JP2010114297A - Multilayer porous electrode foil and method of manufacturing the same, and multilayer solid-state electrolytic capacitor using multilayer porous electrode foil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide multilayer porous electrode foil suitable for efficient production of a multilayer solid-state electrolytic capacitor which is compact, large in capacity, low in ESR (Equivalent Series Resistance) and thin and to provide a method of manufacturing the same, and to provide the multilayer solid-state electrolytic capacitor using the multilayer porous electrode foil. <P>SOLUTION: Tantalum foil or niobium foil is used as a base (1), and tantalum or niobium and a different-phase component which is not phase-soluble with it are mixed to form a film. A laminate (7) is formed by bringing a plurality of filmed bases (1) and spacers (3) sandwiched between the bases (1) into contact with one another, and after the tantalum or niobium and different-phase component are subjected to grain-growth through a vacuum heat treatment of the laminate, the different-phase component and spacers (3) are selectively etched. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrode foil of an electrolytic capacitor using tantalum or niobium, in particular, a multilayer porous electrode foil suitable as an electrode foil of a multilayer solid electrolytic capacitor constituted by laminating a plurality of electrode foils, and the production thereof The present invention also relates to a method and a multilayer solid electrolytic capacitor using the multilayer porous electrode foil.

  Along with the downsizing and higher functionality of electronic devices, the processing speed of CPUs has increased year by year, and the operating clock frequency has reached several GHz. In order to cope with higher speeds, decoupling capacitors around the CPU are strongly required to have low ESR (equivalent series resistance), low ESL (equivalent series inductance), and small size and large capacity (high ripple current). It has become. In addition, with the thinning of cellular phones and notebook computers, the demand for thinning capacitors has been increasing.

  As a capacitor satisfying such requirements, a solid electrolytic capacitor in which tantalum, niobium or aluminum having a large surface area is used as an anode body, a dielectric is formed on the surface thereof by anodic oxidation, and a conductive polymer is formed as a cathode. It is used by taking advantage of each feature.

  From the viewpoint of increasing the capacitance and reducing the ESR of the solid electrolytic capacitor, it is effective to stack and electrically connect thin solid electrolytic capacitor elements.

  Usually, in an aluminum electrolytic capacitor, an etched aluminum foil whose surface area is expanded by AC etching is used as an anode and a cathode. A conventional aluminum electrolytic capacitor is a wound cylindrical type in which a separator is sandwiched between an anode foil and a cathode foil, and it is difficult to reduce the thickness in terms of manufacturing method.

  On the other hand, in recent years, multilayer aluminum capacitors have been developed and marketed, in which an etched aluminum foil is anodized, and a cathode made of a conductive polymer is formed thereon to form a capacitor element, and a plurality of the obtained capacitor elements are laminated. Has been. Since the etched aluminum foil is as thin as about 100 μm, it is possible to produce a thin capacitor even if capacitor elements are stacked. However, since aluminum has a lower dielectric constant than tantalum and niobium, even in a laminated aluminum capacitor in which electrode foils are laminated, the capacitance per volume of the capacitor is smaller than that of a tantalum capacitor or niobium capacitor.

  On the other hand, in a solid electrolytic capacitor using tantalum or niobium, a porous pellet obtained by compacting powder together with a lead wire and sintering at high vacuum is generally used as an anode body. Since tantalum and niobium have a dielectric constant higher than that of aluminum and use the surface area of a porous material using submicron fine powder, the capacitance per volume is very large. On the other hand, there is a limit to reducing the thickness of the porous pellet due to the manufacturing method called powder sintering, and there is a limit to reducing the height of the capacitor using this. Therefore, when such porous pellets are stacked, the thickness of the capacitor is increased.

  To solve these technical problems, a thin film consisting of tantalum or niobium and a heterogeneous component incompatible with tantalum or niobium is formed on the substrate as a method for obtaining a porous body other than powder sintering. The inventors have proposed that after heat treatment and grain growth, the heterogeneous phase components are dissolved and removed to form a porous layer of tantalum or niobium (for example, Patent Document 1). reference). According to this method, since the fine pores are uniformly distributed, the electrolyte is more easily penetrated, and a porous layer that can be thinned can be obtained, the capacitor element is laminated on the conventional porous pellet. Thus, it is possible to reduce the height of the capacitor.

  However, in order to obtain such a multilayer capacitor, usually, an electrode foil is cut out to form an anode element, and the obtained anode element is individually anodized to form a cathode layer (conductive polymer layer, graphite layer, or Ag). After the layer is formed, the capacitor elements (anode portions and cathode portions) are electrically and mechanically connected to each other by welding to the lead frame, conductive adhesive, or the like.

  In the process of making such capacitor elements individually and laminating and joining them, manufacturing efficiency is reduced, and in the process of laminating and joining capacitor elements, stress is applied to the capacitor elements from the outside, and leakage current is reduced. There is a problem that the yield is reduced, for example, an increase.

  With respect to such problems, it is conceivable to laminate a plurality of electrode foils into an anode body for the purpose of efficiently producing a capacitor. For example, Patent Document 2 describes a laminated electrode foil in which aluminum foils are laminated, punched, and connected by welding lead frames.

