Cyanide-free electro-coppering liquid as well as preparation method and application thereof

Abstract

The invention relates to cyanide-free copper electroplating liquid, and relates to the technical field of electroplating. The cyanide-free copper electroplating liquid is prepared from a main coordination agent, an auxiliary coordination agent, conducting salt, a brightener and an additive. The cyanide-free electrocoppering liquid can guarantee the binding force of a plating layer and the stability of the electrocoppering liquid, a copper plating layer meeting the preplating requirement can be obtained, the binding force of the copper plating layer and a base body is good, crystals are fine and semi-glossy, the electrocoppering liquid is stable, good dispersing capacity and deep plating capacity are achieved, the current efficiency is superior to that of cyanide electrocoppering, and the cyanide-free electrocoppering liquid is expected to replace cyanide electrocoppering.

Description

Technical Field

[0001] The present invention relates to the technical field of electroplating, and particularly to a cyanide-free copper electroplating solution, a preparation method thereof and an application thereof. Background Art

[0002] Copper is a soft metal rich in ductility and easy to be machined mechanically, with excellent electrical and thermal conductivity. Based on the characteristics that copper has good stability in water, salt solutions and acids without dissolved oxygen and in a reducing atmosphere, the copper plating layer is mainly used as an intermediate layer between steel and other plating layers and is widely used in protective and decorative plating layers (such as in automobiles, building materials, household appliances, etc.). Based on the good electrical conductivity and ductility of copper, copper plating has great application value in intermediate plating layers for plastic metallization, printed circuit boards (PCBs), IC packaging technology, and very large scale integrated circuit chip technology.

[0003] Copper electroplating solutions are divided into two categories: cyanide copper electroplating and cyanide-free copper electroplating. The advantages of cyanide copper electroplating electrolyte are good throwing power and covering power, simple electrolyte composition, easy maintenance, and being suitable for the underlaying of steel parts and zinc and aluminum alloy products, etc. Its disadvantages are that the electrolyte contains a large amount of highly toxic cyanide, the waste water and waste gas generated during electroplating endanger the health of operators and pollute the environment, and the electrolyte has poor stability. Cyanide-free copper electroplating can also be divided into acidic copper electroplating and alkaline copper electroplating. Acidic copper electroplating is mainly used for plating thick copper layers on nickel or copper substrates. The intermediate layer for underlaying needs to be solved by alkaline copper electroplating. All along, many discussions have been carried out on the research of alkaline copper electroplating processes, and copper plating systems such as pyrophosphate, hydroxyethylidene diphosphonic acid, citrate, EDTA, ethylenediamine, etc. have emerged, but each has its own defects. The conventional process flow of cyanide-free alkaline copper electroplating is: degreasing → water washing → pickling → water washing → electroless copper plating → water washing.

[0004] The development of cyanide-free copper electroplating technology aims to replace the toxic cyanide copper electroplating process to meet the increasingly strict environmental protection regulations and improve the environmental performance of the process. In the cyanide copper electroplating solution, due to the strong complexing ability of NaCN to copper ions, it has good throwing power and covering power, the coating has fine crystallization, the plating solution is alkaline and has degreasing ability, so that a coating with good adhesion can be obtained. Therefore, cyanide copper electroplating has incomparable advantages and is widely used. However, cyanide copper electroplating has low current efficiency, contains a large amount of CN- ions, is highly toxic, and is not conducive to environmental protection. For decades, electroplating workers have been committed to testing cyanide-free copper electroplating to replace cyanide copper electroplating. Cyanide-free copper electroplating processes such as pyrophosphate system copper electroplating, citrate copper electroplating, fluoborate copper electroplating, sulfamic acid copper electroplating, and double complexing agent copper electroplating have emerged successively, but due to various degrees of disadvantages, it is difficult to be widely promoted and used. Summary of the Invention

[0005] In view of the above problems, the present invention provides a cyanide-free electroplating copper solution, which can ensure the adhesion of the coating and the stability of the plating solution, can obtain a copper coating that meets the requirements of pre-plating, has good adhesion between the copper coating and the substrate, fine crystallization and semi-gloss appearance, stable plating solution, good dispersion ability and throwing power, and the current efficiency is better than that of cyanide copper plating, and it is expected to replace cyanide copper plating.

