Flexible printed circuit board with segmented bonding

Abstract

The utility model relates to a segmented bonding flexible printed circuit board, which comprises a base layer, a first connecting glue layer, a flexible board layer, a second connecting glue layer and a fixed rigid-flexible transition connecting layer, and is characterized in that one side or two opposite sides of the base layer are bonded and fixed with the flexible board layer through the first connecting glue layer; and the rigid-flexible transition connecting layer is bonded and fixed on one side, back on to the base layer, of the flexible plate layer through a second connecting adhesive layer. According to the flexible printed circuit board, the rigid-flexible transition connecting layer is arranged, so that the bending radius of the transition part of the bending area and the non-bending area is large, and the problem that a conductor, an insulating layer or a base material in the flexible printed circuit board is easy to break or peel off due to a high stress state caused by stress concentration is solved; and the service life of the flexible printed circuit board in bending use is prolonged.

Description

Technical Field

[0001] This invention relates to the field of flexible printed circuit board technology, specifically to a segmented bonded flexible printed circuit board. Background Technology

[0002] Traditional printed circuit boards (PCBs) are made of rigid materials, consisting of epoxy resin, fiberglass cloth, and copper foil. After high-temperature lamination and curing, they are bonded together to form a single unit, possessing excellent rigidity and providing good support and fixation during soldering and installation. However, PCBs are generally rigid and can only perform two-dimensional connections, meaning connections are made on the surface of the PCB. If the connection points are not on the same surface, conductive wires are required to establish conductivity, thus placing high demands on the space requirements of electronic products. To address this issue, designers have developed a flexible PCB made of materials with good bending properties, such as rolled copper or high-ductility electrolytic copper, to ensure its superior bending performance.

[0003] For example, Chinese Patent Publication No. CN105491789B proposes a flexible printed circuit board, which, through the different settings of the bending and non-bending areas, enables the production of flexible, small, lightweight, and bendable printed circuit boards at a lower manufacturing cost.

[0004] However, this type of flexible printed circuit board has the following problems in use: The bending and non-bending areas of the flexible printed circuit board are determined by the presence of rigid plates in those areas, allowing the board to bend. However, stress concentration can easily occur at the transition between the bending and non-bending areas due to changes in the bending angle. This stress concentration effect is particularly pronounced at 90° bends due to the smaller bending radius. This high-stress state can easily lead to breakage or peeling of the conductors, insulating layers, or substrate inside the flexible circuit board. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] This invention provides a segmented, bonded flexible printed circuit board, which solves the problems mentioned in the background art.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution: a segmented bonded flexible printed circuit board, comprising a base layer, a first connecting adhesive layer, a flexible board layer, a second connecting adhesive layer, and a rigid-flexible transition connection layer. The flexible board layer is bonded and fixed to one side or opposite sides of the base layer using the first connecting adhesive layer. The rigid-flexible transition connection layer is bonded and fixed to the side of the flexible board layer facing away from the base layer using the second connecting adhesive layer. The rigid-flexible transition connection layer comprises two rigid boards, an elastomer, two elastomer capping plates, and two sets of multi-particle filler groups. The two ends of the elastomer are respectively... The elastic body is fixedly connected to two rigid plates. Each end of the elastic body forms a cavity structure, and each cavity structure contains a set of multiple filler particles. Two elastic body cover plates cover the two cavity structures respectively, and the elastic body cover plates are bonded to the elastic body with adhesive. The two rigid plates, the flexible plate layer, and the area of ​​the base layer corresponding to the rigid plates constitute the non-bending area of ​​the segmented bonded flexible printed circuit board. The area of ​​the elastic body, the flexible plate layer, and the area of ​​the base layer corresponding to the elastic body constitutes the bending area of ​​the segmented bonded flexible printed circuit board.

[0009] Preferably, the rigid plate is configured as a metal plate structure or a plastic plate structure, the elastomer and the elastomer cover plate are both configured as rubber materials with a certain degree of elasticity, and the multi-particle filler group includes multiple spherical or cylindrical particles, and the particles constituting the multi-particle filler group have a certain amount of movable gaps in the cavity structure.

[0010] In a further preferred embodiment, the base layer includes a copper foil layer, an upper adhesive layer, a lower adhesive layer, an upper protective film, and a lower protective film. The upper and lower protective films are respectively disposed on opposite sides of the copper foil layer, and the copper foil layer and the upper protective film are bonded and fixed together by the upper adhesive layer, and the copper foil layer and the lower protective film are bonded and fixed together by the lower adhesive layer.

[0011] In a further preferred embodiment, the upper adhesive layer, the lower adhesive layer, the first connecting adhesive layer, and the second connecting adhesive layer are all formed by solidification of at least one of polyester adhesives, epoxy adhesives, acrylic adhesives, and polyimide adhesives, and the upper protective film, the lower protective film, and the flexible plate layer are all made of polyimide film.

