Rigid-flex board uncovering process and rigid-flex board

Abstract

The invention discloses a rigid-flex board uncovering process and a rigid-flex board, and the rigid-flex board uncovering process comprises the steps: preparing an inner-layer flexible board, a first rigid board base material, a second rigid board base material, a first single-sided flexible board, a second single-sided flexible board and a laminated thermosetting adhesive, the first hard board base material, the second hard board base material and the laminated thermosetting adhesive are all provided with avoiding areas matched with the area to be uncovered. Laminating the second single-sided soft board, the second hard board base material, the inner-layer soft board, the first hard board base material and the first single-sided soft board from bottom to top, wherein the laminated thermosetting adhesive is laminated between the soft board and the hard board base material which are adjacent to each other; processing a second metal circuit and an uncovering groove surrounding the to-be-uncovered area on the surfaces of the first single-sided soft board and the second single-sided soft board; and carrying out uncovering treatment on areas, positioned in the uncovering grooves, on the first single-sided soft board and the second single-sided soft board. According to the method, the uncovering groove can be machined through the etching process, a laser depth-controlled cutting process does not need to be adopted, and the equipment cost of small-batch production is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of printed circuit board processing, and particularly relates to a process for uncovering the cover of a rigid-flex printed circuit board and a rigid-flex printed circuit board. Background Art

[0002] A rigid-flex printed circuit board is a type of printed circuit board, which combines a flexible printed circuit board (referred to as a flexible board for short) and a rigid printed circuit board (referred to as a rigid board for short). The processing technology of a rigid-flex printed circuit board includes an uncovering process. With the development of laser technology, the uncovering process also applies the laser controlled-depth cutting process. However, the cutting accuracy of laser controlled-depth cutting will be affected by factors such as laser beam divergence and material thermal deformation, and the price of laser cutting equipment is expensive, which is not conducive to the application scenario of small batch production. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention provides a process for uncovering the cover of a rigid-flex printed circuit board and a rigid-flex printed circuit board, which can process uncovering grooves through an etching process without using a laser controlled-depth cutting process, thereby reducing the equipment cost of small batch production.

[0004] On the one hand, an embodiment of the present invention provides a process for uncovering the cover of a rigid-flex printed circuit board, including: Preparation of semi-finished products: Prepare an inner flexible board, a first rigid board substrate, a second rigid board substrate, a first single-sided flexible board, a second single-sided flexible board, and a laminated thermosetting adhesive. The inner flexible board is processed with a first metal circuit, and the first rigid board substrate, the second rigid board substrate, and the laminated thermosetting adhesive are all processed with avoidance areas adapted to the area to be uncovered; Laminating and pressing: Stack and press the second single-sided flexible board, the second rigid board substrate, the inner flexible board, the first rigid board substrate, and the first single-sided flexible board in sequence from bottom to top, wherein the laminated thermosetting adhesive is stacked between adjacent flexible boards and rigid board substrates; Processing of outer layer circuits: Process a second metal circuit and an uncovering groove surrounding the area to be uncovered on the surfaces of the first single-sided flexible board and the second single-sided flexible board; Uncovering treatment: Perform uncovering treatment on the areas of the first single-sided flexible board and the second single-sided flexible board located within the uncovering groove to expose the inner flexible board.

[0005] According to some embodiments of the present invention, the processing of the outer layer circuits includes: Perform full-panel electroplating on the semi-finished product obtained by laminating and pressing to form a copper layer with a preset thickness on the surfaces of the first single-sided flexible board and the second single-sided flexible board; Attach a dry film on the copper layer, and perform exposure development and etching and film stripping processes to process second metal circuits and uncovering grooves surrounding the area to be uncovered on the surfaces of the first single-sided flexible board and the second single-sided flexible board.

[0006] According to some embodiments of the present invention, the uncovering groove is provided with a starting wire groove, and the width of the starting wire groove is greater than the width of the uncovering groove.

[0007] According to some embodiments of the present invention, the uncovering groove encloses a rectangular area, and the starting wire groove is arranged on the short side of the rectangular area.

[0008] According to some embodiments of the present invention, the width of the uncovering groove is 0.5 ± 0.05 mm.

