Bending-resistant flexible circuit board and preparation method thereof

Abstract

The invention provides a bending-resistant flexible circuit board and a preparation method thereof. According to the flexible circuit board, the first bending area, the second bending area, the third bending area and the bending area of the through groove are arranged, the first bending area and the second bending area play roles of main bending and secondary bending respectively, the third bending area can be twisted, swung and deformed, the through groove can release bending or twisting stress, and the bending or twisting stress can be released. The flexible circuit board is changed from traditional pure bending deformation into combined deformation which takes torsional swing deformation as a main part and bending deformation as an auxiliary part, so that the bending stress borne by the flexible circuit board is greatly reduced, and the flexible circuit board has good dynamic bending performance. The flexible circuit board can be made of a material with a conventional thickness, the application range is wider, and the material cost and the manufacturing difficulty are reduced. In addition, the bonding layer of the flexible circuit board is not provided with an opening, so that the risk that the edge of the opening is layered and exploded is completely eradicated.

Description

Technical Field

[0001] The present application relates to the technical field of circuit boards, and in particular to a bending-resistant flexible circuit board and a preparation method thereof. Background Art

[0002] Foldable screen mobile phones have the characteristics of being foldable, having large screens, and having small storage space, and have achieved rapid development in recent years. The number of folding times of foldable screen mobile phones has also increased from tens of thousands to hundreds of thousands or even millions of times, and the bending resistance of the flexible printed circuit board (FPC) responsible for the electrical connection between the folding screens has also increased accordingly.

[0003] At present, in order to improve the dynamic bending performance of FPC (bending times of 300,000 times or more), the industry mostly adopts a multi-layer thin single-panel stacking structure and a design of setting openings (buried holes) (Airgap) in the bending area glue layer (for example, Bonding Sheet, abbreviated as BS). However, the shortcomings and disadvantages of this design are as follows: the material cost of the flexible copper clad laminate (FCCL) and the adhesive layer of the single-sided composite stack is relatively high (compared to the stack of single-sided and double-sided panels); the opening area is 10mm*15mm or even larger, and there is a risk of thermal expansion in the process (such as lamination of the protective layer and lamination of the reinforcement sheet, etc.) causing delamination and explosion of the opening edge; for the sake of bending performance, the FCCL and the protective layer need to be made of thinner materials. For example, the copper foil layer thickness in the FCCL is ≤12μm, the substrate layer thickness is ≤12.5μm, and the protective layer thickness is ≤27.5μm. The material cost and process difficulty are relatively high; for the sake of bending performance, the line conductor layer thickness is ≤18μm, which is not suitable for products with thick conductor circuit design requirements. Summary of the invention

[0004] In view of this, the present application proposes a bending-resistant flexible circuit board and a preparation method thereof to solve at least one of the above problems.

[0005] An embodiment of the present application provides a flexible circuit board that is resistant to bending, comprising at least one flexible substrate layer and at least one conductive circuit layer formed on the surface of the flexible substrate layer. The flexible circuit board has a blind groove and a through groove, and a portion of the surface of the flexible substrate layer is exposed from the blind groove. The through groove penetrates the flexible circuit board along the thickness direction.

[0006] The flexible circuit board includes a bending area, and the bending area includes a first bending area, a second bending area, a third bending area and a through groove. The first bending area is an area in the flexible circuit board corresponding to the blind groove. Along the length direction of the flexible circuit board, the second bending area is an area located on both sides of the through groove. Along the width direction of the flexible circuit board, the third bending area is an area for connecting two adjacent second bending areas.

[0007] In one embodiment, along the width direction of the flexible circuit board, the width of the first bending zone is 0.5-3 mm, and the width of the second bending zone is greater than or equal to 3 mm.

[0008] In one embodiment, along the length direction of the flexible circuit board, the width of the third bending zone is greater than or equal to 0.5 mm.

[0009] In one embodiment, the orthographic projection of the third bending zone along the thickness direction of the flexible circuit board is a straight line, an oblique line, a V-shape, a U-shape or an S-shape.

