Manufacturing method of a high-precision thin rigid-flex printed circuit board with densely assembled plates

Abstract

The present invention discloses a manufacturing method for a high-precision thin rigid-flexible printed circuit board with densely assembled plates. An auxiliary cushion layer is manufactured and laminated with a flexible cover film, and then the auxiliary cushion layer of the whole board is subjected to controlled-depth milling, and the part corresponding to the flexible area is retained to form a milling layer as a whole; then, a first opening is made in the milling layer corresponding to the rigid area, and a groove body is formed at the edge of the flexible area. The groove body is provided with connection positions to form a punching layer as a whole; a flexible core board is manufactured and attached to the punching layer, and then the connection positions are cut off to form a flexible board; a rigid core board is manufactured; and a high-flow epoxy prepreg is used to make a second opening corresponding to the flexible area to form an opening epoxy prepreg; the above-mentioned board layers are stacked and laminated, and after forming, the flexible auxiliary cushion layer is removed to form a rigid-flexible printed circuit board; the overall processing technology forms a process-based, batch, and industrial processing condition, and the front and back processes cooperate with each other to form a related technology that matches before and after.

Description

Technical Field

[0001] The present invention relates to the field of printed circuit board manufacturing, particularly to the field of rigid-flex printed circuit board manufacturing, and more particularly to a method for manufacturing a high-precision thin rigid-flex printed circuit board with dense panel layout. Background Art

[0002] In the field of digital video, in order to achieve powerful but compact devices, as a core component, the circuit board needs to have the characteristics of flexible installation, ultra-thin design, and high density. Therefore, the rigid-flex printed circuit board, which has the characteristics of both rigid and flexible boards and can adapt to complex electronic component layouts and compact space limitations, has become the first choice.

[0003] When manufacturing such rigid-flex printed circuit boards using traditional processing methods, the following problems exist:

[0004] (1) Since the size of the unit board is relatively small, the panel layout density is large during panel layout. If the method of making the outer layer circuit pattern by first opening windows and then laminating is adopted, after the prepreg corresponding to the flexible area is opened, its glass fibers are cut into several shorter sizes. During lamination, the binding force of the glass fiber cloth itself decreases, and it is easy to flow with the resin flow. However, the glass fibers themselves (relative to the resin) do not flow. Therefore, problems such as the prepreg or glass fibers overflowing from the rigid-flex bonding position are likely to occur, which not only affects the appearance quality but also increases the cleaning difficulty. Further, if a low-resin-flow prepreg is selected to solve the above-mentioned resin overflow problem, problems such as poor interlayer bonding force after lamination will occur. If the pressure is increased to improve the interlayer bonding force, excessive deformation is likely to occur, affecting the circuit accuracy, and the surface layer is sunken after lamination, making it difficult to make the surface circuit pattern.

[0005] (2) Since the size of such rigid-flex printed circuit boards is generally small, in actual production, multiple units are combined into a large panel to improve efficiency. However, since the cover film of the flexible board is only attached to the flexible area of the rigid-flex printed circuit board, a large number of cover films need to be attached on one panel, and the shape and size of the cover films are not uniform, resulting in increased alignment and attachment quantity during attachment, and increased processing costs.

[0006] Therefore, in order to solve the above-mentioned problems, a method for manufacturing a high-precision thin rigid-flex printed circuit board with dense panel layout is needed. Summary of the Invention

[0007] The present invention aims to solve the comprehensive problems existing in the rigid-flex printed circuit board in the prior art during processing, such as glue overflow at the rigid-flex connection position or low lamination reliability. A manufacturing method for a high-precision thin rigid-flex printed circuit board with dense panel layout is proposed. The rigid-flex printed circuit board is designed and processed in a panel layout manner during processing. The rigid-flex printed circuit board is designed with a forming line. The area within the forming line is the effective area, and other areas are invalid areas. The effective area includes a flexible area and a rigid area. The manufacturing method includes the following steps:

[0008] S10: Take a first cushion layer and a second cushion layer for the first lamination to form an auxiliary cushion layer, and then take a flexible cover film and perform a second lamination with the auxiliary cushion layer to form a cover film cushion layer.

