Chemical reduction gold plating solution

Abstract

The invention belongs to the field of chemical plating, and particularly discloses a chemical reduction gold plating solution. The chemical reduction gold plating solution comprises, by mass concentration, 2-6 g / L of gold salt, 0.02-0.08 g / L of a stabilizer, 5-10 g / L of a complexing agent, 2-8 g / L of a reducing agent, 1-4 g / L of a homogenizing agent and 0.06-0.12 g / L of a composite inhibitor. The composite inhibitor is prepared from pentaethylene glycol dimethyl sulfonate and beta-alanine benzyl ester p-toluenesulfonate. The chemical reduction gold plating solution has excellent gold cylinder stability, the solution is still clear and free of sediment after being used for 8 months, and a gold plating layer prepared through the chemical reduction gold plating solution is bright, free of color difference and gold bumps on the surface, compact and flat in surface, free of folding plating cracks and small in thickness range; and the use requirements of gold plating of high-precision electronic devices can be met.

Description

Technical Field

[0001] The invention belongs to the field of chemical plating, and in particular relates to a chemical reduction gold plating solution. Background Art

[0002] Gold plating has excellent corrosion resistance, wear resistance, ductility, plasticity, high conductivity and good welding performance, making it widely used in metal plating on the surface of electronic devices, integrated circuits, printed circuit boards, relays, connectors and other products. However, traditional chemical reduction gold plating liquid generally has the following disadvantages: (1) The color difference of the gold plating layer is large, which makes the color difference between different batches of products or the same batch of products large, affecting the appearance of the product; (2) The surface of the gold plating layer is uneven and there are folding cracks; (3) The stability of the gold cylinder of the gold plating liquid is poor, and the precipitation phenomenon occurs. The above problems affect the application of chemical reduction gold plating liquid and the performance of chemical reduction gold plating products. Summary of the invention

[0003] In order to overcome the problems existing in the prior art, one of the purposes of the present invention is to provide a chemical reduction gold plating solution.

[0004] A second object of the present invention is to provide a chemical reduction gold plating method.

[0005] The third object of the present invention is to provide the application of the above-mentioned chemical reduction gold plating solution in the field of product gold plating.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The first aspect of the present invention provides a chemical reduction gold plating solution, comprising the following components in mass concentrations: 2-6 g / L of gold salt, 0.02-0.08 g / L of stabilizer, 5-10 g / L of complexing agent, 2-8 g / L of reducing agent, 1-4 g / L of homogenizing agent, and 0.06-0.12 g / L of composite inhibitor; the composite inhibitor comprises pentaethylene glycol dimethanesulfonate and β-alanine benzyl ester toluenesulfonate.

[0008] Due to the inhomogeneity of the metal surface, there are large differences in the gold deposition rate. If no inhibitor is added, the formed gold coating will have unevenness. Although the inhibitor in the prior art can inhibit the deposition rate of the gold coating, it cannot selectively inhibit the deposition rate of the gold, so that the thickness range of the obtained gold coating is still large, which has a certain impact on the performance of the gold coating. The present invention uses a composite inhibitor containing pentaethylene glycol dimethanesulfonate and β-alanine benzyl ester toluenesulfonate. There is a synergistic effect between the two, which can determine the directional growth of the crystal face on the metal surface. The composite inhibitor can be preferentially adsorbed on the crystal face with a larger deposition rate, inhibiting the deposition rate of the gold coating on the crystal face with a larger deposition rate, so that the gold deposition rate on the metal surface tends to be consistent, so that the obtained gold coating has higher density and flatness, and reduces the thickness range of the gold coating.

[0009] Preferably, the composite inhibitor comprises a mixture of pentaethylene glycol dimethanesulfonate and β-alanine benzyl ester p-toluenesulfonate in a mass concentration ratio of (1-4):1.

[0010] Preferably, in the chemical reduction gold plating solution, the mass concentration of pentaethylene glycol dimethanesulfonate is 0.04-0.08 g / L; the mass concentration of β-alanine benzyl ester p-toluenesulfonate is 0.02-0.04 g / L.

[0011] Preferably, the gold salt is selected from at least one of sodium gold sulfite and potassium gold sulfite.