[0006] In order to achieve the above object, the present invention provides a cyanide-free electroplating copper solution, which is prepared from raw materials with the following concentrations:

[0007]

[0008]

[0009] The coating formed by the above cyanide-free electroplating copper solution has good flatness, fine, uniform and dense grains, and strong adhesion to the substrate. The plating solution exhibits good dispersion ability and covering ability, and can deposit a copper coating with excellent brightness, chemical and electrochemical stability. Brighteners and additives must be added to the plating solution to improve the quality and performance of the coating; the plating solution lacking additives is only suitable for parts with a coating thickness not exceeding 1 μm.

[0010] In one embodiment, the main complexing agent includes DTPA, and the auxiliary complexing agent includes succinimide.

[0011] In order to avoid the high toxicity of traditional cyanide electroplating copper, the problem of waste liquid treatment, and the instability of sulfur-containing cyanide-free electroplating copper solutions, the cyanide-free electroplating copper-tin alloy process in this time uses DTPA as the main complexing agent for electroplating copper. Utilizing its hydrolysis mechanism in aqueous solution, the plating solution will ultimately hydrolyze into non-toxic substances whether under acidic or alkaline conditions. Moreover, the synthesis process of DTPA is mature. Although its unit price is slightly higher than that of HEDP, the comprehensive cost can be reduced by 10% - 15% by reducing the dosage of auxiliary additives (such as not requiring various auxiliary agents in the ethylenediamine system). The combined use of the coating additive and DTPA can functionally improve the electroplating copper-tin alloy, improve the throwing power and leveling ability of the plating solution. Although this may slightly reduce the polarization of the plating solution, it can still effectively refine the coating particles, improve the density of the coating, significantly improve the macroscopic morphology of the coating, and enhance the stability of the plating solution. In addition, the DTPA electroplating copper-tin alloy plating solution has high stability, is not easy to deteriorate after long-term use, the plating solution remains clear, and no single substance precipitates, which is an ideal environmentally friendly electroplating copper solution.

[0012] In one embodiment, the conductive salts include: Cu2(C4H6O3)2·3H2O, Sn2(C4H6O3)2, and K4(C4H6O3)2·3H2O.

[0013] In one embodiment, the mass ratio of Cu2(C4H6O3)2·3H2O, Sn2(C4H6O3)2, and K4(C4H6O3)2·3H2O is 2:1:1.

[0014] In one embodiment, the brightener includes at least one of nicotinic acid, indoleacetic acid, polydiaminourea, and ethoxy-2-alkynol ether.

[0015] The addition of the above brightener can make the crystal grains of the coating obtained in the plating solution become fine and dense, greatly improving the microscopic morphology of the coating. Using these brighteners can obtain a golden yellow fully bright coating, significantly improving the brightness effect and uniformity of the coating.

[0016] In one embodiment, the additive includes a surfactant and an accelerator;

[0017] The surfactant includes at least one of sodium dodecyl sulfate, polyethylene glycol, alkylaryl sulfonate, and alkylnaphthalene sulfonate; the accelerator includes at least one of sodium polydithiopropane sulfonate and sodium 3-mercapto-1-propane sulfonate.

[0018] The above surfactant has good dispersion ability and covering ability of the plating solution, and excellent chemical and electrochemical stability. And it can obtain a bright and uniform coating during the cyanide-free electroplating of copper, greatly improving the microscopic morphology and appearance quality of the coating.

[0019] In one embodiment, the mass ratio of the surfactant to the accelerator is 1:(5-7); the accelerator includes sodium polydithiopropane sulfonate and sodium 3-mercapto-1-propane sulfonate, and the mass ratio of sodium polydithiopropane sulfonate to sodium 3-mercapto-1-propane sulfonate is (4-6):1.

[0020] The present invention also provides a method for preparing the cyanide-free electroplating copper solution, including the following steps: heating water, adding a main complexing agent and an auxiliary complexing agent, stirring and dissolving, adding an additive and a brightener to obtain a plating solution, and adjusting the pH value to obtain a cyanide-free electroplating copper solution.

[0021] In one embodiment, the pH value is adjusted to 9-10.

[0022] In one embodiment, when the pH value of the plating solution ≥ 6.9, sulfuric acid is added to lower the pH value to 5.5-6.9 to dissolve the raw materials.

[0023] The present invention also provides the application of the cyanide-free electroplating copper solution in electroplating copper.

[0024] The present invention also provides an electroplating copper method, including the following steps: degreasing, water washing, pickling, water washing, electroplating copper using the cyanide-free electroplating copper solution, and water washing.

