Impurity removal device and impurity removal method for aluminum plating solution, aluminum deposition device, and method for manufacturing aluminum-plated product

Abstract

The purpose of the present invention is to provide: an impurity removal device and an impurity removal method for an aluminum plating solution, with which it is possible to decompose and remove water in a nonaqueous aluminum plating solution and to efficiently remove impurities derived from water; or an aluminum deposition device.　According to one embodiment of the present invention, an impurity removal device for an aluminum plating solution, by which water-derived impurities contained in the aluminum plating solution are removed from the aluminum plating solution, is provided with: a positive electrode and a negative electrode that are immersed in the aluminum plating solution; and a power supply device that applies a voltage between the positive electrode and the negative electrode. The positive electrode is formed of aluminum metal.

Description

Apparatus and method for removing impurities from aluminum plating solution, aluminum deposition apparatus, and method for manufacturing aluminum plated products

[0001] The present invention relates to an impurity removal apparatus and method for decomposing and removing water-derived impurities from an aluminum plating solution, an aluminum deposition apparatus, and a method for manufacturing aluminum plated products.

[0002] Because the standard redox potential of aluminum is lower than its hydrogen evolution potential (-1.66 V vs. SHE), aluminum is difficult to electrochemically precipitate from water, the most common solvent.

[0003] Therefore, in order to establish aluminum plating technology, non-aqueous aluminum plating methods such as organic solvents, molten salts, and ionic liquids have been investigated. Non-aqueous electrolytes can also be used in electronic devices such as capacitors and batteries, but if water is present in the non-aqueous aluminum plating solution, the electrolysis of water and the electrodeposition reaction compete, resulting in a deterioration of electrodeposition efficiency. In addition, the electrolysis of water produces gas, which can adversely affect the aluminum deposited film.

[0004] To solve the above problems, for example, Patent Document 1 proposes a method for removing water from a non-aqueous aluminum plating solution by electrolysis using a film electrode assembly made of a non-metallic material.

[0005] Japanese Patent Publication No. 2013-133480

[0006] However, the above-mentioned membrane electrode assembly uses electrodes made of non-metallic materials such as oxides with porous current collectors, and a solid electrolyte made of ceramics or the like placed between these electrodes. Such membrane electrode assemblies have lower electrical conductivity compared to metallic materials. Therefore, when decomposing and removing water from a non-aqueous aluminum plating solution, there are concerns that power consumption will increase and running costs will rise.

[0007] Therefore, the present invention aims to provide an impurity removal apparatus and method for aluminum plating solutions, an aluminum deposition apparatus, and a method for manufacturing aluminum plated products that can efficiently remove water-derived impurities from non-aqueous aluminum plating solutions.

[0008] To solve the above problems, according to one aspect of the present invention, an impurity removal apparatus for an aluminum plating solution that removes water-derived impurities contained in the aluminum plating solution comprises a liquid tank for storing the aluminum plating solution, an anode and a cathode provided in the liquid tank, and a power supply device for applying a voltage between the anode and the cathode, wherein the anode is made of metallic aluminum.

[0009] Furthermore, it is preferable that multiple anodes and cathodes are provided.

[0010] Furthermore, it is preferable that the power supply unit has a polarity switching mechanism that switches the polarity of the output unit connected to the anode and the output unit connected to the cathode, respectively, so that the polarity of the anode or cathode is reversed.

[0011] The polarity switching mechanism preferably sets a scheduled time for switching the polarity of the output section of the power supply after the polarity of the anode or cathode has reversed, based on the energizing time of the current flowing between the anode and the cathode before the polarity of the anode and the cathode reverses, and performs the polarity swapping of the anode or cathode based on the scheduled switching time. Furthermore, it is preferable that the cathode be made of metallic aluminum.

[0012] On the other hand, the aluminum plating solution is preferably an electroplated aluminum plating solution containing an aluminum halide in a non-aqueous solvent. Furthermore, the non-aqueous solvent is preferably a dialkyl sulfone. In addition, it is preferable that the aluminum plating solution contains ammonium chloride and tetramethylammonium chloride.

[0013] Furthermore, the liquid tank preferably includes an inlet into which the aluminum plating solution before impurities are removed flows in, and an outlet into which the aluminum plating solution after impurities have been removed flows out, with a filter for removing solid matter provided between the outlet and the anode.

[0014] Furthermore, one aspect of the present invention is an aluminum deposition apparatus comprising the aforementioned aluminum plating solution impurity removal apparatus, a deposition tank in which the aluminum plating solution after impurity removal from the aluminum plating solution impurity removal apparatus is stored, a deposition cathode immersed in the aluminum plating solution in the deposition tank for depositing aluminum, and a deposition anode immersed in the aluminum plating solution in the deposition tank.

