WO2024139605A1 - Manufacturing process for asymmetric rigid-flex board - Google Patents

Abstract

A manufacturing process for an asymmetric rigid-flex board. The manufacturing process comprises: providing a flexible core board and first rigid core boards; respectively laminating and bonding the first rigid core boards on opposite sides of the flexible core board so as to form a thin rigid-flex bonding layer; performing windowing treatment on the first rigid core boards to form deflection areas at windowing positions; arranging gaskets in windows of the first rigid core boards; respectively laminating and bonding second rigid core boards on opposite sides of the thin rigid-flex bonding layer to form a thick rigid-flex bonding layer; performing windowing treatment on the second rigid core boards, wherein bonding layer portions of the second rigid core boards are located directly above the gaskets; providing copper foils, and respectively laminating and bonding the copper foils on opposite sides of the thick rigid-flex bonding layer, so as to form a laminated structure and pressing same; and performing electroless copper plating on the laminated structure, manufacturing an outer circuit, applying a solder mask, performing surface treatment, and uncovering and taking out the gaskets to prepare the asymmetric rigid-flex board.

Description

Manufacturing process of asymmetric rigid-flex PCB

This application claims priority to the Chinese patent application filed on December 30, 2022 and application number 202211721813.0, the entire contents of which are incorporated by reference into this application.

Technical Field

The present application relates to the technical field of printed circuit boards, for example, to a manufacturing process of an asymmetric rigid-flexible board.

Background technique

Rigid-flex PCB combines the flexibility of flexible PCB and the durability of rigid PCB, and can realize three-dimensional assembly under different conditions. It is widely used in industry, high-end medical, military equipment and other consumer portable electronics.

Due to the development needs of multi-modular electronic products, in order to meet the assembly requirements of different application functions of each module, in the same rigid-flex PCB, some areas can be satisfied with low-layer wiring, while other areas require higher-layer wiring to meet more complex functions, or the number of layers is the same, so asymmetric rigid-flex PCBs have emerged.

In the related art, the specific manufacturing process of the asymmetric rigid-flexible circuit board is as follows: Step 1, stacking the flexible core board and the first rigid core board and performing the first pressing to form a thin rigid-flexible board, and after pressing, drilling, hole-forming, wiring, solder mask and surface treatment are performed on the thin rigid-flexible board; Step 2, stacking the thin rigid-flexible board and the second rigid core board and performing the window opening treatment and the second pressing once to form a thick rigid-flexible board, and after pressing, drilling, hole-forming, wiring, solder mask and surface treatment are performed on the thick rigid-flexible board; Step 3, opening the cover of the rigid-flexible bonding area to obtain an asymmetric rigid-flexible circuit board.

However, the above production method has the following defects: the secondary pressing process is adopted, and the production cycle is long; the deformation amount of the thin rigid-flexible board and the thick rigid-flexible board during the secondary pressing is different, which is easy to cause board bursting during pressing, and two solder masks are required. The rigid-flexible circuit board is prone to solder mask color difference and appearance defects, resulting in low production yield.

Summary of the invention

The present application provides a manufacturing process for an asymmetric rigid-flexible board, which can effectively shorten the production cycle, has no solder mask color difference, and has a high production yield.

An embodiment of the present application provides a manufacturing process of an asymmetric rigid-flexible board, including:

Providing a flexible core board and a first rigid core board, and laminating and bonding the first rigid core board on opposite sides of the flexible core board to form a thin rigid-flexible bonding layer;

Performing window processing on the first rigid core board to form a flexure area at the window opening;

Disposing a gasket in the window of the first rigid core plate;

Providing a second rigid core board, and laminating and bonding the second rigid core boards on opposite sides of the thin rigid-flexible bonding layer to form a thick rigid-flexible bonding layer;

The second rigid core plate is subjected to a windowing process so that the thickness of the thick rigid-flexible bonding layer is different on opposite sides of the flexure zone, wherein the bonding layer portions respectively bonded to the second rigid core plate are located directly above the gasket;

Providing copper foils, laminating and bonding the copper foils on opposite sides of the thick rigid-flex bonding layer to form a laminated structure;

Pressing the stacked structure so that the stacked structure forms a thick rigid-flexible bonding area and a thin rigid-flexible bonding area on opposite sides of the flexure area;

Perform copper plating, hole forming, outer layer circuit making, solder resist and surface treatment on the stacked structure; and

The stacked structure is uncovered to expose and remove the gasket, thereby obtaining the asymmetric rigid-flex board.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of an asymmetric rigid-flex board according to an embodiment of the present application.

