Preparation method of high-thermal-conductivity thick copper coil circuit board

Abstract

The invention relates to the technical field of printed circuit board manufacturing, in particular to a preparation method of a high-thermal-conductivity thick copper coil circuit board, which comprises the following steps: S1, mixing a thermal conductive filler with cyanate ester resin to form a modified thermal conductive adhesive film; s2, carrying out surface treatment on the thick copper foil to obtain a surface-modified micro-nano composite thick copper foil; s3, laminating according to the alternating sequence of the conductive layers and the insulating bonding layers to form a multi-layer pre-laminated structure; s4, executing a gradient hot pressing process to obtain a composite substrate; s5, the composite substrate in the S4 is subjected to annealing treatment, and a stable composite substrate is obtained; s6, forming an anti-etching pattern on the surface of the stable composite substrate in S5; and S7, performing post-treatment to obtain a finished product of the high-thermal-conductivity thick copper coil circuit board. According to the invention, the thick copper coil circuit board with high heat conductivity, high bonding strength and low internal stress is prepared through a synergistic process of material modification, interface construction, gradient hot pressing and stress release.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board manufacturing technology, and in particular to a method for preparing a high thermal conductivity thick copper coil circuit board. Background Technology

[0002] Thick copper coil circuit boards, due to their excellent current-carrying capacity, are widely used in fields with stringent thermal management requirements, such as high-power power modules, new energy vehicle electronic control systems, and high-power LED lighting. In these circuit boards, the insulating dielectric layer plays a dual role of electrical isolation and mechanical support. In traditional manufacturing processes, the insulating dielectric layer usually uses ordinary prepreg, whose thermal conductivity is generally lower than 0.8 W / m·K. This makes it difficult to quickly dissipate the Joule heat generated by the thick copper coil, leading to local heat accumulation and the formation of hot spots, which seriously affects the reliability and power output capability of electronic devices. To improve heat dissipation performance, some existing technologies attempt to add high thermal conductivity fillers to the resin. However, due to limitations in the interfacial compatibility between the filler and the resin, as well as the process flowability and brittleness caused by high filler content, it is often difficult to simultaneously achieve thermal conductivity, processing performance, and mechanical toughness.

[0003] Meanwhile, the core challenges in manufacturing thick copper circuit boards lie in the reliability of the bond between the thick copper layer and the insulating dielectric layer, as well as the control of internal stress. The significant difference in the coefficients of linear expansion between copper and the insulating material easily leads to enormous interlayer shear stress during high-temperature lamination and subsequent thermal processes. Existing technologies often employ chemical roughening or blackening treatments to increase mechanical anchoring force, but these are insufficient to form chemical bonds, resulting in insufficient long-term reliability and prominent issues such as blistering, delamination, and overall board warping in thick copper layers. Furthermore, the etching of thick copper lines is challenging due to the significant lateral etching effect, making linewidth control difficult and further restricting the manufacturing yield of high-precision coil circuit boards. Therefore, there is an urgent need to develop a method for preparing high thermal conductivity thick copper coil circuit boards to solve the aforementioned technical problems. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides a method for preparing a high thermal conductivity thick copper coil circuit board.

[0005] A method for fabricating a high thermal conductivity thick copper coil circuit board includes the following steps: S1: The thermally conductive filler is mixed with cyanate ester resin, and after vacuum stirring and degassing, it is coated to form a modified thermally conductive adhesive film. S2: Surface treatment is performed on thick copper foil. First, a roughening layer is formed on its surface, and then a nano-composite coating is deposited on the surface of the roughening layer to obtain a surface-modified micro-nano composite thick copper foil. S3: The micro-nano composite thick copper foil of S2 is used as the conductive layer, and the modified thermally conductive adhesive film of S1 is used as the insulating adhesive layer. The conductive layer and the insulating adhesive layer are stacked in an alternating order, and pre-fixed by local hot-press spot welding to form a multi-layer pre-stacked structure. S4: The multilayer pre-stacked structure formed in S3 is placed in a vacuum hot press and a gradient hot pressing process is performed. The composite substrate is obtained by pressing and curing through a low temperature and low pressure stage and a high temperature and high pressure stage in sequence. S5: Anneal the composite substrate from S4, then cool it to obtain a stable composite substrate after stress relief. S6: An anti-etching pattern is formed on the surface of the stable composite substrate of S5, and the thick copper layer in the uncovered area is etched to form a semi-finished thick copper coil circuit board with a preset circuit pattern. S7: Post-process the surface of the circuit pattern of the S6 thick copper coil circuit board semi-finished product to finally obtain the high thermal conductivity thick copper coil circuit board finished product.

[0006] Optionally, S1 specifically includes: S11: Weigh the thermally conductive filler and cyanate ester resin in a weight ratio of 7:3, and add 0.5%-2.0% of the total weight of the thermally conductive filler as silane coupling agent; S12: Add the thermally conductive filler, the silane coupling agent and the cyanate ester resin into a stirring container, and premix for 15 min to 30 min at a speed of 800 rpm to 1200 rpm to obtain a preliminary mixture. S13: Transfer the preliminary mixture to a vacuum mixer and deaerator, and stir and deaerate for 30 min to 60 min under the conditions of vacuum degree of -0.09MPa to -0.1MPa and speed of 600rpm to 1000rpm to obtain the deaerated thermal conductive paste. S14: The degassed thermally conductive adhesive is applied to the release film using a coating machine, with the coating thickness controlled at 50μm-120μm to form a modified thermally conductive adhesive film.

[0007] Optionally, the thermally conductive filler is selected from spherical alumina or aluminum nitride, and the cyanate resin is selected from bisphenol A type cyanate resin or phenolic type cyanate resin.

[0008] Optionally, S2 specifically includes: S21: Prepare rolled copper foil with a thickness of 210μm-420μm, and perform degreasing and pickling pretreatment on its surface; S22: The pretreated rolled copper foil is placed in an electroplating tank and electrochemical deposition is performed using a DC current density of 15A / dm²-25A / dm². The electroplating time is 30s-90s, and the plating solution is a copper sulfate system, forming a needle-like roughening layer on the surface of the copper foil. S23: The copper foil after forming the needle-like roughened layer is immersed in a deposition solution containing 0.5 g / L-1.5 g / L graphene oxide and 2 g / L-4 g / L dopamine, and the solvent is a Tris buffer solution with a pH of 8.0-8.5. The reaction is carried out at a temperature of 40℃-50℃ for 30 min-60 min to deposit a graphene oxide-polydopamine composite coating on the surface of the needle-like roughened layer. S24: Take out the copper foil after the composite coating is deposited, rinse it with deionized water, and dry it at 60℃-80℃ for 10min-20min to obtain a surface-modified micro-nano composite thick copper foil.