[0010] In one embodiment, the thickness of the flexible substrate layer is 12.5 to 50 μm, and the thickness of the conductive circuit layer is 9 to 35 μm.

[0011] In one embodiment, when the number of the conductive circuit layer is greater than or equal to three, the flexible circuit board further includes at least one adhesive layer, and the adhesive layer is located between one of the flexible substrate layers and one of the conductive circuit layers.

[0012] In one embodiment, the flexible circuit board further includes a protective layer, the protective layer is located on the outer side of the outermost conductive circuit layer, and the blind groove and the through groove both penetrate the protective layer.

[0013] In one embodiment, the flexible circuit board further includes a conductive structure, and the conductive structure is used to electrically connect adjacent conductive circuit layers.

[0014] An embodiment of the present application provides a method for preparing a flexible circuit board that is resistant to bending, comprising the following steps:

[0015] A copper-clad laminate is provided, wherein the copper-clad laminate comprises a flexible substrate layer and a copper foil layer disposed on at least one surface of the flexible substrate layer, and the copper foil layer is manufactured to form a conductive circuit layer;

[0016] A protective layer is arranged on the outer side of the outermost conductive circuit layer to obtain an intermediate; the protective layer has a blind groove, and a part of the surface of the flexible substrate layer is exposed from the blind groove;

[0017] A through groove is provided on the intermediate body, wherein the through groove penetrates the intermediate body along the thickness direction to obtain the flexible circuit board;

[0018] Among them, the flexible circuit board includes a bending zone, and the bending zone includes a first bending zone, a second bending zone, a third bending zone and a through groove; the first bending zone is an area in the flexible circuit board corresponding to the blind groove; along the length direction of the flexible circuit board, the second bending zone is an area located on both sides of the through groove; along the width direction of the flexible circuit board, the third bending zone is an area connecting adjacent second bending zones.

[0019] In one embodiment, before the step of setting a protective layer on the outer side of the outermost conductive circuit layer, the preparation method also includes: laminating an adhesive layer and a substrate on the side of the conductive circuit layer away from the flexible substrate layer, the substrate including a dielectric layer and a metal layer, and the adhesive layer being located between the conductive circuit layer and the dielectric layer; and forming the metal layer to form another conductive circuit layer.

[0020] The flexible circuit board described in the present application is provided with a first bending zone, a second bending zone, a third bending zone and a through groove. The first bending zone and the second bending zone play the role of main bending and secondary bending respectively. The third bending zone can be torsional and swinging deformation, and the through groove can release bending or torsional stress, so that the flexible circuit board is transformed from the traditional pure bending deformation to a combined deformation with torsional and swinging deformation as the main and bending deformation as the auxiliary, thereby greatly reducing the bending stress borne by the flexible circuit board, and thus making the flexible circuit board have good dynamic bending performance. The flexible circuit board described in the present application does not need to select thinner materials for bending performance considerations, so materials of conventional thickness can be selected, which has a wider range of applications and reduces material costs and process difficulty. In addition, there is no opening (Airgap) design in the adhesive layer of the flexible circuit board described in the present application, so the risk of delamination and explosion of the opening edge is eliminated. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A cross-sectional view of a flexible circuit board provided in accordance with one embodiment of the present application.

[0022] Figure 2 for Figure 1 The diagram is a schematic plan view of the structure of a bending area of ​​a flexible printed circuit board in one embodiment.

[0023] Figure 3 for Figure 1 The diagram is a schematic plan view of the structure of a bending area of ​​a flexible printed circuit board in another embodiment.

[0024] Figure 4 for Figure 1 The diagram is a schematic plan view of the structure of a bending area of ​​a flexible printed circuit board in another embodiment.

[0025] Figure 5 for Figure 1The diagram is a schematic plan view of the structure of a bending area of ​​a flexible printed circuit board in another embodiment.

[0026] Figure 6 for Figure 1 The diagram shows a planar structure diagram of the second bending area and the third bending area of ​​the flexible circuit board in one embodiment.

