Phosphorus-free environment-friendly silver etching solution as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of silver etching liquid, and particularly discloses phosphorus-free environment-friendly silver etching liquid as well as a preparation method and application thereof. The phosphorus-free environment-friendly silver etching solution is prepared from the following components in percentage by mass: 25 to 40 percent of inorganic acid, 10 to 20 percent of organic acid, 1 to 5 percent of silver chelating agent, 5 to 12 percent of alkalescent salt, 3 to 5 percent of 2-mercapto benzimidazole derivative, 1 to 3 percent of methoxypolyethylene glycol and the balance of water. The 2-sulfydryl benzimidazole derivative is at least one of 2-sulfydryl-5-methoxy benzimidazole, 2-sulfydryl-5-methyl benzimidazole and 5-amino-2-sulfydryl benzimidazole, and the 2-sulfydryl benzimidazole derivative is at least one of 2-sulfydryl-5-methoxy benzimidazole, 2-sulfydryl-5-methyl benzimidazole and 5-amino-2-sulfydryl benzimidazole. According to the formula, phosphoric acid is not added, all the components cooperate to achieve rapid etching, high-precision patterns and no crevice corrosion and silver after-tack phenomena, waste water is easy to treat, and the cost is lower.

Description

Technical Field

[0001] This invention belongs to the field of silver etching solution technology, and particularly relates to a phosphorus-free environmentally friendly silver etching solution, its preparation method and application. Background Technology

[0002] With the rapid development of the information age and continuous breakthroughs in flat panel display technology, OLED (Organic Light Emitting Diode) displays, with their significant advantages such as self-illumination, thinness, and flexibility, have become the mainstream display technology in fields such as smartphones, tablets, and high-end TVs. In the OLED panel manufacturing process, silver etching solution is one of the key chemical materials, undertaking the crucial task of precisely etching the silver electrode layer and constructing micron-level fine circuits. Its performance directly determines the conductivity uniformity, resolution, light reflectivity, and overall display efficiency of the OLED panel, and is an important foundation for ensuring the quality of OLED displays.

[0003] Currently, CN120249979A discloses a silver etching solution composition and its application. Based on a total mass percentage of 100 wt%, the composition includes: 10-20 wt% organic carboxylic acid, 20-40 wt% phosphoric acid, 4-6 wt% oxidant, 0.1-1 wt% metal protectant, 0.01-2 wt% alcohol ether solvent, 0.1-1 wt% sulfur-containing silver ion complexing agent, and the balance being deionized water. The phosphoric acid includes inorganic phosphoric acid and / or organic phosphonic acid. This silver etching solution composition exhibits good open-face stability, meets the required lateral etching amount, and produces a good lateral etching morphology. However, the addition of phosphoric acid to the silver etching solution leads to excessively high viscosity, causing uneven mass transfer and resulting in uneven etching. This can cause wire lifting or peeling, obvious crevice corrosion at the edges of the pattern, and severe silver re-adhesion. Summary of the Invention

[0004] The purpose of this invention is to overcome the obvious crevice corrosion at the edge of the pattern and the silver re-adhesion phenomenon during the etching process, and to provide a phosphorus-free environmentally friendly silver etching solution, its preparation method and application.

[0005] One of the objectives of this invention is to provide a phosphorus-free, environmentally friendly silver etching solution, comprising the following components by mass percentage: 25-40% inorganic acid, 10-20% organic acid, 1-5% silver chelating agent, 5-12% weakly basic salt, 3-5% 2-mercaptobenzimidazole derivative, 1-3% polyethylene glycol monomethyl ether, and the balance being water. The structural formula of the 2-mercaptobenzimidazole derivative is shown in formula (1) below: Equation (1); In formula (1), R1 and R2 are each independently hydrogen, amino, C1-C3 alkyl or C1-C3 alkoxy.

[0006] Preferably, the 2-mercaptobenzimidazole derivative is at least one of 2-mercapto-5-methoxybenzimidazole, 2-mercapto-5-methylbenzimidazole, and 5-amino-2-mercaptobenzimidazole.

[0007] Preferably, the inorganic acid is a mixture of sulfuric acid and nitric acid, and does not contain phosphoric acid.

[0008] Preferably, the organic acid is at least one selected from acetic acid, succinic acid, citric acid, malic acid, lactic acid, tartaric acid, and salicylic acid.

