CN104349570A - Rigid-flexible-combined circuit board and manufacturing method thereof - Google Patents

Abstract

A rigid-flex circuit board comprising a flexible circuit board, a first covering layer, a second covering layer, a first lamination film, a second lamination film, a third conductive circuit layer and a fourth conductive circuit layer, the The first covering layer and the second covering layer are formed on opposite sides of the flexible circuit board, and both the first covering layer and the second covering layer cover the exposed area of the flexible circuit board, and also cover part of the first lamination area and a part of the second pressing area, the first pressing film and the second pressing film are pressed on opposite sides of the flexible circuit board, and are in contact with the first pressing area and the second pressing area Correspondingly, the third conductive circuit layer is formed on the surface of the first laminated film, and the fourth conductive circuit layer is formed on the surface of the second laminated film. The invention also provides a method for manufacturing the rigid-flex circuit board.

Description

Rigid-flex circuit board and manufacturing method thereof

technical field

The invention relates to the field of circuit board production, in particular to a soft-hard combination circuit board and a production method thereof.

Background technique

Printed circuit boards have been widely used due to their advantages such as high assembly density. For the application of the circuit board, please refer to the literature Takahashi, A. Ooki, N. Nagai, A. Akahoshi, H. Mukoh, A. Wajima, M. Res. Lab, High density multilayer printed circuit board for HITAC M-880, IEEE Trans . on Components, Packaging, and Manufacturing Technology, 1992, 15(4): 1418-1425.

Rigid-flex circuit board is a circuit board structure including interconnected flexible boards and rigid boards, which can not only have the flexibility of flexible circuit boards, but also include the hardness of rigid circuit boards. Rigid-flex circuit boards can be used in components such as camera modules or battery modules, and the proportion of applications in mid-to-high-end consumer electronics products, such as smartphones and ultrabooks, is increasing day by day. In order to meet the miniaturization requirements of electronic products, the thickness of the rigid-flex circuit board also needs to be further reduced.

Contents of the invention

Therefore, it is necessary to provide a rigid-flex circuit and a manufacturing method thereof, which can effectively reduce the thickness of the rigid-flex circuit board.

A method for manufacturing a rigid-flex circuit, comprising the steps of: providing a flexible circuit board, including an exposed area and a first pressing area and a second pressing area connected to opposite sides of the exposed area; A first cover layer and a second cover layer are respectively formed on the opposite sides, and both the first cover layer and the second cover layer cover the exposed area of the flexible circuit board, and cover the part of the first pressure layer connected to the two ends of the exposed area. bonding area and part of the second pressing area; providing a first pressing film, a second pressing film, a first copper foil and a second copper foil, the first pressing film has a first opening corresponding to the exposed area, The second lamination film has a second opening corresponding to the exposed area; stacking and laminating the first copper foil, the first lamination film, the flexible circuit board, the second lamination film and the second copper foil to obtain a multilayer The substrate, the first opening and the second opening both correspond to the exposed area, the first lamination film is in contact with the first covering layer located at the first lamination area and the second lamination area, the The second lamination film is in contact with the second covering layer located in the first lamination area and the second lamination area; and selectively removes part of the first copper foil to form a third conductive circuit layer, and at the same time exposes the corresponding first 1. Removing the copper foil, selectively removing part of the second copper foil to form the fourth conductive circuit layer, and removing the second copper foil corresponding to the exposed area to expose the exposed area of the flexible circuit board.

A rigid-flex circuit board comprising a flexible circuit board, a first covering layer, a second covering layer, a first lamination film, a second lamination film, a third conductive circuit layer and a fourth conductive circuit layer, the The flexible circuit board includes sequentially connected exposed areas and a first pressing area and a second pressing area connected to opposite ends of the exposed area, and the first covering layer and the second covering layer are formed on the opposite sides of the flexible circuit board. On both sides, the first cover layer and the second cover layer both cover the exposed area of the flexible circuit board, and also cover part of the first press-fitting area and part of the second press-fitting area connected to both ends of the exposed area, so The first pressing film and the second pressing film are pressed on opposite sides of the flexible circuit board, and correspond to the first pressing area and the second pressing area, and the first covering layer has a distance away from The first pressing surface of the flexible circuit board, the first pressing surface is only in direct contact with the first pressing film, and the second covering layer has a second pressing surface away from the flexible circuit board. The second pressing surface is only in direct contact with the second pressing film, the third conductive circuit layer is formed on the surface of the first pressing film, and the fourth conductive circuit layer is formed on the second pressing film. glued film surface.

