Electroplating solution and method for producing plated member

Abstract

To provide an electroplating solution which hardly causes a hydrogen generation reaction.SOLUTION: According to an aspect of the present invention, there is provided an electroplating solution including water, a metal ion, and an organic solvent, wherein the organic solvent includes an aprotic organic compound having an ether group in a chemical structure, and a molar amount of the organic compound in the electroplating solution is 20% or more with respect to a molar amount of the water.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electroplating solution and a method for producing a plated member. [Background technology]

[0002] Patent Document 1 discloses a technology for providing a zinc alloy plated member that not only imparts excellent corrosion resistance to a substrate but also can be used as a sliding member, and a plating solution for producing the zinc alloy plating.

[0003] Specifically, Patent Document 1 discloses a zinc alloy plated member comprising: a substrate having a metallic surface; and a zinc alloy plated coating provided on the substrate, the zinc alloy plated coating having a chemical composition containing, by mass %, 2% to 8% Ni and 0.1% to 3% Mo, with the balance being Zn and impurities, a hardness of 150 Hv to 350 Hv, and a thickness of 0.1 μm to 30 μm. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-032571 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when electroplating is performed using an aqueous solvent, the water contained in the electroplating solution may be electrolyzed to generate hydrogen, a so-called hydrogen generation reaction. Such hydrogen generation can cause hydrogen embrittlement of the base material being plated. Therefore, it is desirable to provide an electroplating solution that is less likely to cause the hydrogen generation reaction. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided an electroplating solution comprising water, metal ions, and an organic solvent, wherein the organic solvent comprises an aprotic organic compound having an ether group in its chemical structure, and the molar amount of the organic compound in the electroplating solution is 20% or more relative to the molar amount of water.

[0007] With this configuration, it is possible to provide an electroplating solution that is less likely to cause a hydrogen generation reaction. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a photograph showing the carbon tool steel and precipitates according to Test Example 3. [Figure 2] FIG. 1 is a diagram showing XRD patterns of precipitates according to Test Examples 1 and 2. [Figure 3] FIG. 10 is a diagram showing XRD patterns of precipitates according to Test Examples 3 and 4. [Figure 4] 10 is a photograph showing copper and precipitates according to Test Example 7. [Figure 5] FIG. 1 shows XRD patterns of Test Examples 5 to 10. [Figure 6] 1 is a photograph showing the carbon tool steel and precipitates according to Test Example 12. [Figure 7] FIG. 1 shows XRD patterns of Test Examples 11 to 16. [Figure 8] FIG. 1 shows XRD patterns of Test Examples 11 to 16. [Figure 9] FIG. 1 shows XRD patterns of Test Examples 17 to 21. [Figure 10] FIG. 1 shows XRD patterns of Test Examples 22 to 25. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. Various features shown in the following embodiments can be combined with each other.

[0010] [Electroplating solution] The electroplating solution of this embodiment is a water-based electroplating solution that contains water, an organic solvent, and metal ions.

[0011] The water contained in the electroplating solution of this embodiment is, for example, pure water. The water may be, for example, electrolyzed water, distilled water, filtered water, etc. The water may also be water containing a certain amount of impurities, such as so-called tap water.

[0012] The organic solvent contained in the electroplating solution of this embodiment contains an aprotic organic compound having an ether group in its chemical structure. By incorporating such an organic compound, an electroplating solution that is less likely to induce a hydrogen generation reaction can be realized. While the reason for this is unclear, it is believed that such an organic compound appropriately coordinates with the metal ions described below in the electroplating solution, thereby appropriately controlling the reaction behavior during the plating process (details will be described later). Such organic compounds may have various chemical structures. As an example, the organic compound may have a cyclic structure in its chemical structure. This configuration can further suppress the hydrogen generation reaction. In this case, the organic compound may not have an ether group in the cyclic structure, but may have an ether group in the cyclic structure. In other words, the organic compound may contain a cyclic ether compound. This configuration can stabilize the three-dimensional structure of the organic compound, thereby allowing the organic compound to coordinate with the metal ions more stably. The cyclic ether compound may be composed of one or more substances selected from the group consisting of tetrahydrofuran (THF), dioxane, dioxolane, trioxolane, tetrahydropyran, and crown ether. According to this configuration, the three-dimensional structure of the organic compound can be stabilized, and therefore the organic compound can be coordinated to the metal ion more stably. Examples of organic compounds having an ether group at a site other than the cyclic structure include cyclopentyl methyl ether, cyclopentyl ethyl ether, and cyclohexyl methyl ether. From another perspective, the cyclic structure may be a five- or six-membered ring. According to this configuration, the three-dimensional structure of the organic compound can be stabilized, and therefore the organic compound can be coordinated to the metal ion more stably. Therefore, five- or six-membered cyclic ether compounds such as THF and dioxane are particularly preferred as organic compounds.

