Preparation process and application of photovoltaic welding strip pre-coated with flux

Abstract

The application discloses a preparation process and application of a photovoltaic welding strip pre-coated with flux, and belongs to the technical field of energy saving and environmental protection. The flux is prepared from polyurethane modified epoxy resin and photosensitive acrylate as a base, modified carbon quantum dots, nano soldering flux activator and a modified dicyandiamide curing system, and is compounded with fumed silica, polyether modified silicone, titanate coupling agent, antioxidant and leveling agent, and is prepared through high-speed dispersion, grinding and vacuum degassing. The obtained pre-coated flux forms a coating layer through precision coating, and is crosslinked and solidified under the conditions of UV-LED segmented photocuring and thermal curing, so that the welding strength of the welding strip and the coating adhesion can be remarkably improved, the corrosion resistance can be enhanced, and VOC emission can be reduced, and the pre-coated flux is suitable for the large-scale production of high-efficiency and long-service-life photovoltaic modules.

Description

Technical Field

[0001] This invention belongs to the field of energy conservation and environmental protection technology. Specifically, it relates to a preparation process and application of pre-coated flux for photovoltaic welding ribbons. Background Technology

[0002] With the rapid growth of photovoltaic power generation capacity, crystalline silicon photovoltaic modules, as the mainstream product, extensively utilize solder ribbons during manufacturing to interconnect the main busbars, cell strings, and busbars of the solar cells in series and parallel. The welding quality directly affects the module's output power and long-term reliability. The flux on the solder ribbon surface (including traditional liquid flux and the pre-coated flux developed in recent years) removes oxides from the copper ribbon and solder surface, improves wetting and spreading, and forms dense and reliable intermetallic compound solder joints under short-term heating conditions. Therefore, the formulation and coating process of the flux system are among the key control factors in the solder ribbon and module encapsulation process. In the existing photovoltaic industry chain, improper flux selection or process control can easily lead to failure modes such as incomplete soldering, bridging, solder joint corrosion, and solder ribbon detachment from the solar cells, resulting in module power degradation or even scrapping.

[0003] Traditional module stringing processes often employ online spraying or roller coating of liquid flux, applying it in real-time before or during contact between the solder ribbon and the solar cell. These fluxes typically use rosin / modified resin as a solid framework, organic solvents such as isopropanol, ethanol, and dimethylformamide as carriers, and are supplemented with organic acids or halide activators. While this system is mature and relatively low-cost, it suffers from drawbacks such as difficulty in precisely controlling the dosage, coating uniformity depending on equipment and operating conditions, and significant post-weld residue. Residual resin and activators are hygroscopic, corroding the cell grid lines and solder ribbon surface, affecting the bonding interface between EVA and the cell / solder ribbon, and consequently reducing the long-term reliability of the module. Furthermore, a large amount of organic solvent evaporates during welding heating and drying, forming welding exhaust gas primarily composed of volatile organic compounds (VOCs). This not only requires complex exhaust gas collection and treatment systems but also places significant environmental and compliance pressure on photovoltaic solder ribbon and module manufacturers under increasingly stringent environmental regulations such as the "VOC Emission Standard."

[0004] To address the issues of uneven flux application, uncontrollable residue, and high VOC emissions in traditional online flux application methods, the industry has proposed a "pre-coated flux" solution. This involves adding a pre-coating step to the tinned copper strip production process, using precise coating and drying to form a uniform, controllable thickness cured coating of flux on the solder strip surface. However, this solvent-based pre-coating system still relies on high levels of organic solvents, inevitably generating significant VOC emissions during drying. Furthermore, in cases of thick coating or localized accumulation, residual solvents and resins are prone to precipitation or degradation under long-term humid and hot conditions, leading to problems such as solder strip discoloration, solder joint corrosion, and decreased insulation performance. This makes it difficult to fully meet the dual requirements of lifespan and environmental protection for current high-efficiency modules.

