CN113573461A

CN113573461A - Semi-flexible circuit board and manufacturing method thereof

Info

Publication number: CN113573461A
Application number: CN202010359080.5A
Authority: CN
Inventors: 何明展; 彭满芝; 钟浩文; 李彪
Original assignee: Avary Holding Shenzhen Co Ltd; Qing Ding Precision Electronics Huaian Co Ltd
Current assignee: Avary Holding Shenzhen Co Ltd; Qing Ding Precision Electronics Huaian Co Ltd
Priority date: 2020-04-29
Filing date: 2020-04-29
Publication date: 2021-10-29
Anticipated expiration: 2040-04-29
Also published as: CN113573461B

Abstract

The application provides a semi-flexible circuit board, wherein an inner laminated structure comprises a plurality of hard circuit layers which are laminated; the first intermediate circuit layer is arranged on the surface of the inner lamination and comprises a first flexible insulating film and a first intermediate circuit layer, and the first intermediate circuit layer is arranged on one side, away from the inner lamination, of the first flexible insulating film; a first inner layer opening penetrating the first intermediate wiring layer to expose a part of the first flexible insulating film; the first outer stacking structure is arranged on one side, away from the inner stacking structure, of the first middle circuit layer and comprises a plurality of first hard board circuits which are arranged in a stacking mode; the first outer layer opening penetrates through a plurality of first hard board circuits which are arranged in a stacked mode so as to expose the first inner layer opening; the projection of the first outer layer opening on the inner laminated structure completely covers the projection of the first inner layer opening on the inner laminated structure, and part of the first middle circuit layer is exposed from the first outer layer opening to form a copper-remaining area. The application also provides a manufacturing method of the semi-flexible circuit board.

Description

Semi-flexible circuit board and manufacturing method thereof

Technical Field

The application relates to the technical field of circuit boards, in particular to a semi-flexible circuit board and a manufacturing method thereof.

Background

The multi-morphism of the electronic product enables the circuit board to be bent to meet the requirement, and the circuit board is bent to different angles, so that the three-dimensional assembly of the electronic finished product is realized. The conventional flexible printed circuit board includes a Flexible Printed Circuit (FPC), a rigid-flex circuit, or a semi-flex circuit.

For electronic products with a requirement of a half bending area, the circuit board is usually required to be bent during assembly so as to achieve the bending effect. Although the rigid-flexible circuit board and the flexible circuit board have certain advantages in large-angle bending, the manufacturing process is complex and the cost is high; the conventional semi-flexible folding plate can save the assembly space, so that the electronic product can be developed towards smaller and more portable direction, but the semi-flexible folding area is usually only a single layer or a double layer, and the circuit board has low circuit layout flexibility and lower wiring density.

How to solve the above problems needs to be considered by those skilled in the art.

Disclosure of Invention

In view of the above, the present application provides a half flex circuit board, including:

an inner laminate comprising a plurality of hard wire layers arranged in a stack;

the first intermediate circuit layer is arranged on the surface of the inner lamination and comprises a first flexible insulating film and a first intermediate circuit layer, and the first intermediate circuit layer is arranged on one side, away from the inner lamination, of the first flexible insulating film;

a first inner layer opening penetrating the first intermediate wiring layer to expose a part of the first flexible insulating film;

the first outer lamination is arranged on one side, away from the inner lamination, of the first middle circuit layer and comprises a plurality of first hard board circuits which are arranged in a laminated mode;

a first outer layer opening penetrating through a plurality of the first hard board lines stacked to expose the first inner layer opening; and

the projection of the first outer layer opening on the inner laminated structure completely covers the projection of the first inner layer opening on the inner laminated structure, and part of the first middle circuit layer is exposed from the first outer layer opening to form a copper-remaining area.

In one embodiment, the method further comprises: a second intermediate circuit layer, the first intermediate circuit layer and the second intermediate circuit layer being disposed on opposite sides of the inner layer stack, the second intermediate circuit layer including a second flexible insulating film, a second intermediate circuit layer, and a second inner layer opening, the second intermediate circuit layer and the second inner layer opening being disposed on a side of the second flexible insulating film away from the inner layer stack, the second inner layer opening penetrating the second intermediate circuit layer to expose at least a portion of the second flexible insulating film; and

and the second outer laminated structure is arranged on one side, far away from the inner laminated structure, of the second middle circuit layer.

In an embodiment, the half-flex circuit board defines a hard board area and a half-flex area, the first inner opening is disposed in the half-flex area, the first outer layer stack, the first middle circuit layer covered by the first outer layer stack, and the inner layer stack are disposed in the hard board area, and the copper-remaining area protrudes from the hard board area to the half-flex area.

In one embodiment, a surface roughness Rz of the first flexible insulating film away from the surface of the inner laminate is in a range of 0.5 to 2.6.

In one embodiment, the copper-remaining region protrudes to the first inner layer opening by a distance in a range of 0.05mm to 0.5 mm.

In one embodiment, the first flexible insulating film has an elongation of 2% to 16%, the inner laminate further includes a first insulating layer, the first outer laminate further includes a second insulating layer, and the first insulating layer and the second insulating layer have an elongation of 1% to 2%.

