PtRu alloy plating solution and PtRu alloy film plating method

Abstract

To provide a PtRu alloy plating solution by which a high-quality PtRu alloy film can be obtained, in which deposition efficiency is excellent and occurrence of crack etc. are suppressed.SOLUTION: The present invention relates to a PtRu alloy plating solution. The PtRu alloy plating solution includes a divalent Pt salt, either Ru sulfate or Ru nitrate, and sulfuric acid and sulfamic acid. The PtRu alloy plating solution has a chloride concentration of between 0.1 mg / L and 300 mg / L. The composition of the PtRu alloy plating solution preferably includes a Pt concentration of between 1 g / L and 15 g / L, a Ru concentration of between 0.1 g / L and 10 g / L, a total sulfuric acid concentration of between 10 g / L and 200 g / L, and a sulfamic acid concentration of between 0.1 g / L and 20 g / L.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a PtRu alloy plating solution for forming an alloy plating film made of a PtRu alloy. More specifically, the present invention relates to a PtRu alloy plating solution that has excellent deposition efficiency and is suitable for producing a crack-free PtRu alloy film. The present invention also relates to a plating method for a PtRu alloy film using the plating solution. [Background technology]

[0002] Precious metal plating, including Pt plating, is used in a wide range of fields, including decorative items and jewelry, as well as electrode materials for electronic and electrical equipment and conductive coating materials.Since many precious metals have excellent electrical conductivity, chemical stability, hardness, and other mechanical properties, the scope 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] Against this backdrop, there is an increasing demand for precious metal plating with high hardness and excellent barrier properties for use on the terminals and connectors (plugs and receptacles) of electronic devices such as smartphones and tablet devices. Connectors for these various electronic devices are formed by applying a base layer of Ni or other metal to a conductive substrate such as a Cu alloy, followed by the application of a precious metal plating film. For connectors designed for repeated insertion and removal, if the plating film on the outer surface easily wears off, it not only impairs the appearance but also exposes the base layer and increases contact resistance due to oxidation, creating extremely undesirable conditions for the electronic device. Therefore, there is a demand for precious metal plating films with high hardness and excellent wear resistance for connectors.

[0004] Until now, precious metal plating for connectors has been performed using gold (Au), platinum (Pt), etc. Much knowledge has been gained about gold (Au) and platinum (Pt) plating, and suitable plating solutions and plating conditions are known. For example, many platinum plating solutions are known that use platinum salts (platinum complexes) such as dinitrodiammine platinum and dinitrosulfide platinum as the metal source. However, as mentioned above, there is a demand for precious metal plating films with higher hardness, and there is a need for the development of precious metal plating films with new compositions.

[0005] Candidates for plating films with higher hardness than precious metal plating films such as Au and Pt include those made of alloyed precious metals. The present inventors have found potential in PtRu alloy films as a precious metal alloy plating film that is moderately hard and cost-effective. Ru is also a type of precious metal, but since it is harder than Pt, alloying it with Pt is expected to increase the hardness of the coating. Furthermore, since Ru, like Pt, is chemically stable, PtRu alloy films also have excellent corrosion resistance. Since Ru plating is also known as a form of precious metal plating, its findings can also be utilized. Known Ru plating solutions include Ru salts such as sulfates and chlorides (Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 1,779,457 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-49485 Summary of the Invention [Problem to be solved by the invention]

[0007] However, there are currently few practical prior art techniques for alloy plating solutions suitable for producing PtRu alloy films. In this regard, alloy plating solutions are typically obtained by mixing metal salts of the alloying metals with an appropriate conductive salt. As mentioned above, the metal salts used in Pt and Ru plating solutions are publicly known, and this knowledge can also be used for PtRu alloy plating solutions. However, the present inventors have examined plating solutions using Pt and Ru salts that have been used to date and found that they are not necessarily optimal in terms of their plating solution properties.

