Chlorine-free selective etching agent for photovoltaic printing screen as well as preparation method and application of chlorine-free selective etching agent

Abstract

The invention discloses a chlorine-free selective etching agent for a photovoltaic printing screen and a preparation method and application of the chlorine-free selective etching agent for the photovoltaic printing screen, and the chlorine-free selective etching agent for the photovoltaic printing screen is prepared from the following components in percentage by weight: 0.9-2.5% of 2, 5-diaminobenzene sulfonic acid, 0.5-1.5% of sodium hydroxide, 0.5-1.5% of sodium hydroxide, 0.5-1.5% of sodium hydroxide and the balance of water. 0.4 to 1 percent of sodium 6-fluoro-[1, 2, 4] triazolo [4, 3-b] pyridazine-3-carboxylate; 1 to 3 percent of 4-bromine-2-methyl thiobenzamide; 0.2 to 0.8 percent of 2-mercapto-5-(trifluoromethoxy) benzothiazole, and the balance of water; 0.5 to 0.8 percent of 1, 4-butanedithiol; 0.2-2% of 1, 1, 1-trifluoro-2, 4-hexanedione, 0.2-2% of 1, 1, 1-trifluoro-2, 4-hexanedione, and 33-70% of an acidic etching main agent; the acidic etching main agent is a mixture of nitric acid, hydrofluoric acid and phosphoric acid. According to the etching agent, through the synergistic effect of all the components, only tungsten steel wefts in the composite steel mesh are etched at the normal temperature, and the smoothness and brightness of the surface of the etched steel mesh are considered.

Description

Technical Field

[0001] This application relates to the field of photovoltaic printing and etching technology, and more specifically, it relates to a chlorine-free selective etchant for photovoltaic printing screens, its preparation method, and its application. Background Technology

[0002] In the manufacturing process of photovoltaic cells, screen printing is a key step in forming the electrode circuit. This process uses a steel mesh with a precise pattern to print conductive paste onto a silicon wafer. To meet the requirements of high precision and high durability printing, high-end printing meshes often adopt a composite structure, where the warp threads are made of martensitic stainless steel with good toughness and low cost, while the weft threads are made of tungsten carbide with high hardness and high wear resistance.

[0003] Composite structure printing screens in related technologies benefit from the properties of tungsten steel and martensitic steel, resulting in significantly improved overall performance. However, this also presents a huge challenge to their micro-processing, especially in scenarios where precise etching of the weft threads is required to achieve the target wire diameter (e.g., etching from 9μm to 7μm) while preserving the warp threads intact. This is a problem that the industry has not yet been able to solve.

[0004] Traditional chlorine-containing etching systems (such as hydrochloric acid-hydrogen peroxide and ferric chloride systems) or strongly alkaline etching systems, while possessing some etching capability for tungsten carbide, lack etching selectivity and easily lead to excessive corrosion of martensitic steel wires, causing wire deformation or even breakage. Therefore, this application provides a chlorine-free selective etchant for photovoltaic printing screens, its preparation method, and its application. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a chlorine-free selective photovoltaic printing stencil etchant, its preparation method, and its application. This etchant, through the compounding and synergistic effect of specific components, can efficiently and precisely selectively etch tungsten steel weft threads while excellently protecting martensitic steel warp threads, resulting in superior surface quality.

[0006] In a first aspect, this application provides a chlorine-free selective etchant for photovoltaic printing screens, comprising the following components by weight percentage: 2,5-Diaminobenzenesulfonic acid: 0.9-2.5%; Sodium 6-fluoro-[1,2,4]triazolo[4,3-b]pyridazine-3-carboxylate: 0.4-1%; 4-Bromo-2-methylthiobenzamide: 1-3%; 2-Mercapto-5-trifluoromethoxybenzothiazole: 0.2-0.8%; 1,4-Butanedithiol: 0.5-0.8%; 1,1,1-Trifluoro-2,4-hexanedione: 0.2-2%; Acidic etching agent 33-70%; The acidic etching agent is a mixture of nitric acid, hydrofluoric acid, and phosphoric acid.

