Manufacturing method of rigid-flex printed circuit board with high precision and independent alignment

Abstract

The invention discloses a manufacturing method of a high-precision independent alignment rigid-flexible combined board, which comprises a rigid board layer, a flexible board layer and a prepreg layer in a lamination direction, and comprises the following steps of: manufacturing a false cover film layer; manufacturing a rigid plate windowing area for the rigid plate layer and the prepreg layer, and sequentially stacking and laminating the layers to form a laminated plate; manufacturing a first dry film pattern, exposing the pseudo covering film layer, manufacturing a second dry film pattern to cover the pseudo covering film layer, and performing etching and film stripping processing; a solder mask is manufactured, a third dry film pattern is manufactured, a flexible board alignment target is manufactured and formed, and a rigid-flexible combined board is formed through processing; a window is opened firstly, a cover is opened firstly, a false cover film layer is used for replacing a traditional cover film, the mode of opening the cover later is changed, a flexible plate alignment target is manufactured and placed in the final manufacturing process, an independent alignment system of a flexible plate area during welding is formed, the influence on precision in the machining process is reduced, and a high-precision machining and high-precision welding foundation is formed.

Description

Technical Field

[0001] The present invention relates to the field of circuit board design and processing, and particularly to a method for manufacturing a rigid-flex printed circuit board (PCB) with high-precision independent alignment. Background Art

[0002] A rigid-flex PCB (also known as a rigid-flex or flexible-rigid PCB) combines the support performance of a rigid board and the bendability of a flexible board, resulting in excellent effects such as flexible installation, high reliability, and a wide range of application scenarios. Therefore, rigid-flex PCBs are increasingly used in various fields.

[0003] In some electronic modules that require high precision and thinness, there are designs with pads or gold fingers distributed on flexible circuit boards. Such rigid-flex PCBs generally require not only a relatively thin and light structure but also high-precision performance for both the rigid and flexible boards during welding.

[0004] Currently, for such rigid-flex PCBs, traditional processing methods are generally used, combined with control measures such as calculating the expansion and contraction of the board material, adjusting processing accuracy, and improving operation standardization in each processing step to improve product accuracy.

[0005] However, on the one hand, the current methods for improving accuracy are all control methods during the processing process, rather than improvements or breakthroughs in processing technology. Due to factors such as process capabilities, human factors, and environmental factors, uncertain impacts on processing will occur. Therefore, the method of improving accuracy from the control aspect has limited effects and many uncertain influencing factors. On the other hand, due to the different materials of the rigid and flexible boards of the rigid-flex PCB, during and after the processing, due to environmental influences, there may be differences in expansion and contraction. Generally, welding is performed by aligning the rigid board and then welding components to the rigid and flexible boards. As a result, in some rigid-flex PCBs with high-precision requirements, problems such as inaccurate alignment and deviation of the flexible board during welding occur, resulting in welding failures or poor welding quality. This problem is difficult to effectively solve by improving control capabilities during the processing process.

[0006] Based on the above background and problems, there is a need to provide a processing method for high-precision and thin rigid-flex PCBs that can form a high-precision independent alignment system. Summary of the Invention

[0007] The present invention aims to solve the problems in the prior art that the improvement of the processing effect of high-precision and thin rigid-flex PCBs by enhancing control capabilities has limited improvement in high-precision processing effects and it is difficult to achieve high-precision alignment welding. The present invention provides a method for manufacturing a rigid-flex PCB with high-precision independent alignment, including a rigid board layer, a flexible board layer, and a prepreg layer in the stacking direction.

[0008] The manufacturing method includes the following steps: S10: Fabricate a pseudo-cover film layer, which is composed of a surface copper layer, a first adhesive layer, a cover film PI layer, and a second adhesive layer stacked in sequence.