[0009] S20: Laser mill the auxiliary cushion layer in the cover film cushion layer, retain the part corresponding to the flexible area, and form a flexible auxiliary cushion layer. The cover film cushion layer forms a milled layer.

[0010] S30: Die-cut the milled layer. The die-cutting forms a first opening corresponding to the rigid area and forms a groove at the edge of the flexible area. Connection positions are distributed on the groove. The milled layer forms a die-cut layer.

[0011] S40: Manufacture and form a flexible core board, perform surface roughening treatment, and attach it to the die-cut layer to form a flexible board.

[0012] S50: Manufacture and form a rigid core board; and take a high-flow glue prepreg to make a second opening corresponding to the flexible area to form an opening prepreg.

[0013] S60: Stack the opening prepreg and the rigid core board on the surface of the flexible board in sequence from the inside to the outside, and perform lamination. Then, uncover and process, and remove the flexible auxiliary cushion layer. After forming, the rigid-flex printed circuit board is formed.

[0014] Further, the die-cutting includes die-cutting a plurality of compensation openings at the position of the invalid area, and the plurality of compensation openings are separated from the effective area.

[0015] Further, the first opening is larger than the rigid area.

[0016] Further, the surface roughening treatment is as follows: first perform plasma treatment on the flexible core board, and then perform micro-etching treatment.

[0017] Further, the size of the flexible core board is larger than that of the die-cut layer on one side.

[0018] Further, the pressure of the first lamination is greater than the pressure of the second lamination, and the time of the first lamination is greater than the time of the second lamination.

[0019] Further, the first pressing is as follows: using a pressure of 18 kg / cm² to 25 kg / cm², at a temperature of 120 °C to 160 °C, pressing for 20 seconds to 26 seconds.

[0020] Further, the second pressing is as follows: using a pressure of 12 kg / cm² to 15 kg / cm², at a temperature of 120 °C to 160 °C, pressing for 12 seconds to 20 seconds.

[0021] Further, the hardness of the first cushion layer is greater than that of the second cushion layer.

[0022] Further, the hardness of the first cushion layer is: HRC70 to HRC85, and the hardness of the second cushion layer is: HRC40 to HRC50.

[0023] The technical solution of the present invention first makes a covering film cushion layer through a whole-board production, and then performs whole-board punching in the subsequent process, replacing the existing manual or machine single-piece attachment of the covering film process, realizing batch and industrial production and processing, greatly improving the production efficiency, reducing the labor cost, and at the same time reducing the errors and defective product rates caused by manual operations, solving the problems in the prior art such as easy misalignment and increased attachment quantity during large-batch attachment of the covering film, and rising processing costs; by first pressing the first cushion layer and the second cushion layer with different hardnesses, and then pressing with the flexible covering film, the consistency and stability of the whole structure can be ensured; and by using the difference in the two pressing parameters, different bonding forces between layers are realized. On the one hand, it ensures the tight bonding between layers and also avoids surface defects caused by rapid pressing, providing a flatter working surface, and solving the problems in the prior art such as surface layer depression after pressing, making it difficult to produce circuit patterns on the surface; on the other hand, it can also provide a smooth peeling effect by removing the flexible auxiliary cushion layer during the subsequent processing; by opening windows in the high-flowing epoxy prepreg, a greater depth control tolerance is provided for the subsequent use of controlled-depth milling, solving the depth control problem in the prior art processing due to the thin plate body during the controlled-depth milling process; by designing and manufacturing the windowed epoxy prepreg and laminating and pressing it together with the flexible auxiliary cushion layer with different hardnesses, the relatively hard first cushion layer provides an overall support for the subsequent process of attaching to the punching layer, and during the subsequent pressing process, it can effectively prevent the position of the windowed epoxy prepreg from being overly deformed; while the second cushion layer uses its soft characteristics to play a main buffering and conforming role during the pressing process; and due to the slight epoxy flow characteristics of the second cushion layer itself, it can offset the excess epoxy flow generated by the windowed epoxy prepreg during the pressing process, solving the problems in the prior art such as the epoxy prepreg or glass fiber being easily overflowed from the rigid-flexible bonding position during pressing, affecting the appearance quality and increasing the cleaning difficulty; the overall processing technology forms a process-based, batch, and industrial processing condition, and the front and back processes cooperate with each other to form a related technology that matches before and after. Description of the Drawings

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for describing 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.

