A manufacturing method of an ultra-thin planar transformer coil thick copper PCB

Abstract

The present application belongs to the technical field of ultra-thin planar transformer, and particularly relates to a manufacturing method of an ultra-thin planar transformer coil thick copper PCB, which comprises the following steps: base material pretreatment, selecting an epoxy resin PP filled copper-clad plate as a base material, performing inner layer pattern and micro-etching treatment on the surface of the base material to remove the oxide layer and form a rough surface; polishing the edge of the base material to remove burrs and optimize the flatness of the base material; steel mesh printing, adopting a nano steel mesh vacuum printing process to print the area other than the coil copper layer pattern on the surface of the pretreated base material. By dividing the 2N layer PCB into two N layer units for manufacturing, the flatness of the base material is improved by polishing the ceramic, the alignment error between layers is reduced, and the manufacturing difficulty is reduced; the vacuum glue filling process reduces the air bubbles between layers, and the multi-layer thick copper PCB can realize more ultra-thin design under the premise of not affecting the performance, thereby meeting the requirements of customers on the thick copper ultra-thin design of special products.

Description

Technical Field

[0001] This invention belongs to the field of planar transformer technology, specifically a method for manufacturing a thick copper PCB for an ultra-thin planar transformer coil. Background Technology

[0002] With the surge in demand for high-power-density planar transformers in fields such as new energy vehicles, 5G base stations, and ultra-thin power adapters, the need for multilayer integration of ultra-thin thick copper PCBs (copper layer thickness 80-120μm, overall thickness ≤0.5mm / single layer) for coils is becoming increasingly urgent. Currently, the fabrication of multilayer ultra-thin thick copper PCBs mostly adopts a "one-time lamination molding" process, which involves directly laminating 2N layers (N is a positive integer and N≤6) or even more of substrate with adhesive film and then pressing them together to achieve multilayer integration of coils.

[0003] However, this process has significant bottlenecks: On the one hand, the manufacturing difficulty of 2N-layer PCBs is much higher than that of two N-layer PCBs. When 2N-layer substrates are stacked, the interlayer alignment accuracy requirements become more stringent with the number of layers (≤±0.05mm). The traditional PP thick copper filling method is prone to deformation of the original copper pits at high temperatures. As the number of stacked layers doubles, the cumulative error increases non-linearly, resulting in coil pattern misalignment and a finished product yield of less than 70%. At the same time, 2N-layer lamination requires higher temperatures (≥190℃) and pressures (≥2.5MPa), which are more than 30% higher than the lamination parameters of N-layers. This not only easily leads to substrate warping and a doubled risk of copper layer detachment, but also requires dedicated high-precision lamination equipment. The equipment investment cost is more than 40% higher than that of N-layer PCB manufacturing, and the difficulty of implementation increases exponentially. On the other hand, the cost of 2N-layer PCBs is significantly higher. The entire board is scrapped after a single lamination failure, and the material loss cost is three times that of two N-layer PCBs, resulting in exponential cost waste. Furthermore, the process window for subsequent processes such as etching and surface treatment of 2N-layer PCBs narrows by 50% as the number of layers increases, requiring additional testing and rework processes. The labor and time costs increase by 50% compared to manufacturing two N-layer PCBs separately, thus multiplying the cost burden.

[0004] Furthermore, in the existing fabrication of multilayer ultra-thin thick copper PCBs, traditional thick PP filling methods are insufficient to meet the interlayer insulation and thinning requirements of 2N-layer PCBs. The interlayer bubble rate increases to over 15% with the number of layers, resulting in insufficient transformer withstand voltage performance. On the other hand, if screen-mesh copper pits are used for resin filling, the uneven gap problem caused by the doubling of the number of layers is exacerbated, and there is a lack of effective filling methods. Therefore, a method for fabricating ultra-thin planar transformer coil thick copper PCBs is proposed to address the above problems. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for manufacturing an ultra-thin planar transformer coil thick copper PCB, thereby solving the technical problems mentioned in the background art.