[0009] Preferably, the silver chelating agent is glycine and / or ethylenediaminetetraacetic acid.

[0010] Preferably, the weakly basic salt is at least one of sodium bicarbonate, sodium carbonate, sodium oxalate, and sodium sulfite.

[0011] Preferably, the molecular weight of the polyethylene glycol monomethyl ether is 500-1000.

[0012] Preferably, the polyethylene glycol monomethyl ether is at least one of MPEG-500, MPEG-550, MPEG-750, and MPEG-1000.

[0013] The second objective of this invention is to provide a method for preparing the above-mentioned phosphorus-free environmentally friendly silver etching solution, comprising the following steps: Inorganic acid, organic acid, silver chelating agent, weak alkaline salt, 2-mercaptobenzimidazole derivative and polyethylene glycol monomethyl ether were added to water in sequence, and after stirring and filtration, a phosphorus-free environmentally friendly silver etching solution was obtained.

[0014] The third objective of this invention is to provide a phosphorus-free environmentally friendly silver etching solution or a phosphorus-free environmentally friendly silver etching solution prepared by the above-mentioned method for use in flat panel OLED displays.

[0015] Compared with the prior art, the beneficial effects of the present invention are: (1) The 2-mercaptobenzimidazole derivative of the present invention contains a thiol group and an imidazole ring in its molecule. The thiol group forms a strong chemical adsorption film with the silver surface, especially in the high curvature area at the edge of the pattern, where the adsorption is more compact, which is equivalent to forming a "protective layer" at the edge, slowing down the excessive erosion of the edge by the acid and preventing the gap from widening. The thiol group in its molecular structure can also form a reversible complex with free silver ions, further reducing the activity of silver ions in the solution, and also reducing the probability of contact between silver ions and the substrate silver, preventing the physical adhesion of reduced silver, and reducing the occurrence of silver re-adhesion.

[0016] (2) The silver etching solution of the present invention uses nitric acid as a strong oxidant. Nitric acid oxidizes metallic silver into silver ions. Its rapid oxidation ability can ensure the etching rate and meet the efficiency requirements of industrial production. At the same time, sulfuric acid provides a high concentration of hydrogen ions to promote the oxidation reaction of silver by nitric acid. Sulfate ions can form a weak coordination with silver ions to help stabilize silver ions in the solution and reduce uneven etching caused by excessive local concentration. Moreover, the present invention does not add phosphoric acid to avoid silver deposition and prevent silver back-sticking and pattern defects.

[0017] (3) The silver chelating agent of the present invention can form a stable water-soluble chelate with silver ions. It has a high stability constant and can reduce the concentration of free silver ions to a very low level, thus avoiding the silver ions being reduced on the substrate surface and forming silver back-adhesion.

[0018] (4) The weak alkaline salt of the present invention can buffer the pH change in local areas during the etching process, maintain the overall pH stability of the solution, avoid severe etching caused by a sudden drop in pH in the edge area, and reduce the formation of gaps.

[0019] (5) The polyethylene glycol monomethyl ether of the present invention can reduce the surface tension of the etching solution, so that the solution can be evenly spread on the silver surface and avoid the difference in etching rate caused by uneven wetting in some areas. At the same time, its long chain structure can moderately hinder the rapid diffusion of inorganic acid molecules to the edge, balance the etching rate of the edge and the plane, and effectively avoid the phenomenon of excessive etching at the edge. Furthermore, the present invention strictly controls the molecular weight of polyethylene glycol monomethyl ether to be 500-1000. When the molecular weight is less than 500, the molecular chain is too short and the surface activity is insufficient, making it difficult to form an effective adsorption layer on the silver surface. When the molecular weight is greater than 1000, the molecular chain is too long, the diffusion rate decreases, the dynamic adsorption capacity deteriorates, and the etching uniformity may be affected. When the molecular weight of polyethylene glycol monomethyl ether is 500-1000, it can significantly reduce the surface tension of the etching solution, so that it can be evenly spread on the silver surface and avoid crevice corrosion caused by uneven wetting.