[0009] Optionally, S3 specifically includes: S31: Provide two micro-nano composite thick copper foils prepared by S2, and one modified thermally conductive adhesive film prepared by S1; and place the modified thermally conductive adhesive film between the two micro-nano composite thick copper foils, and stack them in the order of micro-nano composite thick copper foil, modified thermally conductive adhesive film and micro-nano composite thick copper foil from top to bottom, so that the edges of each layer are aligned to form an initial stacked structure; S32: Place the initial stacked structure on the worktable of the spot welding equipment, and use a hot-press spot welding head to perform local spot welding fixation in the preset non-circuit pattern area. The spot welding temperature is 180℃-200℃, the spot welding pressure is 0.2MPa-0.5MPa, the single spot welding time is 1s-3s, and the spacing of the spot welding dot matrix is ​​30mm-50mm. S33: After completing the welding of all spot welding points, a multi-layer pre-stacked structure is obtained.

[0010] Optionally, S4 specifically includes: S41: Place the multilayer pre-stacked structure obtained in S3 on the working platform of the vacuum hot press, close the press and evacuate the cavity to maintain the cavity vacuum degree below 10Pa. S42: Execute the low temperature and low pressure stage, raise the temperature from room temperature to 120℃-130℃ at a heating rate of 1.5℃ / min-2.5℃ / min, and at the same time raise the pressure to 0.5MPa-1.0MPa and maintain it for 10min-20min; S43: Perform the high temperature and high pressure stage, raise the temperature to 220℃-240℃ at a heating rate of 2.0℃ / min-3.0℃ / min, and at the same time raise the pressure to 3.5MPa-5.0MPa and maintain it for 60min-90min; S44: While maintaining a pressure of 3.5MPa-5.0MPa, the temperature is reduced to room temperature at a cooling rate of 1.0℃ / min-2.0℃ / min. Then, the pressure is released and the press is turned on to remove the composite substrate.

[0011] Optionally, S5 specifically includes: S51: Place the composite substrate prepared in S4 in an oven, close the oven door and introduce nitrogen gas, and raise the temperature inside the oven from room temperature to 160℃-180℃ at a heating rate of 1.0℃ / min-2.0℃ / min. S52: Anneal the composite substrate for 4-6 hours at a temperature of 160℃-180℃, keeping the temperature inside the oven constant. S53: After the annealing process is completed, turn off the oven heating power and allow the composite substrate to cool naturally to room temperature in the oven. Then, take out the stable composite substrate after stress relief.

[0012] Optionally, S6 specifically includes: S61: Clean the surface of the stable composite substrate obtained in S5 by spraying an acidic cleaner at a temperature of 40℃-50℃ for 2-5 minutes, then rinsing with deionized water and drying. S62: Apply a photosensitive dry film to the cleaned and stable composite substrate surface. The film application temperature is 100℃-120℃, the film application pressure is 0.3MPa-0.5MPa, and the film application speed is 1.0m / min-1.5m / min. S63: Place the substrate after film application in an exposure machine and perform alignment exposure using a photomask with a preset circuit pattern. The exposure energy is 80mJ / cm²-120mJ / cm². S64: Place the exposed substrate in the developer solution, which is a 1.0%-1.5% sodium carbonate aqueous solution. The developing temperature is 28℃-32℃ and the developing time is 40s-80s. Remove the photosensitive dry film in the unexposed area to expose the surface of the thick copper layer to be etched, forming an anti-etching pattern. S65: Place the developed substrate in an acidic etching solution, control the temperature of the etching solution to 50℃-55℃, and the spray pressure to 0.2MPa-0.3MPa, so that the thick copper layer not covered by the anti-etching pattern is completely removed to form the preset circuit pattern. S66: Place the etched substrate in a stripping solution, which is a 2.0%-3.0% sodium hydroxide aqueous solution. The stripping temperature is 45℃-55℃ and the stripping time is 60s-120s. Remove the photosensitive dry film from the circuit surface, rinse with deionized water and dry to obtain a thick copper coil circuit board semi-finished product.

[0013] Optionally, S7 specifically includes: S71: The thick copper coil circuit board semi-finished product obtained in S6 is placed in a micro-etching tank and micro-etched and roughened using a sodium persulfate-sulfuric acid system micro-etching solution. The concentration of sodium persulfate in the micro-etching solution is 80g / L-120g / L, the volume concentration of sulfuric acid is 3%-5%, the micro-etching temperature is 30℃-40℃, the micro-etching time is 60s-120s, and the micro-etching depth is controlled to be 1μm-3μm. S72: After the micro-etching roughening of the circuit board, use deionized water to overflow clean for 2-5 minutes to remove the residual micro-etching solution on the surface. S73: Place the cleaned circuit board in an organic solder resist coating tank, and coat it with an imidazole organic solder resist agent. The solder resist agent concentration is 5%-10%, the coating temperature is 40℃-50℃, the coating time is 60s-90s, and the thickness of the organic solder resist film is controlled to be 0.2μm-0.5μm. S74: Clean the circuit board coated with organic solder resist film with deionized water for 1-3 minutes to remove excess solder resist residue from the surface. S75: Place the cleaned circuit board in an oven and dry it at 80℃-100℃ for 10min-20min to obtain a finished product of a high thermal conductivity thick copper coil circuit board.

[0014] The beneficial effects of this invention are: This invention significantly improves the thermal conductivity of the insulating dielectric layer by modifying it and using a high-filler thermally conductive filler compounded with a cyanate ester resin system. Simultaneously, by constructing a micro-nano composite structure of a roughened layer and a nano-composite coating on the surface of a thick copper foil, and utilizing the active groups in the nano-coating to undergo a chemical cross-linking reaction with the cyanate ester resin, a synergistic enhancement of physical anchoring and chemical bonding between the thick copper layer and the insulating dielectric layer is achieved, effectively solving the technical problems of low interfacial bonding strength and easy delamination and blistering in thick copper circuit boards.

