Electroplating solution and manufacturing method of rhodium alloy coating

Abstract

The invention discloses an electroplating solution and a manufacturing method of a rhodium alloy plating layer. Each liter of the electroplating solution comprises the following components: rhodium salt, a pH regulator, alloy element salt, a phosphorus-containing additive, a low stress agent, a wetting agent and the balance of water. Wherein the alloy element salt comprises iridium sulfate and / or indium sulfate. According to the electroplating liquid, alloy elements are introduced, meanwhile, the additives are added, and electroplating current parameters are changed, so that a plating layer has low stress and high toughness, and meanwhile, the specific advantage of high hardness of a rhodium plating layer is reserved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor coating technology, and in particular to a method for manufacturing a high-toughness coating. Background Art

[0002] The electroplating process is an excellent method for manufacturing metal coatings. It has the characteristics of low cost, wide controllable range of process parameters, high coating purity, and fast deposition rate. It is an indispensable process step in high-tech industries such as micro-electromechanical systems that require extremely fine structures. It is used to cast specific metal structures at the micro-nano scale. Electroplated rhodium has high hardness, low contact resistance and excellent corrosion resistance, and is usually used for electrical contact or physical contact structures. However, along with high hardness comes high brittleness, which makes it easy to break under external force, greatly limiting its application scenarios and service life.

[0003] Currently, the most common electroplated rhodium alloy is rhodium-ruthenium alloy. Since ruthenium itself has a high hardness, it does not lose much hardness after alloying. Therefore, the rhodium-ruthenium alloy has limited help in improving toughness. Summary of the invention

[0004] The purpose of the present application is to solve the problem of high brittleness and easy fracture of rhodium plating in the prior art. The present application provides an electroplating solution and a method for manufacturing a rhodium alloy plating, which can manufacture a rhodium alloy plating with high toughness.

[0005] In order to achieve the above objectives, this application adopts the following technical solutions:

[0006] In a first aspect, the present application provides an electroplating solution, wherein each liter of the electroplating solution comprises the following components by weight:

[0007]

[0008] The balance is water and a pH regulator; wherein the alloy element salt comprises iridium sulfate and / or indium sulfate, and the pH regulator makes the pH range of the electroplating solution be 0.2-3.

[0009] The electroplating solution of the present application is suitable for application in the field of electronic products and semiconductors. The alloy element salt selects iridium sulfate and / or indium sulfate that matches the lattice of rhodium as much as possible. On the one hand, the internal stress and grain refinement caused by lattice mismatch are reduced. On the other hand, the electrode potential of the alloy element matches rhodium, which can avoid the phenomenon of being unable to precipitate; finally, the content of the alloy element salt is moderate. Too low a content will promote solid solution strengthening and grain refinement, which is not conducive to the improvement of coating toughness, and too high a content is prone to produce a crystalline second phase, and performance loss is serious. And the use of phosphorus-containing additives can reduce internal defects in the coating, and by adding low stress agents and wetting agents to relieve stress and hydrogen precipitation, a rhodium alloy coating with higher toughness is obtained. Therefore, the electroplating solution of the present application can better solve the problem of low toughness and easy fracture of the rhodium coating.

[0010] In a possible implementation, the rhodium salt is selected from one or more of rhodium sulfate, rhodium phosphate, rhodium sulfate-phosphate, rhodium chloride, rhodium iodide, rhodium nitrate, and rhodium chloride.

[0011] In a possible implementation, the phosphorus-containing additive is selected from one or more of sodium phosphite, potassium dihydrogen phosphite, and diammonium hydrogen phosphite.

[0012] In a possible implementation, the low stress agent is selected from one or both of magnesium sulfate and selenic acid.

[0013] In a possible implementation, the wetting agent is a surfactant.

[0014] In a possible implementation, the wetting agent is selected from one or both of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

[0015] The electroplating solution includes the following components in mass-volume concentration:

[0016]

[0017] The balance is water and pH adjuster.

[0018] In one possible implementation, the pH regulator is sulfuric acid.

[0019] In a second aspect, the present application provides a method for manufacturing a rhodium alloy coating, comprising the following steps:

[0020] Using the electroplating solution, immersing the base material into the electroplating solution;

[0021] The electroplating treatment is performed on the substrate to be electroplated, wherein the electroplating treatment is performed in a constant current, and the current density of the constant current is 0.5-6A / dm 2 , the plating solution temperature is maintained at 30-70℃;

[0022] The base material with the coating is taken out from the electroplating solution and annealed. The annealing temperature is 100-400°C and the holding time is 1-10h.

