Etching solution for circuit board and preparation method thereof

Abstract

The invention discloses an etching solution for a circuit board and a preparation method thereof, and relates to the technical field of etching solutions, the etching solution is prepared from the following components by weight: 10-25 parts of hydrogen peroxide, 8-20 parts of tartaric acid, 6-12 parts of ethylenediamine tetraacetic acid, 15-30 parts of phosphoric acid, 6-15 parts of a synergist, 0.1-1 part of 3-aminotriazole, 1-10 parts of ethylene glycol, 1-1-hydroxyethylidene-1, 2, 4-triazole-1, 2, 4-triazole-1, 2, 4-triazole-1, 2, 4-triazole-1, 2, 4-triazole-1, 2, 4-triazole-1, 2, 4-triazole-1, 2, 4-triazole-1, 3-triazole-1 1, 1-diphosphonic acid is 0.05 to 0.2 part, and deionized water is 50 to 80 parts; according to the etching solution, through the synergistic effect of all the components, the optimal balance between the etching rate and precision is achieved, the etching solution is stable in performance and long in service life, and high-uniformity and high-quality fine circuit manufacturing can be achieved.

Description

Technical Field

[0001] This invention relates to the field of etching solution technology, and more specifically to an etching solution for circuit boards and its preparation method. Background Technology

[0002] With the rapid development of electronic technology, printed circuit boards (PCBs), as the core carrier of electronic products, face increasingly stringent manufacturing requirements. Etching, as a key step in PCB manufacturing, directly determines the precision of circuit patterns, the ability to control line width, and the overall performance of the product.

[0003] Currently, the etching solutions widely used in industry mainly include copper chloride etching solutions, alkaline etching solutions, and acidic etching solutions. Among them, acidic etching solutions using hydrogen peroxide as an oxidant are widely used due to their advantages such as fast etching rate, high copper ion solubility, and strong regenerability. Existing acidic etching solutions typically consist of hydrogen peroxide, acidic media (such as sulfuric acid or phosphoric acid), complexing agents (such as EDTA), and corrosion inhibitors, achieving selective dissolution of the copper layer through an oxidation-complexation mechanism.

[0004] However, as electronic products become smaller and denser, the requirements for PCB circuit precision are increasing, posing numerous challenges to existing etching solutions:

[0005] First, lateral etching is severe. Traditional etching solutions tend to produce isotropic etching during the etching process, resulting in significant lateral etching, which makes the lines thinner and the edges more skewed, making it difficult to meet the precision requirements of fine circuit manufacturing;

[0006] Secondly, the surface wetting performance is poor. The wettability of the etching solution on the substrate surface directly affects the etching uniformity. Existing etching solutions often have problems such as excessive surface tension and insufficient wetting, which easily form bubbles and cause uneven etching.

[0007] Secondly, the stability of the etching process needs to be improved. During the etching process, the accumulation of metal ion concentration, the decomposition of hydrogen peroxide, and fluctuations in pH value can all affect the consistency and controllability of the etching effect.

[0008] Finally, existing additive systems have limited functionality. Additives in traditional etching solutions are mostly single-function components, lacking synergistic effects and making it difficult to simultaneously meet multiple performance requirements such as high precision, high stability, and high surface quality.

[0009] Therefore, there is an urgent need to develop a new etching solution formulation that can effectively suppress lateral etching, improve wetting performance and etching accuracy, and enhance system stability to meet the technical requirements of modern precision PCB manufacturing. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the present invention aims to provide an etching solution for circuit boards and its preparation method. The etching solution of the present invention achieves the best balance between etching rate and precision through the synergistic effect of its components. In particular, the introduction of an innovative synergist significantly improves wettability and effectively inhibits lateral etching, thereby greatly improving the resolution and edge clarity of the circuit. The etching solution has stable performance, long service life, and can achieve high uniformity and high quality fine circuit manufacturing.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] An etching solution for circuit boards, by weight, is composed of the following components: 10-25 parts hydrogen peroxide, 8-20 parts tartaric acid, 6-12 parts ethylenediaminetetraacetic acid, 15-30 parts phosphoric acid, 6-15 parts synergist, 0.1-1 part 3-aminotriazole, 1-10 parts ethylene glycol, 0.05-0.2 parts 1-hydroxyethylidene-1,1-diphosphonic acid, and 50-80 parts deionized water.

