JP5808866B2 - Non-aqueous electroplating method and non-aqueous electroplating apparatus - Google Patents

Description

  The present invention relates to an electroplating method using a nonaqueous plating solution and a nonaqueous electroplating apparatus for carrying out the method.

  In many cases, metal electroplating processes use an aqueous solution as a plating solution. Aqueous electroplating is positioned as a low-cost process because the aqueous plating solution has low volatility and is easy to manage and wastewater treatment is relatively easy.

  On the other hand, by using water as a plating solution solvent, the types of metal elements that can be electrochemically deposited have been limited. Metal elements such as aluminum (Al), titanium (Ti), and magnesium (Mg), which are expected as functional metal thin films, have a large affinity for oxygen and their redox potential is lower than that of water. Therefore (because the standard electrode potential is negative), it was difficult to electroplate these metal species from an aqueous solution.

For the purpose of electroplating a base metal with a redox potential (base metal) or an alloy film containing the same, an organic solvent, a molten salt, or the like, which has a stable potential region (potential window) that does not undergo electrolysis, is wider than water. Electroplating (so-called non-aqueous electroplating) has been studied. For example, in aluminum plating, as an organic solvent-based plating solution, aluminum chloride (AlCl ₃ ) and lithium aluminum hydride (LiAlH ₄ ), or AlCl ₃ and lithium hydride (LiH) are ether (for example, diethyl ether). And those dissolved in tetrahydrofuran) are known. However, since these plating solutions have ignitability and high flammability, there is a problem that strict care is required for handling.

  Therefore, electroplating using a molten salt (so-called ionic liquid) that exists as a liquid at room temperature as a highly safe solvent (for example, a solvent having characteristics such as high chemical stability, nonflammability, and low vapor pressure). Has been studied. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 5-51785) discloses an aluminum halide (A), a monoalkylpyridinium halide, a dialkylpyridinium halide, a 1-alkylimidazolium halide, and a 1,3-dialkylimidazolium halogen. In a plating bath obtained by mixing and melting at least one compound (B) selected from the group consisting of chemical compounds in a molar ratio of “A: B = 1: 1 to 3: 1”, 0.1% of polystyrene or polymethylstyrene is added. An electroaluminum plating bath containing ˜50 g / L is disclosed. According to Patent Document 1, it is said that there is no danger of explosion or ignition, and an aluminum film exhibiting a smooth and dense glossy surface can be formed with good workability at normal or low temperatures.

  Further, in Patent Document 2 (Japanese Patent Laid-Open No. 1-132791), the upper part of a plating tank containing a molten salt plating solution of aluminum chloride and butylpyridinium chloride or a plating solution obtained by adding an organic solvent to this and an anode can be opened and closed freely. In addition, the plating solution storage tanks are also sealed, both tanks are provided with inert inlets, both tanks are connected by a circulation pipe, and the barrel is a cathode of an aluminum shaft inside the plating tank. An electro-aluminum plating apparatus pivoted on is disclosed. According to Patent Document 2, the plating apparatus is configured such that the plating tank and the storage tank are hermetically sealed, and both tanks are connected by a circulation pipe, so that the plating solution can be transferred to the entire storage tank. Therefore, the plating solution is not oxidized.

  Non-Patent Document 1 reports a study on crystal electrodeposition of nickel (Ni), cobalt (Co), and aluminum alloys thereof. According to Non-Patent Document 1, nanoscale electroplating of Ni, Co, and their Al alloys is possible from ionic electrolytes (room temperature molten salts and ionic liquids) having a wider electrochemical window than aqueous electrolytes. It has been shown.

Japanese Patent Laid-Open No. 5-51785 JP-A-1-132791

W. Freyland, C.A.Zell, S. Zein El Abedin, F. Endres: “Nanoscale electrodeposition of metals and semiconductors from ionic liquids”, Electrochimica Acta 48 (2003) 3053-3061.

  As described above, non-aqueous electroplating solutions are generally low in chemical stability, so if they come into contact with moisture or oxygen in the atmosphere, the plating solution tends to be oxidized and decomposed, resulting in decreased current efficiency or There was a problem that the finish of the deteriorated. In particular, in a plating solution using aluminum chloride, aluminum chloride itself reacts with water (for example, moisture in the atmosphere) to generate hydrogen chloride, so that not only the stability of electroplating but also work safety is ensured. From the viewpoint, there is a difficulty in handling that the plating solution cannot be substantially exposed to the atmosphere.

  Although the plating bath described in Patent Document 1 is safe even if it comes into contact with oxygen and moisture, it is in a dry oxygen-free atmosphere (in dry nitrogen or argon) from the viewpoint of maintaining the stability of the plating bath and the plating properties. ). That is, it can be said that the conventional handling has been continued in that it is desirable not to expose the plating solution to the atmosphere.

  In addition, the electroaluminum plating apparatus described in Patent Document 2 has a sealed structure in which an electroplating tank is made an inert atmosphere by dry nitrogen, argon, or the like. Even in a slight electrode position adjustment operation, an operation of transferring all the plating solution to the storage tank and then releasing the plating tank is essential, and there is a problem that the operability of the plating apparatus is poor.