[0023] In a possible implementation, a direct current power source is used to electroplate a substrate material to be electroplated, wherein the direct current power source:

[0024] In one possible implementation, the equivalent current density ranges from 0.05 to 4.8 A / dm 2 ;

[0025] and / or a duty cycle range of 10%-90%;

[0026] and / or a frequency range of 1-10000Hz.

[0027] In a possible implementation, the electroplating anode is made of platinum or titanium platinum material, and / or the distance between the substrate material to be plated and the electrode is in the range of 2-20 cm.

[0028] In a possible implementation, the base material is pre-treated before coating to make the surface of the base material clean, conductive and hydrophilic.

[0029] In a possible implementation, during the electroplating process, the operating temperature range of the plating solution is 40-60°C.

[0030] In a third aspect, the present application also provides a method for testing the fracture toughness of a coating, comprising the following steps:

[0031] S1. Select a substrate material with a sacrificial layer, and electroplate a metal film to be tested on the sacrificial layer, and the coating thickness reaches the calibrated film thickness;

[0032] S2, corroding the sacrificial layer, releasing the coating and leveling it, and obtaining a coating sample;

[0033] S3, fixing the release surface of the coating sample on the sample stage upward;

[0034] S4, perform nanoindentation test;

[0035] S5. Test and obtain the hardness H, modulus E and maximum load P of the coating sample during the test, and measure the crack length of the residual indentation;

[0036] S6. Calculate the fracture toughness of the coating: Among them, K c is the fracture toughness, α is taken as 0.016, E is the modulus, H is the hardness, P is the maximum load, and c is the crack length.

[0037] In a possible implementation, the surface of the sacrificial layer is ground and polished to be smooth and flat.

[0038] In a possible implementation, the material of the sacrificial layer is any one of copper, silver, zinc and nickel.

[0039] In a possible implementation, in step S1, a mask is used to determine the shape of the coating.

[0040] In a possible implementation, the diameter of the coating sample is greater than 50 μm, and the thickness of the calibration film is greater than 3 μm.

[0041] In a possible implementation, in step S1, a layer of high-hardness metal is continuously electroplated on the surface of the metal film to be tested as a support layer, and the area of ​​the support layer is larger than the area of ​​the plated sample.

[0042] In a possible implementation, in step S4, a continuous stiffness method or a quasi-static method is used to perform a nanoindentation test, and the maximum test depth is 8-15% of the thickness of the coating sample.

[0043] In a possible implementation, in step S4, the maximum test depth is 10% of the sample thickness.

[0044] Compared with the prior art, the advantages of the present application are: preparing the electroplating solution of rhodium-iridium alloy or rhodium-indium alloy, introducing alloy elements while adding additives and changing the current parameters of electroplating, so that the coating has lower stress and higher toughness, while retaining the high hardness unique to the rhodium coating.

[0045] Instruction Manual

[0046] Figure 1 In one embodiment of the present application, a SEM image of the residual indentation on the rhodium plated layer after the nanoindentation test. DETAILED DESCRIPTION

[0047] To describe the technical content, structural features, achieved purpose and effect of the invention in detail, the technical solution of the present application will be described below in conjunction with the embodiment of the present application. Obviously, the described embodiment is only a part of the embodiment of the present application, rather than all embodiments. In the following description, for the purpose of explanation, many specific details are set forth to provide a detailed description of various exemplary embodiments or embodiments of the invention. However, various exemplary embodiments may also be implemented without these specific details or in the case of one or more equivalent arrangements. In addition, various exemplary embodiments may be different, but need not be exclusive.

[0048] In the study of rhodium-ruthenium alloy coatings, the applicant found that the brittleness of rhodium coatings mainly comes from several aspects: internal stress, microcracks, hydrogen evolution, and small grain size. These problems can be improved to a certain extent by optimizing the electroplating parameters, such as pulse electroplating. In addition, the above problems can also be improved by adjusting the composition of the electroplating solution.

[0049] In this application, salts of alloying elements are added to the electroplating solution to increase the toughness of the coating by alloying. Electroplating rhodium plating solutions usually include rhodium sulfate, rhodium phosphate, and a mixed system of sulfuric acid-rhodium phosphate. The salts of the alloying elements need to match the plating solution system to avoid the introduction of other anions. Due to the high hardness of rhodium, the introduction of most alloying elements will reduce the hardness and lose key performance, so the selection and content of alloying elements are crucial.