[0012] Preferably, the stabilizer is 2-mercaptobenzimidazole carboxylic acid.

[0013] Preferably, the complexing agent is thiazole-4-carboxylic acid. The stabilizer (2-mercaptobenzimidazole carboxylic acid) and the complexing agent (thiazole-4-carboxylic acid) in the present invention can greatly improve the stability of the chemical reduction gold plating solution. The chemical reduction gold plating solution is still clear and transparent and does not change color after 8 months of normal use, so that the use period of the chemical reduction gold plating solution greatly exceeds the half-year use period of potassium cyanide gold salt.

[0014] Preferably, the reducing agent is thiourea. The reducing agent in the present invention has a high reducing activity and can continuously reduce gold.

[0015] Preferably, the homogenizing agent is sodium pentosan polysulfone. The homogenizing agent sodium pentosan polysulfone can evenly promote the growth sites of new crystal nuclei during the gold precipitation process, improve the catalytic activity of gold, and promote the continuous reduction of gold.

[0016] Preferably, the chemical reduction gold plating solution further comprises an acidic pH regulator and / or an alkaline pH regulator. The present invention uses an acidic pH regulator and / or an alkaline pH regulator to adjust the pH of the chemical reduction gold plating solution to a pH of 6-7.

[0017] Preferably, the alkaline pH regulator is selected from sodium hydroxide, potassium hydroxide or a combination thereof.

[0018] Preferably, the alkaline pH regulator is a sodium hydroxide solution with a mass percentage of 5 to 15%.

[0019] Preferably, the acidic pH regulator is selected from sulfuric acid; more preferably, the acidic pH regulator is a sulfuric acid solution with a mass percentage of 5 to 15%.

[0020] Preferably, the chemical reduction gold plating solution also contains a solvent.

[0021] Preferably, the solvent comprises water.

[0022] Preferably, the pH of the chemical reduction gold plating solution is 6-7.

[0023] Preferably, the chemical reduction gold plating solution is used at 25-35°C.

[0024] The second aspect of the present invention provides a chemical reduction gold plating method, comprising the following steps: immersing a workpiece to be plated in the chemical reduction gold plating solution of the first aspect of the present invention for chemical reduction gold plating at 25-35°C.

[0025] The third aspect of the present invention provides the use of the chemical reduction gold plating solution described in the first aspect of the present invention in the field of product gold plating.

[0026] Preferably, the product comprises an electronic device, an integrated circuit, a printed circuit board, a relay or a connector.

[0027] The beneficial effects of the present invention are as follows: the chemical reduction gold plating solution of the present invention has excellent gold cylinder stability, the solution is still clear and has no precipitation after being used for 8 months, and the gold plating layer prepared by using the chemical reduction gold plating solution of the present invention is bright, has no color difference and gold nodules on the surface, has a dense and flat surface without folding cracks, and has a very small thickness difference, which can meet the use requirements of gold plating of high-precision electronic devices. DETAILED DESCRIPTION

[0028] The specific implementation of the present invention is further described in detail below in conjunction with examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are processes that are not particularly described in detail below, they can be implemented or understood by those skilled in the art with reference to the prior art. The reagents or instruments used that do not indicate the manufacturer are all conventional products that can be purchased commercially.

[0029] In some embodiments of the present invention, the present invention provides a chemical reduction gold plating solution, comprising the following components in mass concentrations: 2-6 g / L of gold salt, 0.02-0.08 g / L of stabilizer, 5-10 g / L of complexing agent, 2-8 g / L of reducing agent, 1-4 g / L of uniforming agent, and 0.06-0.12 g / L of composite inhibitor; the composite inhibitor comprises pentaethylene glycol dimethanesulfonate and β-alanine benzyl ester toluenesulfonate.

[0030] In some embodiments of the present invention, the mass concentration of gold salt in the chemical reduction gold plating solution can be selected from 2g / L, 2.5g / L, 3g / L, 3.5g / L, 4g / L, 4.5g / L, 5g / L, 5.5g / L, and 6g / L.

[0031] In some embodiments of the present invention, the mass concentration of the stabilizer in the chemical reduction gold plating solution can be selected from 0.02g / L, 0.03g / L, 0.04g / L, 0.05g / L, 0.06g / L, 0.07g / L, and 0.08g / L.

