TWI454191B - Flexible circuit board and method for manufacturing same - Google Patents

Description

Flexible circuit board and manufacturing method thereof

The invention relates to a method for manufacturing a circuit board, in particular to a flexible circuit board and a manufacturing method thereof.

In the development of high-frequency flexible circuit boards, a teflon base insulating material is often used as a base layer material, and the base layer material comprises a layer of polyimide (PI) and two layers respectively disposed on the polycrystalline layer. The Teflon layer on opposite sides of the amine layer. In the process of the flexible circuit board, a blind hole is often formed in the base layer by using a laser etch hole technique, and then the inner wall of the blind hole is plated to form a conductive blind hole. Since the outer layer of the Teflon layer has a weaker absorption capacity for the laser energy, and the inner layer of the polyimine layer has a stronger absorption capacity for the laser energy, the inner layer is aggregated when the laser is etched. The imine layer absorbs more energy than the Teflon layer of the outer layer, resulting in a polycondensation of the polyimine layer, resulting in deformation of the pore shape and a decrease in yield.

It is an object of the present invention to provide a flexible circuit board having a high yield and a method of fabricating the same.

A manufacturing method of a flexible circuit board, comprising the steps of: providing a flexible double-sided copper-clad substrate comprising an insulating base layer and a first copper foil layer and a second copper foil layer disposed on opposite sides of the insulating base layer The insulating layer comprises a polyimide layer and a Teflon layer disposed on opposite sides of the polyimide layer; and the first copper is formed on the flexible double-sided copper substrate by mechanical drilling. a through hole of the foil layer, the insulating base layer and the second copper foil layer; covering the first plating resist layer and the second plating resist layer on the surface of the first copper foil layer and the second copper foil layer, respectively, the first plating resist layer has an opening One end opening of the through hole is exposed in the opening, and the second plating resist covers the opposite opening of the through hole; the inner wall of the through hole and the surface of the second anti-plating layer are formed on the surface of the through hole a continuous conductive film; a continuous plating metal layer is formed on the surface of the conductive film away from the second copper foil layer by electroplating, and is formed on the inner wall of the through hole and the surface of the second anti-plating layer located in the through hole Continuous conductive film and formed on the conductive film surface The electroplated metal layer constitutes a conductive blind hole; the first anti-plating layer and the second anti-plating layer are removed; and the first copper foil layer and the second copper foil layer are respectively formed into a first conductive line pattern and a second conductive line pattern, Flexible circuit board.

A flexible circuit board made by the above method, comprising an insulating base layer, a first conductive line pattern and a second conductive line pattern disposed on opposite sides of the insulating base layer, a conductive film and a plated metal layer, the insulating base layer comprising a poly a bismuth imide layer and a Teflon layer disposed on opposite sides of the polyimide layer, the first conductive line pattern and the second conductive line pattern respectively adjacent to the two Teflon layers, the flexible circuit board having The first conductive line pattern and the second conductive line pattern respectively have conductive lines around the corresponding openings of the through holes through the through holes of the first conductive line pattern, the insulating base layer and the second conductive line pattern, and the conductive film Forming a surface of the conductive line continuously adjacent to the opening of the through hole of the first conductive line pattern, an inner wall of the through hole, and an opening of the through hole adjacent to the second conductive line pattern, so that the conductive film and the conductive film The second conductive line pattern is in contact with the side surface of the through hole and closes the opening of the through hole adjacent to the second conductive line pattern to electrically connect the second conductive line pattern, the plating gold A continuous layer formed on the conductive film away from the surface of the second conductive trace pattern.

Compared with the prior art, the manufacturing method of the flexible circuit board firstly forms a through hole by mechanical drilling, and then forms a conductive blind hole in the through hole, and forms a conductive blind hole compared to the laser etching method. The mechanical drilling method avoids the shrinkage of the polyimine layer caused by the different absorption energy of the laser energy of the Teflon layer and the polyimide layer in the insulating base layer, thereby preventing the deformation of the pore shape. In addition, due to the mature technology of mechanical drilling, the quality of the through-holes produced is excellent, and multiple flexible flexible copper-clad substrates can be drilled at the same time, which reduces the cost and improves the efficiency. The flexible circuit board of this embodiment can be used to fabricate a rigid-flex circuit board.

Flexible double-sided copper-clad substrate: 100

Conductive blind hole: 110

Through hole: 111

First anti-plating layer: 121

Opening: 1211

Second plating resistance: 122

First copper foil layer: 131

Second copper foil layer: 132

Insulation base layer: 140

Polyimine layer: 141

Teflon layer: 142

Conductive film: 151

Plating metal layer: 152

Flexible circuit board: 160

First conductive line pattern: 161

Second conductive line pattern: 162

1 is a schematic cross-sectional view of a copper clad substrate formed with through holes.