  Non-Patent Document 1 is an academic paper that considers the mechanism of crystal electrodeposition from an ionic liquid, and does not specifically discuss the handling of the electroplating solution, the electroplating method of the aluminum alloy, and the electroplating apparatus. .

  Against this backdrop, electroplating methods and electroplating that combine high safety, high workability, and soundness of the plating film for the electroplating of metals with a low redox potential (base metals) and alloy films containing them. The device was highly desired. Accordingly, an object of the present invention is to provide a non-aqueous electroplating capable of safely and efficiently electroplating a base metal and an alloy containing the base metal even in an air atmosphere (in an atmosphere released to the air). It is an object of the present invention to provide a method and a non-aqueous electroplating apparatus that enables the method and has high operability.

  (I) According to one aspect of the present invention, there is provided a method of electroplating an object to be plated using a non-aqueous plating solution, wherein the non-aqueous plating solution is a metal halide (metal halide) to be plated. An organic compound that forms an ion pair with the metal halide, and further uses a hydrophobic liquid that is phase-separated from the non-aqueous plating solution and has a specific gravity smaller than that of the non-aqueous plating solution. Provided is a non-aqueous electroplating method in which the upper surface of the non-aqueous plating solution is liquid-sealed.

In the non-aqueous electroplating method (I) according to the present invention, the following improvements and changes can be made.
(I) The object to be plated passes through the hydrophobic liquid layer for liquid-sealing the non-aqueous plating solution and is immersed in the non-aqueous plating solution to be electroplated, and then the hydrophobic liquid Is taken out through the layer.
(Ii) The hydrophobic liquid comprises at least one of liquid paraffin and silicone oil.
(Iii) The organic compound comprises at least one of a dialkylimidazolium salt, a pyridinium salt, an aliphatic phosphonium salt, and a quaternary ammonium salt.
(Iv) In the non-aqueous plating solution, the molar concentration of the metal halide is 1 to 3 times the molar concentration of the organic compound.
(V) The metal halide contains at least an aluminum halide.
(Vi) The metal halide is composed of two or more metal halides.

  (II) According to another aspect of the present invention, there is provided a plating apparatus for performing electroplating on an object to be plated, wherein the electroplating is performed by the nonaqueous electroplating method according to the present invention. I will provide a.

(III) According to still another aspect of the present invention, a plating apparatus for performing electroplating on an object to be plated,
A plating tank whose upper surface is released in order to perform electroplating by inserting and removing the object to be plated;
A plating solution storage tank for storing a non-aqueous plating solution containing a metal halide to be plated (metal halide) and an organic compound forming an ion pair with the metal halide;
A hydrophobic liquid storage tank for storing a hydrophobic liquid having a specific gravity smaller than that of the non-aqueous plating solution and phase-separated from the non-aqueous plating solution;
A plating solution circulation pipe and a plating solution circulation pump for connecting the plating solution storage tank and the plating tank and circulating the non-aqueous plating solution;
Provided is a non-aqueous electroplating apparatus comprising a hydrophobic liquid circulation pipe and a hydrophobic liquid circulation pump for connecting the hydrophobic liquid storage tank and the plating tank and circulating the hydrophobic liquid.

In the non-aqueous electroplating apparatus (III) according to the present invention, the following improvements and changes can be added.
(Vii) a first liquid temperature control mechanism for controlling the temperature of the non-aqueous plating solution at a position in contact with the non-aqueous plating solution in the plating tank, and a position in contact with the hydrophobic liquid in the plating tank And a second liquid temperature control mechanism for controlling the temperature of the hydrophobic liquid.
(Viii) a third liquid temperature control mechanism for controlling the temperature of the non-aqueous plating solution in the plating solution storage tank, and a fourth for controlling the temperature of the hydrophobic liquid in the hydrophobic liquid storage tank. And a liquid temperature control mechanism.

  According to the present invention, there is provided a non-aqueous electroplating method capable of safely and efficiently electroplating a base metal and an alloy containing the base metal even in an air atmosphere (in an atmosphere released to the air). Can be provided. Moreover, the non-aqueous electroplating apparatus for implementing the said plating method can be provided.

It is a schematic diagram which shows an example of the non-aqueous electroplating method which concerns on this invention. It is a schematic diagram which shows another example of the non-aqueous electroplating method which concerns on this invention. It is a schematic diagram which shows an example of the non-aqueous electroplating apparatus which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments taken up here, and can be appropriately combined and improved without departing from the technical idea of the present invention.

(Non-aqueous electroplating method)
FIG. 1 is a schematic view showing an example of a non-aqueous electroplating method according to the present invention. As shown in FIG. 1, the non-aqueous electroplating of the present invention comprises a non-aqueous plating solution 101 and a hydrophobic liquid 102 that is phase-separated from the non-aqueous plating solution 101 and has a specific gravity smaller than that of the non-aqueous plating solution 101. The hydrophobic liquid 102 is used in a state where the upper surface of the non-aqueous plating solution 101 is liquid-sealed. The non-aqueous plating solution 101 is shielded from the atmosphere by being sealed with a hydrophobic liquid 102. As a result, intrusion of moisture in the atmosphere into the non-aqueous plating solution 101 can be prevented, and invasion of oxygen can also be suppressed, and the non-aqueous plating solution 103 is utilized by using the plating tank 103 whose upper surface is open to the atmosphere (that is, in an atmospheric atmosphere). Water-based plating can be performed.

