JPH03231414A - Solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To prevent deformation of a capacitor element, deterioration of an oxide film, and crack of a conductive macromolecule by forming a capacitor by winding a film-forming metal foil where a dielectric oxide film is formed at a winding core of a required material and a required shape and a spacer. CONSTITUTION:An anode lead 1 is caulking-fixed to a highly pure Al foil anode foil 2 which is made by forming a dielectric oxide film, a conductive macromolecular polypyrrole film 3 is formed by chemical oxidative polymerization, and a capacitor element which is formed along with a separator paper 4 is wound around a winding core 5 which is in cylindrical shape or polygonal cylindrical shape with a ceramic or chemical-resistance material for creating a solid electrolytic capacitor. After winding this capacitor element, if a winding core is left, neither cavity nor void is generated within the capacitor element, mechanical strength against stress is enhanced, and deformation of the capacitor element, deterioration of an oxide film, and crack of a conductive macromolecule are prevented even if press stress is applied in the case of sheathing of the resin mold, thus restricting generation of leak current and short-circuit failure and obtaining a solid electrolytic capacitor with stable and improved electrical characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a solid electrolytic capacitor in which a conductive polymer film is formed as a solid electrolyte on the surface of a dielectric oxide film.

[Prior Art] Solid electrolytic capacitors generally form an oxide film, which is a dielectric, on the surface of a film-forming metal (electrode foil) such as aluminum or tantalum, and on this oxide film, manganese dioxide, TCNQ complex, etc. It is constructed by sequentially forming a solid electrolyte layer and a conductor layer.

Capacitors using manganese dioxide as a solid electrolyte have drawbacks such as the dielectric oxide film being easily damaged during the manufacturing process, while capacitors using TCNQ complexes have drawbacks such as poor thermal stability.

In response to this, in recent years, a conductive polymer film (chemical oxidation polymerization film) that is chemically oxidized and polymerized using an oxidizing agent is formed on the anodic oxide film (2), and is wound together with separator paper (spacer) and cathode foil to form a capacitor element. A solid electrolytic capacitor has been proposed in which a conductive polymer film (electrolytic oxidative polymer film) is formed by electrolytic oxidative polymerization after forming a conductive polymer film.

This solid electrolytic capacitor has large capacitance and good temperature and frequency characteristics, but the conductive polymer film formed by chemical oxidation polymerization or electrolytic oxidation polymerization has almost no film repairability. During the process, in order to avoid
Particularly during exterior packaging, if stress is applied to the capacitor element due to heating of the resin mold, pressure during injection of molten resin, etc., the capacitor element may be deformed, causing deterioration of the oxide film, cracks in the conductive polymer, etc. The problem was that the product had a large leakage current. When this leakage current becomes extremely large, short circuit failures and the like occur.

Furthermore, along with this, there are still some points to be improved, such as an increase in the tangent of the loss angle (tan δ) and an increase in the distribution of capacitance.

On the other hand, conventionally, when winding a capacitor element, a winding core made of iron or the like is used to form the element around this core, and then the winding core is removed. A cavity is formed in the needle, and this cavity itself or a gap formed between turns around this cavity becomes a factor that weakens the mechanical strength of the capacitor element against stress.

[Problems to be Solved by the Invention] As explained above, in conventional solid electrolytic capacitors that use a conductive polymer film as a solid electrolyte, the conductive polymer film has almost no film repairability, so the resin When stress is applied to the capacitor element during mold packaging, the capacitor element deforms, causing deterioration of the oxide film, cracking of the conductive polymer, etc., resulting in the deterioration of various characteristics.

The present invention was proposed in order to solve the problems of the prior art, and its purpose is to provide a solid electrolytic capacitor that uses a conductive polymer film as a solid electrolyte, in which the capacitor element is covered with a resin mold. Even when stress is applied, it is possible to prevent deformation of the capacitor element, deterioration of the oxide film, and cracking of the conductive polymer, resulting in low leakage current, fewer short circuit defects, and improved electrical characteristics as a capacitor. An object of the present invention is to provide an excellent solid electrolytic capacitor that is stable and good.

[Means for Solving the Problems] The present invention solves the problem that in conventional solid electrolytic capacitors, a cavity formed at the center of the winding of a capacitor element causes a decrease in the mechanical strength of the capacitor element against stress. This is what we focused on.