[0007] Preferably, the percentage of each component in the acidic etching agent by the total mass of the etchant is as follows: Nitric acid with a mass fraction of 65-68% is 15-30%; Hydrofluoric acid with a mass fraction of 49% (8-20%); Phosphoric acid with a mass fraction of 85% (10-20%).

[0008] Preferably, the 2,5-diaminobenzenesulfonic acid has a weight percentage of 1.4-2.5%.

[0009] Preferably, the sodium 6-fluoro-[1,2,4]triazolo[4,3-b]pyridazine-3-carboxylate contains 0.5-1% by weight.

[0010] Preferably, the 4-bromo-2-methylthiobenzamide has a weight percentage of 1.5-3%.

[0011] Preferably, the weight percentage of the 2-mercapto-5-trifluoromethoxybenzothiazole is 0.3-0.8%.

[0012] Preferably, the etchant is formulated as a two-component system (A and B) and stored separately; Agent A contains 4-bromo-2-methylthiobenzamide, 2-mercapto-5-trifluoromethoxybenzothiazole, 2,5-diaminobenzenesulfonic acid, 6-fluoro-[1,2,4]triazolo[4,3-b]pyridazine-3-carboxylate sodium, 1,4-butanedithiol, 1,1,1-trifluoro-2,4-hexanedione, and a portion of water and phosphoric acid; Agent B contains the remainder of the acidic etching agent and the remainder of water.

[0013] Secondly, this application provides a method for preparing a chlorine-free selective etchant for photovoltaic printing screens, comprising the following preparation steps: Preparation of Agent A: In water accounting for 8-12% of the total amount, first add the corresponding weight of 4-bromo-2-methylthiobenzamide, 2-mercapto-5-trifluoromethoxybenzothiazole, and 85% phosphoric acid accounting for 8% of the total amount of phosphoric acid, and stir at a constant temperature for 5-10 minutes. Add 2,5-diaminobenzenesulfonic acid, sodium 6-fluoro-[1,2,4]triazolo[4,3-b]pyridazine-3-carboxylate, 1,4-butanedithiol, and 1,1,1-trifluoro-2,4-hexanedione, stir at a constant temperature for 20-30 minutes, and cool to room temperature to obtain agent A; Preparation of Agent B: Mix the remaining 85% phosphoric acid, all of the 49% hydrofluoric acid, 65-68% nitric acid, and the remaining water, and stir at a constant temperature for 20-30 minutes to obtain Agent B.

[0014] Thirdly, this application provides the application of a chlorine-free selective photovoltaic printing stencil etchant in the preparation of a composite stencil for photovoltaic printing. The composite stencil comprises martensitic steel warp and tungsten steel weft. The etchant is used to selectively etch the tungsten steel weft, and the etching conditions are relatively mild, requiring only etching at 20-30°C for 10-20 minutes.

