CN116583005A

CN116583005A - Copper-clad plate, flexible circuit board and electronic equipment

Info

Publication number: CN116583005A
Application number: CN202310842084.2A
Authority: CN
Inventors: 罗浩; 李昕; 张思颖
Original assignee: Honor Device Co Ltd
Current assignee: Honor Device Co Ltd
Priority date: 2023-07-11
Filing date: 2023-07-11
Publication date: 2023-08-11

Abstract

The application discloses a copper-clad plate, a flexible circuit board and electronic equipment. The copper-clad plate comprises: the medium layer comprises a plurality of air holes inside; the signal layer is formed on the first surface of the dielectric layer; the grounding layer is formed on the second surface of the dielectric layer; the first surface and the second surface are opposite surfaces, and the first surface refers to the second surface. Thus, by adding the air cavity in the dielectric layer, the dielectric constant of the air cavity is low, so that the dielectric constant of the dielectric layer can be reduced, and further, the dielectric loss can be reduced, and the signal insertion loss can be reduced. The flexible circuit board comprises a copper-clad plate, a first covering film is formed on a third surface of the copper-clad plate, and a second covering film is formed on a fourth surface of the copper-clad plate; the shielding film is formed on the surface of the first covering film, which is away from the dielectric layer. Therefore, the thickness of the flexible circuit board can be reduced, and the signal insertion loss can be effectively reduced, so that the flexible circuit board can meet the requirements of electronic equipment.

Description

Copper-clad plate, flexible circuit board and electronic equipment

Technical Field

The present application relates to the field of electronic devices, and in particular, to a flexible circuit board, and an electronic device.

Background

The folding screen device comprises a first body, a second body, a rotating shaft and a flexible circuit board. The first machine body and the second machine body are positioned on two sides of the rotating shaft, and the flexible circuit board spans the rotating shaft and is connected with the main board in the first machine body and the second machine body so as to realize signal transmission between the first machine body and the second machine body.

The folding screen device requires high thickness of the flexible circuit board. Under the condition that the thickness of the folding screen equipment is unchanged or reduced, if the thickness of the flexible circuit board is too large, the flexible circuit board can not be installed, and the top screen problem is easy to generate during assembly; if the thickness of the flexible circuit board is too small, signal insertion loss may be increased. It can be seen that the existing flexible circuit board cannot meet the requirements of the folding screen device.

Disclosure of Invention

The application provides a copper-clad plate, a flexible circuit board and electronic equipment, which are used for solving the problem that the flexible circuit board cannot meet the requirements of folding screen equipment.

In a first aspect, the present application provides a copper-clad plate, comprising: the medium layer comprises a plurality of air holes inside; the signal layer is formed on the first surface of the dielectric layer; the grounding layer is formed on the second surface of the dielectric layer; the first surface and the second surface are opposite surfaces, and the first surface refers to the second surface. Thus, by adding the air cavity in the dielectric layer, the dielectric constant of the air cavity is low, so that the dielectric constant of the dielectric layer can be reduced, and further, the dielectric loss can be reduced, and the signal insertion loss can be reduced.

In some implementations, the plurality of air voids are uniformly dispersed in the dielectric layer. Therefore, the dielectric constants of all areas in the dielectric layer can be guaranteed to be the same, so that dielectric loss is effectively reduced, and signal insertion loss is further effectively reduced.

In some implementations, the dielectric layer is made of a fluororesin material; the air cavity is formed by a filler comprising at least one of hollow glass microspheres and hollow silica. In this way, the fluororesin material is used as the material of the medium layer, so that the flexible circuit board manufactured later is softer and easier to install; the dielectric constant of the fluororesin material is relatively low, and the dielectric constant of the dielectric layer can be effectively reduced by mixing a plurality of air voids in the fluororesin material with low dielectric constant. In this way, dielectric losses can be further reduced to reduce signal insertion loss.

In some implementations, the ratio of the total volume of filler to the volume of fluororesin material is 30% to 40%. The particle size of the filler is 3-10 mu m. Thus, the dielectric constant of the dielectric layer can be effectively reduced, so that the dielectric loss is reduced, and the signal insertion loss is reduced.

In some implementations, the surface of the filler includes a modifying layer; the modified layer is used for improving the binding force of the filler and the dielectric layer. Therefore, the filler can be uniformly dispersed in the medium layer, the phenomenon of agglomeration or sedimentation is avoided, and the mechanical property of the copper-clad plate can be improved.

In some implementations, the modification layer includes a fluorocarbon bond layer; the fluorocarbon bond layer is formed by grafting modification of filler and fluorine-containing silane coupling agent. The fluorine-containing silane coupling agent comprises one of heptadecafluorodecyl triethoxysilane, heptadecafluorodecyl trimethoxysilane, tridecafluorooctyl triethoxysilane or tridecafluorooctyl trimethoxysilane. The fluorocarbon bond layer is formed by the steps of: hydrolyzing the fluorine-containing silane coupling agent to obtain a hydroxyl product, wherein the reaction formula is as follows:

；

grafting the hydroxyl product with the filler to form a fluorocarbon bond layer on the surface of the filler, wherein the reaction formula is as follows:

。

therefore, the hydroxyl number on the surface of the filler can be reduced, the acting force of hydrogen bonds between the fillers is weakened, the dispersibility of the fillers is improved, and the phenomenon of aggregation or sedimentation of the fillers is avoided. Meanwhile, the compatibility of the filler and the fluororesin material is good, and the interface binding force of the filler and the dielectric layer is improved.

In some implementations, the modifying layer includes a positive charge layer; the positive charge layer is formed by modifying the filler and the cationic surface modifier. The medium layer comprises fluorine resin colloidal particles suspended in water, the fluorine resin colloidal particles are negatively charged, so that the fluorine resin colloidal particles are adsorbed by the positive charge layer, and a fluorine resin modified layer is formed on the joint surface of the filler and the medium layer. Thus, the fluororesin modified layer on the surface of the filler can improve the compatibility with the medium layer made of fluororesin material, and further improve the interface binding force between the filler and the medium layer. Meanwhile, the adjacent fillers repel each other due to the same charge, so that the dispersibility of the fillers can be improved, and the phenomenon of aggregation or sedimentation of the fillers is avoided.