  The object to be plated 104 and the counter electrode 105 are entirely immersed and arranged in a non-aqueous plating solution 101 and connected to a power source 107 via a lead wire 106. By energizing, the object to be plated 104 is entirely covered with a plating film.

  As the counter electrode 105, an insoluble electrode (for example, platinum, titanium-platinum, etc.) may be used, or a soluble electrode made of a metal to be plated may be used. When a dissolvable electrode is used, metal ions consumed by plating are automatically replenished, and the metal ion concentration in the plating solution can be maintained within a certain range. In particular, in the case of continuous plating, it is preferable to use a soluble electrode because metal ions are automatically replenished in accordance with the amount of energization.

  When the object to be plated 104 is disposed in the non-aqueous plating solution 101, the object to be plated 104 passes through the layer of the hydrophobic liquid 102 and is immersed in the non-aqueous plating solution 101. For this reason, even when an aqueous plating pretreatment liquid or pure water for washing the plating pretreatment liquid remains on the surface of the object to be plated 104, the water content thereof passes through the hydrophobic liquid 102 layer. There is also an effect that is eliminated by the hydrophobic liquid 102.

  The non-aqueous plating solution 101 includes a metal halide to be plated (metal halide) and an organic compound that forms an ion pair with the metal halide. As the metal halide used in the present invention, a chloride or bromide of a base metal (a metal having a negative standard electrode potential, such as tin, nickel, cobalt, chromium, zinc, or aluminum) can be suitably used. The metal halide used is preferably an anhydrous salt. Note that the present invention is not limited to base metal electroplating, not to mention electroplating of alloys containing base metals, but also to electroplating of noble metals (metals having a positive standard electrode potential, such as copper and gold). You may use it. The metal halide may be a mixture of two or more different metal halides.

  As the organic compound (an organic compound that forms an ion pair with the metal halide) used in the present invention, at least one of a dialkylimidazolium salt, a pyridinium salt, an aliphatic phosphonium salt, and a quaternary ammonium salt is preferably used. Can do. More specifically, examples of the dialkylimidazolium salt include 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium iodide, 1 -Butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium iodide and the like. Examples of the pyridinium salt include methylpyridinium chloride, methylpyridinium bromide, methylpyridinium iodide, ethylpyridinium chloride, ethylpyridinium bromide, ethylpyridinium iodide, butylpyridinium chloride, butylpyridinium bromide, and butylpyridinium iodide. Examples of the aliphatic phosphonium salt include ethyl tributyl phosphonium chloride, ethyl tributyl phosphonium bromide, ethyl tributyl phosphonium iodide, methyl tributyl phosphonium chloride, methyl tributyl phosphonium bromide, methyl tributyl phosphonium iodide and the like. Examples of the quaternary ammonium salt include tetraethylammonium bromide, trimethylethylammonium chloride, and tetrabutylammonium chloride.

  The organic compound and the metal halide are preferably mixed and melted at a molar ratio of “1: 1 ≦ organic compound: metal halide ≦ 1: 3”, and “1: 1.5 ≦ organic compound: metal halide”. More preferred is a molar ratio of "Chemicals ≤ 1: 3". When the molar concentration of the metal halide is less than or equal to the molar concentration of the organic compound, the plating deposition rate is remarkably reduced, and the plating deposition uniformity is deteriorated. On the other hand, when the molar concentration of the metal halide is higher than three times the molar concentration of the organic compound, the viscosity of the non-aqueous plating solution 101 increases and the current efficiency of plating decreases.

  When a mixture of two or more different metal halides is used as the metal halide (ie, in the case of alloy plating), the molar ratio of “1: 1 ≦ organic compound: whole metal halide ≦ 1: 3” It is preferable to mix and melt with. Strictly speaking, the ratio of the metal species to be mixed depends on the deposition efficiency (precipitation ratio) for each metal species, but generally matches the composition ratio of the alloy to be plated.

  The hydrophobic liquid 102 used in the present invention is phase-separated from the non-aqueous plating solution 101 (in other words, has low compatibility with the non-aqueous plating solution 101) and has a lower specific gravity than the non-aqueous plating solution 101. Is preferred. In particular, the specific gravity is more preferably less than 1, for example, liquid paraffin or silicone oil can be suitably used.

  The hydrophobic liquid 102 is a liquid that is liquid at room temperature (20 to 25 ° C.) and phase-separated from water. The viscosity is not particularly limited as long as it can be stirred at room temperature, but a lower viscosity is preferable. The average molecular weight of the hydrophobic liquid 102 is not particularly limited as long as the above conditions are satisfied. For example, the average molecular weight is preferably 200 or more and 1000 or less.

The plating temperature is preferably 20 to 80 ° C., more preferably 25 to 60 ° C. in consideration of workability. The energization condition is preferably performed at a current density of 0.01 A / dm ² or more and 10 A / dm ² or less by direct current or pulse current. Thereby, a uniform plating film with high current efficiency can be formed. If the current density is too high, the decomposition of the compound, the unevenness of the plating film, and the decrease in current efficiency occur, which is not preferable. The current efficiency is preferably 30% or more and more preferably 80% or more from the viewpoint of production efficiency.