FIG. 2 is a cross-sectional view of an asymmetric rigid-flex board according to an embodiment of the present application.

FIG3 is a schematic diagram of the structure of a thin rigid-flex bonding layer prepared in step S10 and step S20 in the manufacturing process of an embodiment of the present application.

FIG. 4 is a schematic diagram of the structure of the stacked structure prepared in step S30 and step S40 in the manufacturing process of an embodiment of the present application.

FIG. 5 is a schematic structural diagram of a stacked structure prepared in step S50 in a manufacturing process according to an embodiment of the present application.

FIG. 6 is a schematic structural diagram of a stacked structure prepared in step S60 in a manufacturing process according to an embodiment of the present application.

FIG. 7 is a flow chart of a manufacturing process of an asymmetric rigid-flex board provided in one embodiment of the present application.

FIG. 8 is another flow chart of a manufacturing process of an asymmetric rigid-flex board provided in an embodiment of the present application.

In the figure:

1. flexible core board; 101. first core board; 102. second core board; 103. first bonding layer; 2. A rigid core board; 3. A second adhesive layer; 4. A third adhesive layer; 5. A second rigid core board; 6. A fourth adhesive layer; 7. Copper foil; 8. A flexure area; 9. A thin rigid-flexible bonding area; 10. A thick rigid-flexible bonding area; 11. A gasket; 12. A covering layer; 13. A transition slope; 14. Copper holes; 15. Solder joints.

Detailed ways

In the description of this application, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

1 and 2 , the asymmetric rigid-flex board includes at least one flexure region 8 , and a thin rigid-flex region 9 and a thick rigid-flex region 10 are respectively disposed on opposite sides of each flexure region 8 .

2 to 6 , the present application provides a manufacturing process of an asymmetric rigid-flexible board, as shown in FIGS. 7 and 8 , including the following steps:

In S10, a flexible core board 1 and a first rigid core board 2 are provided, and the first rigid core board 2 is respectively laminated and bonded on opposite sides of the flexible core board 1 to form a thin rigid-flexible bonding layer;

The first rigid core board 2 is subjected to a window opening process to expose a portion of the flexible core board 1, so that the thin rigid-flexible bonding layer forms a flexure area 8 at the window opening;

In S20, a gasket 11 is arranged in the window of the first rigid core plate 2;

In S30, a second rigid core board 5 is provided, and the second rigid core boards 5 are sequentially stacked and bonded on opposite sides of the thin rigid-flexible bonding layer to form a thick rigid-flexible bonding layer;

The second rigid core plate 5 is subjected to windowing treatment so that the thickness of the thick rigid-flexible bonding layer is different on opposite sides of the flexure area 8, wherein the bonding layer portion bonded to the second rigid core plate 5 is located directly above the gasket 11;

In S40, copper foil 7 is provided, and copper foil 7 is respectively laminated and bonded on opposite sides of the thick rigid-flexible bonding layer to form a laminated structure. Referring to FIG. 4 , the laminated structure is composed of a flexible core board 1, a first rigid core board 2, a second rigid core board 5, and copper foil 7 and an adhesive layer thereof;

In S50, the laminated structure is pressed so that the laminated structure forms a thick rigid-flexible bonding area 10 and a thin rigid-flexible bonding area 9 on opposite sides of the flexure area 8, wherein the copper foil 7 serves as the outer layer of the thick rigid-flexible bonding area 10 and the thin rigid-flexible bonding area 9;

In S60, the stacked structure is subjected to copper deposition and hole forming, outer layer circuits are made, solder resist and surface treatment are performed;

In S70 , the stacked structure is uncovered to remove the portion of the stacked structure located above the gasket 11 , thereby exposing the gasket 11 and taking it out, thereby obtaining an asymmetric rigid-flex board.

