Platinum-ruthenium alloy plating solution and method for plating platinum-ruthenium alloy film

Abstract

A plating solution is provided that is excellent in deposition efficiency and is capable of forming a platinum-ruthenium alloy plating film having a wide range of ruthenium concentrations. [Solution] The present invention relates to a platinum-ruthenium alloy plating solution containing a platinum complex salt and a ruthenium complex salt. In the present invention, the platinum complex salt is a platinum complex salt whose anion component is a halogen, and the ruthenium complex salt is a trivalent ruthenium complex salt whose anion component is a halogen. In the present invention, when ruthenium is precipitated from a ruthenium halide, the addition of a platinum complex salt whose anion component is a halogen improves the ruthenium precipitation efficiency, allowing the formation of platinum-ruthenium alloy plating films of a wide range of compositions.

Description

[Technical Field]

[0001] The present invention relates to a plating solution for forming a platinum-ruthenium alloy plating film by electroplating. More specifically, the present invention relates to a platinum-ruthenium alloy plating solution that can form platinum-ruthenium alloy plating films with a wide range of alloy compositions (ruthenium concentrations) and that is excellent in terms of deposition efficiency. The present invention also relates to a plating method for forming a platinum-ruthenium alloy plating film using the platinum-ruthenium alloy plating solution. [Background technology]

[0002] Plating films made of precious metals such as platinum and palladium are used in a wide range of fields, including decorative items and jewelry, as well as electrode materials and contact materials for electronic and electrical equipment.Since many precious metals have excellent electrical conductivity, chemical stability, hardness, and other mechanical properties, the range of use of precious metal plating is expanding from fields that focus on the rarity and appearance of precious metals to fields that emphasize functionality.

[0003] Because precious metals are rare metals, the impact of price fluctuations must be taken into consideration when expanding their range of use. For example, the price of palladium has risen significantly in recent years, and the use of other precious metal plating films as an alternative to palladium plating films has been considered. Regarding price fluctuations of precious metals, platinum and ruthenium have shown relatively stable price trends, and ruthenium in particular is cheaper than platinum. Furthermore, ruthenium plating films have advantages other than price, including high hardness and excellent wear resistance among precious metals, as well as good corrosion resistance and low contact resistance. Therefore, ruthenium plating films are still used in the above-mentioned applications.

[0004] However, while ruthenium plating films have high hardness, they are also noted to be somewhat brittle and difficult to thicken. Therefore, an alloy plating film in which ruthenium is alloyed with platinum has been proposed as an effective use of ruthenium. The present applicant has long been interested in platinum-ruthenium alloy plating films, and has proposed a platinum-ruthenium alloy plating solution and a multilayer film using a platinum-ruthenium alloy plating film, which are intended for use as protective films for terminals and connectors of electronic devices such as smartphones (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-56187 [Patent Document 2] Japanese Patent Publication No. 2023-56185 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-49485 Summary of the Invention [Problem to be solved by the invention]

[0006] Considering the advantages of ruthenium in terms of price and properties, it is predicted that the demand for plating solutions capable of forming platinum-ruthenium alloy plating films will increase in the future. However, as pointed out in the above Patent Document 1, there are currently very few prior art technologies that are practical for use in platinum-ruthenium alloy plating solutions.

[0007] One possible reason for this is that platinum complex salts and ruthenium complex salts suitable as ruthenium sources for platinum-ruthenium alloy plating solutions have not yet been identified. Generally, alloy plating solutions are obtained by mixing suitable metal complex salts with plating solutions for each metal to be alloyed. Regarding platinum-ruthenium alloy plating, many platinum plating solutions using platinum complex salts are known. On the other hand, there are not many types of ruthenium plating solutions, and the most commonly used one at present is a ruthenium plating solution that uses a ruthenium complex salt containing an Ru-N-Ru structure as the metal source (Patent Document 3). However, this ruthenium complex salt has a complex structure, which makes its synthesis time-consuming and also presents stability problems.

[0008] Furthermore, platinum-ruthenium alloy plating solutions are required to be able to form alloy films with a desired alloy composition (ruthenium concentration) in addition to deposition efficiency. In particular, when the above-mentioned advantages of ruthenium, such as hardness and cost, are taken into consideration, platinum-ruthenium alloy plating films with a higher ruthenium concentration may be required. In this regard, the platinum-ruthenium alloy plating film of Patent Document 1 is useful in terms of deposition efficiency, but the upper limit of the ruthenium concentration of the platinum-ruthenium alloy plating film that can be formed is around 20 mass %, and it has been difficult to form alloy plating films with a ruthenium concentration higher than this.