[0015] Furthermore, in one aspect of the present invention, in a method for removing impurities from an aluminum plating solution that are derived from water, it is preferable to immerse a cathode and an anode made of metallic aluminum in the aluminum plating solution, and to apply a voltage between the anode and cathode immersed in the aluminum plating solution to cause an electric current to flow through the aluminum plating solution. It is even more preferable that the anode and cathode are switched to opposite polarities according to the energizing time of the current that flowed through the anode and cathode tube before the polarity of the anode or cathode reverses. Furthermore, one aspect of the present invention is a method for manufacturing an aluminum-plated product, in which a cathode and an anode made of metallic aluminum are immersed in an aluminum plating solution, a voltage is applied between the anode and cathode immersed in the aluminum plating solution to pass an electric current through the aluminum plating solution, and once the aluminum has been deposited on the cathode, an electrode with an article for coating aluminum attached is immersed in the aluminum plating solution, and instead of the cathode, an electrode with the article for coating aluminum attached is used to pass an electric current between the anode and the electrode with the article for coating aluminum to coat the article with aluminum. The above configurations can be combined with each other as appropriate.

[0016] According to the present invention, it is possible to provide an impurity removal apparatus and method for an aluminum plating solution, an aluminum deposition apparatus, and a method for manufacturing an aluminum plated product, which can efficiently remove water-derived impurities from the aluminum plating solution.

[0017] This is a schematic diagram of an impurity removal device for aluminum plating solution according to one embodiment of the present invention. This is a cross-sectional view of the aluminum plating solution impurity removal device 100 shown in Figure 1 along the A-A cross-sectional line. This is a circuit diagram of the power supply unit 2 and electrode 3 provided in the aluminum plating solution impurity removal device according to one embodiment of the present invention, showing an example of the connection state of the polarity reversal switch 200 in the power supply unit 2. This is a circuit diagram of the power supply unit 2 and electrode 3 provided in the aluminum plating solution impurity removal device according to one embodiment of the present invention, showing an example of the connection state of the polarity reversal switch 200 in the power supply unit 2. This is a circuit diagram of the power supply unit 2 and electrode 3 provided in the aluminum plating solution impurity removal device according to one embodiment of the present invention, showing a circuit when multiple anodes 3a and cathodes 3b are connected to the polarity reversal switch 200. This is a schematic diagram of an aluminum deposition device according to one embodiment of the present invention. This is a schematic diagram of an aluminum deposition unit provided in the aluminum deposition device according to one embodiment of the present invention.

[0018] Next, an aluminum plating solution impurity removal apparatus according to one embodiment of the present invention will be described with reference to Figure 1. The aluminum plating solution impurity removal apparatus 100 shown in Figure 1 includes a liquid tank 1 for storing an aluminum plating solution 10 that undergoes a treatment to remove water-derived impurities, an electrode 3 consisting of an anode 3a and a cathode 3b made of metallic aluminum, a power supply 2 for applying voltage to the electrode 3, an outlet 5 for discharging the aluminum plating solution after impurity removal, an inlet 6 for receiving the aluminum plating solution containing impurities, and a filter 4 provided between the electrode 3 and the outlet 5. In this specification, the anode 3a is also referred to as the impurity removal anode, the cathode 3b as the impurity removal cathode, and the electrode 3 as the impurity removal electrode.

[0019] The aluminum plating solution impurity removal device 100, when removing water-derived impurities from the aluminum plating solution 10, first stores the aluminum plating solution 10 to be subjected to impurity removal treatment in the liquid tank 1, then applies a voltage between the anode 3a and the cathode 3b, and passes a weak current, as detailed below, through the aluminum plating solution 10 to remove water-derived impurities contained in the aluminum plating solution. Note that water-derived impurities may include water itself or substances naturally formed when water molecules combine with chemical substances constituting the aluminum plating solution.

[0020] Incidentally, aluminum plating solutions are usually strictly controlled to prevent water contamination. This is because if even a small amount of water molecules are present in the aluminum plating solution, and aluminum is deposited on a cathode immersed in the solution, the electrolysis of water molecules and the plating reaction will compete on the cathode surface, preventing the proper formation of the aluminum deposition film. Furthermore, even if an aluminum deposition film is formed, the gas generated by the electrolysis of water molecules can cause plating defects such as pits and pinholes, significantly degrading the appearance, function, and other quality of the aluminum deposition film. For these reasons, strict water control is necessary for aluminum plating solutions.

[0021] However, because aluminum plating solutions are highly hygroscopic, even small amounts of moisture adhering to the substrate or surface of the item to be plated, as well as water vapor in the atmosphere, inevitably become mixed into the non-aqueous aluminum plating solution.

[0022] On the other hand, as mentioned above, the standard oxidation-reduction potential of aluminum is lower than the hydrogen evolution potential (-1.66 V vs. SHE). Therefore, if the aluminum plating solution contains water-derived impurities, electrolysis will begin at a potential higher than that at which aluminum is deposited. Thus, in one embodiment of the present invention, an impurity removal device for aluminum plating solutions focuses on the fact that, by passing an electric current through a plating solution containing water molecules, the electrolysis of water will theoretically begin before the deposition of aluminum at the moment the electric current begins to flow through the plating solution.