[0025] Figure 1 Process flow schematic diagram of an embodiment of the present invention;

[0026] Figure 2 Planar schematic diagram of the densely joined boards of an embodiment of the present invention

[0027] Figure 3 Cross-sectional schematic diagram of the auxiliary cushion layer of an embodiment of the present invention;

[0028] Figure 4 Cross-sectional schematic diagram of the milling layer of an embodiment of the present invention;

[0029] Figure 5 Planar schematic diagram of the punching layer of an embodiment of the present invention;

[0030] Figure 6 For Figure 5 A-A cross-sectional schematic diagram of;

[0031] Figure 7 Cross-sectional schematic diagram of the flexible board of an embodiment of the present invention;

[0032] Figure 8 For Figure 7 Planar schematic diagram of;

[0033] Figure 9 Cross-sectional schematic diagram of the stacked structure of an embodiment of the present invention;

[0034] Figure 10 Cross-sectional schematic diagram of the laminated board of an embodiment of the present invention;

[0035] Figure 11 Physical slice diagram of the rigid-flexible combination position of the laminated board of an embodiment of the present invention;

[0036] Figure 12 Planar schematic diagram of the rigid-flexible board of an embodiment of the present invention.

[0037] Explanation of the attached reference numerals: PB - Dense veneer; FD - Partially enlarged position; 10 - Auxiliary cushion layer; 100 - First cushion layer; 100a - PI layer of the first cushion layer; 100b - Adhesive layer of the first cushion layer; 200 - Second cushion layer; 200a - PI layer of the second cushion layer; 200b - Adhesive layer of the second cushion layer; 20 - Milling layer; 2010 - Flexible covering film; 2020 - Flexible auxiliary cushion layer; 30 - Die-cutting layer; 3010 - First opening; 3020 - Groove body; 3030 - Connection position; 3040 - Compensation opening; 40 - Flexible core board; 50 - Flexible board; 60 - Rigid core board; 70 - Windowed prepreg; 7010 - Second opening; 80 - Stacked structure; 80A - Laminated board; 90 - Rigid-flex board.

[0038] The realization of the object, functional features and advantages of the present invention will be further described with reference to the embodiments and the accompanying drawings. Detailed implementation manners

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0040] It should be noted that all directional indications (such as up, down, left, right, front, back, inside, outside, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0041] In addition, the descriptions such as "first" and "second" in the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0042] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0043] Please refer to Figure 1 , Figure 1 which is a schematic process flow diagram of the implementation manner of the present invention.

[0044] The manufacturing process of the embodiment of the present invention includes implementing each step flow in Figure 1 , and the following will further illustrate each step flow in Figure 1 step by step.

[0045] In the processing of the rigid-flexible printed circuit board of this embodiment, a panelized design and processing method is adopted, and a forming line is designed. The area within the forming line is the effective area, and other areas are the ineffective areas. The effective area includes a flexible area and a rigid area.

[0046] Please refer to Figure 2 , Figure 2 , which is a schematic plan view of the dense panel of the embodiment of the present invention.

[0047] For the case where the rigid-flexible printed circuit board with a small unit size forms a dense panel PB in this embodiment, the processability and technical problems in the processing are solved.

[0048] To facilitate a clearer description of the technical process of this embodiment, the following figures all use Figure 2 the locally enlarged position FD of the panel structure for illustration.

[0049] Please refer to Figure 3 , Figure 3 , which is a schematic cross-sectional view of the auxiliary cushion layer of the embodiment of the present invention.

[0050] Step S10:

[0051] Take the first cushion layer 100 and the second cushion layer 200 for the first lamination to form the auxiliary cushion layer 10, and then take the flexible cover film 2010 and the auxiliary cushion layer 10 for the second lamination to form the cover film cushion layer.

[0052] The first cushion layer 100 is composed of the PI layer 100a of the first cushion layer and the adhesive layer 100b of the first cushion layer laminated; the second cushion layer 200 is composed of the PI layer 200a of the second cushion layer and the adhesive layer 200b of the second cushion layer laminated.

