TWI850065B - Flexible printed circuit with bending resistance and preparation method thereof - Google Patents

Abstract

The present application provides a flexible printed circuit with bending resistance and a preparation method thereof. The flexible printed circuit comprises a bending area with a first bending area, a second bending area, a third bending area, and a groove. The first bending area serves as a main bending area, and the second bending area serves as a secondary bending area. The third bending area can twist and swing deformation, and the groove can release bending or torsional stress, so that the bending stress borne by the flexible printed circuit is greatly reduced, resulting in good dynamic bending performance of the flexible printed circuit. The flexible printed circuit can be made of materials of conventional thickness, with a wider application range and reduced material cost and process difficulty. In addition, the adhesive layer of the flexible printed circuit does not have an airgap, thus eliminating the risk of layered explosion of the opening edge.

Description

Bending-resistant flexible circuit board and preparation method thereof

This application relates to the field of circuit board technology, and in particular to a bending-resistant flexible circuit board and its preparation method.

Folding screen mobile phones have the characteristics of being foldable, having large screens, and requiring small storage space, and have achieved rapid development in recent years. The number of folding times of folding 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 circuit board (FPC) responsible for the electrical connection between the folding screens has also increased accordingly.

12μm、基材層厚度

12.5μm，防護層厚度

27.5μm，材料成本和製程難度相對較高；出於彎折性能考慮，線路導體層厚度

18μm，不適用於有厚導體電路設計要求的產品。 At present, in order to improve the dynamic bending performance of FPC (bending times of 300,000 times or more), the industry often 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 design has the following shortcomings and disadvantages: 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 during the process (such as lamination of the protective layer and the reinforcement sheet, etc.), which may cause the edge of the opening to delaminate and explode; for bending performance considerations, the FCCL and the protective layer need to be made of thinner materials, for example, the thickness of the copper foil layer in the FCCL is

12μm, substrate layer thickness

12.5μm, protective layer thickness

27.5μm, the material cost and process difficulty are relatively high; for bending performance considerations, the thickness of the line conductor layer

18μm, not suitable for products requiring thick conductor circuit design.

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

An embodiment of the present application provides a bending-resistant flexible circuit board, which includes at least one flexible substrate layer and at least one conductive line layer formed on the surface of the flexible substrate layer. The flexible circuit board has a blind groove and a through groove, and part 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.

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, a blind groove and a through groove. The first bending area is the 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 the area located on both sides of the through groove. Along the width direction of the flexible circuit board, the third bending area is the area used to connect two adjacent second bending areas.

In one implementation, along the width direction of the flexible circuit board, the width of the first bending area is 0.5-3 mm, and the width of the second bending area is greater than or equal to 3 mm.

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

In one embodiment, the orthographic projection of the third bending area 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.

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

In one embodiment, when the number of the conductive circuit layer is greater than or equal to three layers, 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.

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

In one embodiment, the flexible circuit board further includes a conductive structure, and the conductive structure is used to electrically connect the adjacent conductive line layer.

An embodiment of the present application provides a method for preparing a bending-resistant flexible circuit board, comprising the following steps: providing a copper-clad plate, the copper-clad plate comprising a flexible substrate layer and a copper foil layer disposed on at least one surface of the flexible substrate layer, and manufacturing the copper foil layer to form a conductive line layer; providing a protective layer on the outer side of the outermost conductive line layer to obtain an intermediate; the protective layer has a blind groove, and a portion of the surface of the flexible substrate layer is exposed from the blind groove; providing a through groove on the intermediate, and the through groove is formed along the thickness direction. The intermediate body is penetrated in the direction of the flexible circuit board to obtain the flexible circuit board; wherein 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, a blind groove and a through groove; the first bending area is the 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 the area located on both sides of the through groove; along the width direction of the flexible circuit board, the third bending area is the area connecting the adjacent second bending areas.

In one embodiment, before the step of providing a protective layer on the outer side of the outermost conductive circuit layer, the preparation method further includes: pressing 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, the adhesive layer being located between the conductive circuit layer and the dielectric layer; and manufacturing the metal layer to form another conductive circuit layer.