2 is a schematic cross-sectional view showing the copper foil layer on both sides of the copper-clad substrate of FIG. 1 covering the anti-plating layer.

3 is a schematic cross-sectional view showing a state in which a conductive film is formed on the copper clad substrate of FIG. 2.

4 is a schematic cross-sectional view showing a metal conductive layer formed on the surface of the conductive film in FIG.

FIG. 5 is a schematic cross-sectional view showing the copper-clad substrate of FIG. 4 after the plating resist is removed.

Fig. 6 is a schematic cross-sectional view showing a flexible circuit board obtained by forming a copper foil layer on both sides in Fig. 5 to form a conductive wiring pattern.

The transparent printed circuit board provided by the present technical solution will be further described in detail below with reference to the accompanying drawings and embodiments.

Referring to FIG. 1 to FIG. 6 , an embodiment of the present invention provides a method for fabricating a flexible circuit board, including the following steps:

First Step: Referring to FIG. 1, a flexible double-sided copper-clad substrate 100 is provided, and a through hole 111 is formed in the flexible double-sided copper-clad substrate 100 by mechanical drilling.

The flexible double-sided copper clad substrate 100 includes an insulating base layer 140 and a first copper foil layer 131 and a second copper foil layer 132 disposed on opposite sides of the insulating base layer 140. The insulating base layer 140 includes a polyimide layer 141 and a Teflon layer 142 disposed on opposite sides of the polyimide layer 141. In this embodiment, the Teflon layer 142 has a thickness of 6.25 micrometers. The imine layer 141 has a thickness of 12.5 microns. The first copper foil layer 131 and the second copper foil layer 132 are respectively disposed adjacent to the two layers of the Teflon layer 142. In this embodiment, the first copper foil layer 131 and the second copper foil layer 132 have a thickness of 12 Micron. The through hole 111 penetrates the first copper foil layer 131, the insulating base layer 140, and the second copper foil layer 132.

It can be understood that, after the through hole 111 is formed, a conductive layer can be formed on the inner wall of the through hole 111, and a portion of the conductive film 151 corresponding to the inner wall of the through hole 111 in the subsequent step can be formed on the surface of the conductive layer, the conductive layer The formation may be performed by a plating through hole (PTH) process, a black hole process, or a black shadow process.

Step 2: Referring to FIG. 2, the first anti-plating layer 121 and the second anti-plating layer 122 are respectively covered on the surfaces of the first copper foil layer 131 and the second copper foil layer 132, and the first plating resist 121 has an opening 1211. The opening 1211 is in communication with the through hole 111, and the opening 1211 is larger than the through hole 111 at the first copper foil layer 131, so that the first copper foil layer 131 is exposed at a portion around the opening of the through hole 111. In the opening 1211 of the first plating resist, the second plating resist 122 covers the entire surface of the second copper foil layer 132 and covers the through hole 111 to open at the second copper foil layer 132.

In the manufacturing process, the materials for forming the first plating resist 121 and the second plating resist 122 may be, but not limited to, an anti-plating dry film, a plating resist tape, or a plating resistive strippable adhesive. If the first plating resist 121 and the second plating resist 122 are formed by using the anti-plating dry film, the anti-plating dry film is applied to the surfaces of the first copper foil layer 131 and the second copper foil layer 132, and then the plating resist is applied by ultraviolet irradiation. The dry film polymerization reaction forms a stable substance attached to the first copper foil layer 131 and the second copper foil layer 132, thereby achieving the function of blocking plating and etching. If the first plating resist 121 and the second plating resist 122 are formed by using a plating resist tape or a plating resistive strippable adhesive, the first copper foil layer 131 and the second copper foil layer 132 may be directly adhered to the surface of the first copper foil layer 131 and the second copper foil layer 132.

Step 3: Referring to FIG. 3, on the surface of the first plating resist 121, the first copper foil layer 131 is exposed on the surface of the opening 1211 of the first plating resist, the inner wall of the through hole 111, and the second plating resist 122 is located. A conductive film 151 is formed on the surface of the through hole 111 and the surface of the second plating resist 122 away from the second copper foil layer 132.

