TWI491321B - 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 the field of flexible circuit boards, and in particular to a flexible circuit board having a reinforcing sheet and a manufacturing method thereof.

With the continuous 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. To achieve electrical connection between different circuits. In order to obtain FPCB with better flexing performance, it has become a research hotspot to improve the flexural properties of the base film materials used in FPCB. See the literature Electrical Insulation Maganize, Volume 5, Issue 1, Jan.-Feb., 1989 Papers: 15-23, "Applications of Polyimide Films to the Electrical and Electronic Industries in Japan."

In order to meet the design requirements for the versatility of foldable digital products, the number of digital components mounted on the surface of the FPCB has also increased accordingly. However, FPCB with good flexural performance compared with rigid boards has low mechanical strength, low load carrying capacity, and FPCB is easy to use during installation, such as installing digital devices in Surface Mount Technology (SMT). Cracked or damaged, unable to carry larger quality or a larger number of digital devices, hindering the development of multi-functional folding digital products. In addition, with the number The increase in the frequency of the transmitted digital signal in the bit product increases the performance requirements for the electromagnetic mask of the board.

In view of this, it is necessary to provide a flexible circuit board and a manufacturing method thereof to improve the mechanical strength and electromagnetic shielding performance of the flexible circuit board.

A flexible circuit board comprising a first conductive pattern, an insulating layer, a second conductive pattern, a conductive adhesive layer and a reinforcing sheet. The first conductive pattern and the second conductive pattern are formed on opposite sides of the insulating layer. The first conductive pattern includes an electrically connected ground wire and a first connection terminal. The second conductive pattern includes a second connection terminal electrically connected to the first connection terminal. The second connection terminal is used to mount a grounding part. The conductive adhesive layer is located between the first conductive pattern and the reinforcing sheet. The reinforcing sheet includes a metal base layer and at least one surface plating layer formed on a surface of the metal base layer. The at least one surface plating layer is electrically connected to the first connection terminal by the conductive adhesive layer.

A method for fabricating a flexible circuit board, comprising the steps of: providing a flexible copper clad laminate comprising a first conductive layer, an insulating layer and a second conductive layer, wherein the first conductive layer and the second conductive layer are located on opposite sides of the insulating layer; Forming the first conductive layer into a first conductive pattern, the first conductive pattern comprising an electrically connected ground wire and a first connection terminal, the second conductive layer forming a second conductive pattern, the second conductive pattern including a first connection terminal electrically connected to the second connection terminal, the second connection terminal is used for mounting a grounding component; a reinforcing sheet is provided, the reinforcing sheet comprises a metal base layer and at least one surface formed on the surface of the metal base layer Surface plating; and forming a conductive adhesive layer on the at least one surface plating layer, the reinforcing sheet is adhered to the first conductive pattern by the conductive adhesive layer to electrically connect the reinforcing sheet to the first layer Connection terminal.

The technical solution provides a flexible circuit board obtained by the manufacturing method, and has a first conductive pattern, a second conductive pattern and a reinforcing sheet. The second conductive pattern can mount a grounded component. The reinforcing sheet is mounted on one side of the first conductive pattern, and is electrically connected to the grounding terminal of the second conductive pattern through the conductive adhesive layer and the via hole, so as to support the grounded part on the second conductive pattern A conductive pattern acts as a conductive mask. The presence of the surface plating layer allows the reinforcing sheet to have a small and stable electrical resistance value, and the heat resistance and appearance of the reinforcing sheet are improved.

10‧‧‧Flexible CCL

11‧‧‧Insulation

111‧‧‧Through hole

12‧‧‧First conductive layer

120‧‧‧First conductive graphic

121‧‧‧Grounding conductor

122‧‧‧First connection terminal

123‧‧‧First connection plate

124‧‧‧First reinforcement

13‧‧‧Second conductive layer

130‧‧‧Second conductive pattern

131‧‧‧Second connection terminal

132‧‧‧ Grounding terminal

133‧‧‧ Signal Terminal

134‧‧‧second connector

135‧‧‧ second reinforcement

140‧‧‧First cover film

141‧‧‧ openings

150‧‧‧second cover film

151‧‧‧Opening the window

160‧‧‧ Conductive adhesive layer

170‧‧‧ Strengthening film

171‧‧‧metal basement

172‧‧‧ surface coating

100‧‧‧Flexible circuit board

1 is a top plan view of a flexible circuit board provided by a first embodiment of the present technical solution.

2 is a top plan view of the other side of the flexible circuit board provided by the first embodiment of the present technical solution.

