A high-stability chemical copper plating solution and preparation method thereof

Abstract

The present application relates to the field of chemical copper plating technology, and more particularly to a high-stability chemical copper plating solution and a preparation method thereof. A high-stability chemical copper plating solution, by mass concentration, includes the following preparation raw materials: 6-10g / L of copper sulfate pentahydrate, 17-20g / L of a reducing agent, 30-35g / L of a complexing agent, 20-25g / L of a buffer, 0.02-0.03g / L of a stabilizer, 0.008-0.01g / L of a surfactant, wherein the reducing agent is composed of 37% formaldehyde and pyrrolidine tetrafluoroborate in a mass ratio of 5:3. The high-stability chemical copper plating solution of the present application has significant technical advantages in improving deposition rate, stability, coating quality and high and low temperature resistance, and can be widely used in surface treatment processes in the fields of electronics, communications, aerospace, etc.

Description

Technical Field

[0001] The present application relates to the technical field of chemical copper plating, and in particular to a high-stability chemical copper plating solution and a preparation method thereof. Background Art

[0002] Chemical copper is widely used in chemical production. It first appeared in 1957 when Cahill published the first chemical copper plating solution similar to modern ones. The plating solution was alkaline copper tartaric acid plating solution and formaldehyde was the reducing agent. With the development of printed circuit boards, a huge market has been provided for the development of chemical copper plating technology. In the production of printed circuit boards, chemical copper plating is used to precipitate copper as the wall surface of the through hole and the basic circuit path. Chemical copper plating is also suitable for the decorative plastic industry, where copper, nickel, gold, silver and other metals are deposited on non-conductive surfaces as a base as needed.

[0003] The basic components of PCB chemical copper plating solution are: copper salt, complexing agent, reducing agent and additives. The copper salt is CuSO4·5H2O. The commonly used reducing agent is formaldehyde. The reducing ability of formaldehyde increases with the increase of pH value, so NaOH needs to be added to maintain the pH value. The complexing agent is a multi-component complexing agent system of ethylenediaminetetraacetic acid (EDTA), potassium sodium tartrate and triethanolamine. One is to reduce the amount of EDTA and reduce costs, and the other is to improve the stability of the plating solution and improve the quality of the coating.

[0004] The process flow of PCB chemical copper deposition is: swelling - degumming - pre-neutralization - neutralization water washing - degreasing - micro-etching - pre-impregnation - activation - acceleration - copper deposition. Except for the process from pre-impregnation to activation, water washing is required after the other processes. Chemical copper deposition is the last step of chemical copper deposition for circuit boards and is the key to quality assurance of hole metallization in the PCB manufacturing process.

[0005] After the PCB board passes through the activation tank to adsorb colloidal palladium, the palladium nucleus adsorbed on the inner wall of the hole is exposed after the colloidal palladium is debonded in the acceleration tank. After each batch of boards enters the copper plating tank, the palladium nucleus acts as a catalyst to catalyze the deposition of copper on the substrate board, but the palladium exposed in the hole is leached, peeled off and diffused into the copper plating solution to varying degrees. With the increase in the number of board batches (quantity), the palladium content in the chemical plating solution accumulates to a certain concentration, and multiple active sites for copper ion precipitation will be formed in the plating solution. The stability of the chemical plating solution decreases, which eventually leads to the precipitation of copper powder in the plating solution during the copper deposition process and copper on the tank wall, which seriously affects the service life of the chemical copper plating solution.

[0006] There are two problems with the current copper plating process technology. One is to increase the deposition rate, but the chemical copper plating solution is unstable. The other is to increase the stability of the chemical copper plating solution, but the deposition rate will decrease. Summary of the invention

[0007] The purpose of the present application is to provide a high-stability chemical copper plating solution and a preparation method thereof in view of the deficiencies in the current technology. The high-stability chemical copper plating solution of the present application ensures excellent stability while maintaining a high deposition rate, reduces the frequency of maintenance while obtaining a good copper deposition layer quality, increases the service life of the chemical copper solution, prolongs the decomposition time of the plating solution, and promotes production efficiency.

