Ceramic coil for quick charger and preparation method of ceramic coil

Abstract

The invention discloses a ceramic coil for a quick charger and a preparation method of the ceramic coil, and relates to the technical field of quick chargers and transformers. Comprising the following steps: step 1, taking a copper-clad plate as a substrate, and forming a primary coil and a secondary coil through CAD coil pattern drawing, photoresist coating, exposure, development, etching, washing and drying; 2, the primary coil and the secondary coil are subjected to laser drilling, and through silk-screen printing hole filling and ball mounting, the primary coil and the secondary coil serve as conducting columns; 3, the lower surfaces of the primary coil and the secondary coil are coated with heat-conducting insulating layer slurry respectively, curing is conducted, a heat-conducting insulating layer is formed, and a primary coil A and a secondary coil B are obtained; 4, enabling the heat-conducting insulating layers of the multiple groups of secondary coils B to face upwards and the heat-conducting insulating layers of the multiple groups of primary coils A to face downwards, aligning and overlapping, carrying out primary hot pressing, and cooling to obtain coils; and attaching the heat-conducting insulating layer of the coil to the ceramic substrate, performing secondary hot pressing, and cooling to obtain the ceramic coil.

Description

Technical Field

[0001] This invention relates to the field of fast chargers and transformers, specifically a ceramic coil for a fast charger and its preparation method. Background Technology

[0002] With the development of electronic information, electronic devices have become an indispensable part of human life, and their battery life and charging efficiency have increasingly become core objectives pursued by consumers. This demand has directly driven the rapid development of fast chargers towards higher power, miniaturization, and convenience.

[0003] As a core component of fast chargers, the coil directly affects the power density, energy conversion efficiency, and operating temperature of the charger. However, traditional fast charger coils are mostly made of copper wire wound around an iron core, relying on a wound transformer. Although this structure is low-cost, it has many problems that severely limit the development and application of fast chargers, specifically in the following aspects: First, traditional wire-wound coils require reserved space for winding, and to ensure mechanical assembly tolerances and electrical insulation safety, the assembly gap between the core and the coil is relatively large, making it difficult to reduce the size of the transformer, directly affecting the miniaturization requirements of fast chargers. Second, traditional fast chargers require complex production processes such as winding, impregnation, and curing, resulting in low automation and limited production efficiency. Third, the solder joints between the winding and the pins have high contact resistance and are at risk of detachment under vibration, leading to low soldering stability. Fourth, the traditional wire-wound process results in high coil leakage inductance and distributed capacitance, leading to low conversion efficiency at high frequencies, typically below 85%. Most importantly, on the one hand, due to the limitations of traditional wire-wound coils, heat needs to be conducted to the outer shell through the winding and frame, resulting in a long heat dissipation path and insufficient heat dissipation performance. When operating at high power, the coil temperature can reach over 150°C, significantly reducing stability and directly affecting the lifespan and safety of the fast charger. On the other hand, the insulation layer between the windings in traditional fast chargers is mostly made of ordinary resin material, which typically withstands temperatures below 120°C. This poor heat resistance makes the product prone to aging under high-power charging scenarios, leading to insulation failure and seriously affecting the product's lifespan and safety. In conclusion, solving the above problems and developing a ceramic coil for fast chargers is of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide a ceramic coil for a fast charger and a method for preparing the same, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preparing a ceramic coil for a fast charger includes the following steps: Step 1: Using a copper-clad laminate as a substrate, draw coil patterns using CAD, apply photoresist, expose, develop, etch, wash, and dry to form the primary coil and secondary coil. Step 2: Laser drilling of primary and secondary coils, followed by screen printing to fill the holes and inserting balls to serve as conduction posts; Step 3: Coat the lower surfaces of the primary coil and the secondary coil with thermally conductive insulating paste, and cure to form a thermally conductive insulating layer, thus obtaining primary coil A and secondary coil B; Step 4: Align and stack multiple sets of secondary coils B with their thermally conductive insulation layers facing upwards and multiple sets of primary coils A with their thermally conductive insulation layers facing downwards. Perform a first hot press, then cool to obtain the coil. Attach the thermally conductive insulation layer of the coil to the ceramic substrate, perform a second hot press, then cool to obtain the ceramic coil.

