A laminated busbar hot pressing process for new energy vehicles

Abstract

The application discloses a laminated busbar hot pressing process for new energy vehicles, comprising the following steps: S1: material pretreatment: surface oil removal, pickling and passivation treatment are carried out on the busbar conductor, and plasma activation treatment is carried out on the insulating film. Through the accurate pretreatment of the conductor and the insulating film, gradient hot pressing and segmented pressure maintaining, segmented cooling and whole-process pressure maintaining and targeted post-treatment, the application not only completely solves the core problems such as interlayer peeling caused by insufficient interfacial bonding force of the conductor and the insulating film, insulation failure caused by extensive hot pressing parameters, warping deformation caused by too fast cooling pressure release and interlayer bubble residue affecting the electric conduction and heat dissipation and vehicle safety and the like existing in the traditional single temperature pressing process, but also realizes high-performance indexes such as busbar interlayer peeling strength ≥ 8 N / cm, insulation resistance ≥ 10 12 Ω and size precision control within ±0.1 mm, and meanwhile, the standardized process parameters are suitable for upgrading of traditional equipment and large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of hot pressing process technology for laminated busbars, and in particular to a hot pressing process for laminated busbars used in new energy vehicles. Background Technology

[0002] As a core transmission component of the high-voltage system in new energy vehicles, laminated busbars have advantages such as high integration, flexible wiring, and low parasitic inductance. Traditional hot-pressing processes for laminated busbars often use a single temperature and pressure, which has the following drawbacks: 1. Incomplete conductor surface treatment leads to insufficient interfacial bonding between the insulation film and the conductor, making it prone to delamination under long-term vibration conditions; 2. Coarse control of hot-pressing parameters easily leads to aging or melting of the insulation film, causing insulation failure; 3. Rapid pressure release during cooling can cause warping and deformation of the busbar, making it difficult to guarantee dimensional accuracy; 4. Interlayer air bubbles are difficult to remove, affecting conductivity and heat dissipation efficiency, and in severe cases, causing local overheating and threatening the safety of the entire vehicle. In view of the above, this application proposes a hot-pressing process for laminated busbars used in new energy vehicles. Summary of the Invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a hot pressing process for laminated busbars for new energy vehicles.

[0004] This invention proposes a hot-pressing process for laminated busbars used in new energy vehicles, comprising the following steps: S1: Material pretreatment: The busbar conductor is subjected to surface degreasing, pickling, and passivation treatment, and the insulating film is subjected to plasma activation treatment; S2: Layered positioning: The conductor and insulating film are stacked sequentially according to the preset structure, and positioning pins and positioning clamps are used to achieve precise positioning, with positioning accuracy controlled within ±0.05mm; S3: Gradient hot pressing and segmented pressure holding: Place the laminated assembly into the hot press, first heat it to 80-100℃ at a rate of 5℃ / min, apply 5-8MPa pressure for pre-pressing for 3-5min; then heat it to 120-150℃, apply 10-15MPa pressure for hot pressing for 8-12min; finally heat it to 160-180℃, apply 8-10MPa pressure for final pressing for 5-8min; S4: Cooling and Shaping: A segmented cooling method is adopted. First, the temperature is naturally cooled to 100-120℃ and held for 5 minutes. Then, the temperature is cooled to room temperature at a rate of 10℃ / min, and a holding pressure of 3-5MPa is maintained throughout the process. S5: Post-processing and inspection: After hot pressing, the busbars are deburred and edge-sealed, and then insulation resistance, dielectric strength, interlayer peel strength and dimensional accuracy are tested.

[0005] Preferably, in step S1, the busbar conductor is made of either copper or aluminum, and the passivation treatment uses a chromate passivation solution with a passivation time of 30-60 seconds; the insulating film is made of either PET or PP, and the plasma activation treatment power is 300-500W with a treatment time of 60-120 seconds. During the plasma activation treatment, active groups are introduced to enhance the affinity between the insulating film and the conductor and adhesive, thus preventing interlayer separation.

[0006] Preferably, in step S3, the parallelism of the hot platen of the hot press is controlled within ±0.02 mm, and nitrogen protection is used during the hot pressing process to prevent conductor oxidation.

