JPH04273424A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To reduce an impedance and to stabilize a characteristic. CONSTITUTION:A solid electrolyte 4 is formed on a sintered pellet 1 of tantalum or the like; a carbon layer is formed on the solid electrolyte 4. At this time, this assembly is first immersed in a low-concentration carbon suspension and dried. Then, the assembly is immersed in a high-concentration carbon suspension and dried. Then, the assembly is immersed again in the low-concentration carbon suspension. By means of the first low-concentration carbon suspension, said carbon suspension 5 creeps effectively into the solid electrolyte 4. A carbon layer 6 having a prescribed thickness is formed by the next high-concentration carbon suspension. When this assembly is immersed in a third low-concentration carbon suspension, an external-film carbon layer 7 is formed, and the crack of the carbon layer 6 is mended.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid electrolytic capacitor, and more particularly, to a method for manufacturing a solid electrolytic capacitor that can improve impedance characteristics.

0002

2. Description of the Related Art Taking a tantalum solid electrolytic capacitor as an example, the manufacturing method thereof will be explained. First, tantalum powder is sintered to obtain sintered pellets. At this time, an anode lead is implanted in the sintered pellet.

Next, after forming a dielectric oxide film, a solid electrolyte such as manganese dioxide is formed. Then, a carbon layer and a silver layer are sequentially formed on the same solid electrolyte, and this is used as a cathode layer.

[0004] After welding an anode terminal member for external lead to the anode lead and attaching the cathode terminal member for external lead to the cathode layer via a conductive adhesive, a resin exterior body is formed by a resin molding method or a dipping method. form.

[0005]

[Problems to be Solved by the Invention] The carbon layer is formed by immersing sintered pellets in a carbon suspension, pulling them up and drying them, but in order to lower the resistance of the solid electrolyte, it is necessary to add carbon to the solid electrolyte. It is necessary to infiltrate the inside of the

[0006] Conventionally, therefore, the carbon concentration of the above-mentioned suspension is made low to increase its permeation rate.

However, this method has a problem in that resistance values vary due to the low concentration. On the other hand, if the carbon concentration is increased, the resistance value cannot be lowered because carbon does not penetrate into the solid electrolyte. Further, there is a problem that cracks are likely to occur during drying.

[0008]

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned conventional circumstances, and its structural features are that after forming a dielectric oxide film on a sintered pellet of valve metal powder,
In a method for manufacturing a solid electrolytic capacitor in which a solid electrolyte is formed and a carbon layer and a silver layer are successively formed on the solid electrolyte to form a cathode layer, when forming the carbon layer, the sintered pellets are first heated at a low concentration. The method consists of immersing it in a carbon suspension and drying it, then immersing it in a high concentration carbon suspension and drying it, and then immersing it in a low concentration carbon suspension again and drying it.

[0009]

[Operation] First, low concentration carbon penetrates into the solid electrolyte. Next, a carbon layer with a uniform thickness is formed on the solid electrolyte due to the high concentration of carbon. Thereafter, cracks in the carbon layer that occurred during drying are repaired by dipping the carbon layer in the low-concentration carbon suspension again.

0010

EXAMPLE First, as shown in FIG. 1, tantalum powder is sintered to obtain tantalum pellets 1. At this time, an anode lead 2 made of, for example, a tantalum wire is implanted in the tantalum pellet 1.

After inserting the solid electrolyte creep prevention plate 3 into the anode lead 2 and forming a dielectric oxide film on the tantalum pellet 1, manganese dioxide 4 as a solid electrolyte is formed.

Next, as a first step of forming a carbon layer, the carbon is immersed in a carbon suspension having a low concentration (for example, 0.5% concentration), and the carbon is infiltrated into the manganese dioxide 4.
Pull it up and dry it at 150°C for 10 minutes. In FIG. 2, the carbon 5 that has penetrated into the manganese dioxide 4 is shown in a dot shape for convenience.

[0013] Thereafter, as a second step of forming a carbon layer, it is immersed in a high concentration (for example, 10% concentration) carbon suspension, pulled out, and dried at 150°C for 10 minutes. Thereby, as shown in FIG. 3, a carbon layer 6 of a predetermined thickness is formed.

Cracks occur in the carbon layer 6 when it is heated and dried. In order to repair this, as the third step of forming a carbon layer, a low concentration (for example, 0.5% concentration) is applied again.
immersed in carbon suspension, pulled up and heated at 150°C for 1
Dry for 0 minutes. As a result, as illustrated in FIG. 4, an outer carbon layer 7 is formed on the carbon layer 6 to repair the cracks.

Thereafter, a silver layer is formed in the same manner as in the prior art, and a cathode terminal member for external extraction is attached to the silver layer via a conductive adhesive. Further, an anode terminal member for external extraction is also welded to the anode lead.

[0016] Then, a resin exterior body is formed by a resin molding method or by dipping into a resin liquid.

[0017] Examples and comparative examples using Aquadac (trade name, manufactured by Acheson Industries, Inc., USA) as the carbon will be described below. <<Example 1>> (1) In the first step of carbon layer formation, the concentration of the carbon suspension was 0.5%, and the drying conditions were 150° C. for 10 minutes.

■ In the second step of carbon layer formation, the concentration of the carbon suspension was 10%, and the drying conditions were 150°C and 10%.
It was a minute.

■ In the third step of carbon layer formation, the concentration of the carbon suspension was again set to 0.5%, and the drying conditions were 150°C.
, 10 minutes.

