Mercaptosulfonic acid cyanide-free gold plating electroplating solution as well as preparation method and application thereof

Abstract

The invention discloses a sulfydryl sulfonic acid cyanide-free gold-plating electroplating solution and a preparation method and application thereof, and belongs to the technical field of electroplating, the sulfydryl sulfonic acid cyanide-free gold-plating electroplating solution comprises a gold source, a complexing agent, an additive and a pH buffering agent; the gold source is gold mercaptosulfonate; and the pH value of the mercaptosulfonic acid cyanide-free gold plating electroplating solution is 2-13. The sulfydryl sulfonic acid cyanide-free gold-plating electroplating solution provided by the invention does not contain extremely toxic substances, and the adopted sulfydryl sulfonic acid gold salt has higher stability, so that the sulfydryl sulfonic acid cyanide-free gold-plating electroplating solution has higher stability and longer service life; and even after high and low temperature change, illumination, long-time storage or long-time electroplating, the clear and transparent state and the same electroplating effect are still kept, so that the performance of the electroplated gold-plated part is effectively guaranteed, the purity of the gold-plated part is greater than 99.9%, and the gold-plated part is good in bonding property, low in porosity, flat, compact, golden and bright in appearance and beneficial to being applied to manufacturing of electronic devices and semiconductors.

Description

Technical Field

[0001] The invention relates to the technical field of electroplating, and more specifically to a mercaptosulfonic acid cyanide-free gold plating solution and a preparation method and application thereof. Background Art

[0002] Gold has extremely high chemical stability, good electrical conductivity, thermal conductivity, oxidation resistance, corrosion resistance, high temperature resistance, wear resistance, brightness, anti-discoloration, solderability and low contact resistance, and can be hot-pressed bonded. Its gold-plated parts have a wide range of applications in electronic devices and semiconductor manufacturing.

[0003] The traditional gold plating process usually uses the cyanide gold plating system. Although it has the advantages of high stability, long service life, and excellent performance of gold-plated parts, cyanide is a highly toxic substance and does not meet the requirements of green electroplating and sustainable development. Therefore, the non-toxic and pollution-free cyanide-free gold plating system is gradually replacing the cyanide gold plating system.

[0004] However, the currently used cyanide-free gold plating system still has the following two problems: First, the gold plating solution has low stability and short service life. The Chinese patents with publication numbers CN109881223A and CN105441996A disclose sulfurous acid system gold plating solution and thiosulfate system gold plating solution respectively. However, both sulfite ions and thiosulfate ions have the problem of easy decomposition, causing gold ions to lose ligands, disproportionation reaction to generate gold precipitation, resulting in failure of the gold plating solution. Second, the performance of gold-plated parts is poor. The Chinese patents with publication numbers CN105401180A and CN101906649A disclose succinimide system gold plating solution and hydantoin system gold plating solution respectively. The coordination bonds formed between succinimide and hydantoin and gold ions are weak, thereby reducing the polarization during electroplating, affecting the crystallinity of the gold-plated parts, and causing the purity, bonding, porosity, flatness, density, brightness and other properties of the gold-plated parts to decrease. In addition, in order to ensure the stability of the cyanide-free gold plating solution and the performance of the gold-plated parts, it is usually necessary to add a variety of complexing agents. However, some complexing agents will participate in the electrochemical reaction during the electroplating process or undergo self-decomposition reactions and become ineffective, reducing the stability of the cyanide-free gold plating solution, or the coordination effect of the complexing agent is too strong and side reactions occur, affecting the performance of the gold-plated parts. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects of the prior art, provide a mercaptosulfonic acid cyanide-free gold plating solution and a preparation method and application thereof, utilize the synergistic effect between mercaptosulfonic acid gold salt and complexing agent, additive and pH buffer that do not contain highly toxic substances, improve the stability and service life of the gold plating solution, and effectively improve the performance of the gold-plated parts.

