Preparation method of heat dissipation type thick copper PCB for high-power coil

Abstract

The invention relates to the field of PCB manufacturing, in particular to a heat dissipation type thick copper PCB preparation method for a high-power coil, and the method comprises the following steps: S1, modifying original high-thermal-conductivity fibers to obtain surface modified high-thermal-conductivity fibers; s2, mixing the surface-modified high-thermal-conductivity fibers with a resin glue solution, and performing impregnation and drying to obtain a composite prepreg; s3, forming a thick copper coil circuit on the insulating base material through an etching process; s4, performing press fit treatment to obtain a PCB semi-finished product with a high-thermal-conductivity fiber layer embedded in the middle; s5, performing drilling processing on the PCB semi-finished product obtained in the S4; s6, appearance plate milling is conducted, and a metal edge covering layer is manufactured in an edge covering area; and S7, post-processing is carried out on the PCB after metal edge covering in the step S6. According to the invention, by constructing the three-dimensional heat dissipation network composed of the high heat conduction fiber layer, the heat conduction through holes and the plate edge metal edge covering layer, efficient heat dissipation of the thick copper coil plate is realized under the condition that an external fan is not needed.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing technology, and in particular to a method for preparing a heat-dissipating thick copper PCB for high-power coils. Background Technology

[0002] In high-power electronic devices, thick copper coil printed circuit boards (PCBs) are widely used in power modules, wireless charging, and new energy fields due to their advantages such as high current carrying capacity and high coil inductance. When the thick copper coil is energized, the resistive loss of the coil itself generates a large amount of Joule heat, causing the PCB surface temperature to rise sharply. To ensure the operational stability and lifespan of components, the industry typically requires that the PCB surface operating temperature not exceed 80°C.

[0003] Currently, the mainstream heat dissipation solution in the industry is to install a small fan on the outside of the PCB to remove heat through forced air cooling. However, this solution has significant limitations in practical applications: on the one hand, due to the limited internal space of the equipment, the installation position and size of the fan often cannot meet the ideal heat dissipation requirements; on the other hand, as a moving part, the fan poses reliability risks during long-term operation and is prone to dust accumulation, leading to a decrease in heat dissipation efficiency and increasing system maintenance costs. Therefore, how to achieve efficient heat dissipation of thick copper coil PCBs without the need for an external fan has become a pressing technical challenge in this field. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides a method for fabricating a heat-dissipating thick copper PCB for high-power coils.

[0005] A method for fabricating a heat-dissipating thick copper PCB for high-power coils includes the following steps: S1: The original high thermal conductivity fiber is soaked in a surfactant solution of a predetermined concentration, then dried and modified with a surface coupling agent to obtain surface-modified high thermal conductivity fiber. S2: The surface-modified high thermal conductivity fiber obtained in S1 is mixed with resin solution, and after impregnation and drying, a composite semi-cured sheet is obtained. S3: Thick copper coil lines are formed on an insulating substrate by etching process, and the surface of the thick copper coil lines is roughened to obtain an inner core board with thick copper coils. S4: At least two layers of composite prepreg are stacked sequentially on one side of the inner core board, and conductive copper foil is stacked on the outermost layer to form a stack to be pressed. After pressing, a PCB semi-finished product with a high thermal conductivity fiber layer embedded in the middle is obtained. S5: Drill holes in the PCB semi-finished product obtained in S4 to form heat-conducting through holes that penetrate the PCB board surface and the inner coil. S6: Mill the PCB board after processing in S5 to form an edge-sealing area on the edge of the PCB board, and make a metal edge-sealing layer in the edge-sealing area. S7: Post-process the PCB board after metal edging in S6 to obtain the final heat dissipation thick copper PCB for high-power coils.

[0006] Optionally, S1 specifically includes: S11: Prepare an aqueous solution of sodium dodecylbenzenesulfonate with a mass fraction of 0.5%-2.0% as a surfactant solution, immerse the original high thermal conductivity fiber in the surfactant solution, and soak it at a temperature of 20℃-40℃ for 20-40 minutes to obtain pretreated high thermal conductivity fiber. S12: Take out the pretreated high thermal conductivity fiber from S11 and dry it in an oven at 60℃-80℃ for 30-60 minutes to obtain the dried pretreated high thermal conductivity fiber. S13: Prepare a silane coupling agent alcohol solution with a mass fraction of 1.0%-3.0%, immerse the pretreated high thermal conductivity fiber after drying S12 into the silane coupling agent alcohol solution, and perform a soaking and modification treatment at a temperature of 40℃-60℃ for 10-30 minutes to obtain coupling agent modified high thermal conductivity fiber. S14: Take out the coupling agent modified high thermal conductivity fiber of S13 and dry it in an oven at 50℃-70℃ for 20-40 minutes to obtain surface modified high thermal conductivity fiber.

[0007] Optionally, the resin solution is an epoxy resin solution, and its preparation method includes the following steps: First, weigh out 40%-50% bisphenol A type epoxy resin, 10%-20% phenolic epoxy resin, 1%-2.5% dicyandiamide curing agent, 0.05%-0.25% 2-methylimidazole accelerator, and the remainder is acetone solvent according to the mass percentage. Then, the weighed bisphenol A epoxy resin, phenolic epoxy resin and acetone solvent are added to the reaction vessel and stirred at 300-500 rpm for 30-60 minutes at a temperature of 40℃-60℃ to completely dissolve the resin and obtain a resin mixture. Finally, the weighed dicyandiamide curing agent and 2-methylimidazole accelerator are added to the resin mixture, and the mixture is stirred for 60-90 minutes at a temperature of 40℃-60℃ until the curing agent and accelerator are completely and evenly dispersed, thus obtaining the epoxy resin solution.

[0008] Optionally, S2 specifically includes: S21: Surface-modified high thermal conductivity fibers are woven into a fiber cloth, wherein the warp and weft density of the fiber cloth is 60-80 threads / inch and the thickness is 0.05mm-0.15mm; S22: Inject the resin solution into the impregnation tank, and control the temperature of the resin solution in the impregnation tank to be 25℃-35℃ and the viscosity to be 300-800 centipoise. S23: The fiber cloth obtained in S21 is passed through the impregnation tank in S22 at a conveying speed of 1.5m / min-3.0m / min, so that the fiber cloth is fully impregnated with the resin solution to obtain the impregnated fiber cloth. S24: The fiber cloth impregnated with S23 is sent into a vertical drying oven for segmented drying. The first stage of drying is at a temperature of 80℃-100℃ and a drying time of 2-5 minutes. The second stage of drying is at a temperature of 120℃-150℃ and a drying time of 3-8 minutes. The third stage of drying is at a temperature of 150℃-170℃ and a drying time of 1-3 minutes. After drying, a semi-cured composite semi-cured sheet is obtained.

[0009] Optionally, S3 specifically includes: S31: Prepare an insulating substrate with double-sided copper foil, wherein the thickness of the insulating substrate is 0.1mm-0.5mm and the thickness of the copper foil is 3oz-10oz; S32: A dry film is laminated onto the surface of a double-sided copper-clad insulating substrate, and after exposure and development, an etch-resistant circuit pattern is formed to obtain a substrate with an etch-resistant pattern. S33: Place the substrate obtained in S32 in an etching solution, control the temperature of the etching solution to 45℃-55℃, and the etching pressure to 1.5kg / cm²-2.5kg / cm², and perform etching treatment until the copper foil not protected by the anti-etching pattern is completely removed, and obtain a substrate with thick copper coil lines. S34: Remove the etch-resistant pattern from the substrate surface with thick copper coil lines obtained in S33 to obtain an inner core board with exposed thick copper coil lines. S35: The inner core board with exposed thick copper coil circuitry in S34 is subjected to surface roughening treatment by sandblasting. The sandblasting medium is alumina sand, the sandblasting pressure is 2.0 kg / cm²-4.0 kg / cm², and the sandblasting time is 30-90 seconds, to obtain the inner core board with roughened thick copper coil circuitry.

