Pt-ruthenium alloy plating solution and method for plating pt-ruthenium alloy film

Abstract

The present application relates to a PtRu alloy plating solution comprising: any one of a 2-valent Pt salt, a Ru sulfate or a Ru nitrate, and sulfuric acid and sulfamic acid, wherein the chlorine concentration is 0.1 mg / L or more and 300 mg / L or less. As the composition of the PtRu alloy plating solution, it is preferable that the Pt concentration be 1 g / L or more and 15 g / L or less, the Ru concentration be 0.1 g / L or more and 10 g / L or less, the total sulfuric acid concentration be 10 g / L or more and 200 g / L or less, and the sulfamic acid concentration be 0.1 g / L or more and 20 g / L or less. The PtRu alloy plating solution according to the present application can obtain a high-grade PtRu alloy film having excellent deposition efficiency and in which cracking and the like are suppressed.

Description

TECHNICAL FIELD

[0001] The present application relates to a PtRu alloy plating solution for forming an alloy plating film composed of a PtRu alloy. More specifically, it relates to a PtRu alloy plating solution which is excellent in deposition efficiency and is suitable for manufacturing a PtRu alloy film free of cracks. In addition, the present application relates to a plating method of a PtRu alloy film using the plating solution. BACKGROUND

[0002] The plating of noble metals including Pt plating is used in a wide range of fields such as electrode materials for electronic / electrical devices, conductive coating materials, and the like, in addition to being used for ornaments / jewelry and the like. Since many noble metals are excellent in mechanical properties such as electrical conductivity, chemical stability, hardness, and the like, the plating of noble metals has expanded its range of use from fields focusing on the rarity and appearance of noble metals to fields valuing functionality.

[0003] In this background, the plating of noble metals applied to terminals or connectors (plug, socket) of electronic devices such as smartphones or tablet terminals, although high in hardness and excellent in interruption properties, is required to be increased. In the connector class of such various electronic devices, a noble metal plating film is formed after base plating of Ni or the like is performed on a substrate of Cu alloy or the like which is electrically conductive. Also, in the connector class used on the premise of repeated plugging and unplugging, if the plating film on the outer surface is easily shaved off and peeled, in addition to the appearance being damaged, it becomes a state extremely undesirable for the electronic device in terms of exposure of the base layer or increase in contact resistance due to oxidation. Therefore, the noble metal plating film of the connector class is required to be a plating film high in hardness and excellent in wear resistance.

[0004] As the plating of noble metals of the connector class, Au, Pt, and the like have been used so far. As for Au plating or Pt plating, there have been many understandings so far, and appropriate plating solutions or plating conditions are known. For example, as a Pt plating solution, there are many known Pt plating solutions using Pt salts (Pt complexes) such as dinitrodiamine Pt, dinitrosulfide Pt, and the like as a metal source. However, as described above, in the case where a noble metal plating film higher in hardness is required, development of a noble metal plating film of a new constitution is required.

[0005] As a plating film having higher hardness than a noble metal such as Au or Pt, a plating film composed of an alloyed noble metal alloy can be exemplified. Here, as a noble metal alloy plating film having moderately high hardness and being also useful in terms of cost, the inventors have found the possibility thereof in a PtRu alloy film. Ru is also a kind of noble metal, but is a metal having higher hardness than Pt, and thus high hardening of the film by alloying with Pt is expected. In addition, Ru is also chemically stable like Pt, and thus the PtRu alloy film is also excellent in corrosion resistance. Furthermore, Ru plating is also widely known as one of the ways of noble metal plating, and thus it is considered that the knowledge and insights thereof can also be utilized. As a plating solution for Ru, a plating solution containing a Ru salt such as a sulfate or a chloride is known (Patent Document 2).

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: U.S. Patent No. 1779457

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2001-49485 SUMMARY

[0010] PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] However, as for an alloy plating solution suitable for manufacturing a PtRu alloy film, the current situation is that there is almost no practical prior art. In this regard, an alloy plating solution is generally obtained by mixing a metal salt of an alloyed metal and a suitable conductive salt. As described above, the metal salts used in Pt plating solutions and Ru plating solutions are well known, and thus the knowledge and insights thereof can also be utilized for a PtRu alloy plating solution. However, according to the inventors, a study was made on the plating solutions based on Pt salts and Ru salts applied so far, and as a result, it was confirmed that the plating solutions were not necessarily the best in terms of the characteristics as plating solutions.