[0008] In a first aspect, the present application provides a high-stability chemical copper plating solution, which adopts the following technical solution:

[0009] A high-stability chemical copper plating solution comprises the following raw materials, measured by mass concentration: 6-10 g / L of copper sulfate pentahydrate, 17-20 g / L of a reducing agent, 30-35 g / L of a complexing agent, 20-25 g / L of a buffer, 0.02-0.03 g / L of a stabilizer, and 0.008-0.01 g / L of a surfactant, wherein the reducing agent is composed of formaldehyde with a mass concentration of 37% and pyrrolidine tetrafluoroborate in a mass ratio of 5:3.

[0010] By adopting the above technical scheme, copper sulfate pentahydrate: as the source of copper ions, it is the basic substance for copper deposition. Reducing agent (formaldehyde + pyrrolidine tetrafluoroborate): the combined use can effectively reduce copper ions to metallic copper and deposit them on the substrate. Formaldehyde is a commonly used reducing agent, while pyrrolidine tetrafluoroborate not only helps the reduction process, but also improves the stability at low temperatures, improves the deposition rate and the quality of the coating. Complexing agent: forms a stable complex with copper ions, which helps to control the concentration of free copper ions, thereby affecting the deposition rate and the quality of the coating. Buffer: adjusts and maintains the pH value of the plating solution to ensure the stability of the plating solution environment, which is conducive to the smooth progress of the copper plating reaction. Stabilizer: by reducing the impact of by-products (such as monovalent copper) in the plating solution, improves the overall stability of the plating solution, reduces the maintenance frequency, and extends the service life. At the same time, it improves the high and low temperature resistance and adhesion of the coating, and also improves the tolerance of the plating solution to leached palladium, which is conducive to improving the stability and service life of the plating solution. Surfactant: Reduces the surface tension of the liquid and makes the liquid more evenly distributed on the surface of the substrate, thereby obtaining a smoother and more uniform coating. In short, through the careful selection and proportioning of components, the high-stability chemical copper plating solution prepared ensures excellent stability at a high deposition rate, while obtaining a good copper deposition layer quality, reducing the frequency of maintenance, increasing the service life of the chemical copper solution, extending the decomposition time of the plating solution, and promoting production efficiency.

[0011] Preferably, the preparation method of the pyrrolidine tetrafluoroborate is as follows: according to molar fractions, 5 parts of 1,4-dichlorobutane, 6 parts of diethylamine, 5 parts of sodium carbonate, and 5 parts of tetrafluoroboric acid are added to 40 parts of acetonitrile, heated to 90°C and reacted for 28-32 hours, cooled to room temperature to obtain a reaction solution, the reaction solution is filtered to obtain a filtrate, the filtrate is concentrated under reduced pressure, and then 50 parts of anhydrous ethanol is added for recrystallization, and a filter cake is obtained after filtration, and the filter cake is vacuum dried to constant weight to obtain pyrrolidine tetrafluoroborate.

[0012] By adopting the above technical scheme, the preparation method of pyrrolidine tetrafluoroborate involves a series of chemical reaction steps, firstly, 1,4-dichlorobutane, diethylamine, sodium carbonate and tetrafluoroboric acid are heated in acetonitrile for reaction, cooled and filtered to obtain filtrate after a specific time, and then pyrrolidine tetrafluoroborate is obtained by reduced pressure concentration and recrystallization. This compound has multiple functions in chemical copper plating solution, including acting as a reducing agent with formaldehyde to promote the reduction and deposition of copper ions, improving the stability of the plating solution and the quality of the coating at low temperature, and improving the stability and service life of the overall plating solution through synergistic effects with other components, thereby improving production efficiency and coating quality.

[0013] Preferably, the stabilizer consists of a first stabilizer and a second stabilizer in a mass ratio of 5:2-3.

[0014] Preferably, the first stabilizer is composed of 6-thioguanine, dimethyldiallylammonium chloride-based amine polymer and 5,5-dimethylhydantoin in a mass ratio of 3:2:3.

[0015] By adopting the above technical solution, the tolerance of the plating solution to leached palladium is further enhanced through the synergistic effect of specific compounds, such as the combination of 6-thioguanine, dimethyldiallyl ammonium chloride-based amine polymer and 5,5-dimethylhydantoin, which helps to extend the service life and decomposition time of the plating solution. The introduction of the second stabilizer, in synergy with the first stabilizer, not only improves the stability of the plating solution, but also improves the density, uniformity and bonding between the coating and the substrate.