  FIG. 2 is a schematic view showing another example of the non-aqueous electroplating method according to the present invention. As shown in FIG. 2, the non-aqueous electroplating method of the present embodiment is the same as that of the above-described embodiment (in that a part of each of the workpiece 204 and the counter electrode 205 is immersed and arranged in the non-aqueous plating solution 101. (See FIG. 1). When energized, a plating film is selectively deposited on the portion 204 to be plated in the portion immersed in the non-aqueous plating solution 101. By using the plating method of this embodiment, it becomes possible to easily and partially coat the object to be plated 204 with a plating film without masking with an insulating tape or the like. Other functions and effects are the same as those of the above-described embodiment.

(Non-aqueous electroplating equipment)
FIG. 3 is a schematic diagram showing an example of a non-aqueous electroplating apparatus according to the present invention. As shown in FIG. 3, the non-aqueous electroplating apparatus 300 of the present invention includes a plating tank 303 whose upper surface is open to the atmosphere, and the plating tank 303 contains a non-aqueous plating solution 101 and a hydrophobic liquid 102. The non-aqueous plating solution 101 is contained and is sealed from the atmosphere by being sealed with a hydrophobic liquid 102.

  The non-aqueous electroplating apparatus 300 includes a plating solution storage tank 306 for storing the non-aqueous plating solution 101, a hydrophobic liquid storage tank 307 for storing the hydrophobic liquid 102, a plating solution storage tank 306, and a plating tank. In order to circulate the hydrophobic liquid 102 by connecting the plating liquid circulation pipe 308 and the plating liquid circulation pump 309 for connecting the non-aqueous plating liquid 101 with the 303 and the hydrophobic liquid storage tank 307 and the plating tank 303. And a hydrophobic liquid circulation pipe 310 and a hydrophobic liquid circulation pump 311. The forward path and the return path of the plating solution circulation pipe 308 are connected to the bottom of the plating tank 303. The return path of the hydrophobic liquid circulation pipe 310 is connected to the bottom of the plating tank 303, but the forward path of the hydrophobic liquid circulation pipe 310 is the upper part of the plating tank 303 (the nonaqueous plating solution 101 and the hydrophobic liquid 102 are plated with the plating tank). When it is accommodated in 303, it is connected to a region where a layer of the hydrophobic liquid 102 is formed.

  When the non-aqueous plating solution 101 is stored in the plating tank 303, the hydrophobic liquid 102 is first supplied from the forward path of the hydrophobic liquid circulation pipe 310 connected to the upper part of the plating tank 303, and then the plating tank 303 A non-aqueous plating solution 101 is supplied from an outward path of a plating solution circulation pipe 308 connected to the bottom. Thereby, the non-aqueous plating solution 101 can be introduced into the plating tank 303 without being exposed to the atmosphere. When discharging the non-aqueous plating solution 101 from the plating tank 303, first discharge the non-aqueous plating solution 101 from the return path of the plating solution circulation pipe 308 connected to the bottom of the plating tank 303, and then the plating tank 303 The hydrophobic liquid 102 is discharged from the return path of the hydrophobic liquid circulation pipe 310 connected to the bottom. Thereby, similarly to the introduction of the non-aqueous plating solution 101, the non-aqueous plating solution 101 can be discharged from the plating tank 303 without being exposed to the atmosphere. Further, the nonaqueous plating solution 101 can be circulated by simultaneously supplying and discharging the nonaqueous plating solution 101 by the plating solution circulation pipe 308 and the plating solution circulation pump 309.

  In FIG. 3, the case where a long continuous body is used as the to-be-plated body 304 is shown. The object to be plated 304 passes through the hydrophobic liquid 102 layer and is immersed in the non-aqueous plating solution 101 to be electroplated, and then passes through the hydrophobic liquid 102 layer and is taken out. An energizing roll 312 is disposed above the opening surface of the plating tank 303, and a sink roll 313 is disposed in a region of the plating tank 303 in which the nonaqueous plating solution 101 is accommodated. In addition, a counter electrode 305 is disposed in parallel to the object to be plated 303 so as to face the object to be plated 304 in a region where the nonaqueous plating solution 101 is accommodated in the plating tank 303. The shape and number of the counter electrodes 305 are not particularly limited, and may be, for example, a parallel plate or a cylinder. The plated body 304 is wound around the energizing roll 312 and the sink roll 313, and the plated body 304 is conveyed and energized during plating.

  The plating solution temperature is preferably controlled as appropriate depending on the type of non-aqueous plating solution 101 used. In order to accurately and stably control the temperature of the non-aqueous plating solution 101, the liquid temperatures of the non-aqueous plating solution 101 and the hydrophobic liquid 102 are preferably the same. Therefore, the first liquid temperature control mechanism 314 for controlling the temperature of the non-aqueous plating solution 101 in the region in the plating tank 303 in which the non-aqueous plating solution 101 is accommodated (location that contacts the non-aqueous plating solution 101). Is provided, and a second liquid temperature control for controlling the temperature of the hydrophobic liquid 102 in a region (a portion in contact with the hydrophobic liquid 102) in which the layer of the hydrophobic liquid 102 in the plating tank 303 is accommodated A mechanism 315 is preferably provided.

