JPH06163326A - Solid electrolytic capacitor and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a highly reliable solid electrolytic capacitor which has stable electric characteristics by using a capacitor element formed by winding electrode foil. CONSTITUTION:After impregnating a capacitor element with oxidyzer solution, the capacitor element is impregnated with organic solid electrolytic solution and a first electrolytic layer 61 is formed on the surface of electrode foil 1 by chemical polymerization. Then, a second and the subsequent electrolytic layers 62 are formed by using a solution of organic solid electrolyte and an oxidyzer solution in this order. The oxidyzer solution is prevented from directly acting the first electrolytic layer 61 and to an oxide film layer 5 on the surface of the anode electrode foil 1 and the deterioration of ESR characteristics, etc., is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor and a method for manufacturing the same, and more particularly to a solid electrolytic capacitor using a solid electrolyte made of an organic conductive compound.

[0002]

2. Description of the Related Art In recent years, electronic components have been made into chips due to demands for miniaturization of electronic equipment and efficiency of mounting on a printed circuit board. Along with this, there are increasing demands for making electrolytic capacitors into chips and reducing their height. Also, due to the diversification of electronic devices, various characteristics are required for chip-type electrolytic capacitors.

Also in the solid electrolytic capacitor, in addition to the solid electrolyte made of a metal oxide semiconductor such as manganese dioxide, a solid electrolyte made of an organic conductive compound such as tetracyanoquinodimethane (TCNQ), polypyrrole, polyaniline is used as the solid electrolytic capacitor. Has been proposed. Solid electrolytic capacitors using these organic conductive compounds have higher electrical conductivity than manganese dioxide,
Great improvement in electrical characteristics, especially ESR characteristics, can be expected.

In order to form an electrolyte layer made of an organic conductive compound such as polypyrrole, for example, the anode body is dipped in a pyrrole solution containing an oxidizing agent to form a pyrrole thin film on the surface of the anode body (chemical polymerization). ), And then applying a voltage (electrolytic polymerization) while immersing it in a solution in which pyrrole is dissolved (electropolymerization).

In such a proposal, a solid electrolyte layer cannot be obtained with an electrolyte layer formed only by chemical polymerization,
As a result, it is very difficult to maintain the initial electrical characteristics for a long period of time due to poor moisture resistance, and the adhesion to the surface of the anode body subjected to etching treatment, that is, the impregnation rate into the etching pit is poor. However, there is a background that a desired capacitance cannot be obtained because the function of drawing out the electrode of the electrolyte layer is not sufficient. On the other hand, according to electrolytic polymerization,
Although a strong electrolyte layer was obtained, it was necessary to apply a voltage to the anode body. However, a dielectric (oxide film layer) that is an insulator is formed on the surface of the anode body, and it is difficult to directly form an electrolyte layer on the surface of the anode body by electrolytic polymerization. Therefore, as a pretreatment, an electrolyte layer is first formed by chemical polymerization, and electrolytic polymerization is performed using this electrolyte layer as an electrode to obtain a strong electrolyte layer.

[0006]

However, in electrolytic polymerization, since a voltage is applied in a pyrrole solution containing an oxidant, it is difficult to reuse this pyrrole solution, and the individual capacitors are not reused. Combined with the complexity of applying voltage to the element and rigorously managing the liquid level to prevent the pyrrole solution from creeping up to the terminal part of the capacitor element, it is not always optimal for mass production. There was a difficult side to say.

Therefore, it is conceivable to form an electrolyte layer made of polypyrrole by only chemical polymerization. In that case, in order to achieve sufficient adhesion to the anode body, it is necessary to perform immersion in a pyrrole solution containing an oxidizing agent several times. Alternatively, it is conceivable to perform the step of impregnating the pyrrole solution and the oxidant solution separately several times. In particular, when a capacitor element is formed by winding foil-like aluminum as a bipolar electrode body together with a separator, it is necessary to generate an electrolyte layer having a sufficient thickness even in the central portion of the capacitor element together with the impregnation rate to the anode foil. Must be considered. However, when the capacitor element is immersed or impregnated for several times, polypyrrole is generated at the end face portion of the capacitor element, and the polypyrrole near the end face impedes the subsequent penetration of the pyrrole solution or the like.

