Electroplating gold plating solution and method of electroplating gold and gold plating layer

Abstract

The application relates to the technical field of electroplating gold, and discloses an electroplating gold plating solution, an electroplating gold method and a gold plating layer. The electroplating gold plating solution contains a gold source, a conductive salt, a buffer salt, an organic phosphonic acid compound and a double-sulfur bond containing complexing compound, wherein the organic phosphonic acid compound is selected from one or more than two of hydroxyethylidene diphosphonic acid, aminotri(methylene) phosphonic acid and 2-hydroxyphosphonylethanoic acid; the double-sulfur bond containing complexing compound is selected from one or more than two of polydithiobispropane sulfonic acid sodium, 3-mercapto propane sulfonic acid sodium and dithiodiglycolic acid; and the weight ratio of the gold source, the organic phosphonic acid compound and the double-sulfur bond containing complexing compound is 1:(40-60):(10-40), wherein the amount of the gold source is calculated according to gold elements. The plating solution provides high-quality electroplating effect, improves the performance of the plating layer and the stability of the plating solution, meets the environmental protection requirements, and meets the market demand for efficient and safe electroplating technology.

Description

Technical Field

[0001] This invention relates to the field of gold plating technology, specifically to a gold plating solution, a gold plating method, and a gold plating layer. Background Technology

[0002] In modern industry, electroplating technology is widely used for the decoration and protection of metal surfaces. Among these, gold plating is widely adopted due to its excellent conductivity, corrosion resistance, and aesthetic appeal. Traditional gold plating solutions typically use cyanide as the main component of the formulation. Although cyanide can provide high-quality coatings, its toxicity necessitates strict safety measures during the electroplating process, and the treatment of waste liquid also presents significant challenges.

[0003] Currently, cyanide-free sulfite systems are often used to replace traditional cyanide-containing plating solutions, thereby reducing environmental harm. However, sulfite ions in cyanide-free sulfite systems are easily decomposed, making the plating solution unstable and prone to forming defects during electrodeposition. This results in a rough coating with pores and protrusions, which may affect the electrical properties of the deposited gold. For example, defects may lead to reduced conductivity of the gold coating or poor stability under high-temperature conditions. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of existing technologies, such as the high toxicity of traditional gold plating solutions, the instability of cyanide-free sulfite systems, the susceptibility to defects during electroplating, and the poor electrical properties of the resulting gold plating layer. This invention provides a gold plating solution, a method for gold plating, and a gold plating layer. This solution offers superior electroplating results, improves the performance of the plating layer and the stability of the solution, while meeting environmental protection requirements and satisfying market demand for efficient and safe electroplating technology. The electroplating solution of this invention exhibits good stability, remaining effective even after 7 weeks of storage, and contains no highly toxic metal ions, effectively inhibiting nickel-gold substitution. It boasts excellent environmental and safety performance, achieving cyanide-free electroplating. The resulting gold plating layer is not only bright and undiscolored but also has a uniform appearance, good adhesion, and excellent electrical properties.

[0005] To achieve the above objectives, the present invention provides an electroplating gold plating solution, wherein the electroplating gold plating solution contains a gold source, a conductive salt, a buffer salt, an organophosphonic acid compound, and a disulfide bond-containing coordination compound; wherein the organophosphonic acid compound is selected from one or more of hydroxyethylidene diphosphonic acid, aminotrimethylene phosphonic acid, and 2-hydroxyphosphonoacetic acid; and the disulfide bond-containing coordination compound is selected from one or more of sodium disulfide dipropane sulfonate, sodium 3-mercaptopropane sulfonate, and dithiodiglycolic acid.

[0006] The weight ratio of the gold source, the organophosphonic acid compound, and the disulfide-containing coordination compound is 1:(40-60):(10-40), wherein the amount of the gold source is calculated as gold element.

[0007] Preferably, the concentration of gold ions in the electroplating gold plating solution is 1-20 g / L.

[0008] Preferably, in the electroplating gold plating solution, the concentration of the organophosphonic acid compound is 1-60 g / L.

[0009] Preferably, in the electroplating gold plating solution, the concentration of the disulfide-containing coordination compound is 1-30 g / L.

[0010] Preferably, the concentration of the conductive salt in the electroplating gold plating solution is 40-120 g / L.

[0011] Preferably, the conductive salt is sodium sulfite.

[0012] Preferably, the buffer salt is a combination of citric acid and disodium hydrogen phosphate.

[0013] Preferably, the gold source is sodium gold sulfite.

[0014] Preferably, the organophosphonic acid compound is 2-hydroxyphosphonoacetic acid, and the disulfide-containing coordination compound is sodium polydisulfide dipropane sulfonate.

[0015] Preferably, the weight ratio of the organophosphonic acid compound to the disulfide-containing coordination compound is 1-3:1.

[0016] Preferably, the organophosphonic acid compound is a combination of hydroxyethylidene diphosphate and 2-hydroxyphosphonoacetic acid, and the disulfide-containing coordination compound is a combination of sodium polydisulfide dipropane sulfonate and dithiodiglycolic acid.

[0017] Preferably, the weight ratio of hydroxyethylidene diphosphate to 2-hydroxyphosphonoacetic acid is 1:2-4, and the weight ratio of sodium polydisulfide dipropane sulfonate to dithiodiglycolic acid is 1:2-4.

