KR20030013046A - Anode-Cathode-Agitator Combined Type Electrodeposition Apparatus - Google Patents

Abstract

PURPOSE: An integral type electroplating apparatus is provided which has superior mobility as a simple and micro electroplating apparatus by integrally constructing the anode, cathode and agitator and driving the agitator using a motor, enables plating treatment even in a small space and small plating solution, and obtains plating layer of superior properties by maximization of agitation effect. CONSTITUTION: In an electroplating apparatus which is installed in an electrolytic cell(31) to perform electroplating, the integral type electroplating apparatus comprises a cylindrical housing(30); a driving means that is mounted on the inner part of the housing to generate rotational driving force; an agitator that is rotated by the driving means to agitate an electrolyte(32) inside the electrolytic cell; an anode(21) which is extended by vertically penetrating the housing, the lower part of which is dipped into the electrolyte, and to the upper part of which a (+) terminal(23a) of plating D.C current is connected; and a cathode(22) which is extended by vertically penetrating the housing with the cathode being spaced apart from the anode in a certain distance, the lower part of which is dipped into the electrolyte, and to the upper part of which a (-) terminal(23b) of plating D.C current is connected. The integral type electroplating apparatus comprises a cylindrical housing(30); a driving means that is mounted on the inner part of the housing to generate rotational driving force; a cathode(22) which is physically removably connected to a rotational shaft(25a) of the driving means to agitate an electrolyte(32) inside the electrolytic cell(31), and to the upper part of which a (-) terminal(23b) of plating D.C current is electrically connected through the rotational shaft and the housing; and an anode(21) which is extended by vertically penetrating the housing, which is dipped into the electrolyte with the anode being formed in a cylindrical structure so that the lower part of the anode encircles the cathode, and to the upper part of which a (+) terminal(23a) of plating D.C current is connected.

Description

Anode-Cathode-Agitator Combined Type Electrodeposition Apparatus}

The present invention relates to a positive electrode-cathode-stirrer integrated electroplating apparatus, and in particular, the positive electrode-cathode-stirrer is integrated into a single body, simple and ultra-portable, excellent in mobility, plating is possible in a small space and a small plating solution, stirring effect It relates to an integrated electroplating apparatus that can obtain a plated layer of excellent properties according to the maximization of.

The conventional electroplating apparatus has a problem in that a large space is secured because separation of the anode and the cathode and installation of an additional stirring device are required.

Conventional electroplating apparatuses include a batch plating method and a barrel plating method (J.-P. Celis, M. De Bonte and JR Roos, Trans. IMF, 72 (2)). , 1994, 89-93). The principle of the electroplating method is also applied to the continuous production line.

First, the batch plating method is generally the most used technique. In this method, the positive electrode 1 and the negative electrode 2 are respectively installed in the electrolytic solution (or plating solution or plating bath) 10 in the electrolytic cell 11 as shown in FIG. It is a method of electrodepositing the desired plating layer 9 on the surface of the cathode 2 by flowing to an anode.

This method has a problem in that the surface properties and the plated layer properties vary depending on the stirring method (depending on the stirring method). In addition, agitation apparatus must be additionally installed and nonuniformity of agitation effect is the biggest problem. The physical properties of the plating layer vary depending on the stirring method, and it is difficult to find a suitable stirring device. Since the stirring apparatus must be additionally installed, the apparatus becomes complicated and there is a problem that the size of the plating apparatus is enlarged.

The barrel plating method is a method of stirring by rotating the cathode itself. This method has a structure in which the anode 1 is formed in a cylindrical shape as shown in Fig. 2, and a cathode 2, which is rotationally driven, is embedded therein.

This method can improve the plating efficiency, but there is a problem that the material to be plated is present inside the cylindrical anode 1 so that the replacement of the plated body is more cumbersome than other devices, and the shape of the plated body is limited. Receive. In addition, there is a problem in that the concentration gradient of the electrolyte is not generated because the flow of the electrolyte 10 is not active inside and outside the anode (1).

In addition, there is a limit in structurally miniaturization in the barrel plating method, so that it is difficult to move to a desired place and install it in a narrow space, and the consumption of the plating liquid (electrolyte) is relatively large and applied to a plated body having various shapes. There is a problem that it is difficult.

