JP2006261439A - Solid electrolytic capacitor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor in which a large capacity can be attained without increasing the overall dimension, and to provide its manufacturing process. <P>SOLUTION: A sintered body of powder of valve action metal having a particle size smaller than that of conventional powder is employed as an anode body 24 of a capacitor element 12 in a solid electrolytic capacitor 10 and a dielectric oxide film 26 is formed on its surface followed, and a precoat layer 28 is formed. When two kinds or more of dopants are used for forming the precoat layer 28, the dopant also adheres to the surface of the insulating dielectric oxide film 26 thus imparting n-conductivity. When an auxiliary precoat layer 30 is formed by electrolytic polymerization using an AC current superposed with a positive DC bias current, the auxiliary precoat layer 30 is formed easily and such parts in the surface of the dielectric oxide film 26 as the precoat layer 28 is not formed, e. g. the interior of micro pores is covered with the auxiliary precoat layer 30. Subsequently, a conductive polymer layer 32 is formed by electrolytic polymerization. Consequently, an electrode area is enlarged without increasing the overall dimension of the capacitor element 12 and a capacitance emergence rate of the solid electrolytic capacitor 10 is enhanced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solid electrolytic capacitor and a method for manufacturing the same, and more particularly, for example, to a solid electrolytic capacitor having a fine void inside an anode body and a method for manufacturing the same.

  Conventionally, for solid electrolytic capacitors, a dielectric oxide film is formed on the surface of an anode body made of a sintered body of valve action metal by electrolytic oxidation treatment, and a cathode layer made of a solid electrolyte is formed on the dielectric oxide film It has been known. The valve metal is a metal on which a very dense and durable dielectric oxide film is formed by electrolytic oxidation treatment, and includes tantalum, niobium, aluminum, titanium, and the like.

  As the solid electrolyte, a conductive inorganic material such as manganese dioxide, or a conductive organic material such as a TCNQ (7,7,8,8-tetracyanoquinodimethane) complex salt or a conductive polymer is used. In particular, among solid electrolytes, the electrical conductivity of conductive polymers such as polypyrrole, polyaniline, polythiophene or their derivatives is higher than that of manganese dioxide and TCNQ complex salts. If formed on the film, a solid electrolytic capacitor having low ESR (equivalent series resistance) and excellent high frequency characteristics can be provided.

  In the case of forming a cathode layer using a conductive polymer such as polypyrrole, a chemical polymerization method or an electrolytic polymerization method is conventionally used. The chemical polymerization method is a method in which a monomer is oxidatively polymerized with an oxidizing agent to form a cathode layer made of a conductive polymer on the anode body. The electrolytic polymerization method is a method in which a monomer is oxidatively polymerized by an oxidation reaction generated at the anode in electrolysis to form a cathode layer made of a conductive polymer on the anode.

  In the method using the chemical polymerization method, an oxidant is deposited on the dielectric oxide film, and then the monomer is oxidatively polymerized by bringing it into contact with a monomer solution or gas that becomes a conductive polymer. Thus, a conductive polymer layer is formed on the dielectric oxide film. However, the conductive polymer layer formed by this method has drawbacks such as weak strength, easily unevenness, and low electrical conductivity compared to the conductive polymer layer formed by the electrolytic polymerization method. is there.

  On the other hand, when the electropolymerization method is used, it is possible to form a conductive polymer layer that is generally strong and has high electrical conductivity and is uniform and of good quality. However, since the dielectric oxide film is an insulator, the lead wire cannot be used as an electrode for power feeding, and a conductive polymer layer is directly formed on the dielectric oxide film using electrolytic polymerization. Was very difficult.

  As a means to solve this, after forming a conductive polymer film by chemical polymerization on the dielectric oxide film and making the surface conductive, a conductive polymer film by electrolytic polymerization is formed on this conductive polymer film A method has been proposed (for example, Patent Document 1).

In addition, as a method of forming the conductive polymer layer on the precoat layer (conductive film), the present applicant changes the feeding point to the precoat layer by the external electrode every predetermined time. Has proposed a method for making the thickness of the film uniform (for example, Patent Document 2).
Japanese Examined Patent Publication No. 4-74853 [H01G 9/02] JP-A-11-283878 [H01G 9/028, H01G 13/00]

  As for solid electrolytic capacitors, it is required to increase the capacity without increasing the outer diameter of the solid electrolytic capacitors than the conventional dimensions. In order to increase the capacity of the solid electrolytic capacitor, it is necessary to increase the surface area of the anode body. As one of the methods, it is conceivable to reduce the size of the particles constituting the sintered body. In other words, the surface area of the anode body can be increased without increasing the external dimensions and weight by making the particle size of the sintered body particles smaller than the conventional one while having the same volume and density as the conventional anode body. Can do.