[0009] According to some embodiments of the present invention, the width of the starting wire groove is greater than or equal to 2 mm.

[0010] According to some embodiments of the present invention, the distance between the starting wire groove and the functional unit is greater than or equal to 5 mm.

[0011] According to some embodiments of the present invention, the base materials of the first single-sided flexible board and the second single-sided flexible board are PI films with a thickness greater than or equal to 25 μm.

[0012] According to some embodiments of the present invention, after the uncovering process, it further includes: Attach and cure a covering film on the surface of the semi-finished product obtained by the uncovering process; Perform surface treatment on the cured semi-finished product.

[0013] On the other hand, an embodiment of the present invention provides a rigid-flex printed circuit board, which is processed by the above-mentioned uncovering process of the rigid-flex printed circuit board.

[0014] The embodiments of the present invention have at least the following beneficial effects: Process an avoidance area on the first rigid board substrate, the second rigid board substrate and the laminated thermosetting adhesive, then laminate and press the second single-sided flexible board, the second rigid board substrate, the inner-layer flexible board, the first rigid board substrate and the first single-sided flexible board, and process uncovering grooves on the surfaces of the first single-sided flexible board and the second single-sided flexible board, and then use the uncovering grooves for uncovering treatment to expose the inner-layer flexible board. In this way, the uncovering grooves can be processed by the etching process, without using the laser controlled-depth cutting process, without arranging laser cutting equipment, and reducing the equipment cost of small-batch production.

[0015] The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of embodiments in conjunction with the accompanying drawings, where: Figure 1 is a flowchart of the steps of the process for uncovering the cover of a rigid-flex printed circuit board according to an embodiment of the present invention; Figure 2 is a schematic diagram of the laminated structure of the semi-finished product preparation steps of the process for uncovering the cover of a rigid-flex printed circuit board according to an embodiment of the present invention; Figure 3 is one of the schematic diagrams of the laminated structure of the laminated pressing steps of the process for uncovering the cover of a rigid-flex printed circuit board according to an embodiment of the present invention; Figure 4 is another schematic diagram of the laminated structure of the laminated pressing steps of the process for uncovering the cover of a rigid-flex printed circuit board according to an embodiment of the present invention; Figure 5 is a schematic diagram of the laminated structure of the outer layer circuit processing steps of the process for uncovering the cover of a rigid-flex printed circuit board according to an embodiment of the present invention; Figure 6 is a plan view of the outer layer circuit processing steps of the process for uncovering the cover of a rigid-flex printed circuit board according to an embodiment of the present invention; Figure 7 is a plan view of the uncovering treatment steps of the process for uncovering the cover of a rigid-flex printed circuit board according to an embodiment of the present invention.

[0017] Reference numerals: Inner flexible board 100, first rigid board substrate 200, second rigid board substrate 300, first single-sided flexible board 400, second single-sided flexible board 500, laminated thermosetting adhesive 600, area to be uncovered 101, uncovering groove 102, starting wire groove 103, avoidance area 201, functional unit 110. Detailed Description of the Embodiment

[0018] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present invention and should not be construed as limiting the present invention.

[0019] In the description of the present invention, it should be understood that for the orientation descriptions, such as up, down, front, back, left, right, etc., the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

[0020] In the description of the present invention, "several" means one or more, "multiple" means more than two. Understandings such as "greater than", "less than", and "exceeding" do not include the corresponding number, while understandings such as "above", "below", and "within" include the corresponding number. If there is a description of "first", "second", etc., it is only for the purpose of distinguishing technical features and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or the sequence relationship of the indicated technical features.

[0021] In the description of the present invention, unless otherwise clearly defined, terms such as "set", "installed", and "connected" should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific content of the technical solution.

