阅读说明：本技术 电路板及其制作方法 (Circuit board and manufacturing method thereof ) 是由 郭宏艳 何明展 沈芾云 韦文竹 于 2020-06-23 设计创作，主要内容包括：一种电路板,包括信号传输层、分别设于信号传输层两侧的第一接地层与第二接地层,信号传输层包括信号线及屏蔽线,屏蔽线围绕信号线设置；电路板包括主体区及弯折区,第一接地层包括位于弯折区的第一网格部、位于主体区的第一连接垫与接地线,第一连接垫通过第一导电孔电连接信号线,接地线通过第二导电孔电连接屏蔽线及第二接地层,接地线与第二接地层中的至少一者用于接地；第二接地层包括位于弯折区的第二网格部,第一网格部与第二网格部中的铜呈网格状分布,其中第一网格部与第二网格部的铺铜率大于或等于70％,第一网格部与第二网格部的铜层厚度低于第一接地层与第二接地层位于主体区的铜层的厚度。还提供一种电路板制作方法。(A circuit board comprises a signal transmission layer, a first grounding layer and a second grounding layer, wherein the first grounding layer and the second grounding layer are respectively arranged on two sides of the signal transmission layer; the circuit board comprises a main body area and a bending area, the first grounding layer comprises a first grid part positioned in the bending area, a first connecting pad positioned in the main body area and a grounding wire, the first connecting pad is electrically connected with the signal wire through a first conductive hole, the grounding wire is electrically connected with the shielding wire and a second grounding layer through a second conductive hole, and at least one of the grounding wire and the second grounding layer is used for grounding; the second grounding layer comprises a second grid part positioned in the bending area, copper in the first grid part and the second grid part is distributed in a grid shape, wherein the copper spreading rate of the first grid part and the second grid part is more than or equal to 70%, and the thickness of the copper layer of the first grid part and the second grid part is less than that of the copper layer of the first grounding layer and the second grounding layer positioned in the main body area. A circuit board manufacturing method is also provided.)

1. The utility model provides a circuit board, includes the signal transmission layer, locates respectively first ground plane and the second ground plane of signal transmission layer both sides, its characterized in that: the signal transmission layer comprises a signal wire and a shielding wire, and the shielding wire is arranged around the signal wire; the circuit board comprises a main body area and a bending area, the first grounding layer comprises a first grid part positioned in the bending area, a first connecting pad positioned in the main body area and a grounding wire, the first connecting pad is electrically connected with the signal wire through a first conductive hole, the grounding wire is electrically connected with the shielding wire and the second grounding layer through a second conductive hole, and at least one of the grounding wire and the second grounding layer is used for grounding; the second grounding layer comprises a second grid part located in the bending area, copper in the first grid part and the second grid part is distributed in a grid shape, wherein the copper spreading rate of the first grid part and the second grid part is greater than or equal to 70%, and the thickness of the copper layer of the first grid part and the second grid part is lower than that of the copper layer of the first grounding layer and the second grounding layer located in the main body area.

2. The circuit board of claim 1, wherein: the thickness of the copper layers of the first grid part and the second grid part ranges from 6 micrometers to 9 micrometers.

3. The circuit board of claim 1, wherein: the circuit board further comprises a dielectric layer positioned among the second grounding layer, the signal transmission layer and the first grounding layer, a first covering layer covering the first grounding layer and a second covering layer covering the second grounding layer.

4. The circuit board of claim 3, wherein: the dielectric layer is made of low-loss materials and comprises polyimide, modified polyimide or liquid crystal high polymer.

5. The circuit board of claim 3, wherein: the length L of the bending region meets the following formula L ═ α R, wherein α is the radian required to be bent, and R is the bending radius; r satisfies the following formula: and R ═ D/2+ c [ (100-Eb)/Eb ] -D, wherein D is the thickness of the dielectric layer, c is the thickness of the copper layer, Eb is the elongation of the copper layer, and D is the thickness of the first cover layer and the second cover layer.

6. The circuit board of claim 3, wherein: the first covering layer is provided with an opening to expose the first connecting pad, the opening is provided with a solder mask layer, the solder mask layer surrounds and exposes the first connecting pad, and the first connecting pad is further provided with a surface treatment layer.