The application also provides a manufacturing method of the semi-flexible circuit board, which comprises the following steps:

stacking a plurality of hard circuit layers to form an inner stacked structure;

forming a first intermediate circuit layer on the surface of the inner lamination, wherein the first intermediate circuit layer comprises a surface copper area and a first flexible insulating film, and the surface copper area is arranged on one side, away from the inner lamination, of the first flexible insulating film;

providing a first release film, and attaching the first release film to the surface of the surface copper area far away from the inner lamination;

stacking a plurality of first hard board circuits on the surface of the first middle circuit layer to form a first outer stacked structure and a glue flowing area;

forming a first outer layer opening penetrating through the first outer layer stack structure, and exposing the surface of the first release film far away from the first middle circuit layer and the gummosis area; and

and removing the first release film, and etching the exposed surface copper area to obtain a first inner layer opening and a copper remaining area, wherein the first inner layer opening penetrates through the first intermediate circuit layer to expose at least part of the first flexible insulating film.

In one embodiment, the method comprises: a second intermediate circuit layer is formed on the surface of the inner laminated structure far away from the first intermediate circuit layer, the second intermediate circuit layer comprises a second hard circuit layer and a second flexible insulating film, and the second hard circuit layer is arranged on one side, far away from the inner laminated structure, of the second flexible insulating film;

providing a second release film, wherein the second release film is attached to the surface, away from the inner lamination, of the second intermediate circuit layer;

forming a second outer lamination and a second outer layer opening on the surface of the second middle circuit layer far away from the inner lamination, so that the surface of the second release film far away from the second middle circuit layer is exposed; and

and removing the second release film, and etching the second intermediate circuit layer to obtain a second inner layer opening, wherein the second inner layer opening penetrates through the second hard circuit layer to expose at least part of the second flexible insulating film.

In an embodiment, the first hard board circuit is formed by stacking an insulating layer and a copper layer, the insulating layer is preset with an opening corresponding to the first release film, and the copper layer of the first hard board circuit is etched to make a hollow region of the copper layer corresponding to the first release film so as to form the first outer layer opening.

In one embodiment, the first flexible insulating film and the second flexible insulating film are etched away from the surface of the inner stack, and a surface roughness Rz of the first flexible insulating film and the second flexible insulating film away from the surface of the inner stack ranges from 0.5 to 2.6.

Compared with the prior art, the semi-flexible circuit board and the manufacturing method thereof enable the semi-flexible area of the semi-flexible circuit board to be arranged on any layer or any position of the circuit board, and are simple to process, flexible in circuit board layout and high in wiring density.

Drawings

Fig. 1 is a schematic cross-sectional view of a half flex circuit board according to a first embodiment of the present application.

Fig. 2 is a schematic view of a manufacturing process of a half flex circuit board according to a first embodiment of the present application.

Fig. 3 is a schematic view of a manufacturing process of a half flex circuit board according to a first embodiment of the present application.

Fig. 4 is a schematic view of a manufacturing process of a half flex circuit board according to a first embodiment of the present application.

Fig. 5 is a schematic view of a manufacturing process of a half flex circuit board according to a first embodiment of the present application.

Fig. 6 is a schematic view of a manufacturing process of a half flex circuit board according to a first embodiment of the present application.

Fig. 7 is a schematic view of a manufacturing process of a half flex circuit board according to a first embodiment of the present application.

Fig. 8 is a schematic view of a manufacturing process of a half flex circuit board according to a first embodiment of the present application.

Fig. 9 is a schematic view of a manufacturing process of a half flex circuit board according to a first embodiment of the present application.

Fig. 10 is a schematic cross-sectional view of a half flex circuit according to a second embodiment of the present application.

Fig. 11 is a schematic view of a manufacturing process of a semi-flex circuit board according to a second embodiment of the present application.

Fig. 12 is a schematic view of a manufacturing process of a half flex circuit board according to a second embodiment of the present application.

Fig. 13 is a schematic view of a manufacturing process of a half flex circuit board according to a second embodiment of the present application.

Fig. 14 is a schematic view of a manufacturing process of a half flex circuit board according to a second embodiment of the present application.

Fig. 15 is a schematic view of a manufacturing process of a half flex circuit board according to a second embodiment of the present application.

Fig. 16 is a schematic view of a manufacturing process of a half flex circuit board according to a second embodiment of the present application.

Fig. 17 is a schematic view of a manufacturing process of a half flex circuit board according to a second embodiment of the present application.

Fig. 18 is a schematic view of a manufacturing process of a half flex circuit board according to a second embodiment of the present application.

