A cyanide-free gold plating solution containing mercapto sulfonic acid and its preparation method and application

Abstract

The application discloses a mercapto sulfonic acid cyanide-free gold plating solution and a preparation method and application thereof, and belongs to the technical field of electroplating. The mercapto sulfonic acid cyanide-free gold plating solution comprises a gold source, a complexing agent, an additive and a pH buffer. The gold source is a mercapto sulfonic acid gold salt. The pH of the mercapto sulfonic acid cyanide-free gold plating solution is 2-13. The mercapto sulfonic acid cyanide-free gold plating solution provided by the application does not contain a highly toxic substance. The mercapto sulfonic acid gold salt used has high stability, so that the mercapto sulfonic acid cyanide-free gold plating solution has high stability and a long service life. Even after high and low temperature changes, illumination, long-time storage or long-time electroplating, the mercapto sulfonic acid cyanide-free gold plating solution still maintains a clear and transparent state and the same electroplating effect, thereby effectively guaranteeing the performance of a gold-plated part obtained by electroplating. The gold-plated part has a purity of greater than 99.9%, good combination, low porosity, a smooth and dense surface and a golden and bright appearance, and is favorable for application in electronic devices and semiconductor manufacturing.

Description

TECHNICAL FIELD

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

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

[0003] Traditional gold plating processes usually use cyanide gold plating systems, which have the advantages of high stability, long service life and excellent performance of gold-plated parts, but cyanide is a toxic substance and does not meet the requirements of green electroplating and sustainable development. Therefore, non-toxic and non-polluting cyanide-free gold plating systems are gradually replacing cyanide gold plating systems.

[0004] However, the current cyanide-free gold plating system still has the following two problems: 1. Low stability and short service life of the gold plating solution. Chinese patents CN109881223A and CN105441996A disclose sulfite and thiosulfate gold plating solutions, respectively. However, both sulfite ions and thiosulfate ions are prone to decomposition, which causes the loss of ligand of gold ions and the generation of gold precipitate through disproportionation reaction, resulting in the failure of the gold plating solution. 2. Poor performance of gold-plated parts. Chinese patents CN105401180A and CN101906649A disclose succinimide and hydantoin gold plating solutions, respectively. The coordination bond between succinimide and hydantoin and gold ions is weak, which further reduces the polarization effect during electroplating and affects the crystallinity of the gold-plated parts, resulting in the decline of the purity, adhesion, porosity, flatness, density, brightness and other properties of the gold-plated parts. In addition, in order to ensure the stability of the cyanide-free gold plating solution and the performance of the gold-plated parts, multiple complexing agents are usually added. However, some complexing agents will participate in the electrochemical reaction during electroplating or undergo self-decomposition reaction and fail, which reduces the stability of the cyanide-free gold plating solution, or the complexing agents have too strong coordination effect and cause side reactions, which affects the performance of the gold-plated parts. SUMMARY

[0005] The present application aims to overcome the above-mentioned defects in the prior art and provide a mercaptosulfonic acid cyanide-free gold plating solution and a preparation method and application thereof. The mutual synergistic effect between the mercaptosulfonic acid gold salt, complexing agents, additives and pH buffers, which do not contain toxic substances, improves the stability and service life of the gold plating solution and effectively improves the performance of the gold-plated parts.

[0006] To achieve the above-mentioned purpose, the technical solution of the present application is as follows:

[0007] The cyanide-free gold plating solution of mercapto sulfonic acid comprises a gold source, a complexing agent, an additive and a pH buffer; the gold source is a mercapto sulfonic acid gold salt; the pH of the cyanide-free gold plating solution of mercapto sulfonic acid is 2-13; the preparation method of the mercapto sulfonic acid gold salt comprises the following steps:

[0008] (1) Dissolve gold in aqua regia, and add deionized water to the obtained syrup-like solution to remove nitrogen oxides to obtain a chloroauric acid solution; adjust the pH of the chloroauric acid solution to 6-7 by using a pH buffer to obtain a first reaction liquid;

[0009] (2) Dissolve a mercapto sulfonate in deionized water, and adjust the pH of the solution to 9-13 by using a pH buffer to obtain a second reaction liquid;

[0010] (3) Mix the first reaction liquid and the second reaction liquid to obtain the mercapto sulfonic acid gold salt.