In some implementations, the thickness of the dielectric layer is greater than or equal to a preset distance between the signal layer and the ground layer. Therefore, a sufficient distance can be ensured between the signal layer and the ground layer, dielectric loss is reduced, line capacitance in the signal layer is reduced, and signal insertion loss is further reduced.

In a second aspect, the present application provides a flexible circuit board comprising: the copper-clad plate provided in the first aspect; the first covering film is formed on the third surface of the copper-clad plate; the third surface is the surface of the signal layer, which is away from the dielectric layer; the second covering film is formed on the fourth surface of the copper-clad plate, and the fourth surface is the surface of the grounding layer, which is away from the dielectric layer; and the shielding film is formed on the surface of the first covering film, which is away from the dielectric layer. Therefore, when the thickness of the flexible circuit board is reduced, the signal insertion loss is effectively reduced, and the flexible circuit board comprising the copper-clad plate can meet the requirements of electronic equipment.

In some implementations, the signal layer includes at least one trace layer formed at intervals on the first surface; the first covering film comprises a first adhesive layer and a first isolation layer which are mutually adhered; the first adhesive layer covers at least one wiring layer and is formed on the first surface; the first isolation layer is attached to the shielding film. The second covering film comprises a second adhesive layer and a second isolation layer which are mutually adhered; the surface of the second adhesive layer, which is away from the second isolation layer, is attached to the outer surface of the grounding layer. Thus, the wiring layer can be utilized to lay lines for signal transmission; the signal layer can be surrounded by the grounding layer and the shielding film to form an electromagnetic shielding structure of the flexible circuit board so as to play a role in shielding signal interference.

In a third aspect, the present application provides an electronic device comprising the flexible circuit board provided in the second aspect. The flexible circuit board can reduce the thickness, does not occupy the space in the thickness direction of the electronic equipment, can effectively reduce the signal insertion loss and meets the requirements of the electronic equipment.

Drawings

In order to more clearly illustrate the technical solution of the present application, the drawings that are needed in the embodiments will be briefly described below, and it will be obvious to those skilled in the art that other drawings can be obtained from these drawings without inventive effort.

Fig. 1 is a schematic structural diagram of an electronic device 100 according to an embodiment of the present application;

fig. 2 is a schematic diagram of an internal structure of an electronic device 100 according to an embodiment of the present application;

FIG. 3 is a schematic view of a structure of a compliance plate 50;

fig. 4 is a schematic structural view of a copper-clad plate 60 according to an embodiment of the present application;

fig. 5 is a schematic view of an exploded structure of a copper-clad plate 60 according to an embodiment of the present application;

FIG. 6 is a flow chart of a method for forming a fluorocarbon bond layer 1061 on a surface of a filler 105 according to an embodiment of the application;

FIG. 7 is a flow chart of forming a positive charge layer 1062 on the surface of the filler 105 according to an embodiment of the present application;

FIG. 8 is a flow chart of a combination of a dielectric layer 101 and a filler 105 with a positively charged layer 1062 provided by an embodiment of the application;

fig. 9 is a schematic structural diagram of a combination of a dielectric layer 101 and a filler 105 with a positive charge layer 1062 according to an embodiment of the present application;

fig. 10 is a flowchart of a method for manufacturing a copper-clad plate 60 according to an embodiment of the present application;

fig. 11 is a process flow chart for preparing a copper-clad plate 60 according to an embodiment of the present application;

fig. 12 is a schematic structural diagram of a flexible circuit board 70 according to an embodiment of the present application;

fig. 13 is an exploded view of a flexible circuit board 70 according to an embodiment of the present application;

fig. 14 is a schematic size diagram of a flexible circuit board 70 according to an embodiment of the present application;

fig. 15 is a flowchart of a method for manufacturing a flexible circuit board 70 according to an embodiment of the present application;

fig. 16 is a process flow diagram of preparing a flexible circuit board 70 provided in an embodiment of the present application;

fig. 17 is a schematic diagram illustrating a signal insertion loss test of a flexible circuit board 70 and a conventional flexible board 50 according to an embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly described below with reference to the drawings in the embodiments of the present application. It will be apparent that the described embodiments are some, but not all, embodiments of the application. Based on the embodiments of the present application, other embodiments that may be obtained by those of ordinary skill in the art without making any inventive effort are within the scope of the present application.

Hereinafter, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first", "a second", etc. may explicitly or implicitly include one or more such feature. In the description of the present application, unless otherwise indicated, the meaning of "a plurality" is two or more.

Furthermore, in the present application, directional terms "upper", "lower", etc. are defined with respect to the orientation in which the components are schematically disposed in the drawings, and it should be understood that these directional terms are relative concepts, which are used for description and clarity with respect thereto, and which may be changed accordingly in accordance with the change in the orientation in which the components are disposed in the drawings.

The electronic device according to the embodiment of the application includes, but is not limited to, a mobile phone, a folding screen mobile phone, a notebook computer, a tablet computer, a laptop computer, a personal digital assistant, or a wearable device. The following description will be made with respect to an electronic device as a folding screen mobile phone.

Fig. 1 is a schematic structural diagram of an electronic device 100 according to an embodiment of the present application.

As shown in fig. 1, in some embodiments, an electronic device 100 may include a first body 10, a second body 20, a hinge 30, and a screen 40. The first body 10 and the second body 20 are separately disposed at both sides of the axis direction of the rotation shaft 30, and the first body 10 and the second body 20 are respectively connected with the rotation shaft 30 and can rotate through the rotation shaft 30, so that an included angle between the first body 10 and the second body 20 is reduced until the electronic device is in a folded state, or an included angle between the first body 10 and the second body 20 is increased until the electronic device is in an unfolded state.

The screen 40 covers the first body 10, the second body 20, and the rotation shaft 30, and is connected to the first body 10 and the second body 20, respectively. Illustratively, the screen 40 may employ a pliable screen. The state shown in fig. 1 is a schematic view of the electronic device 100 in an unfolded state, where the first body 10 and the second body 20 are parallel distributed on two sides of the rotating shaft 30, so as to flatten the flexible screen.