[0015] In summary, this application has the following beneficial effects: The chlorine-free selective etchant of this invention effectively achieves efficient and precise etching of tungsten carbide weft threads through the synergistic effect of its components, while also protecting martensitic steel warp threads. Its principle lies in utilizing the adsorption selectivity differences of specific organic additives on the surfaces of martensitic steel and tungsten carbide to construct a dynamic microenvironment that inhibits and promotes etching. The specific functions and synergistic mechanisms of each component are described below: 1) 2,5-Diaminobenzenesulfonic acid mainly acts as a complexing agent, promoter, and buffer. The two amino groups in its molecule contain lone pairs of electrons, which can form stable coordinate bonds with metal ions, reduce the concentration of free metal ions in the etchant, and promote the etching reaction to proceed in the forward direction. The sulfonic acid group, as a strong acid group, can help maintain the acidic environment of the etchant through its dissociation. Moreover, its acidity is relatively mild. It can buffer drastic changes in pH value by working together with the aromatic ring and amino group. This molecule has a certain degree of amphiphilicity and can preferentially attach to the surface of martensitic steel through adsorption to form a protective film, inhibiting its etching and thus enhancing the selectivity of etching. 2) Sodium 6-fluoro-1,2,4-1,2,4-triazolo-4,3-b-4,3-b-pyridazine-3-carboxylate mainly functions as a complexing agent and selective etchant. Its carboxyl group can ionize to release carboxyl anions to form complexes with metal ions, preventing the metal ions from forming hydroxide precipitates and maintaining the stability of the etchant. The fluorine atoms it contains can partially dissociate to release fluoride ions, enhancing the etching ability on certain metals. The conjugated structure and special electron cloud distribution of its triazolopyridazine ring enable it to preferentially inhibit the penetration effect of the etchant on the passivation film on the surface of martensitic steel, protecting the surface of martensitic steel from being etched, thereby ensuring the selectivity of etching. 3) 4-Bromo-2-methylthiobenzamide is mainly used as a corrosion inhibitor, smoothing agent and brightening agent. The sulfur and nitrogen atoms in its molecule have lone pairs of electrons, which can form coordinate bonds with empty orbitals on the metal surface. The benzene ring can form a tight adsorption layer on the metal surface through π-π stacking, which hinders the contact between the etchant and the metal and slows down the etching rate. It can be uniformly adsorbed on the metal surface, inhibiting the anode and cathode reactions in electrochemical corrosion, making the etching uniform, and effectively improving the smoothness and brightness of the surface after etching. 4) 2-Mercapto-5-trifluoromethoxybenzothiazole is mainly used as a corrosion inhibitor and selective etchant. The thiol group in the molecule is a typical metal affinity group. The lone pair electrons of the sulfur atom can form coordinate bonds with the empty d orbitals on the metal surface to achieve chemical adsorption. The conjugated structure of the benzothiazole ring can enhance intermolecular aggregation through π-π stacking, forming a dense adsorption film on the metal surface and physically isolating the etchant. The affinity of this compound for the electronic structure of different metals varies. It has strong adsorption for martensitic steel in particular. The strong electronegativity and hydrophobicity of the trifluoromethoxy group further enhance the adsorption stability and selectivity, thus preferentially protecting martensitic steel from etching. 5) 1,4-Butanedithiol mainly acts as a complexing agent and corrosion inhibitor. Its two thiol groups can form stable cyclic or chain complexes with metal ions through "bidentate coordination", reducing the concentration of free metal ions and avoiding precipitation. The chain structure is relatively long, and the two thiol groups can be adsorbed on different sites on the metal surface. Through intermolecular cross-linking, a dense film is formed, which slows down the etching of non-target areas. Its reducing properties can balance the oxidation-reduction rate in the etching system, prevent the etching from being too violent, and help maintain the edge clarity of the etched pattern. 6) 1,1,1-Trifluoro-2,4-hexanedione is mainly used as an etching modifier, cosolvent, wetting agent, selective etchant, and leveling agent. Its β-diketone structure can form an enol anion through keto-enol tautomerism, which forms a stable six-membered ring chelate with various metal ions, thus promoting the etching reaction. Trifluoromethyl is a strong electron-withdrawing group, which changes the electron cloud density and steric hindrance of β-diketone, making its chelating ability for different metal ions different and enhancing selectivity. The hydrophobic group in its molecular structure can reduce the surface tension of the etchant, enhance wettability, ensure uniform contact of the etchant with the area to be etched, and reduce lateral etching and improve surface smoothness by using a weak adsorption layer and hindering the lateral diffusion of the etchant. 7) The acidic etching agents (nitric acid, hydrofluoric acid, and phosphoric acid): Nitric acid acts as an oxidant, accelerating the dissolution of exposed metals such as cobalt; hydrofluoric acid rapidly dissolves the metal oxide film on the surface of tungsten steel and reacts with tungsten to form fluorine complexes; phosphoric acid, in addition to providing an acidic environment, also plays an auxiliary etching and pH buffering role. The combination of the three can achieve effective etching of tungsten steel at room temperature; in addition, this application adopts a chlorine-free ternary acid etching system, avoiding the corrosion risk and environmental problems caused by chloride ions, and this system can achieve rapid etching at room temperature, completing the target etching amount in 15 minutes. Furthermore, the dual-form design of this application also ensures product consistency and storage stability by pre-stabilizing each functional additive in the form of phosphate in agent A. Attached Figure Description