[0006] In a more optimized manner, the raw materials of the thermally conductive insulating layer slurry, by mass parts, are: 45-55 parts polyimide liquid, 4-6 parts toughening agent, 45-55 parts modified aluminum nitride powder, and 25-35 parts NMP.

[0007] More preferably, the polyimide adhesive is PI-2540 with a solid content of 28-32%; the toughening agent is nitrile rubber; and the copper clad laminate includes IMS copper clad laminate or FR-4 copper clad laminate. The modified aluminum nitride powder is prepared by adding aluminum nitride and 3-aminopropyltriethoxysilane to ethanol, stirring and drying to obtain modified aluminum nitride powder; the raw materials of the modified aluminum nitride powder, by mass parts, are: 95-105 parts aluminum nitride, 1-3 parts 3-aminopropyltriethoxysilane, and 75-85 parts ethanol.

[0008] In a more optimized manner, the thickness of the copper clad laminate is 0.2~0.5mm; the number of turns of the primary coil and the secondary coil is 5~20 turns, the line width is 0.2~0.8mm, and the line spacing is 0.1~0.3mm; the ceramic substrate is made of aluminum nitride and has a thickness of 0.25~0.32mm; the ceramic substrate serves as the support and heat dissipation base for the coil, and its lower surface can be bonded with a metal heat sink (such as a copper sheet) to enhance heat dissipation; the thickness of the thermally conductive insulating layer is 50~100μm.

[0009] More preferably, the curing is a staged gradient curing, wherein the temperature of the first stage (removing solvent) is 75~85℃ and the time is 25~35min; the temperature of the second stage (preliminary curing) is 115~125℃ and the time is 25~35min; the temperature of the third stage (complete curing) is 175~185℃ and the time is 0.5~1.5h; and the temperature of the fourth stage (post-treatment) is 245~255℃ and the time is 25~35min.

[0010] In a more optimized manner, the pressure in the first hot pressing is 0.4~0.6MPa, the temperature is 195~205℃, and the holding time is 25~35min; the pressure in the second hot pressing is 0.2~0.4MPa, the temperature is 145~155℃, and the holding time is 15~25min.

[0011] In a further embodiment, the working principle of this application is as follows: when the fast charger is powered on, the current passes through the primary coil to generate an alternating magnetic field, and the secondary coil generates an induced current through electromagnetic induction to achieve energy transfer; the thermally conductive insulating layer serves both electrical isolation and heat conduction, and the heat generated by the coil is transferred to the ceramic substrate through the thermally conductive insulating layer, and then diffused to the outside through the ceramic substrate to achieve efficient heat dissipation; the planar coil structure (IMS planar structure) reduces leakage flux and improves electromagnetic coupling efficiency.

[0012] More preferably, the polyimide solution is a phosphazene cyclic polyimide solution; its preparation method is as follows: S1-1: Under a nitrogen atmosphere, 4-vinylphenol was added to tetrahydrofuran, and hexachlorocyclotriphosphazene was added under an ice bath. The mixture was heated to 25-35°C, stirred for 5-7 hours, purified and dried to obtain vinylchlorocyclotriphosphazene. S1-2: Vinyl chloride triphosphazene, cysteine, and photoinitiator were added to tetrahydrofuran and reacted at 30-40°C for 3-5 hours under ultraviolet light. After cooling, purification and drying, amino-terminated phosphazene rings were obtained. S1-3: Under a nitrogen atmosphere, 4,4'-diaminodiphenyl ether and bis(4-aminophenyl)dimethylsilane are added to DMF and reacted in an ice bath for 20-40 min. Then, 4,4'-biphenyl ether dianhydride is added and reacted at a constant temperature for 3-5 h. Finally, an amino-terminated phosphazene ring is added and reacted at a constant temperature for 1-3 h. The mixture is then diluted with deionized water to a solid content of 28-32% to obtain a phosphazene ring-based polyimide solution.