[0009] The present invention has been made in light of the above background, and provides a plating solution for forming platinum-ruthenium alloy plating films, which has excellent deposition efficiency and can form platinum-ruthenium alloy plating films with a wide range of compositions (ruthenium concentrations). The present invention also clarifies a plating method for producing high-quality platinum-ruthenium alloy plating films using this platinum-ruthenium alloy plating solution. [Means for solving the problem]

[0010] In order to solve the above problems, the present inventors attempted to optimize the ruthenium complex salt and platinum complex salt, which are the metal sources of platinum-ruthenium alloy plating solutions. The present inventors first investigated the use of ruthenium complex salts containing halogens as the anion components as ruthenium complex salts. Halides have a relatively simple structure, making them easy to synthesize and obtain, and also offering good stability. However, little is known about the usefulness of ruthenium halides in plating solutions. Therefore, the present inventors investigated the properties of ruthenium plating solutions containing ruthenium halides and searched for platinum complex salts to be mixed with these ruthenium plating solutions to form platinum-ruthenium alloy films.

[0011] As a result, the present inventors have found that it is preferable to use a platinum complex salt containing a halogen as an anion component. In an alloy plating solution, the use of a common anion component for each metal complex salt is not surprising in itself, from the perspective of reducing factors inhibiting the deposition of each metal. However, the present inventors have found that in a plating solution for depositing ruthenium from a ruthenium halide, the addition of a platinum complex salt containing a halogen as an anion component also improves the deposition efficiency of ruthenium. The effect of improving the deposition efficiency of ruthenium by such platinum codeposition contributes to an increase in the deposition rate of the platinum-ruthenium alloy plating film as well as an increase in the ruthenium concentration in the alloy film. The present inventors have thus investigated a composition (additive) that can optimize the ruthenium and platinum complex salts and improve the quality of the platinum-ruthenium alloy plating film, and have arrived at the present invention.

[0012] That is, the present invention relates to a platinum-ruthenium alloy plating solution containing a platinum complex salt and a ruthenium complex salt, wherein the platinum complex salt is a platinum complex salt whose anion component is a halogen, and the ruthenium complex salt is a trivalent ruthenium complex salt whose anion component is a halogen. Hereinafter, the composition of the platinum-ruthenium alloy plating solution according to the present invention will be explained, along with a method for producing a platinum-ruthenium alloy plating film using this platinum-ruthenium alloy plating solution.

[0013] (A) Composition of the Platinum-Ruthenium Alloy Plating Solution of the Present Invention The platinum-ruthenium alloy plating solution according to the present invention contains, as essential components, a ruthenium complex salt and a platinum complex salt, which are metal sources. The platinum-ruthenium alloy plating solution also contains halogen ions derived from these complex salts, which are also essential components.

[0014] (i) Ruthenium complex salts As described above, the ruthenium complex salt used in the present invention is a trivalent ruthenium complex salt having a halogen as the anion component. This trivalent ruthenium complex salt must be present in the ruthenium plating solution at least during the plating process. Specific examples of preferred trivalent ruthenium complex salts include hexachlororuthenate(III), hexabromorthenate(III), and hexafluororuthenate(III), with sodium salts of these being preferred. Particularly preferred is hexabromorthenate(III) (sodium hexabromorthenate(III)) whose anion component is bromine (Br).

[0015] The ruthenium concentration in the alloy plating solution is preferably 0.5 g / L or more and 20 g / L or less in terms of ruthenium metal. If the ruthenium concentration is below the lower limit, there is a problem that ruthenium deposition does not proceed. Furthermore, an excessively high ruthenium concentration increases the cost of the plating solution, so the ruthenium concentration is more preferably 1.0 g / L or more and 6.0 g / L or less.

[0016] (ii) Platinum complex salts The platinum complex salt applicable to the present invention is a platinum complex salt having a halogen as the anion component. The platinum valence of the platinum complex salt in the present invention is not particularly limited, but a divalent platinum complex salt is preferred. Specific examples of preferred platinum complex salts include divalent platinum complex salts such as tetrachloroplatinate(II), tetrabromoplatinate(II), and tetrafluoroplatinate(II), with sodium salts of these being preferred. Particularly preferred is tetrabromoplatinate(II) (sodium tetrabromoplatinate(II)) in which the anion component is bromine (Br). The anion component of the platinum complex salt is preferably a halogen, the same as that of the ruthenium complex salt.