[0020] (6) The silver etching solution of the present invention is phosphorus-free, the formula avoids pollution, and the components work together to achieve rapid etching and high-precision patterns without gap corrosion and silver back-adhesion. In addition, the wastewater is easy to treat and the cost is lower. Attached Figure Description

[0021] The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this invention, illustrate exemplary embodiments and provide explanations, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 (a) is a planar SEM image of the etching solution after etching in Example 1, and (b) is a cross-sectional SEM image of the etching solution after etching in Example 1. Figure 2(a) is a planar SEM image of the etching solution used in Comparative Example 1, and (b) is a cross-sectional SEM image of the etching solution used in Comparative Example 1. Figure 3 In the middle section, (a) is a planar SEM image of the etching solution used in Comparative Example 2, and (b) is a cross-sectional SEM image of the etching solution used in Comparative Example 2. Figure 4 (a) is a planar SEM image of the etching solution used in Comparative Example 3 after etching, and (b) is a cross-sectional SEM image of the etching solution used in Comparative Example 3 after etching. Figure 5 (a) is a planar SEM image of the etching solution used in Comparative Example 4, and (b) is a cross-sectional SEM image of the etching solution used in Comparative Example 4. Figure 6 (a) is a planar SEM image of the etching solution used in Comparative Example 5, and (b) is a cross-sectional SEM image of the etching solution used in Comparative Example 5. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1 A phosphorus-free, environmentally friendly silver etching solution comprises the following components by mass percentage: Inorganic acid 40%, organic acid 10%, silver chelating agent 3%, weak basic salt 8.5%, 2-mercaptobenzimidazole derivative 4%, polyethylene glycol monomethyl ether 2%, balance water; Among them, the inorganic acid is obtained by mixing sulfuric acid and nitric acid in a mass ratio of 1:1; the organic acid is tartaric acid; the silver chelating agent is glycine; the weak basic salt is sodium carbonate; the 2-mercaptobenzimidazole derivative is 2-mercapto-5-methoxybenzimidazole; and the polyethylene glycol monomethyl ether is MPEG-500. A method for preparing a phosphorus-free, environmentally friendly silver etching solution includes the following steps: Inorganic acid, organic acid, silver chelating agent, weak alkaline salt, 2-mercaptobenzimidazole derivative and polyethylene glycol monomethyl ether were added to water in sequence, and after stirring and filtration, a phosphorus-free environmentally friendly silver etching solution was obtained.

[0024] Example 2 A phosphorus-free, environmentally friendly silver etching solution comprises the following components by mass percentage: Inorganic acid 25%, organic acid 20%, silver chelating agent 1%, weak basic salt 5%, 2-mercaptobenzimidazole derivative 3%, polyethylene glycol monomethyl ether 1%, balance water; The inorganic acid is obtained by mixing sulfuric acid and nitric acid in a mass ratio of 2:1; the organic acid is malic acid; the silver chelating agent is ethylenediaminetetraacetic acid; the weakly basic salt is sodium bicarbonate; the 2-mercaptobenzimidazole derivative is 2-mercapto-5-methylbenzimidazole; and the polyethylene glycol monomethyl ether is MPEG-550. A method for preparing a phosphorus-free, environmentally friendly silver etching solution includes the following steps: Inorganic acid, organic acid, silver chelating agent, weak alkaline salt, 2-mercaptobenzimidazole derivative and polyethylene glycol monomethyl ether were added to water in sequence, and after stirring and filtration, a phosphorus-free environmentally friendly silver etching solution was obtained.

[0025] Example 3 A phosphorus-free, environmentally friendly silver etching solution comprises the following components by mass percentage: Inorganic acid 30%, organic acid 15%, silver chelating agent 5%, weakly basic salt 12%; 2-mercaptobenzimidazole derivative 5%, polyethylene glycol monomethyl ether 3%, balance water; The inorganic acid is obtained by mixing sulfuric acid and nitric acid in a mass ratio of 1:2; the organic acid is obtained by mixing succinic acid and lactic acid in a mass ratio of 1:1; the silver chelating agent is obtained by mixing glycine and ethylenediaminetetraacetic acid in a mass ratio of 1:1; the weakly basic salt is sodium oxalate; the 2-mercaptobenzimidazole derivative is 5-amino-2-mercaptobenzimidazole; and the polyethylene glycol monomethyl ether is MPEG-750. A method for preparing a phosphorus-free, environmentally friendly silver etching solution includes the following steps: Inorganic acid, organic acid, silver chelating agent, weak alkaline salt, 2-mercaptobenzimidazole derivative and polyethylene glycol monomethyl ether were added to water in sequence, and after stirring and filtration, a phosphorus-free environmentally friendly silver etching solution was obtained.