[0015] This invention, through a gradient hot pressing process combined with annealing, effectively releases the thermal stress accumulated during the pressing process while ensuring the resin is fully cured and cross-linked. This significantly reduces the warpage of thick copper circuit boards and improves the alignment accuracy and product yield of subsequent processes. Attached Figure Description

[0016] 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.

[0017] Figure 1 This is a schematic diagram of the method for preparing a thick copper coil circuit board according to an embodiment of the present invention. Detailed Implementation

[0018] 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.

[0019] 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.

[0020] 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.

[0021] Example 1 like Figure 1 As shown, a method for fabricating a high thermal conductivity thick copper coil circuit board includes the following steps: S1: The thermally conductive filler is mixed with cyanate ester resin, and after vacuum stirring and degassing, it is coated to form a modified thermally conductive adhesive film. S2: Surface treatment is performed on thick copper foil. First, a roughening layer is formed on its surface, and then a nano-composite coating is deposited on the surface of the roughening layer to obtain a surface-modified micro-nano composite thick copper foil. S3: The micro-nano composite thick copper foil of S2 is used as the conductive layer, and the modified thermally conductive adhesive film of S1 is used as the insulating adhesive layer. The conductive layer and the insulating adhesive layer are stacked in an alternating order, and pre-fixed by local hot-press spot welding to form a multi-layer pre-stacked structure. S4: The multilayer pre-stacked structure formed in S3 is placed in a vacuum hot press and a gradient hot pressing process is performed. The composite substrate is obtained by pressing and curing through a low temperature and low pressure stage and a high temperature and high pressure stage in sequence. S5: Anneal the composite substrate from S4, then cool it to obtain a stable composite substrate after stress relief. S6: An anti-etching pattern is formed on the surface of the stable composite substrate of S5, and the thick copper layer in the uncovered area is etched to form a semi-finished thick copper coil circuit board with a preset circuit pattern. S7: Post-process the surface of the circuit pattern of the S6 thick copper coil circuit board semi-finished product to finally obtain the high thermal conductivity thick copper coil circuit board finished product.

[0022] S1 specifically includes: S11: Weigh the thermally conductive filler and cyanate ester resin in a weight ratio of 7:3, and add 1.2% of the total weight of the thermally conductive filler as silane coupling agent. S12: Add the thermally conductive filler, silane coupling agent and cyanate ester resin into a stirring container and premix for 20 minutes at a speed of 1000 rpm to obtain a preliminary mixture. S13: Transfer the preliminary mixture to a vacuum mixer and deaerator, and stir and deaerate for 45 minutes under the conditions of vacuum degree of -0.098MPa and rotation speed of 800rpm to obtain the deaerated thermal conductive paste; S14: The degassed thermally conductive adhesive is applied onto the release film using a coating machine, with the coating thickness controlled at 80μm, to form a modified thermally conductive adhesive film.

[0023] The thermally conductive filler is selected from spherical alumina, and the cyanate ester resin is selected from bisphenol A type cyanate ester resin.

[0024] S2 specifically includes: S21: Prepare a rolled copper foil with a thickness of 280μm, and perform degreasing and pickling pretreatment on its surface; S22: The pretreated rolled copper foil is placed in an electroplating tank and electrochemical deposition is performed using a DC current with a current density of 20A / dm². The electroplating time is 60s and the plating solution is a copper sulfate system, forming a needle-like roughening layer on the surface of the copper foil. S23: The copper foil after forming the needle-like roughened layer is immersed in a deposition solution containing 1.0 g / L graphene oxide and 3 g / L dopamine, and the solvent is Tris buffer with a pH of 8.3. The reaction is carried out at a temperature of 45℃ for 45 min to deposit a graphene oxide-polydopamine composite coating on the surface of the needle-like roughened layer. S24: Take out the copper foil after the composite coating is deposited, rinse it with deionized water, and dry it at 70°C for 15 minutes to obtain a surface-modified micro-nano composite thick copper foil.

[0025] S3 specifically includes: S31: Provide two micro-nano composite thick copper foils prepared by S2, and one modified thermally conductive adhesive film prepared by S1; and place the modified thermally conductive adhesive film between the two micro-nano composite thick copper foils, and stack them in the order of micro-nano composite thick copper foil, modified thermally conductive adhesive film and micro-nano composite thick copper foil from top to bottom, so that the edges of each layer are aligned to form an initial stacked structure; S32: Place the initial stacked structure on the worktable of the spot welding equipment, and use a hot-press spot welding head to perform local spot welding and fixation in the preset non-circuit pattern area. The spot welding temperature is 190℃, the spot welding pressure is 0.35MPa, the single spot welding time is 2s, and the spacing of the spot welding dot matrix is ​​40mm. S33: After completing the welding of all spot welding points, a multi-layer pre-stacked structure is obtained.

[0026] S4 specifically includes: S41: Place the multilayer pre-stacked structure obtained in S3 on the working platform of the vacuum hot press, close the press and evacuate the cavity to maintain the cavity vacuum at 8 Pa. S42: Execute the low temperature and low pressure stage, raise the temperature from room temperature to 125℃ at a heating rate of 2.0℃ / min, and at the same time raise the pressure to 0.8MPa and hold for 15min; S43: Perform the high temperature and high pressure stage, raise the temperature to 230℃ at a heating rate of 2.5℃ / min, and simultaneously raise the pressure to 4.2MPa and maintain it for 75min; S44: While maintaining a pressure of 4.2 MPa, the temperature is reduced to room temperature at a cooling rate of 1.5 °C / min. Then, the pressure is released and the press is turned on to remove the composite substrate.

[0027] S5 specifically includes: S51: Place the composite substrate prepared in S4 in an oven, close the oven door and introduce nitrogen gas, and raise the temperature inside the oven from room temperature to 170°C at a heating rate of 1.5°C / min. S52: Anneal the composite substrate for 5 hours at a constant temperature of 170℃ in the oven. S53: After the annealing process is completed, turn off the oven heating power and allow the composite substrate to cool naturally to room temperature in the oven. Then, take out the stable composite substrate after stress relief.