[0006] To achieve the above object, the technical solution of the present invention is as follows: A mercaptosulfonic acid cyanide-free gold plating electroplating solution, comprising a gold source, a complexing agent, an additive and a pH buffer; the gold source is mercaptosulfonic acid gold salt; the pH of the mercaptosulfonic acid cyanide-free gold plating electroplating solution is 2-13; the preparation method of the mercaptosulfonic acid gold salt comprises the following steps: (1) dissolving gold in aqua regia, and adding deionized water to the obtained syrupy solution to remove nitrogen oxides, thereby obtaining a chloroauric acid solution, and adjusting the pH of the chloroauric acid solution to 6-7 using a pH buffer to obtain a first reaction solution; (2) dissolving the mercaptosulfonate in deionized water, and adjusting the pH of the solution to 9-13 using a pH buffer to obtain a second reaction solution; (3) Mixing the first reaction solution and the second reaction solution to obtain the mercaptosulfonate gold salt.

[0007] Furthermore, in step (3), the molar concentration ratio of the gold ions in the first reaction solution to the mercaptosulfonate in the second reaction solution is 1:5 to 1:15. Specifically, if the molar concentration ratio is lower than 1:5, the obtained mercaptosulfonate gold salt has low stability and is prone to gold precipitation. If the molar concentration ratio is higher than 1:15, the cost is increased.

[0008] Further, the amount of the gold source is such that the molar concentration of gold ions in the mercaptosulfonic acid cyanide-free gold plating solution is 0.03mol / L to 0.20mol / L. Preferably, the amount of the gold source is such that the molar concentration of gold ions in the mercaptosulfonic acid cyanide-free gold plating solution is 0.03mol / L to 0.12mol / L.

[0009] Further, the concentration of the additive in the mercaptosulfonic acid cyanide-free gold plating electroplating solution is 0.10 g / L to 5.00 g / L. Preferably, the concentration of the additive in the mercaptosulfonic acid cyanide-free gold plating electroplating solution is 0.80 g / L to 1.50 g / L.

[0010] Further, the molar concentration ratio of the gold ions in the mercaptosulfonic acid cyanide-free gold plating electroplating solution to the complexing agent is 1:2 to 1:40. Specifically, if the molar concentration ratio is lower than 1:2, the stability and service life of the mercaptosulfonic acid cyanide-free gold plating electroplating solution cannot meet the requirements, and if the molar concentration ratio is higher than 1:40, the mercaptosulfonic acid cyanide-free gold plating electroplating solution is prone to precipitating crystals, thereby affecting the performance of the gold-plated parts. Preferably, the molar concentration ratio of the gold ions in the mercaptosulfonic acid cyanide-free gold plating electroplating solution to the complexing agent is 1:4 to 1:20.

[0011] Furthermore, the complexing agent includes at least one of hydantoin, organic amine and amino acid. Specifically, the addition of the complexing agent can further improve the stability and service life of the mercaptosulfonic acid cyanide-free gold plating solution, making the performance of the gold-plated parts obtained by electroplating more excellent.

[0012] Optionally, in step (2), the mercaptosulfonate includes at least one of 2-mercaptoethanesulfonate, 3-mercapto-1-propanesulfonate, 2,3-dimercaptopropanesulfonate, 4-mercapto-1-butanesulfonate, 3,4-dimercaptobutanesulfonate, and 2,4-dimercaptobutanesulfonate.

[0013] Specifically, mercaptosulfonate gold salt has high stability, mercaptosulfonate can form strong coordination bonds with gold ions, does not have the problem of easy decomposition itself, and is compatible with a variety of complexing agents and additives, so that the mercaptosulfonic acid cyanide-free gold plating solution using the mercaptosulfonate system has high stability and a long service life.

[0014] Optionally, the hydantoin includes at least one of 5,5-dimethylhydantoin, 1,5,5-trimethylhydantoin, 1-(hydroxymethyl)-5,5-dimethylhydantoin, 1,3-dihydroxymethyl-5,5-dimethylhydantoin and 2-thio-5,5-dimethylhydantoin.