[0016] Preferably, the preparation method of the second stabilizer is: add 5,5′-dimethyl-2,2′-bipyridine, bromoacetamide, and azobisisobutyronitrile to carbon tetrachloride, heat to reflux temperature and react for 24 hours, and rotary evaporate the carbon tetrachloride to obtain an intermediate product; then add the intermediate product, butyl lithium, and ethyl p-hydroxybenzoate to toluene, heat to reflux temperature and react for 24 hours, rotary evaporate to remove toluene, wash with distilled water 5 times, and vacuum dry to constant weight to obtain the second stabilizer.

[0017] By adopting the above technical scheme, 5,5′-dimethyl-2,2′-bipyridine and bromoacetamide are reacted under the initiation of azobisisobutyronitrile to obtain an intermediate product, and then the intermediate product is reacted with ethyl p-hydroxybenzoate to obtain a second stabilizer, which can cooperate with copper ions and complex with reaction by-products to make the copper solution have excellent stability, and can also improve the copper plating rate and the density and uniformity of the copper plating layer and the bonding force between the copper plating layer and the substrate. In addition, it also synergizes with the first stabilizer to further improve the stability of the plating solution, which helps to extend the service life and decomposition time of the plating solution.

[0018] Preferably, the usage ratio of 5,5′-dimethyl-2,2′-bipyridine, bromoacetamide, azobisisobutyronitrile and carbon tetrachloride is 2mmol:2mmol:0.5mmol:150mL; the ratio of intermediate product, butyl lithium, ethyl p-hydroxybenzoate and toluene is 2mmol:2mmol:1mmol:250mL.

[0019] Preferably, the complexing agent is composed of potassium sodium tartrate and tetrahydroxypropylethylenediamine in a mass ratio of 3:2.

[0020] By adopting the above technical scheme, potassium sodium tartrate and tetrahydroxypropyl ethylenediamine, as complexing agents, play a vital role in the chemical copper plating solution. They can form a stable complex with copper ions, and this complexing action helps to improve the deposition rate of copper and the stability of the coating. First, potassium sodium tartrate is a strong complexing agent that can effectively combine with copper ions to form a stable complex. The formation of this complex helps to control the release rate of copper ions in the plating solution, thereby making the deposition process of copper more stable and uniform. In addition, potassium sodium tartrate can also improve the adhesion and ductility of the coating, making the copper coating more durable. Secondly, tetrahydroxypropyl ethylenediamine is also an effective complexing agent that can form a stable complex with copper ions. Compared with potassium sodium tartrate, tetrahydroxypropyl ethylenediamine has a stronger complexing ability and can more effectively control the release rate of copper ions. At the same time, tetrahydroxypropyl ethylenediamine can also improve the glossiness and flatness of the coating, making the copper coating more beautiful. When potassium sodium tartrate and tetrahydroxypropyl ethylenediamine are mixed in a mass ratio of 3:2, a synergistic effect will occur between them. This synergistic effect can not only further improve the copper deposition rate and the stability of the coating, but also improve the physical properties of the coating. Both potassium sodium tartrate and tetrahydroxypropyl ethylenediamine can promote the reduction reaction of copper ions, but their reduction abilities are different. When the two are mixed, they can promote each other's reduction reaction, thereby increasing the copper deposition rate. Jointly control the release rate of copper ions: potassium sodium tartrate and tetrahydroxypropyl ethylenediamine can both form stable complexes with copper ions, but their complexing abilities are different. When the two are mixed, they can jointly control the release rate of copper ions, making the copper deposition process smoother and more uniform.

[0021] Both potassium sodium tartrate and tetrahydroxypropylethylenediamine can improve the physical properties of the coating, but their improvement effects are different. When the two are mixed, they can jointly improve the physical properties of the coating, making the copper plating layer stronger and more durable.

[0022] Preferably, the surfactant is polyvinyl pyrrolidone.

[0023] Preferably, the buffer is one of sodium carbonate and potassium carbonate.

