A manufacturing process of a rigid-flex printed circuit board

Abstract

The application discloses a manufacturing process of a rigid-flexible combination board, which comprises the following steps: providing a flexible core board, a first adhesive layer and a first rigid core board, sequentially laminating the first adhesive layer and the first rigid core board on opposite sides of the flexible core board, performing windowing treatment on the first adhesive layer and the first rigid core board, and forming a flexure area in the window; providing a gasket, the gasket comprising sequentially laminated polyimide adhesive tape with low hardness, pure glue and a first cover film, and arranging the gasket in the window so that the polyimide adhesive tape is adjacent to the flexible core board and the first cover film is away from the flexible core board; pressing and performing copper hole sinking, outer layer circuit manufacturing, solder mask and surface treatment on the pressed structure; and taking out the gasket to obtain the rigid-flexible combination board. The application uses flow semi-cured sheets as the adhesive layer to avoid uneven board surface, and the gasket is deformed to prevent glue during pressing, so that the rigid-flexible combination board can be obtained through one-time pressing, and the production cycle is short.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board technology, and more particularly to a manufacturing process for a rigid-flex board. Background Technology

[0002] A rigid-flex PCB is a printed circuit board that combines a flexible board and a rigid board through interlayer distribution. Rigid-flex PCBs have changed the traditional planar design concept, expanding to a three-dimensional space, which greatly facilitates product design and application while increasing manufacturing difficulty.

[0003] The flexible region of a rigid-flex plate is formed by removing a specific layer of the rigid plate to expose the flexible region. The process of removing the specific rigid plate layer is called the capping process. Currently, the capping of rigid-flex plates generally involves first opening a window in the inner dielectric layer, then pressing it together with the flexible and rigid plates as a whole, and finally removing the cap by milling grooves.

[0004] In the manufacturing process of existing rigid-flex PCBs, non-flowing prepregs are usually used as the medium layer material to prevent excessive glue overflow in the medium layer during subsequent lamination. However, after the entire board is laminated, the non-flowing medium layer has poor glue filling properties, resulting in obvious depressions on the outer surface of the laminated rigid-flex PCB. This leads to an uneven surface of the rigid-flex PCB, which has a significant impact on subsequent processing.

[0005] To address the unevenness of the rigid-flex PCB surface, the manufacturing process involves first stacking and pressing non-flowing prepreg sheets onto the rigid areas of the flexible core board. Then, flowing prepreg sheets are used to bond the rigid and flexible core boards together. Adhesive-blocking gaskets are added within the openings between the prepreg sheets and the rigid core board to prevent the flowing prepreg from flowing and contaminating the flexible areas. Finally, the entire board is laminated a second time. However, this method requires a second lamination, resulting in a long production cycle. Furthermore, the adhesive-blocking gaskets are typically made of polytetrafluoroethylene (PTFE), which has high hardness. Since the gaskets usually have a clearance fit with the openings, they hardly deform during lamination, allowing a small amount of flowing prepreg to still flow into the gaps between the gaskets and the openings, leading to poor adhesive-blocking performance. Summary of the Invention

[0006] The purpose of this invention is to provide a manufacturing process for a rigid-flexible bonded plate that is simple to operate, can effectively prevent glue overflow during the pressing process, and has a short production cycle.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A manufacturing process for a rigid-flex plate is provided, comprising the following steps:

[0009] Step S10: Provide a flexible core board, a first adhesive layer and a first rigid core board. The first adhesive layer and the first rigid core board are sequentially stacked on both sides of the flexible core board. The first adhesive layer and the first rigid core board are windowed to form a flexural area. The first adhesive layer is a flowable semi-cured sheet.

[0010] Step S20: Provide a gasket, the gasket comprising a polyimide tape with low adhesive hardness, pure adhesive and a first cover film stacked sequentially, the gasket being disposed within an opening in the first adhesive layer and the first rigid core board, such that the polyimide tape is adjacent to the flexible core board and the first cover film is away from the flexible core board;

[0011] Step S30: Pressing;

[0012] Step S40: Perform copper plating on the laminated structure, fabricate outer layer circuitry, apply solder mask and surface treatment.

[0013] Step S50: Remove the gasket to obtain the rigid-flexible bond plate.

[0014] As a preferred manufacturing process for rigid-flex PCBs, the polyimide tape has a layer thickness of 25 μm to 75 μm.

[0015] As a preferred embodiment of the manufacturing process for rigid-flex PCBs, the hardness of the polyimide tape is less than that of the first cover film and the pure adhesive.