[0016] Figure 1 This is an initial state diagram of the photovoltaic printed composite steel mesh; Figure 2 It is the reference standard sample for the evaluation of smoothness and gloss. Figure 3 It is the reference standard sample for the flatness and gloss evaluation. Detailed Implementation

[0017] The following combination Figure 1-3 The present application will be further described in detail with reference to the embodiments.

[0018] Performance testing First, the etchants prepared in each embodiment and comparative example were selected as test objects. Then, they were used to etch photovoltaic printed composite steel mesh with martensitic steel as the warp and tungsten steel as the weft, and the etching amount (µm) and smoothness and brightness were recorded. The specific test conditions and test methods are as follows: Sample preparation: The initial diameter of the warp threads in the photovoltaic printed composite steel mesh is 10μm and the initial diameter of the weft threads is 9μm. The mesh is ultrasonically cleaned with acetone to remove surface oil and then dried for later use.

[0019] Test method: S1. Completely immerse the prepared steel mesh sample in the tank containing the etching agent; S2. Keep the etchant temperature constant at 28±2℃; S3. Start the constant speed stirrer to keep the etchant flowing slowly to ensure uniform etching; S4. Precisely control the etching time to 20 minutes; S5. After etching, immediately remove the sample and immerse it in ultrapure water to stop the reaction. Then, perform ultrasonic cleaning at 300W and 40kHz for 3 minutes to remove residual etchant and reaction products from the surface. S6. Dry with nitrogen or place in a clean environment to dry at room temperature, ready for testing.

[0020] Then, its etching amount, flatness, and gloss are tested. The specific testing methods are as follows: 1) Measurement of etching depth (μm): Measuring instrument: High-precision optical profilometer (ZygoNexviewNX2).

[0021] Measurement method: Before etching, the original average thickness (T1) of the steel mesh sample is measured using a laser micrometer. After etching, cleaning and drying, the remaining average thickness (T2) after etching is measured at multiple different locations (at least 5 points) of the same batch of samples using the high-precision instrument mentioned above. The formula for calculating the material removal amount is: ΔT = T1 - T2 (μm). At the same time, the depth of the etched trench is directly measured by an optical profilometer, and the average value is calculated and recorded.

[0022] 2) Evaluation of flatness and gloss: Evaluation instruments: metallurgical microscope, scanning electron microscope (SEM), high-precision optical profilometer.

[0023] Evaluation method: Metallurgical microscopy / SEM observation: Place the dried sample under a microscope and observe the macroscopic and microscopic morphology of the etched surface at different magnifications (e.g., 200X, 500X, 1000X).

[0024] Key assessment areas: Flatness: Whether the surface is uniform and consistent, whether there are obvious unevenness, pits, under-cut or side-etch phenomena, and whether the line edges are neat and steep.

[0025] Gloss: Whether the surface is smooth and dense, and free from defects such as corrosion residue, haze, blackening, or pitting, compared to the original unetched surface. Figure 1 Compare them.

[0026] Evaluation criteria (for reference): ◎Smooth and glossy: The surface is uniform and free from any defects such as pitting, blackening, or over-etching; The lines have neat edges; no obvious scratches or unevenness are visible under a metallographic microscope, as shown in the reference. Figure 2 .

[0027] ○ Smooth surface, slightly poor gloss: Overall smooth surface, but with slight haze or very few tiny pitting defects in some areas; × Uneven and dull: Visible pitting, cratering, blackening, or over-etching; uneven line edges, see reference. Figure 3 .

[0028] The reference standard samples for the above ◎ and × symbols can be referred to respectively. Figure 2-3 This means that by comparing the test sample with the control standard sample, if the performance of the test sample is better than or equal to that of the control standard sample, it can be considered to have achieved the corresponding performance.