  However, even when such a laminated electrode foil structure is applied to a solid electrolytic capacitor using tantalum or niobium, there is no sufficient gap between the laminated electrode foils, and the contact between the electrode foils makes the anodic oxidation uniform to the inside. It becomes difficult to carry out, resulting in a decrease in capacitance and an increase in leakage current. Further, in the subsequent cathode forming step, it is difficult to uniformly form the cathode up to the inside of the electrode foil.

Thus, although solid electrolytic capacitors using tantalum and niobium are small and large in capacity, there are still technical problems in thinning and stacking, and there are technical problems in terms of capacitor productivity. is there.
JP 2008-217161 A JP 61-30020 JP

  The present invention has been made to solve such problems, and is suitable for efficiently producing a multilayer solid electrolytic capacitor having a small size, a large capacity, a low ESR, and a thin shape. Another object of the present invention is to provide a laminated porous electrode foil, a method for producing the same, and a laminated solid electrolytic capacitor using the laminated porous electrode foil.

  The multilayer porous electrode foil according to the present invention is obtained by laminating a plurality of porous electrode foils each having a porous layer made of tantalum, niobium, tantalum alloy or niobium alloy on a base material. A gap is provided between the porous electrode foils, and the porous electrodes are electrically connected to each other.

  More specifically, the base material has unformed portions where the porous layer is not formed, the unformed portions are welded to each other, and the laminated porous electrodes are electrically connected to each other Is done. Alternatively, the base material is composed of at least two portions where the porous layer is formed and an unformed portion between the adjacent formed portions, and the center portion of the unformed portion is folded and laminated. Yes. The substrate is preferably made of tantalum, niobium, a tantalum alloy or a niobium alloy.

  The gap is preferably 10 μm or more and 500 μm or less.

  On the other hand, in the method for producing a laminated porous electrode foil according to the present invention, a foil is prepared by mixing tantalum, niobium, a tantalum alloy or a niobium alloy and a heterophasic component incompatible with these on a substrate. Forming and laminating the foils in a state where the spacers are sandwiched between the film forming parts of the plurality of foils, and welding the non-film forming parts of the foils together to form a laminate. After the grain growth of tantalum, niobium, tantalum alloy or niobium alloy and the different phase component by heat treatment, the different phase component and the spacer are selectively removed by etching.

  Alternatively, tantalum, niobium, a tantalum alloy or a niobium alloy and a heterophasic component incompatible with these are mixed to form a double-row film forming unit on the substrate, and the adjacent film forming unit Folding the center of the undeposited part between them, with the spacers sandwiched between the film-deposited parts, the foils are pressure-bonded to form a laminate, and vacuum heat-treated to form tantalum and niobium In addition, the tantalum alloy or niobium alloy and the heterogeneous phase component are grown, and then the heterophasic component and the spacer are selectively removed by etching.

  It is preferable that the thickness of the spacer is 10 μm or more and 500 μm or less.

  When the vacuum heat treatment is performed, it is preferable to perform the vacuum heat treatment while pressurizing the laminate.

  Moreover, it is preferable that the heterogeneous component is copper and the spacer is a copper foil.

  The multilayer solid electrolytic capacitor according to the present invention uses the multilayer porous electrode foil according to the present invention.

  Since the laminated porous electrode foil of the present invention uses tantalum, niobium, tantalum alloy or niobium alloy, the capacitance of the electrolytic capacitor can be increased as compared with the etched aluminum foil. The laminated electrode foils are connected with a gap between the electrode foils. For this reason, it is possible to perform anodic oxidation uniformly to the inside of the electrode foil in the laminated state, and it is possible to appropriately form the cathode to the inside of the electrode. Therefore, a multilayer solid electrolytic capacitor having excellent capacitor characteristics can be manufactured extremely efficiently.

  The inventors of the present invention have dramatically improved the electrostatic capacity by using a laminated porous electrode foil in which a plurality of porous electrode foils made of tantalum or niobium are laminated and connected to an anode of a solid electrolytic capacitor. And the present invention was completed by finding that a solid electrolytic capacitor can be produced efficiently.

  In the laminated porous electrode foil of the present invention, a plurality of porous electrode foils in which a porous layer made of tantalum, niobium, tantalum alloy or niobium alloy is formed on a substrate are laminated and connected. Since tantalum or niobium is used, the capacitance per volume can be increased as compared with the case of using an aluminum foil. The laminated porous electrode foils are electrically connected to each other, and a gap is formed between the porous electrode foils. For this reason, it is possible to uniformly anodize the inside of the porous electrode foil in a laminated state and subsequently form a cathode to obtain a capacitor element. Therefore, a multilayer solid electrolytic capacitor having excellent capacitor characteristics can be efficiently manufactured as compared with a conventional method in which capacitor elements are individually manufactured and stacked and connected.