All of the above electroplating methods are technologies developed for mass production and have a structure in which anode / cathode / stirrers are separated from each other. Not suitable as a device.

Accordingly, the present invention has been made in view of the problems of the prior art, and its first object is an integrated electroplating apparatus which is simple and ultra-compact and has excellent mobility as a monolithic-cathode-stirrer as an integrated type, and is capable of plating even in a small space. To provide.

The second object of the present invention is to provide an electroplating apparatus capable of electroplating with an electrolyte much smaller than the absolute amount of the electrolyte required for the conventional electroplating apparatus by implementing the overall size in a very small size.

The third object of the present invention is to agitate the electrolyte while rotating the cathode and the cathode and the anode itself at a high speed, so the concentration gradient of the electrolyte does not occur, so that the roughness of the surface of the plating layer is uniform and dense, thereby obtaining a plating layer having excellent bonding strength between the substrate and the plating layer. To provide an integrated electroplating apparatus that can be.

A fourth object of the present invention is to provide an integrated electroplating apparatus which can achieve a plating layer having excellent physical properties by maximizing the stirring effect by sufficient stirring under the control of the stirring speed and the method of the electrolyte solution.

A fifth object of the present invention is to provide an electroplating apparatus capable of plating a plated body having various shapes by being located at an open position of the cathode.

1 is a schematic cross-sectional view of an electroplating apparatus according to a conventional batch plating method,

2 is a schematic cross-sectional view of an electroplating apparatus according to a conventional barrel plating method;

3A and 3B are schematic perspective views showing an installation state thereof and a schematic perspective view of an electroplating apparatus using a stirring rod according to a first embodiment of the present invention;

4 is a schematic perspective view showing an electroplating apparatus incorporating a battery while using a stirring rod according to a second embodiment of the present invention;

5 is a schematic perspective view showing an electroplating apparatus using a cathode type stirrer according to a third embodiment of the present invention;

6 is a schematic perspective view showing an electroplating apparatus incorporating a battery while using a cathode stirrer according to a fourth embodiment of the present invention;

7 is a schematic perspective view showing an electroplating apparatus using a positive and negative simultaneous stirring type stirrer according to a fifth embodiment of the present invention;

8 is a schematic perspective view showing an electroplating apparatus incorporating a battery while using a positive and negative asynchronous stirring mixers according to a sixth embodiment of the present invention;

9A and 9B are ATM images showing the surface and cross-sectional properties of 100% Ni coating film specimens obtained using a conventional electroplating apparatus,

10A and 10B are ATM images showing the surface and cross-sectional properties of 100% Ni coating film specimens obtained using the electroplating apparatus according to the present invention;

11 is an enlarged photograph of a metal microscope of a side of a prior art specimen for comparing the correlation between the substrate and the plated layer and the thickness difference of the plated layer,

12 is an enlarged photograph of a metal microscope of a side of a specimen of the present invention for comparing the correlation between the substrate and the plated layer and the thickness difference of the plated layer,

13 is a 100 pole figure of a prior art specimen using an X-ray diffractometer to know the internal structure of the plating layer,

14 is a 100-pole diagram of the specimen of the present invention using an X-ray diffractometer to know the internal structure of the plating layer.

* Explanation of Signs of Major Parts of Drawings *

21,21a, 21b; Anodes 22, 22a and 22b; cathode

23; Current supply device 24; Stirring Rod

25; Motor 25a; Axis of rotation

26; Speed regulating devices 27; Power supply

28; Battery 29; Exchange chuck

30; Housing 31; Electrolyzer

32; Electrolyte solution 33; Vertical frame

33a; Horizontal frame 33b; clamp

34; Base

In order to achieve the above object, the present invention is an electroplating apparatus installed in the electrolytic cell to perform electroplating, the cylindrical housing, the drive means mounted to the inside of the housing to generate a rotational drive force, by the drive means A stirrer for rotating and agitating the electrolyte in the electrolytic cell, an anode extending through the housing up and down, the lower end being immersed in the electrolyte, and having a positive terminal connected to a positive terminal of a plating DC current at an upper end thereof; It provides an integrated electroplating apparatus, characterized in that it extends through the housing up and down at a certain distance, the lower end is immersed in the electrolyte, and the negative end is connected to the upper end of the plating DC current.