Depending on the rotation directions of the first body 10 and the second body 20, the flexible screen may be hidden inside the body when the electronic device 100 is in the folded state, or may be surrounded outside the body. Wherein when the first body 10 and the second body 20 are folded toward the front of the flexible screen, the flexible screen is hidden inside the body when the electronic device 100 is in a folded state, such an electronic device may be referred to as an internal folding screen electronic device, for example: an inner folding screen mobile phone; when the first body 10 and the second body 20 are folded toward the back of the flexible screen, the flexible screen is wrapped around the exterior of the body when the electronic device 100 is in a folded state, and such an electronic device 100 may be referred to as an external folding screen electronic device, such as an external folding screen cell phone.

Fig. 2 is a schematic diagram of an internal structure of the electronic device 100 according to an embodiment of the present application.

As shown in fig. 2, in some embodiments, the first body 10 may include a first main circuit board 11 and a first sub circuit board 12, the first main circuit board 11 being located at an upper half of the first body 10, and the first sub circuit board 12 being located at a lower half of the first body 10. Batteries and/or other functional modules may be arranged between the first main circuit board 11 and the first sub circuit board 12. The side of the first body 10 may include a first antenna (not shown) with which signal transmission is performed. Wherein the signals may include radio frequency signals, communication signals, and the like.

Also, the second body 20 may include a second main circuit board 21 and a second sub circuit board 22, the second main circuit board 21 being located at an upper half of the second body 20, and the second sub circuit board 22 being located at a lower half of the second body 20. Batteries and/or other functional modules may be laid out between the second main circuit board 21 and the second sub circuit board 22. The side of the second body 20 may include a second antenna (not shown) with which signal transmission is performed.

In order to realize signal transmission, a plurality of flexible boards (Flexible Printed Circuit, FPC) 50 are generally disposed in the first body 10 and the second body 20, and the flexible boards 50 have excellent characteristics such as light weight, thin thickness, and free bending and folding, for the electronic device 100 is a folding screen mobile phone.

Illustratively, the first main circuit board 11 is connected to the first antenna through the first flexible board 501, and signal transmission between the first main circuit board 11 and the first antenna is achieved by using the first flexible board 501. The first main circuit board 11 is connected to the first sub circuit board 12 through the second flexible board 502, and signal transmission between the first main circuit board 11 and the first sub circuit board 12 is achieved by the second flexible board 502. The third flexible board 503 spans the rotation shaft 30 in the first direction and connects the first main circuit board 11 and the second main circuit board 21 to achieve signal transmission between the first body 10 and the second body 20. Wherein the first direction is a direction perpendicular to the rotation shaft 30. The second main circuit board 21 is connected to the second sub circuit board 22 and the second antenna through the fourth flexible board 504, and signal transfer between the second main circuit board 21 and the second sub circuit board 22, signal transfer between the second main circuit board 21 and the second antenna, and signal transfer between the second sub circuit board 22 and the second antenna are achieved by the fourth flexible board 504.

With the trend of light and thin electronic devices 100, the internal accommodating space of the electronic device 100 is smaller and smaller. Based on the internal structure layout of the electronic device 100, the plurality of flexible boards 50 laid out in the electronic device 100 may need to traverse the battery area or traverse the functional module, etc. Thus, the flexible board 50 occupies a space in the thickness direction of the electronic device 100, which affects the electronic device 100 to be thin and lightweight. Therefore, the electronic apparatus 100 has a high demand for the thickness of the compliance board 50.

Fig. 3 is a schematic diagram of the structure of a compliance plate 50.

As shown in fig. 3, the flexible board 50 includes a shielding film layer 51, a first protective film layer 52, a signal film layer 53, a dielectric film layer 54, a ground film layer 55, and a second protective film layer 56, which are laminated in this order in the thickness direction (z-axis direction).

The shielding film layer 51 is covered on the first protective film layer 52. The shielding film layer 51 is used for shielding electromagnetic interference and avoiding other electromagnetic signals from interfering with the flexible board 50.

The first protective film 52 covers the signal film 53 for protecting the signal film 53.

The signal film layer 53 includes radio frequency wiring layers (not shown) disposed at intervals, and the radio frequency wiring layers are used for routing lines to transmit signals. The signal film layer 53 is covered on the dielectric film layer 54, so that the first protective film layer 52 can be covered on the dielectric film layer 54 between two adjacent radio frequency wiring layers. It is also understood that the signal film layer 53 is embedded in the first protective film layer 52. The material of the signal film layer 53 may be copper.

The dielectric layer 54 is a supporting layer of the flexible board 50 and has characteristics of insulation, breakdown resistance, discoloration resistance, and the like. The dielectric layer 54 may be Polyimide (PI), liquid crystal polymer (liquid crystal polymer, LCP), polyether ether ketone (PEEK), or the like.

The ground film layer 55 covers the surface of the dielectric film layer 54 remote from the signal film layer 53. The ground film layer 55 is used for grounding to ensure the safety of the use of the flexible board 50. The grounding film layer 55 and the shielding film layer 51 enclose the signal film layer 53 to form an electromagnetic shielding structure of the flexible board 50, so as to play a role in shielding signal interference.

The second protective film layer 56 covers the surface of the ground film layer 55 far away from the dielectric film layer 54, and the second protective film layer 56 is used for protecting the ground film layer 55.

The first protective film 52 and the second protective film 56 have the same structure. The first protective film layer 52 includes a first Polyimide film (PI) 522 and a first adhesive 521, and the first Polyimide film 522 is covered on the signal film layer 53 and the dielectric film layer 54 by the first adhesive 521; the second protective film layer 56 includes a second Polyimide film (PI) 562 and a second adhesive 561, and the second Polyimide film 562 is covered on the ground film layer 55 by the second adhesive 561.

