Preparation method of printed circuit board of new energy automobile

Abstract

The invention belongs to the technical field of circuit board preparation, and particularly relates to a preparation method of a printed circuit board of a new energy automobile. And S0, substrate pretreatment and patterning process: sequentially executing the steps of base pattern platemaking, pattern transfer, etching, plated-through hole processing, solder resist coating and surface treatment to complete the previous preparation of the PCB substrate. The method comprises the following steps: S1, preparing heat-conducting coating slurry: mixing an insulating resin base solution and a high-heat-conductivity insulating filler according to a volume ratio of (15-35): 100, and performing high-speed stirring and ultrasonic dispersion to form the heat-conducting coating slurry; s2, ultrasonic-assisted spraying: spraying the heat-conducting coating slurry prepared in the step S1 on the surface of the PCB substrate subjected to previous treatment through high-pressure spraying equipment, and applying 20-40 kHz ultrasonic vibration to the slurry in the spraying process; and S3, step-type curing and post-processing are carried out, wherein pre-curing and thermocuring are carried out on the sprayed PCB substrate in sequence. The invention provides a method which is small in improvement of an existing PCB preparation process and can remarkably improve the overall heat dissipation performance of the PCB.

Description

Technical Field

[0001] This invention belongs to the field of circuit board manufacturing technology, specifically relating to a method for manufacturing printed circuit boards for new energy vehicles. Background Technology

[0002] The rapid development of new energy vehicles has placed extremely high demands on the reliability of their core electronic components (such as VCU, MCU, BMS, etc.). These components are typically high-power and highly integrated, generating a large amount of heat during operation. As the carrier of these components, the heat dissipation performance of the printed circuit board directly affects the stability and lifespan of the entire system.

[0003] In existing technologies, the PCB manufacturing process typically includes steps such as pattern making, pattern transfer, etching, hole metallization, solder mask coating, and surface treatment. Among these, the insulating protective coating (such as solder mask ink) applied during the surface treatment stage primarily functions to prevent short circuits and protect the circuitry from moisture and contamination. However, traditional insulating protective coating materials (such as epoxy resin) are themselves poor conductors of heat, with a thermal conductivity typically below 0.3 W / (m·K). The presence of this "heat insulation film" severely hinders the dissipation of heat generated by power devices on the PCB to the external environment, leading to heat accumulation and becoming one of the main hidden dangers for the failure of electronic systems in new energy vehicles.

[0004] To address heat dissipation issues, existing technologies primarily focus on modifying the PCB structure, such as using metal substrates (e.g., aluminum substrates), adding heat sinks, or employing thermal vias. However, these methods suffer from high costs, complex manufacturing processes, and increased weight and size, making them unsuitable for all types of circuit boards. Therefore, it remains difficult to find a mature method that effectively improves the heat dissipation capacity of the surface insulation layer while maintaining the lightweight and low-cost advantages of standard PCB structures.

[0005] Therefore, there is an urgent need in this field for a new method that makes only minor improvements to the existing PCB manufacturing process but can significantly improve its overall heat dissipation performance. Summary of the Invention

[0006] To address the aforementioned problems in the existing technology, this invention provides a method for preparing printed circuit boards for new energy vehicles.

[0007] The objective of this invention can be achieved through the following technical solutions: A method for manufacturing a printed circuit board for new energy vehicles includes the following steps: S0: Substrate Pre-treatment and Patterning Process: The following steps are performed sequentially: base pattern making, pattern transfer, etching, metallization hole processing, solder mask coating, and surface treatment to complete the front-end preparation of the PCB substrate. S1: Thermally Conductive Coating Slurry Preparation: Insulating resin base liquid and high thermally conductive insulating filler are mixed at a volume ratio of (15-35):100, and after high-speed stirring and ultrasonic dispersion, a thermally conductive coating slurry is formed. S2: Ultrasonic Assisted Spraying: The thermally conductive coating slurry prepared in step S1 is sprayed onto the surface of the PCB substrate that has completed the front-end treatment using a high-pressure spraying device. During the spraying process, ultrasonic vibration of 20–40 kHz is applied to the slurry. S3: Stepped Curing and Post-treatment: The sprayed PCB substrate is subjected to pre-curing and thermal curing in sequence. The pre-curing conditions are 80–90°C for 15–20 minutes, and the thermal curing conditions are 150–160°C for 45–60 minutes.

