JP2015079913A - Method for manufacturing electrode foil for electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrode foil for an electrolytic capacitor capable of stably manufacturing the electrode foil having a high surface expansion rate.SOLUTION: A method for manufacturing an electrode foil for an electrolytic capacitor includes: a mother die preparation process S1 for preparing a mother die having projections arranged according to a predetermined pattern manufactured using electroforming; an oxide film creation process S3 for creating an oxide film on the surface of the electrode foil; a pattern transfer process S4 for depressing the projections of the mother die onto the surface of the electrode foil after the process S3 to form dimples to be etch pits; a remaining film removal process S5 for applying a voltage to the electrode foil after the process S4 in an electrolytic solution to remove the oxide film remaining in the dimples; and an etching process S 6 for etching the electrode foil after the process S5. In the process S5, a voltage at a level of destroying the oxide film remaining in the dimples is applied.

Description

  The present invention relates to a method for producing an electrode foil for an electrolytic capacitor.

  In an electrolytic capacitor, a wound electrode foil on which an oxide dielectric film is formed is used as an electrode. In order to realize a large-capacity electrolytic capacitor, a process such as etching for expanding the surface area (hereinafter referred to as “surface expansion process”) is generally performed in the manufacturing process of the electrode foil.

  As a conventional method for manufacturing an electrode foil including a surface expansion process, for example, in Patent Document 1, a matrix having protrusions is pressed against the surface of the electrode foil on which an oxide film is formed to form depressions that become etch pits on the surface. Is disclosed. According to this manufacturing method, since the position of the etch pit can be controlled with high accuracy, an electrode foil having a high surface expansion ratio can be obtained.

JP-A-11-74162

  However, in the above conventional manufacturing method, an oxide film may remain in all or part of the depression formed on the surface of the electrode foil. If the oxide film remains in the depression, the depression does not sufficiently function as an etching start point, and as a result, the surface of the electrode foil cannot be sufficiently expanded.

  This invention is made | formed in view of the said situation, The place made into the subject is providing the manufacturing method of the electrode foil for electrolytic capacitors which can manufacture the electrode foil which has a high surface expansion rate stably. It is in.

  In order to solve the above problems, a method for producing an electrode foil for an electrolytic capacitor according to the present invention includes (1) a mother that prepares a mother die having protrusions arranged in a predetermined pattern, which is produced using an electroforming method. A mold preparation process, (2) an oxide film generation process for generating an oxide film on the surface of the electrode foil, and (3) a mold protrusion is pressed against the surface of the electrode foil after the oxide film generation process, and an etch pit is formed on the surface. (4) a pattern transfer step for forming a dent, and (4) a residual film removal step for removing the oxide film remaining in the dent by applying a voltage to the aluminum foil after the pattern transfer step in the electrolyte solution; And an etching step of etching the electrode foil after the residual film removal step, and in the residual film removal step, a voltage that can destroy the oxide film remaining in the depression is applied.

  According to this configuration, the oxide film remaining in the depression can be removed by the residual film removal step performed before the etching step, so that the surface expansion ratio decreases according to the degree of remaining oxide film. Can be prevented. That is, according to this structure, all the dents can function sufficiently as etching starting points, and an electrode foil having a high surface expansion ratio can be stably manufactured.

  In the said manufacturing method, it is preferable to make the voltage applied in a residual film removal process larger than the withstand voltage of the oxide film which remains in a hollow. According to this configuration, the oxide film remaining in the depression can be reliably destroyed and removed.

  It is preferable that the manufacturing method further includes a surface polishing step for polishing the surface of the electrode foil, which is performed before the oxide film generation step. According to this structure, since the quality of the oxide film produced | generated in an oxide film production | generation process improves, the selectivity of the etching in an etching process can be improved.