  The gap provided between the laminated porous electrode foils may be at least about 5 μm or more, but is preferably a gap of 10 μm or more. This is because a conductive polymer serving as a cathode is efficiently formed inside the porous electrode foil. Normally, in solid electrolytic capacitors using conductive polymers, after the porous electrode foil is anodized, polypyrrole, polythiophene, etc. are impregnated and polymerized inside. It is difficult to form the conductive polymer cathode layer inside the porous electrode foil, and it is necessary to repeat the impregnation polymerization a plurality of times. When the conductive polymer cathode layer formed at one time is thin, the conductive polymer layer can be formed relatively uniformly up to the inside of the porous electrode foil, but the production efficiency is lowered. On the other hand, if the conductive polymer cathode layer formed at one time is thick, the conductive polymer layer cannot be formed uniformly to the inside of the porous electrode foil, and capacitors such as capacitance, loss, and ESR can be formed. It is not possible to satisfy these characteristics. Even when the gap between the porous electrode foils is less than 10 μm, it is possible to form the conductive polymer cathode layer to the inside by thinning the conductive polymer cathode layer formed at one time. By having the above gap, the conductive polymer cathode layer can be easily impregnated.

  On the other hand, the gap is preferably 500 μm or less. Even if the gap is larger than 500 μm, the capacitor manufacturing process is not affected. However, if the gap is increased, the thickness of the laminated electrode foil increases, which is not preferable from the viewpoint of reducing the thickness of the capacitor.

  Although the case where a conductive polymer is used as the cathode has been described here, the same applies to the case where manganese dioxide is formed as the cathode.

  Some tantalum alloys and niobium alloys are added with a trace amount of an element that improves leakage current, thermal stability, and the like of an anodized film serving as a dielectric of an electrolytic capacitor. Specific examples of the additive element include trace metal elements such as W, Zr, Ti, Hf, and Al, and dopants such as P, N, and B that are added in a small amount in a conventional tantalum pellet. In addition, tantalum-niobium alloys exhibit intermediate characteristics according to the composition ratio of tantalum and niobium, and are obviously included in these alloys.

  The substrate is preferably a tantalum foil or a niobium foil, but an aluminum foil can also be used. The tantalum foil or niobium foil is used because it forms an oxide film exhibiting excellent insulating properties by anodic oxidation.

  In one aspect of the method for producing a laminated porous electrode foil of the present invention, [1] a tantalum, niobium, tantalum alloy or niobium alloy and a heterogeneous component incompatible with these are formed on a substrate. Forming a foil, and [2] pressure-bonding the foils in a state where a spacer is sandwiched between the film-forming portions of the plurality of foils, and welding the non-film-forming portions of the foil A step of forming a laminated body, [3] a step of growing grains of tantalum, niobium, a tantalum alloy or a niobium alloy and a different phase component by vacuum heat treatment, and [4] a step of selectively etching the different phase component and the spacer. And divided.

  Hereinafter, each step will be described in detail. In the following, the case where a porous layer made of tantalum is formed on a tantalum foil as a base material will be described, but the same applies to the case where other materials and combinations thereof are used for the base material and the porous layer. 1 to 4 are a perspective view and a cross-sectional view showing a flow of a method for producing a laminated porous electrode foil according to one embodiment of the present invention.

[1] A step of forming a foil by mixing tantalum, niobium, a tantalum alloy or a niobium alloy and a heterophasic component incompatible with these on the base material. First, a tantalum foil is formed on the base material (1, 11). ) And a heterogeneous component not mixed with tantalum to form a foil including a film-forming part (5, 15) and a non-film-forming part (6, 16). Various methods can be considered as a method of forming a mixed film, but it is preferable to use a simultaneous sputtering or simultaneous vapor deposition method of tantalum and a different phase component. In these thin film formation processes, a thin film is formed by a substance flying at the atomic or cluster level adhering to the substrate. Therefore, a thin film in which tantalum and a different phase component are finely mixed in nano order can be easily obtained with good reproducibility, which is preferable.

  The film thickness at the time of film formation can be arbitrarily adjusted in consideration of the thickness and surface area of the porous layer to be obtained, that is, the target capacitance. In the case of the same film formation conditions, the actual surface area relative to the film formation area increases in proportion to the film thickness, so that a larger capacitance can be obtained by increasing the film thickness.

  It is desirable that the heterogeneous component mixed with tantalum is in a range of 30 to 70% by volume. In order to selectively remove the heterogeneous component and obtain a porous layer made of tantalum, the heterophasic component and tantalum must be structurally connected to each other. If the heterogeneous component is less than 30% by volume, the structural linkage of the heterogeneous component is deteriorated, and the subsequent selective etching process does not remove the heterogenous component, resulting in a porous structure having a large surface area. . On the other hand, if the heterogeneous component exceeds 70% by volume, the structural connection of tantalum is deteriorated and the strength of the obtained porous structure is weakened. However, this is only a guide, and does not limit the amount of the heterophasic component added. Depending on the degree of orientation of the film, which differs depending on the film forming method, and the design of the porous layer, an addition amount outside this range may be employed.

  The composition ratio between tantalum and the different phase component during film formation is determined in consideration of the porosity of the finally obtained porous layer. In the present invention, since the heterogeneous component that can be selectively removed is used, the heterophasic component does not remain in the finally obtained porous layer. Therefore, a porous electrode foil having a higher porosity can be obtained as the number of different phase components increases. The heterogeneous component is selected from a metal component that does not substantially dissolve in tantalum, an oxide that is thermodynamically stable against tantalum, and the like. As the metal component, an alkaline earth metal such as magnesium or calcium, or a metal such as copper or silver can be used. However, it is preferable to use copper as the heterogeneous component because of economy and ease of film formation and selective etching.

