JP3399515B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a solid electrolytic capacitor <br/> down service, a method of manufacturing a solid electrolytic capacitor particularly with conductive polymer electrolyte.

[0002]

2. Description of the Related Art An electrolytic capacitor is formed by forming an oxide film layer serving as a dielectric on the surface of an anode electrode which is made of a valve metal such as tantalum or aluminum and has fine holes and etching pits. It has a configuration that draws out.

The electrode is pulled out from the oxide film layer by the conductive electrolyte layer. Therefore, in the electrolytic capacitor, the electrolyte layer serves as a true cathode. For example, in an aluminum electrolytic capacitor, a liquid electrolyte is used as a true electrode, and a cathode electrode only serves to electrically connect this liquid electrolyte to an external terminal.

The electrolyte layer functioning as a true cathode is required to have adhesion, denseness, and uniformity with the oxide film layer.
In particular, the adhesiveness inside the fine holes of the anode electrode or inside the etching pit has a great influence on the electrical characteristics, and various electrolyte layers have been proposed in the past.

A solid electrolytic capacitor uses a solid electrolyte having conductivity instead of a liquid electrolyte lacking impedance characteristics in a high frequency region because it is ionic conductive. Among them, manganese dioxide, 7, 7 and 8 are used. , 8-
Tetracyanoquinodimethane (TCNQ) complexes are known.

The solid electrolyte layer made of manganese dioxide is
It is generated by immersing an anode element made of a tantalum sintered body in a manganese nitrate aqueous solution and thermally decomposing it at a temperature of around 300 ° C to 400 ° C. In a capacitor using such a solid electrolyte layer, the oxide film layer is easily damaged during the thermal decomposition of manganese nitrate, which tends to increase the leakage current, and the specific resistance of manganese dioxide itself is high. It was difficult to obtain satisfactory impedance characteristics. Further, the lead wires are damaged by the heat treatment, and it is necessary to separately provide an external terminal for connection as a post process.

As a solid electrolytic capacitor using a TCNQ complex, the one described in JP-A-58-191414 is known, and the TCNQ complex is melted by heat and immersed in an anode electrode to apply a solid. It forms an electrolyte layer. This TCNQ complex has high conductivity and can obtain good results in frequency characteristics and temperature characteristics.

However, since the TCNQ complex has the property of melting and then transitioning to an insulator in a short time, it is difficult to control the temperature in the manufacturing process of the capacitor, and the TCNQ complex itself lacks heat resistance, so that it cannot be printed on a printed circuit board. Significant characteristic changes are observed due to the heat of soldering during mounting.

In order to solve the disadvantages of these manganese dioxide and TCNQ complex, it has been attempted to use a conductive polymer such as polythiophene or polypyrrole as the solid electrolyte layer.

The conductive polymers represented by polythiophene and polypyrrole are mainly chemical oxidative polymerization (chemical polymerization).
And the electrolytic oxidative polymerization method (electrolytic polymerization). Among them, in electrolytic polymerization, it is necessary to apply a voltage to an object that forms a film, so it is difficult to apply it to an anode electrode for an electrolytic capacitor having an oxide film layer that is an insulator on the surface, and oxidation is difficult. On the surface of the coating layer, a conductive precoat layer, for example, a conductive polymer film chemically polymerized using an oxidizing agent as a precoat layer, and then using this precoat layer as an electrode to form an electrolyte layer by electrolytic polymerization, etc. Has been proposed (JP-A-63-173313 and JP-A-63-158829: precoating with manganese dioxide).

However, in addition to the complicated manufacturing process for forming the precoat layer in advance, in electrolytic polymerization, a solid electrolyte layer is formed in the vicinity of the external electrode for polymerization arranged on the surface of the anode electrode to be coated. It was very difficult to continuously form a conductive polymer film having a uniform thickness over a wide range.

[0012]

Therefore, the foil-shaped anode electrode and cathode electrode are wound up with a separator interposed therebetween,
To form a so-called wound type capacitor element, and to impregnate the wound capacitor element with a solution obtained by adding an oxidizing agent to a monomer solution to form an electrolyte layer composed of a conductive polymer film formed only by chemical polymerization. Tried.

Such a wound-type capacitor element is well known in aluminum electrolytic capacitors. By holding the conductive polymer layer with a separator, the complexity of electrolytic polymerization is avoided and the surface area is also large. It was expected that the capacity would be expanded by using foil electrodes. Furthermore,
It was expected that the use of the wound-type capacitor element would allow the electrodes of both electrodes and the separator to be held with a constant tightening force and contribute to the adhesion between the electrodes of both electrodes and the electrolyte layer.