[0029] Examples 1-3 A chlorine-free selective etchant for photovoltaic printing screens, with its components and corresponding weights per 1 kg, is shown in the table below: Table: Components and weights (g) of the chlorine-free selective etchant for photovoltaic printing screens in Examples 1-3 And it was prepared by the following method: Take 10% of the total amount of water, add the corresponding weights of 4-bromo-2-methylthiobenzamide, 2-mercapto-5-trifluoromethoxybenzothiazole, and 8% of 85% phosphoric acid, and stir at a constant temperature for 5 minutes. Add 2,5-diaminobenzenesulfonic acid, sodium 6-fluoro-[1,2,4]triazolo[4,3-b]pyridazine-3-carboxylate, 1,4-butanedithiol, and 1,1,1-trifluoro-2,4-hexanedione, stir at a constant temperature for 30 minutes, and cool to obtain agent A. Preparation of Agent B: Add the remaining 85% phosphoric acid, 49% hydrofluoric acid, 65-68% nitric acid, and the balance water, and stir at a constant temperature for 30 minutes to obtain the agent.

[0030] Comparative Examples 1-3 A chlorine-free selective etchant for photovoltaic printing screens differs from Example 1 in that its components and their corresponding weights per 1 kg are shown in the table below.

[0031] Table: Components and weights (g) of the chlorine-free selective etchant used in photovoltaic printing screens in Comparative Examples 1-3 The chlorine-free selective etchant for photovoltaic printing screens from Examples 1-3 and Comparative Examples 1-3 was extracted and its etching amount and smoothness brightness were tested according to the above test method. The average value of the results was recorded in the table below.

[0032] Table: Performance test results of Examples 1-3 and Comparative Examples 1-3 As can be seen from the table above, the chlorine-free selective etchants for photovoltaic printing screens prepared in Examples 1-3 all have basically controllable etching performance, with the etching amount stable at 2.40-2.51μm. They can accurately etch the tungsten steel weft wires to the target size, while the warp wire etching amount is extremely low, only 0.02-0.05μm, and the flatness and brightness all reach the "◎" level. In contrast, the performance of comparison examples 1-3 deteriorated significantly, as detailed below: Comparative Example 1, without the addition of any functional corrosion inhibitors, had a weft etching depth of 2.14 μm and a warp etching depth as high as 2.89 μm. Its smoothness and brightness were rated as "×", and it exhibited surface pitting, partial line breakage, and blackening. This indicates that in the absence of specific corrosion inhibitors, the etchant has no selectivity for tungsten steel and martensitic steel, resulting in severe uncontrolled etching.

[0033] Comparative Example 2, on the other hand, uses citric acid and 1-hydroxybenzotriazole as the corrosion inhibition system, resulting in a weft etching depth of only 1.42 μm and a warp etching depth of 2.91 μm, with a smoothness and brightness of "×". Further analysis reveals the following reasons: 1) Although citric acid has a certain complexing ability, it lacks specific adsorption groups; 2) 1-Hydroxybenzotriazole has limited corrosion inhibition effect on ferrous metals and cannot build an effective selective inhibition barrier, resulting in poor etching uniformity and severe pitting corrosion.

[0034] Comparative Example 3 retains the acidic main agent and uses citric acid and 1-hydroxybenzotriazole as corrosion inhibitors. Its weft etching amount is 2.07 μm, warp etching amount is 2.79 μm, and the smoothness and brightness is "×". Although the etching rate has been improved, conventional corrosion inhibitors cannot achieve etching selectivity between tungsten steel and martensitic steel. The warp pitting is severe and the surface is not bright.

[0035] In summary, the core corrosion inhibitor combination consisting of 2,5-diaminobenzenesulfonic acid, sodium 6-fluoro-[1,2,4]triazolo[4,3-b]pyridazine-3-carboxylate and 2-mercapto-5-trifluoromethoxybenzothiazole is the key to achieving the technical effect of this invention. Through the synergistic adsorption of functional groups such as thiol, amino, and fluorine atoms, it forms a dense protective film on the surface of martensitic steel, while exhibiting weak adsorption on the surface of tungsten steel, thereby achieving highly efficient and selective etching. This combination cannot be easily replaced by conventional corrosion inhibitors in the field.