[0008] While alloy plating solutions are required to be able to form alloy films of the desired composition, their deposition efficiency is also important. Furthermore, considering the functions of protecting the substrate and ensuring corrosion resistance, cracking should be suppressed until an alloy film of the desired thickness is formed. According to the present inventors, it is not possible to obtain a practical PtRu alloy plating solution with these properties based solely on the knowledge of the prior art.

[0009] Therefore, the present invention aims to provide a plating solution for forming a PtRu alloy film that has excellent deposition efficiency and can produce a high-quality PtRu alloy film with suppressed cracking, etc. The present invention also clarifies a plating method for producing a PtRu alloy film with high hardness and excellent corrosion resistance using this PtRu alloy plating solution. [Means for solving the problem]

[0010] To solve the above problems, the inventors conducted preliminary investigations into alloy plating solutions in which several Ru salts were mixed with a Pt plating solution, and investigated the selection of suitable Ru salts and the composition of the plating solution. As mentioned above, Ru chloride and Ru sulfate are well-known Ru salts for Ru plating solutions.

[0011] As a result of this investigation, the inventors have confirmed that while it is possible to form a PtRu alloy film using either Ru chloride or Ru sulfate, simply mixing one of them into a Pt plating solution is not suitable. Specifically, alloy plating solutions containing Ru sulfate as the Ru salt have poor deposition efficiency, and it takes time to ensure the thickness of the PtRu alloy film. On the other hand, alloy plating solutions containing Ru chloride as the Ru salt have satisfactory deposition efficiency, but Pt deposition failure occurs over time, making the plating solution unstable and hindering long-term use. Therefore, in order to maintain the stability of PtRu alloy plating solutions using Ru chloride, the plating temperature must be set relatively low (below 45°C) even at the expense of deposition efficiency. Despite this consideration for stability, it has been confirmed that plating solutions containing Ru chloride can sometimes develop cracks as the film thickness increases.

[0012] The present inventors have considered that the reason for Pt non-deposition in the PtRu alloy plating solution containing the above-mentioned Pt salt and Ru chloride is that chlorine in the solution excessively stabilizes Pt. They have also considered that Ru chloride, which can supply excessive chlorine to the plating solution, should not be used, but that problems such as stability can be eliminated by using other Ru salts and controlling the chlorine content within a range that does not inhibit Pt deposition. Based on this consideration, the present inventors have conducted extensive research and have come up with a PtRu alloy plating solution that uses Ru sulfate or Ru nitrate as the Ru salt and controls the chlorine content within a suitable range.

[0013] That is, the present invention is a PtRu alloy plating solution containing a divalent Pt salt, either Ru sulfate or Ru nitrate, sulfuric acid, and sulfamic acid, and having a chlorine concentration of 0.1 mg / L to 300 mg / L. The composition of the PtRu alloy plating solution according to the present invention and a method for producing a PtRu alloy film using this PtRu alloy plating solution are described below.

[0014] (A) Composition of the PtRu alloy plating solution according to the present invention The PtRu alloy plating solution according to the present invention contains, as essential components, divalent Pt salt and Ru salt, which are metal sources, as well as sulfuric acid and sulfamic acid.

[0015] Suitable divalent platinum salts include inorganic acid salts containing at least one of sulfate (SO), sulfo (SO), nitro (NO), nitrate (NO), amine (NH), aquo (HO), and hydroxyl (OH). Specific examples include platinum sulfate (PtSO), platinum dinitrosulfide (Pt(SO)(NO), platinum nitrate (Pt(NO), dinitrodiammine platinum (Pt(NH)(NO), diaminedichloro platinum (Pt(NH)Cl), trichloroamine platinum acid (HPtCl(NH)) or its salt, tetranitro platinum acid (HPtCl) or its salt, tetrasulfo platinum acid (HPt(SO)) or its salt, and tetraammine platinum phosphate (HPt(NH)). Among these, particularly preferred Pt salts are Pt sulfate, Pt dinitrosulfide, and Pt dinitrodiammine.