Exemplary, thickness H of shielding film layer 51 ₅₁ The thickness of the signal film layer 53 is about 10 μm, the thickness H of the first adhesive 521 is about 12 μm ₅₂₁ And thickness H of the second adhesive 561 ₅₆₁ All about 15 μm, the thickness H of the first polyimide film 522 ₅₂₂ And thickness H of second polyimide film 562 ₅₆₂ All are about 12.5 μm, and the thickness H of the dielectric film 54 is ₅₄ The thickness H of the ground film layer 55 is about 50 μm ₅₅ About 12. Mu.m. Wherein the thickness H of the first adhesive 521 ₅₂₁ The distance between the first polyimide film 522 and the dielectric film layer 54 (the state shown in fig. 3) may be determined, or the distance between the first polyimide film 522 and the signal film layer 53 may be determined.

Referring again to fig. 3, since the signal film 53 is embedded in the first adhesive 521, the thickness of the signal film 53 does not affect the thickness H of the flexible board 50 ₅₀ . Thus, thickness H of flexible board 50 ₅₀ To sum the thicknesses of the other film layers except the signal film layer 53, exemplary, H ₅₀ Thickness H of flexible plate 50 =127 μm ₅₀ Affecting the thickness of the electronic device 100. When the electronic apparatus 100 is thinned, the internal accommodation space of the electronic apparatus 100 is reduced. Then, if the thickness H of the compliance plate 50 ₅₀ Too large, may not be installed and may easily create a roof problem during assembly. Therefore, the thickness H of the compliance plate 50 needs to be ₅₀ And (3) reducing.

Since dielectric layer 54 is the layer having the greatest ratio of thickness of compliance plate 50 relative to the other layers, compliance plate 50 thickness H is reduced ₅₀ Is to fall in a common wayThickness H of low dielectric film 54 ₅₄ . However, the thickness H of the dielectric film 54 ₅₄ The decrease may result in a decrease in the distance between the signal film layer 53 and the ground film layer 55. Thickness H of dielectric film 54 ₅₄ When the distance between the signal film layer 53 and the ground film layer 55 is smaller than the preset distance, the dielectric loss is increased, so that the capacitance of the circuit in the signal film layer 53 is increased, and the signal insertion loss is increased. It can be seen that the existing flexible board cannot meet the requirements of the electronic device 100.

In order to reduce signal insertion loss when reducing the thickness of the flexible circuit board, the embodiment of the application provides a copper-clad plate and the flexible circuit board so as to meet the requirements of the electronic equipment 100.

Fig. 4 is a schematic structural diagram of a copper-clad plate 60 according to an embodiment of the present application.

As shown in fig. 4, in some embodiments, the copper-clad plate 60 may include: dielectric layer 101, signal layer 103, and ground layer 104.

The dielectric layer 101 is a supporting layer of the copper-clad plate 60, and has the characteristics of insulation, breakdown resistance, discoloration resistance and the like.

Since dielectric loss is proportional to the dielectric constant (Dk) of the dielectric material, the dielectric layer 101 needs to have a low dielectric constant in order to reduce the dielectric loss and the signal insertion loss.

The interior of the dielectric layer 101 includes a plurality of air voids 102. Inside the air cavity 102 is air, which has the lowest dielectric constant, and exemplary, the dielectric constant of air is 1 (F/m). Thus, the dielectric constant of the dielectric layer 101 can be reduced, and dielectric loss can be reduced, so that signal insertion loss can be reduced.

Fig. 5 is a schematic diagram of an exploded structure of a copper-clad plate 60 according to an embodiment of the present application.

As shown in fig. 5, in some embodiments, the dielectric layer 101 may include a first surface 1011 and a second surface 1012 opposite each other, wherein the first surface 1011 references the second surface 1012. The signal layer 103 is formed on the first surface 1011 of the dielectric layer 101; the ground layer 104 is formed on the second surface 1012 of the dielectric layer 101.

The signal layer 103 is used for routing lines to transmit signals. The ground layer 104 is used for grounding to shield interference signals. The signal layer 103 and the ground layer 104 may be made of copper. Thus, the first surface 1011 and the second surface 1012 of the dielectric layer 101 are both surrounded by copper material, and a double-sided copper-clad plate structure can be formed.

Referring again to fig. 4, exemplary, dielectric layer 101 thickness H ₁₀₁ May be about 70 μm, and the thickness H of the signal layer 103 may be about ₁₀₃ May be about 6 μm, and the thickness H of the ground layer 104 may be about ₁₀₄ May be about 6. Mu.m.

According to the copper-clad plate 60 provided by the embodiment of the application, the air cavity 102 is added in the dielectric layer 101, so that the dielectric constant of the dielectric layer 101 can be reduced, and further, the dielectric loss is reduced, so that the signal insertion loss is reduced. Thus, the copper-clad laminate 60 has high signal transmission speed and low transmission loss, so as to ensure that the flexible circuit board including the copper-clad laminate 60 can meet the requirements of the electronic device 100.

In some embodiments, the dielectric layer 101 may be made of a fluororesin material, which has heat resistance, low temperature impact resistance, combustion resistance, chemical resistance, and electrical insulation.

For example, the fluororesin material may include Chlorotrifluoroethylene (CTFE) and the like, and Chlorotrifluoroethylene has excellent electric properties, heat and chemical resistance and the like.

Table 1 shows the performance comparison of chlorotrifluoroethylene with polyimide.

TABLE 1 comparison of the Properties of chlorotrifluoroethylene and polyimide

。

Referring to table 1, the film thickness refers to the thickness of the dielectric layer 101 made of the above material in μm; the rebound force refers to a response force to an applied object after the material is compressed by a certain proportion and reaches mechanical balance, and the unit is g. The elasticity determines the softness of the material, the lower the elasticity, the softer the material; the higher the resilience, the harder the material.

Illustratively, the chlorotrifluoroethylene has a resiliency of 4.93g at a film thickness of 50 μm; the polyimide had a repulsive force of 20.04g at a film thickness of 25. Mu.m. Then, it is estimated that the polyimide has a larger elastic force than that of chlorotrifluoroethylene when the film thickness is 50. Mu.m.

As can be seen, as the supporting layer of the copper-clad plate 60, the chlorotrifluoroethylene has a lower resilience force than the commonly used polyimide, and the lower resilience force makes the dielectric layer 101 softer, and thus makes the flexible circuit board softer and the flexible circuit board easier to assemble.