[0012] In an alloy plating solution, it is required to be able to form an alloy film of a target composition, but the deposition efficiency thereof is also important. In addition, in view of the functions of protection of a substrate and ensuring corrosion resistance, generation of cracks should be suppressed before an alloy film of a desired thickness is formed. According to the inventors, a PtRu alloy plating solution practical in these characteristics cannot be obtained only with the knowledge and insights of the prior art.

[0013] Therefore, the object of the present application is to provide a PtRu alloy plating solution excellent in deposition efficiency and capable of obtaining a high-quality PtRu alloy film in which generation of cracks and the like is suppressed, with respect to a plating solution for forming a PtRu alloy film. Furthermore, a plating method for manufacturing a PtRu alloy film having high hardness and excellent corrosion resistance using the PtRu alloy plating solution is clarified.

[0014] Means for solving the problem

[0015] In order to solve the above problem, the present inventors made preliminary confirmation of an alloy plating solution in which several Ru salts were mixed in a Pt plating solution. The selection of a suitable Ru salt and the plating solution composition were studied. Here, as the Ru salt of the Ru plating solution, as described above, Ru chloride and Ru sulfate are well known.

[0016] Then, as a result of this study, the present inventors confirmed that either of Ru chloride and Ru sulfate can be used to form a PtRu alloy film, but it is not appropriate to mix either of them alone in a Pt plating solution. That is, in the case of an alloy plating solution using Ru sulfate as the Ru salt, there is a point that the deposition efficiency is poor, and it takes time to ensure the thickness of the PtRu alloy film. On the other hand, it was confirmed that the deposition efficiency of an alloy plating solution using Ru chloride as the Ru salt is satisfactory, but as the plating time passes, un-deposited Pt occurs, the plating solution becomes unstable, and this causes a hindrance to long-term use. Therefore, in a PtRu alloy plating solution based on Ru chloride, in order to maintain the stability of the plating solution, even at the expense of the deposition efficiency, the plating temperature has to be set to a lower temperature (45°C or lower). Furthermore, it was confirmed that even taking such stability into account, in a plating solution containing Ru chloride, cracks sometimes occur as the thickness of the film increases.

[0017] As the main reason for the un-deposition of Pt in a PtRu alloy plating solution containing the above-mentioned Pt salt and Ru chloride, the present inventors considered that the chlorine in the liquid makes Pt excessively stable. Furthermore, it was considered that instead of using Ru chloride which can supply excessive chlorine to the plating solution, by controlling the chlorine content within a range that does not hinder the deposition of Pt while applying other Ru salts, it is possible to eliminate problems such as stability. The present inventors made intensive studies based on this consideration, and as a result, came up with a PtRu alloy plating solution in which Ru sulfate or Ru nitrate is applied as the Ru salt, and the chlorine content is controlled within an appropriate range.

[0018] That is, the present invention is a PtRu alloy plating solution containing a divalent Pt salt, either of a Ru sulfate or a Ru nitrate, and sulfuric acid and sulfamic acid, and the chlorine concentration is 0.1 mg / L or more and 300 mg / L or less. Hereinafter, the composition of the PtRu alloy plating solution to which the present invention relates will be described, and a method for manufacturing a PtRu alloy film using the PtRu alloy plating solution will be described.

[0019] (A) Composition of the PtRu alloy plating solution to which the present invention relates

[0020] The PtRu alloy plating solution to which the present invention relates contains a divalent Pt salt and a Ru salt as metal sources, and sulfuric acid and sulfamic acid as essential constituent components.

[0021] As the 2-valent Pt salt, an inorganic acid salt containing at least any one of a sulfate group (SO4) or a sulfonic group (SO3), a nitro group (NO2), a nitric acid group (NO3), an amine (NH3), an acetic acid group (AcO) (H2O), a hydroxyl group (OH) is preferably used. As specific examples, there can be listed a Pt sulfate (PtSO4), a Pt dinitrosulfide (Pt(SO4)(NO3)2), a Pt nitrate (Pt(NO3)2), a Pt dinitrodiamine (Pt(NH3)2(NO3)2), a Pt diamine dichloride (Pt(NH3)2Cl2), a Pt trichloroamine acid (HPtCl3(NH3)) or a salt thereof, a Pt tetranitrate acid (H2PtCl4) or a salt thereof, a Pt tetrasulfonic acid (H6Pt(SO3)4) or a salt thereof, a Pt tetramine phosphoric acid (H2Pt(NH3)4) or a salt thereof, and the like. Among them, particularly preferable Pt salts are a Pt sulfate, a Pt dinitrosulfide, a Pt dinitrodiamine.