[0026] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that an equal mass of 2-mercaptobenzothiazole was used instead of the 2-mercaptobenzimidazole derivative, as detailed below: A phosphorus-free, environmentally friendly silver etching solution comprises the following components by mass percentage: Inorganic acid 40%, organic acid 10%, silver chelating agent 3%, weak basic salt 8.5%, 2-mercaptobenzothiazole 4%, polyethylene glycol monomethyl ether 2%, balance water; The inorganic acid is obtained by mixing sulfuric acid and nitric acid in a mass ratio of 1:1; the organic acid is tartaric acid; the silver chelating agent is glycine; the weakly basic salt is sodium carbonate; and the polyethylene glycol monomethyl ether is MPEG-500. A method for preparing a phosphorus-free, environmentally friendly silver etching solution includes the following steps: Inorganic acid, organic acid, silver chelating agent, weak alkaline salt, 2-mercaptobenzothiazole and polyethylene glycol monomethyl ether were added to water in sequence, and after stirring and filtration, a phosphorus-free environmentally friendly silver etching solution was obtained.

[0027] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that polyethylene glycol is used instead of polyethylene glycol monomethyl ether by the same mass, as follows: A phosphorus-free, environmentally friendly silver etching solution comprises the following components by mass percentage: Inorganic acid 40%, organic acid 10%, silver chelating agent 3%, weak basic salt 8.5%, 2-mercaptobenzimidazole derivative 4%, polyethylene glycol 2%, balance water; Among them, the inorganic acid is obtained by mixing sulfuric acid and nitric acid in a mass ratio of 1:1; the organic acid is tartaric acid; the silver chelating agent is glycine; the weakly basic salt is sodium carbonate; the 2-mercaptobenzimidazole derivative is 2-mercapto-5-methoxybenzimidazole; and the polyethylene glycol is PEG-400. A method for preparing a phosphorus-free, environmentally friendly silver etching solution includes the following steps: Inorganic acid, organic acid, silver chelating agent, weak alkaline salt, 2-mercaptobenzothiazole and polyethylene glycol were added to water in sequence, and after stirring and filtration, a phosphorus-free environmentally friendly silver etching solution was obtained.

[0028] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that polyethylene glycol monomethyl ether MPEG-350 was used instead of polyethylene glycol monomethyl ether MPEG-500, as detailed below: A phosphorus-free, environmentally friendly silver etching solution comprises the following components by mass percentage: Inorganic acid 40%, organic acid 10%, silver chelating agent 3%, weak basic salt 8.5%, 2-mercaptobenzimidazole derivative 4%, polyethylene glycol monomethyl ether 2%, balance water; Among them, the inorganic acid is obtained by mixing sulfuric acid and nitric acid in a mass ratio of 1:1; the organic acid is tartaric acid; the silver chelating agent is glycine; the weakly basic salt is sodium carbonate; the 2-mercaptobenzimidazole derivative is 2-mercapto-5-methoxybenzimidazole; and the polyethylene glycol monomethyl ether is MPEG-350. A method for preparing a phosphorus-free, environmentally friendly silver etching solution includes the following steps: Inorganic acid, organic acid, silver chelating agent, weak alkaline salt, 2-mercaptobenzimidazole derivative and polyethylene glycol monomethyl ether were added to water in sequence, and after stirring and filtration, a phosphorus-free environmentally friendly silver etching solution was obtained.

[0029] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that polyethylene glycol monomethyl ether MPEG-2000 was used instead of polyethylene glycol monomethyl ether MPEG-500, as detailed below: A phosphorus-free, environmentally friendly silver etching solution comprises the following components by mass percentage: Inorganic acid 40%, organic acid 10%, silver chelating agent 3%, weak basic salt 8.5%, 2-mercaptobenzimidazole derivative 4%, polyethylene glycol monomethyl ether 2%, balance water; Among them, the inorganic acid is obtained by mixing sulfuric acid and nitric acid in a mass ratio of 1:1; the organic acid is tartaric acid; the silver chelating agent is glycine; the weak basic salt is sodium carbonate; the 2-mercaptobenzimidazole derivative is 2-mercapto-5-methoxybenzimidazole; and the polyethylene glycol monomethyl ether is MPEG-2000. A method for preparing a phosphorus-free, environmentally friendly silver etching solution includes the following steps: Inorganic acid, organic acid, silver chelating agent, weak alkaline salt, 2-mercaptobenzimidazole derivative and polyethylene glycol monomethyl ether were added to water in sequence, and after stirring and filtration, a phosphorus-free environmentally friendly silver etching solution was obtained.