[0008] As a further aspect of the present invention, in step S1, the high thermal conductivity insulating filler is selected from one or more of boron nitride (BN), alumina (Al2O3), and aluminum nitride (AlN) in combination.

[0009] As a further embodiment of the present invention, the high thermal conductivity insulating filler is a compound of boron nitride and alumina in a volume ratio of 1:2, or a compound of alumina and alumina in a volume ratio of 1:3.

[0010] As a further aspect of the present invention, in step S1, the insulating resin base liquid is epoxy resin or modified epoxy resin; the high-speed stirring speed is 2000–2200 rpm, and the time is 30–40 minutes; the ultrasonic dispersion frequency is 40–45 kHz, and the processing time is 1–1.2 hours.

[0011] As a further aspect of the present invention, in step S2, the process parameters of the high-pressure spraying are: spraying pressure 0.4–0.5 MPa, spraying distance 15–20 cm; and the spraying environment is controlled at a temperature of 25±3°C and a relative humidity of 40%–60%.

[0012] As a further aspect of the present invention, in step S3, after the thermosetting step, a post-heat treatment step is further included, wherein the post-heat treatment is performed at 120°C for 30 minutes.

[0013] As a further aspect of the present invention, after step S3, a step of performing a plasma surface treatment on the cured coating is included, wherein the plasma surface treatment uses a mixture of argon and oxygen gas.

[0014] The beneficial effects of this invention are as follows: 1. By establishing an optimized volume ratio (15-35:100) between high thermal conductivity insulating fillers (such as boron nitride and alumina) and insulating resin matrix, and utilizing a high-speed stirring and ultrasonic dispersion composite process, a highly efficient thermally conductive network pathway was successfully constructed within the coating. This significantly improves the coating's thermal conductivity, representing an order-of-magnitude leap compared to traditional coatings, and reduces the temperature in the core area. Crucially, the selected fillers themselves possess excellent insulation properties, which, combined with the dense cross-linked structure formed by the resin matrix, ensures that the coating maintains a stable high level of volume resistivity while achieving high thermal conductivity.

[0015] 2. By combining high-speed stirring at 2000-2200 rpm and ultrasonic dispersion at 40-45 kHz in S1, nanoscale uniform dispersion of the filler in the base liquid is achieved (scraper fineness reaches 12μm), eliminating microscopic defects caused by filler agglomeration at the source. Then, through precision spraying at 0.4-0.5 MPa in S2, a dense coating with uniform thickness (deviation controllable within ±1.5μm), smooth surface, and no defects is finally formed. Attached Figure Description

[0016] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0017] Figure 1 This is a process flow diagram of the present invention; Detailed Implementation

[0018] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following describes the specific implementation methods, structures, and features of the present invention in conjunction with the accompanying drawings and preferred embodiments.

[0019] The following combination Figure 1 The preparation process of the thermally conductive coating of the present invention will be described in detail.

[0020] A method for manufacturing a printed circuit board for new energy vehicles includes the following steps: S0: Substrate pretreatment and patterning process: The process involves sequentially performing the following steps: pattern making, pattern transfer, etching, metallization hole processing, solder mask coating, and surface treatment to complete the front-end fabrication of the PCB substrate. The substrate pretreatment and patterning process sequentially executes the following key steps: pattern making → pattern transfer → etching → metallization hole processing → solder mask coating → surface treatment, ultimately producing a PCB substrate that can be used for the preparation of thermally conductive coatings.

