JP2003059777A - METHOD FOR MAKING SOUND AMORPHOUS Nb OXIDE FILM AND METHOD FOR PRODUCING Nb SOLID ELECTROLYTIC CAPACITOR - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sound amorphous Nb oxide film having a heat resistance sufficient as a capacitor and to provide an inexpensive lightweight Nd solid electrolytic capacitor exhibiting a performance similar to that of a Ta solid electrolytic capacitor through the same structure of the same shape. SOLUTION: The method for producing a solid electrolytic capacitor comprises a step for removing Nb gas phase oxides or impurities from the surface of an Nb porous body by chemical cleaning prior to formation, a step for forming a dielectric film of amorphous Nb oxide on the surface of the Nb porous body by formation, a step for detecting a defect by thermally cracking a defective part of the dielectric film, a step for removing the defective part by chemical cleaning, and a step for repairing the defective part by formation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for improving the quality of an amorphous Nb oxide film formed on a Nb metal surface, and more particularly to a method for manufacturing an Nb solid electrolytic capacitor.

[0002]

2. Description of the Related Art A solid electrolytic capacitor has an anode-dielectric-
It has a structure of a cathode, and generally has a structure in which an oxide film is formed as a dielectric layer on the surface layer of a metal having valve action as an anode (valve action metal), and a solid electrolyte layer is formed thereon as a cathode. Has become. Here, the valve action metal is a metal capable of forming an oxide film whose thickness can be controlled by anodic oxidation, and includes Nb, Al, Ta, Ti and H.
It refers to f, Zr, etc., but in reality, two of Al and Ta are mainly used. Of these, for Al, an etching foil is often used as an anode, and Ta is powder-sintered to form a porous body, which is used as an anode. Among the solid electrolytic capacitors, the porous sintered body type electrolytic capacitor can be made particularly small and large in capacity, so that there is a strong demand as a component that meets the needs for downsizing such as mobile phones and information terminal devices.

However, since Ta, which is currently used as a metal for a porous sintered body type electrolytic capacitor, is expensive, the unit price of the Ta solid electrolytic capacitor is high and the adoption of the Ta solid electrolytic capacitor is not widespread. This is because the reserves of Ta are small, and the annual supply is also small, so that the balance between supply and demand is unstable. Since it is unlikely that the price of Ta will be improved in the future, a material for a porous solid electrolytic capacitor which replaces Ta is required. One of the candidates is T for solid electrolytic capacitors.
Nb is said to exhibit the same performance as a, and its reserves are 100 times more than Ta, which is very large, so it is inexpensive,
Since it is distributed and produced all over the world, stable supply is possible. Furthermore, since the specific gravity of Nb is as small as about 1/2 that of Ta, it is possible to further reduce the weight, and it is expected that Nb solid electrolytic capacitors will become the mainstream in the future.

The standard manufacturing process of the Nb solid electrolytic capacitor will be described below with reference to FIG. (1) Formation of Nb Porous Body Nb powder formulation A binder is added to and mixed with Nb powder in order to improve press moldability. Press and sinter Insert the element lead wire of the anode into the Nb mixed powder,
Press-mold into a cylindrical shape. Then, the press-formed product was subjected to 1000 to 1400 in high vacuum (10 ⁻⁴ Pa or less).
Sintering is performed by heating at 0 ° C. to form a Nb porous body.

(2) Dielectric formation (chemical conversion treatment (S91)) The Nb porous body is immersed in an electrolytic aqueous solution of phosphoric acid or the like together with the counter electrode as an anode, and a chemical conversion voltage is applied to the surface of the Nb porous body. An Nb oxide film to be a dielectric is formed (anodic oxidation method). At this time, the thickness of the Nb oxide film is determined by the condition of the formation voltage (Vf (formation bolt)), and the characteristics of the capacitor are determined. The electrolytic solution had a concentration of 0.6 vol. % Phosphoric acid aqueous solution or the like is used.

(3) Cathode formation (S92) A solid electrolyte layer is formed as a cathode on the oxide film of the Nb porous body formed in the previous step. As the solid electrolyte, manganese dioxide, a conductive polymer obtained by polymerizing pyrrole, thiophene, or a derivative thereof is used.

(4) Graphite layer formation (S93), A
g layer formation (S94), lead frame bonding (S95),
Mold exterior (S96) A graphite layer and an Ag paste layer are formed on the solid electrolyte layer. Next, the lead frame anode part is joined to the element lead wire of the anode by spot welding, and Ag
The lead frame cathode portion is bonded to the paste layer with adhesive silver. Finally, the whole body is covered with a resin to complete the Nb solid electrolytic capacitor having the structure shown in FIG.

[0008]

The Nb solid electrolytic capacitor manufactured by the above conventional process has the following problems. (1) Leakage current (Leakage C
current (hereinafter referred to as LC)) is large and unstable. (2) Due to the heat of the mold exterior at the time of manufacturing the capacitor, the solder joint at the time of mounting the capacitor, or the thermal effect at the time of use after mounting the capacitor. LC characteristics deteriorate,
With the same shape and the same structure, performance equivalent to that of Ta solid electrolytic capacitor cannot be obtained. This has been the cause of not being put to practical use, although it has long been known that Nb can be used as a capacitor.

The present invention has been made in view of the above problems in the prior art, and provides an amorphous Nb oxide film which is sound and has sufficient heat resistance as a capacitor. Another object of the present invention is to provide a high-performance Nb solid electrolytic capacitor, and finally to provide an inexpensive and lightweight Nb solid electrolytic capacitor having the same shape and structure as the Ta solid electrolytic capacitor.

[0010]

The inventor, when considering an Nb solid electrolytic capacitor, reached a practical level of quality because the dielectric formed on the Nb surface was an imperfect one including a defective portion. Paying attention to the fact that the defect does not occur, the defect part is an oxide part in which the properties required as a dielectric are impaired by impurities such as Mg, Ni, Fe, Zr, and Mn existing on the Nb surface and other causes. Figured out.

Of these, Mg and N existing on the surface of Nb
Impurities such as i, Fe, Zr, and Mn cannot be completely removed even in the Nb refining process, and are inevitably left. The oxide part in which the properties required as a dielectric are impaired has conductivity, which is formed in a part of an amorphous Nb oxide film (Nb ₂ O ₅ ) which is ideal as a dielectric.
It refers to a crystalline Nb oxide that deteriorates LC characteristics. The crystalline Nb oxides were NbO and NbO ₂ which are also called lower Nb oxides. In addition, since the crystalline Nb oxide (NbO, NbO ₂ (lower Nb oxide)) has a lower heat resistance than the amorphous Nb oxide film (Nb ₂ O ₅ ), the oxide film is affected by heat such as mold reflow. When stress is applied to the crystalline N
It was also found that the LC characteristics were deteriorated by the generation of cracks in the portion where the b oxide was present.

