A method for preparing a flux-coated photovoltaic ribbon

Abstract

This invention relates to the field of flux preparation technology, specifically a method for preparing a pre-coated flux for photovoltaic solder ribbon, comprising the following steps: loading a corrosion inhibitor onto a nano-loaded material, encapsulation treatment, surface hydrophilic modification, and flux preparation. This invention effectively solves the problems of traditional water-based halogen-free pre-coated fluxes lacking slow-release protection and prone to premature reaction and consumption, leading to long-term storage failure, through the synergistic effect of nano-loading, chitosan encapsulation, and hydrophilic modification. Simultaneously, it overcomes the problems of existing nano-container systems being difficult to stably disperse in water-based systems and prone to aggregation and precipitation, preventing corrosive media from penetrating along defects and accelerating corrosion. It retains the environmental advantages of water-based halogen-free, VOC-free, and wash-free properties, while achieving long-term controllable release of the corrosion inhibitor and dual protection through film-forming hydrophobic barrier, significantly improving the storage stability and corrosion resistance of photovoltaic solder ribbons in humid and hot environments.

Description

Technical Field

[0001] This invention relates to the field of flux preparation technology, specifically to a method for preparing a pre-coated flux for photovoltaic soldering ribbon. Background Technology

[0002] Photovoltaic solder ribbon, also known as tin-plated copper ribbon, is a conductive interconnect material for photovoltaic modules. It consists of a copper base ribbon and tin alloy solder plated on the surface of the copper base ribbon. When photovoltaic solder ribbon and cell electrodes are stored for a long time, an oxide film is easily formed on the surface, which hinders the solder bonding and leads to poor soldering and desoldering. Therefore, flux needs to be applied during soldering to remove the oxide film and promote wetting.

[0003] Currently, pre-coated flux on solder ribbons has become the industry mainstream. Before leaving the factory, photovoltaic solder ribbons are uniformly coated and cured with flux using specialized equipment, and then supplied after winding. This process eliminates the need for module manufacturers to store, mix, and spray flux, reducing equipment investment and maintenance. Furthermore, pre-coated flux can remove oxides from the solder and base material surfaces during welding, reducing surface tension and promoting solder spread, thereby achieving a reliable electrical connection.

[0004] Water-based halogen-free flux, as the mainstream pre-coated flux for photovoltaic solder ribbons, is mainly composed of deionized water, organic weak acid, surfactant, corrosion inhibitor, and film-forming agent. Although water-based halogen-free pre-coated flux has achieved environmental protection requirements such as VOC-free, halogen-free, and no-wash, it still has significant defects in long-term storage reliability. Conventional corrosion inhibitors are mostly directly dispersed in the water-based halogen-free flux system, lacking a slow-release and protective structure. When the solder ribbon is pre-coated, dried, or stored in a normal temperature or humid environment after leaving the factory, the corrosion inhibitor will react prematurely with the organic acid, moisture, and oxygen in the system, or quickly adsorb onto the metal surface and be consumed, resulting in rapid initial failure and no effective protection in the later stage. After long-term storage, there is no longer enough corrosion inhibitor in the pre-coating layer to play a role, making the photovoltaic solder ribbon more susceptible to oxidation and corrosion in humid environments, thus affecting its service life.

[0005] To address the issue of long-term protection by corrosion inhibitors, the field of metal anti-corrosion coatings has developed technologies that utilize nano-containers to load corrosion inhibitors and encapsulate them with pH-responsive polymers. This enables the on-demand release of corrosion inhibitors in corrosive microenvironments. However, these nano-container-corrosion inhibitor composite systems are typically used in solvent-based coatings or epoxy coatings. Their preparation process involves organic solvents, which conflicts with the environmental requirements of water-based fluxes, making them unsuitable for direct application in water-based flux systems. Furthermore, nano-containers themselves typically possess strong hydrophilicity and high surface polarity. If directly added to water-based fluxes, they will experience severe agglomeration and precipitation due to hydrogen bonding, failing to achieve stable and uniform dispersion. This results in uneven distribution of the corrosion inhibitor on the solder strip surface, preventing the formation of a uniform protective layer. On the other hand, during the solder strip drying and film formation process, nanoparticles are prone to migration and aggregation with moisture evaporation, producing defects such as the "coffee ring" effect or film cracking. These nanoparticles become channels for water vapor and corrosive media penetration, accelerating localized corrosion.