[0013] The molar amount of the organic compound in the electroplating solution is 20% or more relative to the molar amount of water. This configuration provides an electroplating solution that suppresses the hydrogen generation reaction and enables more efficient electroplating. More specifically, the molar amount of the organic compound in the electroplating solution is 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90% relative to the molar amount of water, and may be within a range between any two of the values ​​exemplified here. For example, the molar amount of the organic compound in the electroplating solution is 20 to 90%, 25 to 80%, 30 to 70%, or 35 to 65% relative to the molar amount of water. These molar amounts are particularly preferred when the organic compound is dioxane or THF.

[0014] The electroplating solution of this embodiment may contain an organic solvent other than the organic compounds described above. For example, the electroplating solution may contain a water-soluble organic solvent such as an alcohol-based solvent, a glycol-based solvent, an ether alcohol-based solvent, an amide-based solvent, or an ester-based solvent. The electroplating solution of this embodiment may also contain an organic solvent (typically a hydrocarbon solvent, etc.) other than the various water-soluble organic solvents described above, as long as it does not deviate from the object of the invention. Even in this case, it is preferable that the water and the organic solvent are mixed without separation in the electroplating solution of this embodiment.

[0015] The metal ions contained in the electroplating solution of this embodiment are selected from among metal ions that can be present in the electroplating solution. Examples of such metal ions include nickel ions, chromium ions, gold ions, zinc ions, and molybdenum ions. In particular, the metal ions may contain at least zinc ions. This configuration provides an electroplating solution capable of performing aqueous electroplating of suitable zinc-containing metals. The metal ions may also be composed of zinc ions and other metal ions capable of forming alloys with zinc. Examples of such other metal ions include iron ions, cobalt ions, nickel ions, and chromium ions, as well as combinations of two or more of these. When the metal ions are composed of two or more metal elements, the amount of each metal ion may be calculated as a weighted average of the amount of each metal ion based on the metal ion composition ratio. The molar amount of the metal ion may be at least 5% or more of the total molar amount of water and the organic compound. This configuration provides an electroplating solution capable of more effectively performing metal ion-based metal electroplating. For example, the molar amount of the metal ions may be 5% or more and 20% or less relative to the total molar amount of water and the organic compound. This configuration provides an electroplating solution that enables more efficient metal ion-based electroplating. More specifically, the molar amount of the metal ions may be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30% relative to the total molar amount of water and the organic compound, or may be within a range between any two of the values ​​exemplified here. For example, the molar amount of the metal ions is preferably 5-30%, 5-20%, 6-25%, 7-20%, 10-20%, or 10-12% relative to the total molar amount of water and the organic compound. Such molar amounts are particularly preferred when the metal ions are zinc ions and the organic solvent is THF or dioxane. By setting the temperature in this range, the possibility of the hydrogen generation reaction occurring can be further reduced.

[0016] The metal ion source may be any substance capable of releasing metal ions in solution, such as chlorides, sulfates, carbonates, or ammonium salts of the metal ions, or a mixture thereof. Examples of zinc ion sources include ZnO, Zn(OH)2, ZnCl2, ZnSO4, ZnCO3, Zn(SO3NH2)2, zinc acetate, and zinc methanesulfonate. The zinc ion source may also be a mixture of two or more of these. Examples of nickel ion sources include NiCl2, NiSO4, NiSO4·6H2O, NiCO3, Ni(SO3NH2)2, nickel acetate, and nickel methanesulfonate. The nickel ion source may also be a mixture of two or more of these. For electroplating solutions for nickel-zinc alloy plating, the metal ion sources may be appropriately combined as described above.

[0017] The pH of the electroplating solution of this embodiment can be appropriately selected depending on the type of object to be electroplated and the type of metal film to be plated. For example, the electroplating solution can be acidic. The lower limit of the pH of the electroplating solution is, for example, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, or 2.4, and may be within a range between any two of the values ​​exemplified here. The upper limit of the pH of the electroplating solution is, for example, 7, 6.5, 6, 5.5, 5, 4.5, 4, 3.5, 3, or 2.5, and may be within a range between any two of the values ​​exemplified here. The pH of the electroplating solution is, for example, a value within a range of 1 to 7, 1.5 to 5, 1.6 to 4, 2 to 3.5, 2.2 to 3.2, or 2.3 to 2.5.

[0018] The electroplating solution of this embodiment may contain various additives other than those described above, such as a pH adjuster, a pH buffer, a complexing agent, an accelerator, a brightener, and a wetting agent.

[0019] [Method of manufacturing plated components] Next, an example of a method for manufacturing a plated member using the above-described electroplating solution will be described. First, an electroplating solution, an anode member, and a cathode member are prepared. While any method can be used to prepare (prepare) the electroplating solution, for example, the electroplating solution is prepared by measuring pre-prepared pure water, an organic solvent, and a metal salt so that the water, organic compound, and metal ions are in a predetermined molar ratio, and then mixing them so that they are uniformly dissolved.

