JPH0451466Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] This invention relates to a solid electrolytic capacitor using lead dioxide as a solid electrolyte, and particularly relates to an improvement of a separator that holds a solid electrolyte layer. [Prior Art] Solid electrolytic capacitors use a so-called valve metal on which an insulating oxide film of aluminum, tantalum, niobium, etc. is formed as an anode, the insulating oxide film is used as a dielectric layer, and lead dioxide, etc. is formed on the top surface of the valve metal. A metal oxide semiconductor is formed as a solid electrolyte, and a cathode extraction means such as a conductive paste is provided outside of the solid electrolyte. The shape of the anode electrode is made by sintering valve metal into a porous block shape, but it is easier to form a capacitor element by winding or laminating thin plate valve metal in the form of foil, and it also has a solid electrolyte layer. It is often used because it is easy to precipitate. In general, a solid electrolytic capacitor having a wound or laminated structure has a separator interposed between adjacent anode layers, as shown in Japanese Patent Application No. 61-282777, for example. This separator is made of paper, glass fiber cloth, polymeric woven fabric or non-woven fabric, and serves to provide an appropriate gap for penetrating the reaction mother liquor for solid electrolyte precipitation and to retain the mother liquor. [Problems that the invention aims to solve] Lead dioxide as a solid electrolyte has higher conductivity than manganese dioxide, which has been widely used in the past, and does not require high-temperature treatment during electrolyte precipitation. The series resistance value is low, and the deterioration of the dielectric oxide film is small. Therefore, a solid electrolytic capacitor with excellent high frequency characteristics and loss characteristics can be obtained. However, when a solid electrolytic capacitor is actually created, the expected high frequency characteristics and loss characteristics cannot be obtained. This is because the above-mentioned separator is an insulating material, so the electrical conductivity decreases in the separator portion, and the high electrical conductivity of lead dioxide is not utilized. Therefore, in this invention, we improved the separator and
The purpose is to improve the conductivity of a solid electrolyte layer held by a separator to obtain a solid electrolytic capacitor with excellent characteristics. [Means for solving the problem] The solid electrolytic capacitor of this invention consists of a thin plate electrode made of valve metal with a dielectric oxide film formed on the surface, a capacitor element that is wound or laminated with a separator superimposed on it, and In solid electrolytic capacitors in which a lead dioxide electrolyte layer is deposited by immersion in a solution containing lead ions, the separator is made of carbon fiber,
It is characterized by the use of stainless steel fiber. [Function] According to this invention, since the separator holding lead dioxide is a conductive material, the conductivity of the solid electrolyte layer is improved, and the equivalent series resistance value inside the electrolytic capacitor using the solid electrolyte can be reduced. In the case of electrolytic capacitors using a liquid electrolyte, if a conductive separator is used, a short circuit may occur between the defective part of the anode's insulating oxide film and the cathode material, or between adjacent anodes. In the case of a solid electrolyte using lead, there is no risk of short circuiting because lead dioxide covers the surface of the oxide film layer and the surface of the separator. [Example] This invention will be explained below based on an example. FIG. 1 is a partially exploded perspective view showing the element structure of the wound solid electrolytic capacitor of this invention. As shown in the figure, an anode 1 made of a valve metal foil such as aluminum cut into strips has been enlarged by etching and then a dielectric oxide film layer is formed on the surface by anodization.
Further, an anode lead 2 for drawing out the electrode is attached to a predetermined location of the electrode 1 by means such as welding or caulking. A separator 3 made of a conductive material cut to approximately the same size as the anode 1 is stacked on top of the other and wound from one end to form a cylindrical capacitor element 4. This capacitor element 4 is immersed in a mixture of an aqueous solution containing divalent lead ions such as lead acetate and an aqueous solution of an oxidizing agent such as ammonium persulfate to precipitate lead dioxide. A solid electrolytic capacitor is completed by providing conductive cathode means such as carbon paste or silver paste, and storing it in an external case or attaching a cathode lead if necessary. FIG. 2 shows another embodiment of the solid electrolytic capacitor element of this invention, in which band-shaped anodes 10 and 11 made of two valve metal foils are used. As in the embodiment shown in FIG. 1, enlarging the surface area by etching and forming a dielectric oxide film layer by anodizing are performed in advance. These anodes 10 and 11 are placed facing each other, and two sheet-like separators 13 made of a conductive material are placed between the anodes 10 and 11 and wound from one end to form a capacitor element 14. ing. And this capacitor element 14
Then, a reaction mother liquor containing lead ions is impregnated, and a solid electrolyte layer made of lead dioxide is formed and deposited in the gap between the separators 13 . Leads 15 and 16 for leading out the electrodes are attached to these anodes 10 and 11, respectively, by means such as welding. Further, the outer periphery of the capacitor element 14 may be sealed with resin or the like, if necessary. In this embodiment, since the two anodes are arranged opposite each other, a non-polar structure is achieved, and in this case, a conductive paste for drawing out the anode is not required. Note that although all of these embodiments have exemplified a wound structure, the capacitor element structure of this invention is not limited to a wound structure, but a laminated structure in which plate-shaped anodes and separators are sequentially stacked. It may also be a structural element. Next, we will compare the characteristics of the solid electrolytic capacitor of this invention and a conventional capacitor that uses an insulating material for the separator. First, a high-purity aluminum foil whose surface had been enlarged by etching was prepared as an anode. A dielectric oxide film was formed on the surface of this aluminum foil by applying a voltage of 70 V in a boric acid bath at 95°C. The capacitance at this time was 18.5 μF/10 cm ² (measured in a boric acid bath). Next, this anode foil was cut into a size of 6×27 mm, and an anode lead wire was connected to one end of the foil by ultrasonic welding. As [Example 1] of this invention, carbon fiber cloth (manufactured by Nippon Carbon Co., Ltd., thickness 300m) cut to approximately the same size was layered and wound around this anode foil, and as [Example 2], stainless steel fiber (manufactured by Tokyo Steel, 150 μm thick) was wound to create a capacitor element. In addition, as [Comparative Example 1], a capacitor element was prepared using insulating glass fiber (manufactured by Honshu Paper Industries, thickness: 80 μm) as a separator. Add these capacitor elements to 50g of lead acetate and 30g of water.
The sample was immersed in a mixture of an aqueous solution in which 75 g of samonium persulfate was dissolved in 75 g of water, and kept in a constant temperature bath at 80° C. for 15 minutes to precipitate lead dioxide. The capacitor element was then washed with water and dried. After repeating this process five times, colloidal carbon was applied to the capacitor, silver paste was further applied to the outer surface of the capacitor, and a cathode lead was connected to obtain a solid electrolytic capacitor. When the capacitance, loss (Tan δ), leakage current, and equivalent series resistance (ESR) at 100 KHz of these solid electrolytic capacitors were measured, the results shown in Table 1 were obtained.