  It is preferable that the said manufacturing method performs a residual film removal process and an etching process in the same electrolyte solution. According to this configuration, since the remaining film removing step and the etching step can be performed continuously, the time required for manufacturing can be shortened. Moreover, according to this structure, since two processes can be performed in one space, a manufacturing facility can also be saved.

  In the manufacturing method, the shape of the protrusion can be, for example, a cylindrical shape, a conical shape, a polygonal prism shape, a polygonal pyramid shape, or a hemispherical shape.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the electrode foil for electrolytic capacitors which can manufacture the electrode foil which has a high surface expansion rate stably can be provided.

It is a flowchart of the manufacturing method of the electrode foil for electrolytic capacitors which concerns on this invention. It is a schematic diagram which shows a mother die preparation process. It is the (A) top view and (B) sectional view of the mother die manufactured in the mother die preparation process. It is a schematic diagram which shows a surface grinding | polishing process. It is a schematic diagram which shows an oxide film production | generation process. It is a schematic diagram which shows a pattern transfer process. It is a photograph of the surface of the electrode foil after a pattern transfer process. It is a schematic diagram which shows a residual film removal process. It is a photograph of the surface of the electrode foil after a residual film removal process. It is the photograph of the surface of the electrode foil after a residual membrane | film | coat removal process, Comprising: (A) made the applied voltage too small, (B) made the applied voltage too large, (C) made the application time too long. It is a picture of the case. It is a schematic diagram which shows an etching process. It is a photograph of the surface of the electrode foil after an etching process. It is a schematic diagram which shows the modification of a mother die preparation process. It is the (A) top view and (B) sectional view of the mother mold manufactured in the modification of a mother mold preparation process.

  Hereinafter, an embodiment of a method for manufacturing an electrode foil for an electrolytic capacitor according to the present invention (hereinafter simply referred to as “manufacturing method”) will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the manufacturing method according to the present invention includes a master mold preparation step S1, a surface polishing step S2, an oxide film generation step S3, a pattern transfer step S4, a remaining film removal step S5, and an etching step S6. The master block preparation step S1 may be performed only once, and the master block preparation step S1 does not have to be performed every time the surface polishing step S2 and subsequent steps are performed.

[Mother mold preparation process]
In the mother die preparation step S1, a mother die 7 having protrusions arranged in a predetermined pattern, which is manufactured using an electroforming method, is prepared. In the manufacture of the mother die 7, first, the silicon substrate 1 such as a silicon wafer coated with the photoresist 2 is irradiated with the UV light 5 of the UV light source 4 through the photomask 3 (FIG. 2A), and the photoresist 2. Is patterned (FIG. (B)), anisotropic etching is performed on the silicon substrate 1 with the photoresist 2 thus obtained (FIG. (C)), and then the photoresist 2 is peeled from the silicon substrate 1 By doing so, the prototype 6 is created ((D) in the figure). Thereafter, nickel is electrodeposited on the master 6 by electroforming (FIG. (E)), and the master 6 is completed by removing the master 6 (FIG. (F)).

  The mother die 7 includes a main body 7a and a plurality of protrusions 7b having the same shape. As shown in FIG. 3A, the protrusions 7b are arranged in a predetermined pattern on one surface of the main body 7a. The distance between the vertices of the adjacent protrusions 7b is D (as an example, 2.5 μm), and the triangle T defined by the vertices of the three adjacent protrusions 7b is an equilateral triangle. As shown in FIG. 3B, the protrusion 7b has a quadrangular pyramid shape with a height of H (for example, 0.5 μm) and an apex angle of θ (for example, 70.6 °). have. Note that FIG. 3B is a cross-sectional view taken along line BB of the mother die 7 shown in FIG.

  In the present invention, the shape and arrangement pattern of the protrusions 7b are not particularly limited. For example, the shape of the protrusion 7b may be a conical shape, a polygonal pyramid shape including a triangular pyramid or a quadrangular pyramid, a cylindrical shape, a polygonal prism shape including a triangular prism or a quadrangular prism, or a hemispherical shape.