[0023] Therefore, the aluminum plating impurity removal device 100 in this embodiment removes water molecules from the aluminum plating solution by passing a small current through it, thereby reducing the regeneration of water-derived impurities that are naturally generated when water molecules mix with the chemical substances constituting the aluminum plating solution. Incidentally, the amount of water molecules removed from the aluminum plating solution is proportional to the transfer of electrons to and from the water molecules. Compared to the removal of water molecules by a film electrode assembly that uses a lot of non-metallic materials as in conventional technology, it is considered that using electrodes made of a highly conductive metallic material, as in the aluminum plating impurity removal device 100 of this embodiment, is more efficient in terms of power consumption. Therefore, the aluminum plating impurity removal device 100 in this embodiment of the present invention uses an anode made of metallic aluminum.

[0024] On the other hand, since aluminum plating solutions containing water-derived impurities contain only a very small amount of water, it is difficult to visually confirm whether the impurity removal device 100 for the aluminum plating solution is functioning in a factory or other location. Therefore, it is preferable to pass an electric current through the aluminum plating solution and make the deposition of aluminum visible on the cathode side so that it can be inferred that the impurity removal device 100 for the aluminum plating solution is functioning. This is because, as mentioned earlier, the electrolysis of water molecules begins before the deposition of aluminum, so the deposition of aluminum at the cathode can be indirectly confirmed to indicate that the removal of water molecules is taking place. However, in this case, aluminum will be deposited on the cathode side. Generally, if aluminum is deposited in the aluminum plating solution, the concentration of aluminum compounds in the aluminum plating solution will fluctuate. Therefore, removing water-derived impurities may degrade the properties of the aluminum plating solution.

[0025] For such technical problems, it is also advantageous to form the anode with metallic aluminum. This is because metallic aluminum has a relatively high electrical conductivity among metals and can supplement the aluminum that would otherwise precipitate on the cathode when removing impurities derived from water. On the anode side, when current flows, the electrode components dissolve into the aluminum plating solution. Therefore, the concentration of the aluminum plating solution changes little, and even if dissolution occurs, the impact on the aluminum plating solution is small. Also, as the current density, a current of 0.1 mA / cm ２ or more up to 100 mA / cm ２ is passed between the anode and the cathode so that it flows through the aluminum plating solution. By doing so, it is possible to efficiently remove impurities derived from water while reducing the amount of aluminum deposited on the cathode. Therefore, it is preferable to set such a current density.

[0026] Note that the anode made of metallic aluminum preferably contains as little as possible silicon (Si) that is insoluble in the plating solution, and iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), chromium (Cr), titanium (Ti) whose standard electrode potential is nobler than aluminum (Al) and comparable, and magnesium (Mg) whose standard electrode potential is baser than aluminum. For example, it is preferable to use metallic aluminum such that Fe is 1.0 mass% or less, Cu, Mn, Mg, Zn are 0.05 mass% or less, and Ti is 0.03 mass% or less. The constituent elements other than aluminum contained in these metallic aluminums are preferably 1.00 mass% or less with respect to the total mass of all the constituent elements including aluminum. More preferably, it is 0.10 mass% or less, and still more preferably 0.01 mass% or less.

[0027] On the other hand, the cathode may be a metallic material having electrical conductivity, such as Cu or nickel (Ni), but metallic aluminum with the same material as the anode and the total content of the above-mentioned elements being 1.00 mass% or less is preferred. Thereby, the possibility of contaminating the aluminum plating solution can be reduced.

[0028] The aluminum plating solution 10 in this embodiment may be an electroaluminum plating solution in which an aluminum salt is melted in a non-aqueous solvent. As the aluminum salt, an aluminum halide is preferable. For example, aluminum chloride (AlCl ３ ), aluminum bromide (AlBr ３ ), aluminum iodide (AlI ３ ), etc. can be mentioned, and aluminum chloride is particularly preferable. Examples of the non-aqueous solvent include dialkyl sulfone, alkylimidazolium halide, and alkylpyridinium halide. Specific examples of the alkylimidazolium halide include 1-ethyl-3-methylimidazolium chloride (EMIC), 1-butyl-3-methylimidazolium chloride (BMIC), and 1-methyl-3-propylimidazolium chloride (MPIC). Specific examples of the alkylpyridinium halide include 1-butylpyridinium chloride (BPC), 1-ethylpyridinium chloride (EPC), 1-butyl-3-methylpyridinium chloride (BMPC), etc.

[0029] Incidentally, at least one nitrogen-containing compound selected from the group consisting of (1) dialkyl sulfone, (2) a molten salt composed of an aluminum halide, and (3) an ammonium halide, a hydrogen halide salt of a primary amine, a hydrogen halide salt of a secondary amine, a hydrogen halide salt of a tertiary amine, and a quaternary ammonium salt represented by the general formula: R １ R ２ R ３ R ４ ·X (R １ to R ４ are the same or different alkyl groups, and X represents a counter anion for a quaternary ammonium cation) is preferably one of the aluminum plating solutions.

[0030] Also, as the dialkyl sulfone described above, specifically, those having 1 to 6 carbon atoms in the alkyl group such as dimethyl sulfone, diethyl sulfone, dipropyl sulfone, dihexyl sulfone, and methyl ethyl sulfone (which may be linear or branched) can be exemplified. However, from the viewpoints of good electrical conductivity and easy availability, dimethyl sulfone can be preferably employed.

