Rigid-flex board and preparation method therefor

Abstract

A rigid-flex board and a preparation method therefor. The rigid-flex board comprises a first soft board structure (10), a first covering film (20), and a second soft board structure (30) which are sequentially stacked; each of the first soft board structure (10) and the second soft board structure (30) comprises a flexible region (101) and a rigid region (102); a first prepreg (40) is provided between the rigid region (102) of the first soft board structure (10) and the rigid region (102) of the second soft board structure (30); a first hard board structure (50) is formed on the side of the first soft board structure (10) away from the second soft board structure (30); a second hard board structure (60) is formed on the side of the second soft board structure (30) away from the first soft board structure (10); a second prepreg (70) is provided between the first hard board structure (50) and the first soft board structure (10); a third prepreg (80) is provided between the second hard board structure (60) and the second soft board structure (30); the first prepreg (40), the second prepreg (70) and the third prepreg (80) are all flow-type prepregs.

Description

Rigid-flex circuit board and preparation method thereof

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 1, 2023, with application number 202311649432.0. The entire contents of the above application are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of rigid-flex PCBs, for example, to a rigid-flex PCB and a method for preparing the same. Background Art

[0003] With the continuous upgrading of artificial intelligence (AI) products, conventional small-capacity, low-speed memory or storage hard drives can no longer meet the requirements of ultra-high computing power and storage. Conventional solid-state drives lack the gold finger plug-in function of memory, and conventional memory modules lack the high storage capacity of solid-state drives. If both the gold finger plug-in function and the high storage capacity function are required, the space occupied will be large. The conventional methods used in the industry to produce non-layered high-rise rigid-flex boards cannot meet the international standard gold finger plug-in thickness requirements during the production process.

[0004] Summary of the Invention

[0005] The present application provides a rigid-flex board and a preparation method thereof, which can ensure the reliability and bending performance of the structure while ensuring that the thickness of the gold finger meets the requirements.

[0006] According to one aspect of the present application, a rigid-flex board is provided, comprising:

[0007] A first soft board structure, a first covering film, and a second soft board structure are sequentially stacked; the first soft board structure and the second soft board structure each include a flexible region and a rigid region, and the rigid region is arranged around the flexible region;

[0008] The first covering film covers a side surface of the flexible area of ​​the first soft board structure adjacent to the second soft board structure, and covers a side surface of the flexible area of ​​the second soft board structure adjacent to the first soft board structure; the first covering film located in the flexible area extends to the rigid area of ​​the first soft board structure and the rigid area of ​​the second soft board structure and covers a portion of the rigid area;

[0009] A first prepreg is provided between the rigid area of ​​the first soft board structure and the rigid area of ​​the second soft board structure, the first prepreg covers the surface of the first soft board structure adjacent to the second soft board structure that is not covered by the first covering film, and covers the surface of the second soft board structure adjacent to the first soft board structure that is not covered by the first covering film;

[0010] A first hard board structure is formed on a side of the first soft board structure away from the second soft board structure; a second hard board structure is formed on a side of the second soft board structure away from the first soft board structure; the first hard board structure and the second hard board structure are located in a rigid area;

[0011] A second prepreg is provided between the first rigid board structure and the first flexible board structure; the second prepreg is located in the rigid area;

[0012] A third prepreg is provided between the second rigid board structure and the second flexible board structure; the third prepreg is located in the rigid area;

[0013] The first prepreg, the second prepreg and the third prepreg are all flow-type prepregs.

[0014] Optional rigid-flex boards include:

[0015] a second covering film and a third covering film;

[0016] The second covering film covers a side surface of the flexible region of the first flexible board structure away from the second flexible board structure, the third covering film covers a side surface of the flexible region of the second flexible board structure away from the first flexible board structure, and the second covering film and the third covering film located in the flexible region extend to the rigid region and cover a portion of the rigid region;

[0017] The second prepreg covers the second covering film in the rigid area and the surface of the first soft board structure not covered by the second covering film away from the second soft board structure; the third prepreg covers the third covering film in the rigid area and the surface of the second soft board structure not covered by the third covering film away from the first soft board structure.

[0018] Optionally, the thickness of the first covering film is greater than the thickness of the first prepreg.

[0019] Optionally, the difference between the thickness of the first covering film and the thickness of the first prepreg is in the range of 5-20 μm.

[0020] Optionally, the rigid-flex board also includes:

[0021] A fourth prepreg, a third hard board structure, a fifth prepreg, a fourth hard board structure, a sixth prepreg and a fifth hard board structure are sequentially stacked on a side of the first hard board structure away from the first soft board structure;

[0022] A seventh prepreg, a sixth hard board structure, an eighth prepreg, a seventh hard board structure, a ninth prepreg and an eighth hard board structure are sequentially stacked on a side of the second hard board structure away from the second soft board structure;

[0023] Among them, the fourth prepreg, the fifth prepreg, the sixth prepreg, the seventh prepreg, the eighth prepreg and the ninth prepreg are all flow-type prepregs.

[0024] Optionally, the first flexible board structure and the second flexible board structure include a first copper layer, a flexible board substrate, and a second copper layer stacked in sequence;

[0025] The first rigid board structure, the second rigid board structure, the third rigid board structure, the fourth rigid board structure, the fifth rigid board structure, the sixth rigid board structure, the seventh rigid board structure and the eighth rigid board structure all include a third copper layer, a rigid board substrate and a fourth copper layer stacked in sequence.

[0026] Optionally, the first cover film includes a first adhesive layer, a first polyimide film (PI) layer, and a second adhesive layer stacked in sequence; the first adhesive layer is located on a side of the first PI layer adjacent to the first flexible board structure, and the second adhesive layer is located on a side of the first PI layer adjacent to the second flexible board structure; or,

[0027] The first covering film includes a third adhesive layer, a second PI layer, a fourth adhesive layer, a third PI layer and a fifth adhesive layer stacked in sequence; the third adhesive layer is located on a side of the second PI layer adjacent to the first soft board structure, and the fifth adhesive layer is located on a side of the third PI layer adjacent to the second soft board structure.

