Manufacturing method of high-frequency multi-order HDI rigid-flex printed circuit board

Abstract

The invention discloses a manufacturing method of a high-frequency multi-order HDI rigid-flex board, and relates to the technical field of circuit board preparation, and the method comprises the following steps: S10, manufacturing a soft board layer sub-board and a high-frequency layer sub-board; s20, electric milling windowing is conducted on the multiple pieces of PP; s30, laminating and pressing the soft board layer daughter board, the high-frequency layer daughter board and the windowed PP to form a first composite board; s40, conducting and insulating integrated treatment is carried out on the first composite board; s50, manufacturing a copper foil signal layer daughter board, an outer layer daughter board, a soft board expansion layer daughter board and an FR4 rigid support layer daughter board, and forming deep control grooves for ventilation in PP and each daughter board waste area; s60, laminating the copper foil signal layer sub-board, the outer layer sub-board, the soft board expansion layer sub-board and the FR4 rigid support layer sub-board with the first composite board in sequence; and S70, sequentially carrying out construction of a high-density interconnection structure, surface functionalization treatment and depth-controlled milling uncovering on the mother board. The method has the beneficial effects that the product yield is improved, the production efficiency is optimized, and the labor cost is saved.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing technology, and more specifically, to a method for manufacturing a high-frequency multi-stage HDI rigid-flex board. Background Technology

[0002] Rigid-flex PCBs, as high-end electronic interconnect solutions, are widely used in aerospace, medical devices, mobile communications, and wearable electronics. Their structure combines the support of a rigid board with the flexibility of a flexible board, enabling three-dimensional assembly and improving system integration and reliability. However, as electronic products evolve towards higher frequencies, higher speeds, and higher densities, the manufacturing process of multi-stage high-density interconnect (HDI) rigid-flex PCBs is becoming increasingly complex, facing numerous technical challenges.

[0003] Currently, the industry-standard manufacturing process for multi-stage HDI rigid-flex boards encompasses sub-board preparation, PP (prepreg) processing, multiple laminations of the motherboard, and pattern transfer. Specifically, this process includes staged processing of the flexible and rigid sub-boards, multiple laminations, laser and mechanical drilling, electroplating for hole filling, resin plugging, circuit imaging, and surface treatment. However, this process suffers from the following significant problems: First, in the area where soft and hard are bonded, because the dielectric layer is thin and the gas is difficult to completely escape during the pressing process, delamination, plate bursting and whitening of the dielectric are likely to occur after high-temperature baking (such as 150℃×2 hours). Secondly, the hard-soft bonding area and the uncovered area are prone to height differences, which brings alignment and uniformity problems to subsequent pattern transfer, etching and surface treatment processes. Secondly, cleaning residual adhesive at the bottom of the metal blind channel relies on manual operation, which is not only inefficient and labor-intensive, but also increases labor costs. Therefore, the present invention provides a method for manufacturing a high-frequency multi-stage HDI rigid-flex plate, which can completely eliminate air in the medium during the pressing process, solve the problem of height difference in the soft and hard bonding area, and eliminate the need for manual removal of residual adhesive after the finished product is unsealed, thereby improving product yield, optimizing production efficiency and saving labor costs. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a method for manufacturing a high-frequency multi-stage HDI rigid-flex plate, which can completely eliminate air in the medium during the pressing process, solve the problem of height difference in the soft and hard bonding area, and eliminate the need for manual removal of residual adhesive after the finished product is unsealed, thereby improving product yield, optimizing production efficiency, and saving labor costs.

[0005] The technical solution adopted by this invention to solve its technical problem is: a method for manufacturing a high-frequency multi-stage HDI rigid-flex plate, wherein the improvement is that the method for manufacturing the high-frequency multi-stage HDI rigid-flex plate includes the following steps: S10, for manufacturing flexible PCB layer boards and high-frequency layer boards; S20, perform electric milling to open windows on multiple PP sheets, so that the opening range between adjacent PP sheets is distributed in a stepped manner; S30, the flexible board, the high-frequency board and the PP after the window are opened are stacked and pressed to form the first composite board; S40, the first composite plate is subjected to integrated conductive and insulating treatment; S50 is used to manufacture copper foil signal layer sub-boards, outer layer sub-boards, flexible board extension layer boards, and FR4 rigid support layer boards, and depth control grooves are opened in the PP and each sub-board waste area for ventilation. S60, the copper foil signal layer sub-board, outer layer sub-board, flexible board extension layer sub-board and FR4 rigid support layer sub-board are sequentially pressed with the first composite board to obtain the master board of all laminations; S70, the motherboard is sequentially constructed with a high-density interconnect structure, surface functionalized, and controlled-depth milling and uncovering to obtain a high-frequency multi-stage HDI rigid-flex board.