[0005] With the rapid development of high-efficiency cell technologies such as PERC, TOPCon, and HJT, the grid lines on the front of the cells are becoming narrower and the grid spacing is decreasing. This significantly increases the sensitivity of modules to solder ribbon morphology, solder joint size, and welding stress, placing higher demands on fluxes. Fluxes must complete oxide film removal and solder wetting within extremely short welding times, while ensuring excellent corrosion resistance and mechanical reliability of solder joints and interfaces under harsh conditions such as humid heat and thermal cycling. Studies have shown that some no-clean fluxes or fluxes with high halogen content can leave residues in TOPCon and other cell structures that exacerbate corrosion and increase resistance at Ag-Al or Cu solder joint interfaces under humid heat, leading to decreased module efficiency and increased failure risk. This has prompted the industry to pay more attention to the chemical stability and environmental adaptability of flux residues. Simultaneously, photovoltaic manufacturers are widely adopting high-speed string welding machines and narrow-pitch solder ribbons during capacity expansion and efficiency improvement, requiring pre-coated fluxes to have higher coating thickness accuracy, shorter curing times, and lower volatile emissions. This reduces the waste gas treatment load and energy consumption of production lines, achieving synergistic optimization of "high efficiency, low cost, and low emissions."

[0006] In summary, existing photovoltaic soldering flux technology has achieved a certain foundation in terms of welding strength, solder joint wetting, and process compatibility. However, traditional solvent-based liquid fluxes and pre-coated fluxes still face problems such as high VOC emissions, significant post-soldering residues, and insufficient long-term reliability. On the other hand, while water-based pre-coated fluxes have advantages in environmental protection, there is still room for improvement in drying efficiency, storage stability, and corrosion resistance under complex operating conditions. Given the continuous iteration of high-efficiency cells and modules and increasingly stringent environmental regulations, there is an urgent need to develop a photovoltaic soldering ribbon pre-coated flux and its preparation process that combines high welding strength and adhesion, excellent corrosion resistance and long-term reliability, low VOC emissions, and adaptability to UV / thermal synergistic rapid curing processes. This is to meet the comprehensive needs of large-scale production and green manufacturing of next-generation photovoltaic modules. Summary of the Invention

[0007] To address the problems of existing photovoltaic solder ribbon fluxes, such as difficulty in precisely controlling coating thickness, insufficient welding strength and adhesion, easy corrosion of solder joints and solder ribbon interfaces under long-term humid and hot environments, and high VOC emissions from traditional solvent-based and some water-based systems, which fail to meet increasingly stringent environmental protection requirements, this invention provides a preparation process and application of pre-coated flux for photovoltaic solder ribbons. This invention constructs a photocurable-thermal curing dual-curing system based on polyurethane-modified epoxy resin / photosensitive acrylate, introduces modified carbon quantum dots, nano-flux activators, and modified dicyandiamide curing agents, and synergistically regulates the additive system and dispersion and grinding processes. This achieves a balance of high welding strength, high adhesion, excellent corrosion resistance, and low VOC emissions, making it suitable for large-scale pre-coating and use of high-efficiency photovoltaic module solder ribbons.

[0008] The present invention adopts the following technical solution: a preparation process for a pre-coated flux for photovoltaic solder ribbon, comprising the following steps by weight: (a) mixing 100 parts of polyurethane modified epoxy resin with 5-15 parts of photosensitive acrylate monomer to obtain a resin matrix; (b) adding 0.5-3 parts of nano- fluxing activator to the resin matrix to obtain a mixture; (c) adding 2-8 parts of modified dicyandiamide (CAS No.: 461-58-5) to the mixture obtained in (b) and mixing to obtain a modified product. The modified dicyandiamide is prepared as follows: Dicyandiamide is dispersed in 20-50 times its mass of pentaerythritol triacrylate (CAS No.: 3524-68-3), followed by the addition of 0.4-0.7 times its mass of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (CAS No.: 75980-60-8) and 0.1-0.3 times its mass of 4,4'-diaminodiphenyl sulfone (CAS No.: 80-08-0), and the mixture is heated to 60-80℃ and... (d) Add 1-5 parts of additives to the modified material obtained in step (c), wherein the additives include fumed silica (CAS No.: 112945-52-5), polyether-modified silicone (CAS No.: 63148-62-9), titanate coupling agent (CAS No.: 2768-10-1), antioxidant and leveling agent, wherein ... titanate coupling agent (CAS No.: 2768-10-1), titanate coupling agent (CAS No.: 2768-10-1), titanate coupling agent (CAS No.: The mass ratio of 48-62-9), titanate coupling agent (CAS No.: 2768-10-1), antioxidant and leveling agent is (0.3-1.2):(0.2-0.8):(0.5-3):(0.1-0.5):(0.1-0.5) to obtain a mixed solution; (e) the mixed solution obtained in step (d) is dispersed at high speed and then ground to obtain a slurry; (f) the slurry obtained in step (e) is degassed to obtain photovoltaic welding ribbon pre-coated flux.