Description of the main elements

Semi-flexible circuit board

1, 2

Inner laminate

10, 20

Hard wiring layer

101, 201

First

insulating layers

102, 202

Conductive posts

103, 203

Solder mask

105, 205

First

intermediate circuit layers

11, 21

First flexible

insulating films

111, 211

First

conductive traces

112, 212

First

inner layer openings

113, 213

First

outer laminate

12, 22

First hardboard line

121, 221

First

outer layer openings

123, 223

Second intermediate wiring layer 23

Second flexible insulating film 231

Second conductive traces 232

Second inner layer opening 233

Second outer layer structure 24

Second hard board circuit 241

Second outer layer opening 243

Copper remaining regions

151, 251

Glue flow area

152, 252

Microstructures

153, 253

Copper facing regions

16, 26

First release film

171, 271

Second release film 272

Second insulating

layers

173, 273

Copper layers 174, 274

Hard plate regions

18, 28

Semi-flex regions

19, 29

The following detailed description will further illustrate the present application in conjunction with the above-described figures.

Detailed Description

The following description will refer to the accompanying drawings to more fully describe the present disclosure. There is shown in the drawings exemplary embodiments of the present application. This application may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. These exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals designate identical or similar components.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, as used herein, the terms "comprises," "comprising," "includes" and/or "including" or "having" and/or "having," integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

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. Furthermore, unless otherwise defined herein, terms such as those defined in commonly used dictionaries should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present application and will not be interpreted in an idealized or overly formal sense.

The following description of exemplary embodiments refers to the accompanying drawings. It should be noted that the components depicted in the referenced drawings are not necessarily shown to scale; and the same or similar components will be given the same or similar reference numerals or similar terms.

Embodiments of the present application will now be described in further detail with reference to the accompanying drawings.

First embodiment

As shown in fig. 1, a half flex circuit 1 according to a first embodiment of the present application is provided. The semi-flexible circuit board 1 includes an inner layer stack 10, a first middle circuit layer 11 and a first outer layer stack 12, the first middle circuit layer 11 is disposed on one side of the inner layer stack 10, and the first outer layer stack 12 is disposed on one side of the first middle circuit layer 11 away from the inner layer stack 10.

In one embodiment, the inner layer stack 10 includes at least one hard wire layer 101, the hard wire layer 101 is separated from the first intermediate wire layer 11 by a first insulating layer 102, and the hard wire layer 101 and the first intermediate wire layer 11 can be electrically connected by a conductive pillar 103. In other embodiments, the inner stacked structure 10 may include a plurality of hard circuit layers 101 stacked one on another, the hard circuit layers 101 and the first middle circuit layer 11 may be separated by a first insulating layer 102, and the hard circuit layers 101 and the first middle circuit layer 11 may be electrically connected by conductive pillars 103.

In an embodiment, the material of the first insulating layer 102 is organic, and the composition of the first insulating layer 102 may include polypropylene. In one embodiment, the elongation of the first insulating layer 102 made of polypropylene may be 1% to 2%, the material of the hard circuit layer 101 may be copper, the elongation of the hard circuit layer 101 made of copper may be 2% to 16%, and when the hard circuit layer 101 and the first insulating layer 102 are stacked to form the inner layer stack 10, the overall elongation of the inner layer stack 10 may be 1% to 2%. In other embodiments, the composition of the first insulating layer 102 may also include polyimide.

The first intermediate wiring layer 11 includes a first flexible insulating film 111, a first conductive wiring 112, and a first inner layer opening 113. The first flexible insulating film 111 is disposed on the surface of the inner stack 10, the first conductive trace 112 is disposed on the surface of the first flexible insulating film 111, the first conductive trace 112 is disposed on a side of the first flexible insulating film 111 away from the inner stack 10, and the first inner opening 113 penetrates the first conductive trace 112 to expose at least a portion of the first flexible insulating film 111. The composition of the first flexible insulating film 111 includes polyimide, and in one embodiment, the material of the first flexible insulating film 111 is polyimide. The surface of the first flexible insulating film 111 includes a microstructure 153, and the surface roughness Rz of the microstructure 153 may range from 0.1 to 4, 0.1 to 0.5, 0.5 to 1.5, 1.5 to 2.6, 2.6 to 4, preferably 0.5 to 2.6.

The first outer layer stack 12 is disposed on the surface of the first conductive traces 112 away from the first flexible insulating film 111, and in an embodiment, the wiring of the first outer layer stack 12 may be multi-layered.

The first outer layer stack 12 includes at least one layer of first hard board wires 121 and at least one first outer layer opening 123, in an embodiment, the first outer layer stack 12 includes a plurality of layers of first hard board wires 121 stacked one on another and a first outer layer opening 123, and the first outer layer opening 123 penetrates through the plurality of layers of first hard board wires 121 stacked one on another to expose the first inner layer opening 113.

In one embodiment, the first flexible insulating film 111 has an elongation of 30% to 70%. After the half bending area 19 is bent, the resistance change rate is less than 5%.

The half flex circuit board 1 further includes a copper remaining area 151 and a glue flowing area 152, wherein the copper remaining area 151 and the glue flowing area 152 are disposed in an exposed area of the first outer layer opening 123 compared with the first inner layer opening 113. The projected area of the first outer layer opening 123 on the inner layer stack 10 is larger than the projected area of the first inner layer opening 113 on the inner layer stack 10, and the first conductive trace 112 of the first intermediate trace layer 11 is exposed from the first outer layer opening 123 to form a copper remaining region 151. The copper-left region 151 is adjacent to the first inner layer opening 113, and a distance of the copper-left region 151 away from a boundary of the first inner layer opening 113 may range from 0.05mm to 0.5mm from a boundary of the first inner layer opening 113. In one embodiment, the projection of the first outer layer opening 123 on the inner layer stack 10 completely covers the projection of the first inner layer opening 113 on the inner layer stack 10.

