JP2011014590A - Method for manufacturing solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a solid electrolytic capacitor, the method achieving both a lower cost in a cleaning process and a reduced environmental load.SOLUTION: A method for manufacturing a solid electrolytic capacitor includes the steps of: preparing an anode body (S10); forming a dielectric film on a surface of the anode body (S20); obtaining a capacitive element by forming a solid electrolyte layer comprising a conductive polymer on a surface of the dielectric film (S30); and cleaning the capacitive element using a cleaning solution containing a saccharide (S40).

Description

  The present invention relates to a method for manufacturing a solid electrolytic capacitor, and more particularly to a method for manufacturing a solid electrolytic capacitor capable of achieving both reduction in cost of a cleaning process included in the manufacturing process and reduction in environmental load. Is.

  In the solid electrolytic capacitor, a dielectric oxide film is formed, for example, by electrolytic oxidation treatment on the surface of an anode body made of valve metal, and an electrolytic solution, manganese dioxide, conductive material is further formed on the dielectric oxide film. It is manufactured by forming a cathode layer by adhering a conductive substance such as a conductive polymer compound. Here, the valve metal is a metal that forms a very dense and highly durable dielectric oxide film by electrolytic oxidation treatment, and includes, for example, aluminum, tantalum, titanium, niobium, and the like. Further, as the conductive polymer compound, for example, a conductive polymer such as polythiophene, polypyrrole, polyaniline, TCNQ (7,7,8,8-tetracyanoquinodimethane) complex salt, or the like can be employed. According to this type of electrolytic capacitor, since the dielectric oxide film is very thin, a capacitor having a small size and a large capacity can be obtained as compared with other paper capacitors and film capacitors.

  When a solid electrolyte layer is formed as a cathode layer in the manufacturing process of the solid electrolytic capacitor, for example, by using polythiophene, particularly 3,4-ethylenedioxythiophene, low ESR due to a high dielectric constant compared to the case of using polypyrrole or the like. (Equivalent Series Resistance) and high yield of materials by slow polymerization reaction can be achieved. In this case, it is effective to use ammonium persulfate or ferric salt as the oxidizing agent, and organic sulfonate as the dopant, and particularly organic ferric acid ferric salt represented by paratoluenesulfonic acid ferric salt. It is valid.

  In the formation of the solid electrolyte layer by such a polymerization reaction, impurities (for example, iron salt which is a residual dopant component, excess organic sulfonic acid, unreacted monomer, polymer and monomer are formed on the generated solid electrolyte layer. Intermediate oligomers, etc.) remain. For this reason, there arises a problem that the reliability of the obtained capacitor, in particular, resistance to high temperature storage is lowered. Moreover, such a problem is not a problem peculiar to the case where the organic sulfonic acid ferric salt is used, and similarly occurs when the solid electrolyte layer is formed by other methods. Therefore, after the step of forming the solid electrolyte layer in the manufacturing process of the solid electrolytic capacitor, it is preferable to perform a cleaning step for removing the impurities and ensuring the reliability of the solid electrolytic capacitor.

  And as a cleaning liquid used in the said washing | cleaning process, it is known that use of the cleaning liquid containing a chelating agent is effective, for example (for example, refer patent document 1 and 2). Thereby, since a chelating agent takes in and wash | cleans the metal ion etc. which are the impurities adhering to the surface of a solid electrolyte layer, a high cleaning effect is acquired.

JP 2006-104314 A JP 2009-10163 A

  However, when a cleaning liquid containing a chelating agent is used as described in Patent Documents 1 and 2, sufficient waste liquid treatment is required to reduce the environmental burden. Moreover, the cleaning liquid containing a chelating agent is relatively expensive. Considering the recent demand for lower prices, it is required to reduce the cost of the cleaning process by simplifying the waste liquid treatment and adopting an inexpensive cleaning liquid.

  Therefore, an object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor capable of realizing both reduction in cost of a cleaning process and reduction in environmental load.