The inventor further studied, and the crystalline Nb oxide was formed by contacting the surface of metal Nb with the atmosphere and bonding with oxygen in the atmosphere during the process of manufacturing a capacitor. Nb vapor-phase oxide and metal Nb have a strong affinity with oxygen and the reaction rate of oxidation of metal Nb is large at the stage of anodic oxidation, so that oxygen diffusion into Nb becomes non-uniform, and it is unavoidable in the amorphous Nb oxide film. Nb oxide that is partially formed in a selective manner and impurities existing on the surface of the metal Nb inhibit the sound oxide formation of Nb in the anodizing step of Nb. I found that there are 3 types.

Based on the above findings, the root cause of the defective portion that deteriorates the performance of the solid electrolytic capacitor, that is, the performance of the amorphous Nb oxide film as a dielectric is Mg, Ni, Fe, Zr, Mn, etc. existing on the Nb surface. And the crystalline Nb oxide in the amorphous Nb oxide film (Nb surface layer as Nb vapor phase oxide), which are inevitably formed respectively, but the impurities and crystalline Nb
It was found that it is possible to form a sound amorphous Nb oxide film after the removal of each oxide after the oxide is formed, and the present invention has been completed. At this time, impurities (Mg, Ni, Fe, Z
(r, Mn, etc.) focuses on the property of being more easily dissolved in acid or alkali than Nb, and crystalline Nb oxide (NbO,
NbO ₂ (lower Nb oxide) is focused on the characteristics that it is more soluble in acid and alkali and that it has lower heat resistance than amorphous Nb oxide.

In order to solve the above-mentioned problems, a method for improving the soundness of an amorphous Nb oxide film according to the first aspect of the present invention is a method for forming a Nb oxide film having an amorphous Nb oxide film on its surface.
It is characterized in that a first treatment for heating the metal body is performed, a second treatment for chemically cleaning the Nb metal body is performed, and a third treatment for oxidizing the Nb metal body is performed.

Here, the first treatment is a treatment for generating cracks in the defective portion of the amorphous Nb oxide film, the second treatment is a treatment for removing the defective portion, and the third treatment is for the defective portion. This is the process of restoration.

Originally, it was difficult to visually identify the defective portion (crystalline portion) in the thin film amorphous Nb oxide film, and it was also difficult to detect it by an analytical instrument because it was a minute defect. In the present invention, the fact that the crystalline portion of the oxide film has a lower mechanical strength than the amorphous portion against the stress applied by heating can be detected for the first time. As a result, the crystalline portion of the oxide film, that is, the defective portion is detected as a crack generated therein. It is presumed that the cracks are finely generated not only at the boundary between the amorphous portion and the crystalline portion but also inside the region of the crystalline portion. Since the chemical cleaning liquid easily penetrates into the cracked portions, the chemical cleaning liquid can be dissolved and removed in a short time, and the defect can be efficiently removed. Further, it is possible to easily remove impurities which are presumed to be under the crystalline oxide. Furthermore, the voids formed by removing the defective portion in the third treatment can be repaired, and the amorphous Nb oxide film can be made sound.

The term "Nb metal body" as used herein refers to a porous body obtained by vacuum sintering Nb powder, an Nb foil produced by rolling or electrolysis, and has a form suitable for use as a solid electrolytic capacitor. ing. Further, the heating in the first treatment may be performed in the atmosphere. At this time, the larger the heating temperature and time, the more effectively the cracks can be generated, but the heating temperature is preferably 100 to 300 ° C. 100 ° C. is the lower limit temperature at which the effect of heat stress is produced, and 300 ° C. is the upper limit temperature at which the Nb metal body is not oxidized in the atmosphere. It is particularly preferable that the temperature is higher than the temperature that may be received after being mounted as a capacitor within this temperature range, and the solder reflow temperature (240 to 260).
(° C) is a guide. The holding time for heating is preferably 10 seconds or more.

In order to solve the above-mentioned problems, a method for improving the soundness of an amorphous Nb oxide film according to the second invention of the present application is the method of the first invention, wherein the chemical cleaning is Nb having an oxidation number lower than that of Nb ⁵⁺ oxide. It is characterized in that the Nb metal body is immersed in one or more aqueous solutions of an acid and an alkaline solution that dissolves an impurity element contained in the oxide or Nb metal body. The present invention is Nb having a lower oxidation number than Nb ⁵⁺ oxide (amorphous Nb oxide).
Oxides (NbO, NbO ₂ (lower Nb oxides)), that is, the defective portion utilizes the property of being easily dissolved in acid or alkali, and by this, only the defective portion can be selectively dissolved and removed. Becomes

The present application provided to solve the above problems
A method for soundening an amorphous Nb oxide film according to the third invention
In the first invention, the chemical cleaning is sulfuric acid and nitric acid.
Acid and potassium hydroxide and sodium hydroxide and ammonia
An acid containing at least one from the group consisting of
Is a treatment of immersing a Nb metal body in an alkaline aqueous solution
It is characterized by The present invention is Nb⁵⁺Oxide (Amol
Nb oxide (Nb oxide) with a lower oxidation number than
O, NbO_Two(Lower Nb oxide)), that is, defective portion
Uses the property of being easily dissolved in acid and alkali.
As a result, only defective parts are selectively dissolved and removed.
It is possible to In this case, the acid and alkaline aqueous solution
Nb ⁵⁺Sulfuric acid that does not dissolve the oxide and Nb metal body itself,
Nitric acid, potassium hydroxide, sodium hydroxide, ammonia
Is good.

In order to solve the above-mentioned problems, a method for sounding an amorphous Nb oxide film according to a fourth invention of the present application is the method of the first invention, wherein a chemical conversion voltage is applied in the chemical conversion liquid with the Nb metal body as an anode. To form an amorphous Nb oxide film, and the third treatment is N
This is a process of oxidizing the Nb metal body by applying a formation voltage with the b metal body as an anode, and the value of the formation voltage of the third treatment is set to be equal to or less than the value of the formation voltage at the time of forming the amorphous Nb oxide film. The thickness of the oxide film formed first is the target thickness as a dielectric, and the restoration of the oxide film is controlled to be equal to or less than the initial thickness of the oxide film in the third treatment, while the soundness of the amorphous Nb oxide film is improved. Therefore, the capacitor performance as designed can be secured. If the formation voltage value in this step is higher than the formation voltage value at the time of forming the amorphous Nb oxide film,
The entire oxide film grows and becomes thicker, but at the same time, a defective portion is formed again, which is not preferable in order to improve the soundness of the oxide film.