The semi-flexible circuit board 1 defines a hard board area 18 and a semi-flexible area 19, a first inner opening 113 and a first outer opening 123 are disposed in the semi-flexible area 19, and a first outer stacked structure 12 and a first middle circuit layer 11 and an inner stacked structure 13 covered by the first outer stacked structure are disposed in the hard board area 18.

In an embodiment, the exposed region of the first flexible insulating film 111 is located in the half bending region 19, the first outer stacked structure 12 is not disposed in the half bending region 19, the first inner opening 113 penetrates at least a portion of the half bending circuit board 1 to expose the first flexible insulating film 111, and the half bending circuit board 1 can be bent at the half bending region 19. The copper-remaining region 151 can increase the bending strength of the semi-bending circuit board 1.

In one embodiment, the half-bending region 19 may include at least three polypropylene first insulating layers 102, at least two copper hard circuit layers 101 and at least one polyimide first flexible insulating film 111, the multi-layer structure is stacked, and the half-bending region 19 is suitable for the following formula:

R＝(d/n+c)×(100-E_B)/E_B (1)

α＝180×I/(π×R) (2)

where R is the minimum bend radius, c is the thickness of the hard wiring layer 101, d is the sum of the thicknesses of the first insulating layers 102, n is the number of the first insulating layers 102, and E_BIn the elongation of the hard wiring layer 101, α is a bending angle per unit length, and I is a unit arc length.

When d/n is 50 μm, c is 50 μm, E_B30%, R233 μm, α 246 °; that is, in a preferred embodiment, the bending angle of the half bending region 19 may be up to 246 °.

The half flex circuit board 1 further comprises a solder mask layer 105, and the solder mask layer 105 is disposed on the outer side of the half flex circuit board 1.

The application also provides a manufacturing method of the semi-flexible circuit board 1, which comprises the following steps:

step S1: as shown in fig. 2, a plurality of hard wiring layers 101 are stacked to form an inner stack 10, a first intermediate wiring layer 11 is formed on the surface of the inner stack 10, the first intermediate wiring layer 11 includes a first copper-facing region 16 and a first flexible insulating film 111, and the first copper-facing region 16 is provided on the first flexible insulating film 111 on the side away from the inner stack 10.

The inner laminated structure 10 may be a prefabricated structure, a single-sided copper-clad plate is disposed on one surface of the inner laminated structure 10, and the single-sided copper-clad plate is processed by using an image transfer process to obtain the first intermediate circuit layer 11, in an embodiment, the inner laminated structure 10 may include at least one hard circuit layer 101, the hard circuit layer 101 and the first intermediate circuit layer 11 are separated by a first insulating layer 102, and the hard circuit layer 101 may be electrically connected with the first intermediate circuit layer 11 by a conductive column 103; in other embodiments, the inner stacked structure 10 may include a plurality of hard circuit layers 101 stacked one on another, the hard circuit layers 101 and the first middle circuit layer 11 may be separated by a first insulating layer 102, and the hard circuit layers 101 and the first middle circuit layer 11 may be electrically connected by conductive pillars 103.

Step S2: as shown in fig. 3, a first release film 171 is provided, and the first release film 171 is attached to the surface of the surface copper region 16 away from the inner lamination 10.

Step S3: as shown in fig. 4 and fig. 5, at least one layer of the first hard board circuit 121 is stacked on the surface of the first intermediate circuit layer 11 to form a first outer stacked structure 12 and a sealant region 152.

A second insulating layer 173 and a copper layer 174 are sequentially formed on the surface of the first intermediate circuit layer 11 away from the inner lamination 10 by build-up lamination. In one embodiment, the second insulating layer 173 is disposed opposite to the inner layer stack 10, a portion of the second insulating layer 173 opposite to the first release film 171 is removed to expose the first release film 171, a copper layer 174 is provided opposite to the inner layer stack 10, the second insulating layer 173 and the copper layer 174 are pressed, and the copper layer 174 covers the second insulating layer 173 and the first release film 171.

Step S4: as shown in fig. 5 and fig. 6, a first outer layer opening 123 penetrating through the first outer layer stack 12 is formed, so that the surface of the first release film 171 away from the first intermediate circuit layer 11 and the tape flow region 152 are exposed.

The laminated second insulating layer 173 and the copper layer 174 are processed by an image transfer process, so that the copper layer 174 is patterned to obtain the first hard board circuit 121 and form the first outer stack 12, and a portion of the copper layer 174 covering the first release film 171 is removed, specifically, a hollow area is formed after etching.

