JP4776567B2 - Manufacturing method of solid electrolytic capacitor - Google Patents

Description

The present invention relates to a method for producing a solid electrolytic capacitor having a conductive polymer as a solid electrolyte.

  2. Description of the Related Art Conventionally, in recent years, along with the reduction in size and weight of electronic devices, there has been a demand for a high-frequency capacitor having a low impedance in the high-frequency region and having a small size and a large capacity. Therefore, even for a solid electrolytic capacitor using a conductive polymer as an electrolyte, further reduction in ESR (Equivalent Series Resistance) is required as a characteristic improvement in a high frequency band. Here, the conductive polymer refers to a polymer obtained by polymerizing pyrrole, thiophene, furan, aniline, or the like.

  As a method for forming the conductive polymer, there are a chemical polymerization method and an electrolytic polymerization method. In general, a conductive polymer film formed by an electrolytic polymerization method is superior in conductivity to a conductive polymer film formed by a chemical polymerization method, and a strong film can be formed. When a conductive polymer produced by an electropolymerization method is used as a solid electrolyte layer, its surface tends to be smooth, its adhesion to the cathode lead layer formed thereon is poor, and ESR in a high frequency region is low. It will increase.

On the other hand, as a method for reducing ESR, improving the adhesion between the solid electrolyte layer and the cathode lead layer is performed. For example, a technique for embedding conductive powder in a conductive polymer to provide irregularities on the surface of the solid electrolyte layer and strengthening the adhesion with the cathode lead layer (for example, Patent Document 1), or a conductive polymer by electrolytic polymerization A technique (for example, Patent Document 2) that forms a conductive polymer by chemical polymerization to improve the adhesion to the cathode lead layer is known.
JP-A-7-94368 JP 2000-133549 A

However, the former technique (Patent Document 1) has a problem that the solid electrolyte layer becomes thick due to the presence of the conductive powder, and the capacitor becomes large.
In the latter technique (Patent Document 2), since the conductive polymer is formed by chemical polymerization after the conductive polymer is formed by electrolytic polymerization, there is a problem that the number of processes increases and manufacturing is not easy.

In view of the above problems, the present invention provides a method for producing a solid electrolytic capacitor that produces a solid electrolyte excellent in adhesion to the cathode lead layer and is small, excellent in ESR characteristics, and easy to manufacture. Objective.

In order to solve the above problems, the present invention provides a method for producing a solid electrolytic capacitor having a solid electrolyte layer, wherein the solid electrolyte layer includes a conductive polymer having an electrolytic polymerization conductive polymer and a chemical polymerization conductive polymer. The conductive polymer hybrid layer has an electropolymerization reaction and the metal ions and / or metal oxides in an electropolymerization solution containing metal ions and / or metal oxide ions that can be electrolytically oxidized. It is formed by performing a chemical polymerization reaction using an oxidizing agent generated by electrolytic oxidation of product ions.

The metal ions and / or metal oxide ions are at least selected from the group consisting of iron (II) ions, nickel (II) ions, ruthenium (II) ions, manganese (II) ions, manganate ions, and chromate ions. It is preferable that 1 type is included.

  According to the solid electrolytic capacitor according to the present invention, the conductive polymer hybrid layer has good adhesion with the cathode lead layer formed thereon, the contact area is increased, and the current collection is improved. ESR can be reduced. Moreover, since the conductive polymer hybrid layer contains an electropolymerized conductive polymer and a chemically polymerized conductive polymer, a solid electrolytic capacitor excellent in ESR can be realized while maintaining a small size.

  Also, according to the method for manufacturing a solid electrolytic capacitor according to the present invention, the conductive polymer hybrid layer is formed by performing chemical polymerization during electrolytic polymerization, so that the ESR characteristic can be obtained without increasing the number of steps. An excellent solid electrolytic capacitor can be manufactured by a simple manufacturing method. Moreover, since chemical polymerization in the electrolytic polymerization solution occurs due to the generation of an oxidizing agent near the surface of the polymer film, the contact resistance between the electrolytic polymerization conductive polymer and the chemical polymerization conductive polymer is small and the conductivity is good. The conductive polymer hybrid layer is obtained and contributes to the reduction of ESR.