In the above operation, by first opening windows in the first rigid core board 2 and the second rigid core board 5 respectively, and then stacking the flexible core board 1, the first rigid core board 2, the second rigid core board 5 and the copper foil 7 in sequence, a stacking structure with different thicknesses can be formed on the opposite sides of the flexure area 8, thereby achieving a one-time pressing to obtain an asymmetric rigid-flexible board with a thick rigid-flexible bonding area 10 and a thin rigid-flexible bonding area 9. This design can not only effectively shorten the production cycle of the asymmetric rigid-flexible board, but also the deformation of the entire stacking structure tends to be consistent during the pressing process, and the board explosion phenomenon is not easy to occur. It can also complete the solder mask once after pressing, and can effectively avoid the secondary solder mask causing the thin rigid-flexible bonding area 9 and the thick rigid-flexible bonding area 10 to have solder mask color difference, thereby solving the appearance defect problem of the asymmetric rigid-flexible board, and at the same time can avoid the dust adhering to the outer circuit board after the first solder mask.

Referring to Figure 4, the copper foil 7 has no window treatment and can cover the thick rigid-flexible bonding area 10 and the thin rigid-flexible bonding area 9 at the same time. Referring to Figure 5, after lamination, the copper foil 7 can serve as the outer layer of the thick rigid-flexible bonding area 10 and the thin rigid-flexible bonding area 9 at the same time. At the same time, during the lamination process, the part of the adhesive layer of the second rigid core board 5 suspended above the gasket 11 will tilt downward and abut against the gasket 11 to form a supporting slope, and support the part of the copper foil 7 located above the gasket 11, so that the copper foil 7 forms a stepped structure after lamination, and the part of the copper foil 7 in the thick rigid-flexible bonding area 10 and the thin rigid-flexible bonding area 9 can smoothly transition through the transition slope 13, so that when making the outer layer circuit, the entire film can be pasted to the outer surface of the copper foil 7 at one time, which is convenient for film pasting, so as to improve the pasting yield and the production efficiency of the outer layer circuit, and further shorten the production cycle of the asymmetric rigid-flexible board.

In one embodiment, referring to FIG. 2-FIG 6 , in S10 , the flexible core board 1 and the first rigid core board 2 are bonded by the second adhesive layer 3 , and the second adhesive layer 3 is subjected to window opening treatment at the position corresponding to the window opening of the first rigid core board 2 to expose the flexible core board 1 .

In one embodiment, in S20 , the gasket 11 is disposed in the windows of the second adhesive layer 3 and the first rigid core board 2 simultaneously to prevent the second adhesive layer 3 from being deformed and overflowing into the flexure zone 8 during lamination.

In one embodiment, referring to FIG. 3 , the thickness of the gasket 11 is H1 , the sum of the thicknesses of the first rigid core plate 2 and the second adhesive layer 3 is H2 , and H1 = H2 ± 0.05 mm.

In one embodiment, the width of the gasket 11 is smaller than the width of the window of the first rigid core board 2 , so as to facilitate the placement of the gasket 11 in the windows of both the first rigid core board 2 and the second adhesive layer 3 .

5, the spacing between the gasket 11 and the thick rigid-flexible bonding area 10 is L2, and the spacing between the gasket 11 and the thin rigid-flexible bonding area 9 is L3, and L2 and L3 are 0.2mm to 1mm. In other embodiments, L2 and L3 are 0.3mm, 0.5mm, 0.8mm, etc. If L2 and L3 are too large, the gasket 11 will not be able to prevent glue overflow, and if L2 and L3 are too small, it will increase the difficulty of installing the gasket 11. This design can ensure that the gasket 11 can prevent glue overflow. effect, and can reduce the difficulty of installing the gasket 11.

In one embodiment, the flexible core board 1 is a single-layer board or a multi-layer board.

In this embodiment, referring to FIG. 2 to FIG. 6 , the flexible core board 1 is a double-layer board.

In S10 , the flexible core board 1 includes a first core board 101 and a second core board 102 , and the first core board 101 and the second core board 102 are bonded by a first bonding layer 103 .

In one embodiment, the first adhesive layer 103 is subjected to a window opening process corresponding to the flexure area 8 .

In one embodiment, the copper foil 7 is adhered to the opposite sides of the thick rigid-flex bonding layer through the fourth adhesive layer 6 .

It should be noted that the thin rigid-flexible bonding area 9 is composed of a flexible core board 1, a second adhesive layer 3, a first rigid core board 2, a fourth adhesive layer 6 and a copper foil 7, and the thick rigid-flexible bonding area 10 is composed of a flexible core board 1, a second adhesive layer 3, a first rigid core board 2, a third adhesive layer 4, a second rigid core board 5, a fourth adhesive layer 6 and a copper foil 7.