[0006] Furthermore, in step S10, the specific manufacturing steps of the flexible PCB layer include: Cutting: The flexible circuit board core consisting of 0.25μm PI and 18μm copper thickness is cut into layers L05-06, L07-08 and L09-10. Baking plate: High-temperature baking is applied to layers L05-06, L07-08, and L09-10 to dry the moisture molecules in the copper coating; Drilling: Drill holes in layer L07-08; Hole metallization: Copper plating is applied to drilled holes to make them conductive on both sides; Flexible circuit board layer fabrication: Dry film is successively applied to layers L05-06, L07-08 and L09-10, the required circuit area is cured by film alignment and UV exposure, the unexposed dry film is dissolved, the bare copper layer is etched and the film is removed, so as to expose the inner layer circuit pattern on the upper layer of the flexible circuit board. AOI processing: Using an Eagle Eye AOI machine to scan, identify and process open and short circuit sections with defects in the inner layer circuit diagram; Browning: Browning treatment is performed on layers L05-06, L07-08, and L09-10; Applying and pressing the cover film: The cover film, which is composed of PI with a thickness of 25μm and adhesive with a thickness of 25μm, is applied to both sides of layers L05-06, L07-08 and L09-10, and the cover film is pressed to each flexible board core using a high-speed press. Apply high-temperature tape: Apply high-temperature tape to the outside of the cover film on the top surface of layer L05-06 and the bottom surface of layer L09-10; Measurement of expansion and contraction: The expansion and contraction coefficient of the flexible board sub-board is measured.

[0007] Furthermore, the high-frequency layer sub-board is manufactured as follows: Material preparation: Cut Rogers RO4350B high-frequency board to the design size to obtain layers L03-04 and L11-L12; Baking plate: High-temperature baking is used to dry the water vapor molecules in layers L03-04 and L11-L12. High-frequency layer circuit fabrication: Based on the expansion and contraction coefficient of the flexible circuit board, the process involves attaching dry film to layers L03-04 and L11-L12, aligning the film and curing the required circuit area with UV exposure, dissolving the unexposed dry film, etching the exposed copper layer, and removing the film to expose the high-frequency layer circuit pattern on top of the high-frequency layer.

[0008] Furthermore, in step S20, during the process of milling and opening windows on multiple PP sheets, the PP sheets between the high-frequency layer sub-board and the flexible board sub-board are milled and opened using three different milling and opening files, and the PP sheets between adjacent flexible board cores are milled and opened using two different milling and opening files.

[0009] Furthermore, in step S40, the specific steps for performing integrated conductivity and insulation treatment on the first composite board include: Drilling: Through holes in layers L03-L12 are drilled using mechanical drilling, and blind holes in layers L03-04 are drilled using laser drilling. Hole metallization: The walls of blind holes and through holes are plated with copper and VCP to form a conductive layer. Resin plugging: Fill the through holes with resin ink to ensure insulation; Copper plating: A layer of copper with a thickness greater than 12μm is plated onto the resin ink.

[0010] Furthermore, in step S50, the copper foil signal layer sub-board includes layers L02 and L13, and the outer layer sub-board includes layers L01 and L14. Layers L02, L13, L01, and L14 are all copper foil layers. Before the copper foil layers are laminated with the first composite board, copper foil signal layer circuit fabrication, copper foil signal layer AOI processing, outer layer circuit fabrication, and outer layer AOI processing are performed sequentially. Two PP sheets are embedded between layers L01 and L02, between layers L02 and L03, between layers L12 and L13, and between layers L13 and L14.

[0011] Furthermore, the fabrication steps of the flexible printed circuit board extension layer include: Cutting: The flexible circuit board core consisting of 0.25μm PI and 18μm copper thickness is cut out using a cutting machine to form L15-16 and L17-18 layers. Baking plate: High-temperature baking of layers L15-16 and L17-18 to dry out the moisture molecules in the copper coating; Fabrication of extended layer circuitry on flexible circuit boards: Dry film is applied to layers L15-16 and L17-18 in sequence, the required circuitry area is cured by film alignment and UV exposure, the unexposed dry film is dissolved, the bare copper layer is etched, and the film is removed to expose the inner layer circuitry pattern on the upper layer of the flexible circuit board. AOI processing: Using an Eagle Eye AOI machine to scan, identify and process open and short circuit sections with defects in the inner layer circuit diagram; Browning: Browning treatment is applied to layers L15-16 and L17-18; Applying and pressing the cover film: The cover film, which is composed of PI with a thickness of 25μm and adhesive with a thickness of 25μm, is applied to both sides of the L15-16 and L17-18 layers, and the cover film is pressed to each flexible board core using a high-speed press. Apply high-temperature tape: Apply high-temperature tape to the outside of the cover film on the top surface of layer L15-16 and the bottom surface of layer L17-18; Measurement of expansion and contraction: The expansion and contraction coefficient of the flexible board extension layer is measured.