[0006] Furthermore, existing nano-container-corrosion inhibitor composite systems mostly employ small-molecule silane coupling agents for surface modification to improve the dispersibility of nanoparticles in epoxy resins or polyurethanes. However, the modified nanoparticles still primarily function as physical fillers and lack the dual functions of slow corrosion inhibitor release and the formation of a hydrophobic film after deposition. While these conventional modification methods can solve the dispersion problem, they cannot endow the flux residue film with long-term resistance to humid heat corrosion, nor can they achieve intelligent, on-demand release before the corrosion inhibitor is depleted. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a method for preparing a pre-coated flux for photovoltaic welding ribbons, comprising the following steps: S1, preparation of modified corrosion inhibitor: S11, loading corrosion inhibitor onto nano-supported material: dissolve the corrosion inhibitor in anhydrous ethanol to prepare a corrosion inhibitor solution with a concentration of 15-20 g / L, add the pretreated nano-supported material to the corrosion inhibitor solution, ultrasonically disperse for 30 min, and use a vacuum-assisted impregnation method, repeating negative pressure-normal pressure cycles 2-3 times under a vacuum of 0.08-0.1 MPa, maintaining negative pressure for 5-10 min and normal pressure for 3-5 min each time, then continuously stirring and adsorbing for 12 h, centrifuging at 10000 rpm for 15 min to collect the product, washing with anhydrous ethanol 2-3 times, drying to obtain the nano-supported material loaded with corrosion inhibitor, for later use; the mass-to-volume ratio of the nano-supported material to the corrosion inhibitor solution is 1 g: (20-30) mL.

[0008] Mesoporous silica nanoparticles or halloysite nanotubes are used to vacuum-assisted load benzotriazole or methylbenzotriazole, locking the corrosion inhibitor within the nanopores; the outer chitosan membrane forms a semi-permeable barrier, preventing the corrosion inhibitor from freely diffusing and being consumed in the early stages of storage, thus realizing the transformation of the corrosion inhibitor from a one-time release to a long-term controllable supply.

[0009] S12. Encapsulation treatment: Chitosan is encapsulated in nanomaterials loaded with corrosion inhibitors, and glutaraldehyde solution is added dropwise to carry out a cross-linking reaction to obtain encapsulated nanoparticles.

[0010] S13. Surface hydrophilic modification: The coated nanoparticles were dispersed in anhydrous ethanol, and methoxy polyethylene glycol-silane was added. The mixture was magnetically stirred at room temperature for 24 h under nitrogen protection. The product was collected by centrifugation at 10,000 rpm for 15 min, washed 2-3 times with anhydrous ethanol, and dried to obtain modified nanoparticles.

[0011] The PEG long chains grafted onto the surface of nanoparticles effectively overcome the van der Waals forces and hydrogen bonds between nanoparticles through a strong steric hindrance effect, enabling them to be stably and uniformly dispersed in water-based fluxes, thus avoiding agglomeration and precipitation.

[0012] S2. Preparation of flux: Add 2 / 3 of the deionized water and the co-solvent to the reaction vessel and stir and mix evenly at 35-45℃. While stirring, add the film-forming agent, organic acid and antioxidant in sequence and continue stirring until all components are completely dissolved. Slowly add organic amine to adjust the pH of the system to 4.5-5.5. Then add surfactant and modified nanoparticle-water solution to the system. After stirring for 30 min, treat with ultrasonic power of 300-500W for 10-20 min to obtain flux.

[0013] By mass percentage, the composition is 8-10% organic acid, 5-7% organic amine, 5-8% film-forming agent, 0.3-0.6% surfactant, 5-10% cosolvent, 0.1-0.5% antioxidant, 1-2% modified nanoparticles, and the balance is deionized water. The modified nanoparticle-aqueous solution is obtained by dissolving the modified nanoparticles in the remaining deionized water of the formulation.