  However, when such a sintered body is used as an anode body, since the pores in the sintered body are further smaller than in the prior art, a dielectric oxide film is formed as in the prior arts of Patent Documents 1 and 2. Even if the precoat layer is formed only on the anode body by chemical polymerization, it is difficult to form the precoat layer on the surface in very small pores. In addition, the precoat layer adheres to the outer surface of the sintered body first, and the voids on the surface of the sintered body necessary for the substance forming the precoat layer to enter the sintered body are further reduced, and It becomes difficult to cover the voids inside the bonded body with the precoat layer.

  Further, since the prepolymer layer formed by chemical polymerization is formed by depositing conductive polymer monomers on the surface of the sintered body, the precoat layer originally has many gaps.

  Therefore, even when a conductive polymer layer formed by electrolytic polymerization is grown on the basis of such a precoat layer, the gap between the precoat layers is hardly filled, and there are many at the interface between the conductive polymer layer and the dielectric oxide film. The gap remains.

  Since the capacitance of the capacitor is determined by the facing area of the cathode layer formed by sandwiching the anode body and the dielectric oxide film, even when the surface area of the anode body is increased, the surface area of the opposing conductive polymer layer increases so much. Without it, it was not possible to lead to a large increase in the capacity of the solid electrolytic capacitor.

  Therefore, a main object of the present invention is to provide a solid electrolytic capacitor capable of increasing the capacity without increasing the outer diameter and a method for manufacturing the same.

The invention of claim 1 includes (a) a step of forming a dielectric oxide film on the surface of an anode body made of a sintered body of valve action metal, (b) two or more dopant agents on the dielectric oxide film, Forming a precoat layer by chemical polymerization using an oxidant and a monomer that becomes a conductive polymer by oxidative polymerization; (c) on a portion of the surface of the dielectric oxide film where the precoat layer is not formed; Auxiliary electrodes made of a conductive polymer layer by electrolytic polymerization in which a negative voltage is not applied to the anode body by superimposing a positive DC bias current on the alternating current between the anode body and the electrode for electrolytic polymerization. A step of forming a precoat layer, and (d) conductive by electrolytic polymerization using a dopant agent, an oxidant, and a monomer that becomes a conductive polymer by oxidative polymerization on the precoat layer and the auxiliary precoat. Comprising forming a molecular layer, a solid electrolytic capacitor manufacturing method.

  In the first aspect of the invention, first, a dielectric oxide film is formed on the surface of the anode body made of a sintered body of the valve action metal. Then, a precoat layer is formed on the dielectric oxide film by chemical polymerization using two or more dopant agents, an oxidant, and a monomer that becomes a conductive polymer by oxidative polymerization. The precoat layer has many gaps, and the precoat layer is hard to be formed on the surface of the anode body, such as in the microscopic voids inside the anode body, so that only the dielectric oxide film remains.

  Next, when a current is passed between the anode body and the electrode for electrolytic polymerization so that a negative charge is not applied to the anode body by superimposing a positive current bias current on the alternating current, a dielectric oxide film that is an insulator The charge / discharge current flows on the portion of the surface where the precoat layer is not formed. At this time, if two or more kinds of dopant agents are used at the time of the previous precoat layer formation, these dopant agents adhere to the surface of the dielectric oxide film, and the dielectric oxide film is charged with an electrochemical charge. It becomes easy to attract radical cations generated by polymerization. For this reason, it becomes easy to form an auxiliary | assistant precoat layer, and the clearance gap between precoat layers can be filled efficiently.

  Finally, when the conductive polymer layer is formed by electrolytic polymerization, the conductive polymer layer grows on the precoat layer and the auxiliary precoat layer, and the entire surface of the anode body has a certain thickness. Covered with.

  Invention of Claim 2 is a manufacturing method of the solid electrolytic capacitor of Claim 1 which uses a sulfonic acid type compound for at least 1 sort (s) of a 2 or more types of dopant agent in a step (b).