[0015] Optionally, the organic amine includes at least one of ethylenediamine, propylenediamine, diethylenetriamine, tetraethylenepentamine, tetramethylethylenediamine, N-methylethylenediamine, N-ethylethylenediamine, N-propylethylenediamine, N-(2-hydroxyethyl)ethylenediamine, hydroxyethylethylenediaminetriacetic acid, ethylenediaminetetraacetic acid and ethylenediaminetetrapropionic acid.

[0016] Optionally, the amino acid includes at least one of glycine, alanine, aspartic acid, glutamic acid, cysteine, N-acetyl-L-cysteine ​​and glutathione.

[0017] Optionally, the additive includes one or more of cobalt sulfate, potassium antimony tartrate, arsenic trioxide, polyethylene glycol, and polyacetimide. Specifically, the addition of additives can optimize the performance of the electroplating solution, further improve the dispersion and covering ability of the gold plating solution, and enable it to improve the crystallinity of the electroplating process within a wider range of pH and average current density, thereby improving the purity, bonding, porosity, flatness, density, brightness and other properties of the gold-plated parts.

[0018] Optionally, the pH buffer includes one or more of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium hydroxide, and hydrochloric acid. Specifically, the addition of the pH buffer can adjust the electroplating solution to a specified pH, so that the electroplating solution maintains a stable pH.

[0019] The present invention also discloses a method for preparing the mercaptosulfonic acid cyanide-free gold plating solution as described above, comprising the following steps: sequentially mixing mercaptosulfonic acid gold salt with a complexing agent and an additive, adding a pH buffer to the obtained mixed solution to adjust the pH to 2-13, filtering, and fixing the volume to obtain the mercaptosulfonic acid cyanide-free gold plating solution.

[0020] Specifically, the mercaptosulfonic acid cyanide-free gold plating electroplating solution of the present invention does not contain highly toxic substances, has high stability and a long service life, and has good electroplating stability.

[0021] The present invention also discloses a gold plating method using the mercaptosulfonic acid cyanide-free gold plating solution as described above, comprising the following steps: immersing a piece to be gold-plated in the mercaptosulfonic acid cyanide-free gold plating solution for electroplating to obtain a gold-plated piece; the electroplating temperature is 40°C to 50°C; the average current density of the electroplating is 0.2ASD to 5.0ASD; and the electroplating method is periodic square wave pulse electroplating.

[0022] Specifically, the mercaptosulfonic acid cyanide-free gold plating solution of the present invention has excellent electroplating performance and can obtain high-performance gold-plated parts within a wider range of pH and average current density.

[0023] The invention also discloses an application of the mercaptosulfonic acid cyanide-free gold plating solution in the manufacture of electronic devices and / or semiconductors.

[0024] Implementing the embodiments of the present invention will have the following beneficial effects: The mercaptosulfonic acid gold salt used in the mercaptosulfonic acid cyanide-free gold plating electroplating solution provided by the present invention has high stability and can stably exist even under the condition of pH <1. Compared with sulfite ions and thiosulfate ions, succinimide and hydantoin, mercaptosulfonic acid salt can form a stronger coordination bond with gold ions and does not have the problem of easy decomposition itself, thereby ensuring the high stability and long service life of the mercaptosulfonic acid cyanide-free gold plating electroplating solution. In addition, the mercaptosulfonic acid gold salt has high compatibility with a variety of complexing agents and additives, and can coexist with them to further improve the stability and service life of the gold plating solution, thereby effectively ensuring the performance of the gold-plated parts obtained by electroplating.

[0025] The mercaptosulfonic acid cyanide-free gold plating electroplating solution provided by the present invention does not contain highly toxic substances, has high stability and a long service life, can be stably stored at room temperature for more than 6 months, and remains clear and transparent even under conditions of high and low temperature changes, light, long-term storage or long-term electroplating, without precipitation generation or discoloration.

[0026] The mercaptosulfonic acid cyanide-free gold plating electroplating solution provided by the present invention has simple components, and the gold plating solution after long-term storage or long-term electroplating has the same electroplating effect as a newly configured gold plating solution, and does not cause problems such as self-decomposition of components or failure of the gold plating solution, and has good electroplating stability.

[0027] The mercaptosulfonic acid cyanide-free gold plating electroplating solution provided by the invention has excellent performance, good dispersibility and covering ability, and can obtain high-performance gold-plated parts within a wider range of pH and average current density.