7. A circuit board manufacturing method is characterized by comprising the following steps:

providing a first copper-clad plate, wherein the first copper-clad plate comprises a first base material, a first copper layer and a second copper layer, the first copper layer and the second copper layer are respectively arranged on two sides of the first base material, the first copper layer forms a signal transmission layer, the second copper layer forms a second grounding layer, the signal transmission layer comprises a signal wire and a shielding wire, the second grounding layer comprises a second grid part, copper of the second grid part is distributed in a grid shape, and the copper spreading rate of the second grid part is more than or equal to 70%;

providing a second copper-clad plate, wherein the second copper-clad plate comprises a second base material and a third copper layer arranged on one side of the second base material, the second copper-clad plate is laminated on the signal transmission layer, and the first base material and the second base material form a dielectric layer;

forming a first grounding layer on the third copper layer, wherein the first grounding layer comprises a first grid part, copper in the first grid part is distributed in a grid shape, and the copper spreading rate of the first grid part is greater than or equal to 70%;

and forming a first conductive hole electrically connecting the first connecting pad and the signal line and a second conductive hole electrically connecting the grounding line, the shielding line and the second grounding layer.

8. The method for manufacturing a circuit board according to claim 7, wherein: after the first ground layer is formed, the method further comprises:

and performing copper reduction treatment on the copper layers in the first grid part and the second grid part to reduce the thickness of the copper layers.

Technical Field

The application relates to a circuit board and a manufacturing method thereof.

Background

With the continuous progress of science and technology, electronic products are developed in the directions of light, thin, short and small, and the application of the soft board is wider and wider. In addition, with the development of wearable electronic technology, the circuit board needs higher deflection performance to meet the requirements of activities of all parts of the body. Meanwhile, the arrival of the 5G era makes the frequency and efficiency of wireless transmission higher, and how to meet the dual requirements of bending and high-speed transmission become the current hot.

The circuit board for high-frequency transmission at present is generally provided with a signal wire arranged in an intermediate layer, and the upper side and the lower side of the signal wire are grounded. Because the signal line of stripline design has ground plane on both sides, therefore impedance is easy to control, and the shielding is better simultaneously. The thicker the dielectric thickness, the less signal loss during high frequency transmission.

The disadvantage of this design is that as the requirement for low loss increases, the bending performance of the transmission line decreases as the thickness of the transmission line increases, and especially the product no longer has the capability of dynamic bending. Resulting in difficulty in application to wearing products requiring dynamic bending and having a required life.

Disclosure of Invention

Accordingly, a flexible circuit board for high frequency signal transmission and a method for fabricating the same are provided.

The embodiment of the application provides a circuit board, which comprises a signal transmission layer, a first grounding layer and a second grounding layer, wherein the first grounding layer and the second grounding layer are respectively arranged on two sides of the signal transmission layer; the circuit board comprises a main body area and a bending area, the first grounding layer comprises a first grid part positioned in the bending area, a first connecting pad positioned in the main body area and a grounding wire, the first connecting pad is electrically connected with the signal wire through a first conductive hole, the grounding wire is electrically connected with the shielding wire and the second grounding layer through a second conductive hole, and at least one of the grounding wire and the second grounding layer is used for grounding; the second grounding layer comprises a second grid part located in the bending area, copper in the first grid part and the second grid part is distributed in a grid shape, wherein the copper spreading rate of the first grid part and the second grid part is greater than or equal to 70%, and the thickness of the copper layer of the first grid part and the second grid part is lower than that of the copper layer of the first grounding layer and the second grounding layer located in the main body area.

Further, the thickness of the copper layer of the first grid part and the second grid part ranges from 6 μm to 9 μm.

Furthermore, the circuit board further comprises a dielectric layer positioned among the second grounding layer, the signal transmission layer and the first grounding layer, a first covering layer covering the first grounding layer and a second covering layer covering the second grounding layer.

Further, the dielectric layer material is a low-loss material, and the dielectric layer material includes polyimide, modified polyimide or liquid crystal high polymer.