[0021] S1: Preparation of thermally conductive coating slurry: The insulating resin base liquid and the high thermal conductivity insulating filler were mixed at a volume ratio of (15-35):100, and a homogeneous slurry was formed by high-speed stirring and ultrasonic dispersion. The high thermal conductivity insulating filler was selected from one or more of boron nitride, alumina, and aluminum nitride. The insulating resin base liquid was epoxy resin or modified epoxy resin, which has high temperature stability and high adhesion. The filler compounding can use a volume ratio of boron nitride to alumina of 1:2 (D50 of 5μm and 3μm respectively), or a volume ratio of aluminum nitride to alumina of 1:3 (D50 of 8μm and 2μm respectively). The slurry dispersion process parameters were: high-speed stirring speed of 2000–2200 rpm, time of 30–40 minutes, ultrasonic frequency of 40–45 kHz, and processing time of 1–1.2 hours. The resulting slurry was homogeneous and stable. The slurry consists of the following components: Insulating resin base liquid: Epoxy resin or modified epoxy resin with better thermal shock resistance and low water absorption is used as the matrix, which has excellent stability and adhesion at high temperature.

[0022] High thermal conductivity insulating filler: One or more of boron nitride (BN), alumina (Al2O3), and aluminum nitride (AlN) are selected and compounded. The filler plays a role in constructing thermally conductive pathways in the slurry.

[0023] Mixing ratio: The volume ratio of insulating resin base liquid to high thermal conductivity insulating filler is (15-35):100. By adjusting this ratio, the thermal conductivity and mechanical properties of the coating can be balanced to obtain a high thermal conductivity insulating composite coating.

[0024] S1 Performance Summary: By using high-speed rotation (2000-2200 rpm) and ultrasonic dispersion (40-45 kHz), a composite coating with high thermal conductivity and insulation with stable viscosity and leveling properties and consistent batch-to-batch performance was prepared. This ensured that the thermally conductive and heat-resistant fillers were uniformly dispersed at the nano / micron level in the epoxy resin, eliminating local electric field concentration points caused by filler agglomeration.

[0025] S2: Ultrasonic Assisted Spraying Process A high-pressure spraying device is used to uniformly spray the thermally conductive coating slurry onto the PCB surface. The spraying pressure is 0.4–0.5 MPa, and the spraying distance is 15–20 cm. During the spraying process, ultrasonic vibration of 20–40 kHz is applied to assist in slurry atomization and prevent filler sedimentation, thereby improving coating density and interfacial adhesion. Environmental parameters are controlled at a temperature of 25±3°C and a relative humidity of 40%–60%, as this temperature and humidity range helps to achieve a moderate solvent evaporation rate, avoiding coating cracks or blistering defects. After ultrasonic-assisted spraying, the slurry forms a uniform film on the substrate surface to avoid sagging or cracking defects. Combined with a stepped curing process, internal stress is effectively released, reducing the risk of thermal mismatch.

[0026] Spraying equipment and environment: High-pressure spraying equipment is used to spray the prepared thermally conductive coating slurry onto the PCB board surface that has completed the previous processing.

[0027] The spraying process should be carried out in a controlled environment. It is recommended that the ambient temperature be 25±3°C and the relative humidity be 40%–60% to avoid defects such as sagging or cracking of the coating due to environmental fluctuations.

[0028] Core process parameters and control: Basic parameters: spraying pressure is controlled at 0.4–0.5 MPa, and the distance between the spray gun and the PCB surface (spray distance) is maintained at 15–20 cm.

[0029] Ultrasonic Assistance: During the spraying process, ultrasonic vibrations of 20–40 kHz are applied to the slurry. This technology effectively assists in slurry atomization, prevents filler sedimentation and agglomeration during spraying, and is key to ensuring uniform coating thickness, smooth surface, dense film, and good adhesion to the substrate. It also significantly improves the dispersion stability of fillers in the resin matrix. Combined with a dynamic pressure feedback system, the ultrasonic vibration frequency is adjusted in real time to avoid localized overheating affecting slurry performance, ensure a constant spraying flow rate, and adapt to different film thickness requirements in different areas.