However, when the wound capacitor element is impregnated with a monomer solution and an oxidizing agent to form a solid electrolyte by chemical oxidative polymerization in the capacitor element, a manila paper or the like used in an ordinary electrolytic capacitor is used. The separator causes a chemical reaction with the oxidant, which not only impairs the oxidizing action of the oxidant, but also causes an accident such as a short circuit due to damage to the separator.

Therefore, the use of glass paper or the like for the separator was also examined, but the normal thickness is 80 to 200.
It is difficult to make a glass paper of μm as thin as a separator such as Manila paper having a thickness of 40 μm.
Moreover, since the bending strength is rather weak, it becomes difficult to miniaturize the product. Further, since glass paper is non-hydrophilic, it is difficult to form a dense and uniform layer of conductive polymer, that is, a solid electrolyte layer, which may adversely affect the electrical characteristics of the product.

Therefore, an object of the present invention is to provide a dense and uniform solid electrolyte layer inside a wound type capacitor element to obtain a solid electrolytic capacitor having excellent electric characteristics and a large capacity.

[0017]

[0018]

[0019]

[0020]

[0021]

SUMMARY OF THE INVENTION The present invention is a solid electrolytic capacitor.
In the method of manufacturing a capacitor, an anode electrode foil and a cathode electrode foil
And a separator made of non-woven fabric mainly composed of synthetic fibers
The capacitor element wound through the
Immerse it in water at ℃ for 1 to 10 minutes and remove it from the separator.
After dissolving and removing the inder, remove the monomer solution and the oxidizer.
Solid state by impregnation and chemical polymerization in the capacitor element
It is characterized by generating a quality. And this product
In addition to the manufacturing method, the binder in the separator is dissolved and removed.
And then the capacitor element at 80 ° C to 120 ° C
And then impregnate with the monomer solution and oxidant
You can also do it.

In this manufacturing method, the capacitor
Put the element in water at 80 ℃ to 100 ℃ for 1 to 10 minutes.
Dipping process and the capacitor at 80 ° C to 120 ° C
Repeat the step of drying the device at least twice more to improve
Suitable for

In this way, the anode electrode foil and the cathode electrode foil are
Through a separator made of non-woven fabric mainly composed of synthetic fibers
The wound capacitor element at 80 ℃ to 100 ℃
Vine in separator by immersing in water for 1 to 10 minutes
Dissolved and removed the dar is typified by vinylon fiber, etc.
Non-woven fabric mainly composed of synthetic fibers was used as a separator
In that case, it becomes difficult to obtain desired capacitance characteristics and heat resistance.
The reason is not clear, but
Nonwoven fabrics composed mainly of synthetic fibers are used to bond fibers together.
A binder as a binder is indispensable, and this binder
Is based on the finding that

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a solid electrolytic capacitor according to the manufacturing method of the present invention, which is an anode electrode foil 1 made of a valve metal such as aluminum and having an oxide film layer formed on the surface thereof,
The cathode electrode foil 2 and the cathode electrode foil 2 are wound around a separator 3 made of a non-woven fabric containing vinylon fiber as a main component to form a capacitor element 1.
Form 0. Then, in this capacitor element 10,
Impregnated with 4-ethylenedioxythiophene and an oxidizing agent,
Polyethylenedioxythiophene produced by the chemical polymerization reaction in the capacitor element 10 is held by the separator 3 as the solid electrolyte layer 5.

The anode foil 1 is made of a valve metal such as aluminum. As shown in FIG. 2, the surface of the anode foil 1 is roughened by an electrochemical etching process in a chloride aqueous solution to form a large number of etching pits. 8 forming. Further, a voltage is applied to the surface of the anode electrode foil 1 in an aqueous solution of ammonium borate or the like to form an oxide film layer 4 serving as a dielectric.

The cathode electrode foil 2 is made of aluminum or the like similarly to the anode electrode foil 1, and has a surface which is only subjected to etching treatment.

Lead wires 6 and 7 for connecting the respective electrodes to the outside are connected to the anode electrode foil 1 and the cathode electrode foil 2 by known means such as stitching and ultrasonic welding. The lead wires 6 and 7 are made of aluminum or the like,
The anode electrode foil 1 and the cathode electrode foil 2 are connected to each other and to an external connection portion for electrical connection with the outside, and are led out from the end surface of the wound capacitor element 10.