  For the same reason as described above, a third liquid temperature control mechanism 316 for controlling the temperature of the non-aqueous plating solution 101 is disposed in the plating solution storage tank 306, and the hydrophobic liquid storage tank 307 has a hydrophobic liquid. A fourth liquid temperature control mechanism 317 for controlling the temperature of 102 is preferably provided. By adjusting the liquid temperature of the non-aqueous plating solution 101 and the hydrophobic liquid 102 in both storage tanks to the desired solution temperature in advance, the liquid temperature control in the plating tank 303 is performed when the solution is supplied to the plating tank 303. Can be performed efficiently.

  The present invention will be described in more detail with reference to specific examples. However, the following examples show specific examples of the contents of the present invention, and the present invention is not limited to these examples. The present invention can be variously changed and modified by those skilled in the art within the scope of the technical idea disclosed in this specification.

(Example 1)
Anhydrous aluminum chloride (AlCl ₃ , manufactured by Wako Pure Chemical Industries, Ltd.) is used as the metal halide, and 1-ethyl-3-methylimidazolium chloride (EMIMCl, manufactured by Kanto Chemical Co., Ltd.) is used as the organic compound. A non-aqueous plating solution was obtained by mixing at a molar ratio of “AlCl ₃ = 1: 2”. The non-aqueous plating solution was prepared in a glove box under an argon atmosphere (temperature 25 ° C., relative humidity 5%). The prepared nonaqueous plating solution (60 mL) was placed in a glass 100 mL beaker.

  Next, liquid paraffin (manufactured by Kanto Chemical Co., Inc.) was used as the hydrophobic liquid, and 40 mL was poured into the beaker containing the previous non-aqueous plating solution, and the non-aqueous plating solution was liquid-sealed with the hydrophobic liquid. This was used as the evaluation solution of Example 1.

  In order to investigate the effect of atmospheric exposure (the effect of moisture in the air), an air atmosphere glove box was introduced that introduced air (temperature 25 ° C, relative humidity 60%) with adjusted temperature and relative humidity. The temperature and humidity of the introduced air were adjusted using a humidity controller (EFA5-100-A, manufactured by GL Sciences Inc.) after passing air through a gas washing bottle containing pure water. The evaluation solution of Example 1 was transferred from an argon atmosphere glove box to an air atmosphere glove box and exposed to temperature-humidity controlled air (humid air) for a predetermined time.

Electroplating was performed as follows. Copper foil (purity 99.9%, length x width x thickness = 20 mm x 35 mm x 0.1 mm) is used as the object to be plated, and aluminum plate (purity 99.9%, length x width x thickness = 25 mm x 35) as the counter electrode mm × 2 mm) was used. The object to be plated and the counter electrode to which the lead wires were respectively connected were immersed in the evaluation solution so as to face each other in the beaker with an interval of 30 mm. Both lead wires were connected to a constant current power source, and electroplating was performed (current density = -1 A / dm ² , plating time = 30 minutes, plating solution temperature = 25 ° C.). After completion of electroplating, the plated object was washed with acetone and pure water, and dried with nitrogen gas to obtain a test material for measurement.

  The above electroplating was performed using the evaluation solution exposed to temperature / humidity-controlled air (humid air) for 2, 12, and 24 hours, and the current efficiency in each evaluation solution was calculated. The precipitation amount of the plated aluminum was determined by actual measurement, and this was compared with the precipitation amount calculated based on the current value of the coulomb meter, and the ratio (percentage) of the actual precipitation amount to the calculated precipitation amount was determined as the current efficiency. The structure of the plating bath and the calculation result of the current efficiency of electroplating performed using the plating bath are shown in Table 1 described later.

(Comparative Example 1)
Except not using a hydrophobic liquid, it carried out similarly to the said Example 1, the evaluation solution of the comparative example 1 was prepared, and each test material was produced. The composition of the plating bath and the calculation result of the current efficiency are also shown in Table 1.

  As shown in Table 1, in Comparative Example 1 in which the non-aqueous plating solution was not liquid-sealed with a hydrophobic liquid, the current efficiency was reduced to 56% by exposure to wet air for 2 hours, and further exposure to wet air for 12 hours. After that, the current efficiency became 0% (aluminum itself no longer deposited). That is, it was confirmed that the non-aqueous plating solution was significantly deteriorated by moisture in the air. In Comparative Example 1, generation of white smoke considered to be hydrogen chloride gas was observed with exposure of the non-aqueous plating solution to wet air.

  On the other hand, in Example 1 according to the present invention, the non-aqueous plating solution was liquid-sealed with liquid paraffin, so that there was almost no change in current efficiency due to exposure to wet air. However, the current efficiency was in a very good state of 99%. In Example 1, generation of white smoke was not observed even when exposed to wet air.

(Example 2)
The evaluation solution of Example 2 is prepared in the same manner as in Example 1 except that silicone oil (KF-96L-1cs, manufactured by Shin-Etsu Chemical Co., Ltd.) is used as the hydrophobic liquid. did. The composition of the plating bath and the calculation result of the current efficiency are also shown in Table 1. As shown in Table 1, even in Example 2, since the non-aqueous plating solution was sealed with silicone oil, there was almost no change in current efficiency due to exposure to wet air. However, the current efficiency was very good at 100%. In addition, no white smoke was observed during exposure to wet air. From this result, it was confirmed that silicone oil is also effective as a hydrophobic liquid.