[0018] Preferably, the weight ratio of the organophosphonic acid compound to the disulfide-containing coordination compound is 4-6:2.

[0019] Preferably, the weight ratio of the gold source, the organophosphonic acid compound, the disulfide-containing coordination compound, and the conductive salt is 1:(40-60):(10-40):(20-90), wherein the amount of the gold source is calculated as gold element.

[0020] Preferably, the pH value of the electroplating gold plating solution is 7-9.

[0021] A second aspect of the present invention provides a method for electroplating gold, the method comprising: immersing a substrate in the electroplating gold plating solution, and then using the substrate as a cathode to conduct electroplating.

[0022] Preferably, the electroplating temperature is 40-70°C.

[0023] Preferably, the current density of the electroplating is 0.1-2 A / dm³. 2 .

[0024] Preferably, the electroplating time is 10-30 minutes.

[0025] Preferably, the substrate is a nickel substrate.

[0026] A third aspect of the present invention provides a gold plating layer, which is obtained by electroplating using the above-described electroplating gold method.

[0027] Preferably, the thickness of the gold plating layer is 0.1-0.3 μm.

[0028] The electroplating gold plating solution of this invention utilizes specific components of organophosphonic acid compounds and disulfide-bonded coordination compounds as complexing agents and dispersants, respectively. This avoids the use of toxic cyanides while effectively improving the stability of the plating solution, resulting in excellent chemical stability. No anti-oxidation measures are required during use, and the solution can operate stably in air. Even after seven weeks of storage, the plating solution does not exhibit turbidity or discoloration and remains effective. Furthermore, the gold plating layer obtained using the electroplating gold plating solution of this invention has fine grains, excellent density and smoothness, good corrosion resistance, and good adhesion to the substrate. The gold plating layer is not only bright but also free of color difference, with low roughness and high gloss. Moreover, the gold plating layer obtained using the electroplating gold plating solution of this invention exhibits excellent electrical properties, a lower corrosion potential, and superior plating properties. Attached Figure Description

[0029] Figure 1 Here is a surface SEM image of the gold plating layer prepared in Example 1;

[0030] Figure 2 Here is a surface SEM image of the gold plating layer prepared in Example 2;

[0031] Figure 3 This is a cross-sectional SEM image of the gold plating obtained in Example 2;

[0032] Figure 4 This is a cross-sectional SEM-EDS image of the gold plating prepared in Example 2;

[0033] Figure 5 This is a surface SEM image of the gold coating prepared in Comparative Example 1;

[0034] Figure 6 This is a surface SEM image of the gold coating prepared in Comparative Example 2;

[0035] Figure 7 This is a surface SEM image of the gold coating prepared in Comparative Example 3;

[0036] Figure 8 This is a surface SEM image of the gold plating layer prepared in Comparative Example 4;

[0037] Figure 9 This is a surface SEM image of the gold coating prepared in Comparative Example 5;

[0038] Figure 10 This is a macroscopic photograph of the gold plating prepared in Comparative Example 6;

[0039] Figure 11 This is a surface SEM image of the gold plating prepared in Comparative Example 6. Detailed Implementation

[0040] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0041] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0042] This invention first provides an electroplating gold plating solution containing a gold source, a conductive salt, a buffer salt, an organophosphonic acid compound, and a disulfide-bonded coordination compound. The organophosphonic acid compound and the disulfide-bonded coordination compound are used as a complexing agent and a dispersant, respectively. The use of these two substances significantly improves the stability of the plating solution. The resulting plating solution remains effective even after 7 weeks of storage without becoming cloudy or discolored. Furthermore, the plating solution described in this invention is more environmentally friendly.

[0043] In this invention, the organophosphonic acid compound is selected from one or more of hydroxyethylidene diphosphate, aminotrimethylene phosphonic acid, and 2-hydroxyphosphonoacetic acid. The organophosphonic acid compound allows for selective adsorption on the metal substrate surface to inhibit the substitution between metal and gold elements during the electroplating of a gold layer using the aforementioned gold plating solution. Once the metal substrate surface is completely covered by electroplated gold, it does not affect the subsequent gold deposition process, thereby avoiding problems such as incomplete plating or poor coating thickness uniformity, improving the uniformity and gloss of the coating surface, and enhancing the electrical properties of the coating.

[0044] In this invention, the disulfide-containing coordination compound is selected from one or more of sodium disulfide dipropane sulfonate, sodium 3-mercaptopropane sulfonate, and dithiodiglycolic acid. The disulfide-containing coordination compound used in this invention can be used to improve the uniformity and density of the electroplated layer.

[0045] In this invention, the synergistic effect between the organophosphonic acid compound and the disulfide-containing coordination compound can effectively improve the density and smoothness of the gold plating layer obtained by the electroplating gold plating solution, and the gold plating layer has good adhesion to the metal substrate, making it less prone to peeling off, thus significantly improving the electrical properties of the obtained gold plating layer.

[0046] In this invention, in order to ensure the stability of the plating solution and improve the density and electrical properties of the subsequently obtained coating, the weight ratio of the gold source, the organophosphonic acid compound and the disulfide-containing coordination compound is further defined as 1:(40-60):(10-40), preferably 1:(42-58):(12-35), more preferably 1:(48-57):(15-30), and even more preferably 1:(50-56):(18-25), wherein the amount of the gold source is calculated as gold element.