In this embodiment, the process of forming the conductive film 151 may be, but not limited to, a through hole plating (PTH) process, a black hole process, or a black shadow process. The through hole plating process refers to plating a thin layer of copper on the surface of the first plating resist 121 by a chemical reaction, the first copper foil layer 131 is exposed on the surface of the opening 1211 of the first plating resist, and the inner wall of the through hole 111. The surface of the second plating resist 122 located in the through hole 111 and the second plating resist 122 are away from the surface of the second copper foil layer 132 to form the conductive film 151. The black hole forming process is to dip the fine graphite and carbon black powder on the surface of the first plating resist 121, the first copper foil layer 131 is exposed on the surface of the opening 1211 of the first plating resist, and the inner wall of the through hole 111, The surface of the second plating resist 122 located in the through hole 111 and the surface of the second plating resist 122 away from the second copper foil layer 132 form a conductive film, which is a conductive film formed by physical action. The black shadow process is a direct electroplating method, mainly using a slightly alkaline liquid to which a black shadow agent is added as a plating solution, and electroplating using graphite as an electrode, so that the surface of the first plating resist 121 and the first copper foil layer 131 are exposed. The surface of the hole 1211, the inner wall of the through hole 111, the surface of the second plating resist 122 located in the through hole 111, and the surface of the second plating resist 122 away from the second copper foil layer 132 form a conductive film 151. In this embodiment, the conductive film 151 is formed by a black hole method.

Fourth Step: Referring to FIG. 4, a continuous plating metal layer 152 is formed on the surface of the conductive film 151 by a plating method, a conductive film 151 and a plating metal layer 152 formed on the inner wall of the through hole 111, and the second resistance. The conductive film 151 and the plated metal layer 152 formed on the surface of the plating layer 122 in the through hole 111 together constitute a conductive blind hole 110 electrically connecting the first copper foil layer 131 and the second copper foil layer 132.

The material of the plated metal layer 152 is, but not limited to, copper, tin, nickel or gold. One end of the conductive blind hole 110 adjacent to the second plating resist 122 is in contact with the second copper foil layer 132, and the other end opposite to the conductive blind hole 110 is formed on the surface of the first copper foil layer 131. The conductive blind vias 110 electrically connect the first copper foil layer 131 and the second copper foil layer 132.

Step 5: Referring to FIG. 5, the first plating resist 121 and the second plating resist 122 overlying the flexible double-sided copper clad substrate 100 are removed.

The stripping process may be performed by removing the first plating resist 121 and the second plating resist 122, and the conductive film 151 and the plating metal layer 152 covering the outer surfaces of the first plating resist 121 and the second plating resist 122 are also removed. The first copper foil layer 131 and the second copper foil layer 132 are exposed. The conductive film 151 and the plated metal layer 152 formed on the surface of the second plating resist 122 located in the through hole 111 are retained by the adhesion force with the hole wall of the through hole 111.

Step 6: Referring to FIG. 6, the first copper foil layer 131 and the second copper foil layer 132 are respectively formed into a first conductive line pattern 161 and a second conductive line pattern 162, thereby obtaining a flexible circuit board 160. In this embodiment, the method of forming the first conductive line pattern 161 and the second conductive line pattern 162 may employ an image transfer process and an etching process.

The flexible circuit board 160 of the embodiment of the present invention includes an insulating base layer 140, first conductive line patterns 161 and second conductive line patterns 162 disposed on opposite sides of the insulating base layer 140, and conductive blind holes 110. The insulating base layer 140 includes a polyimide layer 141 and a Teflon layer 142 disposed on opposite sides of the polyimide layer. The flexible circuit board 160 has a through hole 111 extending through the first conductive line pattern 161, the insulating base layer 140, and the second conductive line pattern 162. The first conductive line pattern 161 and the second conductive line pattern 162 are respectively in the through hole. Each of the corresponding openings of 111 has a conductive line. The conductive via hole 110 includes a conductive film 151 and a plating metal layer 152. The conductive film 151 is continuously formed on the surface of the conductive line adjacent to the opening of the through hole 111 of the first conductive line pattern 161, and the through hole 111 The inner wall and the through hole 111 are adjacent to the opening of the second conductive line pattern 162, so that the through hole 111 is closed adjacent to the opening of the second conductive line pattern 162, and the conductive film 151 and the second conductive line pattern The side surfaces of the 162 located in the through hole 111 are in contact to electrically connect the second conductive line pattern 162. The plating metal layer 152 is continuously formed on the surface of the conductive film 151 away from the second conductive line pattern 162. The material of the conductive film 151 may be graphite, carbon black or copper, and the material of the plating metal layer 152 may be copper, tin, nickel or gold.

In this embodiment, the through hole 111 is first formed by mechanical drilling, and then the conductive blind hole 110 is formed by plating in the through hole 111, and the conductive blind hole 110 is formed compared to the laser etching method, and the mechanical drilling method is used. The polyimine layer 141 is prevented from being shrunk due to the difference in the absorption energy of the laser energy by the Teflon layer 142 and the polyimide layer 141 in the insulating base layer 140, thereby preventing the deformation of the pore shape. In addition, due to the mature technology of mechanical drilling, the quality of the through-holes produced is excellent, and multiple flexible flexible copper-clad substrates can be drilled at the same time, which reduces the cost and improves the efficiency.