[2] A process of forming a laminate by pressing the foils together with the spacers interposed between the film forming parts of the plurality of foils and welding the non-film forming parts of the foils. The base film (1, 11) is aligned with the film forming part (5, 15) and the non-film forming part (6, 16), and a spacer ( 3 and 13), and the foils are laminated by pressure bonding.

  In this case, in order to join the laminated base materials (1, 11) to each other electrically and mechanically, the base materials are welded at the non-film-forming portions (6, 16). As a welding method, various methods such as electron beam welding, laser beam welding, and resistance welding can be considered, but resistance welding is preferable from the viewpoint of simplicity of operation.

  The timing of lamination may be considered after film formation, heat treatment, or after selective etching by heat treatment to obtain a porous electrode foil. However, handling in a porous state is not preferable because it may damage the porous structure due to friction between the foils and external stress.

  In addition, there is no uniform gap between the laminated foils, and when a part of the porous layer comes into contact, the anodic oxidation cannot be uniformly performed to the inside, or in the subsequent cathode formation process, the conductive polymer It becomes difficult to form the layer to the inside, and the capacitor characteristics are deteriorated.

  The spacers (3, 13) in the present invention play a role of ensuring a gap between the porous electrode foils finally obtained by heat treatment and pickling. As the spacers (3, 13), those having a uniform thickness, smoothness, substantially not dissolved in tantalum, and can be selectively etched can be used. Specifically, magnesium foil, copper foil, silver foil, or the like can be used, but it is preferable to use copper foil from the viewpoints of economy and that smooth foils of various thicknesses can be easily obtained. . When stacking and heat treatment are performed without the spacers (3, 13), gaps between the electrode foils are not uniform, waviness is caused by the heat treatment, and conversely, sintering of the stacked tantalum proceeds. Therefore, it is not preferable because the heterogeneous component is trapped between the base materials and cannot be removed.

  The thickness of the copper foil used for the spacers (3, 13) can be appropriately set between 10 μm and 500 μm according to the gap between the porous electrode foils. When a copper foil is sandwiched between the spacers (3, 13) and the copper foil and the tantalum-copper mixed film are in close contact with each other, a vacuum heat treatment is performed, and sintering proceeds between the copper and the copper foil of the mixed film. Since copper and copper foil are completely removed by selective etching, a uniform gap corresponding to the thickness of the copper foil is finally formed between the porous electrode foils by such a method. In addition, by changing the thickness of the copper foil, a gap is formed in the finally obtained multilayer porous electrode foil without causing a significant increase in thickness and according to the capacitor manufacturing process. be able to.

[3] Step of growing tantalum or niobium and heterogeneous components by vacuum heat treatment Each of the laminates (7, 17) obtained in the second step is heat-treated in a vacuum to obtain tantalum and heterophasic components as grains. Grow. By grain growth, each of tantalum and the different phase component is structurally connected, and by removing the different phase component, a porous layer having a stable structure can be obtained. In this laminate, if there is a gap between the spacer and the mixed film made of tantalum-copper, the gap between the finally obtained porous electrode foils becomes thicker than designed. Further, when the laminate is heat treated as it is, undulation may occur. In order to avoid these, it is preferable to perform vacuum heat treatment while pressurizing the laminated body, and it is effective to perform vacuum heat treatment while applying pressure by a vacuum hot press or the like.

[4] Step of selectively removing heterogeneous components and spacers The heterophasic components and spacers are selectively removed by etching. Before the etching, it is preferable that the laminated body (7, 17) is cut into a target shape and then the laminated body (8, 18) after the cutting is etched. This is to prevent the gap between the foils from being affected during the cutting process.

  Since tantalum has corrosion resistance, various acids and alkalis can be used. When copper is used as the heterogeneous component and copper foil is used as the spacer, a solution of ferric chloride or cupric chloride can be used in addition to nitric acid and hydrogen peroxide. The heterogeneous phase component is selectively removed by etching, then washed with water and dried to obtain the laminated porous electrode foil (9, 19) of the present invention.

  FIG. 5 is a perspective view and a cross-sectional view showing the flow of the method for manufacturing a laminated porous electrode foil according to another aspect of the present invention.

  Also in this embodiment, a tantalum, niobium, tantalum alloy or niobium alloy and a heterophasic component incompatible with these are mixed and formed on the base material (21) to form a double-layered foil. More specifically, as shown in FIG. 5, a film forming part (25) in which films are formed on both sides is formed, and a non-film forming part (26) is formed between the film forming parts (25). This aspect is generally applied to the production of a two-layer porous electrode foil, but it is possible to have three or more layers within the allowable range of the design of the solid electrolytic capacitor. May be further laminated and electrically connected to each other to obtain a multilayer porous electrode foil.

  Thereafter, as shown in FIG. 5, the non-film-formation part (26) of the base material (21) is folded back with the spacer (23) interposed therebetween, and the film-formation parts (25) of the foil are aligned and pressure-bonded. Thereby, a laminated body is formed. In this case, since the base material (21) is continuous and the upper and lower foils are electrically connected to each other, a welding step is not necessary.

  The subsequent steps of vacuum heat treatment and selective etching are the same as those described above.