[0022] On the other hand, as the Ru salt, a Ru sulfate (RuSO4) or a Ru nitrate (Ru(NO3)2) is applied. As described above, a Ru chloride can be applied to Ru plating, but in the case of application to PtRu alloy plating, it can cause an excess of chlorine in the plating solution to become a main cause of non-deposition of Pt and the like. In order to suppress non-deposition while making the appearance of the plated film also good, the Ru salt is limited to any one of a Ru sulfate or a Ru nitrate. Further, a Ru sulfate is particularly preferable.

[0023] In addition, the PtRu alloy plating solution according to the present application is an aqueous solution obtained by dissolving the above-mentioned Pt salt and Ru salt in sulfuric acid and sulfamic acid. The free sulfuric acid and sulfamic acid in the plating solution are sometimes also generated from the above-mentioned Pt salt and Ru salt. The sulfuric acid and sulfamic acid become necessary components that function as a conductive salt in the plating solution. In addition, the sulfamic acid also has the effect of making the appearance of the plated film uniform.

[0024] Further, the PtRu alloy plating solution according to the present application has a chlorine concentration of 0.1 mg / L or more and 300 mg / L or less. If the chlorine concentration is less than 0.1 mg / L, the plating solution is in a state equivalent to a chlorine-free state, and the deposition efficiency of Pt and Ru decreases, and thus effective plating operation cannot be performed. Further, if the chlorine concentration exceeds 300 mg / L, the stabilization of Pt by chlorine becomes a main factor of non-deposition of Pt. In addition, an excessive chlorine concentration becomes a main factor of generation of cracks in the alloy film in film formation of 1 μm or more. The chlorine concentration is preferably 0.1 mg / L or more and 200 mg / L or less, and more preferably 0.1 mg / L or more and 100 mg / L or less. Note that the reason why the deposition efficiency is improved by the inclusion of chlorine in the above range in the PtRu alloy plating solution according to the present application is not clear. It is also presumed that chlorine forms a certain complex as a chloride ion, or that chlorine acts on Pt and / or Ru as a chlorine atom, but the mechanism is not clear.

[0025] The control of the chlorine concentration in the PtRu alloy plating solution according to the present application can be performed by using a raw material in which the chlorine concentration in a Pt salt and a Ru salt is reduced, and simultaneously adding a chloride to the plating solution. As the chloride to be added at this time, for example, ammonium chloride, Pt chloride, Ru chloride, and the like can be given. In addition, a chloride of an alkali metal or an alkaline earth metal such as sodium chloride and magnesium chloride can be added simultaneously with the addition of an alkali metal salt or an alkaline earth metal salt to be described later.

[0026] The content of each component in the PtRu alloy plating solution according to the present application is preferably as follows: the Pt concentration is 1 g / L or more and 15 g / L or less, the Ru concentration is 0.1 g / L or more and 10 g / L or less, the total sulfuric acid concentration is 10 g / L or more and 200 g / L or less, and the sulfamic acid concentration is 0.1 g / L or more and 20 g / L or less. If the Pt concentration and the Ru concentration are less than the lower limit values, film formation does not proceed. On the other hand, if the Pt concentration and the Ru concentration exceed the upper limit values, it is difficult to suppress the generation of cracks in the formation of a plated film having a thickness.

[0027] In addition, the composition of the PtRu alloy film formed from the PtRu alloy plating solution according to the present application can be adjusted according to the ratio of the Pt concentration to the Ru concentration of the alloy plating solution. According to the present inventors' studies, in order to obtain a PtRu alloy film having a suitably high hardness, it is preferable that the ratio of the Pt concentration to the Ru concentration (Ru concentration (g / L) / Pt concentration (g / L)) be 0.1 or greater and 0.8 or less. The composition of the PtRu alloy film formed at this concentration ratio is a PtRu alloy having a Ru concentration of 2 to 20 mass%. In the case where the above ratio is low, a PtRu alloy film having a Ru concentration that is too low is obtained, and a hardness that is the same as that of Pt is obtained. In addition, even if the Ru concentration exceeds 20%, the hardness of the PtRu alloy film does not much increase, and thus the above ratio need not exceed 0.8. In addition, if the Ru concentration in the plating solution is too high, there is a problem in that the deposition efficiency decreases. A more preferable range of the above ratio is 0.1 or greater and 0.5 or less.

