Stabilizer for cyanide-containing gold-silver electroplating solution, electroplating solution, and electroplating method

Abstract

The present invention relates to the technical field of electroplating. Disclosed are a stabilizer for a cyanide-containing gold-silver electroplating solution, an electroplating solution, and an electroplating method. The stabilizer is hydantoin or a derivative thereof, and the molar ratio of the stabilizer to silver ions in the cyanide-containing gold-silver electroplating solution is 2 or above. The gold-silver electroplating solution comprises a water-soluble cyanide-containing gold salt, a water-soluble cyanide-containing silver salt, a conductive salt, the stabilizer, and water; and the concentration of gold ions is 1-20 g / L, the concentration of silver ions is 0.3-10 g / L, and the concentration of the conductive salt is 10-120 g / L. The stabilizer of the present invention has excellent protection capability for the silver ions in the cyanide-containing gold-silver electroplating solution, and can also function as a leveling agent; the electroplating solution has extremely high stability, and there is no need to additionally add free cyanide ions and a leveling agent, which is relatively friendly to the manufacturing process in semiconductor chip manufacturing involving a photoresist; and gold-silver alloy plating layers having different gold contents can be obtained simply by changing the current density and without changing an electroplating apparatus and the electroplating solution.

Description

Stabilizer for cyanide-containing gold-silver electroplating solution, electroplating solution and electroplating method Technical Field

[0001] The invention belongs to the technical field of electroplating and relates to a stabilizer for a cyanide-containing gold-silver electroplating solution, an electroplating solution and an electroplating method. The gold-silver electroplating solution has high stability and does not contain free cyanide ions, and is suitable for use in semiconductor chips. Background Art

[0002] When packaging semiconductor chips, pure gold is often used to ensure chip performance due to its superior properties. Partially replacing gold with silver could significantly reduce packaging costs. Furthermore, gold-silver alloys have lower electrical resistance and higher thermal conductivity than pure gold, helping to improve chip heat dissipation and increase electrical interconnect density.

[0003] The use of electroplating technology to prepare gold-silver alloy packaging structures instead of pure gold packaging structures has some technical requirements for gold-silver electroplating solutions that are the same as other application scenarios, such as high stability; and some requirements that are different from other application scenarios, such as: (1) it cannot cause the photoresist on the chip to be packaged to swell, and (2) it is convenient to manufacture gold-silver coatings with different gold contents to form a composite structure to simultaneously meet the packaging structure's multiple requirements for hardness, roughness, and resistance to sulfurization and oxidation.

[0004] Gold-silver alloy electroplating solutions are categorized as either cyanide-containing or cyanide-free. Gold and silver ions exhibit higher complexation constants with cyanide ions, making them more stable than cyanide-free solutions. However, silver ions are photosensitive, and in addition to the cyanide component inherent in potassium silver cyanide, free cyanide ions are typically introduced into the plating solution to prevent the silver ions from decomposing in the presence of light. Besides posing a significant safety risk, free cyanide ions can also swell the photoresist, reducing the manufacturing precision of the circuits. Therefore, developing stabilizers and corresponding plating solutions for cyanide-containing gold-silver electroplating solutions that are free of free cyanide ions while ensuring high plating solution stability is currently a challenge in the industry.

[0005] CN104099653B discloses a technical solution for preparing a gold-silver alloy using a potassium aurous cyanide and potassium silver cyanide electroplating solution. The plating solution has a pH of 6.5-7.0 and contains 2-5 mL / L of oxalate as a leveling agent (see paragraphs 160-165 of the specification). Because the plating solution does not contain a protective agent for silver ions, such as free cyanide ions, and because the cyanide ions provided by the main salt have poor coordination with silver ions within this pH range, the stability of the electroplating solution is poor.