  In the invention of claim 2, since the sulfonic acid compound is excellent in electron donating property, the conductivity of the precoat layer is improved by using the sulfonic acid compound during chemical polymerization, and as a result, the ESR of the solid electrolytic capacitor is increased. Can be reduced.

  Invention of Claim 3 is a manufacturing method of the solid electrolytic capacitor of Claim 1 or 2 which uses the silane coupling agent which has a mercapto group for at least 1 sort (s) of 2 or more types of dopant agents in step (b). .

  In the invention of claim 2, when a silane coupling agent having a mercapto group is used during chemical polymerization, the mercapto group is oxidized by the oxidizing agent to form a sulfone group, and the sulfone group acts as a dopant agent. For this reason, the electrical conductivity of a precoat layer can be improved and, as a result, ESR of a solid electrolytic capacitor can be reduced.

  Further, since the silane coupling agent having a mercapto group is bonded to the surface of the anode body and the precoat layer, the adhesion between the dielectric oxide film and the precoat layer is improved, and the ESR of the solid electrolytic capacitor is reduced.

  Invention of Claim 4 is used in any one of Claim 1 thru | or 3 which uses the same dopant agent as the dopant agent in step (d) for the at least 2 sorts of dopant agent of the 2 or more types of dopant agent in step (b). This is a method for producing a solid electrolytic capacitor.

  In the invention of claim 4, by using at least two kinds of dopant agents used in the precoat layer as the dopant agent of the conductive polymer layer, a series of conductivity in the precoat layer and the conductive polymer layer is improved.

  The invention according to claim 5 is an anode body made of a sintered body of valve action metal, a dielectric oxide film formed on the surface of the anode body, and a conductive polymer containing two or more dopant agents on the dielectric oxide film. A pre-coat layer formed on the surface of the dielectric oxide film, an auxiliary pre-coat layer formed of a conductive polymer on a portion where the pre-coat layer is not formed, and electrolytic polymerization on the pre-coat layer and the auxiliary pre-coat layer It is a solid electrolytic capacitor provided with the conductive polymer layer formed by this.

  The invention of claim 5 has the same action as that of the invention of claim 1.

  The invention according to claim 6 is the solid electrolytic capacitor according to claim 5, wherein at least one of the two or more dopant agents comprises a sulfonic acid compound.

  The invention of claim 6 has the same function as that of the invention of claim 2.

  The invention according to claim 7 is the solid electrolytic capacitor according to claim 5 or 6, wherein at least one of the two or more dopant agents comprises a silane coupling agent having a mercapto group.

  The invention of claim 7 exhibits the same action as that of the invention of claim 3.

  Invention of Claim 8 consists of the same dopant agent as 2 types of dopant agents in which at least 2 types of dopant agents of 2 or more types of dopant agents are contained in a conductive polymer layer in any one of Claim 5 thru | or 7 It is a solid electrolytic capacitor of description.

  The invention of claim 8 exhibits the same operation as that of the invention of claim 4.

  According to the present invention, for example, even when a sintered body using a valve metal powder having a particle diameter smaller than that of the conventional one is used for the anode body, the precoat layer is formed using two or more kinds of dopant agents. Thereby, formation of an auxiliary | assistant precoat layer is accelerated | stimulated and the whole surface of an anode body can be covered with a conductive polymer layer. For this reason, the surface area on which the conductive polymer layer is formed increases, and the electrode area of the solid electrolytic capacitor increases. Therefore, the capacity can be increased without increasing the outer diameter of the solid electrolytic capacitor.

  The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

  A solid electrolytic capacitor 10 according to one embodiment of the present invention shown in FIG. 1 has a carbon layer 14 and a silver paste layer 16 formed on the surface of a capacitor element 12, and leads for electrode extraction of the silver paste layer 16 and the capacitor element 12. A metal terminal plate 20 is attached to each of the wires 18, and an outer shell 22 made of epoxy resin or the like is formed on these.