[0030] Comparative Example 5 A silver etching solution comprises the following components in weight percentages: 18% lactic acid, 40% orthophosphoric acid, 6% sodium 3-nitrobenzenesulfonate, 0.8% octanol phosphate, 1% dipropylene glycol butyl ether, 0.8% 3,6-dithia-1,8-octanediol, with the balance being water. A method for preparing a silver etching solution includes the following steps: Lactic acid, phosphoric acid, sodium 3-nitrobenzenesulfonate, octanol phosphate, dipropylene glycol butyl ether, and 3,6-dithia-1,8-octanediol were added to water in sequence, and after stirring and filtration, a silver etching solution was obtained.

[0031] Performance testing At 40°C, the ITO-Ag-ITO (thickness of 68Å-1000Å-68Å) samples from the OLED manufacturing process to be etched were immersed in Examples 1-3 and Comparative Examples 1-5 of the present invention for etching, wherein the etching time was 60s, then rinsed with ultrapure water for 1min, and finally dried with high-purity nitrogen.

[0032] SEM was used to observe the cross-section of the sample to assess whether crevice corrosion was present on the substrate morphology; SEM was used to observe the plane of the sample to assess whether silver re-adhesion was present on the substrate, specifically as follows: Figure 1-6 .

[0033] in, Figure 1 (a) is a planar SEM image of the etching solution after etching in Example 1, and (b) is a cross-sectional SEM image of the etching solution after etching in Example 1. Figure 2(a) is a planar SEM image of the etching solution used in Comparative Example 1, and (b) is a cross-sectional SEM image of the etching solution used in Comparative Example 1. Figure 3 In the middle section, (a) is a planar SEM image of the etching solution used in Comparative Example 2, and (b) is a cross-sectional SEM image of the etching solution used in Comparative Example 2. Figure 4 (a) is a planar SEM image of the etching solution used in Comparative Example 3 after etching, and (b) is a cross-sectional SEM image of the etching solution used in Comparative Example 3 after etching. Figure 5 (a) is a planar SEM image of the etching solution used in Comparative Example 4, and (b) is a cross-sectional SEM image of the etching solution used in Comparative Example 4. Figure 6 (a) is a planar SEM image of the etching solution used in Comparative Example 5, and (b) is a cross-sectional SEM image of the etching solution used in Comparative Example 5.

[0034] The etching effect was evaluated based on the following criteria: silver adhesion: no silver adhesion, marked as A; a small amount of silver adhesion, marked as B; a large amount of silver adhesion, marked as C; and corrosion in the crevices: no corrosion in the crevices, marked as √; corrosion in the crevices, marked as ×. The specific details are shown in Table 1.

[0035] Table 1 .

[0036] Combination Figure 1-6 As shown in Table 1, the etching effect of the silver etching solution obtained in Examples 1-3 of the present invention is significantly better than that in Comparative Examples 1-5.

[0037] Comparing Example 1 and Comparative Example 1, it can be seen that the silver etching solution of Example 1 contains a 2-mercaptobenzimidazole derivative, while the silver etching solution of Comparative Example 1 contains a 2-mercaptobenzothiazole. After etching with the silver etching solution of Comparative Example 1, severe crevice corrosion occurs, which fully demonstrates that the 2-mercaptobenzimidazole derivative can form more stable chelate bonds on the silver surface than 2-mercaptobenzothiazole, and can more effectively inhibit crevice corrosion and alleviate silver sticking.

