JP2004228418A - Capacitor element in solid electrolytic capacitor, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid a solid electrolyte layer from being formed in the portion of an anode wire 2, when forming the solid electrolyte layer made of manganese dioxide to an anode chip body 1, in a capacitor element comprising the anode chip body 1 made of the sintered powder of a valve action metal and the anode wire 2 protruding from an end surface 1a of the anode chip body. <P>SOLUTION: On the end surface 1a of the anode chip body 1 wherefrom the anode wire 2 is protruded, a coating 5 made of a synthetic resin is so formed as to cover the whole of the end surface with the coating. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a capacitor element used in a solid electrolytic capacitor using a valve metal such as tantalum or aluminum, and a method for manufacturing the same.
[0002]
[Prior art]
Generally, in manufacturing a capacitor element used for this type of solid electrolytic capacitor, the following method is employed.
[0003]
That is, first, as shown in FIG. 1, powder of a valve action metal such as tantalum or the like is applied to a porous anode tip body 1 from one end face 1a of the anode tip body 1 by a valve action metal such as tantalum. , And then sintering. Then, this porous anode tip body 1 is immersed in a chemical conversion solution such as a phosphoric acid aqueous solution. By performing an anodic oxidation treatment of applying a direct current between the electrode and the anode wire, a dielectric film such as tantalum pentoxide is formed on the surface of each metal particle in the anode tip body.
[0004]
Next, the anode tip body 1 is immersed in an aqueous manganese nitrate solution so that one end face 1a of the anode tip body 1 faces upward and the one end face 1a is located substantially near the liquid level, and the manganese nitrate aqueous solution is immersed. Is permeated to the inside of the anode chip body 1 and then fired a plurality of times to form a solid electrolyte layer of manganese dioxide on the surface of the dielectric film in the anode chip body.
[0005]
Then, a method is adopted in which a cathode film having a graphite layer and a metal layer such as silver or nickel as an upper layer is formed on a portion of the surface of the anode chip body 1 other than the one end surface 1a.
[0006]
By the way, in the manufacturing process of the capacitor element described above, when forming the solid electrolyte layer of manganese dioxide, the aqueous solution of manganese nitrate travels over the dielectric film formed at the base of the anode wire to a portion above the dielectric film. As a result, the solid electrolyte layer is also formed on the portion of the surface of the anode wire 2 where the dielectric film is formed and on the portion before the dielectric film, so that the solid electrolytic capacitor is assembled as a completed product. At this time, when an anode lead terminal made of a metal plate is fixed to the anode wire 2 by welding or the like, the solid electrolyte layer formed up to the base of the anode wire as described above with respect to the anode lead terminal is formed. As a result, an electrical short-circuit occurred and a large number of defective products were generated.
[0007]
Therefore, conventionally, before the step of forming the dielectric film or after the step of forming the dielectric film, the base of the anode wire 2 is made of a fluororesin or the like as shown in FIG. A ring 4 made of a synthetic resin having water repellency is fitted or attached, or, as shown in FIG. 3, a synthetic resin having water repellency is dissolved in a solvent and applied, followed by drying. By performing the step of forming the solid electrolyte layer of manganese dioxide in this state, the solid electrolyte layer is formed up to the base of the anode wire 2 by the ring of the water-repellent synthetic resin. The blocking is performed by the body 3 or the coating 4 (for example, see FIGS. 10 and 11 of Patent Document 1).
[0008]
[Patent Document 1]
JP-A-7-66079
[Problems to be solved by the invention]
However, the method of fitting and attaching the ring body 3 to the base of the anode wire 2 as described above has the following problems.
[0010]
That is, the ring body 3 fitted and attached to the anode wire 2 only comes into contact with one end surface 1a of the anode tip body 1, so that the lower surface of the ring body 3 and the anode tip body A gap is inevitably formed between the first end surface 1a of the anode chip 1 and the one end surface 1a of the anode tip body 1 due to unevenness.
[0011]
In addition to this, between the outer peripheral surface of the anode wire 2 and the inner peripheral surface of the ring body 3 fitted thereto, to facilitate the work of fitting the ring body 3 to the anode wire 2. A gap is inevitably formed for making the inner diameter of the through hole in the ring body 3 larger than the diameter of the anode wire 2 and for burrs generated when the ring body 3 is punched from a material plate. ing.
[0012]
For this reason, when the anode tip body 1 is immersed in a manganese nitrate aqueous solution in a process for forming a solid electrolyte layer, the aqueous solution of manganese nitrate is connected to the lower surface of the ring body 3 and the anode tip body by capillary action. 1 flows into the gap between the one end face 1a of the ring body 3 and then passes through the gap between the inner peripheral face of the ring body 3 and the outer peripheral face of the anode wire 2 to reach the upper face side of the ring body 3. Therefore, the rise of the manganese nitrate aqueous solution cannot be completely prevented by the ring body 4, and a solid electrolyte layer is also formed on the upper surface side of the ring body 3 of the anode wire 2. Therefore, the rate of occurrence of defective products when assembling as a completed solid electrolytic capacitor is still considerably high.
