JP2773499B2 - Solid electrolytic capacitor and method of manufacturing the same - 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 and a method for manufacturing the same.

[0002]

2. Description of the Related Art Modern electronic circuits operate at high frequencies. Its also the frequency characteristic capacitor incorporated in the electronic circuit for, in particular good performance requested to the capacity change rate and the equivalent series resistance (hereinafter referred to as ESR).

A solid electrolytic capacitor which is one of such capacitors uses a sintered body obtained by sintering fine powder of a valve metal such as tantalum or aluminum. Then, an oxide film is electrochemically provided on the sintered body, and then a solid electrolyte layer made of manganese dioxide is provided. The solid electrolyte layer is formed by impregnating an aqueous solution of manganese dioxide and using a thermal decomposition method. After forming the solid electrolyte layer, carbon and silver paste are sequentially applied to the surface to form a cathode layer.

The frequency characteristics of a solid electrolytic capacitor can be improved as the conductivity of the solid electrolyte layer increases.

[0005]

However, the electric conductivity of the conventional manganese dioxide forming the solid electrolyte layer is about 0.01 to 0.05 S / cm, which is a relatively low value. Therefore, there is a disadvantage that it is difficult to improve the frequency characteristics of the solid electrolytic capacitor.

In particular, the ESR has a disadvantage that it is larger than other capacitors, for example, a ceramic capacitor, a film capacitor, and an aluminum electrolytic capacitor using an organic semiconductor as a solid electrolyte.

An object of the present invention is to provide a solid electrolytic capacitor capable of improving the above-mentioned drawbacks and improving the frequency characteristics, and a method of manufacturing the same.

[0008]

In order to achieve the above object, the invention of claim 1 is to provide an anodic oxide film, a solid electrolyte layer and a cathode layer sequentially on a sintered body made of a fine powder of a valve action metal. Lead / dioxide in solid electrolytic capacitors
An object of the present invention is to provide a solid electrolytic capacitor having a solid electrolyte layer made of a mixture of manganese dioxide and lead dioxide in a manganese ratio of 80 to 90/20 to 10 .

A second aspect of the present invention is a method of manufacturing a solid electrolytic capacitor in which an anodic oxide film, a solid electrolyte layer, and a cathode layer are sequentially formed on a sintered body made of a fine powder of a valve metal. After the formation, the manganese nitrate
After impregnation pyrolyzed liquid by immersing the down solution, solid, characterized in that decompose impregnated is heat the liquid was immersed in a manganese nitrate solution were suspended lead dioxide to form a solid electrolyte layer An object of the present invention is to provide a method for manufacturing an electrolytic capacitor.

The manganese nitrate solution in which lead dioxide is suspended has a relatively high viscosity and is hardly impregnated.
Therefore, it is preferable to first impregnate a manganese nitrate solution in which lead dioxide is not suspended and perform a thermal decomposition treatment to precipitate only manganese dioxide. Then, when manganese dioxide is deposited to some extent in the pores inside the sintered body, a manganese nitrate solution in which lead dioxide is suspended is impregnated and thermally decomposed to precipitate a mixture of manganese dioxide and lead dioxide.

[0011]

The electric conductivity of the solid electrolyte layer when the content ratio of manganese dioxide MnO ₂ and lead dioxide PbO ₂ is changed is shown in FIG.
It becomes as follows. That is, as is apparent from FIG.
The higher the content of lead dioxide, the higher the conductivity and the better the frequency characteristics.

However, only lead dioxide has a low adhesion strength due to chemical precipitation and is easily peeled. Therefore, lead dioxide is always used as a mixture with manganese dioxide. And the ratio is therefore PbO ₂ / MnO ₂ = 80
~ 90 / 20-10 is good.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
First, a fine powder of tantalum is formed into a square shape, sintered,
A sintered body having a size of 1.8 mm × 0.9 mm × 1.80 mm and a weight of 20 mg is formed.

Next, this sintered body is immersed in a phosphoric acid solution at a temperature of 50 ° C., and formed at 75 V to form an anodic oxide film.

After forming the anodic oxide film, the sintered body is immersed in a 20% manganese nitrate aqueous solution, impregnated with the solution, and then left in a furnace at a temperature of 260 ° C. to be thermally decomposed. And it re-forms after thermal decomposition.

After the re-formation, the sintered body is immersed in an aqueous solution of manganese nitrate in which 10% by weight of lead dioxide is mixed and suspended, and thermally decomposed and re-formed under the same conditions as described above.

After the re-chemical formation, the mixed amount of lead dioxide is sequentially increased to 3
It is immersed in an aqueous solution of manganese nitrate changed to 0 wt%, 50 wt%, 70 wt% and 80 wt%, thermally decomposed and reformed under the same conditions as above to form a solid electrolyte layer.

After forming the solid electrolyte layer, colloidal carbon and silver paste are applied to form a cathode layer. After forming the cathode layer, it is connected to a lead frame and molded with an epoxy resin to form an exterior.

In the above embodiment, the solid electrolyte layer is formed by first impregnating only the manganese dioxide aqueous solution without mixing lead dioxide, but this treatment may be omitted. That is, the manganese dioxide aqueous solution in which lead dioxide is mixed and suspended may be impregnated from the beginning.