[0028] According to another aspect of the present application, a method for preparing a rigid-flex circuit board is provided, comprising:

[0029] Providing a first soft board structure and a second soft board structure; wherein the first soft board structure and the second soft board structure each include a flexible region and a rigid region, and the rigid region is arranged around the flexible region;

[0030] A first covering film and a first prepreg are provided between the first soft board structure and the second soft board structure; wherein the first covering film covers a side surface of the flexible region of the first soft board structure adjacent to the second soft board structure, and covers a side surface of the flexible region of the second soft board structure adjacent to the first soft board structure; and the first covering film located in the flexible region extends to the rigid region of the first soft board structure and the rigid region of the second soft board structure and covers a portion of the rigid region; the first prepreg is located between the rigid region of the first soft board structure and the rigid region of the second soft board structure, and the first prepreg covers a surface of the first soft board structure adjacent to the second soft board structure not covered by the first covering film, and covers a surface of the second soft board structure adjacent to the first soft board structure not covered by the first covering film;

[0031] A second prepreg and a first rigid board structure are provided; wherein the second prepreg and the first rigid board structure are located in the rigid area, the second prepreg is located between the first rigid board structure and the first flexible board structure, and the first rigid board structure is located on a side of the first flexible board structure away from the second flexible board structure;

[0032] A third prepreg and a second rigid board structure are provided; wherein the third prepreg and the second rigid board structure are located in the rigid area, the third prepreg is located between the second rigid board structure and the second flexible board structure, and the second rigid board structure is located on a side of the second flexible board structure away from the first flexible board structure;

[0033] The first prepreg, the second prepreg and the third prepreg are all flow-type prepregs.

[0034] Optionally, after arranging the first cover film and the first prepreg between the first flexible board structure and the second flexible board structure, the method further includes:

[0035] A second covering film and a third covering film are provided; wherein the second covering film covers a side surface of the flexible region of the first flexible board structure away from the second flexible board structure, and the third covering film covers a side surface of the flexible region of the second flexible board structure away from the first flexible board structure, and the second covering film and the third covering film located in the flexible region extend to the rigid region and cover a portion of the rigid region;

[0036] A first adhesive blocking gasket and a second adhesive blocking gasket are provided; wherein the first adhesive blocking gasket and the second adhesive blocking gasket are located in the flexible area; the first adhesive blocking gasket is located on a side of the second covering film away from the first covering film, and the second adhesive blocking gasket is located on a side of the third covering film away from the first covering film;

[0037] After the third prepreg and the second hard board structure are provided, the method further comprises:

[0038] A fourth prepreg, a third hard board structure, a fifth prepreg, a fourth hard board structure, a sixth prepreg, and a fifth hard board structure are stacked in sequence on a side of the first hard board structure away from the first soft board structure; the fifth hard board structure is located on a side of the fourth prepreg away from the first soft board structure;

[0039] A seventh prepreg, a sixth hard board structure, an eighth prepreg, a seventh hard board structure, a ninth prepreg, and an eighth hard board structure are stacked in sequence on a side of the second hard board structure away from the second soft board structure; the eighth hard board structure is located on a side of the seventh prepreg away from the second soft board structure; wherein the fourth prepreg, the fifth prepreg, the sixth prepreg, the seventh prepreg, the eighth prepreg, and the ninth prepreg are all flow-type prepregs;

[0040] Remove the fourth prepreg, the third rigid board structure, the fifth prepreg, the fourth rigid board structure, the sixth prepreg, the fifth rigid board structure, the seventh prepreg, the sixth rigid board structure, the eighth prepreg, the seventh rigid board structure, the ninth prepreg and the eighth rigid board structure located in the flexible area by a decapping process;

[0041] Remove the first glue blocking gasket and the second glue blocking gasket; wherein, the boundary of the first glue blocking gasket away from the first soft board structure coincides with the boundary of the first hard board structure away from the first soft board structure; the boundary of the second glue blocking gasket away from the second soft board structure coincides with the boundary of the second hard board structure away from the second soft board structure.

[0042] Optionally, after forming the seventh prepreg, the sixth hard board structure, the eighth prepreg, the seventh hard board structure, the ninth prepreg and the eighth hard board structure stacked in sequence, the method further includes:

[0043] The first hard board structure, the second semi-cured sheet, the first soft board structure, the first covering film, the first semi-cured sheet, the second soft board structure, the third semi-cured sheet, the second hard board structure, the second covering film, the third covering film, the first glue blocking gasket, the second glue blocking gasket, the fourth semi-cured sheet, the third hard board structure, the fifth semi-cured sheet, the fourth hard board structure, the sixth semi-cured sheet, the fifth hard board structure, the seventh semi-cured sheet, the sixth hard board structure, the eighth semi-cured sheet, the seventh hard board structure, the ninth semi-cured sheet and the eighth hard board structure are pressed together by aluminum alloy aluminum sheets. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The following is a brief introduction to the drawings required for describing the embodiments.

[0045] FIG1 is a schematic structural diagram of a rigid-flex board provided in Example 1 of the present application.

[0046] FIG2 is a schematic structural diagram of another rigid-flex board provided in Example 1 of the present application.

[0047] FIG3 is a schematic structural diagram of another rigid-flex board provided in Example 1 of the present application.

[0048] FIG4 is a schematic structural diagram of another rigid-flex board provided in Example 1 of the present application.

[0049] FIG5 is a schematic structural diagram of another rigid-flex board provided in Example 1 of the present application.

[0050] FIG6 is a flow chart of a method for preparing a rigid-flex circuit board provided in Example 2 of the present application.

[0051] FIG7 is a flow chart of another method for preparing a rigid-flex circuit board provided in Example 2 of the present application.