In order to solve the above-mentioned problems, a method for sounding an amorphous Nb oxide film according to a fifth invention of the present application is the first invention, wherein after the first to third treatments are performed, The processing from the processing to the third processing is repeated at least one or more times. As a result, even if the first to third treatments are performed, the amorphous Nb
Even if a defective portion remains in the oxide film, it is possible to completely remove the defective portion by the first to third treatments after the second treatment. Therefore, it is possible to finally restore a healthy film, and it is possible to further improve the soundness of the amorphous Nb oxide film. The repeated execution may be judged by the LC measurement by the sampling inspection after the completion of the third treatment.

A method of manufacturing an Nb solid electrolytic capacitor according to a sixth invention of the present application, which is provided to solve the above-mentioned problems, comprises:
A dielectric film is formed on the surface of the porous body by performing a chemical conversion treatment by an electrochemical reaction using a porous body made of a valve metal as an anode in a chemical conversion liquid, and a solid electrolyte layer is formed on the surface of the porous body. In the method of manufacturing a solid electrolytic capacitor, which comprises forming electrodes on the
A surface cleaning step of removing Nb vapor-phase oxides or impurities on the surface of the Nb porous body by chemical cleaning before forming the dielectric film, and an amorphous Nb oxide on the surface of the Nb porous body by chemical conversion treatment. And a dielectric forming step of forming a dielectric film. In the present invention, Nb vapor-phase oxide or impurities that cause defects as an amorphous Nb oxide film are removed in advance to remove Nb.
By cleaning the surface of the porous body, it is possible to improve the soundness of the amorphous Nb oxide film as a dielectric formed by the chemical conversion treatment to be performed later, and thus to manufacture the Nb solid electrolytic capacitor having excellent performance. It will be possible.

A method of manufacturing an Nb solid electrolytic capacitor according to a seventh invention of the present application, which is provided to solve the above problems, comprises:
A dielectric film is formed on the surface of the porous body by performing a chemical conversion treatment by an electrochemical reaction using a porous body made of a valve metal as an anode in a chemical conversion liquid, and a solid electrolyte layer is formed on the surface of the porous body. In the method of manufacturing a solid electrolytic capacitor, which comprises forming electrodes on the
A dielectric forming step of forming a dielectric film made of an amorphous Nb oxide on the surface of a porous body made of Nb by chemical conversion treatment; a defect removing step of removing a defective portion of the dielectric film by chemical cleaning; and a chemical conversion treatment And a defect repairing step of repairing the defective portion according to.
In the present invention, the defective portion of the dielectric film formed by chemical cleaning, that is, crystalline Nb oxide (NbO, Nb) is used.
O ₂ (lower Nb oxide) and impurities can be removed. Further, since the voids formed by removing the defective portion are repaired, the amorphous Nb oxide film can be made sound, and eventually, the Nb solid electrolytic capacitor having excellent performance can be manufactured.

The method of manufacturing an Nb solid electrolytic capacitor according to the eighth invention of the present application, which is provided for solving the above-mentioned problems, comprises:
A dielectric film is formed on the surface of the porous body by performing a chemical conversion treatment by an electrochemical reaction using a porous body made of a valve metal as an anode in a chemical conversion liquid, and a solid electrolyte layer is formed on the surface of the porous body. In the method of manufacturing a solid electrolytic capacitor, which comprises forming electrodes on the
A surface cleaning step of removing Nb vapor-phase oxides or impurities on the surface of the Nb porous body by chemical cleaning before forming the dielectric film, and an amorphous Nb oxide on the surface of the Nb porous body by chemical conversion treatment. And a defect removing step of removing a defective portion of the dielectric film by chemical cleaning, and a defect repairing step of repairing the defective portion by chemical conversion treatment. And In the present invention, Nb vapor-phase oxides or impurities that cause defects in the dielectric film are removed in advance, and the defective part of the dielectric film formed even after that, that is, crystalline Nb oxide (NbO, NbO _2). (Lower N
By removing the (b oxide)), the cause that deteriorates the capacitor performance can be removed. Furthermore, since the void created by the removal of the defective portion is restored, the soundness of the amorphous Nb oxide film as the dielectric on the Nb porous body can be improved, and by extension, the Nb solid electrolytic capacitor having excellent performance can be obtained. It becomes possible to manufacture.

A method for manufacturing an Nb solid electrolytic capacitor according to the ninth invention of the present application, which is provided to solve the above-mentioned problems, comprises:
A dielectric film is formed on the surface of the porous body by performing a chemical conversion treatment by an electrochemical reaction using a porous body made of a valve metal as an anode in a chemical conversion liquid, and a solid electrolyte layer is formed on the surface of the porous body. In the method of manufacturing a solid electrolytic capacitor, which comprises forming electrodes on the
A dielectric forming step of forming a dielectric film made of an amorphous Nb oxide on the surface of a porous body made of Nb by chemical conversion treatment; a defect detecting step of causing cracks in a defective portion of the dielectric film by heating; It is characterized by comprising a defect removing step of removing the defective portion by cleaning and a defect repairing step of repairing the defective portion by chemical conversion treatment.

Originally, it was difficult to visually identify the defective portion (crystalline portion) in the thin film of the dielectric film, and it was difficult to detect it even by an analytical instrument because it was a minute defect.
In the present invention, the fact that the crystalline portion of the dielectric film has a lower mechanical strength than the amorphous portion against the stress applied by heating can be detected for the first time. As a result, the crystalline portion of the dielectric film, that is, the defective portion is detected as a crack generated therein. It is presumed that the cracks are finely generated not only at the boundary between the amorphous portion and the crystalline portion but also inside the region of the crystalline portion. Since the chemical cleaning liquid easily penetrates into the cracked portions, the chemical cleaning liquid can be dissolved and removed in a short time, and the defect can be efficiently removed.
Further, it is possible to easily remove impurities which are presumed to be under the crystalline oxide. Further, the voids formed by removing the defective portion in the defect repairing process can be repaired, the soundness of the amorphous Nb oxide film as a dielectric can be improved, and, as a result, Nb having excellent performance can be obtained.
It is possible to manufacture a solid electrolytic capacitor. The heating in the defect detection step may be performed in the atmosphere. At this time,
The larger the heating temperature and time, the more effectively the cracks can be generated, but the heating temperature is 100 to 3
00 ° C is desirable. 100 ° C. is the lower limit temperature at which the effect of heat stress is produced, and 300 ° C. is the upper limit temperature at which the Nb porous body is not oxidized in the atmosphere. It is particularly preferable that the temperature is higher than the temperature that may be received after the capacitor is mounted in this temperature range, and the solder reflow temperature (240 to 260 ° C.) is a standard. The holding time for heating is preferably 10 seconds or more.