[0050] In one embodiment of the present application, an electroplating solution includes the following components: a rhodium salt, an alloy element salt, an acid, a phosphorus-containing additive, a low-stress agent, a wetting agent, and deionized water, wherein the alloy element salt includes iridium sulfate and / or indium sulfate.

[0051] In the present application, the inventors intentionally select alloy elements that match the rhodium lattice as much as possible, such as iridium, indium, and ruthenium, so as to reduce the internal stress and grain refinement caused by the lattice mismatch; in addition, in order to avoid the phenomenon of precipitation failure, alloy elements that match the electrode potential of rhodium, such as iridium, indium, and ruthenium, are selected in the present application; finally, the content of alloy elements should be moderate. Too low a content will promote solid solution strengthening and grain refinement, which is not conducive to improving toughness, while too high a content will easily produce a crystalline second phase, resulting in serious performance loss.

[0052] In some embodiments, the rhodium salt is selected from one or more of rhodium sulfate, rhodium phosphate, rhodium sulfate-phosphate, rhodium chloride, rhodium iodide, rhodium nitrate, and rhodium chloride.

[0053] In some embodiments, the phosphorus-containing additive is selected from one or more of sodium phosphite, potassium dihydrogen phosphite, and diammonium hydrogen phosphite. The phosphorus-containing additive can form a stable complex with metal ions, increase the activation energy of metal ion reduction, thereby helping to form a more delicate and compact coating, while helping to reduce defects such as pinholes and pitting in the coating, reduce internal defects in the coating, and improve the density and corrosion resistance of the coating.

[0054] In some embodiments, the low stress agent is selected from magnesium sulfate and / or selenic acid. The low stress agent can reduce the internal stress of the coating, improve the ductility, prevent the coating from cracking, improve the adhesion of the coating, and improve the quality of the coating. Magnesium sulfate (MgSO4): Adding magnesium sulfate to the electroplating solution can increase the conductivity of the solution, and due to the presence of excess sulfate ions (SO4 2-), which can reduce the reverse reaction of the complex reaction, thereby improving the cathode current efficiency, and making the coating crystals refined and reducing internal stress.

[0055] In some embodiments, the wetting agent is a surfactant, and the role of the surfactant is to reduce the surface tension of the plating solution, making it easier for the plating solution to evenly wet the surface of the plated workpiece, fill narrow gaps, refine grains, help hydrogen precipitation, reduce the generation of gas pinholes and pits, and improve the quality and uniformity of the coating.

[0056] In one embodiment, the wetting agent is selected from sodium dodecyl sulfate and / or sodium dodecylbenzene sulfonate. Sodium dodecyl sulfate is a common wetting agent. As a surfactant, it can significantly reduce the surface tension of the electroplating solution, making it difficult for small hydrogen bubbles to remain on the surface of the workpiece, thereby reducing and eliminating gas pinholes and pitting defects in the coating. In addition, sodium dodecyl sulfate also has a certain cathode polarization function, which helps to refine the crystallization of the coating and improve the brightness of the coating.

[0057] In some embodiments, the plating solution contains the following components in mass-volume concentrations:

[0058]

[0059] The balance is deionized water and a pH regulator, wherein the pH regulator is an acid, preferably sulfuric acid, which can adjust the pH range of the electroplating solution to between 0.2 and 3.

[0060] In one embodiment of the present application, a method for manufacturing a rhodium alloy coating using the above-mentioned electroplating solution is provided, which specifically comprises:

[0061] 1. The substrate material is pre-treated before coating to make the surface of the substrate clean, conductive and hydrophilic;

[0062] 2. Immerse the substrate material in the plating solution;

[0063] 3. Use a DC power supply to electroplate the base material to be electroplated. The electroplating process is carried out under a constant current. The current density of the constant current is 0.5-6A / dm 2 , the plating solution temperature is maintained at 30-70℃;

[0064] 4. Take the plated substrate material out of the electroplating solution and perform annealing treatment. The annealing heating rate is 1-10°C / min, the annealing temperature is 100-400°C, and the holding time is 1-10h.

[0065] In one embodiment of the present application, the current density of the electroplating process can be 0.6, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0. The DC power supply: the peak current range is 0.5-6A / dm 2 .