[0052] FIG8 is a schematic diagram of the processing structure of a rigid-flex board provided in Example 2 of the present application. DETAILED DESCRIPTION

[0053] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. The described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0054] The terms "first", "second" etc. in this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchangeable in appropriate circumstances, so that the embodiments of the application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their modifications are intended to cover non-exclusive inclusions, for example, in addition to comprising the process, method, system, product or equipment of a series of steps or units shown in the embodiments of the application, also include other processes, methods, systems, products or equipment of this series of steps or units not clearly listed, or other steps or units inherent to these processes, methods, systems, products or equipment.

[0055] Example 1

[0056] An embodiment of the present application provides a rigid-flexible board. Figure 1 is a structural schematic diagram of a rigid-flexible board provided in Example 1 of the present application. Referring to Figure 1, the rigid-flexible board includes: a first soft board structure 10, a first covering film 20, and a second soft board structure 30 stacked in sequence; the first soft board structure 10 and the second soft board structure 30 both include a flexible area 101 and a rigid area 102, and the rigid area 102 is arranged around the flexible area 101; the first covering film 20 covers a side surface of the flexible area 101 of the first soft board structure 10 adjacent to the second soft board structure 30, and covers a side surface of the flexible area 101 of the second soft board structure 30 adjacent to the first soft board structure 10; the first covering film 20 located in the flexible area 101 extends to both sides to the rigid area 102, and covers part of the rigid area 102.

[0057] The first prepreg 40 is located between the rigid area 102 of the first soft board structure 10 and the rigid area 102 of the second soft board structure 30. The first prepreg 40 covers the surface of the first soft board structure 10 adjacent to the second soft board structure 30 that is not covered by the first cover film 20, and covers the surface of the second soft board structure 30 adjacent to the first soft board structure 10 that is not covered by the first cover film 20.

[0058] A first hard board structure 50 and a second hard board structure 60; the first hard board structure 50 and the second hard board structure 60 are located in the rigid area 102, and the first hard board structure 50 is located on the side of the first soft board structure 10 away from the second soft board structure 30; the second hard board structure 60 is located on the side of the second soft board structure 30 away from the first soft board structure 10; a second semi-cured sheet 70 is arranged between the first hard board structure 50 and the first soft board structure 10; the second semi-cured sheet 70 is located in the rigid area 102; a third semi-cured sheet 80 is arranged between the second hard board structure 60 and the second soft board structure 30; the third semi-cured sheet 80 is located in the rigid area 102; wherein, the first semi-cured sheet 40, the second semi-cured sheet 70 and the third semi-cured sheet 80 are all flow-type semi-cured sheets.

[0059] The first cover film 20 may include a glue layer and a PI layer, and the glue layer may be a pure glue layer. The first flexible board structure 10 and the second flexible board structure 30 may be pressed together by the first prepreg 40. Since the thickness of the rigid board substrate in the rigid-flex board processing structure must be greater than 50μm, and the first and second flexible board structures 10 and 30 require excessive current, the thickness of the first and second flexible board structures 10 and 30 needs to be set very thick. For example, the thickness of the first and second flexible board structures 10 and 30 can both be set to 35μm.

[0060] If a low-flow semi-cured sheet is used between two soft boards to avoid entering the flexible area 101, the low-flow semi-cured sheet will generally use a three-in-one covering material to ensure that the interlayer circuit is fully filled. The overflow amount of the low-flow semi-cured sheet is within 1.5 mm. The thickness of the low-flow semi-cured sheet needs to be set thicker to ensure the reliability of the filling. Therefore, the use of a low-flow semi-cured sheet will make the overall size of the structure thicker and the surface uneven, which will lead to quality problems such as unclean resin polishing. In the embodiment of the present application, the first semi-cured sheet 40 uses a flowable semi-cured sheet. The overflow amount of the flowable semi-cured sheet is in the range of more than 5 mm, which can ensure the reliability of the filling under the condition of very thin thickness, and the first covering film 20 can prevent the first semi-cured sheet 40 from flowing into the flexible area 101. While ensuring the reliability of the structural filling and the bending performance, the overall size of the structure can be reduced to ensure that the thickness of the gold finger of the structure meets the requirements. The first hard board structure 50 is pressed together with the first soft board structure 10 through the second prepreg 70, and the second hard board structure 60 is pressed together with the second soft board structure 30 through the third prepreg 80. The second prepreg 70 and the third prepreg 80 are thin flow-type prepregs, which can reduce the thickness of the device structure while ensuring the reliability of the device, making it easier to achieve the gold finger plug-in thickness meeting international standards.

[0061] The rigid-flex board provided by the technical solution of the embodiment of the present application includes: a first flexible board structure 10, a first covering film 20 and a second flexible board structure 30 which are stacked in sequence; the first flexible board structure 10 and the second flexible board structure 30 both include a flexible area 101 and a rigid area 102, and the rigid area 102 is arranged around the flexible area 101; the first covering film 20 covers a side surface of the flexible area 101 of the first flexible board structure 10 adjacent to the second flexible board structure 30, and covers a side surface of the flexible area 101 of the second flexible board structure 30 adjacent to the first flexible board structure 10; the first covering film 20 located in the flexible area 101 extends to the rigid area 102 on both sides and covers part of the rigid area 102; a first semi-cured sheet 40; the first semi-cured sheet 40 is located between the rigid area 102 of the first flexible board structure 10 and the rigid area 102 of the second flexible board structure 30, and the first semi-cured sheet 40 covers the second semi-cured sheet not covered by the first covering film 20 A soft board structure 10 is adjacent to the surface of the second soft board structure 30, and covers the surface of the second soft board structure 30 adjacent to the first soft board structure 10 that is not covered by the first covering film 20; a first hard board structure 50 and a second hard board structure 60; the first hard board structure 50 and the second hard board structure 60 are located in the rigid area 102, and the first hard board structure 50 is located on the side of the first soft board structure 10 away from the second soft board structure 30; the second hard board structure 60 is located on the side of the second soft board structure 30 away from the first soft board structure 10; a second semi-cured sheet 70 is arranged between the first hard board structure 50 and the first soft board structure 10; the second semi-cured sheet 70 is located in the rigid area 102; a third semi-cured sheet 80 is arranged between the second hard board structure 60 and the second soft board structure 30; the third semi-cured sheet 80 is located in the rigid area 102; wherein the first semi-cured sheet 40, the second semi-cured sheet 70 and the third semi-cured sheet 80 are all flow-type semi-cured sheets. The first prepreg 40 is a thin, flowing prepreg. The first covering film 20 can prevent the first prepreg 40 from flowing into the flexible area 101. The second prepreg 70 and the third prepreg 80 are thin, flowing prepregs, which can reduce the overall size of the structure while ensuring the reliability of the structural filling and the bending performance, thereby ensuring that the thickness of the gold finger of the structure meets the requirements.