[0028] The gold-plated parts obtained by electroplating with the mercaptosulfonic acid cyanide-free gold plating solution provided by the present invention have a purity greater than 99.9%, good bonding, low porosity, flatness and density, and a golden and bright appearance, which is conducive to application in electronic device and semiconductor manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The linear sweep voltammetry curves of hydantoin gold salt, sulfite gold salt and mercaptosulfonate gold salt in Example 1 (the test potential is compared to the electrode potential of a saturated calomel electrode).

[0030] Figure 2 This is the cross-sectional morphology of the gold-plated part prepared when the average current density is 1.0 ASD in Example 3. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited in any way.

[0032] Example 1 The mercaptosulfonic acid cyanide-free gold plating solution of this embodiment includes the following components in concentrations: 0.06 mol / L mercaptosulfonic acid gold salt, 0.40 mol / L 5,5-dimethylhydantoin, 1.20 g / L polyethylene glycol, and appropriate amounts of sodium hydroxide and dipotassium hydrogen phosphate. The pH of the mercaptosulfonic acid cyanide-free gold plating solution of this embodiment is 7.

[0033] The method for preparing the mercaptosulfonic acid cyanide-free gold plating solution of the present embodiment comprises the following steps: (1) Gold is dissolved in aqua regia, and deionized water is added to the obtained syrupy solution to remove nitrogen oxides, thereby obtaining a chloroauric acid solution. The pH of the chloroauric acid solution is adjusted to 7 using a sodium hydroxide solution, thereby obtaining a first reaction solution.

[0034] (2) Dissolve 3-mercapto-1-propane sulfonate in deionized water, and adjust the pH of the solution to 10 with a sodium hydroxide solution to obtain a second reaction solution.

[0035] (3) Mixing the first reaction solution and the second reaction solution to obtain 3-mercapto-1-propane sulfonate gold salt, wherein the molar concentration ratio of the gold ions in the first reaction solution to the 3-mercapto-1-propane sulfonate salt in the second reaction solution is 1:8.

[0036] (4) The 3-mercapto-1-propane sulfonic acid gold salt obtained in step (3) is sequentially mixed with 5,5-dimethylhydantoin and polyethylene glycol, and dipotassium hydrogen phosphate is added to the obtained mixed solution to adjust the pH to 7, thereby obtaining a mercaptosulfonic acid cyanide-free gold plating solution.

[0037] The 3-mercapto-1-propane sulfonate gold salt solution prepared in this example has high stability, wherein a strong coordination bond is formed between the 3-mercapto-1-propane sulfonate and the gold ions, causing the deposition potential of gold to move significantly to the negative direction, such as Figure 1 As shown, Figure 1 The linear sweep voltammetry curves of hydantoin gold salt, sulfite gold salt and mercaptosulfonate gold salt are shown in FIG. 3-mercapto-1-propane sulfonate gold salt solution prepared in this embodiment is fully complexed with 3-mercapto-1-propane sulfonate. When the pH value is adjusted to 0.5, the 3-mercapto-1-propane sulfonate gold salt solution remains clear and transparent, and has no problem of easy self-decomposition, and no precipitation or discoloration occurs.

[0038] The mercaptosulfonic acid cyanide-free gold plating solution prepared in this embodiment does not contain highly toxic substances and can be stored at room temperature for more than 6 months. Even under high and low temperature changes, light, long-term storage or long-term electroplating, it still remains clear and transparent without precipitation generation or discoloration.

[0039] The electroplating is performed using the mercaptosulfonic acid cyanide-free gold plating solution of the present embodiment, the electroplating anode is a platinum titanium mesh, and the electroplating cathode is a 20mm×20mm×0.1mm silicon optical wafer with a sputtered Au seed layer on the surface. The anode and cathode are immersed in the electroplating solution of the present embodiment for electroplating, and a periodic square wave pulse electroplating method is adopted. The electroplating temperature is 40°C; the average current density of the electroplating is 0.2ASD~5.0ASD, and gold-plated parts with a purity greater than 99.9%, good bonding, low porosity, flatness and density, and a golden and bright appearance can be obtained.

