JPH0451045B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention relates to an improvement in a solid electrolytic capacitor using a foil-like film-forming metal as an anode. [Prior art] Solid electrolytic capacitors use a metal (also called valve metal) that forms an insulating oxide film, such as aluminum or tantalum, as an anode, and a dielectric layer is formed on the surface of this metal electrode by means such as anodizing. An insulating oxide film layer is formed as a body, and a conductive polymer such as a semiconductor metal oxide such as manganese dioxide or lead dioxide or a complex salt of tetracyanoquinodimethane is formed on the surface of the insulating oxide film layer as an electrolyte layer. It has a structure in which a conductive layer is provided on the outer surface for drawing out the cathode. The anode electrode of a solid electrolytic capacitor is known to be made of a porous block made by sintering film-forming metal powder, or made of metal foil or wire. Among these anode electrodes, those in which a film-forming metal surface rolled into a foil shape is etched to enlarge the surface and then wound or laminated (for example, Japanese Utility Model Publication No. 35-28651), Since the surface area of the dielectric material per unit volume can be increased, it is possible to downsize the capacitor, and it has been used in the past. However, in the case of coiled or laminated foil electrodes, the gap between the electrode foil layers is extremely small, and if the solid electrolyte is immersed in this gap, the solid electrolyte may not penetrate into the narrow space between the electrodes. Alternatively, even if it permeates, the amount is small, so that a sufficient effect of repairing the deterioration of the dielectric oxide film layer cannot be obtained, causing an increase in leakage current and short-circuit accidents. [Problems to be Solved by the Invention] This invention improves the above-mentioned drawbacks, and prevents short-circuit accidents in solid electrolytic capacitors using foil electrodes, and provides a reliable solid electrolytic capacitor with excellent electrical characteristics. The purpose is to obtain electrolytic capacitors. [Means for Solving the Problems] The solid electrolytic capacitor of the present invention has a dielectric oxide film layer formed on the surface thereof, and a metal electrode foil having an anode electrode extraction means and a separator are overlapped and wound or wound. A solid electrolyte layer is provided between the internal anode electrodes of the laminated capacitor element by being held by the separator, and a solid electrolyte layer is also formed on the external surface of the capacitor element in continuity with the solid electrolyte layer between the internal anode electrodes. A conductive layer for drawing out the cathode is further provided outside the solid electrolyte layer formed on the external surface of the capacitor element, and the separator is made of a porous material such as paper, glass fiber cloth, heat-resistant nonwoven fabric, etc. This is what was used. [Examples] The present invention will be explained in more detail based on Examples below. FIG. 1 is a partially exploded perspective view showing the structure of a capacitor element 1 of a solid electrolytic capacitor of the present invention. In the figure, a metal foil 2 made of aluminum, tantalum, or the like is cut into strips, and its surface is subjected to an etching process to enlarge the surface, if necessary. A dielectric oxide film layer is formed on the surface by anodizing. Further, an anode lead 3 is connected to the metal foil 2 at right angles to its longitudinal direction by a connecting means such as welding. Then, a separator 4 made of a flexible, thin band-shaped porous material such as paper or glass fiber, having approximately the same width as the metal foil 2, is overlapped with the metal foil 2 and wound from one end to form the capacitor element 1. is forming. Note that the end of the winding of the capacitor element 1 is fixed with a fixing means such as adhesive or adhesive tape. The capacitor element 1 thus formed is impregnated with a solid electrolyte such as manganese dioxide, lead dioxide, tetracyanoquinodimethane, etc. by known means. As a result, the impregnated solid electrolyte covers the interlayers of the metal foil 2 and the external surface of the capacitor element 1, and the solid electrolyte layer covers the wound metal foil 2.
It is also formed on the outer surface of the capacitor element 1 continuously to the solid electrolyte layer between the metal foils 2. The outer surface of the capacitor element 1 on which the solid electrolyte layer is formed is provided with a conductive drawing layer and an exterior means. FIG. 2 is a sectional view of the solid electrolytic capacitor of the present invention in a completed state. In the figure,
The capacitor element 1 that has been impregnated with the solid electrolyte is housed in a bottomed cylindrical metal case 5 from the end surface opposite to the drawer side of the anode lead 3. A conductive paste 6 is filled between the periphery of the capacitor element 1 and the inner surface of the metal case 5.
An electrical connection is made to a cathode lead 7 connected to the bottom surface of the metal case 5 via the metal case 5 . On the other hand, the anode lead 3 is drawn out from the open end of the metal case 5 , and the open end of the metal case 5 is sealed with a sealing resin 8 . Next, we created a solid electrolytic capacitor with this structure and compared its characteristics. (Example of the present invention) First, as a capacitor element, a high-purity aluminum foil with a thickness of 80 μm is used as an anode electrode. This aluminum foil is enlarged in advance by etching treatment, and then a voltage of 150 V is applied in a phosphate-ammonium aqueous solution. A dielectric oxide film was formed by an anodic oxidation reaction. This anode electrode has a width of 6
mm, and the length was 25 mm, and the anode lead was connected to the approximate center of the anode electrode by ultrasonic welding. Next, a glass fiber cloth with a thickness of 80 μm was cut to the same size as the anode electrode, and both were overlapped and wound from the end face to form a cylindrical capacitor element. This capacitor element was dissolved in an aqueous solution (70g of lead acetate and 130g of ammonium persulfate dissolved in 140g of water).
℃), and then the capacitor element was pulled out of the aqueous solution and dried to form a solid electrolyte layer of lead dioxide. This capacitor element was fixed inside an aluminum outer case using conductive paste (XA167 manufactured by Fujikura Kasei), and the open end of the outer case was sealed by injecting thermosetting epoxy resin. (Comparative Example) For comparison with the capacitor of this invention, the same anode electrode as the one of the present invention was used, and a capacitor element was made by winding only the anode electrode without overlapping glass fibers, and a solid electrolyte was used. A solid electrolytic capacitor for comparison was produced under exactly the same conditions as the inventive example, including the method of formation and storage in the outer case. The electrical characteristics (capacitance, loss, leakage current) of 20 capacitors each of the inventive example and comparative example were investigated, and a voltage of 30 V was applied at 130°C.
The number of short circuit occurrences after time aging was investigated. The results are shown in the table below.