[0032] In some embodiments of the present invention, the mass concentration of the complexing agent in the chemical reduction gold plating solution can be selected from 5g / L, 5.5g / L, 6g / L, 6.5g / L, 7g / L, 7.5g / L, 8g / L, 8.5g / L, 9g / L, 9.5g / L, and 10g / L.

[0033] In some embodiments of the present invention, the mass concentration of the reducing agent in the chemical reduction gold plating solution can be selected from 2g / L, 2.5g / L, 3g / L, 3.5g / L, 4g / L, 4.5g / L, 5g / L, 5.5g / L, 6g / L, 6.5g / L, 7g / L, 7.5g / L, and 8g / L.

[0034] In some embodiments of the present invention, the mass concentration of the leveling agent in the chemical reduction gold plating solution can be selected from 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, and 4 g / L.

[0035] In some embodiments of the present invention, the mass concentration of the composite inhibitor in the chemical reduction gold plating solution can be selected from 0.06g / L, 0.07g / L, 0.08g / L, 0.09g / L, 0.1g / L, 0.11g / L, and 0.12g / L.

[0036] In some embodiments of the present invention, the composite inhibitor comprises a mixture of pentaethylene glycol dimethanesulfonate and β-alanine benzyl p-toluenesulfonate in a mass concentration ratio of (1 to 4): 1, for example, the mass concentration ratio of pentaethylene glycol dimethanesulfonate and β-alanine benzyl p-toluenesulfonate can be selected from 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 3:1, 3.5:1, and 4:1.

[0037] In some embodiments of the present invention, in the chemical reduction gold plating solution, the mass concentration of pentaethylene glycol dimethanesulfonate is 0.04-0.08 g / L; the mass concentration of β-alanine benzyl ester p-toluenesulfonate is 0.02-0.04 g / L.

[0038] In some embodiments of the present invention, the mass concentration of pentaethylene glycol dimethanesulfonate in the chemical reduction gold plating solution can be selected from 0.04 g / L, 0.045 g / L, 0.05 g / L, 0.055 g / L, 0.06 g / L, 0.065 g / L, 0.07 g / L, 0.075 g / L, and 0.08 g / L.

[0039] In some embodiments of the present invention, the mass concentration of β-alanine benzyl ester p-toluenesulfonate in the chemical reduction gold plating solution can be selected from 0.02 g / L, 0.025 g / L, 0.03 g / L, 0.035 g / L, and 0.04 g / L.

[0040] In some embodiments of the present invention, the gold salt is selected from at least one of sodium gold sulfite and potassium gold sulfite.

[0041] In some embodiments of the present invention, the stabilizer is 2-mercaptobenzimidazole carboxylic acid.

[0042] In some embodiments of the present invention, the complexing agent is thiazole-4-carboxylic acid. The stabilizer (2-mercaptobenzimidazole carboxylic acid) and the complexing agent (thiazole-4-carboxylic acid) in the present invention can greatly improve the stability of the chemical reduction gold plating solution. The chemical reduction gold plating solution is still clear and transparent and does not change color after 8 months of normal use, so that the use period of the chemical reduction gold plating solution greatly exceeds the half-year use period of potassium cyanide gold salt.

[0043] In some embodiments of the present invention, the reducing agent is thiourea. The reducing agent in the present invention has a high reducing activity and can continuously reduce gold.

[0044] In some embodiments of the present invention, the leveling agent is sodium pentosan polysulfone. The leveling agent sodium pentosan polysulfone can evenly promote the growth sites of new crystal nuclei during the gold precipitation process, improve the catalytic activity of gold, and promote the continuous reduction of gold.

[0045] In some embodiments of the present invention, the chemical reduction gold plating solution further comprises an acidic pH regulator and / or an alkaline pH regulator. The present invention uses an acidic pH regulator and / or an alkaline pH regulator to adjust the pH of the chemical reduction gold plating solution to a pH of 6-7.

[0046] In some embodiments of the present invention, the alkaline pH adjuster is selected from sodium hydroxide, potassium hydroxide or a combination thereof.

