High-selectivity silver etching solution and preparation method and etching process thereof

Abstract

The invention relates to the technical field of etching solutions, in particular to a high-selectivity silver etching solution and a preparation method and etching process thereof, the high-selectivity silver etching solution comprises inorganic acid, organic acid, a passivator, a chelating agent, an oxidation enhancer, a dispersing agent and the balance of deionized water, and the high-selectivity silver etching solution is prepared by optimizing the variety proportion of the inorganic acid, the organic acid, the passivator, the chelating agent, the oxidation enhancer and the dispersing agent. According to the invention, a selective oxidation and corrosion inhibition synergistic mechanism and dynamic complexation are utilized, so that the aluminum substrate corrosion (Al < damage >) is obviously reduced, the problem of silver ion readsorption is inhibited, the cycle life of the etching liquid is prolonged, and the hazardous waste treatment cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of etching solutions, and in particular to a highly selective silver etching solution and a preparation method and an etching process thereof. Background Art

[0002] Silver etchant is a chemical solution used to selectively remove metallic silver layers, achieving controlled etching through redox reactions and complexation. Its core function is to dissolve silver and form a stable complex, while simultaneously inhibiting excessive corrosion in non-target areas through corrosion inhibitors, ensuring a smooth surface and sharp edges after etching.

[0003] In microelectronic devices (such as OLEDs and sensors), silver (Ag) is widely used as an electrode material due to its excellent conductivity. However, in the technical development of silver etching solutions, aluminum substrate corrosion and silver ion re-adsorption are key challenges that restrict etching efficiency and product quality. Traditional silver etching solutions are mostly based on a phosphoric acid-nitric acid-acetic acid mixed acid system. Although they have strong etching ability, their strong acidity and oxidizing properties can easily cause non-selective corrosion of the aluminum substrate, leading to substrate damage and device failure. At the same time, the silver ions released during the etching process will be re-adsorbed on the aluminum surface or react with the etching solution components to form precipitates, which not only shortens the life of the etching solution, but also causes silver residue, affecting etching accuracy and product yield.

[0004] Patent CN114277373B is based on a strong acid oxidation system of nitric acid and acetic acid, with the addition of polyhydroxy compounds and silver ion complexing agents (such as EDTA). By complexing free silver ions, the silver ions are reduced in contact with the aluminum substrate, further reducing the corrosion of the aluminum substrate, substrate damage and device failure. However, the problem of silver ion re-adsorption is not completely solved, especially in multi-layer films (such as ITO / Ag / ITO), where insoluble compound residues are easily formed.

[0005] Patent CN119040893A uses a phosphoric acid-nitric acid-sulfonic acid composite system to stabilize the dissolution of silver ions through strong oxidizing properties and buffering effects. However, the high phosphoric acid content (>40wt%) in this solution will increase the viscosity of the etching solution, resulting in uneven etching and the risk of over-etching. At the same time, the addition amount of nitrosyl salt needs to be precisely controlled (0.1-5wt%), resulting in a narrow process window. In actual applications, stability is easily affected by concentration fluctuations.

[0006] Patent CN118600429A uses nitric acid and phosphoric acid as the main etchants, and tartaric acid and EDTA as stabilizers. While promoting the oxidation of silver in the etching solution, it effectively buffers the speed of the silver oxidation reaction and controls the stability of the silver etching rate. However, the high concentration of strong acid system and the environmental unfriendliness of EDTA greatly increase the etching cost.

[0007] Therefore, the core of the prior art is to solve the problems of protection of the aluminum substrate and dynamic regulation of silver ions in the etching process. SUMMARY

[0008] The application aims to provide a high-selectivity silver etching solution, a preparation method thereof and an etching process, which significantly reduce aluminum damage and inhibit silver ion re-adsorption by optimizing the proportion and synergistic effect of each component, and are environmentally friendly and suitable for the manufacture of OLEDs, flexible circuit boards and other devices.

[0009] To achieve the above-mentioned purpose, the application provides a high-selectivity silver etching solution, a preparation method thereof and an etching process, which comprise inorganic acid, organic acid, passivation agent, chelating agent, oxidation enhancer, dispersant and deionized water.

[0010] The inorganic acid is nitric acid, and the weight percentage is 6-8%.

[0011] The organic acid is tartaric acid, and the weight percentage is 12-15%.

[0012] The passivation agent is polyaspartic acid sodium, and the weight percentage is 2-3%.