[0006] GB2046794A and CH629260A5 also disclose technical solutions for preparing gold-silver alloys using potassium gold cyanide and potassium silver cyanide electroplating solutions. These solutions do not contain free cyanide ions, but instead use polymer additives such as polyethyleneimine or polyethylene oxide as brighteners. Firstly, due to the lack of a protective agent for silver ions, these plating solutions have poor stability. Secondly, polyethyleneimine or polyethylene oxide easily co-deposits in the coating, leading to excessive internal stress and the formation of pores in the coating after annealing, reducing the corrosion resistance of the coating. Technical issues

[0007] The present invention aims to provide a stabilizer for a cyanide-containing gold-silver electroplating solution, as well as a corresponding electroplating solution and an electroplating method. The stabilizer has excellent protection for silver ions in the cyanide-containing gold-silver electroplating solution, preventing the silver ions from photodecomposing, and can also act as a leveler, so that no additional leveler is required to be added to the gold-silver electroplating solution. The electroplating solution has extremely high stability, does not require the addition of free cyanide ions, and is relatively friendly to semiconductor chip manufacturing processes involving photoresists. The electroplating method can easily obtain gold-silver alloy coatings with different gold contents, thereby obtaining corresponding composite structures, thereby simultaneously meeting the multiple requirements of semiconductor chip packaging structures for hardness, roughness, and resistance to sulfidation and oxidation. Technical Solutions

[0008] One aspect of the present invention is to provide a stabilizer for a cyanide-containing gold-silver electroplating solution. The stabilizer is hydantoin or a derivative thereof, and the molar ratio of the stabilizer to the silver ions in the cyanide-containing gold-silver electroplating solution is greater than 2, preferably 2-20.

[0009] The stabilizer hydantoin or its derivative provided by the present invention, on the one hand, acts as a complexing agent for silver ions, prevents the photoreduction of silver ions, and improves the stability of the electroplating solution. The molar ratio of hydantoin to silver ions is above 2, preferably 2-20, to ensure coordination and complexation with silver ions. The molar ratio of hydantoin or its derivative to silver ions is higher than 20, which may cause the viscosity of the plating solution to be too high, thereby reducing the uniformity of the electroplating thickness. On the other hand, in addition to the complexation with silver ions, hydantoin or its derivative and silver ions achieve a synergistic effect, playing the role of a crystallization regulator. Separate silver plating or gold plating both require the addition of a crystallization regulator in the electroplating solution, but the technical solution of the present invention does not require the addition of a crystallization regulator and can also obtain a very smooth coating.

[0010] Furthermore, the hydantoin derivative is 5,5-dimethylhydantoin (CAS number: 77-71-4), 1,3-dihydroxymethyl-5,5-dimethylhydantoin (CAS number: 6440-58-0) or 1-aminohydantoin (CAS number: 6301-02-6), preferably 5,5-dimethylhydantoin.

[0011] Another aspect of the present invention is to provide a gold-silver electroplating solution, which comprises a water-soluble cyanide-containing gold salt, a water-soluble cyanide-containing silver salt, a conductive salt, the above-mentioned stabilizer and water; the gold ion concentration is 1-20 g / L, the silver ion concentration is 0.3-10 g / L, and the conductive salt concentration is 10-120 g / L.

[0012] Furthermore, the pH value of the gold-silver electroplating solution is 8-10. When the pH value is lower than 8, the complexing ability of the stabilizer and silver ions decreases, resulting in poor stability of the plating solution; when the pH value is higher than 10, it will have an adverse effect on the photoresist.

[0013] Furthermore, the water-soluble cyanide-containing gold salt is preferably potassium aurous cyanide (molecular formula KAu(CN)2), with a gold ion concentration of 1-20 g / L. If the concentration is less than 1 g / L, the coating is prone to scorching during electroplating; if it exceeds 20 g / L, the effect of carryover increases costs. The water-soluble cyanide-containing silver salt is preferably potassium silver cyanide (molecular formula KAg(CN)2), with a silver ion concentration of 0.3-10 g / L. The ratio of gold to silver in the coating can be adjusted by adjusting the silver ion concentration in the electroplating solution to meet different application requirements.

[0014] The inventors discovered that when the gold and silver ion concentrations are within the aforementioned range, the gold content of the resulting gold-silver alloy coating can be varied using the same electroplating solution and equipment by simply adjusting the current density. Specifically, a lower current density yields a lower gold content in the gold-silver alloy coating, while a higher current density yields a higher gold content. The inventors also discovered that when the gold content of the gold-silver alloy coating is within a moderate range (20-50 wt%), the hardness and roughness meet the requirements for semiconductor chip packaging; however, resistance to sulfidation and oxidation requires a gold content of at least 60 wt%. Therefore, a composite packaging structure can be designed: the gold content of the main body of the packaging structure is within a moderate range to achieve the required hardness and roughness; simultaneously, a much thinner protective layer is formed on the outer surface of the main body of the packaging structure, without affecting the overall hardness and roughness, while still meeting the requirements for sulfidation and oxidation resistance.

