Semi-flexed circuit board and preparation method thereof

Abstract

The present application provides a semi-flexible circuit board, comprising an intermediate flexible stack, an inner rigid stack, a first adhesive layer, an intermediate flexible stack, another first adhesive layer, and an outer rigid stack stack stacked in sequence. The inner rigid stack comprises a base layer and an inner circuit layer provided on two opposite surfaces of the base layer. The intermediate stack comprises a covering layer and a first intermediate circuit layer and a second intermediate circuit layer provided on two opposite surfaces of the covering layer, respectively. The outer rigid stack comprises a second adhesive layer, a first outer circuit layer, a third adhesive layer, and a second outer circuit layer stacked in sequence. The second intermediate circuit layer comprises a copper-retaining area, the copper-retaining area being defined by a first opening, the second adhesive layer being provided with a second opening, the third adhesive layer being provided with a third opening, and part of the covering layer being exposed to the first opening, the second opening, and the third opening. The semi-flexible circuit board is divided into a rigid board area and a semi-flexible area, and the semi-flexible area corresponds to the first opening and the second opening. The present application also provides a method for preparing a semi-flexible circuit board.

Description

Technical Field

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

[0002] The increasing diversity of electronic products has necessitated the bending of circuit boards. By bending circuit boards into various angles, three-dimensional assembly of finished electronic products is possible. Flexible circuit boards are categorized into three types: flexible printed circuit boards (FPCs), rigid-flex boards, and semi-flexible boards.

[0003] Electronic products requiring a semi-flex zone typically require bending the circuit board during assembly to achieve this effect. While rigid-flex and flexible circuit boards offer certain advantages in large-angle bending, their manufacturing process is complex and costly. Conventional semi-flex boards can save assembly space, enabling the development of smaller and lighter electronic products. However, the semi-flex zone offers limited circuit layout flexibility and low wiring density. Summary of the Invention

[0004] In order to solve the above shortcomings of the background technology, it is necessary to provide a semi-flexible circuit board and a preparation method thereof.

[0005] The present application provides a semi-flexible circuit board, comprising an inner rigid laminate, at least two intermediate flexible laminates, and an outer rigid laminate. The at least two intermediate flexible laminates are disposed on opposite surfaces of the inner rigid laminate, and the outer rigid laminate is disposed on a surface of the intermediate flexible laminate away from the inner rigid laminate. A first adhesive layer is disposed between the inner rigid laminate and adjacent intermediate flexible laminates, and another first adhesive layer is disposed between the outer rigid laminate and adjacent intermediate flexible laminates. The inner rigid laminate comprises a base layer and an inner circuit layer disposed on opposite surfaces of the base layer. The intermediate laminate comprises a cover layer and a first and second intermediate circuit layer disposed on opposite surfaces of the cover layer. The outer rigid laminate comprises a second adhesive layer, a first outer circuit layer, a third adhesive layer, and a second outer circuit layer, stacked in sequence. The first intermediate circuit layer is disposed between the second intermediate circuit layer and the inner circuit layer, the first outer circuit layer is disposed between the second outer circuit layer and the second intermediate circuit layer, the second intermediate circuit layer includes a copper retention area defining a first opening, the second adhesive layer has a second opening, and the third adhesive layer has a third opening. The orthogonal projection of the second opening on the cover layer completely overlaps with the orthogonal projection of the first opening on the cover layer, the orthogonal projection of the second opening on the cover layer is located within the orthogonal projection of the third opening on the cover layer, and a portion of the cover layer is exposed to the first, second, and third openings. Along the extension direction of the semi-flexible circuit board, the semi-flexible circuit board is divided into a rigid board area and a semi-flexible area. The rigid board area includes an outer rigid laminate structure, a portion of the intermediate flexible laminate structure corresponding to the outer rigid laminate structure, and a portion of the inner rigid laminate structure. The semi-flexible area corresponds to the first opening and the second opening.

[0006] In some possible implementations, the number of intermediate flexible stacking structures is more than two, the number of outer rigid stacking structures is two, the more than two intermediate flexible stacking structures are respectively arranged on the two opposite surfaces of the inner rigid stacking structure, and the two outer rigid stacking structures are respectively arranged on the surfaces of the two outermost intermediate flexible stacking structures. Along the thickness direction of the semi-flexed circuit board, the semi-flexed area is located at the center position of the semi-flexed circuit board or deviates from the center position of the semi-flexed circuit board.