[0006] Includes the following steps: S1: Pretreatment of inner thick copper substrate. Epoxy resin PP filled copper clad laminate is selected as the substrate. Pattern transfer etching is performed on the surface of the substrate to remove the oxide layer and form a clean and rough surface.

[0007] S2: Steel mesh printing, using nano steel mesh printing technology to print the area on the surface of the pretreated substrate except for the area of ​​the filler coil copper pattern, to provide a board plane positioning reference for subsequent multi-layer PP lamination. S3: Disassemble and fabricate single-layer coil boards. Based on the design requirements of planar transformer coils, the 2N-layer coil is split into two groups of N-layer coil units. Fabricate a single-layer coil board for each group of N-layer coil units excluding the copper foil: S31: Nano steel mesh printing, using a nano steel mesh with adjustable steel sheet to print the substrate, vacuum filling the high temperature dry film with resin, and pressing it onto the surface of the printed substrate. The thickness of the adjustable steel sheet can be adjusted to adapt to different specifications of substrates. S32: Exposure and development. Ultraviolet light is used to expose the substrate after vacuum resin treatment. After exposure, a developing solution is used to develop the substrate, forming a coil pattern and strengthening the curing of the resin material. S33: Thick copper electroplating, the developed substrate is placed in an acidic copper sulfate electroplating solution for electroplating, so that a copper layer of a predetermined thickness is formed in the coil pattern area; S34: The electroplated copper substrate is immersed in a stripping solution and then polished with ceramic to remove excess resin and roughen the surface to facilitate multilayer board lamination. S35: The inner coil layer and original copper are filled with resin and then baked at high temperature to complete the production of the inner thick copper layer filling coil board. S4: PP selection and lamination preparation: Select PP of appropriate thickness according to the withstand voltage and frequency requirements of the planar transformer; alternately laminate the N-layer single-layer coil board of each group with the selected PP to form a laminated assembly; S5: Vacuum filling and grouping synthesis. Vacuum high temperature PP pressing process is used for the stacked components. The interlayer air is discharged through the vacuum environment to reduce bubbles. Then, vacuum lamination is performed to obtain two N-layer coil units respectively. S6: Unit integration, a selected thickness of PP is laid between two N-layer coil units, and vacuum filling and vacuum lamination processes are used again to achieve the integrated integration of the two N-layer coil units, forming a 2N-layer ultra-thin copper PCB. S7: Outer layer processing and inspection. The outer layer processing is performed on the laminated PCB, followed by inspection of coil impedance, withstand voltage performance and interlayer alignment accuracy. The thick copper PCB of ultra-thin planar transformer coils that meet the requirements is selected.

[0008] Preferably, in step S4, within the withstand voltage frequency range of 1000V to 10000V, the withstand voltage frequency value of the planar transformer is positively correlated with the thickness of its insulation layer. That is, when the withstand voltage frequency value of the planar transformer increases towards 10000V, the thickness of the planar transformer increases accordingly; when the withstand voltage frequency value of the planar transformer decreases towards 1000V, the thickness of the planar transformer decreases accordingly.

[0009] As a preferred embodiment, the vacuum filling process in steps S5 and S6 is achieved by the coordinated use of a nano-stencil printer and a vacuum filling machine. From the time the nano-stencil printer finishes printing until the vacuum filling machine starts filling, and from the time the filling is completed until the lamination process begins after the filling is cured, a vacuum curing environment is maintained throughout the process to ensure that there are no air bubbles remaining between the layers of the substrate to be laminated.

[0010] Preferably, the ceramic polishing in step S1 is done using a grinding wheel.

[0011] Preferably, the nano-steel mesh printing in step S2 uses high-temperature resistant resin ink.

[0012] Preferably, in the vacuum lamination process of steps S5 and S6, the lamination time is positively correlated with the number of layers.

[0013] Preferably, in step S33, the thickness of the copper layer after thick copper electroplating is less than 150 μm to meet the conductivity requirements of the planar transformer.

