce the number of structural layers and complexity; and the rigid board 50 is provided on the outermost prepreg 40, also forming a sandwich structure of flexible board 10 and rigid board 50. The transition layer between adjacent flexible boards 10 is preferably a sawtooth structure 42 or a wavy structure 43, and the transition layer between flexible board 10 and rigid board 50 is preferably a wedge structure 41.

[0045] As an example, the bending portions of the flexible board 10 differ across different layers; multiple through holes are provided, each corresponding to a different bending portion. Figure 5 The diagram shows a three-layer flexible printed circuit board (FPCB) 10 structure. The bending portion of each FPCB 10 is different. The rigid board 50 has through holes corresponding to the bending portions of each layer, and the exposed portions correspond to the shielding layers of each layer. The flexible-rigid composite board with different layer bending allows the FPCB 10 to be bent and assembled arbitrarily, and the assembled finished product has a small size, meeting the characteristics of being lightweight, thin, and small.

[0046] As an example, the rigid board 50 is an FR4 copper-clad laminate, which mainly provides support; the core board 11 is a polyimide film (PI film), which has high strength and high stability. The thickness of the rigid board 50 is 27μm to 33μm, the thickness of the polyimide film is 23μm to 27μm, and the thickness of the copper foil 12 is 10μm to 14μm. By controlling the thickness of each layer, a thinner rigid-flex board product can be obtained.

[0047] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0048] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0049] The above provides a detailed description of the rigid-flex PCB laminate structure provided by this utility model. Specific examples have been used to illustrate the principle and implementation of this utility model. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this utility model. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this utility model. Therefore, the content of this specification should not be construed as a limitation of this utility model.

Claims

1. A rigid-flexible laminated structure, characterized in that, Includes flexible printed circuit boards (FPCBs), cover films, shielding films, prepregs, and rigid boards. The flexible circuit board has at least one layer, and each layer of the flexible circuit board includes a core board and copper foil disposed on the upper and lower surfaces of the core board; the upper and lower surfaces of the flexible circuit board where bending is required are respectively covered with the cover film; the shielding film is attached to the side of the cover film away from the flexible circuit board; The upper and lower surfaces of the flexible board are respectively covered with the prepreg, and the prepreg is in contact with the cover film and the shielding film; the rigid board is attached to the side of the prepreg away from the flexible board. The prepreg has a transition layer embedded in it, which is used to alleviate stress concentration at the junction of the rigid board and the flexible board or / and at the junction of the flexible board and the flexible board.

2. The rigid-flex PCB laminate structure according to claim 1, characterized in that, The transition layer includes a wedge-shaped structure, with the thinner end of the wedge-shaped structure close to the flexible plate and the thicker end of the wedge-shaped structure close to the rigid plate.

3. The rigid-flex PVC laminate structure according to claim 2, characterized in that, Multiple wedge structures are provided, and the multiple wedge structures are spaced apart on the horizontal plane.

4. The rigid-flex PVC laminate structure according to claim 1, characterized in that, The transition layer includes a serrated structure, which is distributed in strip-like intervals or in a planar overall distribution on the prepreg.

5. The rigid-flex PCB laminate structure according to claim 1, characterized in that, The transition layer includes a wavy structure, which is distributed in strip-like intervals or in a planar overall distribution on the prepreg.

6. The rigid-flex PCB laminate structure according to claim 1, characterized in that, When multiple flexible boards are provided, the multiple flexible boards are stacked sequentially, and a cover film, a shielding film and a prepreg are provided between adjacent flexible boards; and the rigid board is provided on the outermost prepreg.

7. The rigid-flex PCB laminate structure according to claim 6, characterized in that, The flexible boards of different layers have different bending points; multiple through holes are provided, each corresponding to a different bending point.

8. The rigid-flex PCB laminate structure according to claim 1, characterized in that, The thickness of the cover film and the shielding film is the same as the thickness of the cured sheet.

9. The rigid-flex PCB laminate structure according to claim 1, characterized in that, The rigid board is an FR4 copper-clad laminate; the core board is a polyimide film.

10. The rigid-flex PCB laminate structure according to claim 9, characterized in that, The thickness of the rigid plate is 27μm to 33μm, the thickness of the polyimide film is 23μm to 27μm, and the thickness of the copper foil is 10μm to 14μm.

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