[0062] Optionally, referring to Figure 1, the rigid-flexible board also includes: a second covering film 90 and a third covering film 100; the second covering film 90 covers the side surface of the flexible area 101 of the first soft board structure 10 away from the second soft board structure 30, and the third covering film 100 covers the side surface of the flexible area 101 of the second soft board structure 30 away from the first soft board structure 10, and the second covering film 90 and the third covering film 100 located in the flexible area 101 extend to the rigid area 102 and cover part of the rigid area 102; the second semi-cured sheet 70 covers the second covering film 90 in the rigid area 102 and the surface of the first soft board structure 10 away from the second soft board structure 30 not covered by the second covering film 90; the third semi-cured sheet 80 covers the third covering film 100 in the rigid area 102 and the surface of the second soft board structure 30 away from the first soft board structure 10 not covered by the third covering film 100.

[0063] The second cover film 90 and the third cover film 100 can be composed of a PI layer and an adhesive layer. The adhesive layer can be a pure adhesive layer, and the PI layer is located on the side of the pure adhesive layer away from the flexible board structure. The second cover film 90 and the third cover film 100 can protect the circuits on the flexible board structure. Because the second cover film 90 and the third cover film 100 have poor bonding strength with the prepreg, if the second cover film 90 and the third cover film 100 are directly applied to cover the entire flexible board structure and then pressed together, the rigid-flex board is prone to delamination. Therefore, the second cover film 90 and the third cover film 100 in the flexible region 101 are extended to the rigid region 102, and the covering portion of the first flexible board structure 10 and the second flexible board structure 30 located within the rigid region 102 can be reduced. This design can reduce the adhesion of the second cover film 90 and the third cover film 100 to the prepreg, allowing most of the prepreg to be directly bonded to the flexible board structure. The bonding strength between the flexible board structure and the prepreg is high, which can effectively reduce the delamination of the rigid-flex board.

[0064] Optionally, the thickness of the first cover film 20 is greater than the thickness of the first prepreg 40 .

[0065] Since the flexible areas of the first soft board structure 10 and the second soft board structure 30 are easy to bend, the first covering film 20 can provide support for the glue blocking gasket required in the subsequent preparation process, which can reduce the difficulty of installing the glue blocking gasket, ensure that the subsequent preparation of the glue blocking gasket can prevent glue overflow, and simplify the process.

[0066] Optionally, the difference between the thickness of the first cover film 20 and the thickness of the first prepreg 40 is in the range of 5-20 μm.

[0067] If the difference between the thickness of the first covering film 20 and the thickness of the first semi-cured sheet 40 is less than 5 μm, the first semi-cured sheet 40 may flow glue to the flexible area 101, reducing the reliability of the device. If the difference between the thickness of the first covering film 20 and the thickness of the first semi-cured sheet 40 is greater than 20 μm, the bending degree of the first soft board structure 10 and the second soft board structure 30 may be too large, making the performance of the subsequent preparation of the glue blocking gasket to prevent glue overflow worse. Therefore, setting the difference between the thickness of the first covering film 20 and the thickness of the first semi-cured sheet 40 to 5-20 μm can ensure that the subsequent preparation of the glue blocking gasket can play a role in preventing glue overflow, while reducing the difficulty of installing the glue blocking gasket, simplifying the process, and ensuring the reliability of the device.

[0068] Optionally, Figure 2 is a structural schematic diagram of another rigid-flexible board provided in Example 1 of the present application. Referring to Figure 2, the rigid-flexible board also includes: a fourth semi-cured sheet 110, a third hard board structure 120, a fifth semi-cured sheet 130, a fourth hard board structure 140, a sixth semi-cured sheet 150 and a fifth hard board structure 160 stacked in sequence; the fourth semi-cured sheet 110, the third hard board structure 120, the fifth semi-cured sheet 130, the fourth hard board structure 140, the sixth semi-cured sheet 150 and the fifth hard board structure 160 are all located in the rigid area 102, and the fifth hard board structure 160 is located on the side of the fourth semi-cured sheet 110 away from the first soft board structure 10.

[0069] The rigid-flexible board also includes: a seventh semi-cured sheet 170, a sixth hard board structure 180, an eighth semi-cured sheet 190, a seventh hard board structure 200, a ninth semi-cured sheet 210 and an eighth hard board structure 220 stacked in sequence; the seventh semi-cured sheet 170, the sixth hard board structure 180, the eighth semi-cured sheet 190, the seventh hard board structure 200, the ninth semi-cured sheet 210 and the eighth hard board structure 220 are all located in the rigid area 102, and the eighth hard board structure 220 is located on the side of the seventh semi-cured sheet 170 away from the second soft board structure 30; wherein, the fourth semi-cured sheet 110, the fifth semi-cured sheet 130, the sixth semi-cured sheet 150, the seventh semi-cured sheet 170, the eighth semi-cured sheet 190 and the ninth semi-cured sheet 210 are all flow-type semi-cured sheets.