[0009] S20: Fabricate a laminate. Make a rigid board opening area on the rigid board layer, make a prepreg layer opening area on the prepreg layer, stack the pseudo-cover film layer, the rigid board layer, the prepreg layer, and the flexible board layer in sequence to form a layered stack structure, and set a first auxiliary layout structure on one side of the pseudo-cover film layer and a second auxiliary layout structure on one side of the flexible board layer to form a press-fit stack structure; the pseudo-cover film layer is disposed in the rigid board opening area; press the press-fit stack structure, and the layered stack structure is pressed to form a laminate, and the horizontal aspect of the laminate is divided into a rigid board area and a flexible board area.

[0010] S30: Attach a first dry film layer to both sides of the laminate, and perform exposure and development processes in sequence to form a first dry film pattern, and the pseudo-cover film layer is exposed. Then, attach a second dry film layer to the area of the pseudo-cover film layer of the laminate, and perform exposure and development processes in sequence to form a second dry film pattern, and the second dry film pattern completely covers the pseudo-cover film layer to form a dry film pattern board as a whole; perform etching and film stripping processes on the dry film pattern board to form a circuit pattern board.

[0011] S40: Make a rigid board solder mask layer on the rigid board area of the circuit pattern board, and make a flexible board solder mask layer on the surface of the flexible board layer to form a solder mask layer circuit board.

[0012] S50: Perform a film stripping process on the solder mask layer circuit board to remove the second dry film pattern. Then, attach a third dry film layer to the entire surface on one side of the pseudo-cover film layer of the solder mask layer circuit board, and perform exposure, development, etching, and film stripping processes in sequence to fabricate a flexible board alignment target on the surface copper layer, and the rigid-flex printed circuit board is formed through overall processing.

[0013] Further, the manufacturing method of the pseudo-cover film layer is as follows: Take a double-sided flexible copper clad laminate, etch all the copper layers on one side of the double-sided flexible copper clad laminate by using the processing method of circuit patterns, fabricate a circuit pattern including the surface copper layer on the other copper layer, and then perform cutting to form the pseudo-cover film layer.

[0014] Further, the size of the surface copper layer is smaller than that of the first adhesive layer on each side.

[0015] Furthermore, the size of the windowed area of the rigid board layer is the size of the flexure area of the rigid-flex board; the size of the windowed area of the prepreg layer is less than or equal to the size of the windowed area of the rigid board layer on one side.

[0016] Furthermore, the size of the pseudo cover film layer is greater than the size of the windowed area of the rigid board layer on one side.

[0017] Furthermore, the first auxiliary layout structure is a conformal layout structure, which is composed of a first steel plate layer, a first release layer, and a first conformal film layer layout. The first release layer is provided between the first steel plate layer and the first conformal film layer, and between the first conformal film layer and the layered stack structure; the first conformal film layer is formed by laminating conformal films of greater than or equal to one layer.

[0018] Furthermore, the second auxiliary layout structure is a sizing layout structure, which is composed of a second steel plate layer, a second release layer, and a second conformal film layer layout. The second release layer is provided between the second steel plate layer and the second conformal film layer, and between the second conformal film layer and the layered stack structure; the second conformal film layer is formed by laminating one layer of conformal film.

[0019] Furthermore, the first dry film layer is a thin dry film layer with a thickness less than or equal to 25 μm.

[0020] Furthermore, the second dry film layer is a thick dry film layer with a thickness greater than or equal to 40 μm.

[0021] Furthermore, the third dry film layer is a thick dry film layer with a thickness greater than or equal to 40 μm.