The best mode for carrying out the present invention will be described below.
FIG. 1 is a cross-sectional view of a solid electrolytic capacitor showing an embodiment of the present invention. In the solid electrolytic capacitor of the present embodiment, a dielectric film 2 and a solid electrolyte layer 3 are formed on the peripheral surface of an anode body 1 made of a valve metal that has an anode lead 10 planted thereon, on the solid electrolyte layer 3. The capacitor element 8 has the first cathode lead layer 4 and the second cathode lead layer 5 formed thereon. In the capacitor element 8, an anode lead frame 20 is connected to the anode lead 10, and a cathode lead frame 21 is connected to the second cathode lead layer 5 via a conductive adhesive (not shown). A sheathing resin is coated around the capacitor element 8 so that the ends of the anode lead frame 20 and the cathode lead frame 21 are drawn out to the outside. As described above, the solid electrolytic capacitor according to the present embodiment is configured. Note that the cathode lead layer formed on the solid electrolyte 3 may have a single-layer structure instead of the laminated structure of the first cathode lead layer 4 and the second cathode lead layer 5.

  The solid electrolyte layer 3 has a conductive polymer hybrid layer 32 containing an electropolymerized conductive polymer and a chemically polymerized conductive polymer. Specifically, the solid electrolyte layer 3 includes the conductive precoat layer 31 formed on the dielectric film 2 and the conductive conductivity formed on the conductive precoat layer 31 and in contact with the first cathode lead layer 4. And a polymer hybrid layer 32. The conductive polymer specifically refers to a polymer obtained by polymerizing a heterocyclic compound such as pyrrole, thiophene or furan, an aromatic compound such as aniline, or a derivative thereof as a monomer. The electropolymerized conductive polymer refers to a conductive polymer formed by electrolytic polymerization. The chemical polymerization conductive polymer refers to a conductive polymer formed by chemical polymerization.

The conductive polymer hybrid layer 32 is formed by generating a chemical polymerization reaction simultaneously with the electrolytic polymerization reaction, and has a structure in which the chemically polymerized conductive polymer is mixed in the electrolytic polymerization conductive polymer. Accordingly, fine irregularities are formed on the surface of the conductive polymer hybrid layer 32 as compared with a film of a simple electropolymerized conductive polymer.
The anode element 1, the dielectric film 2, the first cathode extraction layer 4, and the second cathode extraction layer 5 constituting the capacitor element 8 are made of various materials in the same manner as known solid electrolytic capacitors.

Next, the manufacturing method of the solid electrolytic capacitor of this Embodiment is demonstrated.
First, an anode body 1 made of a valve metal is anodized to form a dielectric film 2 on the surface, and then, for example, a conductive precoat layer 31 such as a conductive polymer layer by chemical polymerization or a manganese dioxide layer by thermal decomposition. Is formed on the surface of the dielectric film 2.

  Next, a conductive polymer hybrid layer 32 including an electropolymerized conductive polymer and a chemically polymerized conductive polymer is formed on the surface of the conductive precoat layer 31. This conductive polymer hybrid layer 32 is an electrolysis in which a small amount of a metal ion capable of electrolytic oxidation or a metal oxide ion capable of electrolytic oxidation is added in advance to a solution containing at least a monomer that forms a conductive polymer and a supporting electrolyte. As shown in FIG. 2 (a), an anode body element 1A on which a conductive precoat layer 31 is formed is immersed in this electrolytic polymerization liquid, and a part of this anode body element 1A is externally applied. It is formed by contacting the anode rod or connecting the electrode for electrolytic polymerization to the anode lead 10 and starting the polymerization reaction by energizing the cathode plate and the anode element 1A disposed in the electrolytic polymerization solution.