(Example 3)
Anhydrous aluminum chloride (AlCl ₃ , manufactured by Wako Pure Chemical Industries, Ltd.) is used as the metal halide, and butylpyridinium chloride (BPCl, manufactured by Kanto Chemical Co., Ltd.) is used as the organic compound. “BPCl: AlCl ₃ = 1: 1.5” A non-aqueous plating solution was prepared by mixing so that the molar ratio was. Other than that was carried out similarly to Example 1, and prepared the evaluation solution of Example 3, and produced each test material. The composition of the plating bath and the calculation result of the current efficiency are also shown in Table 1.

(Comparative Example 2)
Except not using a hydrophobic liquid, it carried out similarly to the said Example 3, and prepared the evaluation solution of the comparative example 2, and produced each test material. The composition of the plating bath and the calculation result of the current efficiency are also shown in Table 1.

  As shown in Table 1, in Comparative Example 2 in which the non-aqueous plating solution was not sealed with a hydrophobic liquid, the current efficiency tended to decrease with increasing wet air exposure time, The current efficiency decreased to 82% when exposed to wet air, decreased to 21% when exposed to wet air for 12 hours, and further decreased to 0% when exposed to wet air for 24 hours. No precipitation of aluminum was observed. On the other hand, in Example 3, there was almost no change in current efficiency due to exposure to wet air, and for example, it was confirmed that the current efficiency was maintained at a very good state of 95% even after exposure to wet air for 24 hours. It was.

Example 4
Anhydrous aluminum chloride (manufactured by Wako Pure Chemical Industries, Ltd., AlCl ₃ ) is used as the metal halide, and tetrabutylammonium chloride (manufactured by Kanto Chemical Co., Inc., TBACl) is used as the organic compound, and “TBACl: AlCl ₃ = 1: 1.5 To prepare a non-aqueous plating solution. The electroplating conditions were “current density = −0.1 A / dm ² , plating time = 300 minutes”. Except for these, the evaluation solution of Example 4 was prepared in the same manner as in Example 1, and each test material was prepared. The composition of the plating bath and the calculation result of the current efficiency are also shown in Table 1.

(Comparative Example 3)
Except not using a hydrophobic liquid, it carried out similarly to the said Example 4, and prepared the evaluation solution of the comparative example 3, and produced each test material. The composition of the plating bath and the calculation result of the current efficiency are also shown in Table 1.

As shown in Table 1, in Comparative Example 3 in which the non-aqueous plating solution was not sealed with a hydrophobic liquid, the current efficiency was as low as 20% when exposed to wet air for 2 hours, and after 12 hours of exposure to wet air. The current efficiency was 0% and no aluminum deposition was observed. On the other hand, in Example 4, the current efficiency was lower than in Examples 1 to 3, but the current efficiency hardly changed even when the wet air exposure time was increased. In addition, it is considered that the reason why the current efficiency itself of Example 4 was low was that the amount of the aluminum complex contributing to aluminum precipitation was insufficient in the non-aqueous plating solution because the dissolution amount of AlCl ₃ was somewhat small. Moreover, since the viscosity of the non-aqueous plating solution was high, there is a possibility that the conductivity was affected.

(Example 5)
Anhydrous aluminum chloride (manufactured by Wako Pure Chemical Industries, Ltd., AlCl ₃ ) is used as the metal halide, and methyltributylphosphonium chloride (manufactured by Nippon Chemical Industry Co., Ltd., MTBPCl) is used as the organic compound, and “MTBPCl: AlCl ₃ = 1: A non-aqueous plating solution was prepared by mixing at a molar ratio of 1.5 ". Other than that was carried out similarly to Example 4, and prepared the evaluation solution of Example 5, and produced each test material. The composition of the plating bath and the calculation result of the current efficiency are also shown in Table 1.

(Comparative Example 4)
Except not using a hydrophobic liquid, it carried out similarly to the said Example 5, the evaluation solution of the comparative example 4 was prepared, and each test material was produced. The composition of the plating bath and the calculation result of the current efficiency are also shown in Table 1.

As shown in Table 1, in Comparative Example 4 in which the non-aqueous plating solution was not sealed with a hydrophobic liquid, the current efficiency was as low as 18% when exposed to humid air for 2 hours, and after 12 hours of exposure to wet air. The current efficiency was 0% and no aluminum deposition was observed. On the other hand, in Example 5, the current efficiency did not change even when the wet air exposure time increased. The reason why the current efficiency itself of Example 5 was low is considered to be related to the amount of AlCl ₃ dissolved in the non-aqueous plating solution, the solution viscosity, and / or the conductivity, as in Example 4. .

