JPH11135366A - Solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the dimension of a sintered body of a solid electrolytic capacitor by a thinned oration of its insulating plate, and increase its electrostatic capacity without changing its outside dimension, by providing in the root of its anode lead wire its thin insulating plate with a specific thickness. SOLUTION: In a sintered body 1 of a solid electrolytic capacitor, a fine power of a metal with a valve action is compressed and molded in the state of drawing out therefrom an anode lead wire 2 made of the metal with the valve action to sinter the fine powder. Further, on the root of the anode lead wire 2, such an insulating plate 3 made of Teflon (R) or a silicon rubber, etc., as a circular plate is fitted. Making the thickness of this insulating plate 3 smaller than 0.2 mm, its size is so selected as to protrude its end portion 3a from a side surface 1a of the sintered body 1. In this case, making the protruded length of the insulating plate 3 from the sintred body 1 to be not smaller than 0.1 mm, the crawling-up of a liquid when forming a solid electrolyte layer is prevented to eliminate fault such as a shorting. As a result, the electrostatic capacity of the capacitor is increased, and its size is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor, and more particularly, to a solid electrolytic capacitor capable of increasing the capacitance and reducing its size.

[0002]

2. Description of the Related Art In a solid electrolytic capacitor such as a tantalum solid electrolytic capacitor, for example, fine powder of a valve metal such as tantalum or aluminum is embedded in advance at one end of an anode lead wire made of a valve metal such as tantalum. Then, a rectangular or cylindrical sintered body formed by sintering at a high temperature in a vacuum is used. An oxide film, a solid electrolyte layer, a carbon layer and a silver layer are sequentially provided on the sintered body to form a capacitor element. In this case, in particular, when forming the solid electrolyte layer, a treatment such as immersing the sintered body in a manganese nitrate solution or the like is performed. However, if the liquid adheres to the anode lead wire drawn out of the sintered body, a short circuit failure occurs. In addition, it becomes difficult to weld the anode terminal to the anode lead wire. For this reason, a 0.2 mm thick disk-shaped insulating plate made of Teflon or the like is usually arranged at the root of the anode lead wire to prevent the liquid from rising.

[0003]

The size of a sintered body is usually on the order of several mm. Therefore, even if the insulating plate has a thickness of about 0.2 mm, the ratio of the insulating plate to the entire capacitor element is relatively large. In the case of a solid electrolytic capacitor in which the overall dimensions including the exterior are limited to a predetermined value, means for enlarging the sintered body may be considered to increase the capacitance. However, an anode terminal must be connected to the anode lead wire drawn out of the sintered body, and therefore, the anode lead wire cannot be shortened to a predetermined value or more. It is easy to expose from the surface, which is not preferable. Further, when the whole is miniaturized by setting the capacitance to a predetermined value, the size of the sintered body cannot be changed, and accordingly, the thickness of the exterior becomes thinner and the withstand voltage decreases.

An object of the present invention is to provide a solid electrolytic capacitor which can improve the above-mentioned drawbacks, increase the capacitance, and reduce the size.

[0005]

In order to solve the above problems, the present invention provides an oxide film, a solid electrolyte layer and a cathode layer on a sintered body made of a valve metal from which an anode lead wire is drawn. The present invention also provides a solid electrolytic capacitor characterized in that an insulating plate having a thickness of less than 0.2 mm is arranged at the root of a lead wire for an anode.

That is, in the present invention, the thickness of the insulating plate is made smaller than the conventional thickness of 0.2 mm. Therefore, the dimensions of the sintered body can be increased by the reduced thickness without changing the external dimensions, and the capacitance can be increased. And when the capacity is kept constant without changing the size of the sintered body,
External dimensions can be reduced and downsized.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a sintered body, which is obtained by compression molding and sintering a fine powder of a valve action metal in a state where an anode lead wire 2 made of a valve action metal is drawn out.