[0040] Example 2 The mercaptosulfonic acid cyanide-free gold plating electroplating solution of this embodiment includes the following components in concentrations: 0.04 mol / L mercaptosulfonic acid gold salt, 0.20 mol / L tetramethylethylenediamine, 0.25 mol / L glycine, 1.00 g / L cobalt sulfate, and appropriate amounts of sodium hydroxide and potassium dihydrogen phosphate. The pH of the mercaptosulfonic acid cyanide-free gold plating electroplating solution of this embodiment is 4.

[0041] The method for preparing the mercaptosulfonic acid cyanide-free gold plating solution of the present embodiment comprises the following steps: (1) Gold is dissolved in aqua regia, and deionized water is added to the obtained syrupy solution to remove nitrogen oxides, thereby obtaining a chloroauric acid solution. The pH of the chloroauric acid solution is adjusted to 6 using a sodium hydroxide solution, thereby obtaining a first reaction solution.

[0042] (2) Dissolve 2-mercaptoethane sulfonate in deionized water, and adjust the pH of the solution to 12 with a sodium hydroxide solution to obtain a second reaction solution.

[0043] (3) Mixing the first reaction solution and the second reaction solution to obtain 2-mercaptoethane sulfonate gold salt, wherein the molar concentration ratio of the gold ions in the first reaction solution to the 2-mercaptoethane sulfonate salt in the second reaction solution is 1:10.

[0044] (4) The 2-mercaptoethanesulfonic acid gold salt obtained in step (3) is sequentially mixed with tetramethylethylenediamine, glycine, and cobalt sulfate, and potassium dihydrogen phosphate is added to the obtained mixed solution to adjust the pH to 4, thereby obtaining a mercaptosulfonic acid cyanide-free gold plating solution.

[0045] The 2-mercaptoethanesulfonic acid gold salt solution prepared in this example has high stability.

[0046] The mercaptosulfonic acid cyanide-free gold plating solution prepared in this embodiment does not contain highly toxic substances and can be stored at room temperature for more than 6 months. Even under high and low temperature changes, light, long-term storage or long-term electroplating, it still remains clear and transparent without precipitation generation or discoloration.

[0047] The electroplating is performed using the mercaptosulfonic acid cyanide-free gold plating solution of this embodiment. The electroplating anode is a platinum-titanium mesh, and the electroplating cathode is a 20mm×20mm×0.1mm silicon pattern sheet with a Au seed layer sputtered on the surface. The photoresist defines that the electroplating pattern area is 100μm long, 100μm wide, and 150μm apart. The anode and cathode are immersed in the electroplating solution of this embodiment for electroplating. The periodic square wave pulse electroplating method is adopted. The electroplating temperature is 45°C. The average current density of the electroplating is 0.2ASD~3.0ASD. Gold-plated parts with a purity greater than 99.9%, good bonding, low porosity, flatness, density, and golden and bright appearance can be obtained.

[0048] Example 3 The mercaptosulfonic acid cyanide-free gold plating electroplating solution of this embodiment includes the following components in concentrations: 0.10 mol / L mercaptosulfonic acid gold salt, 0.42 mol / L 1-(hydroxymethyl)-5,5-dimethylhydantoin, 0.50 mol / L glutamic acid, 0.80 g / L potassium antimony tartrate, and appropriate amounts of sodium hydroxide and dipotassium hydrogen phosphate. The pH of the mercaptosulfonic acid cyanide-free gold plating electroplating solution of this embodiment is 11.

[0049] The method for preparing the mercaptosulfonic acid cyanide-free gold plating solution of the present embodiment comprises the following steps: (1) Gold is dissolved in aqua regia, and deionized water is added to the obtained syrupy solution to remove nitrogen oxides, thereby obtaining a chloroauric acid solution. The pH of the chloroauric acid solution is adjusted to 7 using a sodium hydroxide solution, thereby obtaining a first reaction solution.