Such an inconvenience can be prevented to some extent by first impregnating the capacitor element with the oxidant solution and then impregnating the pyrrole solution. That is, the polypeel generated by the chemical polymerization reaction has a property of being generated in a direction of penetrating into the oxidant solution, and if the capacitor element is previously impregnated with the oxidant solution, polypyrrole permeates into the inside of the capacitor element. This is because it becomes easier.

However, it has been found that when such a manufacturing process is carried out, the electrical characteristics of the manufactured solid electrolytic capacitor, particularly tan δ and ESR characteristics, deteriorate. Although the mechanism thereof is unknown, it is considered that the oxidizing agent solution which is impregnated prior to the pyrrole solution has some action on the oxide film layer on the surface of the anode foil and the electrolyte layer already formed.

In view of the above situation, an object of the present invention is to provide a solid electrolytic capacitor using a capacitor element formed by winding an electrode foil, which has stable electric characteristics and high reliability. Is to realize.

[0011]

The present invention relates to a solid electrolytic capacitor, in which a step of forming a capacitor element by winding an anode foil and a cathode electrode foil together with a separator, and an oxidant solution and an organic solid electrolyte solution are applied to the capacitor element. Separately impregnating step, impregnating the capacitor element with the oxidant solution and then with the organic solid electrolyte solution to generate a first electrolyte layer by a chemical polymerization reaction on the surface of the electrode foil,
After that, the second and subsequent electrolyte layers are formed in the order of the organic solid electrolyte solution and the oxidizing agent solution. Also,
The solid electrolytic capacitor manufactured by this manufacturing method is characterized by using glass paper as a separator.

[Action]

In the present invention, the electrolyte layer 6 is first formed so as to penetrate into the oxidant solution with which the capacitor element 4 is impregnated. Therefore, electrode foil (anode foil 1, cathode foil 2)
Even in the case of the capacitor element 4 formed by winding, the electrolyte layer 6 such as polypyrrole is not generated only on the end face thereof, and the electrolyte layer 6 easily penetrates into the inside of the capacitor element 4. And in the subsequent impregnation,
First, the pyrrole solution is impregnated, and then the oxidant solution is impregnated. Then, this is repeated several times. Then,
Since the chemical polymerization reaction occurs with the impregnation of the oxidant solution,
The oxidant solution does not directly act on the already formed electrolyte layer 6 and the oxide film layer 5 on the surface of the anode electrode foil 1, and it is possible to prevent deterioration of tan δ, ESR characteristics and the like.

In the second and subsequent impregnations with the pyrrole solution, the wettability of the pyrrole solution is improved because the electrolyte layer 6 made of polypyrrole has already been formed. Therefore, polypyrrole is not generated only on the end face of the capacitor element 4, the electrolyte layer 6 easily penetrates to the central portion of the capacitor element 4, and the adhesion with the anode foil 1, that is, the impregnation rate is improved.

Further, in the present invention, as the separator 3,
I use glass paper. This is because when a separator made of paper such as manila paper is used, it is first oxidized by the oxidant solution impregnated into the capacitor element, and the oxidative capacity of the oxidant solution is reduced accordingly, which is sufficient for the pyrrole solution. This is to prevent a difficult chemical polymerization reaction from occurring. Therefore, a separator made of another material may be used as long as the separator is not affected by the oxidizing agent solution.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing a capacitor element used in a manufacturing process according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a conceptual structure of an anode foil surface in the embodiment.

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 pre-etched to increase its surface area.
The oxide film layer 5 is formed by chemical conversion treatment. The oxide film layer 5 is made of aluminum oxide in which the surface of the anode foil is oxidized and serves as a capacitor dielectric.