Then, as shown in FIG. 2B, in the polymerization reaction, the electrolytic polymerization reaction is performed using the anode element 1A as the anode, and at the same time, the metal ions or metal oxide ions M ^{n + that} can be electrooxidized are converted into the anode ( The surface of the anode body element 1A and a polymer film formed on the anode body element 1A by the main polymerization reaction) and the vicinity of the surface are electrolytically oxidized to have a high valence. The formed metal ions or metal oxide ions M ^{(n + α) +} act as an oxidizing agent to oxidize nearby monomers and perform a chemical polymerization reaction. In addition, since the high-valent metal ion or metal oxide ion M ^{(n + α) +} functioning as an oxidant is reduced by the chemical polymerization reaction, the low-valent metal ion or metal oxide ion that can be electrolytically oxidized Returning to M ^{n +} , electrolytic oxidation is performed again in the vicinity of the anode. By repeating this, the chemical polymerization reaction is maintained. For example, when a small amount of ferrous ion (Fe ²⁺ ) is added to the electrolytic polymerization solution in advance and the polymerization reaction is started, in addition to the electrolytic polymerization reaction, ferrous ion (Fe ²⁺ ) is oxidized on the anode and ferric iron is added. Ions (Fe ³⁺ ) are generated, and the ferric ions (Fe ³⁺ ) oxidize nearby monomers to generate a chemical polymerization reaction.

  As described above, an electrolytic polymerization conductive polymer film is formed on the surface of the anode element 1A by an electrolytic polymerization reaction, and at the same time, fine chemical polymerization is performed on the surface of the electrolytic polymerization conductive polymer film by a chemical polymerization reaction. A conductive polymer film is appropriately formed, whereby the conductive polymer hybrid layer 32 in which the chemically polymerized conductive polymer is mixed in the electropolymerized conductive polymer is formed.

Here, electrolytically oxidizable metal ions or metal oxide ions are included in the electrolytic polymerization solution in a range of 2.5 × 10 ⁻⁵ mol / l to 1.0 × 10 ⁻⁴ mol / l. Is preferred. If the amount of electrolytically oxidizable metal ions and / or metal oxide ions contained in the electrolytic polymerization solution is 2.5 × 10 ⁻⁵ mol / l or more, chemical polymerization is sufficiently performed in the electrolytic polymerization solution. As a result, the surface of the conductive polymer hybrid layer 32 becomes rough, and the adhesion between the solid electrolyte layer 3 and the first cathode lead layer 4 is further improved. Moreover, if the amount of the metal ions and / or metal oxide ions is 1.0 × 10 ⁻⁴ mol / l or less, the proportion of the electropolymerized conductive polymer that is stronger than the chemically polymerized conductive polymer and has a small ESR. Therefore, a strong film is easily formed, and the conductivity is improved, so that the effect of reducing ESR is easily obtained.

  One or more types of metal ions or metal oxide ions may be contained in the electrolytic polymerization solution. Further, the metal ion and metal oxide ion to be used are not particularly limited as long as they are electrolytically oxidizable, but those in which the state of low valence and high valence easily react reversibly by an oxidation-reduction reaction are preferable. Examples include iron (II) ions, nickel (II) ions, ruthenium (II) ions, manganese (II) ions, manganate ions, chromate ions, and the like. These metal ions and metal oxide ions may be added to the electrolytic polymerization solution in the form of various inorganic salts or organic salts.

  After the solid electrolyte layer 3 is formed as described above, the first cathode extraction layer 4 and the second cathode extraction layer 5 are formed on the conductive polymer hybrid layer 32 of the solid electrolyte layer 3 to form the capacitor element 8. Is produced. Thereafter, the cathode lead frame 21 is connected to the second cathode lead layer 5 of the manufactured capacitor element 8, and the anode lead 10 and the anode lead frame 20 are connected. Then, the exposed cathode lead frame 21 and anode lead frame 20 are bent along the exterior to complete the solid electrolytic capacitor of the present embodiment shown in FIG. .

  The above-mentioned solid electrolytic capacitor can be appropriately changed within the scope of the claims and the equivalent meaning. For example, the solid electrolytic capacitor of the present invention may have a structure as shown in FIG. A plurality of capacitor elements having the conductive polymer hybrid layer 32 of the present invention in the solid electrolyte layer 3 may be produced and laminated.

Example 1
An anode element 1A in which the dielectric coating layer 2 was formed on the peripheral surface of the sintered body (anode body) 1 having the anode lead 10 and the conductive precoat layer 31 was formed thereon was produced. Next, 0.018 mol / l of pyrrole as a monomer, 0.004 mol / l of alkylnaphthalene sulfonate as a supporting electrolyte, and 2.5 × 10 ⁻⁵ mol / l of ferrous ion to be electrolytically oxidized are generated. Anode element 1A is immersed in an electrolytic polymerization solution (10 L) containing ferrous sulfate, and electricity is passed between anode element 1A and the cathode plate in the electrolytic polymerization solution in the same manner as in a known electrolytic polymerization method. Thus, the conductive polymer hybrid layer 32 in which the electropolymerized conductive polymer and the chemically polymerized conductive polymer are mixed on the conductive precoat layer 31 of the anode element 1A is formed as described above, and the solid electrolyte Layer 3 was formed.