[0016] As a preferred embodiment of the manufacturing process of the rigid-flex plate, the thickness of the gasket is H1, and the total depth of the opening between the first rigid core plate and the first adhesive layer is H2, 0≤H1-H2≤0.04mm.

[0017] As a preferred embodiment of the manufacturing process of the rigid-flexible bonded plate, the portion of the rigid-flexible bonded plate other than the flexural area forms a rigid-flexible bonded area, and the gasket and the rigid-flexible bonded area have a distance L, where L is 0.1mm to 0.5mm.

[0018] As a preferred embodiment of the manufacturing process of the rigid-flex plate, when the rigid-flex plate has multiple rigid core plates, after step S20, step S21 is further included: providing at least one second adhesive layer and at least one second rigid core plate, the second adhesive layer and the second rigid core plate are sequentially stacked on the side of the first rigid core plate away from the first adhesive layer, the second adhesive layer and the second rigid core plate cover the flexural area, and the second adhesive layer is bonded to the first cover film of the gasket.

[0019] As a preferred embodiment of the manufacturing process of the rigid-flex plate, step S50 specifically includes step S51, uncovering process: removing the portion of the second adhesive layer and the second rigid core plate facing the flexural area to expose the gasket.

[0020] Step S52: Remove the gasket.

[0021] As a preferred embodiment of the manufacturing process for rigid-flex PCBs, the flexible core board is a single-layer board.

[0022] As a preferred embodiment of the manufacturing process of the rigid-flex plate, before step S10, step S11 is further included: providing a second cover film and covering the flexural area of ​​the flexible core plate with the second cover film.

[0023] In step S20, the gasket is attached to the side of the second cover film facing away from the flexible core board.

[0024] As a preferred embodiment of the manufacturing process of the rigid-flexible plate, in step S30, the pressing parameters are: pressure of 380-550 psi, hot pressing temperature of 185-210℃, and pressing time of 60-180 min.

[0025] The beneficial effects of this invention are as follows: The first adhesive layer uses a flowable semi-cured sheet, which has better glue filling properties and can effectively improve the unevenness of the rigid-flex board surface. At the same time, since the bottom layer of the gasket uses a polyimide tape with low glue hardness, the polyimide tape will deform and squeeze the first adhesive layer at the window during the pressing process, thereby playing a role in preventing glue from flowing and contaminating the flexural area of ​​the flexible core board. This allows the rigid-flex board to be produced in one pressing, thereby effectively shortening the production cycle of the rigid-flex board and facilitating operation and production control. Attached Figure Description

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0027] Figure 1 This is a schematic diagram of the rigid-flexible plate according to an embodiment of the present invention.

[0028] Figure 2 This is a schematic diagram of the rigid-flexible plate according to another embodiment of the present invention.

[0029] Figure 3 This is a schematic diagram of the manufacturing structure of steps S10 and S20 in the manufacturing process of the present invention.

[0030] Figure 4 This is a schematic diagram of the structure of the gasket in an embodiment of the present invention.

[0031] Figure 5 This is a schematic diagram of the manufacturing structure of step S21 in another embodiment of the manufacturing process of the present invention.

[0032] Figure 6 This is a schematic diagram of the manufacturing structure of step S40 in another embodiment of the manufacturing process of the present invention.

[0033] In the picture:

[0034] 1. Flexible core board; 2. First adhesive layer; 3. First rigid core board; 4. Second adhesive layer; 5. Second rigid core board; 6. Third adhesive layer; 7. Copper foil; 8. Flexural area; 9. Rigid-flexible bonding area; 10. Gasket; 101. Polyimide tape; 102. Pure adhesive; 103. First cover film; 11. Second cover film. Detailed Implementation

[0035] To make the technical problems solved by the present invention, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0037] Reference Figure 1 and Figure 2 The rigid-flex plate includes a flexural region 8 and a rigid-flexural bonding region 9. The rigid-flex plate includes at least one rigid core plate. Figure 1 A rigid-flex plate with a single-layer rigid core. Figure 2 It is a rigid-flex duct plate with a multi-layer rigid core.

[0038] Taking a rigid-flex liner with a single-layer rigid core as an example, refer to Figure 1 , Figure 3 and Figure 4 The present invention provides a manufacturing process for a rigid-flexible plate, comprising the following steps:

[0039] Step S10: Provide a flexible core board 1, a first adhesive layer 2, and a first rigid core board 3. The first adhesive layer 2 and the first rigid core board 3 are sequentially stacked on both sides of the flexible core board 1. The first adhesive layer 2 and the first rigid core board 3 are windowed, forming a flexural area 8 within the window. The portion of the flexible core board 1 excluding the flexural area 8, the first adhesive layer 2, and the first rigid core board 3 together form a rigid-flexible bonding area 9.