[0038] Comparing Example 1 and Comparative Example 2, it can be seen that polyethylene glycol was added to the silver etching solution in Example 1, while polyethylene glycol monomethyl ether was added to the silver etching solution in Comparative Example 2. After etching with the silver etching solution in Comparative Example 2, corrosion appeared in the gaps, which fully demonstrates that the single-end active structure of polyethylene glycol monomethyl ether makes its adsorption density on the silver surface more uniform, which can more effectively regulate the corrosion rate of the etching solution on silver and effectively prevent the etchant from excessively attacking the edge of the pattern. Further comparing Example 1 with Comparative Examples 3 and 4, it can be seen that the molecular weight of polyethylene glycol monomethyl ether in the silver etching solution of Example 1 is between 500 and 1000. During the etching process, it is easier to quickly and uniformly wet the silver surface, protect the substrate, and prevent the silver from sticking back.

[0039] Comparing Example 1 and Comparative Example 5, it can be seen that the silver etching solution of Example 1 includes inorganic acid, organic acid, silver chelating agent, weak basic salt, 2-mercaptobenzimidazole derivative, and polyethylene glycol monomethyl ether, but does not include phosphoric acid. Compared with the silver etching solution of Comparative Example 1, which includes lactic acid, orthophosphoric acid, sodium 3-nitrobenzenesulfonate, octanol phosphate, dipropylene glycol butyl ether, and 3,6-dithia-1,8-octanediol, the silver etching solution of Example 1 is superior to that of Comparative Example 5. The components work synergistically to achieve rapid etching, high-precision patterns, and seamless corrosion and silver re-adhesion.

[0040] It should be noted that the above-disclosed embodiments are only illustrative of the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, any person skilled in the art should understand that any modifications, changes, or equivalent substitutions made without departing from the scope of the technical solutions of the present invention should fall within the scope of protection of the present invention.

Claims

1. A phosphorus-free, environmentally friendly silver etching solution, characterized in that, It includes the following components by mass percentage: 25-40% inorganic acid, 10-20% organic acid, 1-5% silver chelating agent, 5-12% weak basic salt, 3-5% 2-mercaptobenzimidazole derivative, 1-3% polyethylene glycol monomethyl ether, and the balance being water. The structural formula of the 2-mercaptobenzimidazole derivative is shown in formula (1) below: Equation (1); In formula (1), R1 and R2 are each independently hydrogen, amino, C1-C3 alkyl or C1-C3 alkoxy.

2. The phosphorus-free environmentally friendly silver etching solution according to claim 1, characterized in that, The 2-mercaptobenzimidazole derivative is at least one of 2-mercapto-5-methoxybenzimidazole, 2-mercapto-5-methylbenzimidazole, and 5-amino-2-mercaptobenzimidazole.

3. The phosphorus-free environmentally friendly silver etching solution according to claim 1, characterized in that, The inorganic acid is a mixture of sulfuric acid and nitric acid, and does not contain phosphoric acid.

4. The phosphorus-free environmentally friendly silver etching solution according to claim 1, characterized in that, The organic acid is at least one of acetic acid, succinic acid, citric acid, malic acid, lactic acid, tartaric acid, and salicylic acid.

5. The phosphorus-free environmentally friendly silver etching solution according to claim 1, characterized in that, The silver chelating agent is glycine and / or ethylenediaminetetraacetic acid.

6. The phosphorus-free environmentally friendly silver etching solution according to claim 1, characterized in that, The weakly basic salt is at least one of sodium bicarbonate, sodium carbonate, sodium oxalate, and sodium sulfite.

7. The phosphorus-free environmentally friendly silver etching solution according to claim 1, characterized in that, The molecular weight of the polyethylene glycol monomethyl ether is 500-1000.

8. The phosphorus-free environmentally friendly silver etching solution according to claim 1, characterized in that, The polyethylene glycol monomethyl ether is at least one of MPEG-500, MPEG-550, MPEG-750, and MPEG-1000.

9. A method for preparing the phosphorus-free environmentally friendly silver etching solution according to any one of claims 1-8, characterized in that, Includes the following steps: Inorganic acid, organic acid, silver chelating agent, weak alkaline salt, 2-mercaptobenzimidazole derivative and polyethylene glycol monomethyl ether were added to water in sequence, and after stirring and filtration, a phosphorus-free environmentally friendly silver etching solution was obtained.

10. A phosphorus-free environmentally friendly silver etching solution according to any one of claims 1-8 or a phosphorus-free environmentally friendly silver etching solution prepared by the preparation method according to claim 9, applied to flat panel display OLED.

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