[0014] Preferably, in step S7, laser imaging CCD recognition processing is used, and the dimensional accuracy error of the processed PCB is ≤ ±0.05mm.

[0015] As a preferred option, if the coil design requires a different number of layers in step S3, it can be divided into multiple coil units according to the principle that the number of layers in each coil unit is ≤6, and then integrated according to the process in steps S4-S7.

[0016] The beneficial effects of this invention are: (1) Optimization of manufacturing difficulty and cost: By splitting the 2N-layer PCB into two N-layer units, ceramic polishing is used to improve the flatness of the substrate, reduce the alignment error between layers, and reduce the manufacturing difficulty; the vacuum filling process reduces interlayer bubbles, reduces the failure rate of lamination, and reduces material loss. At the same time, the split manufacturing reduces the risk of scrapping the whole board and significantly reduces costs.

[0017] (2) Adaptability and performance improvement: The PP thickness is selected according to the withstand voltage frequency to make the PCB adaptable to the performance requirements of different application scenarios; the stencil printing provides a precise positioning reference and improves the accuracy of the coil pattern; the vacuum filling reduces air bubbles, and the PP pressing enhances the interlayer insulation and bonding strength, significantly improving the withstand voltage performance and reliability of the PCB.

[0018] (3) Strong process versatility: The specific data is simplified to expand the protection range, and the unit can be flexibly split according to the total number of coil layers to adapt to PCB manufacturing with different number of layers. At the same time, it is compatible with different withstand voltage and frequency requirements, and has a wider range of applications. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] In the attached diagram: Figure 1 This is a flowchart of the manufacturing method of the present invention. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0022] To further illustrate the technical means and effects of the present invention, the following describes the technical solution of the present invention in conjunction with preferred embodiments of the present invention. However, the present invention is not limited to the scope of the embodiments.

[0023] Specific implementation examples are given below.

[0024] Please see Figure 1 This invention provides a method for manufacturing an ultra-thin planar transformer coil thick copper PCB, comprising the following steps: S1: Substrate pretreatment. Ceramic-filled copper clad laminate is selected as the substrate. The substrate surface is degreased and micro-etched to remove the oxide layer and form a rough surface. The substrate edges are ceramic-polished to remove burrs and optimize the substrate flatness. S2: Stencil printing, which uses stencil printing technology to print coil graphic markings on the surface of the pretreated substrate, providing a positioning reference for subsequent dry film lamination and exposure development. S3: Disassemble and fabricate single-layer coil boards. Based on the design requirements of the planar transformer coil, the 2N-layer coil is split into two groups of N-layer coil units, and a single-layer coil board is fabricated for each group of N-layer coil units: S31: Nano steel mesh printing, using a nano steel mesh with adjustable steel strips to print the substrate, vacuum filling the high-temperature dry film with resin, and pressing it onto the surface of the printed substrate. The adjustable steel strips can be adjusted to adapt to different specifications of substrates. S32: Exposure and development. Ultraviolet light is used to expose the substrate after vacuum resin treatment. After exposure, a developing solution is used to develop the substrate, forming a coil pattern and strengthening the curing of the resin material. S33: Thick copper electroplating, the developed substrate is placed in an acidic copper sulfate electroplating solution for electroplating, so that a copper layer of a predetermined thickness is formed in the coil pattern area; S34: The electroplated copper substrate is immersed in a stripping solution and then polished with ceramic to remove excess resin and roughen the surface to facilitate multilayer board lamination. S35: The inner coil layer and original copper are filled with resin and then baked at high temperature to complete the production of the inner thick copper layer filling coil board. S4: PP selection and lamination preparation: Select PP of appropriate thickness according to the withstand voltage and frequency requirements of the planar transformer; alternately laminate the N-layer single-layer coil board of each group with the selected PP to form a laminated assembly; S5: Vacuum filling and grouping synthesis. Vacuum filling process is used for the stacked components. The interlayer air is discharged through the vacuum environment to reduce air bubbles. Then, vacuum lamination is performed to obtain two N-layer coil units. S6: Unit integration, a selected thickness of PP is laid between two N-layer coil units, and vacuum filling and vacuum lamination processes are used again to achieve the integrated integration of the two N-layer coil units, forming a 2N-layer ultra-thin copper PCB. S7: Shape processing and inspection. The laminated PCB is shaped and then the coil impedance, withstand voltage performance and interlayer alignment accuracy are inspected to screen out the ultra-thin planar transformer coil thick copper PCB that meets the requirements. First, the substrate condition is optimized through substrate pretreatment (including ceramic polishing) to solve the problem of edge burrs in traditional substrates. Then, stencil printing provides a precise positioning benchmark to avoid subsequent pattern offset. Next, a splitting strategy is adopted to produce single-layer coil boards, reducing the difficulty of multi-layer stacking. Then, the PP thickness is selected according to the withstand voltage frequency to achieve scene adaptation. Vacuum filling reduces interlayer bubbles, and PP pressing improves the interlayer bonding strength. Finally, processing and testing ensure the quality of the finished product. The whole process covers four major innovations: "split integration, scene adaptation, precise positioning, and low bubble filling", laying the foundation for subsequent dependent claims.

