JPH1136099A - Plating device and plating method thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electroplating device capable of treatment in a state in which the electrole potential is almost zero while the increase of hydrogen ions in an electrolyte is suppressed by providing the inside of an electrolyte with an auxiliary electrode for recovering a gas generated in the electrolyte along the gas dispersion anodic electrode face. SOLUTION: The space between an anode 2 and a cathode 3 is applied with suitable voltage from a rectifier 8. Along the surface of the anode 2, an auxiliary electrode 6 of titanium metal applied with platinum plating is provided, and, fundamentally, the auxiliary electrode 6 is only suspended and is not connected to both electrodes. Then, the surface of the auxiliary electride 6 on the side closer to the anode 2 is negatively electrified, and the surface on the side of the cathode 3 is positively electrified. Thus, the auxiliary electrode 6 is formed into a bipolar electrode. Therefore, on the surface of the side of the anode of the auxiliary electrode 6, hydrogen ions are gathered, and gaseous hydrogen is generated, but, this is recovered by a recovering device 9 and is pulled out from a pump 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a novel plating apparatus and a plating method using the same.

[0002]

2. Description of the Related Art In general, in electrolytic plating, an anode material to be supplied with a metal material to be electroplated is used. However, when the metal to be plated is contained in an electrolytic solution, When the anode material is supplied from another material, a material which does not change even in the electrolytic reaction is used. Then, a material that does not change even if the anode potential increases is used. On the other hand, gas diffusion electrodes are used in fuel cells and the like, but have not been generally used for electrolytic plating. For example, if a hydrogen gas diffusion electrode is used, the concentration of hydrogen ions in the electrolytic solution naturally increases, the pH decreases, and the electrolysis conditions are changed.

[0003] On the other hand, tin-silver alloy plating is an alloy plating that has attracted attention as a plating alloy on bumps, which is currently expected as a connection method replacing the wire bonding method used for printed wiring boards. However, despite the very wide use of this alloy plating, it has not yet been fully commercialized. One reason for this is that no plating method has been found for performing this type of plating. Therefore, in order to use hydrogen ions, no harmful substances such as cyan gas are involved, and a plating method using a hydrogen gas diffusion electrode that uses hydrogen gas itself as an anode (metal surface technology (published by the Electrochemical Society)) Shu, 1989, Vol. 40, No. 9, 1037-
1038), and we considered its use.

[0004] However, it has been found that even with this hydrogen gas diffusion electrode, there is a problem that there is no suitable anode material for performing alloy plating. That is, an anode material suitable for this type of alloy plating is that the anode voltage is reduced to a potential at which iodine is not deposited. Among the currently used anode materials, the only electrode that satisfies this condition is the hydrogen gas diffusion electrode. The hydrogen gas diffusion electrode is an electrode that hardly applies a voltage to the anode because the hydrogen gas itself is used as an anode.On the other hand, the hydrogen gas diffusion electrode reduces the pH of the electrolyte solution to reduce the hydrogen gas to hydrogen ions and release the hydrogen gas into the electrolyte solution. It has an extremely lowering effect, and has been difficult to use as an anode for plating for continuous electrolysis for a long time.

As a gas diffusion electrode used in a fuel cell, a secondary battery, an electrochemical reactor, or the like, a gas diffusion electrode in which a current collector coated with a noble metal is bonded or embedded is used (Japanese Patent Publication No. 6-7488). No.).

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide an electrolytic plating method capable of treating an electrode at almost zero potential while suppressing an increase in hydrogen ions in the electrolyte. An apparatus and such a plating method are provided. Another object of the present invention is to provide a plating apparatus and a plating method using the hydrogen gas diffusion electrode that can perform plating treatment for a long time.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problems, and the present invention has a cathode electrode and an anode electrode, an electrolytic solution provided therebetween, and an anode electrode. In the electroless or electrolytic type plating apparatus having a gas chamber on the outside, by providing an auxiliary electrode in the electrolytic solution along the gas diffusion anode electrode surface to collect gas generated in the electrolytic solution. Further, the present invention provides an electrolytic plating apparatus and a plating method capable of treating an anode electrode at almost zero potential.