A disk-shaped insulating plate 3 made of Teflon, silicone rubber, silicone resin, or the like is fitted and arranged at the root of the anode lead wire 2. This insulating plate 3
The thickness is thinner than 0.2 mm, and the end 3 a has a size protruding from the side surface 1 a of the sintered body 1. The thickness of the insulating plate 3 is preferably about 0.1 mm, and the capacitance of the capacitor can be increased. The effect of reducing the size can be increased, and the work of fitting the lead wire 2 to the anode lead 2 is difficult because it is too thin. And it is easy to prevent a defect such as cutting. Further, the length of the insulating plate 3 protruding from the sintered body 1 is preferably 0.10 mm or more, and it is easy to prevent the liquid from creeping up when forming the solid electrolyte layer, and the effect of reducing short circuit failure and the like is great. Become. Further, when the sintered body is square, as shown in FIG.
1 is used as two opposing side surfaces 1-1a and 1-1b of the sintered body 1-1.
The structure protrudes only from Further, as another example, as shown in FIG.
It may be configured to protrude from all of the two side surfaces 1-2a, 1-2b, 1-2c, and 1-2d. In this case, the latter insulating plate 3-2 is more effective in preventing the liquid from crawling up more effectively than the former insulating plate 3-1 and has an excellent effect of reducing the withstand voltage failure. When the sintered body 1-3 has a cylindrical shape, for example, as shown in FIG. 2C, the structure is such that the end of the insulating plate 3-3 protrudes from the entire side surface 1-3a.

After disposing the insulating plate 3, the sintered body 1 is subjected to a chemical conversion treatment to provide an oxide film 4 having a thickness of about 200 Å to 6000 Å. On the surface of the oxide film 4, a solid electrolyte layer 5 made of manganese dioxide or the like is provided. Further, on the surface of the solid electrolyte layer 5, a carbon layer 6 made of a carbon paste is provided. A silver layer 7 made of silver paste is provided on the surface of the carbon layer 6,
It is a capacitor element. Then, the carbon layer 6 and the silver layer 7 are combined and used as a cathode layer.

A cathode terminal 9 is connected to the silver layer 7 by a silver conductive paste 8. An anode terminal 10 is connected to the anode lead wire 2. Then, the capacitor element, a part of the cathode terminal 9 and a part of the anode terminal 10 are covered with an exterior 11 such as epoxy resin to form a solid electrolytic capacitor 12.

Next, a method of manufacturing the solid electrolytic capacitor 12 will be described. First, a binder in which camphor, an acrylic resin, or the like is dissolved in an organic solvent is added to and mixed with fine powder of a valve metal such as tantalum, aluminum, or niobium. After mixing, the mixture is heated to remove the organic solvent by volatilization. Next, the fine powder of the valve action metal is compression-molded into a square or cylindrical shape by a press or the like with the anode lead wire 2 made of a valve action metal such as tantalum pulled out. After the compression molding, the sintered body 1 is formed by sintering at a high temperature in an atmosphere such as a vacuum.

After sintering, a disk-shaped insulating plate 3 made of Teflon, silicone rubber, silicone resin or the like is arranged at the root of the anode lead wire 2.

The tip of the anode lead wire 2 drawn from the sintered body 1 is welded to a metal plate such as aluminum or stainless steel. Then, in this state, the sintered body 1 is immersed in a chemical conversion solution such as nitric acid or phosphoric acid to a predetermined level by visual observation or the like to form a chemical conversion treatment, and has a thickness of 200 Å to
An oxide film of about 000 angstroms is formed.