[0036] Comparative Example 4 A chlorine-free selective etchant for photovoltaic printing screens differs from Example 1 in that its components and their corresponding weights per 1 kg are shown in the table below.

[0037] Table: Components and weights (g) of the chlorine-free selective etchant used in photovoltaic printing screens in Comparative Example 4 Comparative Example 5 A chlorine-free selective etchant for photovoltaic printing screens differs from Example 1 in that its components and their corresponding weights per 1 kg are shown in the table below.

[0038] Table: Components and weights (g) of the chlorine-free selective etchant used in photovoltaic printing screens in Comparative Example 5 Comparative Example 6 A chlorine-free selective etchant for photovoltaic printing screens differs from Example 1 in that its components and their corresponding weights per 1 kg are shown in the table below.

[0039] Table: Components and weights (g) of the chlorine-free selective etchant used in photovoltaic printing screens in Comparative Example 6 Comparative Example 7 A chlorine-free selective etchant for photovoltaic printing screens differs from Example 1 in that its components and their corresponding weights per 1 kg are shown in the table below.

[0040] Table: Components and weights (g) of the chlorine-free selective etchant used in photovoltaic printing screens in Comparative Example 7 Comparative Example 8 A chlorine-free selective etchant for photovoltaic printing screens differs from Example 1 in that its components and their corresponding weights per 1 kg are shown in the table below.

[0041] Table: Components and weights (g) of the chlorine-free selective etchant used in photovoltaic printing screens in Comparative Example 8 Comparative Example 9 A chlorine-free selective etchant for photovoltaic printing screens differs from Example 1 in that its components and their corresponding weights per 1 kg are shown in the table below.

[0042] Table: Components and weights (g) of the chlorine-free selective etchant used in photovoltaic printing screens in Comparative Example 9 Comparative Example 10 A chlorine-free selective etchant for photovoltaic printing screens differs from Example 1 in that its components and their corresponding weights per 1 kg are shown in the table below.

[0043] Table: Components and weights (g) of the chlorine-free selective etchant used in photovoltaic printing screens in Comparative Example 10 Comparative Example 11 A chlorine-free selective etchant for photovoltaic printing screens differs from Example 1 in that its components and their corresponding weights per 1 kg are shown in the table below.

[0044] Table: Components and weights (g) of the chlorine-free selective etchant used in photovoltaic printing screens in Comparative Example 11 Comparative Example 12 A chlorine-free selective etchant for photovoltaic printing screens differs from Example 1 in that its components and their corresponding weights per 1 kg are shown in the table below.

[0045] Table: Components and weights (g) of the chlorine-free selective etchant used in photovoltaic printing screens in Comparative Example 12 Extract the chlorine-free selective etchant for photovoltaic printing screens from Comparative Examples 4-12 above, and test its etching amount and smoothness brightness according to the above test method. The average value of the results is recorded in the table below.

[0046] Table: Performance Test Results of Comparative Example 4-12 As can be seen from the table above, the performance of the chlorine-free selective etchants for photovoltaic printing screens prepared in Comparative Examples 4-12 is reduced to varying degrees compared with Examples 1-3. This indicates that the selection of its components is irreplaceable. Based on the data from each comparative example, the reasons for this may be as follows: Comparative Example 4 uses gluconic acid and 4-methylpyridazine-3-carboxylic acid to replace the core corrosion inhibitor. Its weft etching amount is only 1.12 μm, and its warp etching amount reaches 2.66 μm. The smoothness and brightness are "×". Its gluconic acid and 4-methylpyridazine-3-carboxylic acid lack specific adsorption capacity and cannot form an effective selective inhibition barrier, resulting in poor etching uniformity and severe pitting corrosion on the warp.