[0020] The anode member is made of a conductive material that can be applied with an external voltage to create a potential difference. The anode member is configured to, for example, dissolve during electroplating to release the metal ions contained in the electroplating solution. For example, when the metal ions are zinc ions, the anode member is made of metallic zinc. Furthermore, the anode member is preferably insoluble in the electroplating solution when no voltage is applied. The anode member may be made of any material, including, for example, a metal capable of releasing metal ions in the electroplating solution, such as an elemental metal or an alloy. For example, when the metal ions are zinc ions, the anode member may be made of zinc metal or a material obtained by adding various additives, such as aluminum, to the zinc metal. The anode member may also be an insoluble anode member that does not dissolve during electroplating. Examples of insoluble anode members include lead alloys, ferrite, platinum, platinum-coated titanium, iridium oxide-coated titanium, carbon, and lead. Such an anode member can be appropriately selected depending on the type and composition of the metal ions, the molar concentration in the electroplating solution, and the like.

[0021] The cathode member is configured so that a voltage is applied to it during electroplating so that it has a lower potential than the anode member. The cathode member is configured so that metal ions in the electroplating solution are attracted by an electric field based on the potential, causing a reduction reaction on the surface of the cathode member. This causes a reduction reaction of the metal ions around the cathode member, allowing a metal film formed by the reduced metal ions to be deposited on the surface of the cathode member. The cathode member is, for example, a member to be plated, and may have any shape. In addition, when preparing the anode member and the cathode member, each of the cathode member and the anode member may be subjected to various pretreatments, such as water washing, hot water washing, degreasing, acid cleaning, electrolytic cleaning, acid activation, neutralization, and strike plating.

[0022] Next, the anode member and the cathode member are immersed in the electroplating solution. For example, in this manufacturing method, at least a portion of the prepared electroplating solution is contained in a pre-prepared container, and the prepared anode member and the cathode member are immersed in the electroplating solution contained in the container. Note that a permeable membrane that allows preferential or selective permeation of metal ions in the electroplating solution may be interposed between the immersed anode member and the anode member.

[0023] Next, the anode member and the cathode member are connected to a power supply so that a voltage can be applied between them. The power supply may be a DC power supply, a pulse power supply, a PR (Periodic Reverse) power supply, etc. From the viewpoint of controlling the cation current in the electroplating solution during plating, the power supply is preferably a power supply capable of controlling the current, such as a DC power supply.

[0024] Next, a voltage is applied between the anode member and the cathode member, depositing a metal film on the surface of the cathode member. This results in a plated member. The metal film is also called a plated object or a plated coating. The current density of the current flowing between the anode member and the cathode member when the voltage is applied is arbitrary, but specific examples include 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 mA / cm. 2and may be within a range between any two of the numerical values ​​exemplified here. From the viewpoint of improving the plating speed, a higher current density is preferable, while from the viewpoint of providing a metal film with small particle diameters and excellent gloss and smoothness, a lower current density is preferable. In order to perform electroplating in various modes depending on the application and situation, it is preferable to use an electroplating solution that can perform electroplating over a wide range of current densities (especially one with a small lower limit of current density).

[0025] The plated member thus obtained comprises a cathode member as a base material and a metal film deposited on the surface of the cathode member. The thickness of the metal film can be adjusted depending on the degree of electroplating (e.g., expressed as current density x time), but specific examples include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 μm, and may be within a range between any two of the values ​​exemplified here. The average particle diameter of the metal microparticles constituting the metal film tends to depend on the current density, etc., but specific examples include 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 nm, and may be within a range between any two of the values ​​exemplified here. If a pretreatment such as strike plating has been performed, the plated member may have an additional layer between the cathode member and the metal film. The plated member thus obtained may be subjected to any post-treatment such as washing with water, activation with nitric acid, or chromate treatment.

[0026] The electroplating solution of this embodiment is unlikely to cause a hydrogen generation reaction when used in an electroplating process. A hypothetical mechanism is described below. Although it is unclear, ligands such as water molecules are coordinated around metal ions in the electroplating solution. For example, it is believed that four molecules or ions are tetrahedronally coordinated around a divalent zinc ion. In this case, applying a voltage between an anode member and a cathode member induces the metal ions and the ligands toward the cathode member, where electrons are exchanged on the surface of the cathode member. This transfer of electrons not only to the metal ions but also to the surrounding ligands may result in a reduction reaction of not only the metal ions but also the ligands. When the ligands are water molecules, a hydrogen generation reaction due to the reduction reaction of the water molecules may cause hydrogen embrittlement of the cathode member to be plated or the plating itself. Therefore, adding an organic solvent containing the above-mentioned organic compound to the electroplating solution makes it easier for organic compounds with a predetermined structure to be coordinated to metal ions in the electroplating solution during electroplating. This is thought to reduce the possibility of water molecules coordinating with metal ions, thereby suppressing the hydrogen generation reaction.