[0022] Please refer to Figure 1 , this embodiment discloses a process for uncovering a rigid-flex board, including steps S100 to S400. It should be noted that the steps in this embodiment are numbered only for the convenience of review and understanding, rather than limiting the execution order of the steps. The content of each step is described in detail below: S100. Preparation of semi-finished products: Prepare an inner flexible board 100, a first rigid board substrate 200, a second rigid board substrate 300, a first single-sided flexible board 400, a second single-sided flexible board 500, and a laminated thermosetting adhesive 600. The inner flexible board 100 is processed with a first metal circuit, and the first rigid board substrate 200, the second rigid board substrate 300, and the laminated thermosetting adhesive 600 are all processed with a relief area 201 adapted to the area 101 to be uncovered; Exemplarily, please refer to Figure 2, the inner flexible printed circuit board 100 includes a flexible printed circuit board substrate (such as a polyimide film, commonly known as a PI film, as shown by the label L2 / L3-PI) and copper foil attached to one or both sides of the flexible printed circuit board substrate (as shown by the label L2-Cu). The number of inner flexible printed circuit boards 100 can be one or more, and different first metal circuits, such as functional circuits and / or pads, are processed on the multiple inner flexible printed circuit boards 100. The first rigid printed circuit board substrate 200 and the second rigid printed circuit board substrate 300 can use the same substrate, such as FR4 (glass fiber reinforced epoxy composite material). It should be noted that no copper foil is attached to the surfaces of the first rigid printed circuit board substrate 200 and the second rigid printed circuit board substrate 300, and the first rigid printed circuit board substrate 200 and the second rigid printed circuit board substrate 300 only serve as supports for the rigid board area (the area outside the area to be uncovered). The structures of the first single-sided flexible printed circuit board 400 and the second single-sided flexible printed circuit board 500 are the same, and both the first single-sided flexible printed circuit board 400 and the second single-sided flexible printed circuit board 500 include a flexible printed circuit board substrate and copper foil attached to one side of the flexible printed circuit board substrate. Among them, the processing process of the inner flexible printed circuit board 100 includes blanking, drilling, dry film pasting, exposure and development, etching and stripping, covering film pasting and curing. In this way, the first metal circuit can be processed on the inner flexible printed circuit board 100, and the surface of the first metal circuit is protected by pasting a covering film. It should be noted that the processing processes of different inner flexible printed circuit boards 100 are the same, so they will not be elaborated here. The processing processes of the first rigid printed circuit board substrate 200, the second rigid printed circuit board substrate 300 and the laminated thermosetting adhesive 600 include blanking and cutting. The incoming materials of the first rigid printed circuit board substrate 200, the second rigid printed circuit board substrate 300 and the laminated thermosetting adhesive 600 are all in sheet structures. The purpose of blanking is to divide the materials from the original size of the incoming materials into sizes suitable for production, and the purpose of cutting is to cut out a clearance area 201 on the materials that is adapted to the area to be uncovered 101, so as to expose the corresponding area of the inner flexible printed circuit board 100 in the subsequent process. Among them, the cutting process of the first rigid printed circuit board substrate 200 and the second rigid printed circuit board substrate 300 can use a routing process to route the corresponding clearance areas. The processing processes of the first single-sided flexible printed circuit board 400 and the second single-sided flexible printed circuit board 500 include blanking and drilling. The first single-sided flexible printed circuit board 400 and the second single-sided flexible printed circuit board 500 do not need to perform circuit processing at this stage, and corresponding alignment holes and / or via holes are processed on the first single-sided flexible printed circuit board 400 and the second single-sided flexible printed circuit board 500 through drilling. After all the semi-finished products are prepared, the next step of processing can be carried out.

[0023] S200, Laminating and Pressing: Stack and laminate the second single-sided flexible printed circuit board 500, the second rigid printed circuit board substrate 300, the inner flexible printed circuit board 100, the first rigid printed circuit board substrate 200 and the first single-sided flexible printed circuit board 400 in the order from bottom to top, and the laminated thermosetting adhesive 600 is stacked between adjacent flexible printed circuit boards and rigid printed circuit board substrates; Exemplarily, please refer to Figure 2 and Figure 3, the semi-finished products are laminated and pressed according to a preset lamination order. For example, the second single-sided flexible board 500, the second rigid board substrate 300, the inner-layer flexible board 100, the first rigid board substrate 200, and the first single-sided flexible board 400 are stacked in a bottom-up order, and then pressed, for example, by means of transfer pressure for pressing and curing. Among them, the laminated thermosetting adhesive 600 is stacked between adjacent flexible boards and rigid board substrates, which can bond the flexible boards and rigid board substrates. Among them, the laminated thermosetting adhesive 600 has processed an avoidance area 201 in the semi-finished product preparation stage, which can prevent the laminated thermosetting adhesive 600 from melting and flowing into the area to be uncovered 101 during the pressing process. It is worth mentioning that please refer to Figure 4 , when the number of inner-layer flexible boards 100 is multiple, adjacent inner-layer flexible boards 100 are also bonded by the laminated thermosetting adhesive 600.