[0010] Optionally, S4 specifically includes: S41: Prepare at least two composite prepreg sheets and one conductive copper foil, wherein the thickness of the conductive copper foil is 0.5oz-2oz; S42: The inner core board of the S3 thick copper coil circuit is browned by immersing the inner core board in browning solution, controlling the temperature of browning solution at 30℃-40℃, and the treatment time at 60-120 seconds, to obtain an inner core board with a browning film formed on the surface. S43: At least two composite prepreg sheets are stacked sequentially on one side of the inner core board on which a brown film is formed on the surface, with no gap between adjacent composite prepreg sheets to form a prepreg stack. S44: A conductive copper foil is stacked on the outermost side of the prepreg stack, so that the rough surface of the conductive copper foil contacts the prepreg stack to obtain a preliminary stacked structure. S45: Place the preliminary composite structure on the support plate of the vacuum press, and place a release film and a buffer pad on the top and bottom of the preliminary composite structure respectively to form the composite structure to be pressed.

[0011] Optionally, S4 further includes: S46: Place the stacked structure to be pressed obtained in S45 into the working area of ​​the vacuum press, close the vacuum press chamber door, and evacuate the vacuum level inside the chamber to 50Pa-200Pa; S47: Increase the pressing temperature at a heating rate of 1.5℃ / min-3.0℃ / min; when the temperature reaches 120℃-150℃, apply a first-stage pressure of 0.5MPa-1.5MPa; when the temperature reaches 180℃-220℃, increase the pressure to a second-stage pressure of 2.0MPa-4.0MPa, and maintain the temperature and pressure for 60-90 minutes. S48: After the pressing time is reached, stop heating and reduce the temperature to below 60℃ at a cooling rate of 1.0℃ / min-2.0℃ / min. Then open the vacuum press chamber door, remove the pressed board, and obtain a PCB semi-finished product with a high thermal conductivity fiber layer embedded in the middle.

[0012] Optionally, S5 specifically includes: S51: Perform X-Ray drilling target positioning on the PCB semi-finished product obtained in S4. Drill positioning targets at the four corners of the PCB semi-finished product. The diameter of the positioning targets is 1.0mm-1.5mm and the depth penetrates the PCB semi-finished product. S52: Fix the PCB semi-finished product with the drill target positioning completed on the worktable of the CNC drilling machine, and perform drilling program alignment with the positioning target as the reference, with the alignment accuracy controlled within ±0.05mm. S53: The first type of drill bit is used to pre-drill holes in the PCB semi-finished product. The cutting angle of the first type of drill bit is 140°-160°, the drilling speed is 60-80 kilo rpm, the feed rate is 1.0 m / min-1.8 m / min, and the drilling depth is 90% of the thickness of the PCB semi-finished product to form a pre-drilled hole. S54: Use a second type of drill bit to finish the pre-drilled hole formed in S53. The cutting edge angle of the second type of drill bit is 100°-120°, the drilling speed is 90-110 kilorpm, and the feed rate is 0.8m / min-1.2m / min. The drill bit penetrates the PCB semi-finished product to form a heat-conducting through hole that runs through the PCB board surface and the inner layer coil. The diameter of the heat-conducting through hole is 0.2mm-0.5mm.

[0013] Optionally, S6 specifically includes: S61: Fix the PCB board processed by S5 onto the worktable of a CNC milling machine. Use a two-stage profile milling method. First, use a rough milling cutter with a diameter of 1.5mm-2.5mm, a speed of 30-40 rpm, and a feed rate of 1.0m / min-1.5m / min to perform rough milling along the PCB outline, leaving a margin of 0.1mm-0.2mm. Then, use a finish milling cutter with a diameter of 1.0mm-1.5mm, a speed of 40-50 rpm, and a feed rate of 0.5m / min-1.0m / min to mill to the final size, forming a PCB board with an edge-sealing area. S62: Perform edge cleaning treatment on the PCB board with the edge-wrapped area obtained in S61. Place the PCB board in a plasma cleaning equipment and clean it for 10-20 minutes with a mixture of oxygen and carbon tetrafluoride gas under vacuum conditions of 50Pa-100Pa and power of 500W-1000W to obtain the PCB board with cleaned edge. S63: After cleaning the PCB board edges obtained in S62, a metal cladding layer is made. First, the board is immersed in a chemical copper plating solution at 30℃-40℃ for 20-40 minutes to deposit a chemical copper layer with a thickness of 1μm-3μm. Then, the board is placed in an electroplating copper bath and electroplated at a current density of 1.5A / dm²-2.5A / dm² for 60-120 minutes to form a metal cladding layer with a total thickness of 15μm-50μm.

[0014] Optionally, S7 specifically includes: S71: After metal edging is completed in S6, a solder resist layer is made on the PCB board. Photosensitive solder resist ink is screen-printed or sprayed onto the PCB board surface. The thickness of the solder resist ink is controlled to be 15μm-25μm. After pre-baking at 75℃-85℃ for 20-40 minutes, exposure and development are performed. The temperature of the developing solution is 28℃-32℃, and the developing pressure is 1.5kg / cm²-2.5kg / cm². After development, it is placed in an oven at 150℃-160℃ for 30-60 minutes to cure and form a solder resist layer. S72: Surface treatment is performed on the PCB board for which the solder mask layer is formed in S71. The PCB board is immersed in a chemical nickel-gold plating solution, and the chemical nickel plating temperature is controlled at 80℃-90℃, the nickel plating time is 20-40 minutes, and the nickel layer thickness is 3μm-8μm. Then it is immersed in a chemical gold plating solution, and the chemical gold plating temperature is controlled at 80℃-90℃, the gold plating time is 5-15 minutes, and the gold layer thickness is 0.05μm-0.15μm, to obtain the final heat dissipation type thick copper PCB for high-power coils.

[0015] The beneficial effects of this invention are: This invention utilizes high thermal conductivity fibers, which have a thermal conductivity far exceeding that of ordinary glass fibers, to create a composite prepreg. This prepreg is then organically combined with thermally conductive through-holes and a metal edging structure on the board edge. This constructs a three-dimensional, highly efficient heat dissipation network that connects the internal heat source to the external environment, enabling the heat generated by the thick copper coil to be quickly conducted to the board edge and dissipated.

[0016] This invention effectively solves the technical problem that high thermal conductivity fibers are prone to fuzzing, hole deformation, or hole blockage during drilling and shaping by introducing fiber surface modification treatment, segmented drilling process, and rough milling followed by fine milling in the preparation method, thus greatly improving the processing yield. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the PCB fabrication method according to an embodiment of the present invention. Detailed Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should also be noted that, to make the embodiments more comprehensive, the following embodiments are the best and preferred embodiments, and those skilled in the art can use other alternative methods to implement some well-known technologies; moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0020] It should be noted that the use of terms such as "an embodiment," "an embodiment," "an exemplary embodiment," and "some embodiments" in the specification indicates that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the art.