[0027] Considering this point of view, the organic compound may be configured to coordinate to at least one (for example, one) of the coordination sites of the metal ion described below. With this configuration, it is possible to reduce the possibility that water molecules are reduced when the metal ion is reduced.

[0028] The above embodiment may be provided in the following aspects.

[0029] (1) An electroplating solution comprising water, metal ions, and an organic solvent, wherein the organic solvent contains an aprotic organic compound having an ether group in its chemical structure, and the molar amount of the organic compound in the electroplating solution is 20% or more relative to the molar amount of water.

[0030] According to this configuration, it is possible to provide an electroplating solution that can suppress the hydrogen generation reaction and perform electroplating more efficiently.

[0031] (2) The electroplating solution according to (1) above, wherein the organic compound has a cyclic structure in its chemical structure.

[0032] With this configuration, the hydrogen generation reaction can be further suppressed.

[0033] (3) The electroplating solution according to (2) above, wherein the organic compound includes a cyclic ether compound.

[0034] According to this configuration, the three-dimensional structure of the organic compound can be stabilized, and therefore the organic compound can be coordinated to the metal ion more stably.

[0035] (4) The electroplating solution according to (3) above, wherein the cyclic ether compound is composed of one or more substances selected from the group consisting of tetrahydrofuran, dioxane, dioxolane, trioxolane, tetrahydropyran, and crown ether.

[0036] According to this configuration, the three-dimensional structure of the organic compound can be stabilized, and therefore the organic compound can be coordinated to the metal ion more stably.

[0037] (5) The electroplating solution according to any one of (2) to (4) above, wherein the cyclic structure is a five-membered ring or a six-membered ring.

[0038] According to this configuration, the three-dimensional structure of the organic compound can be stabilized, and therefore the organic compound can be coordinated to the metal ion more stably.

[0039] (6) The electroplating solution according to any one of (1) to (5) above, wherein the metal ions contain at least zinc ions.

[0040] According to this configuration, it is possible to provide an electroplating solution that can perform suitable aqueous electroplating of zinc-containing metals.

[0041] (7) The electroplating solution according to any one of (1) to (6) above, wherein the molar amount of the metal ions is at least 5% or more of the total molar amount of the water and the organic compound.

[0042] According to this configuration, it is possible to provide an electroplating solution that can more suitably perform electroplating of a metal based on metal ions.

[0043] (8) The electroplating solution according to (7) above, wherein the molar amount of the metal ions is 5% or more and 20% or less of the total molar amount of the water and the organic compound.

[0044] According to this configuration, it is possible to provide an electroplating solution that can more suitably perform electroplating of a metal based on metal ions.

[0045] (9) A method for producing a plated member, the method comprising: preparing the electroplating solution according to any one of (1) to (8) above, an anode member, and a cathode member; immersing the anode member and the cathode member in the electroplating solution; and applying a voltage between the anode member and the cathode member to deposit a metal film on a surface of the cathode member, thereby obtaining the plated member. Of course, this is not the case.

[0046] Finally, while various embodiments of the present disclosure have been described, they are presented as examples and are not intended to limit the scope of the invention. The novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. Such embodiments and modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the inventions and their equivalents as defined in the claims. [Example]

[0047] The present invention will be explained in more detail by way of the following examples, but the present invention is not limited to the following examples (test examples).

[0048] 1. Test example when zinc ions are used as metal ions First, a test example in which zinc ions are used as metal ions, in other words, zinc plating is performed, will be described.

[0049] 1.1. Relationship between the presence or absence of organic compounds and electroplating <Preparing for test examples> First, the inventors obtained electroplating solutions according to Test Examples 1 to 4 and plated members using the electroplating solutions in the following manner.

[0050] [Test Example 1] The inventors obtained an electroplating solution according to Test Example 1 by mixing 1 mol of zinc sulfate heptahydrate (ZnSO4·7H2O, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.0%) and 0.5 mol of sodium sulfate (Na2SO4, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.0%) with pure water as a solvent.

[0051] Next, the inventors applied a zinc plate as an anode member and a carbon tool steel plate (model number SK85, manufactured by Musashino Metal Industries Co., Ltd., 1 cm x 5 cm x 2.5 mm thick, exposed area 1 cm) as a cathode member to the electroplating solution according to Test Example 1. 2 ) and was immersed.

[0052] Next, the inventors investigated the current density between the anode and cathode members at room temperature (approximately 27°C) without stirring and at a current density of 50 mA / cm 2 A voltage was applied to the impregnated anode and cathode members for 10 minutes so that the temperature was such that the precipitate formed on the surface of the carbon tool steel.

[0053] [Test Example 2] The inventors have found that the current density between the anode and cathode members is 10 mA / cm 2 An electroplating solution according to Test Example 2 and a deposit according to Test Example 2 were obtained by the same process as in Test Example 1, except that the current application time was 50 minutes.