[0011] Further, in step (3), the molar concentration ratio of gold ions in the first reaction liquid to mercapto sulfonate in the second reaction liquid is 1:5-1:15. Specifically, if the molar concentration ratio is lower than 1:5, the obtained mercapto sulfonic acid gold salt has low stability and is easy to precipitate gold; if the molar concentration ratio is higher than 1:15, the cost increases.

[0012] Further, the amount of the gold source is such that the molar concentration of gold ions in the cyanide-free gold plating solution of mercapto sulfonic acid is 0.03-0.20 mol / L. Preferably, the amount of the gold source is such that the molar concentration of gold ions in the cyanide-free gold plating solution of mercapto sulfonic acid is 0.03-0.12 mol / L.

[0013] Further, the concentration of the additive in the cyanide-free gold plating solution of mercapto sulfonic acid is 0.10-5.00 g / L. Preferably, the concentration of the additive in the cyanide-free gold plating solution of mercapto sulfonic acid is 0.80-1.50 g / L.

[0014] Further, the molar concentration ratio of gold ions in the cyanide-free gold plating solution of mercapto sulfonic acid to the complexing agent is 1:2-1:40. Specifically, if the molar concentration ratio is lower than 1:2, the stability and service life of the cyanide-free gold plating solution of mercapto sulfonic acid cannot meet the requirements; if the molar concentration ratio is higher than 1:40, the cyanide-free gold plating solution of mercapto sulfonic acid is easy to precipitate crystals, thereby affecting the performance of the gold-plated part. Preferably, the molar concentration ratio of gold ions in the cyanide-free gold plating solution of mercapto sulfonic acid to the complexing agent is 1:4-1:20.

[0015] Further, the complexing agent comprises 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 cyanide-free gold plating solution of mercapto sulfonic acid, and make the performance of the gold-plated part more excellent.

[0016] Optionally, in step (2), the mercapto sulfonate comprises at least one of 2-mercaptoethane sulfonate, 3-mercapto-1-propane sulfonate, 2,3-dimercapto propane sulfonate, 4-mercapto-1-butane sulfonate, 3,4-dimercapto butane sulfonate, and 2,4-dimercapto butane sulfonate.

[0017] Specifically, the gold salt of mercapto sulfonic acid has high stability, the mercapto sulfonate can form a strong coordination bond with gold ions, has no problem of easy decomposition itself, and is compatible with various complexing agents and additives, so that the cyanide-free gold plating solution of mercapto sulfonic acid using the mercapto sulfonate system has high stability and long service life.

[0018] Optionally, the hydantoin comprises at least one of 5,5-dimethyl hydantoin, 1,5,5-trimethyl hydantoin, 1-(hydroxymethyl)-5,5-dimethyl hydantoin, 1,3-dihydroxymethyl-5,5-dimethyl hydantoin, and 2-thio-5,5-dimethyl hydantoin.

[0019] Optionally, the organic amine comprises 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.

[0020] Optionally, the amino acid comprises at least one of glycine, alanine, aspartic acid, glutamic acid, cysteine, N-acetyl-L-cysteine, and glutathione.

[0021] Optionally, the additive comprises one or two or more of cobalt sulfate, potassium antimony tartrate, arsenic trioxide, polyethylene glycol, and polyacetimide. Specifically, the addition of the additive can optimize the performance of the plating solution, further improve the dispersing and covering abilities of the gold plating solution, and make it improve the crystallinity of the plating process in a wider pH and average current density use range, thereby improving the purity, adhesion, porosity, flatness, density, brightness, and other performances of the gold-plated part.

[0022] Optionally, the pH buffer comprises one or two or more of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium hydroxide, and hydrochloric acid. Specifically, the addition of the pH buffer can adjust the plating solution to a specified pH, so that the plating solution maintains stable pH.

[0023] The application further discloses a preparation method of the mercapto sulfonic acid cyanide-free gold plating solution, which comprises the following steps: sequentially mixing a mercapto sulfonic acid gold salt with a complexing agent and an additive, adding a pH buffer into the obtained mixed solution to adjust the pH to 2-13, and filtering and constant volume to obtain the mercapto sulfonic acid cyanide-free gold plating solution.

[0024] Specifically, the mercapto sulfonic acid cyanide-free gold plating solution has no toxic substance, high stability, long service life and good plating stability.