In one embodiment, before S10, the step of: designing a panel for the asymmetric rigid-flex board, that is, designing the arrangement positions of the thick rigid-flex area 10 and the thin rigid-flex area 9 of the asymmetric rigid-flex board.

In this embodiment, referring to FIG. 1 , the asymmetric rigid-flex board includes a plurality of first regions and a plurality of second regions, the first region is configured to be designed as a thin rigid-flex region 9, the second region is configured to be designed as a thick rigid-flex region 10, the plurality of first regions are arranged at intervals along the first direction to form a row of first regions, the plurality of first regions are arranged at intervals along the second direction, the first direction and the second direction are perpendicular, the plurality of second regions are arranged at intervals along the first direction to form a row of second regions, and two rows of intervals of second regions are arranged between two adjacent rows of first regions. This design enables two rows of thick rigid-flex regions 10 to be arranged between two adjacent rows of thin rigid-flex regions 9 on the manufactured asymmetric rigid-flex board, so as to ensure that the copper foil 7 of the laminated structure forms a "convex" stepped structure after lamination, which is convenient for film pasting.

In one embodiment, referring to Figures 2 to 6, before S10, the step of stacking a covering layer 12 on the flexing area 8 of the flexible core board 1 and attaching a gasket 11 to the side of the covering layer 12 facing away from the flexible core board 1 to protect the circuit of the flexible core board 1 in the flexing area 8 to prevent the circuit from being oxidized or damaged.

In one embodiment, the cover layer 12 is a cover film.

In one embodiment, the opposite sides of the covering layer 12 are respectively inserted into the portion of the second adhesive layer 3 located in the thick rigid-flexible bonding area 10 and the portion located in the thin rigid-flexible bonding area 9, and the covering layer 12 is only inserted into a portion of the second adhesive layer 3, so that most of the second adhesive layer 3 can be bonded to the flexible core board 1. Since the bonding force between the covering layer 12 and the second adhesive layer 3 is poor, and the expansion coefficient of the covering layer 12 is large, after the covering layer 12 is directly applied to cover the entire flexible core board 1 for pressing, the asymmetric rigid-flexible board is prone to delamination. This design can reduce the covering layer 12, so that most of the second adhesive layer 3 is directly bonded to the flexible core board 1, and the bonding between the flexible core board 1 and the second adhesive layer 3 is improved. The combined force is relatively high, which can effectively reduce the delamination of asymmetric rigid-flex boards.

In one embodiment, referring to FIG. 4 to FIG. 6 , in S30 , the adhesive layer for bonding the second rigid core board 5 is the third adhesive layer 4 , that is, the first rigid core board 2 is bonded to the second rigid core board 5 through the third adhesive layer 4 .

In one embodiment, referring to FIG. 4 , there is a spacing L1 between the third adhesive layer 4 and the thin rigid-flexible bonding area 9, and L1 is 1 mm to 5 mm. In one embodiment, L1 is 3 mm, 3.5 mm, 4 mm, 5 mm, etc. This design can effectively form a preset slope in the flexure area 8 after the third adhesive layer 4 is pressed, thereby ensuring that the copper foil 7 forms a transition slope 13.

In one embodiment, the flexible core board 1, the first rigid core board 2, the second rigid core board 5, and the copper foil 7 are respectively bonded using a flowable semi-cured sheet or a non-flowable semi-cured sheet, that is, the first adhesive layer 103, the second adhesive layer 3, the third adhesive layer 4, and the fourth adhesive layer 6 can be a flowable semi-cured sheet or a non-flowable semi-cured sheet.

In one embodiment, in S50, the pressing parameters are: pressure of 150 to 550 psi, hot pressing temperature of 185 to 210°C, and pressing time of 60 to 180 min.

In one embodiment, referring to FIG. 6 , in S60 , the stacked structure is formed with copper holes 14 by copper deposition, and is formed with solder joints 15 by solder resist.

In one embodiment, the copper plating, outer layer circuit making, solder resist and surface treatment processes in S60 and the cover removal process in S70 may adopt related processing techniques, which will not be described in detail.