[0070] The first hard board structure 50 and the third hard board structure 120 can be pressed together by the fourth prepreg 110, the third hard board structure 120 and the fourth hard board structure 140 can be pressed together by the fifth prepreg 130, and the fourth hard board structure 140 and the fifth hard board structure 160 can be pressed together by the sixth prepreg 150; the second hard board structure 60 and the sixth hard board structure 180 can be pressed together by the seventh prepreg 170, and the sixth hard board structure 180 and the seventh hard board structure 200 can be pressed together by the eighth prepreg 190. Together, the seventh rigid board structure 200 and the eighth rigid board structure 220 are pressed together by the ninth semi-cured sheet 210; the fourth semi-cured sheet 110, the fifth semi-cured sheet 130, the sixth semi-cured sheet 150, the seventh semi-cured sheet 170, the eighth semi-cured sheet 190 and the ninth semi-cured sheet 210 are all thin flowable semi-cured sheets, which can reduce the overall thickness of the structure while ensuring the reliability of the device, and achieve the international standard gold finger plug-in thickness requirement of 1.57mm+ / -0.1mm for the 20-layer non-layered rigid-flexible board.

[0071] Optionally, Figure 3 is a structural schematic diagram of another rigid-flexible board provided in Example 1 of the present application. Referring to Figure 3, the first soft board structure 10 and the second soft board structure 30 both include a first copper layer 11, a soft board substrate 12, and a second copper layer 13 stacked in sequence; the first hard board structure 50, the second hard board structure 60, the third hard board structure 120, the fourth hard board structure 140, the fifth hard board structure 160, the sixth hard board structure 180, the seventh hard board structure 200, and the eighth hard board structure 220 both include a third copper layer 51, a hard board substrate 52, and a fourth copper layer 53 stacked in sequence.

[0072] The material of the rigid board substrate 52 can be a high-speed material with a flame-retardant grade (FR4). The selection of FR4 high-speed material should meet the requirements of the fifth-generation rapid peripheral component interconnect (PCIE5.0). High-speed materials can be set according to needs. Figure 3 also includes green oil 230, which is configured as a protective device. Figure 3 shows a 20-layer rigid-flex board structure. According to international standards, the thickness of the rigid board substrate must be greater than 50μm. The copper thickness of the first copper layer 11 and the second copper layer 13 on both sides of the flexible board substrate 12 is 35μm. Due to excessive current, the first prepreg 40 is a flowable prepreg. The first cover film 20 can prevent the first prepreg 40 from flowing into the flexible area 101. While ensuring the reliability of the structural filling and the bending performance, it can reduce the overall size of the structure and ensure that the thickness of the structure's gold finger meets the requirements. The copper thickness of the third copper layer 51 and the fourth copper layer 53 on both sides of the rigid board substrate 52 is 18μm. The prepreg between the flexible board structure and the rigid board structure, and between the rigid boards, is a thin, flowing prepreg. This ensures that the international standard gold finger plug-in thickness of 1.57mm + / - 0.1mm for 20-layer rigid-flex boards is achieved while ensuring device reliability. The rigid-flex board manufacturing method is energy-saving and environmentally friendly, highly efficient, low-energy, highly operational, and stable in reliability. The gold finger plug-in thickness in Figure 3 is 1.618mm, meeting the international standard gold finger plug-in thickness of 1.57mm + / - 0.1mm for 20-layer rigid-flex boards.

[0073] Alternatively, FIG4 is a schematic structural diagram of another rigid-flexible board provided in Example 1 of the present application. Referring to FIG4 , the first cover film 20 includes a first adhesive layer 21, a first PI layer 22, and a second adhesive layer 23 stacked in sequence; the first adhesive layer 21 is located on the side of the first PI layer 22 adjacent to the first flexible board structure 10, and the second adhesive layer 23 is located on the side of the first PI layer 22 adjacent to the second flexible board structure 30. Alternatively, FIG5 is a schematic structural diagram of another rigid-flexible board provided in Example 1 of the present application. Referring to FIG5 , the first cover film 20 includes a third adhesive layer 24, a second PI layer 25, a fourth adhesive layer 26, a third PI layer 27, and a fifth adhesive layer 28 stacked in sequence; the third adhesive layer 24 is located on the side of the second PI layer 25 adjacent to the first flexible board structure 10, and the fifth adhesive layer 28 is located on the side of the third PI layer 27 adjacent to the second flexible board structure 30.

[0074] The second cover film 90 and the third cover film 100 each include a PI layer 92 and an adhesive layer 91. Adhesive layer 91 can be a pure adhesive layer, and PI layer 92 is located on the side of adhesive layer 91 away from the flexible circuit board structure. PI layer 92 is provided to protect the circuitry of the flexible circuit board substrate 12, while adhesive layer 91 provides a bonding effect.

[0075] Example 2

[0076] The present embodiment provides a method for preparing a rigid-flexible board based on the above embodiment. FIG6 is a flow chart of a method for preparing a rigid-flexible board provided in the second embodiment of the present application. Referring to FIG6 , the preparation method includes:

[0077] S310 , providing a first soft board structure and a second soft board structure; wherein the first soft board structure and the second soft board structure both include a flexible region and a rigid region, and the rigid region is arranged around the flexible region.

[0078] S320. A first covering film and a first semi-cured sheet are arranged between the first soft board structure and the second soft board structure; wherein the first covering film covers a side surface of the flexible area of ​​the first soft board structure adjacent to the second soft board structure, and covers a side surface of the flexible area of ​​the second soft board structure adjacent to the first soft board structure; the first covering film located in the flexible area extends toward both sides to the rigid area and covers part of the rigid area; the first semi-cured sheet is located between the rigid area of ​​the first soft board structure and the rigid area of ​​the second soft board structure, and the first semi-cured sheet covers a surface of the first soft board structure adjacent to the second soft board structure that is not covered by the first covering film, and covers a surface of the second soft board structure adjacent to the first soft board structure that is not covered by the first covering film.