The flexible circuit board described in the present application is provided with a bending area having a first bending area, a second bending area, a third bending area and a through groove. The first bending area and the second bending area respectively play the role of primary bending and secondary bending, the third bending area can be deformed by twisting and swinging, 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 twisting 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 this 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 airgap design in the adhesive layer of the flexible circuit board described in this application, thus eliminating the risk of delamination and board explosion at the edge of the opening.

100: Flexible circuit board

10: Flexible substrate layer

20: Conductive line layer

30: Adhesive layer

40: Protective layer

50: Conductive structure

11:Dual panel

12: Single panel

101: Blind slot

102: Through slot

110: Bend area

111: First bend area

112: Second bend area

113: The third bend

21: Copper foil layer

60: Substrate

61: Dielectric layer

62:Metal layer

70: Intermediate

x: length direction

y: width direction

z: thickness direction

Figure 1 is a cross-sectional view of a flexible circuit board provided in an embodiment of this application.

FIG2 is a schematic diagram of the planar structure of the bending area of the flexible circuit board shown in FIG1 in one embodiment.

FIG3 is a schematic diagram of the planar structure of the bending area of the flexible circuit board shown in FIG1 in another embodiment.

FIG4 is a schematic diagram of the planar structure of the bending area of the flexible circuit board shown in FIG1 in another embodiment.

FIG5 is a schematic diagram of the planar structure of the bending area of the flexible circuit board shown in FIG1 in another embodiment.

FIG6 is a schematic diagram of the planar structure of the second bending area and the third bending area of the flexible circuit board shown in FIG1 in one embodiment.

FIG. 7 is a schematic diagram of the planar structure of the second bending area and the third bending area of the flexible circuit board shown in FIG. 1 in another embodiment.

FIG8 is a schematic diagram of the planar structure of the second bending area and the third bending area of the flexible circuit board shown in FIG1 in another embodiment.

FIG9 is a schematic diagram of the planar structure of the second bending area and the third bending area of the flexible circuit board shown in FIG1 in another embodiment.

FIG10 is a schematic diagram of the planar structure of the second bending area and the third bending area of the flexible circuit board shown in FIG1 in another embodiment.

Figures 11 to 14 are cross-sectional views of the preparation of a flexible circuit board provided in an embodiment of this application.

Unless otherwise defined, all technical and scientific terms used in this article have the same meaning as those commonly understood by technicians in the technical field of the embodiment of this application. The terms used in this article are only for the purpose of describing specific implementation methods and are not intended to limit the embodiment of this application.

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

It will be understood that when a layer is referred to as being "on" another layer, it may be directly on the other layer or there may be intervening layers therebetween. Conversely, when a layer is referred to as being "directly on" another layer, there are no intervening layers.

Embodiments of the present application are described herein with reference to cross-sectional views, which are schematic views of idealized embodiments (and intermediate configurations) of the present application. As such, variations in the shapes illustrated due to manufacturing processes and/or tolerances are to be expected. Therefore, embodiments of the present application should not be construed as limited to the specific shapes of the regions illustrated herein, but should include deviations in shape resulting, for example, from manufacturing. The regions illustrated in the figures are merely schematic in themselves, 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.

The following is a detailed description of some implementation methods of this application in conjunction with the attached figures. In the absence of conflict, the following implementation methods and features in the implementation methods can be combined with each other.

Please refer to FIG. 1 . In a first aspect, the present application provides a bending-resistant flexible circuit board 100 , which includes at least one flexible substrate layer 10 and at least one conductive circuit layer 20 formed on a 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 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 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; or, the flexible circuit board 100 may also include more than three conductive circuit layers 20.

As shown in FIG1 , 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 the 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 of through grooves 102 is not limited in this application.

As shown in FIG. 1 and FIG. 2 , 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, a blind groove 101, and a through groove 102. The first bending area 111 is a region of the flexible circuit board 100 corresponding to the blind groove 101, and the first bending area 111 does not carry the pattern of the conductive line layer 20. In this embodiment, the first bending area 111 is roughly the region 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 an area located on both sides of the through slot 102, and the second bending area 112 can carry the pattern of the conductive line layer 20. In this embodiment, as shown in FIG. 2, the second bending area 112 is roughly an area formed by the flexible substrate layer 10, the conductive line layer 20 and the adhesive layer 30 on the left or right side of the through slot 102. Observed 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. 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 line layer 20.