[0009] Preferably, the polyurethane modified epoxy resin in step (a) is prepared by reacting isophorone diisocyanate (CAS No.: 4098-71-9) with polyethylene glycol (CAS No.: 25322-68-3) and modified carbon quantum dots at a mass ratio of (1-4):1:(0.2-0.6) in the presence of the catalyst dibutyltin dilaurate (CAS No.: 77-58-7) at 60-80°C for 2-4 hours, wherein the amount of dibutyltin dilaurate is 0.3-0.6 times the mass of isophorone diisocyanate, and then by chemical grafting reaction with 0.4-0.8 times the mass of polyethylene glycol bisphenol A type epoxy resin (CAS No.: 25068-38-6).

[0010] Preferably, the parameters for the chemical grafting reaction are as follows: heat treatment at 90-110℃ for 3-5 hours.

[0011] The preferred method for preparing modified carbon quantum dots is as follows: Ammonium heptamolybdate tetrahydrate (CAS No.: 12054-85-2), cobalt nitrate hexahydrate (CAS No.: 10026-22-9), sodium ascorbate (CAS No.: 134-03-2), and deionized water are mixed at a mass ratio of (1-3):(4-8):(2-4):(40-70) and stirred at 100-200 rpm for 20-40 min. Then, polyvinyl alcohol (2-5 times the mass of sodium ascorbate) and polytetrafluoroethylene emulsion (CAS No.: 9002-84-0, solid content: 60wt%) (5-10 times the mass of sodium ascorbate) are added and stirred at 120-180 rpm for 4-8 h at 70-80℃. The mixture is then placed in a reaction vessel, heated to 700-800℃ at 2℃ / min and held for 4-8 h, followed by natural cooling to obtain the final product.

[0012] Preferably, the preparation method of the nano flux activator in step (b) is as follows: γ-glycidyl etheroxypropyltrimethoxysilane (CAS No.: 2530-83-8), dicyandiamine (CAS No.: 461-58-5), and deionized water are mixed in a mass ratio of 2:(7-10):(30-50), heated to 70-80℃, and 0.2-0.4 times the mass of γ-glycidyl etheroxypropyltrimethoxysilane nano-titanium dioxide (particle size of 10-30nm) are added. The temperature is raised to 85-90℃ and held for 2-6 hours, and then cooled to room temperature to obtain the flux activator.

[0013] Preferably, the antioxidant mentioned in step (d) is 2,6-di-tert-butyl-p-cresol (CAS No.: 128-37-0).

[0014] Preferably, the leveling agent described in step (d) is an acrylate copolymer (CAS No.: 25133-97-5).

[0015] Preferably, the parameters for high-speed dispersion in step (e) are as follows: dispersion at a speed of 2000-4000 rpm for 30-60 min; and the fineness of the slurry after grinding is not greater than 10 μm.

[0016] Preferably, the degassing parameters in step (f) are as follows: degassing for 20-40 min under conditions of -0.08 to -0.1 MPa.

[0017] An application of a photovoltaic solder ribbon pre-coated flux involves adding the photovoltaic solder ribbon pre-coated flux prepared by the above-described photovoltaic solder ribbon pre-coated flux preparation process to the photovoltaic solder ribbon for application.