[0021] Generally, terms can be understood at least partly from their use in context. For example, depending at least partly on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in a singular sense, or a combination of features, structures, or characteristics in a plural sense. Additionally, the term "based on" can be understood not necessarily to convey an exclusive set of factors, but rather, alternatively, depending at least partly on the context, to allow for the presence of other factors that are not necessarily explicitly described.

[0022] Example 1 like Figure 1 As shown, a method for fabricating a heat-dissipating thick copper PCB for high-power coils includes the following steps: S1: The original high thermal conductivity fiber is soaked in a surfactant solution of a predetermined concentration, then dried and modified with a surface coupling agent to reduce its surface energy, thus obtaining surface-modified high thermal conductivity fiber. S2: The surface-modified high thermal conductivity fiber obtained in S1 is mixed with resin liquid, and after impregnation and drying, a composite semi-cured sheet with high thermal conductivity is obtained. S3: Thick copper coil lines are formed on an insulating substrate by etching process, and the surface of the thick copper coil lines is roughened to obtain an inner core board with thick copper coils. S4: At least two layers of composite prepreg are stacked sequentially on one side of the inner core board, and conductive copper foil is stacked on the outermost layer to form a stack to be pressed. After pressing, a PCB semi-finished product with a high thermal conductivity fiber layer embedded in the middle is obtained. S5: Drill holes in the PCB semi-finished product obtained in S4 to form heat-conducting through holes that penetrate the PCB board surface and the inner coil. S6: Mill the PCB board after processing in S5 to form an edge area on the edge of the PCB board, and make a metal edge layer in the edge area to connect the metal edge layer with the ground network or thermally conductive copper layer of the inner layer of the PCB. S7: Post-processing is performed on the PCB board after metal edging in S6 to obtain the final heat dissipation thick copper PCB for high-power coils. The high thermal conductivity fiber layer, thermally conductive vias and metal edging layer together form a three-dimensional heat dissipation network.

[0023] S1 specifically includes: S11: Prepare a 1.0% sodium dodecylbenzenesulfonate aqueous solution as a surfactant solution, immerse the original high thermal conductivity fiber in the surfactant solution, and soak it at 30°C for 30 minutes to obtain pretreated high thermal conductivity fiber. S12: Take out the pretreated high thermal conductivity fiber from S11 and dry it in an oven at 70°C for 45 minutes to obtain the dried pretreated high thermal conductivity fiber. S13: Prepare a 2.0% (w / w) silane coupling agent alcohol solution, immerse the pretreated high thermal conductivity fiber after drying S12 into the silane coupling agent alcohol solution, and perform a immersion modification treatment at 50°C for 20 minutes to obtain coupling agent modified high thermal conductivity fiber. S14: Take out the coupling agent modified high thermal conductivity fiber of S13 and dry it in an oven at 60°C for 30 minutes to obtain surface modified high thermal conductivity fiber.

[0024] The resin solution is an epoxy resin solution, and its preparation method includes the following steps: First, weigh out 45% bisphenol A type epoxy resin, 15% phenolic epoxy resin, 2.0% dicyandiamide curing agent, 0.15% 2-methylimidazole accelerator, and the remainder is acetone solvent according to the mass percentage. Then, the weighed bisphenol A type epoxy resin, phenolic epoxy resin and acetone solvent are added to the reaction vessel and stirred at 400 rpm for 45 minutes at 50°C to completely dissolve the resin and obtain a resin mixture. Finally, the weighed dicyandiamide curing agent and 2-methylimidazole accelerator are added to the resin mixture, and the mixture is stirred at 50°C for 75 minutes until the curing agent and accelerator are completely and evenly dispersed, thus obtaining the epoxy resin solution.

[0025] S2 specifically includes: S21: Surface-modified high thermal conductivity fibers are woven into a fiber cloth, wherein the warp and weft density of the fiber cloth is 70 threads / inch and the thickness is 0.10 mm; S22: Inject the resin solution into the impregnation tank, and control the temperature of the resin solution in the impregnation tank to be 30°C and the viscosity to be 500 centipoise. S23: The fiber cloth obtained in S21 is passed through the impregnation tank in S22 at a conveying speed of 2.2m / min, so that the fiber cloth is fully impregnated with the resin solution to obtain the impregnated fiber cloth; S24: The fiber cloth impregnated with S23 is sent into a vertical drying oven for segmented drying. The first stage of drying is at a temperature of 90℃ for 3 minutes, the second stage is at a temperature of 135℃ for 5 minutes, and the third stage is at a temperature of 160℃ for 2 minutes. After drying, a semi-cured composite semi-cured sheet is obtained.

[0026] S3 specifically includes: S31: Prepare an insulating substrate with double-sided copper foil, wherein the thickness of the insulating substrate is 0.3 mm and the thickness of the copper foil is 6 oz; S32: A dry film is laminated onto the surface of a double-sided copper-clad insulating substrate, and after exposure and development, an etch-resistant circuit pattern is formed to obtain a substrate with an etch-resistant pattern. S33: Place the substrate obtained in S32 in the etching solution, control the temperature of the etching solution to 50℃ and the etching pressure to 2.0kg / cm², and perform etching treatment until the copper foil not protected by the anti-etching pattern is completely removed, and obtain a substrate with thick copper coil lines. S34: Remove the etch-resistant pattern from the substrate surface with thick copper coil lines obtained in S33 to obtain an inner core board with exposed thick copper coil lines. S35: The inner core board with exposed thick copper coil circuitry in S34 is subjected to surface roughening treatment by sandblasting. The sandblasting medium is alumina sand, the sandblasting pressure is 3.0 kg / cm², and the sandblasting time is 60 seconds, to obtain the inner core board with roughened thick copper coil circuitry.

[0027] S4 specifically includes: S41: Prepare at least two composite prepreg sheets and one conductive copper foil, wherein the thickness of the conductive copper foil is 1 oz; S42: The inner core board of the S3 thick copper coil circuit is browned by immersing the inner core board in browning solution, controlling the temperature of browning solution at 35℃ and the treatment time at 90 seconds, to obtain an inner core board with a browning film formed on the surface. S43: At least two composite prepreg sheets are stacked sequentially on one side of the inner core board on which a brown film is formed on the surface, with no gap between adjacent composite prepreg sheets to form a prepreg stack. S44: A conductive copper foil is stacked on the outermost side of the prepreg stack, so that the rough surface of the conductive copper foil contacts the prepreg stack to obtain a preliminary stacked structure. S45: Place the preliminary composite structure on the support plate of the vacuum press, and place a release film and a buffer pad on the top and bottom of the preliminary composite structure respectively to form the composite structure to be pressed.

[0028] S4 also includes: S46: Place the stacked structure to be pressed obtained in S45 into the working area of ​​the vacuum press, close the vacuum press chamber door, and evacuate the vacuum level inside the chamber to 100Pa; S47: Increase the pressing temperature at a heating rate of 2.0℃ / min; when the temperature reaches 135℃, apply a first-stage pressure of 1.0MPa; when the temperature reaches 200℃, increase the pressure to a second-stage pressure of 3.0MPa and maintain the temperature and pressure for 75 minutes. S48: After the pressing time is reached, stop heating and reduce the temperature to below 60℃ at a cooling rate of 1.5℃ / min. Then open the vacuum press chamber door, remove the pressed board, and obtain a PCB semi-finished product with a high thermal conductivity fiber layer embedded in the middle.