[0008] At this time, if the auxiliary electrode is formed into a mesh-shaped conductor, the surface area becomes large, and an efficient plating apparatus and method can be obtained. Further, it is preferable to provide a collecting means for capturing generated hydrogen just above the auxiliary electrode. Further, the auxiliary electrode
It is preferred that the metal conductor has at least one mesh. In addition, the surface of the auxiliary electrode is coated with a noble metal, or the one carrying a noble metal powder,
It is suitable. The noble metal is preferably selected from platinum, palladium, ruthenium, rhodium, iridium and gold. The anode electrode is of a hydrogen gas diffusion type, and the gas is preferably hydrogen. In the plating method, a metal film or an alloy film is obtained in an electroless or electrolytic form from a gas chamber provided outside the anode electrode by electrolytic deposition from an electrolytic solution between the cathode electrode and the anode electrode. An auxiliary electrode is provided in the electrolytic solution along the gas diffusion anode electrode surface, and the electrolytic treatment is performed while collecting the gas generated in the electrolytic solution.

The essential point of the present invention is to use a combination of a gas diffusion electrode and an auxiliary electrode for an electrolytic plating process. As described above, the gas diffusion electrode is usually used as a fuel cell, a gas concentration cell, or the like. In the present invention, other things can be considered, but usually, since a hydrogen gas diffusion electrode is preferably used, the following description will be basically basically given with reference to an example of a hydrogen gas diffusion electrode, but other gases can be used. is there. That is, when a hydrogen gas diffusion electrode is used as an anode, a gas diffusion electrode utilizing the reaction of H ₂ → 2H ⁺ + 2e ⁻ is obtained. Since this reaction is used, the anode can be effectively used as an electrode to which almost no potential is applied.

That is, in this hydrogen gas diffusion electrode, an anode reaction occurs as an electrode by converting hydrogen into hydrogen ions at the anode. This anode voltage is 0 V because it is the oxidation potential of hydrogen, and it can be said that the anode voltage is an electrode to which no anode voltage is applied. However, when this electrode is used, as shown in the above equation, hydrogen ions having an equimolar amount to the electrolytic amount flow out into the electrolytic cell through the electrode interface. The inflow of hydrogen ions depends on the pH in the electrolytic cell.
Therefore, the electrode was not suitable for a plating method for performing electrolysis for a long time. That is, if the use of the anode is continued for a long time, the hydrogen ion concentration in the plating solution increases as the electrode reaction proceeds, so that the pH in the plating solution decreases. For this reason, plating conditions may be changed and plating failure may occur. Therefore, use of this electrode was not usually considered.

The present invention overcomes this disadvantage by using an auxiliary electrode. In the present invention, the auxiliary electrode is provided with an auxiliary electrode for recovering hydrogen gas generated in the electrolytic solution in the electrolytic solution along the anode electrode surface. Normally, the auxiliary electrode is used without being connected to either of the electrodes, but if required, an appropriate potential can be applied. The potential is selected so that the reaction from hydrogen ions to hydrogen gas can be efficiently performed.

First, an anode electrode for use in an alloy plating apparatus was examined as follows.
Here, the case of plating a tin-silver alloy will be described, but the same applies to other alloy plating or simple metal or noble metal plating.

For the tin electrode, one of the metals of the alloy to be plated, the silver ions in the bath prior to electrolysis will have a large excess of potassium iodide due to the equilibrium reaction between silver iodide and silver ions as silver iodide. When the tin electrode is immersed in this plating bath because it is only present in the solution, the dissolution reaction of metallic tin; S
In the case of n → Sn ²⁺ + 2e ⁻ (E ⁰ = 0.14), surplus electrons cause silver ions in the plating solution to easily precipitate and easily form displacement plating. Since the standard potential of silver is originally noble, the alloy plating composition is such that one tin
Coatings present at about 5% by weight are desirable. Therefore, the silver concentration is suppressed as low as possible. Therefore, the concentration of silver present in the electrolyte is set low.
Thus, the incorrect deposition of silver at the anode makes it difficult to control the concentration of silver in the coating.