[0047] In some preferred embodiments, the organophosphonic acid compound is 2-hydroxyphosphonoacetic acid. In this preferred embodiment, the organophosphonic acid compound can be uniformly adsorbed on the substrate surface, promoting the adsorption and reduction of gold sulfite ions, the orderly deposition of gold atoms, and the resulting dense and smooth gold layer. The disulfide-containing coordination compound is sodium polydisulfide dipropane sulfonate. In this preferred embodiment, the disulfide-containing coordination compound can effectively improve the dispersion of metal ions in the electroplating solution, thereby improving the uniformity and density of the electroplated layer. While maintaining a good dispersion effect, it also has excellent water resistance, which can further improve the corrosion resistance and service life of the electroplated layer.

[0048] In a further preferred embodiment, when the organophosphonic acid compound is 2-hydroxyphosphonoacetic acid and the disulfide-containing coordination compound is sodium disulfide dipropane sulfonate, the weight ratio of the 2-hydroxyphosphonoacetic acid to the sodium disulfide dipropane sulfonate is 1-3:1. Specifically, the weight ratio of the 2-hydroxyphosphonoacetic acid to the sodium disulfide dipropane sulfonate can be 1:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, 2.8:1, or 3:1.

[0049] In some preferred embodiments, the organophosphonic acid compound is a combination of hydroxyethylidene diphosphate and 2-hydroxyphosphonoacetic acid, and the disulfide-containing coordination compound is a combination of sodium polydisulfide dipropane sulfonate and dithiodiglycolic acid.

[0050] In a further preferred embodiment, to further improve the stability of the electroplating gold plating solution, when the organophosphonic acid compound is a combination of hydroxyethylidene diphosphate and 2-hydroxyphosphonoacetic acid, the weight ratio of hydroxyethylidene diphosphate to 2-hydroxyphosphonoacetic acid is 1:2-4; when the disulfide-containing coordination compound is a combination of sodium polydisulfide dipropane sulfonate and dithiodiglycolic acid, the weight ratio of sodium polydisulfide dipropane sulfonate to dithiodiglycolic acid is 1:2-4. Specifically, the weight ratio of hydroxyethylidene diphosphate and 2-hydroxyphosphonoacetic acid can be 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.4, 1:2.5, 1:2.8, 1:3, 1:3.2, 1:3.5, 1:3.8 or 1:4; the weight ratio of sodium polydisulfide dipropane sulfonate and dithiodiglycolic acid can be 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.4, 1:2.5, 1:2.8, 1:3, 1:3.2, 1:3.5, 1:3.8 or 1:4.

[0051] In a further preferred embodiment, when the organophosphonic acid compound is a combination of hydroxyethylidene diphosphate and 2-hydroxyphosphonoacetic acid, and the disulfide-containing coordination compound is a combination of sodium polydisulfide dipropanesulfonate and dithiodiglycolic acid, the weight ratio of the organophosphonic acid compound to the disulfide-containing coordination compound is 4-6:2. Specifically, the weight ratio of the organophosphonic acid compound to the disulfide-containing coordination compound can be 4:2, 4.2:2, 4.4:2, 4.8:2, 5:2, 5.2:2, 5.5:2, 5.8:2, or 6:2.

[0052] In some embodiments, the gold source is sodium gold sulfite. More preferably, the concentration of gold ions in the electroplating gold plating solution is 1-20 g / L, more preferably 1-10 g / L. When the concentration of gold ions in the electroplating gold plating solution is less than 1 g / L, the cathode deposition efficiency will be too low, and the electroplating solution will become unstable, with gold easily depositing in the plating solution rather than on the cathode surface. When the concentration of gold ions in the electroplating gold plating solution is greater than 20 g / L, although it does not affect the stability of the electroplating solution or the appearance and physical properties of the coating, the gold is wasted due to the carry-over of the plating solution after the plating is completed, leading to increased costs.

[0053] In some preferred embodiments, the concentration of the organophosphonic acid compound in the gold plating solution is 1-60 g / L, preferably 30-50 g / L. In this invention, when the concentration of the organophosphonic acid compound in the gold plating solution is within the range defined by this invention, the density and smoothness of the gold plating layer obtained using the gold plating solution can be further improved, and the stability of the gold plating solution can be further improved. When the concentration of the organophosphonic acid in the gold plating solution is greater than 60 g / L, the complexation ability between the organophosphonic acid compound and monovalent gold will be strengthened, resulting in an overly dense electroplated film, which may cause poor soldering. When the concentration of the organophosphonic acid compound is less than 1 g / L, it will affect the stability of the gold plating solution and cause the gold plating layer to become rough.

[0054] In some preferred embodiments, the concentration of the disulfide-containing coordination compound in the electroplating gold plating solution is 1-30 g / L, preferably 10-20 g / L. In this invention, when the concentration of the disulfide-containing coordination compound in the electroplating gold plating solution is within the range defined by this invention, it ensures better adhesion between the gold plating layer obtained using the gold plating solution of this invention and the substrate. Furthermore, when the concentration of the disulfide-containing coordination compound is greater than 30 g / L, it will lead to the doping of sulfur elements into the gold plating layer obtained using the electroplating gold plating solution, causing embrittlement of the gold plating layer and a decrease in adhesion.

[0055] In this invention, the conductive salt is sodium sulfite.