According to another feature of the invention, the present invention is an electroplating apparatus installed in the electrolytic cell to perform the electroplating, the cylindrical housing, the drive means mounted to the inside of the housing to generate a rotational drive force, the rotating shaft of the drive means It is physically detachably coupled to the agitator and agitates the electrolyte solution in the electrolytic cell, and electrically extends to the upper end through the rotating shaft and the housing to connect the negative terminal of the DC current for plating and the housing up and down. It provides a one-piece electroplating apparatus, characterized in that formed in a cylindrical structure so as to extend through and the lower end to surround the negative electrode is immersed in the electrolyte, the positive electrode is connected to the upper end of the plating DC current.

According to still another aspect of the present invention, the present invention provides an electroplating apparatus installed in an electrolytic cell to perform electroplating, comprising: a cylindrical housing, driving means mounted inside the housing to generate a rotational driving force, and the driving means. A positively coupled to the rotating shaft physically detachable and agitating the electrolyte in the electrolytic cell and electrically extending to the upper end through the rotating shaft and the housing to connect the positive terminal of the DC current for plating, and the rotating shaft of the driving means. The negative electrode coupled to the physically detachably coupled to the electrolytic solution and electrically extending to the upper end through the rotating shaft and the housing while being electrically connected to the negative terminal of the DC current for plating, and the lower end of the positive electrode and the negative electrode. Is characterized in that the support means for supporting the housing to be immersed into the electrolyte solution Provide a body electroplating apparatus.

The anode is made of a soluble material to be plated or an insoluble material coated with IrO ₂ on Ti, and the cathode is made of a conductive material.

The rotatable cathode is made of a conductive wire or plate, the stirrer is preferably insoluble in the electrolyte solution and composed of a stirring rod made of a plastic material.

In addition, the device of the present invention, the chuck for supporting the detachable stirrer or the cathode and the anode having a stirring function supported on the front end of the rotating shaft, and the built-in upper portion of the housing the operating power supply of the drive means and the DC current for plating It further comprises a power supply for supplying a speed control device for controlling the stirring amount of the electrolyte by controlling the rotational speed of the rotating means of the drive means is mounted to the housing.

The present invention may also include a separate power supply for supplying the operating power of the driving means and the DC current for plating, instead of the integrated power supply.

Further, the anode is preferably made of a cylindrical mesh structure so that the cathode inside.

As described above, in the present invention, the anode-cathode-stirrer is integrally formed to provide a simple, ultra-portable, excellent mobility, and can be processed even in a small space and a small electrolyte, and a plating layer having excellent physical properties can be obtained by maximizing the stirring effect.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

3a and 3b is a perspective view showing a schematic perspective view of the electroplating apparatus using a stirring rod according to the first embodiment of the present invention and its installation state, Figure 4 is a stirring rod according to a second embodiment of the present invention A schematic perspective view showing an electroplating apparatus incorporating a battery while in use.

First, referring to FIGS. 3A and 3B, the electroplating apparatus of the first embodiment includes a motor 25, which is used to rotationally drive the stirring bar 24 in the middle of the cylindrical housing 30, of the motor 25. The rotating shaft 25a is equipped with an exchange chuck 29 for detachably supporting a stirring rod 24 made of a relatively light material, for example, a plastic material, which is insoluble in the electrolyte solution 32.

In the electroplating apparatus, as shown in FIG. 3B, the front end penetrates the housing 30 up and down, respectively, and the front end part is immersed into the electrolyte solution 32 of the electrolytic cell 31, and a current supply device for supplying the DC current for plating to the rear end part ( The positive electrode 21 and the negative electrode 22 to which the positive and negative terminals 23a and 23b of 23 are connected are arranged at a predetermined distance.

When the soluble electrode is used, the anode 21 uses a material to be plated or an insoluble material coated with IrO ₂ (iridium oxide) on Ti (titanium), and a conductive material or a conductive wire plated on the cathode 22 is used. do. The distance between the positive electrode and the negative electrode 21, 22 and the distance between the stirring bar 24 can be set in the range of 10mm-100mm.

The electroplating apparatus also includes a speed regulating device 26 for controlling the rotational speed of the motor 25 that drives the stirring rod 24 to rotate for proper agitation of the electrolyte solution 32 at the rear end of the housing 30. It includes a power supply device 27 for supplying an operating power for this.