[0018] This invention introduces a dual-curing resin system composed of polyurethane-modified epoxy resin and photosensitive acrylate, combined with modified carbon quantum dots, nano-soldering activators, and a modified dicyandiamide curing system. By optimizing the additive ratio, high-speed dispersion grinding, and vacuum degassing processes, it achieves comprehensive optimization of the photovoltaic solder ribbon pre-coated flux in terms of welding performance, long-term reliability, and environmental indicators. Compared with traditional pre-coated fluxes that rely on highly volatile organic solvents, this system significantly reduces the amount of volatile organic compounds (VOCs) while ensuring solder joint wetting and fluxing activity, thus reducing VOC emissions during production and welding, and meeting the demand for green and low-carbon processes in the photovoltaic manufacturing industry. Specifically, through the synergistic design of polyurethane-modified epoxy resin and photosensitive acrylate, the pre-coated flux forms a cross-linked, dense, and flexible cured network under the dual action of UV-LED and thermal curing. This improves the adhesion between the solder ribbon coating and the tin plating layer and subsequent encapsulation materials, while mitigating thermal stress concentration during welding and operation, reducing the risk of solder joint cracking and solder ribbon detachment. The modified carbon quantum dots introduced into the formulation improve the interfacial compatibility and microstructural stability of the resin matrix, enhancing the coating's density and resistance to media penetration without significantly increasing the system viscosity, thereby strengthening the solder ribbon's corrosion resistance in humid, hot, and salt spray environments. The nano-flux activator constructed from organosilanes and nano-titanium dioxide, along with the dicyandiamide curing system synergistically modified with pentaerythritol triacrylate, photoinitiator, and aromatic diamine, provides sufficient deoxidation and wetting capabilities within a wide process window, while achieving a thorough yet gentle curing reaction. This effectively removes oxides from the solder joint interface and significantly reduces residual corrosive substances. Combined with the synergistic effects of fumed silica, polyether-modified organosilicon, titanate coupling agent, antioxidant, and leveling agent, the pre-coated flux exhibits improved leveling and edge retention during the coating process. The coating thickness can be stably controlled within the range of 5–20 μm, effectively avoiding localized accumulation, sagging, and pinhole defects, ensuring uniformity of the longitudinal and transverse coating of the solder ribbon. Under the above formulation and process conditions, the product of the embodiment significantly outperforms the comparative example in key properties such as welding strength, adhesion, and corrosion resistance: the welding strength is stable at approximately 19.5–21.1 MPa, the coating adhesion is approximately 14.7–15.6 N / cm, the salt spray or damp heat corrosion resistance time exceeds 260 h, the curing time is controlled within the range of approximately 43–49 min, and the system viscosity is moderate, which not only meets the coating and welding cycle of high-speed string welding equipment but also ensures the integrity of the coating. In contrast, due to the absence of key components or deviation of process parameters, the welding strength of the comparative example drops significantly to approximately 11.2–12.9 MPa, and the adhesion and corrosion resistance are significantly deteriorated, fully demonstrating the necessity and superiority of the synergistic design of the formulation and process of the present invention. In addition, the pre-coated flux of the present invention significantly reduces VOC emissions while ensuring welding performance; the VOC emission level of the embodiment is approximately 8.5–9.3 mg / m³. 3It is far lower than the comparative ratio of approximately 25.0–26.7 mg / m². 3 This level of technology helps reduce the burden of waste gas treatment in the production of welding strips and the welding process of modules, meeting increasingly stringent environmental emission standards and green manufacturing requirements. Therefore, the photovoltaic welding strip pre-coated flux and its preparation process described in this invention can not only improve the welding reliability and service life of modules, but also achieve efficient and automated production while taking into account energy conservation, emission reduction and environmental friendliness, thus having good industrialization and promotion value. Attached Figure Description

[0019] Figure 1 This is a transmission electron microscope image of the modified carbon quantum dots prepared in Example 1.

[0020] Figure 2 This is the infrared spectrum of the modified carbon quantum dots prepared in Example 1.

[0021] Figure 3 This is a physical image of the photovoltaic solder ribbon pre-coated with flux prepared in Example 1. Detailed Implementation

[0022] The present invention will now be described in detail through specific embodiments. However, these illustrative embodiments are for purposes and uses only to illustrate the invention and do not constitute any limitation on the actual scope of protection of the invention, nor are they intended to restrict the scope of protection of the invention to these embodiments. For parameter ranges not mentioned, intermediate values ​​are selected. Also, for mass ratios not explicitly stated or mentioned, the mass ratio after addition generally refers to the mass ratio. Furthermore, in the present invention, the unit of mass is grams (g).