[0012] Furthermore, the FR4 rigid support layer sub-board includes layers L19-20, and the specific manufacturing steps of layers L19-20 include: Material preparation: Cut out FR4 substrates with a thickness of 0.2mm, and coat both sides of the FR4 substrate with copper with a thickness of 35μm; Fabrication of FR4 rigid support layer circuitry: The process involves attaching dry film onto layers L19-20, aligning the circuitry area with a film and curing it with UV exposure, dissolving the unexposed dry film, etching the exposed copper layer, and removing the film to expose the inner layer circuitry pattern on the upper layer of the FR4 rigid support layer sub-board. AOI processing: Using an Eagle Eye AOI machine to scan, identify and process open and short circuit sections with defects in the inner layer circuit diagram; Browning: Browning treatment is performed on layers L19-20.

[0013] Furthermore, in step S50, the dimensions of the depth control groove are 2.0mm*2.5mm.

[0014] Furthermore, in step S70, the specific method for constructing the high-density interconnect structure of the motherboard is as follows: mechanical drilling, hole metallization, electroplating to fill the holes, and resin plugging are performed on the motherboard in sequence.

[0015] Furthermore, the specific method for surface functionalization of the motherboard is as follows: the motherboard is sequentially processed with outer layer circuitry, solder mask printing, character printing, and immersion gold plating.

[0016] Furthermore, the specific method for controlling the depth of the motherboard to remove the cover is as follows: use four different milling files to control the depth of the motherboard to separate the unwanted media from the motherboard and remove the unwanted media.

[0017] The beneficial effects of this invention are as follows: The stepped distribution of the opening range between adjacent PP panels ensures uniform glue overflow in the hard-soft bonding area between the flexible board layer and the high-frequency layer after lamination, thus solving the problem of height difference between the hard-soft bonding area and the uncovering area. Furthermore, the different PP openings also ensure uniform PP glue overflow after blind groove uncovering, eliminating the need for manual cleaning of residual PP glue at the bottom. By creating controlled-depth ventilation grooves in the PP and each sub-board waste area, the quality problem of preventing bulging and delamination in the hard-soft bonding area during lamination venting and baking after drilling is improved. Therefore, this invention can completely eliminate air from the medium during lamination, solving the height difference problem in the hard-soft bonding area, and eliminating the need for manual cleaning of residual glue after the finished product is uncovered, thereby improving product yield, optimizing production efficiency, and saving labor costs. Attached Figure Description

[0018] Figure 1 This is an overall flowchart of a method for manufacturing a high-frequency multi-stage HDI rigid-flex plate according to the present invention. Figure 2 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 1 ; Figure 3 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 2 ; Figure 4 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 3 ; Figure 5 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 4 ; Figure 6 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 5 ; Figure 7 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 6 ; Figure 8 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 7 ; Figure 9 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 8 ; Figure 10 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 9 ; Figure 11 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 10 ; Figure 12 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 10 one; Figure 13 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 10 two; Figure 14 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 10 three; Figure 15 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 10 Four; Figure 16 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 10 five; Figure 17 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 10 six; Figure 18 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 10 seven; Figure 19 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 10 eight; Figure 20 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 10 Nine; Figure 21 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 2 ten; Figure 22 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 2 eleven; Figure 23 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 2 twelve; Figure 24 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 2 Thirteen; Figure 25 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 2 fourteen; Figure 26 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 2 fifteen; Figure 27 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 2 sixteen; Figure 28 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 2 Seventeen; Figure 29 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 2 eighteen; Figure 30 The manufacturing steps of a high-frequency multi-stage HDI rigid-flex plate according to the present invention are as follows: Figure 2 nineteen. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] The following will clearly and completely describe the concept, specific structure, and technical effects of the present invention in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. Furthermore, all connections / linkages involved in the patent do not simply refer to direct contact between components, but rather to the ability to form a better connection structure by adding or reducing connecting accessories according to specific implementation conditions. The various technical features in this invention can be combined interactively without contradicting each other.