  The capacitor element 12 includes an anode body 24 to which an electrode lead wire 18 is attached, a dielectric oxide film 26 by electrolytic oxidation treatment, a precoat layer 28 by chemical polymerization, an auxiliary precoat layer 30 by electrolytic polymerization, and a conductivity by electrolytic polymerization. In this case, the functional polymer layer 32 is laminated. A laminate of the precoat layer 28, the auxiliary precoat layer 30 and the conductive polymer layer 32 is a cathode layer 34, and the anode body 24 and the cathode layer 34 are two electrodes insulated by an insulating dielectric oxide film 26. Acts as

  For the anode body 24, a sintered body of a valve action metal such as tantalum, niobium, titanium, or aluminum is used. The sintered body is obtained by baking and solidifying a valve action metal powder. A large number of minute depressions are formed on the surface of the sintered body, and a large number of minute holes are present therein. By making the particle size of the powder smaller than that of the conventional one, the size of the dents and holes becomes smaller than that of the conventional one. For example, in a conventionally used sintered body formed of tantalum powder having a particle size of 10 to 200 μm, the average diameter (pore diameter) of pores inside the sintered body is 0.5 to 1.0 μm. On the other hand, when a sintered body is formed using a tantalum powder containing 1% or more of a powder having a particle diameter of 2 μm or less, the average diameter (pore diameter) of pores inside the sintered body is 0.05. It becomes very small with ~ 0.2 μm.

The dielectric oxide film 26 is a very thin insulating film such as tantalum oxide (Ta ₂ 0 ₅ ) or aluminum oxide (Al ₂ O ₃ ) obtained by electrolytic oxidation of tantalum or aluminum.

  For the precoat layer 28, the auxiliary precoat layer 30, and the conductive polymer layer 32, a resin obtained by adding a dopant agent such as a sulfonic acid compound to a conductive polymer such as polypyrrole, polythiophene, polyaniline, and derivatives thereof is used. The dopant agent is an anionic surfactant such as aromatic sulfonate, carboxylate, sulfate ester salt or phosphate ester salt, or nonionic surfactant such as ester salt, ether salt, ester ether salt or alkanolamide salt. It is an agent. For example, there are alkyl naphthalene sulfonic acid and sodium alkyl ether sulfate as an anionic surfactant, and polyoxyethylene nonyl phenyl ether as a non-ionic surfactant.

  When the solid electrolytic capacitor 10 is manufactured, first, an anode body 24 of a tantalum sintered body having a width of 2.33 mm, a length of 1.75 mm, and a thickness of 0.95 mm, for example, is prepared. . Then, a part of the anode body 24 and the electrode lead wire 18 are immersed in a 0.02 wt% phosphoric acid aqueous solution, and these are electrolytically oxidized by applying a voltage, so that the anode body 24 and the electrode lead lead are obtained. A dielectric oxide film 26 is formed on a part of the surface of the wire 18.

  The anode body 24 is immersed in, for example, an aqueous solution of hydrogen peroxide having a concentration of 1 mol / l and sulfuric acid having a concentration of 0.2 mol / l for 10 minutes, and then the anode body 24 is subjected to, for example, an alkylnaphthalene sulfone having a concentration of 0.05 mol / l. It is made to contact with the solution or gas of the pyrrole monomer which becomes an electroconductive polymer (polypyrrole) by the oxidative polymerization of acid and a concentration of 0.1 mol / l. As a result, the pyrrole monomer undergoes oxidative polymerization while containing sulfuric acid and alkylnaphthalene sulfonic acid as dopant agents, and a polypyrrole precoat layer 28 is formed on the surface of the dielectric oxide film 26. Since this precoat layer 28 is formed so that the pyrrole monomer adheres to the surface of the dielectric oxide film 26, many gaps are opened in the precoat layer 28, from which the dielectric oxide film is formed. 26 appears. Further, the alkylnaphthalene sulfonic acid is taken into the precoat layer 28 and is simultaneously deposited on the surface of the dielectric oxide film 26.

  In addition, sulfuric acid acts not only as a dopant agent but also as a pH adjuster. Due to this action, hydrogen peroxide exhibits an oxidizing action.