[0022] In the technical solution of the present invention, first, the techniques of first windowing, first opening the cover, and using a pseudo cover film layer to press the cover film layer at the rigid-flex position of the rigid-flex board together are adopted, effectively changing the traditional post-opening processing method that requires overall pressing first and then opening the cover after processing. The post-opening processing has a greater impact on the expansion and contraction of the rigid-flex board. Therefore, the processing accuracy of the rigid-flex board is improved, and by using the effective conversion of the pseudo cover film layer, the surface of the flexible board in the final flexure area has the form of a flexible board alignment target, effectively forming an independent alignment system for the flexible board area during welding. And the flexible board alignment target is formed in a later process, minimizing the impact of the processing of this target on the processing of the rigid-flex board itself, thereby minimizing the impact on the accuracy and effectively improving the processing accuracy; in the overall processing flow, improvements in structure are made, realizing improvements in first windowing and one-time pressing structures, and forming improvements in the effective cooperation between each process, enabling the flow processing of each layer of circuit pattern, and forming a method for processing the flexible board alignment target in a later process, improving the processing feasibility of the product. Brief Description of the Drawings

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0024] Figure 1 Schematic process flow diagram of the embodiment of the present invention; Figure 2 Cross-sectional structure schematic diagram of the lamination structure of the embodiment of the present invention; Figure 3 Cross-sectional structure schematic diagram of the laminate formed in the embodiment of the present invention; Figure 4 Cross-sectional structure schematic diagram of the dry film pattern board formed in the embodiment of the present invention; Figure 5 Cross-sectional structure schematic diagram of the circuit pattern board formed in the embodiment of the present invention; Figure 6 Cross-sectional structure schematic diagram of the solder mask layer circuit board formed in the embodiment of the present invention; Figure 7 Cross-sectional structure schematic diagram of the dry film layer circuit board formed in the embodiment of the present invention; Figure 8 Cross-sectional structure schematic diagram of the rigid-flexible printed circuit board formed in the embodiment of the present invention; Figure 9 For the embodiment of the present invention Figure 8 Top view plane structure schematic diagram.

[0025] Explanation of the reference numerals in the drawings: Label Name Label Name 10 Press-fitting stacked structure 600 Second auxiliary layout structure 10A Layered stacked structure 610 Second contact layer release film 100 Flexible board layer 620 Second covering film 110 First flexible board circuit layer 630 Second middle layer release film 120 Flexible board PI layer 640 Second steel plate layer 130 Second flexible board circuit layer 20 Laminated board 200 Rigid board layer 20A Rigid board area 210 First rigid board circuit layer 20B Rigid board area 220 Rigid board insulation dielectric layer 30 Dry film pattern board 230 Second rigid board circuit layer 140 First dry film pattern 300 Prepreg layer 150 Second dry film pattern 400 Pseudo covering film layer 40 Circuit pattern board 410 Surface copper layer 1310 Flexible board surface circuit pattern 420 First adhesive layer 2110 Rigid board surface circuit pattern 430 Covering film PI layer 50 Solder mask layer circuit board 440 Second adhesive layer 1320 Flexible board solder mask layer 500 First auxiliary layout structure 2120 Rigid board solder mask layer 510 First contact layer release film 60 Dry film layer circuit board 520 First covering film layer 160 Third dry film layer 530 First middle layer release film 70 Rigid-flex board 540 First steel plate layer 4110 Flexible board alignment target The realization of the object of the present invention, functional features and advantages will be further described in conjunction with the embodiments with reference to the drawings. Embodiment

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0027] It should be noted that all the directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative positional relationship, movement conditions, etc. between components in a specific posture (as shown in the attached drawings). If the specific posture changes, the directional indications will change accordingly.

[0028] In addition, in the present invention, descriptions such as "first" and "second" are only for descriptive purposes and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0029] Please refer to Figure 1 , Figure 1 , which is a schematic process flow diagram of the embodiment of the present invention.

[0030] The method for manufacturing a rigid-flexible printed circuit board with high-precision independent alignment provided by the embodiment of the present invention is processed according to the Figure 1 process flow, and the following will be described step by step according to the processing steps.

[0031] Please refer to Figure 2 , Figure 2 , which is a schematic cross-sectional structure diagram of the lamination and stacking structure of the embodiment of the present invention.