[0024] In a second aspect, the present application provides a method for preparing a high-stability chemical copper plating solution, using the following technical solution: As a general technical concept, the present application also provides a method for preparing the above-mentioned high-stability chemical copper plating solution, comprising the following steps:

[0025] Add 6-10g of copper sulfate pentahydrate, 17-20g of reducing agent, 30-35g of complexing agent, 20-25g of buffer, 0.02-0.03g of stabilizer and 0.008-0.01g of surfactant to an appropriate amount of deionized water and mix well, then dilute the mixed solution to 1L to obtain a high-stability chemical copper plating solution.

[0026] In summary, the beneficial technical effects of this application are:

[0027] 1. High deposition rate: By using a specific reducing agent combination and complexing agent, the chemical copper plating solution can achieve a higher copper deposition rate and improve production efficiency.

[0028] 2. Excellent stability: Adding ingredients such as stabilizers and surfactants can keep the plating solution stable during long-term use, reduce the frequency of maintenance, and extend the service life of the plating solution.

[0029] 3. Good copper plating layer quality: By optimizing the formula and process parameters, the chemical copper plating solution can form a dense, flat and uniform copper plating layer on the surface of the substrate, improving the quality and performance of the plating layer.

[0030] 4. Improve high and low temperature resistance: The addition of stabilizer can improve the high and low temperature resistance of the copper layer and enhance its stability in use under different environmental conditions.

[0031] 5. Synergistic effect: Through the synergistic effect of multiple ingredients, such as 6-thioguanine, 5,5-dimethylhydantoin and dimethyldiallyl ammonium chloride amine polymer, the plating solution's tolerance to leached palladium is further enhanced, which is beneficial to increasing the service life of the copper plating solution and extending the decomposition time of the plating solution.

[0032] 6. Improve the bonding strength: The synergistic effect of the second stabilizer and the first stabilizer not only improves the stability of the plating solution, but also enhances the bonding strength between the copper plating layer and the substrate, thereby improving the overall performance of the plating layer. DETAILED DESCRIPTION

[0033] The embodiments of the present application will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0034] Preparation Example 1 Preparation of pyrrolidine tetrafluoroborate

[0035] The preparation method of pyrrolidine tetrafluoroborate is as follows: according to the molar fractions, 5 mol of 1,4-dichlorobutane, 6 mol of diethylamine, 5 mol of sodium carbonate and 5 mol of tetrafluoroboric acid are added to 40 mol of acetonitrile, heated to 90°C and reacted for 30 hours, cooled to room temperature to obtain a reaction liquid, the reaction liquid is filtered to obtain a filtrate, the filtrate is concentrated under reduced pressure, and then 50 mol of anhydrous ethanol is added for recrystallization, a filter cake is obtained after filtration, and the filter cake is vacuum dried to constant weight to obtain pyrrolidine tetrafluoroborate.

[0036] Preparation Example 2 Preparation of the Second Stabilizer

[0037] The preparation method of the second stabilizer is as follows: 2mmol5,5′-dimethyl-2,2′-bipyridine, 2mmolbromoacetamide, and 0.5mmolazobisisobutyronitrile are added to 150mL carbon tetrachloride, heated to reflux temperature and reacted for 24 hours, and the carbon tetrachloride is rotary evaporated to obtain an intermediate product; then 2mmol of the intermediate product, 2mmol butyl lithium, and 1mmol ethyl p-hydroxybenzoate are added to 250mL toluene, heated to reflux temperature and reacted for 24 hours, the toluene is rotary evaporated, and then washed with distilled water 5 times, and vacuum dried to constant weight to obtain the second stabilizer.

[0038] Example 1

[0039] A high-stability chemical copper plating solution comprises the following raw materials, measured by mass concentration: 6 g / L of copper sulfate pentahydrate, 17 g / L of a reducing agent, 30 g / L of a complexing agent, 20 g / L of sodium carbonate, 0.02 g / L of a stabilizer, and 0.008 g / L of polyvinyl pyrrolidone, wherein the reducing agent is composed of formaldehyde with a mass concentration of 37% and pyrrolidine tetrafluoroborate in a mass ratio of 5:3, the stabilizer is composed of a first stabilizer and a second stabilizer in a mass ratio of 5:2, the first stabilizer is composed of 6-thioguanine, dimethyldiallylammonium chloride-based amine polymer and 5,5-dimethylhydantoin in a mass ratio of 3:2:3, and the complexing agent is composed of potassium sodium tartrate and tetrahydroxypropylethylenediamine in a mass ratio of 3:2.

