TWI507119B - Flexible printed circuit board and method for manufacturing the same - Google Patents

Description

Flexible circuit board and manufacturing method thereof

The present invention relates to circuit board technology, and in particular to a flexible circuit board and a method of fabricating the same.

With the development of foldable digital products such as folding mobile phones and slider phones, the Flexible Printed Circuit Board (FPCB), which is light, thin, short, small and bendable, is widely used in digital products. Realize the electrical connection between different circuits. With the increasingly powerful functions of consumer digital products, improving the electromagnetic shielding performance of flexible circuit boards has become one of the important research topics in the field of circuit board technology.

The flexible circuit board typically forms a cover layer for protecting the conductive pattern from one side of the conductive pattern away from the insulating layer. A common method for avoiding electromagnetic interference is to form a layer of conductive ink (eg, silver paste ink) on the cover layer by printing, and fill the opening in the cover layer with the conductive ink layer to electrically connect to the conductive pattern. Ground wire. However, the thickness of the conductive ink layer formed by printing is usually in the range of 8-15 μm. On the one hand, the high-frequency current that induces electromagnetic interference has a skin effect, so that the current acts only on the surface of the conductive ink layer to be extremely shallow at a few micrometers. The thickness, as such, a large amount of conductive ink will be wasted; on the other hand, the thickness of the conductive ink layer is large, resulting in poor folding resistance, when folding assembly, that is, the flexible portion of the flexible circuit board When the bending is performed to mount the flexible circuit board to the digital device, cracking may occur, so that the conductive ink layer cannot effectively shield electromagnetic interference. In order to solve the above problems, there is an electromagnetic wave shielding film which can be bonded to a flexible circuit board by press-bonding, which comprises a conductive adhesive layer, a metal mask layer and a base film layer which are sequentially stacked. The metal mask layer of the electromagnetic wave shielding film is electrically connected to the grounding line of the conductive pattern of the flexible circuit board by the conductive adhesive layer. However, attaching the electromagnetic wave shielding film has high requirements on the manufacturing process of the flexible circuit board. The parameters such as the temperature and pressure of the electromagnetic wave protective film of different types of the protective film are directly related to the rupture condition of the conductive particles of the conductive adhesive layer and the contact area with the grounding wire. If the pressing parameter is improperly controlled, the electromagnetic wave The protective film is difficult to achieve the desired electromagnetic shielding effect.

In view of the above, it is necessary to provide a flexible circuit board and a manufacturing method thereof for improving the electromagnetic shielding performance of the flexible circuit board without affecting the flexibility of the flexible circuit board.

A flexible circuit board comprising an insulating layer, a conductive pattern formed on the insulating layer, a cover layer covering the conductive pattern, and a continuous metal sputter layer. The conductive pattern includes a ground line and a signal transmission line. The cover layer has a through hole for exposing at least a portion of the ground line. The metal sputter layer is formed by sputtering on a surface of the cover layer away from the conductive pattern, a hole wall of the through hole, and a surface of the ground line exposed from the through hole, thereby being electrically connected to the ground line.

A method for fabricating a flexible circuit board, comprising the steps of: providing a flexible copper clad plate comprising an insulating layer and a conductive layer attached to the insulating layer; forming the conductive layer into a conductive pattern, the conductive pattern comprising a ground line and a signal transmission line; forming a cover layer covering the conductive pattern, the cover layer having a through hole, the ground line being at least partially violent Exposing the via hole; and forming a continuous metal sputter layer by sputtering a surface of the cap layer away from the conductive pattern, a hole wall of the via hole, and a surface of the ground line exposed from the via hole, the metal sputter layer Electrically connected to the ground line.

The manufacturing method of the flexible circuit board provided by the technical solution forms a conductive pattern on the flexible copper clad plate and forms a cover film to protect the conductive pattern, and then is electrically connected to the conductive pattern by low temperature vacuum sputtering on the cover film. The metal sputter of the ground wire. The metal sputtering layer has small thickness, saves raw materials, and has strong adhesion with the flexible circuit board, is less prone to cracking, and is beneficial to improving electromagnetic shielding performance of the flexible circuit board.