[0054] [Test Example 3] The inventors mixed zinc chloride (ZnCl) (Sigma-Aldrich, purity 98%), pure water as a solvent, and 1,4-dioxane (Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.5%+) in a molar ratio of 1:3:3, thereby obtaining an electroplating solution according to Test Example 3.

[0055] Next, the inventors applied a zinc plate as an anode member and a carbon tool steel plate (model number SK85, manufactured by Musashino Metal Industries Co., Ltd., 1 cm x 5 cm x 2.5 mm thick, exposed area 1 cm) as a cathode member to the electroplating solution according to Test Example 3. 2 ) and was immersed.

[0056] Next, the inventors investigated the current density between the anode and cathode members at room temperature (approximately 27°C) without stirring, and found that the current density was 2 mA / cm 2 A voltage was applied to the impregnated anode and cathode members for 60 minutes so that the anode and cathode members were at the same temperature. As a result, a precipitate was obtained on the surface of the carbon tool steel. FIG. 1 is a photograph showing the carbon tool steel and the precipitate according to Test Example 3. In FIG. 1, (A) is the carbon tool steel used as the cathode member, and (B) is the precipitate deposited on the surface of the carbon tool steel.

[0057] [Test Example 4] The inventors have found that the current density between the anode member and the cathode member is 1 mA / cm 2An electroplating solution according to Test Example 4 and a deposit according to Test Example 4 were obtained by the same process as Test Example 3, except that the current application time was 120 minutes. Test Examples 3 and 4 are examples in which zinc ions were used as the metal ions and dioxane was used as the organic compound.

[0058] <Evaluation method for plated members in test examples> The inventors performed X-ray diffraction (XRD) measurements on the precipitates of Test Examples 1 to 4 obtained by the above process by irradiating them with CuKα radiation, and obtained XRD patterns showing the relationship between 2θ and XRD intensity. A MiniFlex (manufactured by Rigaku) ​​was used as the XRD measurement device. The inventors then compared the obtained XRD patterns of Test Examples 1 to 4 with reference patterns in the Inorganic Crystal Structure Database (ICSD) to identify the substances contained in the precipitates.

[0059] <Evaluation results of Test Examples 1 to 4> Next, the evaluation results of the precipitates obtained by the above-mentioned processes in Test Examples 1 to 4 will be described. Fig. 2 shows XRD patterns of the precipitates in Test Examples 1 and 2. Fig. 3 shows XRD patterns of the precipitates in Test Examples 3 and 4.

[0060] As shown in Figures 2 and 3, major zinc peaks (such as a 002 reflection peak appearing near 2θ = 36 degrees, a 100 reflection peak appearing near 2θ = 39 degrees, a 101 reflection peak appearing near 2θ = 43 degrees, and a 102 reflection peak appearing near 2θ = 54 degrees) were observed in all of the deposits of Test Examples 1 to 4. The peak near 2θ = 45 degrees is attributed to the carbon tool steel used as the cathode member. This indicates that the deposits of Test Examples 1 to 4 contain zinc as the main component, i.e., that they were zinc-plated.

[0061] On the other hand, as shown in Figure 2, no peak was observed in the 2θ range of 8 to 9 degrees in Test Example 1, whereas a peak was observed in the XRD pattern of Test Example 2 at 2θ = 8 to 9 degrees, which was not observed in Test Example 1 (or was buried in the background). This peak was identified as a peak derived from Zn4(OH)6SO4·5H2O. Such zinc-based hydroxides are thought to be generated due to the reduction of water molecules, not the reduction of zinc ions, around the cathode member. These results suggest that when plating is performed using the electroplating solutions of Test Examples 1 and 2, reducing the current density may increase the likelihood of a hydrogen generation reaction.

[0062] On the other hand, as shown in FIG. 3, the deposits in Test Example 3 exhibited a current density (2 mA / cm) lower than those in Test Examples 1 and 2. 2 ), no peak was observed in the range of 2θ = 8 to 9 degrees (or the peak was so small that it was difficult to distinguish it from the background). In Test Example 4, the current density was even lower than in Test Example 3 (1 mA / cm 2 ), no peaks similar to those observed in the XRD pattern of Test Example 2 were observed in the 2θ range of 8 to 9 degrees. Instead, a small peak identified as originating from Zn5(OH)8Cl2·H2O was observed near 2θ = 11 to 12 degrees. The intensity of this peak was barely distinguishable from the background compared to the intensity of the peak originating from Zn4(OH)6SO4·5H2O in Test Example 2. Therefore, it is believed that the deposit of Test Example 4 contained only trace amounts of Zn4(OH)6SO4·5H2O compared to Test Example 2. These results suggest that by using an electroplating solution containing water and an organic solvent containing an aprotic organic compound with an ether group in its chemical structure, metal (zinc) plating with reduced hydrogen generation reaction can be performed over a wider range (especially in the low current density region) than conventional plating methods.