[0040] The method for preparing the above-mentioned high-stability chemical copper plating solution comprises the following steps:

[0041] Add 6g of copper sulfate pentahydrate, 17g of reducing agent, 30g of chelating agent, 20g of sodium carbonate, 0.02g of stabilizer and 0.008g of polyvinyl pyrrolidone to an appropriate amount of deionized water and mix well, then adjust the mixed solution to 1L to obtain a high-stability chemical copper plating solution.

[0042] Example 2

[0043] A high-stability chemical copper plating solution comprises the following raw materials, measured by mass concentration: 10 g / L of copper sulfate pentahydrate, 20 g / L of a reducing agent, 35 g / L of a complexing agent, 25 g / L of potassium carbonate, 0.03 g / L of a stabilizer, and 0.01 g / L of polyvinyl pyrrolidone, wherein the reducing agent is composed of formaldehyde with a mass concentration of 37% and pyrrolidine tetrafluoroborate in a mass ratio of 5:3, the stabilizer is composed of a first stabilizer and a second stabilizer in a mass ratio of 5:3, the first stabilizer is composed of 6-thioguanine, dimethyldiallylammonium chloride-based amine polymer and 5,5-dimethylhydantoin in a mass ratio of 3:2:3, and the complexing agent is composed of potassium sodium tartrate and tetrahydroxypropylethylenediamine in a mass ratio of 3:2.

[0044] The method for preparing the above-mentioned high-stability chemical copper plating solution comprises the following steps:

[0045] Add 10 g of copper sulfate pentahydrate, 20 g of reducing agent, 35 g of complexing agent, 25 g of potassium carbonate, 0.03 g of stabilizer, and 0.01 g of polyvinyl pyrrolidone to an appropriate amount of deionized water and mix well, then dilute the mixed solution to 1 L to obtain a high-stability chemical copper plating solution.

[0046] Example 3

[0047] A high-stability chemical copper plating solution comprises the following raw materials, measured by mass concentration: 8 g / L of copper sulfate pentahydrate, 19 g / L of a reducing agent, 33 g / L of a complexing agent, 22 g / L of sodium carbonate, 0.025 g / L of a stabilizer, and 0.009 g / L of polyvinyl pyrrolidone, wherein the reducing agent is composed of formaldehyde with a mass concentration of 37% and pyrrolidine tetrafluoroborate in a mass ratio of 5:3, the stabilizer is composed of a first stabilizer and a second stabilizer in a mass ratio of 5:2.5, the first stabilizer is composed of 6-thioguanine, dimethyldiallylammonium chloride-based amine polymer and 5,5-dimethylhydantoin in a mass ratio of 3:2:3, and the complexing agent is composed of potassium sodium tartrate and tetrahydroxypropylethylenediamine in a mass ratio of 3:2.

[0048] The method for preparing the above-mentioned high-stability chemical copper plating solution comprises the following steps:

[0049] Add 8g of copper sulfate pentahydrate, 19g of reducing agent, 33g of complexing agent, sodium carbonate, 22g of potassium carbonate, 0.025g of stabilizer, and 0.009g of polyvinyl pyrrolidone to an appropriate amount of deionized water and mix well, then adjust the mixed solution to 1L to obtain a high-stability chemical copper plating solution.

[0050] Comparative Example 1

[0051] The same as Example 3, except that the stabilizer is a first stabilizer, and the first stabilizer is composed of 6-thioguanine, dimethyldiallyl ammonium chloride-based amine polymer and 5,5-dimethylhydantoin in a mass ratio of 3:2:3.

[0052] Comparative Example 2

[0053] The same as Example 3, except that the stabilizer is a second stabilizer.

[0054] Comparative Example 3

[0055] The same as Example 3, except that the first stabilizer is 6-thioguanine.

[0056] Comparative Example 4

[0057] The same as Example 3, except that the first stabilizer is a dimethyldiallylammonium chloride-based amine polymer.

[0058] Comparative Example 5

[0059] The same as Example 3, except that the first stabilizer is 5,5-dimethylhydantoin.