[0025] In step S4, within the withstand voltage frequency range of 1000V to 10000V, the withstand voltage frequency value of the planar transformer is positively correlated with its own thickness. That is, when the withstand voltage frequency value of the planar transformer increases towards 10000V, the thickness of the planar transformer increases accordingly; when the withstand voltage frequency value of the planar transformer decreases towards 1000V, the thickness of the planar transformer decreases accordingly.

[0026] In the vacuum filling process in steps S5 and S6, the vacuum degree is controlled to be ≤-0.09MPa. The vacuum environment is maintained during the filling process until lamination begins to ensure that there are no air bubbles left between the layers. The key parameters (vacuum degree) and operational requirements of the vacuum filling process are limited. A vacuum degree of ≤-0.09MPa can effectively remove interlayer air and maintain vacuum until lamination begins. This can avoid the secondary introduction of air bubbles during the filling process, directly echoing the innovation of "low-bubble filling", ensuring no air bubbles remain between layers and improving the reliability of PCB insulation.

[0027] In step S1, the ceramic polishing is performed using a grinding wheel. After polishing, the roughness Ra of the substrate edge is ≤1.6μm. Grinding with a grinding wheel can efficiently remove burrs from the edges of the substrate. Roughness control can ensure the sealing of the PP during subsequent lamination and avoid interlayer gaps caused by uneven edges. Combined with the substrate pretreatment process, it solves the problem of scratching the adhesive film on the edges of traditional substrates.

[0028] The stencil printing in step S2 uses high-temperature resistant ink, and the line width error of the printed graphic logo is ≤ ±0.02mm; High-temperature resistant ink can withstand subsequent high-temperature processes such as electroplating and lamination, preventing the markings from falling off. Precise line width error can provide a reliable positioning benchmark for exposure and development, realizing the innovation of "precise positioning" and improving the accuracy of coil pattern production.

[0029] In the vacuum lamination process in steps S5 and S6, the lamination temperature is controlled at 160-288℃, the lamination pressure is controlled at 1.5-2.0MPa, and the lamination time is adjusted according to the number of layers. The lamination time and the number of layers are positively correlated. This parameter range ensures that the PP is fully melted and bonded, while avoiding substrate warping and copper layer detachment caused by high temperature and high pressure. The time can be adjusted as needed to adapt to coil units with different numbers of layers, ensuring the quality of interlayer bonding after disassembly and integration.

[0030] In step S33, the thickness of the copper layer after thick copper electroplating is less than 150μm to meet the conductivity requirements of the planar transformer. This thickness satisfies the high conductivity requirements of planar transformers for coils, ensuring current carrying capacity, while also adapting to the overall thickness requirements of ultra-thin PCBs, avoiding excessive copper layer thickness that could lead to PCB exceeding specifications, thus balancing conductivity and ultra-thin characteristics.