[0028] S6 specifically includes: S61: The surface of the stable composite substrate obtained in S5 is cleaned by spraying an acidic cleaner at 45°C for 3 minutes, followed by rinsing with deionized water and drying. S62: Apply a photosensitive dry film to the cleaned and stable composite substrate surface at a film application temperature of 110℃, a film application pressure of 0.4MPa, and a film application speed of 1.2m / min. S63: Place the substrate after film application in an exposure machine and perform alignment exposure using a photomask with a preset circuit pattern. The exposure energy is 100mJ / cm². S64: Place the exposed substrate in the developer solution, which is a 1.2% sodium carbonate aqueous solution. The development temperature is 30℃ and the development time is 60s. Remove the photosensitive dry film in the unexposed area to expose the surface of the thick copper layer to be etched, forming an anti-etching pattern. S65: Place the developed substrate in an acidic etching solution, control the temperature of the etching solution to 52°C and the spray pressure to 0.25MPa, so that the thick copper layer not covered by the anti-etching pattern is completely removed to form the preset circuit pattern. S66: Place the etched substrate in a stripping solution, which is a 2.5% sodium hydroxide aqueous solution. The stripping temperature is 50℃ and the stripping time is 90s. Remove the photosensitive dry film from the circuit surface, rinse with deionized water and dry to obtain a thick copper coil circuit board semi-finished product.

[0029] S7 specifically includes: S71: The thick copper coil circuit board semi-finished product obtained in S6 is placed in a micro-etching tank and micro-etched and roughened using a sodium persulfate-sulfuric acid system micro-etching solution. The concentration of sodium persulfate in the micro-etching solution is 100g / L, the volume concentration of sulfuric acid is 4%, the micro-etching temperature is 35℃, the micro-etching time is 90s, and the micro-etching depth is controlled to be 2μm. S72: After the micro-etching roughening of the circuit board, use deionized water to overflow clean for 3 minutes to remove the residual micro-etching solution on the surface. S73: Place the cleaned circuit board in an organic solder resist coating tank, and coat it with an imidazole organic solder resist agent with a flux concentration of 8%, a coating temperature of 45℃, a coating time of 75s, and control the thickness of the organic solder resist film to be 0.3μm. S74: Clean the circuit board coated with organic solder resist film with deionized water for 2 minutes to remove excess solder resist residue from the surface. S75: Place the cleaned circuit board in an oven and dry it at 90°C for 15 minutes to obtain a finished product of a high thermal conductivity thick copper coil circuit board.

[0030] Example 2 S1: Weigh the thermally conductive filler and cyanate ester resin at a weight ratio of 7:3, wherein the thermally conductive filler is aluminum nitride, the cyanate ester resin is phenolic cyanate ester resin, and add 0.5% of the total weight of the thermally conductive filler with silane coupling agent; then add aluminum nitride, silane coupling agent and phenolic cyanate ester resin into a stirring container and premix at 800 rpm for 15 min to obtain a preliminary mixture; then transfer the preliminary mixture to a vacuum stirrer and degas at a vacuum of -0.09 MPa and a speed of 600 rpm for 30 min to obtain a degassed thermally conductive paste; finally, apply the thermally conductive paste to the surface of the release film using a coating machine, controlling the coating thickness to 50 μm, to form a modified thermally conductive film; S2: A rolled copper foil with a thickness of 210 μm was selected, and its surface was pretreated by degreasing and pickling. Then, the pretreated rolled copper foil was placed in an electroplating tank, and electrochemical deposition was performed using a direct current with a current density of 15 A / dm² for 30 s. The plating solution used a copper sulfate system, thereby forming a needle-like roughened layer on the surface of the copper foil. After that, the copper foil with the needle-like roughened layer was immersed in a deposition solution containing 0.5 g / L graphene oxide and 2 g / L dopamine, with Tris buffer solution at pH 8.0 as the solvent. The reaction was carried out at 40 °C for 30 min, so that a graphene oxide-polydopamine composite coating was deposited on the surface of the needle-like roughened layer. Finally, the copper foil with the composite coating was taken out, rinsed with deionized water, and dried at 60 °C for 10 min to obtain a surface-modified micro-nano composite thick copper foil. S3: Take two micro-nano composite thick copper foils prepared in S2 and one modified thermally conductive adhesive film prepared in S1. Place the modified thermally conductive adhesive film between the two micro-nano composite thick copper foils and stack them in the following order from top to bottom: micro-nano composite thick copper foil, modified thermally conductive adhesive film, and micro-nano composite thick copper foil, aligning the edges of each layer to form an initial stacked structure. Then, place the initial stacked structure on the worktable of the spot welding equipment and use a hot-press spot welding head to perform local spot welding and fixation in the preset non-circuit pattern area. The spot welding temperature is 180℃, the spot welding pressure is 0.2MPa, the single spot welding time is 1s, and the spot welding dot spacing is 30mm. After all spot welding points are completed, a multi-layer pre-stacked structure is obtained. S4: The multilayer pre-stacked structure obtained in S3 is placed on the working platform of a vacuum hot press. The press is closed and the cavity is evacuated to maintain a vacuum level of 10 Pa. Then, a low-temperature and low-pressure stage is performed, with the temperature increased from room temperature to 120°C at a heating rate of 1.5°C / min, while the pressure is increased to 0.5 MPa and held for 10 min. On this basis, a high-temperature and high-pressure stage is performed, with the temperature increased to 220°C at a heating rate of 2.0°C / min, while the pressure is increased to 3.5 MPa and held for 60 min. Then, while maintaining a pressure of 3.5 MPa, the temperature is reduced to room temperature at a cooling rate of 1.0°C / min. The pressure is then released and the press is opened to obtain the composite substrate. S5: Place the composite substrate obtained in S4 in an oven, close the oven door and introduce nitrogen gas, and raise the temperature inside the oven from room temperature to 160℃ at a heating rate of 1.0℃ / min; after the temperature reaches 160℃, keep it at a constant temperature for 4 hours to anneal the composite substrate; after annealing, turn off the oven heating power and allow the composite substrate to cool naturally to room temperature inside the oven. After taking it out, a stable composite substrate after stress relief is obtained. S6: First, clean the surface of the stable composite substrate obtained in S5 by spraying with an acidic cleaner at 40°C for 2 minutes, followed by rinsing with deionized water and drying. Then, attach a photosensitive dry film to the cleaned stable composite substrate surface at a temperature of 100°C, a pressure of 0.3 MPa, and a speed of 1.0 m / min. Next, place the substrate in an exposure machine and perform alignment exposure using a photomask with a preset circuit pattern at an exposure energy of 80 mJ / cm². After exposure, place the substrate in a 1.0% sodium carbonate aqueous solution. The substrate is developed in an aqueous solution at a temperature of 28°C for 40 seconds to remove the photosensitive dry film from unexposed areas and form an etch-resistant pattern. Next, the developed substrate is placed in an acidic etching solution at a temperature of 50°C and a spray pressure of 0.2 MPa to completely remove the thick copper layer not covered by the etch-resistant pattern, forming a pre-defined circuit pattern. Finally, the etched substrate is stripped in a 2.0% sodium hydroxide aqueous solution at a temperature of 45°C for 60 seconds. After stripping, the substrate is rinsed with deionized water and dried to obtain a semi-finished thick copper coil circuit board. S7: The semi-finished thick copper coil circuit board obtained in S6 is placed in a micro-etching tank and subjected to micro-etching roughening treatment using a sodium persulfate-sulfuric acid system. The sodium persulfate concentration is 80 g / L, the sulfuric acid volume concentration is 3%, the micro-etching temperature is 30℃, the micro-etching time is 60 s, and the micro-etching depth is controlled to be 1 μm. After micro-etching, the board is overflow-washed with deionized water for 2 min to remove residual micro-etching solution from the surface. The cleaned circuit board is then placed in an organic solder resist coating tank and coated with an imidazole organic solder resist with a solder resist concentration of 5%, a coating temperature of 40℃, a coating time of 60 s, and an organic solder resist thickness of 0.2 μm. The board is then rinsed again with deionized water for 1 min to remove excess solder resist residue from the surface. Finally, the cleaned circuit board is placed in an oven and dried at 80℃ for 10 min to obtain the finished thick copper coil circuit board with high thermal conductivity.