[0060] Comparative Example 6

[0061] The same as Example 3, except that the complexing agent is potassium sodium tartrate.

[0062] Comparative Example 7

[0063] The same as Example 3, except that the complexing agent is tetrahydroxypropylethylenediamine.

[0064] Performance Testing

[0065] The high stability chemical copper plating solutions prepared in Examples 1 to 3 and Comparative Examples 1 to 7 were respectively subjected to chemical copper plating. The process conditions were: temperature 35° C., time 20 minutes, the part to be plated was a resin board, and after the conventional chemical copper plating process, the surface palladium activation treatment and reduction treatment, the chemical copper plating process can be directly carried out to carry out the above-mentioned chemical copper plating; and the following tests were carried out, and the test results are shown in Table 1.

[0066] 1. Sedimentation rate test: The sedimentation rate is determined by the weight gain method, and the calculation formula is as follows:

[0067] v=(m1-m0)×10000 / (ρ×A×t);

[0068] Where v is the deposition rate, μm / h; m0 and m1 are the mass of the plated part before and after plating, respectively, g; ρ is the relative density of copper, 8.93 g / cm 3 ; A is the surface area of ​​the plated part, cm2 ; t is the plating time, h;

[0069] 2. Adhesion test: Use the 100-grid test method, use 3M610 tape to tear, no peeling is OK, and peeling is NG;

[0070] 3. Plating solution stability test: Since it takes a long time for the plating solution to decompose naturally, in order to shorten the experimental time, an accelerated method is generally used. The present invention uses a palladium chloride accelerated test to test the stability of the plating solution: add 15mL PdCl2 (0.18g / L) to 50mL of the plating solution at a temperature of 60°C, and record the decomposition time of the plating solution, that is, the time required to produce a large amount of red copper powder and hydrogen;

[0071] 4. Backlight level: After copper deposition, place the test piece in a slicer and cut it. Grind it with a grinder to grind off 1 / 2 of the hole diameter of the slice, and grind the other side of the slice to about 2mm from the edge of the hole. After grinding, wipe the copper chips and glue residue in the hole with a soft cloth, and use a microscope to magnify 50 times to detect the condition in the hole. Use the backlight principle (if the chemical copper is deposited evenly, the lower light cannot be seen through, the entire hole wall appears completely black, and the backlight level is 10) to check the uniformity of chemical copper deposition on the hole wall of each hole. The backlight level is required to reach above level 8.

[0072] Table 1 Performance test

[0073] project Deposition rate (μm / h) Backlight level / level Decomposition time / min Coating bonding strength Example 1 3.3 10 722 OK Example 2 3.8 10 735 OK Example 3 3.5 10 731 OK Comparative Example 1 4.1 8.5 536 OK Comparative Example 2 4.3 9 482 OK Comparative Example 3 3.9 9 605 OK Comparative Example 4 4.0 9 612 OK Comparative Example 5 4.1 9 621 OK Comparative Example 6 3.1 9 663 OK Comparative Example 7 2.9 8.5 657 OK

[0074] Analyzing the data in Table 1, we can see that:

[0075] 1) The high-stability chemical copper plating solution prepared in Examples 1 to 3 has a high deposition rate as well as excellent stability and high backlight level. While obtaining good copper deposition layer quality, it reduces the frequency of maintenance, increases the service life of the chemical copper solution, prolongs the decomposition time of the plating solution, and promotes production efficiency.

[0076] 2) The performance comparison analysis of the high stability chemical copper plating solution prepared in combination with Example 3 and Comparative Examples 1 to Comparative Examples 5 shows that the stabilizer is composed of the first stabilizer and the second stabilizer in a mass ratio of 5:2.5, and the first stabilizer is composed of 6-thioguanine, dimethyldiallyl ammonium chloride-based amine polymer and 5,5-dimethylhydantoin in a mass ratio of 3:2:3. The synergistic effect between the combination of 6-thioguanine, dimethyldiallyl ammonium chloride-based amine polymer and 5,5-dimethylhydantoin is used to further enhance the tolerance of the plating solution to leached palladium, which helps to extend the service life and decomposition time of the plating solution. The introduction of the second stabilizer, in synergy with the first stabilizer, not only improves the stability of the plating solution, but also improves the density, uniformity and bonding between the coating and the substrate, thereby improving the backlight level.

