JPH09213572A - Solid state electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease a leakage current and reduce short-circuit failure, by forming a recess in a sintered body in the root of an anode lead wire, and filling the recess with insulating resin. SOLUTION: Fine powder of tantalum or the like is used as the powder of valve action metal. A tantalum wire or the like is used as an anode lead wire. One end of the anode lead wire 1 is buried in the valve action metal powder, and the other end is led out and forms a sintered body 2. The sintered body 2 is formed as a rectangular parallelopiped or a cylinder as a whole. In particular, a recess 4 is formed in the sintered body 2 of a root part 3 of the anode lead wire 1. The recess 4 is polygonal or cylindrical, and the volume is preferable to be about 2-10% of the whole volume of the sintered body 2. The recess 4 is filled with insulating resin 5 such as fluororesin, silicone resin and epoxy resin.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a solid electrolytic capacitor.

[0002]

2. Description of the Related Art Capacitors such as tantalum solid electrolytic capacitors are usually manufactured by pressing fine powder of tantalum or the like into a cylindrical or rectangular parallelepiped with the anode lead wire of the tantalum wire or the like being pulled out, and then vacuum forming. A sintered body formed by sintering at a high temperature is used. Then, as shown in FIG. 2, a cathode layer 23 including an anodized film 21, a manganese dioxide layer 22, a carbon layer and a silver layer (or a copper layer) is sequentially provided on the sintered body 20. Further, a washer 26 made of Teflon is inserted into the root portion 25 of the anode lead wire 24, and an anode terminal 27 is connected to the cathode lead 23.
8 is connected. Further, the resin exterior 29 is provided by a resin molding method, a resin dipping method, or the like.

[0003]

However, in the conventional solid electrolytic capacitor 30 of FIG. 2, mechanical stress is applied to the root portion 25 of the anode lead wire 24 during the manufacturing process. Therefore, the anodic oxide film 31 formed on the surface of the root portion 25 of the anode lead wire 24 is easily cracked.
The cracked portion of the anodic oxide film 31 has a lower resistance than that of the normal anodic oxide film 21, and a current easily flows. Therefore, when a voltage is applied to the solid electrolytic capacitor 30, the charging current passes through the cracks in the anodic oxide film 31, and the manganese dioxide layer 22, the cathode layer 23, and the cathode terminal 28.
It becomes easier to flow through. As a result, the leakage current of the solid electrolytic capacitor 30 increases, and there is a drawback that a short circuit defect is likely to occur.

An object of the present invention is to provide a solid electrolytic capacitor which is capable of improving the above-mentioned drawbacks, reducing leakage current, and reducing short circuit defects.

[0005]

The present invention provides a solid electrolytic capacitor in which an anodized film, a semiconductor layer, and a cathode layer are sequentially provided on a sintered body made of a powder of valve metal, from which an anode lead wire is drawn, The solid electrolytic capacitor is characterized in that a recess is provided in the sintered body at the base of the anode lead wire and the recess is filled with an insulating resin.

Since the sintered body at the root of the anode lead wire is provided with a recess, the distance between the root of the anode lead and the surface of the sintered body from the cathode terminal becomes long, and the resistance of the surface becomes large. .

Further, since the recess is filled with the resin, the root portion of the anode lead wire can be more firmly fixed. Therefore, even if mechanical stress is applied to the anode lead wire during the manufacturing process, it is possible to prevent cracks from occurring in the anodized film at the root of the anode lead wire. Therefore, the leakage current characteristics of the solid electrolytic capacitor can be improved, and short circuit defects can be reduced.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. Fine powder of tantalum or the like is used as the powder of the valve metal. A tantalum wire or the like is used as the anode lead wire. Then, as shown in FIG. 1, one end of the anode lead wire 1 is embedded in the powder and the other end is pulled out to form a sintered body 2. The sintered body 2 is formed in a rectangular parallelepiped shape or a cylindrical shape as a whole.

And, in particular, the root portion 3 of the anode lead wire 1
The recess 4 is formed in the sintered body 2. The concave portion 4 has a polygonal shape or a cylindrical shape, and has a volume of 2 to 1 of the total volume of the sintered body 2.
A size of about 0% is preferable. That is, if the size of the concave portion 4 is less than 2%, the effect of reducing the leakage current or the short circuit failure is low, and if it is more than 10%, the capacity is greatly reduced and it is difficult to reduce the size.

The recess 4 is filled with an insulating resin 5 such as fluororesin, silicon resin, or epoxy resin.
It is preferable that the insulating resin 5 is higher than the depth of the recess 4 and protrudes from the surface of the sintered body 2 to be filled. As a result, the insulating property can be improved, the root portion 3 of the anode lead wire 1 can be fixed, and the mechanical stress can be alleviated.

Further, the sintered body 2 is sequentially provided with an anodized film 6, a semiconductor layer 7 such as manganese dioxide, a cathode layer 8 including a carbon layer and a silver paste layer (or a copper paste layer).

Then, the anode terminal 9 is welded to the anode lead wire 1, and the cathode terminal 10 is connected to the cathode layer 8 by the conductive resin 11.

The entire capacitor element in which the anodic oxide film 6 and the like are provided on the sintered body 2 is covered with the resin exterior 12. Further, the tips of the anode terminal 9 and the cathode terminal 10 are bent toward the lower surface along the surface of the resin sheath 12.

