JP2010287632A - Method of manufacturing electrolytic capacitor, and electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an electrolytic capacitor using aluminum as metal which accompanies alkali treatment. <P>SOLUTION: The method of manufacturing the electrolytic capacitor includes a coating forming process of forming an oxide coating 2 on a surface of the aluminum formed in a form of a metal layer 1, and an alkali treatment process of dipping the aluminum formed with the oxide coating 2 in an alkali solution. Preferably, a solution of a sodium hydroxide has a concentration of 0.01 to 0.5 wt.%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrolytic capacitor manufacturing method, and more particularly to an electrolytic capacitor manufacturing method capable of improving the capacity of an electrolytic capacitor without increasing a large manufacturing process. Moreover, it is related with the electrolytic capacitor manufactured by the electrolytic capacitor manufacturing method which concerns.

  The multilayer electrolytic capacitor has, for example, a structure in which the capacitor element 101 shown in FIG. 2 is stacked. The capacitor element 101 is formed as follows. First, after forming the metal layer 111 with a metal having a valve action such as aluminum, the oxide film 112 that is a dielectric is formed by oxidizing the metal layer 111 after removing a portion that functions as an anode (hereinafter referred to as an anode portion 120). . Subsequently, after an electrolyte layer 113 (eg, manganese dioxide, polypyrrole, polythiophene, etc.) is formed on the oxide film 112, a cathode layer is formed by, for example, laminating a carbon layer 114 and a silver paste layer 115 thereon. The capacitor element 101 is used. A portion of the capacitor element 101 where the cathode layer is formed is referred to as a cathode portion 110. The oxide film 112 may be formed including the anode portion 120.

  As shown in FIG. 3, the required number of capacitor elements 101 are stacked, the cathode portions 110 are electrically connected to each other with a conductive adhesive 103, and the anode portions 120 are electrically connected to each other by welding 104. . Further, the cathode terminal 116 is connected to the cathode portion 110 via a conductive adhesive, and the anode terminal 126 is connected to the anode portion 120 by welding, and the capacitor element 101 body is molded and insulated with the resin 105.

  By the way, as the “metal having a valve action”, niobium, tantalum or the like is used in addition to aluminum. Aluminum is widely used because it has a lower dielectric constant than niobium, tantalum, and the like, but has high developability and is easy to mold. In the case of using aluminum, in order to compensate for the drawback of low dielectric constant, it is required to increase the capacitance of the electrolytic capacitor by increasing the surface area by utilizing the point of high developability. Therefore, after forming aluminum into a foil shape, as shown in FIG. 4, the surface is etched to form irregularities in the etched portion 107, and the surface area is further increased. Theoretically, if the accuracy of this etching process is improved and the surface is made finer, the surface area is enlarged. However, it is difficult to set such conditions, and there is a technical limit to enlarge the surface area.

  Therefore, heat treatment (for example, see Patent Document 1) or chemical treatment (for example, see Patent Document 2) after the etching process and the formation of the oxide film 112 have been proposed. Therefore, it is expected that the capacity of the electrolytic capacitor can be further increased by performing heat treatment and chemical treatment together with etching treatment.

JP 2007-59629 A JP 2003-59777 A JP-A-60-157215

  Here, the technique of Patent Document 2 is an example in which niobium (Nb) is used as a metal having a valve action. However, according to Patent Document 3, “the pH should not exceed 9.5, because rapid and uncontrollable dissolution of the aluminum oxide film can occur under such conditions. , Using sodium hydroxide, potassium hydroxide or a strongly basic solution is impractical. "(Page 71, upper left). That is, it is stated that when aluminum is used as the valve metal, alkali treatment cannot be performed, and in particular, sodium hydroxide which is a general-purpose and inexpensive alkaline solution cannot be used.

  Accordingly, in view of the above-described usefulness of aluminum as a valve metal and the effectiveness of alkali treatment described in Patent Document 2, an electrolytic capacitor manufacturing method using aluminum as a valve metal, the electrolytic capacitor being accompanied by alkali treatment It is an object of the present invention to provide a manufacturing method.