[0007] In some possible implementations, the number of intermediate flexible stacking structures and outer rigid stacking structures is two, the two intermediate flexible stacking structures are respectively arranged on the two opposite surfaces of the inner rigid stacking structure, and the two outer rigid stacking structures are respectively arranged on the surfaces of the two intermediate flexible stacking structures. Along the thickness direction of the semi-flexed circuit board, the semi-flexed area is located at the center of the semi-flexed circuit board.

[0008] In some possible implementations, the cover layer is made of polyimide, and the base layer and the first adhesive layer are made of polypropylene.

[0009] In some possible implementations, the semi-flexed circuit board further includes a protective layer, which covers at least the surface and sidewalls of the third adhesive layer exposed to the second outer circuit layer.

[0010] The present application also provides a method for preparing a semi-flexible circuit board, comprising the following steps: providing an inner rigid stack and at least two intermediate flexible stacks, respectively arranging the at least two intermediate flexible stacks on opposite surfaces of the inner rigid stack, disposing a first adhesive layer between the inner rigid stack and an adjacent intermediate flexible stack, and disposing another first adhesive layer between the outer rigid stack and an adjacent intermediate flexible stack, wherein the inner rigid stack includes a base layer and an inner circuit layer disposed on opposite surfaces of the base layer, the intermediate stack includes a cover layer and a first intermediate circuit layer and a second intermediate circuit layer disposed on opposite surfaces of the cover layer, the first intermediate circuit layer being disposed between the second intermediate circuit layer and the inner circuit layer, the second intermediate circuit layer located on the outer side including a waste area and a copper retention area disposed around the waste area; and attaching a release film to the waste area. An outer-layer rigid stack is disposed on a second intermediate circuit layer having a release film. The outer-layer rigid stack includes a second adhesive layer, a first outer circuit layer, a third adhesive layer, and a second outer circuit layer stacked in sequence. The first outer circuit layer is disposed between the second outer circuit layer and the second intermediate circuit layer. The second adhesive layer is provided with a second opening. The third adhesive layer is provided with a third opening. The orthogonal projection of the second opening on the cover layer completely overlaps with the orthogonal projection of the first opening on the cover layer. The orthogonal projection of the second opening on the cover layer is located within the orthogonal projection of the third opening on the cover layer. The release film is disposed in the second opening and exposed to the third opening. The release film is removed to expose a waste area. The waste area is etched away so that a portion of the cover layer is exposed to the first opening, the second opening, and the third opening defined by the copper retention area, thereby obtaining a semi-flexed circuit board.

[0011] In some possible implementations, providing the outer rigid laminate specifically includes: sequentially laminating a second adhesive layer and a first copper foil layer on a second intermediate circuit layer having a release film; etching the first copper foil layer to obtain a first outer circuit layer; sequentially laminating a third adhesive layer and a second copper foil layer on the first outer circuit layer; and removing a portion of the second copper foil layer corresponding to the release film, exposing the release film to the second copper foil layer. When etching the waste area, the second copper foil layer is also etched to form the second outer circuit layer.

[0012] In some possible implementations, the number of intermediate flexible stacking structures and outer rigid stacking structures is two, the two intermediate flexible stacking structures are respectively arranged on the two opposite surfaces of the inner rigid stacking structure, and the two outer rigid stacking structures are respectively arranged on the surfaces of the two intermediate flexible stacking structures. Along the thickness direction of the semi-flexed circuit board, the semi-flexed area is located at the center of the semi-flexed circuit board.

[0013] In some possible implementations, the cover layer is made of polyimide, and the base layer and the first adhesive layer are made of polypropylene.

[0014] In some possible implementations, the preparation method further includes disposing a protective layer on the second outer circuit layer, wherein the protective layer at least covers the surface and sidewalls of the third adhesive layer exposed to the second outer circuit layer.

[0015] The semi-flexing zone of the present application can be set at any layer or any position of the circuit board, and the number of semi-flexing zones can be set according to actual needs. The processing is simple, the circuit board layout is flexible, and the wiring density is high. Furthermore, since there are at least two intermediate flexible stacks, the stress to which the semi-flexing zone is subjected during bending can be reduced, thereby increasing the maximum bendable angle. According to the requirements of the maximum bendable angle in actual applications, the number and position distribution of the intermediate flexible stacks can be appropriately adjusted to meet the customer's personalized customization needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of an inner layer rigid stack structure and a double-sided copper clad substrate provided in one embodiment of the present application.

