A method for manufacturing a rigid-flexible board to improve signal stability

Abstract

The invention discloses a method for manufacturing a rigid-flexible board for improving signal stability. The method comprises the following steps: taking a flexible insulating dielectric layer, making an opening window, attaching the flexible insulating dielectric layer with the window to one side of a copper layer, electroplating a tin layer on the other side of the copper layer, taking a backing plate, adhering one side of the tin layer to the backing plate, preparing resin ink on the window groove, attaching a rigid-flexible insulating dielectric layer and a second copper layer to one side of the resin ink in sequence, removing the backing plate, manufacturing a rigid board layer on the surface, drilling a through hole in the area of ​​the resin ink, electroplating, and performing a cover-lifting process to form a rigid-flexible board. By using the resin ink to replace the flexible insulating dielectric layer, the material properties of the insulating dielectric layer on the wall of the through hole are made similar, the copper electroplating effect is good, the uniformity and flatness of the copper layer on the hole wall are effectively improved, no special electroplating is required, electroplating resources are saved, and the treatment and discharge of wastewater and waste liquid are reduced.

Description

Technical Field

[0001] The present invention relates to the field of manufacturing flexible circuit boards or rigid-flex boards, and in particular to a method for manufacturing a rigid-flex board that improves signal stability. Background Art

[0002] A type of high-precision and high-reliability rigid-flex circuit board used in the fields of intelligent connected vehicles and low-altitude aircraft requires high signal transmission performance.

[0003] The vertical stacked structure of the rigid-flex PCB consists of a rigid board layer and a flexible board layer. Generally, the rigid insulating dielectric layer material of the rigid board layer is different from the flexible insulating dielectric layer material of the flexible board layer (for example, the rigid insulating dielectric layer material is epoxy resin, and the flexible insulating dielectric layer material is polyimide). Therefore, during the electroplating process, for the electroplating processing of the through-holes of the rigid-flex PCB, due to the different materials, the copper plating effect of the through-hole wall is also different. It is easy to produce a problem that the through-hole electroplating effect of the rigid board layer is better, while the electroplating effect of the flexible board layer is insufficient, resulting in insufficient copper thickness of the hole wall of the flexible board layer, or excessive thickness to produce copper nodules, etc., affecting the transmission of electrical signals or other models through the through-hole.

[0004] To address the above issues, currently, methods generally used include adjusting the electroplating parameters (for example, adjusting the electroplating current and time, using a low current and long time electroplating method), or plasma treatment of the inner wall of the through hole, to improve the same basic conditions of different material layers during the electroplating process.

[0005] However, for products with high signal stability requirements, this type of method still has difficulty in ensuring that the uniformity and flatness of the copper on the hole wall after through-hole electroplating meet the application requirements. On the other hand, there is a problem of excessive electroplating waste liquid, which increases the burden of wastewater and waste liquid treatment.

[0006] Based on the above background and problems, it is necessary to provide a method for manufacturing a rigid-flexible circuit board that improves signal stability. Summary of the Invention

[0007] The present invention aims to provide a method for manufacturing a rigid-flexible board with improved signal stability, targeting rigid-flexible boards with high signal stability requirements. The method is intended to address the problems of the uniformity and flatness of the hole wall copper failing to meet application requirements during the through-hole electroplating process, as well as the generation of a large amount of wastewater and waste liquid due to excessive electroplating. The method comprises the following steps:

[0008] S10: Take a flexible insulating dielectric layer, make an opening window, and form a window dielectric layer; take a copper layer, and attach the window dielectric layer to one side of the copper layer to form a flexible copper clad layer, and the opening window forms a window groove.

[0009] S20: electroplating a tin layer onto the other side of the copper layer of the flexible copper clad layer to form a flexible copper clad tin plated structure, taking a pad, and pasting one side of the tin layer onto the pad to form the pad support structure.

[0010] S30: preparing resin ink for the window opening groove, and performing baking, curing and polishing to form a resin filling plate.

[0011] S40: sequentially attaching a rigid-flexible insulating dielectric layer and a second copper layer to one side of the resin ink of the resin-filled board, removing the backing plate, and forming a flexible core board.