That is, the solid electrolytic capacitor according to the present invention is a solid electrolytic capacitor that uses a capacitor element formed by winding a spacer and a film-forming metal foil on which a dielectric oxide film has been formed, in which the capacitor element is formed by winding a spacer. A chemical oxidation polymer film, an electrolytic oxidation polymer film, which has a cylindrical or polygonal cylinder core made of ceramic or chemical-resistant material at the center of the rotation, and the film-forming metal foil and spacer are formed at least in sequence; It is characterized in that it is provided with a conductive coating film, and an electrode lead terminal is led out from the film-forming metal foil and the conductive coating film.

[Function] The function of the present invention having the above configuration is as follows.

First, in the present invention, a capacitor element is formed using a winding core made of ceramic or a chemical-resistant material, and the winding core remains at the center of the winding of the capacitor element even after the capacitor element is wound. , no cavities or voids are formed in the formed capacitor element, and mechanical strength against stress is high. Therefore, even if pressure stress is applied to the element during resin mold exterior packaging, it is possible to prevent deformation of the capacitor element, deterioration of the oxide film, cracking of the conductive polymer, etc., thereby reducing the leakage current value and the occurrence of short circuit failures. , the electrical characteristics as a capacitor can be made stable and good.

By the way, if the winding core is simply left at the center of the winding of the capacitor element, depending on the material of the winding core, there is a risk that the winding core will deteriorate due to various subsequent treatments, but in the present invention, Since the material of the winding core is limited to ceramic or chemical-resistant materials, the winding core will not deteriorate due to various treatments after winding. Therefore, the mechanical strength of the winding core against stress is reliably maintained even after various treatments.
As described above, the leakage current can be reduced, the occurrence of short circuit failures can be reduced, and the electrical characteristics of the capacitor can be made stable and good.

[Example] An example of the solid electrolytic capacitor according to the present invention will be specifically described below with reference to the drawings.

First, as shown in FIG. 1, the anode lead 1 was attached by caulking to a high-purity aluminum foil with a dielectric oxide film formed thereon, 401 tm thick and 3 mm wide.
The anode foil 2 was obtained by cutting into mm pieces. This anode foil 2
After being immersed in a mol/u pyrrole/ethanol solution for 5 minutes, it was further immersed in a 0.5 m o 1/l ammonium persulfate aqueous solution for 5 minutes to form a polypyrrole film 3 by chemical oxidative polymerization.

Next, a separator paper (spacer) 4 is layered on this anode foil 2, and a capacitor element 6 is created by winding it in a spiral using a ceramic cylindrical winding core 5 with a diameter of 1 mm.
Thereafter, the dielectric oxide film was repaired by re-forming.

Subsequently, this conde/su element 6 was immersed in an acetonitrile solution containing 1 mol/J of pyrrole monomer and 1 mol/U of sodium paratoluenesulfonate as a supporting electrolyte, and the chemically polymerized polypyrrole was used as an anode.
Constant current electrolytic oxidative polymerization (1 mA/'cm) is applied between the external cathode and
A polypyrrole film was formed by electrolytic oxidation polymerization.

Thereafter, the capacitor element 6 is immersed in colloidal carbon to form a carbon layer, and then silver paste is applied to form a conductive coating, and as shown in FIG. Welding and the cathode side were fixed with silver adhesive. The capacitor element 6 thus fixed to the metal frame 7 was molded with thermosetting epoxy resin 8 to complete a solid electrolytic capacitor with a rating of 10V and a nominal capacitance of 10 μF.

The solid electrolytic capacitor of this embodiment configured as described above operates as follows.

That is, since the ceramic winding core 5 is formed while remaining inside the capacitor element 6, no cavities or voids are formed within the capacitor element 6, and the mechanical strength against stress is high. In this case, in particular, since ceramic is used as the material for the winding core 5, there is no fear that the winding core 5 will deteriorate even during various treatments after winding, and stable mechanical strength can be maintained. Therefore, in this example,
Even if pressure stress is applied to the capacitor element 6 during molding with the thermosetting epoxy resin 8, there is no risk of deformation of the capacitor element 6, deterioration of the oxide film, cracks in the conductive polymer, etc. as in the conventional case. There is no. Therefore, the leakage current can be made much smaller than in the past, the occurrence of short circuit failures can be reduced, and the electrical characteristics of the capacitor can be made stable and good.