When the electrolytic treatment is carried out not with the electrode type as in the present invention but with a normal anode-cathode, when the anode voltage is low, a good matte white metal film is deposited when the anode voltage is low. A green to black film is gradually deposited on the anode. However, the bath voltage rises sharply simultaneously with the formation of the film, and the film deposited on the cathode surface has a high electrolytic potential.

When a silver electrode is used, the silver in the plating bath is dissolved in an excess potassium iodide solution after silver ions first generate silver iodide. However, from the formation reaction, there is a strong tendency to form a complex with ammonium ions and triethylamine which are present in a large amount in the electrolyte solution rather than forming silver iodide, so that precipitation occurs when silver ions alone are put into the plating bath. Does not dissolve easily. Similarly, when silver ions are immersed in a plating bath and electrolyzed as an anode, such a phenomenon occurs at the interface between the silver electrode and the solution, so that a dissolution reaction does not easily occur and an insoluble film is formed. The film formed at the anode does not conduct electricity, and as a result, the bath voltage increases, and eventually the current is poorly supplied, and the electrolysis becomes difficult. In the case of a silver electrode, when the plating film also has a low voltage, a good matte white metal film is deposited, but a green to black film is gradually deposited on the anode as the electrolysis is continued. However, the bath voltage rises sharply simultaneously with the formation of the film.

When an electrolytic treatment for tin-silver alloy plating is started using a hydrogen gas diffusion electrode as an anode with respect to the above electrodes, the pH starts to decrease simultaneously with the start of the electrolysis. After a while, iodine starts to precipitate at the anode, and the decrease in pH value stops. However, since the precipitated potassium iodide does not dissolve or decompose, it becomes impossible to continue the electrolytic treatment to a certain degree or more. That is,
Generally, the hydrogen gas diffusion electrode did not generate gas generated at the insoluble anode as described above. However, iodine precipitated near the anode during the electrolytic plating. It is considered that the same electrode reaction as when an indium oxide electrode was used occurred.

On the other hand, in the plating apparatus of the present invention,
An improved hydrogen gas diffusion electrode is used. In the hydrogen gas diffusion electrode, an anode reaction occurs as an electrode by converting hydrogen into hydrogen ions at the anode. This anode voltage is 0 V because it is the oxidation potential of hydrogen, and it can be said that the anode voltage is an electrode to which no anode voltage is applied. However, when this electrode is used, hydrogen ions having an equimolar amount to the electrolytic amount flow out into the electrolytic cell through the electrode interface. Since the inflow of hydrogen ions lowers the pH in the electrolytic cell, the electrode was not suitable for a plating method for performing electrolysis for a long time.

That is, in the improved hydrogen gas diffusion electrode according to the present invention, unlike the case where electrolysis is carried out with a normal hydrogen gas diffusion electrode, as described above, the fluctuation of pH is relatively gradual. Therefore, no precipitation of iodine occurred. Then, the obtained cathode film was a matte white film. With other anode materials, if plating is performed for 30 minutes or more, silver deposits on the anode or iodine is adsorbed on the cathode, causing powder plating such as an abnormal eutectoid phenomenon to occur. However, the problem of film formation is further reduced by the plating anode electrode and the plating method of the present invention.

That is, if an auxiliary electrode is provided in the vicinity of the hydrogen gas diffusion electrode anode and is not connected to either electrode, the auxiliary electrode becomes a bipolar electrode, and hydrogen gas is generated on the negatively charged surface. . In the plating apparatus of the present invention, a bipolar phenomenon occurs between the auxiliary electrode and the anode. Thus, in the present invention, the term "bipolar electrode" is a metal auxiliary electrode, which acts as a cathode on its surface on its anode side, its cathode side surface acting as an anode, and the anode side surface The hydrogen ions are reduced,
Hydrogen gas is generated in the electrolytic cell and can be recovered.