[0031] As the ammonium halide that can be employed as the nitrogen-containing compound, ammonium chloride, ammonium bromide, etc. are preferable from the viewpoint of the deposition of the aluminum film. Further, in the hydrogen halide salts of primary amines to tertiary amines, as the primary amines to tertiary amines, those having 1 to 6 carbon atoms in the alkyl group such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, tripropylamine, hexylamine, and methyl ethylamine (which may be linear or branched) may be used. Examples of the hydrogen halide include hydrogen chloride and hydrogen bromide. General formula: R １ R ２ R ３ R ４ N·X (R １ ~R ４ represents the same or different alkyl groups, and X represents a counter anion for the quaternary ammonium cation) in the quaternary ammonium salt represented by R １ ~R ４ Examples of the alkyl group represented by include those having 1 to 6 carbon atoms such as methyl group, ethyl group, propyl group, and hexyl group (which may be linear or branched). Examples of X include halide ions such as chloride ion, bromide ion, and iodide ion, as well as BF ４ － and PF ６ － etc. can be exemplified. Specific compounds include tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, tetraethylammonium tetrafluoroborate, etc.

[0032] The ideal blending ratio of dialkylsulfone, aluminum halide, and nitrogen-containing compound is, for example, 1.5 to 5.0 moles of aluminum halide per 10 moles of dialkylsulfone, with 2.0 to 4.2 moles being more desirable for aluminum precipitation. The ideal ratio of nitrogen-containing compound is 0.01 to 2.0 moles, with 0.05 to 1.5 moles being more desirable.

[0033] While the aluminum film deposited from this aluminum plating solution is highly pure and possesses excellent mechanical properties, this aluminum plating solution is hygroscopic, making it highly susceptible to contamination of the non-aqueous aluminum plating solution with water from the product surface and water vapor in the atmosphere.

[0034] Furthermore, in aluminum plating solutions consisting of a non-aqueous solvent and a molten salt of aluminum halide, water is present in the non-aqueous aluminum plating solution. ４ ― Ya Al ２ Cl ７ － The hydroxyl group of aluminum ions reacts with aluminum halides, such as those represented by [examples of halides], producing hydrogen halides and bonding with the ion species. This indicates that the composition of the aluminum plating solution has changed due to the contamination with water, and that continued contamination with water will lead to deterioration of the plating solution. Furthermore, even a small amount of water in the aluminum plating solution can cause competition between the electrolysis of water and the plating reaction on the product acting as the cathode, potentially preventing the proper formation of the aluminum deposition film. In addition, gas generation due to the electrolysis of water can cause plating defects such as pits and pinholes, potentially leading to a significant decrease in the appearance, function, and other quality of the aluminum deposition film.

[0035] Therefore, in this embodiment, the aluminum plating solution impurity removal device 100 removes water-derived impurities from the aluminum plating solution stored in the solution tank 1 by passing an electric current through the aluminum plating solution, as described above. This is because the standard oxidation-reduction potential of aluminum is lower than the hydrogen evolution potential, so hydrogen, which constitutes water molecules, is deposited on the cathode surface rather than aluminum.

[0036] In this embodiment, the aluminum plating solution impurity removal device 100 has multiple anodes 3a and multiple cathodes 3b arranged alternately, as shown in Figure 1. After immersing the electrodes, which consist of multiple pairs of anodes and cathodes, in the aluminum plating solution 10 with multiple pairs of anodes and cathodes arranged alternately, power is supplied from the power supply device 2 so that a voltage is applied between the anodes 3a and cathodes 3b, thereby flowing an electric current through the aluminum plating solution. In this way, the surface area of ​​the cathodes 3b in contact with the aluminum plating solution is increased, making it possible to efficiently remove water-derived impurities dispersed in the aluminum plating solution.

[0037] Furthermore, the aluminum plating solution impurity removal apparatus 100 in the embodiment of the present invention is provided with a non-conductive protrusion 11 that protrudes from the inner wall of the liquid tank 1 toward the internal space at a position between the anode 3a and the cathode 3b. Figure 2 is a cross-sectional view along the dashed line A-A shown in Figure 1, and is a view from the A-A cross-section in the direction of the arrow in Figure 1. As can be seen in Figure 2, this protrusion 11 protrudes from the inner wall of the liquid tank 1 in a direction perpendicular to the arrangement direction of the anode 3a and cathode 3b. The arrangement is such that the protrusion 11 is interposed between the lower ends and left and right ends of adjacent plate-shaped anodes 3a and cathodes 3b. As a result, when each electrode is plate-shaped and arranged so that the surface with the widest area faces the widest surface of the adjacent electrode, the ends (edges) of the adjacent electrodes do not directly face each other in the plating solution. In other words, when viewed from the opposing direction of adjacent electrodes, the protrusion 11 is interposed so as to cover the ends (edges) of each electrode.

[0038] As a result, the non-conductive protrusions 11 are located on the shortest path between the corresponding ends of the anode 3a and cathode 3b. Therefore, when current is passed through the aluminum plating solution, the concentration of the electric field at the ends of each electrode 3 is suppressed, thereby suppressing abnormal elution at the end of the anode 3a and abnormal deposition of aluminum at the end of the cathode 3b.

