阅读说明：本技术 柔性电路板及该柔性电路板制作方法 (Flexible circuit board and manufacturing method thereof ) 是由 沈芾云 何明展 徐筱婷 于 2018-08-23 设计创作，主要内容包括：本发明提出一种柔性电路板的制作方法,其包括以下步骤：提供一基底；通过涂布方式在基底的相对两个表面上涂布一接着溶液并经干燥处理形成两个接着层,接着溶液含有接着剂及溶剂,接着溶液的黏度为5000毫帕·秒；在每个接着层背离基底的表面上分别形成第一铜层与第二铜层；蚀刻第一铜层和第二铜层以分别形成第一信号线路层和第二信号线路层；以及在第一信号线路层和第二信号线路层的表面上分别包覆绝缘层。上述制作方法制备的柔性电路板介质损耗低。另外,本发明还提供一种柔性电路板。(The invention provides a manufacturing method of a flexible circuit board, which comprises the following steps: providing a substrate; coating an adhesive solution on two opposite surfaces of the substrate in a coating mode and drying to form two adhesive layers, wherein the adhesive solution contains an adhesive and a solvent, and the viscosity of the adhesive solution is 5000 mPa.s; respectively forming a first copper layer and a second copper layer on the surface of each adhesion layer departing from the substrate; etching the first copper layer and the second copper layer to form a first signal line layer and a second signal line layer, respectively; and respectively coating insulating layers on the surfaces of the first signal circuit layer and the second signal circuit layer. The flexible circuit board prepared by the manufacturing method has low dielectric loss. In addition, the invention also provides a flexible circuit board.)

1. A manufacturing method of a flexible circuit board comprises the following steps:

providing a substrate;

coating an adhesive solution on two opposite surfaces of the substrate in a coating manner, and drying to form two adhesive layers, wherein the substrate and the two adhesive layers formed on the substrate form a substrate together, the adhesive solution contains an adhesive and a solvent, and the viscosity of the adhesive solution is 5000 mPas;

respectively forming a first copper layer and a second copper layer on the surface of each adhesion layer, which is far away from the substrate;

etching the first copper layer and the second copper layer to form a first signal wiring layer and a second signal wiring layer, respectively; and

and respectively coating insulating layers on the surfaces of the first signal circuit layer and the second signal circuit layer.

2. The method of manufacturing of claim 1, wherein: the drying treatment temperature is 100 ℃, and the treatment time is 5 minutes.

3. The method of manufacturing of claim 1, wherein: the manufacturing method further comprises the following steps:

pressing the other two prepared substrates onto the surfaces of the corresponding insulating layers respectively;

forming a third copper layer on the surface of the adhesion layer, far away from the insulating layer, of one of the two substrates, forming a fourth copper layer on the surface of the adhesion layer, far away from the insulating layer, of the other one of the two substrates, and forming at least one through hole in a penetrating manner along the stacking direction of the substrate, the adhesion layer, the first copper layer, the second copper layer, the insulating layer, the third copper layer and the fourth copper layer;

electroplating the wall of the through hole to form an electroplated layer, thereby obtaining a conductive hole for electrically connecting the first copper layer, the second copper layer, the third copper layer and the fourth copper layer; and

etching the third and fourth copper layers to form first and second ground layers, respectively.

4. The method of manufacturing of claim 3, wherein: the manufacturing method further comprises the following steps:

covering films are respectively coated on the surfaces of the first ground layer and the second ground layer.

5. A flexible circuit board comprises a substrate, a first signal circuit layer, a second signal circuit layer and two insulating layers, wherein the first signal circuit layer and the second signal circuit layer are respectively formed on two opposite surfaces of the substrate, the two insulating layers respectively coat the surfaces of the first signal circuit layer and the second signal circuit layer, the substrate comprises a substrate and two adhesion layers formed on the substrate, the two adhesion layers are formed by coating adhesion solutions on the two opposite surfaces of the substrate in a coating mode and drying the adhesion solutions, the adhesion solutions contain adhesion agents and solvents, the viscosity of the adhesion solutions is 5000 mPa.s, and the adhesion agents contain 35-65% by mass of substrate precursor, 10-15% by mass of carboxyl modified polyphenyl ether, 10-15% by mass of bisphenol F type epoxy resin, and, 0 to 1.5 percent of silane coupling agent, 5 to 20 percent of silicon dioxide filler and 10 to 20 percent of flame-retardant filler.