[0017] The platinum concentration in the alloy plating solution is preferably 0.5 g / L or more and 20 g / L or less in terms of platinum metal. If the platinum concentration is below the lower limit, the film formation rate of the platinum-ruthenium alloy plating film decreases. On the other hand, if the platinum concentration exceeds the upper limit, platinum is preferentially deposited and the co-deposition ratio of ruthenium decreases. The platinum concentration is more preferably 1.0 g / L or more and 4.0 g / L or less.

[0018] In the platinum-ruthenium alloy plating solution according to the present invention, which contains a platinum complex salt and a ruthenium complex salt, the ratio of the platinum concentration to the ruthenium concentration in the plating solution (platinum concentration:ruthenium) is preferably 1:10 or more and 4:1 or less on a metal basis. If the platinum concentration ratio is too low, the deposition rate of the platinum-ruthenium alloy plating film tends to be slow. On the other hand, if the platinum concentration ratio is too high, the ruthenium ratio in the plating film will be low.

[0019] (iii) Halogen ions As described above, the platinum-ruthenium alloy plating solution of the present invention uses platinum complex salts and ruthenium complex salts whose anion components are halogens. Therefore, the plating solution contains halogen ions derived from these complex salts. The halogen ions have the effect of stabilizing the platinum complex salts and ruthenium complex salts.

[0020] The halogen ions are present in an amount in excess of the theoretical amount of halogen ions derived from the platinum complex salt and the ruthenium complex salt, thereby stabilizing the complex salts and achieving a uniform deposit appearance. The content of the excess halogen ions relative to the platinum complex salt and the ruthenium complex salt is preferably 2 to 200 times the total molar amount of the platinum complex salt and the ruthenium complex salt. More preferably, it is 4 to 100 times the total molar amount, and even more preferably, it is 6 to 30 times the total molar amount. However, an excess of halogen ions may increase the specific gravity and viscosity of the plating solution, resulting in a decrease in deposition efficiency and an increase in the amount of halogen gas generated at the anode. The excess halogen ions relative to the ruthenium complex salt and the platinum complex salt refer to the total amount of halogen ions in the ruthenium plating solution, excluding the theoretical amount of halogen ions derived from the ruthenium complex salt and the platinum complex salt.

[0021] In order to make the content of halogen ions in the alloy plating solution of the present invention excessive relative to the platinum complex salt and the ruthenium complex salt, a halogen compound such as hydrochloric acid (HCl), hydrobromic acid (HBr), a chloride such as sodium chloride (NaCl), a bromide such as sodium bromide (NaBr), or sodium iodide (NaI) is added to the alloy plating solution. When such a halogen compound is added, a bromine compound is particularly preferred because it is less likely to cause corrosion of the base metal. Furthermore, when a halogen compound is added to the alloy plating solution to contain excess halogen ions, the halogen ions may be different from the halogens in the anion components of the platinum complex salt and the ruthenium complex salt described above, but are preferably the same.

[0022] (iv) Conductive salt The platinum-ruthenium alloy plating solution according to the present invention preferably contains a conductive salt. The inclusion of a conductive salt in the plating solution results in uniform deposition appearance and crack suppression. This effect is particularly noticeable in plating treatments at high current densities. The conductive salt is at least one of boric acid, borates, phosphoric acid, phosphates, saturated monocarboxylic acids having two or more carbon atoms, saturated monocarboxylic acid salts having two or more carbon atoms, saturated dicarboxylic acids having three or more carbon atoms, saturated dicarboxylic acid salts having three or more carbon atoms, saturated hydroxycarboxylic acids, saturated hydroxycarboxylic acid salts, aminosulfonic acid, aminosulfonic acid salts, aminocarboxylic acids, and aminocarboxylic acid salts. Preferred conductive salts are boric acid, borates, phosphoric acid, phosphates, acetic acid, and acetate salts. When the conductive salt is a salt, sodium salts are preferred. The conductive salt may contain at least one of the above-mentioned compounds, and may be used alone or in combination.

[0023] The conductive salt content is preferably 0.001 mol / L or more and 2.0 mol / L or less. If it is less than 0.001 mol / L, the range of current densities that can be applied to the cathode becomes narrow, which can lead to concerns about uneven plating appearance and cracking in the platinum-ruthenium alloy plating film. Furthermore, adding excessive conductive salt reduces deposition efficiency. Therefore, adding conductive salt in excess of 2.0 mol / L is not preferred. A more preferred conductive salt content is 0.01 mol / L or more and 1.0 mol / L or less.