[0024] After lamination and pressing, all the flexible boards and rigid board substrates are pressed into a semi-finished product. Please refer to Figure 3 , assuming that the number of inner-layer flexible boards 100 is one and has double-sided copper foils, taking the metal layer (i.e., copper foil layer) as the division standard for different layers, the semi-finished product after lamination and pressing has 4 metal layers. The 4 metal layers are the copper foil layer of the first single-sided flexible board 400, the copper foil layers on the two opposite surfaces of the inner-layer flexible board 100, and the copper foil layer of the second single-sided flexible board 500. The 4 metal layers are sequentially marked as L1 layer, L2 layer, L3 layer, and L4 layer. Mark Cu represents the copper layer, mark PI represents the PI film, mark AD represents the laminated thermosetting adhesive 600, mark CVL represents the cover film, mark FR4 represents the rigid board substrate. The L1 layer and the L4 layer are both outer layers, and the L2 layer and the L3 layer are both inner layers. After lamination and pressing, the first rigid board substrate 200 and the substrate of the first single-sided flexible board 400 between the L1 layer and the L2 layer form the substrate layer of the L1 layer. Similarly, the second rigid board substrate 300 and the substrate of the second single-sided flexible board 500 form the substrate layer of the L4 layer. Among them, the substrate layers of the L1 layer and the L4 layer are both rigid structures. After lamination and pressing, the first single-sided flexible board 400 covers the first rigid board substrate 200, which can protect the avoidance area 201 of the first rigid board substrate 200 and prevent subsequent processing from affecting the inner-layer flexible board 100 (such as the L2 layer). Similarly, the second single-sided flexible board 500 can protect the inner-layer flexible board 100 (such as the L3 layer).

[0025] S300. Outer-layer circuit processing: Process the second metal circuit and the uncovering groove 102 around the area to be uncovered 101 on the surfaces of the first single-sided flexible board 400 and the second single-sided flexible board 500; Exemplarily, please refer to Figure 4 and Figure 5, due to the stacking of the first rigid substrate 200 and the second rigid substrate 300, the semi-finished product obtained after lamination and pressing, although some areas are flexible structures due to the existence of the avoidance area 201, most areas are rigid structures. Therefore, the outer layer circuits (the circuits of the L1 layer and the L4 layer) can be processed on the surface of the semi-finished product according to the process of rigid boards, that is, the second metal circuits are processed on the surfaces of the first single-sided flexible board 400 and the second single-sided flexible board 500. In addition, in order to facilitate subsequent lid removal, a lid removal groove 102 needs to be etched on the surfaces of the first single-sided flexible board 400 and the second single-sided flexible board 500. The lid removal groove 102 is arranged around the area to be removed, and all the metal in the lid removal groove 102 is etched to expose the substrate of the first single-sided flexible board 400 or the second single-sided flexible board 500.

[0026] S400, Lid removal treatment: Perform lid removal treatment on the areas of the first single-sided flexible board 400 and the second single-sided flexible board 500 that are located within the lid removal groove 102 to expose the inner flexible board 100.

[0027] Exemplarily, please refer to Figure 6 and Figure 7 , after processing the lid removal groove 102 on the periphery of the area to be removed 101, the area to be removed 101 and the non-removal area can be separated. The first single-sided flexible board 400 and the second single-sided flexible board 500 within the area to be removed 101 can be lifted and torn off through auxiliary tools (such as a small knife or tweezers), thereby completing the lid removal treatment to expose the inner flexible board 100.

[0028] Compared with the laser controlled-depth cutting of the related technology, in this embodiment, the lid removal groove 102 can be processed through the etching process, without using the laser controlled-depth cutting process and without arranging laser cutting equipment, reducing the equipment cost for small-batch production.