  Next, as shown in FIG. 2, the electrolytic polymerization electrode 36 connected to the anode side of the power source 38 is connected to the electrode lead-out lead 18 of the anode body 24. The anode body 24 and the counter electrode 40 for electropolymerization connected to the cathode side of the power source 38 are, for example, alkylnaphthalenesulfonic acid having a concentration of 0.05 mol / l, ammonium persulfate having a concentration of 0.1 mol / l, and a concentration of 0.1 mol / l. It is immersed in an electrolytic solution 42 of an aqueous solution containing 1 pyrrole monomer. Then, a current of 0.8 mAms / P in which a positive current bias current is superimposed on an alternating current of 100 kHz is passed between the anode body 24 and the counter electrode 40 for electrolytic polymerization for 90 minutes. At this time, by superimposing a positive current bias current on the alternating current, a negative voltage is not applied to the anode body 24 to prevent the dielectric oxide film 26 from being destroyed. Further, the voltage value applied to the anode body 24 is set lower than the voltage value when the dielectric oxide film 26 is formed. This is because, since the thickness of the dielectric oxide film 26 is determined by the applied voltage, if a higher voltage is applied to the anode body 24 in the electrolytic solution 42 containing sulfuric acid than when the dielectric oxide film 26 is formed, the dielectric oxide film The thickness of 26 will increase. Therefore, the thickness of the dielectric oxide film 26 is not changed in this way.

  As a result, a charge / discharge current flows on a portion of the surface of the dielectric oxide film 26 that is an insulator where the precoat layer 28 is not formed. At this time, if two types of dopant agents, that is, sulfuric acid and alkylnaphthalene sulfonic acid are used when the precoat layer 28 is formed, these dopant agents adhere to the surface of the dielectric oxide film 28, and the dielectric oxide film 28. The surface of the substrate is electrochemically charged and easily attracts radical cations generated by electrolytic polymerization. Therefore, the thin, uniform and dense auxiliary precoat layer 30 is easily formed here, and the gaps of the precoat layer 28 can be efficiently filled. In particular, the auxiliary precoat layer 30 is also formed in a portion where it is difficult to form the precoat layer 28, such as a minute hole of the anode body 24, and covers the entire surface of the anode body 24.

  The conductive polymer of the auxiliary precoat layer 30 contains alkyl naphthalene sulfonic acid and sulfuric acid produced by decomposition of ammonium persulfate as a dopant agent.

  Further, the anode body 24 is supported in another electrolytic cell shown in FIG. 3, and for example, a pyrrole monomer having a concentration of 0.1 mol / l, an ammonium persulfate having a concentration of 0.1 mol / l, and an alkyl having a concentration of 0.05 mol / l. It is immersed in an electrolytic solution 44 of an aqueous solution containing naphthalene sulfonic acid. Then, the external electrode piece 48 connected to the anode side of the power source 46 is immersed in the electrolytic solution 44 so as to be able to approach and separate from the side surface of the anode body 24. Further, the cathode electrode piece 50 connected to the cathode of the power source 46 is immersed in the electrolytic solution 44 and disposed below the bottom of the anode body 24. Then, the external electrode piece 48 is brought into contact with the auxiliary precoat layer 30 (FIG. 1) on the surface of the anode body 24, and this region is used as a feeding point P to supply power to the auxiliary precoat layer 30. A conductive polymer layer 32 of polypyrrole is formed. The conductive polymer layer 32 also contains, as a dopant agent, alkyl naphthalene sulfonic acid and sulfuric acid produced by decomposition of ammonium persulfate, like the polypyrrole of the auxiliary precoat layer.

  In this case, if an elastic metal piece is used for the external electrode piece 48 and the external electrode piece 48 is pressed against the side surface of the anode body 24, the external electrode piece 48 is elastically deformed and contacts the anode body 24 with a light pressure. To do. As a result, the power supply to the auxiliary precoat layer 30 is stabilized and the mechanical impact on the auxiliary precoat layer 30 is alleviated, and damage to the auxiliary precoat layer 30 and the dielectric oxide film 26 that is the base layer thereof is prevented. .

  Further, the external electrode piece 48 is attached to the switching device 52 on the electrolytic cell. The switching device 52 moves the position of the electrode piece 48 horizontally, swings, or moves up and down, and thereby the position of the feeding point P with respect to the anode body 24 moves.

  For example, as shown in FIG. 4, when the external electrode piece 48 is moved up and down by the switching device 52, the external electrode piece 48 reciprocates between the low position and the high position of the anode body 24. A uniform conductive polymer layer 32 is formed over the entire length.

  When the conductive polymer layer 32 reaches a predetermined thickness, the external electrode piece 48 is separated from the anode body 24 and the anode body 24 is taken out from the electrolytic solution 44. Then, the anode body 24 is washed and dried to complete the capacitor element 12.