Compared with the prior art, in the rigid-flex circuit board and its manufacturing method provided by this technical solution, the first covering layer and the second covering layer of the flexible circuit board are formed on the soft area of the rigid-flex circuit board and only Part of it extends into the hard area, and the film is directly laminated on both sides of the flexible circuit board. Compared with the prior art, the film is laminated after the protective layer is formed on the entire surface of the flexible circuit board, which can effectively reduce the thickness of the rigid area of the flexible circuit board.

Description of drawings

Fig. 1 is a schematic cross-sectional view of a flexible circuit board provided by an embodiment of the technical solution.

FIG. 2 is a schematic cross-sectional view of the flexible circuit board in FIG. 1 after the first covering layer and the second covering layer are formed on both sides.

Fig. 3 is a schematic cross-sectional view of the first laminated film provided by the embodiment of the technical solution.

Fig. 4 is a schematic cross-sectional view of the second laminated film provided by the embodiment of the technical solution.

Fig. 5 is a schematic cross-sectional view of the first copper foil and the second copper foil provided by the technical solution.

6 is a schematic cross-sectional view of a multi-layer substrate obtained after laminating the flexible circuit board, the first lamination film, the second lamination film, the first copper foil and the second copper foil.

FIG. 7 is a schematic cross-sectional view of the multi-layer substrate in FIG. 6 after forming through holes.

FIG. 8 is a schematic cross-sectional view of the inner wall of the through hole in FIG. 7 after metal plating is formed.

FIG. 9 is a schematic cross-sectional view of the first copper foil in FIG. 8 to form a third conductive circuit layer, and the second copper foil to form a fourth conductive circuit layer.

10 is a schematic cross-sectional view of a rigid-flex circuit board obtained after the first solder resist layer is formed on one side of the third conductive circuit layer in FIG. 9 and the second solder resist layer is formed on the fourth conductive circuit layer side.

11 is a schematic cross-sectional view of the electrical contact pad of the rigid-flex circuit board of FIG. 10 after forming a protective layer.

Description of main component symbols

Rigid-flex circuit board 100 multilayer substrate 10 flexible circuit board 110 exposed area 1101 first nip zone 1102 second nip zone 1103 first insulating layer 111 first surface 1111 second surface 1112 first conductive circuit layer 112 second conductive line layer 113 first covering layer 114 first bonding surface 1141 second overlay 115 Second bonding surface 1151 Conductive Via 11 through hole 12 metal coating 13 first lamination film 120 first opening 121 second lamination film 130 second opening 131 first copper foil 150 Second copper foil 160 third conductive circuit layer 151 The fourth conductive circuit layer 161 first solder mask 171 first opening 1711 Second solder mask 172 second opening 1721 first electrical contact pad 1511 second electrical contact pad 1611 The protective layer 180

The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings.

Detailed ways

The method for manufacturing a rigid-flex circuit board provided in the first embodiment of the technical solution includes the following steps:

The first step, please refer to FIG. 1 , is to provide a flexible circuit board 110 .

The flexible circuit board 110 is a circuit board fabricated with conductive circuits. The flexible circuit board 110 can be a single-sided circuit board or a double-sided circuit board. In this embodiment, the flexible printed circuit board 110 is taken as an example for illustration. The flexible circuit board 110 includes a first conductive circuit layer 112, a first insulating layer 111 and a second conductive circuit layer 113. The first insulating layer 111 includes opposite first surfaces 1111 and second surfaces 1112. The first conductive circuit layer 112 forms On the first surface 1111 of the first insulating layer 111 , the second conductive circuit layer 113 is formed on the second surface 1112 of the first insulating layer 111 .