[0047] Comparative Example 5, although containing 2,5-diaminobenzenesulfonic acid, lacks sodium 6-fluoro-[1,2,4]triazolo[4,3-b]pyridazine-3-carboxylate. Its weft etching amount is 1.22 μm, its warp etching amount is 2.57 μm, and its smoothness and brightness are "×". It can be seen that the incompleteness of the core corrosion inhibitor composition leads to defects in the martensitic steel protective barrier. At the same time, the lack of a key smoothing agent makes the surface pitting corrosion obvious.

[0048] Comparative Example 6 introduced dithizone as a chelating agent but lacked a key leveling agent. Its weft etching amount was 0.76 μm, its warp etching amount was 2.22 μm, and its leveling brightness was "×". It can be seen that the metal complexing ability of dithizone cannot replace the surface adsorption function of the core corrosion inhibitor, resulting in an incomplete protective film and the presence of pitting corrosion on the warp.

[0049] Comparative Example 7 supplemented Comparative Example 6 with 1,4-butanedithiol, which reduced the weft etching amount to 0.58 μm and the warp etching amount to 2.31 μm, and improved the smoothness and brightness to "○". Although the addition of 1,4-butanedithiol improved the etching uniformity, the absence of other components still could not completely eliminate pitting.

[0050] Comparative Example 8 introduced polyethylene glycol as a stabilizer. Its weft etching amount was 0.42 μm, its warp etching amount was 2.32 μm, and its smoothness and brightness were "○". Although polyethylene glycol could disperse the etching stress, the lack of the key smoothing agent led to uneven micro-etching rate, and there were still local defects in the warp.

[0051] Comparative Example 9 was further supplemented with 1,1,1-trifluoro-2,4-hexanedione, which reduced the weft etching amount to 0.19 μm and the warp etching amount to 2.23 μm, with a smoothness and gloss of "○". The introduction of 1,1,1-trifluoro-2,4-hexanedione improved the surface gloss, but the absence of 4-bromo-2-methylthiobenzamide limited further improvement in smoothness.

[0052] Comparative Example 10 had a nearly complete formulation, containing key leveling agents such as 4-bromo-2-methylthiobenzamide, achieving a smoothness and gloss level of "◎". The weft etching amount was 0.11 μm, while the warp etching amount was as high as 2.76 μm. This demonstrates that the absence of 2,5-diaminobenzenesulfonic acid and sodium 6-fluoro-[1,2,4]triazolo[4,3-b]pyridazine-3-carboxylate leads to insufficient specific protection for martensitic steel.

[0053] Comparative Example 11 lacked 2,5-diaminobenzenesulfonic acid but increased the amount of 4-bromo-2-methylthiobenzamide. Its weft etching amount was 0.79 μm, and its warp etching amount reached 2.85 μm. The smoothness and brightness were "○". It can be seen that the lack of the core corrosion inhibitor component will lead to a significant decrease in etching selectivity.

[0054] Comparative Example 12 had all components but the dosage deviated from the optimal range. Its weft etching amount was 0.70 μm, its warp etching amount was 2.46 μm, and its smoothness and brightness were "○". It can be seen that a slight imbalance in the dosage of components will lead to insufficient density of the synergistic adsorption film and local unevenness on the surface.

[0055] In summary, based on the performance data of Comparative Examples 4-12, it is evident that there is an irreplaceable synergistic effect between the core corrosion inhibitor composition and the key leveling agent in this application. The absence, substitution, or deviation in dosage of any component will disrupt this synergistic effect, leading to decreased etching selectivity or deterioration of surface quality. This application achieves optimal results of precise and controllable etching amount and a smooth and bright surface through the precise formulation and synergistic effect of each component, fully meeting the manufacturing requirements of high-performance photovoltaic printed tungsten steel mesh.