[0029] It should be noted that, in order to avoid repetition, only the key steps in the process are described in this embodiment, and the steps of other processes, such as the grinding treatment before etching and the browning treatment before lamination, can refer to the related technology and will not be elaborated in this embodiment.

[0030] Among them, the processing of the outer layer circuit includes: Perform full-panel electroplating on the semi-finished product obtained by lamination and pressing to form a copper layer with a preset thickness on the surfaces of the first single-sided flexible board 400 and the second single-sided flexible board 500; Attach a dry film on the copper layer, and perform exposure, development, and etching and stripping treatment to process the second metal circuit and the lid removal groove 102 surrounding the area to be removed 101 on the surfaces of the first single-sided flexible board 400 and the second single-sided flexible board 500.

[0031] Exemplarily, please refer to Figure 3, the semi-finished product after lamination can be regarded as a rigid board, and the copper foils of the first single-sided flexible board 400 (as shown by the label L1-Cu) and the second single-sided flexible board 500 (as shown by the label L4-Cu) can be regarded as the outer-layer copper foils of the rigid board. Please refer to Figure 5 , by performing full-panel electroplating on the semi-finished product, a layer of copper (as shown by the labels L1-Cu-2 and L4-Cu-2) can be deposited on the surface of the outer-layer copper foil to form a copper layer with a preset thickness. In addition, full-panel electroplating can also perform hole electroplating on the holes obtained by outer-layer drilling, so as to achieve signal conduction between different layers. After pasting a dry film on the copper layer and undergoing exposure development and etching and stripping treatment, a second metal circuit and a cover-opening groove 102 can be processed on the outer-layer copper foil of the semi-finished product. Among them, the second metal circuit and the cover-opening groove 102 can be processed synchronously or separately. For example, first perform the first dry-film pasting, exposure development and etching and stripping treatment to obtain the second metal circuit, and then perform the second dry-film pasting, exposure development and etching and stripping treatment to obtain the cover-opening groove 102. It is worth mentioning that during the process of processing the cover-opening groove 102, the copper electroplated in the area to be uncovered 101 needs to be retained to increase the hardness of the area to be uncovered 101 and reduce the difficulty of uncovering.

[0032] Please refer to Figure 6 and Figure 7 , the cover-opening groove 102 is provided with a starting wire groove 103, and the starting wire groove 103 is the starting position of uncovering. The width of the starting wire groove 103 (as shown by the label D1 in Figure 6 ) is greater than the width of the cover-opening groove 102 (as shown by the label D2 in Figure 6 ), which can conveniently cut and lift the flexible board structure located in the area to be uncovered 101. Exemplarily, the cover-opening groove 102 encloses a rectangular area, and the starting wire groove 103 is arranged on the short side of the rectangular area. During the production process, in order to improve production efficiency, for the small-sized functional units 110, usually multiple functional units 110 are spliced together to form a splicing board; multiple splicing boards are spliced together again to form a production board, so that multiple functional units 110 can be processed synchronously. As shown in Figure 6As shown, a plurality of functional units 110 are arranged on a splicing board. To facilitate uncovering the cover, through reasonable position arrangement, the flexible board areas of the functional units 110 are arranged together as much as possible to form a rectangular area, typically a long strip area. The starting groove 103 is arranged on the short side of the rectangular area, which can facilitate lifting the flexible board structure located in the area to be uncovered 101 and tearing it along the uncovering groove 102. Among them, the width of the uncovering groove 102 is 0.5 ± 0.05 mm (millimeter), which can form a groove with a certain depth between the same layer of copper foils to facilitate uncovering the cover. The width of the starting groove 103 is greater than or equal to 2 mm, which is convenient for the auxiliary tool to cut the knife to cut open the flexible board substrate at the corresponding position of the starting groove 103. The distance between the starting groove 103 and the functional unit 110 (as shown by the mark D3 in Figure 6 is greater than or equal to 5 mm, which can avoid damaging the functional unit 110 when uncovering the cover. The substrates of the first single-sided flexible board 400 and the second single-sided flexible board 500 are PI films with a thickness greater than or equal to 25 μm (micrometer).

