JPH03297120A - Electrolytic capacitor - Google Patents

Abstract

PURPOSE:To reduce a loss, to maintain a stable characteristic and to realize a small size by a method wherein a separator is laid between an anode electrode and a cathode electrode and the separator containing a polyamideimide fiber is used. CONSTITUTION:A high-purity aluminum foil 90mum in thickness is used for an anode 2 of a capacitor element 1; it is etched electrochemically; after that, 90V is applied to the surface by an anodic oxidation treatment; a dielectric layer of aluminum oxide is formed. An aluminum foil 50mum in thickness is used for a cathode foil; it is cut to be a belt shape in the same manner as the anode foil. Extraction leads 5, 6 for electrode extraction use are connected to the electrode foils; a belt-shaped separator 3, 40mum in thickness, composed of a polyamideimide fiber is laid between both electrode foils; it is wound at a winding tension of 2kg; the capacitor element is constituted. Then, the element is impregnated with an electrolyte whose main solute is ammonium adipate; an electrolytic capacitor is formed. Thereby, the smallsized electrolytic capacitor whose loss is small is formed, a stable characteristic is maintained and a small size is realized.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an electrolytic capacitor in which an electrolyte is held between electrodes by a separator.

[Conventional technology]

Electrolytic capacitors use at least a so-called valve metal, in which an insulating oxide film is formed on the surface of a metal such as aluminum, tantalum, or niobium, for the anode electrode, and the anode metal is heated to a desired thickness by anodizing or other operations. An insulating oxide film is formed and this film is used as a dielectric layer. There are various shapes of anode electrodes, but the main one has an element structure in which a long foil-like material is wound together with a similarly long separator and a cathode. There are also laminated capacitor elements in which foil electrodes and separators are stacked one on top of the other. In these capacitor elements, a liquid or solid electrolyte is held by a separator, and this electrolyte comes into direct contact with the dielectric oxide film layer and functions as a true cathode. Although outside the scope of the present invention, devices are known in which a block-shaped porous valve metal body is used as an anode without using a separator in the element. The liquid electrolyte used is one obtained by dissolving an organic acid, an inorganic acid, or a salt thereof in various organic solvents such as ethylene glycol and T-phthyrolactone, or water. As the solid electrolyte, semiconductor inorganic compounds such as manganese dioxide and lead dioxide, and conductive organic compounds such as tetracyanoquinodimethane, polyacetylene, and polypyrrole are used. As described above, the separator has the function of holding the electrolyte between the electrodes and preventing short circuit between the anode and the cathode. In the case of liquid electrolytes, paper is often used as the material for the separator, and its raw materials are often made from relatively long-fiber pulp called kraft or Manila hemp fibers. Further, in the case of a solid electrolyte using manganese dioxide which requires a thermal conversion process, a thin glass fiber cloth without paper removal may be used.

[Problem to be solved by the invention]

The functions required of the separator are to maintain the necessary and sufficient amount of electrolyte between the anode and cathode electrodes, and to maintain sufficient conductivity to prevent loss characteristics from worsening since it is interposed between the two electrodes. That is required. However, if the thickness and density of the separator are reduced more than necessary in order to improve conductivity, accidents such as short circuits between electrodes may occur. In addition, it is difficult to make the separator thinner than a certain level; the practical limit is about 20 gm for paper, and several tens of μm for glass fiber. This may cause inconveniences such as. Furthermore, in the case of electrolytic capacitors using liquid electrolytes, the manufacturing or operating temperature range is extremely high (although this does not occur when solid electrolytes, especially manganese dioxide, are used).
When converting manganese nitrate immersed in a capacitor element into manganese dioxide, the process of thermally converting it at a temperature of 250°C or higher is repeated, so the separator may also be required to be heat resistant. This invention aims to solve the above-mentioned problems, and aims to obtain an electrolytic capacitor with excellent characteristics by employing a new separator.

[Means for Solving the Problems] The electrolytic capacitor of the present invention is formed by winding or laminating a separator interposed between an anode electrode on which a dielectric oxide film layer is formed and a cathode electrode, The present invention is characterized in that the separator contains polyamide-imide fibers. Polyamide-imide resin has a structure with the basic skeleton of , and has extremely high thermal stability as well as excellent mechanical properties such as tensile strength and elastic modulus, and has traditionally been used as a resin processed product for various purposes. It is being The separator used in this invention is made of polyamide-imide fibers made into a sheet, or mixed with existing pulp or Manila hemp fibers. Polyamide-imide fibers with cellulose diameters of 10 μm or less are in practical use, and by using such particularly thin fibers, a thin separator with a thickness of 20 μm or less can be obtained. [Function] As mentioned above, polyamide-imide fiber has extremely high tensile strength, heat resistance, and chemical resistance, so a separator using this fiber in its entirety or as a mixture has high tensile strength as well as Has heat resistance and chemical resistance. Therefore, the tension applied to the separator during manufacturing of the wound element can be increased, and the capacitor element can be wound up firmly. Furthermore, since a thinner separator can be used than before to obtain the same tensile strength, the capacitance value per unit volume is increased and loss is reduced. Furthermore, since it has excellent heat resistance and chemical resistance, it is not affected by high temperature treatment or generated gases, unlike when forming a manganese dioxide electrolyte.