In this 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 twisted and swung to deform, and is the main body participating in the torsion deformation between the adjacent second bending zones 112. The hollow gap of the through groove 102 is used to release the bending or torsion stress of the area, so that the bending resistance of the flexible circuit board 100 is better.

As shown in FIG. 1 , in some embodiments, the flexible circuit board 100 further includes a protective layer 40. The protective layer 40 is located on the outer side of the outermost conductive circuit layer 20, and the blind slot 101 and the through slot 102 both penetrate the protective layer 40. In this embodiment, the protective layer 40 is a cover-lay (CVL). The protective layer 40 is used to protect the conductive circuit layer 20 from being invaded by external water vapor or scratched by foreign objects. The thickness of the protective layer 40 can be 17.5~55μm, which is suitable for products with thick conductor circuit design. Specifically, the thickness of the base material layer (e.g., polyimide PI) in the covering film layer can be 7.5~25μm, and the thickness of the adhesive layer (e.g., acrylic hot melt adhesive AD) in the covering film layer can be 10~30μm.

As shown in FIG. 1 , the flexible circuit board 100 also includes a conductive structure 50. The conductive structure 50 is used to electrically connect the adjacent conductive line layer 20. The conductive structure 50 can be a conductive hole or a conductive column, etc., and this application does not limit it.

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

As shown in FIG. 4 , 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 5-10 times of r. That is, the bending deformation of the second bending zone 112 is smaller, and the stress of the corresponding circuit bending is smaller.

As shown in FIG. 5 , in some embodiments, along the length direction x of the flexible circuit board 100, the width of the third bending area 113 is greater than or equal to 0.5 mm. In this way, it is possible to ensure that the third bending area 113 has a certain strength so that it can be twisted and swung.

As shown in Figures 6 to 10, 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 stress generated by the corresponding circuit smaller.

In some embodiments, the thickness of the flexible substrate layer 10 is 12.5-50 μm, and the thickness of the conductive line layer 20 is 9-35 μm. 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 the main bending and the secondary bending, and the third bending area 113 can be twisted and swung to deform, 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 this application does not need to select thinner materials for bending performance considerations. The flexible circuit board 100 described in this application can use materials of conventional thickness, which has a wider range of applications.

In some embodiments, the material of the flexible substrate layer 10 may be, but is not limited to, polyimide (PI), polyester (PET), polyethylene naphthalate diformic acid glycol ester (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 is not limited to, BS (epoxy-based pure rubber).

Please refer to Figures 11 to 14 and Figure 1. The second aspect of this application provides a method for preparing a bending-resistant flexible circuit board 100, which includes steps S10 to S50. It can be understood that the numbering of the steps is intended to clearly describe the specific preparation method, and does not limit the order of the steps.

Please refer to Figure 11, step S10, providing a copper-clad laminate (not shown), the copper-clad laminate includes 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 made into a conductive circuit layer 20. In this embodiment, the copper-clad laminate includes 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 made into a conductive circuit layer 20, and the conductive circuit layer 20 can be formed by an image transfer process and an etching process.

Please refer to Figure 12, step S20, the adhesive layer 30 and the substrate 60 are pressed on the side of the conductive line 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 line layer 20 and the dielectric layer 61. The dielectric layer 61 can be but 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 plate.

Please refer to 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., and this application does not limit this.

In some embodiments, further layers may be added on the outer side of the conductive circuit layer 20 to form a flexible circuit board 100 having more than three conductive circuit layers 20.

Please refer to Figure 14, step S40, a protective layer 40 is provided on the outer side of the outermost conductive circuit layer 20 to obtain an intermediate 70. The protective layer 40 has a blind groove 101, and part of the surface of the flexible substrate layer 10 is exposed from the blind groove 101.

Please refer to Figure 1, 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 a flexible circuit board 100. The through groove 102 can be formed by, but not limited to, punching or UV cutting.