[0025] The application further discloses a gold plating method using the mercapto sulfonic acid cyanide-free gold plating solution, which comprises the following steps: immersing a gold-plated part into the mercapto sulfonic acid cyanide-free gold plating solution to perform electroplating, so as to obtain a gold-plated part; the temperature of the electroplating is 40-50 DEG C; the average current density of the electroplating is 0.2-5.0 ASD; and the electroplating mode is a periodic square wave pulse electroplating.

[0026] Specifically, the mercapto sulfonic acid cyanide-free gold plating solution has excellent electroplating performance, and high-performance gold-plated parts can be obtained in a wide pH and average current density range.

[0027] The application further discloses an application of the mercapto sulfonic acid cyanide-free gold plating solution in electronic devices and / or semiconductor manufacturing.

[0028] The application has the following beneficial effects:

[0029] The mercapto sulfonic acid gold salt used in the mercapto sulfonic acid cyanide-free gold plating solution has high stability, and can exist stably even under the condition of pH<1; compared with sulfite ions and thiosulfate ions, succinimide and hydantoin, the mercapto sulfonic acid salt can form a strong coordination bond with gold ions, and has no problem of easy decomposition, so that the high stability and long service life of the mercapto sulfonic acid cyanide-free gold plating solution are ensured. In addition, the mercapto sulfonic acid gold salt has high compatibility with various complexing agents and additives, and can coexist with the complexing agents and additives to further improve the stability and service life of the gold plating solution, so that the performance of the gold-plated part obtained by electroplating is effectively ensured.

[0030] The mercapto sulfonic acid cyanide-free gold plating solution has no toxic substance, high stability and long service life, and can be stably stored for more than 6 months at room temperature; even under the conditions of high and low temperature change, illumination, long-time storage or long-time electroplating, the solution still maintains a clear and transparent state, and no precipitation or discoloration occurs.

[0031] The thiol sulfonic acid cyanide-free gold plating solution provided by the application has simple components, and the plating effect of the gold plating solution after long-time storage or long-time plating is the same as that of a newly prepared gold plating solution, without problems such as component self-decomposition or plating solution failure, and has good plating stability.

[0032] The thiol sulfonic acid cyanide-free gold plating solution provided by the application has excellent performance, and has good dispersing and covering abilities, and can obtain high-performance gold-plated parts in a wide pH and average current density range.

[0033] The gold-plated part obtained by using the thiol sulfonic acid cyanide-free gold plating solution provided by the application has a purity of greater than 99.9%, good binding, low porosity, flatness and compactness, and a golden and bright appearance, and is beneficial to application in electronic devices and semiconductor manufacturing. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 Linear sweep voltammogram (test potential relative to the electrode potential of saturated calomel electrode) of the hydantoin gold salt, the gold sulfite and the gold thiol sulfonic acid salt in Example 1.

[0035] Figure 2 Cross-sectional morphology of the gold-plated part prepared when the average current density is 1.0 ASD in Example 3. DETAILED DESCRIPTION

[0036] The application is further described below in combination with specific examples, but the application is not limited in any way by the examples.

[0037] Example 1

[0038] The thiol sulfonic acid cyanide-free gold plating solution of the example includes the following components at the following concentrations: 0.06 mol / L of a gold thiol sulfonic acid salt, 0.40 mol / L of 5,5-dimethylhydantoin, 1.20 g / L of polyethylene glycol, and appropriate amounts of sodium hydroxide and dipotassium hydrogen phosphate. The pH of the thiol sulfonic acid cyanide-free gold plating solution of the example is 7.

[0039] The preparation method of the thiol sulfonic acid cyanide-free gold plating solution of the example includes the following steps:

[0040] (1) Dissolve gold in aqua regia, and add deionized water to the obtained syrup-like solution to remove nitrogen oxides, to obtain a chloroauric acid solution. Adjust the pH of the chloroauric acid solution to 7 by using a sodium hydroxide solution, to obtain a first reaction solution.

[0041] (2) Dissolve 3-mercapto-1-propane sulfonate in deionized water, and adjust the pH of the solution to 10 by using a sodium hydroxide solution, to obtain a second reaction solution.

[0042] (3) mixing the first reaction solution and the second reaction solution to obtain 3-mercapto-1-propane sulfonic acid gold salt, wherein the molar concentration ratio of gold ions in the first reaction solution to 3-mercapto-1-propane sulfonic acid salt in the second reaction solution is 1:8.