[0016] On the other hand, Ru salts are Ru sulfate (RuSO4) or Ru nitrate (Ru(NO3)2). As mentioned above, Ru chloride can be used for Ru plating, but when used for PtRu alloy plating, it can cause excess chlorine in the plating solution, leading to Pt not being deposited. To prevent non-deposition while also ensuring a good appearance of the plating film, the Ru salt is limited to either Ru sulfate or Ru nitrate. Ru sulfate is particularly preferred.

[0017] The PtRu alloy plating solution according to the present invention is an aqueous solution in which the Pt salt and Ru salt are dissolved in sulfuric acid and sulfamic acid. The sulfuric acid and sulfamic acid released in the plating solution may also be generated from the Pt salt and Ru salt. Sulfuric acid and sulfamic acid are essential components that act as conductive salts in the plating solution. Sulfamic acid also has the effect of making the appearance of the plating film uniform.

[0018] The PtRu alloy plating solution of the present invention has a chlorine concentration adjusted to a range of 0.1 mg / L to 300 mg / L. A plating solution with a chlorine concentration of less than 0.1 mg / L is essentially chlorine-free, resulting in reduced Pt and Ru deposition efficiency and inefficient plating. A chlorine concentration exceeding 300 mg / L stabilizes Pt, resulting in Pt not being deposited. Excessive chlorine concentration can also cause cracks in alloy films formed to a thickness of 1 μm or greater. The chlorine concentration is preferably 0.1 mg / L to 200 mg / L, more preferably 0.1 mg / L to 100 mg / L. The reason why the deposition efficiency improves when a certain range of chlorine is included in the PtRu alloy plating solution of the present invention is unclear. Possible mechanisms include the formation of some kind of complex with chlorine ions, or the interaction of chlorine atoms with Pt and / or Ru, but these mechanisms remain unclear.

[0019] The chlorine concentration of the PtRu alloy plating solution according to the present invention can be controlled by adding chlorides to the plating solution while using raw Pt and Ru salts with reduced chlorine concentrations. Examples of chlorides to be added include ammonium chloride, Pt chloride, and Ru chloride. Furthermore, chlorides of alkali metals or alkaline earth metals, such as sodium chloride or magnesium chloride, may be added to the plating solution in addition to the alkali metal salts or alkaline earth metal salts described below.

[0020] The contents of each component in the PtRu alloy plating solution according to the present invention are preferably as follows: Pt concentration is 1 g / L to 15 g / L, Ru concentration is 0.1 g / L to 10 g / L, total sulfuric acid concentration is 10 g / L to 200 g / L, and sulfamic acid concentration is 0.1 g / L to 20 g / L. If the Pt and Ru concentrations are below their lower limits, film formation may not proceed smoothly. On the other hand, if the Pt and Ru concentrations exceed their upper limits, it may be difficult to prevent cracks from occurring when forming a thick plating film.

[0021] The composition of the PtRu alloy film formed using the PtRu alloy plating solution according to the present invention can be adjusted by adjusting the ratio of the Pt concentration to the Ru concentration in the alloy plating solution. According to the inventors' studies, in order to obtain a PtRu alloy film with a suitably high hardness, the ratio of the Pt concentration to the Ru concentration (Ru concentration (g / L) / Pt concentration (g / L)) is preferably set to 0.1 or more and 0.8 or less. The PtRu alloy film formed at this concentration ratio has a composition of a PtRu alloy with an Ru concentration of 2% to 20% by mass. If the ratio is too low, the PtRu alloy film will have an excessively low Ru concentration and will have a hardness similar to that of Pt. Furthermore, since the hardness of the PtRu alloy film does not increase significantly even if the Ru concentration exceeds 20%, the ratio does not need to exceed 0.8. Furthermore, if the Ru concentration in the plating solution is too high, the deposition efficiency may decrease. A more preferable range for the ratio is 0.1 or more and 0.5 or less.