[0014] After the flux is pre-coated onto the surface of the photovoltaic ribbon, during the drying process, the moisture is gradually dried out. The PEG segments lose their hydration support, and the hydrophilic PEG segments gradually collapse and become tightly entangled with the surrounding water molecules and hydrophilic film-forming agents. On the one hand, this guides the modified nanoparticles to be uniformly arranged in the wet film, resisting the coffee ring effect. On the other hand, when the moisture is completely evaporated, the chitosan shell layer on the surface of the nanoparticles that was originally covered by the PEG segments is exposed. The nanoparticles uniformly arranged on the surface of the photovoltaic ribbon form a dense composite film with low surface energy. This film can effectively block the adhesion and intrusion of external moisture, providing the first layer of passive moisture protection for the photovoltaic ribbon.

[0015] Preferably, the nano-supporting material is one of mesoporous silica nanoparticles or halloysite nanotubes. When the nano-supporting material is halloysite nanotubes, the nano-supporting material needs to undergo acid washing and pore-expanding pretreatment. When the nano-supporting material is mesoporous silica nanoparticles, the nano-supporting material needs to be dried at 110°C for 1 hour.

[0016] Preferably, the acid washing and pore-expanding pretreatment process is as follows: Halloysite nanotubes are added to hydrochloric acid solution, stirred at 20-40℃ for 6-12h, centrifuged, repeatedly washed with deionized water until neutral, and dried at 60-100℃ to obtain acid-washed and pore-expanded halloysite nanotubes; the molar concentration of hydrochloric acid solution is 1-4mol / L, and the mass-volume ratio of halloysite nanotube powder to hydrochloric acid solution is 1g:(15-20)mL.

[0017] Preferably, the corrosion inhibitor is selected from benzotriazole and methylbenzotriazole.

[0018] Preferably, the cosolvent is selected from one or two of ethylene glycol, isopropanol, and ethylene glycol butyl ether; the film-forming agent is selected from waterborne polyurethane or polyvinyl alcohol, preferably nonionic; the organic acid is selected from one or two of succinic acid and DL-malic acid; the antioxidant is selected from hydroquinone; the organic amine is selected from AMP-95 or triethanolamine; and the surfactant is selected from one of sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, or alkynyl glycol.

[0019] Preferably, the specific process of S12, the encapsulation treatment, is as follows: the nano-supported material loaded with corrosion inhibitor is added to a chitosan encapsulation solution with a mass fraction of 1-3%, stirred at room temperature for 2-6 hours, centrifuged at 10000 rpm for 15 minutes, and the obtained product is washed with deionized water; the washed product is redispersed in deionized water, and a glutaraldehyde solution with a concentration of 0.5-1.5% is added dropwise to the solution, wherein the mass ratio of glutaraldehyde to chitosan is (0.05-0.15):1, which refers to the mass ratio of glutaraldehyde to chitosan used in preparing the chitosan encapsulation solution, so that glutaraldehyde reacts with the amino groups on the chitosan chain to form a Schiff base reaction, the product is collected by centrifugation, washed with deionized water, and vacuum dried at 40-50℃ to obtain the encapsulated nanoparticles; the mass-volume ratio of the nano-supported material loaded with corrosion inhibitor to the chitosan encapsulation solution is 1 g: (10-20) mL.

[0020] The high-density cross-linked network formed by the Schiff base reaction between glutaraldehyde and chitosan amino groups significantly improves the structural stability of the chitosan shell. Within the flux pH range of 4.5-5.5, this shell remains dense, effectively inhibiting premature leakage of the corrosion inhibitor. As the solder ribbon is stored in a humid and hot environment for extended periods, the shell undergoes slow hydrolysis or swelling, allowing the corrosion inhibitor to gradually diffuse and be released.

