JP2003347167A - Capacitor element used for solid electrolytic capacitor and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce equivalent series resistance (ESR) without upsizing a capacitor element which comprises a metal anode body 1 for valve action, a dielectric film formed to the anode body, and a solid electrolyte layer 4 stacked on the dielectric film of the anode body. <P>SOLUTION: The solid electrolyte layer 4 has a laminating structure where a plurality of solid electrolyte films 4a and 4b are laminated with an insulating film 4c between. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a solid electrolytic capacitor made of a valve metal such as tantalum or niobium.
The present invention relates to a capacitor element used for this and a method for manufacturing the capacitor element.

[0002]

2. Description of the Related Art Generally, a capacitor element used in a solid electrolytic capacitor of this type is formed by sintering a powder of a valve metal such as tantalum or niobium into a porous chip, and more precisely, a surface of an anode body. Form a dielectric film with high electrical insulation on the surface of each metal powder in the anode body,
A solid electrolyte layer is formed on the outer peripheral surface of the anode body so that the solid electrolyte layer overlaps the dielectric film. Further, a cathode comprising a graphite layer and a metal layer is formed on the surface of the solid electrolyte layer. The configuration is such that a side electrode film is formed.

[0003] This type of solid electrolytic capacitor has the advantage that the capacitance per unit volume is large due to the large surface area of the portion of the solid electrolyte layer in contact with the dielectric film. The surface area of a portion of the solid electrolyte layer in the capacitor element to be used that does not contact the dielectric film is much smaller than the surface area of the portion of the solid electrolyte layer that contacts the dielectric film. The electrolyte layer has a significant equivalent series resistance (ESR),
Further, it is known that this equivalent series resistance (ESR) is substantially inversely proportional to the surface area of a portion of the solid electrolyte layer that does not contact the dielectric film.

[0004]

However, in the conventional capacitor element, the surface area of the portion of the solid electrolyte layer formed on the surface of the anode body that is not in contact with the dielectric film is the solid electrolyte of the anode body. Since the surface area of the solid electrolyte layer is approximately equal to the surface area of the portion where the layer is formed, in order to reduce the equivalent series resistance (ESR) of the solid electrolyte layer,
In order to increase the surface area in the portion of the solid electrolyte layer that does not contact the dielectric film, the surface area in the portion of the anode body where the solid electrolyte layer is formed must be large, and therefore the outer dimensions of the anode body must be large. Therefore, there is a problem that the size of the capacitor element is increased, and eventually the size and weight of the solid electrolytic capacitor as a finished product are increased.

An object of the present invention is to reduce the equivalent series resistance in the solid electrolyte layer while keeping the size of the capacitor element small.

[0006]

Means for Solving the Problems To achieve this technical object, a capacitor element according to the present invention is composed of at least an anode body made of a valve metal, a dielectric film formed on the anode body, In a capacitor element comprising an anode body and a solid electrolyte layer formed so as to overlap the dielectric film, the solid electrolyte layer electrically connects a plurality of solid electrolyte films to each other with an insulating film interposed therebetween. In a laminated structure. "

[0007] The manufacturing method according to the present invention comprises a step of forming at least a dielectric film on an anode body made of a valve metal, and a step of laminating a solid electrolyte layer on the dielectric film on the anode body. Forming a solid electrolyte layer, the step of forming the solid electrolyte layer comprises stacking a plurality of solid electrolyte membranes so as to be electrically connected to each other with an insulating film interposed therebetween. This is a step of forming a structure. "

[0008]

The solid electrolyte layer of the capacitor element is formed by laminating a plurality of solid electrolyte membranes so as to be electrically connected to each other with an insulating layer interposed therebetween. The surface area of a portion of the layer that does not contact the dielectric film can be increased by the number of the plurality of solid electrolyte membranes without increasing the outer dimensions of the anode body.

That is, according to the present invention, the equivalent series resistance (ESR) in the solid electrolyte layer of the capacitor element for a solid electrolytic capacitor is increased by increasing the size of the capacitor element, and further, as a solid electrolytic capacitor as a finished product using the capacitor element. The size can be significantly reduced without increasing the size and weight of the capacitor.

Further, according to the manufacturing method of the present invention, a capacitor element having the above-described effects can be manufactured at low cost.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a porous anode body obtained by solidifying and molding a valve metal powder such as tantalum or niobium into a chip shape and then firing the same. One end surface 1a of the anode body 1 has Similarly, an anode wire 2 made of tantalum is fixed so as to protrude upward, and a ring body 3 made of a water-repellent synthetic resin is fitted and attached to the base of the anode wire 2 with respect to the anode body 1. I have.

The anode body 1 is immersed in a chemical solution such as a phosphoric acid aqueous solution, and in this state, an anodic oxidation treatment of applying a direct current between the anode rod 1 and the chemical solution is performed. Thereby, all the surfaces of the anode body 1, more specifically,
A highly insulating dielectric film such as tantalum pentoxide is formed on the surface of the valve metal powder.

Next, the first solid electrolyte membrane 4a and the second solid electrolyte
A solid electrolyte layer 4 having a laminated structure formed by laminating the solid electrolyte membrane 4b and the insulating film 4c therebetween is formed.

First, as shown in FIG. 2, the anode body 1 is immersed in a solid electrolyte solution B such as a manganese nitrate aqueous solution contained in a processing tank A, up to the ring body 3 as shown in FIG. By repeating the process of infiltrating the solution for solid electrolyte into the inside of the anode body 1, pulling it out of the solution for solid electrolyte, drying, and firing, a plurality of times, the surface of the anode body 1 The first solid electrolyte film 4a made of a metal oxide such as manganese is formed so that the solid electrolyte film 4a overlaps the dielectric film.