[0007] Preferably, the specific logical steps of S3 are as follows: S301: Hot press preheating calibration: Start the hot press and preheat the hot plate to the initial temperature. Use a precision testing tool to calibrate the parallelism of the hot plate to ±0.02mm to ensure uniform pressure transmission and avoid local false pressure or overpressure. At the same time, turn on the nitrogen protection system and adjust the nitrogen flow rate to 10-15L / min to create an inert atmosphere in the hot press chamber and remove air in advance to prevent oxidation of the conductor surface during subsequent heating. S302: Place the stacked components that have completed layer positioning smoothly into the center of the lower hot plate of the hot press, ensuring that the edge of the component is aligned with the limiting structure of the hot plate, to avoid displacement of the component during the hot pressing process, and to lay the foundation for uniform heating and pressing in the future. S303: Set the heating rate to 5℃ / min, and heat from the initial temperature of 50℃ to 80-100℃. Slow heating can avoid thermal deformation of the insulating film due to instantaneous high temperature, and at the same time allow the internal temperature of the stack to be gradually and evenly conducted, preventing uneven gas expansion caused by interlayer temperature difference. S304: When the hot plate temperature stabilizes at 80-100℃, slowly apply a pressure of 5-8MPa at a rate of 0.5MPa / s and maintain the pressure for 3-5 minutes. This pressure is called "light compression". The purpose is to allow the layers of the laminated assembly to initially adhere, and at the same time, to allow the residual air between the layers and the small molecules of gas volatilized from the adhesive to be discharged in an orderly manner, so as to avoid the formation of bubbles due to gas being trapped under high pressure later. Maintain the low pressure for 3-5 minutes to ensure that the gas is fully discharged and that the insulating film is not deformed prematurely due to excessive pressure. S305: Maintain a heating rate of 5℃ / min, heating from 80-100℃ to 120-150℃. This temperature range is the "optimal curing temperature" for the adhesive that is compatible with the insulating film. This ensures that the adhesive melts and diffuses fully to the interface between the conductor and the insulating film to form a uniform adhesive layer, while preventing the insulating film from aging or degrading due to excessive temperature. S306: After the temperature stabilizes at 120-150℃, increase the pressure to 10-15MPa at a rate of 1MPa / s and maintain the pressure for 8-12 minutes. Under high pressure, the molten adhesive can more fully wet the interface between the conductor and the insulating film, fill in minor interface defects, and enhance intermolecular forces. The 8-12 minute holding time ensures that the adhesive is completely cured, forming a high-strength adhesive layer, thus solving the problem of insufficient interlayer bonding in traditional processes from the root. S307: Continue heating at a rate of 5℃ / min from 120-150℃ to 160-180℃, which can further enhance the interlayer molecular activity, make the interface between the conductor and the insulating film more tightly bonded, and at the same time, make the uncured adhesive completely cured, enhancing the overall density of the structure. S308: After the temperature stabilizes at 160-180℃, reduce the pressure to 8-10MPa and maintain the pressure for 5-8 minutes. By reducing the pressure, the insulation film and conductor will undergo slight thermal expansion at high temperatures. The medium pressure can ensure continuous bonding between layers without causing irreversible deformation of the component due to thermal expansion caused by high pressure. The 5-8 minute pressure holding time ensures that the component is stably formed at high temperature, avoiding warping due to structural instability during subsequent cooling. S309: After the final pressure stage, maintain the nitrogen protective atmosphere and the basic holding pressure of 3-5 MPa, stop the heating process, and prepare to enter the subsequent cooling stage.

[0008] Preferably, in step S5, the edge sealing is performed using either hot melt adhesive or UV-curable adhesive, with an insulation resistance test standard ≥10¹²Ω, dielectric strength ≥20kV / mm, and interlayer peel strength ≥8N / cm.

[0009] Preferably, the conductor thickness of the stacked busbar is 0.5-3 mm, the insulation film thickness is 0.1-0.3 mm, and the number of stacked layers is 2-8.

[0010] Preferably, the specific logical steps of S4 are as follows: S401: After the final pressure stage in S3, keep the nitrogen protective atmosphere in the hot press unchanged, and slowly reduce the pressure from 8-10MPa at the final pressure to 3-5MPa to avoid gaps or rebound between the layers of the laminated components caused by a sudden drop in pressure. Keep the pressure constant throughout the process until it cools to room temperature. S402: Turn off the heating module of the hot press, turn on the cooling system to preheat, and at the same time confirm that the temperature monitoring device and pressure monitoring device in the hot press cavity are working properly to avoid parameter loss during the cooling process; S403: Without activating the forced cooling device, it relies on the natural heat dissipation of the hot plate of the hot press to cool the laminated busbar from 160-180℃ to 100-120℃. The natural cooling rate is slow, which allows the internal and surface temperatures of the busbar to drop synchronously, avoiding thermal stress caused by "external cold and internal heat" which can lead to warping or cracking of the busbar. S404: When the busbar temperature is stable at 100-120℃, maintain this temperature for 5 minutes to further balance the temperature of each area of ​​the busbar, making the interlayer molecular arrangement more stable, and at the same time reducing stress accumulation during subsequent rapid cooling, laying the foundation for precise shaping. S405: Start the hot press cooling system and set the cooling rate to 10℃ / min to cool the busbar from 100-120℃ to room temperature of 25℃. Uniform cooling can control the shrinkage rate of the busbar and avoid deformation caused by drastic shrinkage due to rapid cooling. The 10℃ / min rate has been verified to ensure production efficiency and adapt to the shrinkage characteristics of copper / aluminum conductors and insulating films, preventing dimensional deviations. During the cooling process, a holding pressure of 3-5MPa is maintained until the busbar reaches room temperature. The purpose of the holding pressure is to "constrain" the shape of the busbar during the shrinkage process, ensuring that it conforms to the preset mold contour and avoiding problems such as warping and bulging during shrinkage. Ultimately, the dimensional accuracy of the busbar is controlled within ±0.1mm. S406: After the busbar temperature drops to room temperature, first turn off the nitrogen protection system, then slowly release the holding pressure at a rate of 0.1 MPa / s to avoid the busbar rebounding due to sudden pressure release. Then turn on the hot press and take out the cooled and shaped laminated busbar.