[0063] 1.2. Relationship between metal ion concentration and electroplating results The inventors also prepared electroplating solutions for each of Test Examples 5 to 10, in which the molar amount of metal ions relative to the molar amount of water and organic compounds was changed as a parameter, and analyzed the composition of the deposits obtained from the electroplating solutions.

[0064] <Preparation of test examples and evaluation methods> First, the inventors mixed zinc chloride (ZnCl), water, and 1,4-dioxane in the molar ratios shown in the table below to obtain electroplating solutions according to Test Examples 5 to 10. The details of each raw material were the same as those explained in Test Examples 3 and 4. The inventors measured the pH of the obtained electroplating solutions according to Test Examples 5 to 10 using a pH meter (manufactured by HORIBA). [Table 1]

[0065] Next, the inventors, in the same manner as in Test Examples 3 and 4, immersed a zinc plate as an anode member and a copper plate material as a cathode member (Model No. CU-113321, manufactured by Nilaco Corporation, 1 cm × 1.5 cm × thickness 0.10 mm, purity 99.96%, immersion area 1 cm) in the electroplating solutions of Test Examples 5 to 10. 2 ) was immersed.

[0066] Next, the inventors performed the experiments for each of Test Examples 5 to 10 under the conditions of room temperature (approximately 27°C) without stirring, where the current density between the anode member and the cathode member was 1 mA / cm 2 A voltage was applied to the impregnated anode and cathode members so that the voltage was 0.01 V. The voltage application time in Test Example 5 was 30 minutes, and the voltage application time in Test Examples 6 to 10 was 1 hour. As a result, a deposit was obtained on the surface of the copper plate. That is, Test Example 7 was obtained by the same method as Test Example 4, except that the cathode member was a copper plate. Figure 4 is a photograph showing copper and the deposit in Test Example 7. In Figure 4, (C) is copper as the cathode member, and (D) is the deposit deposited on the copper surface. As shown in Figure 4, it has been experimentally demonstrated that this plating solution can be used for plating not only when the cathode member is carbon tool steel, but also for plating various members such as copper.

[0067] As in Test Examples 3 and 4, the inventors performed XRD measurements on the precipitates of Test Examples 5 to 10 obtained by the above process by irradiating them with CuKα radiation, obtained XRD patterns showing the relationship between the XRD intensity for each 2θ, and identified the substances contained in the precipitates by comparing the obtained XRD patterns of Test Examples 5 to 10 with reference patterns in the Inorganic Crystal Structure Database (ICSD).

[0068] <Evaluation results of Test Examples 5 to 10> Fig. 5 shows the XRD patterns of Test Examples 5 to 10. As shown in Fig. 5, in all of the deposits of Test Examples 5 to 10, major zinc peaks (002 reflection peak appearing near 2θ = 36 degrees, 100 reflection peak appearing near 2θ = 39 degrees, 101 reflection peak appearing near 2θ = 43 degrees, and 102 reflection peak appearing near 2θ = 54 degrees, etc.) were observed, similar to Test Examples 3 and 4. This indicates that the metal deposited on the surface of the cathode member of Test Examples 5 to 10 contains zinc as a main component, i.e., zinc plating was performed.

[0069] On the other hand, a small peak identified as being derived from Zn5(OH)8Cl2·H2O was observed around 2θ = 11 to 12 degrees in Test Examples 5, 6, and 10. As mentioned above, Zn5(OH)8Cl2·H2O is one of the substances generated as a result of the hydrogen generation reaction during plating, so the smaller the intensity of the corresponding peak, in other words, the smaller the amount of Zn5(OH)8Cl2·H2O generated, the more the hydrogen generation reaction is suppressed.

[0070] Furthermore, in Test Examples 8, 9, and 10, one peak other than those derived from metallic zinc and Zn5(OH)8Cl2·H2O was observed in each of the ranges of 2θ = 32 to 33 degrees, 34 to 35 degrees, and 55 to 57 degrees. These peaks were identified as those derived from Zn(OH)2. Since Zn(OH)2, like Zn5(OH)8Cl2·H2O, is also one of the substances generated by the hydrogen evolution reaction, the smaller the intensity of this peak, i.e., the smaller the amount of Zn(OH)2 produced, the more suppressed the hydrogen evolution reaction is.

[0071] In particular, in Test Examples 6, 7, and 8, the peak intensities of both Zn5(OH)8Cl2·H2O and Zn(OH)2 were smaller than those of Test Examples 5, 9, and 10, and therefore it can be said that these electroplating solutions are particularly suitable for suppressing the occurrence of the hydrogen evolution reaction. Furthermore, Test Examples 5 to 10 experimentally demonstrated that plated members can be produced while suppressing HER even when the cathode member is a member other than carbon tool steel.