[0021] Preferably, the mass-to-volume ratio of the encapsulated nanoparticles to anhydrous ethanol is 1 g:(50-100) mL, and the mass ratio of methoxy polyethylene glycol-silane to the encapsulated nanoparticles is (0.1-0.3):1.

[0022] Preferably, the chitosan encapsulation solution is prepared by dissolving chitosan in a dilute acetic acid aqueous solution with a concentration of 3%, and the glutaraldehyde solution is prepared by dissolving glutaraldehyde in deionized water.

[0023] Preferably, flux is pre-coated onto the surface of the photovoltaic ribbon by dip coating or spray coating, and dried at 80-120℃ for 1-5 minutes to form a film. The flux is used to improve the storage stability of the photovoltaic ribbon in a humid environment and delay the corrosion of the copper surface.

[0024] This invention has at least one of the following technical effects: Through the synergistic effect of nano-loading, chitosan encapsulation, and hydrophilic modification, this invention effectively solves the problem of corrosion inhibitors in traditional water-based halogen-free pre-coated fluxes lacking slow-release protection and being easily consumed prematurely, leading to long-term storage failure. At the same time, it overcomes the problem that existing nano-container systems are difficult to disperse stably in water-based systems and are prone to agglomeration and precipitation. It effectively alleviates the problem of coffee ring effect and film defects that easily occur when existing nano-container systems are dried, and avoids the corrosive medium penetrating along the defects to accelerate corrosion. It retains the environmental advantages of water-based halogen-free, VOC-free, and wash-free, while achieving long-term controllable release of corrosion inhibitors and dual protection of hydrophobic barrier film formation, significantly improving the storage stability and corrosion resistance of photovoltaic ribbons in humid and hot environments.

[0025] In addition, this invention achieves the dual functions of passive hydrophobic barrier and slow release of corrosion inhibitor, solving the industry pain points of traditional water-based flux corrosion inhibitors such as rapid consumption in the early stage, failure in the later stage, hydrophilic film formation, and easy corrosion. Detailed Implementation

[0026] 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 limit the scope of protection of the invention to these embodiments. All equivalent transformations or simple substitutions made based on the substantive content of this application should fall within the scope of protection of this application. For parameter ranges not mentioned, intermediate values ​​are selected. Furthermore, for mass percentages or weight percentages not explicitly stated or mentioned, they generally refer to the final concentration after addition.

[0027] The singular forms “for,” “or,” “a,” “any,” and “the” used in this application are intended to include the plural forms unless the context clearly indicates otherwise.

[0028] Example 1

[0029] S1. Preparation of modified corrosion inhibitors.

[0030] S11. Corrosion inhibitor loaded on nanomaterial: Mesoporous silica nanoparticles (MSN) were dried at 110℃ for 1 h and set aside. 1.5 g of benzotriazole was dissolved in 100 mL of anhydrous ethanol to prepare a corrosion inhibitor solution with a concentration of 15 g / L. 3 g of mesoporous silica nanoparticles were added to the prepared corrosion inhibitor solution and ultrasonically dispersed for 30 min. Vacuum-assisted impregnation was performed, and the negative pressure-normal pressure cycle was repeated 3 times under a vacuum of 0.08-0.1 MPa. Each cycle was maintained under negative pressure for 5 min and normal pressure for 5 min. After that, the mixture was continuously stirred and adsorbed for 12 h. The product was collected by centrifugation at 10000 rpm for 15 min, washed 3 times with anhydrous ethanol, and dried to obtain the nanomaterial loaded with the corrosion inhibitor for use.

[0031] S12. Encapsulation treatment: 3g of the corrosion inhibitor-loaded nanomaterial was added to 45mL of a 2% (w / w) chitosan encapsulation solution. The mixture was stirred at room temperature for 4h, centrifuged at 10000rpm for 15min, and the resulting product was washed with deionized water. The washed product was redispersed in 10 times its mass of deionized water, and then 9mL of a 1% glutaraldehyde solution was added dropwise to the solution. The mass ratio of glutaraldehyde to chitosan was 1:10. The glutaraldehyde reacted with the amino groups on the chitosan chains to form a Schiff base reaction. The product was collected by centrifugation at 10000rpm for 15min, washed with deionized water, and dried under vacuum at 50℃ to obtain the encapsulated nanoparticles. The vacuum degree was 0.08-0.1MPa.