[0039] In particular, aluminum plating solutions in regions with excessively high current densities may undergo deterioration. To suppress such deterioration, protrusions 11 are provided in the solution tank 1.

[0040] Furthermore, the aluminum plating solution impurity removal apparatus 100 in the embodiment of the present invention is equipped with an inert gas bubble generating tube 12 at the bottom of the inner space of the liquid tank 1. The inert gas bubble generating tube 12 has a plurality of fine holes formed therein, and inert gas is released into the aluminum plating solution in the form of bubbles. An inert gas supply unit (not shown) is connected to the inert gas bubble generating tube 12 for supplying dry inert gas, and an inert gas, such as argon gas, is supplied from the inert gas supply unit.

[0041] The inert gas bubbles released from the inert gas bubble generating tube 12 agitate the aluminum plating solution in the liquid tank 1. This allows the efficiently circulating aluminum plating solution to come into contact with the surface of the electrode 3, enabling the removal of water-derived impurities mixed in the aluminum plating solution.

[0042] In this embodiment, the aluminum plating solution impurity removal device 100 uses an inert gas bubble tube 12 as a means of stirring the aluminum plating solution. However, the embodiments of the present invention are not limited to this. For example, an impeller and its rotating mechanism may be provided inside the liquid tank 1 to stir the aluminum plating solution.

[0043] Based on the relationship between the standard electrode potentials for hydrogen generation from aluminum and protons, in a non-aqueous aluminum plating solution containing water, simply immersing metallic aluminum will generate hydrogen while aluminum dissolves from the metallic aluminum into the aluminum plating solution. Furthermore, this phenomenon occurs for all metals whose standard electrode potential is less noble than that for hydrogen generation, regardless of the application of electric current.

[0044] Therefore, it is preferable that the aluminum purity of the metallic aluminum used as the anode be 90 mass% or higher. When using low-purity aluminum with an aluminum purity of less than 90 mass% as the electrode, it is preferable to equip the plating apparatus with an electrolytic mechanism or chemical treatment tank for recovering impurities contained in the low-purity aluminum deposited in the non-aqueous aluminum plating solution, and a filter for filtering out impurities in the form of fine particles.

[0045] Therefore, the aluminum plating solution impurity removal device 100 in the embodiment of the present invention is provided with a filter 4 for filtering out impurities in the form of fine particles. This filter 4 only needs to be insoluble in the aluminum plating solution. Preferably, a filter made of glass fibers is used, specifically a filter made of glass fibers wrapped around a stainless steel core. The filter 4 is preferably placed near the outlet 5 of the liquid tank 1. In this way, after the removal of water-derived impurities by the impurity removal device 100, the treated aluminum plating solution can be immediately supplied to a deposition tank for depositing aluminum, making it possible to deposit high-quality aluminum.

[0046] On the other hand, the cathode 3b is not particularly limited as long as it is a metal material with good conductivity. This is because, as long as a negative potential is applied from the cathode 3b side, there is almost no leaching into the aluminum plating solution. However, as long as a noble potential is applied from the anode 3a side, the metallic aluminum, which is a component of the anode 3a, will leach into the aluminum plating solution, causing the anode 3a to be consumed.

[0047] To avoid such one-sided consumption of the anode 3a, the aluminum plating solution impurity removal apparatus in the second embodiment of the present invention is equipped with a polarity switching mechanism that switches the polarity of the output section of the power supply connected to the anode and the output section of the power supply connected to the cathode, so that the polarity of the anode 3a or cathode 3b is reversed by the power supply unit 2.

[0048] The difference between the aluminum plating solution impurity removal apparatus 100 of the first embodiment of the present invention and the second embodiment of the present invention is, as described above, that as time passes while current is passed through the aluminum plating solution, the electrode shown in Figure 1 as anode 3a is repeatedly switched between cathode 3b, anode 3a, cathode 3b, anode 3a, and anode 3a, and that the electrode shown in Figure 1 as cathode 3b is repeatedly switched between anode 3a, cathode 3b, anode 3a, cathode 3b in synchronization with the change in polarity of anode 3a.

[0049] Thus, because each electrode synchronously reverses its polarity from anode 3a to cathode 3b, or from cathode 3b to anode 3a, the power supply unit 2 is equipped with a polarity switching mechanism that synchronously reverses the polarity of the output units 2a and 2b of the power supply unit 2, one from positive to negative and the other from negative to positive. This polarity switching mechanism can be achieved, for example, by a polarity reversal switch 200 connected to a DC power supply 201 provided inside the power supply unit 2, as shown in Figures 3A to C. Figure 3C is a circuit diagram showing only the DC power supply 201, polarity reversal switch 200, anode 3a, and cathode 3b provided inside the power supply unit 2 shown in Figure 1. Figures 3A and 3B show only one pair of electrodes from the multiple pairs of electrodes shown in Figure 3C, and Figure 3A shows the polarity reversal switch 200 in the arrangement of anode 3a and cathode 3b shown in Figure 1. Figure 3B shows the transition from anode 3a to cathode 3b and vice versa when the polarity reversal switch 200 is switched. The dotted arrows in Figures 3A and 3B indicate the direction in which the current flows. As shown in Figures 3A and 3B, the polarity reversal switch 200, which reverses the polarity of the output sections 2a and 2b of the power supply unit 2, changes the connection relationship between the DC power supply 201 and the pair of electrodes, thereby switching each of the pair of electrodes from anode 3a to cathode 3b, or from cathode 3b to anode 3a.