6. The flexible circuit board of claim 5, wherein: the two substrates are respectively pressed on the surfaces of the corresponding insulating layers, the first grounding layer and the second grounding layer respectively form the surfaces of the adhesion layers of the two substrates, which are far away from the insulating layers, each conductive hole comprises a through hole which penetrates through the substrate, the adhesion layers, the first signal circuit layer, the second signal circuit layer, the insulating layers, the first grounding layer and the second grounding layer along the laminating direction of the substrate, and an electroplated layer formed on the hole wall of the through hole, and the conductive holes are used for electrically connecting the first signal circuit layer, the second signal circuit layer, the first grounding layer and the second grounding layer.

7. The flexible circuit board of claim 6, wherein: the flexible circuit board further comprises two cover films, and the two cover films are coated on the surfaces of the first grounding layer and the second grounding layer.

8. The flexible circuit board of claim 5, wherein: the substrate precursor is selected from one or more of fluorinated cyclic ester modified polyamic acid and silsesquioxane modified polyamic acid.

9. The flexible circuit board of claim 5, wherein the silane coupling agent is one or more selected from the group consisting of N- β -gamma-aminopropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, methacryloxypropyltrimethoxysilane, and mercaptopropyltrimethoxysilane.

10. The flexible circuit board of claim 5, wherein: the solvent is selected from one or more of carbitol acetate, cyclohexanone and methylcyclohexane.

Technical Field

The present invention relates to a flexible printed circuit board and a method for manufacturing the same, and more particularly, to a flexible printed circuit board with low transmission loss and a method for manufacturing the same.

Background

With the progress of current information and communication technologies, electronic information products have advanced into the gigahertz era, and terminal electronic products are increasingly demanding strong demands for high security and high transmission quality, such as mobile phones, car phones, and wireless communication, and the high security and high transmission quality are developing toward high frequency.

The dielectric loss factor (Df) and the relative dielectric constant (Dk) of the existing polyimide substrate material are relatively high, even though the application requirements of high-speed signal transmission and complete signals under all high frequencies are not easily and completely met by improving the circuit design, because the high DK can slow down the signal transmission rate, the high Df can partially convert the signals into heat energy to be lost in the substrate material, and in addition, the material is easy to absorb moisture in the manufacturing process to influence the electrical property, so that the transmission loss is improved. The liquid crystal polymer has good electrical property, but the process difficulty is high, and the preparation efficiency is reduced.

Disclosure of Invention

In view of the above, it is desirable to provide a flexible circuit board with low transmission loss and a method for manufacturing the same to solve the above problems.

A manufacturing method of a flexible circuit board comprises the following steps:

providing a substrate;

coating an adhesive solution on two opposite surfaces of the substrate in a coating manner, and drying to form two adhesive layers, wherein the substrate and the two adhesive layers formed on the substrate form a substrate together, the adhesive solution contains an adhesive and a solvent, and the viscosity of the adhesive solution is 5000 mPas;

respectively forming a first copper layer and a second copper layer on the surface of each adhesion layer, which is far away from the substrate;

etching the first copper layer and the second copper layer to form a first signal wiring layer and a second signal wiring layer, respectively; and

and respectively coating insulating layers on the surfaces of the first signal circuit layer and the second signal circuit layer.

A flexible circuit board comprises a substrate, a first signal circuit layer, a second signal circuit layer and two insulating layers, wherein the first signal circuit layer and the second signal circuit layer are respectively formed on two opposite surfaces of the substrate, the two insulating layers respectively coat the surfaces of the first signal circuit layer and the second signal circuit layer, the substrate comprises a substrate and two adhesion layers formed on the substrate, the two adhesion layers are formed by coating adhesion solutions on the two opposite surfaces of the substrate in a coating mode and drying the adhesion solutions, the adhesion solutions contain adhesion agents and solvents, the viscosity of the adhesion solutions is 5000 mPa.s, and the adhesion agents contain 35-65% by mass of substrate precursor, 10-15% by mass of carboxyl modified polyphenyl ether, 10-15% by mass of bisphenol F type epoxy resin, and, 0 to 1.5 percent of silane coupling agent, 5 to 20 percent of silicon dioxide filler and 10 to 20 percent of flame-retardant filler.