  Finally, the carbon layer 14 and the silver paste layer 16 are laminated on the surface of the conductive polymer layer 32 of the capacitor element 12 shown in FIG. 1, and the metal terminal plate 20 is placed on the electrode lead-out lead 18 and the silver paste layer 16, respectively. Install. And after forming the outer shell 22 with the epoxy resin etc. in the capacitor | condenser element 12 which attached the metal terminal board 20, the aging process is performed by a predetermined voltage, and the solid electrolytic capacitor 10 is completed.

  As described above, when two kinds of dopant agents of sulfuric acid and alkylnaphthalene sulfonic acid are used at the time of forming the precoat layer 28, the surface of the dielectric oxide film 26 becomes conductive by this action. For this reason, if an alternating current in which a direct current bias current is superimposed is passed between the anode body 24 and the electrolytic polymerization counter electrode 40, the charge / discharge current generated on the surface of the dielectric oxide film 26 can easily flow, and the auxiliary precoat layer 30 is formed in a portion of the surface of the dielectric oxide film 26 where the precoat layer 28 is not formed, such as inside a minute hole, and can cover the entire surface of the anode body 24. Therefore, the electrode area of the capacitor element 12 is increased as the diameter of the powder of the sintered body of the anode body 24 is reduced, and as a result, the capacitance is increased without increasing the outer diameter of the solid electrolytic capacitor 10. can do.

  Further, by including the same dopant, that is, sulfuric acid and alkylnaphthalenesulfonic acid, in the precoat layer 28, the auxiliary precoat layer 30, and the conductive polymer layer 32, the series of conductivity is improved, and the electrostatic capacitance of the solid electrolytic capacitor 10 is improved. Capacity can be increased.

  Table 1 shows the results of evaluation performed on this effect. In this test, a sintered body was prepared from a powder containing 5% or more of a powder having a particle size of 1 μm or less, and this sintered body was used for the anode body 24. The average diameter of the pores in the sintered body is 0.16 μm, and the pores having a diameter of 0.2 μm or less occupy 57% of the total pores and the diameter is 0.1 μm or less. Accounted for 14% of the total.

  And the solid electrolytic capacitor of Example 1 and the comparative example 1 was created with the manufacturing method similar to said manufacturing method. However, in Example 1, for example, alkyl naphthalene sulfonic acid having a concentration of 0.7% by weight was used when the precoat layer 28 was formed. In Comparative Example 1, no alkyl naphthalene sulfonic acid was used. And the electrostatic capacitance and capacity | capacitance appearance rate of the solid electrolytic capacitor of Example 1 and the comparative example 1 were measured, the average value for 40 units | sets was calculated about each value, and it showed in Table 1.

  Here, this capacity appearance rate is solidification with respect to the capacity in water (capacitance measured by immersing a solid electrolytic capacitor using a capacitor element in which only the dielectric oxide film 26 is formed on the anode body 24 in an acid solution). It represents the percentage of the ratio of the capacitance (capacitance of the solid electrolytic capacitor 10 using the finished capacitor element 12).

  From Table 1, the capacitance (CAP) and the capacity appearance rate of the solid capacitor of Example 1 are larger than those of Comparative Example 1, and not only sulfuric acid is used as a dopant agent when the precoat layer 28 is formed. The effect using alkyl naphthalene sulfonic acid appears. In other words, the auxiliary precoat layer 30 covers the gaps of the precoat layer 28 such as in fine pores with the alkyl naphthalene sulfonic acid, and the area of the cathode layer and then the electrode of the solid electrolytic capacitor 10 is expanded. It has increased. Moreover, it is thought that the effect of improving a series of conductivity by using the same dopant for the precoat layer 28, the auxiliary precoat layer 30, and the conductive polymer layer 32 is also exhibited.

  In particular, the effect is large when the particle diameter of the powder of the valve action metal in the sintered body contains, for example, 5% or more of those having a particle size of 1 μm or less. The effect is particularly great when the sintered body contains 30% or more of pores having a diameter of 0.2 μm or less. Further, when 3% or more of pores having a diameter of 0.1 μm or less are included, the effect becomes larger and is preferable. That is, when a sintered body is formed using a powder having a particle size much smaller than that of a conventionally used powder, for example, 1 μm or less, and this is used for the anode body 24, the dimensions of the anode body 24 are reduced. The surface area of the anode body 24 can be increased without increasing the size. Moreover, according to the method for manufacturing the solid electrolytic capacitor 10, the conductive polymer layer 28 can be formed in such a small hole. The area of the polymer layer 28 is increased, and the capacity of the solid electrolytic capacitor 10 can be increased. In particular, as the size (diameter) of the pores in the sintered body is reduced, the surface area of the anode body 24 is increased, and the formation area of the conductive polymer layer 28 is increased accordingly. Can be further increased.