[0066] In one embodiment of the present application, the DC power supply: the equivalent current range is 0.05-4.8A / dm 2 ;

[0067] In one embodiment of the present application, the DC power supply: the duty cycle range is 10%-90%;

[0068] In one embodiment of the present application, the DC power supply has a frequency range of 1-10000 Hz.

[0069] In one embodiment of the present application, the electroplating anode is made of platinum or titanium platinum material.

[0070] In one embodiment of the present application, the distance between the substrate material to be coated and the electrode is in the range of 2-20 cm.

[0071] In a preferred embodiment of the present application, during the electroplating process, the operating temperature range of the plating solution is 40-60°C, such as 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, and 60°C.

[0072] In one embodiment, the rhodium coating is produced as follows:

[0073] 1. Plating bath

[0074] ① Use rhodium sulfate to prepare the electroplating solution, Rh 2+ Ion concentration range 1-4g / L;

[0075] ② Use sulfuric acid with a concentration range of 30-100g / L to adjust the pH value of the plating solution to a pH range of 0.2-3;

[0076] ③ Iridium sulfate and indium sulfate are selected as alloy element salts, corresponding to rhodium-iridium alloy and rhodium-indium alloy, and the concentration range of iridium sulfate or indium sulfate in the electroplating solution is 0.1-10g / L;

[0077] ④ Sodium phosphite is used as the phosphorus-containing additive, and the concentration range in the plating solution is 1-10g / L;

[0078] ⑤ Magnesium sulfate can be used as a low-stress agent, wherein the concentration of magnesium sulfate in the plating solution is in the range of 5-20 g / L; or selenic acid can be used as a low-stress agent, wherein the concentration of selenic acid in the plating solution is in the range of 0.1-4 g / L;

[0079] ⑥ Sodium dodecyl sulfate is used as a wetting agent, with a concentration range of 0.01-1g / L in the plating solution.

[0080] 2. Electroplating

[0081] ①Use platinum or titanium platinum anode, the electrode distance range is 2-20cm.

[0082] ② Pre-treatment: ensure the substrate surface is clean, conductive and hydrophilic.

[0083] ③The working temperature range of the plating solution is 30-70℃, and the optimal working temperature is 40-60℃.

[0084] ④Electroplating parameter range: Use DC or pulse power supply, where the current density range of DC power supply is 0.5-6A / dm 2 , the optimal current density range is 1-3A / dm 2 ; The peak current range of the pulse power supply is 0.5-6A / dm 2 , the equivalent current range is 0.05-4.8A / dm 2 , the duty cycle range is 10%-90%, and the frequency range is 1-10000Hz.

[0085] 3. Annealing

[0086] After plating, the coating and the base material can be annealed together, or the coating can be released and then annealed. The main purpose of annealing is stress release and recrystallization. During the annealing process, tools can be used to reinforce the external force to maintain the shape of the coating during the stress release process.

[0087] Annealing parameter range: heating rate 1-10℃ / min, annealing temperature 100-400℃, holding time 1-10h.

[0088] After the above-mentioned electroplating, in order to further improve the performance of the coating, a series of tests were also carried out on the coating, such as the coating fracture toughness test. In order to quantitatively characterize the toughness of the coating, the nanoindentation method to test the fracture toughness is a convenient and effective method. However, the traditional coating fracture toughness test method is limited by the coating itself, such as thickness, residual stress, etc., and its results do not have absolute quantitative significance. In order to quantitatively analyze the fracture toughness of the coating as much as possible and compare it, the present application also proposes a method for nanoindentation testing of fracture toughness, comprising the following steps:

[0089] S1. Select a substrate material with a sacrificial layer, and electroplate a metal film to be tested on the sacrificial layer, and the coating thickness reaches the calibrated film thickness. Among them, the sacrificial layer can be made of metals such as copper, silver, zinc, and nickel, which can be corroded by a specific corrosive solution without corroding the substrate and the subsequent electroplated coating. The sacrificial layer can be deposited on the surface of the substrate by electroplating or sputtering. To ensure a smooth surface, it can be properly polished. A mask can be used to determine the shape of the coating, the coating diameter is greater than 50μm, and the coating thickness is greater than 3μm.

[0090] S2, corrode the sacrificial layer, release the coating and level it, and obtain the coating sample. Generally speaking, if the coating sample size is sufficient, it can be directly transferred to prepare the nanoindentation sample, and only the surface needs to be leveled after electroplating. If the coating sample size is small, in step S1, after electroplating the metal film to be tested, continue to electroplating a larger area of ​​high-hardness metal as a support layer and level it.