[0031] Example 3 S1: Weigh the thermally conductive filler and cyanate ester resin at a weight ratio of 7:3, wherein the thermally conductive filler is spherical alumina, the cyanate ester resin is bisphenol A type cyanate ester resin, and add 2.0% of the total weight of the thermally conductive filler with silane coupling agent; then add the spherical alumina, silane coupling agent and bisphenol A type cyanate ester resin into a stirring container and premix at 1200 rpm for 30 min to obtain a preliminary mixture; then transfer the preliminary mixture to a vacuum stirring degasser and stir and degas at a vacuum degree of -0.1 MPa and a speed of 1000 rpm for 60 min to obtain a degassed thermally conductive paste; finally, apply the thermally conductive paste to the surface of the release film using a coating machine, controlling the coating thickness to be 120 μm, to form a modified thermally conductive film; S2: A 420 μm thick rolled copper foil was selected, and its surface was pretreated by degreasing and pickling. Then, the pretreated rolled copper foil was placed in an electroplating tank, and electrochemical deposition was performed using a DC current density of 25 A / dm² for 90 s. The plating solution used a copper sulfate system, thereby forming a needle-like roughened layer on the surface of the copper foil. The copper foil with the needle-like roughened layer was then immersed in a deposition solution containing 1.5 g / L graphene oxide and 4 g / L dopamine, with Tris buffer solution at pH 8.5 as the solvent. The reaction was carried out at 50 °C for 60 min, so that a graphene oxide-polydopamine composite coating was deposited on the surface of the needle-like roughened layer. Finally, the copper foil with the composite coating was removed, rinsed with deionized water, and dried at 80 °C for 20 min to obtain a surface-modified micro-nano composite thick copper foil. S3: Take two micro-nano composite thick copper foils prepared in S2 and one modified thermally conductive adhesive film prepared in S1. Place the modified thermally conductive adhesive film between the two micro-nano composite thick copper foils and stack them in the following order from top to bottom: micro-nano composite thick copper foil, modified thermally conductive adhesive film, and micro-nano composite thick copper foil, aligning the edges of each layer to form an initial stacked structure. Then, place the initial stacked structure on the worktable of the spot welding equipment and use a hot-press spot welding head to perform local spot welding and fixation in the preset non-circuit pattern area. The spot welding temperature is 200℃, the spot welding pressure is 0.5MPa, the single spot welding time is 3s, and the spot welding dot spacing is 50mm. After all spot welding points are completed, a multi-layer pre-stacked structure is obtained. S4: The multilayer pre-stacked structure obtained in S3 is placed on the working platform of a vacuum hot press. The press is closed and the cavity is evacuated to maintain a vacuum level of 9 Pa. Then, a low-temperature and low-pressure stage is performed, with the temperature increased from room temperature to 130°C at a heating rate of 2.5°C / min, while the pressure is increased to 1.0 MPa and held for 20 min. On this basis, a high-temperature and high-pressure stage is performed, with the temperature increased to 240°C at a heating rate of 3.0°C / min, while the pressure is increased to 5.0 MPa and held for 90 min. Then, while maintaining a pressure of 5.0 MPa, the temperature is reduced to room temperature at a cooling rate of 2.0°C / min. The pressure is then released and the press is opened to obtain the composite substrate. S5: Place the composite substrate obtained in S4 in an oven, close the oven door and introduce nitrogen gas, and raise the temperature inside the oven from room temperature to 180℃ at a heating rate of 2.0℃ / min; after the temperature reaches 180℃, keep it at a constant temperature for 6 hours to anneal the composite substrate; after annealing, turn off the oven heating power and allow the composite substrate to cool naturally to room temperature inside the oven. After taking it out, a stable composite substrate after stress release is obtained. S6: First, clean the surface of the stable composite substrate obtained in S5 by spraying with an acidic cleaner at 50°C for 5 minutes, followed by rinsing with deionized water and drying. Then, attach a photosensitive dry film to the cleaned stable composite substrate surface at a temperature of 120°C, a pressure of 0.5 MPa, and a speed of 1.5 m / min. Next, place the substrate in an exposure machine and perform alignment exposure using a photomask with a preset circuit pattern at an exposure energy of 120 mJ / cm². After exposure, place the substrate in a 1.5% sodium carbonate aqueous solution. The substrate is developed in an aqueous solution at a temperature of 32°C for 80 seconds to remove the photosensitive dry film from unexposed areas and form an etch-resistant pattern. Next, the developed substrate is placed in an acidic etching solution at a temperature of 55°C and a spray pressure of 0.3 MPa to completely remove the thick copper layer not covered by the etch-resistant pattern, forming a pre-defined circuit pattern. Finally, the etched substrate is stripped in a 3.0% sodium hydroxide aqueous solution at a temperature of 55°C for 120 seconds. After stripping, it is rinsed with deionized water and dried to obtain a semi-finished thick copper coil circuit board. S7: The semi-finished thick copper coil circuit board obtained in S6 is placed in a micro-etching tank and subjected to micro-etching roughening treatment using a sodium persulfate-sulfuric acid system micro-etching solution. The sodium persulfate concentration is 120 g / L, the sulfuric acid volume concentration is 5%, the micro-etching temperature is 40℃, the micro-etching time is 120 s, and the micro-etching depth is controlled to be 3 μm. After micro-etching, the board is overflow-washed with deionized water for 5 min to remove residual micro-etching solution from the surface. The cleaned circuit board is then placed in an organic solder resist coating tank and coated with an imidazole organic solder resist with a solder resist concentration of 10%, a coating temperature of 50℃, a coating time of 90 s, and an organic solder resist thickness of 0.5 μm. It is then rinsed again with deionized water for 3 min to remove excess solder resist residue from the surface. Finally, the cleaned circuit board is placed in an oven and dried at 100℃ for 20 min to obtain the finished thick copper coil circuit board with high thermal conductivity.