[0013] Preferably, the synergist is prepared by the following steps: dispersing polyethylene glycol diacrylate, 2-methyl-2-acrylate-2-sulfoethyl ester, and allyltrimethylammonium chloride in an ethanol / water mixed solvent, adjusting the pH of the solution, bubbling with nitrogen to remove oxygen, then adding potassium persulfate, and polymerizing under a nitrogen atmosphere and continuous stirring. After the reaction is completed, the product is cooled and purified by acetone precipitation to obtain the synergist.

[0014] Potassium persulfate decomposes under heating conditions to generate sulfate free radicals, which initiate free radical polymerization of the vinyl and acrylate groups of the monomers. 2-Methyl-2-acrylate-2-sulfoethyl ester provides anionic sulfonic acid groups, allyltrimethylammonium chloride provides cationic quaternary ammonium groups, and polyethylene glycol diacrylate, as a bifunctional crosslinking agent, forms a three-dimensional network structure during polymerization, resulting in an amphoteric surface-active polymer network structure containing both positive and negative ionic groups.

[0015] Preferably, the ratio of polyethylene glycol diacrylate, 2-methyl-2-acrylate-2-sulfoethyl ester, allyltrimethylammonium chloride, ethanol / water mixed solvent, and potassium persulfate is 1~7g:7.6~44.5g:2~8g:50~200mL:0.05~0.6g.

[0016] Preferably, the molecular weight of polyethylene glycol diacrylate is 200~1000 Da.

[0017] Preferably, the volume ratio of ethanol to deionized water in the ethanol / water mixed solvent is 1:3~4.

[0018] Preferably, the pH of the system is adjusted to 6.5-7.5 using sodium hydroxide solution.

[0019] Preferably, the nitrogen bubbling time is 20-50 minutes.

[0020] Preferably, the polymerization reaction conditions are 50~80℃ for 6~12h.

[0021] The present invention also claims a method for preparing an etching solution for the circuit board, comprising the following steps: adding tartaric acid, ethylenediaminetetraacetic acid, and phosphoric acid to deionized water, stirring and mixing at 30-50°C for 1-2 hours, then adding an synergist, 3-aminotriazole, ethylene glycol, and 1-hydroxyethylidene-1,1-diphosphonic acid, and finally adding hydrogen peroxide, stirring and mixing at 25-35°C for 1-2 hours to obtain the etching solution.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. This invention provides an etching solution for circuit boards. Hydrogen peroxide, as a strong oxidant, provides sufficient etching kinetics. Tartaric acid and ethylenediaminetetraacetic acid work synergistically to complex and chelate, effectively preventing the precipitation and formation of metal ions. Phosphoric acid maintains a suitable acidic environment to promote the etching reaction. 3-Aminotriazole acts as a corrosion inhibitor to selectively protect the substrate from excessive corrosion. Ethylene glycol adjusts the solution viscosity and improves fluidity. 1-Hydroxyethylidene-1,1-diphosphonic acid can both chelate and catalytically decompose metal ions of hydrogen peroxide to stabilize hydrogen peroxide and inhibit scale formation in the system. The synergist significantly improves etching precision and surface quality through its unique amphoteric surface active structure. The synergistic effect of each component achieves efficient, uniform, and controllable etching results.