[0013]
On the other hand, the method of forming the coating 4 by applying and drying a synthetic resin dissolved in a solvent on the base portion of the anode wire 2 as in the latter method is to apply the coating 4 to the anode tip 1. Since it is possible to completely adhere to both the end face 1a and the outer peripheral surface of the anode wire 2 without any gap, it is possible to reliably prevent the aqueous solution of manganese nitrate from traveling to the anode wire 2 but to the contrary. There was a problem as described above.
[0014]
That is, in the step of forming the solid electrolyte layer, gas is generated when the manganese nitrate is thermally decomposed into manganese dioxide by baking the anode chip body after infiltrating the manganese nitrate aqueous solution into the anode chip body, and this gas is generated. With the manganese nitrate and / or manganese dioxide accompanying, as shown by arrows in FIG.
[0015]
In this case, since the coating 4 formed on the base of the anode wire 2 is configured so that the diameter thereof is as small as possible as in the latter case, one end surface 1a of the anode tip body 1 is conventionally used. Gas generated at the time of firing will also be ejected toward the anode wire 2 from the portion outside the coating 4, and manganese nitrate and / or manganese dioxide accompanying the gas ejected from this portion will be applied to the anode wire 2. There was a problem of adhesion.
[0016]
An object of the present invention is to solve these problems.
[0017]
[Means for Solving the Problems]
To achieve this technical object, the capacitor element of the present invention is:
`` In a capacitor element comprising an anode chip body obtained by sintering powder of valve action metal and an anode wire protruding from one end surface of the anode chip body,
A coating made of a synthetic resin is formed on one end surface of the anode tip body from which the anode wire protrudes, so as to cover the entire one end surface. "
It is characterized by:
[0018]
Further, the production method of the present invention,
"A step of forming an anode tip body from which an anode wire projects from one end surface by sintering a valve metal powder, a step of forming a dielectric film on the anode tip body, and following these steps, A method of forming a solid electrolyte layer of manganese dioxide by infiltration and baking of an aqueous solution of manganese nitrate with respect to the anode chip body, and a step of forming a cathode film on the solid electrolyte,
Prior to the step of forming the solid electrolyte layer, a step of forming a coating made of a synthetic resin on one end surface of the anode tip body where the anode wire protrudes, so as to cover the entirety of the one end surface is provided. I have. "
It is characterized by:
[0019]
[Action and Effect of the Invention]
In this manner, by forming a coating made of a synthetic resin on one end surface of the anode wire from which the anode wire protrudes, the anode chip is penetrated with an aqueous solution of manganese nitrate therein. When the anode tip body is immersed in an aqueous solution of manganese nitrate for the purpose, it is possible to prevent the aqueous solution of manganese nitrate from reaching the portion of the anode wire by the coating, and In addition, the gas generated when the aqueous solution of manganese nitrate infiltrated into the anode chip body is thermally decomposed into manganese dioxide by firing is mixed with manganese nitrate and / or manganese dioxide. Spouting from the anode wire toward the anode wire can be prevented by the coating.
[0020]
Therefore, according to the present invention, when the solid electrolyte layer of manganese dioxide is formed on the anode chip body, the solid electrolyte layer can be reliably prevented from being formed up to the portion of the anode wire, so that the solid electrolytic capacitor is assembled as a completed product. In this case, the occurrence rate of defective products in which an electrical short-circuit occurs between the anode-side lead terminal fixed to the anode wire and the solid electrolyte layer and becomes a defective product can be greatly reduced.
[0021]
In particular, as described in claim 2, by extending the coating covering one end face of the anode tip body to a portion adjacent to the one end face of the outer peripheral side face of the anode tip body, during the firing. Since the gas can be prevented from being ejected from the portion near the anode wire in the outer peripheral side surface of the anode tip body by the coating, the solid electrolyte layer can be more reliably prevented from being formed on the anode wire. The effect can be promoted.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings (FIGS. 4 to 6).
[0023]
First, as shown in FIG. 4, a tantalum powder is solidified on a porous anode tip body 1 so that an anode wire 2 protrudes from one end face 1a of the anode tip body 1, and then sintered.
[0024]
Next, a coating 5 made of a water-repellent synthetic resin such as a fluororesin is formed on one end face 1a of the anode chip body 1 so as to cover the entire one end face 1a.
[0025]
Note that the step of forming the coating 5 may be performed after the step of forming a dielectric film described later, that is, performed before the step of forming a solid electrolyte layer described later.
[0026]
Next, the anode tip body 1 is immersed in a chemical conversion solution such as a phosphoric acid aqueous solution, and in this state, a direct current is applied between the electrode in the chemical formation solution and the anode wire 2 to perform an anodic oxidation treatment. Is performed, a dielectric film such as tantalum pentoxide is formed on the surface of each metal particle in the anode tip body 1.
[0027]
Next, the anode tip body 1 is immersed in an aqueous solution of manganese nitrate until the end face 1a of the anode tip body 1 faces upward and the coating 5 covering the one end face 1a is located substantially at the liquid level. By repeating a plurality of times of infiltrating the aqueous solution of manganese nitrate into the inside of the anode chip body 1 and then withdrawing and firing, a solid electrolyte layer of manganese dioxide is formed on the surface of the dielectric film in the anode chip body.