[0047] In some embodiments of the present invention, the alkaline pH regulator is a sodium hydroxide solution with a mass percentage of 5-15%.

[0048] In some embodiments of the present invention, the acidic pH regulator is selected from sulfuric acid; in some embodiments of the present invention, the acidic pH regulator is a sulfuric acid solution with a mass percentage of 5-15%.

[0049] In some embodiments of the present invention, the chemical reduction gold plating solution further contains a solvent.

[0050] In some embodiments of the present invention, the solvent comprises water.

[0051] In some embodiments of the present invention, the pH of the chemical reduction gold plating solution is 6-7. For example, the pH can be selected from 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, and 7.

[0052] In some embodiments of the present invention, the chemical reduction gold plating solution is used at 25-35°C. For example, the chemical reduction gold plating solution in the present invention can be used for chemical reduction gold plating at any temperature of 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, and 35°C.

[0053] In some embodiments of the present invention, the present invention further provides a chemical reduction gold plating method, comprising the following steps: immersing the workpiece to be plated in the above-mentioned chemical reduction gold plating solution for chemical reduction gold plating at 25-35°C.

[0054] In some embodiments of the present invention, the workpiece to be plated includes an electronic device, an integrated circuit, a printed circuit board, a relay, or a connector.

[0055] In some embodiments of the present invention, the present invention also provides the use of the above chemical reduction gold plating solution in the field of product gold plating.

[0056] In some embodiments of the invention, the product includes an electronic device, an integrated circuit, a printed circuit board, a relay, or a connector.

[0057] The implementation of the present invention is further described in detail below in conjunction with specific embodiments:

[0058] Example 1

[0059] This example provides a chemical reduction gold plating solution, which includes the following components in mass concentrations: 4 g / L sodium gold sulfite, 0.06 g / L pentaethylene glycol dimethanesulfonate, 0.03 g / L β-alanine benzyl p-toluenesulfonate, 4 g / L thiourea, 2 g / L sodium pentosan polysulfone, 8 g / L thiazole-4-carboxylic acid, and 0.060 g / L 2-mercaptobenzimidazole carboxylic acid. The solvent in the chemical reduction gold plating solution is water.

[0060] The pH of the chemical reduction gold plating solution in this example is 6.5.

[0061] Example 2

[0062] This example provides a chemical reduction gold plating solution, which includes the following components in mass concentrations: 2 g / L sodium gold sulfite, 0.04 g / L pentaethylene glycol dimethanesulfonate, 0.02 g / L β-alanine benzyl p-toluenesulfonate, 2 g / L thiourea, 1 g / L sodium pentosan polysulfone, 5 g / L thiazole-4-carboxylic acid, and 0.02 g / L 2-mercaptobenzimidazole carboxylic acid. The solvent in the chemical reduction gold plating solution is water.

[0063] The pH of the chemical reduction gold plating solution in this example is 6.5.

[0064] Example 3

[0065] This example provides a chemical reduction gold plating solution, which includes the following components in mass concentrations: 2 g / L sodium gold sulfite, 0.04 g / L pentaethylene glycol dimethanesulfonate, 0.02 g / L β-alanine benzyl p-toluenesulfonate, 4 g / L thiourea, 2 g / L sodium pentosan polysulfone, 8 g / L thiazole-4-carboxylic acid, and 0.06 g / L 2-mercaptobenzimidazole carboxylic acid. The solvent in the chemical reduction gold plating solution is water.

[0066] The pH of the chemical reduction gold plating solution in this example is 6.5.

[0067] Comparative Example 1

[0068] This example provides a chemical reduction gold plating solution, which includes the following components in mass concentrations: 2 g / L sodium gold sulfite, 4 g / L thiourea, 2 g / L sodium pentosan polysulfone, 8 g / L thiazole-4-carboxylic acid, and 0.06 g / L 2-mercaptobenzimidazole carboxylic acid. The solvent in the chemical reduction gold plating solution is water.

[0069] The pH of the chemical reduction gold plating solution in this example is 6.5.