[0056] In some preferred embodiments, the weight ratio of the gold source, the organophosphonic acid compound, the disulfide-containing coordination compound, and the conductive salt is 1:(40-60):(10-40):(20-90), preferably 1:(42-58):(12-35):(40-80), more preferably 1:(48-57):(15-30):(50-75), and even more preferably 1:(50-56):(18-25):(60-72), wherein the amount of the gold source is based on the elemental gold.

[0057] In some preferred embodiments, the concentration of the conductive salt in the gold plating solution is 40-120 g / L, preferably 50-80 g / L. In this embodiment, limiting the concentration of the conductive salt can further improve the stability of the plating solution and the uniformity of the plating layer during the electroplating process. When the concentration of the conductive salt in the gold plating solution is less than 40 g / L, the uniformity of the plating layer will decrease, the controllable current density during the electroplating process will be low, and it may even lead to decomposition of the plating solution and poor stability of the plating solution.

[0058] In this invention, the composition of the buffer salt is not limited. More preferably, the buffer salt is a combination of citric acid and disodium hydrogen phosphate, and the weight ratio of the citric acid to the disodium hydrogen phosphate in the buffer salt is 1:5-7.

[0059] In this invention, the pH value of the electroplating gold solution is 7-9. To further improve the stability of the electroplating gold solution, the pH value of the solution is maintained near weak acidity or neutrality, i.e., the pH value of the solution is limited to 7-9. When the pH of the electroplating gold solution is below 7, the long-term stability of the solution deteriorates. When the pH of the solution is above 9.0, the photoresist dissolves or undergoes seepage, and the coating appearance becomes uneven due to the difficulty in reducing gold.

[0060] According to some embodiments of the present invention, the electroplating gold plating solution contains a gold source, a conductive salt, a buffer salt, an organophosphonic acid compound, and a disulfide-containing coordination compound; the weight ratio of the gold source, the organophosphonic acid compound, and the disulfide-containing coordination compound is 1:(40-60):(10-40), wherein the amount of the gold source is calculated as gold element; the organophosphonic acid compound is 2-hydroxyphosphonoacetic acid, and the disulfide-containing coordination compound is sodium polydisulfide dipropane sulfonate.

[0061] According to other embodiments of the present invention, the electroplating gold plating solution contains a gold source, a conductive salt, a buffer salt, an organophosphonic acid compound, and a disulfide-containing coordination compound; the weight ratio of the gold source, the organophosphonic acid compound, and the disulfide-containing coordination compound is 1:(40-60):(10-40), wherein the amount of the gold source is calculated based on gold element; the organophosphonic acid compound is 2-hydroxyphosphonoacetic acid, and the disulfide-containing coordination compound is sodium polydisulfide dipropane sulfonate; the weight ratio of the organophosphonic acid compound and the disulfide-containing coordination compound is 1-3:1.

[0062] According to other embodiments of the present invention, the electroplating gold plating solution contains a gold source, a conductive salt, a buffer salt, an organophosphonic acid compound, and a disulfide-bonded coordination compound; the weight ratio of the gold source, the organophosphonic acid compound, and the disulfide-bonded coordination compound is 1:(40-60):(10-40), wherein the amount of the gold source is calculated as gold element; the organophosphonic acid compound is 2-hydroxyphosphonoacetic acid, and the disulfide-bonded coordination compound is sodium polydisulfide dipropanesulfonate; the weight ratio of the organophosphonic acid compound and the disulfide-bonded coordination compound is 1-3:1; in the electroplating gold plating solution, the concentration of gold ions is 1-20 g / L, the concentration of the organophosphonic acid compound is 1-60 g / L, the concentration of the disulfide-bonded coordination compound is 1-30 g / L, and the concentration of the conductive salt is 40-120 g / L.

[0063] According to other embodiments of the present invention, the electroplating gold plating solution contains a gold source, a conductive salt, a buffer salt, an organophosphonic acid compound, and a disulfide-containing coordination compound; the weight ratio of the gold source, the organophosphonic acid compound, and the disulfide-containing coordination compound is 1:(40-60):(10-40), wherein the amount of the gold source is based on gold element; the organophosphonic acid compound is 2-hydroxyphosphonoacetic acid, and the disulfide-containing coordination compound is sodium polydisulfide dipropane sulfonate; the weight ratio of the organophosphonic acid compound and the disulfide-containing coordination compound is... The weight ratio is 1-3:1; the weight ratio of the gold source, the organophosphonic acid compound, the disulfide-containing coordination compound, and the conductive salt is 1:(40-60):(10-40):(20-90), wherein the amount of the gold source is calculated as gold element; in the electroplating gold plating solution, the concentration of gold ions in the electroplating gold plating solution is 1-20 g / L, the concentration of the organophosphonic acid compound is 1-60 g / L, the concentration of the disulfide-containing coordination compound is 1-30 g / L, and the concentration of the conductive salt is 40-120 g / L.

[0064] According to other embodiments of the present invention, the electroplating gold plating solution contains a gold source, a conductive salt, a buffer salt, an organophosphonic acid compound, and a disulfide-containing coordination compound; the weight ratio of the gold source, the organophosphonic acid compound, and the disulfide-containing coordination compound is 1:(40-60):(10-40), wherein the amount of the gold source is based on the elemental gold; the organophosphonic acid compound is a combination of hydroxyethylidene diphosphate and 2-hydroxyphosphonoacetic acid, and the disulfide-containing coordination compound is a combination of sodium polydisulfide dipropane sulfonate and dithiodiglycolic acid.