The potential at which hydrogen ions are converted into hydrogen gas is very small. For this reason, it is sufficiently possible to reduce hydrogen ions only by using an auxiliary electrode generated from the voltage of the electrolytic cell. However, as described above, an appropriate potential can be applied to the auxiliary electrode if necessary.

In the plating apparatus of the present invention, by suspending a plurality of metal mesh electrodes, a larger bipolar phenomenon is caused, and the flow of hydrogen ions into the electrolytic cell can be suppressed to the minimum.

In addition, iodine adhered to the anode and generated when electrolysis was performed only with the hydrogen gas diffusion electrode could be prevented from being deposited on the anode by hanging a plurality of bipolar electrodes, that is, a network of auxiliary electrodes. It becomes possible to prevent approach and adsorption of iodine ions in the electrolytic solution. Therefore, it is considered that the installation of the auxiliary electrode is effective.

In this case, the adsorption of iodine ions to the anode and the precipitation of iodine were hindered by the arrangement of the auxiliary electrodes, and actual precipitation and the like did not occur. A decrease in pH due to an increase in the concentration of hydrogen ions was suppressed to such an extent that electrolysis could be continued.
In performing the tin-silver alloy plating, the hydrogen gas diffusion electrode was considered to be the most effective electrode.

Next, the plating apparatus and the plating method of the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

[0025]

Embodiment 1 [Plating Apparatus] FIG. 1 is a perspective view schematically showing one example of a plating apparatus of the present invention. This figure is a cross-sectional view schematically showing only the components of the plating apparatus of the present invention, and the structural parts are omitted. The electrolytic cell (1) has a normal structure,
An electrolytic solution (4) is contained in a tank (1) having left and right anodes (2) and cathodes (3) as hydrogen gas diffusion electrodes. A hydrogen gas chamber outside the anode gas diffusion electrode (2)
(5) is provided through which hydrogen is supplied into the electrolyte (4). Hydrogen is supplied to the gas chamber (5) from an inlet (11), and the remaining hydrogen gas is consumed by an outlet (12).
Is discharged from

That is, the member to be plated is a cathode
Anode attached to (3) and forming the cathode itself
(2) was a hydrogen gas diffusion electrode. The surface area of this gas diffusion electrode was 40 cm ² , and the gap between the electrodes was 5 mm. The structure of the gas diffusion electrode is hydrophilic carbon black (AB-12, manufactured by Denki Kagaku Kogyo Co., Ltd.), hydrophobic carbon black (AB-7, manufactured by Denki Kagaku Kogyo Co., Ltd.), and polytetrafluoroethylene dispersion (Daikin) as a binder. It is a carbon electrode composed of D-1) manufactured by Industrial Co., Ltd.
The catalyst was platinum and 0.56 mg / d in the reaction layer of the gas diffusion electrode.
cm ^{3 was} carried. The plating electrolytic bath (4) is between its anode and cathode, the components of which depend on the material to be plated. Then, these material components were adjusted to a predetermined concentration and placed in a cell.

Further, along the surface of the anode (2), an auxiliary electrode network (6) made of titanium metal plated with platinum was provided.
A hydrogen gas recovery unit (9) is provided on the upper part, and hydrogen gas can be recovered by a pump (10). In the hydrogen gas chamber (5),
Hydrogen gas is appropriately supplied from the inlet (11) from the outside.

An appropriate voltage is applied between the anode (2) and the cathode (3) from the rectifier (8). Basically, the auxiliary electrode (6) is merely suspended and not connected to any of the electrodes. Then, the auxiliary electrode near the anode
The surface of (6) is negatively charged, and the cathode side surface is positively charged. Therefore, the auxiliary electrode (6) becomes a bipolar electrode. For this reason, on the surface of the anode-side auxiliary electrode, hydrogen ions collect and hydrogen gas is generated.
The pressure of the generated hydrogen gas is measured by a low-pressure manometer (13), collected by a collector (9), and extracted by a pump (10).