[0028]
When forming the solid electrolyte layer, when the anode tip body 1 is immersed in a manganese nitrate aqueous solution, the coating 5 prevents the manganese nitrate aqueous solution from reaching the anode wire 2. Therefore, the formation of the solid electrolyte layer on the anode wire 2 due to the propagation of the manganese nitrate aqueous solution can be reliably reduced.
[0029]
Further, the gas generated when the aqueous solution of manganese nitrate permeated into the anode tip body 1 is thermally decomposed into manganese dioxide by firing is mixed with the manganese nitrate and / or manganese dioxide in the anode tip body 1. Since it is possible to prevent the ejection from the end face 1a toward the anode wire 2 by the coating 5, the solid electrolyte layer is formed on the anode wire due to the gas generated during firing. It can be reduced reliably.
[0030]
In this case, the coating 5 covering the one end surface 1a of the anode tip body 1 is coated with a short length S portion of the outer peripheral side surface 1b of the anode tip body 1 adjacent to the one end surface 1a as shown in FIG. To cover the portion of the short length S, the gas from the portion of the short length S close to the anode wire 2 in the outer peripheral side surface 1b of the anode tip body 1 at the time of the sintering. Can be prevented by the coating 5, the formation of the solid electrolyte layer on the anode wire 2 due to the gas generated at the time of firing can be reduced more reliably.
[0031]
It is preferable that the short length S be equal to or less than 1/10 of the height H of the anode tip body 1.
[0032]
When the step of forming the solid electrolyte layer is completed in this manner, a portion of the surface of the anode chip body 1 other than the one end surface 1a is provided with a graphite layer and a base having a metal layer such as silver or nickel as an upper layer. By forming the film, a completed capacitor element is obtained.
[0033]
By the way, as described above, when forming the coating 5 covering the whole end surface 1a of the anode tip body 1 and the portion of the outer peripheral side surface 1b having the short length S, the following method is used. Can be adopted.
[0034]
That is, as shown in FIG. 5 and FIG. 6, the anode tip body 1 is placed in a posture in which one end face 1a is directed downward, and a coating member having concave portions 6a, 7a at its front ends on both left and right sides thereof. The coating members 6 and 7 are disposed so as to reciprocate in the horizontal direction, and the coating members 6 and 7 are supplied to the recesses 6 a and 7 a in the state of a synthetic resin in a liquid state. At the same time, the anode chips 1 are sandwiched from both left and right sides by being moved forward, so that the recesses 6a and 7a are formed at the one end face 1a of the anode chip body 1 and the short length S portion of the outer peripheral side face 1b. , A liquid synthetic resin supplied in advance is applied, and the liquid synthetic resin is dried by heating or the like to form the coating 5.
[0035]
Further, in another method, the anode tip body 1 is placed in a posture in which one end surface 1a is directed upward, sideways, or obliquely upward, and in this state, while rotating around the anode wire 2, one end of the anode tip body 1 is rotated. The coating 5 may be formed by applying a liquid synthetic resin by dripping to a corner portion between the end surface 1a and the outer peripheral side surface 1b, and then drying the resin by heating or the like.
[Brief description of the drawings]
FIG. 1 is a vertical sectional front view of an anode tip body.
FIG. 2 is a longitudinal sectional front view of an anode tip body manufactured by a conventional manufacturing method.
FIG. 3 is a longitudinal sectional front view of an anode tip body according to another conventional manufacturing method.
FIG. 4 is a vertical sectional front view of the anode tip body according to the manufacturing method in the embodiment of the present invention.
FIG. 5 is a perspective view showing a state in which a synthetic resin is applied to the anode tip body in the embodiment of the present invention.
FIG. 6 is a sectional view taken along line VI-VI of FIG. 5;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Anode tip body 1a One end face 1b of anode tip body Peripheral side face of anode tip body 2 Anode wire 5 Coating

Claims (3)

In a capacitor element including an anode chip body obtained by sintering a valve metal powder and an anode wire protruding from one end surface of the anode chip body,
A capacitor element in a solid electrolytic capacitor, wherein a coating made of a synthetic resin is formed on one end surface of the anode chip body from which the anode wire protrudes, so as to cover the entirety of the one end surface. 2. The solid electrolytic capacitor according to claim 1, wherein a coating covering one end surface of the anode chip body is extended to a portion adjacent to the one end surface on an outer peripheral side surface of the anode chip body. 3. Capacitor element. Forming an anode tip body having an anode wire protruding from one end surface by sintering a valve metal powder, forming a dielectric film on the anode tip body, and following these steps, A method of forming a solid electrolyte layer of manganese dioxide by infiltration and baking of a manganese nitrate aqueous solution into the chip body, and a step of forming a cathode film on the solid electrolyte,
Before the step of forming the solid electrolyte layer, a step of forming a coating made of a synthetic resin on one end surface of the anode tip body from which the anode wire protrudes, so as to cover the entirety of the one end surface, A method for manufacturing a capacitor element in a solid electrolytic capacitor.

Images