10‧‧‧Flexible CCL

11‧‧‧Insulation

12‧‧‧ Conductive layer

120‧‧‧Electrical graphics

121‧‧‧ Grounding wire

122‧‧‧Signal transmission line

123‧‧‧Connecting Department

13‧‧‧ Cover film

130‧‧‧ Coverage

131‧‧‧ first surface

132‧‧‧ second surface

133‧‧‧ side

134‧‧‧ third surface

135‧‧‧through hole

136‧‧‧ hole wall

140‧‧‧Metal Sputter

15‧‧‧Flexible circuit board unit

100‧‧‧Flexible circuit board

101‧‧‧Product Area

200‧‧‧vacuum sputtering device

201‧‧‧ cathode

202‧‧‧Anode

203‧‧‧coating cavity

204‧‧‧temperature controller

205‧‧‧ Vacuuming device

206‧‧‧ gas supply device

1 is a partial cross-sectional view of a flexible circuit board according to a first embodiment of the present technical solution.

2 is a partial structural schematic view of a flexible copper clad laminate provided by a second embodiment of the present technical solution.

FIG. 3 is a partial structural schematic view showing a conductive pattern formed on the flexible copper clad laminate.

Figure 4 is a cross-sectional view of Figure 3 taken along line IV-IV.

FIG. 5 is a schematic view showing the structure of attaching a cover film to the flexible copper clad laminate.

Figure 6 is a partial cross-sectional view showing a flexible copper clad laminate formed with a cover layer.

FIG. 7 is a schematic structural view of a vacuum sputtering apparatus according to a second aspect of the present technical solution.

FIG. 8 is a cross-sectional view showing a flexible circuit board unit obtained by cutting the flexible circuit board shown in FIG. 1.

The flexible circuit board provided by the technical solution and the manufacturing method thereof will be further described in detail below with reference to the accompanying drawings and the embodiments.

Referring to FIG. 1 , a first embodiment of the present technology provides a flexible circuit board 100 including an insulating layer 11 , a conductive pattern 120 , a cover layer 130 , and a metal sputter layer 140 . The flexible circuit board 100 may include a plurality of flexible circuit board units 15 arranged in sequence.

The insulating layer 11 may be a polyester (PET) film or a polyimide film (PI) film.

The conductive pattern 120 is formed on the insulating layer 11. The conductive pattern 120 may be made of copper, and includes a ground line 121 and a signal transmission line 122. In this embodiment, the grounding wire 121 and the signal transmission line 122 are both elongated and arranged side by side. Each of the grounding wires 121 has a connecting portion 123 at its center.

The cover layer 130 covers the conductive pattern 120. The cover layer 130 has a first surface 131, a second surface 132, a side surface 133 and a third surface 134. The first surface 131 is away from the insulating layer 11. The third surface 134 is in contact with the insulating layer 11. The second surface 132 and the side surface 133 are both in contact with the conductive pattern 120. The second surface 132 is located between the first surface 131 and the third surface 134 and is parallel to the first surface 131. The side surface 133 is coupled between the second surface 132 and the third surface 134. The cover layer 130 further has a through hole 135 penetrating the first surface 131 and the second surface 132. The through hole 135 has a hole wall 136 connected between the first surface 131 and the second surface 132. The ground line 121 is partially exposed to the through hole 135. Specifically, the connection portion 123 of the grounding wire 121 is exposed to the through hole 135.

Of course, the through hole 135 may also be larger, so that the grounding wire 121 is entirely exposed to the through hole 135, such that the cover layer 130 does not have parallel to the first surface. And a second surface 132 that is in contact with the conductive pattern 120. The side surface 133 is also in the same plane as the hole wall 136.