[0024] (v) Other components (oxidizing sacrificial agents) The platinum-ruthenium alloy plating solution according to the present invention may contain, in addition to the above-described ruthenium complex salt, platinum complex salt, conductive salt, and halogen compound, known additives used in electroplating solutions, such as pH buffers, stabilizers, and brighteners.

[0025] A preferred optional component in the platinum-ruthenium alloy plating solution according to the present invention is an oxidizing sacrificial agent comprising a reducing agent component. The oxidizing sacrificial agent reduces ruthenium with a valence of three or higher and halogen gas by oxidizing near the anode, thereby imparting stability over time to the plating solution. Ruthenium is a metal whose valence is easily changed, and trivalent ruthenium (Ru 3+ ) to tetravalent ruthenium (Ru 4+ ) and a change in valence. In the present invention, the anion components of the platinum complex salt and the ruthenium complex salt are halogen ions, which are oxidized at the anode to generate halogen gas. This halogen gas may oxidize trivalent ruthenium to tetravalent ruthenium, causing a change in valence. These changes in the valence of ruthenium may also occur simultaneously.

[0026] In the present invention, it is trivalent ruthenium that is deposited on the surface of the substrate (cathode) as a platinum-ruthenium alloy plating film. Therefore, the decrease in trivalent ruthenium due to the above-mentioned change in valence can affect the deposition efficiency of the alloy film. Furthermore, halogen gas generated by the oxidation of halogen ions can become dissolved in the plating solution. This dissolved halogen gas may be reduced at the cathode, reducing the deposition efficiency of ruthenium. This decrease in deposition efficiency due to the change in valence of trivalent ruthenium and halogen ions tends to occur over time during the plating process.

[0027] When an oxidizing sacrificial agent comprising a reducing agent component is added to the platinum-ruthenium alloy plating solution of the present invention, the oxidizing sacrificial agent sacrificially oxidizes prior to trivalent ruthenium near the anode, thereby suppressing the above-mentioned change in valence. The action of such an oxidizing sacrificial agent suppresses a decrease in the deposition efficiency of ruthenium, allowing the plating process to continue.

[0028] The reducing agent component that serves as the oxidizing sacrificial agent is preferably any one of formic acid or formate, oxalic acid or oxalate, sugar, and sugar alcohol. Suitable sugars include glucose, fructose, maltose, and trehalose, and suitable sugar alcohols include sorbitol, mannitol, xylitol, and lactitol. The content of the oxidizing sacrificial agent is preferably 0.05 mol / L or more and 0.5 mol / L or less. A content of less than 0.05 mol / L fails to sufficiently suppress the aforementioned change in the valence of ruthenium and halogen ions. Addition in excess of 0.5 mol / L not only fails to provide any further improvement, but also increases the specific gravity and viscosity of the plating solution, resulting in a decrease in the deposition rate, which is undesirable.

[0029] However, in the platinum-ruthenium alloy plating solution of the present invention, the addition of an oxidation sacrificial agent is not essential. In the present invention, the codeposition of platinum has the effect of promoting the deposition of ruthenium, so it is less susceptible to the influence of valence change than a ruthenium plating solution intended for the deposition of ruthenium alone. Therefore, in the present invention, a suitable deposition state of the platinum-ruthenium alloy can be obtained without the addition of an oxidation sacrificial agent.

[0030] The concentration of each component in a platinum-ruthenium alloy plating solution can be measured using inductively coupled plasma emission spectroscopy (ICP) or ion chromatography (IC). Other analytical instruments, such as high-performance liquid chromatography (HPLC), high-performance liquid chromatography mass spectrometry (LC-MS, LC-MS / MS), Fourier transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR), can also be used. Furthermore, halogen concentrations can be measured using the DPD (diethyl-p-phenylenediamine) method (colorimetric or spectrophotometric), iodine method, and amperometric method (polarographic method), which are known methods for measuring residual halogen concentrations in solutions. Measurements can also be performed using testers, instruments, and measurement kits used for these methods.

[0031] The platinum-ruthenium alloy plating solution according to the present invention can be produced by mixing a platinum complex salt, a trivalent ruthenium complex salt, a halogen compound for adjusting the halogen ion content appropriately, a conductive salt, and other additives. Alternatively, the above components may be dissolved in high concentrations in advance to prepare a stock solution, which may then be diluted appropriately to prepare the bath.