[0043] (4) mixing 3-mercapto-1-propane sulfonic acid gold salt obtained in step (3) with 5,5-dimethylhydantoin and polyethylene glycol in sequence, and adding dipotassium hydrogen phosphate into the obtained mixed solution to adjust the pH to 7, to obtain a mercapto sulfonic acid cyanide-free gold plating solution.

[0044] The 3-mercapto-1-propane sulfonic acid gold salt solution prepared in the present example has high stability, wherein a strong coordination bond is formed between 3-mercapto-1-propane sulfonic acid salt and gold ions, so that the gold deposition potential is greatly moved to the negative direction, as shown in FIG. 1. Figure 1 FIG. 1 is a linear sweep voltammetry curve diagram of hydantoin gold salt, gold sulfite and gold mercapto sulfonic acid salt. Figure 1 The gold ions in the 3-mercapto-1-propane sulfonic acid gold salt solution prepared in the present example are fully complexed with 3-mercapto-1-propane sulfonic acid salt, and the pH is adjusted to 0.5, and the 3-mercapto-1-propane sulfonic acid gold salt solution still remains clear and transparent, without the problem of easy decomposition, without the generation of precipitate or discoloration, etc.

[0045] The mercapto sulfonic acid cyanide-free gold plating solution prepared in the present example does not contain toxic substances, and can be stored for more than 6 months at room temperature. Even under the conditions of high and low temperature changes, light, long-term storage or long-term plating, etc., it still remains clear and transparent, without the generation of precipitate or discoloration, etc.

[0046] The mercapto sulfonic acid cyanide-free gold plating solution of the present example is used for plating, the anode for plating is platinum titanium mesh, and the cathode for plating is a 20mmx20mmx0.1mm silicon wafer with a sputtered Au seed layer on the surface. The anode and the cathode are immersed in the plating solution of the present example for plating, and a periodic square wave pulse plating mode is adopted, and the plating temperature is 40°C; the average current density for plating is 0.2ASD~5.0ASD, and a gold plated part with purity greater than 99.9%, good adhesion, low porosity, smooth and dense, and golden appearance can be obtained.

[0047] Example 2

[0048] The mercapto sulfonic acid cyanide-free gold plating solution of the present example includes the following components with the following concentrations: 0.04mol / L of 3-mercapto-1-propane sulfonic acid gold salt, 0.20mol / L of tetramethyl ethylenediamine, 0.25mol / L of glycine, 1.00g / L of cobalt sulfate, and appropriate amounts of sodium hydroxide and potassium dihydrogen phosphate. The pH of the mercapto sulfonic acid cyanide-free gold plating solution of the present example is 4.

[0049] The preparation method of the thiol sulfonic acid cyanide-free gold plating solution of the embodiment comprises the following steps:

[0050] (1) Dissolve gold in aqua regia, and add deionized water to the obtained syrup-like solution to remove nitrogen oxides to obtain a chloroauric acid solution. Adjust the pH of the chloroauric acid solution to 6 by using a sodium hydroxide solution to obtain a first reaction liquid.

[0051] (2) Dissolve 2-mercaptoethanesulfonate in deionized water, and adjust the pH of the solution to 12 by using a sodium hydroxide solution to obtain a second reaction liquid.

[0052] (3) Mix the first reaction liquid and the second reaction liquid to obtain a 2-mercaptoethanesulfonic acid gold salt, wherein the molar concentration ratio of gold ions in the first reaction liquid to 2-mercaptoethanesulfonate in the second reaction liquid is 1:10.

[0053] (4) Mix the 2-mercaptoethanesulfonic acid gold salt obtained in step (3) with tetramethyl ethylenediamine, glycine, and cobalt sulfate in sequence, and add potassium dihydrogen phosphate to the obtained mixed solution to adjust the pH to 4 to obtain a thiol sulfonic acid cyanide-free gold plating solution.

[0054] The 2-mercaptoethanesulfonic acid gold salt solution prepared in the embodiment has high stability.

[0055] The thiol sulfonic acid cyanide-free gold plating solution prepared in the embodiment does not contain a highly toxic substance, can be stored at room temperature for more than 6 months, and remains clear and transparent without precipitation or discoloration even under conditions of temperature change, light, long-term storage, or long-term plating.