[0070] Comparative Example 2

[0071] This example provides a chemical reduction gold plating solution, which includes the following components in mass concentrations: 2 g / L sodium gold sulfite, 0.04 g / L pentaethylene glycol dimethanesulfonate, 0.02 g / L β-alanine benzyl p-toluenesulfonate, 4 g / L thiourea, 8 g / L thiazole-4-carboxylic acid, and 0.06 g / L 2-mercaptobenzimidazole carboxylic acid. The solvent in the chemical reduction gold plating solution is water.

[0072] The pH of the chemical reduction gold plating solution in this example is 6.5.

[0073] Comparative Example 3

[0074] This example provides a chemical reduction gold plating solution, which includes the following components in mass concentrations: 2 g / L sodium gold sulfite, 0.04 g / L pentaethylene glycol dimethanesulfonate, 0.02 g / L β-alanine benzyl p-toluenesulfonate, 4 g / L thiourea, 2 g / L sodium pentosan polysulfone, and 0.06 g / L 2-mercaptobenzimidazole carboxylic acid. The solvent in the chemical reduction gold plating solution is water.

[0075] The pH of the chemical reduction gold plating solution in this example is 6.5.

[0076] Comparative Example 4

[0077] This example provides a chemical reduction gold plating solution, which includes the following components in mass concentrations: 2 g / L sodium gold sulfite, 0.04 g / L pentaethylene glycol dimethanesulfonate, 0.02 g / L β-alanine benzyl p-toluenesulfonate, 4 g / L thiourea, 2 g / L sodium pentosan polysulfone, and 8 g / L thiazole-4-carboxylic acid. The solvent in the chemical reduction gold plating solution is water.

[0078] The pH of the chemical reduction gold plating solution in this example is 6.5.

[0079] When the chemical reduction gold plating solution in Examples 1 to 3 of the present invention and Comparative Examples 1 to 4 is used for chemical reduction plating, the substrate to be plated is placed in the chemical reduction gold plating solution, chemical plating is performed at an operating temperature of 30° C. for 30 minutes, and then the substrate is taken out to complete the chemical reduction gold plating process.

[0080] The various properties of the substrate after the chemical reduction gold plating operation are tested. The specific test method is as follows:

[0081] (1) Thickness and thickness range test: Each test group uses five substrates as test objects to compare the appearance brightness, gold nodules, and uniformity. If the range is ≤0.05μm and the substrate is bright and has no gold nodules, it is recorded as "excellent"; if 0.05μm < range ≤0.1μm, the substrate is bright with occasional gold nodules, it is recorded as "good"; if 0.1μm < range ≤0.15μm and the substrate is slightly dark with obvious gold nodules, it is recorded as "poor"; if 0.15μm < range ≤0.2μm, the substrate is black with color difference, it is recorded as "poor"; if the range is >0.2μm, it is recorded as "very poor".

[0082] (2) Folding crack test: Each test group has 5 substrates, and the surface of the substrate is evaluated for folding cracks. Specifically: if the surface is dense and flat without folding cracks, it is recorded as excellent; if there are occasional fine cracks on the surface, which are very small and can only be observed under 3000 times SEM, it is recorded as good; if the cracks are large and generally visible at 1000 times magnification, it is recorded as poor; if there are many cracks on the gold surface, which are visible at 500 times magnification, it is recorded as poor; if the cracks on the gold surface are visible at 200 times or less, it is recorded as very poor.

[0083] (3) Stability of the gold tank. The experimental volume of each test group is 5 tank solutions, which are used normally for 8 months. The stability of the gold tank is evaluated after 8 months of use. Specifically, if the solution is clear and transparent and does not change color within 8 months, it is recorded as excellent; if the solution is clear within 8 months, but there is a little red solid precipitation on the tank wall, it is recorded as good; if the solution is a little red within 8 months, it is recorded as poor; if the solution is obviously red and turbid within 8 months, it is recorded as poor; if the solution is turbid and seriously discolored within 6 months, it is recorded as very poor.

[0084] (4) Gold layer adhesion index: if the tape is torn three times without powder falling off, it is excellent; if the tape is torn three times with slight powder falling off at the edge, it is good; if the tape is torn three times with lumps falling off at the edge, it is poor; if the tape is torn three times with lumps falling off in the middle, it is poor.

[0085] The performance data of the chemical reduction gold plating solutions in Examples 1 to 3 and Comparative Examples 1 to 4 measured according to the above test method are shown in Table 1 below.