[0032] The method for manufacturing a rigid-flexible printed circuit board with high-precision independent alignment provided by the embodiment of the present invention includes a rigid board layer 200, a flexible board layer 100, and a prepreg layer 300 in the stacking direction. The manufacturing method includes the following steps: S10: Manufacture a pseudo-cover film layer 400, which is composed of a surface copper layer 410, a first adhesive layer 420, a cover film PI layer 430, and a second adhesive layer 440 stacked in sequence; in this embodiment, the manufacturing method of the pseudo-cover film layer 400 is to take a double-sided flexible copper clad laminate, etch all the copper layers on one side of the double-sided flexible copper clad laminate by using the processing method of circuit patterns, and manufacture a circuit pattern including the surface copper layer 410 on the other copper layer, and then cut it to form the pseudo-cover film layer 400.

[0033] In this embodiment, the pseudo-cover film layer 400 is used to replace the traditional polyimide and adhesive layer cover film. On the one hand, since this embodiment adopts the method of directly laminating the cover film to the surface of the rigid-flexible printed circuit board, the bonding effect between the rigid board and the flexible board is enhanced, and the pseudo-cover film layer plays the role of the cover film. On the other hand, a surface copper layer 410 is provided on the surface to serve as a copper layer basis for finally manufacturing the flexible board alignment target 4110.

[0034] The pseudo-cover film layer 400 can be formed by processing a double-sided flexible copper clad laminate. Since the dielectric layer material of the double-sided flexible copper clad laminate is generally polyimide, and the cover film material required for the flexible board is also generally polyimide, and the adhesive layers (i.e., the first adhesive layer 420 and the second adhesive layer 440) between the copper layer and the polyimide layer of the copper clad laminate are relatively thin, it is therefore preferably formed by processing a double-sided flexible copper clad laminate to have good processability for the pseudo-cover film layer 400.

[0035] The size of the surface copper layer 410 is less than that of the first adhesive layer 420 on one side. Generally, it is less than the size of the first adhesive layer by 0.2 mm to 2.0 mm on one side, while the sizes of the first adhesive layer 420, the cover film PI layer 430, and the second adhesive layer 440 are generally equal. Thus, after subsequent lamination, the sides of the first adhesive layer 420, the cover film PI layer 430, and the second adhesive layer 440 are exposed outside the surface copper layer 410, preventing problems such as edge warping, and providing a better material bonding basis for subsequent production of attaching dry film and production of solder mask layer.

[0036] Please continue to refer to Figure 2 , and please refer to Figure 3 , Figure 3 which is a schematic cross-sectional structure diagram of the laminate formed in the embodiment of the present invention.

[0037] S20: Fabricate the laminate 20. Make a rigid board opening area 200K on the rigid board layer 200, make a prepreg layer opening area 300K on the prepreg layer 300. Stack the pseudo-cover film layer 400, the rigid board layer 200, the prepreg layer 300, and the flexible board layer 100 in sequence to form a layered stack structure 10A. The pseudo-cover film layer 400 is disposed in the rigid board opening area 200K, and a first auxiliary layout structure 500 is disposed on one side of the pseudo-cover film layer 400, and a second auxiliary layout structure 600 is disposed on one side of the flexible board layer 100 to form a lamination stack structure 10. Press the lamination stack structure 10. The layered stack structure 10A is laminated to form the laminate 20. The horizontal aspect of the laminate 20 is divided into a rigid board area 20A and a flexible board area 20B.

[0038] In this step, openings are made in the rigid board layer 200 and the prepreg layer 300. When laminating, the flexible board layer 100 is exposed to form a "front cover opening" processing method (opening the cover means removing the rigid board layer covering the flexure area of the rigid-flex board to expose the flexible board layer. Generally, the "back cover opening" processing method is used, that is, the whole is a rigid board during the processing, and after the processing is completed, the rigid board layer covering the flexure area is removed). The front cover opening method actually first makes an opening in the covering layer of the flexure area. When laminating, there is no rigid board layer in this area, and the rigid-flex combination area is directly formed by laminating. The front cover opening method is generally applicable to the rigid-flex board product type with a relatively small height difference at the rigid-flex combination position (the thickness of the uncovered area is relatively thin) because glue overflow of the prepreg layer may occur during lamination.