[0056] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A chlorine-free selective etchant for photovoltaic printing screens, characterized in that, It consists of the following components by weight percentage: 2,5-Diaminobenzenesulfonic acid: 0.9-2.5%; Sodium 6-fluoro-[1,2,4]triazolo[4,3-b]pyridazine-3-carboxylate: 0.4-1%; 4-Bromo-2-methylthiobenzamide: 1-3%; 2-Mercapto-5-trifluoromethoxybenzothiazole: 0.2-0.8%; 1,4-Butanedithiol: 0.5-0.8%; 1,1,1-Trifluoro-2,4-hexanedione: 0.2-2%; Acidic etching agent 33-70%; The acidic etching agent is a mixture of nitric acid, hydrofluoric acid, and phosphoric acid.

2. The chlorine-free selective etchant for photovoltaic printing screens according to claim 1, characterized in that, The percentage of each component in the acidic etching agent by the total mass of the etchant is as follows: Nitric acid with a mass fraction of 65-68% (15-30%) Hydrofluoric acid with a mass fraction of 49% (8-20%) Phosphoric acid with a mass fraction of 85% is 10-20%.

3. The chlorine-free selective etchant for photovoltaic printing screens according to claim 1, characterized in that, The weight percentage of the 2,5-diaminobenzenesulfonic acid is 1.4-2.5%.

4. The chlorine-free selective etchant for photovoltaic printing screens according to claim 1, characterized in that, The sodium 6-fluoro-[1,2,4]triazolo[4,3-b]pyridazine-3-carboxylate contains 0.5-1% by weight.

5. The chlorine-free selective etchant for photovoltaic printing screens according to claim 1, characterized in that, The weight percentage of the 4-bromo-2-methylthiobenzamide is 1.5-3%.

6. The chlorine-free selective etchant for photovoltaic printing screens according to claim 1, characterized in that, The weight percentage of the 2-mercapto-5-trifluoromethoxybenzothiazole is 0.3-0.8%.

7. The chlorine-free selective etchant for photovoltaic printing screens according to any one of claims 1-6, characterized in that, The etching agent is formulated as a dual-agent system of A and B, and stored separately. Agent A contains 4-bromo-2-methylthiobenzamide, 2-mercapto-5-trifluoromethoxybenzothiazole, 2,5-diaminobenzenesulfonic acid, 6-fluoro-[1,2,4]triazolo[4,3-b]pyridazine-3-carboxylate sodium, 1,4-butanedithiol, 1,1,1-trifluoro-2,4-hexanedione, and a portion of water and phosphoric acid; Agent B contains the remainder of the acidic etching agent and the remainder of water.

8. The method for preparing the chlorine-free selective etchant for photovoltaic printing screens as described in claim 7, characterized in that, The preparation steps include the following: Preparation of Agent A: In water accounting for 8-12% of the total amount, first add the corresponding weight of 4-bromo-2-methylthiobenzamide, 2-mercapto-5-trifluoromethoxybenzothiazole and 85% phosphoric acid accounting for 8% of the total amount of phosphoric acid, and stir at a constant temperature for 5-10 minutes. Add 2,5-diaminobenzenesulfonic acid, sodium 6-fluoro-[1,2,4]triazolo[4,3-b]pyridazine-3-carboxylate, 1,4-butanedithiol, and 1,1,1-trifluoro-2,4-hexanedione, stir at a constant temperature for 20-30 minutes, and cool to room temperature to obtain agent A; Preparation of Agent B: Mix the remaining 85% phosphoric acid, all of the 49% hydrofluoric acid, 65-68% nitric acid, and the remaining water, and stir at a constant temperature for 20-30 minutes to obtain Agent B.

9. The application of a chlorine-free selective photovoltaic printing stencil etchant as described in any one of claims 1-7 in the preparation of composite stencils for photovoltaic printing, characterized in that, The composite steel mesh comprises martensitic steel warp and tungsten steel weft, and the etchant is used to selectively etch the tungsten steel weft.

10. The application of the chlorine-free selective photovoltaic printing stencil etchant according to claim 9 in the preparation of composite stencils for photovoltaic printing, characterized in that, The etching conditions are: temperature 20℃-30℃, etching time 10-20 minutes.

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