  A method for producing a solid electrolytic capacitor according to the present invention includes a step of preparing an anode body, a step of forming a dielectric film on the surface of the anode body, and a solid electrolyte made of a conductive polymer on the surface of the dielectric film. The method includes a step of obtaining a capacitor element by forming a layer and a step of cleaning the capacitor element with a cleaning liquid containing sugar.

  The present inventor has studied a policy for realizing both reduction in cost of the cleaning process and reduction in environmental load. As a result, by adopting a cleaning liquid containing sugar, the sugar as a solute takes in metal ions, which are impurities adhering to the surface of the solid electrolyte layer, and is washed away. It was found that a high cleaning effect can be obtained in the same manner as in the cleaning liquid. Furthermore, by adopting a cleaning liquid containing sugar, it is not necessary to carry out costly waste liquid treatment as in the case of a cleaning liquid containing a chelating agent, and the environmental burden can be reduced. In addition, a cleaning liquid containing sugar is less expensive than a cleaning liquid containing a chelating agent. As described above, according to the method for manufacturing a solid electrolytic capacitor of the present invention, it is possible to realize both reduction in cost of the cleaning process and reduction of environmental load by employing the cleaning liquid containing sugar in the cleaning process. . In the present application, “sugar” includes sugar alcohol (eg, xylitol).

  In the method for producing a solid electrolytic capacitor, the sugar may contain glucose in its structure.

  In the method for producing a solid electrolytic capacitor, the sugar may include at least one sugar selected from the group consisting of glucose, sucrose, lactose, maltose, trehalose, and starch.

  In the method for producing a solid electrolytic capacitor, the solvent of the cleaning liquid can be any of water, an organic solvent, or a mixture of water and an organic solvent.

  In the method for producing a solid electrolytic capacitor, the sugar concentration in the cleaning liquid is preferably 0.01% by mass or more and 20% by mass or less.

  In the method for producing a solid electrolytic capacitor, in the step of obtaining a capacitor element, the solid electrolyte layer may be formed by chemical polymerization.

  As is clear from the above description, according to the method for manufacturing a solid electrolytic capacitor of the present invention, there is provided a method for manufacturing a solid electrolytic capacitor capable of realizing both reduction in cost of the cleaning process and reduction of environmental load. Can be provided.

It is a flowchart which shows the outline of the manufacturing method of a solid electrolytic capacitor. It is a schematic sectional drawing which shows the structure of the capacitor | condenser element contained in a solid electrolytic capacitor. It is a schematic sectional drawing which shows a solid electrolytic capacitor structure.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

  Referring to FIG. 1, in the method for manufacturing a solid electrolytic capacitor in one embodiment of the present invention, an anode body preparation step is first performed as a step (S10). In this step (S10), referring to FIG. 2, first, a raw material powder that is a powder of a valve action metal is prepared, and in a state where one end side in the longitudinal direction of the anode lead 15 is embedded in the raw material powder, The anode body 11 is formed into a desired shape. And the anode body 11 in which one end side of the anode lead 15 is embedded is obtained by sintering the molded raw material powder. Here, the anode lead 15 and the anode body 11 are preferably made of the same valve metal.

  Next, as shown in FIG. 1, a dielectric film forming step is performed as a step (S20). In this step (S20), referring to FIG. 2, anode body 11 produced in step (S10) is immersed in an acid solution such as nitric acid or phosphoric acid, and electrolytic formation is performed. A dielectric film 12 is formed on the surface layer of the anode body 11.

  Next, with reference to FIG. 1, a solid electrolyte layer formation process is implemented as process (S30). In this step (S30), the solid electrolyte layer 13 made of a conductive polymer is formed on the dielectric film 12 as shown in FIG. 2 by chemical oxidative polymerization or electrolytic oxidative polymerization. Thereby, the capacitor element is completed. When the solid electrolyte layer 13 is formed by the chemical oxidative polymerization method, a method of immersing the anode body 11 on which the dielectric film 12 is formed in a chemical polymerization solution containing at least a monomer, an oxidant, and a dopant, the chemical polymerization solution Is applied to the anode body 11 on which the dielectric film 12 is formed, each of the monomer solution and the oxidant solution is immersed in the anode body 11 on which the dielectric film 12 is formed, each of the monomer solution and the oxidant solution. The method of apply | coating to the anode body 11 in which the dielectric film 12 was formed, etc. can be employ | adopted.