After forming the oxide film 4, manganese dioxide or T
A solid electrolyte layer 5 made of a CNQ salt and an organic conductive polymer is formed. In order to form the solid electrolyte layer 5, the sintered body 1 is placed in a manganese nitrate solution or the like with the lead surface side of the anode lead wire 2 facing upward. Then, immersion is performed visually so as not to exceed the insulating plate 3. Thereby, the liquid adheres to and impregnates the sintered body 1. After the impregnation, a treatment according to the type of the solution is performed to form the solid electrolyte layer 5. That is, if the solution is a manganese nitrate solution, the sintered body 1 is immersed in the manganese nitrate solution to impregnate the solution, then thermally decomposed, and further subjected to rechemical treatment. Then, the concentration of the manganese nitrate solution is sequentially increased, and the steps of impregnation, thermal decomposition, and re-chemical treatment are repeated to form a solid electrolyte layer 5 of manganese dioxide having a predetermined thickness. The following various methods are used to form the solid electrolyte layer 5 made of an organic conductive polymer. That is, in the first method, the sintered body 1 is immersed in a solution of the organic conductive polymer. After immersion, it is washed with an organic solvent such as alcohol. After washing, dry and evaporate the solvent.
If necessary, the steps from immersion to drying are repeated to form a predetermined thickness. In the second method, the sintered body 1 is immersed in a solution of the undoped polymer. After immersion, wash and dry. The process from immersion to drying is repeated a predetermined number of times as necessary, to form a undoped polymer film having a predetermined thickness.
After forming this film, the sintered body 1 is put in a doping solution for several tens of minutes.
It is immersed in contact for several minutes to several hours, and is doped with a polymer film to impart conductivity, thereby forming an organic conductive polymer film.
In the third method, the sintered body 1 is immersed in a solution containing doping ions in a monomer such as aniline, pyrrole, or thiophene. Next, the sintered body 1 is immersed in a solution of an oxidizing agent to cause a chemical polymerization reaction, thereby forming a film of an organic conductive polymer. In the fourth method, the sintered body 1 is immersed in a solution of a monomer such as aniline or pyrrole containing no doping ions. Next, the sintered body 1 is immersed in a solution of an oxidizing agent to cause a chemical polymerization reaction, thereby forming a polymer film. After the formation of the polymer film, the sintered body 1 is immersed in a doping solution and brought into contact with the film to impart conductivity to form a film of the organic conductive polymer. Note that the dopant is a substance having a dissociation constant substantially equal to or smaller than that of naphthalenesulfonic acid or a derivative thereof, and an anion of the dopant smaller than that of naphthalenesulfonic acid or a derivative thereof. Such dopants include, for example, sulfoisophthalic acid, sulfosuccinic acid, methanesulfonic acid, phenolsulfonic acid, sulfosalicylic acid, benzenesulfonic acid, benzenedisulfonic acid, alkylbenzenesulfonic acid and derivatives thereof, camphorsulfonic acid, sulfoacetic acid, and sulfoacetic acid. Acids such as aniline and diphenolsulfonic acid or salts of these acids are used. The doping solution has, for example, a composition in which a dopant or a dopant and an oxidizing agent are dissolved in an organic solvent. The concentration of the dopant or the oxidizing agent in the solution is set to 0.1.
The range of 01 to 1 mol / l is preferred. As the organic solvent, for example, ketones, esters, alcohols, aromatic hydrocarbons, nitrile acid, cellosolves, nitrogen-containing compounds, and the like are used. Further, as the solution of the oxidizing agent, not only the oxidizing agent but also a solution to which a dopant is added or a solution of a salt of the oxidizing agent and the dopant may be used. As the oxidizing agent, a salt having an oxidation potential of 0.8 V or more with respect to the hydrogen reference electrode, such as a second iron salt, a persulfate, or a vanadate, is used. By the way, when an element is formed from tantalum powder, the more the CV value of the tantalum powder increases and the capacitance per volume increases, the more difficult it is to impregnate the liquid inside the element. Therefore, in order to form a conductive polymer film having good characteristics, it is necessary to use a conductive polymer solution or the like having a high concentration. Among the polymers, polyaniline is a suitable substance because it has a high solubility in a solvent and can prepare a solution having a relatively high concentration.

After forming the solid electrolyte layer 5, a carbon paste is applied to form a carbon layer 6. A silver paste is applied to the surface of the carbon layer 6 to form a silver layer 7. Then, the solid electrolyte layer 5, the carbon layer 6, and the silver layer 7 are used as a cathode layer.

After the silver layer 7 is formed, a cathode terminal 9 is connected to the silver layer 7 by a silver conductive paste 8 and an anode terminal 10 is connected to the anode lead wire 3 by resistance welding or the like. Then, the exterior 11 is formed by a resin molding method, a resin dipping method, or the like. After the exterior 11 is formed, aging treatment is performed, and the cathode terminal 9 and the anode terminal 10 are bent along the surface of the exterior 11 to form the solid electrolytic capacitor 12.

[0017]

Next, an embodiment of the present invention will be described. Example 1: A sintered body is obtained by compressing and molding a tantalum fine powder and sintering it in a vacuum at a temperature of 1300 to 1600 ° C. to a size of 0.42 mm × 0.72 mm × 0.65 mm square. The lead wire for the anode made of tantalum is drawn out. At the root of the anode lead wire, a disk-shaped Teflon insulating plate having a thickness of 0.1 mm and a diameter of 0.8 mm is arranged. Then, the oxide film is heated at a temperature of 5 ° C.
It is immersed in a nitric acid aqueous solution at 0 ° C. to a predetermined level visually, and a direct current voltage of 30 V is applied to form a chemical conversion treatment.
Further, the solid electrolyte layer is formed by immersing the sintered body in a manganese nitrate solution to impregnate the liquid, thereafter thermally decomposing and re-chemically forming, and repeating the process from impregnation to re-chemical formation several times. . Further, a carbon layer and a silver layer are formed by applying a carbon paste and a silver paste, respectively. The cathode terminal is connected to the silver layer by a silver conductive paste. The anode terminal is connected to the anode lead wire 2 by resistance welding. The exterior is made of epoxy resin and is formed by a transfer molding method. Due to these conditions, rating 1
A 0 V, 1.5 μF tantalum solid electrolytic capacitor is formed.