[0012] (III) Beneficial Effects

[0013] Compared with the prior art, the present invention provides a segmented bonding flexible printed circuit board, which has the following advantages:

[0014] This segmented flexible printed circuit board, through the setting of a rigid-flexible transition connection layer, allows for the production of flexible, small-sized, lightweight, and bendable printed circuit boards at a lower manufacturing cost by different settings of bending and non-bending areas during use. In addition, the cooperation of two rigid plates and an elastomer allows for a larger bending radius at the transition between the bending and non-bending areas, avoiding the high stress state caused by stress concentration, which can easily lead to the breakage or peeling of conductors, insulation layers, or substrates inside the flexible circuit board, thus improving the service life of the flexible printed circuit board during bending. Attached Figure Description

[0015] Figure 1 A cross-sectional view of a flexible printed circuit board that is segmented and bonded according to the implementation scheme;

[0016] Figure 2 for Figure 1 A schematic diagram showing the division between the non-bending and bending areas of a flexible printed circuit board with segmented bonding.

[0017] Figure 3 This is a cross-sectional view of the rigid-flexible transition connection layer according to the implementation scheme, omitting the elastomeric capping plate.

[0018] Figure 4 This is a cross-sectional view of the base layer according to the implementation plan.

[0019] In the diagram: 10. Base layer; 11. Copper foil layer; 12. Upper adhesive layer; 13. Lower adhesive layer; 14. Upper protective film; 15. Lower protective film; 20. First connecting adhesive layer; 30. Flexible board layer; 40. Second connecting adhesive layer; 50. Rigid-flexible transition connecting layer; 51. Rigid board; 52. Elastomer; 521. Cavity structure; 53. Elastomer cover plate; 54. Multi-particle filler group. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please see Figures 1 to 4A segmented flexible printed circuit board includes a base layer 10, a first adhesive layer 20, a flexible board layer 30, a second adhesive layer 40, and a rigid-flexible transition connection layer 50. The flexible board layer 30 is bonded and fixed to one side or opposite sides of the base layer 10 using the first adhesive layer 20, and the rigid-flexible transition connection layer 50 is bonded and fixed to the side of the flexible board layer 30 facing away from the base layer 10 using the second adhesive layer 40.

[0022] In this embodiment, the base layer 10 includes a copper foil layer 11, an upper adhesive layer 12, a lower adhesive layer 13, an upper protective film 14, and a lower protective film 15. The upper protective film 14 and the lower protective film 15 are respectively disposed on opposite sides of the copper foil layer 11, and the copper foil layer 11 and the upper protective film 14 are bonded and fixed together by the upper adhesive layer 12, while the copper foil layer 11 and the lower protective film 15 are bonded and fixed together by the lower adhesive layer 13. The base layer 10 is a conventional technology for existing flexible printed circuit boards and will not be described in detail here.

[0023] In this embodiment, the rigid-flexible transition connection layer 50 includes two rigid plates 51, an elastomer 52, two elastomer capping plates 53, and two sets of multi-particle filler groups 54. The rigid plates 51 can be metal or plastic, and the elastomers 52 and capping plates 53 can be made of rubber with a certain degree of elasticity. The two ends of the elastomer 52 are fixedly connected to the two rigid plates 51, and each end of the elastomer 52 forms a cavity structure 521, each cavity structure 521 containing a set of multi-particle filler groups 54. The multi-particle filler groups 54 include multiple spherical or cylindrical particles. The particles constituting the multi-particle filler groups 54 have certain gaps within the cavity structures 521. The placement of the particles within the cavities is an innovative design based on material mechanics and stress dispersion principles. The cavity within the elastomer, filled with multiple particles, can be considered a special type of "shock absorber" or "stress diffuser." When a circuit board is subjected to bending forces, these particles can move freely within the cavities, thus dispersing and absorbing stress. During bending, the circuit board is subjected to bending forces from different directions. Traditional flexible circuit boards, lacking effective stress dispersion mechanisms, often experience stress concentration in the bending area. The placement of these particles within the cavities can be considered as forming a "stress network" within the elastomer. When bending forces act on the circuit board, these particles can move within the cavities like "springs," dispersing stress over a larger area and preventing stress concentration. The movement of these particles within the cavities also provides a certain degree of shock absorption. When the circuit board is subjected to impact or vibration, these particles can absorb some energy, reducing damage to the circuit board. This shock absorption effect is particularly important in high-frequency vibration or impact environments, significantly improving the reliability and durability of the circuit board. Due to the mobility of the particles within the cavities, the elastomer can better adapt to various bending angles. During bending, the particles move with the bending motion, keeping the elastomer in a uniform bending state. This design not only improves the bending performance of the circuit board but also reduces the risk of damage due to excessive bending. Although the particles have a certain degree of mobility within the cavities, the interactions between them and with the elastomers enhance the overall structural strength of the circuit board. This reinforcement makes the circuit board more stable under external forces, less prone to deformation or damage. In applications requiring larger bending angles, particles with rounder shapes and moderate sizes can be selected; while in applications requiring higher structural strength, particles with more regular shapes and larger sizes can be selected. Two elastomer cover plates 53 respectively cover the two cavity structures 521, and the elastomer cover plates 53 are bonded to the elastomers 52 with adhesive, ensuring that the particles are filled within the cavity structures 521 and preventing leakage.