[0065] According to other embodiments of the present invention, the electroplating gold plating solution contains a gold source, a conductive salt, a buffer salt, an organophosphonic acid compound, and a disulfide-containing coordination compound; the weight ratio of the gold source, the organophosphonic acid compound, and the disulfide-containing coordination compound is 1:(40-60):(10-40), wherein the amount of the gold source is based on gold element; the organophosphonic acid compound is a combination of hydroxyethylidene diphosphate and 2-hydroxyphosphonoacetic acid, the disulfide-containing coordination compound is a combination of sodium polydisulfide dipropanesulfonate and dithiodiglycolic acid, and the weight ratio of the organophosphonic acid compound and the disulfide-containing coordination compound is 4-6:2.

[0066] According to other embodiments of the present invention, the electroplating gold plating solution contains a gold source, a conductive salt, a buffer salt, an organophosphonic acid compound, and a disulfide-bonded coordination compound; the weight ratio of the gold source, the organophosphonic acid compound, and the disulfide-bonded coordination compound is 1:(40-60):(10-40), wherein the amount of the gold source is based on gold element; the organophosphonic acid compound is a combination of hydroxyethylidene diphosphate and 2-hydroxyphosphonoacetic acid, with a weight ratio of hydroxyethylidene diphosphate and 2-hydroxyphosphonoacetic acid of 1:2-4; the disulfide-bonded coordination compound is a combination of sodium polydisulfide dipropane sulfonate and dithiodiglycolic acid, with a weight ratio of sodium polydisulfide dipropane sulfonate and dithiodiglycolic acid of 1:2-4.

[0067] According to other embodiments of the present invention, the electroplating gold plating solution contains a gold source, a conductive salt, a buffer salt, an organophosphonic acid compound, and a disulfide-containing coordination compound; the weight ratio of the gold source, the organophosphonic acid compound, and the disulfide-containing coordination compound is 1:(40-60):(10-40), wherein the amount of the gold source is based on gold element; the organophosphonic acid compound is a combination of hydroxyethylidene diphosphate and 2-hydroxyphosphonoacetic acid, with a weight ratio of hydroxyethylidene diphosphate and 2-hydroxyphosphonoacetic acid of 1:2-4; the disulfide-containing coordination compound is a combination of sodium polydisulfide dipropane sulfonate and dithiodiglycolic acid, with a weight ratio of sodium polydisulfide dipropane sulfonate and dithiodiglycolic acid of 1:2-4; the weight ratio of the organophosphonic acid compound and the disulfide-containing coordination compound is 4-6:2.

[0068] According to other embodiments of the present invention, the electroplating gold plating solution contains a gold source, a conductive salt, a buffer salt, an organophosphonic acid compound, and a disulfide-bonded coordination compound; the weight ratio of the gold source, the organophosphonic acid compound, and the disulfide-bonded coordination compound is 1:(40-60):(10-40), wherein the amount of the gold source is based on gold element; the organophosphonic acid compound is a combination of hydroxyethylidene diphosphate and 2-hydroxyphosphonoacetic acid, and the weight ratio of hydroxyethylidene diphosphate to 2-hydroxyphosphonoacetic acid is 1:2. -4; the disulfide-containing coordination compound is a combination of sodium disulfide dipropane sulfonate and dithiodiglycolic acid, with a weight ratio of sodium disulfide dipropane sulfonate to dithiodiglycolic acid of 1:2-4; the weight ratio of the organophosphonic acid compound to the disulfide-containing coordination compound is 4-6:2; in the electroplating gold plating solution, the concentration of gold ions in the electroplating gold plating solution is 1-20 g / L, the concentration of the organophosphonic acid compound is 1-60 g / L, and the concentration of the disulfide-containing coordination compound is 1-30 g / L.

[0069] According to other embodiments of the present invention, the electroplating gold plating solution contains a gold source, a conductive salt, a buffer salt, an organophosphonic acid compound, and a disulfide-bonded coordination compound; the weight ratio of the gold source, the organophosphonic acid compound, and the disulfide-bonded coordination compound is 1:(40-60):(10-40), wherein the amount of the gold source is based on gold element; the organophosphonic acid compound is a combination of hydroxyethylidene diphosphate and 2-hydroxyphosphonoacetic acid, and the weight ratio of hydroxyethylidene diphosphate to 2-hydroxyphosphonoacetic acid is 1:2. -4; the disulfide-containing coordination compound is a combination of sodium disulfide dipropane sulfonate and dithiodiglycolic acid, with a weight ratio of sodium disulfide dipropane sulfonate to dithiodiglycolic acid of 1:2-4; the weight ratio of the organophosphonic acid compound to the disulfide-containing coordination compound is 4-6:2; the weight ratio of the gold source, the organophosphonic acid compound, the disulfide-containing coordination compound, and the conductive salt is 1:(40-60):(10-40):(20-90), wherein the amount of the gold source is calculated as gold element.