[0033] In addition, the uncovering process further includes: Pressing and curing a cover film on the surface of the semi-finished product obtained by the uncovering process can protect the second metal circuit of the semi-finished product. Before pressing, the cover film is pre-opened to facilitate exposing the corresponding pad positions. Then, the surface of the cured semi-finished product is treated to protect the exposed pads.

[0034] This embodiment also discloses a circuit board, which is processed by the above-mentioned uncovering process of the rigid-flex printed circuit board. The uncovering groove 102 can be processed by an etching process, without using a laser-controlled depth cutting process and without arranging laser cutting equipment, reducing the equipment cost of small-batch production.

[0035] The above has described the embodiments of the present invention in detail with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the purpose of the present invention.

Claims

1. A process for uncovering the cover of a rigid-flex printed circuit board, characterized in that, Including: Semi-finished product preparation: Prepare an inner flexible board (100), a first rigid board substrate (200), a second rigid board substrate (300), a first single-sided flexible board (400), a second single-sided flexible board (500), and a laminated thermosetting adhesive (600). The inner flexible board (100) is processed with a first metal circuit. The first rigid board substrate (200), the second rigid board substrate (300), and the laminated thermosetting adhesive (600) are all processed with an avoidance area (201) adapted to the area to be uncovered (101). Laminated pressing: Stack and press the second single-sided flexible board (500), the second rigid board substrate (300), the inner flexible board (100), the first rigid board substrate (200), and the first single-sided flexible board (400) in order from bottom to top, where the laminated thermosetting adhesive (600) is stacked between adjacent flexible boards and rigid board substrates. Outer circuit processing: Process a second metal circuit and an uncovering groove (102) surrounding the area to be uncovered (101) on the surfaces of the first single-sided flexible board (400) and the second single-sided flexible board (500). Uncovering treatment: Perform an uncovering treatment on the areas of the first single-sided flexible board (400) and the second single-sided flexible board (500) located within the uncovering groove (102) to expose the inner flexible board (100).

2. The uncovering process of the rigid-flex printed circuit board according to claim 1, wherein The outer circuit processing includes: Performing full-panel electroplating on the semi-finished product obtained by the laminated pressing process to form a copper layer with a preset thickness on the surfaces of the first single-sided flexible board (400) and the second single-sided flexible board (500). Sticking a dry film on the copper layer, and performing exposure development and etching and stripping treatment to process a second metal circuit and an uncovering groove (102) surrounding the area to be uncovered (101) on the surfaces of the first single-sided flexible board (400) and the second single-sided flexible board (500).

3. The soft and hard combination board uncovering process according to claim 1 or 2, characterized in that The uncovering groove (102) is provided with a starting groove (103), and the width of the starting groove (103) is greater than the width of the uncovering groove (102).

4. The uncovering process of the rigid-flex printed circuit board according to claim 3, characterized in that The uncovering groove (102) encloses a rectangular area, and the starting groove (103) is provided on the short side of the rectangular area.

5. The uncovering process of the rigid-flex printed circuit board according to claim 3, characterized in that, The width of the uncovering groove (102) is 0.5 ± 0.05 mm.

6. The process for uncovering a rigid-flexible board according to claim 5, characterized in that: The width of the starting groove (103) is greater than or equal to 2 mm.

7. The uncovering process of the rigid-flex printed circuit board according to claim 4, 5 or 6, characterized in that The distance between the starting groove (103) and the functional unit (110) is greater than or equal to 5 mm.

8. The process for uncovering a rigid-flexible board according to claim 1, characterized in that: The substrates of the first single-sided flexible board (400) and the second single-sided flexible board (500) are PI films with a thickness greater than or equal to 25 μm.

9. The process for uncovering a rigid-flexible board according to claim 1, characterized in that: After the uncovering treatment, it further includes: Sticking and curing a covering film on the surface of the semi-finished product obtained by the uncovering treatment. Performing surface treatment on the cured semi-finished product.

10. A rigid-flex printed circuit board, characterized in that, Obtained by the uncovering process of the flexible-rigid combination board according to any one of claims 1 to 9.

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