In the description of this article, it should be understood that the terms "upper", "lower", "left", "right", etc., and the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of description and simplified operation, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of this application. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

In the description of this specification, the description with reference to the terms "an embodiment", "example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

In addition, it should be understood that although this specification is described according to implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims (10)

1. A manufacturing process of an asymmetric rigid-flexible board, comprising:

   Providing a flexible core board and a first rigid core board, and laminating and bonding the first rigid core board on opposite sides of the flexible core board to form a thin rigid-flexible bonding layer;

   Performing window processing on the first rigid core board to form a flexure area at the window opening;

   Disposing a gasket in the window of the first rigid core plate;

   Providing a second rigid core board, and laminating and bonding the second rigid core boards on opposite sides of the thin rigid-flexible bonding layer to form a thick rigid-flexible bonding layer;

   Performing window processing on the second rigid core board so that the thickness of the thick rigid-flexible bonding layer is different on opposite sides of the flexure area, wherein the bonding layer portion bonded to the second rigid core board is located directly above the gasket;

   Providing copper foils, laminating and bonding the copper foils on opposite sides of the thick rigid-flex bonding layer to form a laminated structure;

   Pressing the stacked structure so that the stacked structure forms a thick rigid-flexible bonding area and a thin rigid-flexible bonding area on opposite sides of the flexure area;

   Perform copper plating, hole forming, outer layer circuit making, solder resist and surface treatment on the stacked structure; and

   The stacked structure is uncovered to expose and remove the gasket, thereby obtaining the asymmetric rigid-flex board.
2. The manufacturing process of the asymmetric rigid-flex board according to claim 1, wherein before providing the flexible core board and the first rigid core board, it also includes panel designing the asymmetric rigid-flex board;

   The asymmetric rigid-flexible board includes multiple first areas and multiple second areas, the first areas are configured to be designed as the thin rigid-flexible area, the second areas are configured to be designed as the thick rigid-flexible area, the multiple first areas are arranged at intervals along a first direction to form a row of the first areas, the multiple rows of the first areas are arranged at intervals along a second direction, the first direction is perpendicular to the second direction, the multiple second areas are arranged at intervals along the first direction to form a row of the second areas, and two rows of the second areas are arranged between two adjacent rows of the first areas.
3. According to the manufacturing process of the asymmetric rigid-flexible board according to claim 1, wherein, in S30, the bonding layer bonding the second rigid core board is a third bonding layer, and the length of the third bonding layer has a spacing L1 with the thin rigid-flexible bonding area, and L1 is 1 mm to 5 mm.
4. The manufacturing process of the asymmetric rigid-flexible board according to any one of claims 1 to 3, wherein the first rigid core board is respectively stacked and bonded on opposite sides of the flexible core board, the flexible core board and the first rigid core board are bonded by a second adhesive layer, and the second adhesive layer corresponds to the first A window opening process is performed at the window opening position of a rigid core board;

   The thickness of the gasket is H1, the sum of the thickness of the first rigid core board and the second adhesive layer is H2, and H1 = H2 ± 0.05 mm.
5. According to the manufacturing process of the asymmetric rigid-flexible board according to claim 4, there is a spacing L2 between the gasket and the thick rigid-flexible bonding area, and there is a spacing L3 between the gasket and the thin rigid-flexible bonding area, and L2 and L3 are 0.2mm to 1mm.
6. According to the manufacturing process of the asymmetric rigid-flexible board according to any one of claims 1 to 3, before providing the flexible core board and the first rigid core board, it also includes: providing a covering layer, and covering the covering layer on the flexure area of the flexible core board.
7. The manufacturing process of the asymmetric rigid-flexible board according to any one of claims 1 to 3, wherein the flexible core board is a single-layer board or a multi-layer board.
8. The manufacturing process of an asymmetric rigid-flexible board according to claim 7, wherein the flexible core board comprises a first core board and a second core board, and the first core board and the second core board are bonded by a first adhesive layer.
9. According to the manufacturing process of the asymmetric rigid-flexible composite board according to any one of claims 1 to 3, the flexible core board, the first rigid core board, the second rigid core board, and the copper foil are respectively bonded with a flowable prepreg or a non-flowable prepreg.
10. According to the manufacturing process of the asymmetric rigid-flexible board according to any one of claims 1 to 3, wherein, in the copper plating, outer layer circuit making, solder mask and surface treatment of the stacked structure, the pressing parameters are: pressure of 150 to 550 psi, hot pressing temperature of 185 to 210°C, and pressing time of 60 to 180 min.