[0053] The design of the auxiliary cushion layer 10 is mainly used to make up for the height difference brought by the open window prepreg 70 in the subsequent process of stacked lamination and pressing, making the pressed board surface more flat, providing an ideal planar condition for the production of the subsequent surface circuit pattern, and forming the auxiliary cushion layer 10 by laminating the first cushion layer 100 and the second cushion layer 200 with different pressing hardnesses, rather than choosing an integrally formed cushion layer, in order to give play to the different hardness characteristics of the first cushion layer 100 and the second cushion layer 200 and provide different functions in the processing process.

[0054] Furthermore, the hardness of the first cushion layer 100 is greater than that of the second cushion layer 200. The first cushion layer 100 provides overall support for the subsequent process and the punching layer 30, and can effectively prevent excessive deformation of the position of the window semi-cured sheet 70 during the subsequent lamination process. The second cushion layer 200 uses its soft properties to play a major buffering and coating role during the lamination process. Moreover, due to the slight glue flow characteristics of the second cushion layer 200 itself, it can offset the excess glue flow generated by the window semi-cured sheet 70 during the lamination process, and at the same time guide the glass fiber to avoid the window position, thereby avoiding the glass fiber overflow that may occur after the subsequent cover is removed.

[0055] It is worth mentioning that since the auxiliary pad layer 10 formed by pressing the first pad layer 100 and the second pad layer 200 together has a height difference with the windowed semi-cured sheet 70 in the stacked structure 80 of the subsequent process, the number of layers of the first pad layer 100 and the second pad layer 200 can be appropriately increased during processing according to the height of the windowed semi-cured sheet 70. For example, two layers of the first pad layer 100 and two layers of the second pad layer 200 are pressed together to form the auxiliary pad layer 10.

[0056] Optionally, the hardness of the first cushion layer 100 is HRC70 to HRC85, and the hardness of the second cushion layer 200 is HRC40 to HRC50.

[0057] This embodiment adopts a step-by-step pressing process, in particular, the pressure of the first pressing is greater than the pressure of the second pressing, and the time of the first pressing is greater than the time of the second pressing, in order to ensure a good bond between the first cushion layer 100 and the second cushion layer 200, thereby enhancing the interlayer bonding force. In addition, the pressure and time of the first pressing are both greater than the pressure of the second pressing, so that the bonding force between the first cushion layer 100 and the second cushion layer 200 is greater than the bonding force between the flexible covering film 2010 and the auxiliary cushion layer 10, thereby providing a processing basis for removing the flexible auxiliary cushion layer 2020 after molding.

[0058] Optionally, the first pressing is: using a pressure of 18kg / cm² to 25kg / cm², at a temperature of 120℃ to 160℃, pressing for 20 seconds to 26 seconds; the second pressing is: using a pressure of 12kg / cm² to 15kg / cm², at a temperature of 120℃ to 160℃, pressing for 12 seconds to 20 seconds.

[0059] Please refer to Figure 4 , Figure 4 Schematic cross-sectional view of a milled layer according to an embodiment of the present invention.

[0060] Step S20:

[0061] Laser milling is performed on the auxiliary cushion layer 10 in the covering film cushion layer, and the part corresponding to the flexible area is retained to form the flexible auxiliary cushion layer 2020, and the covering film cushion layer forms the milled layer 20.

[0062] In this embodiment, part of the auxiliary cushion layer 10 in the covering film cushion layer is selectively removed by milling, and the part corresponding to the flexible area is retained, so as to form the flexible auxiliary cushion layer 2020, which provides a supporting effect for the flexible area during lamination and also provides a processing basis for subsequent processes; this process requires high precision to ensure that the surrounding structures or materials are not damaged, and since the thickness of the covering film cushion layer is small, laser controlled-depth milling is used to achieve high-precision cutting.

[0063] Please refer to Figure 5 and Figure 6 , Figure 5 which is a plan view of the die-cut layer of the embodiment of the present invention; Figure 6 is Figure 5 the schematic cross-sectional view of A-A of

[0064] Step S30:

[0065] The milled layer 20 is die-cut. The die-cutting forms the first opening 3010 in the corresponding rigid area and forms the groove body 3020 at the edge of the flexible area. The connecting positions 3030 are distributed on the groove body 3020, and the milled layer 20 forms the die-cut layer 30.