The flexible circuit board 110 is substantially rectangular, and includes an exposed area 1101 and a first pressing area 1102 and a second pressing area 1103 connected to opposite sides of the exposed area 1101 . The exposed area 1101 is also rectangular, which is used to form the flexible area of the rigid-flex circuit board. The first pressing area 1102 and the second pressing area 1103 are used for fixed connection with the rigid circuit board. In this embodiment, in the plane where the flexible circuit board 110 is located, the extending direction from the first pressing area 1102 to the second pressing area 1103 is defined as the length direction, and the direction perpendicular to the above-mentioned extending direction is defined as the width direction . The first conductive circuit layers 112 all extend along the lengthwise direction, and both extend from the first pressing area 1102 to the second pressing area 1103 through the exposed area 1101 .

The thickness of the first insulating layer 111 is 10 microns to 15 microns, and the thickness of the first conductive circuit layer 112 and the second conductive circuit layer 113 is 8 microns to 12 microns. During the manufacturing process of the flexible circuit board 110 , a roll-to-roll method can be adopted to improve the efficiency of the flexible circuit board 110 manufacturing.

The second step, please refer to FIG. 2 , is to form a first cover layer 114 on the side of the first conductive circuit layer 112 of the flexible circuit board 110 , and form a second cover layer 115 on the side of the second conductive circuit layer 113 .

In this embodiment, both the first covering layer 114 and the second covering layer 115 completely cover the exposed area 1101 of the flexible circuit board 110, and the length of the first covering layer 114 and the second covering layer 115 is longer than that of the exposed area 1101. length, the first covering layer 114 and the second covering layer 115 also cover part of the first pressing region 1102 and part of the second pressing region 1103 connected to both ends of the exposed region 1101 . The first covering layer 114 has a first bonding surface 1141 away from the first conductive circuit layer 112 , and the second covering layer 115 has a second bonding surface 1151 away from the second conductive circuit layer 113 . The material of the first covering layer 114 and the second covering layer 115 may be polyimide.

The third step, please refer to FIG. 3 to FIG. 5 , provides the first lamination film 120 , the second lamination film 130 , the first copper foil 150 and the second copper foil 160 .

Please refer to FIG. 3 , the first laminated film 120 can be a common prepreg, or a low-fluidity prepreg. A first opening 121 corresponding to the exposed area 1101 of the flexible circuit board 110 is formed in the first lamination film 120 .

Please refer to FIG. 4 , the structure of the second lamination film 130 is basically the same as that of the first lamination film 120 , and the second lamination film 130 can be a common prepreg or a low-fluidity prepreg. A second opening 131 corresponding to the exposed area 1101 of the flexible circuit board 110 is formed in the second lamination film 130 .

The first copper foil 150 and the second copper foil 160 are preferably continuous rolled copper foils, but may also be continuous electrolytic copper foils as shown in FIG. 5 .

In this embodiment, the first lamination film 120 , the second lamination film 130 , the first copper foil 150 and the second copper foil 160 have the same length. The thickness of the first laminated film 120 and the second laminated film 130 is 35 microns to 45 microns, and the thickness of the first copper foil 150 and the second copper foil 160 is 20 microns to 25 microns.

The fourth step, please refer to Figure 6, align the flexible circuit board 110, the first lamination film 120, the second lamination film 130, the first copper foil 150 and the second copper foil 160 and press them into a whole , to obtain a multilayer substrate 10 .

During alignment, the first copper foil 150, the first lamination film 120, the flexible circuit board 110, the second lamination film 130, and the second copper foil 160 are stacked in sequence, and the first opening 121 of the first lamination film 120 Both the second opening 131 of the second lamination film 130 correspond to the exposed area 1101 of the flexible circuit board 110 . After lamination, the first covering layer 114 is in direct contact with the first lamination film 120 only with the corresponding parts of the first lamination area 1102 and the second lamination area 1103, and the second lamination layer 115 is in contact with the first lamination area 1103. Portions corresponding to the pressing area 1102 and the second pressing area 1103 are directly and only in contact with the second pressing film 130 .

After lamination, both the first lamination film 120 and the second lamination film 130 are solidified to form a hard part, and the first lamination film 120 becomes an insulating layer between the first conductive circuit layer 112 and the first copper foil 150 , and the second lamination film 120 The two laminated films 130 become a rigid insulating layer between the second conductive circuit layer 113 and the second copper foil 160 .