In one embodiment, the material of the second insulating layer 173 is organic, and the composition of the second insulating layer 173 may include polypropylene. In one embodiment, the elongation of the second insulating layer 173 made of polypropylene material may be 1% to 2%, the elongation of the copper layer 174 may be 2% to 16%, and when the copper layer 174 and the second insulating layer 173 are stacked to form the first outer stack 12, the overall elongation of the first outer stack 12 may be 1% to 2%. In other embodiments, the composition of the second insulating layer 173 may also include polyimide.

In an embodiment, the first outer laminate 12 includes a plurality of hard circuit layers, as shown in fig. 6 and 7, the steps S3 and S4 may be repeated a plurality of times, so that the first outer laminate 12 has a multi-layer circuit structure.

Step S5: as shown in fig. 8, the first release film 171 is removed, and the exposed surface copper region 16 is etched to obtain a first inner layer opening 113 and a copper remaining region 151, wherein the first inner layer opening 113 penetrates through the first intermediate circuit layer 11 to expose at least a portion of the first flexible insulating film 111.

In an embodiment, the copper-remaining region 151 remains during the etching process, the surface of the first flexible insulating film 111 away from the inner stack 10 is etched to obtain the microstructure 153, and the etching process can remove the residual glue of the first release film 171.

In one embodiment, the composition of the first flexible insulating film 111 includes polyimide.

Step S6: as shown in fig. 9, the first outer laminate 12 is surface-treated.

The surface of the first outer laminate 12 remote from the first intermediate circuit layer 11 is subjected to surface treatment to form a solder mask layer 105.

According to the semi-flexible circuit board 1 and the manufacturing method thereof, the semi-flexible area 19 of the semi-flexible circuit board 1 can be arranged on any layer or any position of the semi-flexible circuit board 1, and the semi-flexible circuit board is simple to process, flexible in layout and high in wiring density.

Second embodiment

Fig. 10 shows a half flex circuit 2 according to a second embodiment of the present application. Semi-flexible folded circuit board 2 includes that inlayer is folded and is constructed 20, first middle circuit layer 21, first outer fold 22, second middle circuit layer 23 and the outer fold 24 of second, and first middle circuit layer 21 and second middle circuit layer 23 set up in the both sides that the inlayer folded and constructed 20 mutually back of the body mutually, and first outer fold 22 sets up in first middle circuit layer 21 and keeps away from inlayer folded and construct 20 one side, and the outer fold 24 of second sets up in second middle circuit layer 23 and keeps away from inlayer folded and construct 20 one side.

In one embodiment, the inner layer stack 20 includes at least one hard wire layer 201, the hard wire layer 201 is separated from the first intermediate wire layer 21 and the second intermediate wire layer 23 by a first insulating layer 202, and the hard wire layer 201 can be electrically connected to the first intermediate wire layer 21 and the second intermediate wire layer 23 by a conductive pillar 203. In other embodiments, the inner stacked structure 20 may include a plurality of hard wire layers 201 stacked one on another, the plurality of hard wire layers 201, the hard wire layers 201 and the first intermediate wire layer 21, and the hard wire layers 201 and the second intermediate wire layer 23 may be separated by a first insulating layer 202, and the plurality of hard wire layers 201, the hard wire layers 201 and the first intermediate wire layer 21, and the hard wire layers 201 and the second intermediate wire layer 23 may be electrically connected by conductive pillars 203.

In an embodiment, the material of the first insulating layer 202 is organic, and the composition of the first insulating layer 202 may include polypropylene. In one embodiment, the elongation of the first insulating layer 202 made of polypropylene may be 1% to 2%, the material of the hard circuit layer 201 may be copper, the elongation of the hard circuit layer 201 made of copper may be 2% to 16%, and when the hard circuit layer 201 and the first insulating layer 202 are stacked to form the inner layer stack 20, the overall elongation of the inner layer stack 20 may be 1% to 2%. In other embodiments, the composition of the first insulating layer 202 may also include polyimide.

The first intermediate wiring layer 21 includes a first flexible insulating film 211, a first conductive wiring 212, and a first inner layer opening 213. The first flexible insulating film 211 is disposed on the surface of the inner stack 20, the first conductive trace 212 is disposed on the surface of the first flexible insulating film 211, the first conductive trace 212 is disposed on a side of the first flexible insulating film 211 away from the inner stack 20, and the first inner opening 213 penetrates the first conductive trace 212 to expose at least a portion of the first flexible insulating film 211. The composition of the first flexible insulating film 211 includes polyimide, and in one embodiment, the material of the first flexible insulating film 211 is polyimide. The first flexible insulating film 211 surface includes a microstructure 253, and the surface roughness Rz of the microstructure 253 may range from 0.1 to 4, 0.1 to 0.5, 0.5 to 1.5, 1.5 to 2.6, 2.6 to 4, preferably 0.5 to 2.6.

The first outer layer stack 22 is disposed on the surface of the first conductive traces 212 away from the first flexible insulating film 211, and in an embodiment, the wiring of the first outer layer stack 22 may be multi-layered.

The first outer layer stack 22 includes at least one layer of first hard board lines 221 and at least one first outer layer opening 223. in an embodiment, the first outer layer stack 22 includes a plurality of layers of first hard board lines 221 stacked one on another and a first outer layer opening 223, and the first outer layer opening 223 penetrates through the plurality of layers of first hard board lines 221 stacked one on another to expose the first inner layer opening 213.