[0066] By die-cutting the rigid area to form the first opening 3010, sufficient adhesion space can be provided for the rigid plate layer during the subsequent lamination process, so as to ensure a good lamination effect; at the same time, several groove bodies 3020 are die-cut at the edge of the corresponding flexible area to form the effect that several connecting positions 3030 are distributed in the through groove. On the one hand, the groove body 3020 can be used as the design basis for the connecting position 3030, which is convenient for maintaining the integrity of the overall structure in the subsequent process, so that the flexible covering film 2010 in the flexible plate area and the flexible covering film 2010 in the invalid area form an integral body, which is convenient for batch processing, forming all integral processing, and realizing a batch and industrialized processing process; and the groove body 3020 formed by die-cutting as a whole makes the flexible covering film 2010 not interfere with the lamination process and effect of the plate body itself, provides sufficient space for the rigid plate lamination to flow glue, prevents problems such as excessive extrusion of the flexible plate area by the flowing glue, and at the same time provides a processing basis for removing the flexible auxiliary cushion layer 2020 in the subsequent process. Different areas are die-cut together, and the flexible covering film 2010 in the invalid area is retained, so that the milled layer 20 forms the effect of batch processing, and the function of setting the connecting position 3030.

[0067] Furthermore, the first opening 3010 is larger than the rigid area, providing sufficient glue flow space during the subsequent lamination process, ensuring the adhesion force between the rigid plate layers, and helping to solve the problem of insufficient interlayer bonding force that may occur in the traditional method.

[0068] Optionally, the first opening 3010 is greater than the rigid region by more than 50 μm to 2.0 mm.

[0069] Since the flexible cover film 2010 in the invalid region is retained, and the flexible cover film 2010 may cause problems such as poor interlayer bonding force in the rigid plate region, the punching also includes punching a plurality of compensation openings 3040 at the positions of the invalid regions, and the plurality of compensation openings 3040 are separated from the effective region, so that the resin glue layer during the lamination process can flow and fill the gaps between different layers, to ensure good interlayer adhesion, effectively improve the interlayer adhesion force, and effectively avoid problems such as insufficient interlayer glue flow space and uneven distribution of the resin glue layer, resulting in insufficient interlayer bonding force.

[0070] In addition, it is worth noting that after subsequent lamination, compensation openings 3040 are also made at the positions where the tool holes are made, which can ensure that the tool holes are not made to the cover film region within the laminated layer during the production of the tool holes, and prevent the problem that when the plate body in the subsequent process passes through the process of processing with the chemical solution, the tool holes penetrate the chemical solution through the cover film layer into the interior of the circuit board plate body.

[0071] Optionally, the distance between the plurality of compensation openings 3040 and the effective region is greater than 20 μm.

[0072] Please refer to Figure 7 , Figure 7 which is a cross-sectional schematic diagram of the flexible board according to the embodiment of the present invention; Figure 8 is Figure 7 a plan schematic diagram of

[0073] Step S40:

[0074] Manufacture and form a flexible core board 40, perform surface roughening treatment, and attach it to the punching layer 30 to form a flexible board 50.

[0075] In this embodiment, the surface roughening treatment is: first perform plasma treatment on the flexible core board 40, and then perform micro-etching treatment.

[0076] That is, the plasma treatment changes the roughness of the surface of the insulating dielectric layer of the flexible core board 40, and then the micro-etching (or super-roughening) treatment increases the roughness of the surface of the circuit pattern on the surface of the flexible core board 40, so that the combination between the punching layer 30 and the flexible core board 40 can be more firm, and the bonding force formed between the two is greater than the bonding force between the second cushion layer 200 and the surface of the flexible cover film 2010, providing a processing basis for removing the flexible auxiliary cushion layer 2020 after uncovering, and using the difference in bonding force to effectively prevent the flexible cover film 2010 from being pulled and blistered when removing the flexible auxiliary cushion layer 2020.