[0040] Step S20: Provide a gasket 10. The gasket 10 includes a polyimide tape 101 with low adhesive hardness, pure adhesive 102 and a first cover film 103 stacked sequentially. The gasket 10 is provided in the opening between the first adhesive layer 2 and the first rigid core board 3 so that the polyimide tape 101 is adjacent to the flexible core board 1 and the first cover film 103 is away from the flexible core board 1.

[0041] Step S30, the first laminated structure consisting of the pressing gasket 10, the flexible core plate 1, the first adhesive layer 2, and the first rigid core plate 3;

[0042] Step S40: Perform copper plating, fabricate outer layer circuitry, apply solder mask and surface treatment on the first laminated structure.

[0043] Step S50: Remove the gasket 10 to obtain the rigid-flexible bonded plate.

[0044] In the above operation, the first adhesive layer 2 is a flowable semi-cured sheet. The flowable semi-cured sheet has better glue filling properties, which can effectively improve the unevenness of the rigid-flex board surface. At the same time, since the bottom layer of the gasket 10 is made of polyimide tape 101 with low glue hardness, the polyimide tape 101 will deform and squeeze the first adhesive layer 2 at the window during the pressing process. This will play a role in preventing glue from flowing and contaminating the flexural area 8 of the flexible core board 1 in the first adhesive layer 2 at the window, so that the rigid-flex board can be made in one pressing, thereby effectively shortening the production cycle of the rigid-flex board and facilitating operation and production control.

[0045] The greater the thickness of the polyimide tape 101, the lower its hardness. The hardness can be controlled by adjusting the thickness of the polyimide tape 101 to meet the production requirements of rigid-flex boards of different specifications. The thickness of the gasket 10 can be increased by the pure adhesive 102 and the first cover film 103 to ensure that the gasket 10 always matches the openings of the first rigid core board 3 and the first adhesive layer 2.

[0046] Because the existing secondary lamination process requires stacking and pressing non-flowing prepreg onto the flexible core board, and at least two flowing prepregs are needed to bond the flexible core board and the rigid core board during the secondary lamination to ensure that delamination does not occur after lamination, and the expansion and contraction of the first lamination cannot be controlled, resulting in poor alignment between the overall layers.

[0047] The present invention produces a rigid-flex plate by pressing in one step. During the manufacturing process, the amount of material used in the first adhesive layer 2 between the flexible core plate 1 and the first rigid core plate 3 can be reduced, which helps to reduce the manufacturing cost and avoids the problem of poor interlayer alignment in the rigid-flex plate.

[0048] In another embodiment, reference Figures 2 to 6 The rigid-flex plate is a multi-layer rigid core plate. The manufacturing process of the multi-layer rigid core plate includes the following steps:

[0049] Step S10: Provide a flexible core board 1, a first adhesive layer 2 and a first rigid core board 3. The first adhesive layer 2 and the first rigid core board 3 are sequentially stacked on both sides of the flexible core board 1. The first adhesive layer 2 and the first rigid core board 3 are windowed, and a flexural area 8 is formed in the window.

[0050] Step S20: Provide a gasket 10. The gasket 10 includes a polyimide tape 101 with low adhesive hardness, pure adhesive 102 and a first cover film 103 stacked sequentially. The gasket 10 is provided in the opening between the first adhesive layer 2 and the first rigid core board 3 so that the polyimide tape 101 is adjacent to the flexible core board 1 and the first cover film 103 is away from the flexible core board 1.

[0051] Step S21: Provide at least one second adhesive layer 4 and at least one second rigid core plate 5. The second adhesive layer 4 and the second rigid core plate 5 are sequentially stacked on the side of the first rigid core plate 3 away from the first adhesive layer 2. The second adhesive layer 4 and the second rigid core plate 5 cover the flexural area 8. The second adhesive layer 4 is bonded to the first cover film 103 of the gasket 10.

[0052] Step S22: Provide a third adhesive layer 6 and a copper foil 7. On the side of the second rigid core board 5 away from the second adhesive layer 4, the third adhesive layer 6 and the copper foil 7 are stacked in sequence. The third adhesive layer 6 blocks the flexural area 8. The copper foil 7 can be used as a substrate for fabricating the outer layer circuit.