[0022] The PtRu alloy plating solution according to the present invention preferably contains an anionic surfactant in addition to the essential components described above, namely, Pt salt, Ru salt, sulfuric acid, and / or sulfamic acid. The anionic surfactant has the effect of suppressing Pt and Ru from remaining undeposited and promoting their uniform deposition. As the anionic surfactant, stearates, sulfonates, sulfates, and sulfamates, which have surfactant properties, can be used. Preferred examples include alkyl sulfates and alkylbenzene sulfonates. A specific preferred salt is lauryl sulfate, which is an alkali sulfate.

[0023] When an anionic surfactant is added, its concentration is preferably 10 mg / L or more and 500 mg / L or less. If the concentration is less than the lower limit, it is ineffective. If the concentration is more than the upper limit, it inhibits the deposition of Pt and Ru.

[0024] Furthermore, the PtRu alloy plating solution according to the present invention preferably contains an alkali metal or alkaline earth metal. The alkali metal or alkaline earth metal acts as a reducing agent in the plating solution, promoting the deposition of Pt and Ru while forming a plating film with good corrosion resistance. The alkali metal or alkaline earth metal can coexist with an anionic surfactant, but the addition of the alkali metal or alkaline earth metal can reduce the amount of anionic surfactant added. Mg is particularly preferred as the alkali metal or alkaline earth metal. However, due to their ionization tendency, alkali metals or alkaline earth metals do not precipitate in the plating film.

[0025] When an alkali metal or alkaline earth metal is added to a PtRu alloy plating solution, it is preferable to add a salt thereof, and preferred are sulfates, sulfites, nitrates, oxides, hydroxides, etc. Mg is cited as a preferred alkaline earth metal, and preferred magnesium salts include magnesium sulfate, magnesium sulfite, magnesium nitrate, magnesium oxide, magnesium hydroxide, magnesium acetate, magnesium citrate, magnesium lactate, magnesium stearate, etc., which are preferably added when preparing the plating solution.

[0026] The concentration of alkali metal or alkaline earth metal in the PtRu alloy plating solution is preferably 1 g / L or more and 20 g / L or less. If it is less than 1 g / L, it is ineffective. If it exceeds 20 g / L, the deposition efficiency decreases.

[0027] The PtRu alloy plating solution according to the present invention may contain, in addition to the metal salt, sulfuric acid, sulfamic acid, anionic surfactant, and alkali metal or alkaline earth metal described above, known additives used in plating solutions, such as pH buffers, complexing agents, and stabilizers.

[0028] In addition, when measuring the Pt, Ru, sulfuric acid, sulfamic acid, and chlorine concentrations in a PtRu alloy plating solution, the plating solution can be analyzed and measured using inductively coupled plasma atomic 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. In addition to the above analytical methods, chlorine concentration can also be measured using the diethyl-p-phenylenediamine (DPD) method (colorimetric or spectrophotometric), iodine method, and amperometric method (polarographic method), which are known methods for measuring chlorine (residual chlorine) in solutions. Measurements can also be performed using testers, instruments, and measurement kits used for these methods. The presence of Pt and Ru in the formed PtRu alloy plating film and the composition of the plating film can be measured by electron probe microprobe analysis (EPMA), energy dispersive X-ray spectroscopy (EDX), X-ray fluorescence analysis (XRF), etc.

[0029] The PtRu alloy plating solution according to the present invention can be produced by dissolving the Pt salt and Ru salt in sulfuric acid and sulfamic acid to prepare a stock solution, which can then be appropriately diluted. Alternatively, the Pt salt may first be dissolved in sulfuric acid, and then the Ru salt may be dissolved therein to prepare a stock solution for dilution. Adjustment of the chlorine concentration and addition of an anionic surfactant, etc., are preferably performed at the dilution stage. Alternatively, the chlorine concentration of the stock solution may be adjusted to prepare a PtRu alloy plating solution.