[0027] Figure 7 for Figure 1 The diagram shows a planar structure diagram of the second bending region and the third bending region of the flexible circuit board in another embodiment.

[0028] Figure 8 for Figure 1 The diagram shows a planar structure diagram of the second bending region and the third bending region of the flexible circuit board in another embodiment.

[0029] Fig. 9 for Figure 1 The diagram shows a planar structure diagram of the second bending region and the third bending region of the flexible circuit board in another embodiment.

[0030] Fig.10 for Figure 1 The diagram shows a planar structure diagram of the second bending region and the third bending region of the flexible circuit board in another embodiment.

[0031] Figures 11 to 14 A cross-sectional view of a method for preparing a flexible circuit board is provided in one embodiment of the present application.

[0032] Main component symbols

[0033] Flexible circuit board 100

[0034] Flexible substrate layer 10

[0035] Conductive circuit layer 20

[0036] Adhesive layer 30

[0037] Protective layer 40

[0038] Conductive structure 50

[0039] Double-sided board 11

[0040] Single sided board 12

[0041] Blind Slot 101

[0042] Through groove 102

[0043] Bending zone 110

[0044] The first bending area 111

[0045] The second bending area 112

[0046] The third bending area 113

[0047] Copper foil layer 21

[0048] Base plate 60

[0049] Dielectric layer 61

[0050] Metal layer 62

[0051] Intermediate 70

[0052] Length direction x

[0053] Width direction y

[0054] Thickness direction z

[0055] The following specific implementation manner will further illustrate the embodiments of the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the technical field of the present application. The terms used herein are only for the purpose of describing specific implementation methods and are not intended to limit the present application embodiments.

[0057] It should be noted that all directional indications in the embodiments of the present application (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0058] It will be understood that when a layer is referred to as being “on” another layer, it can be directly on the other layer or intervening layers may be present therebetween. In contrast, when a layer is referred to as being “directly on” another layer, there are no intervening layers present.

[0059] Here, the embodiments of the present application are described with reference to the cross-sectional views, which are schematic diagrams of the idealized embodiments (and intermediate configurations) of the present application. Thus, it is foreseeable that the shapes of the diagrams are different due to manufacturing processes and / or tolerances. Therefore, the embodiments of the present application should not be interpreted as being limited to the specific shapes of the regions illustrated here, but should include deviations in shapes such as those produced due to manufacturing. The regions shown in the figures are themselves only schematic, and their shapes are not intended to illustrate the actual shapes of the devices, and are not intended to limit the scope of the present application.

[0060] Some embodiments of the present application are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0061] See also Figure 1 In a first aspect, the present application provides a flexible circuit board 100 that is resistant to bending, which includes at least one flexible substrate layer 10 and at least one conductive circuit layer 20 formed on the surface of the flexible substrate layer 10. In this embodiment, the flexible circuit board 100 includes a double-sided board 11 (including a flexible substrate layer 10 and two conductive circuit layers 20 formed on two opposite surfaces of the flexible substrate layer 10), a single-sided board 12 (including a flexible substrate layer 10 and two conductive circuit layers 20 formed on two opposite surfaces of the flexible substrate layer 10), and an adhesive layer 30 located between the double-sided board 11 and the single-sided board 12, and the adhesive layer 30 is located between the flexible substrate layer 10 of the single-sided board 12 and the conductive circuit layer 20 of the double-sided board 11. That is, in this embodiment, the flexible circuit board 100 includes two flexible substrate layers 10, three conductive circuit layers 20, and one adhesive layer 30. In other embodiments, the flexible circuit board 100 may be a single-sided board 12, which includes a flexible substrate layer 10 and a conductive circuit layer 20 (without an adhesive layer 30); or, the flexible circuit board 100 may be a double-sided board 11, which includes a flexible substrate layer 10 and two conductive circuit layers 20 (without an adhesive layer 30) formed on opposite surfaces of the flexible substrate layer 10, respectively; or, the flexible circuit board 100 may also include more than three conductive circuit layers 20.