Further, the length L of the bending region satisfies the following formula L ═ α × R, where α is the radian required to be bent, and R is the bending radius; r satisfies the following formula: and R ═ D/2+ c [ (100-Eb)/Eb ] -D, wherein D is the thickness of the dielectric layer, c is the thickness of the copper layer, Eb is the elongation of the copper layer, and D is the thickness of the first cover layer and the second cover layer.

Furthermore, the first covering layer is provided with an opening to expose the first connecting pad, the opening is provided with a solder mask layer, the solder mask layer surrounds and exposes the first connecting pad, and the first connecting pad is further provided with a surface treatment layer.

A circuit board manufacturing method comprises the following steps:

providing a first copper-clad plate, wherein the first copper-clad plate comprises a first base material, a first copper layer and a second copper layer, the first copper layer and the second copper layer are respectively arranged on two sides of the first base material, the first copper layer forms a signal transmission layer, the second copper layer forms a second grounding layer, the signal transmission layer comprises a signal wire and a shielding wire, the second grounding layer comprises a second grid part, copper of the second grid part is distributed in a grid shape, and the copper spreading rate of the second grid part is more than or equal to 70%;

providing a second copper-clad plate, wherein the second copper-clad plate comprises a second base material and a third copper layer arranged on one side of the second base material, the second copper-clad plate is laminated on the signal transmission layer, and the first base material and the second base material form a dielectric layer;

forming a first grounding layer on the third copper layer, wherein the first grounding layer comprises a first grid part, copper in the first grid part is distributed in a grid shape, and the copper spreading rate of the first grid part is greater than or equal to 70%;

and forming a first conductive hole electrically connecting the first connecting pad and the signal line and a second conductive hole electrically connecting the grounding line, the shielding line and the second grounding layer.

Further, after the first ground layer is formed, the method further includes:

and performing copper reduction treatment on the copper layers in the first grid part and the second grid part to reduce the thickness of the copper layers.

The circuit board of this application sets up the bending region. The first outer layer comprises a first grid part located in the bending area. The second outer layer includes a second mesh portion located at the inflection region. The copper in the first grid part and the second grid part is distributed in a grid shape. Wherein the copper spreading rate of the first grid part and the second grid part is more than or equal to 70 percent. The first grid part and the second grid part are in a grid shape so as to facilitate the bending of the circuit board. And when the copper laying rate of the grid is more than or equal to 70 percent, the isolation between the signal wire and other functional devices can be more than 40dB, thereby realizing good isolation.

Drawings

Fig. 1 is a sectional view of a circuit board according to a first embodiment of the present application.

Fig. 2 is a sectional view of a circuit board according to a second embodiment of the present application.

Fig. 3 is a top view of a signal transmission layer of the circuit board shown in fig. 1.

Fig. 4 is a plan view of a first mesh portion of a first ground layer of the circuit board shown in fig. 1.

Fig. 5 is a plan view of a second mesh portion of a second ground layer of the circuit board shown in fig. 1.

Fig. 6 is a cross-sectional view of the first copper-clad unit according to the third embodiment of the present invention.

Fig. 7 is a cross-sectional view of the first copper layer forming the inner wiring layer and the second copper layer forming the second outer layer of the first copper-clad unit shown in fig. 6.

Fig. 8 is a cross-sectional view of the structure shown in fig. 7 with a second copper-clad unit attached.

Fig. 9 is a cross-sectional view of the third copper layer forming the first outer layer of the second copper-clad unit shown in fig. 8.

Fig. 10 is a cross-sectional view of the first mesh portion and the second mesh portion of the structure shown in fig. 9 after copper reduction.

Fig. 11 is a cross-sectional view of the structure of fig. 10 after forming a first conductive via and a second conductive via.

Fig. 12 is a cross-sectional view of the structure of fig. 11 with a first cover layer attached to the first outer layer and a second cover layer attached to the second outer layer.

Fig. 13 is a cross-sectional view of the structure of fig. 12 after a solder mask layer and a surface treatment layer are formed on the first connection pads.