[0030] The metal salts used in preparing the plating solution are as described above. These metal salts may be chlorine-free or may contain chlorine as long as the chlorine concentration in the plating solution does not exceed the upper limit. In particular, for Ru salts, such as Ru sulfate or Ru nitrate, high-purity Ru sulfate or Ru nitrate may be used, but chlorine-containing Ru sulfate or Ru nitrate may also be used. For example, Ru sulfate, in which the chlorine in Ru chloride has been replaced with sulfuric acid, can also be used. The Ru chloride replacement can be achieved by neutralizing Ru chloride to form a hydroxide, which is then dissolved, recovered, and washed with sulfuric acid and nitric acid to obtain Ru sulfate or Ru nitrate containing trace amounts of chlorine. Meanwhile, for divalent Pt salts, Pt salts containing chlorine as a constituent element (e.g., diaminedichloroPt) can also be used, but even in this case, the chlorine concentration of the plating solution must be within the range of the present invention.

[0031] (B) Plating method for PtRu alloy film according to the present invention Next, a method for producing a PtRu alloy film using the PtRu alloy plating solution according to the present invention will be described. The PtRu alloy plating solution according to the present invention is acidic, preferably having a pH of 1 or less. If the pH exceeds 1, cracks will occur in the plating film, resulting in a decrease in corrosion resistance. The lower limit of the pH is preferably 0.1.

[0032] The temperature of the plating solution is preferably 45°C or higher and 65°C or lower. Since the solution temperature is related to deposition efficiency, deposition efficiency is poor at temperatures below 45°C. On the other hand, operation at high temperatures above 65°C can cause problems such as deterioration of jigs. In this regard, when Ru chloride is used as the Ru salt in a PtRu alloy plating solution, plating cannot be performed at temperatures above 45°C from the perspective of long-term stability of the plating solution. With the PtRu alloy plating solution of the present invention, plating is possible at temperatures above 45°C, and temperatures above 50°C are preferred.

[0033] The current density during film formation was 2.0 A / dm 2 More than 10A / dm 2 Less than 2.0A / dm is preferred. 2 If the current is less than 10A / dm, it is inefficient to form a plating film of the required thickness. 2If the temperature exceeds this range, the plating film may become discolored. [Effects of the Invention]

[0034] As explained above, the PtRu alloy plating solution of the present invention uses Ru sulfate as both a Pt salt and a Ru salt, and further limits the chlorine concentration to suppress factors that impair the long-term stability of the plating solution, such as Pt failure during the plating process. The PtRu alloy plating solution of the present invention has better deposition efficiency than plating solutions that use chlorine-free Ru sulfate, and is also excellent in stability and has advantages in terms of temperature control.

[0035] The present invention is useful for forming a plating film made of a PtRu alloy of suitable composition. This PtRu alloy film is made of a PtRu alloy that is harder than Pt and other alloys. Furthermore, the PtRu alloy film is also less susceptible to cracking, has good corrosion resistance, and excels in environmental barrier properties against the substrate. This PtRu alloy film has a uniform metallic luster and a good appearance. Due to these advantages, the PtRu alloy plating solution of the present invention is useful as a protective plating layer for connectors and terminals of smartphones and the like, and is durable against repeated insertion and removal. It is also useful as a plating film for jewelry and the like. DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, an embodiment of the present invention will be described. In this embodiment, a PtRu alloy plating solution was produced using Pt dinitrosulfide (Pt(SO4)(NO3)2), a Pt salt, and Ru sulfate, a Ru salt, as raw materials. Then, the chlorine concentration was adjusted to prepare multiple PtRu alloy plating solutions, and PtRu alloy films were formed from them.