[0029] S5 specifically includes: S51: Perform X-Ray drilling target positioning on the PCB semi-finished product obtained in S4. Drill positioning targets at the four corners of the PCB semi-finished product. The diameter of the positioning targets is 1.2mm and the depth penetrates the PCB semi-finished product. S52: Fix the PCB semi-finished product with the drill target positioning completed on the worktable of the CNC drilling machine, and perform drilling program alignment with the positioning target as the reference, with the alignment accuracy controlled within ±0.05mm. S53: A first-type drill bit is used to pre-drill holes in the PCB semi-finished product. The first-type drill bit has a cutting angle of 150°, a drilling speed of 70 kilo rpm, a feed rate of 1.4 m / min, and a drilling depth of 90% of the thickness of the PCB semi-finished product to form a pre-drilled hole. S54: Use a second type of drill bit to finish the pre-drilled hole formed in S53. The cutting edge angle of the second type of drill bit is 110°, the drilling speed is 100 rpm, and the feed rate is 1.0 m / min. The drill bit penetrates the PCB semi-finished product to form a heat-conducting through hole that runs through the PCB board surface and the inner layer coil. The diameter of the heat-conducting through hole is 0.3 mm.

[0030] S6 specifically includes: S61: Fix the PCB board processed by S5 onto the worktable of the CNC milling machine. Use a two-stage profile milling method. First, use a rough milling cutter with a diameter of 2.0mm, a speed of 35,000 rpm, and a feed rate of 1.2m / min to perform rough milling along the outline of the PCB, leaving a margin of 0.15mm. Then, use a finish milling cutter with a diameter of 1.2mm, a speed of 45,000 rpm, and a feed rate of 0.8m / min to mill to the final size, forming a PCB board with an edge-sealing area. S62: Perform edge cleaning treatment on the PCB board with the edge-wrapped area obtained in S61. Place the PCB board in a plasma cleaning equipment and clean it for 15 minutes with a mixture of oxygen and carbon tetrafluoride under a vacuum of 80Pa and a power of 800W to obtain the PCB board with cleaned edges. S63: After cleaning the PCB board edges obtained in S62, a metal cladding layer is made. First, the board is immersed in a 35°C chemical copper plating solution for 30 minutes to deposit a 2μm thick chemical copper layer. Then, the board is placed in an electroplating copper bath and electroplated at a current density of 2.0A / dm² for 90 minutes to form a metal cladding layer with a total thickness of 30μm.

[0031] S7 specifically includes: S71: After metal edging is completed in S6, a solder resist layer is made on the PCB board. Photosensitive solder resist ink is screen-printed or sprayed on the PCB board surface. The thickness of the solder resist ink is controlled to be 20μm. After pre-baking at 80℃ for 30 minutes, it is exposed and developed. The temperature of the developing solution is 30℃ and the developing pressure is 2.0kg / cm². After development, it is placed in an oven at 155℃ for 45 minutes to cure and form a solder resist layer. S72: The PCB board with the solder mask layer formed in S71 is surface treated by immersing it in a chemical nickel-gold plating solution, controlling the chemical nickel plating temperature at 85℃, the nickel plating time at 30 minutes, and the nickel layer thickness at 5μm. Then it is immersed in a chemical gold plating solution, controlling the chemical gold plating temperature at 85℃, the gold plating time at 10 minutes, and the gold layer thickness at 0.10μm, to obtain the final heat dissipation type thick copper PCB for high-power coils.

[0032] Example 2 S1: Using raw high thermal conductivity fibers, a 0.5% sodium dodecylbenzenesulfonate aqueous solution was prepared as a surfactant solution. The raw high thermal conductivity fibers were immersed in this surfactant solution and treated at 20°C for 20 minutes to obtain pretreated high thermal conductivity fibers. The pretreated high thermal conductivity fibers were then removed and dried in a 60°C oven for 30 minutes. Next, a 1.0% silane coupling agent alcohol solution was prepared, and the dried pretreated high thermal conductivity fibers were immersed in the silane coupling agent alcohol solution and treated at 40°C for 10 minutes. Finally, the coupling agent-modified high thermal conductivity fibers were removed and dried in a 50°C oven for 20 minutes to obtain surface-modified high thermal conductivity fibers. S2: Weigh out 40% bisphenol A epoxy resin, 10% phenolic epoxy resin, 1% dicyandiamide curing agent, and 0.05% 2-methylimidazole accelerator according to the mass percentage, with the remainder being acetone solvent. Add the bisphenol A epoxy resin, phenolic epoxy resin, and acetone solvent to a reaction vessel and stir at 300 rpm for 30 minutes at 40°C until the resin is completely dissolved to obtain a resin mixture. Then add the dicyandiamide curing agent and 2-methylimidazole accelerator and continue stirring at 40°C for 60 minutes to obtain an epoxy resin adhesive. Surface-modified high-performance epoxy resin is then added to the mixture. Thermally conductive fibers are woven into a fiber cloth with a warp and weft density of 60 threads / inch and a thickness of 0.05 mm. Resin solution is injected into an impregnation tank, and the resin solution temperature is controlled at 25°C and the viscosity at 300 centipoise. The fiber cloth is then conveyed through the impregnation tank at a speed of 1.5 m / min for impregnation. Subsequently, it is sent to a vertical drying oven for segmented drying. The first stage of drying is at a temperature of 80°C for 2 minutes, the second stage is at a temperature of 120°C for 3 minutes, and the third stage is at a temperature of 150°C for 1 minute. After drying, a composite semi-cured sheet is obtained. S3: Prepare a double-sided copper-clad insulating substrate with a thickness of 0.1 mm and a copper foil thickness of 3 oz. A dry film is then applied to the surface of the double-sided copper-clad insulating substrate. After exposure and development, an etch-resistant circuit pattern is formed, resulting in a substrate with an etch-resistant pattern. The substrate is then placed in an etching solution, with the temperature controlled at 45°C and the etching pressure at 1.5 kg / cm², for etching until all copper foil not protected by the etch-resistant pattern is completely removed, resulting in a substrate with thick copper coil circuitry. The etch-resistant pattern is then removed, resulting in an inner core board with exposed thick copper coil circuitry. The inner core board is then subjected to surface roughening treatment using sandblasting. The sandblasting medium is alumina sand, the sandblasting pressure is 2.0 kg / cm², and the sandblasting time is 30 seconds, resulting in a roughened inner core board with thick copper coil circuitry. S4: Prepare two composite prepreg sheets and one conductive copper foil with a thickness of 0.5 oz. First, perform browning treatment on the inner core board of the thick copper coil circuit by immersing the inner core board in the browning solution, controlling the temperature of the browning solution at 30°C, and the treatment time at 60 seconds to obtain an inner core board with a browning film formed on the surface. Then, stack two composite prepreg sheets sequentially on one side of the inner core board, with no gaps between adjacent composite prepreg sheets to form a prepreg stack. Next, stack the conductive copper foil on the outermost side of the prepreg stack, so that the rough surface of the conductive copper foil is in contact with the prepreg stack to obtain a preliminary stacked structure. Place the preliminary stacked structure on the vacuum press bearing plate. Release films and buffer pads are placed at the top and bottom respectively to form a stack to be pressed. The stack to be pressed is then placed in the working area of ​​a vacuum press, the chamber door is closed and the vacuum level inside the chamber is evacuated to 50 Pa. The temperature is increased at a rate of 1.5 °C / min. When the temperature reaches 120 °C, the first stage pressure of 0.5 MPa is applied. When the temperature reaches 180 °C, the pressure is increased to the second stage pressure of 2.0 MPa and maintained at the temperature and pressure for 60 minutes. After the pressing is completed, heating is stopped and the temperature is reduced to below 60 °C at a rate of 1.0 °C / min. The chamber door is then opened and the board is removed to obtain a PCB semi-finished product with a high thermal conductivity fiber layer embedded in the middle. S5: X-Ray drilling target positioning is performed on the PCB semi-finished product obtained in S4. Positioning targets with a diameter of 1.0 mm are drilled at the four corners of the PCB semi-finished product, penetrating the PCB semi-finished product. The PCB semi-finished product with drilling target positioning is then fixed on the CNC drilling machine worktable. The drilling program is aligned with the positioning targets as a reference, and the alignment accuracy is controlled within ±0.05 mm. Subsequently, a first type of drill is used to pre-drill holes in the PCB semi-finished product. The first type of drill bit has a cutting edge angle of 140°, a drilling speed of 60 rpm, a feed rate of 1.0 m / min, and a drilling depth of 90% of the thickness of the PCB semi-finished product, forming a pre-drilled hole. Then, a second type of drill is used to finish the pre-drilled hole. The second type of drill bit has a cutting edge angle of 100°, a drilling speed of 90 rpm, a feed rate of 0.8 m / min, and the hole penetrates the PCB semi-finished product, forming a heat-conducting through hole that penetrates the PCB board surface and the inner layer coil. The diameter of the heat-conducting through hole is 0.2 mm. S6: Fix the PCB board processed in S5 onto the CNC milling machine table. Use a two-stage contour milling method. First, use a 1.5mm diameter rough milling cutter at a speed of 30 rpm and a feed rate of 1.0m / min to rough mill along the PCB outline, leaving a 0.1mm allowance. Then, use a 1mm diameter finish milling cutter at a speed of 40 rpm and a feed rate of 0.5m / min to mill to the final dimensions, forming a PCB board with an edge-sealed area. Finally, clean the edges of the PCB board with the edge-sealed area. The PCB board was placed in a plasma cleaning device and cleaned for 10 minutes with a mixture of oxygen and carbon tetrafluoride under a vacuum of 50 Pa and a power of 500 W to obtain a cleaned PCB board. Then, a metal cladding layer was made on the cleaned PCB board. First, it was immersed in a chemical copper plating solution at a temperature of 30°C for 20 minutes to deposit a chemical copper layer with a thickness of 1 μm. Then, it was placed in an electroplating copper bath and electroplated at a current density of 1.5 A / dm² for 60 minutes to form a metal cladding layer with a total thickness of 15 μm. S7: Post-processing of the PCB board after metal edging in S6. First, a solder mask layer is made by screen printing photosensitive solder mask ink on the PCB board surface, controlling the thickness of the solder mask ink to 15μm. After pre-baking at 75℃ for 20 minutes, it is exposed and developed. The developer temperature is 28℃ and the developing pressure is 1.5kg / cm². After development, it is placed in a 150℃ oven for curing for 30 minutes to form a solder mask layer. Then, the PCB board with the solder mask layer is surface treated by immersing it in a chemical nickel-gold plating solution, controlling the chemical nickel plating temperature at 80℃ and the nickel plating time at 20 minutes to form a nickel layer with a thickness of 3μm. Then, it is immersed in a chemical gold plating solution, controlling the chemical gold plating temperature at 80℃ and the gold plating time at 5 minutes to form a gold layer with a thickness of 0.05μm. Finally, a heat dissipation thick copper PCB for high-power coils is obtained.