[0091] S3. Fix the release surface of the plated sample on the sample table with the release surface facing upward. You can use hot melt adhesive or other bonding methods to fix the plated sample on the sample table to ensure that the sample is completely flat and not tilted. The surface of the plated sample that contacts the sacrificial layer is the release surface, and the release surface is selected as the indentation test surface. Since the surface of the sacrificial layer is smooth and flat before electroplating, the release surface should also be smooth and flat for easy testing.

[0092] S4. Perform nanoindentation test. The nanoindentation test is performed using a continuous stiffness method or a quasi-static method, with a maximum test depth of 8-15% of the coating sample thickness, preferably 10% of the coating sample thickness to avoid surface and substrate effects.

[0093] S5. Test to obtain the hardness H, modulus E and maximum load P of the coating sample during the test, and measure the crack length of the residual indentation.

[0094] S6. Calculate the fracture toughness of the coating: Among them, K c is the fracture toughness, α is taken as 0.016, E is the modulus, H is the hardness, P is the maximum load, and c is the crack length.

[0095] Comparative Example:

[0096] Each liter of the electroplating solution includes 10 g of rhodium sulfate, 60 g of sulfuric acid, and 0.5 g of sodium dodecyl sulfate, which are dissolved and fixed to volume using pure deionized water.

[0097] Electroplating uses a DC power supply with a current density of 2A / dm 2 , plating solution temperature 50℃.

[0098] The electroplating time is 1h and the coating thickness is 5μm.

[0099] Annealing parameters: heating rate 5℃ / min, annealing temperature 250℃, holding time 2h.

[0100] Fracture toughness 0.5MPa·m 1 / 2 .

[0101] Embodiment 1:

[0102] Each liter of the electroplating solution includes 10 g of rhodium sulfate, 60 g of sulfuric acid, 0.5 g of indium sulfate, 2 g of sodium phosphite, 10 g of magnesium sulfate, and 0.5 g of sodium dodecyl sulfate, which are dissolved and fixed to volume using pure deionized water.

[0103] Electroplating uses a DC power supply with a current density of 2A / dm 2 , plating solution temperature 50℃.

[0104] The electroplating time is 1h and the coating thickness is 5μm.

[0105] Annealing parameters: heating rate 5℃ / min, annealing temperature 250℃, holding time 2h.

[0106] Fracture toughness 1.5MPa·m 1 / 2 .

[0107] Embodiment 2:

[0108] Each liter of the electroplating solution includes 10 g of rhodium sulfate, 60 g of sulfuric acid, 1 g of indium sulfate, 2 g of sodium phosphite, 10 g of magnesium sulfate, and 0.5 g of sodium dodecyl sulfate, which are dissolved and fixed to volume using pure deionized water.

[0109] Electroplating uses a DC power supply with a current density of 2A / dm 2 , plating solution temperature 50℃.

[0110] The electroplating time is 1h and the coating thickness is 5μm.

[0111] Annealing parameters: heating rate 5℃ / min, annealing temperature 250℃, holding time 2h.

[0112] Fracture toughness 1.8MPa·m 1 / 2 .

[0113] Embodiment 3:

[0114] Each liter of the electroplating solution includes 10 g of rhodium sulfate, 60 g of sulfuric acid, 1.5 g of indium sulfate, 2 g of sodium phosphite, 10 g of magnesium sulfate, and 0.5 g of sodium dodecyl sulfate, which are dissolved and fixed to volume using pure deionized water.

[0115] Electroplating uses a DC power supply with a current density of 2A / dm 2 , plating solution temperature 50℃.

[0116] The electroplating time is 1h and the coating thickness is 5μm.

[0117] Annealing parameters: heating rate 5℃ / min, annealing temperature 250℃, holding time 2h.

[0118] Fracture toughness 2MPa·m 1 / 2 .

[0119] Embodiment 4:

[0120] Each liter of the electroplating solution includes 10 g of rhodium sulfate, 60 g of sulfuric acid, 1 g of iridium sulfate, 2 g of sodium phosphite, 10 g of magnesium sulfate, and 0.5 g of sodium dodecyl sulfate, which are dissolved and fixed to volume with pure deionized water.

[0121] Electroplating uses a DC power supply with a current density of 2A / dm 2 , plating solution temperature 50℃.

[0122] The electroplating time is 1h and the coating thickness is 5μm.

[0123] Annealing parameters: heating rate 5℃ / min, annealing temperature 250℃, holding time 2h.