[0037] To prepare the plating solution, first, equal amounts of Pt dinitrosulfide (Pt(SO4)(NO3)2) and Ru sulfate (RuSO4) were added to sulfuric acid and sulfamic acid to prepare a basic bath with a Pt concentration of 10 g / L, a Ru concentration of 1 g / L, a total sulfuric acid concentration of 80 g / L, and a sulfamic acid concentration of 5 g / L. Then, 100 mg / L of sodium lauryl sulfate (Emal®, manufactured by Kao Corporation) was added as an anionic surfactant, and 4 g / L of magnesium sulfate as an alkaline earth metal salt was added. Furthermore, NaCl was added to adjust the chlorine concentration so that the chlorine concentration in the plating solution was 0.1 mg / L to 500 mg / L. Finally, the pH was adjusted to 0.4 to prepare a PtRu alloy plating solution.

[0038] For comparison, a PtRu alloy plating solution using Ru chloride (RuCl3) as the Ru salt was also investigated in this embodiment. This PtRu alloy plating solution was prepared by dissolving Pt salt and Ru chloride in sulfuric acid and sulfamic acid to obtain a stock solution with the same Pt ​​and Ru concentrations as described above. This stock solution was diluted and additives were added in the same manner as in this embodiment to obtain a PtRu alloy plating solution.

[0039] PtRu alloy films were formed using the nine plating solutions with different chlorine concentrations prepared above. The plating conditions were as follows: a Cu plate (20 mm × 40 mm × 0.1 mm) was used as the substrate sample, the bath temperature was 60°C, and the current density was 4.0 A / dm 2 The plating time was adjusted to 30 to 60 minutes, aiming for a film thickness of 5 μm.

[0040] After plating, the substrates were removed, the average film thickness was measured, and the appearance was inspected to determine whether cracks or incomplete deposition were present. The deposition efficiency was calculated based on the mass difference between the substrate samples before and after plating. Furthermore, to confirm the corrosion resistance of the PtRu alloy film, electrolysis cycle tests were performed on the samples after film deposition. The electrolysis cycle test consisted of applying a voltage of 5 V for 30 seconds to each sample in a 5% by mass sodium chloride solution (room temperature), which was repeated as one cycle. The corrosion resistance was evaluated based on the number of cycles required until the underlying Cu was exposed, up to a maximum of 200 cycles. The evaluation results are shown in Table 1.

[0041] [Table 1]

[0042] Table 1 shows that the deposition efficiency of a chlorine-free plating solution (chlorine concentration 0 mg / L), i.e., plating solution No. 1, which uses Ru sulfate as the Ru salt, is low and therefore not practical. Furthermore, it can be seen that the deposition efficiency improves with increasing chlorine concentration compared to plating solution No. 2, which contains 0.1 mg / L of chlorine. However, cracks were observed in the PtRu alloy film at a chlorine concentration of 500 mg / L (No. 8). Furthermore, in the case of plating solution No. 9, which uses Ru chloride as the Ru salt, cracks were observed in the PtRu alloy film and undeposited areas were observed on the substrate. As can be seen from Table 1, the samples with cracks in the PtRu alloy film also had poor corrosion resistance. In contrast, the PtRu alloy films formed using PtRu alloy plating solutions with appropriately controlled chlorine concentrations were confirmed to have excellent corrosion resistance (Nos. 2 to 7).

[0043] Second embodiment From the results of the first embodiment, it was confirmed that it is possible to efficiently form a high-quality PtRu alloy film by using Ru sulfate as the Ru salt and appropriately adjusting the chlorine concentration. In this embodiment, PtRu alloy plating solutions with different Ru concentrations were produced, and the structure and properties of the PtRu alloy films formed from these solutions were evaluated.

[0044] As in the first embodiment, a stock solution of platinum dinitrosulfide and ruthenium sulfate dissolved in sulfuric acid was diluted, and magnesium sodium lauryl sulfate was added to prepare a PtRu alloy plating bath. Here, the amount of Ru sulfate dissolved during the preparation of the stock solution was adjusted to produce PtRu alloy plating solutions with Ru concentrations of 1 g / L, 2 g / L, 3 g / L, 4 g / L, and 5 g / L. These plating solutions were identical except for two conditions: the Ru concentration and the total sulfuric acid concentration. All solutions had a platinum concentration of 10 g / L, a magnesium concentration of 4 g / L, and a pH of 0.4. The chlorine concentration was also common, at 0.5 mg / L.