[0012] S50: forming a first rigid board layer on the upper surface of the flexible core board and a second rigid board layer on the lower surface to form a multi-layer laminated board.

[0013] S60: drilling through holes in the area of ​​the multi-layer laminate corresponding to the resin ink, and performing electroplating, so that the through holes form conductive vias, and the whole plate is formed into a conductive via board.

[0014] S70: performing a cover-lifting process on the via plate to form the rigid-flexible board.

[0015] Furthermore, the tin layer is adhered to the pad using an adhesive layer, and the adhesive layer is a polypropylene adhesive layer or an epoxy resin adhesive layer.

[0016] Furthermore, the resin ink is prepared in the window opening groove by using silk screen ink, and the resin ink is silk screen printed and filled into the window opening groove.

[0017] Furthermore, the main component of the resin ink is the same as the material of the rigid insulating dielectric layer of the rigid board layer.

[0018] Furthermore, the attaching of the rigid-flexible insulating dielectric layer is to attach a rigid insulating dielectric layer to the rigid board area and to attach a flexible insulating dielectric layer to the flexible board area.

[0019] Furthermore, the step of removing the backing plate comprises milling from one side of the backing plate to the tin layer or the copper layer using a depth-controlled milling method.

[0020] Furthermore, after the backing plate is removed, tin stripping and copper reduction treatment is performed.

[0021] Furthermore, the forming of the multi-layer laminate is:

[0022] Take a plurality of the flexible core boards and stack them up.

[0023] A rigid insulating dielectric layer is provided to the rigid board area between adjacent layers of the flexible core board,

[0024] A flexible insulating dielectric layer is provided to the flexible board area between adjacent layers of the flexible core board.

[0025] Furthermore, the flexible insulating dielectric layer is pre-enlarged toward the rigid board area.

[0026] Furthermore, after the electroplating, the via holes are plugged, baked and cured, and polished in sequence.

[0027] The technical solution of the present invention uses a reverse processing flow to open windows in the flexible insulating dielectric layer and fill them with resin ink to form a pattern of the flexible insulating dielectric layer, thereby achieving the effect of replacing the flexible insulating dielectric layer with the resin ink at the through-hole position, making the insulating dielectric layer material performance of the through-hole wall similar, providing a good hole wall condition foundation for subsequent electroplating processing, achieving a good copper plating effect, and effectively improving the uniformity and flatness of the hole wall copper layer. According to application requirements and structural requirements, a reasonable processing process is designed to form an organically coordinated manufacturing method with complete key process processes. At the same time, there is no need to perform special parameter adjustment, process adjustment, time adjustment, etc., and the electroplating parameters of ordinary electroplated through holes can be used for processing, which effectively saves electroplating resources and reduces the treatment and discharge of wastewater and waste liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0029] Figure 1 A process flow chart of an embodiment of the present invention;

[0030] Figure 2 A schematic diagram of the cross-sectional structure of a flexible copper clad layer formed in accordance with an embodiment of the present invention;

[0031] Figure 3 A schematic diagram of a cross-sectional structure of a flexible copper-clad tin-plated structure formed in accordance with an embodiment of the present invention;

[0032] Figure 4 A schematic cross-sectional view of a pad support structure formed in accordance with an embodiment of the present invention;

[0033] Figure 5 A schematic cross-sectional view of a resin-filled plate according to an embodiment of the present invention;

[0034] Figure 6 A schematic diagram of the cross-sectional structure of a flexible core board formed according to an embodiment of the present invention;

[0035] Figure 7 A schematic diagram of a cross-sectional structure of a multi-layer laminated board produced according to an embodiment of the present invention;

[0036] Figure 8 A schematic diagram of a cross-sectional structure of a via plate formed in accordance with an embodiment of the present invention;

[0037] Figure 9 A schematic cross-sectional view of a plate for filling a via hole according to an embodiment of the present invention;

[0038] Figure 10 Schematic diagram of the cross-sectional structure of a rigid-flex board manufactured according to an embodiment of the present invention.

[0039] Description of Figure Numbers:

[0040]

[0041]

[0042] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0043] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0044] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, inside, outside, etc.) are only used to explain the relative position relationship and movement status between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0045] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referenced. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this disclosure, "plurality" means at least two, such as two or three, unless otherwise specifically defined.