[0030] Stable spraying parameters and strict environmental control (25±3°C, 40%-60% RH) ensure that the coating thickness of each board and each batch of products is highly consistent.

[0031] S3: Stepped curing and post-treatment: After spraying, pre-curing and heat curing are performed sequentially: pre-curing conditions are 80–90°C for 15–20 minutes to initially fix the coating morphology and remove solvents; heat curing conditions are 150–160°C for 45–60 minutes to promote full cross-linking of the resin and the formation of a dense three-dimensional network. A subsequent post-heat treatment at 120°C for 30 minutes can be introduced to further improve the cross-linking density and interfacial compatibility. After curing, the coating achieves a glass transition temperature of 148–158°C and a volume resistivity ≥1.2 × 10⁻⁶. 15The coating exhibits a thermal conductivity of 2.8–3.1 W / (m·K) with a maximum strength of Ω·cm. Optional plasma surface treatment enhances hydrophobicity and anti-fouling capabilities, with a contact angle >90°, effectively suppressing leakage current in humid environments. After aging at 85°C / 85%RH for 1000 hours, the coating's performance degradation is less than 8%, meeting the long-life thermal management requirements of high-power-density circuit boards and high-current modules. Stepped curing not only optimizes the coating's microstructure but also achieves stress gradient release at the molecular level, significantly improving the coating's structural stability and reliability under thermal cycling and high-humidity environments, preventing microcrack propagation caused by internal stress concentration. This progressive energy release mechanism results in tighter interfacial bonding, further suppressing thermo-mechanical coupling failure. Ultimately, this achieves a breakthrough in coating durability for long-term service under extreme conditions, providing a solid guarantee for efficient heat dissipation and safe operation of electronic devices. Furthermore, by optimizing the synergistic effect of ultrasonic-assisted frequency and the stepped curing temperature control curve, the residual stress of the coating can be further reduced by approximately 20%, increasing thermal cycling durability to over 2000 cycles.

[0032] Stepped curing process: Pre-curing: First, pre-curing is carried out at a temperature of 80–90°C for 15–20 minutes. This stage aims to initially fix the coating morphology and promote the slow evaporation of most of the solvent, avoiding pinholes or blistering caused by rapid solvent evaporation during subsequent high-temperature curing, thus ensuring the density of the coating and the quality of the interfacial bonding. Temperature selection criteria: This temperature range is precisely set above the boiling point of most solvents, providing sufficient vapor pressure to drive their slow and orderly evaporation, but far below the initiation temperature of the resin system's vigorous cross-linking reaction. This avoids microscopic defects (such as pinholes and blistering) caused by solvent boiling.

[0033] Timing selection criteria: 15–20 minutes is based on the critical time window for solvent to diffuse from the interior of the coating to the surface and completely evaporate at typical coating thicknesses. This duration ensures that the coating achieves initial mechanical strength (“setting”) without prematurely forming a dense cross-linked network that traps residual solvent.

[0034] Thermal Curing: The resin is then placed in an oven at 150–160°C for 45–60 minutes for thermal curing. This stage is crucial for the full cross-linking of the resin matrix, forming a dense three-dimensional network structure that imparts the final mechanical strength and thermal conductivity to the coating. 150–160°C has been identified as the optimal cross-linking reaction window for this resin system. At this temperature, the resin molecular chains acquire sufficient mobility, maximizing the probability of functional group collisions, thereby driving the cross-linking reaction to proceed efficiently and fully, forming a dense three-dimensional network structure. 45–60 minutes is the minimum time required to ensure the cross-linking reaction is nearly complete (>95%). Too short a time results in insufficient cross-linking, affecting mechanical strength and thermal properties; too long a time may lead to polymer degradation or energy waste. This time period is critical for achieving a high glass transition temperature (Tg) and excellent thermal conductivity.