[0032] Comparative Example 1 Step 1: Select a standard FR-4 copper-clad laminate with a thickness of 1.6mm as the substrate. The copper layer thickness on the surface of the copper-clad laminate is 35μm. First, clean it with an acidic cleaner at 40℃ for 2 minutes, then rinse with deionized water and dry it. Then, attach a photosensitive dry film to the surface of the copper-clad laminate. The film attaching temperature is controlled at 105℃, the film attaching pressure is controlled at 0.3MPa, and the film attaching speed is controlled at 1.0m / min. After the film is attached, expose it using a circuit photomask. The exposure energy is controlled at 90mJ / cm². Then, develop it in a 1.0% sodium carbonate aqueous solution. The development temperature is controlled at 30℃, and the development time is controlled at 60s, thereby forming an anti-etching layer of the preset circuit pattern. Step 2: Place the copper-clad board with the resist layer in an acidic etching solution for etching. The etching solution temperature is controlled at 50℃, the spray pressure is controlled at 0.2MPa, and the etching time is controlled at 120s to remove the copper layer not covered by the resist layer and form a copper coil circuit pattern. After etching, place the circuit board in a 2.0% sodium hydroxide aqueous solution for stripping. The stripping temperature is controlled at 50℃ and the stripping time is controlled at 90s. Then rinse with deionized water and dry. Step 3: Perform surface anti-oxidation treatment on the circuit board with the circuit pattern formed. Specifically, immerse the circuit board in an imidazole organic solder resist solution with a solder resist concentration of 5%, a treatment temperature of 40℃, and a treatment time of 60s. After treatment, rinse with deionized water for 1 minute and dry in an 80℃ oven for 10 minutes to obtain the finished traditional copper coil circuit board.

[0033] 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) 3.82 2.95 3.41 0.36 Copper layer peel strength N / mm 2.31 1.74 2.08 1.02 Volume resistivity Ω·cm 3.6×10^14 2.8×10^14 3.2×10^14 1.1×10^14 Dielectric breakdown strength kV / mm 42.7 35.4 39.8 24.6 Board warpage % 0.18 0.34 0.27 0.69 Line etching side etching amount μm 18 26 22 41 Resistance change rate after thermal cycling (-40℃~125℃, 200 cycles) % 1.9 3.8 2.7 6.9 Temperature rise under high current load (20A, 10min) ℃ 21.6 29.4 24.8 43.7 As can be seen from the data in Table 1 above, Example 1 exhibits the best performance in terms of thermal conductivity, peel strength, volume resistivity, dielectric breakdown strength, board warpage, etch depth, resistance change rate after thermal cycling, and temperature rise under high current operation. This indicates that Example 1 achieves a more coordinated matching relationship among the thermally conductive adhesive film preparation, micro-nano composite thick copper foil construction, gradient hot pressing, stress release during annealing, and post-processing parameters. On the one hand, the spherical alumina / bisphenol A cyanate resin system establishes a relatively continuous thermal conductivity pathway while ensuring insulation. On the other hand, the needle-like roughening layer and the graphene oxide-polydopamine composite coating together improve the interfacial bonding stability between the copper layer and the insulating layer. Combined with a vacuum of 8 Pa, two-stage hot pressing at 125℃ / 230℃, and annealing at 170℃, the interlayer voids and residual stress are effectively reduced. Therefore, a thick copper coil circuit board with high thermal conductivity, high bonding strength, good dimensional stability, and low temperature rise under high current operation is finally obtained. Although Example 2 also adopted the overall process route of the present invention, its process parameters were generally at a lower level. The degree of thermally conductive filler coupling modification was weaker, the film thickness was thinner, and the degree of copper foil micro-nano composite modification was lower. At the same time, the hot pressing and post-processing conditions were also relatively mild. Therefore, it was weaker than Example 1 in terms of the continuity of the internal thermal conductive network, the interfacial bonding strength, and the long-term thermal stability. Example 3 used higher upper limit parameters. Although the thermal conductivity and peel strength were still significantly better than those of Comparative Example 1, the higher film thickness, hot pressing temperature, holding time, and post-processing strength easily caused local stress concentration and dimensional control fluctuations. Therefore, it was inferior to Example 1 in terms of warpage, thermal cycling stability, and etching accuracy. This shows that higher parameters are not always better; rather, a balance needs to be achieved between interfacial bonding, thermal conductive construction, and stress control. Comparative Example 1 employs a traditional FR-4 copper-clad laminate direct pattern transfer and surface anti-oxidation treatment. It lacks a dedicated thermally conductive insulating layer, micro-nano composite modification of the thick copper interface, and synergistic control through gradient hot pressing and annealing. Therefore, it exhibits the lowest thermal conductivity, lowest peel strength, highest warpage, and highest resistivity change rate after thermal cycling. Furthermore, it experiences the highest temperature rise under a 20A load condition, indicating that the traditional structure cannot meet the performance requirements of high thermal conductivity, high bonding stability, and high-current applications. In summary, Example 1 provides the optimal parameter combination, achieving the best balance between thermal conductivity, interface bonding ability, electrical insulation performance, circuit forming quality, and long-term service stability. Therefore, it can be considered the preferred embodiment of this invention.