[0031] In step S7, laser cutting is used to process the shape, and the dimensional accuracy error of the processed PCB is ≤ ±0.05mm; Compared to traditional mechanical milling, laser cutting reduces burrs and chipping. Its precise dimensional accuracy ensures the compatibility of PCBs with components such as planar transformer cores, avoiding assembly problems caused by dimensional deviations.

[0032] If the coil design requires a different number of layers in step S3, it can be divided into multiple coil units according to the principle that the number of layers in each coil unit is ≤6, and then integrated according to the process in steps S4-S7. When the total number of layers is specified to be non-2N layers (such as 3N layers), it can be split according to "the number of layers in each coil unit ≤ 6 layers". This breaks the limitation of traditional processes that can only adapt to a fixed number of layers, further demonstrating the beneficial effect of "strong process flexibility" and enabling the method to cover the production of ultra-thin and thick copper PCBs with more layer requirements.

[0033] More specifically, step S1: Substrate pretreatment Resin-filled copper clad laminate was selected as the substrate. The substrate was placed in a degreasing tank and soaked in an alkaline degreasing agent (concentration 5wt%) at 50℃ for 10 minutes to remove surface oil. After degreasing, the substrate is transferred to a micro-etching tank and immersed in a micro-etching solution (sulfuric acid + hydrogen peroxide system) at room temperature for 3 minutes. The micro-etching depth is controlled at 0.8 μm to remove the surface oxide layer and form a rough surface. The micro-etched substrate is fixed on a sandblasting machine, and the edges of the substrate are polished with an 800-grit grinding wheel at a speed of 100 mm / s until the surface roughness Ra of the substrate is ≤1.6 μm. Burrs are removed and the flatness is optimized to complete the substrate pretreatment.

[0034] Step S2: Stencil Printing Place the pretreated substrate on the worktable of the stencil printing machine and adjust the printing position so that the printing area matches the subsequent coil pattern area; High-temperature resistant ink (temperature resistance ≥200℃) is used to print coil graphic markings on the substrate surface using a stencil printing machine. The printing pressure is controlled at 0.2MPa and the printing speed is 50mm / s. After printing, the substrate is placed in a drying oven and dried at 120℃ for 5 minutes to cure the ink. The final printed graphic logo line width error is ≤±0.05mm, providing a positioning reference for subsequent processes.

[0035] Step S3: Disassemble and fabricate a single-layer coil board In this embodiment, the 12-layer coil is divided into two groups of 6-layer coil units, and a single-layer coil board is made for each group: S31: Dry film lamination: A high-temperature resistant dry film (40μm thick) is placed on the surface of the printed substrate and put into a vacuum press. The pressing temperature is set to 85℃, the pressure to 0.4MPa and the time to 45s to achieve a tight bond between the dry film and the substrate. S32: Exposure and Development: Place the substrate with the dry film attached into an exposure machine, and expose it with ultraviolet light of wavelength 365nm, based on the graphic markings printed on the stencil, with the exposure energy controlled at 100mJ / cm²; after exposure, place the substrate into a development machine, and develop it with a 1.2wt% sodium carbonate solution at 28°C for 75s to remove the dry film in the unexposed areas, forming a dry film protective layer for the coil pattern; S33: Thick copper electroplating: Place the developed substrate into an electroplating tank, add acidic copper sulfate electroplating solution (containing 210g / L copper sulfate, 55g / L sulfuric acid, 65mg / L chloride ions, and 0.8mL / L brightener), set the electroplating current density to 3A / dm², temperature to 23℃, and time to 75min, so that a copper layer with a thickness of 100μm is formed in the coil pattern area; S34: Dry film stripping and etching: The electroplated substrate is placed in a stripping tank and immersed in an alkaline stripping solution (concentration 8wt%) at 55℃ for 12 minutes to remove the surface dry film protective layer; then the substrate is placed in an etching machine and etched at 42℃ for 6 minutes using an acidic copper chloride etching solution (containing 190g / L copper chloride, 55mL / L hydrochloric acid, 35g / L sodium chloride, and 2.5g / L corrosion inhibitor) to remove the copper layer in the non-coil pattern area; S35: Surface treatment: The etched substrate is placed in an activation tank and immersed in a 0.8wt% sulfuric acid solution at room temperature for 8 seconds to remove the oxide layer on the coil surface; then nickel-gold plating is performed, first nickel plating (temperature 85℃, time 15min, nickel layer thickness 6μm), then gold plating (temperature 90℃, time 2min, gold layer thickness 0.15μm) to complete the fabrication of the single-layer coil board.