[0013] The chelating agent is thiomalic acid, and the weight percentage is 1-1.5%.

[0014] The oxidation enhancer is cerium ammonium nitrate, and the weight percentage is 5-7%.

[0015] The dispersant is polyethylene glycol (PEG-400), and the weight percentage is 0.5-1%.

[0016] The application further comprises a preparation method of a high-selectivity silver etching solution, which comprises the following steps:

[0017] Tartaric acid is slowly added to pure water, and stirred until completely dissolved to obtain a tartaric acid solution;

[0018] Polyaspartic acid sodium is added to the tartaric acid solution, and continues to be stirred for 10 minutes until uniformly dispersed to obtain solution A;

[0019] The solution A is stirred, and cerium ammonium nitrate is added in portions under stirring to obtain solution B;

[0020] Concentrated nitric acid is added dropwise to the solution B, and the temperature is controlled to be not more than 40°C to obtain a mixed solution;

[0021] Thiomalic acid is added to the mixed solution and stirred for 5 minutes;

[0022] Polyethylene glycol is slowly added dropwise to the mixed solution, and the mixed solution is stirred until transparent and uniform.

[0023] The mixed solution was fixed to volume with pure water and stirred for 10 minutes to obtain an etching solution;

[0024] The pH of the etching solution was tested with a pH meter, with the target range being 3.8-4.2.

[0025] The present invention also includes an etching process for a highly selective silver etching solution, comprising the following steps:

[0026] Take the ITO / Ag / ITO substrate out of the sealed bag and cut it into 5cm*5cm pieces. Use an air gun to blow away impurities on the surface of the substrate and set aside for use.

[0027] Prepare etching solution, pour the prepared etching solution into the etcher and heat it to 40.0℃;

[0028] Place the treated 5cm×5cm ITO / Ag / ITO substrate into the etcher for spray etching with a spray pressure of 0.1MPa and an etching time of O / E 50%;

[0029] The etched substrate was rinsed with pure water for 1 minute and then dried with nitrogen to remove water stains on the surface.

[0030] The invention discloses a highly selective silver etching solution, a preparation method thereof, and an etching process. By optimizing the proportions of various components including an inorganic acid, an organic acid, a passivating agent, a chelating agent, an oxidation enhancer, and a dispersant, and utilizing a synergistic mechanism of selective oxidation and corrosion inhibition and dynamic complexation, the invention significantly reduces aluminum substrate corrosion (Al damage) and inhibits the problem of silver ion re-adsorption, thereby increasing the cycle life of the etching solution and reducing hazardous waste treatment costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art.

[0032] Figure 1 and Figure 2 This is a SEM comparison of aluminum surfaces treated with a conventional etching solution (left) and the etching solution of the present invention (right).

[0033] Figure 3 The present invention is a flow chart of a method for preparing a highly selective silver etching solution.

[0034] Figure 4 The present invention is a flow chart of an etching process of a high-selectivity silver etching solution. DETAILED DESCRIPTION

[0035] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0036] Example 1:

[0037] The components in the highly selective silver etching solution include, by mass percentage:

[0038] Nitric acid 6%, tartaric acid 12%, sodium polyaspartate 2%, thiomalic acid 1%, ceric ammonium nitrate 5%, polyethylene glycol 0.5% and water 73.5%.

[0039] Example 2:

[0040] The components in the highly selective silver etching solution include, by mass percentage:

[0041] Nitric acid 7%, tartaric acid 13%, sodium polyaspartate 2.5%, thiomalic acid 1.2%, ceric ammonium nitrate 6%, polyethylene glycol 0.8% and water 69.5%.

[0042] Example 3:

[0043] The components in the highly selective silver etching solution include, by mass percentage:

[0044] Nitric acid 8%, tartaric acid 15%, sodium polyaspartate 3%, thiomalic acid 1.5%, ceric ammonium nitrate 7%, polyethylene glycol 1.0% and water 64.5%.

[0045] Example 4:

[0046] The components in the highly selective silver etching solution include, by mass percentage:

[0047] Nitric acid 6%, tartaric acid 14%, sodium polyaspartate 2%, thiomalic acid 1%, ceric ammonium nitrate 6%, polyethylene glycol 0.5% and water 70.5%.

[0048] Example 5:

[0049] The components in the highly selective silver etching solution include, by mass percentage:

[0050] Nitric acid 7%, tartaric acid 12%, sodium polyaspartate 2.5%, thiomalic acid 1.5%, ceric ammonium nitrate 5%, polyethylene glycol 0.8% and water 71.2%.