[0050] In this way, initially, metallic aluminum dissolves from the electrode set as the anode 3a, causing the electrode itself to wear down. On the other hand, aluminum is deposited from the aluminum plating solution onto the electrode set as the cathode 3b. When the current flowing between the anode 3a and cathode 3b reaches a predetermined duration, or when the metallic aluminum deposited on the electrode set as cathode 3b completely covers it and reaches a certain thickness, the electrode that was set as the anode 3a is set as the cathode 3b, and at the same time, the electrode that was set as cathode 3b is set as the anode 3a. This causes the metallic aluminum that had been deposited on the surface of the electrode newly set as the anode 3a to dissolve into the aluminum plating solution, and metallic aluminum begins to deposit on the surface of the electrode newly set as the cathode 3b. As a result, even if the material of the electrode initially set as cathode 3b is made of a metal other than aluminum, the dissolution of that metal into the aluminum plating solution can be minimized. This also reduces the wear and tear on the electrode that was initially set as the anode 3a.

[0051] Furthermore, when switching the electrode that was initially set as cathode 3b to anode 3a, it is preferable to adjust the time for setting anode 3a or the time for switching from anode 3a to cathode 3b so that the time is shorter than the time for which current was passed between anode 3a and cathode 3b when cathode 3b was initially set as cathode 3b and immersed in the aluminum plating solution. In particular, with the aluminum plating solution of the above composition, the amount of metallic aluminum deposited at cathode 3b is slightly less than the amount of metallic aluminum eluted from anode 3a. On the other hand, the amount of metallic aluminum deposited at cathode 3b is theoretically proportional to the integral value of the current and the time of current flow in the aluminum plating solution. Therefore, when switching the electrode that was initially set as cathode 3b to anode 3a, it is preferable to control the time for setting anode 3a and applying current to the aluminum plating solution so that it does not exceed the integral value of the time and current initially set at cathode 3b. By doing so, the aluminum deposited on the surface of the electrode initially set as the cathode 3b will not completely dissolve into the aluminum plating solution when it is then set as the anode 3a, thereby reducing the dissolution of the constituent materials of the electrode initially set as the cathode 3b into the aluminum plating solution.

[0052] On the other hand, if the cathode 3b is also made of metallic aluminum, it is preferable because it eliminates the need to strictly control the energizing time and current value. If the cathode 3b is metallic aluminum, then the components that dissolve from the electrode into the aluminum plating solution will be almost entirely metallic aluminum, without having to worry about the integral values ​​of the time and current set for the anode 3a, and it is possible to suppress the mixing of other metallic components into the aluminum plating solution during the removal of water-derived impurities.

[0053] In the second embodiment of the present invention, the polarity reversal switch 200 of the aluminum plating solution impurity removal device is configured to activate the switching operation of the switch 200 in conjunction with a timer (not shown). The polarity switching mechanism having the timer and the polarity reversal switch 200 records the time for which current is passed between the anode and the cathode, and sets the next switching time from the recorded time. It is preferable to set this switching time to a time shorter than the recorded time. On the other hand, once the reversal of the polarity of the anode or cathode is completed, the time is measured again. Then, when the next switching time is reached, the polarity of the anode or cathode is reversed based on the aforementioned switching time. Although the polarity reversal switch 200 shown in Figure 3 is a mechanical switch, the polarity switching mechanism of the present invention is not limited to this, and may also be implemented using semiconductor elements such as transistors to realize the switching function, or it may be implemented using semiconductor elements to reverse the polarity of the output sections 2a and 2b of the power supply unit 200 based on a trigger signal issued by a digital processor or central processing unit. Furthermore, the power supply unit 200 may be equipped with a current measuring means, and the amount of electricity since the previous polarity switching operation may be calculated using the measurement value of the current measuring means and a timer (not shown), and the polarity may be switched by the polarity switching mechanism based on the calculated amount of electricity.

[0054] Next, an aluminum deposition apparatus using the aforementioned aluminum plating solution impurity removal apparatus 100 will be described with reference to Figure 4. This aluminum deposition apparatus includes the aforementioned aluminum plating solution impurity removal apparatus 100, an aluminum deposition unit 101 for applying aluminum plating to an object using the aluminum plating solution from which water-derived impurities have been removed by the aluminum plating solution impurity removal apparatus 100, and a plating solution transport pipe 102 connected between the aluminum plating solution impurity removal apparatus 100 and the aluminum deposition unit 101.