[0035] Post-heat treatment (optional): To further enhance performance, a post-heat treatment at 120°C for 30 minutes can be performed. This promotes the continued reaction of residual functional groups, enhances crosslinking density, improves the interfacial compatibility between the coating and the PCB substrate, and releases internal stress. The coating prepared by the above process exhibits excellent thermal stability and electrical insulation, and its coefficient of thermal expansion matches well with the FR-4 substrate, effectively preventing delamination or cracking under temperature cycling. Choosing 120°C (below the main curing temperature but above Tg) aims to operate at a temperature where the coating system has sufficient chain segment mobility to release internal stress without causing overall structural relaxation. This temperature also activates residual, less reactive functional groups to continue reacting. Therefore, 30 minutes is an empirical balance point for sufficient internal stress relaxation and near-complete completion of residual crosslinking reactions.

[0036] Performance metrics and post-processing: After complete step-by-step curing, the coating exhibits excellent overall performance: Glass transition temperature (Tg): up to 148–158°C, superior to conventional epoxy coatings; volume resistivity ≥1.2×10⁻⁶. 15 The coating has a thermal conductivity of 2.8–3.1 W / (m·K) and exhibits excellent long-term reliability. After 1000 hours of aging testing in a high-temperature and high-humidity environment of 85°C / 85%RH, the coating's performance degradation rate is less than 8%.

[0037] Enhanced Post-Treatment: To further improve the coating's durability in harsh environments, a plasma surface treatment can be added. This plasma surface treatment uses a mixture of argon and oxygen gas. The argon-oxygen mixture utilizes argon ion bombardment for physical activation (increasing surface micro-roughness), while simultaneously using oxygen plasma to introduce oxygen-containing polar groups and perform chemical modification. By precisely controlling the mixing ratio, a specific microstructure and chemical composition are constructed on the surface. This treatment significantly enhances the coating's hydrophobicity and anti-fouling ability, increasing its water contact angle to greater than 90° and effectively suppressing leakage current caused by condensation in humid environments.

[0038] S4: Finished Product Inspection and Packaging: Electrical performance testing and visual inspection are performed on the cured PCB products. Qualified products are cleaned and moisture-proofed and packaged using the following testing methods and standards.

[0039] Scraper fineness: measured using a 0-25μm Hegman scraper fineness meter according to GB / T 1724-2019 standard.

[0040] Coating thickness and uniformity: Ten points were randomly selected on the coating surface using a DEKTAK XT probe profilometer, and the average value and standard deviation were recorded.

[0041] Insulation withstand voltage: According to IPC-TM-650 2.5.7 standard, use Chroma 19053 withstand voltage tester to apply 1500V AC for 60 seconds and observe whether there is a breakdown.

[0042] Insulation resistance: Measured at 500VDC using a Keysight B2985A high resistance meter, in accordance with IPC-TM-650 2.5.17.1 standard.

[0043] Thermal cycling test: According to JESD22-A104F standard, perform 100 cycles from -55°C to +125°C, and recheck the insulation resistance after the test.

[0044] Under a standard light source, trained inspectors conduct visual inspections, and suspicious areas can be verified using a 50x optical microscope. The products are then vacuum-packed for moisture protection.

[0045] Because core components in new energy vehicles, such as high-voltage battery management systems, motor drive controllers, and on-board chargers, typically operate at high voltages of hundreds of volts and withstand high heat from large currents, this working environment poses a severe challenge to the PCB insulation system. Firstly, the high voltage requires the PCB insulation coating to possess extremely high insulation withstand voltage and long-term dielectric reliability to avoid short-circuit risks caused by partial discharge or electrical breakdown. Secondly, the thermal stress generated by high power density requires the insulation material to not only have excellent heat resistance but also good thermal conductivity to aid in heat dissipation. Furthermore, automotive electronics require components to maintain their performance without degradation over a full lifespan of more than fifteen years under harsh environments of various vibrations and high / low temperature cycles, placing extreme demands on the density, uniformity, and adhesion of the PCB insulation coating to the substrate.