[0021] Reference Figure 1 As shown, this invention discloses a method for manufacturing a high-frequency multi-stage HDI rigid-flex plate, which includes the following steps: S10, for manufacturing flexible PCB layer boards and high-frequency layer boards; The specific manufacturing steps for the flexible PCB sub-board include: Cutting materials: such as Figure 2 As shown, a cutting machine is used to cut out flexible circuit board core layers L05-06, L07-08, and L09-10, which consist of 0.25μm thick PI and 18μm thick copper. Baking plate: High-temperature baking is applied to layers L05-06, L07-08, and L09-10 to dry the moisture molecules in the copper coating; Drilling: such as Figure 3 As shown, drilling is performed on layer L07-08; Hole metallization: such as Figure 4 As shown, the drilled hole is copper-plated to make it conductive on both sides; Flexible circuit board fabrication: such as Figure 5 As shown, the process involves attaching dry film to layers L05-06, L07-08, and L09-10, aligning the film, curing the desired circuit area using UV exposure, dissolving the unexposed dry film, etching the exposed copper layer, and stripping the film to expose the inner layer circuit pattern on the upper layer of the flexible circuit board. Specifically, under the temperature and pressure conditions suitable for circuit fabrication, dry film is first attached to the surface of the flexible circuit board, aligned with film, and then exposed to UV light in an exposure machine to cause the unmasked dry film to react, forming the desired circuit pattern on the surface of the flexible circuit board. Then, in the developing section, the film that was not exposed to light is dissolved by the developing solution. In the etching section, the exposed copper is etched away by the acidic etching solution. Finally, in the stripping section, the film is removed by the stripping solution, exposing the upper layer circuit pattern of the flexible circuit board. AOI processing: Using an Eagle Eye AOI machine to scan, identify and process open and short circuit sections with defects in the inner layer circuit diagram; Browning: Browning treatment is performed on layers L05-06, L07-08, and L09-10; Apply and press the cover film: such as Figure 6 and Figure 7 As shown, a cover film composed of PI with a thickness of 25μm and adhesive with a thickness of 25μm is attached to both sides of layers L05-06, L07-08 and L09-10, and a high-speed press is used to press the cover film to each flexible board core. Apply high-temperature tape: such as Figure 8 As shown, high-temperature adhesive tape is attached to the outside of the cover film on the top surface of layer L05-06 and the bottom surface of layer L09-10; Measurement of expansion and contraction: The expansion and contraction coefficient of the flexible PCB sub-board is measured; Furthermore, such as Figure 9 As shown, the high-frequency layer sub-board is manufactured as follows: Material preparation: Cut Rogers RO4350B high-frequency board to the design size to obtain layers L03-04 and L11-L12; Baking plate: High-temperature baking is used to dry the water vapor molecules in layers L03-04 and L11-L12. High-frequency layer circuit fabrication: Based on the expansion and contraction coefficient of the flexible circuit board layer, the process involves successively attaching dry film to layers L03-04 and L11-L12, aligning the film and curing the required circuit area using UV exposure, dissolving the unexposed dry film, etching the exposed copper layer, and removing the film to expose the high-frequency layer circuit pattern on top of the high-frequency layer. It should be noted that the principle of high-frequency layer circuit fabrication is the same as that of flexible circuit board layer circuit fabrication, and will not be elaborated here. S20, perform electric milling to open windows on multiple PPs, so that the opening range between adjacent PPs is distributed in a stepped manner; specifically, in the process of electric milling to open windows on multiple PPs, the PPs between the high-frequency layer sub-board and the flexible board layer board are milled using three different electric milling window files, and the PPs between adjacent flexible board cores are milled using two different electric milling window files. It should be noted that, in this embodiment, as Figure 10-12 As shown, during the process of opening windows in PP by electric milling, non-flowing PP (TG170) and a sheet of low-flowing PP (TG170-45%) need to be selected. Specifically, during lamination, non-flowing PP (TG170) can maintain shape stability, acting like a wall to constrain the boundary of overflowing glue and prevent the glue from flowing randomly to unwanted areas. Low-flowing PP (TG170-45%) can soften and flow fully, filling the tiny gaps and depressions between layers, ensuring no voids, thereby enhancing interlayer bonding and preventing delamination, thus resolving the contradiction between overflowing glue and delamination. It should also be noted that during the windowing process between the high-frequency layer sub-board and the flexible sub-board, the first PP sheet is milled 3-5mm more inward than the second PP sheet, and the second PP sheet is milled 2-3mm more inward than the third PP sheet. Furthermore, two of the PP sheets retain one-third of the area of ​​the rigid-flex PCB bonding area. The first PP sheet is closer to the flexible sub-board, and the third PP sheet is closer to the high-frequency layer sub-board. During the windowing process between adjacent flexible sub-boards, the first PP sheet is milled 5-8mm more inward than the second PP sheet. The first PP sheet is closer to the top surface of layers L07-L08 and L09-L10. S30, the flexible PCB layer, the high-frequency PCB layer, and the windowed PP are laminated and pressed together to form the first composite board; it should be noted that, as Figure 13 As shown, after the pressing is completed, the process edges of the first composite plate need to be treated with degreasing adhesive milling. S40, perform integrated conductivity and insulation treatment on the first composite board; specifically, refer to... Figure 14-17 As shown, the specific steps for performing integrated conductivity and insulation treatment on the first composite board include: Drilling: such as Figure 14 As shown, through holes in layers L03-L12 are drilled using mechanical drilling, and blind holes in layers L03-04 are drilled using laser drilling. Hole metallization: such as Figure 15 As shown, copper plating and VCP filling electroplating are performed on the walls of blind holes and through holes to form a conductive layer in the substrate area in the middle of the first composite board, so that the L03 layer to L12 layer are conductive; wherein, the copper layer produced by copper plating is between 2-5μm, and the thickened copper layer produced by VCP filling electroplating is between 25-35μm. Resin plugging: such as Figure 16 As shown, resin ink is used to fill the through holes to ensure insulation; Copper plating: such as Figure 17 As shown, a copper coating with