[0056] Using the thiol sulfonic acid cyanide-free gold plating solution of the embodiment for plating, the anode for plating is a platinum-titanium mesh, the cathode for plating is a 20mm×20mm×0.1mm silicon pattern piece with a sputtered Au seed layer on the surface, the photoresist defines the plating pattern area with a length of 100μm, a width of 100μm, and a pitch of 150μm. The anode and the cathode are immersed in the plating solution of the embodiment for plating, and a periodic square wave pulse plating mode is used, with a plating temperature of 45℃; the average current density for plating is 0.2ASD~3.0ASD, and a gold-plated part with a purity of greater than 99.9%, good adhesion, low porosity, flatness, compactness, and a golden appearance can be obtained.

[0057] Example 3

[0058] The thiosulfonic acid cyanide-free gold plating solution of this embodiment comprises the following components at the following concentrations: 0.10 mol / L of thiosulfonic acid gold salt, 0.42 mol / L of 1-(hydroxymethyl)-5,5-dimethylhydantoin, 0.50 mol / L of glutamic acid, 0.80 g / L of potassium antimony tartrate, and appropriate amounts of sodium hydroxide and dipotassium hydrogen phosphate. The pH of the thiosulfonic acid cyanide-free gold plating solution of this embodiment is 11.

[0059] The method for preparing the mercaptosulfonic acid-free gold plating solution in this embodiment includes the following steps:

[0060] (1) Dissolve gold in aqua regia and add deionized water to the resulting syrupy solution to remove nitrogen oxides, and obtain chloroauric acid solution. Adjust the pH of the chloroauric acid solution to 7 using sodium hydroxide solution to obtain the first reaction solution.

[0061] (2) Dissolve 4-mercapto-1-butanesulfonate in deionized water and adjust the pH of the solution to 9 using sodium hydroxide solution to obtain the second reaction solution.

[0062] (3) The first reaction solution and the second reaction solution are mixed to obtain gold salt of 4-mercapto-1-butanesulfonate, wherein the molar concentration ratio of gold ions in the first reaction solution and 4-mercapto-1-butanesulfonate in the second reaction solution is 1:12.

[0063] (4) The 4-mercapto-1-butanesulfonic acid gold salt obtained in step (3) is mixed with 1-(hydroxymethyl)-5,5-dimethylhydantoin, glutamic acid and potassium antimony tartrate in sequence, and dipotassium hydrogen phosphate is added to the resulting mixed solution to adjust the pH to 11, so as to obtain a mercaptosulfonic acid cyanide-free gold plating solution.

[0064] The 4-mercapto-1-butanesulfonic acid gold salt solution prepared in this embodiment has high stability.

[0065] 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 conditions such as high and low temperature changes, light exposure, long-term storage, or long-term electroplating, it remains clear and transparent without precipitation or discoloration.

[0066] Electroplating was performed using the mercaptosulfonic acid-free gold plating solution of this embodiment. The anode was a platinum-titanium mesh, and the cathode was a 5mm × 6mm × 0.1mm silicon wafer with a sputtered Au seed layer. The anode and cathode were immersed in the plating solution of this embodiment for electroplating using a periodic square wave pulse electroplating method at a temperature of 50°C. The average current density ranged from 0.5 ASD to 4.2 ASD, all yielding gold-plated parts with a purity greater than 99.9%, good adhesion, low porosity, smooth and dense surface, and a bright golden appearance. Figure 2 As shown.

[0067] Comparative Example 1

[0068] The gold plating solution of the present comparative example is a sulfite cyanide-free gold plating solution, which comprises the following components at the following concentrations: 0.06 mol / L of gold sulfite, 0.56 mol / L of ethylenediaminetetraacetic acid, 0.24 mol / L of glycine, and 0.90 g / L of polyethylene glycol, and an appropriate amount of potassium dihydrogen phosphate. The pH of the gold sulfite cyanide-free plating solution of the present comparative example is 8.

[0069] The gold sulfite solution of the present comparative example has poor stability and is prone to decomposition on its own, and can only be stored at room temperature for about 1 week, after which gold-colored granular precipitates are precipitated and the solution is no longer effective.

[0070] The gold sulfite cyanide-free plating solution prepared in the present comparative example can be stored at room temperature for 2 months, after which black powder precipitates are precipitated and the solution is no longer effective, which is due to the fact that the gold sulfite is prone to decomposition on its own and has low stability.