In addition, in order to specifically verify the effects of the solid electrolytic capacitor according to the embodiment of the present invention (this embodiment product) as described above, a capacitor with the same rating and dimensions with the same configuration except for the winding core was constructed using conventional technology. A solid electrolytic capacitor (conventional product) was manufactured as follows.

That is, in manufacturing the conventional product, a high-purity aluminum foil of the same size with a dielectric oxide film formed thereon was used, an anode lead was attached, and a polypyrrole film was formed by chemical oxidation polymerization. is processed in exactly the same way. In the winding process, unlike the above-mentioned embodiments of the present invention, an iron winding core with a diameter of 1 mm (same size) is used as the winding core, and the anode foil and separator paper (spacer) are overlapped to form a spiral shape. A capacitor element is created by winding it, and then the element is extracted from the iron winding core.

After this, the dielectric oxide film is repaired by reconstitution, and chemical oxidation polymerization is performed, as in the above embodiment according to the present invention.
After performing constant current electrolytic oxidation polymerization to form a polypyrrole film, it is coated with colloidal carbon and silver base and fixed to a metal frame, and finally molded with thermosetting epoxy resin to achieve a rated voltage of 10V and a nominal static electricity. Capacity 10
Completed a μF solid electrolytic capacitor.

Various characteristic tests were conducted using a large number of samples on the solid electrolytic capacitor according to the present invention (this example product) completed as described above and the solid electrolytic capacitor (conventional product) according to the prior art, and the distribution of capacitance was determined. When the range, average value of tan δ and leakage current, and number of short circuits were investigated, the results shown in Table 1 below were obtained.

Table 1 From Table 1, it can be seen that the conventional product has large variations in capacitance distribution, high tan δ, and large leakage current.
Furthermore, while the number of short circuits occurring is large at 85 for 1004 width, in the product of the present invention, the variation in capacitance distribution is small, tan δ is low, and leakage current is small (half of that of conventional product). It can be seen that the number of short circuits was also significantly reduced to 8 out of 1016, about one-tenth of the conventional product.

All of these demonstrate the effects of the winding core 5 in the product of this example.

Note that the present invention is not limited to the above embodiments,
The shape of the winding core may be a polygonal prism, and the cross-sectional shape of the winding core may be, for example, the shapes shown in FIGS. 3 to 5.

These drawings each have a regular octagonal cross-sectional shape (third
Figure), square (Figure 4), regular hexagonal (Figure 5) winding core 5
An example using . These embodiments also provide the same effects as those of the embodiments described above.

Furthermore, the material of the winding core 5 is not limited to ceramic, and other chemically resistant materials can be used as appropriate.

[Effects of the Invention] As explained above, the present invention improves the simple structure of forming a capacitor element using a cylindrical or polygonal pillar-shaped winding core made of ceramic or chemical-resistant material. In comparison, the mechanical strength of the capacitor element against stress can be significantly improved, making it possible to prevent deformation of the element, deterioration of the oxide film, cracking of the conductive polymer, etc. even if stress is applied to the element during resin molding. As a result, it is possible to provide an excellent solid electrolytic capacitor that has low leakage current, less occurrence of short-circuit defects, and stable and good electrical characteristics as a capacitor.

[Brief explanation of drawings]

1 and 2 are diagrams showing one embodiment of a solid electrolytic capacitor according to the present invention. FIG. 1 is a perspective view showing a state of winding, and FIG. FIGS. 3 to 5 are sectional views showing other embodiments of the present invention, and show three types of embodiments with different cross-sectional shapes of the winding core. DESCRIPTION OF SYMBOLS 1...Anode lead, 2...Anode foil, 3...Polypyrrole film, 4...Separator paper (spacer), 5...
Winding core, 6... Capacitor element, 7... Metal frame, 8... Thermosetting epoxy resin.

Claims (1)

[Claims] A solid electrolytic capacitor using a capacitor element formed by winding a film-forming metal foil with a dielectric oxide film and a spacer, wherein the capacitor element has a ceramic or chemical-resistant material at the center of the winding. It has a cylindrical or polygonal columnar core made of material, and the film-forming metal foil and spacer include at least a chemical oxidation polymer film, an electrolytic oxidation polymer film, and a conductive coating film formed in sequence, and the above-mentioned A solid electrolytic capacitor characterized in that an electrode lead terminal is derived from a film-forming metal foil and a conductive coating film.