[0070] According to other embodiments of the present invention, the electroplating gold plating solution contains a gold source, a conductive salt, a buffer salt, an organophosphonic acid compound, and a disulfide-containing coordination compound; the weight ratio of the gold source, the organophosphonic acid compound, and the disulfide-containing coordination compound is 1:(40-60):(10-40), wherein the amount of the gold source is based on gold element; the organophosphonic acid compound is a combination of hydroxyethylidene diphosphate and 2-hydroxyphosphonoacetic acid, and the weight ratio of hydroxyethylidene diphosphate and 2-hydroxyphosphonoacetic acid is 1:2-4; the disulfide-containing coordination compound is a combination of sodium polydisulfide dipropane sulfonate and dithiodiglycolic acid, and the weight ratio of sodium polydisulfide dipropane sulfonate and dithiodiglycolic acid is 1:2-4. The weight ratio of the diglycolic acid is 1:2-4; the weight ratio of the organophosphonic acid compound to the disulfide-containing coordination compound is 4-6:2; the weight ratio of the gold source, the organophosphonic acid compound, the disulfide-containing coordination compound, and the conductive salt is 1:(40-60):(20-40):(20-90), wherein the amount of the gold source is calculated as gold element; in the electroplating gold plating solution, the concentration of gold ions in the electroplating gold plating solution is 1-20 g / L, the concentration of the organophosphonic acid compound is 1-60 g / L, the concentration of the disulfide-containing coordination compound is 1-30 g / L, and the concentration of the conductive salt is 40-120 g / L.

[0071] The present invention further provides a method for electroplating gold, the method comprising: immersing a substrate in the electroplating gold plating solution, and then using the substrate as a cathode to pass an electric current for electroplating.

[0072] In the method described in this invention, in order to ensure the stability of the electroplating solution and the uniformity of the coating appearance, it is necessary to further limit the temperature during electroplating, that is, limit the electroplating temperature to 35-60℃. When the electroplating temperature is higher than 70℃, some of the plating solution will decompose, and at the same time, because the plating solution evaporates too quickly, the properties of the electroplating solution will become unstable.

[0073] In some preferred embodiments, to ensure the stability of the plating solution and the uniformity and adhesion of the plating layer during the electroplating process, the current density for electroplating is limited to 0.1-2 A / dm³. 2 When the current density exceeds the above range, the plating solution may decompose or the coating may become uneven in appearance.

[0074] In some preferred embodiments, the electroplating time is 10-30 minutes.

[0075] In the method described in this invention, the substrate is a metal substrate, preferably a nickel substrate.

[0076] In this invention, the specific process of the electroplating gold method includes: pretreating the substrate, then immersing it in the electroplating gold plating solution, and then using the pretreated substrate as a cathode to perform electroplating.

[0077] Specifically, the pretreatment process includes: degreasing and activation treatment of the substrate to ensure that the substrate surface is clean and free of contamination, which is conducive to good adhesion of the gold plating layer.

[0078] In some embodiments, the specific operation process of the pretreatment includes: washing the substrate with water, then performing ultrasonic degreasing in an environmentally friendly cleaning agent for 30 seconds, then washing with water again, then immersing the washed substrate in sulfuric acid with a concentration of 2-5%wt for 20 seconds, and then washing the immersed substrate with water.

[0079] This invention also provides a gold plating layer obtained by the electroplating method described above using the electroplating gold plating solution of this invention. This gold plating layer is denser and possesses excellent electrical properties and gloss, with a smooth surface free of depressions and protrusions. It exhibits lower roughness and superior plating properties. Furthermore, the thickness of the gold plating layer can be adjusted by precisely controlling the electroplating time and current density in the electroplating method. In some preferred embodiments, the thickness of the gold plating layer is 0.1-0.3 μm.

[0080] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto.

[0081] The concentrations of each component and electroplating process conditions in the electroplating gold plating solutions obtained in the following examples and comparative examples are shown in Table 1.

[0082] Example 1

[0083] Sodium polydisulfide dipropane sulfonate and 2-hydroxyphosphonoacetic acid were completely dissolved in water. The pH of the mixture was then adjusted to 7. A buffer solution (citric acid and disodium hydrogen phosphate) was added and completely dissolved. Sodium gold sulfite and anhydrous sodium sulfite were then added and dissolved, with stirring performed at room temperature (25°C). The pH of the resulting solution was adjusted to 7 to obtain the gold plating solution.

[0084] The nickel substrate is washed with water, then ultrasonically degreased in an environmentally friendly cleaning agent for 30 seconds, and then washed with water again. The washed substrate is then immersed in sulfuric acid with a concentration of 3%wt for 1 minute, and then washed with water again to obtain a pretreated nickel plate. The pretreated nickel plate is then immersed in the electroplating gold plating solution as a cathode for electroplating.

[0085] Example 2

[0086] Sodium polydisulfide dipropane sulfonate and 2-hydroxyphosphonoacetic acid were completely dissolved in water. The pH of the mixture was then adjusted to 7. A buffer solution (citric acid and disodium hydrogen phosphate) was added and completely dissolved. Sodium gold sulfite and anhydrous sodium sulfite were then added and dissolved, with stirring performed at room temperature (25°C). The pH of the resulting solution was adjusted to 7 to obtain the gold plating solution.

[0087] The nickel substrate is washed with water, then ultrasonically degreased in an environmentally friendly cleaning agent for 30 seconds, and then washed with water again. The washed substrate is then immersed in sulfuric acid with a concentration of 3%wt for 20 seconds, and then washed with water again to obtain a pretreated nickel plate. The pretreated nickel plate is then immersed in the electroplating gold plating solution as a cathode for electroplating.