[0024] 2. This invention provides a synergist whose amphoteric surfactant polymer structure significantly reduces surface tension through the synergistic balance of hydrophobic segments and hydrophilic ionic groups, ensuring the formation of a uniform liquid film on the PCB substrate surface by the etching solution. This effectively eliminates bubble formation and enhances penetration in fine lines, thereby achieving a more precise and uniform etching effect. The sulfonic acid anion group provides lone pair electrons to coordinate with empty d orbitals on the copper surface to form a stable chemisorption layer. Simultaneously, it exerts a strong complexing effect to form stable coordination complexes with Cu²⁺ ions in the solution, preventing copper ion hydrolysis and precipitation. The quaternary ammonium cation group and the sulfonic acid anion group work synergistically to... It effectively controls the directionality of etching and significantly suppresses lateral etching. The polyethylene glycol segments endow the synergist molecules with flexibility and solvation stability, assisting the stable adsorption of ionic groups on the copper surface, effectively reducing lateral drilling and significantly improving the accuracy and edge clarity of the circuit pattern. The chelating sites in the synergist polymer structure can form stable chelates with Cu²⁺ ions generated during etching, effectively reducing the concentration of free copper ions, preventing copper salt precipitation and inhibiting side reactions such as catalytic decomposition of hydrogen peroxide. The overall synergistic effect makes the etching kinetics more controllable, achieving a balance between etching rate and accuracy, ensuring the stability of the etching effect and extending the service life of the etching solution. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Of course, the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0026] Unless otherwise specified, all chemical reagents and materials in this invention are purchased from the market or synthesized from raw materials purchased from the market.

[0027] A method for preparing an etching solution for circuit boards includes the following steps:

[0028] (1) Disperse 1~7g of polyethylene glycol diacrylate (molecular weight of 200~1000Da), 7.6~44.5g of 2-methyl-2-acrylate-2-sulfoethyl ester, and 2~8g of allyltrimethylammonium chloride into 50~200mL of ethanol / water mixed solvent (volume ratio of ethanol to deionized water is 1:3~4), adjust the pH of the system to 6.5~7.5 with sodium hydroxide solution, bubble with nitrogen for 20~50min to remove oxygen, then add 0.05~0.6g of potassium persulfate, and polymerize at 50~80℃ under nitrogen atmosphere and continuous stirring for 6~12h. After the reaction is completed, cool the product and purify it by acetone precipitation to obtain the synergist.

[0029] (2) Add 8-20 parts of tartaric acid, 6-12 parts of ethylenediaminetetraacetic acid, and 15-30 parts of phosphoric acid to 50-80 parts of deionized water, stir and mix at 30-50℃ for 1-2 hours, then add 6-15 parts of synergist, 0.1-1 parts of 3-aminotriazole, 1-10 parts of ethylene glycol, and 0.05-0.2 parts of 1-hydroxyethylidene-1,1-diphosphonic acid, and finally add 10-25 parts of hydrogen peroxide, stir and mix at 25-35℃ for 1-2 hours to obtain the etching solution.

[0030] The present invention will be further described below through specific embodiments.

[0031] Example 1

[0032] A method for preparing an etching solution for circuit boards includes the following steps:

[0033] (1) 7g of polyethylene glycol diacrylate (molecular weight 800 Da), 44.5g of 2-methyl-2-acrylate-2-sulfoethyl ester and 8g of allyltrimethylammonium chloride were dispersed in 200mL of ethanol / water mixed solvent (volume ratio of ethanol to deionized water is 1:4). The pH of the system was adjusted to 7.0 with sodium hydroxide solution, and nitrogen was bubbled for 30min to remove oxygen. Then 0.6g of potassium persulfate was added, and the polymerization reaction was carried out at 80℃ under nitrogen atmosphere and continuous stirring for 6h. After the reaction was completed, the product was cooled and purified by acetone precipitation to obtain the synergist.

[0034] (2) Add 2000g of tartaric acid, 1200g of ethylenediaminetetraacetic acid and 3000g of phosphoric acid to 8000g of deionized water and stir and mix at 40°C for 1.5h. Then add 1500g of synergist, 100g of 3-aminotriazole, 1000g of ethylene glycol and 20g of 1-hydroxyethylidene-1,1-diphosphonic acid. Finally add 2500g of hydrogen peroxide and stir and mix at 30°C for 1.5h to obtain the etching solution.