[0032] Furthermore, as described above, it is sufficient for the platinum-ruthenium alloy plating solution according to the present invention to contain a trivalent ruthenium complex salt at the plating treatment stage. Therefore, it is preferable to mix a trivalent ruthenium complex salt even at the production stage of the plating solution, but a ruthenium complex salt with a higher valence (four or more valences) may also be added. This is because even a plating solution containing a ruthenium complex salt with a higher valence can be reduced to a trivalent ruthenium complex salt in the plating solution. In this case, methods for reducing the ruthenium complex salt with a higher valence include adding a reducing agent and electrolytic reduction using dummy electrolysis before the plating treatment.

[0033] (B) Plating method for platinum-ruthenium alloy film using the platinum-ruthenium alloy plating solution according to the present invention Next, a method for producing a platinum-ruthenium alloy plating film using the platinum-ruthenium alloy plating solution according to the present invention will be described.

[0034] In plating treatment using the platinum-ruthenium alloy plating solution according to the present invention, it is preferable to maintain the plating solution in an acidic range. Specifically, the pH is preferably between 0.1 and 4.0. If the pH exceeds 4.0, cracks will occur in the platinum-ruthenium alloy plating film, resulting in a decrease in corrosion resistance. A more preferable pH is between 0.5 and 1.5. Furthermore, the temperature of the plating solution is preferably between 25°C and 95°C. Since the solution temperature is related to deposition efficiency, deposition efficiency is poor at temperatures below 25°C. On the other hand, operation at temperatures above 95°C can cause problems such as volatilization loss of the plating solution and deterioration of the jigs. The solution temperature is more preferably between 45°C and 85°C.

[0035] The current density during plating can be adjusted taking into consideration the concentration of the complex salt in the plating solution and the type of conductive salt, to produce a ruthenium plating film with a desirable appearance. The current density range is 1.0 A / dm 2 More than 30A / dm 2 Less than 1.0A / dm is preferred. 2 It is inefficient to form a platinum-ruthenium alloy plating film of the required thickness at a current of less than 30 A / dm 2 If the current density exceeds 2.0 A / dm, it becomes difficult to prevent the occurrence of defects in the appearance of the plating film. 2 More than 8.0A / dm 2 It is more preferable that:

[0036] (v) Platinum-ruthenium alloy plating film according to the present invention As described above, the platinum-ruthenium alloy according to the present invention can produce a platinum-ruthenium alloy plating film with any desired ruthenium concentration. The platinum-ruthenium alloy plating film according to the present invention can be composed of a platinum-ruthenium alloy having a ruthenium concentration of 10% by mass or more and 90% by mass or less. In particular, the platinum-ruthenium alloy according to the present invention can have a ruthenium concentration of 50% by mass or more. It is difficult to produce a platinum-ruthenium alloy plating film with such a high ruthenium concentration using a conventional platinum-ruthenium alloy plating solution. The ruthenium concentration of the platinum-ruthenium alloy formed according to the present invention can be adjusted by the ratio of the platinum concentration to the ruthenium concentration in the plating solution and the current density.

[0037] The composition (ruthenium concentration) of the platinum-ruthenium alloy plating film can be measured by subjecting the surface or cross section of the film to X-ray fluorescence analysis (XRF), electron microprobe analysis (EPMA), energy dispersive X-ray spectroscopy (EDX), etc. Also, the composition of a solution in which the platinum-ruthenium alloy plating film is dissolved can be analyzed by inductively coupled plasma optical emission spectroscopy (ICP). [Effects of the Invention]

[0038] As described above, the platinum-ruthenium alloy plating solution according to the present invention employs platinum complex salts and ruthenium complex salts whose anion components are halogens. The platinum complex salts and ruthenium complex salts employed in the present invention have relatively simple complex structures, which allows for efficient production and bath preparation of the plating solution. Furthermore, in the present invention, both the platinum complex salt and the ruthenium complex salt are halides, and the codeposition of platinum promotes the deposition of ruthenium, allowing for the production of a platinum-ruthenium alloy plating film with a desired ruthenium concentration at an appropriate deposition rate. [Brief explanation of the drawings]