A method of manufacturing an Nb solid electrolytic capacitor according to the tenth invention of the present application, which is provided to solve the above-mentioned problems, comprises:
A dielectric film is formed on the surface of the porous body by performing a chemical conversion treatment by an electrochemical reaction using a porous body made of a valve metal as an anode in a chemical conversion liquid, and a solid electrolyte layer is formed on the surface of the porous body. In the method of manufacturing a solid electrolytic capacitor, which comprises forming electrodes on the
A surface cleaning step of removing Nb vapor-phase oxides or impurities on the surface of the Nb porous body by chemical cleaning before forming the dielectric film, and an amorphous Nb oxide on the surface of the Nb porous body by chemical conversion treatment. A dielectric forming step of forming a dielectric film consisting of, a defect detecting step of generating a crack in a defective portion of the dielectric film by heating, a defect removing step of removing the defective portion by chemical cleaning, and a chemical conversion treatment. And a defect repairing step of repairing the defective portion. In the invention of the present application, in addition to the ninth invention described above, the Nb gas phase oxide or impurities that cause a defective portion as an amorphous Nb oxide film is removed in advance, and the surface of the Nb porous body is cleaned. Since it is possible to improve the soundness of the amorphous Nb oxide film as a dielectric formed by the chemical conversion treatment carried out from above, it is possible to manufacture an Nb solid electrolytic capacitor having further excellent performance.

The method of manufacturing an Nb solid electrolytic capacitor according to the eleventh invention of the present application, which is provided for solving the above-mentioned problems, is the same as that of the ninth or tenth invention of the present application, except that the defect repairing step is generally performed. After that, at least one or more steps from the defect detection step to the defect repair step are repeated. As a result, even if the defect part remains in the dielectric film even after the first defect detection process to the defect repair process, the defective part is removed by the second and subsequent defect detection processes to the defect repair process. It can be completely removed. Therefore, it is possible to finally obtain a sound dielectric film, and it is possible to manufacture an Nb solid electrolytic capacitor having further excellent performance. The repeated execution may be judged by the LC measurement by the sampling inspection after the defect repairing process is completed.

The method for producing an Nb solid electrolytic capacitor according to the twelfth invention of the present application, which is provided for solving the above-mentioned problems, is the method of the sixth, eighth or tenth invention of the present application, wherein the surface cleaning step is Nb. ⁵⁺ oxide Nb oxide having a lower oxidation number or an acid element that dissolves an impurity element contained in the Nb porous body, or an alkaline aqueous solution, by immersing the Nb porous body in one or more aqueous solutions It is characterized by being. The present invention utilizes the property that Nb gas-phase oxide, which is an Nb oxide having a lower oxidation number than Nb ⁵⁺ oxide, and impurities are easily dissolved in acid and alkali. This makes it possible to clean the Nb surface and to improve the soundness of the amorphous Nb oxide film as a dielectric formed by the chemical conversion treatment which will be performed later. Therefore, the Nb solid electrolyte having further excellent performance can be obtained. Capacitors can be manufactured.

The method for producing an Nb solid electrolytic capacitor according to the thirteenth invention of the present application, which is provided for solving the above-mentioned problems, is the method of the sixth, eighth or tenth invention of the present application, wherein the surface cleaning step is sulfuric acid. And a treatment of immersing the Nb porous body in an acid or alkaline aqueous solution containing at least one selected from the group consisting of nitric acid, potassium hydroxide, sodium hydroxide, and ammonia.
The present invention utilizes the property that Nb gas-phase oxide, which is an Nb oxide having a lower oxidation number than Nb ⁵⁺ oxide, and impurities are easily dissolved in acid and alkali. In this case, the acid or alkali aqueous solution is preferably sulfuric acid, nitric acid, potassium hydroxide, sodium hydroxide, ammonia or the like which does not dissolve the Nb ⁵⁺ oxide and the Nb porous body itself. This makes it possible to clean the Nb surface and to improve the soundness of the amorphous Nb oxide film as a dielectric formed by the chemical conversion treatment which will be performed later. Therefore, the Nb solid electrolyte having further excellent performance can be obtained. Capacitors can be manufactured.

A method for manufacturing an Nb solid electrolytic capacitor according to a fourteenth invention of the present application, which is provided for solving the above-mentioned problems, is the sixth or eighth or tenth or the twelfth or thirteenth invention of the present application, It is characterized in that the Nb porous body whose surface cleaning step has been completed is introduced into the next dielectric body forming step without being exposed to air. This allows
Since a healthy dielectric can be formed on the surface of the Nb porous body whose surface has been cleaned without forming Nb vapor-phase oxide again, it is possible to manufacture an Nb solid electrolytic capacitor having superior performance. Becomes

The method of manufacturing an Nb solid electrolytic capacitor according to the fifteenth invention of the present application, which is provided for solving the above-mentioned problems, is the method of manufacturing the Nb solid electrolytic capacitor according to the seventh to eleventh inventions of the present application, wherein the defect removal step is Nb ⁵⁺ oxide. Nb in an aqueous solution of at least one of an acid and an alkaline aqueous solution which dissolves an impurity element contained in a Nb oxide or Nb porous body having a lower oxidation number.
b It is a process of immersing the porous body. The present invention has a lower oxidation number than Nb ⁵⁺ oxide (amorphous Nb oxide desirable as a dielectric).
O and NbO ₂ (lower Nb oxide), that is, the defective portion utilizes the property of being easily dissolved in acid or alkali. This makes it possible to selectively dissolve and remove only the defective portion, and the amorphous Nb as a dielectric is removed.
Since the soundness of the oxide film can be improved, it is possible to manufacture the Nb solid electrolytic capacitor having further excellent performance. In the manufacturing method including the surface cleaning step in the present invention, the chemical cleaning condition as the defect removing step is not restricted by the chemical cleaning condition of the surface cleaning step,
Both conditions may be the same or different conditions may be used.

The method of manufacturing an Nb solid electrolytic capacitor according to the sixteenth invention of the present application, which is provided for solving the above-mentioned problems, is the method of the seventh to eleventh inventions of the present application, wherein the defect removing step is performed by adding sulfuric acid and nitric acid. At least one selected from the group consisting of potassium hydroxide, sodium hydroxide and ammonia
It is characterized in that it is a treatment of immersing the Nb porous body in an acid or alkaline aqueous solution containing one. The present invention is Nb
Nb oxides (NbO, NbO ₂ ) having a lower oxidation number than ⁵⁺ oxide (amorphous Nb oxide desirable as a dielectric)
(Lower Nb oxide), that is, the defective portion utilizes the property of being easily dissolved in acid or alkali. In this case, the acid or alkali aqueous solution is preferably sulfuric acid, nitric acid, potassium hydroxide, sodium hydroxide, ammonia or the like which does not dissolve the Nb ⁵⁺ oxide and the Nb porous body itself. As a result, only the defective portion can be selectively dissolved and removed, and the amorphous Nb oxide film as a dielectric can be made sound, so that it is possible to manufacture an Nb solid electrolytic capacitor having further excellent performance. Becomes In the manufacturing method including the surface cleaning step in the present invention, the chemical cleaning conditions as the defect removing step are not restricted to the chemical cleaning conditions of the surface cleaning step, and both may be performed under the same conditions, Different conditions may be used.