[0033] Example 3 S1: Using raw high thermal conductivity fibers, a 2.0% sodium dodecylbenzenesulfonate aqueous solution was prepared as a surfactant solution. The raw high thermal conductivity fibers were immersed in this surfactant solution and treated at 40°C for 40 minutes to obtain pretreated high thermal conductivity fibers. The pretreated high thermal conductivity fibers were then removed and dried in an 80°C oven for 60 minutes. Next, a 3.0% silane coupling agent alcohol solution was prepared, and the dried pretreated high thermal conductivity fibers were immersed in the silane coupling agent alcohol solution and treated at 60°C for 30 minutes. Finally, the coupling agent-modified high thermal conductivity fibers were removed and dried in a 70°C oven for 40 minutes to obtain surface-modified high thermal conductivity fibers. S2: Weigh out 50% bisphenol A epoxy resin, 20% phenolic epoxy resin, 2.5% dicyandiamide curing agent, and 0.25% 2-methylimidazole accelerator according to the mass percentage, with the remainder being acetone solvent. Add the bisphenol A epoxy resin, phenolic epoxy resin, and acetone solvent to a reaction vessel and stir at 500 rpm for 60 minutes at 60°C until the resin is completely dissolved to obtain a resin mixture. Then add the dicyandiamide curing agent and 2-methylimidazole accelerator and continue stirring at 60°C for 90 minutes to obtain an epoxy resin adhesive. Surface-modified high-performance epoxy resin is then added to the mixture. Thermally conductive fibers are woven into a fiber cloth with a warp and weft density of 80 threads / inch and a thickness of 0.15 mm. Resin solution is injected into an impregnation tank, and the resin solution temperature is controlled at 35°C and the viscosity at 800 centipoise. The fiber cloth is then conveyed through the impregnation tank at a speed of 3.0 m / min for impregnation. Subsequently, it is sent to a vertical drying oven for segmented drying. The first stage of drying is at a temperature of 100°C for 5 minutes, the second stage is at a temperature of 150°C for 8 minutes, and the third stage is at a temperature of 170°C for 3 minutes. After drying, a composite semi-cured sheet is obtained. S3: Prepare a double-sided copper foil-coated insulating substrate with a thickness of 0.5 mm and a copper foil thickness of 10 oz. A dry film is then applied to the surface of the double-sided copper foil-coated insulating substrate. After exposure and development, an etch-resistant circuit pattern is formed, resulting in a substrate with an etch-resistant pattern. The substrate is then placed in an etching solution, with the temperature controlled at 55°C and the etching pressure at 2.5 kg / cm², for etching until all copper foil not protected by the etch-resistant pattern is completely removed, resulting in a substrate with thick copper coil circuitry. The etch-resistant pattern is then removed, resulting in an inner core board with exposed thick copper coil circuitry. The inner core board is then subjected to surface roughening treatment using sandblasting. The sandblasting medium is alumina sand, the sandblasting pressure is 4.0 kg / cm², and the sandblasting time is 90 seconds, resulting in a roughened inner core board with thick copper coil circuitry. S4: Prepare two composite prepreg sheets and one conductive copper foil, with the copper foil thickness being 2 oz. First, perform browning treatment on the inner core board of the thick copper coil circuit. Immerse the inner core board in the browning solution, controlling the temperature of the browning solution at 40°C and the treatment time at 120 seconds, to obtain an inner core board with a browned film formed on its surface. Then, stack two composite prepreg sheets sequentially on one side of this inner core board, with no gaps between adjacent composite prepreg sheets to form a prepreg stack. Next, stack the conductive copper foil on the outermost side of the prepreg stack, ensuring that the rough surface of the conductive copper foil contacts the prepreg stack, to obtain a preliminary stacked structure. Place the preliminary stacked structure on the vacuum press bearing plate, and... Release film and buffer pad are placed at the top and bottom respectively to form a stack to be pressed. The stack to be pressed is then placed in the working area of ​​a vacuum press, the chamber door is closed and the vacuum level inside the chamber is evacuated to 200 Pa. The temperature is increased at a rate of 3.0 °C / min. When the temperature reaches 150 °C, the first stage pressure of 1.5 MPa is applied. When the temperature reaches 220 °C, the pressure is increased to the second stage pressure of 4.0 MPa and the temperature and pressure are maintained for 90 minutes. After the pressing is completed, heating is stopped and the temperature is reduced to below 60 °C at a rate of 2.0 °C / min. The chamber door is then opened and the board is removed to obtain a PCB semi-finished product with a high thermal conductivity fiber layer embedded in the middle. S5: X-Ray drilling target positioning is performed on the PCB semi-finished product obtained in S4. Positioning targets with a diameter of 1.5mm are drilled at the four corners of the PCB semi-finished product, penetrating the PCB semi-finished product. The PCB semi-finished product with drilling target positioning is then fixed on the CNC drilling machine worktable. The drilling program is aligned with the positioning targets as a reference, and the alignment accuracy is controlled within ±0.05mm. Subsequently, a first type of drill is used to pre-drill holes in the PCB semi-finished product. The first type of drill bit has a cutting edge angle of 160°, a drilling speed of 80 rpm, a feed rate of 1.8m / min, and a drilling depth of 90% of the thickness of the PCB semi-finished product, forming a pre-drilled hole. Then, a second type of drill is used to finish the pre-drilled hole. The second type of drill bit has a cutting edge angle of 120°, a drilling speed of 110 rpm, a feed rate of 1.2m / min, and the hole penetrates the PCB semi-finished product, forming a heat-conducting through hole that penetrates the PCB board surface and the inner layer coil. The diameter of the heat-conducting through hole is 0.5mm. S6: Fix the PCB board processed in S5 onto the CNC milling machine table. Use a two-stage contour milling method. First, use a 2.5mm diameter rough milling cutter at a speed of 40 rpm and a feed rate of 1.5m / min to rough mill along the PCB outline, leaving a 0.2mm allowance. Then, use a 1.5mm diameter finish milling cutter at a speed of 50 rpm and a feed rate of 1.0m / min to mill to the final dimensions, forming a PCB board with an edge-sealed area. Finally, clean the edges of the PCB board with the edge-sealed area. The PCB board was placed in a plasma cleaning device and cleaned for 20 minutes with a mixture of oxygen and carbon tetrafluoride under a vacuum of 100Pa and a power of 1000W to obtain a cleaned PCB board. Then, a metal cladding layer was made on the cleaned PCB board. First, it was immersed in a chemical copper plating solution at a temperature of 40℃ for 40 minutes to deposit a chemical copper layer with a thickness of 3μm. Then, it was placed in an electroplating copper bath and electroplated at a current density of 2.5A / dm² for 120 minutes to form a metal cladding layer with a total thickness of 50μm. S7: Post-processing of the PCB board after metal edging in S6. First, a solder mask layer is made by screen printing photosensitive solder mask ink on the PCB board surface, controlling the thickness of the solder mask ink to be 25μm. After pre-baking at 85℃ for 40 minutes, it is exposed and developed. The developer temperature is 32℃ and the developing pressure is 2.5kg / cm². After development, it is placed in a 160℃ oven for curing for 60 minutes to form a solder mask layer. Then, the PCB board with the solder mask layer is surface treated by immersing it in a chemical nickel-gold plating solution, controlling the chemical nickel plating temperature at 90℃ and the nickel plating time at 40 minutes to form a nickel layer with a thickness of 8μm. Then, it is immersed in a chemical gold plating solution, controlling the chemical gold plating temperature at 90℃ and the gold plating time at 15 minutes to form a gold layer with a thickness of 0.15μm. Finally, a heat dissipation thick copper PCB for high-power coils is obtained.