[0015] Furthermore, the conductive salt is preferably a pyrophosphate, which can be one or more of sodium pyrophosphate, potassium pyrophosphate, or ammonium pyrophosphate. Pyrophosphate can increase the conductivity of the plating solution and improve the uniformity of electroplating. However, a concentration that is too low cannot meet the required conductivity of the plating solution, while a concentration that is too high can increase the viscosity of the plating solution, thereby affecting the electrodeposition of gold or silver.

[0016] Another aspect of the present invention is to provide an electroplating method, wherein the gold and silver electroplating solution is used for electroplating, the electroplating operation temperature is 20-40°C, the electroplating current density is 0.3-1.5A / dm 2When the operating temperature is lower than 20℃, the temperature is difficult to control and the electroplating uniformity deteriorates. When the operating temperature exceeds 40℃, the roughness of the coating tends to increase, which may affect the subsequent welding performance or bonding effect. The electroplating current density is operated at 0.3-1.5 A / dm 2 Within the range, for the same composition of the electroplating solution, the gold content in the coating increases with increasing current density. 2 When the current density is greater than 1.5A / dm 2 There is a risk of the coating burning.

[0017] Furthermore, when the gold content in the gold-silver plating layer is required to be below 50wt%, the current density of the electroplating is 0.3-0.6A / dm 2 When the gold content in the gold-silver plating layer is required to be above 60wt%, the current density of electroplating is 1.1-1.5A / dm 2 .

[0018] The resulting gold-silver alloy electroplated layer is then annealed at a temperature of 270-300°C for 5-120 minutes. Annealing can eliminate stress and improve the performance of the gold-silver alloy electroplated layer. The annealing temperature and time can be determined experimentally within the aforementioned parameter ranges based on the area and thickness of the gold-silver alloy electroplated layer. Generally, larger areas and thicker thicknesses require higher annealing temperatures and longer annealing times.

[0019] Another aspect of the present invention is to provide a product obtained by the above electroplating method. Beneficial effects

[0020] The present invention has the following beneficial technical effects: The stabilizer provided by the present invention has excellent protection for silver ions in cyanide-containing gold-silver electroplating solutions, preventing the photodecomposition of silver ions and also acting as a leveling agent. The electroplating solution provided by the present invention has extremely high stability and does not require the addition of free cyanide ions, making it relatively friendly to semiconductor chip manufacturing processes involving photoresists and eliminating the need for the addition of leveling agents. The electroplating method provided by the present invention can produce gold-silver alloy coatings with different gold contents by simply changing the current density without changing the electroplating equipment or electroplating solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a schematic diagram of a gold-silver alloy packaging structure obtained by using the electroplating solution provided by the present invention.

[0022] Figure numerals: 1-gold-silver alloy packaging structure body, 2-thin layer with high gold content, 3-chip substrate. Modes for Carrying Out the Invention

[0023] The following is a clear and complete description of the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0024] The present invention uses the following analytical testing methods to test the gold-silver electroplating solutions and gold-silver alloy coatings obtained in each embodiment and comparative example.

[0025] (1) Stability test of the plating solution. After the plating solution is prepared, it is placed at room temperature for 24 hours. If the plating solution is clear and no metal film is formed on the surface of the plating solution, it is judged to be stable. If the plating solution is turbid or a metal film is formed on the surface of the liquid, it is judged to be unstable.

[0026] (2) Gold content test of the coating. A 300 nm TiW and an 80 nm Au seed layer were first deposited on the silicon wafer by PVD sputtering. Then, a gold-silver alloy was electroplated on the wafer. The gold and silver content of the coating was tested using SEM-EDX (Zeiss, Sigma 300).

[0027] (3) Roughness test of the coating. A 300 nm thick TiW and an 80 nm thick Au seed layer were first deposited on the silicon wafer by PVD sputtering. Then, a gold-silver alloy was electroplated on the wafer. The roughness of the coating was tested using a laser confocal microscope (KEYENCE, VK-2050).