  In addition to these, various lamination methods and bonding methods are conceivable, but a final lamination method and bonding method suitable for the shape and number of laminations of the target electrode foil can be selected.

  Since the laminated porous electrode foil (9, 19, 29) obtained as described above uses tantalum or niobium, the capacitance of the electrolytic capacitor can be increased compared to the etched aluminum foil. it can. The laminated porous electrode foils are joined together, and there is a gap between the porous electrode foils. For this reason, it is possible to obtain a capacitor element by uniformly anodizing the inside of the porous electrode foil in the laminated state and subsequently forming the cathode. Therefore, a multilayer solid electrolytic capacitor can be efficiently manufactured as compared with a conventional method in which capacitor elements are individually manufactured and stacked and connected.

  Hereinafter, the present invention will be described in detail by way of examples.

Example 1
3 and 4 are a perspective view and a cross-sectional view showing the flow of the manufacturing method of the laminated porous electrode foil of this example.

  As a sputtering target, a tantalum target having a purity of 99.99% and a copper target (both manufactured by High Purity Chemical Co., Ltd.) and a tantalum foil having a width of 50 mm, a length of 110 mm, and a thickness of 50 μm as a substrate (11) (Tokyo Electrolytic Co., Ltd.) And a tantalum target and a copper target are simultaneously sputtered at a predetermined input power ratio in an Ar atmosphere of 1.0 Pa, using a multi-source sputtering apparatus (manufactured by ULVAC, Inc., SBH-2206RDE). The film-forming part (15) which consists of Ta-60vol% Cu was formed into a film in thickness of 10 micrometers. At the time of film formation, a metal mask (not shown) is attached to one surface of the base material (11), and a film forming portion (15) having a width of 10 mm extending in the longitudinal direction of the base material (11) and an unformed film having a width of 5 mm. A film forming pattern in which the portions (16) are alternately arranged was formed. Thereafter, the base material (11) was turned over, and a film forming portion (15) made of Ta-60 vol% Cu was formed to a thickness of 10 μm with the same film formation pattern on the other surface, and both sides were formed into a film. Material (11) was obtained. A single substrate (11) is formed with three rows of film forming portions (15) extending in a row in the longitudinal direction.

  Rolled copper having a width of 10 mm, a length of 110 mm, and a thickness of 18 μm so that only the film forming part (15) of the base material (11) is in close contact with each of the four base materials (11) having both surfaces formed. Three foils (made by Sumitomo Metal Mining Shindoh Co., Ltd.) (13) were aligned and placed, and these were pressed and laminated.

  Then, the non-film-forming parts (16) were joined together by welding with a storage type resistance welding machine (manufactured by Nippon Avionics Co., Ltd., NRW100A / NT-100A) to form a laminate (17).

The obtained laminate (17) is sandwiched between copper plates (not shown) having a thickness of 50 mm, and the atmosphere is 3.0 × 10 ⁻³ Pa or less in a vacuum hot press apparatus (manufactured by Daia Vacuum Co., Ltd.) Heat treatment was performed under the conditions of 0.49 MPa (5 kgf / cm ² ) and 715 ° C. × 1 hr. When the thickness of the laminate (17) after the heat treatment was measured with a caliper, it was 0.4 mm, and no large warp was observed.

  The heat-treated laminate (17) was cut into a strip of 13 × 10 mm so as to include a 10 mm square film forming part (15) and a 3 mm wide non-film forming part (16). Thereafter, it was poured into 2.3 mol / L nitric acid for 2 hours to dissolve the copper foil and copper, washed with water, and dried to obtain a laminated porous electrode foil (19).

  As a result of chemical analysis of the obtained laminated porous electrode foil (19), it was confirmed that the amount of remaining copper was 0.1% by mass or less, and almost all of the copper foil and copper were removed. It was done.

  In addition, a niobium wire (manufactured by Tokyo Electrolytic Co., Ltd.) having a diameter of 0.3 mm was resistance-welded to the non-deposited portion (16) of the obtained laminated porous electrode foil (19), and phosphoric acid at 80 ° C. and 0.6 vol% In an aqueous solution, a chemical conversion treatment was performed at 10 V for 6 hours to form an anodized film on the surface. Thereafter, the sample was immersed in a 30% by mass sulfuric acid aqueous solution, and the capacitance was 120 Hz, 1.5 VDC, 1.0 Vrms using an LCR meter (manufactured by Agilent Technologies, 4263B) with a platinum foil electrode with platinum black as a counter electrode. Was measured. Further, using an ultrahigh resistance / microammeter (manufactured by Advantest, R8340), 7 V was applied and the leakage current after 5 minutes was measured. The measured leakage current (nA) was divided by the capacitance (μF) and the applied voltage (Vm) at the time of leakage current measurement to obtain LC (nA / μFVm). The measurement results are shown in Table 1.

(Example 2)
In FIG. 5, the flow of the manufacturing method of the lamination type porous electrode foil of a present Example is shown with a perspective view and sectional drawing.