[0071] Comparative Example 2

[0072] The gold plating solution of the present comparative example is a hydantoin cyanide-free gold plating solution, which comprises the following components at the following 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 hydantoin cyanide-free gold plating solution of the present comparative example is 7.

[0073] The 5,5-dimethylhydantoin gold salt solution of the present comparative example has high stability.

[0074] The hydantoin cyanide-free gold plating solution prepared in the present comparative example can be stored at room temperature for 4 months, after which gray flocculent precipitates are precipitated.

[0075] The gold plating solution of the present comparative example is a hydantoin cyanide-free gold plating solution, which comprises the following components at the following 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 hydantoin cyanide-free gold plating solution of the present comparative example is 7.

[0076] Comparative Example 3

[0077] The gold plating solution of the present comparative example is a sulfite cyanide-free gold plating solution, which comprises the following components at the following concentrations: 0.06 mol / L of gold sulfite, 0.56 mol / L of ethylenediaminetetraacetic acid, 0.24 mol / L of glycine, and 0.90 g / L of polyethylene glycol, and an appropriate amount of potassium dihydrogen phosphate. The pH of the gold sulfite cyanide-free plating solution of the present comparative example is 8.

[0078] The 3-mercapto-1-propane sulfonic acid gold salt solution prepared in the present comparative example has poor stability and precipitates gold-colored powder precipitates on the day of preparation and is no longer effective.

[0079] Comparative Example 4

[0080] The thiol sulfonic acid cyanide-free gold plating solution of the present comparative example is prepared by changing the molar concentration of 5,5-dimethylhydantoin to 2.50 mol / L only, and other components, concentrations and preparation methods are the same as those of Example 1. The pH of the thiol sulfonic acid cyanide-free gold plating solution of the present comparative example is 7.

[0081] The thiol sulfonic acid cyanide-free gold plating solution prepared in the present comparative example precipitates white crystals during storage at room temperature for 2 months, which will affect the performance of the gold-plated parts.

[0082] Comparative Example 5

[0083] The thiol sulfonic acid cyanide-free gold plating solution of the present comparative example is prepared by not adding 5,5-dimethylhydantoin, and other components, concentrations and preparation methods are the same as those of Example 1. The pH of the thiol sulfonic acid cyanide-free gold plating solution of the present comparative example is 7.

[0084] The thiol sulfonic acid cyanide-free gold plating solution prepared in the present comparative example can be stored at room temperature for more than 6 months.

[0085] The thiol sulfonic acid cyanide-free gold plating solution of the present comparative example is used for electroplating, and the electroplating method is the same as that of Example 1, and a gold-plated part with purity greater than 99.9% and red appearance is obtained.

[0086] Comparative Example 6

[0087] The thiol sulfonic acid cyanide-free gold plating solution of the present comparative example is prepared by not adding polyethylene glycol, and other components, concentrations and preparation methods are the same as those of Example 1. The pH of the thiol sulfonic acid cyanide-free gold plating solution of the present comparative example is 7.

[0088] The thiol sulfonic acid cyanide-free gold plating solution prepared in the present comparative example can be stored at room temperature for more than 6 months.

[0089] The thiol sulfonic acid cyanide-free gold plating solution of the present comparative example is used for electroplating, and the electroplating method is the same as that of Example 1, and a gold-plated part with purity greater than 99.9% but low flatness and density and black appearance and pores is obtained.

[0090] Comparative Example 7

[0091] The thiol sulfonic acid cyanide-free gold plating solution of the present comparative example is prepared by adjusting the pH of the first reaction solution to 2 only, and other components, concentrations and preparation methods are the same as those of Example 2.

[0092] The 2-mercaptoethanesulfonic acid gold salt solution prepared in the present comparative example can only maintain clear transparency for 1 month, and white precipitate appears in the later storage period. The mercapto sulfonic acid cyanide-free gold plating solution prepared using the same can only be used in an environment with a pH of 9-10, and the applicable average current density is only 0.5 ASD-0.9 ASD.

[0093] Comparative Example 8

[0094] The mercapto sulfonic acid cyanide-free gold plating solution of the present comparative example is similar to that of Example 2, except that the pH of the second reaction solution is adjusted to 8, and other components, concentrations and preparation methods are the same.

[0095] The 2-mercaptoethanesulfonic acid gold salt solution prepared in the present comparative example can only maintain clear transparency for 1 month, and white precipitate appears in the later storage period. The mercapto sulfonic acid cyanide-free gold plating solution prepared using the same can only be used in an environment with a pH of 8-9, and the applicable average current density is only 0.8 ASD-1.2 ASD.