In this case, as shown in FIG. 4, the power supply device 27 may also include a battery 28 integrally formed at the rear end of the housing 30 as necessary.

In addition, the plating current supply device 23 may be configured to supply a DC current uniformly by rectifying the AC power supply with a built-in rectifier or using a DC or a battery.

In the electroplating apparatus, as shown in FIG. 3B, the electrolytic cell 31 is installed on the base 34 and the upper end is fixed to the clamp 33b of the horizontal frame 33a extending horizontally from the top of the vertical frame 33.

In the first and second embodiments configured as described above, while stirring the electrolyte solution 32 by adjusting the rotation speed of the stirring rod 24, that is, the motor 25, in the range of 1,000 to 15,000 RPM by the speed adjusting device 26, Plating is performed after the current density of the current supply device 23 is appropriately hung in proportion to the plated body (sample).

In the present invention, as shown, the positive electrode 21, the negative electrode 22, and the stirring bar 24 and the motor 25 are integrally formed, and the distance between the positive electrode 21 and the negative electrode 22 is in the range of 10 mm to 100 mm. It is possible to set to, it is possible to constitute an electroplating device excellent in ultra-portable, as a result electroplating can be made using a small electrolyte in a small electrolytic cell.

In this case, the plated body to be fixed to the cathode 22 using, for example, tongs, etc. is rotated by the motor 25 to the stirring rod 24 at an appropriate rotational speed, the electrolyte solution 32 evenly to the plated body. Since the concentration gradient of the electrolyte is not generated, the surface roughness of the plating layer can be obtained homogeneously.

In addition, when driving the motor 5 according to the second embodiment, the agitation of the electrolyte may be performed using the built-in battery 28 without using the power supply device 27 as in the first embodiment.

Meanwhile, referring to FIGS. 5 and 6, FIG. 5 is an electroplating apparatus using a cathodic agitator according to a third embodiment of the present invention, and FIG. 6 is a cathodic agitator according to a fourth embodiment of the present invention. A schematic perspective view showing an electroplating apparatus incorporating a battery.

As shown in the electroplating apparatus of the third and fourth embodiments, the anode 21a is manufactured in a cylindrical shape using, for example, an insoluble material coated with IrO ₂ (iridium oxide) on Ti (titanium), and a cathode. (22a) is made of a conductive wire or plate in the center of the cylindrical anode (21a) and the rear end is detachably coupled to the exchange chuck 29 that can receive the rotational force of the motor 25 to form a rotatable structure. .

In this case, the cathode 22a is physically coupled to the exchange chuck 29 and electrically connected when coupled to the exchange chuck 29, and passes through an insulated structure inside / outside the rotating shaft 25a. It forms a structure connected to the negative terminal (23b) of the current supply device (23).

The structure of the anode 21a is preferably a mesh structure so that the cathode 22a on which the plated body is supported is located therein so that the cathode 22a can be observed.

The third and fourth embodiments are the same as those of the first and second embodiments except for the structures of the positive electrode 21a and the negative electrode 22a when compared with the first and second embodiments, and thus the same members. The numbers are given and the description is omitted. The difference between the third and fourth embodiments is that the power supply device 27 or the built-in battery 28 is employed to drive the motor 25.

In the third and fourth embodiments, as in the first and second embodiments, the cathode 22a is rotated by the motor 25 without using a separate stirrer to stir the electrolyte solution 32.

When the electroplating is performed using the electroplating apparatus of the third and fourth embodiments described above, as shown in FIG. 3B, the housing is formed so that the positive electrode 21a and the negative electrode 32a are immersed in the electrolyte solution 32 of the electrolytic cell 31. It consists of the state which supported 30. In this case, since the cathode 22a on which the plated body is supported is rotated while being positioned inside the cylindrical anode 21a, the concentration gradient of the electrolyte solution does not occur as in the above embodiment, and the distance and current distribution between the anode and the cathode. Becomes relatively constant, and uniform electrodeposition of the plating layer can be attained.

Figure 7 is an electroplating apparatus using a positive and negative simultaneous stirring type stirrer according to a fifth embodiment of the present invention, Figure 8 is built-in battery while using a positive and negative simultaneous stirring type stirrer according to a sixth embodiment of the present invention A schematic perspective view showing one electroplating apparatus.