a thickness greater than 12μm is plated onto the resin ink; S50 is used to fabricate copper foil signal layer sub-boards, outer layer sub-boards, flexible board extension layer sub-boards, and FR4 rigid support layer sub-boards. Depth control grooves with dimensions of 2.0mm x 2.5mm are created in the PP and waste areas of each sub-board. Figure 25 As shown; Among them, reference Figure 18-19 As shown, the copper foil signal layer sub-board includes layers L02 and L13, as referenced. Figure 20-21 As shown, the outer sub-board includes layers L01 and L14. Layers L02, L13, L01, and L14 are all copper foil layers. Before the copper foil layers are laminated with the first composite board, copper foil signal layer circuit fabrication, copper foil signal layer AOI processing, outer layer circuit fabrication, and outer layer AOI processing are performed sequentially. Furthermore, two PP sheets are embedded between layers L01 and L02, between layers L02 and L03, between layers L12 and L13, and between layers L13 and L14. Reference Figure 22 As shown, the fabrication steps of the flexible printed circuit board extension layer sub-board include: Cutting: The flexible circuit board core consisting of 0.25μm PI and 18μm copper thickness is cut out using a cutting machine to form L15-16 and L17-18 layers. Baking plate: High-temperature baking of layers L15-16 and L17-18 to dry out the moisture molecules in the copper coating; Fabrication of extended layer circuitry on flexible circuit boards: Dry film is applied to layers L15-16 and L17-18 in sequence, the required circuitry area is cured by film alignment and UV exposure, the unexposed dry film is dissolved, the bare copper layer is etched, and the film is removed to expose the inner layer circuitry pattern on the upper layer of the flexible circuit board. AOI processing: Using an Eagle Eye AOI machine to scan, identify and process open and short circuit sections with defects in the inner layer circuit diagram; Browning: Browning treatment is applied to layers L15-16 and L17-18; Applying and pressing the cover film: The cover film, which is composed of PI with a thickness of 25μm and adhesive with a thickness of 25μm, is applied to both sides of the L15-16 and L17-18 layers, and the cover film is pressed to each flexible board core using a high-speed press. Apply high-temperature tape: Apply high-temperature tape to the outside of the cover film on the top surface of layer L15-16 and the bottom surface of layer L17-18; Measurement of expansion and contraction: The expansion and contraction coefficient of the flexible board extended layer is measured; Reference Figure 23 As shown, the FR4 rigid support sub-plate includes layers L19-20, and the specific manufacturing steps of layers L19-20 include: Material preparation: Cut out FR4 substrates with a thickness of 0.2mm, and coat both sides of the FR4 substrate with copper with a thickness of 35μm; Fabrication of the FR4 rigid support layer circuitry: The process involves attaching a dry film onto layers L19-20, aligning the circuitry area using a film and curing it with UV exposure, dissolving the unexposed dry film, etching the exposed copper layer, and removing the film to expose the inner layer circuitry pattern on the upper layer of the FR4 rigid support layer sub-board. It should be noted that the principle of fabricating the FR4 rigid support layer circuitry is the same as that of fabricating flexible circuitry layers, and will not be elaborated here. AOI processing: Using an Eagle Eye AOI machine to scan, identify and process open and short circuit sections with defects in the inner layer circuit diagram; Browning: Browning treatment is applied to layers L19-20; S60, the copper foil signal layer sub-board, outer layer sub-board, flexible board extension layer board, and FR4 rigid support layer board are sequentially laminated with the first composite board to obtain the fully laminated mother board; such as Figure 24 As shown; S70 involves sequentially constructing a high-density interconnect structure, performing surface functionalization, and controlling-depth milling to uncover the motherboard, resulting in a high-frequency, multi-stage HDI rigid-flex board; specifically, such as... Figure 26-28As shown, the specific method for constructing the high-density interconnect structure of the motherboard is as follows: mechanical drilling, hole metallization, electroplating filling, and resin plugging are performed sequentially on the motherboard; the specific method for surface functionalization of the motherboard is as follows: outer layer circuit fabrication, solder mask printing, character printing, and immersion gold are performed sequentially on the motherboard; the specific method for controlled-depth milling and uncovering of the motherboard is as follows: controlled-depth milling is performed on the motherboard using four different milling files to separate the unwanted media from the motherboard and remove the unwanted media; specifically, in this embodiment, controlled-depth milling is performed on the motherboard using four controlled-depth milling files, wherein the first file mechanically controls the depth from the L01 layer to the L05 layer high-temperature tape, the second file controls the depth from the L01 layer to the L16 layer high-temperature tape, the third file mechanically controls the depth from the L20 layer to the L18 layer high-temperature tape, and the fourth file mechanically controls the depth from the L20 layer to the L10 layer high-temperature tape, thereby completing the controlled-depth milling and separating the unwanted media and the unwanted high-temperature tape through controlled-depth milling; It should be noted that, in this embodiment, as Figures 29-30 As shown, after the high-frequency multi-stage HDI rigid-flex board is manufactured, it also needs to undergo laser cutting (using a high-precision laser to cut a large panel into individual small boards with the final design required shape), cleaning (removing dust, oil, chemical ions and other contaminants remaining on the board surface from all previous processes), flight testing (performing electrical performance tests on all network circuits on the board surface), product inspection (conducting a comprehensive inspection of the board surface to check whether the solder mask is intact, whether the characters are clear, whether there are scratches on the gold surface, whether the pads are oxidized, and whether there are defects in the uncovered area), glue application (applying special epoxy resin glue dots at the soft and hard joints of the board surface using precision glue application equipment to improve the bending life of the board surface and prevent cracking), FQC (verifying test data, checking glue application position and quality, confirming product identification, etc.), and packaging and warehousing (sealing with anti-static bags and vacuum moisture-proof packaging, adding desiccant to prevent oxidation and moisture, affixing labels to the packaging, and sending it to a temperature and humidity constant warehouse to await shipment).