[0062] like Figure 1 As shown, the flexible circuit board 100 has a blind groove 101 and a through groove 102. Along the thickness direction z of the flexible circuit board 100, the blind groove 101 does not penetrate the entire flexible circuit board 100, but only penetrates to the outermost conductive circuit layer 20. The blind groove 101 is arranged corresponding to the gap of the outermost conductive circuit layer 20 (not containing the circuit pattern of the conductive circuit layer 20), and part of the surface of the flexible substrate layer 10 is exposed from the blind groove 101, that is, the bottom wall of the blind groove 101 is the flexible substrate layer 10. In this embodiment, both the double-sided board 11 and the single-sided board 12 are provided with a blind groove 101, and the blind groove 101 of the double-sided board 11 and the blind groove 101 of the single-sided board 12 can be arranged correspondingly, and the number thereof is not limited in this application. Along the thickness direction z of the flexible circuit board 100, the through groove 102 penetrates the entire flexible circuit board 100. In this embodiment, the through groove 102 penetrates the double-sided board 11, the adhesive layer 30 and the single-sided board 12 along the thickness direction, and the number thereof is not limited in this application.

[0063] like Figure 1 and Figure 2As shown, the flexible circuit board 100 includes a bending area 110, and the bending area 110 includes a first bending area 111, a second bending area 112, a third bending area 113 and a through groove 102. The first bending area 111 is an area corresponding to the blind groove 101 in the flexible circuit board 100, and the first bending area 111 does not carry the pattern of the conductive circuit layer 20. In this embodiment, the first bending area 111 is roughly the area formed by the flexible substrate layer 10 and the adhesive layer 30 corresponding to the blind groove 101. Along the length direction x of the flexible circuit board 100, the second bending area 112 is the area located on both sides of the through groove 102, and the second bending area 112 can carry the pattern of the conductive circuit layer 20. In this embodiment, as Figure 2 As shown, the second bending area 112 is roughly the area formed by the flexible substrate layer 10, the conductive circuit layer 20 and the adhesive layer 30 on the left or right side of the through groove 102. Observed along the thickness direction z, the shape of the second bending area 112 can be rectangular, that is, the orthographic projection of the second bending area 112 in the thickness direction can be rectangular. Along the width direction y of the flexible circuit board 100, the third bending area 113 is an area for connecting two adjacent second bending areas 112. The third bending area 113 can carry the pattern of the conductive circuit layer 20.

[0064] In the present application, the first bending zone 111 is the main body participating in the bending deformation of the flexible circuit board 100. The second bending zone 112 participates in the bending deformation of the flexible circuit board 100 to a lesser extent and is a secondary bending deformation zone. The third bending zone 113 can be torsional and swing-deformed and is the main body participating in the torsional deformation between adjacent second bending zones 112. The hollow gap of the through groove 102 is used to release the bending or torsional stress of the area, so that the bending resistance of the flexible circuit board 100 is better.

[0065] like Figure 1 As shown, in some embodiments, the flexible circuit board 100 further includes a protective layer 40. The protective layer 40 is located on the outside of the outermost conductive circuit layer 20, and the blind groove 101 and the through groove 102 both penetrate the protective layer 40. In this embodiment, the protective layer 40 is a cover film layer (cover-lay, CVL). The protective layer 40 is used to protect the conductive circuit layer 20 from external water vapor invasion or scratches by foreign objects. The thickness of the protective layer 40 may be 17.5 to 55 μm, which is suitable for products with thick conductor circuit designs. Specifically, the thickness of the base material layer (for example, polyimide PI) in the covering film layer may be 7.5 to 25 μm, and the thickness of the adhesive layer (for example, acrylic hot melt adhesive AD) in the covering film layer may be 10 to 30 μm.

[0066] like Figure 1 As shown, the flexible circuit board 100 further includes a conductive structure 50. The conductive structure 50 is used to electrically connect adjacent conductive circuit layers 20. The conductive structure 50 can be a conductive hole or a conductive column, etc., which is not limited in the present application.

[0067] like Figures 2 to 5 As shown, in the bending zone 110 of the present application, the number of the first bending zone 111, the second bending zone 112, the third bending zone 113 and the through groove 102 and their combinations and matching can be adjusted according to needs, and the present application does not impose any restrictions.