According to the flexible circuit board and the manufacturing method thereof, the adhesive layer in the flexible circuit board is prepared by using the adhesive solution, and the plurality of substrates with the substrates and the adhesive layers are arranged, so that the dielectric loss of the whole circuit board in the process of high-frequency signal transmission is reduced, and the manufacturing is simple.

Drawings

Fig. 1 is a schematic cross-sectional view of a substrate used for manufacturing a flexible circuit board according to an embodiment of the invention.

FIG. 2 is a schematic cross-sectional view of two subsequent layers formed on the substrate shown in FIG. 1.

FIG. 3 is a schematic cross-sectional view of a first copper layer and a second copper layer formed on the two subsequent layers shown in FIG. 2.

Fig. 4 is a schematic cross-sectional view illustrating a first signal line layer and a second signal line layer formed on the first copper layer and the second copper layer shown in fig. 3, respectively.

Fig. 5 is a schematic cross-sectional view of an insulating layer formed on the first signal line layer and the second signal line layer, a substrate laminated on the insulating layer, and a third copper layer and a fourth copper layer formed on the surface of the substrate, respectively, as shown in fig. 4.

Fig. 6 is a schematic cross-sectional view of a via hole formed in the substrate, the first copper layer, the second copper layer, the insulating layer, the third copper layer, and the fourth copper layer shown in fig. 5.

Fig. 7 is a schematic cross-sectional view of the plated layer and the third and fourth copper layers formed on the wall of the through-hole shown in fig. 6, respectively, to form the first and second signal wiring layers.

Fig. 8 is a schematic cross-sectional view of the flexible circuit board obtained after the surfaces of the first signal circuit layer and the second signal circuit layer shown in fig. 7 are coated with a cover film.

Description of the main elements

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

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, 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 invention.

It will be understood that when an element or component is referred to as being "connected" to another element or component, it can be directly connected to the other element or component or intervening elements or components may also be present. When an element or component is referred to as being "disposed on" another element or component, it can be directly on the other element or component or intervening elements or components may also be present.

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 invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The method for manufacturing the flexible circuit board 100 according to an embodiment of the present invention includes the following steps:

step S1: referring to fig. 1, a substrate 10 is provided. The substrate 10 is made of a dielectric material of Polyimide (PI) or glass fiber epoxy resin or polyetheretherketone resin (PEEK).

Step S2: referring to fig. 2, an adhesive solution is coated on two opposite surfaces (not shown) of the substrate 10 by coating and dried to form two adhesive layers 20. The substrate 10 and the two adhesion layers 20 formed on the substrate 10 together form a substrate 200. The drying treatment temperature is 100 ℃, and the treatment time is 5 minutes. The two adhesive layers 20 are stably adhered to opposite surfaces (not shown) of the substrate 10. Each subsequent layer 20 has a thickness of 1 micron to 3 microns.

Step S3: referring to fig. 3, a first copper layer 30 and a second copper layer 40 are respectively formed on the surface of each adhesion layer 20 away from the substrate 10 by a copper cladding process. The curing temperature of the copper coating treatment is 170 ℃, the curing time is 30 minutes, and the pressure is 5 Pa.

Step S4: referring to fig. 4, the first copper layer 30 is etched to form a first signal wiring layer 31, and the second copper layer 40 is etched to form a second signal wiring layer 41.

Step S5: referring to fig. 5, the surfaces of the first signal line layer 31 and the second signal line layer 41 are respectively covered with an insulating layer 50. The insulating layer 50 covers the surfaces of the first signal line layer 31 and the second signal line layer 41, and fills the gaps between the first signal line layer 31 and the second signal line layer 41 and the corresponding adhesion layer 20. The material of the insulating layer 50 is selected from insulating materials having flexibility. Preferably, the insulating material is a resin, such as an epoxy resin. Specifically, the insulating layer 50 is formed by coating a semi-cured (non-flowable, easily deformable) resin on the surfaces of the first signal line layer 31 and the second signal line layer 41 away from the adhesion layer 20, and laminating the semi-cured resin on the first signal line layer 31 and the second signal line layer 41, so that the semi-cured resin flows to fill the gaps between the first signal line layer 31 and the adhesion layer 20 and the gaps between the second signal line layer 41 and the adhesion layer 20.