[0032] S13. Surface hydrophilic modification: 3g of the coated nanoparticles were dispersed in 150mL of anhydrous ethanol, and 0.6g of methoxy polyethylene glycol-silane was added. The mixture was stirred magnetically at 200rpm at room temperature for 24h under nitrogen protection. The product was collected by centrifugation at 10000rpm for 15min, washed 2-3 times with anhydrous ethanol, and dried to obtain the modified nanoparticles.

[0033] S2. Preparation of flux.

[0034] In this embodiment, a total of 100g of flux was prepared, and 1g of modified nanoparticles were ultrasonically dispersed in 20g of deionized water to prepare a modified nanoparticle-water solution for later use.

[0035] Add 46g of deionized water and 8g of ethylene glycol to a reaction vessel and stir until homogeneous at 40°C. While stirring, add 8g of aqueous polyurethane emulsion, 8g of succinic acid, and 0.3g of hydroquinone in sequence, and continue stirring until all components are completely dissolved. Slowly add 6g of AMP-95 to adjust the pH of the system to 4.5-5.5. Then add 0.5g of acetylenic diol and the prepared modified nanoparticle-water solution to the system. Stir for 30 minutes, then treat with ultrasonic power of 400W for 15 minutes. Make up to 100g with deionized water to obtain flux.

[0036] Example 2

[0037] The difference from Example 1 is that the nanomaterial used is halloysite nanotubes (HNTs). 3g of halloysite nanotubes are added to 50mL of hydrochloric acid solution, stirred at 30°C for 8h, centrifuged at 10000rpm for 15min, and then repeatedly washed with deionized water until neutral. After drying at 100°C, acid-washed and expanded halloysite nanotubes are obtained for later use. The molar concentration of hydrochloric acid is 2mol / L. The remaining steps are the same as S11 in Example 1.

[0038] Example 3

[0039] The difference from Example 2 is that the amount of modified nanoparticles added is 2g, the amount of other components remains unchanged, and the total amount of flux is still 100g.

[0040] Example 4

[0041] The difference from Example 1 is that the amount of modified nanoparticles added is 2g.

[0042] Example 5

[0043] The difference from Example 1 is that the corrosion inhibitor used is methylbenzotriazole.

[0044] Example 6

[0045] The difference from Example 1 is that the concentration of the corrosion inhibitor solution is 20 g / L, that is, the amount of benzotriazole added is 2 g.

[0046] Example 7

[0047] The difference from Example 3 is that the concentration of the corrosion inhibitor solution is 20 g / L, that is, the amount of benzotriazole added is 2 g.

[0048] Example 8

[0049] The difference from Example 1 is that the amount of methoxy polyethylene glycol-silane added is 0.9g.

[0050] Example 9

[0051] The difference from Example 5 is that the concentration of the corrosion inhibitor solution is 20 g / L, that is, the amount of methylbenzotriazole added is 2 g.

[0052] The concentrations of the corrosion inhibitor solutions in the above embodiments before and after adsorption were measured to calculate the amount of corrosion inhibitor loaded on the nanomaterial. The specific results are shown in Table 1 below.

[0053] Table 1. Concentration changes of corrosion inhibitor solutions before and after adsorption in Examples 1-9

[0054]

[0055] Comparative Example 1

[0056] The difference from Example 1 is that the corrosion inhibitor was added directly, and the amount of corrosion inhibitor added was 0.08g.

[0057] Comparative Example 2

[0058] The difference from Example 1 is that when the corrosion inhibitor is loaded onto the nano-supported material, it is only stirred and adsorbed under normal pressure for 12 hours, without vacuum assistance, and the remaining steps are the same as in Example 1.

[0059] Comparative Example 3

[0060] The difference from Example 1 is that the nano-supported material for loading corrosion inhibitor is not encapsulated, while the remaining steps are the same as in Example 1.

