JP3082463B2 - Solid electrolytic capacitors - Google Patents

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.

[0002]

2. Description of the Related Art A tantalum or other solid electrolytic capacitor is usually formed by pressing a fine powder of tantalum or the like into a cylindrical shape or a rectangular parallelepiped shape with an anode lead wire drawn out, and then forming the material at high temperature in a vacuum. A sintered body is used. And FIG.
As shown in FIG. 2, anodized film 12, manganese dioxide layer 13, carbon layer 14, silver layer (or copper layer)
15 are sequentially provided, and the anode terminal 5 is connected to the anode lead wire 16 and the cathode terminal 17 is connected to the silver layer 15 and the like to form a capacitor element. In order to provide the silver layer 15 and the like, the sintered body 11 provided with the carbon layer 14 is immersed in a silver paste or a copper paste, and the paste is applied. At this time, in order to increase the area as the cathode, the sintered body is moved in the longitudinal direction by keeping the paste out of contact with the anode lead wire 16.
0% or more of the silver paste 15
8 is a drawing surface 19 of the anode lead wire 16 of the sintered body 11
It is formed so that it comes to the position of. By increasing the area of the silver layer or the like serving as a cathode, tan δ and impedance characteristics can be stabilized.

When a withstand voltage test or a surge withstand voltage test is performed, an absorption current instantaneously flows through the capacitor element. This absorption current flows through the lower part of the resistance. In the conventional capacitor element, the path resistance from the anode lead directly through the silver layer or the like to the cathode terminal is low, so that the absorption current flows through this path.

[0004]

However, when an absorption current flows, heat is generated in the path. Therefore, the manganese dioxide layer and the anodic oxide film near the route are thermally degraded. As a result, the capacitor has a drawback that the leakage current increases and short-circuit failure occurs.

An object of the present invention is to provide a solid electrolytic capacitor which can improve the above drawbacks, reduce the leakage current, and prevent short circuit failure.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention has a valve action in which an anode lead wire is drawn.
Anodized film, semiconductor layer and sintered metal
Inner layer consisting of carbon layer and outer layer containing silver or copper
And a cathode terminal on the outer layer of the cathode layer.
The solid lead pulled out and connected in the opposite direction to the anode lead wire
A solid electrolytic capacitor in which an outer layer of a cathode layer having a tip disposed between 1/4 and 3/5 of the entire length of a sintered body is provided in a body electrolytic capacitor in a drawing direction of a lead wire for an anode. Is provided.

[0007]

According to the present invention, the outer layer of the cathode layer is formed such that its tip is directed toward the lead-out direction of the anode lead wire, and is 1/4 to 3/3 of the total length of the sintered body.
5 is formed on the sintered body. Then , pull out to the outer layer of this cathode layer in the direction opposite to the anode lead wire
Te to connect the cathode terminal. Therefore, the distance between the anode lead wire and the cathode terminal becomes longer, and the resistance becomes larger than before. Therefore, directly the cathode layer from the anode lead wire
The current flowing to the cathode terminal through the outer layer can be reduced.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
In FIG. 1, reference numeral 1 denotes a sintered body, which is obtained by pressing a fine powder of tantalum and sintering it at a high temperature in a vacuum. Reference numeral 2 denotes a tantalum anode lead wire drawn from the sintered body 1. Reference numeral 3 denotes an anodized film provided on the sintered body 1. Reference numeral 4 denotes a semiconductor layer made of manganese dioxide provided on the entire surface of the anodic oxide film 3. Reference numeral 5 denotes a carbon layer, which is laminated on the surface of the semiconductor layer 4 except for the lead-out surface 6 of the anode lead wire 2 and forms an inner layer of the cathode layer. Reference numeral 7 denotes an outer layer of a cathode layer made of silver or copper, which is laminated on the surface of the carbon layer 5 so that the tip 8 comes to １ ／ to ／ of the total length L of the sintered body 1. . 9
Is a cathode terminal connected to the outer layer 7 of the cathode layer, the end 10 of which is aligned with the tip 8 of the outer layer 7, but may be shifted.