The separator 3 is a non-woven fabric mainly composed of vinylon fibers. As another embodiment,
It is also possible to use a non-woven fabric obtained by mixing paper fibers such as glass fibers, polyester fibers, nylon fibers, rayon fibers, and manila paper. The nonwoven fabric has a basis weight of 6 to
36 g / m ² , fiber diameter 5 to 30 μm, thickness 30 to 150
μm and a density of 0.2 to 0.5 g / cm ³ are used.

The capacitor element 10 is formed by winding the above anode electrode foil 1 and cathode electrode foil 2 with the separator 3 interposed therebetween. The dimensions of the bipolar electrode foils 1 and 2 are arbitrary according to the specifications of the solid electrolytic capacitor to be manufactured, and the separator 3 may have a width dimension slightly larger than that of the bipolar electrode foils 1 and 2. .

3,4-ethylenedioxythiophene is
It can be obtained by a known production method disclosed in JP-A-2-15611. Further, as the oxidizing agent, ferric p-toluenesulfonate dissolved in butanol is used. The ratio of butanol and ferric p-toluenesulfonate in this oxidizing agent may be arbitrary, but in the present invention, the ratio is 1 :.
I am using one. The mixing ratio of the 3,4-ethylenedioxythiophene and the oxidizing agent is 1: 3 to 1:15.
Is preferred.

[0031]

EXAMPLES Next, a method of manufacturing a solid electrolytic capacitor according to the present invention and a solid electrolytic capacitor obtained by the method will be specifically described. (Embodiment 1) The anode electrode foil 1 and the cathode electrode foil 2 are made of a valve metal such as aluminum or tantalum, and the surface thereof is subjected to an etching treatment in advance to increase the surface area. The anode electrode foil 1 is further subjected to chemical conversion treatment, and an oxide film layer 4 made of aluminum oxide is formed on the surface. The anode electrode foil 1 and the cathode electrode foil 2 are
The capacitor element 10 is obtained by winding it through a separator 3 made of a non-woven fabric mainly composed of vinylon fiber having a thickness of 50 μm and a basis weight of 12 g / m ² .

In this embodiment, the capacitor element 10
Has a diameter of 4φ, a vertical dimension of 7 mm, and a rated voltage of 1
6 WV and a rated capacitance of 10 μF are used.
Note that lead wires 6 and 7 are electrically connected to the anode electrode foil 1 and the cathode electrode foil 2 of the capacitor element 10, respectively, and project from the end surface of the capacitor element 10.

The capacitor element 10 having the above structure is immersed in 100 ° C. water for 5 minutes to dissolve and remove the binder in the separator. This step may be repeated several times at regular intervals, if necessary.

Next, the capacitor element 10 is provided with 3,4-
Impregnate ethylenedioxythiophene and an oxidizing agent. As the oxidant, ferric p-toluenesulfonate dissolved in butanol is used, and the mixing ratio of 3,4-ethylenedioxythiophene and the oxidant is preferably in the range of 1: 3 to 1:15. In this example, the one of 1: 5 was used.

Then, the capacitor element 10 impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent was added to 25
Polyethylenedioxythiophene, that is, the solid electrolyte layer 5 is formed by the polymerization reaction by leaving it for 15 hours to 2 hours at a polymerization temperature of 150 to 150 ° C.

Regarding the ranges of the polymerization temperature and the standing time, when the polymerization temperature becomes higher, among the electric characteristics of the manufactured solid electrolytic capacitor, the capacitance, tan δ and impedance characteristics are improved, but the leakage current characteristics are Since it tends to deteriorate, the capacitor element 1 to be manufactured
It can be arbitrarily changed within the above range according to the specification of 0.

In this way, the capacitor element 10 in which the solid electrolyte layer 5 is formed on the separator 3 interposed between the anode electrode foil 1 and the cathode electrode foil 2, the solid electrolytic layer is formed by coating the outer periphery of the capacitor element 10 with an exterior resin. Form a capacitor.

(Example 2) As in Example 1, the anode electrode foil 1 and the cathode electrode foil 2 were each made to have a thickness of 50 μm and a basis weight of 12 g / g.
The capacitor element 10 is formed by winding through a separator 3 made of a non-woven fabric mainly composed of m ² vinylon fiber. Then, the capacitor element 10 was immersed in 100 ° C. water for 5 minutes to dissolve and remove the binder in the separator, and then the capacitor element 10 was dried at 100 ° C. for 10 minutes.

As in Example 1, this capacitor element 10 was impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent to produce polyethylenedioxythiophene, which was then covered with an exterior resin to give a rated voltage of 6 A solid electrolytic capacitor having a capacitance of 33 μF and a capacitance of 3 WV is obtained.