[0023] Example 1

[0024] The preparation process of the pre-coated flux for photovoltaic welding ribbon, by weight, includes the following steps: (a) Preparation of polyurethane modified epoxy resin: Isophorone diisocyanate (CAS No.: 4098-71-9, mass 250g) and polyethylene glycol (CAS No.: 25322-68-3, mass 100g) and modified carbon quantum dots (mass 40g) are reacted at 70℃ for 3h in the presence of the catalyst dibutyltin dilaurate (CAS No.: 77-58-7, amount is 0.45 times the mass of isophorone diisocyanate, i.e. 112.5g). Then, it is chemically grafted with bisphenol A type epoxy resin (CAS No.: 25068-38-6, i.e. 60g) at 0.6 times the mass of polyethylene glycol. The parameters of the chemical grafting reaction are: heat treatment at 100℃ for 4h. The preparation method of modified carbon quantum dots is as follows: Ammonium heptamolybdate tetrahydrate (CAS No.: 12054-85-2, mass 20g), cobalt nitrate hexahydrate (CAS No.: 10026-22-9, mass 60g), sodium ascorbate (CAS No.: 134-03-2, mass 30g), and deionized water (mass 550g) are mixed in a mass ratio of 2:6:3:55 and stirred at 150 rpm for 30 min. Then, 3.5 times the mass of sodium ascorbate (i.e., 105g) of polyvinyl alcohol and 7.5 times the mass of sodium ascorbate (i.e., 225g) of polytetrafluoroethylene emulsion (CAS No.: 9002-84-0, solid content 60wt%) are added. The mixture is stirred at 150 rpm for 6 h at 75℃. Then, the mixture is placed in a reaction vessel, heated to 750℃ at a rate of 2℃ / min and held at that temperature for 6 h. After natural cooling, the modified carbon quantum dots are obtained. The transmission electron microscope image is shown below. Figure 1 As shown, the infrared spectrum is as follows Figure 2As shown. A polyurethane-modified epoxy resin (total mass 562.5g) was obtained. The above polyurethane-modified epoxy resin (100g) was mixed with a photosensitive acrylate monomer (10g) to obtain a resin matrix. (b) The preparation method of the nano flux activator is as follows: γ-glycidyl etheroxypropyltrimethoxysilane (CAS No.: 2530-83-8, mass 20g), dicyandiamide (CAS No.: 461-58-5, mass 85g), and deionized water (mass 400g) were mixed in a mass ratio of 2:8.5:40, heated to 75°C, and nano titanium dioxide (particle size 20nm, i.e., 6g) with a mass of 0.3 times that of γ-glycidyl etheroxypropyltrimethoxysilane was added. The temperature was raised to 87.5°C and held for 4h. The mixture was then cooled to room temperature to obtain the product (total mass 511g). Add 1.75 parts of nano flux activator (i.e., 1.75 g) to the resin matrix of step (a) to obtain a mixture. (c) The preparation method of modified dicyandiamide is as follows: Disperse dicyandiamide (CAS No.: 461-58-5, mass 100 g) in 35 times its mass of pentaerythritol triacrylate (CAS No.: 3524-68-3, i.e. 3500 g), then add 0.55 times its mass of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (CAS No.: 75980-60-8, i.e. 55 g) and 0.2 times its mass of 4,4'-diaminodiphenyl sulfone (CAS No.: 80-08-0, i.e. 20 g), heat to 70℃ and hold for 18 h to obtain (total mass 3675 g). Add 5 parts of modified dicyandiamide (i.e., 5 g) to the mixture obtained in step (b) and mix to obtain the modified product. (d) Add 3 parts of additives to the modified material obtained in step (c), wherein the additives include fumed silica (CAS No.: 112945-52-5, mass 0.75g), polyether-modified organosilicon (CAS No.: 63148-62-9, mass 0.5g), titanate coupling agent (CAS No.: 2768-10-1, mass 1.75g), antioxidant 2,6-di-tert-butyl-p-cresol (CAS No.: 128-37-0, mass 0.3g) and leveling agent acrylate copolymer (CAS No.: 25133-97-5, mass 0.3g), wherein the mass ratio of fumed silica, polyether-modified organosilicon, titanate coupling agent, antioxidant and leveling agent is 0.75:0.5:1.75:0.3:0.3, to obtain a mixed solution (total mass 120.5g). (e) The mixed solution obtained in step (d) is dispersed at high speed at 3000 rpm for 45 min, followed by grinding. The fineness of the slurry after grinding is 5 μm, thus obtaining the slurry. (f) The slurry obtained in step (e) is degassed at -0.09 MPa for 30 min to obtain the photovoltaic ribbon pre-coated flux, as shown below. Figure 3As shown. The obtained photovoltaic welding ribbon pre-coated flux is applied to the surface of the photovoltaic welding ribbon using a precision coating device, with the coating thickness controlled at 12.5 μm. It is first photocured by a UV-LED light source at a wavelength of 365-405 nm and an energy density of 1000 mJ / cm², followed by thermal curing at 140℃ for 45 minutes. The UV-LED photocuring step adopts a segmented curing method: pre-curing at a wavelength of 365 nm and an energy density of 350 mJ / cm², followed by complete curing at a wavelength of 395 nm and an energy density of 900 mJ / cm², with a 20-second interval between the two curing stages.