[0035] Example 2

[0036] A method for preparing an etching solution for circuit boards includes the following steps:

[0037] (1) 5g of polyethylene glycol diacrylate (molecular weight 800 Da), 32.2g of 2-methyl-2-acrylate-2-sulfoethyl ester and 6g of allyltrimethylammonium chloride were dispersed in 150mL of ethanol / water mixed solvent (volume ratio of ethanol to deionized water is 1:4). The pH of the system was adjusted to 7.0 with sodium hydroxide solution, and nitrogen was bubbled for 30min to remove oxygen. Then 0.4g of potassium persulfate was added, and the polymerization reaction was carried out at 70℃ under nitrogen atmosphere and continuous stirring for 8h. After the reaction was completed, the product was cooled and purified by acetone precipitation to obtain the synergist.

[0038] (2) Add 1600g of tartaric acid, 1000g of ethylenediaminetetraacetic acid and 2500g of phosphoric acid to 7000g of deionized water and stir and mix at 40°C for 1.5h. Then add 1200g of synergist, 70g of 3-aminotriazole, 700g of ethylene glycol and 15g of 1-hydroxyethylidene-1,1-diphosphonic acid. Finally add 2000g of hydrogen peroxide and stir and mix at 30°C for 1.5h to obtain the etching solution.

[0039] Example 3

[0040] A method for preparing an etching solution for circuit boards includes the following steps:

[0041] (1) 3g of polyethylene glycol diacrylate (molecular weight of 800 Da), 19.9g of 2-methyl-2-acrylate-2-sulfoethyl ester and 4g of allyltrimethylammonium chloride were dispersed in 100mL of ethanol / water mixed solvent (volume ratio of ethanol to deionized water of 1:4). The pH of the system was adjusted to 7.0 with sodium hydroxide solution, and nitrogen was bubbled for 30min to remove oxygen. Then 0.2g of potassium persulfate was added, and the polymerization reaction was carried out at 60℃ under nitrogen atmosphere and continuous stirring for 10h. After the reaction was completed, the product was cooled and purified by acetone precipitation to obtain the synergist.

[0042] (2) Add 1200g of tartaric acid, 800g of ethylenediaminetetraacetic acid and 2000g of phosphoric acid to 6000g of deionized water and stir and mix at 40°C for 1.5h. Then add 900g of synergist, 40g of 3-aminotriazole, 400g of ethylene glycol and 10g of 1-hydroxyethylidene-1,1-diphosphonic acid. Finally add 1500g of hydrogen peroxide and stir and mix at 30°C for 1.5h to obtain the etching solution.

[0043] Example 4

[0044] A method for preparing an etching solution for circuit boards includes the following steps:

[0045] (1) 1g of polyethylene glycol diacrylate (molecular weight 800 Da), 7.6g of 2-methyl-2-acrylate-2-sulfoethyl ester and 2g of allyltrimethylammonium chloride were dispersed in 50mL of ethanol / water mixed solvent (volume ratio of ethanol to deionized water is 1:4). The pH of the system was adjusted to 7.0 with sodium hydroxide solution, and nitrogen was bubbled for 30min to remove oxygen. Then 0.05g of potassium persulfate was added, and the polymerization reaction was carried out at 50℃ under nitrogen atmosphere and continuous stirring for 12h. After the reaction was completed, the product was cooled and purified by acetone precipitation to obtain the synergist.

[0046] (2) Add 800g of tartaric acid, 600g of ethylenediaminetetraacetic acid and 1500g of phosphoric acid to 5000g of deionized water and stir and mix at 40°C for 1.5h. Then add 600g of synergist, 10g of 3-aminotriazole, 100g of ethylene glycol and 5g of 1-hydroxyethylidene-1,1-diphosphonic acid. Finally add 1000g of hydrogen peroxide and stir and mix at 30°C for 1.5h to obtain the etching solution.