In addition, chlorotrifluoroethylene has excellent dielectric properties, and its dielectric constant (Dk) is 2.1. Whereas polyimide has a dielectric constant between 2.5 and 3.5. It can be seen that chlorotrifluoroethylene has a lower dielectric constant than polyimide.

In some embodiments, where the dielectric layer 101 is made from a fluororesin material, the fluororesin material is made from an emulsion, and the fluororesin colloidal particles are mixed with water to form an emulsion, and the fluororesin colloidal particles are suspended in the water. The dielectric layer 101 includes fluororesin colloidal particles suspended in water, the fluororesin colloidal particles being negatively charged, and the particle diameter of the fluororesin colloidal particles being 0.15 to 0.17 μm. In this way, the flexibility of the dielectric layer 101 can be improved, thereby making the flexible circuit board more flexible.

According to the copper-clad plate 60 provided by the embodiment of the application, the fluororesin material is used as the material of the dielectric layer 101, so that the flexible circuit board is softer and is easier to install; the dielectric constant of the dielectric layer 101 can be effectively reduced by mixing a plurality of air voids 102 in a fluororesin material having a low dielectric constant. In this way, dielectric losses can be further reduced to reduce signal insertion loss.

In some embodiments, the plurality of air voids 102 may be uniformly dispersed in the dielectric layer 101. In this way, the dielectric constants of each region in the dielectric layer 101 can be ensured to be the same, so that the dielectric loss is effectively reduced, and the signal insertion loss is further effectively reduced.

In some embodiments, the air voids 102 may be formed from a filler 105, and the filler 105 may include at least one of hollow glass microspheres and hollow silica. The interiors of the hollow glass beads and hollow silica are hollow with air to form air voids 102. Since the air has a low dielectric constant, the dielectric constants of the hollow glass beads and the hollow silicon dioxide are low, and the dielectric loss of the hollow glass beads and the hollow silicon dioxide is low, so that the dielectric loss of the dielectric layer 101 can be reduced. The particle size of the filler 105 may be 3 to 10 μm, and, for example, the particle sizes of the hollow glass beads and the hollow silica may be 3 to 10 μm.

The ratio of the total volume of the filler 105 to the volume of the fluororesin material is 30% to 40%. Thus, the dielectric constant of the dielectric layer 101 can be effectively reduced, thereby reducing dielectric loss and reducing signal insertion loss.

Because the fluororesin material is an organic material, the filler 105 is an inorganic material, and the fluororesin material is a low surface energy material, the interface bonding force between the fluororesin material and the filler 105 is poor, and the organic/inorganic interface defect exists. In this way, the filler 105 is unevenly dispersed in the dielectric layer 101, so that aggregation or sedimentation is easy to occur, and the mechanical properties of the copper-clad plate 60 are affected.

In some embodiments, to avoid agglomeration or sedimentation of the filler 105, the surface of the filler 105 is modified such that the surface of the filler 105 includes a modified layer with which organic/inorganic interface defects are ameliorated to increase the interfacial bonding force of the filler 105 to the dielectric layer 101. In this way, the filler 105 can be uniformly dispersed in the dielectric layer 101, so that agglomeration or sedimentation phenomenon is avoided, and the mechanical property of the copper-clad plate 60 can be improved.

In some embodiments, the modification layer may include a fluorocarbon bond layer 1061; the fluorocarbon bond layer 1061 is formed by graft modification of the filler 105 and the fluorine-containing silane coupling agent 1071. Wherein the fluorine-containing silane coupling agent 1071 may include heptadecafluorodecyltriethoxysilane (C) ₁₆ H ₁₉ F ₁₇ O ₃ Si), heptadecafluorodecyl trimethoxysilane (C) ₁₃ H ₁₃ F ₁₇ O ₃ Si), tridecafluorooctyltriethoxysilane (C) ₁₄ H ₁₉ F ₁₃ O ₃ Si) or tridecafluorooctyltrimethoxysilane (C) ₁₁ H ₁₃ F ₁₃ O ₃ Si).

Fig. 6 is a flowchart of a method for forming a fluorocarbon bond layer 1061 on a surface of a filler 105 according to an embodiment of the present application.

As shown in fig. 6, in some embodiments, the fluorocarbon bond layer 1061 is formed by the following steps S101-S102:

step S101, hydrolyzing the fluorine-containing silane coupling agent 1071 to obtain a hydroxyl product 108, wherein the reaction formula is as follows:

；

In step S102, the hydroxyl product 108 is grafted to the filler 105 to form a fluorocarbon bond layer 1061 on the surface of the filler 105, where the reaction formula is as follows:

。

hydroxyl-OH is arranged on the surface of the hydroxyl product 108, hydroxyl-OH is arranged on the surface of the filler 105, and the hydroxyl product 108 is grafted with the filler 105, so that the number of hydroxyl groups on the surface of the filler 105 can be reduced, the acting force of hydrogen bonds between the fillers 105 is weakened, the dispersibility of the filler 105 is improved, and the aggregation or sedimentation phenomenon of the filler 105 is avoided.

Fluorocarbon bond layer 1061 includes-CF ₃ Bonds to introduce-CF at the surface of the filler 105 ₃ A key. And the surface of the fluororesin material is provided with-CF ₃ The bond, in this way, can make the compatibility of filler 105 and fluororesin material good, improve the organic/inorganic interface defect, in order to improve the interface binding force of filler 105 and dielectric layer 101.

Fig. 7 is a flow chart of forming a positive charge layer 1062 on the surface of the filler 105 according to an embodiment of the present application.

As shown in fig. 7, in some embodiments, the modifying layer may include a positively charged layer 1062; the positive charge layer 1062 is formed by modifying the filler 105 with a cationic surface modifier 1072. In this way, the surface of the filler 105 is modified so that the surface of the filler 105 carries the positive charge layer 1062.

Fig. 8 is a flow chart of a combination of a dielectric layer 101 and a filler 105 with a positively charged layer 1062 provided by an embodiment of the application.

Fig. 9 is a schematic structural diagram of a combination of a dielectric layer 101 and a filler 105 with a positive charge layer 1062 according to an embodiment of the present application. Wherein fig. 9 only schematically shows a schematic structural diagram of four fillers 105 combined with the dielectric layer 101.