  When the solid electrolyte layer 13 is formed by electrolytic oxidation polymerization, for example, the anode body 11 on which the dielectric film 12 is formed is immersed in an electrolytic polymerization solution containing at least a monomer and a dopant, and the anode body 11 is An electrolytic oxidation method can be employed as the anode.

  In the chemical oxidative polymerization method, it is not always necessary to use different materials for the oxidant and the dopant, and a material that also serves as the oxidant and the dopant can be used. In addition to the above materials, an additive such as a surfactant may be added to the chemical oxidation polymerization solution or the electrolytic oxidation polymerization solution. Furthermore, you may implement the thermochemical polymerization which adds heat after the said chemical oxidation polymerization.

  Next, referring to FIG. 1, a cleaning step is performed as a step (S40). In this step (S40), the capacitor element of FIG. 2 produced by the above steps (S10) to (S30) is cleaned using a cleaning liquid. And in the process (S40) in this Embodiment, washing | cleaning is implemented using the washing | cleaning liquid containing sugar.

  Next, a cathode lead layer forming step is performed as a step (S50). In this step (S50), referring to FIG. 3, for example, conductive carbon layer 14A and silver paste layer 14B are sequentially formed on solid electrolyte layer 13 formed in step (S30), thereby leading to cathode extraction. Layer 14 is created.

  Next, with reference to FIG. 1, a terminal connection process is implemented as process (S60). In this step (S60), referring to FIG. 3, for example, anode terminal 18 made of copper or copper alloy is connected to anode lead 15, and cathode terminal 17 made of copper or copper alloy is connected to cathode lead layer 14. Is done. The cathode lead layer 14 and the cathode terminal 17 can be connected by a conductive adhesive 16, for example, as shown in FIG. The anode terminal 18 and the anode lead 15 can be connected by, for example, resistance welding. The cathode lead layer 14 and the cathode terminal 17 may be connected by resistance welding, or the anode terminal 18 and the anode lead 15 may be connected by the conductive adhesive 16.

  Next, with reference to FIG. 1, a coating process is implemented as process (S70). In this step (S70), referring to FIG. 3, the capacitor element is covered with exterior resin 19 so that part of anode terminal 18 and cathode terminal 17 is exposed to the outside. Thereafter, portions of the anode terminal 18 and the cathode terminal 17 exposed from the exterior resin 19 are bent along the exterior resin 19. The solid electrolytic capacitor 1 is completed by the above process.

  In the method for manufacturing a solid electrolytic capacitor in the present embodiment, a cleaning liquid containing sugar is used in the step (S40). As a result, the saccharide, which is a solute, takes in and removes metal ions and the like fixed to the surface of the solid electrolyte layer 13, so that not only a high cleaning effect is obtained, but also the cost of the cleaning agent is reduced. In addition, the adoption of a cleaning liquid containing sugar eliminates the need for costly waste liquid treatment as in the case of a cleaning liquid containing a chelating agent, and reduces the environmental burden. As described above, the manufacturing method of the solid electrolytic capacitor according to the present embodiment employs a cleaning liquid containing sugar in the cleaning process, thereby reducing the cost of the cleaning process and reducing the environmental burden. It is a manufacturing method. In addition, due to the high cleaning effect, it is possible to effectively suppress the decrease in reliability caused by the presence of impurities, particularly the occurrence of a leakage current short circuit during high temperature storage.

  Here, in the method for manufacturing a solid electrolytic capacitor in the present embodiment, the sugar may contain glucose in its structure.

  In the method for producing a solid electrolytic capacitor in the present embodiment, it is preferable to employ glucose, sucrose, lactose, maltose, trehalose, starch, or a combination thereof as the sugar. Thereby, a high cleaning effect can be ensured more reliably. In particular, by adopting starch, a high cleaning effect can be obtained. As the solvent for the cleaning liquid, water, an organic solvent, or a mixture of water and an organic solvent can be employed.