Figure 3 is a schematic cross-sectional view taken along line III-III of Figure 1.

4 is a partial cross-sectional view of a flexible copper clad plate provided by a second embodiment of the present technical solution.

Fig. 5 is a schematic cross-sectional view showing the formation of via holes in the flexible copper clad laminate.

FIG. 6 is a schematic cross-sectional view showing the first conductive pattern and the second conductive pattern.

7 is a schematic cross-sectional view showing the first cover film and the second cover film formed on the flexible copper clad laminate.

FIG. 8 is a schematic cross-sectional view showing the first connection terminal and the second connection terminal.

FIG. 9 is a schematic cross-sectional view showing a surface plating layer formed on a metal base layer provided by a second embodiment of the present technical solution.

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 to FIG. 3 , the first embodiment of the present invention provides a flexible circuit board 100 including an insulating layer 11 , a first conductive pattern 120 , a second conductive pattern 130 , a first cover film 140 , and a second The cover film 150, the conductive adhesive layer 160 and the reinforcing sheet 170.

The insulating layer 11 is configured to carry the first conductive pattern 120 and the second conductive pattern 130. The insulating layer 11 may be a polyester (PET) film or a polyimide film (PI) film.

The first conductive pattern 120 and the second conductive pattern 130 are formed on opposite sides of the insulating layer 11 . The first conductive pattern 120 includes an electrically connected ground wire 121 and a first connection terminal 122. The second conductive pattern 130 includes a second connection terminal 131 electrically connected to the first connection terminal 122. The second connection terminal 131 is used to mount a grounding part. The grounding component can be a component having a masked outer casing (such as a connector, a triode, etc.). The second connection terminal 131 can include a ground terminal 132 and a signal terminal 133. The ground terminal 132 is configured to be electrically connected to the outer casing of the grounding member to be grounded. The signal terminal 133 is for electrically connecting to other signal terminals of the grounding component.

The flexible circuit board 100 further has a via hole 111 penetrating through the first conductive pattern 120, the insulating layer 11 and the second conductive pattern 130. The first connection terminal 122 and the second connection terminal 131 are electrically connected by the via hole 111. Of course, the number of the via holes 111 of the flexible circuit board 100 is not limited to one, and there may be other via holes for performing signal transmission between the first conductive pattern 120 and the second conductive pattern 130.

The first cover film 140 is used to protect the first conductive pattern 120. The first cover film 140 covers the first conductive pattern 120 away from one side of the insulating layer 11 . The first cover film 140 has an opening 141, and the first connection terminal 122 is exposed to the opening 141 and partially fills the opening 141.

The second cover film 150 is used to protect the second conductive pattern 130. The second cover film 150 covers the side of the second conductive pattern 130 away from the insulating layer 11 . The second cover film 150 has a window 151, and the second connection terminal 131 is exposed to the window 151 and partially fills the window 151.

The conductive adhesive layer 160 is located between the first conductive pattern 120 and the reinforcing sheet 170. The conductive adhesive layer 160 fills the opening 141 of the first cover film 140 and is electrically connected to the first connection terminal 122.

The reinforcing sheet 170 includes a metal base layer 171 and at least one surface plating layer 172 formed on a surface of the metal base layer 171. The material of the metal base layer 171 may be stainless steel, aluminum or beryllium copper alloy or the like. The at least one surface plating layer 172 is electrically connected to the first connection terminal 122 by the conductive adhesive layer 160. The surface plating layer 172 may be made of a material having good electrical conductivity such as nickel, gold or silver. The surface plating layer 172 has a thickness ranging from 0.8 μm to 5.0 μm. In this embodiment, the metal base layer 171 is a rectangular plate body, and the surface plating layer 172 is two, one of which is in contact with the conductive adhesive layer 160, and the other is located at the metal base layer 171 away from the conductive layer. One side of the glue layer 160.

The flexible circuit board 100 provided by the first embodiment of the present technical solution has a first conductive pattern 120, a second conductive pattern 130, and a reinforcing sheet 170. The second conductive pattern 130 can mount a grounded part. The reinforcing sheet 170 is mounted on one side of the first conductive pattern 120, and is electrically connected to the ground terminal 132 of the second conductive pattern 130 by the conductive adhesive layer 160 and the via hole 111, so as to be supported on the second conductive pattern 130. The grounded component simultaneously acts as a conductive mask on the first conductive pattern 120. The presence of the surface plating 172 The reinforcing sheet 170 can have a small and stable resistance value, and the heat resistance and appearance of the reinforcing sheet 170 can be improved.