As shown in fig. 8 and 9, in some embodiments, the dielectric layer 101 includes fluorine resin colloidal particles 1013 suspended in water, the fluorine resin colloidal particles 1013 being negatively charged. In this way, the fluorine resin colloidal particles 1013 are adsorbed by the positive charge layer 1062 on the surface of the filler 105, and the fluorine resin modified layer 109 is formed on the bonding surface between the filler 105 and the dielectric layer 101.

The filler 105 with the fluororesin modified layer 109 is used for preparing the dielectric layer 101 of the flexible copper-clad plate 60, and the fluororesin modified layer 109 on the surface of the filler 105 can improve the compatibility with the dielectric layer 101 made of fluororesin materials, improve the organic/inorganic interface defect, and further improve the interface binding force between the filler 105 and the dielectric layer 101. Meanwhile, the adjacent fillers 105 are repelled due to the same positive charges, so that the dispersibility of the fillers 105 can be improved, and the phenomenon of agglomeration or sedimentation of the fillers 105 is avoided.

In some embodiments, referring again to FIG. 4, the thickness H of the dielectric layer 101 ₁₀₁ Greater than or equal to a predetermined distance between the signal layer 103 and the ground layer 104. In this way, a sufficient distance between the signal layer 103 and the ground layer 104 can be ensured, dielectric loss is reduced, and line capacitance in the signal layer 103 is further reduced, so as to reduce signal insertion loss.

Fig. 10 is a flowchart of a method for manufacturing a copper-clad plate 60 according to an embodiment of the present application.

Fig. 11 is a process flow chart for preparing a copper-clad plate 60 according to an embodiment of the present application.

As shown in fig. 10, in some embodiments, the preparation process of the copper-clad plate 60 provided by the embodiment of the present application may include the following steps S201 to S204:

in step S201, the dielectric layer 101 is prepared.

Wherein, the raw materials for preparing the copper-clad plate 60 comprise fluorine resin colloidal particles, a filler 105 and two copper foils.

As shown in fig. 11 (a), a fluororesin colloidal particle is mixed with water to obtain an emulsion-like dielectric layer 101.

In step S202, the filler 105 is mixed into the dielectric layer 101 to obtain a mixed gel.

As shown in fig. 11 (b), a filler 105 is mixed into the emulsion in a corresponding amount according to the volume ratio of the filler 105 to the fluororesin material to obtain a mixed gel, so that the air cavity 102 is introduced into the dielectric layer 101.

In step S203, the mixed glue is coated on a copper foil to form the signal layer 103.

As shown in fig. 11 (c), the mixed glue is uniformly coated on one of the copper foils to form the signal layer 103 on the first surface 1011 of the dielectric layer 101.

In step S204, another copper foil is pressed onto the surface of the mixed glue facing away from the signal layer 103 to form the ground layer 104, thereby obtaining the copper-clad plate 60.

As shown in fig. 11 (d), another copper foil is laminated on the other surface of the mixed glue facing away from the signal layer 103 by a high-temperature lamination process, so as to form a ground layer 104 on the second surface 1012 of the dielectric layer 101.

The copper-clad plate 60 can be prepared through the above process.

It should be noted that, the copper foil coated with the mixed glue in the step S203 may form the ground layer 104, and the copper foil laminated in the step S204 may form the signal layer 103, which is not limited in the embodiment of the present application.

The copper-clad plate 60 provided by the embodiment of the application can reduce the dielectric constant of the dielectric layer 101 by utilizing the air cavity 102 in the dielectric layer 101 so as to reduce dielectric loss; the dielectric constant of the dielectric layer 101 can be reduced by mixing a plurality of air cavities 102 in a fluororesin material with a low dielectric constant, so as to reduce dielectric loss; and a sufficient distance between the signal layer 103 and the ground layer 104 can be ensured to reduce dielectric loss. In this way, the copper-clad plate 60 can more effectively reduce the signal insertion loss, so that the flexible circuit board comprising the copper-clad plate 60 can meet the requirements of the electronic equipment 100.

Fig. 12 is a schematic structural diagram of a flexible circuit board 70 according to an embodiment of the present application.

As shown in fig. 12, in some embodiments, the flexible circuit board 70 may include: the copper-clad laminate 60, the first cover film 201, the second cover film 202, and the shielding film 203. The structural characteristics of the copper-clad plate 60 may refer to the content of the foregoing embodiment, and are not repeated here.

Fig. 13 is an exploded view of a flexible circuit board 70 according to an embodiment of the present application.

As shown in connection with fig. 12 and 13, in some embodiments, the copper-clad plate 60 may include a third surface 601 and a fourth surface 602 that are opposite to each other. The third surface 601 is a surface of the signal layer 103 facing away from the dielectric layer 101, and the fourth surface 602 is a surface of the ground layer 104 facing away from the dielectric layer 101.

The first cover film 201 is formed on the third surface 601 of the copper-clad plate 60, and the first cover film 201 is used for protecting the signal layer 103. The second cover film 202 is formed on the fourth surface 602 of the copper-clad plate 60, and is used for protecting the ground layer 104.

The shielding film 203 is formed on the surface of the first cover film 201 facing away from the dielectric layer 101. Illustratively, the shielding film 203 may have a three-layer structure (not shown in the drawings) of a resin layer, a conductor layer, and a glue layer, the resin layer may be ink or the like, the conductor layer may be copper or silver or the like, and the glue layer may be epoxy or the like.

The shielding film 203 is used for shielding electromagnetic interference and preventing other electromagnetic signals from interfering with the flexible circuit board 70. Further, the signal layer 103 is surrounded by the ground layer 104 and the shielding film 203 to form an electromagnetic shielding structure of the flexible circuit board 70, so as to play a role in shielding signal interference.

In some embodiments, the signal layer 103 includes at least one trace layer 1031 formed at intervals on the first surface 1011 of the dielectric layer 101. The wiring layer 1031 may be formed by etching a break in the signal layer 103 through an etching process. The routing layer 1031 is used for routing wires for signal transmission.