[0055] Figure 5 shows a schematic configuration of the aluminum deposition unit 101. The aluminum deposition unit 101 includes a deposition tank 101a that stores the aluminum plating solution supplied from the aluminum plating solution impurity removal device 100, and a deposition anode 103a and a deposition cathode 103b immersed in the aluminum plating solution 10 stored in the deposition tank. Both the deposition anode 103a and the deposition cathode 103b are connected to a deposition power supply device 105, and a DC voltage supplied from the deposition power supply device 105 is applied between the deposition anode 103a and the deposition cathode 103b to create a current in the aluminum plating solution in the deposition tank 101a, thereby depositing aluminum on the deposition cathode 103a. It is preferable that the current density applied here is greater than the current applied by the aluminum plating solution impurity removal device 100, as this will increase the rate of aluminum deposition on the cathode side.

[0056] On the other hand, the plating solution transport pipe 102 is equipped with a delivery pump 103, which delivers the aluminum plating solution between the aluminum plating solution impurity removal device 100 and the aluminum plating device 101.

[0057] The aluminum plating solution that flows out from the outlet 5 of the aluminum plating solution impurity removal device 100 is already a plating solution that has undergone impurity removal treatment, so it is sent to the aluminum deposition unit 101 by the discharge pump 103 from the plating solution transport pipe 102 on the left side shown in Figure 4, which is connected to the outlet 5.

[0058] Meanwhile, the aluminum plating solution used for plating the object by the aluminum deposition unit 101 is discharged from the aluminum deposition unit 101 to the plating solution transport pipe 102 on the right side of Figure 4, and transported by the delivery pump 103 to the inlet 6 of the aluminum plating solution impurity removal device 100.

[0059] This significantly reduces the opportunities for the aluminum plating solution to come into contact with moisture in the atmosphere, allowing the aluminum plating solution treated by the impurity removal device 100 to be safely supplied to the aluminum deposition unit device 101, where a good aluminum deposition film can be formed. This makes it possible to use the aluminum deposition unit 101 for aluminum plating as a surface treatment for articles. Furthermore, by using the aluminum deposition unit 101 for the purification of high-purity aluminum, it becomes possible to deposit high-purity aluminum with a high yield. In addition, it becomes possible to manufacture aluminum plated products having the following steps. The process involves immersing a cathode and an anode made of metallic aluminum in an aluminum plating solution, applying a voltage between the immersed anode and cathode to pass an electric current through the aluminum plating solution, depositing aluminum on the cathode, immersing an electrode with an article for coating aluminum attached into the aluminum plating solution, and using the electrode with the article for coating aluminum attached, passing an electric current between the deposition anode and the electrode with the article for coating aluminum to coat the article with aluminum. In this embodiment of the method for manufacturing aluminum plated products, the deposition anode and the anode used before the aluminum was deposited may be the same.

[0060] The aluminum plating capacity was confirmed using the Hull cell test method for aluminum plating solutions left in the same environment, one in which water-derived impurities were removed using a single electrode, and the other in which water-derived impurities were removed using multiple pairs of electrodes. This Hull cell test confirmed that, when the energizing time and the amount of electricity (product of current (A) and the time the current was applied (s)) were kept the same, the aluminum plating solution with multiple pairs of electrodes showed a larger aluminum coating area. Further details are provided below.

[0061] In this embodiment, dimethyl sulfone (DMSO) was used as the aluminum plating solution. ２ ), aluminum chloride (AlCl ３ ), ammonium chloride (NH ４ It consists of Cl, tetramethylammonium chloride (TMAC), and the molar ratio of its composition is DMSO ２ : AlCl ３ : NH ４ A Hull cell test was performed using a 267 ml Hull cell test tank on a non-aqueous aluminum plating solution with a Cl:TMAC ratio of 10:3.8:0.2:1.0 to verify the impurity removal capability when metallic aluminum is used as the anode.

[0062] Furthermore, the anode and cathode used were aluminum plates with an aluminum purity of 99.99%. Two anodes and two cathodes were used. The total area of ​​the cathode immersed in the aluminum plating solution was 77 cm². ２ That's what I decided.

[0063] First, a Hull cell test was performed using a Hull cell test apparatus that mimicked the impurity removal apparatus for aluminum plating solution described in the embodiment of the present invention. This apparatus is equipped with a stirring impeller in the container used for the Hull cell test. Then, 267 ml of aluminum plating solution with the aforementioned composition was poured into the container used for the Hull cell test, and two anodes and two cathodes (two pairs of electrodes) were placed so as to be immersed in the aluminum plating solution. Then, the two anodes and the two cathodes were connected in parallel to a power supply unit.

[0064] While stirring the aluminum plating solution with an agitator impeller, a current of 0.16 A was passed through the aluminum plating solution in a container used for the Hull cell test to remove water-derived impurities. The rotation speed of the agitator impeller was set to 1000 rpm, and the temperature of the aluminum plating solution during impurity removal was 120°C.

[0065] On the other hand, as a reference example, the same aluminum plating solution as in the previous example was placed in a Hull cell test container equipped with a stirring impeller, and one anode and one cathode were immersed in the aluminum plating solution. The surface area of ​​the cathode in contact with the aluminum plating solution was 40 cm². ２ Then, the anode and cathode were connected to the power supply.