  Furthermore, in the method for manufacturing a solid electrolytic capacitor in the present embodiment, the sugar concentration of the cleaning liquid used in the step (S40) is preferably 0.01% by mass or more and 20% by mass or less, and 0.1% by mass. It is more preferable that it is 10% by mass or more. If the sugar concentration is less than 0.01% by mass, the ratio of sugar in the cleaning liquid is insufficient, and a sufficient cleaning effect may not be obtained. On the other hand, when the sugar concentration exceeds 20% by mass, the sugar is not sufficiently dissolved in the solvent and may remain attached to the solid electrolyte layer 13 as an impurity during cleaning. Therefore, the sugar concentration is preferably 0.01% by mass or more and 20% by mass or less.

  Moreover, it is preferable that the temperature of the washing | cleaning liquid used in a process (S40) is 10 degreeC or more and 80 degrees C or less. When the temperature of the cleaning liquid is less than 10 ° C., the sugar is not sufficiently dissolved in the solvent, and may adhere to the solid electrolyte layer 13 as an impurity during cleaning. In addition, depending on the type of solvent, the solvent may solidify and may not function as a cleaning liquid. On the other hand, when the temperature of the cleaning liquid exceeds 80 ° C., the solvent evaporates depending on the type of the solvent, and the concentration of the cleaning liquid may become higher than necessary.

  In the method for manufacturing the solid electrolytic capacitor in the present embodiment, the solid electrolyte layer 13 may be formed by chemical polymerization in the step (S30). When the solid electrolyte layer 13 is formed by chemical polymerization, a decrease in the reliability of the solid electrolytic capacitor 1 due to impurities remaining on the solid electrolyte layer 13 becomes a particular problem. Therefore, when the solid electrolyte layer 13 is formed by chemical polymerization, the solid electrolytic capacitor manufacturing method according to the present embodiment that achieves both a reduction in the cost of the cleaning process and a reduction in environmental burden while ensuring a high cleaning effect is employed. Is preferred.

  Example 1 will be described below. An experiment was conducted to investigate the effect of the cleaning liquid used in the cleaning process on the reliability of the solid electrolytic capacitor. The experimental procedure is as follows.

  First, tantalum powder was prepared as a raw material powder, and an anode body was prepared in the same manner as in steps (S10) to (S20) of the above embodiment, and then a dielectric film was formed on the surface layer portion. Next, the chemical oxidation polymerization in which the anode body is dipped in a liquid mixture composed of 3,4-ethylenedioxythiophene, iron (III) paratoluenesulfonate and 1-butanol and then dried is repeated several times. A solid electrolyte layer made of 3,4-ethylenedioxythiophene was formed. Next, the capacitor element on which the solid electrolyte layer was formed was immersed in a 1% by mass starch aqueous solution adjusted to 20 ° C. for 10 minutes. Then, the solid electrolytic capacitor was completed by implementing the process similar to process (S50)-(S70) in the said embodiment (Example 1).

  On the other hand, for comparison, in the same manufacturing process as in Example 1 above, pure water was used as the cleaning liquid (Comparative Example 1), 1-butanol was used as the cleaning liquid (Comparative Example 2), and ethanol was used as the cleaning liquid. The one used (Comparative Example 3) and the one using a butanol solution of a silane coupling agent as a cleaning liquid (Comparative Example 4) were also prepared. 100 solid electrolytic capacitors of Examples and Comparative Examples were each produced.

  Then, the solid electrolytic capacitors of Examples and Comparative Examples thus fabricated were absorbed by moisture (held at a temperature of 60 ° C. and a humidity of 60% for 40 hours), and reflowed (held at a peak of 250 ° C. for 10 seconds, 225 ° C. over 75 ° C.). (Second holding, holding at 200 ° C. or more for 100 seconds, holding at 150 to 180 ° C. for 100 to 120 seconds), and a high temperature storage test at a reliability of 125 ° C. for 1000 hours was performed. And about each solid electrolytic capacitor, the characteristic before a test was compared with the characteristic after a test, and the generation | occurrence | production number of leakage current short was investigated. The test results are shown in Table 1.