[0047] Comparative Example 1

[0048] A method for preparing an etching solution for circuit boards includes the following steps:

[0049] (1) 7g of polyethylene glycol diacrylate (molecular weight of 800 Da) and 44.5g of 2-methyl-2-acrylate-2-sulfoethyl ester were dispersed in 200mL of ethanol / water mixed solvent (volume ratio of ethanol to deionized water of 1:4). The pH of the system was adjusted to 7.0 with sodium hydroxide solution, and nitrogen was bubbled for 30min to remove oxygen. Then 0.6g of potassium persulfate was added, and the polymerization reaction was carried out at 80℃ under nitrogen atmosphere and continuous stirring for 6h. After the reaction was completed, the product was cooled and purified by acetone precipitation to obtain the synergist.

[0050] (2) Add 2000g of tartaric acid, 1200g of ethylenediaminetetraacetic acid and 3000g of phosphoric acid to 8000g of deionized water and stir and mix at 40°C for 1.5h. Then add 1300g of synergist, 200g of allyltrimethylammonium chloride, 100g of 3-aminotriazole, 1000g of ethylene glycol and 20g of 1-hydroxyethylidene-1,1-diphosphonic acid. Finally add 2500g of hydrogen peroxide and stir and mix at 30°C for 1.5h to obtain the etching solution.

[0051] Comparative Example 2

[0052] A method for preparing an etching solution for circuit boards includes the following steps:

[0053] (1) 7g of polyethylene glycol diacrylate (molecular weight of 800 Da) and 16g of allyltrimethylammonium chloride were dispersed in 200mL of ethanol / water mixed solvent (volume ratio of ethanol to deionized water of 1:4). The pH of the system was adjusted to 7.0 with sodium hydroxide solution, and nitrogen was bubbled for 30min to remove oxygen. Then 0.6g of potassium persulfate was added, and the polymerization reaction was carried out at 80℃ under nitrogen atmosphere and continuous stirring for 6h. After the reaction was completed, the product was cooled and purified by acetone precipitation to obtain the synergist.

[0054] (2) Add 2000g of tartaric acid, 1200g of ethylenediaminetetraacetic acid and 3000g of phosphoric acid to 8000g of deionized water and stir and mix at 40°C for 1.5h. Then add 1200g of synergist, 300g of 2-methyl-2-acrylate-2-sulfoethyl ester, 100g of 3-aminotriazole, 1000g of ethylene glycol and 20g of 1-hydroxyethylidene-1,1-diphosphonic acid. Finally, add 2500g of hydrogen peroxide and stir and mix at 30°C for 1.5h to obtain the etching solution.

[0055] Comparative Example 3

[0056] A method for preparing an etching solution for circuit boards includes the following steps:

[0057] 2000g of tartaric acid, 1200g of ethylenediaminetetraacetic acid, and 3000g of phosphoric acid were added to 8000g of deionized water and stirred at 40°C for 1.5h. Then, 200g of polyethylene glycol diacrylate, 900g of 2-methyl-2-acrylate-2-sulfoethyl ester, 400g of allyltrimethylammonium chloride, 100g of 3-aminotriazole, 1000g of ethylene glycol, and 20g of 1-hydroxyethylidene-1,1-diphosphonic acid were added. Finally, 2500g of hydrogen peroxide was added and stirred at 30°C for 1.5h to obtain the etching solution.

[0058] To systematically evaluate the performance of the series of etching solutions, printed circuit board samples were treated with the etching solutions prepared in Examples 1-4 and Comparative Examples 1-3, respectively. The etching process parameters were set as follows: temperature 60°C, immersion time 1 minute. The etching effect was quantitatively characterized using the following methods:

[0059] Copper etching rate determination: Gravimetric analysis was used to accurately measure the mass loss (W1-W2) of the sample before and after etching due to the removal of the copper layer. Combined with the sample's surface area (S), copper density (ρ), and etching time (T), the average etching rate in μm / min was calculated according to the formula: Etching rate = 10000(W1-W2) / (ρ×S×2) / T.