[0011] Preferably, the specific logical steps of S5 are as follows: S501: After cooling and shaping, the motherboard is placed in an ultrasonic cleaner. A neutral cleaning agent with pH 6-8 is used to clean the surface of residual adhesive, oil, and dust. The cleaning temperature is 40-50℃ and the time is 3-5 minutes. Then, it is rinsed with deionized water and dried at 60℃ for 10 minutes. The purpose of cleaning is to avoid impurities affecting the post-processing effect (such as poor edge sealing) and the accuracy of testing (such as interference from contamination in insulation resistance testing). S502: A combination of mechanical grinding and manual finishing is used: First, use a grinding wheel with a speed of 3000r / min to grind the large burrs on the edge of the busbar. When grinding, keep the grinding angle at 15-30° with the edge of the busbar to avoid excessive grinding that could damage the conductor or insulation film. S503: Use 800-1000 grit sandpaper to sand the edges until they are smooth and without sharp edges. After sanding, use compressed air to blow away the metal shavings and insulating debris on the surface to avoid debris residue causing short circuits during subsequent use. S504: Select the appropriate sealing material according to the application scenario of the busbar. For battery packs, use hot melt adhesive; for motor controllers, use UV curing adhesive. S505: Apply adhesive evenly along the edge of the busbar using a dispensing machine. The adhesive layer thickness should be controlled at 0.2-0.3mm to ensure no missed areas or bubbles. After application, the hot melt adhesive needs to be heated and cured at 120-150℃ for 5-8 minutes, and the UV curing adhesive needs to be cured under 365nm ultraviolet light for 20-30 seconds. S506: After the sealant has cured, visually inspect the sealant layer to ensure it is flat and free of cracks, and ensure that the edges of the busbar are completely sealed to prevent moisture and dust from entering the interlayer and causing insulation failure. S507: Use an insulation resistance tester, apply a 1000V DC voltage, test for 60s, and test points cover all conductors and insulation layer interfaces of the busbar; the judgment standard is insulation resistance ≥10¹²Ω. If the test value is lower than the standard, it is necessary to check whether the seal is missing or whether the insulation film is damaged. S508: Use a dielectric strength tester to apply a 50Hz AC voltage at a rate of 500V / s until the test voltage is reached, and hold for 1 minute. The judgment criteria are no breakdown or flashover. If breakdown occurs, the insulation film quality or hot-pressing parameters need to be disassembled and analyzed. S509: Use a universal testing machine to perform a 180° interlayer peel test: Take a busbar sample, separate the conductor and insulation film at one end of the sample, fix them on the upper and lower clamps of the testing machine, set the tensile rate to 50 mm / min, and test the maximum force during the peel process; the judgment standard is that the interlayer peel strength is ≥8 N / cm. If the strength does not meet the standard, the S3 hot pressing parameters need to be checked back. S510: Use a coordinate measuring machine to perform full-dimensional inspection of the key dimensions of the busbar, with no less than 10 inspection points; the judgment criteria are dimensional deviation ≤ ±0.1mm and warpage ≤ 0.1mm / m. If the dimensions are out of tolerance, the S4 cooling and pressure holding parameters or the accuracy of the positioning fixture need to be checked. S511: Busbars that meet all test standards are considered qualified products. After the production batch number and test data are entered, they are put into storage. If a single item fails to meet the standard, the problem type must be marked and the product must be reworked. After rework, it must be retested. If multiple items fail to meet the standard or the product still fails to meet the standard after rework, it is directly judged as scrap to prevent it from flowing into the downstream process.

[0012] Compared with existing technologies, the beneficial effects of this invention are: By performing a full-process surface treatment of degreasing, pickling, and passivation on the conductor, combined with plasma activation treatment of the insulating film, the interfacial affinity between the conductor and the insulating film is greatly improved. Furthermore, by combining gradient hot pressing and segmented pressure holding processes, the interlayer adhesive is fully diffused and cured, resulting in an interlayer peel strength of ≥8N / cm, which is more than 50% higher than that of traditional processes. Even under the high-frequency vibration conditions of long-term operation of new energy vehicles, interlayer peeling can be effectively avoided, ensuring the stability of the busbar structure. By adopting a three-stage gradient hot-pressing mode of "pre-pressing-hot pressing-final pressing", the temperature (80-100℃→120-150℃→160-180℃), pressure (5-8MPa→10-15MPa→8-10MPa) and time parameters of each stage are precisely matched with the characteristics of the insulating film (PET / PP) and the adhesive. This ensures that the adhesive is fully cured while avoiding the aging and melting of the insulating film due to excessive temperature. At the same time, the edge sealing treatment in the post-processing stage further strengthens the insulation protection, making the busbar insulation resistance ≥10¹²Ω and dielectric strength ≥20kV / mm, completely solving the insulation failure risk of traditional processes. This process design employs a segmented cooling scheme of "natural cooling and heat preservation - uniform cooling," maintaining a heat preservation pressure of 3-5 MPa throughout the process. First, natural cooling and 5 minutes of heat preservation are used to balance the temperature difference between the inside and outside of the busbar. Then, uniform cooling at 10℃ / min is used to control the shrinkage rate. Combined with the heat preservation pressure to constrain the shape of the busbar, warping deformation caused by thermal stress concentration is effectively avoided. Ultimately, the dimensional accuracy of the busbar is controlled within ±0.1mm, and the warping amount is ≤0.1mm / m, which fully meets the assembly accuracy requirements of high-voltage components in new energy vehicles. This process, through precise control of the low-pressure pre-compression stage and a slow heating rate, allows residual air and small molecule gases from the interlayer of the laminated components to be fully discharged. This fundamentally avoids the problems of increased conductivity loss and decreased heat dissipation efficiency caused by residual air bubbles in traditional processes. The laminated busbars prepared using this process have stable conductivity and uniform heat dissipation, which can effectively prevent local overheating and significantly reduce the vehicle safety risks caused by busbar failures. It is suitable for the harsh operating conditions of high-voltage systems in new energy vehicles. This invention, through precise pretreatment of conductors and insulating films, gradient hot pressing and segmented pressure holding, segmented cooling and full-process pressure holding, and targeted post-treatment, not only completely solves the core problems of traditional single hot pressing processes, such as interlayer peeling caused by insufficient bonding force between conductors and insulating films, insulation failure caused by coarse hot pressing parameters, warping deformation caused by excessively rapid release of cooling pressure, and interlayer bubble residue affecting conductivity, heat dissipation, and vehicle safety, but also achieves high-performance indicators such as interlayer peel strength ≥8N / cm, insulation resistance ≥10¹²Ω, and dimensional accuracy controlled within ±0.1mm. At the same time, its standardized process parameters are adapted to the upgrading of traditional equipment and large-scale industrial production, taking into account product reliability, assembly compatibility, and production efficiency, and significantly improving the ability of laminated busbars to adapt to the high-voltage and harsh operating conditions of new energy vehicles. Attached Figure Description