The first cover film 201 may include a first adhesive layer 2011 and a first isolation layer 2012 attached to each other. One surface of the first isolation layer 2012 is covered on the signal layer 103 by a first adhesive layer 2011, and the other surface of the first isolation layer 2012 is attached to the shielding film 203. The first glue layer 2011 is covered on the at least one routing layer 1031 and formed on the first surface 1011.

For example, the first isolation layer 2012 may be made of Polyimide (PI) material. The first adhesive layer 2011 is an adhesive, and the adhesive may include epoxy resin or polyurethane.

The structure of the second cover film 202 is the same as that of the first cover film 201. The second cover film 202 includes a second adhesive layer 2021 and a second isolation layer 2022 attached to each other; the surface of the second adhesive layer 2021 facing away from the second isolation layer 2022 is attached to the outer surface of the ground layer 104.

Fig. 14 is a schematic size diagram of a flexible circuit board 70 according to an embodiment of the present application.

As shown in fig. 14, exemplary, in the thickness (z-axis) direction, the thickness H of the shielding film 203 ₂₀₃ All can be about 10 μm, and the thickness H of the first adhesive layer 2011 ₂₀₁₁ And thickness H of the second adhesive layer 2021 ₂₀₂₁ May be about 7.5 μm, and the thickness H of the first isolation layer 2012 may be ₂₀₁₂ And thickness H of the second isolation layer 2022 ₂₀₂₂ All may be about 5. Mu.m. Thickness H of dielectric layer 101 ₁₀₁ May be about 70 μm, and the thickness H of the ground layer 104 may be about ₁₀₄ May be about 6. Mu.m. Wherein, the thickness H of the first adhesive layer 2011 ₂₀₁₁ The distance between the first isolation layer 2012 and the dielectric layer 101 (the state shown in fig. 14) may be determined, and the distance between the first isolation layer 2012 and the signal layer 103 may be determined.

Since the signal layer 103 is embedded in the first adhesive layer 2011, the thickness of the signal layer 103 does not affect the thickness H of the flexible circuit board 70 ₇₀ . Thus, the thickness H of the flexible circuit board 70 ₇₀ To sum the thicknesses of the remaining layers except the signal layer 103, exemplary, H ₇₀ =111 μm. Therefore, the thickness of the flexible circuit board 70 provided by the embodiment of the application is reduced relative to the existing flexible circuit board, so that the flexible circuit board 70 occupies the internal accommodating space of the electronic device, the installation is convenient, and the light and thin electronic device can be realized.

Referring to fig. 3 and 14, the flexible circuit board 70 provided in the embodiment of the application mayThe thickness of each layer is flexibly set. Exemplary, the thickness (H) of the cover films (the first cover film 201 and the second cover film 202) in the flexible circuit board 70 ₂₀₁₁ +H ₂₀₁₂ 、H ₂₀₂₁ +H ₂₀₂₂ ) Is smaller than the thickness (H) of the protective films (first protective film layer 52 and second protective film layer 56) of the conventional flexible board 50 ₅₂₁ +H ₅₂₂ 、H ₅₆₁ +H ₅₆₂ ). Thus, at the thickness H of the flexible circuit board 70 ₇₀ In the case of a decrease, the thickness H of the dielectric layer 101 in the flexible circuit board 70 may be increased ₁₀₁ So that the thickness H of the dielectric layer 101 ₁₀₁ Is greater than or equal to the preset distance between the signal layer 103 and the ground layer 104, so as to ensure that the signal layer 103 and the ground layer 104 have enough distance, reduce dielectric loss, reduce line capacitance in the signal layer 103, and further reduce signal insertion loss.

Fig. 15 is a flowchart of a method for manufacturing a flexible circuit board 70 according to an embodiment of the present application.

Fig. 16 is a process flow diagram of preparing a flexible circuit board 70 provided in an embodiment of the present application.

As shown in fig. 15, in some embodiments, the flexible circuit board 70 provided in the embodiments of the present application may be prepared according to the following steps S301 to S305:

step S301, preparing a copper-clad plate 60.

Referring to fig. 16 (a), the preparation process of the copper-clad plate 60 may refer to the contents of step S201-step S204 provided in the foregoing embodiment, which is not described herein.

In step S302, the wiring layer 1031 is etched in the signal layer 103.

As shown in fig. 16 (b), at least one break is etched in the signal layer 103 by an etching process, thereby forming a plurality of wiring layers 1031.

In step S303, the first cover film 201 and the second cover film 202 are prepared.

As shown in fig. 16 (c), the first adhesive layer 2011 and the first separator 2012 are bonded to each other, thereby obtaining a first cover film 201; the second adhesive layer 2021 and the second insulating layer 2022 are bonded to obtain a second cover film 202.

It should be noted that the process of step S303 may be performed in parallel with the processes of step S301 to step S302.

Step S304, the first cover film 201 and the second cover film 202 are pressed onto the copper-clad plate 60.

As shown in fig. 16 (d), the first cover film 201 is pressed onto the trace layer 1031 of the copper-clad plate 60 by using a quick press, so that the first adhesive layer 2011 covers and surrounds the trace layer 1031; and pressing the second cover film 202 on the ground layer 104 of the copper-clad plate 60, so that the second adhesive layer 2021 is attached to the ground layer 104.

In step S305, the shielding film 203 is pressed to obtain the flexible circuit board 70.

As shown in fig. 16 (e), the shielding film 203 is pressed onto the first separator 2012 of the first cover film 201 by a rapid press, to obtain the flexible circuit board 70.

As shown in fig. 17, the signal insertion loss (dB) of the flexible circuit board 70 provided by the embodiment of the present application and the existing flexible board 50 is tested at different signal transmission frequencies (freq, GHz).

Illustratively, at a signal transmission frequency of 2GHz, the signal insertion loss of the flexible circuit board 70 is about 0.6dB, and the signal insertion loss of the conventional flexible board 50 is about 0.85dB; when the signal transmission frequency is 10GHz, the signal insertion loss of the flexible circuit board 70 is about 1.9dB, and the signal insertion loss of the conventional flexible board 50 is about 3.1dB; at a signal transmission frequency of 20GHz, the signal insertion loss of the flexible circuit board 70 is about 3.05dB, and the signal insertion loss of the conventional flexible board 50 is about 5.5dB.