The method for manufacturing an Nb solid electrolytic capacitor according to the seventeenth invention of the present application, which is provided for solving the above-mentioned problems, is the method of manufacturing the Nb solid electrolytic capacitor according to the seventh to sixteenth inventions, wherein the value of the formation voltage in the defect repairing step is It is characterized in that it is not more than the value of the formation voltage in the dielectric forming step. The thickness of the oxide film formed first is the target thickness of the dielectric, and the repair of the oxide film is controlled to be equal to or less than the initial thickness of the oxide film in the defect repairing process, while the amorphous Nb as the dielectric is controlled.
Since the oxide film can be made sound, the capacitor performance as designed can be secured. If the formation voltage value in this step is made higher than the formation voltage value at the time of forming the dielectric film, the entire dielectric film further grows and becomes thicker, and the capacitance fluctuates. Moreover, when the entire film grows, a defective portion is formed again, which is not preferable in order to improve the soundness of the dielectric film.

The chemical conversion treatment performed in the defect repairing step of the present invention is, as described above, the amorphous N that is a dielectric.
This is a treatment for forming and repairing amorphous Nb oxide in the voids that are the traces of the active removal of the defective portion of the b oxide film, and is one treatment that constitutes a sounding method for the dielectric film (amorphous Nb oxide film). Is. On the other hand, when the Ta solid electrolytic capacitor is manufactured, a dielectric restoration process called re-formation treatment may be performed. However, in order to restore a damaged portion due to damage to the dielectric at the stage of forming the solid electrolyte layer. The present invention is not for making the dielectric film sound, and differs from the present invention in the timing of repair and the purpose of repair.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a flow chart showing an embodiment of a method for manufacturing an Nb solid electrolytic capacitor according to the present invention. In this embodiment, the dielectric forming step (S9) of the conventional manufacturing method shown in FIG.
Before and after 1), a process for improving the soundness of the amorphous Nb oxide film which is a dielectric is added. In addition,
The appearance of the Nb solid electrolytic capacitor obtained by the manufacturing method of the present invention is the same as that of the conventional capacitor shown in FIG. Each step of the manufacturing method will be described below with reference to FIGS. 1 and 2.

(Step S1) Surface cleaning step 6 W of Nb porous body 1 formed by vacuum sintering Nb powder
t. % Nitric acid aqueous solution or 6 wt. % Aqueous solution of potassium hydroxide, and the surface of the porous body was chemically cleaned. By this chemical cleaning, Nb vapor phase oxides and impurities existing on the surface layer of the Nb porous body 1 are removed,
The surface of the Nb porous body 1 is cleaned. Nb used here
The powder press molding and sintering conditions relating to the porous body 1 are the same as those described as the prior art, and the shape and size of the Nb porous body 1 are the capacitance standard 3 which is commercially available.
It was the same as the Ta porous body of the 30 μF Ta solid electrolytic capacitor. In addition to the above-mentioned aqueous solutions, there are acids having an equivalent chemical cleaning power, and aqueous solutions of sulfuric acid, aqueous solutions of sodium hydroxide, and aqueous solutions of ammonia as alkaline solutions. With respect to the Nb porous body 1 on which the chemical cleaning has been completed, neutralization cleaning is performed so that the chemical cleaning liquid does not remain, while the surface of the Nb porous body 1 is controlled to be always covered with a water film without being dried.
It was subjected to the next step.

(Step S2) Dielectric Forming Step The dielectric film 2 was formed on the surface of the Nb porous body 1 whose surface had been cleaned by the anodic oxidation method similar to the conventional manufacturing method. At this time, as a chemical conversion liquid at 80 ° C.
6 vol. % Phosphoric acid aqueous solution, electrostatic capacity 330μ
Anodic oxidation was performed with the standard product of F as the target under a predetermined condition (formation voltage Vf) until the formation current was saturated. The dielectric film (amorphous Nb oxide film) 2 formed at this time may include a defective portion 29 that impairs the performance of the capacitor.

(Step S3) Defect Detection Step The Nb porous body 1 on which the dielectric film 2 was formed was heated to 260 ° C. in the atmosphere, held for 10 seconds, and then naturally cooled after heating. As a result, the crack 2 is formed in the defective portion 29.
9a occurs.

(Step S4) Defect Removal Step 6 wt. % Nitric acid aqueous solution or 6 wt. % Aqueous solution of potassium hydroxide, and the surface of the porous body was chemically cleaned. By this chemical cleaning, the defective portion 29 (including the defective portion having a crack) and impurities (not shown) are removed, and a void 29b is formed in the dielectric film 2. In addition,
In addition to the above aqueous solution, an acid having the same chemical cleaning power, an aqueous sulfuric acid solution as an alkaline aqueous solution, an aqueous sodium hydroxide solution,
There is an aqueous ammonia solution. Nb that has completed this chemical cleaning
The porous body 1 was neutralized and washed so that the chemical cleaning liquid did not remain, while being controlled so that the surface thereof was always covered with a water film without being dried, and the porous body 1 was subjected to the next step.

(Step S5) Defect Repair Process The dielectric film 2 was repaired by the anodic oxidation method on the Nb porous body 1 from which the defective portion 29 of the dielectric film 2 was completely removed. At this time, as a chemical conversion liquid, 0.6 vo of 80 ° C
l. % Phosphoric acid aqueous solution was used and anodization was performed until the formation current was saturated at the same formation voltage value Vf as when the dielectric film was formed. By this treatment, the void 29b is filled with a healthy amorphous Nb oxide film and repaired.

(Step S6) Solid Electrolyte Layer Forming Step Regarding the Nb porous body 1 having the dielectric film 2 formed thereon, a solid electrolyte layer was formed on the dielectric film 2 by any one of the following methods. These forming conditions are the same as those in the conventional manufacturing method. A thiophene derivative is oxidatively polymerized on the dielectric film 2 to form a conductive polymer layer. After soaking in a manganese nitrate solution, a manganese dioxide layer is formed on the dielectric film 2 by thermal decomposition.