The metal sputter layer 140 is formed on the surface of the cap layer 130 away from the conductive pattern 120, the hole wall 136 of the through hole 135, and the surface of the ground line 121 exposed from the through hole 135 by sputtering, thereby electrically connecting with the ground line 121. Sexual connection. The metal sputter layer may be a conductive metal material such as copper, silver, chromium or aluminum, and has a thickness ranging from 0.3 to 0.5 μm. In this embodiment, since the thickness of the metal sputter layer is less than the thickness of the cover layer 130, the metal sputter layer 140 sequentially covers the first surface 131 of the cover layer 130, the hole wall 136, and the ground. The connection portion 123 of the line 121.

The thickness of the metal sputter layer of the flexible circuit board provided by the first embodiment of the present technical solution is small, and a large amount of raw materials can be saved.

The second embodiment of the present technical solution provides a method for manufacturing a flexible circuit board, which includes the following steps:

In a first step, referring to FIG. 2, a flexible copper clad laminate 10 is provided, which includes an insulating layer 11 and a conductive layer 12 attached to the insulating layer 11. The insulating layer 11 may be a polyester (PET) film or a polyimide film (PI) film. The flexible copper clad laminate 10 includes a plurality of product regions 101 arranged in sequence.

In the second step, referring to FIG. 3 and FIG. 4 , the conductive layer 12 is formed into a conductive pattern 120 , and the conductive pattern 120 includes a ground line 121 and a signal transmission line 122 . In this embodiment, the conductive pattern 120 includes a grounding wire 121 and two signal transmission lines 122 in each product area 101. Each of the grounding lines 121 has a connecting portion 123 at a center thereof. Specifically, a photoresist layer may be formed on the conductive layer 12, and a portion of the conductive layer 12 may be removed by exposure, development, etching, or the like. The material, the remaining portion of the conductive material, forms the conductive pattern 120.

In the third step, referring to FIG. 5 and FIG. 6 , a cover layer 130 covering the conductive pattern 120 is formed. The cover layer 130 has a through hole 135 , and the ground line 121 is at least partially exposed to the through hole 135 . . Specifically, the following steps can be taken:

First, a cover film 13 is provided, which may include an adhesive layer and an insulating film layer having opposite first and second surfaces 131 and 132.

Next, a through hole 135 penetrating the first surface 131 and the second surface 132 is formed in the cover film 13 by drilling or punching. The number and position of the through holes 135 correspond to the connecting portion 123 of the grounding wire 121, and the size corresponds to the connecting portion 123 of the grounding wire 121. Each of the through holes 135 has a hole wall 136 connected between the first surface 131 and the second surface 132.

Finally, the second surface 132 is brought close to the conductive pattern 120, the through hole 135 is aligned with the connecting portion 123 of the grounding line 121, and the cover film 13 is pressed against the conductive pattern of the flexible copper clad laminate 10. On one side of the 120, a cover layer 130 is formed on the flexible copper clad laminate 10. First, one side of the adhesive layer of the cover film 13 is brought close to the flexible copper clad laminate 10, and the plurality of through holes 135 are opposed to the connecting portion 123 of the plurality of grounding wires 121, and the cover film 13 is attached. A stacked plate is obtained on the flexible copper clad laminate 10, and the stacked plate is placed in a press machine for pressing. When pressed, the cover film 13 is heated to flow, filling the gaps in the conductive pattern 120, forming a third surface 134 in contact with the insulating layer 11, and being connected between the second surface 132 and the third surface 134. Side 133.

The fourth step, please refer to FIG. 1 and FIG. 7 together, by sputtering the surface of the cover layer 130 away from the conductive pattern 120, the hole wall 136 of the through hole 135, and the connection from the through hole 135. A metal sputter layer 140 is formed on the surface of the ground line 121, and the metal sputter layer 140 is electrically connected to the ground line 121.