In the same manner as in Example 1, after obtaining a base material (21) having a film forming part (25) made of Ta-60 vol% Cu having a thickness of 10 μm and on both surfaces, a film forming part (25) having a width of 10 mm. Two rows were cut out so as to include an undeposited portion (26) having a width of 5 mm therebetween. Thereafter, one rolled copper foil (manufactured by Sumitomo Metal Mining Shindoh Co., Ltd.) (23) having a width of 10 mm, a length of 110 mm, and a thickness of 18 μm is aligned so that both sides of the film forming part (25) are in close contact with each other. It was folded and pinched. Then, it hand-pressed by the surface pressure of 0.98 MPa (10 kgf / cm < ² >), and the laminated body (27) was formed.

  The obtained laminate (27) was vacuum heat-treated under the same conditions as in Example 1. When the thickness of the laminate (27) after the heat treatment was measured with a caliper, it was 0.2 mm, and no large warp was observed. After the heat-treated laminate (27) was cut out to a width of 10 mm and formed into a strip of 12.5 × 10 mm, it was pickled, washed with water and dried in the same manner as in Example 1 to obtain a laminated porous electrode. A foil (29) was obtained.

  The obtained laminated porous electrode foil (29) was anodized in the same manner as in Example 1, and the capacitance and leakage current were measured. The results are shown in Table 1.

(Example 3)
3 and 4 are a perspective view and a cross-sectional view showing the flow of the manufacturing method of the laminated porous electrode foil of this example.

  Niobium target having a purity of 99.9% (manufactured by Tokyo Electrolytic Co., Ltd.) as a sputtering target and a copper target having a purity of 99.99% (manufactured by Koyo Chemical Co., Ltd.) and a substrate (11) having a width of 50 mm and a length of 110 mm A niobium target having a predetermined input power ratio in a 1.0 Pa Ar atmosphere using a multi-layer sputtering apparatus (SBH-2206RDE, manufactured by ULVAC, Inc.) with a 50 μm thick niobium foil (manufactured by Tokyo Electrolytic Co., Ltd.) And a copper target were simultaneously sputtered to form a film forming part (15) made of Nb-60 vol% Cu on the base material (11) with a thickness of 10 μm. At the time of film formation, a metal mask (not shown) is attached to one surface of the base material (11), and a film forming portion (15) having a width of 10 mm extending in the longitudinal direction of the base material (11) and an unformed film having a width of 5 mm. A film forming pattern in which the portions (16) are alternately arranged was formed. Thereafter, the base material (11) was turned over, and the film formation part (15) made of Nb-60 vol% Cu was formed in a thickness of 10 μm with the same film formation pattern on the other surface, and both sides were formed into a film. Material (11) was obtained.

  Rolled copper having a width of 10 mm, a length of 110 mm, and a thickness of 18 μm so that only the film forming part (15) of the base material (11) is in close contact with each of the four base materials (11) having both surfaces formed. It laminated | stacked by aligning and arrange | positioning three foil (made by Sumitomo Metal Mining Shindoh Co., Ltd.) (13). Then, the non-film-forming parts (16) were joined together by welding with a storage type resistance welding machine (manufactured by Nippon Avionics Co., Ltd., NRW100A / NT-100A) to form a laminate (17).

The obtained laminate (17) is sandwiched between copper plates (not shown) having a thickness of 50 mm, and the atmosphere is 3.0 × 10 ⁻³ Pa or less in a vacuum hot press apparatus (manufactured by Daia Vacuum Co., Ltd.) Heat treatment was performed under the conditions of 0.49 MPa (5 kgf / cm ² ) and 715 ° C. × 1 hr. When the thickness of the laminate (17) after the heat treatment was measured with a caliper, it was 0.4 mm, and no large warp was observed. The heat-treated laminate (17) was cut into a strip of 13 × 10 mm so as to include a 10 mm square film forming part (15) and a 3 mm wide non-film forming part (16). Thereafter, it was poured into 2.3 mol / L nitric acid for 2 hours to dissolve the copper foil and copper, washed with water, and dried to obtain a laminated porous electrode foil (19).

  As a result of chemical analysis of the obtained laminated porous electrode foil (19), it was confirmed that the amount of remaining copper was 0.1% by mass or less, and almost all of the copper foil and copper were removed. It was done.

  Then, it anodized similarly to Example 1 and measured the electrostatic capacitance and the leakage current. The results are shown in Table 1.

(Comparative Example 1)
In FIG. 6, the flow of the manufacturing method of the single layer porous electrode foil of this comparative example is shown with a perspective view.

In the same manner as in Example 1, after obtaining a base material (31) having a film-forming part (35) made of Ta-60 vol% Cu having a thickness of 10 μm and having both surfaces formed, A heat treatment of 715 ° C. × 1 hr was performed at × 10 ⁻³ Pa or less.

  After the heat treatment, the film was cut into a strip of 13 × 10 mm so as to include a 10 mm square film forming part (35) and a 3 mm wide non-film forming part (36). Then, it was poured into 2.3 mol / L nitric acid for 2 hours to dissolve copper, washed with water, and dried to obtain a single layer porous electrode foil (38).

  Then, it anodized similarly to Example 1 and measured the electrostatic capacitance and the leakage current. The results are shown in Table 1.

(Comparative Example 2)
In FIG. 6, the flow of the manufacturing method of the single layer porous electrode foil of this comparative example is shown with a perspective view.