[0077] In this embodiment, since the flexible cover film 2010 of the invalid area is retained, a large number of small unit cover films can form a batch processing effect, thus improving production efficiency and consistency. However, it also brings potential problems, that is, when the rigid-flex board 90 is integrally laminated, the flexible cover film 2010 may affect the bonding force between the laminated layers. If the size of the flexible cover film 2010 extends to the board edge, especially the interlayer bonding force at the board edge position. Therefore, the size of the flexible core board 40 is set to be larger than that of the punching layer 30 on one side. On the one hand, it can effectively increase the effective adhesion area of the board edge, improve the bonding strength between the flexible core board 40 and other layers, and make the whole board body more firm during the processing. On the other hand, it can serve as a barrier, especially the part exceeding the board edge, to prevent the chemical solution used in the subsequent processing from seeping into the interior from the board edge, causing damage to the internal components or performance degradation.

[0078] Optionally, the distance that the size of the flexible core board 40 is larger than that of the punching layer 30 on one side is 30 μm to 20 mm.

[0079] Optionally, if the size of the invalid area at the edge of the flexible core board itself is small, the edge of the flexible core board 40 can be extended unilaterally relative to the size of the cover film.

[0080] Optionally, then laser cut the connection position 3030 at the edge of the flexible area; attach the punching layer 30 to the surface of the flexible core board 40. After the attachment is completed, cut off the connection position 3030, preferably using laser cutting, which provides more convenient processing conditions for the subsequent cover opening processing and forming processing of the flexible area, and prevents problems such as pulling on the connection position 3030 during the forming processing, thus causing problems such as deformation of the flexible area.

[0081] Please refer to Figure 9 and Figure 10 , Figure 9 which is a schematic cross-sectional view of the stacked structure of the embodiment of the present invention.

[0082] Step S50:

[0083] Fabricate and form a rigid core board 60; and take a high-flow prepreg to fabricate a second opening 7010 corresponding to the flexible area to form an opening prepreg 70.

[0084] In the subsequent stacked lamination process, since the provided flexible auxiliary cushion layer 2020 can block the overflow of glass fibers, a high-flow prepreg is used here, which can improve the interlayer bonding force, thereby improving the reliability of the board body. Utilizing its good fluidity, it can effectively fill the gap between the rigid core board 60 and the flexible board 50 during the lamination process, and at the same time avoid the problem of insufficient interlayer bonding force caused by low fluidity in the traditional method.

[0085] It should be noted that during the lamination process, the high-flow prepreg may have problems such as resin overflow or glass fiber overflow (the same problem also occurs in the prior art). Resin overflow is caused by the resin being subjected to high temperature and high pressure during lamination, resulting in excessive flow and overflowing from the rigid area to the flexible area. As for glass fiber overflow, it is because several unit boards are assembled into a panel, and the density of the formed panel is relatively large. Since the high-flow prepreg requires more window areas corresponding to the flexible board area, its glass fibers are cut into several shorter sizes. During lamination, the binding force of the glass fiber cloth itself decreases, and it is easy to flow along with the resin. However, the glass fibers themselves (relative to the resin) do not flow. Therefore, the glass fibers will flow from one window area to another (that is, from the area with larger continuous uncut pieces to the cut and dispersed area), resulting in glass fiber extrusion and thus overflowing into the flexible board area.

[0086] When using the second cushion layer 200 with a smaller hardness, it mainly plays a role during lamination. It will also generate a certain degree of conformability and fluidity itself, and counteract the resin overflow of the high-flow prepreg, keeping the resin overflow within a controllable range (for example: <20μm). At the same time, the combination of the first cushion layer 100 and the second cushion layer 200 can make the glass fibers move towards the direction above the second cushion layer 200, thereby preventing the problem of excessive overflow that extends into the flexible area and adheres to the resin, and preventing the problem of excessive overflow caused by the glass fibers pressing against the second cushion layer 200.

[0087] Optionally, the resin content of the high-flow prepreg is 55% to 68%.

[0088] It should be noted that in order to ensure sufficient resin flow space, the window size on the high-flow prepreg is designed to be 20μm to 70μm larger than the size of the flexible auxiliary cushion layer 2020 on one side, which helps to control the direction and range of the resin glue layer flow, reduce or prevent the resin glue layer from overflowing to unnecessary places, thus solving the resin overflow problem that easily occurs in the traditional method of windowing first and then lamination.