[0072] 2. Test examples using zinc ions and nickel ions as metal ions Next, Test Examples 11 to 18 will be described, which are cases where zinc ions and nickel ions are used as metal ions, in other words, where zinc-nickel alloy plating is performed.

[0073] <Preparing for test examples> First, the inventors mixed nickel chloride (NiCl2), zinc chloride (ZnCl2), water, and 1,4-dioxane in the molar ratios shown in the table below to obtain electroplating solutions according to Test Examples 11 to 18. Next, the inventors measured the pH of the obtained electroplating solutions according to Test Examples 11 to 18 using a pH meter (manufactured by HORIBA). Next, the inventors added a zinc plate as an anode member and a carbon tool steel plate (model number SK85, manufactured by Musashino Metal Industry Co., Ltd., 1 cm x 5 cm x 2.5 mm thick, exposed area 1 cm) as a cathode member to the obtained electroplating solutions according to Test Examples 11 to 18. 2) was immersed in the test sample. Thereafter, the inventors applied a voltage to the anode member and the cathode member without stirring in an environment at room temperature (approximately 27°C) so that the current density flowing between the anode member and the cathode member reached the values ​​shown in the table below. The voltage application time in each of Experimental Examples 11 to 21 was 1 hour for Test Examples 12, 14, 16, 17, 19, and 21, and 30 minutes for Test Examples 11, 13, 15, 18, and 20. As a result, a deposit was obtained on the surface of the cathode member. FIG. 6 is a photograph showing the carbon tool steel and the deposit according to Test Example 12. In FIG. 6, (E) is the carbon tool steel used as the cathode member, and (F) is the deposit deposited on the surface of the carbon tool steel. [Table 2]

[0074] Thereafter, the obtained plated members of Test Examples 11 to 21 were subjected to XRD measurement in the same manner as in Test Examples 1 to 10, and the substances contained in the plated portions were identified from the XRD patterns.

[0075] <Evaluation results of Test Examples 11 to 21> 7 and 8 are diagrams showing XRD patterns of Test Examples 11 to 16. PP1 in FIG. 7 represents a nickel-zinc solid solution (Ni 3.2 Zn 0.8 , and Ni 3.68 Zn 0.32 ) XRD pattern of PP2 is Ni2Zn 11 PP3 is the XRD pattern of Zn (metallic zinc).

[0076] As shown in Fig. 7, it was found that the precipitates in Test Examples 11 to 16 contained a nickel-zinc alloy as one of the main components. On the other hand, as shown in Fig. 7, in Test Examples 11 to 14, the nickel-zinc alloy phase was Ni2Zn 11As a main component, Test Examples 15 and 16 were found to contain a nickel-zinc solid solution as a main component. Furthermore, it was found that the plated portion of Test Example 16 further contained metallic zinc. From this perspective, when performing nickel-zinc alloy plating, it is preferable that the total molar amount of nickel ions and zinc ions is 1 / 10 or less, more preferably 1 / 20, of the total molar amount of water and dioxane as an organic compound.

[0077] 8, the XRD patterns of Test Examples 13 and 14 show a peak derived from Zn5(OH)8Cl2·H2O near 2θ = 11 to 12 degrees, as seen in Test Example 5, suggesting that a slight hydrogen generation reaction occurred. On the other hand, the XRD patterns of Test Examples 11, 12, 15, and 16 show no peak near 2θ = 11 to 12 degrees, which indicates that the hydrogen generation reaction was more suppressed than in the other Test Examples.

[0078] 9 is a diagram showing the XRD patterns of Test Examples 17 to 21. Note that PP1 shown in FIG. 9 indicates the XRD pattern of a nickel-zinc solid solution, similar to FIG.

[0079] 9, in all of Test Examples 17 to 21, the peaks were identified as originating from a nickel-zinc solid solution and were observed around 2θ = 42 to 47 degrees. This demonstrates that nickel-zinc alloy plating is possible by using the electroplating solutions of Test Examples 17 to 21, which employ nickel ions and zinc ions as metal ions.

[0080] Among these, the ratio of the intensity of the peak near 2θ=11 to 12 degrees to the intensity of the peak derived from the solid solution was smaller (or not observed) in the XRD patterns of Test Examples 17, 18, and 21 compared to the XRD patterns of Test Examples 19 and 20. Considering that the peak near 2θ=11 to 12 degrees is a peak derived from Zn5(OH)8Cl2·H2O and that the generation of Zn5(OH)8Cl2·H2O is derived from the occurrence of a hydrogen generation reaction, this indicates that when zinc ions and nickel ions are used as metal ions, an electroplating solution that is more likely to suppress the hydrogen generation reaction can be provided when the total molar amount of the metal ions is 1 / 20 (=5%) or less relative to the molar amount of water and organic compounds, regardless of the compounding ratio of these ions.