Next, the values of the ESR of the above-described embodiment, comparative example, and conventional example were obtained by changing the frequency, and the results are shown in FIG.

In this embodiment, when the solid electrolyte layer is formed in the above embodiment, the solid electrolyte layer is manufactured by first impregnating with an aqueous solution of manganese nitrate in which lead dioxide is not suspended and thermally decomposing.

In the comparative example, after treating with an aqueous solution of manganese nitrate in which lead dioxide was not suspended, an aqueous solution of ammonium acetate (2 mol / l) was added to an aqueous solution of lead acetate (1 mol / l).
1 / l) is repeated. The process of immersing in a mixed aqueous solution and then drying is repeated six times to deposit lead dioxide to form a solid electrolyte layer.

In the conventional example, the same conditions as in Example 1 are used except that the solid electrolyte layer is manufactured using only a manganese nitrate aqueous solution without suspending lead dioxide. The concentration of the manganese nitrate aqueous solution is set to five types of 30%, 40%, 60%, 70% and 80%, and the solution is sequentially impregnated with a solution having a high concentration from a low concentration and thermally decomposed.

As is clear from FIG. 1, the ESR of the embodiment is clearly lower than that of the conventional example. For example, at a frequency of 10 ⁶ Hz, the example is 0.15Ω and the conventional example is 0.7Ω, and the former is 3/14 of the latter. Note that the value of the comparative example is 0.11, which is lower than that of the example.

In addition, initial characteristics, characteristics after a heat cycle, and characteristics after a pressure cooker test (hereinafter, referred to as PCT) were determined for the above Examples, Comparative Examples and Conventional Examples, and are shown in Table 1.

Heat cycle temperature -55 ° C to 125 ° C;
This is performed under the condition of 100 cycles. The PCT is at a temperature of 12
It is left for 32 hours in an atmosphere of 1 ° C. and 2 atm. The number of each sample is 20. Margin below.

[0027]

[Table 1]

As is apparent from Table 1, the embodiment is superior to the conventional example in the tan δ and heat leakage characteristics after heat cycle and PCT. In addition, the initial characteristics, the heat cycle, and the tan δ after PCT are superior to those of the comparative example.

For example, with respect to tan δ, the examples are 6/23 of the conventional example after the heat cycle, 3/10 of the comparative example, 8/35 of the conventional example after PCT, and 4/11 of the comparative example. Also, regarding the leakage current, the embodiment is １ ／ after the heat cycle and ／ after PCT as compared with the conventional example.
Becomes Note that, in the example, the initial tan δ is also low at 5/21 compared to the comparative example.

[0030]

As described above , according to the first aspect of the present invention,
Lead dioxide / manganese dioxide = 80-90 / 20-10
Of manganese dioxide and lead dioxide
Since the solid electrolyte layer is formed, the power of the solid electrolyte layer
Conductivity can be increased, thereby improving frequency characteristics such as ESR.
While improving tan δ and leakage current characteristics.
Also, the solid electrolyte layer can be hardly peeled off from the anodic oxide film.
Therefore, the solid electrolyte layer peels off during production or during use, and E
The increase in SR, tan δ, and leakage current can be suppressed.
It is possible to increase the yield and improve the life,
Characteristics can be improved and a solid electrolytic capacitor with high reliability can be obtained.
Can be Further, according to the manufacturing method of the invention of claim 2,
After immersing the aggregate in a manganese nitrate solution to thermally decompose,
Immersed in manganese nitrate solution with suspended lead oxide and thermally decomposed
Nitric acid with good impregnation
Large contact area with anodic oxide film by manganese solution
A solid electrolyte layer can be formed, and manganese dioxide and
Solid electrolyte layer having a portion composed of a mixture with lead dioxide
To improve the frequency characteristics such as ESR.
Solid electrolytic capacitor that can improve tan δ and leakage current characteristics
A densa is obtained.

[Brief description of the drawings]

FIG. 1 shows a frequency characteristic of an equivalent series resistance.

FIG. 2 shows a graph of the conductivity of the solid electrolyte layer with respect to the content ratio of MnO ₂ and PbO ₂ .

Claims (2)

(57) [Claims] 1. A solid electrolytic capacitor in which an anodic oxide film, a solid electrolyte layer and a cathode layer are sequentially provided on a sintered body made of fine powder of a valve action metal, wherein lead dioxide / manganese dioxide =
A solid electrolytic capacitor comprising a solid electrolyte layer made of a mixture of manganese dioxide and lead dioxide in a ratio of 80 to 90/20 to 10 . 2. A method for manufacturing a solid electrolytic capacitor in which an anodic oxide film, a solid electrolyte layer, and a cathode layer are sequentially formed on a sintered body made of fine powder of a valve action metal, wherein the sintered body after forming the anodic oxide film is Immersed in manganese nitrate solution
A method for producing a solid electrolytic capacitor, comprising: immersing in a manganese nitrate solution in which lead dioxide is suspended, impregnating the solution, and thermally decomposing to form a solid electrolyte layer.