[0089] Please refer to Figure 10 、 Figure 11 and Figure 12 , Figure 10 which is a schematic cross-sectional view of the laminated board according to the embodiment of the present invention, Figure 11 which is a physical cross-sectional view of the rigid-flexible bonding position of the laminated board according to the embodiment of the present invention, Figure 12 which is a schematic plan view of the rigid-flexible board according to the embodiment of the present invention.

[0090] Step S60:

[0091] On the surface of the flexible board 50, the open-window prepreg 70 and the rigid core board 60 are stacked in sequence from the inside out to form a stacked structure 80, and then pressed to form a pressed board 80A. After that, the cover is removed for processing, and the flexible auxiliary cushion layer 2020 is removed. Through shaping, a rigid-flex board 90 is formed.

[0092] For the cover removal processing, laser depth-controlled cutting or mechanical depth-controlled milling can be used to remove the cover. Since the groove body 3020 is set in the early stage and the flexible auxiliary cushion layer 2020 is set, the accuracy of the cover removal processing process is relatively improved, and the adhesion force between the flexible auxiliary cushion layer 2020 and the cover film is relatively low, and it can be removed together with the cover removal processing, thereby exposing the flexible cover film 2010 in the flexible area.

[0093] If the thickness of the board is thinner and the thickness of the cover removal is thinner, the "front cover removal" processing method can be used, that is, all the positions of the rigid board layer corresponding to the flexible area are opened before pressing, and then a pressing gasket (release film, covering film) is used as a buffer layer for pressing. After that, the rigid-flex joint is trimmed.

[0094] From Figure 11 It can be seen that after the flexible auxiliary cushion layer 2020 is set, the glue flow of the high-flow glue prepreg to the open-window area is effectively inhibited, and the glass fiber extends upward toward the flexible cover film 2010, that is, the glass fiber is effectively inhibited outside the second open window 7010, avoiding the problem of glass fiber overflow.

[0095] In summary, in this embodiment, the cover film cushion layer is first fabricated for the entire board, and then the entire board is punched in subsequent processes, replacing the cover film attachment process, achieving batch and industrial production and processing, greatly improving production efficiency, reducing labor costs, and at the same time reducing errors and defective rates caused by manual operations, solving the problems in the prior art such as increased alignment and attachment quantity during large-batch attachment of the cover film, resulting in increased processing costs; by first laminating the first cushion layer 100 and the second cushion layer 200 with different hardnesses and then laminating them with the flexible cover film 2010, the consistency and stability of the entire structure can be ensured; and by using the difference in lamination parameters for the two times, different bonding strengths between layers are achieved. On the one hand, it ensures the tight bonding between layers and also avoids surface defects caused by rapid lamination, providing a flatter working surface and solving the problems in the prior art such as depression of the surface layer after lamination, making it difficult to fabricate circuit patterns on the surface; on the other hand, it can also provide a smooth peeling effect by removing the flexible auxiliary cushion layer 2020 during subsequent processing; by opening windows in the high-flowing epoxy prepreg, a greater depth control tolerance is provided for subsequent controlled-depth milling, solving the depth control problem during controlled-depth milling due to the thin board body in the prior art processing; by designing and fabricating the windowed epoxy prepreg 70 and laminating it with the flexible auxiliary cushion layer 2020 with different hardnesses in a stacked manner, the relatively hard first cushion layer 100 provides an overall support for attachment to the punching layer 30 in subsequent processes, and during subsequent lamination, it can effectively prevent excessive deformation of the position of the windowed epoxy prepreg 70; while the second cushion layer 200 uses its soft characteristics to play a major buffering and conforming role during lamination; and due to the slight epoxy flow characteristics of the second cushion layer 200 itself, it can offset the excess epoxy flow generated by the windowed epoxy prepreg 70 during lamination, solving the problems in the prior art such as the epoxy prepreg or fiberglass being easily overflowed from the rigid-flex combination position during lamination, affecting the appearance quality and increasing the cleaning difficulty; the overall processing technology forms a process-based, batch, and industrial processing condition, with the front and back processes cooperating with each other to form a related technology that matches before and after.

[0096] It should be noted that due to the relatively precise design and processing process of the rigid-flex board 90, the structure and dimensions such as the thickness and line width of each layer during the actual processing process are at the micron level. If the drawings are made according to the enlarged scale of the actual structure, the problem of unclear illustration will occur. Therefore, in order to more clearly and intuitively represent the implementation process of the manufacturing method of this embodiment, the drawings of this embodiment are all schematic diagrams of enlarged technical features, which do not represent the dimensions of the actual structure, nor are they enlarged diagrams of the actual structure in equal proportion.