(Example 6)
Anhydrous aluminum chloride (Wako Pure Chemical Industries, Ltd., AlCl ₃ ) and anhydrous nickel chloride (Kanto Chemical Co., Ltd., NiCl ₂ ) are used as the metal halide, and 1-ethyl-3-methylimidazolium chloride is used as the organic compound. (EMITOCl, manufactured by Kanto Chemical Co., Inc.) was used to prepare a non-aqueous plating solution by mixing so that the molar ratio of “EMIMCl: AlCl ₃ : NiCl ₂ = 1: 2: 0.33” was obtained. Otherwise, the same procedure as in Example 1 was performed to prepare the evaluation solution of Example 6, and each sample material was prepared. The composition of the plating bath and the calculation result of the current efficiency are also shown in Table 1. The current efficiency was calculated on the assumption that aluminum was precipitated alone.

(Comparative Example 5)
Except not using a hydrophobic liquid, it carried out similarly to the said Example 6, the evaluation solution of the comparative example 5 was prepared, and each test material was produced. The composition of the plating bath and the calculation result of the current efficiency are also shown in Table 1.

  As shown in Table 1, Comparative Example 5 in which the non-aqueous plating solution was not sealed with a hydrophobic liquid had a low current efficiency of 51% after exposure to wet air for 2 hours, and after 12 hours of exposure to wet air. The current efficiency was 0% and no aluminum deposition was observed. On the other hand, in Example 6, there is almost no change in current efficiency with increasing time of exposure to wet air. Was confirmed.

(Example 7)
Zinc chloride (Kanto Chemical Co., Ltd., ZnCl ₂ ) was used as the metal halide, and 1-ethyl-3-methylimidazolium chloride (Kanto Chemical Co., Ltd., EMIMCl) was used as the organic compound, and “EMIMCl: ZnCl ₂ = A non-aqueous plating solution was prepared by mixing at a molar ratio of 1: 2. Liquid paraffin (manufactured by Kanto Chemical Co., Inc.) was used as the hydrophobic liquid. Others were the same as in Example 1, and the evaluation solution of Example 7 was prepared.

  Electroplating was performed as follows. Nickel foil (99% purity, length x width x thickness = 20 mm x 35 mm x 0.1 mm) was used as the object to be plated, and zinc plate (purity 99.9%, length x width x thickness = 25 mm x 35) as the counter electrode mm × 2 mm) was used. The object to be plated and the counter electrode to which the lead wires were respectively connected were immersed in the evaluation solution so as to face each other in the beaker with an interval of 30 mm. Further, a zinc wire (purity 99.9%, diameter = 1 mm) was immersed in the evaluation solution as a reference electrode. The object to be plated, the counter electrode, and the reference electrode were connected to the electrochemical measurement system (Hokuto Denko Co., Ltd., HZ-5000) via lead wires, and constant potential electroplating was performed (potential = 0.15 V, current supply = 10 C). , Plating solution temperature = 70 ° C). After completion of electroplating, the plated object was washed with acetone and pure water, and dried with nitrogen gas to obtain a test material for measurement. Calculation of current efficiency was performed in the same manner as in Example 1. The composition of the plating bath and the calculation result of the current efficiency are also shown in Table 1.

(Comparative Example 6)
An evaluation solution of Comparative Example 6 was prepared in the same manner as in Example 7 except that the hydrophobic liquid was not used, and each test material was prepared. The composition of the plating bath and the calculation result of the current efficiency are also shown in Table 1.

  As shown in Table 1, Comparative Example 6 in which the non-aqueous plating solution is not sealed with a hydrophobic liquid has a low current efficiency of 40% when exposed to wet air for 2 hours, and after 12 hours of exposure to wet air. The current efficiency was 0% and no zinc deposition was observed. On the other hand, in Example 7, it was confirmed that there is almost no change in current efficiency with increasing time of exposure to wet air.

(Example 8)
Using copper foil (purity 99.9%, length x width x thickness = 20 mm x 35 mm x 0.1 mm) as the object to be plated, the object to be plated wet by pure water cleaning was inserted and installed in the plating bath. Except for this, electroplating was performed in the same manner as in Example 1. As a result, even if the object to be plated wet with pure water was inserted into the plating bath, white smoke due to hydrogen chloride gas was not generated. Further, the formed plating film was silver white and had a uniform appearance, and the current efficiency was the same as that of Example 1. This is considered to be because moisture adhered to the surface of the object to be plated was eliminated when the object to be plated passed through the hydrophobic liquid (here, fluid pipeline).

(Comparative Example 7)
Electroplating was carried out in the same manner as in Example 8 except that no hydrophobic liquid was used. When the object to be plated wet with pure water was immersed in a non-aqueous plating solution, the pure water and the non-aqueous plating solution chemically reacted to generate white smoke due to hydrogen chloride gas. Further, the formed plating film had a dark appearance.

Example 9
Aluminum plating was performed using an electroplating apparatus having a structure as shown in FIG. As the non-aqueous plating solution, as in Example 1, anhydrous aluminum chloride (Wako Pure Chemical Industries, Ltd., AlCl ₃ ) and 1-ethyl-3-methylimidazolium chloride (Kanto Chemical Co., Ltd., EMIMCl) Were mixed so that the molar ratio of “EMIMCl: AlCl ₃ = 1: 2” was used, and liquid paraffin (manufactured by Kanto Chemical Co., Inc.) was used as the hydrophobic liquid. The liquid temperature of the non-aqueous plating solution and the liquid temperature of the hydrophobic liquid were controlled to 30 ° C. by the first and second liquid temperature control mechanisms, respectively. An aluminum plate with a purity of 99.9% was used as the counter electrode, and a long steel strip was used as the object to be plated. When continuous plating was performed for 12 hours at “current density = −1 A / dm ² ”, the appearance of the formed plating film was uniform throughout.