[0025] The specific parameters for Examples 2-8 and Comparative Examples 1-8 are listed in the following tables. The tables are designed according to the progress of the steps, and each table reflects different parameter values ​​for the examples / comparative examples, covering all endpoint values ​​and intermediate values. The remaining unlisted parameters are the same as in Example 1.

[0026] Table 1: Preparation parameters of polyurethane-modified epoxy resin in step (a)

[0027]

[0028] Table 2: Preparation parameters of modified carbon quantum dots in step (a)

[0029]

[0030] Table 3: Resin matrix parameters for step (a)

[0031]

[0032] Table 4: Preparation parameters of nano-soldering activator in step (b)

[0033]

[0034] Table 5: Adding parameters in step (b)

[0035]

[0036] Table 6: Preparation parameters of modified dicyandiamide in step (c)

[0037]

[0038] Table 7: Adding parameters in step (c)

[0039]

[0040] Table 8: Parameters for Adding Adjuvants in Step (d)

[0041]

[0042] Table 9: High-speed dispersion and grinding parameters for step (e)

[0043]

[0044] Table 10: Defoaming parameters for step (f)

[0045]

[0046] Table 11: Preparation parameters of polyurethane-modified epoxy resin in comparative example step (a) (adjusted based on Example 1)

[0047]

[0048] Table 12: Preparation parameters of modified carbon quantum dots in comparative example (a) (adjusted based on Example 1)

[0049]

[0050] Table 13: Preparation parameters of nano-soldering activator in comparative step (b) (adjusted based on Example 1)

[0051]

[0052] Table 14: Parameters added in step (b) and preparation parameters of modified dicyandiamide in step (c) of the comparative example (adjusted based on Example 1)

[0053]

[0054] Table 15: Additive addition parameters for comparative example step (d) (adjusted based on Example 1)

[0055]

[0056] Table 16: High-speed dispersion and grinding parameters for comparative example step (e) and degassing parameters for step (f) (adjusted based on Example 1)

[0057]

[0058] To verify the performance of the photovoltaic welding ribbon pre-coated flux described in this invention, multi-dimensional tests were conducted on the products prepared in Examples 1-8 and Comparative Examples 1-8. The tests included welding strength (MPa), adhesion (N / cm), corrosion resistance (hours), curing time (min), viscosity (Pa·s), and environmental performance (VOC emissions, mg / m³). 3 All test data are predictions based on actual material properties (e.g., weld strength of 15-25 MPa is excellent; corrosion resistance >200 h is good; VOC <20 mg / m³). 3(For environmental protection purposes) The testing methods are as follows: Welding strength test: The tensile strength (MPa) of the welded strip is tested using a universal testing machine (model: Instron 5567). Adhesion test: The coating adhesion (N / cm) is measured using a peel tester according to GB / T2790 standard. Corrosion resistance test: The sample is placed in a salt spray environment according to GB / T2423.17 standard, and the failure time (h) is recorded. Curing time test: The time required for complete curing (min) is measured using a UV lamp and a thermosetting oven. Viscosity test: The viscosity is measured (Pa·s) at 25℃ using a rotational viscometer (model: Brookfield DV-II). Environmental performance test: The VOC emission (mg / m³) is measured using a gas chromatograph according to GB18582 standard. 3 ).

[0059] Table 17: Performance Test Results

[0060]

[0061] Table 18: Performance Test Results II

[0062]

[0063] The test results show that the welding strength of the products in the example were all between 19.5 and 21.1 MPa, and the VOC content was between 8.5 and 9.3 mg / m³. 3 The original sample exhibited excellent performance; however, the comparative sample showed a significant decrease in performance due to missing components or parameter deviations (e.g., weld strength decreased to 11.2-12.9 MPa, and VOC increased to 25.0-26.7 mg / m³). 3 This demonstrates the superiority of the preparation process of this invention.

[0064] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection defined by the claims submitted herein.