  In the present invention, the material of the mother die 7 is not particularly limited. Examples of materials that can replace nickel include nickel alloys such as gold, silver, copper, and nickel cobalt. The nickel alloy is suitable for increasing the hardness and wear durability of the mother die 7.

  The mother die 7 can be used many times in the pattern transfer step S4 described later. Therefore, it is not necessary to perform the matrix preparation step S1 every time the surface polishing step S2 and subsequent steps are performed. As a result of continued use, if the mother die 7 is worn out, the mother die preparing step S1 is performed again to prepare a new mother die 7.

[Surface polishing process]
In the surface polishing step S2, as shown in FIG. 4, from the surface of the electrode foil 10 prepared in advance, the oxide film 11 generated artificially by reaction with oxygen in the atmosphere, that is, managed. The non-uniform oxide film 11 generated under non-existing conditions is removed by polishing in order to perform pattern transfer more reliably. Specifically, mechanical polishing is performed so that the surface of the electrode foil 10 has an average roughness Ra <100 nm. This provides a flat surface that is not oxidized.

  The electrode foil 10 prepared in advance may be anything as long as it can be used as an electrode for an electrolytic capacitor. For example, in the present invention, a high-purity aluminum foil having a purity of 99.9% by weight or more and a thickness of 20 to 300 μm can be used.

  The polishing in the surface polishing step S2 is not limited to mechanical polishing, and may be chemical polishing, mechanical polishing (CMP), electrochemical polishing (electropolishing), or a combination thereof. Moreover, when sufficient flatness is acquired with the aluminum foil 10 before grinding | polishing, surface polishing process S2 can also be skipped. However, in this case, the quality of the oxide film 12 generated in the oxide film generation step S3 is deteriorated and the etching selectivity in the etching step S6 may be deteriorated, so care must be taken.

[Oxide film generation process]
In the oxide film generation step S3, as shown in FIG. 5, the oxide film 12 is artificially generated on the flat surface of the aluminum foil 10 that is not oxidized. Specifically, 5 V anodic oxidation (also referred to as electrochemical oxidation) is performed in an aqueous solution of ammonium adipate to produce an oxide film 12 having a thickness of 5.0 to 7.5 nm. The applied voltage and the thickness of the oxide film 12 are substantially proportional. By changing the applied voltage between 1 V and 20 V, the thickness of the oxide film 12 can be arbitrarily adjusted between 1.0 to 1.5 nm and 20.0 to 30.0 nm.

  In the present invention, the method for producing the oxide film 12 is not particularly limited. As a method for generating the oxide film 12 instead of anodization, there are, for example, air oxidation, thermal oxidation, and chemical oxidation with an oxidizing chemical.

[Pattern transfer process]
In the pattern transfer step S4, as shown in FIG. 6, the projection 7b of the mother die 7 manufactured by electroforming is pressed against the surface of the aluminum foil 10 covered with the oxide film 12, and the surface of the aluminum foil 10 is pressed. A plurality of depressions 10a to be etch pits are formed. For the pressing, it is preferable to use a pressing device that makes the in-plane pressure distribution uniform, that is, can press all the protrusions 7b against the aluminum foil 10 with the same pressure. In this invention, the press apparatus which employ | adopted the flat plate press system, the roll to flat plate press system, and the roll to roll press system can be used, for example.

  The pressing condition is determined experimentally. For example, when the shape, size, and arrangement of the protrusions 7b are as described above, and the thickness of the oxide film 12 is 5.0 to 7.5 nm, aluminum is pressed by pressing at a pressure of 150 MPa for 30 seconds. A recess 10a having substantially the same shape corresponding to the protrusion 7b can be formed on the entire surface of the foil 10. FIG. 7 is a surface photograph of the aluminum foil 10 in which the recess 10a is formed under these conditions.