(Comparative Example 8)
Continuous plating for 12 hours was carried out in the same manner as in Example 9 except that the hydrophobic liquid was not used. As a result, as the plating time passed, the appearance of the formed plating film turned black, and no aluminum deposition was observed after 9 hours.

  As is apparent from the above description, the non-aqueous electroplating method and the non-aqueous electroplating apparatus according to the present invention seal the non-aqueous plating solution with a hydrophobic liquid, thereby allowing the non-aqueous plating solution and the atmosphere to be sealed. It is possible to prevent contact, and it has been demonstrated that it is possible to safely and efficiently electroplate base metals and alloys containing base metals even in an air atmosphere (in an atmosphere released to the air). It was done.

  DESCRIPTION OF SYMBOLS 101 ... Non-aqueous plating solution, 102 ... Hydrophobic liquid, 103, 303 ... Plating tank, 104, 204, 304 ... To-be-plated object, 105, 205, 305 ... Counter electrode, 106 ... Lead wire, 107 ... Power supply, 306 ... Plating Liquid storage tank, 307 ... hydrophobic liquid storage tank, 308 ... plating solution circulation pipe, 309 ... plating solution circulation pump, 310 ... hydrophobic liquid circulation pipe, 311 ... hydrophobic liquid circulation pump, 312 ... energizing roll, 313 ... sink Roll, 314: First liquid temperature control mechanism, 315: Second liquid temperature control mechanism, 316: Third liquid temperature control mechanism, 317: Fourth liquid temperature control mechanism

Claims (11)

A method of electroplating an object to be plated using a non-aqueous plating solution,
The non-aqueous plating solution contains a metal halide to be plated (metal halide) and an organic compound that forms an ion pair with the metal halide,
Further using a hydrophobic liquid phase-separated from the non-aqueous plating solution and having a specific gravity smaller than that of the non-aqueous plating solution,
A non-aqueous electroplating method, wherein an upper surface of the non-aqueous plating solution is liquid-sealed with the hydrophobic liquid. The non-aqueous electroplating method according to claim 1,
The object to be plated passes through the hydrophobic liquid layer that seals the non-aqueous plating solution and is immersed in the non-aqueous plating solution to be subjected to electroplating. A non-aqueous electroplating method characterized by being taken out by passing. In the non-aqueous electroplating method according to claim 1 or 2,
The non-aqueous electroplating method, wherein the hydrophobic liquid comprises at least one of liquid paraffin and silicone oil. In the non-aqueous electroplating method according to any one of claims 1 to 3,
The organic compound is composed of at least one of a dialkylimidazolium salt, a pyridinium salt, an aliphatic phosphonium salt, and a quaternary ammonium salt. In the non-aqueous electroplating method according to any one of claims 1 to 4,
The non-aqueous electroplating method is characterized in that the molar concentration of the metal halide is 1 to 3 times the molar concentration of the organic compound. In the non-aqueous electroplating method according to any one of claims 1 to 5,
The non-aqueous electroplating method, wherein the metal halide contains at least aluminum halide. In the non-aqueous electroplating method according to any one of claims 1 to 6,
The non-aqueous electroplating method, wherein the metal halide comprises two or more metal halides. A plating apparatus for performing electroplating on an object to be plated,
The said electroplating is performed by the nonaqueous electroplating method in any one of Claim 1 thru | or 7, The nonaqueous electroplating apparatus characterized by the above-mentioned. A plating apparatus for performing electroplating on an object to be plated,
A plating tank whose upper surface is released in order to perform electroplating by inserting and removing the object to be plated;
A plating solution storage tank for storing a non-aqueous plating solution containing a metal halide to be plated (metal halide) and an organic compound that forms an ion pair with the metal halide;
A hydrophobic liquid storage tank for storing a hydrophobic liquid having a specific gravity smaller than that of the non-aqueous plating solution and phase-separated from the non-aqueous plating solution;
A plating solution circulation pipe and a plating solution circulation pump for connecting the plating solution storage tank and the plating tank and circulating the non-aqueous plating solution;
A non-aqueous electroplating apparatus comprising a hydrophobic liquid circulation pipe and a hydrophobic liquid circulation pump for connecting the hydrophobic liquid storage tank and the plating tank and circulating the hydrophobic liquid. In the non-aqueous electroplating apparatus according to claim 9,
A first liquid temperature control mechanism for controlling the temperature of the non-aqueous plating solution at a position in contact with the non-aqueous plating solution in the plating tank;
A non-aqueous electroplating apparatus, further comprising a second liquid temperature control mechanism for controlling the temperature of the hydrophobic liquid at a position in contact with the hydrophobic liquid in the plating tank. In the non-aqueous electroplating apparatus according to claim 9 or 10,
A third liquid temperature control mechanism for controlling the temperature of the non-aqueous plating liquid in the plating liquid storage tank;
The non-aqueous electroplating apparatus, further comprising a fourth liquid temperature control mechanism for controlling the temperature of the hydrophobic liquid in the hydrophobic liquid storage tank.

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