[0045] Then, a multilayer substrate (Cu / Ni / Au) was prepared by plating Ni (5 μm thick) / Au (0.1 μm thick) on a Cu substrate similar to that of the first embodiment, and a PtRu alloy film was plated using each PtRu alloy plating solution. The deposition efficiency of each PtRu alloy film was calculated, and composition analysis (Ru concentration measurement) was performed using EDX, followed by measurement of hardness. The Vickers hardness (Hv) was measured using a Vickers hardness tester under a load of 10 g. Corrosion resistance was also evaluated using an electrolysis cycle test, as in the first embodiment. The results are shown in Table 2.

[0046] [Table 2]

[0047] Table 2 shows that the Ru ratio of the PtRu alloy film formed in this embodiment increases with increasing Ru concentration in the plating solution, and is confirmed to be composed of 3 mass % to 12.3 mass % PtRu alloy. It can be seen that the hardness of the PtRu alloy film is higher than that of a Pt film formed with a plating solution containing no Ru salt. The effect of increasing hardness due to the alloying of Ru to Pt is clearly evident even in alloy plating films with 1% Ru.

[0048] In all the PtRu alloy films, no cracks were observed and the corrosion resistance was good.Furthermore, the films had a uniform metallic luster and good appearance. [Industrial Applicability]

[0049] As described above, the PtRu alloy plating solution of the present invention has excellent deposition efficiency and long-term solution stability by optimizing the Ru salt coexisting with the Pt salt and specifying the chlorine concentration. Furthermore, the occurrence of cracks in the PtRu alloy film formed is suppressed. The PtRu alloy film formed by the present invention is composed of a high-hardness PtRu alloy and has good corrosion resistance. The present invention is useful for forming protective plating layers on electronic devices such as connectors and terminals of smartphones and tablet devices, as well as plating films on jewelry and the like.

Claims

1. a divalent Pt salt; either Ru sulfate or Ru nitrate; An electrolytic PtRu alloy plating solution comprising sulfuric acid and sulfamic acid, An electrolytic PtRu alloy plating solution having a chloride ion concentration of 0.1 mg / L or more and 100 mg / L or less.

2. Divalent Pt salts contain sulfate groups (SO ４ ) or sulfo group (SO ３ ), nitro group (NO ２ ), nitrate group (NO ３ ), amine (NH ３ ), aquo group (H ２ 2. The electrolytic PtRu alloy plating solution according to claim 1, wherein the solution is an inorganic acid salt containing at least one of a hydroxyl group (OH) and a hydroxyl group (O).

3. 3. The electrolytic PtRu alloy plating solution according to claim 1, wherein the Pt concentration is from 1 g / L to 15 g / L, the Ru concentration is from 0.1 g / L to 10 g / L, the total sulfuric acid concentration is from 10 g / L to 200 g / L, and the sulfamic acid concentration is from 0.1 g / L to 20 g / L.

4. 4. The electrolytic PtRu alloy plating solution according to claim 1, wherein the ratio of the Pt concentration to the Ru concentration (Ru concentration (g / L) / Pt concentration (g / L)) is 0.1 or more and 0.8 or less.

5. 5. The electrolytic PtRu alloy plating solution according to claim 1, further comprising an anionic surfactant.

6. 6. The electrolytic PtRu alloy plating solution according to claim 1, further comprising an alkali metal or an alkaline earth metal.

7. A method for plating a PtRu alloy film using the electrolytic PtRu alloy plating solution according to any one of claims 1 to 6, comprising: The pH of the electrolytic PtRu alloy plating solution is set to 1 or less, Temperature 45℃ or higher and 65℃ or lower, Current density 2.0A / dm ２ 10A / dm or more ２ The plating method for a PtRu alloy film involves the following plating process.

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