[0013] Figure 1 This is a flowchart of a hot pressing process for a laminated busbar for new energy vehicles proposed in this invention. Detailed Implementation

[0014] The present invention will be further explained below with reference to specific embodiments. Example

[0015] Reference Figure 1 This embodiment proposes a hot-pressing process for laminated busbars used in new energy vehicles, including the following steps: S1: Material pretreatment: The busbar conductor is subjected to surface degreasing, pickling, and passivation treatment, and the insulating film is subjected to plasma activation treatment; The busbar conductor is made of either copper or aluminum, and the passivation treatment uses chromate passivation solution with a passivation time of 30-60s. The insulating film is made of either PET or PP, and the plasma activation treatment power is 300-500W with a treatment time of 60-120s. During the plasma activation treatment, active groups are introduced to enhance the affinity between the insulating film and the conductor and adhesive, thus preventing interlayer separation. S2: Layered positioning: The conductor and insulating film are stacked sequentially according to the preset structure, and positioning pins and positioning clamps are used to achieve precise positioning, with positioning accuracy controlled within ±0.05mm; The conductor thickness of the laminated busbar is 0.5-3mm, the insulation film thickness is 0.1-0.3mm, and the number of layers is 2-8. S3: Gradient hot pressing and segmented pressure holding: Place the laminated assembly into the hot press, first heat it to 80-100℃ at a rate of 5℃ / min, apply 5-8MPa pressure for pre-pressing for 3-5min; then heat it to 120-150℃, apply 10-15MPa pressure for hot pressing for 8-12min; finally heat it to 160-180℃, apply 8-10MPa pressure for final pressing for 5-8min; The parallelism of the hot plate of the hot press is controlled within ±0.02mm, and nitrogen protection is used during the hot pressing process to prevent conductor oxidation. The specific logical steps are as follows: S301: Hot press preheating calibration: Start the hot press and preheat the hot plate to the initial temperature. Use a precision testing tool to calibrate the parallelism of the hot plate to ±0.02mm to ensure uniform pressure transmission and avoid local false pressure or overpressure. At the same time, turn on the nitrogen protection system and adjust the nitrogen flow rate to 10-15L / min to create an inert atmosphere in the hot press chamber and remove air in advance to prevent oxidation of the conductor surface during subsequent heating. S302: Place the stacked components that have completed layer positioning smoothly into the center of the lower hot plate of the hot press, ensuring that the edge of the component is aligned with the limiting structure of the hot plate, to avoid displacement of the component during the hot pressing process, and to lay the foundation for uniform heating and pressing in the future. S303: Set the heating rate to 5℃ / min, and heat from the initial temperature of 50℃ to 80-100℃. Slow heating can avoid thermal deformation of the insulating film due to instantaneous high temperature, and at the same time allow the internal temperature of the stack to be gradually and evenly conducted, preventing uneven gas expansion caused by interlayer temperature difference. S304: When the hot plate temperature stabilizes at 80-100℃, slowly apply a pressure of 5-8MPa at a rate of 0.5MPa / s and maintain the pressure for 3-5 minutes. This pressure is called "light compression". The purpose is to allow the layers of the laminated assembly to initially adhere, and at the same time, to allow the residual air between the layers and the small molecules of gas volatilized from the adhesive to be discharged in an orderly manner, so as to avoid the formation of bubbles due to gas being trapped under high pressure later. Maintain the low pressure for 3-5 minutes to ensure that the gas is fully discharged and that the insulating film is not deformed prematurely due to excessive pressure. S305: Maintain a heating rate of 5℃ / min, heating from 80-100℃ to 120-150℃. This temperature range is the "optimal curing temperature" for the adhesive that is compatible with the insulating film. This ensures that the adhesive melts and diffuses fully to the interface between the conductor and the insulating film to form a uniform adhesive layer, while preventing the insulating film from aging or degrading due to excessive temperature. S306: After the temperature stabilizes at 120-150℃, increase the pressure to 10-15MPa at a rate of 1MPa / s and maintain the pressure for 8-12 minutes. Under high pressure, the molten adhesive can more fully wet the interface between the conductor and the insulating film, fill in minor interface defects, and enhance intermolecular forces. The 8-12 minute holding time ensures that the adhesive is completely cured, forming a high-strength adhesive layer, thus solving the problem of insufficient interlayer bonding in traditional processes from the root. S307: Continue heating at a rate of 5℃ / min from 120-150℃ to 160-180℃, which can further enhance the interlayer molecular activity, make the interface between the conductor and the insulating film more tightly bonded, and at the same time, make the uncured adhesive completely cured, enhancing the overall density of the structure. S308: After the temperature stabilizes at 160-180℃, reduce the pressure to 8-10MPa and maintain the pressure for 5-8 minutes. By reducing the pressure, the insulation film and conductor will undergo slight thermal expansion at high temperatures. The medium pressure can ensure continuous bonding between layers without causing irreversible deformation of the component due to thermal expansion caused by high pressure. The 5-8 minute pressure holding time ensures that the component is stably formed at high temperature, avoiding warping due to structural instability during subsequent cooling. S309: After the final pressure stage is completed, maintain the nitrogen protective atmosphere and the basic holding pressure of 3-5 MPa, stop the heating process, and prepare to enter the subsequent cooling stage. S4: Cooling and Shaping: A segmented cooling method is adopted. First, the temperature is naturally cooled to 100-120℃ and held for 5 minutes. Then, the temperature is cooled to room temperature at a rate of 10℃ / min, and a holding pressure of 3-5MPa is maintained throughout the process. The specific logical steps are as follows: S401: After the final pressure stage in S3, keep the nitrogen protective atmosphere in the hot press unchanged, and slowly reduce the pressure from 8-10MPa at the final pressure to 3-5MPa to avoid gaps or rebound between the layers of the laminated components caused by a sudden drop in pressure. Keep the pressure constant throughout the process until it cools to room temperature. S402: Turn off the heating module of the hot press, turn on the cooling system to preheat, and at the same time confirm that the temperature monitoring device and pressure monitoring device in the hot press cavity are working properly to avoid parameter loss during the cooling process; S403: Without activating the forced cooling device, it relies on the natural heat dissipation of the hot plate of the hot press to cool the laminated busbar from 160-180℃ to 100-120℃. The natural cooling rate is slow, which allows the internal and surface temperatures of the busbar to drop synchronously, avoiding thermal stress caused by "external cold and internal heat" which can lead to warping or cracking of the busbar. S404: When the busbar temperature is stable at 100-120℃, maintain this temperature for 5 minutes to further balance the temperature of each area of ​​the busbar, making the interlayer molecular arrangement more stable, and at the same time reducing stress accumulation during subsequent rapid cooling, laying the foundation for precise shaping. S405: Start the hot press cooling system and set the cooling rate to 10℃ / min to cool the busbar from 100-120℃ to room temperature of 25℃. Uniform cooling can control the shrinkage rate of the busbar and avoid deformation caused by drastic shrinkage due to rapid cooling. The 10℃ / min rate has been verified to ensure production efficiency and adapt to the shrinkage characteristics of copper / aluminum conductors and insulating films, preventing dimensional deviations. During the cooling process, a holding pressure of 3-5MPa is maintained until the busbar reaches room temperature. The purpose of the holding pressure is to "constrain" the shape of the busbar during the shrinkage process, ensuring that it conforms to the preset mold contour and avoiding problems such as warping and bulging during shrinkage. Ultimately, the dimensional accuracy of the busbar is controlled within ±0.1mm. S406: After the busbar temperature drops to room temperature, first turn off the nitrogen protection system, then slowly release the holding pressure at a rate of 0.1MPa / s to avoid the busbar rebounding due to sudden pressure release. Then turn on the hot press and take out the cooled and shaped laminated busbar. S5: Post-processing and inspection: After hot pressing, the busbars