[0025] The copper plating process of this patent is similar to the cyanide copper plating process, and the performance of the copper plating layer after copper plating is also comparable to that of the cyanide system. Experimental comparison shows that DTPA has a more prominent effect on the stability of the plating solution and the performance of the coating than other mainstream complexing agents (such as sodium pyrophosphate, EDTA, etc.) at this stage.

[0026] In one embodiment, the current density of the chemical copper plating is 1-2A / dm 2 , the temperature is 30-60℃.

[0027] The invention also provides a plating layer, which is obtained by chemical copper plating using the cyanide-free copper electroplating solution.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] A cyanide-free copper electroplating solution and a preparation method and application thereof of the present invention are provided. The cyanide-free copper electroplating solution has stability, can obtain a copper coating that meets the pre-plating requirements, has good bonding force between the formed coating and the substrate, and also has compactness and weldability. The coating is finely crystallized and semi-glossy, has good dispersibility and deep plating ability, and has better current efficiency than cyanide copper plating, is expected to replace cyanide copper plating, and is verified by salt spray test, humidity, high and low temperature impact and other experiments to meet national military standards. The present invention overcomes the core technology of cyanide-free environmentally friendly copper plating, solves the problem of clean production in the copper plating industry, has a mature technical system, and has good process stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a high-magnification electron microscope image of the coating formed by Formula 1 in Example 2;

[0031] Figure 2 This is a low-magnification electron microscope image of the coating formed by Formula 1 in Example 2. DETAILED DESCRIPTION

[0032] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0034] source:

[0035] Unless otherwise specified, the reagents, materials, and equipment used in this example are all commercially available sources; unless otherwise specified, the test methods are all conventional test methods in this field.

[0036] Example 1

[0037] The cyanide-free electroplating copper solution of this example is prepared according to the following table

[0038] Table 1 Cyanide-free electroplating copper solution, electroplating conditions

[0039]

[0040] Specific preparation method: Each 1 L of cyanide-free copper plating solution consists of the following substances: 50 - 80 g / L of DTPA, 80 - 90 g / L of succinimide, 60 - 70 g / L of conductive salt, 0.1 - 1 g / L of brightener, 0.1 - 1 g / L of additive, and the balance is pure water;

[0041] Heat the pure water to 50 - 55 °C, add 20 - 30 g of succinimide, 50 - 80 g of DTPA, and 60 - 70 g of conductive salt while stirring, stir until completely dissolved, then add 0.1 - 1 g of additive and 0.1 - 1 g of brightener; take 500 ml of the plating solution with a beaker to measure the pH value. If the pH value of the plating solution is greater than 6.9, add sulfuric acid solution to adjust to promote the dissolution of each raw material, and finally add KOH to adjust to make the pH value reach 9.5.

[0042] In this example, the conductive salt is Cu2(C4H6O3)2·3H2O, Sn2(C4H6O3)2, and K4(C4H6O3)2·3H2O, and the mass ratio of Cu2(C4H6O3)2·3H2O, Sn2(C4H6O3)2, and K4(C4H6O3)2·3H2O in the conductive salt is 2:1:1; the brightener is nicotinic acid, and the brightness and deposition rate of nicotinic acid are good, and its carboxylic acid group forms a stable ternary complex with DTPA; the additive includes a surfactant and an accelerator, and the mass ratio of the surfactant to the accelerator is 1:6. The surfactant is sodium dodecyl sulfate, and the wettability of sodium dodecyl sulfate can optimize the dispersion ability of the plating solution. The accelerator is prepared from sodium polydithiopropane sulfonate (SPS) and sodium 3-mercapto-1-propanesulfonate (MPS) according to a mass ratio of 5:1.

[0043] Example 2

[0044] 1. Using the configuration method of Example 1, electroplating copper solutions were prepared according to Formulas 1, 2, and 3 respectively. The main difference lies in the use of different main complexing agents. Formula 3 is a control experiment for the traditional pyrophosphate system with sodium pyrophosphate. Sodium pyrophosphate will undergo a redox reaction with the sulfur-containing accelerator (such as SPS, MPS) in the additive under alkaline conditions. Therefore, there is no additive in Formula 3. Chemical electroplating was carried out under the electroplating conditions of Example 1, and the performance of the obtained coating was verified.