Next, a method of manufacturing the solid electrolytic capacitor 13 will be described. First, a powder of valve metal is filled in one end of the anode lead wire 1 and the other end is pulled out, and compression molding is performed by a press to form a powder in a vacuum of about 10 ⁻⁴ to 10 ⁻⁵ Torr.
The sintered body 2 is formed by heating at a temperature of about 00 ° C. for several tens of minutes. Then, at the time of molding, a recess 4 is formed in the sintered body 2 of the root portion 3 of the anode lead wire 1.

After forming the sintered body 2, a plurality of sintered bodies 2 are welded to a metal bar such as stainless steel at the tip of the anode lead wire 1. After welding, the sintered body 2 is subjected to chemical conversion by applying a voltage in a chemical conversion solution such as nitric acid or phosphoric acid to form an anodized film 6. After forming the anodized film 6, the recess 4 is filled with the insulating resin 5. The insulating resin 5 may be filled before the sintered body 2 is welded to the metal bar or after the anodic oxide film 6 is formed after the welding to the metal bar. However, the insulating property is improved by performing after the formation of the anodic oxide film 8.

After the insulating resin 5 is filled, the sintered body 2 is dipped in a manganese nitrate solution to impregnate the solution. After the impregnation, the semiconductor layer 7 such as a manganese dioxide layer is formed by firing at a temperature of 200 to 350 ° C. for thermal decomposition. After thermal decomposition, re-formation is performed to repair the anodized film 6 damaged during firing.
Then, the steps of soaking, thermal decomposition and re-chemical conversion are repeated several times to several tens of times as necessary. After the semiconductor layer 7 is formed, carbon is applied to form a carbon layer, and silver paste (or copper paste) is applied to form a silver paste layer (or copper paste layer), which together form the cathode layer 8. . After forming the cathode layer 8, the sintered body 2 is connected to a lead frame, and the anode lead wire 1 and the cathode layer 8 are connected to the anode terminal 9 and the cathode terminal 10, respectively. Then, the resin exterior 11 is formed by a resin molding method (or a resin dipping method).

[0017]

EXAMPLES Next, with respect to the tantalum chip type solid electrolytic capacitors of the examples of the present invention, the initial leakage current and the withstand voltage defective rate were measured together with the same type of capacitors of the conventional example and the comparative example.

The embodiment has the structure shown in FIG.
It is assumed that the volume of the recess 4 with respect to the whole is variously changed.
The conventional example has the structure shown in FIG. Comparative Example 1 has a structure as shown in FIG. 3, and in particular, the sintered body 42 of the root portion 41 of the anode lead wire 40 is flat without recesses. Then, the root portion 41 is connected to the insulating resin 43.
It is covered by. Further, Comparative Example 2 has a structure as shown in FIG. 4, and particularly the root portion 5 of the anode lead wire 50.
A recess 53 is provided in the first sintered body 52, and a washer 54 made of Teflon that is thinner than the depth of the recess 53 is inserted into the recess 53.

The ratings of the samples of the example, the conventional example, the comparative example 1 and the comparative example 2 are 35 V and 10 μm. The number of samples is 500 each. Furthermore, the withstand voltage defect rate is a value when a voltage of 42 V is applied in an atmosphere at a temperature of 23 ° C.

The measurement results are shown in FIG. 5 for the leakage current and in Table 1 for the breakdown voltage defective rate.

As is apparent from FIG. 5, it is clear that the leakage currents of Examples 1 to 5 are lower than those of the conventional example, Comparative example 1 and Comparative example 2. Margin below.

[0022]

[Table 1]

As is clear from Table 1, the breakdown voltage failure rates are 2.0 to 3.8% in Examples 1 to 5 and 8.8 in the conventional example.
%, And Comparative Examples 1 and 2 are 4.8 to 5.2%. That is, Examples 1 to 5 are about 22.7 to 4 of the conventional example.
3.2%, about 38.5 to 79.2 in Comparative Example 1 to Comparative Example 2
It has been reduced to%.

[0024]

As described above, according to the present invention, since the sintered body at the base of the anode lead wire is provided with the recess and the recess is filled with the insulating resin, the leakage current can be reduced and the withstand voltage can be reduced. A solid electrolytic capacitor capable of reducing defects can be obtained.

[Brief description of drawings]

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

FIG. 2 shows a cross-sectional view of a conventional example.

FIG. 3 shows a cross-sectional view of a comparative example.

FIG. 4 shows a cross-sectional view of another comparative example.

FIG. 5 shows a graph of leakage current.

[Explanation of symbols]

1 ... Anode lead wire, 2 ... Sintered body, 3 ... Root part,
4 ... Recessed portion, 5 ... Insulating resin, 6 ... Anodized film, 7
... Semiconductor layer, 8 ... Cathode layer, 12 ... Resin coating, 13 ...
Solid electrolytic capacitor.

Claims (1)

[Claims] 1. A solid electrolytic capacitor in which a anodic oxide film, a semiconductor layer, and a cathode layer are sequentially provided on a sintered body made of a powder of valve action metal from which an anode lead wire is drawn out, and a base portion of the anode lead wire is baked. A solid electrolytic capacitor, characterized in that a recess is provided in the united body, and the recess is filled with an insulating resin.