[0046] Currently, conventional PCB insulation coating preparation processes (such as ordinary stirring combined with spraying) have significant shortcomings. On the one hand, in the material preparation stage, traditional stirring processes struggle to achieve uniform nano / micron-level dispersion of functional fillers in matrices such as epoxy resins. This can easily lead to filler agglomeration, introducing microscopic defects into the insulation layer, which become electric field concentration points and thermal resistance points, posing potential risks for high-voltage breakdown and localized overheating. On the other hand, in the coating process, broad and poorly controlled spraying parameters can easily result in uneven coating thickness, orange peel texture, runs, or bubbles, severely compromising the overall insulation performance and consistency of the coating.

[0047] To fully illustrate the effect of combining S1 and S2, the following embodiments and comparative examples are provided in light of the above. All tests were conducted in accordance with generally accepted standards in the art.

[0048] S1 (Coating Preparation): Take insulating resin base liquid and high thermal conductivity insulating filler in a volume ratio of (15-35):100 parts and place them in a high-speed disperser. First, stir at a high speed of 2100 rpm for 35 minutes, then transfer to an ultrasonic disperser and treat at a frequency of 42.5 kHz for 1.1 hours to obtain a high thermal conductivity insulating composite coating.

[0049] S2 (Spraying and Curing): The composite coating described above is loaded into a high-pressure spray gun and sprayed onto the FR-4 substrate with the completed circuit pattern in a clean room with an ambient temperature of 25°C and a relative humidity of 50%, using a spraying pressure of 0.45 MPa and a spraying distance of 17.5 cm. It is then cured at 150°C for 60 minutes to form an insulating coating.

[0050] result: The prepared insulating resin-based liquid had a scraper fineness of 12 μm and a viscosity (25°C) of 3500 mPa·s, showing no sedimentation after 24 hours of standing. The resulting insulating coating had a smooth and even surface with no visible defects. The average thickness was 24.8 μm, with a thickness deviation (standard deviation) of ±1.5 μm, exhibiting excellent uniformity. Insulation withstand voltage test: under 1500V AC, no breakdown or arcing occurred within 60 seconds. The initial insulation resistance was 5.6 × 10^12 Ω. After thermal cycling test, the insulation resistance was 4.2 × 10^12 Ω, demonstrating high performance retention and excellent reliability.

[0051] Comparative Example 1 (S1 parameter deviation - low speed stirring): All conditions were exactly the same as in Example 1, except that the high speed stirring speed in step S1 was changed from 2100 rpm to 1500 rpm.

[0052] Results and Analysis: The fineness of the obtained base liquid scraper deteriorated to 35μm, with obvious particles visible to the naked eye. After spraying and curing, the coating surface was rough, and filler agglomerates were visible under a microscope. The insulation withstand voltage test broke down at 800V AC. This comparison proves that the stirring speed was too low, which could not achieve sufficient dispersion of the filler and seriously degraded the insulation performance of the final product.

[0053] Comparative Example 2 (S1 parameter deviation - no ultrasonic dispersion): All conditions were exactly the same as in Example 1, except that the ultrasonic dispersion treatment in step S1 was omitted.

[0054] Results and Analysis: The obtained base liquid showed obvious sedimentation and stratification after standing for 2 hours, making stable spraying impossible. The coating structure formed after forced spraying was loose, with an insulation resistance of only 3.8 × 10^8 Ω, which was 4 orders of magnitude lower than that of Example 1. This comparison proves that mechanical stirring alone is insufficient to destroy the secondary structure of the filler, and ultrasonic dispersion is crucial for obtaining nanoscale dispersion and a stable system.

[0055] Comparative Example 3 (S2 parameter deviation - low pressure spraying): The same insulating resin base liquid as in Example 1 was used, except that the spraying pressure in step S2 was changed from 0.45 MPa to 0.2 MPa.

[0056] Results and Analysis: Due to poor atomization, the coating polymerized and sagged on the substrate surface. The coating thickness was extremely uneven, ranging from 18 μm to 48 μm at the measurement points, failing to meet accuracy requirements. Insulation withstand voltage tests showed multiple failures in various areas. This comparison demonstrates that insufficient spraying pressure cannot achieve uniform coating.