Embodiment 2: The size of the insulating plate is 0.1 m in thickness.
m, the same as Example 1 except that the diameter is 0.6 mm.

Example 3 The size of the sintered body was 0.85 mm ×
1.05 mm x 1.20 mm square, and the size of the insulating plate is 0.1 mm thick and 1.1 mm in diameter.
Except for a 10 μF tantalum solid electrolytic capacitor,
The conditions are the same as in the first embodiment.

Embodiment 4: The size of the insulating plate is 0.1 m in thickness.
Example 3 is the same as Example 3 except that m and the diameter are 0.7 mm.

Example 5: The size of the sintered body was 1.62 mm ×
The size of the insulating substrate is set to be 0.15 mm in thickness and 1.7 mm in diameter.
The conditions were the same as in Example 1 except that a tantalum solid electrolytic capacitor of V, 100 μF was used.

Embodiment 6: The size of the insulating plate is 0.1 m in thickness.
Example 5 is the same as Example 5 except that m and the diameter are 1.3 mm.

Then, along with Examples 1 to 6,
In combination with the conventional example, the possible increase rate of the capacitance was obtained, and the defective rate due to the manganese nitrate solution climbing up when forming the manganese dioxide layer was measured. It should be noted that the possible rate of increase of the capacitance can be changed without changing the external dimensions of the capacitor.
Capacitance that can be increased when the sintered body is lengthened by the difference in the thickness of the insulating plate used in each example as compared with the case where the conventional insulating plate having a thickness of 0.2 mm is used. Value of increase rate. The failure due to the liquid creeping up is measured by visually observing the sintered body after forming the manganese dioxide layer. Further, the number of samples is 6500 for each of Examples 1 to 4, and 1000 for each of Examples 5 and 6. The conditions of the conventional example are as follows.

Conventional example 1: The size of the insulating plate is 0.2 m thick
m, the same as Example 1 except that the diameter is 0.6 mm.

Conventional example 2: The size of the insulating plate is 0.2 m in thickness.
Example 3 is the same as Example 3 except that m and the diameter are 0.7 mm.

Conventional Example 3: The size of the insulating plate is set to 0.2 m in thickness.
Example 5 is the same as Example 5 except that m and the diameter are 1.3 mm.

Table 1 shows the measurement results.

[0028]

[Table 1]

As is clear from Table 1, according to the first to sixth embodiments, the capacitance can be increased by 2.6 to 15.2% as compared with the conventional examples 1 to 3.

When comparing Example 5 and Example 6 of the same rating, the diameter of the insulating plate is larger and the ends of the insulating plate protrude from the two side surfaces of the sintered body as shown in FIG. The former capacitor having a smaller structure has a smaller failure rate due to the manganese nitrate solution crawling than the latter having a structure in which the diameter of the insulating plate is small and the end of the insulating plate does not protrude from each side of the insulator. Has declined.

Further, when the first and second embodiments and the third and fourth embodiments having the same rating are compared with each other, FIG.
As shown in (b), the first and third embodiments of the structure in which the ends of the insulating plate protrude from the four side surfaces of the sintered body are shown in FIG.
The defect rate due to the manganese nitrate solution crawling was 2 /
It has decreased to 7 to 5/16.

[0032]

As described above, according to the present invention, the capacitance is increased because the insulating plate having a thickness of less than 0.2 mm is arranged at the base of the anode lead wire drawn out of the sintered body. Thus, a solid electrolytic capacitor that can be downsized can be obtained.

[Brief description of the drawings]

FIG. 1 shows a sectional view of an embodiment of the present invention.

FIG. 2 is a plan view of a sintered body provided with an insulating plate used in another embodiment of the present invention.

[Explanation of symbols]

1 ... sintered body, 2 ... lead wire for anode, 3 ... insulating plate,
4 ... oxide film, 5 ... solid electrolyte layer, 6 ... carbon layer,
7 ... silver layer, 12 ... solid electrolytic capacitor.

Claims (1)

[Claims] 1. A solid electrolytic capacitor in which an oxide film, a solid electrolyte layer, and a cathode layer are provided on a sintered body made of a valve metal from which an anode lead wire has been drawn out. A solid electrolytic capacitor having an insulating plate thinner than 2 mm.