[0045] Formula 1: 60 g of DTPA, 80 g of succinimide, 60 g of conductive salt, 0.1 g of brightener, 0.5 g of additive. It was made up to 1 L of cyanide-free electroplating copper surface treatment material with pure water, and the pH value was adjusted to 9.5. In Formula 1, the concentration of DTPA is 60 g / L, the concentration of succinimide is 80 g / L, the concentration of conductive salt is 60 g / L, the concentration of brightener is 0.1 g / L, and the concentration of additive is 0.5 g / L.

[0046] Formula 2: 80 g of EDTA, 80 g of succinimide, 60 g of conductive salt, 0.1 g of brightener, 0.5 g of additive. It was made up to 1 L of cyanide-free electroplating copper surface treatment material with pure water, and the pH value was adjusted to 9.5. In Formula 2, the concentration of EDTA is 80 g / L, the concentration of succinimide is 80 g / L, the concentration of conductive salt is 60 g / L, the concentration of brightener is 0.1 g / L, and the concentration of additive is 0.5 g / L.

[0047] Formula 3: 100 g of sodium pyrophosphate, 80 g of succinimide, 60 g of conductive salt, 0.1 g of brightener. It was made up to 1 L of cyanide-free electroplating copper surface treatment material with pure water, and the pH value was adjusted to 9.5. In Formula 3, the concentration of sodium pyrophosphate is 100 g / L, the concentration of succinimide is 80 g / L, the concentration of conductive salt is 60 g / L, and the concentration of brightener is 0.1 g / L.

[0048] 2. Performance verification results.

[0049] Table 2 Performance verification results

[0050]

[0051] Note: The corrosion resistance in the above table was verified according to the salt spray test method of the national standard GB / T 10125-2012.

[0052] According to the experimental results, it is concluded that Formula 1 has the best performance. In Formula 2, the coating thickness is uneven, and in Formula 3, the stability of the plating solution performance is poor. The electron microscope image of the coating of Formula 1 is as shown in Figure 1 、 Figure 2 shown, Figure 1It is a high-magnification electron microscope image, which verifies from a microscopic perspective that the coating of Formulation 1 has excellent properties of strong bonding force with the substrate and no cracks / pores; Figure 2 It is a low-magnification electron microscope image, which verifies from a macroscopic perspective that the coating of Formulation 1 has the core technical effect of fine crystallization and semi-gloss.

[0053] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0054] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A cyanide-free electroplating copper solution, characterized in that, Prepared from raw materials with the following concentrations:

2. The cyanide-free copper electroplating solution according to claim 1, wherein The main complexing agent includes DTPA, and the auxiliary complexing agent includes succinimide.

3. The cyanide-free copper electroplating solution according to claim 1, wherein The conductive salts include: Cu2(C4H6O3)2·3H2O, Sn2(C4H6O3)2, and K4(C4H6O3)2·3H2O.

4. The cyanide-free copper electroplating solution according to claim 3, characterized in that, The mass ratio of Cu2(C4H6O3)2·3H2O, Sn2(C4H6O3)2, and K4(C4H6O3)2·3H2O is 2:1:

1.

5. The cyanide-free copper electroplating solution according to claim 1, wherein The brightening agent includes at least one of nicotinic acid, indoleacetic acid, polydiaminourea, and ethoxy-2-ynol ether.

6. The cyanide-free copper electroplating solution according to claim 1, wherein, The additive includes a surfactant and an accelerator; The surfactant includes at least one of sodium dodecyl sulfate, polyethylene glycol, alkylaryl sulfonate, and alkylnaphthalene sulfonate; the accelerator includes at least one of sodium polydithiopropanesulfonate and sodium 3-mercapto-1-propanesulfonate.

7. The cyanide-free copper electroplating solution according to claim 6, wherein, The mass ratio of the surfactant to the accelerator is 1:(5-7); the accelerator includes sodium polydithiopropanesulfonate and sodium 3-mercapto-1-propanesulfonate, and the mass ratio of sodium polydithiopropanesulfonate to sodium 3-mercapto-1-propanesulfonate is (4-6):

1.

8. The preparation method of the cyanide-free copper electroplating solution according to any one of claims 1-7, characterized in that, Including the following steps: heating water, adding the main complexing agent and the auxiliary complexing agent, stirring and dissolving, adding the additive and the brightening agent to obtain a plating solution, and adjusting the pH value to obtain a cyanide-free copper plating solution.

9. Application of the cyanide-free copper plating solution according to any one of claims 1-7 in copper plating.

10. A coating, characterized in that, Obtained by electroless copper plating using the cyanide-free copper plating solution according to any one of claims 1-7.

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