  The electrolytic capacitor manufacturing method according to the present invention includes a film forming step of forming an oxide film on the surface of aluminum formed as a metal layer, and an alkali treatment step of immersing the aluminum on which the oxide film has been formed in an alkaline solution. Including.

According to the said structure, since the alkaline treatment process which immerses aluminum in an alkaline solution is included, the electrostatic capacitance of the manufactured electrolytic capacitor increases.
In the electrolytic capacitor manufacturing method according to the present invention, the alkaline solution is preferably a sodium hydroxide solution.

  According to the said structure, since an alkaline solution is a sodium hydroxide solution, it becomes possible to acquire the above-mentioned effect using a general purpose and cheap reagent. Sodium hydroxide is highly soluble in water and can be easily adjusted to a desired concentration.

In the electrolytic capacitor manufacturing method according to the present invention, the concentration of the sodium hydroxide solution is preferably 0.01 wt% or more and 0.5 wt% or less.
It has been confirmed that a sodium hydroxide solution having a concentration of 0.01 wt% or more and 0.5 wt% or less exhibits the above-mentioned effects remarkably.

  The electrolytic capacitor manufacturing method according to the present invention preferably further includes a heat treatment step of heating the aluminum on which the oxide film has been formed, between the film formation step and the alkali treatment step.

  According to the said structure, since it further includes the heat processing process which heats the aluminum in which the oxide film was formed, in addition to the electrostatic capacitance increase by an alkali treatment process, the electrostatic capacitance increase by a heat processing process can be anticipated.

In the electrolytic capacitor manufacturing method according to the present invention, the heating temperature is preferably 80 ° C. or higher and 300 ° C. or lower.
It has been confirmed that if the heating temperature is 80 ° C. or higher and 300 ° C. or lower, the above-mentioned effects are remarkably exhibited.

Since the electrolytic capacitor according to the present invention is manufactured by the above-described electrolytic capacitor manufacturing method, if the structure is the same, an electrolytic capacitor having a larger capacitance than the conventional one is obtained.
In the electrolytic capacitor according to the present invention, it is preferable that the aluminum on which the oxide film after the alkali treatment step is formed is further covered with a solid electrolyte layer mainly composed of a conductive polymer.

  According to the above configuration, since the aluminum on which the oxide film after the alkali treatment step is formed is further covered with the solid electrolyte layer mainly composed of a conductive polymer, a thin solid electrolyte layer can be easily formed. Can do.

  In the electrolytic capacitor according to the present invention, it is preferable that the conductive polymer is mainly composed of at least one selected from the group consisting of polythiophene, polypyrrole, and polyaniline.

  According to the above configuration, since the conductive polymer is mainly composed of at least one of the group consisting of polythiophene, polypyrrole, and polyaniline, the solid electrolyte layer has high heat resistance, long life, and low resistance. Can be formed.

  ADVANTAGE OF THE INVENTION According to this invention, it is a manufacturing method of the electrolytic capacitor which used aluminum as a valve metal, Comprising: The manufacturing method of the electrolytic capacitor accompanied by an alkali treatment can be provided.

It is drawing explaining one Embodiment of the manufacturing method of the electrolytic capacitor concerning this invention, Comprising: It is an expanded sectional view of the metal layer periphery of the capacitor | condenser element manufactured with the manufacturing method which concerns on this embodiment. It is drawing explaining the manufacturing method of the conventional electrolytic capacitor, Comprising: It is a schematic cross section of the capacitor | condenser element which comprises an electrolytic capacitor. It is drawing explaining the manufacturing method of the conventional electrolytic capacitor, Comprising: It is sectional drawing of an electrolytic capacitor. It is drawing explaining the manufacturing method of the conventional electrolytic capacitor, Comprising: It is an expanded sectional view of the metal layer periphery of the capacitor | condenser element manufactured with the conventional manufacturing method.

  Hereinafter, an embodiment of an electrolytic capacitor manufacturing method and an electrolytic capacitor according to the present invention will be described with reference to FIG. However, the basic manufacturing method of the electrolytic capacitor is as described in the prior art, so it is omitted and only the characteristic part is described.