(Example 3) The capacitor element 10 manufactured in the same manner as in Example 2 was immersed in water at 100 ° C for 5 minutes to dissolve and remove the binder in the separator, and then at 100 ° C.
Then, the capacitor element 10 was dried for 10 minutes, and a series of steps of dipping and drying was repeated twice. As in Example 1, this capacitor element 10 was impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent to produce polyethylenedioxythiophene, and then coated with an exterior resin to obtain a rated voltage of 6.3 WV. A solid electrolytic capacitor having a rated capacitance of 33 μF is obtained.

Next, the electrical characteristics of the solid electrolytic capacitors according to the first to third embodiments and the conventional solid electrolytic capacitors will be compared. (Comparative Example 1) An anode electrode foil and a cathode electrode foil made of aluminum were wound around a separator made of glass paper having a thickness of 150 μm and a basis weight of 20 g / m ² to form a capacitor element. Example 1 impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent
Similar to the above, a solid electrolyte layer made of polyethylenedioxythiophene is generated, and the rated voltage is 16 WV and the rated capacitance is
A solid electrolytic capacitor of 0 μF was formed.

(Comparative Example 2) Anode electrode foils and cathode electrode foils made of aluminum were used, each having a thickness of 50 μm and a basis weight of 12 g / m 2.
^{As in} Example 1, the capacitor element was formed by winding it through a separator made of a non-woven fabric composed mainly of vinylon fiber ² and impregnated with 3,4-ethylenedioxythiophene and an oxidizing agent. Then, a solid electrolyte layer made of polyethylenedioxythiophene is produced to obtain a solid electrolytic capacitor having a rated voltage of 6.3 WV and a rated electrostatic capacity of 33 μF.

The initial characteristics of each of Examples 1 to 3 and Comparative Examples 1 and 2 were measured. The results are shown below. In addition, Example 1 and Comparative Example 1 shown in Table 1
Are rated voltage 20 WV and rated capacitance 10 μF, respectively
In Examples 2 and 3 and Comparative Example 2 shown in Table 2, the rated voltage is 6.3 WV and the rated capacitance is 33 μF. The "capacity appearance rate" indicates the ratio of the measured capacitance to the rated capacitance.

[0044]

[Table 1]

[0045]

[Table 2]

As is clear from Table 1, the solid electrolytic capacitor according to Example 1 exhibited substantially the same level of characteristics as Comparative Example 1 using glass paper. Therefore, the volumetric efficiency of Example 1 using the separator made of the non-woven fabric mainly composed of vinylon fibers is higher than that of Comparative Example 1. Further, as is clear from Table 2, the capacity appearance rate of the solid electrolytic capacitors according to Example 2 and Example 3 is higher than that of Comparative Example 2, and the influence of the binder of the nonwoven fabric made of synthetic fiber is reduced. It is shown that.

[0047]

[0048]

In the manufacturing method of a solid electrolytic capacitor according to this invention, according to the present invention, a capacitor element formed by winding via a separator made of an anode electrode foil and a cathode electrode foil of a non-woven fabric, 80
Since the binder in the separator is dissolved and removed by immersing it in water at ℃ to 100 ℃ for 1 to 10 minutes, or after that, the capacitor element is dried at 80 to 120 ℃, the binder in the nonwoven fabric used as the separator is It is dissolved and removed, and the decrease in capacitance caused by the binder can be prevented.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a capacitor element used in the present invention.

FIG. 2 is a conceptual diagram of an anode foil used in the present invention.

[Explanation of symbols]

1 Anode electrode foil 2 cathode foil 3 separator 4 Oxide film layer 5 Solid electrolyte layer 6,7 lead wire 8 etching pits 10 Capacitor element

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H01G 9/05 H (56) Reference JP-A-3-198316 (JP, A) JP-A-2-141231 (JP, A) JP 63-207114 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01G 9/02

Claims (2)

(57) [Claims] 1. An anode electrode foil and a cathode electrode foil are made of synthetic fiber.
A capacitor element wound with a separator made of a non-woven fabric as a main component is immersed in water at 80 ° C. to 100 ° C. for 1 minute to 10 minutes to dissolve and remove the binder in the separator, and then a monomer solution and an oxidizing agent are added. Impregnate and cond
A method for manufacturing a solid electrolytic capacitor in which a solid electrolyte layer is formed by chemical polymerization in a sensor element . 2. In addition to the method for producing a solid electrolytic capacitor according to claim 1 , the binder element in the separator is dissolved and removed, and then the capacitor element is dried at 80 ° C. to 120 ° C., after which the monomer solution and the oxidizing agent are added. A method for manufacturing a solid electrolytic capacitor impregnated with.