In the same manner as in Example 3, after obtaining a base material (31) having a film forming part (35) made of Nb-60 vol% Cu having a thickness of 10 μm and having both surfaces formed, it was subjected to 3.0 in a high-temperature vacuum furnace. A heat treatment of 715 ° C. × 1 hr was performed at × 10 ⁻³ Pa or less.

  After the heat treatment, the film was cut into a strip of 13 × 10 mm so as to include a 10 mm square film forming part (35) and a 3 mm wide non-film forming part (36). Then, it was poured into 2.3 mol / L nitric acid for 2 hours to dissolve copper, washed with water, and dried to obtain a single layer porous electrode foil (38).

  Then, it anodized similarly to Example 1 and measured the electrostatic capacitance and the leakage current. The results are shown in Table 1.

(Comparative Example 3)
In FIG. 7, the flow of the manufacturing method of the lamination type porous electrode foil of this comparative example is shown with a perspective view.

In the same manner as in Example 1, after obtaining a base material (41) having a film forming portion (45) made of Ta-60 vol% Cu having a thickness of 10 μm and both surfaces formed, a film forming portion (45) having a width of 10 mm. Two rows were cut out so as to include an undeposited portion (46) having a width of 5 mm therebetween. Thereafter, the laminate was folded back and hand pressed at a surface pressure of 0.98 MPa (10 kgf / cm ² ) to form a laminate (47).

  The obtained laminate (47) was vacuum heat-treated under the same conditions as in Example 1. The laminate (47) after the heat treatment was cut out with a width of 10 mm to form a strip of 12.5 × 10 mm, and then pickled, washed with water and dried in the same manner as in Example 1.

  As a result of chemical analysis of the obtained sample (49), the amount of copper remaining was 2.1% by mass. When calculated backward from the amount of copper deposited by sputtering, about 30% of the copper deposited by sputtering was dissolved. It was found that they could not be removed and remained between the electrode foils. Therefore, in this comparative example, it was not possible to produce a laminated porous electrode foil.

(Comparative Example 4)
In FIG. 8, the flow of the manufacturing method of the laminated porous electrode foil of this comparative example is shown with a perspective view.

  Four single layer porous electrode foils (38) obtained in Comparative Example 1 were laminated. Thereafter, the non-film-formed portions (36) were joined together by welding with a storage resistance welding machine (NRW 100A / NT-100A, manufactured by Nippon Avionics Co., Ltd.) to form a laminated porous electrode foil (39). It was 0.35 mm when the thickness of the obtained laminated porous electrode foil (39) was measured with calipers.

  The obtained laminated porous electrode foil (39) was anodized in the same manner as in Example 1, and the capacitance and leakage current were measured. The results are shown in Table 1.

(Comparative Example 5)
An AC-etched aluminum foil consisting of a base material having a thickness of about 30 μm and an etching layer having a thickness of about 40 μm on each side of the base material and having an overall thickness of 110 μm was cut out to 10 × 10 mm.

  A 0.3 mm niobium wire (manufactured by Tokyo Electrolytic Co., Ltd.) was resistance-welded to this, and subjected to a chemical conversion treatment at 80 ° C. in an aqueous ammonium borate solution having a conductivity of 5 mS / cm for 10 V for 6 hours. Formed. Thereafter, the sample was immersed in a 30% by mass sulfuric acid aqueous solution, and the capacitance was 120 Hz, 1.5 VDC, 1.0 Vrms using an LCR meter (manufactured by Agilent Technologies, 4263B) with a platinum foil electrode with platinum black as a counter electrode. Was measured. The measurement results are shown in Table 1.

(Comparative Example 6)
4 sheets of AC-etched aluminum foil each having a total thickness of 110 μm, which is composed of a base material having a thickness of about 30 μm and an etching layer having a thickness of about 40 μm on both sides of the base material. It joined by resistance welding and cut out to 10x10 mm. It was 0.5 mm when the thickness of the obtained laminated body was measured with calipers.

A 0.3 mm niobium wire (manufactured by Tokyo Electrolytic Co., Ltd.) was resistance-welded to this, and subjected to a chemical conversion treatment at 80 ° C. in an aqueous ammonium borate solution having a conductivity of 5 mS / cm for 10 V for 6 hours. Formed. Thereafter, it was immersed in a 30% by mass sulfuric acid aqueous solution at 30 ° C., and a platinum foil electrode with platinum black was used as a counter electrode, using an LCR meter (manufactured by Agilent Technologies, 4263B) under the conditions of 120 Hz, DC 1.5 V, 1.0 Vrms Capacitance was measured. The measurement results are shown in Table 1.

  The laminated porous electrode foils of Examples 1 to 3 of the present invention use tantalum and niobium as materials, and have a large capacity per electrode area and a large capacity per electrode volume. Further, when the laminated porous electrode foils of Examples 1 to 3 and the single-layer porous electrode foils of Comparative Examples 1 and 2 were compared, the capacity per electrode area was almost proportional to the number of laminated layers, and leakage The current values are almost the same. Therefore, it can be seen that the expected characteristics are obtained when the single-layer electrode foils are laminated. This indicates that there is a uniform gap between the porous electrode foils, and uniform anodic oxidation is performed to the inside of the laminated porous electrode foils.