[0053] Step S30: The second laminated structure is composed of the flexible core board 1, the first adhesive layer 2, the first rigid core board 3, the second adhesive layer 4, the second rigid core board 5, the third adhesive layer 6, and the copper foil 7.

[0054] Step S40: Perform copper plating, fabricate outer layer circuitry, apply solder mask and surface treatment on the second laminated structure after lamination;

[0055] Step S51, Uncovering process: Remove the portions of the second adhesive layer 4, the second rigid core plate 5, and the third adhesive layer 6 that are directly opposite the flexural area 8 to expose the gasket 10.

[0056] Step S52: Take out the gasket 10 to obtain a rigid-flexible bonded plate, wherein the part of the flexible core plate 1 excluding the flexural area 8, the first adhesive layer 2, the first rigid core plate 3, the second adhesive layer 4, the second rigid core plate 5, the third adhesive layer 6 and the copper foil 7 together form the rigid-flexible bonded area 9 of the rigid-flexible bonded plate.

[0057] Among them, the first adhesive layer 2, the second adhesive layer 4 and the third adhesive layer 6 are all made of flowable semi-cured sheets.

[0058] During the pressing process, the gasket 10 can support the portion of the second adhesive layer 4, the second rigid core plate 5, and the third adhesive layer 6 that are facing the flexural area 8, so that the overall stress of the second laminated structure is more uniform. Furthermore, the second adhesive layer 4 and the second rigid core plate 5 can uniformly transmit pressure to the gasket 10, allowing the polyimide tape 101 of the gasket 10 to deform uniformly in all directions to prevent adhesive adhesion, which helps to improve the adhesive adhesion prevention effect of the gasket 10.

[0059] It should be noted that the number of the second adhesive layer 4 and the second rigid core plate 5 is the same, and the number of the second adhesive layer 4 and the second rigid core plate 5 is one or more.

[0060] Specifically, when manufacturing rigid-flex boards with single-layer rigid cores or multi-layer rigid cores, the layer thickness of polyimide tape 101 is 25μm to 75μm. The greater the layer thickness of polyimide tape 101, the greater the adhesive thickness, resulting in lower adhesive hardness and making it more prone to deformation during lamination. This design allows for the selection of a suitable layer thickness of polyimide tape 101 based on the production of rigid-flex boards of different specifications, ensuring that the adhesive hardness of polyimide tape 101 meets the adhesive resistance requirements.

[0061] Specifically, when the polyimide tape 101 has a layer thickness of 25μm, it can effectively prevent the first adhesive layer 2 with an inner copper layer thickness of 18μm and 35μm from overflowing; when the polyimide tape 101 has a layer thickness of 50μm, it can effectively prevent the first adhesive layer 2 with an inner copper layer thickness of 70μm from overflowing; and when the polyimide tape 101 has a layer thickness of 75μm, it can effectively prevent the first adhesive layer 2 with an inner copper layer thickness of 105μm from overflowing.

[0062] For example, polyimide tape 101 is pasted to the bottom of the opening of the first rigid core plate 3 and the first adhesive layer 2. The pure adhesive 102 and the first cover film 103 can be designed according to the layer thickness of the polyimide tape 101 so that the gasket 10 matches the opening of the first rigid core plate 3 and the first adhesive layer 2. The pure adhesive 102 and the first cover film 103 can increase the height of the gasket 10 so as to ensure that the gasket 10 can be attached to the second adhesive layer 4. The gasket 10 can be deformed by pressure during pressing.

[0063] In one embodiment, the hardness of the polyimide tape 101 is less than that of the first cover film 103 and the pure adhesive 102. During the pressing process, the first cover film 103 and the pure adhesive 102 have small or almost no deformation, and the pressure can be uniformly transmitted to the polyimide tape 101 through the first cover film 103 and the pure adhesive 102, so that the polyimide tape 101 can deform uniformly in all directions, which helps to improve the adhesive resistance of the gasket 10.

[0064] Specifically, when manufacturing a rigid-flex plate with a single-layer rigid core or a rigid-flex plate with multiple layers of rigid core, the thickness of the gasket 10 is equal to the total opening depth of the first rigid core 3 and the first adhesive layer 2, or the thickness of the gasket 10 is greater than the total opening depth of the first rigid core 3 and the first adhesive layer 2.

[0065] Preferably, refer to Figure 3 In order to ensure that the gasket 10 can deform during the pressing process, the thickness of the gasket 10 is H1, and the total depth of the opening of the first rigid core plate 3 and the first adhesive layer 2 is H2, 0≤H1-H2≤0.04mm.