[0022] It should be noted that, in this embodiment, the manufacturing method of the high-frequency multi-stage HDI rigid-flex board uses a stepped distribution of the opening range between adjacent PPs to ensure uniform glue overflow in the rigid-flex bonding area between the flexible board layer and the high-frequency layer after lamination. This solves the problem of height difference between the rigid-flex bonding area and the uncovering area. Furthermore, different PP openings can also achieve uniform PP glue overflow after blind groove uncovering, eliminating the need for manual cleaning of residual PP glue at the bottom. By opening depth-controlled grooves for ventilation in the PP and each sub-board waste area, the quality problem of preventing bulging and delamination in the rigid-flex bonding area during lamination venting and baking after drilling is improved. Therefore, this invention can completely eliminate air from the medium during the lamination process, solve the height difference problem in the rigid-flex bonding area, and eliminate the need for manual cleaning of residual glue, thereby improving product yield, optimizing production efficiency, and saving labor costs.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The PP used between the soft board layer and the high-frequency board layer in layers L05 and L04, layers L10 and L11, and layers L14 and L15 is designed with different sizes of openings through special electric milling, so that the glue overflow in the soft and hard bonding area is uniform after pressing, thus solving the problem of height difference in the soft and hard bonding area. 2. In the design of PP electric milling, (1-2 pieces of 5*5mm PP blocks are retained in the peeling area between the soft board layer and the high frequency layer and are stuck to the high temperature tape after pressing) to keep the high temperature adhesive and the high frequency layer to reduce gaps and solve problems such as bulging and chemical injection in the peeling area during subsequent processing. 3. Before lamination, a depth control groove is opened in the waste area of ​​the sub-board layer and PP layer in the soft and hard bonding uncovering area to prevent residual chemicals in the depth control groove. The high-temperature adhesive bonding area cannot exceed the uncovering area, which can improve the quality problem of no bulging and delamination in the soft and hard bonding area of ​​the motherboard during lamination venting and baking after drilling. At the same time, it avoids the risk of chemicals seeping into the electroplating. In the subsequent process, the quality problem of delamination caused by bulging is also improved in the character baking. 4. Different PP window openings ensure uniform PP glue overflow after blind slot cover removal, eliminating the need for manual cleaning of PP residue at the bottom. This improves the yield of IC gold plating and signal transmission efficiency at the bottom of the blind slot, while ensuring the quality and reliability of the blind slot. This significantly enhances product reliability and can increase the yield of multi-branch structure products on multi-stage rigid-wound PCBs to 90-98%.