Next, as shown in FIG. 3, the anode body 1 is placed in a synthetic resin solution D (a solution obtained by dissolving a synthetic resin in a solvent or water) contained in a treatment tank C near one end face 1a thereof. The synthetic resin solution is attached to the surface of the first solid electrolyte membrane 4a, or the synthetic resin solution is applied to the surface of the first solid electrolyte membrane 4a by spraying or the like. By drying the attached synthetic resin solution, an insulating film 4c made of synthetic resin is formed on a part of the surface of the first solid electrolyte membrane 4a except for a part thereof.

Then, as shown in FIG. 4, the anode body 1 is immersed again in the solid electrolyte solution B such as an aqueous solution of manganese nitrate contained in the processing tank A to the ring body 3 as shown in FIG. By repeating the process of withdrawing from the solid electrolyte solution, drying, and firing, a plurality of times, the second solid electrolyte membrane 4b made of a metal oxide such as manganese dioxide is replaced with the first solid electrolyte membrane 4a. It is formed so as to partially overlap with the insulating film 4c.

When these steps are completed, the cathode side electrode film 5 made of a graphite film and a metal film such as silver or nickel is formed on the surface of the solid electrolyte layer 4 to complete the capacitor element 10. Product.

As shown in FIG. 5, the capacitor element 10 manufactured as described above has an anode body 1 obtained by sintering powder of a valve metal such as tantalum or niobium into a porous chip, and A dielectric film formed on the surface of each metal powder in the anode body 1; a solid electrolyte layer 4 formed on the anode body 1 so as to overlap the dielectric film;
The solid electrolyte layer 4 electrically connects the first solid electrolyte membrane 4a and the second solid electrolyte membrane 4b to each other with an insulating film 4c interposed therebetween. Thus, the laminated structure is formed by laminating as described above.

That is, the solid electrolyte layer 4 is formed by laminating a first solid electrolyte film 4a and a second solid electrolyte film 4b which overlap with a dielectric film so as to be electrically connected to each other with an insulating film 4c interposed therebetween. Due to the structure, the surface area of a portion of the solid electrolyte layer 4 that is not in contact with the dielectric film can be reduced without increasing the outer dimensions of the anode body 1. Can be increased by a number.

Note that the capacitor element 10 having the above-described structure
As shown by the two-dot chain line in FIG. 5, the anode wire 2 of the capacitor element 10 is fixed between the pair of left and right lead terminals 6 and 7 to one of the lead terminals 6 by welding or the like. By connecting the other lead terminal 7 to the cathode-side electrode film 5 on the outer peripheral surface of the anode body 1 in the capacitor element 10, the entirety of these is sealed with a synthetic resin package 8. And assembled into a solid electrolytic capacitor as a finished product.

Further, the present invention is not limited to the configuration described above, and the insulating film 4c may be formed so as to cover the entire first solid electrolyte film 4a with the insulating film 4c.
A hole is partially formed in the insulating film 4c, and the second solid electrolyte film 4b is overlapped with the entirety of the insulating film 4c.
The solid electrolyte film 4b may be formed so as to be electrically connected to the first solid electrolyte film 4a at the portion of the hole in the insulating film 4c.

Needless to say, the synthetic resin forming the insulating film 4c should be a synthetic resin having heat resistance to the temperature at which the solid electrolyte film 4b is fired.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an anode body used for a capacitor element of the present invention.

FIG. 2 is a view showing a state where a first solid electrolyte membrane is formed on the anode body.

FIG. 3 is a view showing a state in which an insulating film is formed on the anode body so as to overlap the first solid electrolyte film.

FIG. 4 is a diagram showing a state in which a second solid electrolyte film is formed on the anode body so as to overlap the first solid electrolyte film and an insulating film.

FIG. 5 is a vertical sectional front view showing the capacitor element according to the embodiment of the present invention.

[Explanation of symbols]

10 Capacitor element 1 Anode body 2 Anode wire 3 ring body 4 Solid electrolyte layer 4a First solid electrolyte membrane 4b Second solid electrolyte membrane 4c insulating film 5 Cathode side electrode film 6,7 Lead terminal 8 Package body

Claims (3)

[Claims] At least an anode body made of a valve metal, a dielectric film formed on the anode body, and a solid electrolyte layer formed on the anode body so as to overlap the dielectric film. In the capacitor element, the solid electrolyte layer has a laminated structure formed by laminating a plurality of solid electrolyte films so as to be electrically connected to each other with an insulating film interposed therebetween, which is used for a solid electrolytic capacitor. Capacitor element. 2. A capacitor comprising at least a step of forming a dielectric film on an anode body made of a valve metal and a step of forming a solid electrolyte layer on the anode film so as to overlap the dielectric film. In the method for manufacturing an element, the step of forming the solid electrolyte layer is a step of forming a plurality of solid electrolyte films as a laminated structure formed by laminating the solid electrolyte films so as to be electrically connected to each other with an insulating film interposed therebetween. A method for manufacturing a capacitor element used for a solid electrolytic capacitor, characterized by comprising: 3. The solid electrolyte membrane according to claim 2, wherein the step of forming the solid electrolyte layer as a laminated structure includes the steps of: dipping the anode body in a solution for solid electrolyte; Forming an insulating film on a part of the surface of the first solid electrolyte membrane except for a part thereof, and then forming the anode body again into a solid electrolyte solution. Forming a second solid electrolyte membrane so as to overlap a part of the first solid electrolyte membrane and the insulating film by immersing the solid electrolyte into a film and then firing the same. Device manufacturing method.