[0088] Example 3

[0089] Sodium polydisulfide dipropane sulfonate and 2-hydroxyphosphonoacetic acid were completely dissolved in water. The pH of the mixture was then adjusted to 8. A buffer solution (citric acid and disodium hydrogen phosphate) was added and completely dissolved. Sodium gold sulfite and anhydrous sodium sulfite were then added and dissolved, with stirring performed at room temperature (25°C). The pH of the resulting solution was adjusted to 8 to obtain the gold plating solution.

[0090] The nickel substrate is washed with water, then ultrasonically degreased in an environmentally friendly cleaning agent for 30 seconds, and then washed with water again. The washed substrate is then immersed in sulfuric acid with a concentration of 3%wt for 20 seconds, and then washed with water again to obtain a pretreated nickel plate. The pretreated nickel plate is then immersed in the electroplating gold plating solution as a cathode for electroplating.

[0091] Example 4

[0092] The method was implemented according to Example 1, except that hydroxyethylidene diphosphate was replaced with a combination of hydroxyethylidene diphosphate and 2-hydroxyphosphonoacetic acid, and the concentration of hydroxyethylidene diphosphate was 12.5 g / L and the concentration of 2-hydroxyphosphonoacetic acid was 37.5 g / L; sodium polydisulfide dipropane sulfonate was replaced with a combination of sodium polydisulfide dipropane sulfonate and dithiodiglycolic acid, and the concentration of sodium polydisulfide dipropane sulfonate was 0.5 g / L and the concentration of dithiodiglycolic acid was 1.5 g / L.

[0093] Example 5

[0094] The method is the same as in Example 2, except that 2-hydroxyphosphonoacetic acid is replaced with an equal weight of hydroxyethylidene diphosphonic acid.

[0095] Example 6

[0096] The method is the same as in Example 3, except that 2-hydroxyphosphonoacetic acid is replaced with an equal weight of hydroxyethylidene diphosphonic acid.

[0097] Example 7

[0098] The method is the same as in Example 1, except that sodium polydithiopropane sulfonate is replaced with an equal weight of dithiodiglycolic acid.

[0099] Comparative Example 1

[0100] The method described in Example 1 was implemented, except that the electroplating gold plating solution did not contain 2,2'-thiodiacetic acid and 2-hydroxyphosphonoacetic acid.

[0101] Comparative Example 2

[0102] The method was implemented according to Example 1, except that the 2-hydroxyphosphonoacetic acid in the electroplating gold plating solution was replaced with an equal weight of sodium polydisulfide dipropane sulfonate.

[0103] Comparative Example 3

[0104] The method of Example 1 was implemented, except that the sodium polydisulfide dipropane sulfonate in the electroplating gold plating solution was replaced with an equal weight of 2-hydroxyphosphonoacetic acid.

[0105] Comparative Example 4

[0106] The method was implemented according to Example 2, except that the 2-hydroxyphosphonoacetic acid in the electroplating gold plating solution was replaced with hexamethylenediaminetetramethylenephosphonic acid.

[0107] Comparative Example 5

[0108] The method was implemented according to Example 2, except that the sodium polydithiodipropane sulfonate in the electroplating gold plating solution was replaced with an equal weight of 2,2'-thiodiacetic acid.

[0109] Comparative Example 6

[0110] Electroplating was performed using a commercially available gold plating solution (CT-288A 24K cyanide-free environmentally friendly pure gold plating solution, purchased from Tianyue New Materials). The plating parameters were as follows: operating temperature 55℃, current density 0.2A / dm³. 2 The electroplating speed is 1A / h / 0.5g, the stirring rate is greater than 5cm / sec, the anode electrode is a platinum titanium mesh, and the pH value of the electroplating solution is 8.

[0111] Table 1

[0112]

[0113] Test case

[0114] Test Example 1

[0115] The surface and cross-sectional morphology of the gold coatings obtained in Examples 1 and 2 were tested using SEM, and the test results are as follows: Figures 1 to 4 As shown, where Figure 1 and Figure 2 These are the surface morphologies of the gold plating layers prepared in Examples 1 and 2, respectively. Figure 3 This is the cross-sectional morphology of the gold plating prepared in Example 1. Figure 4 This is an EDS image of the gold plating surface prepared in Example 1.

[0116] according to Figure 1 and Figure 2 It can be seen that the plating layer obtained using the electroplating gold plating solution described in this invention has a uniform surface and good density. Furthermore, through… Figure 3 It can be seen that the cross-section of the gold plating layer is dense and the thickness is 0.1 μm.

[0117] In addition, the elemental content of the gold plating obtained in Example 2 was tested by SEM-EDS elemental analysis, and the test results are shown in Table 2.

[0118] Table 2

[0119]

[0120] The results in Table 2 show that the gold content of the gold plating meets the requirements and is free of sulfur, which would cause the gold plating to become brittle.

[0121] Test Example 2

[0122] The surface morphology of the coatings obtained in Comparative Examples 1-5 was tested using SEM, and the test results are as follows: Figures 5 to 9 As shown.

[0123] Among them, according to Figures 5 to 9 It can be seen that the gold coatings prepared in Comparative Examples 1-5 have rough surfaces and poor density.