[0061] Comparative Example 4

[0062] The difference from Example 1 is that the coated nanoparticles are not subjected to surface hydrophilic modification, and the remaining steps are the same as in Example 1.

[0063] Comparative Example 5

[0064] The difference from Example 1 is that the nano-supported material with the corrosion inhibitor is neither encapsulated nor surface-hydrophilic modified, while the rest of the steps are the same as in Example 1.

[0065] Comparative Example 6

[0066] The difference from Example 1 is that the concentration of the corrosion inhibitor solution is 10 g / L, while the rest of the steps are the same as in Example 1.

[0067] Comparative Example 7

[0068] The difference from Example 1 is that no modified nanoparticles are added, that is, no corrosion inhibitor is added, and the remaining steps are the same as step S2 of Example 1.

[0069] Performance testing

[0070] The fluxes prepared in Examples 1-9 and Comparative Examples 1-7 were pre-coated onto the surface of the corresponding photovoltaic ribbon samples by spraying. The samples were dried at 100°C for 3 minutes to form a film. The photovoltaic ribbon samples with pre-coated flux were subjected to accelerated storage aging test, water contact angle measurement, and neutral salt spray test.

[0071] Accelerated storage aging test: According to GB / T2423.3 "Constant damp heat test", the temperature was set at 85℃ and the relative humidity was 85%RH. Samples were taken at 0h, 168h, 336h, 504h, 672h and 840h, and the corrosion area percentage and corrosion level score were recorded at the corresponding storage time.

[0072] Water contact angle measurement: The water contact angle of the photovoltaic ribbons was measured before and at each time point during the storage aging test. The measurement method was as follows: using an optical contact angle meter, the corresponding photovoltaic ribbon sample was placed on a water platform, the droplet profile was photographed by a high-speed camera, and the contact angle was calculated by Young-Laplace fitting. The specific contact angles are shown in Table 2 below.

[0073] Neutral Salt Spray Test: Referencing GB / T10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test", the neutral salt spray test (NSS) method was adopted. Test conditions: NaCl solution concentration (50±5) g / L, pH 6.5-7.2, temperature (35±2)℃, continuous spraying. Sample size was 50mm × 50mm, and spraying time was 96 hours. After the test, the corrosion area percentage was visually assessed and rated according to GB / T6461-2002.

[0074] Table 2. Water contact angle, corrosion area percentage, and corrosion grade rating before and after aging tests for Examples 1-9 and Comparative Examples 1-7.

[0075]

[0076]

[0077] As shown in Table 2, after 840 hours of humid heat aging at 85℃ / 85%RH, the corrosion area of ​​Examples 1-9 was only 9.1%–12.0%, and the corrosion level remained stable at ≤3. In contrast, the corrosion area of ​​Comparative Example 1 (directly added BTA) reached 41.5%, and that of Comparative Example 7 (without corrosion inhibitor) was as high as 63.4%. This indicates that nano-loaded corrosion inhibitors encapsulated by chitosan can prevent rapid consumption of the corrosion inhibitors and provide full-cycle protection.

[0078] Compared with Example 1, Comparative Example 3 (without encapsulation) showed that the corrosion area increased from 12.0% to 48.0% after 840 hours of aging. The contact angle of Comparative Example 3 after aging for 840 hours was 41°, which was 27° lower than that of Example 1. This indicates that the chitosan shell can effectively seal the corrosion inhibitor and prevent premature leakage.

[0079] Vacuum-assisted impregnation can significantly improve the loading efficiency and anti-corrosion effect of corrosion inhibitors. The corrosion area of ​​Comparative Example 2 (without vacuum loading) was 44.2% after 840 hours, which was higher than that of Example 1. This shows that negative pressure cycling can enhance the entry of corrosion inhibitors into nanopores and improve the loading capacity and slow-release stability.

[0080] As can be seen from the initial water contact angles of Examples 1-9, the flux forms a hydrophobic film on the surface of the photovoltaic solder ribbon. As the aging test is prolonged, the water contact angle gradually decreases and the hydrophobicity declines.