[0057] Comparative Example 4 (S2 parameter deviation - high pressure spraying): The same insulating resin base liquid as in Example 1 was used, except that the spraying pressure in step S2 was changed from 0.45 MPa to 0.7 MPa.

[0058] Results and Analysis: High pressure led to excessive atomization and "overspraying," resulting in an average coating thickness of only 13.5 μm and a severe "orange peel" effect on the surface. Due to the excessively thin and non-dense coating, the insulation withstand voltage test failed at 1100V AC. This comparison demonstrates that excessively high spraying pressure can damage the integrity of the coating and lead to material waste.

[0059] The following is the experimental control group. As shown in the table above, only by working synergistically within the process parameter range of the examples (S1: rotation speed 2000-2200 rpm, ultrasonic dispersion 40-45 kHz; S2: spraying pressure 0.4-0.5 MPa) can an insulating coating with extremely high uniformity, excellent insulation, and long-term reliability be prepared, thus meeting the stringent requirements of printed circuit boards for new energy vehicles. The comparative examples demonstrate that deviation from any single parameter leads to a significant decrease in performance.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a printed circuit board for new energy vehicles, characterized in that: The method comprises the following steps: S0: substrate pretreatment and patterning process: sequentially performing bottom plate making, pattern transfer, etching, metal hole processing and solder mask coating to complete the front-end preparation of the PCB substrate; S1: preparation of heat-conducting coating slurry: mixing the insulating resin base liquid and the high-thermal-conductivity insulating filler at a volume ratio of (15-35):100, and after high-speed stirring and ultrasonic dispersion, forming the heat-conducting coating slurry; S2: ultrasonic-assisted spraying: spraying the heat-conducting coating slurry prepared in step S1 on the surface of the PCB substrate by a high-pressure spraying device, and applying ultrasonic vibration of 20-40 kHz to the slurry during the spraying process; S3: stepwise curing and post-processing: sequentially performing pre-curing and heat curing on the sprayed PCB substrate, the pre-curing condition being 80-90°C for 15-20 minutes, and the heat curing condition being 150-160°C for 45-60 minutes; S4: product detection and packaging: performing electrical performance testing and appearance inspection on the cured PCB product, and cleaning and moisture-proof packaging the qualified product.

2. The preparation method of the new energy vehicle printed circuit board according to claim 1, characterized in that: In step S1, the high-thermal-conductivity insulating filler is selected from one or more of boron nitride (BN), aluminum oxide (Al2O3) and aluminum nitride (AlN).

3. The preparation method of the new energy vehicle printed circuit board according to claim 2, characterized in that: The high-thermal-conductivity insulating filler is compounded by boron nitride and aluminum oxide at a volume ratio of 1:2, and aluminum nitride and aluminum oxide at a volume ratio of 1:

3.

4. The preparation method of the new energy vehicle printed circuit board according to claim 1, characterized in that: In step S1, the insulating resin base liquid is epoxy resin or modified epoxy resin; the rotation speed of high-speed stirring is 2000-2200 rpm, and the time is 30-40 minutes; the frequency of ultrasonic dispersion is 40-45 kHz, and the processing time is 1-1.2 hours.

5. The preparation method of the new energy vehicle printed circuit board according to claim 1, characterized in that: In step S2, the process parameters of high-pressure spraying are: spraying pressure 0.4-0.5 MPa, spraying distance 15-20 cm; and the spraying environment is controlled at a temperature of 25±3°C and a relative humidity of 40%-60%.

6. The preparation method of the new energy vehicle printed circuit board according to claim 1, characterized in that: In step S3, after the heat curing step, a post-heating treatment step is further included, and the post-heating treatment condition is 120°C for 30 minutes.

7. The preparation method of the new energy vehicle printed circuit board according to claim 1, characterized in that: After step S3, a step of performing plasma surface treatment on the cured coating is further included, and the plasma surface treatment uses a mixed gas of argon and oxygen.

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