【Example】

The present invention will be explained in more detail below based on Examples. FIG. 1 shows the element structure of an electrolytic capacitor according to the present invention. The figure is a partially exploded front view of a capacitor element 1 with a wound structure, in which valve metal foil such as aluminum or tantalum cut into strips is used as an anode 2.
A separator 3 slightly wider than the anode 2 and a cathode 4 made of metal foil cut to approximately the same width as the anode are superimposed as shown in the figure, and a cylindrical capacitor element 1 is wound from one end thereof. It is something that forms. In this case, two separators 3 are used so that the anode 2 and cathode 4 do not come into contact even on the back side of the winding. Further, a lead-out cord 5.6 for obtaining an electrical connection with the outside is connected to the anode 2 and the cathode 4, respectively, and is led out from the end face of one of the windings. In this capacitor element 1, a liquid or solid electrolyte is permeated into the separator 3 through a predetermined process and maintained therein. The capacitor element 1 that has been subjected to the electrolyte infiltration treatment may be packaged by storing it in a metal case or sealing the outer surface with resin, if necessary. As an example of this invention, an electrolytic capacitor using a liquid electrolyte was first created and its characteristics were investigated. (Example 1 of the present invention) The electrolytic capacitor used in this example of the invention uses a wound type capacitor element, and has a rated voltage of 63V and a rated capacitance of 1000 μF. The capacitor element uses high-purity aluminum foil with a thickness of 90 μm as the anode, and after performing electrochemical etching treatment to expand the surface area of this aluminum foil, the surface is anodized and 90V is applied to it to form aluminum oxide. A dielectric layer was formed. This anode foil was cut into a strip having a width of 24 mm and a length of 450 mm, and an anode lead was connected by crimping. Aluminum foil with a thickness of 50 pm was used as the cathode foil, and was also cut into strips. A part of the glue for drawing out the electrodes was connected to these electrode foils, a band-shaped separator made of polyamideimide fiber with a thickness of 40 μm was interposed between both electrode foils, and a capacitor element was obtained by winding with a winding tension of 2 kg. . Next, this capacitor element was impregnated with an electrolytic solution containing ammonium adipate as the main solute, housed in a cylindrical aluminum case, and the opening was sealed with elastic rubber to form an electrolytic capacitor. (Comparative Example 1) The same anode foil and cathode foil as in Example 1 of the present invention were used. Electrolytic paper made of Manila hemp mixed paper with a thickness of 40 μm was used as the separator, and these sheets were overlapped and wound with a winding tension of 1 kg to form a capacitor element. This capacitor element was impregnated with the same electrolytic solution as in Example 1 of the present invention, and an exterior was applied in the same manner to obtain an electrolytic capacitor. When the characteristics of these electrolytic capacitors were measured, the results shown in Table 1 below were obtained. Note that the loss is the value at 120 Hz, and the leakage current is the value for 1 minute after the rated voltage is applied. Next, an example in which a solid electrolyte is used as the electrolyte will be described. (Example 2 of the present invention) In forming the capacitor element, the same materials as in Example 1 of the present invention were used for the anode side electrode and the separator. Further, the winding tension was also set to the same value as in Example 1 of the present invention. This capacitor element was immersed in a manganese nitrate aqueous solution, and then heated in a heating furnace at 250°C.
It was heated at 110 minutes at °C to convert manganese nitrate into manganese dioxide. This process was repeated three times. (Comparative Example 2) The anode side electrode was the same as in Inventive Example 1, and the separator was made of glass fiber with a thickness of 100 μm and was wound with a winding tension of 1 kg to form a capacitor element. A solid electrolyte layer made of manganese dioxide was formed on this capacitor element in the same manner as in Example 2 of the present invention. When the initial electrical characteristics of the electrolytic capacitor using the solid electrolyte thus prepared were measured, the results shown in Table 2 were obtained. As can be seen from these results, first, in the case of an electrolytic capacitor using a liquid electrolyte, an electrolytic capacitor using the separator of the present invention can be wound with high winding tension. Furthermore, since the fiber diameter is small, the voids between the fibers become uniform, improving the air permeability of the separator. Similarly, by improving air permeability and reducing the distance between the electrodes, a capacitor with low loss can be obtained. Furthermore, in Example 2 of the present invention, the separator can be made thinner, and as a result, the diameter of the capacitor element is reduced. Conversely, if the diameter of the capacitor element is the same as that of the conventional capacitor element, the amount of electrode wrapping can be increased, and the capacitance will increase accordingly.

【Effect of the invention】

As described above, an electrolytic capacitor using a separator containing polyamide-imide fibers of the present invention can be used to form a capacitor element with high tension due to the high mechanical strength of the polyamide-imide fibers. is obtained. Furthermore, since it has excellent heat resistance and can be formed thinner than glass fiber cloth, it is possible to maintain stable characteristics and downsize the capacitor.

[Brief explanation of drawings]

FIG. 1 is a partially exploded front view showing the element structure of the electrolytic capacitor of the present invention. 1. Capacitor element, 2. Anode, 3. Separator, 4. Cathode, 5, 6. Output lead. Patent application: Nippon Chemi-Con Co., Ltd.

Claims (2)

[Claims] (1) A separator made of polyamide-imide fiber is interposed between an anode electrode having a dielectric oxide film layer formed on its surface and a cathode electrode, and is wound or laminated to form a capacitor element, and the separator of the capacitor element An electrolytic capacitor that holds an electrolyte. (2) A separator made of mixed polyamide-imide fiber is interposed between the anode electrode, which has a dielectric oxide film layer formed on its surface, and the cathode electrode, and is wound or laminated to form a capacitor element. An electrolytic capacitor whose separator part holds electrolyte.