Description of the main elements

Circuit board 100

Body region 100a

Bending zone 100b

Signal transmission layer 10

Signal line 11

Shielded wire 12

First ground plane 20

First mesh part 21

First connection pad 22

Ground wire 23

Second ground layer 30

Second mesh part 31

First conductive via 41

Second conductive via 42

Dielectric layer 50

First cover layer 61

Opening 601

Second cover layer 62

Solder mask layer 70

Surface treatment layer 80

First copper-clad plate 101

First substrate 1011

First copper layer 1012

Second copper layer 1013

Second copper-clad plate 102

Second substrate 1021

Third copper layer 1022

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

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Unless defined otherwise, all 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. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

The embodiment of the application provides a circuit board, which comprises an inner layer circuit layer, a first outer layer and a second outer layer, wherein the first outer layer and the second outer layer are respectively arranged on two sides of the inner layer circuit layer; the circuit board comprises a main body area and a bending area, the first outer layer comprises a first grid part positioned in the bending area, a first connecting pad positioned in the main body area and a grounding wire, the first connecting pad is electrically connected with the signal wire through a first conductive hole, the grounding wire is electrically connected with the shielding wire and the second outer layer through a second conductive hole, and at least one of the grounding wire and the second outer layer is used for grounding; the second outer layer comprises a second grid part located in the bending area, copper in the first grid part and the second grid part is distributed in a grid shape, wherein the copper spreading rate of the first grid part and the second grid part is larger than or equal to 70%, and the thickness of the copper layer of the first grid part and the second grid part is smaller than that of the copper layer of the first outer layer and the second outer layer located in the main body area.

An embodiment of the present application further provides a method for manufacturing a circuit board, including:

providing a first copper-clad plate, wherein the first copper-clad plate comprises a first base material, a first copper layer and a second copper layer, the first copper layer and the second copper layer are respectively arranged on two sides of the first base material, the first copper layer forms a signal transmission layer, the second copper layer forms a second grounding layer, the signal transmission layer comprises a signal wire and a shielding wire, the second grounding layer comprises a second grid part, copper of the second grid part is distributed in a grid shape, and the copper spreading rate of the second grid part is more than or equal to 70%;

providing a second copper-clad plate, wherein the second copper-clad plate comprises a second base material and a third copper layer arranged on one side of the second base material, the second copper-clad plate is laminated on the signal transmission layer, and the first base material and the second base material form a dielectric layer;

forming a first grounding layer on the third copper layer, wherein the first grounding layer comprises a first grid part, copper in the first grid part is distributed in a grid shape, and the copper spreading rate of the first grid part is greater than or equal to 70%;

and forming a first conductive hole electrically connecting the first connecting pad and the signal line and a second conductive hole electrically connecting the grounding line, the shielding line and the second grounding layer.

The circuit board of this application sets up the bending region. The first outer layer comprises a first grid part located in the bending area. The second outer layer includes a second mesh portion located at the inflection region. The copper in the first grid part and the second grid part is distributed in a grid shape. Wherein the copper spreading rate of the first grid part and the second grid part is more than or equal to 70 percent. The first grid part and the second grid part are in a grid shape so as to facilitate the bending of the circuit board. And when the copper laying rate of the grid is more than or equal to 70 percent, the isolation between the signal wire and other functional devices can be more than 40dB, thereby realizing good isolation.

Some embodiments of the present application will be described in detail below with reference to the accompanying drawings. The embodiments described below and the features of the embodiments can be combined with each other without conflict.

Referring to fig. 1, a circuit board 100 according to a first embodiment of the present invention includes a signal transmission layer 10, and a first ground layer 20 and a second ground layer 30 respectively located on two sides of the signal transmission layer 10. Referring to fig. 3, the signal transmission layer 10 includes a signal line 11 and a shielding line 12, and the shielding line 12 is disposed around the signal line 11.