[0034] Comparative Example 1 A conventional PCB fabrication method includes the following steps: Step 1: Select a 1.0mm thick double-sided copper-clad laminate as the substrate, with a copper foil thickness of 1oz on the surface of the double-sided copper-clad laminate; attach a dry film to the surface of the copper-clad laminate, and form a preset conductive circuit pattern after exposure and development; then use an etching solution for etching treatment, with the etching temperature controlled at 50℃ and the etching time controlled at 3 minutes; then remove the surface dry film to obtain a circuit board core board with conductive circuit patterns. Step 2: Drill holes in the obtained circuit board core board. The hole diameter is controlled at 0.20 mm and the drilling speed is controlled at 60 rpm. After drilling, the holes are metallized to form a 15 μm thick conductive copper layer on the hole wall to achieve electrical connection between the board layers. Then, the outer layer circuit is formed on the board surface, and a 15 μm thick solder resist ink is coated on the board surface. After pre-baking at 75℃ for 20 minutes, it is cured at 145℃ for 30 minutes to form a solder resist layer. Step 3: Perform surface plating on the PCB board after solder mask treatment. First, perform electroless nickel plating at a temperature of 80℃ for 20 minutes to form a nickel layer with a thickness of 3μm. Then, perform electroless gold plating at a temperature of 80℃ for 5 minutes to form a gold layer with a thickness of 0.10μm. Finally, perform shape processing to obtain a standard PCB finished product.

[0035] Table 1 Comparison of Finished Product Performance Parameters Comparison Projects Test unit Example 1 Example 2 Example 3 Comparative Example 1 thermal conductivity W / (m·K) 3.85 2.96 3.42 0.82 thermal resistance ℃·cm² / W 0.58 0.91 0.73 1.86 Coil full-load steady-state temperature rise ℃ 43.6 58.4 49.7 78.9 Peel strength between thick copper coil and laminated structure N / mm 1.82 1.36 1.58 0.94 Reliability of the bonding between the walls of thermally conductive through-holes (retention rate after thermal shock) % 98.7 95.1 96.9 88.3 Board edge warping resistance % 0.18 0.31 0.24 0.67 Insulation breakdown strength kV / mm 28.6 24.3 26.9 20.8 Rate of change of resistivity after 1000 thermal cycles % 1.9 4.8 3.1 9.7 Finished product qualification rate % 98.2 93.5 95.7 88.6 As can be seen from the data in Table 1 above, Example 1 outperforms Examples 2, 3, and Comparative Example 1 in terms of thermal conductivity, thermal resistance, coil steady-state temperature rise under full load, peel strength, reliability of thermally conductive via wall bonding, board edge warping resistance, insulation breakdown strength, resistance change rate after thermal cycling, and finished product yield. This indicates that the process parameter combination corresponding to Example 1 can achieve a better balance between thermal conductivity, structural bonding performance, electrical insulation performance, and long-term service reliability. Comparative Example 1 only uses the conventional PCB fabrication route, without setting a high thermal conductivity fiber composite prepreg, constructing a dedicated thermally conductive via penetrating the inner coil, or forming a metal cladding layer. Therefore, it has the lowest thermal conductivity, the highest thermal resistance, and the largest temperature rise under full load. Furthermore, its resistance stability and board structure stability after thermal cycling are significantly inferior to the three examples. In contrast, the embodiments of this application significantly improve the overall performance of high-power coil PCBs by constructing a high thermal conductivity fiber layer, a thick copper coil structure, and a synergistic heat dissipation path between thermally conductive vias and a metal cladding layer. Among these, Example 1 has the optimal parameter configuration and can therefore be considered the best embodiment.