On the other hand, the electrolytic solution (4) is supplied from the supply port (14) and circulates at a constant flow rate from the outlet (15), so that the consumed metal ions are automatically captured. The supply ports and outlets are on the bottom and top in the figure, but this is for convenience of illustration and both may be side.

The auxiliary electrode (6) is made of a plurality of metal nets as shown. That is, a shape that can increase the surface area as much as possible is preferable. In the illustration, no potential is applied,
Although it is zero V, an electric potential may be applied so as to favor the generation of hydrogen gas. Further, in the plating apparatus of the present invention,
An ion exchange membrane (16) is provided between the anode (2) and the cathode (3) to prevent halogens and the like formed by the electrolytic treatment from going near other electrodes. Therefore, as the ion exchange membrane, a molecular membrane such as cellophane can be used as long as the membrane does not allow halogen to pass therethrough.

[0031]

Example 2 [Example 1 of Actual Plating Treatment—Electrolytic Tin-Silver Alloy Plating] Next, the composition of the tin-silver alloy plating bath was changed to tin (II) sulfate 0.1
０．３0.3 M, silver nitrate 0.001-0.2 M, citrate 0.4-1.2 M, potassium iodide 1.5-3.0 M,
Succinimide 0.4-0.8M, surface conditioner 1-10
g / l, and a surfactant of 0.2 to 1.5 g, and a tin-silver alloy was electroplated under the following plating conditions using the hydrogen gas diffusion electrode shown in FIG. 1 as an anode.

That is, the plating conditions are a temperature of 25 to 60 ° C.
Mechanical stirring, pH 4-6, current density 0.1-4A / dm
² The tin-silver alloy plating film obtained on the cathode was a matte white film. Since no decomposition product was formed, the plating process could be continued for a long period of time. In this case, the temperature could be from normal temperature to about 60 ° C., but higher temperature has the effect of lowering and suppressing the silver concentration in the plating film, and since the film becomes denser, the temperature is 40 to 50 ° C. It is suitable. At high temperatures, it is difficult to maintain the same conditions due to evaporation of the plating solution. In the pH range of 3.5 to 10, the plating solution is stable as a colorless to yellowish solution. The change in pH changes the silver content in the plating film. When the pH decreases, the current efficiency of the plating film decreases.

In contrast to the method using a combination of a gas diffusion electrode and an auxiliary electrode according to the present invention, when an insoluble material such as a noble metal or carbon is used for the anode as in the prior art, the anode voltage increases and the silver in the cathode film increases. The content and appearance were adversely affected.

[0034]

Example 3 [Example 2 of Actual Plating Treatment: Nickel-Phosphorus Alloy Plating] Using an electrolytic nickel-phosphorus alloy plating solution shown in the following table, electrolytic plating was performed under the plating conditions shown in the table. The test was performed in the case where an electrode made of only nickel or stainless steel was used as the anode, and in the case where an improved hydrogen gas diffusion electrode as shown in the figure was used.

[0035]

[Table 1]

The observation results are as follows. In the case of a nickel electrode, the nickel concentration in the plating solution excessively increased, and ionic color precipitation of insoluble nickel occurred near the anode surface, making it difficult to continue electrolysis. The citric acid added as a complexing agent has an added amount of about 30
% By weight had been decomposed. In the case of a stainless steel electrode, no precipitation of insoluble nickel did not occur, but the color of the plating bath solution changed from dark green to brown. The decomposition of citric acid was around 40% by weight.

In contrast, in the case of the combination of the hydrogen gas diffusion electrode and the auxiliary electrode according to the present invention, no discoloration and precipitation of the plating bath occurred. Almost no decomposition of citric acid could be confirmed. In this case, the pH tends to decrease,
It is considered that the fluctuation of the pH hardly affects the appearance of the film and the phosphorus content.