[0079] S330, setting a second prepreg and a first hard board structure; wherein the second prepreg and the first hard board structure are located in the rigid area, the second prepreg is set between the first hard board structure and the first soft board structure, and the first hard board structure is located on a side of the first soft board structure away from the second soft board structure.

[0080] S340. Arrange a third prepreg and a second rigid board structure. The third prepreg and the second rigid board structure are located in the rigid region. The third prepreg is arranged between the second rigid board structure and the second flexible board structure. The second rigid board structure is located on a side of the second flexible board structure away from the first flexible board structure. The first, second, and third prepregs are all flow-type prepregs.

[0081] The thickness of the first cover film is greater than that of the first prepreg; the difference between the thickness of the first cover film and the thickness of the first prepreg is in the range of 5-20 μm. The first cover film includes a first adhesive layer, a first PI layer, and a second adhesive layer stacked in sequence; the first adhesive layer is located on the side of the first PI layer adjacent to the first flexible board structure, and the second adhesive layer is located on the side of the first PI layer adjacent to the second flexible board structure; or the first cover film includes a third adhesive layer, a second PI layer, a fourth adhesive layer, a third PI layer, and a fifth adhesive layer stacked in sequence; the third adhesive layer is located on the side of the second PI layer adjacent to the first flexible board structure, and the fifth adhesive layer is located on the side of the third PI layer adjacent to the second flexible board structure.

[0082] In the preparation method of the rigid-flexible board provided in the embodiment of the present application, the first semi-cured sheet is a thin and flowing semi-cured sheet, and the first covering film can prevent the first semi-cured sheet from flowing into the flexible area. The second semi-cured sheet and the third semi-cured sheet are thin and flowing semi-cured sheets, which can reduce the overall size of the structure while ensuring the reliability of the structural filling and the bending performance, and ensure that the thickness of the gold finger of the structure meets the requirements.

[0083] Optionally, FIG7 is a flow chart of another method for preparing a rigid-flex circuit board provided in Example 2 of the present application. Referring to FIG7 , the preparation method includes:

[0084] S410 , providing a first soft board structure and a second soft board structure; wherein the first soft board structure and the second soft board structure both include a flexible region and a rigid region, and the rigid region is arranged around the flexible region.

[0085] S420. A first covering film and a first semi-cured sheet are arranged between the first soft board structure and the second soft board structure; wherein the first covering film covers a side surface of the flexible area of ​​the first soft board structure adjacent to the second soft board structure, and covers a side surface of the flexible area of ​​the second soft board structure adjacent to the first soft board structure; the first covering film located in the flexible area extends toward both sides to the rigid area and covers part of the rigid area; the first semi-cured sheet is located between the rigid area of ​​the first soft board structure and the rigid area of ​​the second soft board structure, and the first semi-cured sheet covers a surface of the first soft board structure adjacent to the second soft board structure that is not covered by the first covering film, and covers a surface of the second soft board structure adjacent to the first soft board structure that is not covered by the first covering film.

[0086] S430. Set a second covering film and a third covering film; wherein the second covering film covers a side surface of the flexible area of ​​the first soft board structure away from the second soft board structure, and the third covering film covers a side surface of the flexible area of ​​the second soft board structure away from the first soft board structure. The second covering film and the third covering film located in the flexible area extend to the rigid area and cover part of the rigid area.

[0087] S440, set a first rubber blocking gasket and a second rubber blocking gasket; wherein the first rubber blocking gasket and the second rubber blocking gasket are located in the flexible area; the first rubber blocking gasket is located on the side of the second covering film away from the first covering film, and the second rubber blocking gasket is located on the side of the third covering film away from the first covering film.

[0088] FIG8 is a schematic diagram of a processing structure for a rigid-flex PCB provided in Example 2 of the present application. Referring to FIG8 , the thickness of the first adhesive blocker 240 and the second adhesive blocker 250 can be the distance from the boundary of the third cover film 100 away from the second flexible PCB structure 30 to the boundary of the second rigid PCB structure 60 away from the second flexible PCB structure 30. The first adhesive blocker 240 and the second adhesive blocker 250 are both combined high-temperature PI adhesive blockers, which can prevent the second prepreg 70 and the third prepreg 80 from flowing onto the cover film, thereby preventing prepreg adhesive overflow from affecting device reliability. Furthermore, the boundary of the first adhesive blocker 240 away from the first flexible PCB structure 10 coincides with the boundary of the first rigid PCB structure 5 away from the first flexible PCB structure 10, and the boundary of the second adhesive blocker 250 away from the second flexible PCB structure 30 coincides with the boundary of the second rigid PCB structure 60 away from the second flexible PCB structure 30. This can protect the cover film during the subsequent uncovering process of the rigid-flex PCB, preventing damage to the cover film and thus preventing damage to the circuits on the flexible PCB substrate 12, which could cause device failure.

[0089] S450, setting a second prepreg and a first hard board structure; wherein the second prepreg and the first hard board structure are located in the rigid area, the second prepreg is set between the first hard board structure and the first soft board structure, and the first hard board structure is located on a side of the first soft board structure away from the second soft board structure.

[0090] S460. Arrange a third prepreg and a second rigid board structure. The third prepreg and the second rigid board structure are located in the rigid region, and the third prepreg is arranged between the second rigid board structure and the second flexible board structure. The second rigid board structure is located on a side of the second flexible board structure away from the first flexible board structure. The first, second, and third prepregs are all flow-type prepregs.

[0091] S470, stacking a fourth prepreg, a third hard board structure, a fifth prepreg, a fourth hard board structure, a sixth prepreg and a fifth hard board structure in sequence on a side of the first hard board structure away from the first soft board structure; the fifth hard board structure is located on a side of the fourth prepreg away from the first soft board structure.