[0081] Comparative Example 6 and Comparative Example 1 showed comparable performance at 168 h, but Comparative Example 6 exhibited a superior final corrosion area after 840 h. This indicates that even with low concentration loading, the nano-container and chitosan encapsulation structure still provided a certain degree of sustained release and protection, ensuring that the corrosion inhibitor was not completely depleted in the later stages of the long-term aging test, whereas directly added corrosion inhibitors were consumed more quickly.

[0082] The methoxy-polyethylene glycol-silane hydrophilically modified nanoparticles tend to be uniformly dispersed rather than aggregated during film formation due to the steric hindrance effect provided by the grafted PEG long chains in the wet film stage. Compared with the 51.2% corrosion area of ​​Comparative Example 4 (unmodified) after 840h, the corrosion resistance of the film formed in Example 1 is significantly improved. This indicates that the modified nanoparticles effectively suppress local defects caused by aggregation and migration, which are typical manifestations of the coffee ring effect.

[0083] The complete three-tiered structure of load-encapsulation-hydrophilic modification exhibits the strongest synergistic effect. Comparative Example 5 (without encapsulation and without hydrophilic modification) showed the most severe corrosion (56.9%), demonstrating that the absence of any one of these components leads to a significant decrease in protective capability.

[0084] Table 3. Corrosion Records Before and After Neutral Salt Spray Tests for Examples 1-9 and Comparative Examples 1-7

[0085]

[0086] As can be seen from Tables 2 and 3, the corrosion level of the examples is stable at ≤3, which meets the requirements for long-term storage of photovoltaic welding ribbon.

[0087] The above results demonstrate and describe the basic principles and main features of this application, as well as its advantages.

[0088] Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the equivalents of the appended claims.

Claims

1. A method for preparing a pre-coated flux for photovoltaic soldering ribbon, characterized in that, Includes the following steps: S1. Preparation of modified corrosion inhibitors; S11. Nanomaterial-loaded corrosion inhibitor: Dissolve the corrosion inhibitor in anhydrous ethanol to prepare a corrosion inhibitor solution with a concentration of 15-20 g / L. Add the pretreated nanomaterial-loaded material to the corrosion inhibitor solution and ultrasonically disperse for 30 min. Use a vacuum-assisted impregnation method and repeat the negative pressure-normal pressure cycle 2-3 times under a vacuum of 0.08-0.1 MPa. Each time, maintain negative pressure for 5-10 min and normal pressure for 3-5 min. Then, continue stirring and adsorption for 12 h. Collect the product by centrifugation, wash, and dry to obtain the nanomaterial-loaded corrosion inhibitor. The mass-volume ratio of the nanomaterial-loaded material to the corrosion inhibitor solution is 1 g: (20-30) mL. S12. Encapsulation treatment: Chitosan is encapsulated in nanomaterials loaded with corrosion inhibitors, and glutaraldehyde solution is added dropwise to carry out a cross-linking reaction to obtain encapsulated nanoparticles. S13. Surface hydrophilic modification: The coated nanoparticles were dispersed in anhydrous ethanol, and methoxy polyethylene glycol-silane was added. The mixture was stirred at room temperature for 24 hours under nitrogen protection. The product was collected by centrifugation, washed, and dried to obtain the modified nanoparticles. S2. Preparation of flux: Add 2 / 3 of the deionized water and co-solvent to the reaction vessel and stir at 35-45℃ until homogeneous. While stirring, add the film-forming agent, organic acid and antioxidant in sequence and continue stirring until all components are completely dissolved. Slowly add organic amine to adjust the pH of the system to 4.5-5.

5. Then add surfactant and modified nanoparticle-water solution to the system and stir for 30 min. After stirring, treat with ultrasonic power of 300-500W for 10-20 min to obtain flux. By mass percentage, the composition is 8-10% organic acid, 5-7% organic amine, 5-8% film-forming agent, 0.3-0.6% surfactant, 5-10% cosolvent, 0.1-0.5% antioxidant, 1-2% modified nanoparticles, and the balance is deionized water. The modified nanoparticle-aqueous solution is obtained by dissolving the modified nanoparticles in the remaining deionized water of the formulation.