[0050] (2) Dissolve 4-mercapto-1-butane sulfonate in deionized water, and adjust the pH of the solution to 9 with a sodium hydroxide solution to obtain a second reaction solution.

[0051] (3) Mixing the first reaction solution and the second reaction solution to obtain 4-mercapto-1-butane sulfonate gold salt, wherein the molar concentration ratio of the gold ions in the first reaction solution to the 4-mercapto-1-butane sulfonate salt in the second reaction solution is 1:12.

[0052] (4) The 4-mercapto-1-butanesulfonic acid gold salt obtained in step (3) is sequentially mixed with 1-(hydroxymethyl)-5,5-dimethylhydantoin, glutamic acid, and potassium antimony tartrate, and dipotassium hydrogen phosphate is added to the obtained mixed solution to adjust the pH to 11, thereby obtaining a mercaptosulfonic acid cyanide-free gold plating solution.

[0053] The 4-mercapto-1-butanesulfonic acid gold salt solution prepared in this example has high stability.

[0054] The mercaptosulfonic acid cyanide-free gold plating solution prepared in this embodiment does not contain highly toxic substances and can be stored at room temperature for more than 6 months. Even under high and low temperature changes, light, long-term storage or long-term electroplating, it still remains clear and transparent without precipitation generation or discoloration.

[0055] The electroplating is performed using the mercaptosulfonic acid cyanide-free gold plating solution of this embodiment. The electroplating anode is a platinum titanium mesh, and the electroplating cathode is a 5mm×6mm×0.1mm silicon wafer with a sputtered Au seed layer on the surface. The anode and cathode are immersed in the electroplating solution of this embodiment for electroplating. The periodic square wave pulse electroplating method is adopted. The electroplating temperature is 50°C; the average current density of the electroplating is 0.5ASD~4.2ASD. Gold-plated parts with a purity greater than 99.9%, good bonding, low porosity, flatness and density, and a golden and bright appearance can be obtained, such as Figure 2 shown.

[0056] Comparative Example 1 The plating solution of this comparative example is a cyanide-free gold plating solution of sulfurous acid, which includes the following components in concentrations: 0.06 mol / L of gold sulfite, 0.56 mol / L of ethylenediaminetetraacetic acid, 0.24 mol / L of glycine, 0.90 g / L of polyethylene glycol, and an appropriate amount of potassium dihydrogen phosphate. The pH of the cyanide-free gold plating solution of this comparative example is 8.

[0057] The gold sulfite solution of this comparative example has poor stability and is easily decomposed. It can only be stored at room temperature for about one week. After one week, golden particles precipitate and become ineffective.

[0058] The sulfite cyanide-free gold plating solution prepared in this comparative example can be stored at room temperature for 2 months. After 2 months, black powder precipitation will precipitate and become ineffective. This is because the gold sulfite salt itself is easy to decompose and has low stability.

[0059] Comparative Example 2 The plating solution of this comparative example is a cyanide-free gold plating solution of hydantoin, which includes the following components in concentrations: 0.04 mol / L of 5,5-dimethylhydantoin gold salt, 0.22 mol / L of N-propylethylenediamine, 0.36 mol / L of aspartic acid, 0.70 g / L of arsenic trioxide, and an appropriate amount of hydrochloric acid. The pH of the cyanide-free gold plating solution of this comparative example is 7.

[0060] The 5,5-dimethylhydantoin gold salt solution of this comparative example has higher stability.

[0061] The cyanide-free gold plating solution prepared in this comparative example can be stored at room temperature for 4 months, and gray flocculent precipitates are precipitated after 4 months.

[0062] The cyanide-free gold plating solution of the comparative example was used for electroplating in the same way as in Example 1, and a gold-plated part having a purity greater than 99.9% but low flatness and density and a reddish appearance and pores was obtained.

[0063] Comparative Example 3 Compared with Example 1, the mercaptosulfonic acid cyanide-free gold plating electroplating solution of this comparative example only changes the molar concentration ratio of gold ions in the first reaction solution and 3-mercapto-1-propane sulfonate in the second reaction solution to 1:2, and the other components, concentrations and preparation methods are the same. The pH of the mercaptosulfonic acid cyanide-free gold plating electroplating solution of this comparative example is 7.