The circuit board 100 includes a main body region 100a and a bending region 100 b. The bending region 100b corresponds to a region of the circuit board 100 to be bent. The first ground layer 20 includes a first mesh portion 21 located in the bending region 100 b. In the illustrated embodiment, the bending region 100b is located in the middle region of the circuit board 100, and the two main body regions 100a are respectively located at two sides of the bending region 100 b. Referring to fig. 4 and 5, the second ground layer 30 includes a second mesh portion 31 located in the bending region 100 b. The copper in the first grid part 21 and the second grid part 31 are distributed in a grid shape. Wherein the copper spreading rate of the first grid part 21 and the second grid part 31 is greater than or equal to 70%.

The copper laying rate is more than or equal to 70%, so that the isolation degree of the signal transmission layer 10 from other functional devices can be more than 40dB, and the isolation requirement can be met.

Preferably, the signal transmission layer 10, the first ground layer 20 and the second ground layer 30 may be made of high-ductility rolled copper or electrolytic copper.

The first ground layer 20 further includes a first connection pad 22 and a ground line 23 located in the body region 100 a. The first connection pad 22 is electrically connected to the signal line 11 through a first conductive hole 41. The ground line 23 is electrically connected to the shield line 12 and the second ground layer 30 through a second conductive hole 42. The first connection pad 22 is used for connecting an external device. At least one of the ground line 23 or the second ground layer 30 is used for grounding.

In at least one embodiment, the copper layers of the first ground layer 20 and the second ground layer 30 in the bending region 100b are subjected to a copper reduction process, so that the thickness of the copper layers of the first mesh portion 21 and the second mesh portion 31 is less than that of the copper layer in the body region 100 a. The thickness of the copper layers of the first grid part 21 and the second grid part 31 ranges from 6 μm to 9 μm.

The circuit board 100 further includes a dielectric layer 50 located between the second ground layer 30, the signal transmission layer 10 and the first ground layer 20. In the illustrated embodiment, the dielectric layer 50 is a Liquid Crystal Polymer (LCP) dielectric layer. Referring to fig. 2, in the second embodiment of the present invention, the dielectric layer 50 ' includes a Polyimide (PI) or Modified-Polyimide (MPI) dielectric layer 51 ' and a glue layer 52 '; the Polyimide (PI) or Modified-Polyimide (MPI) dielectric layer 51 'is located between the second ground layer 30, the signal transmission layer 10 and the first ground layer 20, and the adhesive layer 52' is attached to the inner circuit layer 10. The dielectric layer 50 is made of a low-loss material to reduce the signal loss of the signal transmission layer 10.

In the illustrated embodiment, a first cover layer 61 is further disposed on the first ground layer 20. A second cover layer 62 is also provided on the second ground layer 30. The first cover layer 61 has an opening 601 to expose the first connection pad 22.

In the illustrated embodiment, a solder mask layer 70 is disposed at the opening 601. The solder mask layer 70 surrounds and exposes the first connection pads 22. The first connection pad 22 is further provided with a surface treatment layer 80.

The length L of the bending region 100b satisfies the following formula L ═ α × R. Wherein alpha is the radian required to be bent, and R is the bending radius. R satisfies the following formula: r ═ D/2+ c [ (100-Eb)/Eb ] — D. Wherein d is the thickness of the dielectric layer; c is the thickness of the copper layer; eb is the elongation of the copper layer; d is the thickness of the cover layer.

The third embodiment of the present application provides a method for manufacturing the circuit board 100 of the first embodiment. The manufacturing method of the circuit board comprises the following steps:

first, referring to fig. 6, a first copper-clad plate 101 is provided, where the first copper-clad plate 101 includes a first base material 1011, and a first copper layer 1012 and a second copper layer 1013 respectively disposed on two sides of the first base material 1011.

In the illustrated embodiment, the first substrate 1011 is a liquid crystal polymer. It is understood that in other embodiments, the first substrate 1011 may also be a polyimide or a modified polyimide.

In a second step, referring to fig. 7, the first copper layer 1012 is formed into the signal transmission layer 10 and the second copper layer 1013 is formed into the second ground layer 30.

In at least one embodiment, the first copper layer 1012 and the second copper layer 1013 are processed by dry film pasting, exposure, development, etching and film stripping processes to form the signal transmission layer 10 and the second ground layer 30, respectively.