As can be seen from the test results, the signal insertion loss of the flexible circuit board 70 provided by the embodiment of the application is lower than that of the conventional flexible board 50 at the same signal transmission frequency. And, as the signal transmission frequency increases, the signal insertion loss of the conventional flexible board 50 is reduced more than that of the flexible circuit board 70 according to the embodiment of the present application. Therefore, the flexible circuit board 70 provided by the embodiment of the application can effectively reduce the signal insertion loss.

The flexible circuit board 70 provided by the embodiment of the application adopts the dielectric layer 101 with the air cavity 102, so that the dielectric constant of the dielectric layer 101 can be reduced to reduce dielectric loss; meanwhile, the thickness of the cover films (the first cover film 201 and the second cover film 202) is reduced to increase the thickness of the dielectric layer 101 in the case where the thickness of the flexible circuit board 70 is reduced. In this way, a sufficient distance between the signal layer 103 and the ground layer 104 can be ensured, and dielectric loss is reduced, so as to reduce line capacitance in the signal layer 103, and further reduce signal insertion loss. As can be seen, when the thickness of the flexible circuit board 70 is reduced, the signal insertion loss can be effectively reduced, so that the flexible circuit board including the copper-clad plate 60 can meet the requirements of the electronic device 100.

The embodiment of the application also provides electronic equipment, which comprises the flexible circuit board 70 provided by the embodiment. The flexible circuit board 70 can reduce the thickness, does not occupy the space in the thickness direction of the electronic device 100, can effectively reduce the signal insertion loss, and meets the requirements of the electronic device 100.

It is noted that other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of the application following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the application pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope of the application being indicated by the following claims.

It is to be understood that the application is not limited to the precise arrangements and instrumentalities shown in the drawings, which have been described above, and that various modifications and changes may be effected without departing from the scope thereof. The scope of the application is limited only by the appended claims.

Claims

1. The utility model provides a copper-clad plate which characterized in that includes:

a dielectric layer (101), wherein the inside of the dielectric layer (101) comprises a plurality of air cavities (102);

a signal layer (103) formed on the first surface (1011) of the dielectric layer (101);

a ground layer (104) formed on a second surface (1012) of the dielectric layer (101);

wherein the first surface (1011) is opposite to the second surface (1012), and the first surface (1011) is referenced to the second surface (1012).

2. The copper-clad plate according to claim 1, wherein,

a plurality of the air voids (102) are uniformly dispersed in the dielectric layer (101).

3. The copper-clad plate according to claim 1, wherein,

the medium layer (101) is made of fluororesin;

the air voids (102) are formed by a filler (105), the filler (105) comprising at least one of hollow glass microspheres and hollow silica.

4. The copper-clad plate according to claim 3, wherein,

the ratio of the total volume of the filler (105) to the volume of the fluororesin material is 30-40%.

5. The copper-clad plate according to claim 3, wherein,

the particle size of the filler (105) is 3-10 mu m.

6. The copper-clad plate according to claim 3, wherein,

the surface of the filler (105) comprises a modifying layer;

the modified layer is used for improving the binding force of the filler (105) and the dielectric layer (101).

7. The copper-clad plate according to claim 6, wherein,

the modified layer includes a fluorocarbon bond layer (1061);

the fluorocarbon bond layer (1061) is formed by graft modification of the filler (105) and a fluorine-containing silane coupling agent (1071).

8. The copper-clad plate according to claim 7, wherein,

the fluorocarbon bond layer (1061) is formed by:

hydrolyzing the fluorine-containing silane coupling agent (1071) to obtain a hydroxyl product (108), wherein the reaction formula is as follows:

；

grafting the hydroxyl product (108) with the filler (105) to form the fluorocarbon bond layer (1061) on the surface of the filler (105), wherein the reaction formula is as follows:

。

9. The copper-clad plate according to claim 7, wherein,

the fluorine-containing silane coupling agent (1071) includes one of heptadecafluorodecyl triethoxysilane, heptadecafluorodecyl trimethoxysilane, tridecanfluorooctyl triethoxysilane, or tridecanfluorooctyl trimethoxysilane.

10. The copper-clad plate according to claim 6, wherein,

the modifying layer includes a positive charge layer (1062);

the positively charged layer (1062) is formed by modification of the filler (105) with a cationic surface modifier (1072).

11. The copper-clad plate according to claim 10, wherein,

the dielectric layer (101) comprises fluororesin colloidal particles suspended in water, the fluororesin colloidal particles are negatively charged so that the fluororesin colloidal particles are adsorbed by the positive charge layer (1062), and a fluororesin modified layer is formed on the bonding surface of the filler (105) and the dielectric layer (101).

12. The copper-clad plate according to claim 1, wherein,

the thickness of the dielectric layer (101) is greater than or equal to a preset distance between the signal layer (103) and the ground layer (104).

13. A flexible circuit board, comprising:

The copper-clad plate according to any one of claims 1 to 12;

a first cover film (201) formed on a third surface (601) of the copper-clad plate; the third surface (601) is the surface of the signal layer (103) facing away from the dielectric layer (101);

the second covering film (202) is formed on a fourth surface (602) of the copper-clad plate, and the fourth surface (602) is the surface, away from the dielectric layer (101), of the grounding layer (104);

and a shielding film (203) formed on the surface of the first covering film (201) facing away from the dielectric layer (101).

14. The flexible circuit board of claim 13 wherein the flexible circuit board comprises,

the signal layer (103) comprises at least one wiring layer (1031) formed on the first surface (1011) at intervals;

the first covering film (201) comprises a first adhesive layer (2011) and a first isolation layer (2012) which are mutually adhered;

the first adhesive layer (2011) covers at least one of the routing layers (1031) and is formed on the first surface (1011);

the first separator (2012) is attached to the shielding film (203).

15. The flexible circuit board of claim 13 wherein the flexible circuit board comprises,

The second covering film (202) comprises a second adhesive layer (2021) and a second isolation layer (2022) which are mutually adhered;

the surface of the second adhesive layer (2021) facing away from the second isolation layer (2022) is attached to the outer surface of the ground layer (104).

16. An electronic device comprising the flexible circuit board of any of claims 13-15.