[0096] Comparative Example 9

[0097] The mercapto sulfonic acid cyanide-free gold plating solution of the present comparative example is similar to that of Example 2, except that the pH of the first reaction solution is adjusted to 10.

[0098] The first reaction solution prepared in the present comparative example directly precipitates brownish yellow Au(OH)3, and cannot be used to prepare a 2-mercaptoethanesulfonic acid gold salt solution.

[0099] Comparative Example 10

[0100] The mercapto sulfonic acid cyanide-free gold plating solution of the present comparative example is similar to that of Example 2, except that the pH of the second reaction solution is adjusted to 3.

[0101] The 2-mercaptoethanesulfonic acid gold salt solution prepared in the present comparative example precipitates a large amount of white precipitate and is invalid on the day of preparation, and cannot be used in the preparation of a gold plating solution.

[0102] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as limiting the scope of the application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. A cyanide-free gold plating solution for mercapto sulfonic acid, characterized by, The thiol sulfonic acid cyanide-free gold plating solution comprises a gold source, a complexing agent, an additive and a pH buffer; The gold source is a thiol sulfonic acid gold salt; The pH of the thiol sulfonic acid cyanide-free gold plating solution is 2-13; The preparation method of the thiol sulfonic acid gold salt comprises the following steps: (1) dissolving gold in aqua regia, adding deionized water to the obtained syrup-like solution to remove nitrogen oxides, obtaining a chloroauric acid solution, and adjusting the pH of the chloroauric acid solution to 6-7 by using a pH buffer to obtain a first reaction liquid; (2) dissolving a thiol sulfonic acid salt in deionized water, and adjusting the pH of the solution to 9-13 by using a pH buffer to obtain a second reaction liquid; (3) mixing the first reaction liquid and the second reaction liquid to obtain the thiol sulfonic acid gold salt; In step (3), the molar concentration ratio of gold ions in the first reaction liquid to thiol sulfonic acid salt in the second reaction liquid is 1:5-1:15; The amount of the gold source is such that the molar concentration of gold ions in the thiol sulfonic acid cyanide-free gold plating solution is 0.03-0.12 mol / L; The concentration of the additive in the thiol sulfonic acid cyanide-free gold plating solution is 0.80-1.50 g / L; The molar concentration ratio of gold ions in the thiol sulfonic acid cyanide-free gold plating solution to the complexing agent is 1:4-1:20; The complexing agent comprises at least one of hydantoin, organic amine and amino acid.

2. The cyanide-free gold plating solution according to claim 1, wherein, In step (2), the thiol sulfonic acid salt comprises at least one of 2-mercaptoethanesulfonic acid salt, 3-mercapto-1-propanesulfonic acid salt, 2,3-dimercaptopropanesulfonic acid salt, 4-mercapto-1-butanesulfonic acid salt, 3,4-dimercaptobutanesulfonic acid salt and 2,4-dimercaptobutanesulfonic acid salt.

3. The cyanide-free gold plating solution according to claim 1, wherein, The additive comprises one or two or more of cobalt sulfate, potassium antimony tartrate, arsenic trioxide, polyethylene glycol and polyacetyl imide; The pH buffer comprises one or two or more of potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium hydroxide and hydrochloric acid.

4. A method for preparing a cyanide-free gold plating solution of mercaptansulfonic acid according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: Mixing the thiol sulfonic acid gold salt with the complexing agent and the additive in sequence, adding the pH buffer to the obtained mixed solution to adjust the pH to 2-13, filtering and constant volume to obtain the thiol sulfonic acid cyanide-free gold plating solution.

5. A gold plating method using the cyanide-free gold plating solution for mercapto sulfonic acid according to any one of claims 1 to 3, characterized by, The method comprises the following step: immersing a gold-plated part in the thiol sulfonic acid cyanide-free gold plating solution to perform electroplating to obtain a gold-plated part; The temperature of the electroplating is 40-50℃; The average current density of the electroplating is 0.2-5.0 ASD; The electroplating is performed in a periodic square wave pulse mode.

6. Application of the thiol sulfonic acid cyanide-free gold plating solution according to any one of claims 1-3 in electronic devices and / or semiconductor manufacturing.

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