[0046] 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 ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0047] See also Figure 1 , Figure 1 It is a process flow chart of the production method of the present invention.

[0048] The rigid-flexible board for improving signal stability according to the embodiment of the present invention has a planar structure including a rigid board area 10A and a flexible board area 10B, and a vertical stacked structure including a rigid board layer (i.e., the rigid board layer 600 in the accompanying drawings) and a flexible board layer (i.e., the flexible core board 50 in the accompanying drawings); and a manufacturing method thereof includes: Figure 1 The key process flow shown is specifically implemented as follows.

[0049] See also Figure 2 , Figure 2 Schematic diagram of the cross-sectional structure of a flexible copper clad layer formed in accordance with an embodiment of the present invention.

[0050] Step S10:

[0051] Take the first flexible insulating dielectric layer, make an opening window, and form a window dielectric layer 110; take the copper layer 120, and attach the window dielectric layer 110 to one side of the copper layer 120 to form a flexible copper clad layer 10, and the opening window forms a window groove 1110.

[0052] This embodiment adopts the method of first opening a window in the flexible insulating dielectric layer at the position where a hole needs to be drilled later, and then removing the flexible insulating dielectric layer at that position (resin plugging is used for hole filling in the next process), that is, removing the flexible insulating dielectric layer on the hole wall of the through hole to create the basic conditions for material consistency of the through hole; and because the flexible insulating dielectric layer needs to be windowed to match the drilling position, a single-sided flexible copper clad laminate cannot be used to process the flexible insulating dielectric layer.

[0053] In this embodiment, a window is opened in the flexible insulating dielectric layer, and then attached and pressed onto the copper layer 120. Compared with the conventional process, a reverse process is formed (the conventional process is to make a window pattern on the copper layer of the copper clad laminate), providing basic conditions for the subsequent further production of through holes.

[0054] See also Figure 3 Right now Figure 4 ; Figure 3 A schematic diagram of a cross-sectional structure of a flexible copper-clad tin-plated structure formed in accordance with an embodiment of the present invention; Figure 4 This is a schematic cross-sectional structural diagram of a pad support structure formed in accordance with an embodiment of the present invention.

[0055] Step S20:

[0056] A tin layer 210 is electroplated on the other side of the copper layer 120 of the flexible copper clad layer 10 to form a flexible copper clad tin plated structure 20 ; a pad 310 is taken, and one side of the tin layer 210 is adhered to the pad to form the pad support structure 30 .

[0057] The electroplated tin layer 210 is an electroplated tin process using a positive film pattern transfer process. Before tin plating, a dry film needs to be applied to the entire surface where the window groove 1110 is located, and a dry film pattern is made on the entire board to cover the entire surface, and a tin layer 210 is electroplated on the other side. The electroplated tin layer 210 can protect the copper layer and provide a transition layer for the processing of pasting the pad 310 and removing the pad 310 to prevent damage to the copper layer 120.

[0058] In this embodiment, the pad 310 is a phenolic resin pad, a wooden pad, an aluminum sheet or an epoxy resin pad; the tin layer is adhered to the pad 310 using an adhesive layer 320, and the adhesive layer 320 is a polypropylene adhesive layer or an epoxy resin adhesive layer.

[0059] The pad 310 plays a supporting role for the flexible board layer when subsequently making resin ink for the window groove and polishing and attaching the rigid-flexible insulating dielectric layer. Therefore, a pad with a certain hardness can be used. Generally, the pad is thicker than the flexible copper-clad tin-plated structure. It is worth mentioning that scrapped boards with a flat and smooth surface can be used as the pad 310, which effectively plays the role of waste recycling.

[0060] The adhesive layer 320 is used to not only effectively adhere the pad 310, but also because the tin grains of the tin layer 210 are relatively large, when the pad 310 is subsequently removed, the depth of the milling plate is easily caused to cause tin debris to get stuck in the milling cutter, affecting the milling accuracy. The adhesive layer can promote the discharge of tin debris and improve the milling processing effect.

[0061] See also Figure 5 ; Figure 5 Schematic diagram of the cross-sectional structure of the resin filling plate formed in accordance with an embodiment of the present invention.