[0036] Table 2 Comparison of other performance data Comparison Projects Test unit Example 1 Example 2 Example 3 Comparative Example 1 Plate thickness uniformity deviation % 1.6 2.9 2.2 4.8 Hole wall roughness Ra μm 2.1 3.4 2.7 5.2 Hole offset mm 0.028 0.044 0.036 0.081 Z-direction thermal expansion coefficient ppm / ℃ 42 56 48 71 Water absorption rate % 0.11 0.19 0.15 0.34 Dielectric loss factor (1MHz) — 0.012 0.018 0.015 0.026 Volume resistivity Ω·cm 3.8×10^14 2.9×10^14 3.3×10^14 1.6×10^14 Insulation resistance retention rate after damp heat % 96.8 91.2 94.1 84.5 Bond strength between outer copper foil and the board N / mm 1.71 1.28 1.49 0.89 As can be seen from Table 2 above, Example 1 exhibits the best performance in terms of plate thickness uniformity deviation, hole wall roughness, hole position offset, Z-axis thermal expansion coefficient, water absorption rate, dielectric loss factor, volume resistivity, insulation resistance retention rate after damp heat resistance, and bonding strength between the outer copper foil and the plate. This indicates that Example 1 not only excels in heat dissipation performance but also demonstrates better overall performance in terms of processing accuracy, dimensional stability, electrical insulation stability, and environmental adaptability. Further analysis reveals that the surface-modified high thermal conductivity fiber, composite semi-cured sheet lamination structure, thick copper coil roughening treatment, thermally conductive through-hole construction, and the synergistic design of the metal edging layer used in Example 1 result in a tighter interface bonding within the plate, higher hole wall forming quality, and less structural deformation under heat and moisture conditions. Therefore, it can simultaneously achieve lower plate thickness deviation, smaller hole position offset, and higher insulation retention capacity. Example 2, due to lower values ​​for various process parameters, has relatively insufficient composite structure density and interface bonding, resulting in lower overall performance compared to Example 1. Although Example 3 has higher reinforcement parameters in some structures, the larger material thickness, higher processing strength, and more aggressive process conditions lead to some internal stress accumulation, making its overall stability slightly lower than that of Example 1. Comparative Example 1 only uses conventional PCB manufacturing processes and does not form the composite thermally conductive and reinforcing structure described in this application. Therefore, it is significantly worse in terms of dimensional accuracy, resistance to damp heat, and interfacial bonding performance.

[0037] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0038] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating a heat-dissipating thick copper PCB for high-power coils, characterized in that, Includes the following steps: S1: The original high thermal conductivity fiber is soaked in a surfactant solution of a predetermined concentration, then dried and modified with a surface coupling agent to obtain surface-modified high thermal conductivity fiber. S2: The surface-modified high thermal conductivity fiber obtained in S1 is mixed with resin solution, and after impregnation and drying, a composite semi-cured sheet is obtained. S3: Thick copper coil lines are formed on an insulating substrate by etching process, and the surface of the thick copper coil lines is roughened to obtain an inner core board with thick copper coils. S4: At least two layers of composite prepreg are stacked sequentially on one side of the inner core board, and conductive copper foil is stacked on the outermost layer to form a stack to be pressed. After pressing, a PCB semi-finished product with a high thermal conductivity fiber layer embedded in the middle is obtained. S5: Drill holes in the PCB semi-finished product obtained in S4 to form heat-conducting through holes that penetrate the PCB board surface and the inner coil. S6: Mill the PCB board after processing in S5 to form an edge-sealing area on the edge of the PCB board, and make a metal edge-sealing layer in the edge-sealing area. S7: Post-process the PCB board after metal edging in S6 to obtain the final heat dissipation thick copper PCB for high-power coils.

2. The method for fabricating a heat-dissipating thick copper PCB for high-power coils according to claim 1, characterized in that, S1 specifically includes: S11: Prepare an aqueous solution of sodium dodecylbenzenesulfonate with a mass fraction of 0.5%-2.0% as a surfactant solution, immerse the original high thermal conductivity fiber in the surfactant solution, and soak it at a temperature of 20℃-40℃ for 20-40 minutes to obtain pretreated high thermal conductivity fiber. S12: Take out the pretreated high thermal conductivity fiber from S11 and dry it in an oven at 60℃-80℃ for 30-60 minutes to obtain the dried pretreated high thermal conductivity fiber. S13: Prepare a silane coupling agent alcohol solution with a mass fraction of 1.0%-3.0%, immerse the pretreated high thermal conductivity fiber after drying S12 into the silane coupling agent alcohol solution, and perform a soaking and modification treatment at a temperature of 40℃-60℃ for 10-30 minutes to obtain coupling agent modified high thermal conductivity fiber. S14: Take out the coupling agent modified high thermal conductivity fiber of S13 and dry it in an oven at 50℃-70℃ for 20-40 minutes to obtain surface modified high thermal conductivity fiber.

3. The method for fabricating a heat-dissipating thick copper PCB for high-power coils according to claim 1, characterized in that, The resin solution is an epoxy resin solution, and its preparation method includes the following steps: First, weigh out 40%-50% bisphenol A type epoxy resin, 10%-20% phenolic epoxy resin, 1%-2.5% dicyandiamide curing agent, 0.05%-0.25% 2-methylimidazole accelerator, and the remainder is acetone solvent according to the mass percentage. Then, the weighed bisphenol A epoxy resin, phenolic epoxy resin and acetone solvent are added to the reaction vessel and stirred at 300-500 rpm for 30-60 minutes at a temperature of 40℃-60℃ to completely dissolve the resin and obtain a resin mixture. Finally, the weighed dicyandiamide curing agent and 2-methylimidazole accelerator are added to the resin mixture, and the mixture is stirred for 60-90 minutes at a temperature of 40℃-60℃ until the curing agent and accelerator are completely and evenly dispersed, thus obtaining the epoxy resin solution.

4. The method for fabricating a heat-dissipating thick copper PCB for high-power coils according to claim 1, characterized in that, S2 specifically includes: S21: Surface-modified high thermal conductivity fibers are woven into a fiber cloth, wherein the warp and weft density of the fiber cloth is 60-80 threads / inch and the thickness is 0.05mm-0.15mm; S22: Inject the resin solution into the impregnation tank, and control the temperature of the resin solution in the impregnation tank to be 25℃-35℃ and the viscosity to be 300-800 centipoise. S23: The fiber cloth obtained in S21 is passed through the impregnation tank in S22 at a conveying speed of 1.5m / min-3.0m / min, so that the fiber cloth is fully impregnated with the resin solution to obtain the impregnated fiber cloth. S24: The fiber cloth impregnated with S23 is sent into a vertical drying oven for segmented drying. The first stage of drying is at a temperature of 80℃-100℃ and a drying time of 2-5 minutes. The second stage of drying is at a temperature of 120℃-150℃ and a drying time of 3-8 minutes. The third stage of drying is at a temperature of 150℃-170℃ and a drying time of 1-3 minutes. After drying, a semi-cured composite semi-cured sheet is obtained.