[Effect]

In the solid electrolytic capacitor of the present invention, since a porous separator is interposed between the layered anode electrodes, a sufficient amount of solid electrolyte can be retained by the porous separator and present between the anode electrodes. Therefore, sufficient contact is made between the dielectric oxide film layer on the surface of the anode electrode and the solid electrolyte layer. [Effects of the Invention] As described above, according to the present invention, sufficient contact is made between the anode electrode and the solid electrolyte layer, so that capacitance can be reliably extracted and loss can be reduced. In addition, since the chemical formability of the solid electrolyte is maintained,
The deteriorated dielectric oxide film is sufficiently repaired, and leakage current can be reduced and short circuits can be prevented. Furthermore, since it is difficult for external conductive paste to penetrate into the anode electrode portion, short-circuit accidents caused by the conductive paste can be prevented, and a solid electrolytic capacitor with high reliability and excellent electrical characteristics can be obtained.

[Brief explanation of drawings]

FIG. 1 is a partially exploded perspective view showing the element structure of the solid electrolytic capacitor of this invention, and FIG. 2 is a sectional view showing the completed state of the solid electrolytic capacitor of this invention. 1...Capacitor element, 2...Metal foil, 3...
Anode lead, 4... Separator, 5... Metal case, 6... Conductive paste, 7... Cathode lead, 8
...Sealing resin.

Claims (1)

[Claims] 1. A metal electrode foil having a dielectric oxide film layer formed on the surface thereof and provided with an anode electrode extraction means, and a separator are stacked and wound or laminated, and the separator is held between the anode electrodes inside the capacitor element. At the same time, a solid electrolyte layer is formed on the external surface of the capacitor element continuously to the solid electrolyte layer between the internal anode electrodes, and a solid electrolyte layer is formed on the external surface of the capacitor element. A solid electrolytic capacitor characterized by having a conductive layer for drawing out the cathode.