2. The method for preparing a pre-coated flux for photovoltaic soldering strip according to claim 1, characterized in that: The nano-supported material is either mesoporous silica nanoparticles or halloysite nanotubes. When the nano-supported material is halloysite nanotubes, it needs to undergo acid washing and pore-expanding pretreatment. When the nano-supported material is mesoporous silica nanoparticles, it needs to be dried at 110°C for 1 hour.

3. The method for preparing a pre-coated flux for photovoltaic soldering strip according to claim 2, characterized in that: The pickling and pore-expansion pretreatment process is as follows: Halloysite nanotubes were added to hydrochloric acid solution and stirred at 20-40℃ for 6-12 hours. After centrifugation, the nanotubes were repeatedly washed with deionized water until neutral and dried at 60-100℃ to obtain acid-washed and expanded-pore halloysite nanotubes. The molar concentration of the hydrochloric acid solution is 1-4 mol / L, and the mass-volume ratio of halloysite nanotube powder to hydrochloric acid solution is 1 g: (15-20) mL.

4. The method for preparing a pre-coated flux for photovoltaic soldering strip according to claim 1, characterized in that: The corrosion inhibitor is selected from benzotriazole and methylbenzotriazole.

5. The method for preparing a pre-coated flux for photovoltaic soldering strip according to claim 1, characterized in that: The cosolvent is selected from one or two of ethylene glycol, isopropanol, and ethylene glycol butyl ether; the film-forming agent is selected from waterborne polyurethane or polyvinyl alcohol; the organic acid is selected from one or two of succinic acid and DL-malic acid; the antioxidant is selected from hydroquinone; the organic amine is selected from AMP-95 or triethanolamine; and the surfactant is selected from one of sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, or alkynyl glycol.

6. The method for preparing a pre-coated flux for photovoltaic soldering strip according to claim 1, characterized in that: The specific process of S12, the encapsulation treatment, is as follows: the nano-loaded material loaded with corrosion inhibitor is added to a chitosan encapsulation solution with a mass fraction of 1-3%, stirred at room temperature for 2-6 hours, centrifuged at 10000 rpm for 15 minutes, and the obtained product is washed with deionized water; the washed product is redispersed in deionized water, and a glutaraldehyde solution with a concentration of 0.5-1.5% is added dropwise to the solution, wherein the mass ratio of glutaraldehyde to chitosan is (0.05-0.15):1, so that glutaraldehyde reacts with the amino groups on the chitosan chain to form a Schiff base reaction, the product is collected by centrifugation, washed with deionized water, and vacuum dried at 40-50℃ to obtain the encapsulated nanoparticles; The mass-to-volume ratio of the nanomaterial loaded with corrosion inhibitor to the chitosan encapsulation solution was 1 g: (10-20) mL.

7. The method for preparing a pre-coated flux for photovoltaic soldering strip according to claim 1, characterized in that: The mass-to-volume ratio of the encapsulated nanoparticles to anhydrous ethanol is 1 g:(50-100) mL, and the mass ratio of methoxy polyethylene glycol-silane to the encapsulated nanoparticles is (0.1-0.3):

1.

8. The method for preparing a pre-coated flux for photovoltaic soldering strip according to claim 6, characterized in that: The chitosan encapsulation solution is prepared by dissolving chitosan in a dilute acetic acid aqueous solution with a concentration of 3%, and the glutaraldehyde solution is prepared by dissolving glutaraldehyde in deionized water.

9. The application of the flux prepared by the method according to any one of claims 1-8 in improving the storage stability of photovoltaic solder ribbon.

10. A surface treatment method for photovoltaic solder strips, characterized in that, The flux prepared by the method according to any one of claims 1-8 is pre-coated onto the surface of the photovoltaic ribbon by dip coating or spray coating, and dried at 80-120℃ for 1-5 minutes to form a film.

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