[0017] Figure 2 For the general Figure 1 Schematic diagram of the inner layer rigid stack and the double-sided copper clad substrate after lamination and pressing.

[0018] Figure 3 For the general Figure 2 The diagram shows a double-sided copper clad substrate after the original copper layer is etched into a second intermediate circuit layer and a release film is attached.

[0019] Figure 4 For Figure 3The diagram shows a second adhesive layer and a first copper foil layer stacked in sequence and pressed together on the second intermediate circuit layer.

[0020] Figure 5 For the general Figure 4 The diagram shows the first copper foil layer after being etched into the first outer circuit layer.

[0021] Figure 6 For Figure 5 The diagram shows a first outer circuit layer after a third adhesive layer and a second copper foil layer are sequentially stacked and pressed together.

[0022] Figure 7 To remove Figure 6 Schematic diagram of part of the second copper foil layer shown.

[0023] Figure 8 To remove Figure 7 Schematic diagram after etching the release film and etching the second copper foil layer and part of the second intermediate circuit layer.

[0024] Figure 9 For Figure 8 Schematic diagram of a semi-flexed circuit board obtained after a protective layer is provided on the second outer circuit layer.

[0025] Description of main component symbols

[0026] Semi-flexed circuit board 1

[0027] Double-sided copper clad substrate 2

[0028] Release film 3

[0029] Inner layer hard stack 10

[0030] Grassroots 11

[0031] Inner circuit layer 12

[0032] First conductive pillar 13

[0033] Intermediate flexible stacking structure 20

[0034] Covering layer 21

[0035] First intermediate circuit layer 22

[0036] Second intermediate circuit layer 23

[0037] Original copper layer 24

[0038] Plated through hole 25

[0039] First adhesive layer 30

[0040] Outer layer hard stack 40

[0041] Second adhesive layer 41

[0042] First outer circuit layer 42

[0043] The third adhesive layer 43

[0044] Second outer circuit layer 44

[0045] First copper foil layer 45

[0046] Second conductive pillar 46

[0047] Second copper foil layer 47

[0048] The third conductive pillar 48

[0049] Protective layer 50

[0050] Hardboard Area 101

[0051] Semi-bending area 102

[0052] Main area 230

[0053] Waste Area 231

[0054] Copper area 232

[0055] Second opening 410

[0056] Glue flow area 411

[0057] The third opening 430

[0058] First opening 2320

[0059] Width W1

[0060] Thickness direction H

[0061] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0062] The following description will refer to the accompanying drawings to more fully describe the contents of this application. Illustrated in the accompanying drawings are exemplary embodiments of the present application. However, the present application can be implemented in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. These exemplary embodiments are provided to make this application thorough and complete and to fully convey the scope of this application to those skilled in the art. Like reference numerals represent identical or similar components.

[0063] The terms used herein are for the purpose of describing specific exemplary embodiments only and are not intended to limit the present application. As used herein, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms as well. In addition, when used herein, "includes" and / or "comprising" or "including" and / or "including" or "having" and / or "having" integers, steps, operations, components and / or components do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, components, components and / or groups thereof.

[0064] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. In addition, unless explicitly defined herein, terms such as those defined in common dictionaries should be interpreted as having a meaning consistent with their meaning in the relevant art and the content of this application, and will not be interpreted as idealized or overly formal meanings.

[0065] The following describes exemplary embodiments with reference to the accompanying drawings. It should be noted that the components depicted in the accompanying drawings are not necessarily shown to scale; and the same or similar components will be given the same or similar reference numerals or similar technical terms.

[0066] The specific implementation methods of the present application will be described in further detail below with reference to the accompanying drawings.

[0067] One embodiment of the present application provides a method for preparing a semi-flexed circuit board. The order of the steps in the preparation method may be varied, and some steps may be omitted or combined, depending on different requirements. The preparation method comprises the following steps:

[0068] Step S1: Figure 1 As shown, an inner-layer rigid laminate 10 and a double-sided copper-clad substrate 2 are provided. The inner-layer rigid laminate 10 includes a base layer 11 and an inner circuit layer 12 disposed on opposite surfaces of the base layer 11. The double-sided copper-clad substrate 2 includes a cover layer 21, a first intermediate circuit layer 22, and a raw copper layer 24, with the first intermediate circuit layer 22 and the raw copper layer 24 respectively disposed on opposite surfaces of the cover layer 21.