[0013] More preferably, in the vinyl chloride triphosphazene, the mass ratio of 4-vinylphenol to hexachlorocyclotriphosphazene is (2~3):(3~4) by mass parts; in the raw material of the amino-terminated phosphazene ring, there are 5~6.5 parts of vinyl chloride triphosphazene, 1~2 parts of cysteine, and 0.02~0.05 parts of photoinitiator.

[0014] In a more optimized manner, the raw materials of the phosphazene cyclic polyimide adhesive, by mass parts, are: 4-6 parts of 4,4'-diaminodiphenyl ether, 2-3 parts of bis(4-aminophenyl)dimethylsilane, 18-25 parts of 4,4'-biphenyl ether dianhydride, 10-13 parts of amino-terminated phosphazene ring, and 50-60 parts of DMF.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are: This application utilizes a specific component slurry to prepare a thermally conductive and highly insulating layer, combined with a specially designed ceramic coil structure and integrated packaging of the coil and ceramic substrate, to achieve the goals of reducing coil volume, improving heat dissipation performance, enhancing insulation reliability, simplifying production processes, and improving electromagnetic coupling efficiency.

[0016] (1) The ceramic coil prepared in this application is a planar coil structure (IMS planar structure), forming an IMS planar transformer to replace the traditional winding transformer, realizing the flattening and integration of the coil, significantly reducing the volume, and meeting the miniaturization requirements of fast chargers; (2) In this application, a thermally conductive insulating layer is prepared using a specific component slurry, which has high insulation performance (breakdown voltage > 2kV) and thermal conductivity (> 3W / m・K), so that the temperature of the ceramic coil is controlled within 60℃ when operating at high power, which is beneficial to improving the heat dissipation and safety performance of the product; (3) This application optimizes the electromagnetic coupling path by adapting the ceramic coil structure of the fast charger, reduces leakage flux, improves energy transmission efficiency, enhances insulation reliability, improves temperature resistance to over 180°C, reduces short circuit risk, improves electromagnetic coupling efficiency, and makes energy transmission efficiency reach over 95%. (4) This application provides a powder modification and preparation method for thermally conductive insulating layer slurry to ensure the stability and reliability of the insulating layer; (5) This application realizes the integrated packaging of coil and ceramic substrate, which simplifies the production process and improves product consistency.

[0017] (6) This application utilizes 4,4'-diaminodiphenyl ether, bis(4-aminophenyl)dimethylsilane, and 4,4'-biphenyl ether dianhydride to prepare a polyimide backbone, and uses an amino-terminated phosphazene ring as a capping agent to modify and prepare a phosphazene ring-based polyimide adhesive. This combination of rigidity and flexibility is beneficial to improving its own thermal conductivity and insulation properties, while also enhancing the synergy between the components in the thermally conductive and insulating layer slurry, further improving the overall performance of the product. The biphenyl group provides a rigid framework, promotes the orderly stacking of molecular chains, and improves intrinsic thermal conductivity; the silane block provides flexibility, which helps to reduce the stress of the adhesive itself, improve interface stability and bonding force; the phosphazene ring, as an organic-inorganic chain segment, specifically improves the synergy with the modified aluminum nitride powder, while further improving interface stability, and synergistically enhances thermal stability with the biphenyl group. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the ceramic coil. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the following embodiments, parts are by weight; it should be noted that there are no special restrictions on the purchasers of any of the raw materials involved in this invention. Exemplary examples include: PI-2540 is PI-2540 polyimide liquid, purchased from Changchun Gaoqi Polyimide Materials Co., Ltd., model BR-01; nitrile rubber is powdered nitrile rubber, purchased from Shenzhen Wansuyuan Rubber & Plastics Co., Ltd.; aluminum nitride is D50 / 5μm, purity 99.5%, item number 1301002, purchased from Forsmann Technology (Beijing) Co., Ltd.; zirconia spheres have a particle size of 3mm, are F6632, purchased from Beyotime; and IMS copper clad laminate, wherein the copper foil thickness is... The substrate thickness is 0.3 mm and the ceramic substrate is aluminum nitride substrate with dimensions of 30 mm × 20 mm × 0.5 mm and a thermal conductivity of 180 W / m·K. The CAS number of hexachlorocyclotriphosphazene is 940-71-6. The photoinitiator is photoinitiator 1173, purchased from Guangdong Gaoliang Technology Co., Ltd. The CAS number of 4,4'-diaminodiphenyl ether is 101-80-4. The CAS number of bis(4-aminophenyl)dimethylsilane is 54120-40-0. The CAS number of 4,4'-biphenyl ether dianhydride is 1823-59-2. The conventional wound transformer is purchased from Shenzhen Shunluo Electronics Co., Ltd.