Step S6: referring to fig. 5, two additional substrates 200 prepared in steps S1 through S2 are respectively laminated on the surfaces of the corresponding insulating layers 50.

Step S7: referring to fig. 5 and 6, a third copper layer 60 is formed on the surface of the adhesion layer 20 of one of the two substrates 200 away from the insulating layer 50, a fourth copper layer 70 is formed on the surface of the adhesion layer 20 of the other one of the two substrates 200 away from the insulating layer 50, and at least one through hole 80 is formed through the substrate 10, the adhesion layer 20, the first copper layer 30, the second copper layer 40, the insulating layer 50, the third copper layer 60 and the fourth copper layer 70 in the stacking direction.

Step S8: referring to fig. 7, an electroplated layer 81 is formed on the wall of the through hole 80 by electroplating, so as to obtain a conductive via 82 for electrically connecting the first copper layer 30, the second copper layer 40 and the trench. In this embodiment, the material of the plating layer 81 is copper. It is understood that the material of the plating layer 81 may also be selected from other conductive materials.

Step S9: referring to fig. 7, the third copper layer 60 is etched to form a first ground layer 61, and the fourth copper layer 70 is etched to form a second ground layer 71.

Step S10: referring to fig. 8, cover films 90 are respectively coated on the surfaces of the first ground layer 61 and the second ground layer 71, so as to obtain the flexible circuit board 100. The cover film 90 is used to protect the first ground layer 61 and the second ground layer 71.

It is understood that, upon completion of step S6, a plurality of signal wiring layers (not shown) may be formed on the surfaces of the first signal wiring layer 31 and the second signal wiring layer 41 by a layer-adding method according to steps S3 to S5, respectively, to be electrically connected to the first signal wiring layer 31 or the second signal wiring layer 41, respectively, thereby manufacturing the flexible circuit board 100 including a plurality of signal wiring layers. The formation of the multiple signal line layers by the build-up method is a common technique adopted in the industry, and is not described herein.

It is understood that steps S6 through S10 may be omitted and the preparation of the flexible circuit board 100 having two information wiring layers is not affected.

The adhesive solution of a preferred embodiment of the present invention contains an adhesive and a solvent. The viscosity of the subsequent solution was 5000 mPas (CPS).

The adhesive contains 35-65% of base precursor by mass, 10-15% of carboxyl modified polyphenyl ether by mass, 10-15% of bisphenol F type epoxy resin by mass, 0-1.5% of silane coupling agent by mass, 5-20% of silicon dioxide filler by mass and 10-20% of flame-retardant filler by mass.

The substrate precursor can be selected from one or more of fluorinated cyclic ester modified polyamic acid and silsesquioxane modified polyamic acid. The substrate precursor can be cured to form the same material as the substrate 10 to improve the adhesion of the adhesion layer 20 to the substrate 10.

The carboxyl-modified polyphenylene ether is used to increase the relative dielectric constant (Dk) of the adhesive layer 20.

The bisphenol F type epoxy resin is used to reduce the brittleness of the carboxyl-modified polyphenylene ether and thus the brittleness of the formed adhesive layer 20.

The silane coupling agent may be one or more selected from the group consisting of N- β (aminoethyl) -gamma-aminopropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, methacryloxypropyltrimethoxysilane, mercaptopropyltrimethoxysilane (ethyltrimethoxysilane) and the like, and is used to improve the adhesion of the adhesive layer 20 to the substrate 10.

The silica filler is used to improve the dielectric properties and control the expansion and contraction properties of the formed adhesive layer 20.

The flame-retardant filler can be one or more selected from hexaphenoxycyclotriphosphazene and melamine polyphosphate. The flame-resistant filler serves to improve the flame retardancy of the formed adhesive layer 20.

The solvent can be one or more selected from carbitol acetate, cyclohexanone and methylcyclohexane. The solvent is used to dissolve the above-mentioned adhesive to form an adhesive solution.

The following solution was prepared: an adhesive is placed in a container, a predetermined volume of solvent is poured into the container and the adhesive solution is stirred and formed, and the viscosity of the adhesive solution is 5000 millipascal-seconds (CPS).

The following is a further description with reference to specific examples.