Similar to the anode foil 1, the cathode foil 2 is made of foil-shaped aluminum and has an oxide film layer not formed on its surface, but is subjected to etching treatment to increase the surface area.

Then, the anode foil 1 and the cathode foil 2 are
As shown in FIG. 1, the capacitor element 4 is wound with the separator 3 in between. As the separator 3, glass paper having a thickness of 80 μm was used in this example. Here, the reason why the glass paper is used as the separator 3 is to suppress the oxidation reaction between the separator 3 and the oxidant solution with which the capacitor element 4 is impregnated in the next step, and to maintain the oxidizing ability of the oxidizer solution. is there.

Next, the capacitor element 4 is separately impregnated with the oxidant solution and the pyrrole solution. The oxidizer solution was 1.5 mol / l ammonium persulfate and 0.5 mol.
/ L of tetraethylammonium P-toluenesulfonate, which has a high concentration in a substantially saturated state. The impregnation with the oxidant solution was performed for 5 to 20 minutes with the capacitor element 4 placed in a reduced pressure state.

Then, the pyrrole solution is applied to the capacitor element 4 impregnated with the oxidant solution under reduced pressure for 10 minutes to 2 minutes.
Impregnation was carried out for 0 minutes, followed by washing with water and drying. By this impregnation with the pyrrole solution, a chemical polymerization reaction occurs inside the capacitor element 4, and the first electrolyte layer 61 made of polypyrrole is formed on the surface of the anode foil 1. The impregnation time of each of the oxidant solution and the pyrrole solution can be changed as needed, but the impregnation time of the pyrrole solution is about twice that of the oxidant solution.

Next, the capacitor element 4 is again impregnated with the pyrrole solution and the oxidant solution. Here, first, the capacitor element 4 was impregnated with the pyrrole solution under reduced pressure for about 2 minutes,
Then, high-concentration oxidant solution is vacuum impregnated for about 1 minute. The oxidant solution was 1.5 mol, similar to the one impregnated previously.
/ L Ammonium persulfate and 0.5 mol / l tetraethylammonium P-toluenesulfonate. Then, the capacitor element 4 is washed with water, this is repeated several times, and then a drying process is performed. As a result, as shown in FIG.
The second and subsequent electrolyte layers 62 are sequentially formed on the surface of the anode foil 1 of the capacitor element 4.

The capacitor element 4 thus formed
For example, the capacitor element 4 is housed in an outer frame having a housing space, and the opening is sealed with a sealing resin such as epoxy resin to form a solid electrolytic capacitor. Alternatively, the outer surface of the capacitor element 4 may be covered with a mold resin.

In this embodiment, the capacitor element 4 is first impregnated with the oxidant solution and then with the pyrrole solution to form the first electrolyte layer 61. Therefore, it is possible to prevent the chemical polymerization reaction from occurring in the pyrrole solution so that the pyrrole solution permeates the oxidant solution, and the generation of the electrolyte layer only on the end face portion of the capacitor element 4. Then, the capacitor element 4 on which the first electrolyte layer 61 is formed is impregnated with the pyrrole solution and the oxidant solution several times in this order, so that the oxidant solution affects the first electrolyte layer 61. Can be suppressed, and the impregnation rate on the surface of the anode foil 1 can be improved.

Further, since glass paper is used as the separator 3, when the first electrolyte layer 61 is formed, it is not oxidized by the oxidant solution that is impregnated first, and as a result, the oxidant solution is obtained. The oxidative ability of the iron does not decrease. Therefore, a sufficient chemical polymerization reaction with the pyrrole solution is expected, and the impregnation rate can be improved.