[0024] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A method for manufacturing a high-frequency multi-stage HDI rigid-flex plate, characterized in that, The method for manufacturing the high-frequency multi-stage HDI rigid-flex plate includes the following steps: S10, for manufacturing flexible PCB layer boards and high-frequency layer boards; S20, perform electric milling to open windows on multiple PP sheets, so that the opening range between adjacent PP sheets is distributed in a stepped manner; S30, the flexible board, the high-frequency board and the PP after the window are opened are stacked and pressed to form the first composite board; S40, the first composite plate is subjected to integrated conductive and insulating treatment; S50 is used to manufacture copper foil signal layer sub-boards, outer layer sub-boards, flexible board extension layer boards, and FR4 rigid support layer boards, and depth control grooves are opened in the PP and each sub-board waste area for ventilation. S60, the copper foil signal layer sub-board, outer layer sub-board, flexible board extension layer sub-board and FR4 rigid support layer sub-board are sequentially pressed with the first composite board to obtain the master board of all laminations; S70, the motherboard is sequentially constructed with a high-density interconnect structure, surface functionalized, and controlled-depth milling and uncovering to obtain a high-frequency multi-stage HDI rigid-flex board.

2. The method for manufacturing a high-frequency multi-stage HDI rigid-flex plate according to claim 1, characterized in that, In step S10, the specific manufacturing steps of the flexible PCB layer include: Cutting: The flexible circuit board core consisting of 0.25μm PI and 18μm copper thickness is cut into layers L05-06, L07-08 and L09-10. Baking plate: High-temperature baking is applied to layers L05-06, L07-08, and L09-10 to dry the moisture molecules in the copper coating; Drilling: Drill holes in layer L07-08; Hole metallization: Copper plating is applied to drilled holes to make them conductive on both sides; Flexible circuit board layer fabrication: Dry film is successively applied to layers L05-06, L07-08 and L09-10, the required circuit area is cured by film alignment and UV exposure, the unexposed dry film is dissolved, the bare copper layer is etched and the film is removed, so as to expose the inner layer circuit pattern on the upper layer of the flexible circuit board. AOI processing: Using an Eagle Eye AOI machine to scan, identify and process open and short circuit sections with defects in the inner layer circuit diagram; Browning: Browning treatment is performed on layers L05-06, L07-08, and L09-10; Applying and pressing the cover film: The cover film, which is composed of PI with a thickness of 25μm and adhesive with a thickness of 25μm, is applied to both sides of layers L05-06, L07-08 and L09-10, and the cover film is pressed to each flexible board core using a high-speed press. Apply high-temperature tape: Apply high-temperature tape to the outside of the cover film on the top surface of layer L05-06 and the bottom surface of layer L09-10; Measurement of expansion and contraction: The expansion and contraction coefficient of the flexible board sub-board is measured.

3. The method for manufacturing a high-frequency multi-stage HDI rigid-flex plate according to claim 2, characterized in that, The high-frequency layer sub-board is manufactured as follows: Material preparation: Cut Rogers RO4350B high-frequency board to the design size to obtain layers L03-04 and L11-L12; Baking plate: High-temperature baking is used to dry the water vapor molecules in layers L03-04 and L11-L12. High-frequency layer circuit fabrication: Based on the expansion and contraction coefficient of the flexible circuit board, the process involves attaching dry film to layers L03-04 and L11-L12, aligning the film and curing the required circuit area with UV exposure, dissolving the unexposed dry film, etching the exposed copper layer, and removing the film to expose the high-frequency layer circuit pattern on top of the high-frequency layer.

4. The method for manufacturing a high-frequency multi-stage HDI rigid-flex plate according to claim 1, characterized in that, In step S20, during the process of milling and opening windows on multiple PP sheets, the PP sheets between the high-frequency layer sub-board and the flexible board sub-board are milled and opened using three different milling and opening files, and the PP sheets between adjacent flexible board cores are milled and opened using two different milling and opening files.