The second intermediate wiring layer 23 includes a second flexible insulating film 231, a second conductive wiring line 232, and a second inner layer opening 233. The second flexible insulating film 231 is disposed on the surface of the inner stack 20, the second conductive trace 232 is disposed on the surface of the second flexible insulating film 231, the second conductive trace 232 is disposed on the side of the second flexible insulating film 231 away from the inner stack 20, and the second inner opening 233 penetrates the second conductive trace 232 to expose at least a portion of the second flexible insulating film 231. The composition of the second flexible insulating film 231 includes polyimide, and in one embodiment, the material of the second flexible insulating film 231 is polyimide. The surface of the second flexible insulating film 231 includes a microstructure 253, and the surface roughness Rz of the microstructure 253 may range from 0.1 to 4, 0.1 to 0.5, 0.5 to 1.5, 1.5 to 2.6, 2.6 to 4, preferably 0.5 to 2.6.

The second outer stack 24 is disposed on the surface of the second conductive traces 232 away from the second flexible insulating film 231, and in an embodiment, the wiring of the second outer stack 24 may be multi-layered.

The second outer layer stack 24 includes at least one layer of second hard board circuit 241 and at least one second outer layer opening 243, in an embodiment, the second outer layer stack 24 includes a plurality of layers of stacked second hard board circuits 241 and a second outer layer opening 243, and the second outer layer opening 243 penetrates through the plurality of layers of stacked second hard board circuits 241 to expose the second inner layer opening 233.

In one embodiment, the first inner opening 213 and the second inner opening 233 are symmetrically disposed, and the first outer opening 223 and the second outer opening 243 are symmetrically disposed, in other embodiments, the first inner opening 213 and the second inner opening 233, or the first outer opening 223 and the second outer opening 243 may be asymmetrically disposed.

In one embodiment, the first flexible insulating film 211 or the second flexible insulating film 231 has an elongation of 30% to 70%. After the half bending area 29 is bent, the resistance change rate is less than 5%.

The half flex circuit board 2 further includes a copper remaining region 251 and a glue flowing region 252, wherein the copper remaining region 251 and the glue flowing region 252 are disposed in an exposed region of the first outer layer opening 223 compared to the first inner layer opening 213 or an exposed region of the second outer layer opening 243 compared to the second inner layer opening 233. The projected area of the first outer layer opening 223 in the inner layer structure 20 is larger than the projected area of the first inner layer opening 213 in the inner layer structure 20, the projected area of the second outer layer opening 243 in the inner layer structure 20 is larger than the projected area of the second inner layer opening 233 in the inner layer structure 20, the first outer layer structure 22 comprises a first hard board circuit 221 and a first outer layer opening 223, the exposed area of the first conductive circuit 212 from the first outer layer opening 223 is a copper remaining area 251, the exposed area of the second outer layer structure 24 comprises a second hard board circuit 241 and a second outer layer opening 243, and the exposed area of the second conductive circuit 232 from the second outer layer opening 243 is the copper remaining area 251. In one embodiment, the projection of the first outer layer opening 223 on the inner layer structure 20 completely covers the projection of the first inner layer opening 213 on the inner layer structure 20.

The copper remaining region 251 is adjacent to the first inner layer opening 213 and the second inner layer opening 233, and a distance between a boundary of the copper remaining region 251 away from the first inner layer opening 213 and the second inner layer opening 233 and a boundary of the first inner layer opening 213 and the second inner layer opening 233 may be in a range of 0.05mm to 0.5 mm.

The semi-flexible circuit board 2 defines a hard board area 28 and a semi-flexible area 29, a first inner opening 213, a first outer opening 223, a second inner opening 233 and a second outer opening 243 are disposed in the semi-flexible area 29, a first outer layer 22 and a first middle circuit layer 21 and an inner layer 23 covered by the first outer layer 22 are disposed in the hard board area 28, and a second outer layer 24 and a second middle circuit layer 23 and an inner layer 20 covered by the second outer layer are disposed in the hard board area 28.

In an embodiment, the exposed regions of the first flexible insulating film 211 and the second flexible insulating film 231 are located in the half bending region 29, the first outer stacked structure 22 and the second outer stacked structure 24 are not disposed in the half bending region 29, the first inner layer opening 213 and the second inner layer opening 233 respectively penetrate through at least a portion of the half bending circuit board 2 so that the first flexible insulating film 211 and the second flexible insulating film 231 are exposed, and the half bending circuit board 2 can be bent at the half bending region 29. The copper-remaining region 251 can increase the bending strength of the semi-bending circuit board 2.

In one embodiment, the half bending region 29 may include at least three polypropylene first insulating layers 202, at least two copper hard circuit layers 201 and at least two polyimide first flexible insulating films 211, the multi-layer structure is stacked, and the half bending region 29 is adapted to the following formula:

R＝(d/n+c)×(100-E_B)/E_B (1)

α＝180×I/(π×R) (2)

where R is the minimum bend radius, c is the thickness of the hard wire layer 201, d is the sum of the thicknesses of the first insulating layers 202, n is the number of the first insulating layers 202, and E_BTo the elongation of the hard wire layer 201, α is a bending angle per unit length, and I is a unit arc length.