  The same dopant agent, sulfuric acid and alkylnaphthalene sulfonic acid were used when forming the precoat layer 28, the auxiliary precoat layer 30 and the conductive polymer layer 32, but this dopant agent is conductive to the conductive polymer. As long as they are given.

  A silane coupling agent having a mercapto group can also be used when forming with the precoat layer. Examples of the silane coupling agent having a mercapto group include 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane. The mercapto group of the silane coupling agent having a mercapto group is oxidized by the oxidizing agent to become a sulfone group. Since this sulfone group acts as a dopant agent, the conductivity of the precoat layer can be further improved. Further, the silane coupling agent is bonded to the surface of the anode body and the precoat layer, and the adhesion between the dielectric oxide film and the precoat layer is improved. For this reason, ESR of the solid electrolytic capacitor can be reduced.

  Table 2 shows the results of evaluation performed on this effect. In this test, solid electrolytic capacitors of Example 2 and Comparative Example 2 were prepared by using a sintered body using powder having a particle size of 150 kcv for the anode body 24 by the same manufacturing method as the above-described manufacturing method. However, in Example 2, sulfuric acid, for example, 1.14% by weight of alkylnaphthalenesulfonic acid and 0.01M silane coupling agent were used when the precoat layer 28 was formed, but in Comparative Example 2, no alkylnaphthalenesulfonic acid was used. The difference is that, for example, 0.01 M of a silane coupling agent is used. And the electrostatic capacity and capacity | capacitance appearance rate of the solid electrolytic capacitor of Example 2 and the comparative example 2 were measured, the average value for 40 units | sets was calculated about each value, and it showed in Table 2.

  From Table 2, since the electrostatic capacity and the capacity appearance rate of Example 2 are higher than those of Comparative Example 2, three kinds of dopant agents, that is, sulfuric acid and alkylnaphthalene sulfonic acid, are formed when the precoat layer 28 is formed. And the effect using a silane coupling agent appears.

  Further, although a sintered body of valve action metal is used for the anode body 24, a foil of valve action metal whose surface is uneven by etching or the like can also be used.

  Further, as shown in FIG. 2, the electrolytic polymerization electrode 36 connected to the anode side of the power source 38 was connected to the electrode lead-out lead wire 18 of the anode body 24 when the auxiliary precoat layer 30 was formed. An external electrode 53 connected to the anode side of the power source 38 may be used, and this electrode 53 may be brought into contact with the anode body 24. In this case, power is supplied from the external electrode 53 to the anode body 24 around the contact point between the external electrode 53 and the anode body 24.

  And although another electrolytic layer was used for the electrolytic cell forming the auxiliary precoat layer 30 and the electrolytic cell forming the conductive polymer layer 32, the auxiliary precoat layer 30 and the conductive polymer were used using the same electrolytic cell. Layer 32 can also be formed continuously. In particular, when the same material is used for the auxiliary precoat layer 30 and the conductive polymer layer 32, it is preferable in terms of time and economy to use the same electrolytic cell rather than using separate electrolytic layers.

  Further, the pair of external electrode pieces 54 and 56 shown in FIG. 6 may be used instead of the external electrode piece 48 shown in FIG. The external electrode pieces 54 and 56 are formed of an elastic metal piece similar to the external electrode piece 48, and are supported by the switching device 52 so as to sandwich the anode body 24 and move horizontally with respect to both surfaces thereof. When one electrode piece 54 is in contact with the left side of the anode body 24 to supply power, the conductive polymer layer 32 is formed thicker on the left side with the feeding point P as the center than the right side of the anode body 24. Next, when the switching device 52 is activated, the other electrode piece 56 comes into contact with the right side of the anode body 24, the feeding point P also moves to the right side of the anode body 24, and the conductive polymer layer 32 is placed on the left side of the anode body 24. It is formed thicker on the right side than the surface. If the switching device 52 is operated at an appropriate time interval, for example, 30 minutes, and the feeding point P is alternately moved several times, the thickness of the conductive polymer layer 32 is averaged on both the left and right sides of the anode body 24. And uniform.