[Residual film removal process]
As schematically shown in the lowermost drawing of FIG. 6, the oxide film 12 (residual oxide film 12 ′) remains in all or part of the recess 10 a formed by the pattern transfer step S <b> 4. May have. If the remaining oxide film 12 'exists in the depression 10a, the depression 10a does not function sufficiently as an etching start point. Therefore, in the present invention, the residual oxide film 12 ′ is removed by performing the residual film removal step S5 after the pattern transfer step S4.

  In the residual film removal step S5, the aluminum foil 10 with the residual oxide film 12 ′ is immersed in a predetermined electrolyte solution, and a voltage that can electrically destroy the residual oxide film 12 ′ is applied for a predetermined time, The remaining oxide film 12 ′ is removed (see FIG. 8). Specifically, a voltage of 5 to 50 V is applied for 1 msec to 1 sec in a solution containing chloride ions. By setting the applied voltage to be equal to or higher than the withstand voltage of the remaining oxide film 12 ', the remaining oxide film 12' can be reliably removed. The applied voltage profile (waveform) and application time may be determined experimentally. The reason why the solution containing chloride ions is used is to prevent the remaining oxide film 12 'from being repaired by anodic oxidation.

  FIG. 9 is a surface photograph of the aluminum foil 10 after the residual film removing step S5. The aluminum foil 10 shown in FIG. 9 seems to have a larger diameter of the recess 10a than the aluminum foil 10 shown in FIG. 7, but this removes unnecessary residual oxide film 12 ′. Because it was done.

  FIGS. 10A and 10B are surface photographs when the remaining film removal step S5 is performed with the applied voltage being too small (1 V) and too large (100 V). In FIG. 2A where the applied voltage is too small, the remaining oxide film 12 'is hardly removed. For this reason, FIG. 10A is very similar to FIG. On the other hand, in FIG. 5B in which the applied voltage is excessive, the remaining oxide film 12 'is removed, the recess 10a itself is cut, and adjacent recesses 10a are connected to each other. In this case, a high area expansion rate cannot be obtained.

  FIG. 10C is a surface photograph in the case where the remaining film removing step S5 is performed with the application time being excessive (10 seconds). In the figure, the dent 10a is enlarged by a large current that flows after the remaining oxide film 12 'is removed, and the entire surface has a crater shape. Also in this case, a high area expansion rate cannot be obtained.

  Thus, in the residual film removal step S5, the voltage is applied under such a condition that only the residual oxide film 12 ′ in the depression 10a is destroyed and the shape of the depression 10a itself and the oxide film 12 to be left are hardly affected. It is important to apply. In the present invention, applying a current to the aluminum foil 10 to generate a predetermined voltage is also included in “applying voltage”.

[Etching process]
In the etching step S6, the aluminum foil 10 from which the remaining oxide film 12 ′ has been removed is immersed in a predetermined electrolyte solution, and the recess 10a not covered with the oxide film 12 is etched (see FIG. 11). Specifically, as in the remaining film removing step S5, a predetermined voltage is applied in a solution containing chloride ions, and the depression 10a is dug by etching. Thereby, the hollow 10a becomes a deeper hollow 10b. As shown in the figure, portions other than the depression 10a (10b) are covered with the oxide film 12, and are not exposed to the electrolyte solution. For this reason, in the etching step S6, only the depression 10a (10b) is selectively etched.

  FIG. 12 is a photograph of the surface of the aluminum foil 10 after performing the etching step S6. This figure shows that only the depression 10a (10b) is selectively etched.

  The electrolyte solution used in the etching step S6 is preferably the same as the electrolyte solution used in the remaining film removal step S5, which is the previous step. In this way, it is possible to continuously perform the remaining film removing step S5 and the etching step S6 without an interval (interrupting the application of voltage), and the time required for manufacturing can be reduced. Two processes can be performed in the space, and the space for manufacturing equipment can be saved. Of course, the electrolyte solution used in the remaining film removing step S5 and the etching step S6 may be different. Further, an interval may be sandwiched between two processes performed in one space.