[0028] (4) Hardness test of the coating. A 300 nm TiW and an 80 nm Au seed layer were first deposited on the silicon wafer by PVD sputtering. Then, a 10 μm thick gold-silver alloy was electroplated on the wafer. The coating hardness was tested using a hardness tester (Mitutoyo, HM-200). Example 1

[0029] In a 1 L beaker, add 600 mL of deionized water, then add 60 g of potassium pyrophosphate and 30 g of hydantoin to fully dissolve them. Then, add 10 g of potassium cyanide with a gold ion content and 5 g of potassium cyanide with a silver ion content (the molar ratio of hydantoin to silver ion is 6.5). Adjust the pH of the plating solution to 9 and add deionized water to bring the volume of the plating solution to 1000 mL. The electroplating temperature is set to 30°C, a 3 × 3 cm gold-plated silicon wafer is used, and the current density is 0.3 A / dm 2 The electroplating thickness is 10 μm. The annealing temperature after electroplating is 290°C and the annealing time is 30 minutes.

[0030] The gold content in the electroplated coating is 26 wt%, the roughness Ra is 57 nm, the hardness of the coating before annealing is 102 HV, and the hardness of the coating after annealing is 65 HV. The plating solution is stable after being placed for 24 hours. Example 2

[0031] The difference from Example 1 is that the current density is changed to 0.4 A / dm 2 , the other conditions are the same.

[0032] The gold content in the electroplated layer is 31 wt%, the roughness Ra is 63 nm, the hardness of the layer before annealing is 113 HV, and the hardness of the layer after annealing is 62 HV. The plating solution is stable after being placed for 24 hours. Example 3

[0033] Same as Example 1 except that the current density is changed to 0.5 A / dm 2 , the other conditions are the same.

[0034] The gold content in the electroplated layer is 44 wt%, the roughness Ra is 83 nm, the hardness of the layer before annealing is 133 HV, and the hardness of the layer after annealing is 95 HV. The plating solution is stable after being placed for 24 hours. Example 4

[0035] The difference from Example 1 is that the gold ion concentration is changed to 20 g / L, the silver ion concentration is changed to 10 g / L, the potassium pyrophosphate concentration is changed to 120 g / L, the stabilizer is changed to 23.7 g / L of 5,5-dimethylhydantoin (the molar ratio of 5,5-dimethylhydantoin to silver ion is 2), the pH is changed from 9 to 8, and the temperature is changed to 20°C; the other conditions are the same.

[0036] The gold content in the electroplated layer is 38 wt%, the roughness Ra is 82 nm, the hardness of the layer before annealing is 112 HV, and the hardness of the layer after annealing is 85 HV. The plating solution is stable after being placed for 24 hours. Example 5

[0037] The difference from Example 4 is that the pH is changed to 10, the electroplating temperature is changed to 40°C, and the current density is changed to 0.6 A / dm 2 ; Other conditions are the same.

[0038] The gold content in the electroplated coating is 49 wt%, the roughness Ra is 91 nm, the hardness of the coating before annealing is 157 HV, and the hardness of the coating after annealing is 104 HV. The plating solution is stable after being placed for 24 hours. Example 6

[0039] The difference from Example 4 is that the pH is changed to 9, the electroplating temperature is changed to 30°C, and the current density is changed to 0.9 A / dm2 ; Other conditions are the same.

[0040] The gold content in the electroplated coating is 57 wt%, the roughness Ra is 158 nm, the hardness of the coating before annealing is 177 HV, and the hardness of the coating after annealing is 136 HV. The plating solution is stable after being placed in it for 24 hours. Example 7

[0041] The difference from Example 1 is that the current density is changed to 1.0 A / dm 2 , the electroplating thickness was changed to 0.5μm; the other conditions were the same.

[0042] The gold content in the electroplated layer is 66 wt%, the roughness Ra is 24 nm, and the plating solution is stable after being placed in it for 24 hours. Example 8

[0043] The difference from Example 1 is that the current density is changed to 1.3 A / dm 2 , the electroplating thickness was changed to 0.5μm; the other conditions were the same.

[0044] The gold content in the electroplated layer is 73 wt%, the roughness Ra is 27 nm, and the plating solution is stable after being placed for 24 hours. Example 9

[0045] The difference from Example 1 is that the current density is changed to 1.6 A / dm 2 , the electroplating thickness was changed to 0.5 μm, and the other conditions were the same.