[0036] Step S4: PP Selection and Pressing Preparation Each group of 6-layer single-layer coil boards is alternately stacked with selected PP (coil board-PP-coil board...) to form two sets of stacked assemblies, ensuring that the layers in each set are aligned.

[0037] Step S5: Vacuum filling and grouping synthesis Place the two sets of stacked modules into the vacuum filling equipment, turn off the equipment and evacuate the vacuum to ≤-0.09MPa, maintain the vacuum state for 5 minutes, and remove the air between the module layers. Maintain a vacuum environment and inject adhesive (epoxy resin adhesive that matches the PP material) into the interlayer of the module to ensure that the adhesive fills the gaps evenly; The glue-filled components were transferred to a vacuum laminator, and the lamination temperature was set to 170℃, the pressure to 1.8MPa, and the time to 35min for vacuum lamination. After cooling, two 6-layer coil units were obtained.

[0038] Step S6: Unit Integration A selected 0.08mm thick PP layer is laid on the bonding surface of the two 6-layer coil units; Place the stacked units into a vacuum filling device and repeat the vacuum filling operation in step S5 (vacuum degree ≤ -0.09MPa, filling for 5 minutes). The components are transferred to a vacuum laminator and vacuum laminated using the same lamination parameters as in step S5 (170°C, 1.8MPa, 35min) to achieve the integrated integration of two 6-layer coil units, forming a 12-layer ultra-thin copper PCB.

[0039] Step S7: Shape processing and inspection The integrated 12-layer PCB is placed in a laser cutting machine with a laser wavelength of 1064nm, a cutting speed of 80mm / s, and a spot diameter of 0.01mm. The shape is processed according to the design dimensions, and the dimensional accuracy error after processing is ≤±0.02mm. The impedance of the coil is tested using an impedance tester (frequency range 100kHz-1MHz), and the impedance fluctuation is required to be ≤±5%; the withstand voltage performance is tested using a withstand voltage tester (DC1000V, continuous for 60s), and the leakage current is required to be ≤10μA; the interlayer alignment accuracy is tested using an X-ray detector, and the alignment error is required to be ≤±0.01mm. Products that pass all tests are selected as 12-layer ultra-thin copper PCBs suitable for 5G base station planar transformers.

[0040] In the description of this invention, preferred embodiments of the invention have been described in detail above. However, the invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the invention, various simple modifications can be made to the technical solution of the invention, and these simple modifications all fall within the protection scope of the invention.