[0069] In some embodiments, in the double-sided copper clad substrate 2, the cover layer 21 may be made of polyimide (PI), and the elongation of the polyimide cover layer 21 is 30% to 70%. The original copper layer 24 is a rolled copper foil with high flexural strength.

[0070] In the inner layer rigid laminate structure 10 , the base layer 11 is made of polypropylene (PI), and the elongation of the base layer 11 made of polypropylene is 1% to 2%.

[0071] In other embodiments, the double-sided copper clad substrate 2 may further include an adhesive layer (not shown) disposed between the cover layer 21 and the first intermediate circuit layer 22 or between the cover layer 21 and the original copper layer 24 .

[0072] In some embodiments, inner rigid stack 10 includes two inner circuit layers 12, meaning that inner rigid stack 10 can be a double-sided circuit board. The two inner circuit layers 12 are electrically connected via first conductive posts 13. In other embodiments, the number of inner circuit layers 12 included in inner rigid stack 10 can be varied based on practical needs.

[0073] Step S2, such as Figure 2 As shown, the double-sided copper clad substrate 2, the first adhesive layer 30, the inner hard stack 10, another first adhesive layer 30 and another double-sided copper clad substrate 2 are stacked in sequence with the original copper layer 24 facing outward, and then pressed.

[0074] The first adhesive layer 30 is in a semi-cured state and, after lamination, can fill the gaps between the circuits of the first inner circuit layer 12 and the first intermediate circuit layer 22. The first adhesive layer 30 can be made of polypropylene, which has an elongation of 1% to 2%.

[0075] Step S3, as Figure 3 As shown, the original copper layer 24 is etched into a second intermediate circuit layer 23, thereby preparing the double-sided copper-clad substrate 2 into an intermediate flexible laminate 20. That is, the intermediate flexible laminate 20 is placed on the surface of the inner rigid laminate 10 via a first adhesive layer 30. Then, a release film 3 is attached to the second intermediate circuit layer 23.

[0076] The second intermediate circuit layer 23 includes a main region 230, a waste region 231, and a copper-retaining region 232 surrounding the waste region 231. A release film 3 is attached to the waste region 231 of the second intermediate circuit layer 23. In other words, the main region 230 and the copper-retaining region 232 are exposed to the release film 3. In some embodiments, the width W1 of the copper-retaining region 232 is 0.05 mm to 0.5 mm.

[0077] In some embodiments, the second intermediate circuit layer 23 can be fabricated through processes such as lamination, copper plating, exposure, development, etching, and stripping. More specifically, a through hole can be further formed through each double-sided copper-clad substrate 2, each first adhesive layer 30, and the inner rigid laminate 10. During copper plating, a portion of the copper plating is also formed on the inner wall of the through hole, forming a plated through hole 25 for electrically connecting the second intermediate circuit layer 23, the first intermediate circuit layer 22, and the inner circuit layer 12.

[0078] Step S4, as Figure 4 and Figure 5As shown, the second adhesive layer 41 and the first copper foil layer 45 are sequentially stacked on the second intermediate circuit layer 23 having the release film 3, and then pressed.

[0079] The second adhesive layer 41 has a second opening 410. The orthogonal projection of the second opening 410 on the cover layer 21 completely overlaps with the orthogonal projection of the release film 3 on the cover layer 21, so that the second adhesive layer 41 surrounds and connects the release film 3 after lamination.

[0080] The second adhesive layer 41 is in a semi-cured state and can be filled in the circuit gaps of the second intermediate circuit layer 23 after lamination.

[0081] Step S5, as Figure 5 As shown, the first copper foil layer 45 is etched to obtain a first outer circuit layer 42 .

[0082] In some embodiments, the first outer circuit layer 42 can be fabricated through processes such as lamination, copper plating, exposure, development, etching, and stripping. More specifically, a blind via can be further formed through the first copper foil layer 45 and the second adhesive layer 41. During copper plating, a portion of the copper plating fills the blind via to form a second conductive pillar 46 for electrically connecting the first outer circuit layer 42 to the second intermediate circuit layer 23.