[0097] The above are only the preferred embodiments of the present invention, and thus do not limit the patent scope of the present invention. Any equivalent structural transformation made under the inventive concept of the present invention by using the content of the specification and drawings of the present invention, or any direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A manufacturing method of a high-precision thin rigid-flex printed circuit board with dense panel splicing. During the processing of the rigid-flex printed circuit board, a panel splicing method is adopted for design and processing. The rigid-flex printed circuit board is designed with a forming line. The area within the forming line is the effective area, and other areas are the ineffective areas. The effective area includes a flexible area and a rigid area. It is characterized in that, The manufacturing method includes the following steps: S10: Take the first cushion layer and the second cushion layer for the first lamination to form an auxiliary cushion layer, and then take a flexible cover film and perform a second lamination with the auxiliary cushion layer to form a cover film cushion layer; S20: Laser milling is performed on the auxiliary cushion layer in the cover film cushion layer, and the part corresponding to the flexible area is reserved to form a flexible auxiliary cushion layer, and the cover film cushion layer forms a milled layer; S30: Punch the milled layer. The punching forms a first opening corresponding to the rigid area and forms a groove at the edge of the flexible area. The groove is provided with connection positions, and the milled layer forms a punched layer; S40: Manufacture and form a flexible core board, perform surface roughening treatment, and attach it to the punched layer to form a flexible board; S50: Manufacture and form a rigid core board; and take a high-flow adhesive prepreg to make a second opening corresponding to the flexible area to form an opening prepreg; S60: Stack the opening prepreg and the rigid core board on the surface of the flexible board in sequence from the inside to the outside, and perform lamination. Then, perform cover peeling processing and remove the flexible auxiliary cushion layer. After forming, the rigid-flex printed circuit board is formed.

2. The manufacturing method of a high-precision thin rigid-flex printed circuit board with densely assembled panels as claimed in claim 1, characterized in that The punching includes punching and forming a plurality of compensation openings at the position of the invalid area, and the plurality of compensation openings are separated from the valid area.

3. The manufacturing method of a high-precision thin rigid-flex printed circuit board with densely assembled plates as described in claim 1, characterized in that, The first opening is larger than the rigid area.

4. The manufacturing method of a high-precision thin rigid-flex printed circuit board with densely assembled plates as claimed in claim 1, wherein, The surface roughening treatment is as follows: First, perform plasma treatment on the flexible core board, and then perform micro-etching treatment.

5. The manufacturing method of a high-precision thin rigid-flex printed circuit board with densely arranged boards as claimed in claim 1, characterized in that, The size of the flexible core board is larger than that of the punched layer on one side.

6. The manufacturing method of a high-precision thin rigid-flex printed circuit board with densely assembled plates as described in claim 1, characterized in that, The pressure of the first lamination is greater than the pressure of the second lamination, and the time of the first lamination is greater than the time of the second lamination.

7. The manufacturing method of a high-precision thin rigid-flex printed circuit board with densely arranged panels as claimed in claim 1 or 6, wherein The first lamination is as follows: Use a pressure of 18 kg / cm² to 25 kg / cm², at a temperature of 120°C to 160°C, and laminate for 20 seconds to 26 seconds.

8. The manufacturing method of a high-precision thin rigid-flex printed circuit board with dense splicing plates as claimed in claim 1 or 6, characterized in that, The second lamination is as follows: Use a pressure of 12 kg / cm² to 15 kg / cm², at a temperature of 120°C to 160°C, and laminate for 12 seconds to 20 seconds.

9. The manufacturing method of a high-precision thin rigid-flexible printed circuit board with densely arranged splicing plates according to claim 1, characterized in that, The hardness of the first cushion layer is greater than the hardness of the second cushion layer.

10. The manufacturing method of a high-precision thin rigid-flex printed circuit board with densely arranged panels as claimed in claim 1 or 9, characterized in that The hardness of the first cushion layer is: HRC70 to HRC85, and the hardness of the second cushion layer is: HRC40 to HRC50.

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