[0039] In this embodiment, the size of the opening area 200K of the rigid board layer is the size of the flexure area of the rigid-flex board; the size of the opening area 300K of the prepreg layer is less than or equal to the size of the opening area 200K of the rigid board layer on one side, generally less than 0.1 mm to 2.0 mm; the size of the pseudo-covering film layer 400 is greater than the size of the opening area 200K of the rigid board layer on one side, generally greater than 0.2 mm to 2.0 mm.

[0040] The size of the opening area is the size of the "removed" part; setting the size of the opening area 300K of the prepreg layer to be less than or equal to the size of the opening area 200K of the rigid board layer. Since the pseudo-covering film layer 400 is laminated on the outermost layer and the pseudo-covering film layer 400 covers the flexure area during lamination, there is no need to overly consider the accuracy of the prepreg layer 300 extending into the flexure area. That is, even if a certain amount of glue overflows from the prepreg layer 300 into the flexure area, it will not affect the overall structure and performance of the flexure area; and the size of the pseudo-covering film layer 400 is greater than the size of the opening area 200K of the rigid board layer on one side, which can enable the pseudo-covering film layer 400 to effectively and completely cover the flexure area and cover it on the rigid board layer 200 to form a complete protection structure.

[0041] In this embodiment, the first auxiliary layout structure 500 is a covering layout structure. The covering layout structure is composed of a first steel plate layer 540, a first release layer, and a first covering film layer 520 arranged in a layout. A first release layer is provided between the first steel plate layer 540 and the first covering film layer 520, and between the first covering film layer 520 and the hierarchical stacked structure 10A, as shown in the attached Figure 2 figure, the first middle release film 530 and the first contact layer release film 510 are provided; the first covering film layer 520 is formed by stacking one or more covering films.

[0042] In this embodiment, the second auxiliary layout structure 600 is a shaping layout structure. The shaping layout structure is composed of a second steel plate layer 640, a second release layer, and a second covering film layer arranged in a layout. Between the second steel plate layer 640 and the second conformal film layer 620, and between the second conformal film layer 620 and the layered stack structure 10A, a second release layer is provided. As Figure 2 shown, a second middle release film 630 and a second contact layer release film 610 are provided; the second conformal film layer 620 is formed by laminating a single layer of conformal film.

[0043] It should be noted that this embodiment provides a structure of the flexible plate layer 100 on one side, that is, the flexible plate layer is located on the outermost layer of the rigid-flex board. Therefore, during lamination, one side of the rigid plate layer 200 needs to have good conformal ability, so that there is good bonding and filling effect between the layers after lamination, and one side of the flexible plate layer 100 has good shaping ability, so that the flexible plate layer 100 still has good flatness after lamination, and the overall structure forms a single-sided conformal lamination structure; therefore, the first auxiliary layout structure 500 is set as a conformal layout structure, and the first conformal film layer 520 has a larger thickness and higher conformal performance compared with the second conformal film layer 620. For example, materials such as polyolefin film layer, epoxy resin film layer, polyethylene film layer, polypropylene film layer, etc. are used, while the second conformal film layer 620 has relatively small conformal ability. For example, materials with the same material as the first conformal film layer 520 but with a lower glue content can also be used, or film layers with relatively small conformal ability such as polyimide film layer and polytetrafluoroethylene film layer are used.

[0044] Please refer to Figure 4 and Figure 5 , Figure 4 which is a schematic cross-sectional structure diagram of the dry film pattern board formed by the embodiment of the present invention; Figure 5 which is a schematic cross-sectional structure diagram of the circuit pattern board formed by the embodiment of the present invention.