[0024] In this embodiment, the two rigid plates 51, the flexible plate layer 30, and the area of ​​the base layer 10 corresponding to the rigid plates 51 constitute the non-bending area of ​​the segmented bonded flexible printed circuit board. The elastomer 52, the flexible plate layer 30, and the area of ​​the base layer 10 corresponding to the elastomer 52 constitute the bending area of ​​the segmented bonded flexible printed circuit board. In the bending area, the design introduces the elastomer 52 as a transition structure. The two ends of the elastomer 52 are fixedly connected to the two rigid plates 51 respectively, and the interior has a cavity structure 521 filled with a multi-particle filler group 54. These particles have a certain amount of space within the cavity, and when the elastomer 52 bends, the particles can move with the bending action, thereby dispersing and absorbing the stress generated during the bending process. This design effectively avoids the stress concentration problem that may occur when bending traditional flexible circuit boards, extending the service life of the circuit board. The design of the elastomer 52 and its internal filler not only helps to disperse stress but also improves the bending performance of the circuit board. Due to the mobility of the particles within the cavity, the elastomer 52 can better adapt to various bending angles without being damaged by excessive bending. This makes the circuit board exhibit higher reliability and durability in applications requiring frequent bending.

[0025] In this embodiment, the upper adhesive layer 12, the lower adhesive layer 13, the first connecting adhesive layer 20, and the second connecting adhesive layer 40 can all be made of at least one of polyester adhesives, epoxy adhesives, acrylic adhesives, and polyimide adhesives, and form an adhesive layer structure after solidification. The upper protective film 14, the lower protective film 15, and the flexible plate layer 30 can all be made of polyimide film.

[0026] In all the solutions mentioned above, the connection between two components can be selected according to the actual situation, such as bonding, welding, bolt and nut connection, bolt or screw connection, or other known connection methods. They will not be described in detail here. Although embodiments of the present invention have been shown and described above, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations 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 flexible printed circuit board with segmented bonding, comprising a base layer (10), characterized in that Further comprising a first connecting glue layer (20), a flexible plate layer (30), a second connecting glue layer (40) and a rigid-flexible transition connecting layer (50), one side or opposite sides of the base layer (10) are fixedly bonded with the flexible plate layer (30) by the first connecting glue layer (20), and the side of the flexible plate layer (30) away from the base layer (10) is fixedly bonded with the rigid-flexible transition connecting layer (50) by the second connecting glue layer (40), Wherein, the rigid-flexible transition connecting layer (50) comprises two rigid plates (51), an elastomer (52), two elastomer cover plates (53) and two groups of multi-particle filler groups (54), the two ends of the elastomer (52) are fixedly connected with the two rigid plates (51) respectively, each of the two ends of the elastomer (52) is formed with a cavity structure (521), each of the cavity structures (521) contains a group of multi-particle filler groups (54), and the two elastomer cover plates (53) cover the two cavity structures (521) respectively, and the elastomer cover plates (53) and the elastomer (52) are fixedly bonded by an adhesive; The two rigid plates (51), the flexible plate layer (30) and the base layer (10) and the areas corresponding to the rigid plates (51) of the base layer (10) constitute the non-bending area of the sectional bonded flexible printed circuit board, and the elastomer (52), the flexible plate layer (30) and the base layer (10) and the areas corresponding to the elastomer (52) of the base layer (10) constitute the bending area of the sectional bonded flexible printed circuit board.

2. A flexurally flexible printed circuit board according to claim 1, wherein: The multi-particle filler group (54) comprises a plurality of spherical or cylindrical particles, and the particles constituting the multi-particle filler group (54) have movable gaps in the cavity structure (521).

3. A flexibly printed circuit board according to claim 2, wherein: The elastomer (52) and the elastomer cover plate (53) are both provided as rubber materials with certain elasticity.

4. A flexurally flexible printed circuit board according to claim 3, wherein: The rigid plate (51) is provided as a metal plate structure or a plastic plate structure.

5. A flexurally flexible printed circuit board according to any one of claims 1 to 4, characterised in that: The base layer (10) comprises a copper foil layer (11), a top glue layer (12), a bottom glue layer (13), an upper protective film (14) and a lower protective film (15), the opposite sides of the copper foil layer (11) are respectively provided with the upper protective film (14) and the lower protective film (15), and the copper foil layer (11) and the upper protective film (14) are fixedly bonded by the top glue layer (12), and the copper foil layer (11) and the lower protective film (15) are fixedly bonded by the bottom glue layer (13).

6. A flexibly printed circuit board according to claim 5, wherein: The top glue layer (12), the bottom glue layer (13), the first connecting glue layer (20) and the second connecting glue layer (40) are all formed by at least one of polyester adhesive, epoxy adhesive, acrylic adhesive and polyimide adhesive after solidification.

7. A flexibly printed circuit board according to claim 5, wherein: The upper protective film (14), the lower protective film (15) and the flexible plate layer (30) are all provided as polyimide films.

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