are deburred and edge sealed, and then insulation resistance, dielectric strength, interlayer peel strength and dimensional accuracy are tested. The edge sealing is performed using either hot melt adhesive or UV-curable adhesive, with insulation resistance testing standards ≥10¹²Ω, dielectric strength ≥20kV / mm, and interlayer peel strength ≥8N / cm. The specific logical steps are as follows: S501: After cooling and shaping, the motherboard is placed in an ultrasonic cleaner. A neutral cleaning agent with pH 6-8 is used to clean the surface of residual adhesive, oil, and dust. The cleaning temperature is 40-50℃ and the time is 3-5 minutes. Then, it is rinsed with deionized water and dried at 60℃ for 10 minutes. The purpose of cleaning is to avoid impurities affecting the post-processing effect (such as poor edge sealing) and the accuracy of testing (such as interference from contamination in insulation resistance testing). S502: A combination of mechanical grinding and manual finishing is used: First, use a grinding wheel with a speed of 3000r / min to grind the large burrs on the edge of the busbar. When grinding, keep the grinding angle at 15-30° with the edge of the busbar to avoid excessive grinding that could damage the conductor or insulation film. S503: Use 800-1000 grit sandpaper to sand the edges until they are smooth and without sharp edges. After sanding, use compressed air to blow away the metal shavings and insulating debris on the surface to avoid debris residue causing short circuits during subsequent use. S504: Select the appropriate sealing material according to the application scenario of the busbar. For battery packs, use hot melt adhesive; for motor controllers, use UV curing adhesive. S505: Apply adhesive evenly along the edge of the busbar using a dispensing machine. The adhesive layer thickness should be controlled at 0.2-0.3mm to ensure no missed areas or bubbles. After application, the hot melt adhesive needs to be heated and cured at 120-150℃ for 5-8 minutes, and the UV curing adhesive needs to be cured under 365nm ultraviolet light for 20-30 seconds. S506: After the sealant has cured, visually inspect the sealant layer to ensure it is flat and free of cracks, and ensure that the edges of the busbar are completely sealed to prevent moisture and dust from entering the interlayer and causing insulation failure. S507: Use an insulation resistance tester, apply a 1000V DC voltage, test for 60s, and test points cover all conductors and insulation layer interfaces of the busbar; the judgment standard is insulation resistance ≥10¹²Ω. If the test value is lower than the standard, it is necessary to check whether the seal is missing or whether the insulation film is damaged. S508: Use a dielectric strength tester to apply a 50Hz AC voltage at a rate of 500V / s until the test voltage is reached, and hold for 1 minute. The judgment criteria are no breakdown or flashover. If breakdown occurs, the insulation film quality or hot-pressing parameters need to be disassembled and analyzed. S509: Use a universal testing machine to perform a 180° interlayer peel test: Take a busbar sample, separate the conductor and insulation film at one end of the sample, fix them on the upper and lower clamps of the testing machine, set the tensile rate to 50 mm / min, and test the maximum force during the peel process; the judgment standard is that the interlayer peel strength is ≥8 N / cm. If the strength does not meet the standard, the S3 hot pressing parameters need to be checked back. S510: Use a coordinate measuring machine to perform full-dimensional inspection of the key dimensions of the busbar, with no less than 10 inspection points; the judgment criteria are dimensional deviation ≤ ±0.1mm and warpage ≤ 0.1mm / m. If the dimensions are out of tolerance, the S4 cooling and pressure holding parameters or the accuracy of the positioning fixture need to be checked. S511: Busbars that meet all test standards are considered qualified products. After the production batch number and test data are entered, they are put into the warehouse. If a single item fails to meet the standard, the problem type must be marked and the product must be reworked. After rework, it must be retested. If multiple items fail to meet the standard or the product still fails to meet the standard after rework, it is directly judged as scrap to prevent it from flowing into the downstream process. This embodiment, through precise pretreatment of conductors and insulating films, gradient hot pressing and segmented pressure holding, segmented cooling and full-process pressure holding, and targeted post-treatment, not only completely solves the core problems of traditional single hot pressing processes, such as interlayer peeling caused by insufficient bonding force between conductors and insulating films, insulation failure caused by coarse hot pressing parameters, warping deformation caused by excessively rapid release of cooling pressure, and interlayer bubble residue affecting conductivity, heat dissipation, and vehicle safety, but also achieves high-performance indicators such as interlayer peel strength ≥8N / cm, insulation resistance ≥10¹²Ω, and dimensional accuracy controlled within ±0.1mm. At the same time, its standardized process parameters are adapted to the upgrading of traditional equipment and large-scale industrial production, taking into account product reliability, assembly compatibility, and production efficiency, and significantly improving the ability of laminated busbars to adapt to the high-voltage and harsh working conditions of new energy vehicles. Comparing the conventional hot-pressing process for laminated busbars with the hot-pressing process of Example 1, the achieved results are as follows: Comparison Dimensions Conventional laminated busbar hot pressing process The hot pressing process of the laminated busbar of this invention Material pretreatment The conductor was simply degreased, and the insulating film was not specially activated, resulting in insufficient surface cleaning and activation. The conductor undergoes a complete process of degreasing, pickling, and passivation; the insulating film is activated by plasma, significantly improving interfacial affinity. Hot-pressed core mode Single-temperature, single-pressure hot pressing; rudimentary parameter control. Gradient hot pressing + segmented pressure holding (three stages: pre-pressing → hot pressing → final pressing), parameters precisely matched to material properties. Hot pressing key parameters There is no fixed gradient; most temperatures and pressures are single (e.g., 150℃, 12MPa), and the heating rate is not strictly controlled. Heating rate: 5℃ / min; Pre-pressing (80-100℃, 5-8MPa, 3-5min) → Hot pressing (120-150℃, 10-15MPa, 8-12min) → Final pressing (160-180℃, 8-10MPa, 5-8min); Hot plate parallelism: ±0.02mm; Nitrogen protection. Cooling and shaping method Most cooling methods involve natural cooling or rapid forced cooling, resulting in excessively rapid pressure release during the cooling process. Segmented cooling (natural cooling to 100-120℃, holding for 5 minutes → uniform cooling at 10℃ / min to room temperature), maintaining a holding pressure of 3-5MPa throughout the process. Post-treatment measures Simple deburring only, no special edge sealing treatment. Mechanical sanding combined with manual deburring, and edge sealing with hot melt adhesive / UV curing adhesive, provides moisture and stain protection. Interlayer bonding effect Insufficient interfacial bonding leads to easy delamination under long-term vibration conditions, with peel strength typically <5 N / cm. The interlayer bonding is strong, with a peel strength of ≥8N / cm, which is more than 50% higher than that of conventional processes, and it has strong vibration resistance. Insulation performance Insulation failure is easily caused by aging / melting of the insulating film or insufficient edge protection; insulation resistance is mostly <10¹¹Ω and dielectric strength is <15kV / mm. Stable insulation performance, insulation resistance ≥10¹²Ω, dielectric strength ≥20kV / mm, and low risk of insulation failure. Dimensional accuracy and deformation Rapid cooling pressure release makes it prone to warping deformation, with dimensional accuracy mostly above ±0.2mm and significant warping. Dimensional accuracy is controlled within ±0.1mm, and warpage is ≤0.1mm / m, making it suitable for precision assembly requirements. interlayer bubble problem Air bubbles are difficult to expel completely, and residual air bubbles affect electrical conductivity and heat dissipation, easily causing localized overheating. The low-pressure pre-compression stage ensures thorough exhaust with no residual air bubbles, resulting in low electrical loss, uniform heat dissipation, and overall vehicle safety. As can be seen from the table above, the hot pressing process for laminated busbars for new energy vehicles proposed in this invention significantly improves the conductor surface treatment effect, the interfacial bonding force between the insulating film and the conductor, the hot pressing parameter control effect, dimensional accuracy, cooling and shaping effect, insulation performance, and the interlayer bubble removal effect.