[0086] Table 1 Performance data of chemical reduction gold plating solution

[0087]

[0088] As shown in Table 1, the thickness range of the chemical reduction gold plating solution in Examples 1 to 3 does not exceed 0.05 μm, the gold cylinder has excellent stability, the solution is clear and transparent within 8 months, does not change color, the surface of the gold plating layer is dense and flat without folding cracks, the color and brightness are uniform, and the coating adhesion is excellent. When gold is plated on a carrier, the thicker the thickness of the gold plating layer, the greater the deviation, and the more difficult it is to control the thickness range of the gold plating layer. The present invention adjusts the type and amount of components in the chemical reduction gold plating solution to achieve a thickness range of no more than 0.05 μm when the thickness of the gold plating layer is close to 0.4 μm, which is significantly better than the existing chemical reduction gold plating solution.

[0089] Compared with Example 3, the chemical reduction gold plating solution in Comparative Example 1 lacks a composite inhibitor (i.e., pentaethylene glycol dimethanesulfonate and β-alanine benzyl ester toluenesulfonate), and the chemical reduction gold plating solution in Comparative Example 2 lacks a leveling agent (i.e., sodium pentosan polysulfone). The thickness extreme difference, folding cracks and adhesion of Comparative Examples 1 to 2 are significantly reduced, and cannot meet the use requirements of chemical reduction gold plating.

[0090] Compared with Example 3, the chemical reduction gold plating solution in Comparative Example 3 lacks a complexing agent (i.e., thiazole-4-carboxylic acid), and the chemical reduction gold plating solution in Comparative Example 4 lacks a stabilizer (i.e., 2-mercaptobenzimidazole carboxylic acid). The thickness of Comparative Examples 3 to 4 is extremely poor, the stability of the gold cylinder, the folding cracks and the adhesion are greatly reduced, and the use requirements of chemical reduction gold plating cannot be met.

[0091] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A chemical reduction gold plating solution, characterized in that: The components include the following mass concentrations: gold salt 2-6g / L, stabilizer 0.02-0.08g / L, complexing agent 5-10g / L, reducing agent 2-8g / L, homogenizer 1-4g / L, composite inhibitor 0.06-0.12g / L; The composite inhibitor comprises pentaethylene glycol dimethanesulfonate and beta-alanine benzyl ester p-toluenesulfonate.

2. The chemical reduction gold plating solution according to claim 1, characterized in that: The composite inhibitor comprises a mixture of pentaethylene glycol dimethanesulfonate and beta-alanine benzyl ester p-toluenesulfonate in a mass concentration ratio of (1-4):

1.

3. The chemical reduction gold plating solution according to claim 2, characterized in that: In the chemical reduction gold plating solution, the mass concentration of pentaethylene glycol dimethanesulfonate is 0.04-0.08 g / L; the mass concentration of beta-alanine benzyl ester p-toluenesulfonate is 0.02-0.04 g / L.

4. The chemical reduction gold plating solution according to claim 1, characterized in that: The gold salt is selected from at least one of sodium gold sulfite and potassium gold sulfite; And / or, the stabilizer is 2-mercaptobenzimidazole carboxylic acid; and / or, the complexing agent is thiazole-4-carboxylic acid; and / or, the reducing agent is thiourea; And / or, the homogenizing agent is sodium pentosan polysulfone.

5. The chemical reduction gold plating solution according to any one of claims 1 to 4, characterized in that: The chemical reduction gold plating solution also contains a solvent.

6. The chemical reduction gold plating solution according to claim 5, characterized in that: The solvent includes water.

7. The chemical reduction gold plating solution according to claim 6, characterized in that: The pH value of the chemical reduction gold plating solution is 6-7.

8. A chemical reduction gold plating method, characterized in that: The following steps are involved: The workpiece to be plated is immersed in the chemical reduction gold plating solution according to any one of claims 1 to 7 for chemical reduction gold plating at 25-35°C.

9. Use of the chemical reduction gold plating solution according to any one of claims 1 to 7 in the field of product gold plating.

10. The use according to claim 9, characterized in that: The product includes an electronic device, an integrated circuit, a printed circuit board, a relay or a connector.

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