[0038]

Example 4 [Example 3 of Actual Plating Treatment—Electrolytic Iron Plating] Electrolytic iron plating was performed under the plating conditions shown in the table using the electrolytic iron plating solutions shown in the table below. When iron or an insoluble metal is used for a conventional anode, the oxidation of iron (II) ions to iron (III) ions on the anode surface causes oxygen in the plated coating. And there is a tendency to deteriorate the toughness of the film. On the other hand, when an improved hydrogen gas diffusion electrode as shown in the figure was used, a small decrease in pH was observed even in the bath solution, but no effect on the obtained film was observed.

[0039]

[Table 2]

The concentration of iron (III) ions in the plating solution was constant, and no increase in the concentration of iron ions was observed even when the electrolysis was continued. Further, generation of chlorine due to a large amount of chloride in the plating bath solution was also suppressed.

[0041]

Example 5 [Example 4 of Actual Plating Process—Electrolytic Gold Plating] Electrolytic gold plating was performed under the plating conditions shown in the table using the electrolytic gold plating solution shown in the table below. In a conventional gold plating bath, electrolysis is performed using an insoluble anode platinum-plated on a titanium net,
With a weakly acidic gold plating solution, citric acid, a complexing agent added to the plating solution, is oxidized and decomposed. The decomposition products are taken into the film and deteriorate the appearance of the obtained film. In contrast, the use of an improved hydrogen gas diffusion electrode as shown in the figure suppresses the oxidative decomposition of the complexing agent, enables continuous electrolysis for a long time, and suppresses the adverse effect on the formed film. it can.

[0042]

[Table 3]

Similarly, in the case of platinum plating and rhodium plating, the plating apparatus and method of the present invention can obtain favorable results.

[0044]

Example 6 [Example 5 of Actual Plating Process—Chromium Plating] Electrolytic chromium plating was performed under the plating conditions shown in the table using the electrolytic chrome plating solutions shown in the table below. In the conventional plating from chromium (III), the electrode is hardly oxidatively decomposed on the anode surface.However, in the bath liquid, the amount of chromium ion (VI) is strictly regulated. The plating apparatus and method are effective. That is, in the plating method of the present invention, VI chromium ions generated on the anode surface by electrolysis were hardly observed.

[0045]

[Table 4]

When halogen, ammonia or the like is used as the conductive salt, there is a possibility that those substances are deposited on the anode by specific adsorption and oxidation on the anode material.
By providing the auxiliary electrode of the present invention, direct adsorption of these adsorbed substances to the anode material is suppressed.

In the case of electrolytic plating from ions having a plurality of charges, an anode material is selected so as to be a required charged ion in the plating solution, and plating is performed. If a product that becomes an impurity in
The plating solution must be discarded. The use of the electrode having the configuration as in the present invention can suppress generation of plating impurities due to anodic oxidation. In particular, technical effects are remarkable in alloy plating and precious metal plating in which an insoluble anode must be used.

[0048]

The plating apparatus of the present invention has the following technical effects by the structure shown in the figure. That is, the first
In addition, electrolytic plating can be performed at a very low anode electrode potential. That is, it is possible to provide an apparatus and a method which can perform plating with an extremely low electrode potential, particularly in alloy plating or precious metal plating in which an insoluble anode must be used. Also, the present invention provides a plating apparatus and a plating method that do not oxidatively decompose an organic acid such as citric acid contained in a plating bath as a complexing agent or the like. And further, it prevents the formation of oxides that may degrade the plated film, or the formation of impurities in the electrolyte that causes the deterioration, such as precipitation,
Provide a plating method that does not contain chlorine gas or phosphorus.

Second, hydrogen gas can be efficiently generated by the apparatus and the method according to the second and tenth aspects. Third,
According to the apparatus and method according to claims 3 and 11, hydrogen gas can be efficiently recovered.