[0124] Fracture toughness 1.3MPa·m 1 / 2 .

[0125] Embodiment 5:

[0126] Each liter of the electroplating solution includes 10 g of rhodium sulfate, 60 g of sulfuric acid, 1.5 g of iridium sulfate, 2 g of sodium phosphite, 10 g of magnesium sulfate, and 0.5 g of sodium dodecyl sulfate, which are dissolved and fixed to volume with pure deionized water.

[0127] Electroplating uses a DC power supply with a current density of 2A / dm 2 , plating solution temperature 50℃.

[0128] The electroplating time is 1h and the coating thickness is 5μm.

[0129] Annealing parameters: heating rate 5℃ / min, annealing temperature 250℃, holding time 2h.

[0130] Fracture toughness 1.6MPa·m 1 / 2 .

[0131] Embodiment 6:

[0132] Each liter of the electroplating solution includes 10 g of rhodium sulfate, 60 g of sulfuric acid, 2 g of iridium sulfate, 2 g of sodium phosphite, 10 g of magnesium sulfate, and 0.5 g of sodium dodecyl sulfate, which are dissolved and fixed to volume with pure deionized water.

[0133] Electroplating uses a DC power supply with a current density of 2A / dm 2 , plating solution temperature 50℃.

[0134] The electroplating time is 1h and the coating thickness is 5μm.

[0135] Annealing parameters: heating rate 5℃ / min, annealing temperature 250℃, holding time 2h.

[0136] Fracture toughness 1.9MPa·m 1 / 2 .

[0137] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and the scope of protection of the present invention is defined by the attached claims, description and their equivalents.

Claims

1. An electroplating solution, characterized in that: Each liter of the electroplating solution includes the following components by weight: The balance is water and a pH regulator; wherein the alloy element salt comprises iridium sulfate and / or indium sulfate, and the pH regulator makes the pH range of the electroplating solution be 0.2-3.

2. The electroplating solution according to claim 1, characterized in that The rhodium salt is selected from one or more of rhodium sulfate, rhodium phosphate, rhodium sulfate-phosphate, rhodium chloride, rhodium iodide, rhodium nitrate, and rhodium chloride.

3. The electroplating solution according to claim 1, characterized in that The phosphorus-containing additive is selected from one or more of sodium phosphite, potassium dihydrogen phosphite and diammonium hydrogen phosphite.

4. The electroplating solution according to claim 1, characterized in that The low stress agent is selected from one or both of magnesium sulfate and selenic acid.

5. The electroplating solution according to claim 1, characterized in that The wetting agent is a surfactant.

6. The electroplating solution according to claim 5, characterized in that The wetting agent is selected from one or both of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

7. The electroplating solution according to any one of claims 1 to 6, characterized in that: The electroplating solution includes the following components in mass-volume concentration: Rhodium sulfate 2.4-9.6g / L; Iridium sulfate or indium sulfate 0.1-10g / L; Sodium phosphite 1-10g / L; Magnesium sulfate 5-20g / L; Sodium dodecyl sulfate 0.01-1g / L; The balance is water and pH adjuster.

8. The electroplating solution according to claim 7, characterized in that The pH regulator is sulfuric acid.

9. A method for producing a rhodium alloy coating, comprising the following steps: Using the electroplating solution as described in any one of claims 1 to 8, immersing the substrate material in the electroplating solution; The electroplating treatment is performed on the substrate to be electroplated, wherein the electroplating treatment is performed in a constant current, and the current density of the constant current is 0.5-6A / dm 2 , the plating solution temperature is maintained at 30-70℃; The base material with the coating is taken out from the electroplating solution and annealed. The annealing temperature is 100-400°C and the holding time is 1-10h.

10. The manufacturing method according to claim 9, characterized in that: A DC power source is used to electroplate the base material to be electroplated, wherein the DC power source: The equivalent current density range is 0.05-4.8A / dm 2 ; and / or a duty cycle range of 10%-90%; and / or a frequency range of 1-10000Hz.

11. The manufacturing method according to claim 9, characterized in that: The electroplating anode is made of platinum or titanium platinum material, and / or the distance between the substrate material to be plated and the electrode is in the range of 2-20 cm.

12. The manufacturing method according to claim 9, characterized in that: The base material is pre-treated before coating to make the surface of the base material clean, conductive and hydrophilic.

13. The manufacturing method according to claim 9, characterized in that: During the electroplating process, the operating temperature range of the plating solution is 40-60°C.

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