[0028] The PtRu alloy plating solution according to the present application preferably contains an anionic surfactant in addition to the Pt salt, the Ru salt, the sulfuric acid, and / or the sulfamic acid that are described above as necessary components. The anionic surfactant has an effect of suppressing the non-deposition of Pt and Ru and promoting the uniform deposition thereof. In addition to stearate salts and sulfonate salts, a sulfate salt or a sulfamate salt having a surface-activating effect can be used as the anionic surfactant. Preferably, an alkyl sulfate salt, an alkylbenzenesulfonate salt can be listed. As a specific salt, lauryl sulfate salt as a basic sulfate is preferable.

[0029] In the case where the anionic surfactant is added, the concentration thereof is preferably 10 mg / L or greater and 500 mg / L or less. This is because there is no effect below the lower limit value. In addition, if the upper limit value is exceeded, the deposition of Pt and Ru is hindered.

[0030] In addition, the PtRu alloy plating solution according to the present application preferably contains an alkali metal or an alkaline earth metal. The alkali metal or the alkaline earth metal functions as a reducing agent in the plating solution, and has an effect of promoting the deposition of Pt and Ru while forming a plated film having good corrosion resistance. The alkali metal or the alkaline earth metal can coexist with the anionic surfactant, but by adding the alkali metal or the alkaline earth metal, the amount of the anionic surfactant added can be suppressed. As the alkali metal or the alkaline earth metal, Mg is particularly preferable. Note that the alkali metal or the alkaline earth metal does not deposit in the plated film due to the ionization tendency thereof.

[0031] When the alkali metal or the alkaline earth metal is added to the PtRu alloy plating solution, a salt thereof is preferably added, and a sulfate, a sulfite, a nitrate, an oxide, a hydroxide, or the like is preferable. As the preferable alkaline earth metal, Mg can be mentioned, and as the preferable Mg salt, Mg sulfate, Mg sulfite, Mg nitrate, Mg oxide, Mg hydroxide, Mg acetate, Mg citrate, Mg lactate, Mg stearate, or the like is preferably added at the time of building the plating solution.

[0032] The concentration of the alkali metal or the alkaline earth metal in the PtRu alloy plating solution is preferably 1 g / L or more and 20 g / L or less. When it is less than 1 g / L, no effect is obtained. In addition, if it exceeds 20 g / L, the deposition efficiency is reduced.

[0033] In addition, the PtRu alloy plating solution according to the present application can contain a publicly known additive used in the plating solution, in addition to the above-described metal salt, sulfuric acid and sulfamic acid, anionic surfactant, alkali metal or alkaline earth metal. For example, a pH buffer, a complexing agent, a stabilizer, or the like can be contained.

[0034] Note that, in the case of the PtRu alloy plating solution, in the case of measuring the Pt concentration, the Ru concentration, the sulfuric acid concentration, the sulfamic acid concentration, and the chlorine concentration, analysis / measurement can be performed using inductively coupled plasma emission spectroscopy (ICP), ion chromatography (IC) in the state of the plating solution. In addition, a high-performance liquid chromatograph (HPLC), a high-performance liquid chromatograph mass spectrometer (LC-MS, LC-MS / MS), a Fourier transform infrared spectrometer (FT-IR), a nuclear magnetic resonance device (NMR), or the like can be appropriately selected / used as an analysis instrument. In addition, with respect to the chlorine concentration, in addition to the above-described analysis method, measurement can be performed by a DPD (diethyl-p-phenylenediamine) method (colorimetric method or absorbance method), an iodine method, a current method (polarographic method) which are publicly known as a measurement method of chlorine (residual chlorine) in a liquid, and measurement can be performed using a tester, an apparatus, a measurement kit used in these measurement methods. Note that, by performing electron probe micro-analysis (EPMA), energy dispersive X-ray spectroscopy (EDX), fluorescent X-ray analysis (XRF), or the like, the presence of Pt and Ru in the PtRu alloy plating film after film formation and the composition of the plating film can be measured.