The second embodiment of the present technical solution provides a method for fabricating the flexible circuit board 100 as described above, which includes the following steps:

In the first step, referring to FIG. 4, a flexible copper clad laminate 10 is provided, which includes an insulating layer 11, a first conductive layer 12 and a second conductive layer 13. The first conductive layer 12 and the second conductive layer 13 are located on the insulating layer 11. The opposite sides.

In the second step, a via hole 111 is formed in the flexible copper clad laminate 10 to be connected between the first conductive layer 12 and the second conductive layer 13, as shown in FIG. Specifically, the flexible copper clad laminate 10 may be drilled to obtain through holes of the insulating layer 11, the first conductive layer 12 and the second conductive layer 13, and then obtained by electroless plating, electroplating, or the like. A conductive metal layer is formed on the inner wall of the hole, and a space formed by enclosing the conductive metal layer is filled with a material such as ink to obtain the via hole 111.

In the third step, referring to FIG. 6 to FIG. 8 , the first conductive layer 12 is formed into a first conductive pattern 120 , and the first conductive pattern 120 includes an electrically connected ground wire 121 and a first connection terminal 122 . Forming the second conductive layer 13 into the second conductive pattern 130, the second conductive pattern 130 includes a second connection terminal 131 electrically connected to the first connection terminal 122, and the second connection terminal 131 is used to mount the grounding part . A photoresist layer may be formed on the first conductive layer 12 and the second conductive layer 13, and a portion of the conductive material of the first conductive layer 12 and the second conductive layer 13 may be removed by exposure, development, etching, or the like. Forming a conductive pattern.

Specifically, forming the first conductive layer 12 into the first conductive pattern 120 includes the following steps:

First, the first conductive layer 12 is etched to form an electrically connected ground wire 121 and a first land 123.

Next, a first cover film 140 is attached to the first conductive layer 12, and the first cover film 140 has an opening 141 to expose the first lands 123. In this embodiment, the first cover film 140 is formed by ink printing.

Finally, the first lands 123 are surface-coated to form a first connection terminal 122. Specifically, a surface of the first lands 123 exposed to the opening 141 is subjected to surface processing such as gold plating or an organic coating film (OSP) to form a first reinforcing layer 124 partially filling the opening 141. A connection terminal 122.

The method of forming the second conductive layer 13 into the second conductive pattern 130 is substantially the same as the above steps, that is, etching the second conductive layer 13 to form the second connection head 134. Then, a second cover film 150 is attached on the second conductive layer 13, and the second cover film 150 has a window 151 to expose the second connector 134. Finally, the second connection head 134 is surface-coated to form a second reinforcement layer 135 partially filling the window 151 to obtain a second connection terminal 131. The second connection terminal 131 is electrically connected to the first connection terminal 122 through the via hole 111 .

Of course, in the actual production process, the etching of the first conductive layer 12 and the second conductive layer 13 can be performed simultaneously, and the first cover film 140 and the second cover film 150 can be simultaneously applied.

In a fourth step, referring to FIG. 9, a reinforcing sheet 170 is provided. The reinforcing sheet 170 includes a metal base layer 171 and at least one surface plating layer 172 formed on the surface of the metal base layer 171. The metal base layer 171 may be stainless steel, aluminum or beryllium copper alloy or the like. The surface plating layer 172 may be made of a material having good electrical conductivity such as nickel, gold or silver. The surface plating layer 172 may be formed on the surface of the metal base layer 171 by electroplating, electroless plating, chemical vapor deposition, or physical vapor deposition. In the actual production process, a large metal base layer 171 is usually provided, and a surface plating layer 172 is formed on each surface thereof, and then cut into a desired shape.

In the fifth step, a conductive adhesive layer 160 is formed on the at least one surface plating layer 172, and the reinforcing sheet 170 is adhered to the first conductive pattern 120 by the conductive adhesive layer 160 to make the reinforcing sheet 170 electrically Connected to the first connection terminal 122, the flexible circuit board 100 as shown in FIG. 1 is obtained. Specifically, a conductive adhesive film may be attached to the at least one surface plating layer 172. The reinforcing sheet 170 is placed on the first conductive pattern 120 in alignment with the first connection terminal 122. Finally, the conductive adhesive film is subjected to high temperature and high pressure by a conductive adhesive film pressing machine, such that the resin adhesive in the conductive adhesive film is under high temperature and high pressure conditions, and the first cover film 140 and the The surface plating layer 172 of the reinforcing sheet 170 is chemically bonded, and a part of the resin adhesive is heated and flows into the opening 141 of the first covering film 140 to fill the opening 141. The conductive particles in the conductive film are electrically connected between the first connection terminal 122 and the reinforcing sheet 170, thereby obtaining the conductive adhesive layer 160.