[0021] In the following embodiments, the overall structure of the ceramic coil is shown in the schematic diagram. Figure 1 As shown.

[0022] Example 1: A method for preparing a ceramic coil for a fast charger, comprising the following steps: Step 1: Mix 30 parts NMP with 50 parts polyimide slurry (PI-2540, solid content 30%) and stir for 10 minutes until homogeneous; add 50 parts modified aluminum nitride powder and 5 parts toughening agent (nitrile rubber), stir at 500 r / min for 30 minutes, then vacuum to -0.09 MPa and maintain for 20 minutes to degas, to obtain thermally conductive insulating layer slurry; Step 2: Fabrication of IMS planar coils: Using a copper-clad laminate (IMS copper-clad laminate, copper foil thickness of 35μm, substrate thickness of 0.3mm) as the substrate, coil patterns are drawn using CAD. After photoresist coating, exposure, and development, etching is performed (using acidic etching solution (FeCl3 solution), etching temperature of 50℃, time of 3min), followed by washing and drying (washing with deionized water, drying at 120℃) to form the primary coil and secondary coil (the primary coil has 8 turns, line width of 0.5mm, and line spacing of 0.2mm; the secondary coil has 4 turns, line width of 0.6mm, and line spacing of 0.2mm). Step 3: Laser drilling of primary and secondary coils, followed by screen printing to fill the holes and inserting balls to serve as conduction posts; Step 4: Coat the lower surfaces of the primary and secondary coils with thermally conductive insulating paste and cure (stage gradient curing: the first stage temperature is 80℃ for 30 min; the second stage temperature is 120℃ for 30 min; the third stage temperature is 180℃ for 1 h; and the fourth stage temperature is 250℃ for 30 min) to form a thermally conductive insulating layer (the thickness of the thermally conductive insulating layer is 80 μm, the breakdown voltage is 2.5 kV, and the thermal conductivity is 3.2 W / m·K), thus obtaining primary coil A and secondary coil B; Step 5: Align and stack multiple sets of secondary coils B with their thermally conductive insulation layers facing upwards and multiple sets of primary coils A with their thermally conductive insulation layers facing downwards. Perform a first hot pressing (pressure 0.5MPa, temperature 200℃, holding time 30min), then cool to obtain the coil. Attach the thermally conductive insulation layer of the coil to the ceramic substrate (material: aluminum nitride, thickness 0.29mm), perform a second hot pressing (pressure 0.3MPa, temperature 150℃, holding time 20min), then cool to obtain the ceramic coil. The preparation method of modified aluminum nitride powder is as follows: 100 parts of aluminum nitride, 2 parts of 3-aminopropyltriethoxysilane, and 80 parts of ethanol are added to a 500mL polytetrafluoroethylene container, and zirconia balls (ball-to-material ratio of 3:1) are placed in the container. The mixing speed is set to 300r / min and the mixture is mixed for 4h. After mixing, the mixture is poured into an evaporating dish and dried in an 80℃ forced-air oven for 6h. The mixture is then ground through a 100-mesh sieve to obtain modified aluminum nitride powder.