[0064] The 3-mercapto-1-propane sulfonic acid gold salt solution prepared in this comparative example had poor stability, and a golden powder precipitated on the day of preparation, resulting in failure.

[0065] Comparative Example 4 Compared with Example 1, the mercaptosulfonic acid cyanide-free gold plating solution of this comparative example only changes the molar concentration of 5,5-dimethylhydantoin to 2.50 mol / L, and the other components, concentrations and preparation methods are the same. The pH of the mercaptosulfonic acid cyanide-free gold plating solution of this comparative example is 7.

[0066] The mercaptosulfonic acid cyanide-free gold plating solution prepared in this comparative example precipitates white crystals during storage for 2 months at room temperature, which will affect the performance of the gold-plated parts.

[0067] Comparative Example 5 Compared with Example 1, the mercaptosulfonic acid cyanide-free gold plating electroplating solution of this comparative example does not add 5,5-dimethylhydantoin, and the other components, concentrations and preparation methods are the same. The pH of the mercaptosulfonic acid cyanide-free gold plating electroplating solution of this comparative example is 7.

[0068] The mercaptosulfonic acid cyanide-free gold plating solution prepared in this comparative example can be stored at room temperature for more than 6 months.

[0069] The mercaptosulfonic acid cyanide-free gold plating solution of this comparative example was used for electroplating in the same manner as in Example 1, and a gold-plated part having a purity greater than 99.9% and being flat but having a reddish appearance was obtained.

[0070] Comparative Example 6 Compared with Example 1, the mercaptosulfonic acid cyanide-free gold plating electroplating solution of this comparative example does not add polyethylene glycol, and the other components, concentrations and preparation methods are the same. The pH value of the mercaptosulfonic acid cyanide-free gold plating electroplating solution of this comparative example is 7.

[0071] The mercaptosulfonic acid cyanide-free gold plating solution prepared in this comparative example can be stored at room temperature for more than 6 months.

[0072] The mercaptosulfonic acid cyanide-free gold plating solution of this comparative example was used for electroplating, and the electroplating method was the same as that of Example 1, and a gold-plated part with a purity greater than 99.9% but low flatness and density and a black appearance and pores was obtained.

[0073] Comparative Example 7 Compared with Example 2, the mercaptosulfonic acid cyanide-free gold plating solution of this comparative example only adjusts the pH of the first reaction solution to 2, and the other components, concentrations and preparation methods are the same.

[0074] The 2-mercaptoethanesulfonic acid gold salt solution prepared in this comparative example can only remain clear and transparent for 1 month, and white precipitates appear in the later storage period. The mercaptosulfonic acid cyanide-free gold plating solution prepared using the solution can only be used in an environment with a pH of 9 to 10, and the applicable average current density is only 0.5 ASD to 0.9 ASD.

[0075] Comparative Example 8 Compared with Example 2, the mercaptosulfonic acid cyanide-free gold plating solution of this comparative example only adjusts the pH of the second reaction solution to 8, and the other components, concentrations and preparation methods are the same.

[0076] The 2-mercaptoethanesulfonic acid gold salt solution prepared in this comparative example can only remain clear and transparent for 1 month, and white precipitates appear in the later storage period. The mercaptosulfonic acid cyanide-free gold plating solution prepared using the solution can only be used in an environment with a pH of 8 to 9, and the applicable average current density is only 0.8 ASD to 1.2 ASD.

[0077] Comparative Example 9 Compared with Example 2, the mercaptosulfonic acid cyanide-free gold plating solution of this comparative example only adjusts the pH of the first reaction solution to 10.

[0078] The first reaction solution prepared in this comparative example directly precipitates Au(OH)3 brown-yellow precipitate, and cannot prepare mercaptosulfonic acid gold salt solution.

[0079] Comparative Example 10 Compared with Example 2, the mercaptosulfonic acid cyanide-free gold plating solution of this comparative example only adjusts the pH of the second reaction solution to 3.