[0016] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A hot pressing process for laminated busbars used in new energy vehicles, characterized in that, Includes the following steps: S1: Material pretreatment: The busbar conductor is subjected to surface degreasing, pickling, and passivation treatment, and the insulating film is subjected to plasma activation treatment; S2: Layered positioning: The conductor and insulating film are stacked sequentially according to the preset structure, and positioning pins and positioning clamps are used to achieve precise positioning, with positioning accuracy controlled within ±0.05mm; S3: Gradient hot pressing and segmented pressure holding: Place the laminated assembly into the hot press, first heat it to 80-100℃ at a rate of 5℃ / min, apply 5-8MPa pressure for pre-pressing for 3-5min; then heat it to 120-150℃, apply 10-15MPa pressure for hot pressing for 8-12min; finally heat it to 160-180℃, apply 8-10MPa pressure for final pressing for 5-8min; S4: Cooling and Shaping: A segmented cooling method is adopted. First, the temperature is naturally cooled to 100-120℃ and held for 5 minutes. Then, the temperature is cooled to room temperature at a rate of 10℃ / min, and a holding pressure of 3-5MPa is maintained throughout the process. S5: Post-processing and inspection: After hot pressing, the busbars are deburred and edge-sealed, and then insulation resistance, dielectric strength, interlayer peel strength and dimensional accuracy are tested.