When d/n is 50 μm, c is 50 μm, E_B30%, R233 μm, α 246 °; that is, in a preferred embodiment, the bending angle of the half bending area 29 can be up to 246 °.

The half flex circuit board 2 further includes a solder mask layer 205, and the solder mask layer 205 is disposed on the outer side of the half flex circuit board 2.

The application also provides a manufacturing method of the semi-flexible circuit board 2, which comprises the following steps:

step S1: as shown in fig. 11, a plurality of hard circuit layers 201 are stacked to form an inner stacked structure 20, a first intermediate circuit layer 21 and a second intermediate circuit layer 23 are formed on opposite surfaces of the inner stacked structure 20, the first intermediate circuit layer 21 includes a first flexible insulating film 211, the second intermediate circuit layer 23 includes a second flexible insulating film 231, the first intermediate circuit layer 21 and the second intermediate circuit layer 23 each include a surface copper region 26, and the surface copper regions 26 are respectively disposed on the sides of the first flexible insulating film 211 and the second intermediate circuit layer 23 away from the inner stacked structure 20.

The inner laminated structure 20 may be a prefabricated structure, a single-sided copper clad plate is disposed on two opposite surfaces of the inner laminated structure 20, and the first intermediate circuit layer 21 and the second intermediate circuit layer 23 are obtained by processing the single-sided copper clad plate through an image transfer process, in an embodiment, the inner laminated structure 20 may include at least one hard circuit layer 201, the hard circuit layer 201 is spaced from the first intermediate circuit layer 21 and the second intermediate circuit layer 23 by a first insulating layer 202, and the hard circuit layer 201 may be electrically connected with the first intermediate circuit layer 21 and the second intermediate circuit layer 23 by a conductive pillar 203; in other embodiments, the inner stacked structure 20 may include a plurality of hard wire layers 201 stacked one on another, the hard wire layers 201 and the first intermediate wire layer 21 may be separated by a first insulating layer 202, and the hard wire layers 201, the hard wire layers 201 and the first intermediate wire layer 21 may be electrically connected to each other by conductive pillars 203, respectively.

Step S2: as shown in fig. 12 and 13, a first release film 271 and a second release film 272 are provided, the first release film 271 is attached to the surface of the surface copper region 26 away from the inner layer stack 20, and the second release film 272 is attached to the surface of the surface copper region 26 away from the inner layer stack 20.

Step S3: as shown in fig. 13 and 14, at least one layer of the first hard board circuit 221 is stacked on the surface of the first intermediate circuit layer 21 to form a first outer stack 22 and a glue flow region 252, and at least one layer of the second hard board circuit 241 is stacked on the surface of the second intermediate circuit layer 23 to form a first outer stack 22 and a glue flow region 252.

The second insulating layer 273 and the copper layer 274 are formed on the surface of the first intermediate wiring layer 21 away from the inner laminate 20 and the surface of the second intermediate wiring layer 23 away from the inner laminate 20 by lamination.

In one embodiment, the second insulating layer 273 is disposed opposite to the inner layer stack 20, the portion of the second insulating layer 273 opposite to the first release film 271 is removed to expose the first release film 271, the portion of the second insulating layer 273 opposite to the second release film 272 is removed to expose the second release film 272, the copper layer 274 is disposed opposite to the inner layer stack 20, the second insulating layer 273 and the copper layer 274 are pressed, and the copper layer 274 covers the second insulating layer 273, the first release film 271 and the second release film 272.

Step S4: as shown in fig. 14 and 15, a first outer layer opening 223 penetrating through the first outer layer stack 22 is formed, such that the surface of the first release film 271 away from the first middle circuit layer 21 and the glue flowing region 252 are exposed, a second outer layer opening 243 penetrating through the second outer layer stack 24 is formed, such that the surface of the second release film 272 away from the second middle circuit layer 23 and the glue flowing region 252 are exposed.

The laminated second insulating layer 273 and the copper layer 274 are processed by using an image transfer process, so that the copper layer 274 is patterned to obtain the first hard board circuit 221 and form the first outer stack 22, the copper layer 274 is patterned to obtain the second hard board circuit 241 and form the first outer stack 22, and the portion of the copper layer 274 covering the first release film 271 and the second release film 272 is removed, specifically, a hollow area is formed after etching.

In one embodiment, the second insulating layer 273 is made of an organic material, and the second insulating layer 273 may include polypropylene. In one embodiment, the elongation of the second insulating layer 273 made of polypropylene may be 1% to 2%, the elongation of the copper layer 274 may be 2% to 16%, and when the copper layer 274 and the second insulating layer 273 are stacked to form the first outer stack 22 or the second outer stack 24, the overall elongation of the first outer stack 22 or the second outer stack 24 may be 1% to 2%. In other embodiments, the composition of the second insulating layer 273 may also include polyimide.