[0051] The highly selective silver etching solutions of Examples 1-5 of the present invention were used for etching and their performance was evaluated. The results are shown in Table 1.

[0052] Table 1

[0053]

[0054] Comparative Examples 1-3:

[0055]

[0056] Silver etching solutions can be prepared by selecting different oxidant systems and corrosion inhibitor formulations. However, in the above solutions, strong acid system solvents cause substrate damage, and EDTA is unfriendly to the environment, which greatly increases the etching cost.

[0057] Verification data and experimental comparison:

[0058] Indicator Conventional nitric acid system This formulation (Example 3) Etching rate (pm / min) 2.8-3.2 3.5 Aluminum corrosion rate (pm / h) ≥0.3 ≤0.03 <![CDATA[银残留量(mg / m 2 )]]> 15-20 ＜3 Solution lifetime (number of cycles) 30 70

[0059] Note: The composition of traditional nitric acid etching solution is: nitric acid (15%), sulfuric acid (10%), urea (0.5%), and the balance is deionized water.

[0060] The present invention also includes a method for preparing a highly selective silver etching solution, comprising the following steps:

[0061] S101: Slowly add tartaric acid into pure water and stir until completely dissolved to obtain a tartaric acid solution;

[0062] S102: adding sodium polyaspartate to the tartaric acid solution and continuing stirring for 10 minutes until the mixture is evenly dispersed to obtain solution A;

[0063] S103: stirring the solution A, and adding ammonium cerium nitrate in portions under stirring to obtain a solution B;

[0064] S104: adding concentrated nitric acid dropwise to the solution B while controlling the temperature not to exceed 40° C. to obtain a mixed solution;

[0065] S105: adding thiomalic acid to the mixture and stirring for 5 minutes;

[0066] S106: slowly adding polyethylene glycol dropwise to the mixture, and stirring until the mixture is transparent and uniform;

[0067] S107: The mixed solution is fixed to volume with pure water and stirred for 10 minutes to obtain an etching solution;

[0068] S108: Using a pH meter to detect the pH of the etching solution, the target range is 3.8-4.2.

[0069] Specifically: tartaric acid is slowly added to pure water and stirred until completely dissolved, and the temperature is controlled at 25-30°C during stirring; sodium polyaspartate is added to the tartaric acid solution and stirred for 10 minutes until uniformly dispersed to obtain solution A; while stirring, ammonium cerium nitrate is added to solution A in portions to avoid local excessive concentration leading to crystallization (the solution will be orange-yellow) to obtain solution B; concentrated nitric acid is added dropwise to solution B, and the temperature is controlled not to exceed 40°C (cooled in an ice bath if necessary) to prevent violent exotherm to obtain a mixed solution; thiomalic acid is added to the mixed solution and stirred for 5 minutes; polyethylene glycol (PEG-400) is slowly added dropwise to the mixed solution and stirred until the mixed solution is transparent and uniform; the mixed solution is fixed to volume with pure water and stirred for 10 minutes to obtain an etching solution; the pH of the etching solution is measured with a pH meter, and the target range is 3.8-4.2.

[0070] The etching and cleaning steps of the etching solution of Examples 1-5 and Comparative Examples 1-3 are as follows:

[0071] S201: Take the ITO / Ag / ITO substrate out of the sealed bag and cut the substrate into 5cm*5cm pieces. Use an air gun to blow away impurities on the surface of the substrate and set aside for use.

[0072] S202: Prepare an etching solution, pour the prepared etching solution into an etcher and heat it to 40.0° C.;

[0073] S203: Place the processed 5 cm×5 cm ITO / Ag / ITO substrate into an etcher for spray etching at a spray pressure of 0.1 MPa and an etching time of O / E 50% ((1+50%)×EPD);

[0074] Specifically: Before etching, the etching endpoint detection point (Etching Point Detector) of the substrate was observed by naked eyes and the initial etching completion time was recorded; then the processed 5cm×5cm ITO / Ag / ITO substrate was placed in the etcher, the spray pressure was set to 0.1MPa, and the total etching time was set to 150% of the EPD.

[0075] S204: The etched substrate is rinsed with pure water for 1 minute, and then the surface water stains are blown away with nitrogen.