As shown, the electroplating apparatus of the fifth and sixth embodiments respectively attaches the positive electrode 21b and the negative electrode 22b to the exchange chuck 29 so that the positive electrode 21b and the negative electrode 22b itself are detachable. Is rotated to stir the electrolyte solution 32.

For this purpose, the anode 21b is made of, for example, an insoluble material coated with IrO ₂ (iridium oxide) on Ti (titanium), and the cathode 22a is made of a conductive material, and its shape is made of wire or It is made of a plate material, each rear end is detachably coupled to the exchange chuck 29 that can receive the rotational force of the motor 25 to form a rotatable structure. The distance between the positive electrode 21b and the negative electrode 22b can be set in the range of 1mm-100mm.

In this case, the positive electrode 21b and the negative electrode 22b are each physically coupled to the exchange chuck 29 and are electrically connected to each other and pass through an insulated structure inside / outside the rotating shaft 25a to supply the current supply device 23. It forms a structure connected to the (+) and (-) terminals (23a, 23b) of.

The fifth embodiment is an example of using the power supply 27 when driving the motor 25, the sixth embodiment is an electroplating by using the built-in battery 28, instead of the power supply 27 It is a structure that can be implemented.

In the electroplating apparatus of the fifth and sixth embodiments, the agitation of the electrolyte solution 32 may be sufficiently performed by the simultaneous rotation of the positive electrode 21b and the negative electrode 22b, similarly to the first to fourth embodiments. As a result, it is transmitted to each part of the plated body without concentration gradient so that the plating layer obtains uniform surface roughness.

The above-described electroplating apparatus of the first to sixth embodiments is provided with a stirrer which rotates at a high speed inside the apparatus to perform powerful stirring, and to greatly reduce the size of the apparatus compared to the conventional structure, and the structure is greatly simplified. There is. In addition, it can be operated as a battery instead of a power supply, so if a small rectifier (power supply) is used, it can be easily electroplated anywhere in the plating solution.

In the above embodiment, as the motor of the electroplating apparatus has a cylindrical structure, the overall apparatus including the housing also has a cylindrical shape, but is not limited thereto and may be modified into other shapes.

In addition, the plating current supply device 23 and the motor drive power supply 27 may be configured as a single power supply according to the needs of those skilled in the art.

The present invention described above has an integrated structure suitable for miniaturization, but if it is configured to be large in size, it is also possible to apply as an electroplating device for medium and mass production.

(Example)

In order to confirm the electroplating performance of the electroplating apparatus of the present invention described above, electroplating was carried out under the same conditions as described below with the conventional apparatus of FIG.

Electrolyte is used to prepare 100% Ni, using nickel chloride as the main component, with current density of 10A / dm ² , pH of electrolyte 4.0 and electrolyte temperature of 55 ℃. The thickness of the plating layer was prepared to be about 7 μm.

Under the same conditions, the results of observing the surface characteristics of the specimen prepared by the conventional apparatus and the apparatus of the present invention with AFM (Atomic Force Microscope) are the same as those of FIGS.

9A, 9B, 10A, and 10B are ATM images showing the surface and cross-sectional characteristics of 100% Ni-coated film specimens obtained using the electroplating apparatus according to the prior art and the present invention, respectively, and the electroplating apparatus according to the present invention. When using, the surface roughness of the coating film was much more homogeneous and excellent plating layer could be obtained.

In addition, the side of the specimen was observed using a metal microscope to compare the correlation between the substrate and the plating layer and the thickness difference of the plating layer. The observation result is the same as FIG. 11 and FIG. Referring to FIG. 11, it was observed that the plating layer was peeled off by friction with the polishing machine in the process of polishing the surface. However, peeling of the plating layer did not appear in the specimen (FIG. 12) experimented with the apparatus of the present invention.

In order to know the internal structure of the plating layer, the results of experiments using an X-ray diffractometer are shown in FIGS. 13 and 14. FIG. 13 is a 100 pole figure of a specimen prepared by the conventional apparatus, and FIG. 14 is a 100 pole figure of the specimen prepared by the apparatus of the present invention. Comparing the pole strength at 100 poles of these two specimens it can be seen that the specimen produced by the device of the present invention is stronger. This is judged to be much stronger because the plated layer of the specimen produced by the present invention is densely electrodeposited.

Based on the above experimental results, the following results were obtained.