[0039] [Figure 1] 3 is a graph showing the deposition rate of a platinum-ruthenium alloy plating film obtained by platinum-ruthenium alloy plating according to the first embodiment. [Figure 2] 3 is a graph showing the deposition efficiency of a platinum-ruthenium alloy plating film obtained by platinum-ruthenium alloy plating according to the first embodiment. [Figure 3] 3 is a graph showing the deposition efficiency of ruthenium by platinum-ruthenium alloy plating according to the first embodiment. [Figure 4] 3 is a graph showing the platinum concentration of the platinum-ruthenium alloy plating film obtained by the platinum-ruthenium alloy plating of the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0040] First embodiment Hereinafter, an embodiment of the present invention will be described. In this embodiment, a platinum-ruthenium alloy plating solution was produced using sodium hexabromorthenate (III) as a ruthenium complex salt and sodium tetrabromoplatinate (II) as a platinum complex salt, and a platinum-ruthenium alloy plating film was formed using the solution.

[0041] The platinum-ruthenium alloy plating solution was prepared by adding sodium hexabromorthenate(III) (Na3(RuBr6)), sodium tetrabromoplatinate(II) (Na2(PtBr4)), and 20 g / L (0.32 mol / L) of boric acid, 30 g / L (0.37 mol / L) of sodium acetate, and 5 g / L (0.03 mol / L) of sodium dihydrogen phosphate dihydrate to pure water. Furthermore, 25 g / L (0.24 mol / L) of sodium bromide (NaBr) was added as a halogen compound to produce the platinum-ruthenium alloy plating solution. In this embodiment, a ruthenium complex salt was added to achieve a ruthenium concentration of 2 g / L, and the amount of platinum complex salt added was adjusted to achieve platinum concentrations of 0 g / L (no platinum added), 0.5 g / L, 1.0 g / L, and 2.0 g / L, producing platinum-ruthenium alloy plating solutions with four platinum concentrations.

[0042] The total molar concentrations of the platinum complex salt and the ruthenium complex salt in the platinum-ruthenium alloy plating solutions produced in this embodiment are 0.020 M, 0.022 M, 0.025 M, and 0.030 M, respectively. The contents of excess halogen ions in these platinum-ruthenium alloy plating solutions are 12 times, 11 times, 10 times, and 8 times the total molar amount of the platinum complex salt and the ruthenium complex salt, respectively.

[0043] Then, a platinum-ruthenium alloy plating film was formed using the produced platinum-ruthenium alloy plating solution under the following plating conditions. Substrate (cathode): Ni plating 5 μm + Au plating 0.2 μm Cu panel (dimensions 2 cm x 2 cm) Anode: Pt-plated Ti mesh electrode Plating solution temperature: 65℃ Plating solution pH: 1.0 ·Current density: 2.0A / dm 2 , 4.0A / dm 2 , 8.0A / dm 2 Accumulated current: 1.6A min

[0044] After plating, the substrate was removed, the average film thickness was measured, and the appearance was observed to evaluate the presence or absence of cracks. The weight change of the cathode before and after plating was then measured, and the deposition rate and deposition efficiency of the platinum-ruthenium alloy plating film at each current density were calculated. Furthermore, the composition of the platinum-ruthenium alloy film was analyzed by fluorescent X-ray analysis (fluorescent X-ray film thickness meter SFT9550, manufactured by Hitachi High-Tech Science Corporation).

[0045] Regarding the deposition test of a platinum-ruthenium alloy plating film using the platinum-ruthenium alloy plating solution produced in this embodiment, the measurement results of the deposition rate of the platinum-ruthenium alloy plating film are shown in Figure 1. From Figure 1, it can be seen that the deposition rate of the platinum-ruthenium alloy plating film increases as the amount of platinum added to the platinum-ruthenium alloy plating solution increases. In the plating solution (ruthenium plating solution) to which no platinum complex salt is added, the current density was set at 8.0 A / dm 2 Even with the above, the deposition rate is still less than 0.1 μm / min. However, by mixing platinum complex salts into the platinum-ruthenium alloy plating solution, the deposition rate of the plating film exceeds 0.1 μm / min.

[0046] Figure 2 shows the deposition efficiency of the platinum-ruthenium alloy plating film in this embodiment. Figure 3 shows the deposition efficiency of ruthenium calculated from the results of composition analysis of the platinum-ruthenium alloy plating film. Similar to the evaluation results based on deposition rate in Figure 1, Figure 2 confirms that the addition of a platinum complex salt increases the deposition efficiency. Furthermore, Figure 3 confirms that the addition of a platinum complex salt promotes an increase in the deposition efficiency of ruthenium.