[0068] like Figure 4 As shown, in some embodiments, along the width direction y of the flexible circuit board 100, the width W1 of the first bending zone 111 is 0.5-3 mm, and the width W2 of the second bending zone 112 is greater than or equal to 3 mm. In this way, the flexible circuit board 100 can be guaranteed to have good dynamic bending performance. When the flexible circuit board 100 is bent, the minimum bending radius r of the first bending zone 111 is much smaller than the minimum bending radius R of the second bending zone 112, and R is generally 5 to 10 times of r. That is, the bending deformation of the second bending zone 112 is small, and the stress of the corresponding line bending is small.

[0069] like Figure 5 As shown, in some embodiments, along the length direction x of the flexible circuit board 100, the width of the third bending zone 113 is greater than or equal to 0.5 mm. In this way, the third bending zone 113 can be guaranteed to have a certain strength so that it can be twisted and swung.

[0070] like Figures 6 to 10 As shown, in some embodiments, the positive projection of the third bending zone 113 along the thickness direction z of the flexible circuit board 100 is a straight line, an oblique line, a V-shape, a U-shape or an S-shape. That is, when observed along the thickness direction z of the flexible circuit board 100, the shape of the third bending zone 113 can be a straight line, an oblique line, a V-shape, a U-shape or an S-shape. Preferably, the shape of the third bending zone 113 can be a V-shape, a U-shape or an S-shape, which has good torsional swinging ability when the flexible circuit board 100 is bent, reduces the demand for the bending strength of the flexible circuit board 100, and makes the bending and torsional stresses generated by the corresponding circuit smaller.

[0071] In some embodiments, the thickness of the flexible substrate layer 10 is 12.5 to 50 μm, and the thickness of the conductive circuit layer 20 is 9 to 35 μm. Since in the bending area 110 of the flexible circuit board 100 of the present application, the first bending area 111 and the second bending area 112 respectively play the role of primary bending and secondary bending, the third bending area 113 can be twisted and swung, and the through groove 102 can release the bending or torsional stress, so that the bending stress borne by the flexible circuit board 100 is greatly reduced, so that the flexible circuit board 100 has good dynamic bending performance. Therefore, the flexible circuit board 100 described in the present application does not need to select a thinner material for bending performance considerations. The flexible circuit board 100 described in the present application can use materials of conventional thickness, which has a wider range of applications.

[0072] In some embodiments, the material of the flexible substrate layer 10 may be, but not limited to, polyimide (PI), polyester resin (PET), polyethylene terephthalate (PEN), polydimethylsiloxane (PDMS), etc. In this embodiment, the material of the flexible substrate layer 10 is PI. The material of the adhesive layer 30 may be, but not limited to, BS (epoxy-based pure glue).

[0073] See also Figures 11 to 14 as well as Figure 1 In a second aspect, the present application provides a method for preparing a bending-resistant flexible circuit board 100, which includes steps S10 to S50. It is understandable that the numbering of the steps is intended to clearly describe the specific preparation method, and is not intended to limit the order of the steps.

[0074] See also Fig.11 , step S10, providing a copper clad laminate (not shown), the copper clad laminate comprising a flexible substrate layer 10 and a copper foil layer 21 disposed on at least one surface of the flexible substrate layer, and then the copper foil layer 21 is fabricated to form a conductive circuit layer 20. In this embodiment, the copper clad laminate comprises a flexible substrate layer 10 and copper foil layers 21 disposed on two opposite surfaces of the flexible substrate layer 10, one of the copper foil layers 21 is fabricated to form a conductive circuit layer 20, and the conductive circuit layer 20 can be formed by an image transfer process and an etching process.