Fourth, the apparatus and method according to claims 4 and 12 provide both strength and hydrogen gas generation efficiency. Fifth, with the apparatus and the method according to claims 5 and 13, the electrode having no electrode corrosion due to the noble metal surface is obtained, and the hydrogen gas generation efficiency of the auxiliary electrode is increased.

Sixth, in the inventions according to claims 6 and 14, the generation of impurities is minimized by selecting a noble metal. Seventh, in the inventions according to the seventh and fifteenth aspects, alloys and metals can be plated by hydrogen gas diffusion even when the anode potential is zero. Eighth, according to the eighth and sixteenth aspects, the potential of the auxiliary electrode is appropriately maintained with respect to the anode potential, and the hydrogen gas generation efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a configuration of an example of a plating apparatus according to the present invention.

[Explanation of symbols]

 (1) Electrolysis tank (2) Anode (hydrogen gas diffusion electrode) (3) Cathode (4) Electrolysis bath (liquid) (5) Gas chamber (6) Auxiliary electrode (net) (8) Rectifier (9) Hydrogen gas recovery (10) Pump (11) Hydrogen gas supply port (12) Hydrogen gas discharge port (13) Low pressure manometer (14) Electrolyte supply port (15) Electrolyte outlet (16) Ion exchange membrane

Claims (16)

[Claims] A cathode electrode and an anode electrode;
In the meantime, an electrolytic solution is provided, and a plating chamber of an electroless or electrolytic type provided with a gas chamber outside the anode electrode, for recovering gas generated in the electrolytic solution along the anode electrode surface. The plating apparatus, wherein the auxiliary electrode is provided in an electrolytic solution. 2. The plating apparatus according to claim 1, wherein the auxiliary electrode is a mesh-shaped conductor. 3. The plating apparatus according to claim 1, further comprising a collecting means for capturing generated gas immediately above the auxiliary electrode. 4. The structure according to claim 1, wherein the auxiliary electrode has a structure of a metal conductor composed of at least one mesh.
A plating apparatus according to any one of claims 1 to 3. 5. The plating apparatus according to claim 1, wherein the surface of the auxiliary electrode is supported by a noble metal powder or coated with a noble metal. 6. The plating apparatus according to claim 5, wherein the noble metal is selected from platinum, palladium, ruthenium, rhodium, iridium and gold. 7. The gas diffusion electrode is of a hydrogen gas diffusion type, and the gas is hydrogen.
7. The plating apparatus according to any one of 6. 8. The method according to claim 1, wherein an appropriate potential is applied to the auxiliary electrode, and a small current flows between the anode and the auxiliary electrode to promote a reduction reaction of hydrogen ions. The plating apparatus described in the above. 9. A plating method in which a metal film or an alloy film is obtained in an electroless or electrolytic manner from a hydrogen gas chamber provided outside the anode electrode by electrolytic deposition from an electrolytic solution between the cathode electrode and the anode electrode. 5. The plating method according to claim 1, wherein an auxiliary electrode is provided in the electrolytic solution along the anode electrode surface, and the electrolytic treatment is performed while collecting hydrogen gas generated in the electrolytic solution. 10. The plating method according to claim 9, wherein the auxiliary electrode is a mesh-shaped conductor. 11. The plating method according to claim 9, further comprising a recovery means for capturing generated hydrogen immediately above the auxiliary electrode. 12. The plating method according to claim 9, wherein the auxiliary electrode has a structure of a metal conductor composed of at least one mesh. 13. The plating method according to claim 9, wherein a surface of the auxiliary electrode carries a noble metal powder or is coated with a noble metal. 14. The plating method according to claim 13, wherein the noble metal is selected from platinum, palladium, ruthenium, rhodium, iridium, and gold. 15. The plating method according to claim 9, wherein the anode electrode is of a hydrogen gas diffusion type, and the gas is hydrogen. 16. The method according to claim 9, wherein an appropriate potential is applied to the auxiliary electrode, and a small current flows between the anode and the auxiliary electrode to promote a reduction reaction of hydrogen ions. The plating method described.