[0023] Example 2: Based on Example 1, the polyimide adhesive is a phosphazene cyclic polyimide adhesive; the rest is the same as in Example 1, with the specific differences as follows: The preparation method of phosphazene cyclic polyimide adhesive is as follows: S1-1: Under a nitrogen atmosphere, 4-vinylphenol was added to tetrahydrofuran, and hexachlorocyclotriphosphazene was added under an ice bath. The mixture was heated to 30°C, stirred for 6 hours, purified and dried to obtain vinylchlorocyclotriphosphazene (the mass ratio of 4-vinylphenol to hexachlorocyclotriphosphazene was 2.4:3.5). S1-2: 5.87 parts of vinyl chloride triphosphazene, 1.54 parts of cysteine ​​and 0.035 parts of photoinitiator were added to tetrahydrofuran and reacted at 35°C for 4 hours under ultraviolet light. After cooling, purification and drying, amino-terminated phosphazene rings were obtained. S1-3: Under a nitrogen atmosphere, 5 parts of 4,4'-diaminodiphenyl ether and 2.75 parts of bis(4-aminophenyl)dimethylsilane were added to 55 parts of DMF and reacted in an ice bath for 30 min. Then, 22 parts of 4,4'-biphenyl dianhydride were added and reacted at a constant temperature for 4 h. Finally, 11.5 parts of amino-terminated phosphazene ring were added and reacted at a constant temperature for 2 h. The mixture was then diluted with deionized water to a solid content of 30% to obtain a phosphazene ring-based polyimide solution.

[0024] Comparative Example 1: Using a traditional wound transformer.

[0025] Comparative Example 2: Based on Example 2, without the addition of an amino-terminated phosphazene ring; otherwise, it is the same as Example 2, with the following specific differences: The preparation method of phosphazene cyclic polyimide adhesive is as follows: Under a nitrogen atmosphere, 5 parts of 4,4'-diaminodiphenyl ether and 2.75 parts of bis(4-aminophenyl)dimethylsilane were added to 55 parts of DMF and reacted in an ice bath for 30 min. Then, 22 parts of 4,4'-biphenyl dianhydride were added and reacted at a constant temperature for 4 h and 2 h. Finally, deionized water was added to dilute the mixture to a solid content of 30% to obtain a phosphazene cyclic polyimide solution.

[0026] Comparative Example 3: Based on Example 2, bis(4-aminophenyl)dimethylsilane was modified to 3,4'-diaminodiphenyl ether; the rest was the same as in Example 2, with the following specific differences: The preparation method of phosphazene cyclic polyimide adhesive is as follows: S1-1: Under a nitrogen atmosphere, 4-vinylphenol was added to tetrahydrofuran, and hexachlorocyclotriphosphazene was added under an ice bath. The mixture was heated to 30°C, stirred for 6 hours, purified and dried to obtain vinylchlorocyclotriphosphazene (the mass ratio of 4-vinylphenol to hexachlorocyclotriphosphazene was 2.4:3.5). S1-2: 5.87 parts of vinyl chloride triphosphazene, 1.54 parts of cysteine ​​and 0.035 parts of photoinitiator were added to tetrahydrofuran and reacted at 35°C for 4 hours under ultraviolet light. After cooling, purification and drying, amino-terminated phosphazene rings were obtained. S1-3: Under a nitrogen atmosphere, 5 parts of 4,4'-diaminodiphenyl ether and 2 parts of 3,4'-diaminodiphenyl ether were added to 55 parts of DMF and reacted in an ice bath for 30 min. Then, 22 parts of 4,4'-biphenyl ether dianhydride were added and reacted at a constant temperature for 4 h. Finally, 11.5 parts of amino-terminated phosphazene ring were added and reacted at a constant temperature for 2 h. The mixture was then diluted with deionized water to a solid content of 30% to obtain a phosphazene ring-based polyimide solution.