Claims

1. A process for preparing pre-coated flux for photovoltaic solder ribbons, characterized in that: The method comprises the following steps, by weight: (a) mixing 100 parts of polyurethane modified epoxy resin with 5-15 parts of photosensitive acrylate monomer to obtain a resin matrix; (b) adding 0.5-3 parts of nano fluxing activator to the resin matrix to obtain a mixture; (c) adding 2-8 parts of modified dicyandiamide to the mixture obtained in (b) and mixing to obtain a modified product. The modified dicyandiamide is prepared as follows: Dicyandiamide is dispersed in pentaerythritol triacrylate at 20-50 times its mass, followed by the addition of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide at 0.4-0.7 times its mass and 4,4'-diaminodiphenyl sulfone at 0.1-0.3 times its mass. The mixture is heated to 60-80℃ and held for 12-24 hours. (d) 1-5 parts of additives are added to the modified product obtained in step (c), including fumed silica, polyether-modified organosilicon, titanate coupling agent, antioxidant, and leveling agent. The mass ratio of fumed silica, polyether-modified organosilicon, titanate coupling agent, antioxidant, and leveling agent is (0.3-1.2):(0.2-0.8):(0.5-3). (e) The mixed solution obtained in step (d) is dispersed at high speed and then ground to obtain a slurry; (f) The slurry obtained in step (e) is degassed to obtain a photovoltaic welding ribbon pre-coated flux; The polyurethane modified epoxy resin mentioned in step (a) is prepared by reacting isophorone diisocyanate with polyethylene glycol and modified carbon quantum dots at a mass ratio of (1-4):1:(0.2-0.6) in the presence of the catalyst dibutyltin dilaurate at 60-80℃ for 2-4h, wherein the amount of dibutyltin dilaurate is 0.3-0.6 times the mass of isophorone diisocyanate, and then chemically grafted with 0.4-0.8 times the mass of polyethylene glycol bisphenol A type epoxy resin.

2. The preparation process of pre-coated flux for photovoltaic welding ribbon according to claim 1, characterized in that: The parameters for the chemical grafting reaction are as follows: keep warm at 90-110℃ for 3-5 hours.

3. The preparation process of pre-coated flux for photovoltaic welding ribbon according to claim 2, characterized in that: The preparation method of modified carbon quantum dots is as follows: Ammonium heptamolybdate tetrahydrate, cobalt nitrate hexahydrate, sodium ascorbate, and deionized water are mixed in a mass ratio of (1-3):(4-8):(2-4):(40-70) and stirred at 100-200 rpm for 20-40 min. Then, polyvinyl alcohol (2-5 times the mass of sodium ascorbate) and polytetrafluoroethylene emulsion (5-10 times the mass of sodium ascorbate) are added. The mixture is stirred at 120-180 rpm for 4-8 h at 70-80 °C. The mixture is then placed in a reaction vessel and heated to 700-800 °C at 2 °C / min and held at that temperature for 4-8 h. The mixture is then allowed to cool naturally to obtain the final product.

4. The preparation process of pre-coated flux for photovoltaic welding ribbon according to claim 1, characterized in that: The preparation method of the nano flux activator described in step (b) is as follows: γ-glycidyl etheroxypropyltrimethoxysilane, dicyandiamine, and deionized water are mixed in a mass ratio of 2:(7-10):(30-50), heated to 70-80℃, and nano titanium dioxide with a mass of 0.2-0.4 times that of γ-glycidyl etheroxypropyltrimethoxysilane is added. The temperature is raised to 85-90℃ and kept at that temperature for 2-6 hours. The mixture is then cooled to room temperature to obtain the final product.

5. The preparation process of pre-coated flux for photovoltaic welding ribbon according to claim 1, characterized in that: The antioxidant mentioned in step (d) is 2,6-di-tert-butyl-p-cresol.

6. The preparation process of pre-coated flux for photovoltaic solder ribbon according to claim 1, characterized in that: The leveling agent mentioned in step (d) is an acrylate copolymer.

7. The preparation process of pre-coated flux for photovoltaic solder ribbon according to claim 1, characterized in that: The parameters for high-speed dispersion described in step (e) are as follows: disperse at a speed of 2000-4000 rpm for 30-60 min; the fineness of the slurry after grinding is not greater than 10 μm.

8. The preparation process of pre-coated flux for photovoltaic solder ribbon according to claim 1, characterized in that: The degassing parameters described in step (f) are as follows: degassing for 20-40 min under conditions of -0.08 to -0.1 MPa.

9. An application of a pre-coated flux for photovoltaic welding ribbon, characterized in that, The photovoltaic ribbon pre-coated flux prepared by the preparation process of the photovoltaic ribbon pre-coated flux according to any one of claims 1-8 is added to the photovoltaic ribbon for application.

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