[Table] As is clear from the results, the device using the conductive separator of this invention has lower loss and ESR values than the comparative devices, and has excellent high-frequency characteristics with low loss. Next, the results of manufacturing a solid electrolytic capacitor with a non-polar structure shown in FIG. 2 will be shown. [Example 3] was prepared by preparing two sheets of the same anode foil as used in Examples 1 and 2, and winding the same carbon fiber cloth as in Example 1 between the two sheets of anode foil. Created. In addition, [Example 4] was prepared by sandwiching and winding the same stainless fiber cloth as in Example 2. In addition, as [Comparative Example 2], Comparative Example 1
The same glass fiber cloth was sandwiched and wound. These capacitor elements were immersed in the same aqueous solution of lead acetate and ammonium persulfate as in the previous example, and lead dioxide was deposited at the same temperature, time, and number of times to complete a solid electrolytic capacitor. When the characteristics of these solid electrolytic capacitors were measured, the results shown in Table 2 were obtained.

[Effect of idea]

As mentioned above, this idea improves the conductivity of the solid electrolyte layer held by the separator, reduces capacitor loss and high frequency equivalent series resistance, and creates a solid electrolytic capacitor with excellent electrical characteristics. Obtainable.

[Brief explanation of the drawing]

FIG. 1 is a partially exploded perspective view illustrating the element structure of a solid electrolytic capacitor of this invention, and FIG. 2 is a partially exploded perspective view illustrating the element structure of another embodiment of the solid electrolytic capacitor of this invention. be. 1, 10, 11...anode, 2...anode lead,
3, 13... Separator, 4, 14... Capacitor element, 15, 16... Lead.

Claims (1)

[Scope of utility model registration request] A capacitor element consisting of a thin plate electrode made of valve metal with a dielectric oxide film formed on its surface and a separator layered over the capacitor element, which is then immersed in a solution containing lead ions to deposit a lead dioxide electrolyte layer. A solid electrolytic capacitor characterized by using carbon fiber or stainless steel fiber as a separator.