[0045] S30: Attach a first dry film layer to both sides of the laminate 20. The first dry film layer is a thin dry film layer with a thickness less than or equal to 25 μm; and then perform exposure and development processes in sequence to form a first dry film pattern 140, and the pseudo-covering film layer 400 is exposed. Then attach a second dry film layer to the area of the pseudo-covering film layer 400 of the laminate 20. The second dry film layer is a thick dry film layer with a thickness greater than or equal to 40 μm; perform exposure and development processes in sequence to form a second dry film pattern 150, and the second dry film pattern 150 completely covers the pseudo-covering film layer 400, and the overall dry film pattern board 30 is formed (as Figure 4 shown); etch and strip the dry film pattern board 30 to form a circuit pattern board 40 (as Figure 5 shown); the first rigid plate circuit layer 210 is fabricated to form a rigid plate surface circuit pattern 2110, and the second flexible plate circuit layer 130 is fabricated to form a flexible plate surface circuit pattern 1310.

[0046] After forming the laminate, it is first necessary to fabricate the surface circuit pattern of the rigid board layer 200 and the surface circuit pattern of the flexible board layer 100. Using a first dry film layer with a relatively thin thickness can improve the processing accuracy of the circuit pattern and form the processing basis for a high-precision circuit pattern. The area of the pseudo-cover film layer 400 is a flexure area, with a certain drop between it and the rigid board layer 200. At this step, it is not necessary to fabricate the surface circuit pattern on the surface copper layer 410 of the pseudo-cover film layer 400 for the time being. Therefore, it is necessary to protect the surface copper layer 410 separately. Thus, a second dry film layer with a relatively thick thickness is used alone for attachment to ensure that the dry film can be effectively attached to the surface. By using the method of attaching dry films with different thicknesses in different areas, different dry film characteristics required for different areas can be formed.

[0047] Since the second dry film pattern 150 completely covers and protects the pseudo-cover film layer 400, it is only necessary to perform development and etching processing according to the pattern transfer processing parameters required for the surface circuit pattern, and then the required surface circuit pattern can be formed. At the same time, when stripping the thinner first dry film pattern 140, the parameters for stripping the thicker second dry film pattern 150 can be used to strip both the first dry film pattern 140 and the second dry film pattern 150, because it is necessary to reattach the third dry film layer and fabricate the third dry film pattern later. Therefore, it is not necessary to retain the second dry film pattern 150 in the intermediate process.

[0048] Please refer to Figure 6 , Figure 6 which is a schematic cross-sectional structure diagram of the solder mask layer circuit board formed by the embodiment of the present invention; S40: Fabricate a rigid board solder mask layer 2120 on the rigid board area of the circuit pattern board 40, and fabricate a flexible board solder mask layer 1320 on the surface of the flexible board layer 100 to form a solder mask layer circuit board 50.

[0049] It should be noted that after fabricating the solder mask layer, the solder mask layer circuit board 50 can be further surface-treated (such as immersion gold, immersion tin, etc.) to form a finished board in the sense of a rigid-flexible printed circuit board. At the same time, it should be noted that if the surface treatment is fabricated together here, the above-mentioned second dry film pattern 150 cannot be stripped and needs to be stripped after the surface treatment is fabricated, and the second dry film layer needs to be a dry film material resistant to surface treatment (such as anti-electroplated gold).

[0050] In this embodiment, the solder mask layer is fabricated first to form a finished board in the sense of a rigid-flexible printed circuit board, and then the flexible board alignment target 4110 is fabricated later to minimize the influence of the previous processes (solder mask layer fabrication, surface treatment) on the flexible board alignment target 4110.

[0051] Please refer to Figure 7 and Figure 8 , Figure 7Schematic cross-sectional structure diagram of a dry film layer circuit board formed in an embodiment of the present invention; Figure 8 Schematic cross-sectional structure diagram of a rigid-flex printed circuit board formed in an embodiment of the present invention.