[0066] Furthermore, referring to Figure 3 The spacer 10 and the rigid-flexible bonding area 9 have a gap L, which is 0.1mm to 0.5mm. Optionally, L is 0.3mm, 0.4mm, 0.5mm, etc. This design not only facilitates the installation of the spacer 10 in the opening between the first rigid core plate 3 and the first adhesive layer 2, but also effectively controls adhesive overflow to achieve virtually zero adhesive overflow.

[0067] In this embodiment, the flexible core board 1 is a single-layer board.

[0068] Specifically, when manufacturing a rigid-flex board with a single-layer rigid core board or a rigid-flex board with a multi-layer rigid core board, before step S10, step S11 is further included: providing a second covering film 11, covering the flexible core board 1 with the second covering film 11 on the flexural area 8 to protect the circuits of the flexible core board 1 located in the flexural area 8 and prevent the circuits from oxidizing or being damaged.

[0069] Specifically, when manufacturing a rigid-flex plate with a single-layer rigid core or a rigid-flex plate with a multi-layer rigid core, in step S30, the pressing parameters are: pressure of 380-550 psi, hot pressing temperature of 185-210°C, and pressing time of 60-180 min.

[0070] It should be noted that the copper plating, outer layer circuit fabrication, solder masking, and surface treatment processes used in step S40 will not be described in detail here.

[0071] In the description herein, it should be understood that the terms "upper," "lower," "left," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings, and are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, the terms "first" and "second" are used merely for descriptive distinction and have no special meaning.

[0072] In the description of this specification, references to terms such as "an embodiment," "example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0073] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style of the specification is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0074] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A manufacturing process of a rigid-flex printed circuit board, characterized by, The method comprises the following steps: S10, providing a flexible core board, a first adhesive layer and a first rigid core board, sequentially laminating the first adhesive layer and the first rigid core board on opposite sides of the flexible core board, performing windowing treatment on the first adhesive layer and the first rigid core board, and forming a flexure area in the window; S20, providing a gasket, the gasket comprising a polyimide tape with low hardness, pure glue and a first cover film, sequentially laminated, and arranging the gasket in the window of the first adhesive layer and the first rigid core board, so that the polyimide tape is adjacent to the flexible core board, and the first cover film is away from the flexible core board; S30, pressing; S40, performing copper hole sinking, manufacturing outer layer circuit, solder mask and surface treatment on the pressed structure; S50, taking out the gasket, and obtaining the rigid-flexible combination board; The thickness of the polyimide tape is 25-75 μm; The hardness of the polyimide tape is less than the hardness of the first cover film and the pure glue; The thickness of the gasket is H1, the total depth of the window of the first rigid core board and the first adhesive layer is H2, and 0≤H1-H2≤0.04 mm.

2. The manufacturing method of the rigid-flex printed circuit board according to claim 1, wherein The rigid-flexible combination board forms a rigid-flexible combination area except the flexure area, and the gasket and the rigid-flexible combination area have a spacing L, and L is 0.1-0.5 mm.

3. The manufacturing process of a rigid-flex printed circuit board according to any one of claims 1 to 2, wherein, When the rigid-flexible combination board has multiple rigid core boards, after the step S20, the method further comprises the following step S21: providing at least one second adhesive layer and at least one second rigid core board, sequentially laminating the second adhesive layer and the second rigid core board on the side of the first rigid core board away from the first adhesive layer, the second adhesive layer and the second rigid core board shielding the flexure area, and the second adhesive layer being attached to the first cover film of the gasket.

4. The manufacturing method of the FPC / FPCB according to claim 3, wherein In the step S50, the method specifically comprises the following step S51: uncovering treatment, removing the part of the second adhesive layer and the second rigid core board opposite to the flexure area, to expose the gasket; S52, taking out the gasket.

5. The manufacturing process of a rigid-flex printed circuit board according to any one of claims 1 to 2, wherein, The flexible core board is a single-layer board.

6. The manufacturing method of a rigid-flex printed circuit board according to any one of claims 1 to 2, wherein Before the step S10, the method further comprises the following step S11: providing a second cover film, and covering the second cover film on the flexure area of the flexible core board; In the step S20, the gasket is attached on the side of the second cover film away from the flexible core board.

7. The manufacturing method of a rigid-flex printed circuit board according to any one of claims 1 to 2, wherein In the step S30, the pressing parameters are as follows: the pressure is 380-550 psi, the hot pressing temperature is 185-210 ℃, and the pressing time is 60-180 min.

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