[0027] Comparative Example 4: Based on Example 2, 4,4'-diaminodiphenyl ether was replaced with 4,4'-diaminodiphenylmethane, and 4,4'-biphenyl ether dianhydride was replaced with pyromellitic dianhydride; the rest was the same as in Example 2, with the following specific differences: The preparation method of phosphazene cyclic polyimide adhesive is as follows: S1-1: Under a nitrogen atmosphere, 4-vinylphenol was added to tetrahydrofuran, and hexachlorocyclotriphosphazene was added under an ice bath. The mixture was heated to 30°C, stirred for 6 hours, purified and dried to obtain vinylchlorocyclotriphosphazene (the mass ratio of 4-vinylphenol to hexachlorocyclotriphosphazene was 2.4:3.5). S1-2: 5.87 parts of vinyl chloride triphosphazene, 1.54 parts of cysteine ​​and 0.035 parts of photoinitiator were added to tetrahydrofuran and reacted at 35°C for 4 hours under ultraviolet light. After cooling, purification and drying, amino-terminated phosphazene rings were obtained. S1-3: Under a nitrogen atmosphere, 5 parts of 4,4'-diaminodiphenylmethane and 2.75 parts of bis(4-aminophenyl)dimethylsilane were added to 55 parts of DMF and reacted in an ice bath for 30 min. Then, 15 parts of pyromellitic dianhydride were added and reacted at a constant temperature for 4 h. Finally, 11.5 parts of amino-terminated phosphazene rings were added and reacted at a constant temperature for 2 h. The mixture was then diluted with deionized water to a solid content of 30% to obtain a phosphazene ring-based polyimide solution.

[0028] Test Experiment 1: Size Comparison Test: The thickness of the ceramic coils prepared in Examples 1-2 and Comparative Examples 1-4 was compared and tested. The test results are shown in Table 1. Test Experiment 2: Heat dissipation performance test: The ceramic coils prepared in Examples 1-2 and Comparative Examples 1-4 were continuously operated at an output power of 65W for 2 hours, and their temperature was tested. The test results are shown in Table 1. Test Experiment 3: Efficiency Test: The energy transmission efficiency of the ceramic coils prepared in Examples 1-2 and Comparative Examples 1-4 was tested, and the test results are shown in Table 1. Working process: After the fast charger is powered on, the primary coil is connected to the DC voltage after rectification of the mains power, generating an alternating magnetic field. The secondary coil induces a voltage, which is rectified and filtered to charge the electronic device. The heat generated by the coil is quickly transferred to the ceramic substrate through the thermally conductive insulation layer and then dissipated into the air, ensuring long-term stable operation.

[0029] Table 1

[0030] Conclusions: As shown in Table 1 above, the product of this application has a 76% smaller size, a 23°C lower heat dissipation performance, and a 7.5% higher energy transmission efficiency compared to traditional wound transformers, exhibiting high thermal conductivity and insulation performance. Comparative Example 2 shows that the absence of an amino-terminated phosphazene ring reduces the synergistic effect with the modified aluminum nitride powder, resulting in decreased thermal conductivity and insulation performance. Comparative Example 3 shows that replacing bis(4-aminophenyl)dimethylsilane with 3,4'-diaminodiphenyl ether results in a lack of silane segments, decreased flexibility, increased stress, and reduced interface stability and bonding strength, leading to a decline in overall performance. Comparative Example 4 shows that replacing 4,4'-diaminodiphenyl ether with 4,4'-diaminodiphenylmethane and 4,4'-biphenyl ether dianhydride with pyromellitic dianhydride results in a significant decrease in thermal conductivity and a lack of a rigid framework.

[0031] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a ceramic coil for a fast charger, characterized in that: Includes the following steps: Step 1: Using a copper-clad laminate as a substrate, draw coil patterns using CAD, apply photoresist, expose, develop, etch, wash, and dry to form the primary coil and secondary coil. Step 2: Laser drilling of primary and secondary coils, followed by screen printing to fill the holes and inserting balls to serve as conduction posts; Step 3: Coat the lower surfaces of the primary coil and the secondary coil with thermally conductive insulating paste, and cure to form a thermally conductive insulating layer, thus obtaining primary coil A and secondary coil B; Step 4: Align and stack multiple sets of secondary coils B with their thermally conductive insulation layers facing upwards and multiple sets of primary coils A with their thermally conductive insulation layers facing downwards. Perform a first hot press, then cool to obtain the coil. Attach the thermally conductive insulation layer of the coil to the ceramic substrate, perform a second hot press, then cool to obtain the ceramic coil.

2. The method for preparing a ceramic coil for a fast charger according to claim 1, characterized in that: The raw materials of the thermally conductive insulating layer slurry, by mass parts, are: 45-55 parts polyimide liquid, 4-6 parts toughening agent, 45-55 parts modified aluminum nitride powder, and 25-35 parts NMP.