[0062] Step S30:

[0063] A resin ink 410 is prepared in the window groove, and then baked, solidified and polished to form a resin filling plate 40 .

[0064] In this embodiment, the resin ink 410 is made into the window groove 1110 by silk-screening ink, and the resin ink 410 is silk-screened and filled into the window groove; the main component of the resin ink 410 is the same as the material of the rigid insulating medium layer of the rigid board layer.

[0065] As described above, in this embodiment, the flexible insulating dielectric layer at the position where drilling is required later is removed, and then a window groove 1110 is formed. Here, resin ink 410 is used to fill the window groove 1110, which is equivalent to replacing the flexible insulating dielectric layer at the position where drilling is required with resin ink 410, thereby improving the consistency of the material of the insulating dielectric layer on the hole wall of the through hole. In addition, in only one step, the main component of the resin ink 410 is the same as the material of the rigid insulating dielectric layer of the rigid board layer (for example, if the rigid insulating dielectric layer is an epoxy resin composite glass fiber material, then the main component of the resin ink 410 is an epoxy resin material), which can effectively ensure the consistency of the material of the insulating dielectric layer on the hole wall, and provide a good consistency basis condition for the subsequent copper plating process on the hole wall of the through hole.

[0066] After the resin ink 410 is filled, it needs to be baked and cured, and then polished. Since the pad 310 plays a supporting role, it can form a good baking, curing and polishing process, and at the same time play a restraining role, preventing the resin filling plate 40 from expanding and contracting excessively during baking, curing and polishing.

[0067] See also Figure 6 , Figure 6 Schematic diagram of the cross-sectional structure of a flexible core board formed according to an embodiment of the present invention.

[0068] Step S40:

[0069] A rigid-flex insulating dielectric layer 510 (not marked in the drawings) and a second copper layer 520 are sequentially attached to one side of the resin ink 410 of the resin filling board 40 , and the backing board 310 is removed to form a flexible core board 50 .

[0070] In this embodiment, the rigid-flexible insulating dielectric layer 510 is attached by attaching a rigid insulating dielectric layer 5110 to the rigid board area 10A and attaching a flexible insulating dielectric layer 5120 to the flexible board area 10B; the flexible insulating dielectric layer 5120 is pre-enlarged toward the rigid board area 10A, generally by 10 μm to 100 μm.

[0071] This processing method is a reverse process of the ordinary processing method. The ordinary processing method is to use a double-sided copper clad laminate to produce circuit patterns, while the processing method of this embodiment is to first make an opening window on the flexible insulating dielectric layer, and then attach the pressed copper layer 120 to form a single-sided flexible copper clad laminate with a window pattern on the flexible insulating dielectric layer. Here, the insulating dielectric layer and the second copper layer 520 are attached to the single-sided flexible copper clad laminate (after the resin ink 410 is produced), which is equivalent to forming a structural double-sided copper clad laminate.

[0072] Since it is necessary to ensure the rigidity of the rigid board area 10A, ensure the consistency of the insulating dielectric layer material of the through-hole wall, and ensure the flexibility of the flexible board area 10B, a rigid insulating dielectric layer 5110 is attached to the rigid board area 10A, and a flexible insulating dielectric layer 5120 is attached to the flexible board area 10B, thereby effectively adhering the second copper layer while ensuring the consistency of the materials.

[0073] The flexible insulating dielectric layer 5120 is pre-enlarged toward the rigid board area 10A, which can effectively ensure that when the layers of the subsequent rigid-flexible board are pressed together, the rigid board layer covers the flexible board layer, thereby preventing the flexible insulating dielectric layer 5120 of the flexible board layer from being delaminated.

[0074] In this embodiment, the step of removing the backing plate 310 is to use a controlled-depth milling method to mill from one side of the backing plate 310 to the tin layer 210 or the copper layer 120 .

[0075] The pad 310 is an auxiliary tool layer in the processing process. After the processing process is completed, the pad 310 no longer needs to be retained; since the copper layer 120 is covered with the tin layer 210, the depth control milling plate can use the tin layer 210 as a reference layer, that is, when the depth milling is controlled to the tin layer 210, the depth milling will no longer continue. The tin layer 210 can effectively protect the copper layer 120 and prevent the milling plate from damaging the copper layer 120.