2. The hot pressing process for laminated busbars for new energy vehicles according to claim 1, characterized in that, In S1, the busbar conductor is made of either copper or aluminum, and the passivation treatment uses a chromate passivation solution with a passivation time of 30-60s; the insulating film is made of either PET or PP, and the plasma activation treatment power is 300-500W with a treatment time of 60-120s. During the plasma activation treatment, active groups are introduced to enhance the affinity between the insulating film and the conductor and adhesive, thus preventing interlayer separation.

3. The hot pressing process for laminated busbars for new energy vehicles according to claim 1, characterized in that, In S3, the parallelism of the hot plate of the hot press is controlled within ±0.02mm, and nitrogen protection is used during the hot pressing process to prevent conductor oxidation.

4. The hot pressing process for laminated busbars for new energy vehicles according to claim 1, characterized in that, The specific logical steps of S3 are as follows: S301: Hot press preheating calibration: Start the hot press and preheat the hot plate to the initial temperature. Use a precision testing tool to calibrate the parallelism of the hot plate to ±0.02mm to ensure uniform pressure transmission and avoid local false pressure or overpressure. At the same time, turn on the nitrogen protection system and adjust the nitrogen flow rate to 10-15L / min to create an inert atmosphere in the hot press chamber and remove air in advance to prevent oxidation of the conductor surface during subsequent heating. S302: Place the stacked components that have completed layer positioning smoothly into the center of the lower hot plate of the hot press, ensuring that the edge of the component is aligned with the limiting structure of the hot plate, to avoid displacement of the component during the hot pressing process, and to lay the foundation for uniform heating and pressing in the future. S303: Set the heating rate to 5℃ / min, and heat from the initial temperature of 50℃ to 80-100℃. Slow heating can avoid thermal deformation of the insulating film due to instantaneous high temperature, and at the same time allow the internal temperature of the stack to be gradually and evenly conducted, preventing uneven gas expansion caused by interlayer temperature difference. S304: When the hot plate temperature is stable at 80-100℃, slowly apply a pressure of 5-8MPa at a rate of 0.5MPa / s and maintain the pressure for 3-5 minutes. S305: Maintain a heating rate of 5℃ / min, heating from 80-100℃ to 120-150℃. This temperature range is the "optimal curing temperature" for the adhesive that is compatible with the insulating film. This ensures that the adhesive melts and diffuses fully to the interface between the conductor and the insulating film to form a uniform adhesive layer, while preventing the insulating film from aging or degrading due to excessive temperature. S306: After the temperature stabilizes at 120-150℃, increase the pressure to 10-15MPa at a rate of 1MPa / s and maintain the pressure for 8-12 minutes. Under high pressure, the molten adhesive can more fully wet the interface between the conductor and the insulating film, fill in the small defects at the interface, and enhance the intermolecular forces. A holding time of 8-12 minutes ensures that the adhesive is fully cured, forming a high-strength adhesive layer; S307: Continue heating at a rate of 5℃ / min from 120-150℃ to 160-180℃, which can further enhance the interlayer molecular activity, make the interface between the conductor and the insulating film more tightly bonded, and at the same time, make the uncured adhesive completely cured, enhancing the overall density of the structure. S308: After the temperature stabilizes at 160-180℃, reduce the pressure to 8-10MPa and maintain the pressure for 5-8 minutes. By reducing the pressure, the insulation film and conductor will undergo slight thermal expansion at high temperatures. The medium pressure can ensure continuous bonding between layers and prevent irreversible deformation of the component due to thermal expansion caused by high pressure. The 5-8 minute pressure holding time ensures that the component is stably formed at high temperatures. S309: After the final pressure stage, maintain the nitrogen protective atmosphere and the basic holding pressure of 3-5 MPa, stop the heating process, and prepare to enter the subsequent cooling stage.

5. The hot pressing process for laminated busbars for new energy vehicles according to claim 1, characterized in that, In S5, the edge sealing is performed using either hot melt adhesive or UV-curable adhesive, with insulation resistance testing standards ≥10¹²Ω, dielectric strength ≥20kV / mm, and interlayer peel strength ≥8N / cm.