In this embodiment, the anodic oxide film 3
The sintered body 1 is immersed in a chemical conversion solution such as a nitric acid solution or a phosphoric acid solution, and is formed by electrochemical conversion treatment. Further, the semiconductor layer 4 is formed by immersing the sintered body 1 after the formation of the anodic oxide film 3 in a manganese nitrate solution, impregnating the solution, firing and re-chemically forming the semiconductor body 4 several times to a predetermined thickness. Form.

Next, tan δ and breakdown voltage (hereinafter abbreviated as BDV) were measured for the above Examples, Conventional Examples and Comparative Examples, and the results are shown in Table 1. The sample used for the measurement was
This is a tantalum chip type solid electrolytic capacitor rated at 35 V and 10 μF, which is subjected to a chemical conversion treatment at a chemical conversion voltage of 140 V. The number of samples is 10 each.

[0011]

[Table 1]

As apparent from Table 1, according to the first and second embodiments, the BDV is 109-111 V, which is about 1.22-1.25 times higher than that of the conventional example 1.
Further, in Examples 1 and 2, the BDV is increased by about 1.08 to 1.23 times as compared with Comparative Examples 1 and 2, and particularly, tan δ is increased by about 59 to It has decreased by 62%. That is, it is found that providing the outer layer of the cathode layer such that the tip thereof is located at a position of 1/4 to 3/5 of the entire length L of the sintered body is effective for increasing the BDV.

Further, the characteristics and short-circuit failure rate before and after the surge voltage test were measured for Examples and the like, and Table 2 shows the results. Example 3 is Example 1, Example 4 is Example 2, Conventional Example 2 is Conventional Example 1, Comparative Example 3 is Comparative Example 1,
Comparative Example 4 is manufactured under the same conditions as Comparative Example 2. The number of these samples is 10 each. In the surge voltage test, the temperature of the atmosphere was 85 ° C., and the applied voltage was 45.5.
A cycle of charging with V for 30 seconds and discharging in 5 minutes and 30 seconds is repeated 1000 times.

[0014]

[Table 2]

As apparent from Table 2, according to Examples 3 and 4, the leakage current after the test can be reduced to about 29 to 34% and the short-circuit failure rate can be reduced to 0% as compared with Conventional Example 2. it can. In addition, the leakage current of Examples 3 and 4 can be reduced to about 48 to 60% as compared with Comparative Examples 3 and 4.

[0016]

As described above, according to the present invention, the anode
Sintering of metal with valve action
Inner layer consisting of extreme oxide film, semiconductor layer and carbon layer
And a cathode layer consisting of an outer layer containing silver or copper as a component.
A cathode terminal on the outer layer of the cathode layer opposite to the anode lead wire
Of solid electrolytic capacitor
Since the outer layer of the cathode layer is provided so that its tip is located between １ ／ to ／ of the entire length of the sintered body in the drawing direction of the anode lead wire, tan δ increases. Instead, it is possible to obtain a solid electrolytic capacitor capable of improving the breakdown voltage and improving the leakage current characteristics and short-circuit failure.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a state where a cathode terminal is connected to a sintered body according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a state in which a cathode terminal is connected to a conventional sintered body.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sintered body, 2 ... Lead wire for anode, 3 ... Anodized film, 4 ... Semiconductor layer, 5 ... Carbon layer, 7 ... Outer layer,
9 ... Cathode terminal.

Claims (1)

(57) [Claims] An anodic oxide film, a semiconductor layer , and a metal are formed on a sintered body of a metal having a valve action from which an anode lead wire is drawn.
An inner layer consisting of a carbon layer and an outer layer containing silver or copper
And a cathode terminal on the outer layer of the cathode layer.
Was connected in the direction opposite to the lead wire for the anode in the solid electrolytic capacitor connected in a direction opposite to the lead wire for the anode. A solid electrolytic capacitor provided with an outer layer of a cathode layer.