Specifically, the following steps may be included:

First, a vacuum sputtering apparatus 200 and a metal target are provided. The vacuum sputtering apparatus 200 includes a cathode 201 and an anode 202 disposed opposite each other. The vacuum sputtering apparatus 200 further includes a coating chamber 203, a temperature controller 204, a vacuuming device 205, and a gas supply device 206. The metal target may be a high melting point metal, alloy or metal oxide. In this embodiment, the material of the metal target is silver.

Next, the metal target is placed on the cathode 201 of the vacuum sputtering apparatus 200. The cover layer 130 of the flexible copper clad laminate 10 is opposed to the cathode 201, and the flexible copper clad laminate 10 is disposed on the anode 202 of the vacuum sputtering apparatus 200.

Again, the vacuum sputtering apparatus 200 is evacuated and preheated, and after being filled with an inert gas, a high voltage direct current is applied between the cathode 201 and the anode 202 to bring the flexible copper clad laminate 10 close to one of the cover layers 130. A metal sputter layer 140 electrically connected to the ground line 121 is formed on the side. In this embodiment, the coating chamber 203 is evacuated by a vacuuming device 205 to a pressure of about 1.3×10 ⁻³ Pa, and preheated by the temperature controller 204 to a temperature of about 60° C. After the argon gas is filled into the coating chamber 203 by the gas supply device 206, the argon gas is excited by the digital discharge generated by the glow discharge, and the plasma is generated, and the plasma blasts the atoms of the metal target and deposits them in the chamber. The flexible copper clad laminate 10 is adjacent to one side of the cover layer 130 until the thickness of the atoms deposited on the flexible copper clad laminate 10 reaches 0.3-0.5 μm, and the application of voltage is stopped to obtain the flexible circuit board 100 as shown in FIG. The atoms of the metal target are sputtered from the surface of the metal target in various directions under the bombardment of the plasma, so that the obtained flexible copper clad plate 10, even the hole wall 136 of the through hole 135 of the cover film 13 and the same A layer of silver atoms can be uniformly deposited at the junction of the ground line 121. Since the high-frequency current causing electromagnetic interference has a skin effect, the metal sputter layer 140 having a thickness of 0.3-0.5 μm can achieve electromagnetic interference of the mask. The metal sputter layer 140 formed by low-temperature vacuum sputtering not only has a small thickness, saves raw materials, but also has strong adhesion to the flexible circuit board 100 and is less prone to cracking, which is advantageous for improving the electromagnetic shielding performance of the flexible circuit board 100.

In the fifth step, the flexible circuit board 100 is cut to obtain a plurality of flexible circuit board units 15 as shown in FIG. In this way, the flexible circuit board unit 15 can be assembled into the digital product to realize the transmission and processing of the digital signal.

Of course, the fifth step may also be performed between the third step and the fourth step, that is, after forming the cover layer 130 covering the conductive pattern 120, the flexible copper clad laminate 10 is first cut to obtain a plurality of flexible circuit boards. The unit 15 then moves the flexible circuit board unit 15 into the vacuum sputtering apparatus 200 for coating to form a metal sputter layer 140.

The manufacturing method of the flexible circuit board provided by the technical solution forms a conductive pattern on the flexible copper clad plate and forms a cover film to protect the conductive pattern, and then forms a metal sputter layer on the cover film by low temperature vacuum sputtering. The metal sputtering layer has small thickness, saves raw materials, and has strong adhesion with the flexible circuit board, is less prone to cracking, and is beneficial to improving electromagnetic shielding performance of the flexible circuit board.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application of the present invention. Equivalent modifications or variations made by persons skilled in the art in light of the spirit of the invention are intended to be included within the scope of the following claims.