[0066] While stirring the aluminum plating solution with an agitator impeller, a current of 0.16 A was passed through the aluminum plating solution in a container used for the Hull cell test to remove water-derived impurities from the aluminum plating solution. The rotation speed of the agitator impeller was set to 800 rpm, and the temperature of the aluminum plating solution during impurity removal was 95°C. In addition, the arrangement of one pair of electrodes in the example was the same as the arrangement of electrodes in the reference example.

[0067] Next, a Hull cell test was performed on the aluminum plating solutions from the examples and reference examples after impurity removal. For both the examples and reference examples, the test was conducted with an applied current of 1 A, a test temperature of 95°C, and a stirring impeller rotation speed of 500 rpm. The time required for the coating area from the left side of the test piece, which was closest to the anode, to reach 90 mm was measured and compared.

[0068] According to these results, using a plating solution with two anodes and two cathodes to remove impurities reduced the processing time by 71%. In terms of power consumption, the example showed a 57% reduction compared to the reference example. Therefore, it can be seen that by using metallic aluminum not only for the anode but also for the cathode, and by further increasing the number of electrodes in both the anode and the cathode, water-derived impurities can be removed more efficiently.

[0069] Although the present invention has been described above using the above embodiments, the present invention is not limited to the above embodiments. Modifications are possible within the technical scope set forth in the claims of the present invention.

[0070] 1. Liquid tank, 2. Power supply unit, 3. Electrode, 3a. Anode, 3b. Cathode, 4. Filter, 5. Outlet, 6. Inlet, 7. Inert gas supply pipe, 11. Protrusion, 12. Inert gas bubble generation pipe, 13. Cover, 101. Deposition tank, 102. Plating solution transport pipe, 103. Discharge pump, 200. Polarity reversal switch, 201. DC power supply.

Claims

1. An impurity removal apparatus for an aluminum plating solution for removing water-derived impurities contained in the aluminum plating solution, comprising a liquid tank for storing the aluminum plating solution, an anode and a cathode provided in the liquid tank, and a power supply device for applying a voltage between the anode and the cathode, wherein the anode is made of metallic aluminum.

2. The apparatus for removing impurities from an aluminum plating solution according to claim 1, characterized in that a plurality of anodes and cathodes are provided.

3. The apparatus for removing impurities from an aluminum plating solution according to claim 1, characterized in that the power supply unit has a polarity switching mechanism for switching the polarity of the anode and the cathode.

4. The apparatus for removing impurities from an aluminum plating solution according to claim 3, characterized in that the polarity switching mechanism sets a scheduled time for switching the polarity after the polarity of the anode or cathode has reversed, based on the energizing time of the current that was flowing between the anode and the cathode before the polarity of the anode and the cathode reversed, and switches the polarity of the anode or cathode based on the scheduled switching time.

5. The apparatus for removing impurities from an aluminum plating solution according to claim 3, characterized in that the cathode is made of metallic aluminum.

6. The aluminum plating solution is an electroplating solution containing an aluminum halide in a non-aqueous solvent, as described in claim 1, and is an impurity removal apparatus for an aluminum plating solution.

7. The apparatus for removing impurities from an aluminum plating solution according to claim 6, characterized in that the non-aqueous solvent is a dialkyl sulfone.

8. The aluminum plating solution impurity removal apparatus according to claim 7, characterized in that the aluminum plating solution further contains ammonium chloride and tetramethylammonium chloride.

9. The aluminum plating solution impurity removal apparatus according to claim 1, wherein the liquid tank comprises an inlet into which the aluminum plating solution before the removal of water-derived impurities flows in, and an outlet into which the aluminum plating solution after the removal of impurities flows out, and a filter for removing solid matter is provided between the outlet and the anode.

10. An aluminum deposition apparatus comprising: an impurity removal apparatus for an aluminum plating solution according to any one of claims 1 to 9; a deposition tank for storing the aluminum plating solution after the removal of water-derived impurities from the impurity removal apparatus; a deposition cathode immersed in the aluminum plating solution in the deposition tank for depositing aluminum; and a deposition anode for passing an electric current through the aluminum plating solution in the deposition tank between itself and the deposition cathode.

11. A method for removing impurities from an aluminum plating solution, wherein impurities originating from water are removed from the aluminum plating solution, characterized in that a cathode and an anode made of metallic aluminum are immersed in the aluminum plating solution, and a voltage is applied between the anode and cathode immersed in the aluminum plating solution to cause an electric current to flow through the aluminum plating solution.

12. The method for removing impurities from an aluminum plating solution according to claim 11, wherein the anode and the cathode are switched to opposite polarities according to the current flowing between the anode and the cathode until the polarity of the anode or the cathode is reversed.

13. A method for manufacturing an aluminum-plated product, characterized by immersing a cathode and an anode made of metallic aluminum in an aluminum plating solution, applying a voltage between the anode and cathode immersed in the aluminum plating solution to pass an electric current through the aluminum plating solution, immersing an electrode with an article for coating aluminum attached into the aluminum plating solution once the aluminum has been deposited on the cathode, and using the electrode with the article for coating aluminum attached, passing an electric current between the deposition anode and the electrode with the article for coating aluminum to coat the article with aluminum.

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