[0081] 2. Relationship between current density and hydrogen evolution reaction when zinc ions and nickel ions are used as metal ions Next, the relationship between current density and hydrogen generation reaction when zinc ions and nickel ions are used as metal ions, in other words, when zinc-nickel alloy plating is performed, will be described with reference to the results of Test Examples 22 to 25.

[0082] <Preparing for test examples> First, the inventors mixed nickel chloride (NiCl), zinc chloride (ZnCl), water, and 1,4-dioxane in a molar ratio of 0.1:0.9:10:10 to obtain electroplating solutions according to Test Examples 22 to 24. The pH of each of the electroplating solutions according to Test Examples 22 to 24 was 4.5.

[0083] The inventors also mixed zinc sulfate heptahydrate (ZnSO4·7H2O, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.0%), nickel sulfate hexahydrate (NiSO4·6H2O, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.0%), and (Na2SO4, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity 99.0%) in a molar ratio of 3:7:5 to obtain an electroplating solution according to Test Example 25. The pH of the electroplating solution according to Test Example 25 was 4.8.

[0084] Next, the inventors applied a zinc plate as an anode member and a carbon tool steel plate (model number SK85, manufactured by Musashino Metal Industries Co., Ltd., 1 cm × 5 cm × thickness 2.5 mm, exposed area 1 cm) as a cathode member to the electroplating solutions of the obtained Test Examples 22 to 25. 2 The inventors then applied a voltage to the anode member and the cathode member without stirring. The current density applied in each of Test Examples 22 to 24 was 5 mA / cm. 2 In Test Example 25, the current density was 50 mA / cm 2 The voltage application times were 12 minutes in Test Example 22, 1 hour in Test Example 23, 100 minutes in Test Example 24, and 10 minutes in Test Example 25. As a result, a deposit was obtained on the surface of the negative electrode member. The reaction temperature in Test Examples 22 to 24 was room temperature (approximately 27°C), and the reaction temperature in Test Example 25 was 50°C.

[0085] The negative electrode member on which the deposits were deposited was subjected to XRD measurement in the same manner as in the above-mentioned Test Examples, and the XRD patterns of Test Examples 22 to 24 were obtained. Note that, for comparison, the inventors also performed XRD measurement on the negative electrode member on which the deposits of Test Example 25 were deposited, and the XRD pattern of Test Example 25 was obtained.

[0086] [About the test results] Fig. 10 shows the XRD patterns of Test Examples 22 to 25. Note that PP4 in Fig. 10 is a peak derived from the unplated negative electrode member.

[0087] As shown in Figure 10, in all of Test Examples 22 to 24, a peak identified as originating from a nickel-zinc solid solution was observed near 2θ = 42 to 47 degrees. This demonstrated that nickel-zinc alloy plating is possible over a wide range of current densities using electroplating solutions employing nickel and zinc ions as metal ions. Furthermore, in the XRD pattern of Test Example 25, a peak originating from Zn4(OH)6SO4·5H2O was observed near 2θ = 8 to 10 degrees, suggesting the occurrence of a hydrogen evolution reaction. In contrast, in Test Examples 22 to 24, the peak originating from Zn5(OH)8Cl2·H2O, as seen in Test Example 5, was hardly observed near 2θ = 11 to 12 degrees. This indicates that we have successfully provided an electroplating solution capable of suppressing the hydrogen evolution reaction at various current densities.

Claims

1. An electroplating solution comprising: containing water, metal ions, and an organic solvent; the organic solvent contains an aprotic organic compound having an ether group in its chemical structure, the molar amount of the organic compound in the electroplating solution is 20% or more relative to the molar amount of water; Electroplating solution.

2. The electroplating solution according to claim 1, The electroplating solution, wherein the organic compound has a cyclic structure in its chemical structure.

3. The electroplating solution according to claim 2, The electroplating solution, wherein the organic compound contains a cyclic ether compound.

4. The electroplating solution according to claim 3, The electroplating solution, wherein the cyclic ether compound is composed of one or more substances selected from the group consisting of tetrahydrofuran, dioxane, dioxolane, trioxolane, tetrahydropyran, and crown ether.

5. The electroplating solution according to claim 2, The electroplating solution, wherein the cyclic structure is a five-membered ring or a six-membered ring.

6. The electroplating solution according to claim 1, The electroplating solution, wherein the metal ions contain at least zinc ions.

7. The electroplating solution according to claim 1, The electroplating solution has a molar amount of the metal ions that is at least 5% or more of the total molar amount of the water and the organic compound.

8. The electroplating solution according to claim 7, the molar amount of the metal ions is 5% or more and 20% or less of the total molar amount of the water and the organic compound.

9. A method for manufacturing a plated member, comprising: Preparing the electroplating solution according to any one of claims 1 to 8, an anode member, and a cathode member; immersing the anode member and the cathode member in the electroplating solution and applying a voltage between the anode member and the cathode member to deposit a metal film on the surface of the cathode member, thereby obtaining the plated member; A manufacturing method comprising:

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