6. The hot pressing process for laminated busbars for new energy vehicles according to claim 1, characterized in that, The conductor thickness of the stacked busbar is 0.5-3mm, the insulation film thickness is 0.1-0.3mm, and the number of stacked layers is 2-8.

7. The hot pressing process for laminated busbars for new energy vehicles according to claim 1, characterized in that, The specific logical steps of S4 are as follows: S401: After the final pressure stage in S3, keep the nitrogen protective atmosphere in the hot press unchanged, and slowly reduce the pressure from 8-10MPa at the final pressure to 3-5MPa to avoid gaps or rebound between the layers of the laminated components caused by a sudden drop in pressure. Keep the pressure constant throughout the process until it cools to room temperature. S402: Turn off the heating module of the hot press, turn on the cooling system to preheat, and at the same time confirm that the temperature monitoring device and pressure monitoring device in the hot press cavity are working properly to avoid parameter loss during the cooling process; S403: Without activating the forced cooling device, it relies on the natural heat dissipation of the hot plate of the hot press to cool the laminated busbar from 160-180℃ to 100-120℃. The natural cooling rate is slow, which allows the internal and surface temperatures of the busbar to drop synchronously, avoiding thermal stress caused by "external cold and internal heat" which can lead to warping or cracking of the busbar. S404: When the busbar temperature is stable at 100-120℃, maintain this temperature for 5 minutes to further balance the temperature of each area of ​​the busbar, making the interlayer molecular arrangement more stable, and at the same time reducing stress accumulation during subsequent rapid cooling, laying the foundation for precise shaping. S405: Start the hot press cooling system, set the cooling rate to 10℃ / min, and cool the busbar from 100-120℃ to room temperature 25℃. During the cooling process, maintain a holding pressure of 3-5MPa until the busbar drops to room temperature. S406: After the busbar temperature drops to room temperature, first turn off the nitrogen protection system, then slowly release the holding pressure at a rate of 0.1 MPa / s to avoid the busbar rebounding due to sudden pressure release. Then turn on the hot press and take out the cooled and shaped laminated busbar.

8. The hot pressing process for laminated busbars for new energy vehicles according to claim 1, characterized in that, The specific logical steps of S5 are as follows: S501: After cooling and shaping, the motherboard is placed into an ultrasonic cleaner. A neutral cleaning agent with pH 6-8 is used to clean the residual adhesive, oil and dust on the surface. The cleaning temperature is 40-50℃ and the time is 3-5 minutes. Then rinse it with deionized water and dry it at 60℃ for 10 minutes. S502: A combination of mechanical grinding and manual finishing is used: First, use a grinding wheel with a speed of 3000r / min to grind the large burrs on the edge of the busbar. When grinding, keep the grinding angle at 15-30° with the edge of the busbar to avoid excessive grinding that could damage the conductor or insulation film. S503: Use 800-1000 grit sandpaper to sand the edges until they are smooth and without sharp edges. After sanding, use compressed air to blow away the metal shavings and insulating debris on the surface to avoid debris residue causing short circuits during subsequent use. S504: Select the appropriate sealing material according to the application scenario of the busbar. For battery packs, use hot melt adhesive; for motor controllers, use UV curing adhesive. S505: Apply adhesive evenly along the edge of the busbar using a dispensing machine. The adhesive layer thickness should be controlled at 0.2-0.3mm to ensure no missed areas or bubbles. After application, the hot melt adhesive needs to be heated and cured at 120-150℃ for 5-8 minutes, and the UV curing adhesive needs to be cured under 365nm ultraviolet light for 20-30 seconds. S506: After the sealant has cured, visually inspect the sealant layer to ensure it is flat and free of cracks, and ensure that the edges of the busbar are completely sealed to prevent moisture and dust from entering the interlayer and causing insulation failure. S507: Use an insulation resistance tester, apply a 1000V DC voltage, test for 60s, and test points cover all conductors and insulation layer interfaces of the busbar; the judgment standard is insulation resistance ≥10¹²Ω. If the test value is lower than the standard, it is necessary to check whether the seal is missing or whether the insulation film is damaged. S508: Use a dielectric strength tester to apply a 50Hz AC voltage at a rate of 500V / s until the test voltage is reached, and hold for 1 minute. The judgment criteria are no breakdown or flashover. If breakdown occurs, the insulation film quality or hot-pressing parameters need to be disassembled and analyzed. S509: Use a universal testing machine to perform a 180° interlayer peel test: Take a busbar sample, separate the conductor and insulation film at one end of the sample, fix them on the upper and lower clamps of the testing machine, set the tensile rate to 50 mm / min, and test the maximum force during the peel process; the judgment standard is that the interlayer peel strength is ≥8 N / cm. If the strength does not meet the standard, the S3 hot pressing parameters need to be checked back. S510: Use a coordinate measuring machine to perform full-dimensional inspection of the key dimensions of the busbar, with no less than 10 inspection points; the judgment criteria are dimensional deviation ≤ ±0.1mm and warpage ≤ 0.1mm / m. If the dimensions are out of tolerance, the S4 cooling and pressure holding parameters or the accuracy of the positioning fixture need to be checked. S511: Busbars that meet all test standards are considered qualified products. After the production batch number and test data are entered, they are put into storage. If a single item fails to meet the standard, the problem type must be marked and the product must be reworked. After rework, it must be retested. If multiple items fail to meet the standard or the product still fails to meet the standard after rework, it is directly judged as scrap to prevent it from flowing into the downstream process.

Images