[0075] See also Fig.12 , step S20, laminating the adhesive layer 30 and the substrate 60 on the side of the conductive circuit layer 20 away from the flexible substrate layer 10. The substrate 60 includes a dielectric layer 61 and a metal layer 62, and the adhesive layer 30 is located between the conductive circuit layer 20 and the dielectric layer 61. The dielectric layer 61 can be, but is not limited to, a flexible substrate such as PI, PET, PEN, PDMS, etc. In this embodiment, the material of the dielectric layer 61 is PI, and the material of the dielectric layer 61 can be the same as that of the flexible substrate layer 10. In this embodiment, the metal layer 62 is a copper foil layer. That is, the substrate 60 in this embodiment is a copper clad laminate.

[0076] See also Fig.13, step S30, the metal layer 62 is made into another conductive circuit layer 20, and the substrate 60 becomes a single-sided board 12. At the same time, the copper foil layer 21 on the surface can also be made into another conductive circuit layer 20, and the previous copper-clad board becomes a double-sided board 11 after circuit etching. These two conductive circuit layers 20 can also be formed by image transfer process and etching process. It can be understood that while making the conductive circuit layer 20, a conductive structure 50 can also be made in the single-sided board 12 and the double-sided board 11 to electrically connect the conductive circuit layer 20 of the single-sided board 12 with the conductive circuit layer 20 of the double-sided board 11. The conductive structure 50 can be a conductive hole or a conductive column, etc., which is not limited in this application.

[0077] In some embodiments, further layers may be added outside the conductive circuit layer 20 to form a flexible circuit board 100 having more than three conductive circuit layers 20 .

[0078] See also Fig.14 In step S40, a protective layer 40 is disposed outside the outermost conductive circuit layer 20 to obtain an intermediate body 70. The protective layer 40 has a blind groove 101, and a portion of the surface of the flexible substrate layer 10 is exposed from the blind groove 101.

[0079] See also Figure 1 In step S50, a through groove 102 is provided on the intermediate body 70, and the through groove 102 penetrates the intermediate body 70 along the thickness direction to obtain the flexible circuit board 100. The through groove 102 can be formed by, but not limited to, punching or UV cutting.

[0080] like Figure 1 As shown, when the through groove 102 is formed, a bending area 110 is formed on the flexible circuit board 100. The bending area 110 includes a first bending area 111, a second bending area 112, a third bending area 113 and the through groove 102. The first bending area 111 is an area corresponding to the blind groove 101 in the flexible circuit board 100, and the first bending area 111 does not carry the pattern of the conductive circuit layer 20. In this embodiment, the first bending area 111 is roughly the area formed by the flexible substrate layer 10 and the adhesive layer 30 corresponding to the blind groove 101. Figure 2 As shown, along the length direction x of the flexible circuit board 100, the second bending area 112 is the area located on both sides of the through slot 102, and the second bending area 112 carries the pattern of the conductive circuit layer 20. In this embodiment, the second bending area 112 is roughly the area formed by the flexible substrate layer 10, the conductive circuit layer 20 and the adhesive layer 30 on the left or right side of the through slot 102. When viewed along the thickness direction z, the shape of the second bending area 112 can be a rectangle, that is, the orthographic projection of the second bending area 112 in the thickness direction can be a rectangle. Figure 2As shown, along the width direction y of the flexible circuit board 100 , the third bending area 113 is a region for connecting two adjacent second bending areas 112 . The third bending area 113 can carry the pattern of the conductive circuit layer 20 .

[0081] The flexible circuit board 100 described in the present application is provided with a bending area 110 having a first bending area 111, a second bending area 112, a third bending area 113 and a through groove 102. The first bending area 111 and the second bending area 112 respectively play the role of main bending and secondary bending, the third bending area 113 can be torsional and swinging deformation, and the through groove 102 can release bending or torsional stress, so that the flexible circuit board 100 is transformed from the traditional pure bending deformation to a combined deformation with torsional and swinging deformation as the main and bending deformation as the auxiliary, so that the bending stress borne by the flexible circuit board 100 is greatly reduced, and the flexible circuit board 100 has good dynamic bending performance. The flexible circuit board 100 described in the present application does not need to select a thinner material for bending performance considerations, so a material of conventional thickness can be selected, which has a wider range of application and reduces material cost and process difficulty. In addition, there is no opening (Airgap) design in the adhesive layer 30 of the flexible circuit board 100 described in the present application, so the risk of delamination and explosion of the opening edge is eliminated.