[0035] The PtRu alloy plating solution according to the present application can be produced by using a substance in which the above-described Pt salt and Ru salt are dissolved with sulfuric acid and sulfamic acid as a stock solution, and appropriately diluting it. In addition, the Pt salt can be first dissolved with sulfuric acid, and the Ru salt can be then dissolved therein to be used as a stock solution, and diluted. Adjustment of the chlorine concentration, addition of an anionic surfactant, or the like is preferably performed at the above-described dilution stage. In addition, the above-described stock solution can be subjected to adjustment of the chlorine concentration or the like, and a PtRu alloy plating solution can be produced.

[0036] The metal salt used in the plating solution is as described above, but it can be chlorine-free, and can contain chlorine if the chlorine concentration of the plating solution is within the range of the upper limit. In particular, for Ru sulfate or Ru nitrate as the Ru salt, high-purity Ru sulfate or Ru nitrate can be used, but Ru sulfate or Ru nitrate containing chlorine can also be used. For example, Ru sulfate obtained by replacing the chlorine of Ru chloride with sulfuric acid can also be used. The replacement of Ru chloride can be performed by temporarily neutralizing Ru chloride to form a hydroxide, and dissolving / recovering / washing the hydroxide with sulfuric acid / nitric acid to obtain Ru sulfate or Ru nitrate containing a small amount of chlorine. On the other hand, for the 2-valent Pt salt, a Pt salt containing chlorine as a constituent element (diamine dichloro Pt or the like) can also be used, but in this case, the chlorine concentration of the plating solution also needs to be set within the range of the present application.

[0037] (B) Plating method of the PtRu alloy film according to the present application

[0038] Next, the method for producing a PtRu alloy film using the PtRu alloy plating solution according to the present application will be described. The PtRu alloy plating solution according to the present application is acidic, and preferably has a pH of 1 or less. If the pH exceeds 1, cracks are generated in the plated film, and the corrosion resistance is reduced. The lower limit of the pH is preferably 0.1.

[0039] In addition, the temperature of the plating solution is preferably 45°C or higher and 65°C or lower. Since the solution temperature is related to the deposition efficiency, the deposition efficiency is poor at less than 45°C. On the other hand, operation at a high temperature exceeding 65°C has problems such as jig deterioration. In this regard, in the case where Ru chloride is used as the Ru salt of the PtRu alloy plating solution, plating cannot be performed at a temperature of 45°C or higher from the viewpoint of long-term stability of the plating solution. In the PtRu alloy plating solution according to the present application, plating can be performed even at a temperature of 45°C or higher, and is preferably 50°C or higher.

[0040] The current density at the time of film formation is preferably 2.0 A / dm 2 or higher and 10 A / dm 2 or lower. If it is less than 2.0 A / dm 2 , the efficiency in forming a plated film of the desired thickness is low, and if it exceeds 10 A / dm 2 , there is a possibility that a burn will be generated on the plated film.

[0041] Effects of the Invention

[0042] As explained above, the present application relates to a PtRu alloy plating solution in which, together with a Pt salt, Ru sulfate is used as a Ru salt, and the concentration of chlorine is further limited, thereby suppressing factors that hinder the long-term stability of the plating solution, such as non-deposition of Pt during the plating process. The PtRu alloy plating solution according to the present application has a good deposition efficiency, excellent stability, and an advantage in temperature management of the solution temperature, compared to a plating solution using Ru sulfate without chlorine.

[0043] Further, the present application is useful for forming a plating film composed of a PtRu alloy having a suitable composition. The PtRu alloy film is composed of a PtRu alloy having a higher hardness than Pt or the like. In addition, the PtRu alloy film can suppress the generation of cracks, has good corrosion resistance, and has excellent environmental barrier properties with respect to the substrate. The PtRu alloy film has a uniform metallic luster and is also good in appearance. Due to these advantages, the PtRu alloy plating solution according to the present application can be used for a protective plating layer of a connector or terminal of a smartphone or the like, and has durability against repeated insertion and removal. In addition, it is also useful as a plating film of a jewelry or the like. DETAILED DESCRIPTION

[0044] Hereinafter, an embodiment of the present application will be explained. In the present embodiment, a PtRu alloy plating solution was produced using dinitro sulfide Pt (Pt(SO4)(NO3)2) as a Pt salt and Ru sulfate as a Ru salt. Then, the concentration of chlorine was adjusted to prepare a plurality of PtRu alloy plating solutions, and PtRu alloy films were formed from them.