  The electrolytic capacitor manufacturing method according to this embodiment includes a film forming step of forming an oxide film on the surface of aluminum formed as a metal layer, and an alkali treatment step of immersing the aluminum on which the oxide film has been formed in an alkaline solution. It has the feature in the point to include.

  As shown in FIG. 1, aluminum formed in a foil shape is used as a valve metal, and after forming the metal layer 1, the surface is etched by a known method. Since the surface area of the metal layer 1 is expanded by this etching process as shown in FIG. 1, the capacitance of the manufactured electrolytic capacitor is increased.

  Next, the etched aluminum is oxidized except for a portion (hereinafter referred to as an anode portion) that functions as an anode later, thereby forming an oxide film 2 serving as a dielectric on the aluminum surface. This is the film forming process. The oxide film 2 may be formed including the anode part.

  Then, the heat processing process which heats the aluminum in which the oxide film 2 was formed is performed. Specifically, aluminum on which the oxide film 2 is formed is put in an atmosphere at a predetermined temperature for 15 minutes to heat the aluminum. The predetermined temperature is preferably 150 ° C. or more and 300 ° C. or less from the viewpoint of heating effect.

  After the heat treatment step, an alkali treatment step is performed in which the aluminum on which the oxide film 2 is formed is immersed in an alkaline solution. Specifically, the aluminum on which the cooled oxide film 2 has been formed is immersed in an aqueous sodium hydroxide solution having a predetermined concentration for 10 minutes. The predetermined concentration is preferably 0.01 wt% or more and 0.5 wt% or less. If the sodium hydroxide concentration is less than 0.01 wt%, the effect of the alkali treatment may be insufficient. If the sodium hydroxide concentration exceeds 0.5 wt%, the oxide film 2 may be eroded too much. This is because of concern.

  By performing this alkali treatment step, it is considered that aluminum scrap 108 can be prevented from remaining on the surface of the oxide film 112 and a gap 109 can be prevented as shown in FIG. When the gap 109 is generated, it is considered that the later-described electrolyte layer 3 is not formed in the portion, and this causes a decrease in the capacitance of the electrolytic capacitor.

  As shown in FIG. 1, as a result of the removal of the aluminum scrap 108 by the alkali treatment process, the gap 109 disappears, so that the surface area of the metal layer 1 is effectively enlarged, and the capacitance of the electrolytic capacitor is the same as the conventional one. It is thought that it will increase in comparison. Further, it is considered that minute cracks 9 are also formed in the aluminum, and the surface area of the metal layer 1 is increased accordingly, which contributes to an increase in the capacitance of the electrolytic capacitor.

  An electrolyte layer 3 made of a conductive polymer is formed on the oxide film 2. More specifically, for example, by immersing a portion where an aluminum oxide film having been subjected to the alkali treatment step is formed in a solution containing 3,4-ethylenedioxythiophenine, 3,4-ethylenedioxythiophene is immersed. An electrolyte layer 3 made of oxythiophenine is formed by chemical oxidative polymerization.

  Further, the carbon layer is formed on the electrolyte layer 3 by repeatedly immersing the portion where the electrolyte layer 3 is formed in a solution in which carbon is dispersed in a solvent and drying it at a predetermined temperature and time. Furthermore, a silver paste layer is formed by applying and drying a silver paste on the carbon layer. A capacitor element having a cathode layer composed of a laminated film from an electrolyte layer 3 to a silver paste layer through such a process, and having a cathode portion whose surface is covered with a cathode layer and an anode portion made of uncoated aluminum. Complete. In addition, the process from the alkali treatment to the formation of the silver paste layer is performed only on the portion serving as the cathode portion.

  A required number of capacitor elements are stacked, the cathode portions are electrically connected with a conductive adhesive, and the anode portions are electrically connected to each other by welding. Further, a cathode terminal is connected to the cathode portion via a conductive adhesive, and the anode terminal is connected to the anode portion by welding, and the capacitor element body is molded and insulated with resin to complete the electrolytic capacitor.

According to the electrolytic capacitor manufacturing method of the above embodiment, the following effects can be obtained.
(1) In the said embodiment, since the alkaline treatment process which immerses aluminum in an alkaline solution is included, the electrostatic capacitance of the manufactured electrolytic capacitor increases.