(Steps S7 to S10) Graphite layer formation, Ag paste layer formation, lead frame bonding, mold exterior A graphite layer and then an Ag paste layer are formed on the solid electrolyte layer. Next, the lead frame anode part is joined to the element lead wire of the anode by spot welding, and Ag
The lead frame cathode part is bonded to the paste layer with adhesive silver, and finally the whole is molded and covered with resin. The manufacturing conditions of these steps are the same as those of the conventional manufacturing method.

Through the above steps, the Nb solid electrolytic capacitor by the manufacturing method of the present invention is completed. The surface cleaning step, the defect detecting step, or the sounding treatment of the amorphous Nb oxide film (defect detecting step, defect removing step, defect repairing step) can be appropriately omitted.

(Evaluation Method) As a means for measuring the effect of the present invention, the material after the Ag paste layer forming step was used as a test material (n = 5), and the LC characteristics before and after the reflow heating were measured. The LC characteristic measurement conditions were an applied voltage: 4 V, a measurement time: a value of 30 sec after voltage application, and the reflow heating conditions were a heating temperature of 240 ° C., a holding time of 10 seconds, and natural cooling in the air after heating by an air reflow method. Further, the equivalent series resistance (hereinafter referred to as ESR) at a frequency of 100 kHz was measured for the test material before the reflow heating.

Another embodiment of the present invention will be described with reference to FIG. The steps constituting the manufacturing method of the present invention are the same as those in FIG. 1 and the conditions are also the same, but the defect detection step-defect removal step-defect repair step may be performed as necessary in the restoration process P11 of the amorphous Nb oxide film. The point is repeated. The repetition is repeated at the stage when the defect repairing process is completed, and the above-mentioned LC characteristic evaluation is performed. When the solid electrolyte layer is a conductive polymer layer, L
C value 20 μA or less, LC value 2 in case of manganese dioxide layer
The time point at which the value became μA or less was determined to be the end point.

Example 1 According to the flow chart of FIG. 1, the Nb porous body was subjected to a surface cleaning step-dielectric forming step-solid electrolyte layer forming step-graphite layer forming step-Ag paste layer forming step. It was In the surface cleaning process, 6 wt. % Nitric acid aqueous solution was used for chemical cleaning, and the solid electrolyte layer was used as a conductive polymer layer. (Example 2) According to the flowchart of FIG. 1, the Nb porous body was subjected to a surface cleaning step-dielectric forming step-solid electrolyte layer forming step-graphite layer forming step-Ag paste layer forming step. 6w in the surface cleaning process
t. % Aqueous solution of potassium hydroxide was used for chemical cleaning, and the solid electrolyte layer was used as a conductive polymer layer. (Embodiment 3) According to the flowchart of FIG. 1, the Nb porous body is subjected to the following processes: dielectric formation step-defect removal step-defect repair step-solid electrolyte layer formation step-graphite layer formation step-Ag paste layer formation step. It was In the defect removal process, 6 wt. % Nitric acid aqueous solution was used for chemical cleaning, and the solid electrolyte layer was used as a conductive polymer layer. (Embodiment 4) According to the flow chart of FIG. 1, the Nb porous body is subjected to the treatments of dielectric forming step-defect removing step-defect repairing step-solid electrolyte layer forming step-graphite layer forming step-Ag paste layer forming step. It was In the defect removal process, 6 wt. % Aqueous solution of potassium hydroxide was used for chemical cleaning, and the solid electrolyte layer was used as a conductive polymer layer. (Embodiment 5) According to the flowchart of FIG. 1, for Nb porous body, dielectric forming step-defect detecting step-defect removing step-defect repairing step-solid electrolyte layer forming step-graphite layer forming step-Ag paste layer forming step Was processed. In the defect removal process, 6 wt. % Nitric acid aqueous solution was used for chemical cleaning, and the solid electrolyte layer was used as a conductive polymer layer. (Embodiment 6) According to the flowchart of FIG. 1, for Nb porous body, dielectric forming step-defect detecting step-defect removing step-defect repairing step-solid electrolyte layer forming step-graphite layer forming step-Ag paste layer forming step Was processed. In the defect removal process, 6 wt. % Aqueous solution of potassium hydroxide was used for chemical cleaning, and the solid electrolyte layer was used as a conductive polymer layer. (Embodiment 7) According to the flowchart of FIG. 1, for Nb porous body, surface cleaning step-dielectric forming step-defect detecting step-defect removing step-defect repairing step-solid electrolyte layer forming step-graphite layer forming step- The Ag paste layer forming process was performed. Both the surface cleaning process and the defect removal process are 6 wt. % Nitric acid aqueous solution was used for chemical cleaning, and the solid electrolyte layer was used as a conductive polymer layer. (Embodiment 8) According to the flowchart of FIG. 1, for Nb porous body, surface cleaning step-dielectric forming step-defect detecting step-defect removing step-defect repairing step-solid electrolyte layer forming step-graphite layer forming step- The Ag paste layer forming process was performed. Both the surface cleaning process and the defect removal process are 6 wt. % Aqueous solution of potassium hydroxide was used for chemical cleaning, and the solid electrolyte layer was used as a conductive polymer layer. (Embodiment 9) According to the flowchart of FIG. 3, for Nb porous material, surface cleaning step-dielectric forming step-defect detecting step-defect removing step-defect repairing step-defect detecting step-
Defect removal process-defect repair process-defect detection process-defect removal process-defect repair process-solid electrolyte layer formation process-graphite layer formation process-Ag paste layer formation process was performed. In the surface cleaning process, 6 wt. % Potassium hydroxide aqueous solution, 6 wt. % Nitric acid aqueous solution was used for chemical cleaning, and the solid electrolyte layer was used as a conductive polymer layer.
The number of repetitions of the defect detection process-defect removal process-defect repair process was three times as described above.

(Comparative Example 1) As a comparison, according to the flowchart of FIG.
Solid electrolyte layer forming process-graphite layer forming process-Ag
The paste layer forming process was performed. The solid electrolyte layer was a conductive polymer layer. (Comparative Example 2) As a comparison, according to the flowchart of FIG.
The Nb porous body was subjected to the following processes: dielectric formation step-defect detection step-defect repair step-solid electrolyte layer formation step-graphite layer formation step-Ag paste layer formation step.
The solid electrolyte layer was a conductive polymer layer. (Comparative Example 3) As a comparison, according to the flowchart of FIG.
The Ta porous body was subjected to the following processes: dielectric forming step-solid electrolyte layer forming step-graphite layer forming step-Ag paste layer forming step. The solid electrolyte layer was a conductive polymer layer. The Ta porous body used was the same as the Ta porous body of the Ta solid electrolytic capacitor having a capacitance standard of 330 μF that is commercially available. The condition for forming the dielectric is 0.6 vol. % Phosphoric acid aqueous solution was used, and anodization was performed under a predetermined condition (formation voltage Vf ′) until the formation current was saturated, with the target of the standard product having an electrostatic capacity of 330 μF.