[0083] Step S6, as Figure 6 and Figure 7 As shown, a third adhesive layer 43 and a second copper foil layer 47 are sequentially stacked on the first outer circuit layer 42 and then pressed together.

[0084] The third adhesive layer 43 is provided with a third opening 430. The orthogonal projection of the third opening 430 on the cover layer 21 is larger than the orthogonal projection of the release film 3 on the cover layer 21, so that the orthogonal projection of the release film 3 on the cover layer 21 is located within the orthogonal projection of the third opening 430 on the cover layer 21. Therefore, after lamination, the release film 3 is exposed at the third opening 430.

[0085] The third adhesive layer 43 is in a semi-cured state and can be filled in the circuit gaps of the first outer circuit layer 42 after lamination.

[0086] Step S7, as Figure 7 As shown, the portion of the second copper foil layer 47 corresponding to the release film 3 is removed, so that the release film 3 is exposed from the second copper foil layer 47 , and then the release film 3 is removed.

[0087] Step S8, as Figure 7 and Figure 8As shown, the release film 3 is removed to expose the scrap area 231 of the second intermediate circuit layer 23. The second copper foil layer 47 is etched to form the second outer circuit layer 44, and the scrap area 231 of the second intermediate circuit layer 23 is removed by etching. That is, the copper-retained area 232 of the second intermediate circuit layer 23 is not etched away. As a result, a portion of the cover layer 21 is exposed through the first opening 2320, the second opening 410, and the third opening 430 defined by the copper-retained area 232.

[0088] In some embodiments, the second copper foil layer 47 and the second intermediate circuit layer 23 can be etched in the same exposure and development process. Since the waste area 231 of the second intermediate circuit layer 23 is removed, the problem of residual release film 3 can be solved.

[0089] In some embodiments, a microstructure (not shown) is formed on the surface of the portion of the cover layer 21 exposed to the copper-retained area 232, the second opening 410, and the third opening 430 due to the etching process. The surface roughness Rz of the microstructure may be 0.5 to 2.6.

[0090] The second outer circuit layer 44, the third adhesive layer 43, the first outer circuit layer 42, and the second adhesive layer 41 form an outer rigid laminate 40, with the intermediate flexible laminate 20 disposed between the outer rigid laminate 40 and the inner rigid laminate 10. As shown, the outer rigid laminate 40 includes two outer circuit layers. However, in other embodiments, the number of outer circuit layers included in the outer rigid laminate 40 can be varied based on actual needs.

[0091] Among them, since the second opening 410 of the second adhesive layer 41 is connected to the four sides of the release film 3, after the waste area 231 of the second intermediate circuit layer 23 is etched away, the second adhesive layer 41 has a glue flow area 411 located on the copper remaining area 232, and the glue remaining area is exposed to the third opening 430.

[0092] In some embodiments, the second outer circuit layer 44 can be fabricated through processes such as lamination, copper plating, exposure, development, etching, and stripping. More specifically, a blind via can be further formed through the second copper foil layer 47 and the third adhesive layer 43. During copper plating, a portion of the copper plating fills the blind via to form a third conductive pillar 48 for electrically connecting the second outer circuit layer 44 to the first outer circuit layer 42.

[0093] Step S9, as Figure 9 As shown, a protective layer 50 is provided on the second outer circuit layer 44 to obtain a semi-flexed circuit board 1.

[0094] In some embodiments, protective layer 50 covers the surface and sidewalls of third adhesive layer 43 exposed to second outer wiring layer 44 (i.e., the inner wall of third opening 430). In other embodiments, protective layer 50 may also cover a portion of second outer wiring layer 44. The remaining portion of second outer wiring layer 44 not covered by protective layer 50 may be used to connect electronic components (not shown). Protective layer 50 may be made of solder mask ink.

[0095] In some embodiments, surface treatment may be further performed on the second outer circuit layer 44 not covered by the protective layer 50 to prevent oxidation of the second outer circuit layer 44, which could affect its electrical properties. This surface treatment may include forming a protective layer (not shown) using methods such as electroless gold plating or electroless nickel plating, or forming an organic solder resist (OSP, not shown) on the second outer circuit layer 44.