  (2) In the above embodiment, since the alkaline solution is a sodium hydroxide solution, the above-described effects can be obtained using a general-purpose and inexpensive reagent. Sodium hydroxide is highly soluble in water and can be easily adjusted to a desired concentration.

  (3) According to the above embodiment, since the concentration of the sodium hydroxide solution is 0.01 wt% or more and 0.5 wt% or less, it has been confirmed that the effect of increasing the electrostatic capacitance is remarkably exhibited. If the sodium hydroxide concentration is less than 0.01 wt%, the effect of the alkali treatment may be insufficient, and if the sodium hydroxide concentration is 0.5 wt% or more, the oxide film 2 is excessively eroded. Is concerned.

  (4) According to the said embodiment, since the heat processing process which heats the aluminum in which the oxide film 2 was formed is further included, in addition to the electrostatic capacitance increase by an alkali treatment process, the electrostatic capacitance increase by a heat processing process is anticipated. it can.

(5) According to the said embodiment, since the temperature of a heating is 80 degreeC or more and 300 degrees C or less, the effect of the increase in an electrostatic capacitance is shown notably.
(6) According to the above embodiment, the method further includes an etching process for performing an etching process to increase the surface area of the aluminum. A synergistic effect of increased capacity can be expected.

(7) Since the electrolytic capacitor of the said embodiment is manufactured by the above-mentioned electrolytic capacitor manufacturing method, if it is the same structure, it will become an electrolytic capacitor with a large electrostatic capacity compared with the past.
(8) In the electrolytic capacitor of the above embodiment, the aluminum on which the oxide film after the alkali treatment step is formed is further covered with a solid electrolyte layer mainly composed of a conductive polymer, so that a thin solid electrolyte layer can be easily formed. Can be formed.

(9) In the electrolytic capacitor of the above embodiment, since the conductive polymer is a polythiophene type, it is possible to form a solid electrolyte layer having high heat resistance, ultra-long life, and low resistance.
(10) The electrolytic capacitor of the above embodiment has higher durability against high voltage than the conventional electrolytic capacitor. Although the details about the effect are unknown, it is speculated that the structural weakness that reduces the resistance to high voltage is solved by dissolving by alkali treatment.

In addition, you may change this embodiment as follows.
In the above embodiment, the 3,4-ethylenedioxythiophenine film, which is a polythiophene-based conductive polymer, is formed as the electrolyte layer 3, but other configurations may be used. Since it only has to function as an electrolyte layer, another polythiophene-based conductive polymer may be used, or a polypyrrole-based or polyaniline-based conductive polymer may be used.

  In the above embodiment, the conductive polymer is used as the electrolyte layer 3, but other configurations may be used. Other members may be used as long as they are conductive and can form a sufficiently thin layer.

  In the above embodiment, the heating temperature in the heat treatment is preferably 80 ° C. or higher and 300 ° C. or lower, but is not limited to this temperature. Depending on the state of the etching or oxide film, there is a possibility that another temperature will be an appropriate temperature. The same applies to the heating time.

  In the above embodiment, the heating temperature in the heat treatment is preferably 80 ° C. or higher and 300 ° C. or lower, but is not limited to this temperature. Depending on the etching state and the state of the oxide film, it may be appropriate to set other temperatures. The same applies to the heating time.

  -Although heat processing is performed in the said embodiment, it is not essential. Since only the alkali treatment has an effect of increasing the electrostatic capacity, if only such an increase effect is sufficient, the heat treatment may be omitted and the cost may be reduced.

  -In the said embodiment, although the sodium hydroxide solution is used as an alkaline solution, another structure may be sufficient. Similar effects can be expected with potassium hydroxide or other alkalis.

  In the above embodiment, the present invention is applied to the method for manufacturing a multilayer electrolytic capacitor in which capacitor elements are stacked. However, other configurations may be used. The same effect can be obtained by applying the same to a so-called winding type electrolytic capacitor.

  Below, this invention is demonstrated based on an Example and a comparative example. In addition, this invention is not limited to these Examples, These Examples can be changed and changed based on the meaning of this invention, and they are excluded from the scope of the present invention. is not.