In the above Examples and Comparative Examples, the solid electrolyte layer was replaced with a manganese dioxide layer, the other manufacturing conditions were the same, and the test materials of Examples 10 to 18 were used in the order of Examples 1 to 9. The test materials of Comparative Examples 4 to 6 were prepared in the order of Comparative Examples 1 to 3. In addition, Example 1
The defect detection step-defect removal step-defect repair step in 8 was repeated twice.

Table 1 shows the measurement results of LC characteristics and ESR values before and after reflow in Examples 1 to 9 and Comparative Examples 1 to 3.

[Table 1]

Comparative Example 1 (N
Compared to b), LC for all Examples 1-9
The effect of improving the characteristics and ESR value was confirmed. In particular, Examples 7 to 8 are improved to almost the same level as Comparative Example 3 (Ta) corresponding to a Ta solid electrolytic capacitor having a capacitance standard of 330 μF. As can be seen in Comparative Example 2, neither improvement in LC characteristics nor improvement in ESR value was observed in the combination of the defect detection process and the defect repair process.
On the other hand, as shown in Examples 5 and 6, improvement can be made only when a defect removal process is inserted between these processes. The test materials of Examples 7 and 8 are shown in FIG.
The Nb solid electrolytic capacitor was manufactured according to the flowchart of FIG. 3 and the sample material of Example 9 according to the flowchart of FIG. 3, and it was confirmed that the capacitance standard 330 μF was satisfied at all.

Table 2 shows the measurement results of LC characteristics and ESR values before and after reflow of Examples 10 to 18 and Comparative Examples 4 to 6.

[Table 2]

The LC characteristics and ESR values of Examples 10 to 18 were also improved, and the degree of improvement compared with Comparative Examples 4 to 6 was the same as that of Comparative Examples 1 to 3 of Examples 1 to 9. was gotten. In addition, Examples 1-9 and Comparative Examples 1-3
On the other hand, although the LC characteristics are about 1/10 and the ESR values are about 1/2, this is due to the difference in the type of the solid electrolyte layer (conductive polymer layer and manganese dioxide layer). When the Nb solid electrolytic capacitors were prepared according to the flowchart of FIG. 1 for the test materials of Examples 16 and 17 and according to the flowchart of FIG. 3 for the test material of Example 18, all of them meet the capacitance standard of 330 μF. Was confirmed.

[0054]

According to the present invention, the defect portion in the amorphous Nb oxide film can be detected as a crack generated therein by heating in the defect detecting step, and the defect portion can be efficiently cleaned by the chemical cleaning in the defect removing step. Defects can now be removed. Further, it is possible to easily remove impurities which are presumed to be under the crystalline oxide.
Furthermore, it is possible to repair the voids created by the removal of defective parts in the chemical conversion treatment in the defect repair process, and to improve the soundness of the amorphous Nb oxide film, which in turn makes it possible to manufacture Nb solid electrolytic capacitors with excellent performance. Becomes

The Nb surface can be efficiently cleaned by using an acid or alkali aqueous solution suitable for chemical cleaning in the surface cleaning step before the dielectric forming step.

By using an acid or alkali aqueous solution suitable for chemical cleaning in the defect removing step, only defective portions and impurities can be selectively dissolved and removed, and efficient defect removal becomes possible.

The thickness of the oxide film formed in the dielectric forming step is the target thickness of the dielectric, and the repair of the oxide film is controlled to be equal to or less than the original oxide film thickness in the defect repairing step, while the amorphous Nb oxide is oxidized. Since the film can be made sound, the capacitor performance as designed can be secured.

Even if the defective portion remains in the amorphous Nb oxide film as the dielectric even after the first process from the defect detection process to the defect repair process, the process from the defect detection process to the defect repair process is repeated. It is possible to completely remove the defective portion. Therefore, it is possible to finally restore a healthy film,
It is possible to further improve the soundness of the amorphous Nb oxide film.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram showing an embodiment of a method for manufacturing an Nb solid electrolytic capacitor according to the present invention.

FIG. 2 shows Nb at each stage of the manufacturing process in one embodiment of the method for manufacturing an Nb solid electrolytic capacitor according to the present invention.
It is a schematic diagram which shows an oxide film state.

FIG. 3 is a manufacturing process diagram showing another embodiment of the method for manufacturing an Nb solid electrolytic capacitor according to the present invention.

FIG. 4 is a manufacturing process diagram showing a conventional method for manufacturing a Nb solid electrolytic capacitor.

FIG. 5 is an overall schematic diagram showing a configuration of an Nb solid electrolytic capacitor.

[Explanation of symbols] 1 ... Nb porous body 2 ... Amorphous Nb oxide film (dielectric film) 3 ... Element lead wire 4 ... Solid electrolyte layer 5 ... Graphite layer 6 ... Silver paste layer 7 ... Lead frame 8 ... Mold exterior resin 19 ... Nb vapor-phase oxide 29 ... Defect part 29a ... Crack 29b ... Voids S1-S10, S11-S20, S91-S96 ...
Treatment steps P1, P11 ... Sound treatment of amorphous Nb oxide film

Claims (20)