[0092] S480. The seventh semi-cured sheet, the sixth hard board structure, the eighth semi-cured sheet, the seventh hard board structure, the ninth semi-cured sheet and the eighth hard board structure are stacked in sequence on the side of the second hard board structure away from the second soft board structure; the eighth hard board structure is located on the side of the seventh semi-cured sheet away from the second soft board structure; wherein the fourth semi-cured sheet, the fifth semi-cured sheet, the sixth semi-cured sheet, the seventh semi-cured sheet, the eighth semi-cured sheet and the ninth semi-cured sheet are all flow-type semi-cured sheets.

[0093] S490. Remove the fourth semi-cured sheet, the third hard board structure, the fifth semi-cured sheet, the fourth hard board structure, the sixth semi-cured sheet, the fifth hard board structure, the seventh semi-cured sheet, the sixth hard board structure, the eighth semi-cured sheet, the seventh hard board structure, the ninth semi-cured sheet and the eighth hard board structure located in the flexible area through a uncovering process.

[0094] S500, remove the first rubber blocking gasket and the second rubber blocking gasket; wherein, the boundary of the first rubber blocking gasket away from the first soft board structure coincides with the boundary of the first hard board structure away from the first soft board structure; the boundary of the second rubber blocking gasket away from the second soft board structure coincides with the boundary of the second hard board structure away from the second soft board structure.

[0095] The first glue blocking pad and the second glue blocking pad can be removed through a cooling process.

[0096] Optionally, after forming the seventh semi-cured sheet, the sixth hard board structure, the eighth semi-cured sheet, the seventh hard board structure, the ninth semi-cured sheet and the eighth hard board structure which are stacked in sequence, it also includes: pressing the first hard board structure, the second semi-cured sheet, the first soft board structure, the first covering film, the first semi-cured sheet, the second soft board structure, the third semi-cured sheet, the second hard board structure, the second covering film, the third covering film, the first glue blocking gasket, the second glue blocking gasket, the fourth semi-cured sheet, the third hard board structure, the fifth semi-cured sheet, the fourth hard board structure, the sixth semi-cured sheet, the fifth hard board structure, the seventh semi-cured sheet, the sixth hard board structure, the eighth semi-cured sheet, the seventh hard board structure, the ninth semi-cured sheet and the eighth hard board structure through aluminum alloy aluminum sheets.

[0097] Because the prepregs used in the embodiments of this application are all flowable, the structure in the flexible area must be compressed first during lamination to prevent the flowing prepreg from flowing into the flexible area. Aluminum alloy sheets are used as the overmolding material for lamination. While harder than conventional overmolding aluminum sheets, they still offer a slight overmolding function, making them stronger than conventional steel sheets. This ensures structural reliability and the smoothness of the rigid-flex board surface, completely resolving the issue of incomplete resin polishing due to uneven board surfaces and ensuring that the gold finger thickness meets requirements.

[0098] The method for preparing the rigid-flexible board provided in the embodiment of the present application has the same effect as the rigid-flexible board structure provided in any embodiment of the present application.

[0099] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the multiple steps described in this application can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of this application can be achieved. This is not limited herein.

Claims

1. A rigid-flex board, comprising: A first soft board structure, a first covering film, and a second soft board structure are sequentially stacked; The first soft board structure and the second soft board structure each include a flexible region and a rigid region, and the rigid region is arranged around the flexible region; The first covering film covers a side surface of the flexible area of ​​the first soft board structure adjacent to the second soft board structure, and covers a side surface of the flexible area of ​​the second soft board structure adjacent to the first soft board structure, and the first covering film located in the flexible area extends to the rigid area of ​​the first soft board structure and the rigid area of ​​the second soft board structure and covers part of the rigid area; A first prepreg is disposed between the rigid region of the first soft board structure and the rigid region of the second soft board structure, the first prepreg covers the surface of the first soft board structure adjacent to the second soft board structure that is not covered by the first covering film, and covers the surface of the second soft board structure adjacent to the first soft board structure that is not covered by the first covering film; A first hard board structure is formed on a side of the first soft board structure away from the second soft board structure; a second hard board structure is formed on a side of the second soft board structure away from the first soft board structure, and the first hard board structure and the second hard board structure are located in the rigid area; A second prepreg is disposed between the first hard board structure and the first soft board structure; The second prepreg is located in the rigid area; A third prepreg is disposed between the second hard board structure and the second soft board structure; the third prepreg is located in the rigid area; Wherein, the first prepreg, the second prepreg and the third prepreg are all flow-type prepregs.

2. The rigid-flex board according to claim 1, further comprising: a second covering film and a third covering film; The second covering film covers a side surface of the flexible region of the first soft board structure away from the second soft board structure, the third covering film covers a side surface of the flexible region of the second soft board structure away from the first soft board structure, and the second covering film and the third covering film located in the flexible region extend to the rigid region and cover a portion of the rigid region; The second semi-cured sheet covers the second covering film in the rigid area and the surface of the first soft board structure not covered by the second covering film away from the second soft board structure; the third semi-cured sheet covers the third covering film in the rigid area and the surface of the second soft board structure not covered by the third covering film away from the first soft board structure.

3. The rigid-flex board according to claim 1, wherein: The thickness of the first cover film is greater than the thickness of the first prepreg.

4. The rigid-flex board according to claim 3, wherein: The difference between the thickness of the first covering film and the thickness of the first prepreg is in the range of 5-20 μm.

5. The rigid-flex board according to claim 1, further comprising: A fourth prepreg, a third hard board structure, a fifth prepreg, a fourth hard board structure, a sixth prepreg and a fifth hard board structure are sequentially stacked on a side of the first hard board structure away from the first soft board structure; A seventh prepreg, a sixth hard board structure, an eighth prepreg, a seventh hard board structure, a ninth prepreg and an eighth hard board structure are sequentially stacked on a side of the second hard board structure away from the second soft board structure; The fourth prepreg, the fifth prepreg, the sixth prepreg, the seventh prepreg, the eighth prepreg and the ninth prepreg are all flow-type prepregs.