[0046] The gold content in the electroplated layer is 77 wt%, the roughness Ra is 34 nm, and the plating solution is stable after being placed for 24 hours. Example 10

[0047] The difference from Example 1 is that the gold ion concentration is changed to 1 g / L, the silver ion concentration is changed to 0.3 g / L, the potassium pyrophosphate concentration is changed to 10 g / L, the stabilizer is changed to 4.7 g / L of 5,5-dimethylhydantoin (the molar ratio of 5,5-dimethylhydantoin to silver ions is 19.8), the electroplating temperature is changed to 40° C., and the electroplating thickness is changed to 0.5 μm; the other conditions are the same.

[0048] The gold content in the electroplated layer is 35 wt%, the roughness Ra is 12 nm, and the plating solution is stable after being placed in it for 24 hours.

[0049] Comparative Example 1

[0050] The difference from Example 3 is that the hydantoin content is changed to 0 g / L (ie, no hydantoin is added), and the other conditions are the same.

[0051] The gold content in the electroplated coating is 38 wt%, the roughness Ra is 83 nm, the hardness of the coating before annealing is 135 HV, and the hardness of the coating after annealing is 78 HV. A silver film is found on the surface of the coating after the plating solution is left for 24 hours.

[0052] Comparative Example 2

[0053] The difference from Example 3 is that the hydantoin content is changed to 5 g / L (the molar ratio of hydantoin to silver ions is changed to 1.1), and the other conditions are the same.

[0054] The gold content in the electroplated coating is 40 wt%, the roughness Ra is 79 nm, the hardness of the coating before annealing is 145 HV, and the hardness of the coating after annealing is 85 HV. A silver film is found on the surface of the coating after the plating solution is left for 24 hours.

[0055] Comparative Example 3

[0056] The difference from Example 3 is that 30 g / L of hydantoin is replaced by 5 g / L of sodium oxalate monohydrate, and the other conditions are the same.

[0057] The gold content in the electroplated coating is 35 wt%, the roughness Ra is 155 nm, the hardness of the coating before annealing is 127 HV, and the hardness of the coating after annealing is 74 HV. A silver film is found on the surface of the plating solution after the plating solution is left for 24 hours.

[0058] Comparative Example 4

[0059] The difference from Example 3 is that 30 g / L of hydantoin is replaced by 15 g / L of ethylenediamine, and the other conditions are the same.

[0060] The gold content in the electroplated coating is 37 wt%, the roughness Ra is 340 nm, the hardness of the coating before annealing is 168 HV, and the hardness of the coating after annealing is 126 HV. The plating solution is stable after being placed for 24 hours.

[0061] The parameter conditions and performance comparison results of the above examples and comparative examples are shown in Table 1.

[0062] Table 1 Parameter conditions and performance comparison results of various embodiments and comparative examples

[0063] Note: “NA” in the table means “Not Applicable”.

[0064] From the data in Table 1, it can be concluded that in each embodiment, since the stabilizer of the present invention was added to the plating solution, no silver film was formed on the surface of the plating solution after the plating solution was placed for 24 hours, indicating that the stabilizer of the present invention solved the stability problem of the plating solution.

[0065] The data in Table 1 also demonstrates that the annealed hardness and roughness of the coating are significantly correlated with the gold content in the coating. When the gold content in the coating is controlled below 50 wt%, the coating roughness Ra is below 100 nm, and the annealed hardness is less than 105 HV. This is of great significance for replacing pure gold with gold-silver alloys in semiconductor chip packaging structures. A comparison of Examples 1-3, Examples 4-6, and Examples 7-9 shows that increasing the current density can increase the gold content in the coating. Considering that gold-silver alloys, especially those with lower gold content, are less resistant to oxidation or sulfurization than pure gold, this also provides a method for producing gold-silver alloys with higher gold content, thereby improving the oxidation or sulfurization resistance of gold-silver packaging structures. However, a problem is that when the gold content is high, as in Example 6, the coating roughness and annealed hardness are high (gold above 50 wt%), making it unsuitable for semiconductor chip packaging (typical packaging requirements are roughness Ra less than 100 nm and annealed hardness less than 120 HV). Based on this, the electroplating solution of the present invention can be used to create a two-layer packaging structure. As shown in Figure 1, a low current density is first used to prepare a gold-silver alloy packaging structure body 1 with a low gold content, which is then combined with a chip substrate 3 to ensure low roughness and low hardness. The electroplating thickness is approximately 8-12 μm. Then, the same electroplating solution is used on the top surface to prepare a thin layer 2 with a higher gold content at a high current density to improve the oxidation or sulfurization resistance of the gold-silver packaging structure. The electroplating thickness is approximately 10-500 nm. This not only ensures the requirements of low hardness and low roughness, but also ensures the reliability of subsequent welding or bonding. Examples 7-9 show that the roughness Ra of the gold-silver alloy coating with a high gold content is only 24-37 nm when the electroplating thickness is 0.5 μm.