In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. However, the above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art will be covered by the following claims.

Conductive blind hole: 110

Insulation base layer: 140

Polyimine layer: 141

Teflon layer: 142

Conductive film: 151

Plating metal layer: 152

Flexible circuit board: 160

First conductive line pattern: 161

Second conductive line pattern: 162

Claims (8)

A method for manufacturing a flexible circuit board, comprising the following steps:
Providing a flexible double-sided copper-clad substrate comprising an insulating base layer and a first copper foil layer and a second copper foil layer disposed on opposite sides of the insulating base layer, the insulating layer comprising a polyimide layer and a setting a Teflon layer on opposite sides of the polyimide layer;
Forming a through hole penetrating the first copper foil layer, the insulating base layer and the second copper foil layer on the flexible double-sided copper-clad substrate by mechanical drilling;
Covering the first anti-plating layer and the second anti-plating layer on the surface of the first copper foil layer and the second copper foil layer, the first anti-plating layer has an opening, and one end opening of the through hole is exposed in the opening, the second The plating resist covers the opposite opening of the through hole;
Forming a continuous conductive film on the inner wall of the through hole and the surface of the second anti-plating layer in the through hole;
Forming a continuous electroplated metal layer on the surface of the conductive film away from the second copper foil layer by electroplating, forming a continuous conductive film on the inner wall of the through hole and the surface of the second anti-plating layer located in the through hole and The plated metal layer formed on the surface of the conductive film constitutes a conductive blind hole;
Removing the first plating resist layer and the second plating resist layer; and forming the first copper foil layer and the second copper foil layer into the first conductive line pattern and the second conductive line pattern, respectively, to obtain a flexible circuit board. The method of fabricating a flexible circuit board according to claim 1, wherein the ratio of the thickness of each layer of the Teflon layer to the polyimide layer is 1:2. The method of manufacturing the flexible circuit board of claim 1, wherein the opening of the first plating resist at the through hole is larger than the aperture of the through hole, exposing a portion of the first copper foil layer, the inner wall of the through hole and the When the second plating resist is formed on the surface of the through hole to form a continuous conductive film, the conductive film is further formed on the surface of the first copper foil exposed on the opening, and the conductive film is away from the second copper by electroplating. When a continuous plating metal layer is formed on the surface of the foil layer, the plating metal layer is further formed on a surface of the conductive film corresponding to the surface of the first copper foil exposed on the opening. The method of fabricating a flexible circuit board according to claim 3, wherein the conductive film is further covered when the inner wall of the through hole and the surface of the second plating resist located in the through hole form a continuous conductive film The surface of the anti-plating layer and the second anti-plating layer are away from the surface of the second copper foil layer. The method of fabricating a flexible circuit board according to claim 3, wherein the electroplated metal layer is further formed on the surface of the conductive film that forms a continuous electroplated metal layer away from the surface of the second copper foil layer by electroplating. The surface of the first plating resist and the second plating resist are away from the conductive film corresponding to the surface of the second copper foil layer. The method for fabricating a flexible circuit board according to claim 1, wherein the method of forming a continuous conductive film on the inner wall of the through hole and the surface of the second plating resist located in the through hole is a through hole plating process, Black hole process or black shadow process. A flexible circuit board comprising an insulating base layer, a first conductive line pattern and a second conductive line pattern disposed on opposite sides of the insulating base layer, a conductive film and a plated metal layer, the insulating base layer comprising a polyimide layer and a setting The first conductive line pattern and the second conductive line pattern are respectively adjacent to the two Teflon layers on the opposite sides of the polyimine layer, and the flexible circuit board has the first conductive line a pattern, an insulating base layer and a through hole of the second conductive line pattern, wherein the first conductive line pattern and the second conductive line pattern respectively have conductive lines around corresponding openings of the through holes, and the conductive film is continuously formed on the first a conductive circuit pattern adjacent to the surface of the conductive line of the opening of the through hole, an inner wall of the through hole, and the through hole adjacent to the opening of the second conductive line pattern, such that the conductive film and the second conductive line pattern are located The side surface of the through hole contacts and closes the opening adjacent to the opening of the second conductive line pattern to electrically connect the second conductive line pattern, and the plating metal layer is continuously formed on Away from the surface of the second conductive film pattern of the conductive trace. The flexible circuit board of claim 7, wherein the conductive film is made of graphite, carbon black or copper, and the material of the plated metal layer may be copper, tin, nickel or gold.