The signal transmission layer 10 includes a signal line 11 and a shield line 12, and the first shield line 12 is disposed around the signal line 11.

The second ground layer 30 includes a second mesh portion 31 located in the bending region 100 b. The copper in the second mesh part 31 is distributed in a mesh shape. The copper laying rate of the second mesh part 31 is greater than or equal to 70%.

Thirdly, referring to fig. 8, a second copper clad laminate 102 is provided, where the second copper clad laminate 102 includes a second base material 1021 and a third copper layer 1022 disposed on one side of the second base material 1021, and the second base material 1021 is attached to the signal transmission layer 10.

The first substrate 1011 and the second substrate 1021 form a dielectric layer 50 after lamination.

In the illustrated embodiment, the second substrate 1021 is a liquid crystal polymer. It is understood that in other embodiments, the second copper clad laminate 102 further includes a glue layer disposed on the other side of the second substrate 1021. The first substrate 1011 may also be a polyimide or a modified polyimide. The adhesive layer is attached to the signal transmission layer 10.

Fourth, referring to fig. 9, the third copper layer 1022 is formed into the first ground layer 20.

In at least one embodiment, the third copper layer 1022 is processed by applying a dry film, exposing, developing, etching, and stripping process to form the first ground layer 20.

The first ground layer 20 includes a first mesh portion 21 located in the bending region 100 b. The copper in the first mesh part 21 is distributed in a mesh shape. The copper laying rate of the first mesh part 21 is 70% or more.

The first ground layer 20 further includes a first connection pad 22 and a ground line 23 located in the body region 100 a.

In the fifth step, referring to fig. 10, the copper layers in the first grid part 21 and the second grid part 31 are subjected to a copper reduction process to reduce the thickness thereof.

After the copper reduction, the copper layer thickness in the first grid portion 21 and the second grid portion 31 is lower than the copper layer thickness in the body region 100 a.

In at least one embodiment, the thickness of the copper layers in the first grid part 21 and the second grid part 31 ranges from 6 μm to 9 μm.

In at least one embodiment, the copper reduction process is to perform an etching process on the first grid part 21 and the second grid part 31 until the copper layer thickness of the first grid part 21 and the second grid part 31 meets the requirement.

In the sixth step, referring to fig. 11, a first conductive hole 41 electrically connecting the first connection pad 22 and the signal line 11 and a second conductive hole 42 electrically connecting the ground line 23, the shielding line 12 and the second ground layer 30 are formed.

In at least one embodiment, the first conductive via 41 and the second conductive via 42 may be formed by opening and filling conductive material.

Seventh, referring to fig. 12, a first cover layer 61 is attached on the first ground layer 20 and a second cover layer 62 is attached on the second ground layer 30.

The first cover layer 61 has an opening 601 to expose the first connection pad 22.

In an eighth step, referring to fig. 13, a solder mask layer 70 is formed at the opening 601.

The solder mask layer 70 surrounds and exposes the first connection pads 22.

In at least one embodiment, the solder mask layer 70 is formed using a liquid photosensitive solder mask ink.

In a ninth step, referring to fig. 13, the first connection pads 22 are surface-treated to form a surface treatment layer 80.

In at least one embodiment, the surface treatment layer 80 is formed by a chemical gold method, wherein the surface treatment layer 70 may be selected from one or a combination of graphite, gold, nickel palladium gold, tin, silver and organic solder mask. Of course, the surface treatment layer 80 may be omitted.

The circuit board 100 of the present application is provided with a bending region 100 b. The first ground layer 20 includes a first mesh portion 21 located in the bending region 100 b. The second ground layer 30 includes a second mesh portion 31 located in the bending region 100 b. The copper in the first grid part 21 and the second grid part 31 are distributed in a grid shape. Wherein the copper spreading rate of the first grid part 21 and the second grid part 31 is greater than or equal to 70%. The first grid part 21 and the second grid part 31 are in a grid shape to facilitate the bending of the circuit board 100. When the copper laying rate of the grid is greater than or equal to 70%, the isolation between the signal wire 11 and other functional devices is greater than 40dB, so that good isolation is realized.

Although the present application has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.