  On the other hand, in Comparative Example 3 in which no spacer was used, the laminated porous electrode foil could not be obtained without completely melting the copper foil.

  Further, in Comparative Example 4 laminated after being made porous, the capacity per electrode area expected from the number of laminated layers is small, and the leakage current is also large. This is because the porous electrode foils are in contact with each other because they are made porous, so that the anodization is not uniformly performed to the inside, rubbing of handling, A possible cause is that the porous layer was damaged by external stress during welding.

  Since the comparative example 5 is an aluminum foil single layer, the capacity | capacitance per electrode area and the capacity | capacitance per electrode volume are small. In Comparative Example 6, as in Comparative Example 4, the capacity expected from the number of layers was not obtained. This is considered for the same reason as in Comparative Example 4.

  As described above, since the laminated porous electrode foil of the present invention uses tantalum or niobium, the capacitance of the electrolytic capacitor can be increased as compared with the etched aluminum foil. In addition, since the laminated porous electrode foils are joined together and there is a gap between the porous electrode foils, it can be uniformly anodized to the inside of the porous electrode foil in the laminated state, and the cathode It can be formed into a capacitor element. Therefore, a multilayer solid electrolytic capacitor can be efficiently manufactured as compared with a conventional method in which capacitor elements are individually manufactured, stacked, and connected.

It is a flow which shows one Example of the manufacturing method of the lamination type porous electrode foil of this invention with a perspective view. It is a flow which shows one Example of the manufacturing method of the lamination type porous electrode foil of this invention with sectional drawing. It is a flow which shows the manufacturing method of the laminated porous electrode foil of Example 1, 3 with a perspective view. It is a flow which shows the manufacturing method of the laminated porous electrode foil of Example 1, 3 with a perspective view. It is a flow which shows the manufacturing method of the laminated porous electrode foil of Example 2 with a perspective view and sectional drawing. It is a flow which shows the manufacturing method of the single layer porous electrode foil of the comparative examples 1 and 2 with a perspective view. It is a flow which shows the manufacturing method of the laminated porous electrode foil of the comparative example 3 with a perspective view. It is a flow which shows the manufacturing method of the laminated porous electrode foil of the comparative example 4 with a perspective view.

Explanation of symbols

1, 11, 21, 31, 41 Base material 3, 13, 23, 43 Copper foil 4, 14 Welded part 5, 15, 25, 35, 45 Film forming part 6, 16, 26, 36, 46 Non-film forming part 7 , 17, 27, 47 Laminated body 8, 18, 28 Laminated body 9, 19, 29, 39 Laminated porous electrode foil 38 Single-layer porous electrode foil 48, 49 Sample

Claims (11)

  A plurality of porous electrode foils on which a porous layer made of tantalum, niobium, tantalum alloy or niobium alloy is formed are laminated on a base material, and a gap is provided between the porous electrode foils, A laminated porous electrode foil in which the porous electrodes are electrically connected to each other.   The laminated porous electrode foil according to claim 1, wherein the base material has an unformed portion where the porous layer is not formed, and the unformed portions are welded to each other.   The base material is composed of at least two portions where the porous layer is formed and an unformed portion between the adjacent formed portions, and the center portion of the unformed portion is folded and laminated. The laminated porous electrode foil according to claim 1.   The laminated porous electrode foil according to any one of claims 1 to 3, wherein the substrate is made of tantalum, niobium, a tantalum alloy, or a niobium alloy.   The laminated porous electrode foil according to any one of claims 1 to 4, wherein the gap is 10 µm or more and 500 µm or less.   On the base material, tantalum, niobium, tantalum alloy or niobium alloy, and a heterophasic component incompatible with these are mixed to form a foil, and a spacer is formed between the film forming portions of the plurality of foils. In a sandwiched state, the foils are pressure-bonded, and the non-film-formed portions of the foils are welded together to form a laminate, and vacuum heat treatment to produce tantalum, niobium, a tantalum alloy or a niobium alloy and a different phase component. Each of the above-mentioned heterophasic component and the spacer is selectively removed by etching after each of the above-mentioned grains is grown.   On the base material, tantalum, niobium, tantalum alloy or niobium alloy and a heterogeneous component incompatible with these are mixed to form a foil, and no film is formed between the adjacent film forming portions of the foil. Tungsten, niobium, and tantalum alloy by folding the center part of the part and pressing the foils together in a state in which the spacers are sandwiched between the film forming parts of the foil to form a laminate and vacuum heat treatment Alternatively, a method for producing a laminated porous electrode foil, in which after the grain growth of a niobium alloy and a heterogeneous component, respectively, the heterophasic component and the spacer are selectively removed by etching.   The method for producing a laminated porous electrode foil according to claim 6 or 7, wherein the spacer has a thickness of 10 µm or more and 500 µm or less.   The method for producing a laminated porous electrode foil according to any one of claims 6 to 8, wherein when the vacuum heat treatment is performed, the laminate is subjected to a vacuum heat treatment while being pressurized.   The method for producing a laminated porous electrode foil according to any one of claims 6 to 9, wherein the heterogeneous component is copper, and the spacer is a copper foil.   A multilayer solid electrolytic capacitor using the multilayer porous electrode foil according to any one of claims 1 to 5.

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