3. The method for preparing a ceramic coil for a fast charger according to claim 2, characterized in that: The polyimide adhesive is PI-2540 with a solid content of 28-32%; the toughening agent is nitrile rubber; the copper clad laminate includes IMS copper clad laminate or FR-4 copper clad laminate. The modified aluminum nitride powder is prepared by adding aluminum nitride and 3-aminopropyltriethoxysilane to ethanol, stirring and drying to obtain modified aluminum nitride powder; the raw materials of the modified aluminum nitride powder, by mass parts, are: 95-105 parts aluminum nitride, 1-3 parts 3-aminopropyltriethoxysilane, and 75-85 parts ethanol.

4. The method for preparing a ceramic coil for a fast charger according to claim 1, characterized in that: The copper clad laminate has a thickness of 0.2~0.5mm; the primary coil and secondary coil have 5~20 turns, a line width of 0.2~0.8mm, and a line spacing of 0.1~0.3mm; the ceramic substrate is made of aluminum nitride and has a thickness of 0.25~0.32mm; the thermally conductive insulating layer has a thickness of 50~100μm.

5. The method for preparing a ceramic coil for a fast charger according to claim 1, characterized in that: The curing process is a staged gradient curing process. In the staged gradient curing process, the temperature of the first stage is 75~85℃ and the time is 25~35min; the temperature of the second stage is 115~125℃ and the time is 25~35min; the temperature of the third stage is 175~185℃ and the time is 0.5~1.5h; and the temperature of the fourth stage is 245~255℃ and the time is 25~35min.

6. The method for preparing a ceramic coil for a fast charger according to claim 1, characterized in that: In the first hot pressing, the pressure is 0.4~0.6MPa, the temperature is 195~205℃, and the holding time is 25~35min; in the second hot pressing, the pressure is 0.2~0.4MPa, the temperature is 145~155℃, and the holding time is 15~25min.

7. The method for preparing a ceramic coil for a fast charger according to claim 2, characterized in that: The polyimide adhesive is a phosphazene cyclic polyimide adhesive; its preparation method is as follows: S1-1: Under a nitrogen atmosphere, 4-vinylphenol was added to tetrahydrofuran, and hexachlorocyclotriphosphazene was added under an ice bath. The mixture was heated to 25-35°C, stirred for 5-7 hours, purified and dried to obtain vinylchlorocyclotriphosphazene. S1-2: Vinyl chloride triphosphazene, cysteine, and photoinitiator were added to tetrahydrofuran and reacted at 30-40°C for 3-5 hours under ultraviolet light. After cooling, purification and drying, amino-terminated phosphazene rings were obtained. S1-3: Under a nitrogen atmosphere, 4,4'-diaminodiphenyl ether and bis(4-aminophenyl)dimethylsilane are added to DMF and reacted in an ice bath for 20-40 min. Then, 4,4'-biphenyl ether dianhydride is added and reacted at a constant temperature for 3-5 h. Finally, an amino-terminated phosphazene ring is added and reacted at a constant temperature for 1-3 h. The mixture is then diluted with deionized water to a solid content of 28-32% to obtain a phosphazene ring-based polyimide solution.

8. The method for preparing a ceramic coil for a fast charger according to claim 7, characterized in that: In the vinyl chloride triphosphazene, the mass ratio of 4-vinylphenol to hexachlorocyclotriphosphazene is (2~3):(3~4) by mass parts; in the raw material of the amino-terminated phosphazene ring, there are 5~6.5 parts of vinyl chloride triphosphazene, 1~2 parts of cysteine, and 0.02~0.05 parts of photoinitiator.

9. The method for preparing a ceramic coil for a fast charger according to claim 7, characterized in that: The raw materials of the phosphazene cyclic polyimide adhesive, by mass parts, are: 4-6 parts of 4,4'-diaminodiphenyl ether, 2-3 parts of bis(4-aminophenyl)dimethylsilane, 18-25 parts of 4,4'-biphenyl ether dianhydride, 10-13 parts of amino-terminated phosphazene ring, and 50-60 parts of DMF.

10. A ceramic coil prepared by a method for preparing a ceramic coil for a fast charger according to any one of claims 1 to 9.

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