[0124] The coating prepared in Comparative Example 6 was observed, and its macroscopic photograph is shown below. Figure 10 As shown, by Figure 10 It can be seen that the coating obtained using commercially available gold plating solution has poor adhesion to the substrate, with half of the coating peeling off. SEM was used to test the surface morphology of the remaining areas, and the results are as follows: Figure 11 As shown, according to Figure 11 The results show that the plating obtained by electroplating with commercially available electroplating solution has poor density and many depressions.

[0125] Test Example 3

[0126] The corrosion potential, gloss, and roughness of the gold coatings obtained from the test examples and comparative examples are shown in Table 3.

[0127] Corrosion potential: The Cu / Ni / Au layer in 3.5 wt% NaCl solution was analyzed using an Autolab electrochemical workstation (Pgstat302n, Metrohm, Switzerland). The electrolytic cell was cylindrical, and the working electrode had an area of ​​2×2 cm². 2 The Cu / Ni / Au layer was placed in a 3.5 wt% NaCl solution before each experiment, and the open-circuit potential displayed on the workstation was observed. The experiment could only begin after the open-circuit potential stabilized. A platinum sheet electrode with a diameter of 20 mm × 20 mm and a saturated calomel electrode (SCE) were used as the counter electrode and reference electrode, respectively.

[0128] Gloss: The gloss of five points (top, middle, bottom, left, and right) of the 2×2 coating was measured using an LS192 gloss meter, and the average value was taken.

[0129] Roughness: The coating was tested three times each in the transverse and longitudinal directions using a TR200 MAX surface roughness measuring instrument, and the average value was taken.

[0130] Table 3

[0131]

[0132] According to the results in Table 3, the coating obtained by using the electroplating gold plating solution of the present invention has a uniform and dense surface and better adhesion to the substrate. In addition, the coating obtained by electroplating with the electroplating gold plating solution of the present invention also has a lower corrosion potential, higher gloss and lower roughness.

[0133] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An electroplating gold plating solution, characterized in that, The electroplating gold plating solution contains a gold source, a conductive salt, a buffer salt, an organic phosphonic acid compound and a disulfide bond-containing complexing compound, wherein the organic phosphonic acid compound is selected from one or more than two of hydroxyethylidene diphosphonic acid, amino-tris-methylene phosphonic acid and 2-hydroxyphosphonocetic acid; the disulfide bond-containing complexing compound is selected from one or more than two of polydithiodipropyl sulfone sodium and dithiodiglycolic acid; The weight ratio of the gold source, the organic phosphonic acid compound and the disulfide bond-containing complexing compound is 1:(40-60):(10-40), wherein the amount of the gold source is calculated based on gold element. The conductive salt is sodium sulfite, the buffer salt is a combination of citric acid and disodium hydrogen phosphate, the gold source is sodium sulfite gold, and the pH value of the electroplating gold plating solution is 7-9.

2. The electro-gold plating solution of claim 1, wherein, The concentration of gold ions in the electroplating gold plating solution is 1-20 g / L; and / or The concentration of the organic phosphonic acid compound in the electroplating gold plating solution is 1-60 g / L; and / or The concentration of the disulfide bond-containing complexing compound in the electroplating gold plating solution is 1-30 g / L; and / or The concentration of the conductive salt in the electroplating gold plating solution is 40-120 g / L.

3. The electro-gold plating solution of claim 1, wherein, The organic phosphonic acid compound is 2-hydroxyphosphonocetic acid, and the disulfide bond-containing complexing compound is polydithiodipropyl sulfone sodium.

4. The electro-gold plating solution of claim 3, wherein, The weight ratio of the organic phosphonic acid compound and the disulfide bond-containing complexing compound is 1-3:

1.

5. The electro-gold plating solution of claim 1, wherein, The organic phosphonic acid compound is hydroxyethylidene diphosphonic acid and 2-hydroxyphosphonocetic acid, and the disulfide bond-containing complexing compound is polydithiodipropyl sulfone sodium and dithiodiglycolic acid.

6. The electro-gold plating solution of claim 5, wherein, The weight ratio of hydroxyethylidene diphosphonic acid and 2-hydroxyphosphonocetic acid is 1:2-4, and the weight ratio of polydithiodipropyl sulfone sodium and dithiodiglycolic acid is 1:2-4; and / or The weight ratio of the organic phosphonic acid compound and the disulfide bond-containing complexing compound is 4-6:

2.

7. The electro-gold plating solution according to any one of claims 1 to 2, wherein, The weight ratio of the gold source, the organic phosphonic acid compound, the disulfide bond-containing complexing compound and the conductive salt is 1:(40-60):(10-40):(20-90), wherein the amount of the gold source is calculated based on gold element.

8. A method of electroplating gold, characterized by, The method comprises: immersing a substrate in the electroplating gold plating solution according to any one of claims 1-7, and then electroplating the substrate as a cathode after being powered.

9. The electro-gold-plating method according to claim 8, characterized in that, The temperature of the electroplating is 40-70℃; and / or The current density for the electroplating is 0.1-2 A / dm 2 ; and / or The time of the electroplating is 10-30 min; and / or The substrate is a nickel substrate.

10. A gold plating layer characterized by comprising: The gold plating layer is obtained by electroplating using the electroplating gold method according to claim 8 or 9.

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