[0052] S50: Perform film stripping on the solder mask layer circuit board 50 to strip the second dry film pattern 150, and then attach a third dry film layer 160 to the entire surface of the pseudo-cover film layer 400 of the solder mask layer circuit board 50. The third dry film layer is a thick dry film layer with a thickness greater than or equal to 40 μm. Here, a dry film layer identical to the third dry film layer 160 can be attached to the surface of the flexible board layer 100 at the same time to protect the surface circuit pattern 1310 of the flexible board, forming a dry film layer circuit board 60; and then perform exposure, development, etching, and film stripping processes in sequence to fabricate a flexible board alignment target 4110 on the surface copper layer 410, and form a rigid-flex printed circuit board through overall processing.

[0053] It should be noted that if no surface treatment is performed after forming the solder mask layer circuit board 50, the surface treatment can be performed here together so that the flexible board alignment target 4110 also forms a surface treatment layer.

[0054] Since the second dry film pattern 150 serves to completely cover and protect the pseudo-cover film layer 400, it has been fully exposed in the previous process. Therefore, it is impossible to use the second dry film pattern 150 to form a dry film pattern for fabricating the flexible board alignment target 4110. Therefore, it is necessary to first strip the second dry film pattern 150 and then attach the third dry film layer 160, and fabricate the third dry film pattern to achieve the processing of the flexible board alignment target 4110. Since the third dry film layer 160 also needs to be attached to the flexure area, a relatively thick dry film is also required.

[0055] It can be seen that the fabrication of the flexible board alignment target 4110 is carried out after the finished board is formed in the sense of forming a rigid-flex printed circuit board (the rigid-flex printed circuit board still needs to be formed and electrically tested in subsequent processes). Therefore, the influencing factors that may affect the processing of the flexible board alignment target 4110 are minimized to ensure a high degree of matching between the flexible board alignment target 4110 and the gold fingers and pad patterns of the flexible board layer in the flexure area. Moreover, the flexible board alignment target 4110 is located on the outer layer and will not be covered by the cover film layer. Therefore, there is no need to perform further windowing or other processing on the cover film layer, nor will the alignment target be covered due to the unopened window of the cover film layer, resulting in unclear recognition by subsequent alignment optical equipment. This ensures that the subsequent flexible board layer can be independently aligned and welded with the rigid board layer and has high-precision characteristics.

[0056] Please refer to Figure 9 , Figure 9 which is Figure 8 the top view plane structure diagram of an embodiment of the present invention.

[0057] Figure 9The planar view of [the object] includes a rigid board area and a flexible board area. The rigid board area is equipped with an independent alignment target system (prior art, not shown in the figure) and a pad pattern (prior art, not shown in the figure). The flexible board area uses the flexible board alignment target 4110 for independent soldering alignment to ensure high-precision soldering in the flexible board area. Since the first adhesive layer 420 is generally thin and can be ignored, a cover film PI layer can be formed to achieve the effect of a cover film.

[0058] It should be noted that due to different design, processing, and application scenarios of flexible circuit boards in the actual processing and application processes, the drawings of this embodiment are only used to illustrate the implementation process of this embodiment, and do not represent the size ratio of the actual product, nor do they represent the figure enlarged in proportion according to the actual situation.