[0045] In the production of the plating solution, first, dinitro sulfide Pt (Pt(SO4)(NO3)2) and Ru sulfate (RuSO4) were added in equal amounts to sulfuric acid and sulfamic acid to form a basic bath having 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 (registered trademark) manufactured by Kawaken Corporation) was added as an anionic surfactant, and 4 g / L of magnesium sulfate as an alkaline earth metal salt was added in terms of Mg concentration. Further, in order to adjust the concentration of chlorine, NaCl was added in such a manner that the concentration of chlorine in the plating solution becomes 0.1 mg / L to 500 mg / L. Finally, it was adjusted to pH 0.4, and a PtRu alloy plating solution was produced.

[0046] In addition, in the present embodiment, a PtRu alloy plating solution using Ru chloride (RuCl3) as a Ru salt was also studied for comparison. With respect to this PtRu alloy plating solution, a stock solution obtained by dissolving a Pt salt and Ru chloride in sulfuric acid and sulfamic acid was prepared in such a manner that the concentrations of Pt and Ru are the same as above, and a PtRu alloy plating solution was produced by diluting and adding additives as in the present embodiment.

[0047] PtRu alloy films were formed using the nine kinds of plating solutions having different chlorine concentrations manufactured as described above. The plating conditions were as follows: Cu plates (20 mm x 40 mm x 0.1 mm) were used as the substrate samples, the bath temperature was set to 60°C, the current density was set to 4.0 A / dm2, and the plating time was adjusted to 30 minutes to 60 minutes based on a film thickness of 5 μm. 2

[0048] After the plating treatment, the substrate was taken out and the average film thickness was measured, and then appearance observation was performed to evaluate the presence or absence of cracks and the presence or absence of unprecipitation. In addition, the precipitation efficiency was calculated from the mass difference of the substrate samples before and after plating. Furthermore, in order to confirm the corrosion resistance of the PtRu alloy film, electrolytic cycle tests were performed on the samples after film formation. The conditions of the electrolytic cycle tests were as follows: each sample was subjected to a voltage of 5 V for 30 seconds in a 5 mass% sodium chloride solution (temperature: room temperature), and this was repeated as one cycle. Then, the corrosion resistance was evaluated in terms of the number of cycles until the Cu serving as the base was exposed, and the maximum number of cycles was 200. These evaluation results are shown in Table 1.

[0049] [Table 1]

[0050]

[0051] It was confirmed from Table 1 that in the plating solution containing no chlorine (chlorine concentration: 0 mg / L), i.e., the plating solution in which sulfuric acid Ru was used as the Ru salt (No. 1), the precipitation efficiency was low and not practical. In addition, it was known from the plating solution in which the plating solution contained 0.1 mg / L of chlorine (No. 2) that the precipitation efficiency could be improved by increasing the chlorine concentration. However, it was confirmed that cracks were generated in the PtRu alloy film when the chlorine concentration was 500 mg / L (No. 8). In addition, it was confirmed that in the case of the plating solution in which Ru chloride was used as the Ru salt (No. 9), in addition to the generation of cracks in the PtRu alloy film, there were unprecipitated portions on the substrate. It was known from Table 1 that the corrosion resistance of the samples in which cracks were generated in the PtRu alloy film was also poor. In contrast, it was confirmed that the PtRu alloy film formed using the PtRu alloy plating solution in which the chlorine concentration was appropriately controlled was also excellent in corrosion resistance (No. 2 to No. 7).

[0052] Embodiment 2 It was confirmed from the results of the above-described first embodiment that by appropriately adjusting the chlorine concentration while using sulfuric acid Ru as the Ru salt, a PtRu alloy film can be formed with high efficiency and high quality. In this embodiment, PtRu alloy plating solutions in which the Ru concentration was changed were manufactured, and the constitution / properties of the PtRu alloy films formed therefrom were evaluated.

[0053] ​As with the first embodiment, the PtRu alloy plating solution was prepared by diluting a stock solution obtained by dissolving dinitrodithio Pt and Ru sulfate in sulfuric acid, and adding a sodium lauryl sulfate Mg salt. Here, the amount of dissolved Ru sulfate at the time of preparing the stock solution was adjusted to prepare a PtRu alloy plating solution having a Ru concentration of 1 g / L, 2 g / L, 3 g / L, 4 g / L, or 5 g / L. These plating solutions were identical except for the two conditions of Ru concentration and total sulfuric acid concentration. The Pt concentration was 10 g / L in each case, the Mg concentration was 4 g / L in each case, and the pH was 0.4 in each case. In addition, the chlorine concentration was 0.5 mg / L in each case.