In one embodiment, the first outer layer stack 22 and the second outer layer stack 24 may include a plurality of hard circuit layers, and as shown in fig. 15 and 16, the steps S3 and S4 may be repeated a plurality of times, so that the first outer layer stack 22 and the second outer layer stack 24 have a multi-layer circuit structure.

Step S5: as shown in fig. 17, the first release film 271 is removed, and the exposed surface copper region 26 is etched to obtain a first inner layer opening 213 and a copper remaining region 251, wherein the first inner layer opening 213 penetrates through the first intermediate circuit layer 21 to expose at least a portion of the first flexible insulating film 211; the second release film 272 is removed, and the exposed surface copper region 26 is etched to obtain a second inner layer opening 233 and a copper remaining region 251, wherein the second inner layer opening 233 penetrates the second intermediate circuit layer 23 to expose at least a portion of the second flexible insulating film 231.

In an embodiment, the copper-remaining region 251 is remained in the etching process, the surfaces of the first flexible insulating film 211 and the second flexible insulating film 231 away from the inner stack 20 are etched to obtain the microstructure 253, and the residual glue of the first release film 271 and the second release film 272 can be removed in the etching process.

In one embodiment, the composition of the first flexible insulating film 211 and the second flexible insulating film 231 includes polyimide.

Step S6: as shown in fig. 18, the first outer laminate 22 and the second hard sheet wire 241 are subjected to surface treatment.

The surface of the first outer stacked structure 22 remote from the first intermediate wiring layer 21 is surface-treated, and the surface of the second outer stacked structure 24 remote from the second intermediate wiring layer 23 is surface-treated to form a solder mask layer 205.

According to the semi-flexible circuit board 2 and the manufacturing method thereof, the semi-flexible area 29 of the semi-flexible circuit board 2 can be arranged on any layer or any position of the semi-flexible circuit board 2, and the semi-flexible circuit board is simple to process, flexible in layout and high in wiring density.

Hereinbefore, specific embodiments of the present application are described with reference to the drawings. However, those skilled in the art will appreciate that various modifications and substitutions can be made to the specific embodiments of the present application without departing from the spirit and scope of the application. Such modifications and substitutions are intended to be within the scope of the present application.

Claims

1. A semi-flexible circuit board is characterized by comprising:

2. The half flex circuit of claim 1 further comprising:

a second intermediate circuit layer, the first intermediate circuit layer and the second intermediate circuit layer being disposed on opposite sides of the inner layer stack, the second intermediate circuit layer including a second flexible insulating film, a second intermediate circuit layer, and a second inner layer opening, the second intermediate circuit layer and the second inner layer opening being disposed on a side of the second flexible insulating film away from the inner layer stack, the second inner layer opening penetrating the second intermediate circuit layer to expose at least a portion of the second flexible insulating film; and

3. The circuit board of claim 1, wherein the circuit board defines a rigid board area and a semi-flexible area, the first inner opening is disposed in the semi-flexible area, the first outer layer stack and the first middle circuit layer and the inner layer stack covered by the first outer layer stack are disposed in the rigid board area, and the copper-remaining area protrudes from the rigid board area to the semi-flexible area.

4. The semi-flexible wiring board of claim 1, wherein a surface roughness Rz of a surface of the first flexible insulating film away from the inner laminate is in a range of 0.5 to 2.6.

5. The half flex circuit board of claim 1 wherein the distance that the copper-remaining area protrudes toward the first inner layer opening ranges from 0.05mm to 0.5 mm.

6. The semi-flexible folded circuit board of claim 1, wherein the first flexible insulating film has an elongation of 30% to 70%, the inner laminate further includes a first insulating layer, the first outer laminate further includes a second insulating layer, and the first insulating layer and the second insulating layer have an elongation of 1% to 2%.

7. A manufacturing method of a semi-flexible circuit board is characterized by comprising the following steps:

stacking a plurality of hard circuit layers to form an inner stacked structure;

at least one layer of first hard board circuit is arranged on the surface of the first middle circuit layer in a stacking mode to form a first outer stacking structure and a glue flowing area;

8. The method for manufacturing a semi-flex circuit board according to claim 7, comprising:

a second intermediate circuit layer is formed on the surface of the inner laminated structure far away from the first intermediate circuit layer, the second intermediate circuit layer comprises a second hard circuit layer and a second flexible insulating film, and the second hard circuit layer is arranged on one side, far away from the inner laminated structure, of the second flexible insulating film;

9. The method of manufacturing a half flex circuit board according to claim 8, wherein the first hard board circuit is formed by stacking an insulating layer and a copper layer, at least a portion of the insulating layer corresponding to the first release film is removed, and the copper layer of the first hard board circuit is etched to make a hollow region of the copper layer corresponding to the first release film so as to form the first outer layer opening.

10. The method of manufacturing a semi-flexible circuit board according to claim 9, wherein the first flexible insulating film and the second flexible insulating film are etched away from the surface of the inner laminate, and a surface roughness Rz of the first flexible insulating film and the second flexible insulating film away from the surface of the inner laminate is in a range of 0.5 to 2.6.