As shown in FIG. 1 , when the through slot 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 slot 102. The first bending area 111 is a region of the flexible circuit board 100 corresponding to the blind slot 101, and the first bending area 111 does not carry the pattern of the conductive line layer 20. In this embodiment, the first bending area 111 is roughly a region formed by the flexible substrate layer 10 and the adhesive layer 30 corresponding to the blind slot 101. As shown in FIG. 2 , along the length direction x of the flexible circuit board 100, the second bending area 112 is an area located on both sides of the through slot 102, and the second bending area 112 carries the pattern of the conductive line layer 20. In this embodiment, the second bending area 112 is roughly an area formed by the flexible substrate layer 10, the conductive line layer 20 and the adhesive layer 30 on the left or right side of the through slot 102. Observed 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. As shown in FIG. 2 , 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 line layer 20.

The flexible circuit board 100 of 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 primary bending and secondary bending, the third bending area 113 can be deformed by twisting and swinging, and the through groove 102 can release bending or twisting stress, so that the flexible circuit board 100 is transformed from the traditional pure bending deformation to a combined deformation with twisting 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 thus the flexible circuit board 100 has good dynamic bending performance. The flexible circuit board 100 described in this 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, the adhesive layer 30 of the flexible circuit board 100 described in this application does not have an airgap design, thus eliminating the risk of delamination and board explosion at the edge of the opening.

100: Flexible circuit board

10: Flexible substrate layer

20: Conductive line layer

30: Adhesive layer

40: Protective layer

50: Conductive structure

11:Dual panel

101: Blind slot

102: Through slot

110: Bend area

111: First bend area

112: Second bend area

113: The third bend

z: thickness direction

Claims (10)

A flexible circuit board resistant to bending, which is improved in that it includes at least one flexible substrate layer and at least one conductive line layer formed on the surface of the flexible substrate layer, 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 area, and the bending area includes a first conductive line layer formed on the surface of the flexible substrate layer; the first conductive line layer formed on the surface of the flexible substrate layer; the second ... A first bending area, a second bending area, a third bending area, a blind groove and a through groove; the first bending area is the 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 the area located on both sides of the through groove; along the width direction of the flexible circuit board, the third bending area is the area used to connect two adjacent second bending areas. The flexible circuit board as described in claim 1, wherein along the width direction of the flexible circuit board, the width of the first bending area is 0.5-3 mm, and the width of the second bending area is greater than or equal to 3 mm. A flexible circuit board as described in claim 1, wherein the width of the third bending area along the length direction of the flexible circuit board is greater than or equal to 0.5 mm. A flexible circuit board as described in claim 1, wherein 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. The flexible circuit board as described in claim 1, wherein the thickness of the flexible substrate layer is 12.5-50 μm, and the thickness of the conductive line layer is 9-35 μm. As described in claim 1, the flexible circuit board, when the number of the conductive line layer is greater than or equal to three layers, 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 line layers. As described in claim 1, the flexible circuit board further includes a protective layer, the protective layer is located on the outer side of the outermost conductive line layer, and the blind groove and the through groove both penetrate the protective layer. The flexible circuit board as described in claim 1, wherein the flexible circuit board further includes a conductive structure, and the conductive structure is used to electrically connect the adjacent conductive line layer. A method for preparing a bending-resistant flexible circuit board is improved in that it includes the following steps: providing a copper-clad plate, the copper-clad plate including a flexible substrate layer and a copper foil layer disposed on at least one surface of the flexible substrate layer, and manufacturing the copper foil layer to form a conductive line layer; arranging a protective layer on the outer side of the outermost conductive line 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; arranging a through groove on the intermediate, and the through groove penetrates the conductive line layer in the thickness direction; The intermediate body is passed through to obtain the flexible circuit board; wherein 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, a blind groove and a through groove; the first bending area is the 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 the area located on both sides of the through groove; along the width direction of the flexible circuit board, the third bending area is the area connecting the adjacent second bending areas. The preparation method as described in claim 9, wherein before the step of providing a protective layer on the outer side of the outermost conductive circuit layer, the preparation method further comprises: pressing an adhesive layer and a substrate on the side of the conductive circuit layer away from the flexible substrate layer, the substrate comprising a dielectric layer and a metal layer, the adhesive layer being located between the conductive circuit layer and the dielectric layer; and manufacturing the metal layer to form another conductive circuit layer.

Images