11‧‧‧Insulation

120‧‧‧Electrical graphics

121‧‧‧ Grounding wire

122‧‧‧Signal transmission line

123‧‧‧Connecting Department

130‧‧‧ Coverage

131‧‧‧ first surface

132‧‧‧ second surface

133‧‧‧ side

134‧‧‧ third surface

135‧‧‧through hole

136‧‧‧ hole wall

140‧‧‧Metal Sputter

15‧‧‧Flexible circuit board unit

100‧‧‧Flexible circuit board

Claims (10)

A flexible circuit board comprising an insulating layer, a conductive pattern formed on the insulating layer, a cover layer covering the conductive pattern, and a continuous metal sputter layer, the conductive pattern comprising a ground line and a signal transmission line, the cover layer having a through hole, Exposing at least part of the grounding wire, the metal sputtering layer is formed by sputtering on the entire surface of the covering layer away from the conductive pattern, the hole wall of the through hole, and the grounding wire surface exposed from the through hole, thereby electrically connecting with the grounding wire Connecting, wherein the thickness of the metal sputter layer of the cover layer away from the entire surface of the conductive pattern, the thickness of the metal sputter layer of the via hole of the via hole, and the thickness of the metal sputter layer of the ground line surface exposed from the via hole are the same and Both are smaller than the thickness of the cover layer. The flexible circuit board of claim 1, wherein the metal sputter layer has a thickness ranging from 0.3 micrometers to 0.5 micrometers. The flexible circuit board of claim 1, wherein the metal sputter layer is made of silver, copper, chromium or aluminum. The flexible circuit board of claim 1, wherein the cover layer has a first surface, a second surface, and a third surface, the first surface being away from the insulating layer, the third surface being The insulating layer is in contact with the second surface between the first surface and the third surface, the second surface is in contact with the conductive pattern, and the through hole extends through the first surface Two surfaces. A method for fabricating a flexible circuit board, comprising the steps of: providing a flexible copper clad plate comprising an insulating layer and a conductive layer attached to the insulating layer; forming the conductive layer into a conductive pattern, the conductive pattern comprising a ground line and a signal transmission line; forming a cover layer covering the conductive pattern, the cover layer having a through hole, the ground line being at least partially exposed to the through hole; Forming a continuous metal sputter layer by sputtering on the entire surface of the cap layer away from the conductive pattern, the hole wall of the via hole, and the surface of the ground line exposed from the via hole, the metal sputter layer and the ground line electrical Connecting, wherein the thickness of the metal sputter layer of the cover layer away from the entire surface of the conductive pattern, the thickness of the metal sputter layer of the via hole of the via hole, and the thickness of the metal sputter layer of the ground line surface exposed from the via hole are the same and Both are smaller than the thickness of the cover layer. The method of fabricating a flexible circuit board according to claim 5, wherein the forming the continuous metal sputtering layer comprises the steps of: providing a vacuum sputtering device and a metal target, the vacuum sputtering device comprising a cathode disposed oppositely An anode; the metal target is disposed on the cathode, the cover layer of the flexible copper clad plate is opposite to the cathode, the flexible copper clad plate is disposed on the anode; and a voltage is applied between the cathode and the anode Forming a metal sputter layer on the flexible copper clad laminate. The method for fabricating a flexible circuit board according to claim 5, wherein the flexible copper clad laminate comprises a plurality of product regions, and after forming the metal sputter layer, further comprising cutting the flexible cover along a boundary of the plurality of product regions Copper plate, the step of obtaining a plurality of flexible circuit board units. The method for fabricating a flexible circuit board according to claim 5, wherein the flexible copper clad laminate comprises a plurality of product regions, and after forming a cover layer covering the conductive pattern, before forming a metal sputter layer, Cutting the flexible copper clad laminate at a boundary of the plurality of product regions to obtain a plurality of flexible circuit board units. When the metal sputter layer is formed, the cover layer of each flexible circuit board unit is away from the surface of the conductive pattern and the through hole The walls and the surface of the ground line exposed from the vias form a continuous metal sputter. The method for fabricating a flexible circuit board according to claim 5, wherein the metal sputter layer is made of copper, silver, chromium or aluminum. The method for fabricating a flexible circuit board according to claim 5, wherein the metal splashing The thickness of the coating ranges from 0.3 microns to 0.5 microns.