[0076] When the copper layer 120 is thicker, the depth-controlled milling plate can also be milled vertically to the copper layer 120 so as to better observe the depth of the depth-controlled milling plate.

[0077] In this embodiment, after removing the backing plate 310, a tin stripping and copper reduction process is performed. Tin stripping is to use a chemical method to remove excess tin layer 210 to prevent the invisible tin layer 210 from being left untreated. If the selected copper layer 120 is a thick copper layer, a copper reduction process is also required after the tin stripping process to meet the required copper thickness standard.

[0078] See also Figure 7 , Figure 7 Schematic diagram of the cross-sectional structure of a multi-layer laminated board formed according to an embodiment of the present invention.

[0079] Step S50:

[0080] A first rigid board layer 610 is formed on the upper surface of the flexible core board 50 , and a second rigid board layer 620 is formed on the lower surface, to form a multi-layer laminate board 60 .

[0081] In one embodiment, the multi-layer laminate is formed by stacking a plurality of the flexible core boards 50, setting a rigid insulating medium layer 5110 in the rigid board area 10A between the layers of adjacent flexible core boards 50, and setting a flexible insulating medium layer 5120 in the flexible board area 10B between the layers of adjacent flexible core boards 50.

[0082] When the flexible board layer of the product is only a single-sided or double-sided flexible board, the flexible core board 50 is a single layer, and the first rigid board layer 610 and the second rigid board layer 620 are set and pressed together. When there are more than or equal to 3 layers of flexible boards and the flexible boards are layered structures, multiple flexible core boards 50 are required, which are stacked in sequence, and then the first rigid board layer 610 and the second rigid board layer 620 are set towards the outermost layer and pressed together.

[0083] In this embodiment, the flexible insulating dielectric layer 5120 is pre-enlarged toward the rigid board area 10A. The reason for the pre-enlargement is the same as the above-mentioned pre-enlargement.

[0084] See also Figure 8 , Figure 8 Schematic diagram of the cross-sectional structure of the via plate formed in accordance with an embodiment of the present invention.

[0085] Step S60:

[0086] Through holes are drilled in the area of ​​the multi-layer laminate 60 corresponding to the resin ink 410 and electroplated to form via holes 710 , thereby forming a via hole plate 70 as a whole.

[0087] See also Figure 9 , Figure 9 Schematic diagram of the cross-sectional structure of a filled via plate manufactured according to an embodiment of the present invention.

[0088] In this embodiment, the forming of the via plate 70 further includes: after the electroplating, the via holes 710 are sequentially plugged, baked and cured, and polished to form filled via holes 710A, and the entire plate is formed into the filled via plate 70A.

[0089] It can be seen that the position of the opening window processing of the flexible insulating dielectric layer 5120 and the position of the filling of the resin ink 410 correspond to the position of the through hole. The resin ink 410 replaces the flexible insulating dielectric layer 5120 of the corresponding layer, so that the insulating dielectric layer material of the hole wall has a consistent basis, so that the electroplated through hole processing does not require special parameter adjustment, process adjustment, time adjustment, etc., and the electroplating parameters of ordinary electroplated through holes can be used for processing, which effectively saves electroplating resources, reduces the treatment and discharge of wastewater and waste liquid, and the uniformity and flatness of the copper layer on the hole wall are also effectively improved.

[0090] It is worth noting that the single side of the area of ​​the resin ink 410 is larger than the aperture of the through hole, and is generally 20 μm to 100 μm larger depending on the space allowed.

[0091] Furthermore, the via holes can be plugged to improve the reliability of the via holes and enhance the signal transmission performance of the via holes.

[0092] See also Figure 10 , Figure 10 Schematic diagram of the cross-sectional structure of a rigid-flex board manufactured according to an embodiment of the present invention.

[0093] Step S70:

[0094] The via plate 70 is uncovered to form the rigid-flexible board 80 ; the uncovering process can be performed using a conventional rigid-flexible board uncovering process.