5. The method for manufacturing a high-frequency multi-stage HDI rigid-flex plate according to claim 3, characterized in that, In step S40, the specific steps for performing integrated conductivity and insulation treatment on the first composite board include: Drilling: Through holes in layers L03-L12 are drilled using mechanical drilling, and blind holes in layers L03-04 are drilled using laser drilling. Hole metallization: The walls of blind holes and through holes are plated with copper and VCP to form a conductive layer. Resin plugging: Fill the through holes with resin ink to ensure insulation; Copper plating: A layer of copper with a thickness greater than 12μm is plated onto the resin ink.

6. The method for manufacturing a high-frequency multi-stage HDI rigid-flex plate according to claim 5, characterized in that, In step S50, the copper foil signal layer sub-board includes layers L02 and L13, and the outer layer sub-board includes layers L01 and L14. Layers L02, L13, L01, and L14 are all copper foil layers. Before the copper foil layers are laminated with the first composite board, copper foil signal layer circuit fabrication, copper foil signal layer AOI processing, outer layer circuit fabrication, and outer layer AOI processing are performed sequentially. Two PP sheets are embedded between layers L01 and L02, between layers L02 and L03, between layers L12 and L13, and between layers L13 and L14.

7. The method for manufacturing a high-frequency multi-stage HDI rigid-flex plate according to claim 6, characterized in that, The fabrication steps of the flexible printed circuit board extension layer include: Cutting: The flexible circuit board core consisting of 0.25μm PI and 18μm copper thickness is cut out using a cutting machine to form L15-16 and L17-18 layers. Baking plate: High-temperature baking of layers L15-16 and L17-18 to dry out the moisture molecules in the copper coating; Fabrication of extended layer circuitry on flexible circuit boards: Dry film is applied to layers L15-16 and L17-18 in sequence, the required circuitry area is cured by film alignment and UV exposure, the unexposed dry film is dissolved, the bare copper layer is etched, and the film is removed to expose the inner layer circuitry pattern on the upper layer of the flexible circuit board. AOI processing: Using an Eagle Eye AOI machine to scan, identify and process open and short circuit sections with defects in the inner layer circuit diagram; Browning: Browning treatment is applied to layers L15-16 and L17-18; Applying and pressing the cover film: The cover film, which is composed of PI with a thickness of 25μm and adhesive with a thickness of 25μm, is applied to both sides of the L15-16 and L17-18 layers, and the cover film is pressed to each flexible board core using a high-speed press. Apply high-temperature tape: Apply high-temperature tape to the outside of the cover film on the top surface of layer L15-16 and the bottom surface of layer L17-18; Measurement of expansion and contraction: The expansion and contraction coefficient of the flexible board extension layer is measured.

8. The method for manufacturing a high-frequency multi-stage HDI rigid-flex plate according to claim 7, characterized in that, The FR4 rigid support sub-board includes layers L19-20, and the specific manufacturing steps for layers L19-20 include: Material preparation: Cut out FR4 substrates with a thickness of 0.2mm, and coat both sides of the FR4 substrate with copper with a thickness of 35μm; Fabrication of FR4 rigid support layer circuitry: The process involves attaching dry film onto layers L19-20, aligning the circuitry area with a film and curing it with UV exposure, dissolving the unexposed dry film, etching the exposed copper layer, and removing the film to expose the inner layer circuitry pattern on the upper layer of the FR4 rigid support layer sub-board. AOI processing: Using an Eagle Eye AOI machine to scan, identify and process open and short circuit sections with defects in the inner layer circuit diagram; Browning: Browning treatment is performed on layers L19-20.

9. The method for manufacturing a high-frequency multi-stage HDI rigid-flex plate according to claim 1, characterized in that... In step S50, the dimensions of the depth control groove are 2.0mm*2.5mm.

10. The method for manufacturing a high-frequency multi-stage HDI rigid-flex plate according to claim 1, characterized in that, In step S70, the specific method for constructing the high-density interconnect structure of the motherboard is as follows: mechanical drilling, hole metallization, electroplating to fill the holes, and resin plugging are performed on the motherboard in sequence.

11. The method for manufacturing a high-frequency multi-stage HDI rigid-flex plate according to claim 1, characterized in that, The specific method for surface functionalization of the motherboard is as follows: the motherboard is sequentially processed with outer layer circuitry, solder mask printing, character printing, and immersion gold plating.

12. The method for manufacturing a high-frequency multi-stage HDI rigid-flex plate according to claim 1, characterized in that, The specific method for controlling the depth of the motherboard to remove the cover is as follows: use four different milling files to control the depth of the motherboard to separate the unwanted media from the motherboard and remove the unwanted media.

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