[Claims] 1. A first treatment for heating an Nb metal body having an amorphous Nb oxide film formed on its surface layer, a second treatment for chemically cleaning the Nb metal body, and a third treatment for oxidizing the Nb metal body. A sounding method for an amorphous Nb oxide film, characterized by performing a treatment. 2. The method for soundening an amorphous Nb oxide film according to claim 1, wherein the first treatment is a treatment for generating a crack in a defective portion of the amorphous Nb oxide film. 3. The method for recovering an amorphous Nb oxide film according to claim 1, wherein the second treatment is a treatment for removing the defective portion. 4. The method for soundening an amorphous Nb oxide film according to claim 1, wherein the third treatment is a treatment for repairing the defective portion. 5. The chemical cleaning is carried out in any one or more of an acid and an alkaline aqueous solution which dissolves an impurity element contained in an Nb oxide or an Nb metal body having an oxidation number lower than that of Nb ⁵⁺ oxide. The method for sounding an amorphous Nb oxide film according to any one of claims 1 to 4, which is a treatment of immersing the Nb metal body in. 6. The chemical cleaning is a treatment of immersing a Nb metal body in an acid or alkaline aqueous solution containing at least one selected from the group consisting of sulfuric acid and nitric acid, potassium hydroxide, sodium hydroxide and ammonia. Amorphous N according to any one of claims 1 to 4, characterized in that
b Oxidized film restoration method. 7. An amorphous Nb oxide film is formed by applying a formation voltage with the Nb metal body as an anode in a formation solution, and in the third treatment, a formation voltage is applied with the Nb metal body as an anode in the formation solution. It is the process of oxidizing the Nb metal body by carrying out, and the value of the formation voltage of the said 3rd process is made into the value of the formation voltage at the time of the said amorphous Nb oxide film formation, It is characterized by the above-mentioned. The method for soundening an amorphous Nb oxide film according to any one of claims. 8. After performing the first processing to the third processing,
The method for recovering an amorphous Nb oxide film according to any one of claims 1 to 7, wherein the first to third treatments are repeated at least one or more times. 9. A dielectric film is formed on the surface of a porous body by forming a dielectric film on the surface of the porous body by performing a chemical conversion treatment by an electrochemical reaction using a porous body made of a valve metal as an anode in a chemical conversion liquid, and forming a solid electrolyte layer on the surface thereof. In the method for producing a solid electrolytic capacitor, which further comprises an electrode formed thereon and is entirely covered with a mold, a Nb gas-phase oxide or Nb gas phase oxide on the surface of a porous body made of Nb is chemically cleaned before the dielectric film is formed. Amorphous N is formed on the surface of the Nb porous body by a surface cleaning process for removing impurities and a chemical conversion treatment.
and a dielectric forming step of forming a dielectric film made of b oxide, the method for producing an Nb solid electrolytic capacitor. 10. A dielectric film is formed on the surface of a porous body by performing a chemical conversion treatment by electrochemical reaction using a porous body made of a valve metal as an anode in a chemical conversion liquid, and a solid electrolyte layer is formed on the surface layer thereof. And then forming electrodes on it,
In a method for manufacturing a solid electrolytic capacitor, which is entirely encased in a mold, a dielectric forming step of forming a dielectric film made of amorphous Nb oxide on the surface of a porous body made of Nb by chemical conversion treatment, A method of manufacturing an Nb solid electrolytic capacitor, comprising: a defect removing step of removing a defective portion of a body film; and a defect repairing step of repairing the defective portion by chemical conversion treatment. 11. A dielectric film is formed on the surface of a porous body by subjecting a porous body made of a valve metal to a chemical conversion treatment as an anode in a chemical conversion solution by an electrochemical reaction, and a solid electrolyte layer is formed on the surface layer thereof. And then forming electrodes on it,
In a method for manufacturing a solid electrolytic capacitor, which is entirely covered with a mold, a surface cleaning step of removing Nb gas phase oxides or impurities on the surface of a porous body made of Nb by chemical cleaning before forming a dielectric film; A dielectric forming step of forming a dielectric film made of an amorphous Nb oxide on the surface of a porous body made of Nb by a treatment, a defect removing step of removing a defective portion of the dielectric film by a chemical cleaning, and a chemical conversion treatment. A defect repairing step of repairing the defective portion, the method for manufacturing an Nb solid electrolytic capacitor. 12. A dielectric film is formed on the surface of a porous body by subjecting a porous body made of a valve metal to a chemical conversion treatment as an anode in a chemical conversion solution by an electrochemical reaction, and a solid electrolyte layer is formed on the surface thereof. And then forming electrodes on it,
A method of manufacturing a solid electrolytic capacitor, which is entirely covered with a mold, comprising: a dielectric forming step of forming a dielectric film made of an amorphous Nb oxide on the surface of a porous body made of Nb by chemical conversion treatment; Nb comprising a defect detection step of generating a crack in a defective portion of the film, a defect removal step of removing the defective portion by chemical cleaning, and a defect repairing step of repairing the defective portion by chemical conversion treatment. Manufacturing method of solid electrolytic capacitor. 13. A dielectric film is formed on the surface of a porous body by subjecting a porous body made of a valve metal to a chemical conversion treatment as an anode in a chemical conversion solution by an electrochemical reaction, and a solid electrolyte layer is formed on the surface thereof. And then forming electrodes on it,
In a method for manufacturing a solid electrolytic capacitor, which is entirely covered with a mold, a surface cleaning step of removing Nb gas phase oxides or impurities on the surface of a porous body made of Nb by chemical cleaning before forming a dielectric film; A dielectric forming step of forming a dielectric film made of an amorphous Nb oxide on the surface of a porous body made of Nb by a treatment, a defect detecting step of generating a crack in a defective portion of the dielectric film by heating, and a chemical cleaning A method of manufacturing an Nb solid electrolytic capacitor, comprising: a defect removing step of removing the defective portion by means of; and a defect repairing step of repairing the defective portion by chemical conversion treatment. 14. The process from the defect detection process to the defect repair process is repeated at least one or more times after performing the entire process up to the defect repair process.
Alternatively, the method for manufacturing the Nb solid electrolytic capacitor according to claim 13. 15. The surface cleaning step, wherein an acid or alkali aqueous solution that dissolves an impurity element contained in a Nb oxide or Nb porous body having an oxidation number lower than that of Nb ⁵⁺ oxide is used.
The process of immersing the Nb porous body in any one or more aqueous solutions, which is characterized in that
Alternatively, the method for manufacturing the Nb solid electrolytic capacitor according to claim 13. 16. The surface cleaning step comprises immersing the Nb porous body in an acid or alkaline aqueous solution containing at least one selected from the group consisting of sulfuric acid, nitric acid, potassium hydroxide, sodium hydroxide and ammonia. It is processing, The manufacturing method of the Nb solid electrolytic capacitor of Claim 9 or Claim 11 or Claim 13 characterized by the above-mentioned. 17. The method according to claim 9 or 1, wherein the Nb porous body that has been subjected to the surface cleaning step is put into the next dielectric body forming step without being exposed to air.
1 or claim 13 or claim 15 or claim 16
A method for manufacturing the Nb solid electrolytic capacitor as described in any one of 1. 18. The defect removing step comprises at least one of an acid and an alkaline aqueous solution for dissolving an impurity element contained in an Nb oxide having a lower oxidation number than Nb ⁵⁺ oxide or an Nb porous body. The method for producing an Nb solid electrolytic capacitor according to any one of claims 10 to 14, which is a treatment of immersing the Nb porous body in an aqueous solution. 19. A treatment for immersing a Nb porous body in an acid or an alkaline aqueous solution containing at least one selected from the group consisting of sulfuric acid, nitric acid, potassium hydroxide, sodium hydroxide and ammonia in the defect removing step. The method for manufacturing an Nb solid electrolytic capacitor according to claim 10, wherein 20. The Nb solid electrolytic capacitor according to claim 10, wherein the value of the formation voltage in the defect repairing step is set to be equal to or less than the value of the formation voltage in the dielectric forming step. Production method.