[0054] Then, a PtRu alloy film was plated using each of the PtRu alloy plating solutions on a multilayer substrate (Cu / Ni / Au) obtained by plating Ni (thickness 5 μm) / Au (thickness 0.1 μm) on a Cu substrate identical to that of the first embodiment. Each of the PtRu alloy films was subjected to hardness measurement after being subjected to calculation of deposition efficiency and EDX composition analysis (Ru concentration measurement). In the hardness measurement, Vickers hardness (Hv) was measured using a Vickers hardness tester under a load of 10 g. In addition, as with the first embodiment, corrosion resistance was evaluated by an electrolytic cycle test. The results are shown in Table 2.

[0055] [Table 2]

[0056]

[0057] As is clear from Table 2, the PtRu alloy film formed in the present embodiment had a Ru ratio that increased with an increase in the Ru concentration of the plating solution, and was composed of a PtRu alloy having a mass ratio of 3 mass% to 12.3 mass%. The hardness of the PtRu alloy film was higher than that of a Pt film formed using a plating solution in which no Ru salt was added. The effect of the hardness increase due to the alloying of Ru with Pt was clearly apparent even in the alloy plating film having a Ru content of 1%.

[0058] Furthermore, in all of the PtRu alloy films, no cracks were generated, and the corrosion resistance was good. In addition, a uniform metallic luster was exhibited, and the appearance was also good.

[0059] Industrial applicability

[0060] As described above, the PtRu alloy plating solution according to the present application has excellent characteristics of deposition efficiency and long-term stability of the liquid by optimizing the Ru salt coexisting with the Pt salt and by specifying the chlorine concentration. In addition, it is possible to suppress the generation of cracks in the PtRu alloy film formed. The PtRu alloy film formed by the present application is composed of a PtRu alloy having high hardness, and the corrosion resistance is also good. The present application is used not only for a protective plating layer of an electronic device such as a connector, a terminal, or the like of a smartphone, a tablet terminal, or the like, but also for forming a plating film on a jewelry item or the like.

Claims

1. A PtRu alloy plating solution comprising: a 2-valent Pt salt, any one of a Ru sulfate or a Ru nitrate, and sulfuric acid and sulfamic acid, a chlorine concentration of 0.1 mg / L or more and 100 mg / L or less. The 2-valent Pt salt is an inorganic acid salt containing at least any one of a sulfate group SO4 or a sulfonic group SO3, a nitro group NO2, a nitrate group NO3, an amine NH3, an acetic acid group, a hydroxyl group OH. The Pt concentration is 1 g / L or more and 15 g / L or less, the Ru concentration is 0.1 g / L or more and 10 g / L or less, the total sulfuric acid concentration is 10 g / L or more and 200 g / L or less, and the sulfamic acid concentration is 0.1 g / L or more and 20 g / L or less. The ratio of the Pt concentration to the Ru concentration, that is, the Ru concentration / Pt concentration, is 0.1 or more and 0.8 or less, and the units of the Pt concentration and the Ru concentration are both g / L. wherein 5. The PtRu alloy plating solution according to claim 1 or claim 2, comprising an anionic surfactant.

2. The PtRu alloy plating solution of claim 1, wherein, 6. The PtRu alloy plating solution according to claim 1 or claim 2, further comprising an alkali metal or an alkaline earth metal.

3. The PtRu alloy plating solution of claim 1 or claim 2, wherein, 7. A plating method for a PtRu alloy film using the PtRu alloy plating solution according to claim 1 or claim 2, wherein the pH of the PtRu alloy plating solution is set to 1 or less.

4. The PtRu alloy plating solution of claim 1 or claim 2, wherein, 8. The plating method according to claim 7, wherein the PtRu alloy plating solution is used at a temperature of 20°C or higher and 60°C or lower. ​ ​ ​ wherein ​ The plating treatment was performed at a temperature of 45°C or higher and 65°C or lower and a current density of 2.0 A / dm 2 The plating treatment was performed at a temperature of 45°C or higher and 65°C or lower and a current density of 2.0 A / dm 2 The plating treatment was performed at a temperature of

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