[0041] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A method for manufacturing a thick copper PCB for an ultra-thin planar transformer coil, characterized in that, Includes the following steps: S1: Pretreatment of inner thick copper substrate. Epoxy resin PP filled copper clad laminate is selected as the substrate. Pattern transfer etching is performed on the surface of the substrate to remove the oxide layer and form a clean rough surface. S2: Steel mesh printing, using nano steel mesh printing technology to print the area on the surface of the pretreated substrate except for the area of ​​the filler coil copper pattern, to provide a board plane positioning reference for subsequent multi-layer PP lamination. S3: Disassemble and manufacture single-layer coil boards. Based on the design requirements of planar transformer coils, the 2N-layer coil is divided into two groups of N-layer coil units, and single-layer coil boards are manufactured for each group of N-layer coil units excluding copper foil coil units. The fabrication of a single-layer coil board includes the following steps: S31: Nano-steel mesh printing, using a nano-steel mesh printing substrate with adjustable steel sheets, vacuum filling resin with high-temperature resistant dry film, and pressing it onto the surface of the printed substrate. The thickness of the adjustable steel sheets can be adjusted to adapt to different specifications of copper thickness substrates. S32: Exposure and development. Ultraviolet light is used to expose the substrate after vacuum resin treatment. After exposure, a developing solution is used to develop the substrate, forming a coil pattern and strengthening the curing of the resin material. S33: Thick copper electroplating, the developed substrate is placed in an acidic copper sulfate electroplating solution for electroplating, so that a copper layer of a predetermined thickness is formed in the coil pattern area; S34: The electroplated copper substrate is immersed in a stripping solution and then polished with ceramic to remove excess resin and roughen the surface to facilitate multilayer board lamination. S35: The inner coil layer and original copper are filled with resin and then baked at high temperature to complete the production of the inner thick copper layer filling coil board. S4: PP selection and lamination preparation. Based on the withstand voltage and frequency requirements of the planar transformer, select PP of corresponding thickness and alternately laminate the N-layer single-layer coil board of each group with the selected PP to form a laminated assembly. S5: Vacuum filling and grouping synthesis. Vacuum high temperature PP pressing process is used for the stacked components. The interlayer air is discharged through the vacuum environment to reduce bubbles. Then, vacuum lamination is performed to obtain two N-layer coil units respectively. S6: Unit integration, a selected thickness of PP is laid between two N-layer coil units, and vacuum filling and vacuum lamination processes are used again to achieve the integrated integration of the two N-layer coil units, forming a 2N-layer ultra-thin copper PCB. S7: Outer layer processing and inspection. The outer layer processing is performed on the laminated PCB, followed by inspection of coil impedance, withstand voltage performance and interlayer alignment accuracy. The thick copper PCB of ultra-thin planar transformer coils that meet the requirements is selected.

2. The method for manufacturing an ultra-thin planar transformer coil thick copper PCB according to claim 1, characterized in that: In step S4, within the withstand voltage frequency range of 1000V to 10000V, the withstand voltage frequency value of the planar transformer is positively correlated with the thickness of its own insulation layer (PP).

3. The method for manufacturing an ultra-thin planar transformer coil thick copper PCB according to claim 1, characterized in that: The vacuum filling process in steps S5 and S6 is achieved by the coordinated use of a nano-steel screen printing machine and a vacuum filling machine. From the moment the nano-steel mesh printing machine finishes printing until the vacuum filling machine starts filling, and from the moment the filling is completed until the lamination process begins, a vacuum environment is maintained throughout the entire process to ensure that there are no air bubbles remaining between the layers of the substrate to be laminated.

4. The method for manufacturing an ultra-thin planar transformer coil thick copper PCB according to claim 1, characterized in that: The ceramic polishing in step S1 is performed using a grinding wheel.

5. The method for manufacturing an ultra-thin planar transformer coil thick copper PCB according to claim 1, characterized in that: The nano-steel mesh printing in step S2 uses high-temperature resistant resin material ink.

6. The method for manufacturing an ultra-thin planar transformer coil thick copper PCB according to claim 1, characterized in that: In the vacuum lamination process of step S6, the lamination time is positively correlated with the number of layers.

7. The method for manufacturing an ultra-thin planar transformer coil thick copper PCB according to claim 1, characterized in that: In step S33, the thickness of the copper layer after thick copper electroplating is less than 150μm to meet the conductivity requirements of the planar transformer.

8. The method for manufacturing an ultra-thin planar transformer coil thick copper PCB according to claim 1, characterized in that: In step S7, laser imaging CCD is used for identification and processing, and the dimensional accuracy error of the processed PCB is ≤ ±0.05mm.

9. The manufacturing method according to any one of claims 1-8, characterized in that: If the coil design requires a different number of layers in step S3, it can be divided into multiple coil units according to the principle that the number of layers in each coil unit is ≤6, and then integrated according to the process in steps S4-S7.

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