  As shown in Table 1, in the solid electrolytic capacitor of the comparative example, the occurrence of a leakage current short was confirmed in each of 3 to 12 solid electrolytic capacitors, whereas in the solid electrolytic capacitor of Example 1, the leakage current was No short circuit occurred. From this result, according to the method for manufacturing a solid electrolytic capacitor of the present invention that employs a cleaning solution containing sugar (starch) as the cleaning solution, a high cleaning effect can be obtained, and as a result, a highly reliable solid electrolytic capacitor can be manufactured. Is confirmed.

  Next, Example 2 will be described. An experiment was conducted to investigate the effect of sugar concentration in the cleaning solution on the cleaning effect. The experimental procedure is as follows.

  First, in the same procedure as in Example 1, sucrose, trehalose and starch are employed as the solute (sugar) of the washing liquid used in the washing step, and the sugar concentration is changed in the range of 0.01 to 20% by mass. 100 solid electrolytic capacitors were produced under each condition. For the obtained solid electrolytic capacitor, the number of leakage current short-circuits was investigated by the same method as in Example 1. The test results are shown in Table 2.

  When attention is paid to the type of sugar with reference to Table 2, the solid electrolytic capacitor has the highest reliability when starch is employed. From this, it can be said that it is most preferable to employ starch as the sugar as the solvent of the washing liquid employed in the washing step.

  Further, focusing on the sugar concentration in the cleaning liquid, the reliability of the solid electrolytic capacitor is improved by setting the concentration to 0.1% by mass compared to the case where the sugar concentration is 0.01% by mass. On the other hand, the reliability of the solid electrolytic capacitor is improved by setting the concentration to 10% by mass compared to the case where the sugar concentration is 20% by mass. From this, it is considered that when the sugar concentration is less than 0.01% by mass or exceeds 20% by mass, the reliability is further lowered. Therefore, it can be said that the concentration of sugar contained in the cleaning liquid is preferably 0.01% by mass or more and 20% by mass or less. Furthermore, in order to ensure a higher cleaning effect, the concentration of sugar contained in the cleaning liquid is preferably 0.1% by mass or more and 10% by mass or less.

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The method for producing a solid electrolytic capacitor of the present invention can be particularly advantageously applied to a solid electrolytic capacitor that is required to achieve both cost reduction of a cleaning step included in the production process and reduction of environmental load.

  DESCRIPTION OF SYMBOLS 1 Solid electrolytic capacitor, 11 Anode body, 12 Dielectric film | membrane, 13 Solid electrolyte layer, 14 Cathode extraction layer, 14A Conductive carbon layer, 14B Silver paste layer, 15 Anode lead, 16 Conductive adhesive, 17 Cathode terminal, 18 Anode terminal, 19 exterior resin.

Claims (6)

A step of preparing an anode body;
Forming a dielectric film on the surface of the anode body;
A step of obtaining a capacitor element by forming a solid electrolyte layer made of a conductive polymer on the surface of the dielectric film;
And a step of cleaning the capacitor element with a cleaning liquid containing sugar.   The method for producing a solid electrolytic capacitor according to claim 1, wherein the sugar contains glucose in its structure.   3. The solid electrolytic capacitor according to claim 1, wherein the sugar includes at least one sugar selected from the group consisting of glucose, sucrose, lactose, maltose, trehalose, and starch. Production method.   The method for producing a solid electrolytic capacitor according to any one of claims 1 to 3, wherein a solvent of the cleaning liquid is any one of water, an organic solvent, or a mixture of water and an organic solvent.   5. The method for producing a solid electrolytic capacitor according to claim 1, wherein the sugar concentration in the cleaning liquid is 0.01% by mass or more and 20% by mass or less.   The method for producing a solid electrolytic capacitor according to claim 1, wherein in the step of obtaining the capacitor element, the solid electrolyte layer is formed by chemical polymerization.

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