Next, the electrical characteristics of the solid electrolytic capacitors manufactured according to the examples of the present invention were measured. First, as Comparative Example 1, a capacitor element similar to that of the example was prepared and impregnated with a pyrrole solution and an oxidant solution in this order.
Using this capacitor element, a solid electrolytic capacitor having an exterior structure similar to that of the example was obtained. Further, as Comparative Example 2, a capacitor element manufactured up to the first electrolyte layer was prepared in the same manner as in Example, and then this capacitor element was impregnated with an oxidant solution and a pyrrole solution several times in this order.
Then, the capacitance (Cap) and the tangent of the loss angle (ta) of the solid electrolytic capacitors according to the example, the comparative example 1 and the comparative example 2.
nδ) and ESR (100 KHz) were measured. The results are shown below. In each of the examples and the comparative examples, the anode foil is 56 vf.

Cap (μF) tan δ ESR (Ω) Comparative Example 1 2.812 0.1557 1.899 Comparative Example 2 3.065 0.0815 0.522 Example 3.482 0.0468 0.281

As is clear from these results, the solid electrolytic capacitors of the examples have a larger capacitance than that of Comparative Example 1, and the adhesion of the electrolyte layer to the anode foil is
That is, it is understood that the impregnation rate is improved. Further, it is understood that the tan δ and ESR characteristics are also good in comparison with Comparative Example 2, and the influence of the second and subsequent impregnations of the pyrrole solution and the oxidant solution is suppressed.

[0028]

As described above, according to the present invention, in the method of manufacturing a solid electrolytic capacitor, a step of winding a separator and an anode / cathode electrode foil to form a capacitor element,
A step of separately impregnating the capacitor element with an oxidant solution and an organic solid electrolyte solution, wherein the capacitor element is impregnated with the oxidant solution and then with the organic solid electrolyte solution, and the first electrolyte layer is formed by a chemical polymerization reaction. Is produced on the surface of the electrode foil, and then the second and subsequent electrolyte layers are produced in the order of the organic solid electrolyte solution and the oxidizer solution, which enables chemical polymerization reaction several times, and the capacitor element The formation of the electrolyte layer inside becomes easy and dense, the moisture resistance performance is improved, the adhesion on the electrode foil, especially on the anode foil surface is also improved, and the electrical characteristics such as capacitance of the manufactured solid electrolytic capacitor are improved. The characteristics can be improved.

Further, unlike the conventional case, the electrolytic polymerization step is not required, so that the manufacturing process is simplified and no special manufacturing equipment is required. In addition, there is no damage to the oxide film layer due to the voltage application in the electrolytic polymerization step, and in combination with the use of the wound capacitor element, the damage is prevented even if the electrolyte layer is made of polypyrrole which is weak in mechanical strength. be able to. Therefore, the leakage current characteristic can be stably maintained for a long period of time.

Further, when glass paper is used as the separator, it is less susceptible to the oxidation reaction with the oxidant solution that is impregnated when forming the first electrolyte layer, and the oxidizing ability of the oxidant solution does not decrease. . Therefore, the chemical polymerization reaction with the pyrrole solution can be carried out without any trouble, a desired electrolyte layer can be obtained, and electrical characteristics such as capacitance are improved.

[Brief description of drawings]

FIG. 1 is a plan view showing a capacitor element used in a manufacturing process according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a conceptual structure of the surface of the anode foil in the example.

[Explanation of symbols]

 1 Anode Foil 2 Cathode Foil 3 Separator 4 Capacitor Element 5 Oxide Film Layer 6 Electrolyte Layer 61 First Electrolyte Layer 62 Second Electrolyte Layer

Claims (2)

[Claims] 1. A method of oxidizing a capacitor element, comprising the steps of winding an anode and cathode electrode foil together with a separator to form a capacitor element, and impregnating the capacitor element with an oxidant solution and an organic solid electrolyte solution separately. After the impregnation with the agent solution, the organic solid electrolyte solution is impregnated to form a first electrolyte layer on the surface of the electrode foil by a chemical polymerization reaction, and thereafter, the organic solid electrolyte solution and the oxidant solution are added in this order. A method for manufacturing a solid electrolytic capacitor for producing an electrolyte layer. 2. The solid electrolytic capacitor according to claim 1, wherein glass paper is used as the separator.