  As mentioned above, although embodiment of the manufacturing method of the electrode foil for electrolytic capacitors which concerns on this invention was described, this invention is not limited to the structure of embodiment, In the range which does not deviate from the meaning of this invention, various changes are carried out. It is possible to add.

  For example, the projection of the mother die may be a cylindrical shape as described above. In this case, the glass substrate 1 ′ coated with the photoresist 2 ′ is irradiated with the UV light 5 of the UV light source 4 through the photomask 3 (FIG. 13A), and the photoresist 2 ′ is patterned to form the original pattern. 6 'is created ((B) in the figure). Thereafter, nickel is electrodeposited on the original mold 6 ′ by electroforming (FIG. (C)), and the original mold 6 ′ is removed to complete a mother mold 7 ′ made of nickel (FIG. (D)). ).

  FIG. 14 shows an example of the mother die 7 'completed in this way. As shown in FIG. 5A, the protrusions 7b 'are arranged in a predetermined pattern on one surface of the main body 7a'. The distance between the upper surface centers of the adjacent protrusions 7b 'is D (as an example, 2.5 m), and the triangle T defined by the upper surface centers of the three adjacent protrusions 7b' is an equilateral triangle. Further, as shown in FIG. 7B, the protrusion 7b 'has a height H (as an example, 1.5 μm) and a diameter φ (as an example, 1.5 μm). Note that FIG. 14B is a cross-sectional view taken along line BB of the mother die 7 shown in FIG.

  Moreover, in the said embodiment, what was obtained by electrodepositing nickel to the prototype 6, 6 'was used as the mother die 7, 7', but the master mother obtained by electrodepositing nickel to the prototype 6, 6 ' A daughter mother mold may be obtained by further electrodepositing nickel on the mold, and pattern transfer may be performed using the daughter mother mold. According to this configuration, the prototypes 6 and 6 'can be made long lasting.

DESCRIPTION OF SYMBOLS 1 Silicon substrate 1 'Glass substrate 2, 2' Photoresist 3 Photomask 4 UV light source 5 UV light 6, 6 'Prototype 7, 7' Master mold 7a, 7a 'Main body 7b, 7b' Protrusion 10 Electrode foil (aluminum foil)
10a hollow 10b hollow 11 oxide film 12 oxide film 12 'residual oxide film

Claims (5)

A mother die preparing step for preparing a mother die having protrusions arranged in a predetermined pattern, manufactured using an electroforming method,
An oxide film generation step for generating an oxide film on the surface of the electrode foil;
A pattern transfer step of pressing the protrusions of the matrix on the surface of the electrode foil after the oxide film generation step, and forming depressions to be etch pits on the surface;
A voltage is applied to the electrode foil after the pattern transfer step in the electrolyte solution, and the remaining film removing step of removing the oxide film remaining in the depressions;
An etching step of etching the electrode foil after the residual film removing step;
The manufacturing method of the electrode foil for electrolytic capacitors characterized by including this.   The method for producing an electrode foil for an electrolytic capacitor according to claim 1, wherein a voltage applied in the remaining film removing step is made larger than a withstand voltage of the oxide film remaining in the depression.   The method for producing an electrode foil for an electrolytic capacitor according to claim 1 or 2, further comprising a surface polishing step for polishing the surface of the electrode foil, which is performed before the oxide film generation step.   The method for producing an electrode foil for an electrolytic capacitor according to any one of claims 1 to 3, wherein the remaining film removing step and the etching step are performed in the same electrolyte solution.   The method for producing an electrode foil for an electrolytic capacitor according to any one of claims 1 to 4, wherein the shape of the protrusion is a cylindrical shape, a conical shape, a polygonal prism shape, a polygonal pyramid shape, or a hemispherical shape. .