In the fifth step, please refer to FIG. 7 and FIG. 8 together, forming conductive vias 11 in the multilayer substrate 10 .

In this step, the following methods may be used to form conductive vias:

First, the via hole 12 is formed in the multilayer substrate 10 . The through hole 12 can be formed by mechanical drilling or laser ablation, and the through hole 12 can be opened in the area corresponding to the first pressing area 1102 or the second pressing area 1103 .

Then, a metal plating layer 13 is formed on the inner wall of the through hole 12 to obtain the conductive through hole 11 . Electroless plating or electroplating may be used to form the metal plating layer 13 on the inner wall of the through hole 12 . In this embodiment, the metal plating layer 13 is also formed on the surfaces of the first copper foil 150 and the second copper foil 160 . It can be understood that the surfaces of the first copper foil 150 and the second copper foil 160 can also be shielded to avoid the formation of the metal plating layer 13 .

It can be understood that this step may also be forming conductive blind holes in the multilayer substrate 10 . That is, blind holes are formed in the multilayer substrate 10 first, and then metal plating is formed in the holes, so as to obtain conductive blind holes.

The sixth step, please refer to FIG. 9 , selectively removes part of the first copper foil 150 to form at least part of the first copper foil 150 on the surface of the first lamination film 120 The third conductive circuit layer 151, selectively removes part of the second The copper foil 160 is formed by forming at least part of the second copper foil 160 into the fourth conductive circuit layer 161 on the surface of the second lamination film 130 to obtain the rigid-flex circuit board 100 .

The third conductive circuit layer 151 and the fourth conductive circuit layer 161 can be formed by image transfer process and etching process. During the etching process, the first copper foil 150 and the second copper foil 160 corresponding to the exposed area 1101 of the flexible circuit board 110 are also etched away, so that the exposed area 1101 of the flexible circuit board 110 is exposed, forming a flexible circuit board 110. Combined with the soft part of the circuit board 100 .

In this embodiment, during the etching process, a part of the first copper foil 150 and the metal plating layer 13 covering the first copper foil 150 are selectively removed to form the third conductive circuit layer 151 on the surface of the first laminated film 120. Part of the second copper foil 160 and the metal plating layer 13 covering the first copper foil 150 are permanently removed to form the fourth conductive circuit layer 161 on the surface of the second lamination film 130 .

In the seventh step, please refer to FIG. 10 , forming a first solder resist layer 171 on the side of the third conductive circuit layer 151 , and forming a second solder resist layer 172 on the side of the fourth conductive circuit layer 161 .

A plurality of first openings 1711 are formed in the first solder resist layer 171 , and part of the third conductive circuit layer 151 is exposed from the first openings 1711 to form a first electrical contact pad 1511 . A plurality of second openings 1721 are formed in the second solder resist layer 172 , and part of the fourth conductive circuit layer 161 is exposed from the second openings 1721 to form a plurality of second electrical contact pads 1611 .

Please refer to FIG. 11 , after this step, a step of forming a protection layer 180 on the surfaces of the first electrical contact pad 1511 and the second electrical contact pad 1611 may be further included. The protection layer 180 can be an organic solder flux, or a metal protection layer, such as gold or nickel-gold layer.

Please refer to FIG. 10 , this technical solution also provides a rigid-flex circuit board 100 manufactured by the above manufacturing method, which includes a flexible region 108 and two rigid regions 107 connected to both ends of the flexible region 108 .

The rigid-flex circuit board 100 includes a flexible circuit board 110 , a first lamination film 120 , a second lamination film 130 , a third conductive circuit layer 151 and a fourth conductive circuit layer 161 . The flexible circuit board 110 includes a first conductive circuit layer 112 , a first insulating layer 111 , a second conductive circuit layer 113 , a first covering layer 114 and a second covering layer 115 . The first conductive circuit layer 112 and the second conductive circuit layer 113 are formed on two opposite surfaces of the first insulating layer 111 .