[0059] The above is only the preferred embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A manufacturing method of a rigid-flexible printed circuit board with high-precision independent alignment, including a rigid board layer, a flexible board layer, and a prepreg layer in the stacking direction, characterized in that, The manufacturing method includes the following steps: S10: Fabricate a pseudo-cover film layer, which is composed of a surface copper layer, a first adhesive layer, a cover film PI layer, and a second adhesive layer stacked in sequence; S20: Fabricate a laminate. Make a rigid board opening area on the rigid board layer, make a prepreg layer opening area on the prepreg layer, stack the pseudo-cover film layer, the rigid board layer, the prepreg layer, and the flexible board layer in sequence to form a layered stack structure, and set a first auxiliary layout structure on one side of the pseudo-cover film layer and a second auxiliary layout structure on one side of the flexible board layer to form a press-fit stack structure; The pseudo-cover film layer is disposed in the rigid board opening area; Press the press-fit stack structure. The layered stack structure is pressed to form a laminate, and the horizontal aspect of the laminate is divided into a rigid board area and a flexible board area; S30: Attach a first dry film layer to both sides of the laminate, and perform exposure and development processes in sequence to form a first dry film pattern, exposing the pseudo-cover film layer. Then attach a second dry film layer to the area of the pseudo-cover film layer of the laminate, and perform exposure and development processes in sequence to form a second dry film pattern, which completely covers the pseudo-cover film layer, forming a dry film pattern board as a whole; Etch and strip the dry film pattern board to form a circuit pattern board; S40: Make a rigid board solder resist layer on the rigid board area of the circuit pattern board and make a flexible board solder resist layer on the surface of the flexible board layer to form a solder resist layer circuit board; S50: Strip the second dry film pattern from the solder resist layer circuit board. Then attach a third dry film layer to the entire surface of the side of the solder resist layer circuit board where the pseudo-cover film layer is located, and perform exposure, development, etching, and stripping processes in sequence to fabricate a flexible board alignment target on the surface copper layer, and the rigid-flex board is formed through overall processing.

2. The manufacturing method of a rigid-flex printed circuit board with high-precision independent alignment as described in claim 1, characterized in that The manufacturing method of the pseudo-cover film layer is as follows: Take a double-sided flexible copper clad laminate, etch off all the copper layers on one side of the double-sided flexible copper clad laminate by using the processing method of circuit patterns, make a circuit pattern including the surface copper layer on the copper layer on the other side, and then perform cutting to form the pseudo-cover film layer.

3. The manufacturing method of a rigid-flex printed circuit board with high-precision independent alignment as claimed in claim 1 or 2, characterized in that, The size of the surface copper layer is smaller than that of the first adhesive layer on each side.

4. The manufacturing method of a rigid-flex printed circuit board with high-precision independent alignment as described in claim 1, wherein The size of the rigid board layer opening area is the size of the flexure area of the rigid-flex board; the size of the prepreg layer opening area is smaller than or equal to the size of the rigid board layer opening area on each side.

5. A method for manufacturing a rigid-flex printed circuit board with high-precision independent alignment as claimed in claim 1 or 4, characterized in that, The size of the pseudo-cover film layer is larger than the size of the rigid board layer opening area on each side.

6. The manufacturing method of a rigid-flex printed circuit board with high-precision independent alignment as described in claim 1, characterized in that, The first auxiliary layout structure is a covering layout structure, which is composed of a first steel plate layer, a first release layer, and a first covering film layer arranged in a layout; The first release layer is provided between the first steel plate layer and the first covering film layer, and between the first covering film layer and the layered stack structure; The first covering film layer is formed by stacking one or more covering films; 7. The manufacturing method of a rigid-flex printed circuit board with high-precision independent alignment according to claim 1 or 6, characterized in that, The second auxiliary layout structure is a shaping layout structure, which is composed of a second steel plate layer, a second release layer, and a second covering film layer arranged in a layout, A second release layer is provided between the second steel plate layer and the second film covering layer, and between the second film covering layer and the layered stack structure; The second film covering layer is formed by laminating a single layer of film covering.

8. The manufacturing method of a rigid-flex printed circuit board with high-precision independent alignment as claimed in claim 1, wherein The first dry film layer is a thin dry film layer with a thickness less than or equal to 25 μm.

9. The manufacturing method of a rigid-flex printed circuit board with high-precision independent alignment as described in claim 1, characterized in that The second dry film layer is a thick dry film layer with a thickness greater than or equal to 40 μm.

10. The manufacturing method of a rigid-flex printed circuit board with high-precision independent alignment as described in claim 1, characterized in that, The third dry film layer is a thick dry film layer with a thickness greater than or equal to 40 μm.

Images