[0076] The highly selective silver etching solution, preparation method thereof, and etching process of the present invention have the following beneficial effects:

[0077] 1. Aluminum substrate protection mechanism

[0078] Sodium polyaspartate: Carboxylic acid groups coordinate with the hydroxyl groups on the aluminum surface to form a dynamic passivation film. Its self-healing properties can resist the corrosion risk caused by local pH fluctuations. The corrosion rate of the aluminum substrate is ≤0.03μm / h (traditional formula ≥0.3μm / h).

[0079] Nitric acid synergistic control: A weakly acidic environment (pH 3.8-4.2) reduces aluminum activity and avoids violent reactions caused by strong acids (such as phosphoric acid).

[0080] 2. Silver ion re-adsorption inhibition

[0081] Thiomalic acid: contains sulfhydryl (-SH) and carboxylic acid groups, and reacts with Ag + Formation of [Ag(SR)_n] - Stable complex, binding energy is 30% higher than EDTA, re-adsorption capacity is less than 3mg / m 2 .

[0082] Polyethylene glycol (EG-400): Disperses etching products through steric hindrance effect and reduces silver residue on the sidewalls.

[0083] 3. Environmental protection and process compatibility

[0084] Cerium ammonium nitrate replaces nitrosyl acid salts: avoids the use of highly toxic potassium tetranitrosoplatinate and reduces waste liquid COD by 50%.

[0085] Double acid synergy: Nitric acid (inorganic acid) and tartaric acid (organic acid) form an oxidation-complexation synergistic system, which is suitable for ITO / Ag / ITO stacked etching, with a rate difference of <10% (traditional solution>25%).

[0086] The above disclosure is merely one or more preferred embodiments of the present application and is not intended to limit the scope of the present application. A person skilled in the art will understand that all or part of the processes of the above embodiments and equivalent changes made in accordance with the claims of the present application are still within the scope of the present application.

Claims

1. A highly selective silver etching solution, characterized in that, It includes inorganic acid, organic acid, passivator, chelating agent, oxidation enhancer, dispersant and balance water.

2. The highly selective silver etching solution according to claim 1, wherein The inorganic acid is nitric acid, with a weight percentage of 6%-8%.

3. The highly selective silver etching solution according to claim 1, wherein The organic acid is tartaric acid, with a weight percentage of 12%-15%.

4. The highly selective silver etching solution according to claim 1, wherein The passivating agent is sodium polyaspartate, with a weight percentage of 2%-3%.

5. The highly selective silver etching solution according to claim 1, wherein The chelating agent is thiomalic acid, with a weight percentage of 1%-1.5%.

6. The highly selective silver etching solution according to claim 1, wherein The oxidation enhancer is ammonium cerium nitrate, with a weight percentage of 5%-7%.

7. The highly selective silver etching solution according to claim 1, wherein The dispersant is polyethylene glycol, with a weight percentage of 0.5%-1%.

8. A method for preparing a highly selective silver etching solution, for preparing the highly selective silver etching solution according to any one of claims 1 to 7, characterized in that: The following steps are involved: Slowly add tartaric acid into pure water and stir until completely dissolved to obtain a tartaric acid solution; Sodium polyaspartate was added to the tartaric acid solution, and stirring was continued for 10 minutes until the mixture was uniformly dispersed to obtain solution A; Stirring the solution A, and adding ammonium cerium nitrate in portions under stirring to obtain solution B; Add concentrated nitric acid dropwise to the solution B while controlling the temperature not to exceed 40° C. to obtain a mixed solution; Adding thiomalic acid to the mixture and stirring for 5 minutes; Slowly adding polyethylene glycol to the mixture and stirring until the mixture is transparent and uniform; The mixed solution was fixed to volume with pure water and stirred for 10 minutes to obtain an etching solution; The pH of the etching solution was tested with a pH meter, with the target range being 3.8-4.

2.

9. An etching process using a highly selective silver etching solution, comprising: The following steps are involved: Take the ITO / Ag / ITO substrate out of the sealed bag and cut it into 5cm*5cm pieces. Use an air gun to blow away impurities on the surface of the substrate and set aside for use. Prepare etching solution, pour the prepared etching solution into the etcher and heat it to 40.0℃; Place the treated 5cm×5cm ITO / Ag / ITO substrate into the etcher for spray etching with a spray pressure of 0.1MPa and an etching time of O / E 50%; The etched substrate was rinsed with pure water for 1 minute and then dried with nitrogen to remove water stains on the surface.

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