[0047] Regarding the composition of the platinum-ruthenium alloy plating film formed in this embodiment, the relationship between the platinum concentration in the solution and the composition (platinum concentration) of the plating film is shown in Figure 4. As the platinum concentration in the platinum-ruthenium alloy plating solution increases, the platinum concentration of the platinum-ruthenium alloy plating film also increases. In this embodiment, a platinum-ruthenium alloy plating film with a platinum concentration of 40 mass % to 80 mass % could be formed from a platinum-ruthenium alloy plating solution with a platinum concentration of 2.0 g / L (ratio to ruthenium concentration: 1:1). Furthermore, Figure 4 shows that the composition of the platinum-ruthenium alloy is not significantly affected by the current density during plating. This confirms that the composition of the platinum-ruthenium alloy plating film should be controlled by adjusting the composition of the platinum-ruthenium alloy plating solution.

[0048] Second embodiment In this embodiment, the ruthenium complex salt and platinum complex salt were the same as in the first embodiment, sodium hexabromorthenate(III) and sodium tetrabromoplatinate(II), but the concentrations (ruthenium concentration, platinum concentration), the type and content of conductive salt, and the amount of halide (bromide) added were adjusted to produce multiple platinum-ruthenium alloy plating solutions. The production conditions for the platinum-ruthenium alloy plating solutions were the same as in the first embodiment. The compositions of the platinum-ruthenium alloy plating solutions produced in this embodiment are shown in Tables 1 and 2.

[0049] [Table 1]

[0050] [Table 2]

[0051] Platinum-ruthenium alloy plating films were formed using these platinum-ruthenium alloy plating solutions, and the average film thickness and appearance were observed. The plating conditions were as follows. In the following conditions, for alloy plating solutions in which the total concentration of ruthenium and platinum in the solution was less than 12.5 g / L, the current density was set to 2.0 A / dm 2 ~12.0A / dm 2Based on the range above, for alloy plating solutions with a total ruthenium and platinum concentration of 12.5 g / L or more, the current density is set to 12.0 A / dm 2 ~24.0A / dm 2 It was decided.

[0052] Substrate (cathode): Ni plating 5 μm + Au plating 0.2 μm Cu panel (dimensions 2 cm x 2 cm) Anode: Pt-plated Ti mesh electrode Plating solution temperature: 65℃ Plating solution pH: 1.0 ·Current density: 2.0A / dm 2 , 4.0A / dm 2 , 8.0A / dm 2 , 12.0A / dm 2 , 24.0A / dm 2 Accumulated current: 1.6A min

[0053] Regarding the evaluation after plating, in the appearance evaluation, the surface of the platinum-ruthenium alloy plating film was observed under a microscope (magnification 50 times), and those without cracks were judged as pass (◯), and those with cracks or abnormal appearance were judged as fail (×). Furthermore, the composition of the platinum-ruthenium alloy was analyzed in the same manner as in the first embodiment. The test results of this embodiment are shown in Tables 3 and 4.

[0054] [Table 3]

[0055] [Table 4]

[0056] It was confirmed from Tables 3 and 4 that platinum-ruthenium alloy plating films with a wide range of compositions could be formed using the platinum-ruthenium alloy plating solution produced in this embodiment, and that all of these platinum-ruthenium alloy plating films exhibited good appearance without cracks.

[0057] Furthermore, among the platinum-ruthenium alloy plating solutions in Table 1 produced in this embodiment, plating solutions No. 7 and No. 10 are common in terms of the concentrations of platinum complex salt and ruthenium complex salt, the presence or absence of conductive salt, etc., but differ in terms of the presence or absence of sodium formate, an oxidation sacrificial agent. Therefore, the effects of the oxidation sacrificial agent were confirmed for these platinum-ruthenium alloy plating solutions.

[0058] This confirmation test was conducted on plating solutions No. 7 and No. 10. (a) The plating solutions immediately after production were subjected to plating treatment under the same plating conditions as in the first embodiment. (b) The plating solutions were then subjected to electrolysis (192 A min / L: equivalent to applying a current of 1 A for 192 minutes to 1 L of plating solution) while being replenished with platinum complex and ruthenium complex salts corresponding to the deposited platinum and ruthenium. Then, plating treatment was conducted under the same plating conditions as in the first embodiment. The average film thickness and appearance of the plating solutions (a) and (b) were measured and evaluated for the presence or absence of cracks, and the deposition rate was calculated. The test results are shown in Table 5.