  The capacitance was measured for the capacitor manufactured by the electrolytic capacitor manufacturing method described in the above embodiment. Since the manufacturing method is basically the same as that of the embodiment, the description thereof will be omitted, and only the characteristic part will be described in detail below.

  Only the part where the oxide film was formed by the film formation process of the molded aluminum was subjected to the alkali treatment process. Specifically, a sodium hydroxide aqueous solution having a concentration of 0.01 wt% was used, and the portion where the oxide film was formed was immersed for 10 minutes. The heat treatment process was omitted.

  The electrolyte layer 3 has a portion in which an aluminum oxide film having been subjected to the alkali treatment step is formed on a mixed solution of 3,4-ethylenedioxythiophenine, iron (III) P-toluenesulfonate, and 1-butanol. It was formed by dipping.

  Furthermore, the part in which the electrolyte layer 3 was formed was immersed in a solution in which carbon was dispersed in a solvent, and dried at 100 ° C. for 30 minutes twice to form a carbon layer on the electrolyte layer. Further, a silver paste was applied to a thickness of about 5 to 10 μm on the carbon layer and dried to form a silver paste layer.

  The capacitance of the electrolytic capacitor thus manufactured at a frequency of 120 Hz was measured using an LCR meter. The results are shown in Table 1.

  The capacitance at a frequency of 120 Hz of an electrolytic capacitor manufactured in the same manner as in Example 1 except that the sodium hydroxide concentration used for the alkali treatment was 0.20 wt% was measured using an LCR meter. The results are shown in Table 1.

  The capacitance at a frequency of 120 Hz of an electrolytic capacitor produced in the same manner as in Example 1 except that the concentration of sodium hydroxide used for the alkali treatment was 0.50 wt% was measured using an LCR meter. The results are shown in Table 1.

  In the same manner as in Example 1, a heat treatment step for heating aluminum on which the oxide film was formed was added. Specifically, the heating temperature was 50 ° C. and heating was performed for 15 minutes. In the alkali treatment step performed after cooling, a 0.20 wt% sodium hydroxide aqueous solution was used and immersed for 30 minutes. Otherwise, the electrostatic capacity at a frequency of 120 Hz of an electrolytic capacitor produced in the same manner as in Example 1 was measured using an LCR meter. The results are shown in Table 1.

  The capacitance at a frequency of 120 Hz of an electrolytic capacitor produced in the same manner as in Example 4 except that the heating temperature was 150 ° C. was measured using an LCR meter. The results are shown in Table 1. Moreover, the breakdown withstand voltage test was also implemented about the present Example. In this test, a DC voltage was increased by 1 V per second, and the voltage at which a short circuit occurred was measured. The current flowing through the electrolytic capacitor was continuously measured, and it was determined that a short circuit occurred when a current of 500 mA flowed. Such a breakdown voltage test was performed on 10 samples, and the maximum value, the minimum value, and the average value are shown in Table 2.

  The capacitance at a frequency of 120 Hz of an electrolytic capacitor produced in the same manner as in Example 4 except that the heating temperature was 300 ° C. was measured using an LCR meter. The results are shown in Table 1.

  The electrostatic capacity at a frequency of 120 Hz of an electrolytic capacitor produced in the same manner as in Example 4 except that the heating temperature was 350 ° C. was measured using an LCR meter. The results are shown in Table 1.

[Comparative Example 1]
The capacitance at a frequency of 120 Hz of the electrolytic capacitor manufactured in the same manner as in Example 4 except that the heat treatment step and the alkali treatment step were omitted was measured using an LCR meter. The results are shown in Table 1. Moreover, the breakdown withstand voltage test was implemented about 10 samples similarly to Example 5, and the maximum value, the minimum value, and an average value are shown in Table 2.

[Comparative Example 2]
The capacitance at 120 Hz of the electrolytic capacitor manufactured in the same manner as in Example 4 except that the heating temperature was 50 ° C. and a 2.00 wt% sodium hydroxide aqueous solution was used was measured using an LCR meter. It was measured. The results are shown in Table 1.