[0060] Copper dissolution determination: The concentration of copper ions (Cu²⁺) in the etching waste solution was quantified using complexometric titration. 1 mL of the test solution was taken, and the pH was adjusted to 9.5–10.0 with ammonia. Using ammonia violet as an indicator, titration was performed with a 0.025 M EDTA standard solution. At the endpoint, the solution changed from yellow-green to deep purple. The final copper dissolution (g / L) was obtained by multiplying the titration volume (V) by a conversion factor of 1.5885.

[0061] Lateral etching and drilling assessment: The microstructure of the etched circuit pattern was analyzed using a scanning electron microscope (SEM, Hitachi 3400N). The thickness (D), bottom width (A), and top width (B) of the circuit cross-section were measured, and the etching factor was calculated using the formula EF = 2D / (AB). This factor is a key indicator for evaluating the degree of lateral etching; a smaller value indicates a steeper circuit profile and higher etching precision. Simultaneously, the bottom copper interface was carefully observed to determine the presence of drilling and etching residue. Specific results are shown in Table 1.

[0062] Table 1. Etching solution performance test results

[0063] Etching rate (μm / min) Copper solubility (g / L) Etching factor Etching residue Example 1 66 111 1.89 No residue Example 2 62 108 1.96 No residue Example 3 59 105 1.99 No residue Example 4 58 101 2.01 No residue Comparative Example 1 52 92 6.27 No residue Comparative Example 2 36 78 5.43 There are residues Comparative Example 3 31 63 7.64 There are residues

[0064] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An etching solution for a circuit board, characterized by comprising: The etching liquid is prepared by the following components: hydrogen peroxide 10-25 parts, tartaric acid 8-20 parts, ethylenediaminetetraacetic acid 6-12 parts, phosphoric acid 15-30 parts, synergist 6-15 parts, 3-amino triazole 0.1-1 part, ethylene glycol 1-10 parts, 1-hydroxyethylidene-1,1-biphosphonic acid 0.05-0.2 parts, and deionized water 50-80 parts.

2. The etching solution of claim 1, wherein The synergist is prepared by the following steps: dispersing polyethylene glycol diacrylate, 2-methyl-2-propenoic acid-2-sulfoethyl ester, and allyl trimethyl ammonium chloride into an ethanol / water mixed solvent, adjusting the pH of the solution, removing oxygen by nitrogen bubbling, then adding potassium persulfate, and polymerizing under nitrogen atmosphere and continuous stirring, after the reaction, cooling the product, purifying by acetone precipitation, and obtaining the synergist.

3. The etching solution of claim 2, wherein The amount ratio of polyethylene glycol diacrylate, 2-methyl-2-propenoic acid-2-sulfoethyl ester, allyl trimethyl ammonium chloride, ethanol / water mixed solvent, and potassium persulfate is 1-7 g:7.6-44.5 g:2-8 g:50-200 mL:0.05-0.6 g.

4. The etching solution of claim 2, wherein The molecular weight of polyethylene glycol diacrylate is 200-1000 Da.

5. The etching solution of claim 2, wherein The volume ratio of ethanol and deionized water in the ethanol / water mixed solvent is 1:3-4.

6. The etching solution of claim 2, wherein The pH of the system is adjusted to 6.5-7.5 by sodium hydroxide solution.

7. The etching solution of claim 2, wherein The nitrogen bubbling time is 20-50 min.

8. The etching solution of claim 2, wherein The polymerization reaction condition is 50-80 ℃ for 6-12 h.

9. A method for preparing an etching solution for the circuit board as claimed in any one of claims 1 to 8, characterized by, The etching liquid is prepared by the following steps: adding tartaric acid, ethylenediaminetetraacetic acid, and phosphoric acid into deionized water, stirring and mixing at 30-50 ℃ for 1-2 h, then adding synergist, 3-amino triazole, ethylene glycol, and 1-hydroxyethylidene-1,1-biphosphonic acid, and finally adding hydrogen peroxide, stirring and mixing at 25-35 ℃ for 1-2 h.