[0096] Along the extension direction of the semi-flexible circuit board 1, the semi-flexible circuit board 1 is divided into a rigid board area 101 and a semi-flexible area 102. The rigid board area 101 comprises the outer rigid laminate 40 and the portion of the intermediate flexible laminate 20 and the portion of the inner rigid laminate 10 corresponding to the outer rigid laminate 40. The semi-flexible area 102 comprises the portion of the intermediate flexible laminate 20 and the portion of the inner rigid laminate 10 not corresponding to the outer rigid laminate 40. Specifically, the semi-flexible area 102 corresponds to the first opening 2320 and the second opening 410. The semi-flexible circuit board 1 can flex at the semi-flexible area 102. The copper-retained area 232 increases the strength of the semi-flexible circuit board 1 at the flexing node.

[0097] It is understood that, since the present application uses a double-sided copper-clad substrate 2 to fabricate the intermediate flexible stack 20, the original copper layer 24 of the intermediate flexible stack 20, except for the waste area 231 that is etched and unused, can be fabricated into the second intermediate circuit layer 23. Furthermore, by removing the waste area 231, the thickness of the semi-flexing region 102 is reduced. In some embodiments, the thickness of the semi-flexing region 102 is 0.1 mm to 0.3 mm.

[0098] In some embodiments, since the elongation of the polyimide cover layer 21 is greater than that of the first adhesive layer 30 or the base layer 11 made of polypropylene, and the first intermediate circuit layer 22 made of etched and rolled copper foil has a higher flexural ability, the present application arranges the intermediate flexible stack 20 on both sides of the inner rigid stack 10 and positions the cover layer 21 outside the semi-flexing zone 102, so that the semi-flexing zone 102 has a smaller bending radius (i.e., a larger bending angle) when flexing. In other embodiments, even if the double-sided copper-clad substrate 2 further includes an adhesive layer (not shown) positioned between the cover layer 21 and the first intermediate circuit layer 22 or between the cover layer 21 and the original copper layer 24, since the cover layer 21 is positioned outside the semi-flexing zone 102, the flexural performance of the semi-flexing zone 102 can also be improved.

[0099] In some embodiments, the semi-flexing region 102 is located at the center of the semi-flexing circuit board 1 along the thickness direction H of the semi-flexing circuit board 1. However, in other embodiments, the location of the semi-flexing region 102 in the semi-flexing circuit board 1 along the thickness direction H of the semi-flexing circuit board 1 may also be varied. For example, if the outer layer rigid laminate 40 is only provided on the surface of one of the intermediate flexible laminates 20, the semi-flexing region 102 in the resulting semi-flexing circuit board 1 is located on the outer side of the semi-flexing circuit board 1. For another example, if in step S2, the double-sided copper-clad substrate 2 is only provided on one surface of the inner rigid laminate 10 and one or more double-sided copper-clad substrates 2 are provided on the other surface (i.e., the number of the resulting intermediate flexible laminates 20 is greater than two), and the outer layer rigid laminate 40 is only provided on one surface of the outermost intermediate flexible laminate 20, the semi-flexing region 102 in the resulting semi-flexing circuit board 1 is offset from the center of the semi-flexing circuit board 1 along the thickness direction H of the semi-flexing circuit board 1.

[0100] like Figure 9 As shown, one embodiment of the present application further provides a semi-flexible circuit board 1, comprising an inner hard stack 10, a first adhesive layer 30, an intermediate flexible stack 20, another first adhesive layer 30 and an outer hard stack 40 stacked in sequence.

[0101] The inner rigid laminate 10 includes a base layer 11 and an inner circuit layer 12 disposed on opposite surfaces of the base layer 11. The intermediate flexible laminate 20 includes a cover layer 21, a first intermediate circuit layer 22, and a second intermediate circuit layer 23, with the first and second intermediate circuit layers 22, 23 disposed on opposite surfaces of the cover layer 21. The first intermediate circuit layer 22 is disposed between the second intermediate circuit layer 23 and the inner circuit layer 12. The outer rigid laminate 40 includes a second adhesive layer 41, a first outer circuit layer 42, a third adhesive layer 43, and a second outer circuit layer 44, stacked in this order. The first outer circuit layer 42 is disposed between the second outer circuit layer 44 and the second intermediate circuit layer 23.