For the flexible circuit board 100, a grounding component may be mounted on the second connection terminal 131 by a surface mount (SMT) or soldering process, and the ground terminal 132 of the second connection terminal 131 may be connected to the mask housing of the grounding component. The reinforcing sheet 170 is also grounded.

The method for fabricating the flexible circuit board according to the second embodiment of the present invention forms the surface plating layer 172 of a material such as nickel or gold on the metal base layer 171 of a material such as stainless steel to obtain the reinforcing sheet 170. The reinforcing sheet 170 is attached to one side of the first conductive pattern 120, and is electrically connected to the through hole 111 by the conductive adhesive layer 160 to be used for mounting the grounded part. Two connection terminals 131. The reinforcing sheet 170 of the obtained flexible circuit board 100 can function as a conductive mask for the first conductive pattern 120 while supporting the grounding member on the second conductive pattern 130. The presence of the surface plating layer 172 allows the reinforcing sheet 170 to have a small and stable electrical resistance value, and improve the heat resistance and appearance of the reinforcing sheet 170 and the like.

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

111‧‧‧Through hole

120‧‧‧First conductive graphic

122‧‧‧First connection terminal

130‧‧‧Second conductive pattern

131‧‧‧Second connection terminal

140‧‧‧First cover film

141‧‧‧ openings

150‧‧‧second cover film

151‧‧‧Opening the window

160‧‧‧ Conductive adhesive layer

170‧‧‧ Strengthening film

171‧‧‧metal basement

172‧‧‧ surface coating

100‧‧‧Flexible circuit board

Claims (4)

A flexible circuit board comprising a first cover film, a first conductive pattern, an insulating layer, a second conductive pattern, a conductive adhesive layer and a reinforcing sheet, wherein the first conductive pattern and the second conductive pattern are formed on the insulating layer On both sides, the first conductive pattern includes an electrically connected ground wire and a first connection terminal, the first cover film is for protecting the first conductive pattern, and the first cover film has an opening, the first The connection terminal is exposed to the opening, the second conductive pattern includes a second connection terminal electrically connected to the first connection terminal, the second connection terminal is for mounting a grounding part; the flexible circuit board has a through hole a first conductive pattern, a conductive layer and a second conductive pattern, the first connection terminal and the second connection terminal are electrically connected by the via hole; the conductive adhesive layer is located at the first Between the conductive pattern and the reinforcing sheet, the conductive adhesive layer contacts the first cover film and fills an opening of the first cover film, and the reinforcing sheet includes a metal base layer and a metal base layer formed on the surface Coating at least one surface of the material of the surface of nickel plating, gold or silver, by coating the surface of said at least one conductive adhesive layer and the first connection terminal is electrically connected. The flexible circuit board of claim 1, wherein the metal base layer is made of stainless steel, aluminum or beryllium copper. A method for fabricating a flexible circuit board, comprising the steps of: providing a flexible copper clad laminate comprising a first conductive layer, an insulating layer and a second conductive layer, wherein the first conductive layer and the second conductive layer are located on opposite sides of the insulating layer; Forming a via hole connected between the first conductive layer and the second conductive layer in the flexible copper clad laminate; forming the first conductive pattern into the first conductive pattern and forming on the first conductive pattern a first cover film, the first conductive pattern includes an electrically connected ground wire and a first connection terminal, The first cover film has an opening, the first connection terminal is exposed to the opening, the second conductive layer forms a second conductive pattern, and the second conductive pattern includes a second electrically connected to the first connection terminal a connection terminal, the second connection terminal is used for mounting a grounding component; a reinforcing sheet is provided, the reinforcing sheet includes a metal base layer and at least one surface plating layer formed on a surface of the metal base layer, wherein the surface plating layer is made of nickel And a gold or silver layer; and forming a conductive adhesive layer on the at least one surface plating layer, bonding the reinforcing sheet to the first conductive pattern and the first cover film by the conductive adhesive layer, and The conductive adhesive layer fills the opening of the first cover film such that at least one surface plating of the surface of the reinforcing sheet is electrically connected to the first connection terminal. The method for fabricating a flexible circuit board according to claim 3, wherein the forming the first conductive layer to form the first conductive pattern and forming the first cover film on the first conductive pattern comprises the steps of: etching a first conductive layer to form an electrically connected ground wire and a first connection pad; a first cover film is attached on the first conductive layer, the first cover film has an opening to expose the first connection a disk; and surface coating the first land to form a first connection terminal.