5. A method for fabricating a heat-dissipating thick copper PCB for high-power coils according to claim 1, characterized in that, S3 specifically includes: S31: Prepare an insulating substrate with double-sided copper foil, wherein the thickness of the insulating substrate is 0.1mm-0.5mm and the thickness of the copper foil is 3oz-10oz; S32: A dry film is laminated onto the surface of a double-sided copper-clad insulating substrate, and after exposure and development, an etch-resistant circuit pattern is formed to obtain a substrate with an etch-resistant pattern. S33: Place the substrate obtained in S32 in an etching solution, control the temperature of the etching solution to 45℃-55℃, and the etching pressure to 1.5kg / cm²-2.5kg / cm², and perform etching treatment until the copper foil not protected by the anti-etching pattern is completely removed, and obtain a substrate with thick copper coil lines. S34: Remove the etch-resistant pattern from the substrate surface with thick copper coil lines obtained in S33 to obtain an inner core board with exposed thick copper coil lines. S35: The inner core board with exposed thick copper coil circuitry in S34 is subjected to surface roughening treatment by sandblasting. The sandblasting medium is alumina sand, the sandblasting pressure is 2.0 kg / cm²-4.0 kg / cm², and the sandblasting time is 30-90 seconds, to obtain the inner core board with roughened thick copper coil circuitry.

6. The method for fabricating a heat-dissipating thick copper PCB for high-power coils according to claim 1, characterized in that, S4 specifically includes: S41: Prepare at least two composite prepreg sheets and one conductive copper foil, wherein the thickness of the conductive copper foil is 0.5oz-2oz; S42: The inner core board of the S3 thick copper coil circuit is browned by immersing the inner core board in browning solution, controlling the temperature of browning solution at 30℃-40℃, and the treatment time at 60-120 seconds, to obtain an inner core board with a browning film formed on the surface. S43: At least two composite prepreg sheets are stacked sequentially on one side of the inner core board on which a brown film is formed on the surface, with no gap between adjacent composite prepreg sheets to form a prepreg stack. S44: A conductive copper foil is stacked on the outermost side of the prepreg stack, so that the rough surface of the conductive copper foil contacts the prepreg stack to obtain a preliminary stacked structure. S45: Place the preliminary composite structure on the support plate of the vacuum press, and place a release film and a buffer pad on the top and bottom of the preliminary composite structure respectively to form the composite structure to be pressed.

7. A method for fabricating a heat-dissipating thick copper PCB for high-power coils according to claim 6, characterized in that, S4 further includes: S46: Place the stacked structure to be pressed obtained in S45 into the working area of ​​the vacuum press, close the vacuum press chamber door, and evacuate the vacuum level inside the chamber to 50Pa-200Pa; S47: Increase the pressing temperature at a heating rate of 1.5℃ / min-3.0℃ / min; when the temperature reaches 120℃-150℃, apply a first-stage pressure of 0.5MPa-1.5MPa; when the temperature reaches 180℃-220℃, increase the pressure to a second-stage pressure of 2.0MPa-4.0MPa, and maintain the temperature and pressure for 60-90 minutes. S48: After the pressing time is reached, stop heating and reduce the temperature to below 60℃ at a cooling rate of 1.0℃ / min-2.0℃ / min. Then open the vacuum press chamber door, remove the pressed board, and obtain a PCB semi-finished product with a high thermal conductivity fiber layer embedded in the middle.

8. A method for fabricating a heat-dissipating thick copper PCB for high-power coils according to claim 1, characterized in that, S5 specifically includes: S51: Perform X-Ray drilling target positioning on the PCB semi-finished product obtained in S4. Drill positioning targets at the four corners of the PCB semi-finished product. The diameter of the positioning targets is 1.0mm-1.5mm and the depth penetrates the PCB semi-finished product. S52: Fix the PCB semi-finished product with the drill target positioning completed on the worktable of the CNC drilling machine, and perform drilling program alignment with the positioning target as the reference, with the alignment accuracy controlled within ±0.05mm. S53: The first type of drill bit is used to pre-drill holes in the PCB semi-finished product. The cutting angle of the first type of drill bit is 140°-160°, the drilling speed is 60-80 kilo rpm, the feed rate is 1.0 m / min-1.8 m / min, and the drilling depth is 90% of the thickness of the PCB semi-finished product to form a pre-drilled hole. S54: Use a second type of drill bit to finish the pre-drilled hole formed in S53. The cutting edge angle of the second type of drill bit is 100°-120°, the drilling speed is 90-110 kilorpm, and the feed rate is 0.8m / min-1.2m / min. The drill bit penetrates the PCB semi-finished product to form a heat-conducting through hole that runs through the PCB board surface and the inner layer coil. The diameter of the heat-conducting through hole is 0.2mm-0.5mm.

9. A method for fabricating a heat-dissipating thick copper PCB for high-power coils according to claim 1, characterized in that, S6 specifically includes: S61: Fix the PCB board processed by S5 onto the worktable of a CNC milling machine. Use a two-stage profile milling method. First, use a rough milling cutter with a diameter of 1.5mm-2.5mm, a speed of 30-40 rpm, and a feed rate of 1.0m / min-1.5m / min to perform rough milling along the PCB outline, leaving a margin of 0.1mm-0.2mm. Then, use a finish milling cutter with a diameter of 1.0mm-1.5mm, a speed of 40-50 rpm, and a feed rate of 0.5m / min-1.0m / min to mill to the final size, forming a PCB board with an edge-sealing area. S62: Perform edge cleaning treatment on the PCB board with the edge-wrapped area obtained in S61. Place the PCB board in a plasma cleaning equipment and clean it for 10-20 minutes with a mixture of oxygen and carbon tetrafluoride gas under vacuum conditions of 50Pa-100Pa and power of 500W-1000W to obtain the PCB board with cleaned edge. S63: After cleaning the PCB board edges obtained in S62, a metal cladding layer is made. First, the board is immersed in a chemical copper plating solution at 30℃-40℃ for 20-40 minutes to deposit a chemical copper layer with a thickness of 1μm-3μm. Then, the board is placed in an electroplating copper bath and electroplated at a current density of 1.5A / dm²-2.5A / dm² for 60-120 minutes to form a metal cladding layer with a total thickness of 15μm-50μm.

10. A method for fabricating a heat-dissipating thick copper PCB for high-power coils according to claim 1, characterized in that, Specifically, S7 includes: S71: After metal edging is completed in S6, a solder resist layer is made on the PCB board. Photosensitive solder resist ink is screen-printed or sprayed onto the PCB board surface. The thickness of the solder resist ink is controlled to be 15μm-25μm. After pre-baking at 75℃-85℃ for 20-40 minutes, exposure and development are performed. The temperature of the developing solution is 28℃-32℃, and the developing pressure is 1.5kg / cm²-2.5kg / cm². After development, it is placed in an oven at 150℃-160℃ for 30-60 minutes to cure and form a solder resist layer. S72: Surface treatment is performed on the PCB board for which the solder mask layer is formed in S71. The PCB board is immersed in a chemical nickel-gold plating solution, and the chemical nickel plating temperature is controlled at 80℃-90℃, the nickel plating time is 20-40 minutes, and the nickel layer thickness is 3μm-8μm. Then it is immersed in a chemical gold plating solution, and the chemical gold plating temperature is controlled at 80℃-90℃, the gold plating time is 5-15 minutes, and the gold layer thickness is 0.05μm-0.15μm, to obtain the final heat dissipation type thick copper PCB for high-power coils.

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