[0077] 3) The performance comparison analysis of the high stability chemical copper plating solution prepared in combination with Example 3 and Comparative Examples 6-7 shows that the complexing agent is composed of potassium sodium tartrate and tetrahydroxypropyl ethylenediamine in a mass ratio of 3:2, which can form a stable complex with copper ions, and this complexing effect helps to improve the copper deposition rate and the stability of the coating. By utilizing the synergistic effect between them, not only can the copper deposition rate and the stability of the coating be further improved, but also the physical properties of the coating can be improved and the backlight level can be improved.

[0078] The above embodiments are only used to explain the technical solutions of the present application rather than to limit them. Although the above embodiments provide a specific description of the present application, relevant technical personnel should understand that the specific implementation modes of the present invention can still be modified or replaced by equivalents, and any modifications and equivalent replacements that do not depart from the spirit and scope of the present application should be included in the scope of protection of the present application.

Claims

1. A high stability chemical copper plating solution, characterized in that: The preparation raw materials include, by mass concentration: 6-10 g / L of copper sulfate pentahydrate, 17-20 g / L of a reducing agent, 30-35 g / L of a complexing agent, 20-25 g / L of a buffer, 0.02-0.03 g / L of a stabilizer, and 0.008-0.01 g / L of a surfactant, wherein the reducing agent is composed of formaldehyde with a mass concentration of 37% and pyrrolidine tetrafluoroborate with a mass ratio of 5:3; The preparation method of pyrrolidine tetrafluoroborate is as follows: according to molar fractions, 5 parts of 1,4-dichlorobutane, 6 parts of diethylamine, 5 parts of sodium carbonate, and 5 parts of tetrafluoroboric acid are added to 40 parts of acetonitrile, heated to 90° C. and reacted for 28-32 hours, cooled to room temperature to obtain a reaction solution, the reaction solution is filtered to obtain a filtrate, the filtrate is concentrated under reduced pressure, and then 50 parts of anhydrous ethanol is added for recrystallization, and a filter cake is obtained after filtration, and the filter cake is vacuum dried to constant weight to obtain pyrrolidine tetrafluoroborate; The stabilizer is composed of a first stabilizer and a second stabilizer in a mass ratio of 5:2-3; The first stabilizer is composed of 6-thioguanine, dimethyldiallyl ammonium chloride-based amine polymer and 5,5-dimethylhydantoin in a mass ratio of 3:2:3; The preparation method of the second stabilizer is as follows: 5,5′-dimethyl-2,2′-bipyridine, bromoacetamide, and azobisisobutyronitrile are added to carbon tetrachloride, heated to reflux temperature and reacted for 24 hours, and the carbon tetrachloride is removed by rotary evaporation to obtain an intermediate product; the intermediate product, butyl lithium, and ethyl p-hydroxybenzoate are added to toluene, heated to reflux temperature and reacted for 24 hours, toluene is removed by rotary evaporation, and then washed with distilled water for 5 times, and vacuum dried to constant weight to obtain the second stabilizer; The usage ratio of 5,5′-dimethyl-2,2′-bipyridine, bromoacetamide, azobisisobutyronitrile, and carbon tetrachloride is 2mmol:2mmol:0.5mmol:150mL; the ratio of the intermediate product, butyl lithium, ethyl p-hydroxybenzoate, and toluene is 2mmol:2mmol:1mmol:250mL; The complexing agent is composed of potassium sodium tartrate and tetrahydroxypropylethylenediamine in a mass ratio of 3:2; The surfactant is polyvinyl pyrrolidone.

2. A high stability chemical copper plating solution according to claim 1, characterized in that: The buffer is one of sodium carbonate and potassium carbonate.

3. A method for preparing a high-stability chemical copper plating solution according to any one of claims 1 to 2, characterized in that: include: Add 6-10g of copper sulfate pentahydrate, 17-20g of reducing agent, 30-35g of complexing agent, 20-25g of buffer, 0.02-0.03g of stabilizer and 0.008-0.01g of surfactant to an appropriate amount of deionized water and mix well, then dilute the mixed solution to 1L to obtain a high-stability chemical copper plating solution.