[0095] It can be seen that the key to this embodiment is to first realize the process of designing and producing the flexible insulating medium layer 5120 in which the resin ink 410 replaces the through-hole area of ​​the corresponding layer, and then realize the process of effectively producing the conductive hole 710, and realize the process of designing and producing the flexible core board 50 to form the rigid-flexible combination board 80. The overall process has the characteristics of continuity and coordination between the previous and next steps. The filling process of the resin ink 410 is designed according to the production requirements of the conductive hole 710, thereby forming the processing process of the overall rigid-flexible combination board 80.

[0096] It is worth noting that due to the actual design and processing of rigid-flex boards, the actual structural diagrams and the thickness of each layer, line width and other dimensions are all at the micron level. For example, the thickness of each layer is generally between 5μm and 50μm. If the drawings in the specification are made according to the actual proportion, there will be a problem of unclear drawings. Therefore, in order to more clearly show the implementation process of the manufacturing method, the drawings of this embodiment are all schematic diagrams that enlarge the technical features, which do not represent the size of the actual structural diagram, nor do they represent enlarged drawings of the actual structural diagram in proportion.

[0097] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's description and drawings, or direct / indirect applications in other related technical fields, within the scope of the present invention are included in the patent protection scope of the present invention.

Claims

1. A method for fabricating a rigid-flexible board for improving signal stability, wherein the rigid-flexible board has a planar structure comprising a rigid board area and a flexible board area, and a vertically stacked structure comprising a rigid board layer and a flexible board layer; It is characterized by: The production method comprises the following steps: S10: Take a flexible insulating dielectric layer, make an opening window, and form a window dielectric layer; Take a copper layer, and attach the window dielectric layer to one side of the copper layer to form a flexible copper clad layer, and the opening window forms a window groove; S20: electroplating a tin layer on the other side of the copper layer of the flexible copper clad layer to form a flexible copper clad tin plated structure, taking a backing plate, and adhering one side of the tin layer to the backing plate to form the backing plate support structure; S30: using a silk-screen printing ink method to fill the window slot with resin ink, and then performing baking, curing and polishing to form a resin-filled plate; The main component of the resin ink is the same as the material of the rigid insulating dielectric layer of the rigid board layer; S40: attaching a rigid-flexible insulating dielectric layer and a second copper layer to the resin ink side of the resin-filled board in sequence, removing the backing plate, and forming a flexible core board; S50: forming a first rigid board layer on the upper surface of the flexible core board and a second rigid board layer on the lower surface to form a multi-layer laminated board; S60: drilling through holes in the area of ​​the multilayer laminate corresponding to the resin ink, and performing electroplating, wherein the through holes form conductive vias, and the entire laminate is formed into a conductive via plate; S70: performing a cover-lifting process on the via plate to form the rigid-flexible board.

2. A method for manufacturing a rigid-flexible board for improving signal stability according to claim 1, characterized in that: The tin layer is adhered to the pad by using an adhesive layer, wherein the adhesive layer is a polypropylene adhesive layer or an epoxy resin adhesive layer.

3. The method for manufacturing a rigid-flex circuit board for improving signal stability according to claim 1, wherein: The attaching of the rigid-flexible insulating dielectric layer is to attach the rigid insulating dielectric layer to the rigid board area and to attach the flexible insulating dielectric layer to the flexible board area.

4. The method for manufacturing a rigid-flex circuit board for improving signal stability according to claim 1, wherein: The step of removing the backing plate is to use a depth-controlled milling method to mill from one side of the backing plate to the tin layer or the copper layer.

5. A method for manufacturing a rigid-flexible board for improving signal stability according to claim 1 or 4, characterized in that: After the backing plate is removed, tin stripping and copper reduction treatment are performed.

6. The method for manufacturing a rigid-flex circuit board for improving signal stability according to claim 1, wherein: The multi-layer laminate is formed by stacking a plurality of the flexible core boards; providing a rigid insulating dielectric layer to the rigid board area between adjacent layers of the flexible core board; A flexible insulating dielectric layer is provided to the flexible board area between adjacent layers of the flexible core board.

7. A method for manufacturing a rigid-flexible board for improving signal stability according to claim 3 or 6, characterized in that: The flexible insulating dielectric layer is pre-enlarged toward the rigid board area.

8. The method for manufacturing a rigid-flex circuit board for improving signal stability according to claim 1, wherein: The forming of the via plate further includes: after the electroplating, sequentially plugging, baking and curing, and polishing the via holes.

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