[0034] Table 2 Comparison of other performance data Comparison Projects Test unit Example 1 Example 2 Example 3 Comparative Example 1 Water absorption rate (24h, 25℃) % 0.11 0.19 0.16 0.42 Insulation resistance retention rate after moisture absorption (85℃ / 85%RH, 168h) % 94.8 88.6 91.3 73.5 Peel strength retention rate after damp heat (85℃ / 85%RH, 240h) % 91.7 84.2 88.5 69.8 Delamination length after welding thermal shock mm 0.08 0.21 0.14 0.53 Thermal expansion coefficient in the Z direction (50℃-200℃) ppm / ℃ 42 51 47 68 Hole size deviation μm 16 25 21 39 Line width deviation μm 12 20 16 33 Surface insulation resistance (SIR) (85℃ / 85%RH, 100V, 168h) Ω 8.4×10^10 4.9×10^10 6.7×10^10 1.6×10^10 Thermal conductivity retention rate after 1000h aging % 96.2 90.4 93.1 78.7 As can be seen from Table 2 above, Example 1 exhibits the best performance in terms of water absorption rate, insulation resistance retention rate after moisture absorption, peel strength retention rate after damp heat resistance, delamination length after welding thermal shock, Z-axis thermal expansion coefficient, hole size deviation, line width deviation, surface insulation resistance, and thermal conductivity retention rate after 1000 hours of aging. This indicates that Example 1 not only has advantages in thermal conductivity and bonding performance, but also excels in adaptability to damp heat environments, dimensional accuracy retention, and long-term service reliability. This is because the modified thermally conductive adhesive film, micro-nano composite thick copper foil, gradient hot pressing process, and annealing process in Example 1 are more evenly matched, resulting in a denser and more stable interlayer interface, fewer internal defects, and more complete stress release. Therefore, it can maintain good structural integrity and electrical performance stability under subsequent moisture absorption, thermal shock, and long-term aging conditions. Although Example 2 exhibits significantly better overall performance than Comparative Example 1, its thinner thermally conductive adhesive film, lower degree of interface modification, and less stringent hot-pressing and annealing conditions result in less dense internal bonding and lower interface stability compared to Example 1. Consequently, it shows a certain decline in moisture absorption stability, thermal shock resistance to delamination, and performance retention after aging. Example 3, while employing higher process parameters and showing some performance improvements over Example 2, suffers from higher adhesive film thickness, hot-pressing, and post-processing conditions, which can easily lead to additional internal stress and dimensional fluctuations. Therefore, it remains slightly inferior to Example 1 in terms of dimensional accuracy, thermal expansion control, and overall reliability. Comparative Example 1 utilizes conventional FR-4 copper-clad laminate pattern transfer technology, without establishing a dedicated high thermal conductivity insulating layer structure, or performing thick copper interface micro-nano composite modification and gradient hot-pressing-annealing synergistic control. Therefore, it performs the worst in terms of moisture absorption, thermal shock, dimensional accuracy, and long-term reliability, indicating that traditional copper coil circuit boards are insufficient to meet the requirements of high thermal conductivity, high stability, and high reliability applications. In summary, from another set of performance dimensions, Example 1 still exhibits the best overall performance, indicating that this example is more reasonable in terms of material system selection, interface construction, and process parameter matching, and can be regarded as the best example of the present invention.

[0035] 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.

[0036] 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 high thermal conductivity thick copper coil circuit board, characterized in that, Includes the following steps: S1: The thermally conductive filler is mixed with cyanate ester resin, and after vacuum stirring and degassing, it is coated to form a modified thermally conductive adhesive film. S2: Surface treatment is performed on thick copper foil. First, a roughening layer is formed on its surface, and then a nano-composite coating is deposited on the surface of the roughening layer to obtain a surface-modified micro-nano composite thick copper foil. S3: The micro-nano composite thick copper foil of S2 is used as the conductive layer, and the modified thermally conductive adhesive film of S1 is used as the insulating adhesive layer. The conductive layer and the insulating adhesive layer are stacked in an alternating order, and pre-fixed by local hot-press spot welding to form a multi-layer pre-stacked structure. S4: The multilayer pre-stacked structure formed in S3 is placed in a vacuum hot press and a gradient hot pressing process is performed. The composite substrate is obtained by pressing and curing through a low temperature and low pressure stage and a high temperature and high pressure stage in sequence. S5: Anneal the composite substrate from S4, then cool it to obtain a stable composite substrate after stress relief. S6: An anti-etching pattern is formed on the surface of the stable composite substrate of S5, and the thick copper layer in the uncovered area is etched to form a semi-finished thick copper coil circuit board with a preset circuit pattern. S7: Post-process the surface of the circuit pattern of the S6 thick copper coil circuit board semi-finished product to finally obtain the high thermal conductivity thick copper coil circuit board finished product.

2. The method for preparing a high thermal conductivity thick copper coil circuit board according to claim 1, characterized in that, S1 specifically includes: S11: Weigh the thermally conductive filler and cyanate ester resin in a weight ratio of 7:3, and add 0.5%-2.0% of the total weight of the thermally conductive filler as silane coupling agent; S12: Add the thermally conductive filler, the silane coupling agent and the cyanate ester resin into a stirring container, and premix for 15 min to 30 min at a speed of 800 rpm to 1200 rpm to obtain a preliminary mixture. S13: Transfer the preliminary mixture to a vacuum mixer and deaerator, and stir and deaerate for 30 min to 60 min under the conditions of vacuum degree of -0.09MPa to -0.1MPa and speed of 600rpm to 1000rpm to obtain the deaerated thermal conductive paste. S14: The degassed thermally conductive adhesive is applied to the release film using a coating machine, with the coating thickness controlled at 50μm-120μm to form a modified thermally conductive adhesive film.

3. The method for preparing a high thermal conductivity thick copper coil circuit board according to claim 2, characterized in that, The thermally conductive filler is selected from spherical alumina or aluminum nitride, and the cyanate resin is selected from bisphenol A type cyanate resin or phenolic type cyanate resin.

4. The method for preparing a high thermal conductivity thick copper coil circuit board according to claim 1, characterized in that, S2 specifically includes: S21: Prepare rolled copper foil with a thickness of 210μm-420μm, and perform degreasing and pickling pretreatment on its surface; S22: The pretreated rolled copper foil is placed in an electroplating tank and electrochemical deposition is performed using a DC current density of 15A / dm²-25A / dm². The electroplating time is 30s-90s, and the plating solution is a copper sulfate system, forming a needle-like roughening layer on the surface of the copper foil. S23: The copper foil after forming the needle-like roughened layer is immersed in a deposition solution containing 0.5 g / L-1.5 g / L graphene oxide and 2 g / L-4 g / L dopamine, and the solvent is a Tris buffer solution with a pH of 8.0-8.