6. The rigid-flex board according to claim 5, wherein: The first flexible board structure and the second flexible board structure both include a first copper layer, a flexible board substrate and a second copper layer stacked in sequence; The first hard board structure, the second hard board structure, the third hard board structure, the fourth hard board structure, the fifth hard board structure, the sixth hard board structure, the seventh hard board structure and the eighth hard board structure all include a third copper layer, a hard board substrate and a fourth copper layer which are stacked in sequence.

7. The rigid-flex board according to claim 1, wherein: The first covering film includes a first adhesive layer, a first polyimide film PI layer, and a second adhesive layer stacked in sequence; the first adhesive layer is located on a side of the first PI layer adjacent to the first soft board structure, and the second adhesive layer is located on a side of the first PI layer adjacent to the second soft board structure; or The first covering film includes a third adhesive layer, a second PI layer, a fourth adhesive layer, a third PI layer and a fifth adhesive layer stacked in sequence; the third adhesive layer is located on a side of the second PI layer adjacent to the first soft board structure, and the fifth adhesive layer is located on a side of the third PI layer adjacent to the second soft board structure.

8. A method for preparing a rigid-flexible circuit board, comprising: Providing a first soft board structure and a second soft board structure; wherein the first soft board structure and the second soft board structure both include a flexible region and a rigid region, and the rigid region is arranged around the flexible region; A first covering film and a first prepreg are arranged between the first soft board structure and the second soft board structure; wherein the first covering film covers a side surface of the flexible area of ​​the first soft board structure adjacent to the second soft board structure, and covers a side surface of the flexible area of ​​the second soft board structure adjacent to the first soft board structure; and the first covering film located in the flexible area extends to the rigid area of ​​the first soft board structure and the rigid area of ​​the second soft board structure and covers part of the rigid area; the first prepreg is located in the rigid area of ​​the first soft board structure and the rigid area of ​​the second soft board structure The first prepreg covers the surface of the first soft board structure adjacent to the second soft board structure that is not covered by the first covering film, and covers the surface of the second soft board structure adjacent to the first soft board structure that is not covered by the first covering film; A second prepreg and a first hard plate structure are provided; wherein the second prepreg and the first hard plate structure are located in the rigid region, the second prepreg is located between the first hard plate structure and the first soft plate structure, and the first hard plate structure is located on a side of the first soft plate structure away from the second soft plate structure; A third prepreg and a second hard plate structure are provided; wherein the third prepreg and the second hard plate structure are located in the rigid region, the third prepreg is located between the second hard plate structure and the second soft plate structure, and the second hard plate structure is located on a side of the second soft plate structure away from the first soft plate structure; Wherein, the first prepreg, the second prepreg and the third prepreg are all flow-type prepregs.

9. The method for preparing a rigid-flexible board according to claim 8, after providing a first cover film and a first prepreg between the first flexible board structure and the second flexible board structure, further comprising: A second covering film and a third covering film are provided; wherein the second covering film covers a side surface of the flexible region of the first soft board structure away from the second soft board structure, the third covering film covers a side surface of the flexible region of the second soft board structure away from the first soft board structure, and the second covering film and the third covering film located in the flexible region extend to the rigid region and cover a portion of the rigid region; A first rubber blocking pad and a second rubber blocking pad are provided; wherein the first rubber blocking pad and the second rubber blocking pad are located in the flexible area; the first rubber blocking pad is located on a side of the second covering film away from the first covering film, and the second rubber blocking pad is located on a side of the third covering film away from the first covering film; After the third prepreg and the second hard board structure are arranged, the method further comprises: A fourth prepreg, a third hard board structure, a fifth prepreg, a fourth hard board structure, a sixth prepreg and a fifth hard board structure are stacked in sequence on a side of the first hard board structure away from the first soft board structure; the fifth hard board structure is located on a side of the fourth prepreg away from the first soft board structure; The seventh prepreg, the sixth hard board structure, the eighth prepreg, the seventh hard board structure, the ninth prepreg and the eighth hard board structure are stacked in sequence on the side of the second hard board structure away from the second soft board structure; the eighth hard board structure is located on the side of the seventh prepreg away from the second soft board structure; wherein the fourth prepreg, the fifth prepreg, the sixth prepreg, the The seventh prepreg, the eighth prepreg and the ninth prepreg are all flow-type prepregs; The fourth prepreg, the third hard board structure, the fifth prepreg, the fourth hard board structure, the sixth prepreg, the fifth hard board structure, the seventh prepreg, the sixth hard board structure, the eighth prepreg, the seventh hard board structure, the ninth prepreg and the eighth hard board structure are located in the flexible area by a cover removal process; Remove the first rubber blocking pad and the second rubber blocking pad; wherein the boundary of the first rubber blocking pad away from the first soft board structure coincides with the boundary of the first hard board structure away from the first soft board structure; and the boundary of the second rubber blocking pad away from the second soft board structure coincides with the boundary of the second hard board structure away from the second soft board structure.

10. The method for preparing a rigid-flex board according to claim 9, after forming the seventh prepreg, the sixth hard board structure, the eighth prepreg, the seventh hard board structure, the ninth prepreg and the eighth hard board structure stacked in sequence, further comprising: The first hard board structure, the second semi-cured sheet, the first soft board structure, the first covering film, the first semi-cured sheet, the second soft board structure, the third semi-cured sheet, the second hard board structure, the second covering film, the third covering film, the first glue blocking pad, the second glue blocking pad, the fourth semi-cured sheet, the third hard board structure, the fifth semi-cured sheet, the fourth hard board structure, the sixth semi-cured sheet, the fifth hard board structure, the seventh semi-cured sheet, the sixth hard board structure, the eighth semi-cured sheet, the seventh hard board structure, the ninth semi-cured sheet and the eighth hard board structure are pressed together by aluminum alloy aluminum sheets.

Images