1) The thickness of the plating layer was about 1 탆 thicker in the conventional apparatus.

2) The surface characteristics were observed by AFM, and the surface of specimen prepared by the present invention was much more homogeneous.

3) As a result of observing the side microstructure of the bonding force between the substrate and the plated layer, the specimen prepared by the device of the present invention was better.

4) X-ray diffraction analysis shows that the plating layer of the specimen prepared by the present invention is much denser.

As described above, in the present invention, the anode-cathode-stirrer is integrally formed to provide a simple, ultra-portable, excellent mobility, and can be processed even in a small space and a small electrolyte, and a plating layer having excellent physical properties can be obtained by maximizing the stirring effect.

In the above, the present invention has been illustrated and described with reference to specific preferred embodiments, but the present invention is not limited to the above-described embodiments and is not limited to the spirit of the present invention. Various changes and modifications can be made by those who have

Claims (12)

In the electroplating apparatus installed in the electrolytic cell to perform electroplating, Cylindrical housing, Driving means mounted inside the housing to generate a rotational driving force; A stirrer rotated by the driving means to stir the electrolyte in the electrolytic cell; An anode extending through the housing up and down and having a lower end immersed in the electrolyte solution and having a positive terminal connected to a positive terminal of a DC current for plating; Integral electroplating apparatus, characterized in that consisting of a cathode which extends through the housing up and down at a certain distance from the anode and the lower end is immersed in the electrolyte, the negative terminal of the plating DC current is connected to the upper end. In the electroplating apparatus installed in the electrolytic cell to perform electroplating, Cylindrical housing, Driving means mounted inside the housing to generate a rotational driving force; A negative electrode which is physically detachably coupled to the rotating shaft of the driving means and agitates the electrolyte solution in the electrolytic cell and is electrically extended to the upper end through the rotating shaft and the housing to which the (-) terminal of the plating DC current is connected; An integrated electric machine comprising: a positive electrode which extends through the housing up and down and is formed in a cylindrical structure so that the lower end surrounds the negative electrode and is immersed in the electrolyte, and the positive terminal of the plating DC current is connected to the upper end thereof. Plating equipment. In the electroplating apparatus installed in the electrolytic cell to perform electroplating, Cylindrical housing, Driving means mounted inside the housing to generate a rotational driving force; A positive electrode which is physically detachably coupled to the rotating shaft of the driving means and agitates the electrolyte in the electrolytic cell and is electrically extended to the upper end through the rotating shaft and the housing to connect the positive terminal of the DC current for plating; It is physically detachably coupled to the rotating shaft of the driving means and agitates the electrolyte in the electrolytic cell and electrically extends to the upper end through the rotating shaft and the housing, and is composed of a negative electrode connected to the (-) terminal of the DC current for plating. Integral electroplating apparatus, characterized in that. The electroplating apparatus according to any one of claims 1 to 3, wherein the anode is made of a soluble material to be plated or an insoluble material coated with IrO ₂ on Ti, and the cathode is made of a conductive material. 4. The integrated electroplating apparatus of claim 2 or 3, wherein the cathode is made of a wire or a plate with conductivity. 2. The integrated electroplating apparatus of claim 1, wherein the stirrer is insoluble in the electrolyte and is composed of a stirring rod made of a plastic material. The integrated electric machine according to any one of claims 1 to 3, wherein the distal end of the rotary shaft further includes an stirrer or an exchange chuck for detachably supporting a cathode and an anode having a stirring function supported thereon. Plating equipment. The integrated electroplating apparatus according to any one of claims 1 to 3, further comprising a power supply device embedded in an upper portion of the housing for supplying an operating power of a driving means and a DC current for plating. . 9. The integrated electroplating apparatus of claim 8, further comprising a speed adjusting device mounted on the housing to control a rotational speed of the driving means about the rotational axis of the driving means to adjust the stirring amount of the electrolyte. 4. The integrated electroplating apparatus according to any one of claims 1 to 3, further comprising a separate power supply for supplying the operating power of the driving means and the DC current for plating. 3. The integrated electroplating apparatus of claim 2, wherein the anode has a cylindrical mesh structure. The integrated electroplating apparatus according to any one of claims 1 to 3, further comprising supporting means for supporting the housing such that the lower ends of the positive electrode and the negative electrode are immersed into the electrolyte solution.