[Comparative Example 3]
The capacitance at 120 Hz of the electrolytic capacitor manufactured in the same manner as in Example 4 except that the heating temperature was 150 ° C. and a 2.00 wt% sodium hydroxide aqueous solution was used was measured using an LCR meter. It was measured. The results are shown in Table 1.

（静電容量についての評価）
実施例１〜３と比較例１とを比較すると、水酸化ナトリウム溶液の濃度が０．０１ｗｔ％以上０．５ｗｔ％以下においてアルカリ処理を行えば、行わない場合に比べ静電容量が増加することが確認できる。

(Evaluation of capacitance)
When Examples 1 to 3 are compared with Comparative Example 1, the capacitance increases when the alkali treatment is performed at a concentration of the sodium hydroxide solution of 0.01 wt% or more and 0.5 wt% or less as compared to the case where it is not performed. Can be confirmed.

  Moreover, when Example 2 and Examples 4-7 are compared, if the heat processing process is also performed, it can confirm that an electrostatic capacitance increases further. Moreover, since an effect is seen if it is at least 50 degreeC or more and 350 degrees C or less, and Example 5 and 6 are especially effective, it can be guessed that 80 degreeC or more and 300 degrees C or less are especially preferable.

  Comparing Example 4 and Comparative Example 2, it can be seen that, even when heat treatment is performed at the same temperature, the capacitance is greatly reduced when alkali treatment is performed with a sodium hydroxide concentration of 2%. The same can be seen in the comparison between Example 5 and Comparative Example 3. This is probably because the oxide film was eroded by sodium hydroxide, as pointed out in Patent Document 3. On the other hand, if the alkali treatment is performed at 0.5 wt% or less as described above, the capacitance increases. Therefore, if the alkali treatment is performed at an appropriate concentration, the capacitance is increased by the alkali treatment with sodium hydroxide. Can be seen to increase.

(Evaluation for breakdown voltage test)
When Example 5 is compared with Comparative Example 1, it can be seen that the breakdown voltage increases when heat treatment and alkali treatment are performed. The cause of this is not clear, but it is presumed that the structural defects that are easily short-circuited have been removed by alkali treatment.

  The present invention relates to a method for manufacturing an electrolytic capacitor that can improve the capacity of the electrolytic capacitor without greatly increasing the number of manufacturing steps, and thus can be widely used industrially.

  DESCRIPTION OF SYMBOLS 1 ... Metal layer, 2 ... Oxide film, 3 ... Electrolyte layer, 9 ... Crack, 101 ... Capacitor element, 103 ... Conductive adhesive, 104 ... Welding, 105 ... Resin, 107 ... Etched part, 108 ... Aluminum scrap, 109 ... Crevice, 110 ... Cathode part, 111 ... Metal layer, 112 ... Oxide film, 113 ... -Electrolyte layer, 114 ... carbon layer, 115 ... silver paste layer, 116 ... cathode terminal, 120 ... anode part, 126 ... anode terminal.

Claims (8)

A film forming step of forming an oxide film on the surface of aluminum formed as a metal layer;
An alkali treatment step of immersing the aluminum in which the oxide film is formed in an alkali solution;
An electrolytic capacitor manufacturing method comprising:   The method for producing an electrolytic capacitor according to claim 1, wherein the alkaline solution is a sodium hydroxide solution.   The electrolytic capacitor manufacturing method according to claim 2, wherein the concentration of the sodium hydroxide solution is 0.01 wt% or more and 0.5 wt% or less.   The electrolytic capacitor manufacturing method according to any one of claims 1 to 3, further comprising a heat treatment step of heating the aluminum on which the oxide film is formed between the film formation step and the alkali treatment step. .   The electrolytic capacitor manufacturing method according to claim 4, wherein the heating temperature is 80 ° C. or higher and 300 ° C. or lower.   The electrolytic capacitor manufactured by the electrolytic capacitor manufacturing method of any one of Claims 1-5.   The electrolytic capacitor according to claim 6, wherein the aluminum on which the oxide film after the alkali treatment step is formed is further covered with a solid electrolyte layer mainly composed of a conductive polymer.   The electrolytic capacitor according to claim 7, wherein the conductive polymer is mainly composed of at least one selected from the group consisting of polythiophene, polypyrrole, and polyaniline.

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