  As shown in FIG. 7, the pair of external electrode pieces 54 and 56 are arranged symmetrically on both sides of the anode body 24 and simultaneously brought into contact with each other, and the power feeding circuit from the power source 46 is alternately switched by the switching device 52. it can.

  Further, by combining these movements, various movements can be made to the feeding point P.

  Further, although the alternating current having a constant frequency is superimposed on the positive current bias current when the auxiliary precoat layer 30 is formed, the frequency of the alternating current may be changed stepwise or gradually. For example, when the frequency of the alternating current is lowered and the frequency is gradually increased, a dense film is formed at the beginning although the increase in the film thickness is small, and the film formation rate increases with time.

  Further, the specific numerical values such as the dimensions mentioned above are merely examples, and can be appropriately changed as necessary.

It is sectional drawing which shows the solid electrolytic capacitor of one Example of this invention. It is sectional drawing which shows the apparatus which electropolymerizes an auxiliary | assistant precoat layer to an anode body. It is sectional drawing which shows the apparatus which electropolymerizes a conductive polymer layer to an anode body. It is sectional drawing which shows the state which moved the external electrode piece of the electrolytic polymerization apparatus shown in FIG. It is sectional drawing which shows the electrolytic polymerization apparatus of the auxiliary | assistant precoat layer used for the manufacturing method of the solid electrolytic capacitor of another Example of this invention. It is sectional drawing which shows the electropolymerization apparatus of the conductive polymer layer used for the manufacturing method of the solid electrolytic capacitor of another Example of this invention. It is sectional drawing which shows the electropolymerization apparatus of the conductive polymer layer used for the manufacturing method of the solid electrolytic capacitor of another Example 1 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Solid electrolytic capacitor 18 ... Lead wire for electrode extraction 24 ... Anode body 26 ... Dielectric oxide film 28 ... Precoat layer 30 ... Auxiliary precoat layer 32 ... Conductive polymer layer 36 ... Electrode polymerizing electrode 40 ... Electrode polymerization counter electrode electrode

Claims (8)

(A) forming a dielectric oxide film on the surface of an anode body made of a sintered body of valve action metal;
(B) forming a precoat layer on the dielectric oxide film by chemical polymerization using two or more dopant agents, an oxidant and a monomer that becomes a conductive polymer by oxidative polymerization;
(C) A positive DC bias current is superimposed on an AC current between the anode body and the electrode for electrolytic polymerization on a portion of the surface of the dielectric oxide film where the precoat layer is not formed. A step of forming an auxiliary precoat layer made of a conductive polymer layer by electrolytic polymerization in which a current is applied so that no negative voltage is applied to the anode body, and (d) a dopant agent on the precoat layer and the auxiliary precoat A method for producing a solid electrolytic capacitor, comprising: forming a conductive polymer layer by electrolytic polymerization using an oxidant and a monomer that becomes a conductive polymer by oxidative polymerization.   The method for producing a solid electrolytic capacitor according to claim 1, wherein in step (b), a sulfonic acid compound is used as at least one of the two or more dopant agents.   3. The method of manufacturing a solid electrolytic capacitor according to claim 1, wherein in step (b), a silane coupling agent having a mercapto group is used as at least one of the two or more dopant agents.   The solid electrolysis according to any one of claims 1 to 3, wherein the same dopant agent as the dopant agent in step (d) is used for at least two dopant agents of the two or more dopant agents in step (b). Capacitor manufacturing method. An anode body made of a sintered body of valve action metal,
A dielectric oxide film formed on the surface of the anode body;
A precoat layer formed of a conductive polymer containing two or more dopant agents on the dielectric oxide film;
An auxiliary precoat layer formed of a conductive polymer on a portion of the surface of the dielectric oxide film where the precoat layer is not formed, and formed by electrolytic polymerization on the precoat layer and the auxiliary precoat layer. A solid electrolytic capacitor comprising a conductive polymer layer.   The solid electrolytic capacitor according to claim 5, wherein at least one of the two or more dopant agents comprises a sulfonic acid compound.   The solid electrolytic capacitor according to claim 5 or 6, wherein at least one of the two or more dopant agents comprises a silane coupling agent having a mercapto group.   8. The solid electrolytic capacitor according to claim 5, wherein at least two dopant agents of the two or more dopant agents are made of the same dopant agent as the two dopant agents contained in the conductive polymer layer. .

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