[0080] The 2-mercaptoethanesulfonic acid gold salt solution prepared in this comparative example precipitated a large amount of white precipitate, became invalid on the day of preparation, and could not be used in the preparation of gold plating solution.

[0081] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A mercaptosulfonic acid cyanide-free gold plating solution, characterized in that: The mercaptosulfonic acid cyanide-free gold plating solution comprises a gold source, a complexing agent, an additive and a pH buffer; The gold source is mercaptosulfonate gold salt; The pH of the mercaptosulfonic acid cyanide-free gold plating solution is 2 to 13; The preparation method of the mercaptosulfonic acid gold salt comprises the following steps: (1) dissolving gold in aqua regia, and adding deionized water to the obtained syrupy solution to remove nitrogen oxides, thereby obtaining a chloroauric acid solution, and adjusting the pH of the chloroauric acid solution to 6-7 using a pH buffer to obtain a first reaction solution; (2) dissolving the mercaptosulfonate in deionized water, and adjusting the pH of the solution to 9-13 using a pH buffer to obtain a second reaction solution; (3) mixing the first reaction liquid and the second reaction liquid to obtain the mercaptosulfonate gold salt; In step (3), the molar concentration ratio of the gold ions in the first reaction solution to the mercaptosulfonate in the second reaction solution is 1:5 to 1:15; The amount of the gold source is such that the molar concentration of gold ions in the mercaptosulfonic acid cyanide-free gold plating solution is 0.03 mol / L to 0.20 mol / L; The concentration of the additive in the mercaptosulfonic acid cyanide-free gold plating solution is 0.10 g / L to 5.00 g / L; The molar concentration ratio of the gold ions in the mercaptosulfonic acid cyanide-free gold plating solution to the complexing agent is 1:2 to 1:40; The complexing agent includes at least one of hydantoin, organic amine and amino acid.

2. The mercaptosulfonic acid cyanide-free gold plating solution according to claim 1, characterized in that: In step (2), the mercaptosulfonate includes at least one of 2-mercaptoethanesulfonate, 3-mercapto-1-propanesulfonate, 2,3-dimercaptopropanesulfonate, 4-mercapto-1-butanesulfonate, 3,4-dimercaptobutanesulfonate, and 2,4-dimercaptobutanesulfonate.

3. The mercaptosulfonic acid cyanide-free gold plating solution according to claim 1, characterized in that: The amount of the gold source is such that the molar concentration of gold ions in the mercaptosulfonic acid cyanide-free gold plating solution is 0.03 mol / L to 0.12 mol / L; The concentration of the additive in the mercaptosulfonic acid cyanide-free gold plating solution is 0.80 g / L to 1.50 g / L; The molar concentration ratio of the gold ions in the mercaptosulfonic acid cyanide-free gold plating solution to the complexing agent is 1:4-1:

20.

4. The mercaptosulfonic acid cyanide-free gold plating solution according to claim 1, characterized in that: The additives include one or more of cobalt sulfate, potassium antimony tartrate, arsenic trioxide, polyethylene glycol, and polyacetimide; The pH buffer includes one or more of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium hydroxide and hydrochloric acid.

5. A method for preparing the mercaptosulfonic acid cyanide-free gold plating solution as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: The mercaptosulfonic acid gold salt is sequentially mixed with a complexing agent and an additive, and a pH buffer is added to the obtained mixed solution to adjust the pH value to 2-13, and the solution is filtered and fixed to obtain the mercaptosulfonic acid cyanide-free gold plating solution.

6. A gold plating method using the mercaptosulfonic acid cyanide-free gold plating solution as claimed in any one of claims 1 to 4, characterized in that: The method comprises the following steps: immersing the gold-plated piece into the mercaptosulfonic acid cyanide-free gold plating solution for electroplating to obtain the gold-plated piece; The electroplating temperature is 40°C to 50°C; The average current density of the electroplating is 0.2ASD~5.0ASD; The electroplating method is periodic square wave pulse electroplating.

7. Use of the mercaptosulfonic acid cyanide-free gold plating solution as claimed in any one of claims 1 to 4 in the manufacture of electronic devices and / or semiconductors.

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