  Next, a carbon layer (first cathode extraction layer) 4 and a silver paste layer (second cathode extraction layer) 5 were formed on the solid electrolyte layer 3 to produce a capacitor element 8. Thereafter, a cathode lead frame 21 is connected to the silver paste layer 5 of the capacitor element 8, and an anode lead frame 20 is connected to the anode lead 10. The anode lead frame 20 and a part of the cathode lead frame 21 are excluded, and the capacitor is removed. The element 8 was covered with the exterior resin 7, and the exposed lead frames 20 and 21 were bent along the exterior to complete a solid electrolytic capacitor.

(Example 2)
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that ferrous sulfate was produced in an amount of 5.0 × 10 ⁻⁵ mol / l of ferrous sulfate.

(Example 3)
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that ferrous sulfate was produced in an amount of 7.5 × 10 ⁻⁵ mol / l of ferrous sulfate.

(Example 4)
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that ferrous sulfate was produced in an amount of 1.0 × 10 ⁻⁴ mol / l of ferrous sulfate.

(Comparative example)
A solid electrolytic capacitor was produced in the same manner as in Example 1 except that ferrous sulfate was not added. In this case, as the solid electrolyte, only the electropolymerized conductive polymer layer by electropolymerization is formed on the conductive precoat layer 31.
ESR was measured for all the examples and comparative examples. The results are shown in Table 1 and FIG.

From Table 1, Examples 1-4 which superposed | polymerized using the electrolytic polymerization liquid containing a ferrous ion are restrained ESR lower than the comparative example which did not add a ferrous ion.
This is because the conductive polymer hybrid layer 32 has fine irregularities on the surface due to the mixing of the chemically polymerized conductive polymer, and the surface area of the conductive polymer hybrid layer 32 is increased. As a result, the contact area between the solid polymer layer 3 and the carbon layer 4 is increased, the current collection is improved, and the ESR can be reduced. it is conceivable that.

It is sectional drawing which shows the structure of the solid electrolytic capacitor by one Embodiment of this invention. It is a schematic diagram which shows the formation process of the conductive polymer hybrid layer in the manufacturing method of the solid electrolytic capacitor by one Embodiment of this invention. It is sectional drawing which shows another structure of the solid electrolytic capacitor by one Embodiment of this invention. It is a graph which shows the relationship between the addition amount of the ferrous ion in an electrolytic polymerization liquid, and ESR of the obtained solid electrolytic capacitor at the time of manufacture of the solid electrolytic capacitor by one Embodiment of this invention.

Explanation of symbols

1 Anode body 2 Dielectric film 3 Solid electrolyte layer 4 First cathode layer (carbon layer)
5 Second cathode layer (silver paste layer)
7 Exterior resin 8 Capacitor element 10 Anode lead 20 Anode lead frame 21 Cathode lead frame 31 Conductive precoat layer 32 Conductive polymer hybrid layer

Claims (2)

In a method for producing a solid electrolytic capacitor having a solid electrolyte layer,
The solid electrolyte layer has a conductive polymer hybrid layer having an electropolymerized conductive polymer and a chemically polymerized conductive polymer,
The conductive polymer hybrid layer is formed by electrolytic polymerization reaction and electrolytic oxidation of the metal ions and / or metal oxide ions in an electrolytic polymerization solution containing metal ions and / or metal oxide ions that can be electrolytically oxidized. A method for producing a solid electrolytic capacitor, wherein the solid electrolytic capacitor is formed by performing a chemical polymerization reaction using an oxidant that is generated. The metal ions and / or metal oxide ions are at least selected from the group consisting of iron (II) ions, nickel (II) ions, ruthenium (II) ions, manganese (II) ions, manganate ions, and chromate ions. The method for producing a solid electrolytic capacitor according to claim 1 , comprising one kind.

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