[0102] The second intermediate circuit layer 23 includes a copper-retained area 232, which defines a first opening 2320. The second adhesive layer 41 defines a second opening 410. The third adhesive layer 43 defines a third opening 430. A portion of the cover layer 21 is exposed by the first opening 2320, the second opening 410, and the third opening 430 defined by the copper-retained area 232. In some embodiments, the orthogonal projection of the second opening 410 on the cover layer 21 completely overlaps with the orthogonal projection of the first opening 2320 on the cover layer 21. The orthogonal projection of the third opening 430 on the cover layer 21 is larger than the orthogonal projection of the second opening 410 on the cover layer 21, such that the orthogonal projection of the second opening 410 on the cover layer 21 is within the orthogonal projection of the third opening 430 on the cover layer 21.

[0103] Along the extension direction of the semi-flexible circuit board 1, the semi-flexible circuit board 1 is divided into a rigid board area 101 and a semi-flexible board area 102. The rigid board area 101 includes the outer rigid stack 40, as well as a portion of the intermediate flexible stack 20 and a portion of the inner rigid stack 10 corresponding to the outer rigid stack 40. The semi-flexible board 102 comprises the portion of the intermediate flexible stack 20 and the portion of the inner rigid stack 10 not corresponding to the outer rigid stack 40, and the third opening 430. In other words, the semi-flexible board 102 corresponds to the first opening 2320 and the second opening 410.

[0104] The semi-flexing area 102 of the present application can be arranged at any layer or any position of the semi-flexing circuit board 1, and the number of semi-flexing areas 102 can be set according to actual needs, which provides a flexible layout and a high wiring density. Furthermore, since there are at least two intermediate flexible stacking structures 20, the stress to which the semi-flexing area 102 is subjected during bending can be reduced, thereby increasing the maximum bendable angle. Based on the maximum bendable angle required in actual applications, the number and position distribution of the intermediate flexible stacking structures 20 can be appropriately adjusted to meet the customer's personalized customization needs.

[0105] The specific embodiments of the present application have been described above with reference to the accompanying drawings. However, those skilled in the art will appreciate that various modifications and substitutions may be made to the specific embodiments of the present application without departing from the spirit and scope of the present application. Such modifications and substitutions are intended to fall within the scope of the present application.

Claims

1. A semi-flexed circuit board, characterized in that: The invention comprises an inner hard stack, at least two intermediate flexible stacks, and an outer hard stack, wherein the at least two intermediate flexible stacks are respectively arranged on two opposite surfaces of the inner hard stack, the outer hard stack is arranged on a surface of the intermediate flexible stack away from the inner hard stack, a first adhesive layer is arranged between the inner hard stack and the adjacent intermediate flexible stack, and another first adhesive layer is arranged between the outer hard stack and the adjacent intermediate flexible stack; The inner layer hard stack structure includes a base layer and an inner circuit layer provided on two opposite surfaces of the base layer; The intermediate layer stack structure includes a cover layer and a first intermediate circuit layer and a second intermediate circuit layer respectively provided on two opposite surfaces of the cover layer; The outer hard stack structure includes a second adhesive layer, a first outer circuit layer, a third adhesive layer and a second outer circuit layer stacked in sequence; The first intermediate circuit layer is provided between the second intermediate circuit layer and the inner circuit layer, the first outer circuit layer is provided between the second outer circuit layer and the second intermediate circuit layer, the second intermediate circuit layer includes a copper-retained area, the copper-retained area defines a first opening, the second adhesive layer has a second opening, the third adhesive layer has a third opening, the orthogonal projection of the second opening on the cover layer completely overlaps with the orthogonal projection of the first opening on the cover layer, the orthogonal projection of the second opening on the cover layer is located within the orthogonal projection of the third opening on the cover layer, and a portion of the cover layer is exposed to the first opening, the second opening, and the third opening; Along the extension direction of the semi-flexed circuit board, the semi-flexed circuit board is divided into a hard board area and a semi-flexed area. The hard board area includes the outer hard stack structure and part of the middle flexible stack structure and part of the inner hard stack structure corresponding to the outer hard stack structure. The semi-flexed area corresponds to the first opening and the second opening.

2. The semi-flexed circuit board according to claim 1, wherein: The number of the intermediate flexible stacking structures is more than two, and the number of the outer rigid stacking structures is two. The more than two intermediate flexible stacking structures are respectively arranged on the two opposite surfaces of the inner rigid stacking structure, and the two outer rigid stacking structures are respectively arranged on the surfaces of the two outermost intermediate flexible stacking structures. Along the thickness direction of the semi-flexed circuit board, the semi-flexed area is located at the center position of the semi-flexed circuit board or deviates from the center position of the semi-flexed circuit board.