[0059] [Table 5]

[0060] Table 5 shows that for the platinum-ruthenium alloy plating solution (a) immediately after production, regardless of whether or not an oxidizing sacrificial agent was added, both No. 7 and No. 10 plating solutions had good deposition rates and platinum-ruthenium alloy film quality. On the other hand, looking at the results for the platinum-ruthenium alloy plating solution (b) in a running state, the deposition rate of No. 7 platinum-ruthenium alloy plating solution without the addition of an oxidizing sacrificial agent decreased slightly. In contrast, the deposition rate of No. 10 platinum-ruthenium alloy plating solution with the addition of an oxidizing sacrificial agent did not decrease and was nearly the same as that immediately after production. Therefore, it can be said that the oxidizing sacrificial agent is effective in maintaining the deposition rate in a running state. However, the appearance of the platinum-ruthenium alloy film was of good quality in all plating solutions. As mentioned above, considering that the deposition rate in a running state in a plating solution without an oxidizing sacrificial agent was only slightly decreased, it was confirmed that the addition of an oxidizing sacrificial agent is optional, but its addition is effective. [Industrial Applicability]

[0061] The platinum-ruthenium alloy plating solution of the present invention employs a ruthenium complex salt and a platinum complex salt whose anion component is a halogen, which are highly stable and easy to synthesize. According to the present invention, platinum-ruthenium alloy plating films with a wide range of ruthenium concentrations can be easily produced. Furthermore, the platinum-ruthenium alloy plating solution of the present invention also exhibits a good deposition rate for platinum-ruthenium alloy plating films. The platinum-ruthenium alloy plating solution of the present invention is useful for protective plating of connectors and terminals of electronic components and the like, and for electrodes and wiring of electronic and semiconductor devices. The present invention is also useful for forming plating films on jewelry and the like.

Claims

1. A platinum-ruthenium alloy plating solution containing a platinum complex salt and a ruthenium complex salt, The platinum complex salt is a platinum complex salt whose anion component is a halogen, A platinum-ruthenium alloy plating solution characterized in that the ruthenium complex salt is a trivalent ruthenium complex salt whose anion component is a halogen.

2. 2. The platinum-ruthenium alloy plating solution according to claim 1, wherein the platinum metal concentration is from 0.5 g / L to 20 g / L, and the ruthenium metal concentration is from 0.5 g / L to 20 g / L.

3. 3. The platinum-ruthenium alloy plating solution according to claim 1, wherein the ratio of the concentration of metallic platinum to the concentration of metallic ruthenium (platinum concentration:ruthenium) is 1:10 or more and 4:1 or less.

4. 3. The platinum-ruthenium alloy plating solution according to claim 1, wherein the platinum complex salt is tetrabromoplatinic acid or tetrabromoplatinate, and the ruthenium complex salt is hexabromorthenic acid or hexabromorthenic acid salt.

5. 3. The platinum-ruthenium alloy plating solution according to claim 1, further comprising, as a conductive salt, one or more compounds selected from the group consisting of boric acid, borates, phosphoric acid, phosphates, saturated monocarboxylic acids having two or more carbon atoms, saturated monocarboxylic acid salts having two or more carbon atoms, saturated dicarboxylic acids having three or more carbon atoms, saturated dicarboxylic acid salts having three or more carbon atoms, saturated hydroxycarboxylic acids, saturated hydroxycarboxylic acid salts, aminosulfonic acids, aminosulfonic acid salts, aminocarboxylic acids, and aminocarboxylic acid salts.

6. 3. The platinum-ruthenium alloy plating solution according to claim 1, further comprising an oxidation sacrificial agent comprising a reducing agent component.

7. 7. The platinum-ruthenium alloy plating solution according to claim 6, wherein the oxidizing sacrificial agent is any one of formic acid or a formate, oxalic acid or an oxalate, or a sugar or a sugar alcohol.

8. A method for plating a platinum-ruthenium alloy plating film using the platinum-ruthenium alloy plating solution according to claim 1 or 2, comprising: The pH of the platinum-ruthenium alloy plating solution is set to 0.1 or more and 4.0 or less, The bath temperature is set to 25°C or higher and 95°C or lower. Current density: 1.0 A / dm ２ 30A / dm or more ２ A method for plating a platinum-ruthenium alloy plating film, comprising the steps of:

9. A platinum-ruthenium alloy plating film formed by the platinum-ruthenium alloy plating solution according to claim 1 or 2, The platinum-ruthenium alloy plating film contains 10% by mass or more and 90% by mass or less of ruthenium.

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