The flexible circuit board 110 includes an exposed area 1101 and a first pressing area 1102 and a second pressing area 1103 connected to opposite sides of the exposed area 1101 . The exposed area 1101 forms the flexible area 108 of the rigid-flex circuit board 100 .

Both the first covering layer 114 and the second covering layer 115 completely cover the exposed area 1101 of the flexible circuit board 110, and the lengths of the first covering layer 114 and the second covering layer 115 are greater than the length of the exposed area 1101, the first covering The layer 114 and the second covering layer 115 also cover part of the first press-bond region 1102 and part of the second press-bond region 1103 connected to both ends of the exposed region 1101 . The first covering layer 114 has a first bonding surface 1141 away from the first conductive circuit layer 112 , and the second covering layer 115 has a second bonding surface 1151 away from the second conductive circuit layer 113 . Preferably, the length of the first covering layer 114 and the second covering layer 115 extending into the first pressing area 1102 is 0.3 mm to 1.0 mm, and the first covering layer 114 and the second covering layer 115 extend to the first pressing area 1102. The length of the second pressing zone 1103 is 0.3 mm to 1.0 mm.

The first lamination film 120 and the second lamination film 130 are formed on opposite sides of the flexible circuit board 110 and correspond to the first lamination area 1102 and the second lamination area 1103 . The first lamination film 120 is formed on the side of the first conductive circuit layer 112 , and the second lamination film 130 is formed on the side of the second conductive circuit layer 113 . The part of the first pressing surface 1141 extending from the first covering layer 114 to the first pressing area 1102 and the second pressing area 1103 is in direct contact with the first pressing film 120, and the second covering layer 115 extends A portion of the second pressing surface 1151 within the first pressing area 1102 and the second pressing area 1103 is in direct contact with the second pressing film 130 .

The third conductive circuit layer 151 is formed on the surface of the first lamination film 120 away from the first conductive circuit layer 112 , and the fourth conductive circuit layer 161 is formed on the surface of the second lamination film 130 away from the second conductive circuit layer 113 . surface. The first pressing area 1102 and the second pressing area 1103 of the flexible circuit board 110, and the first pressing film 120 and the second pressing area formed on opposite sides of the first pressing area 1102 and the second pressing area 1103 The adhesive film 130 , the third conductive circuit layer 151 and the fourth conductive circuit layer 161 together constitute the rigid region 107 of the rigid-flex circuit board 100 .

The rigid-flex circuit board 100 may further include a first solder resist layer 171 and a second solder resist layer 172 . A plurality of first openings 1711 are formed in the first solder resist layer 171 , and part of the third conductive circuit layer 151 is exposed from the first openings 1711 to form a first electrical contact pad 1511 . A plurality of second openings 1721 are formed in the second solder resist layer 172 , and part of the fourth conductive circuit layer 161 is exposed from the second openings 1721 to form a plurality of second electrical contact pads 1611 .

In the rigid-flex circuit board and its manufacturing method provided by the technical solution, the first covering layer and the second covering layer of the flexible circuit board are formed on the soft area of the rigid-flex circuit board and only partly extend into the hard area , and directly press the film on both sides of the flexible circuit board. Compared with the prior art, the film is laminated after the protective layer is formed on the entire surface of the flexible circuit board, which can effectively reduce the thickness of the rigid area of the flexible circuit board.

It can be understood that those skilled in the art can make various other corresponding changes and modifications according to the technical concept of the present invention, and all these changes and modifications should belong to the protection scope of the claims of the present invention.

Claims (10)

1. a manufacture method for rigid-flexible circuit board, comprises step:

A flexible circuit board is provided, comprises exposed region and be connected to the first pressing district and the second pressing district of the relative both sides of exposed region;

The first cover layer and the second cover layer is formed respectively in the relative both sides of flexible circuit board, described first cover layer and the second cover layer all cover the exposed region of flexible circuit board, and cover the part first pressing district and part second pressing district that are connected with the two ends of exposed region;

There is provided the first pressing film, the second pressing film, the first Copper Foil and the second Copper Foil, described first pressing film has first opening corresponding with exposed region, and described second pressing film has second opening corresponding with exposed region;

Stacking and pressing first Copper Foil, the first pressing film, flexible circuit board, the second pressing film and the second Copper Foil obtain multilager base plate, described first opening and the second opening are all corresponding with described exposed region, described first pressing film contacts with the first cover layer being positioned at the first pressing district and the second pressing district, and described second pressing film contacts with the second cover layer being positioned at the first pressing district and the second pressing district; And

Selective removal part first Copper Foil makes formation the 3rd conductive circuit layer, the first corresponding for exposed region Copper Foil is removed simultaneously, selective removal part second Copper Foil makes formation the 4th conductive circuit layer, is removed by the second corresponding for exposed region Copper Foil simultaneously, exposes the exposed region of flexible circuit board.