[0066] In Comparative Example 3, sodium oxalate monohydrate was used as an additive (see CN104099653B). A white silver film formed on the surface of the plating solution after 24 hours of standing. This was attributed to the photodecomposition of silver ions, indicating that sodium oxalate did not stabilize silver ions. In Comparative Example 1, without the addition of a hydantoin derivative as a silver ion stabilizer, the plating solution became unstable after 24 hours, and the roughness of the coating was also relatively high, further demonstrating the synergistic effect of hydantoin and silver ions acting as grain size regulators. In Comparative Example 2, a small amount of white silver film was observed on the surface of the plating solution after 24 hours of standing, even though the molar ratio of hydantoin to silver ions was less than 2. This indicates that a certain amount of hydantoin is required to complex the silver ions and act as a stabilizer.

[0067] Furthermore, the synergistic use of silver ions and hydantoin or its derivatives also acts as a crystallization modifier. Comparing Example 3 and Comparative Example 4, at the same electroplating thickness, the roughness of the coating was 83 nm when 5,5-dimethylhydantoin was used, but 340 nm when ethylenediamine was used. Although the use of ethylenediamine as an additive provided acceptable plating bath stability, the roughness of the coating after electroplating was excessively high, making the resulting gold-silver alloy clearly unsuitable for semiconductor chip packaging.

[0068] Although the embodiments of the present invention have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art may make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention. The scope of protection of the present invention is defined by the claims and their equivalents.

Claims

1. Stabilizer for cyanide-containing gold and silver electroplating solution, characterized in that, The stabilizer is hydantoin or its derivative, and the molar ratio of the stabilizer to silver ions in the cyanide-containing gold-silver electroplating solution is more than 2, preferably 2 - 20.

2. The stabilizer according to claim 1, wherein The derivative of hydantoin is 5, 5-dimethylhydantoin, 1, 3-dihydroxymethyl-5, 5-dimethylhydantoin or 1-aminohydantoin, preferably 5, 5-dimethylhydantoin.

3. A gold and silver electroplating solution, characterized in that, The gold-silver electroplating solution contains a water-soluble cyanide-containing gold salt, a water-soluble cyanide-containing silver salt, a conductive salt, the stabilizer according to claim 1 or 2, and water; the gold ion concentration is 1 - 20 g / L, the silver ion concentration is 0.3 - 10 g / L, and the conductive salt concentration is 10 - 120 g / L.

4. The gold and silver electroplating solution according to claim 3, wherein, The pH value of the electroplating solution is 8 - 10.

5. The gold and silver electroplating solution according to claim 3, wherein, The water-soluble cyanide-containing gold salt is potassium aurocyanide, and the water-soluble cyanide-containing silver salt is potassium silver cyanide.

6. The gold and silver electroplating solution according to claim 3, characterized in that, The conductive salt is pyrophosphate.

7. The gold and silver electroplating solution according to claim 6, wherein The pyrophosphate is one or more of sodium pyrophosphate, potassium pyrophosphate or ammonium pyrophosphate.

8. An electroplating method, characterized in that, Electroplating is carried out using the gold and silver electroplating solution according to any one of claims 3-7. The operating temperature of electroplating is 20-40 °C, and the current density of electroplating is 0.3-1.5 A / dm 2 .

9. The electroplating method according to claim 8, characterized in that, When the gold content in the gold-silver coating needs to be below 50 wt%, the electroplating current density is 0.3 - 0.6 A / dm 2 ; when the gold content in the gold-silver coating needs to be above 60 wt%, the electroplating current density is 1.1 - 1.5 A / dm 2 .

10. The electroplating method according to claim 8 or 9, characterized in that, The obtained gold-silver alloy electroplated layer is subjected to annealing treatment, the annealing temperature is 270 - 300 °C, and the annealing time is 5 - 120 min.

11. An article obtained by the electroplating method according to any one of claims 8 - 10.

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