5. The reaction is carried out at a temperature of 40℃-50℃ for 30 min-60 min to deposit a graphene oxide-polydopamine composite coating on the surface of the needle-like roughened layer. S24: Take out the copper foil after the composite coating is deposited, rinse it with deionized water, and dry it at 60℃-80℃ for 10min-20min to obtain a surface-modified micro-nano composite thick copper foil.

5. The method for preparing a high thermal conductivity thick copper coil circuit board according to claim 1, characterized in that, S3 specifically includes: S31: Provide two micro-nano composite thick copper foils prepared by S2, and one modified thermally conductive adhesive film prepared by S1; and place the modified thermally conductive adhesive film between the two micro-nano composite thick copper foils, and stack them in the order of micro-nano composite thick copper foil, modified thermally conductive adhesive film and micro-nano composite thick copper foil from top to bottom, so that the edges of each layer are aligned to form an initial stacked structure; S32: Place the initial stacked structure on the worktable of the spot welding equipment, and use a hot-press spot welding head to perform local spot welding fixation in the preset non-circuit pattern area. The spot welding temperature is 180℃-200℃, the spot welding pressure is 0.2MPa-0.5MPa, the single spot welding time is 1s-3s, and the spacing of the spot welding dot matrix is ​​30mm-50mm. S33: After completing the welding of all spot welding points, a multi-layer pre-stacked structure is obtained.

6. The method for preparing a high thermal conductivity thick copper coil circuit board according to claim 1, characterized in that, S4 specifically includes: S41: Place the multilayer pre-stacked structure obtained in S3 on the working platform of the vacuum hot press, close the press and evacuate the cavity to maintain the cavity vacuum degree below 10Pa. S42: Execute the low temperature and low pressure stage, raise the temperature from room temperature to 120℃-130℃ at a heating rate of 1.5℃ / min-2.5℃ / min, and at the same time raise the pressure to 0.5MPa-1.0MPa and maintain it for 10min-20min; S43: Perform the high temperature and high pressure stage, raise the temperature to 220℃-240℃ at a heating rate of 2.0℃ / min-3.0℃ / min, and at the same time raise the pressure to 3.5MPa-5.0MPa and maintain it for 60min-90min; S44: While maintaining a pressure of 3.5MPa-5.0MPa, the temperature is reduced to room temperature at a cooling rate of 1.0℃ / min-2.0℃ / min. Then, the pressure is released and the press is turned on to remove the composite substrate.

7. The method for preparing a high thermal conductivity thick copper coil circuit board according to claim 1, characterized in that, S5 specifically includes: S51: Place the composite substrate prepared in S4 in an oven, close the oven door and introduce nitrogen gas, and raise the temperature inside the oven from room temperature to 160℃-180℃ at a heating rate of 1.0℃ / min-2.0℃ / min. S52: Anneal the composite substrate for 4-6 hours at a temperature of 160℃-180℃, keeping the temperature inside the oven constant. S53: After the annealing process is completed, turn off the oven heating power and allow the composite substrate to cool naturally to room temperature in the oven. Then, take out the stable composite substrate after stress relief.

8. The method for preparing a high thermal conductivity thick copper coil circuit board according to claim 1, characterized in that, S6 specifically includes: S61: Clean the surface of the stable composite substrate obtained in S5 by spraying an acidic cleaner at a temperature of 40℃-50℃ for 2-5 minutes, followed by rinsing with deionized water and drying. S62: Apply a photosensitive dry film to the cleaned and stable composite substrate surface. The film application temperature is 100℃-120℃, the film application pressure is 0.3MPa-0.5MPa, and the film application speed is 1.0m / min-1.5m / min. S63: Place the substrate after film application in an exposure machine and perform alignment exposure using a photomask with a preset circuit pattern. The exposure energy is 80mJ / cm²-120mJ / cm². S64: Place the exposed substrate in the developer solution, which is a 1.0%-1.5% sodium carbonate aqueous solution. The developing temperature is 28℃-32℃ and the developing time is 40s-80s. Remove the photosensitive dry film in the unexposed area to expose the surface of the thick copper layer to be etched, forming an anti-etching pattern. S65: Place the developed substrate in an acidic etching solution, control the temperature of the etching solution to 50℃-55℃, and the spray pressure to 0.2MPa-0.3MPa, so that the thick copper layer not covered by the anti-etching pattern is completely removed to form the preset circuit pattern. S66: Place the etched substrate in a stripping solution, which is a 2.0%-3.0% sodium hydroxide aqueous solution. The stripping temperature is 45℃-55℃ and the stripping time is 60s-120s. Remove the photosensitive dry film from the circuit surface, rinse with deionized water and dry to obtain a thick copper coil circuit board semi-finished product.

9. The method for preparing a high thermal conductivity thick copper coil circuit board according to claim 1, characterized in that, Specifically, S7 includes: S71: The thick copper coil circuit board semi-finished product obtained in S6 is placed in a micro-etching tank and micro-etched and roughened using a sodium persulfate-sulfuric acid system micro-etching solution. The concentration of sodium persulfate in the micro-etching solution is 80g / L-120g / L, the volume concentration of sulfuric acid is 3%-5%, the micro-etching temperature is 30℃-40℃, the micro-etching time is 60s-120s, and the micro-etching depth is controlled to be 1μm-3μm. S72: After the micro-etching roughening process, the circuit board is rinsed with deionized water for 2-5 minutes to remove residual micro-etching solution from the surface. S73: Place the cleaned circuit board in an organic solder resist coating tank, and coat it with an imidazole organic solder resist agent. The solder resist agent concentration is 5%-10%, the coating temperature is 40℃-50℃, the coating time is 60s-90s, and the thickness of the organic solder resist film is controlled to be 0.2μm-0.5μm. S74: Clean the circuit board coated with organic solder resist film with deionized water for 1-3 minutes to remove excess solder resist residue from the surface. S75: Place the cleaned circuit board in an oven and dry it at 80℃-100℃ for 10min-20min to obtain a finished product of a high thermal conductivity thick copper coil circuit board.

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