2. the manufacture method of rigid-flexible circuit board as claimed in claim 1, it is characterized in that, the length that described first cover layer extends to the first pressing district and the second pressing district is respectively 0.3 millimeter to 1 millimeter.

3. the manufacture method of rigid-flexible circuit board as claimed in claim 1, is characterized in that, before formation the 3rd conductive circuit layer and the 4th conductive circuit layer, also comprise formation conductive through hole, form described conductive through hole and comprise step:

Through hole is formed in multilager base plate;

The coat of metal is formed, to obtain conductive through hole at the inwall of described through hole.

4. the manufacture method of rigid-flexible circuit board as claimed in claim 3, it is characterized in that, the described coat of metal is also formed at the surface of the first Copper Foil and the second Copper Foil, when formation the 3rd conductive circuit layer, also remove the part metals coating being covered in the first copper foil surface in the lump, when formation the 4th conductive circuit layer, also remove the part metals coating being covered in the second copper foil surface in the lump.

5. the manufacture method of rigid-flexible circuit board as claimed in claim 1, is characterized in that, be also included in the 3rd conductive circuit layer side and form the first welding resisting layer, form the second welding resisting layer in the 4th conductive circuit layer side.

6. the manufacture method of rigid-flexible circuit board as claimed in claim 1, is characterized in that, adopts the mode of etching to remove the first Copper Foil corresponding to exposed region and the second Copper Foil.

7. a rigid-flexible circuit board, it comprises flexible circuit board, first cover layer, second cover layer, first pressing film, second pressing film, 3rd conductive circuit layer and the 4th conductive circuit layer, described flexible circuit board comprises the exposed region connected successively and the first pressing district being connected to exposed region opposite end and the second pressing district, described first cover layer and the second cover layer are formed at the relative both sides of flexible circuit board, described first cover layer and the second cover layer all cover the exposed region of flexible circuit board, and cover the part first pressing district and part second pressing district that are connected with the two ends of exposed region, described first pressing film and the second pressing film are pressed on the relative both sides of flexible circuit board, and it is corresponding with described first pressing district and the second pressing district, described first cover layer has the first pressing surface away from described flexible circuit board, described first pressing surface only directly contacts with described first pressing film, described second cover layer has the second pressing surface away from described flexible circuit board, described second pressing surface only directly contacts with described second pressing film, described 3rd conductive circuit layer is formed at the first pressing film face, described 4th conductive circuit layer is formed at the second pressing film face.

8. rigid-flexible circuit board as claimed in claim 7, it is characterized in that, described first cover layer and the second cover layer length extended in the first pressing district is 0.3 millimeter to 1.0 millimeters, and described first cover layer and the second cover layer length extended in the second pressing district is 0.3 millimeter to 1.0 millimeters.

9. rigid-flexible circuit board as claimed in claim 7, it is characterized in that, also have conductive through hole in described rigid-flexible circuit board, described conductive through hole runs through described 3rd conductive circuit layer, the first pressing film, flexible circuit board, the second pressing film and the 4th conductive circuit layer.

10. rigid-flexible circuit board as claimed in claim 8, it is characterized in that, also comprise the first welding resisting layer and the second welding resisting layer, described first welding resisting layer is formed at the 3rd conductive circuit layer side, in described first welding resisting layer, there is multiple first opening, part first conductive circuit layer is exposed from described first opening, form the first electric contact mat, described second welding resisting layer is formed at the 4th conductive circuit layer side, in described second welding resisting layer, there is multiple second opening, part second conductive circuit layer is exposed from described second opening, forms the second electric contact mat.