3. The semi-flexed circuit board according to claim 1, wherein: The number of the intermediate flexible stacking structures and the outer rigid stacking structures is two. The two intermediate flexible stacking structures are respectively arranged on the two opposite surfaces of the inner rigid stacking structure, and the two outer rigid stacking structures are respectively arranged on the surfaces of the two intermediate flexible stacking structures. Along the thickness direction of the semi-flexed circuit board, the semi-flexed area is located at the center position of the semi-flexed circuit board.

4. The semi-flexed circuit board according to claim 1, wherein: The material of the covering layer includes polyimide, and the material of the base layer and the first adhesive layer includes polypropylene.

5. The semi-flexed circuit board according to claim 1, wherein: It also includes a protective layer, which covers at least the surface and side wall of the third glue layer exposed to the second outer circuit layer.

6. A method for preparing a semi-flexed circuit board, characterized in that: The steps include: An inner rigid stack and at least two intermediate flexible stacks are provided, and the at least two intermediate flexible stacks are respectively disposed on opposite surfaces of the inner rigid stack. A first adhesive layer is provided between the inner rigid stack and an adjacent intermediate flexible stack, and another first adhesive layer is provided between the outer rigid stack and an adjacent intermediate flexible stack. The inner rigid stack includes a base layer and an inner circuit layer disposed on opposite surfaces of the base layer, and the intermediate stack includes a cover layer and a first intermediate circuit layer and a second intermediate circuit layer disposed on opposite surfaces of the cover layer, respectively. The first intermediate circuit layer is disposed between the second intermediate circuit layer and the inner circuit layer, and the outer second intermediate circuit layer includes a waste area and a copper retention area disposed around the waste area. attaching a release film to the waste area; An outer hard laminate is provided on the second intermediate circuit layer having the release film, the outer hard laminate comprising a second adhesive layer, a first outer circuit layer, a third adhesive layer, and a second outer circuit layer stacked in sequence, the first outer circuit layer being provided between the second outer circuit layer and the second intermediate circuit layer, the second adhesive layer being provided with a second opening, the third adhesive layer being provided with a third opening, the orthogonal projection of the second opening on the cover layer completely overlapping the orthogonal projection of the first opening on the cover layer, the orthogonal projection of the second opening on the cover layer being located within the orthogonal projection of the third opening on the cover layer, and the release film being provided in the second opening and exposed to the third opening; removing the release film to expose the waste area; The waste area is etched away so that a portion of the cover layer is exposed to the first opening, the second opening and the third opening defined by the copper-retaining area, thereby obtaining the semi-flexed circuit board.

7. The method for preparing a semi-flexed circuit board according to claim 6, wherein: The outer layer hard stack structure is specifically provided by: sequentially stacking a second adhesive layer and a first copper foil layer on the second intermediate circuit layer having the release film; etching the first copper foil layer to obtain the first outer circuit layer; sequentially stacking a third adhesive layer and a second copper foil layer on the first outer circuit layer; removing a portion of the second copper foil layer corresponding to the release film so that the release film is exposed from the second copper foil layer; Wherein, when etching the waste area, the second copper foil layer is also etched into a second outer circuit layer.

8. The method for preparing a semi-flexed circuit board according to claim 7, wherein: The number of the intermediate flexible stacking structures and the outer rigid stacking structures is two. The two intermediate flexible stacking structures are respectively arranged on the two opposite surfaces of the inner rigid stacking structure, and the two outer rigid stacking structures are respectively arranged on the surfaces of the two intermediate flexible stacking structures. Along the thickness direction of the semi-flexed circuit board, the semi-flexed area is located at the center position of the semi-flexed circuit board.

9. The method for preparing a semi-flexed circuit board according to claim 8, wherein: The material of the covering layer includes polyimide, and the material of the base layer and the first adhesive layer includes polypropylene.

10. The method for preparing a semi-flexed circuit board according to claim 9, wherein: Also includes: A protective layer is provided on the second outer circuit layer, and the protective layer at least covers the surface and sidewall of the third adhesive layer exposed to the second outer circuit layer.

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