[0082] The above descriptions are some specific implementations of the present application, but they are not limited to these implementations in actual application. For ordinary technicians in this field, other variations and changes made according to the technical concept of the present application should all fall within the protection scope of the present application.

Claims

1. A flexible circuit board resistant to bending, characterized in that: The flexible circuit board comprises at least one flexible substrate layer and at least one conductive circuit layer formed on the surface of the flexible substrate layer, wherein the flexible circuit board has a blind groove and a through groove, a part of the surface of the flexible substrate layer is exposed from the blind groove, and the through groove penetrates the flexible circuit board along the thickness direction; The flexible circuit board includes a bending zone, and the bending zone includes a first bending zone, a second bending zone, a third bending zone and a through groove; the first bending zone is an area in the flexible circuit board corresponding to the blind groove; along the length direction of the flexible circuit board, the second bending zone is an area located on both sides of the through groove; along the width direction of the flexible circuit board, the third bending zone is an area used to connect two adjacent second bending zones.

2. The flexible circuit board according to claim 1, characterized in that: Along the width direction of the flexible circuit board, the width of the first bending zone is 0.5-3 mm, and the width of the second bending zone is greater than or equal to 3 mm.

3. The flexible circuit board according to claim 1, characterized in that: Along the length direction of the flexible circuit board, the width of the third bending zone is greater than or equal to 0.5 mm.

4. The flexible circuit board according to claim 1, characterized in that: The orthographic projection of the third bending zone along the thickness direction of the flexible circuit board is a straight line, an oblique line, a V-shape, a U-shape or an S-shape.

5. The flexible circuit board according to claim 1, characterized in that: The thickness of the flexible substrate layer is 12.5-50 μm, and the thickness of the conductive circuit layer is 9-35 μm.

6. The flexible circuit board according to claim 1, characterized in that: When the number of the conductive circuit layer is greater than or equal to three, the flexible circuit board further comprises at least one adhesive layer, and the adhesive layer is located between one of the flexible substrate layers and one of the conductive circuit layers.

7. The flexible circuit board according to claim 1, characterized in that: The flexible circuit board further comprises a protective layer, which is located on the outer side of the outermost conductive circuit layer, and the blind groove and the through groove both penetrate the protective layer.

8. The flexible circuit board according to claim 1, characterized in that: The flexible circuit board also includes a conductive structure, and the conductive structure is used to electrically connect adjacent conductive circuit layers.

9. A method for preparing a bending-resistant flexible circuit board, characterized in that: The steps include: A copper-clad laminate is provided, wherein the copper-clad laminate comprises a flexible substrate layer and a copper foil layer disposed on at least one surface of the flexible substrate layer, and the copper foil layer is manufactured to form a conductive circuit layer; A protective layer is arranged on the outer side of the outermost conductive circuit layer to obtain an intermediate; the protective layer has a blind groove, and a part of the surface of the flexible substrate layer is exposed from the blind groove; A through groove is provided on the intermediate body, wherein the through groove penetrates the intermediate body along the thickness direction to obtain the flexible circuit board; Among them, the flexible circuit board includes a bending zone, and the bending zone includes a first bending zone, a second bending zone, a third bending zone and a through groove; the first bending zone is an area in the flexible circuit board corresponding to the blind groove; along the length direction of the flexible circuit board, the second bending zone is an area located on both sides of the through groove; along the width direction of the flexible circuit board, the third bending zone is an area connecting adjacent second bending zones.

10. The preparation method according to claim 9, characterized in that: Before the step of setting a protective layer on the outer side of the outermost conductive circuit layer, the preparation method also includes: laminating an adhesive layer and a substrate on the side of the conductive circuit layer away from the flexible substrate layer, the substrate including a dielectric layer and a metal layer, and the adhesive layer being located between the conductive circuit layer and the dielectric layer; and forming the metal layer to form another conductive circuit layer.

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