Using tantalum capacitor elements with carbon layers formed in this manner, 500 tantalum solid electrolytic capacitors with a rating of 4 V and 10 μF were prototyped, and a frequency of 10
When I measured the impedance at 0kHz, it was 1.2
It was ~1.3Ω. <Comparative Example 1> The carbon layer forming step was performed in the first step of Example 1 above.
Similar to Example 1, 500 tantalum solid electrolytic capacitors with a rating of 4 V and 10 μF were manufactured using a tantalum capacitor element that was only processed, and when the impedance at a frequency of 100 kHz was measured, it was 1.5 to 10 Ω. . <<Example 2>> (1) In the first step of carbon layer formation, the concentration of the carbon suspension was 0.5%, and the drying conditions were 150° C. for 10 minutes.

(2) In the second step of carbon layer formation, the concentration of the carbon suspension was 8%, and the drying conditions were 150° C. and 10 minutes.

■ In the third step of carbon layer formation, the concentration of the carbon suspension was again set to 0.5%, and the drying conditions were 150°C.
, 10 minutes.

Using tantalum capacitor elements with carbon layers formed in this way, 500 tantalum solid electrolytic capacitors with a rating of 16 V and 1 μF were prototyped, and a frequency of 10
When I measured the impedance at 0kHz, it was 2.8.
It was ~3.5Ω. <Comparative Example 2> The carbon layer forming step was performed in the first step of Example 2 above.
Similar to Example 2, 500 tantalum solid electrolytic capacitors with a rating of 16 V and 1 μF were fabricated by using tantalum capacitor elements that were only processed, and the impedance at a frequency of 100 kHz was measured, and was found to be 3 to 18 Ω. <<Example 3>> (1) In the first step of carbon layer formation, the concentration of the carbon suspension was 0.5%, and the drying conditions were 150° C. and 10 minutes.

■ In the second step of carbon layer formation, the concentration of the carbon suspension was 15%, and the drying conditions were 150°C and 10%.
It was a minute.

■ In the third step of carbon layer formation, the concentration of the carbon suspension was again set to 0.5%, and the drying conditions were 150°C.
, 10 minutes.

[0026] The tantalum capacitor element with the carbon layer formed in this way has a rating of 34V and 0.22μF.
When we prototyped 500 tantalum solid electrolytic capacitors and measured the impedance at a frequency of 100kHz, we found that
It was 6-7Ω. <Comparative Example 3> The carbon layer forming step was performed in the first step of Example 3 above.
Similar to Example 3, using tantalum capacitor elements that only require a process, 500 tantalum solid electrolytic capacitors with a rating of 35 V and 0.22 μF were prototyped, and the frequency was 100 kHz.
When the impedance was measured, it was 15 to 35Ω. <<Example 4>> (1) In the first step of carbon layer formation, the concentration of the carbon suspension was 0.5%, and the drying conditions were 150° C. for 10 minutes.

■ In the second step of carbon layer formation, the concentration of the carbon suspension was 22%, and the drying conditions were 150°C and 10%.
It was a minute.

■ In the third step of carbon layer formation, the concentration of the carbon suspension was again set to 0.5%, and the drying conditions were 150°C.
, 10 minutes.

Using tantalum capacitor elements with carbon layers formed in this way, 500 tantalum solid electrolytic capacitors with a rating of 4 V and 100 μF were prototyped, and
When I measured the impedance at 00kHz, it was 0.
It was 4-0.5Ω. <Comparative Example 4> The carbon layer forming step was performed in the first step of Example 4 above.
Similar to Example 4, using a tantalum capacitor element that only requires a process, 500 tantalum solid electrolytic capacitors with a rating of 4 V and 100 μF were prototyped, and when the impedance at a frequency of 100 kHz was measured, it was 0.5 to 8 Ω. . <<Example 5>> (1) In the first step of carbon layer formation, the concentration of the carbon suspension was 0.5%, and the drying conditions were 150° C. for 10 minutes.

■ In the second step of carbon layer formation, the concentration of the carbon suspension was 12%, and the drying conditions were 150°C and 10%.
It was a minute.

■ In the third step of carbon layer formation, the concentration of the carbon suspension was again set to 0.5%, and the drying conditions were 150°C.
, 10 minutes.

Using tantalum capacitor elements with carbon layers formed in this way, 500 tantalum solid electrolytic capacitors with a rating of 6 V and 3.3 μF were manufactured as prototypes, and a frequency of 1
When the impedance at 00kHz was measured, 1.
It was 5-1.7Ω. <Comparative Example 5> The carbon layer forming step was performed in the first step of Example 5 above.
Similar to Example 5, 500 tantalum solid electrolytic capacitors with a rating of 6 V and 3.3 μF were prototyped using a tantalum capacitor element that was processed only, and when the impedance at a frequency of 100 kHz was measured, it was 3 to 12 Ω. .

For reference, Table 1 shows the comparison results of each of the above examples and comparative examples. Note that after the third step in each of the above embodiments, immersion in a carbon suspension having a predetermined concentration may be further performed as necessary.

[0034]

[Table 1]

[0035]

[Effects of the Invention] As explained above, according to the present invention,
To form the carbon layer, first immerse it in a low concentration carbon suspension, then immerse it in a high concentration carbon suspension,
By immersing the solid electrolytic capacitor in the low-concentration carbon suspension again, a solid electrolytic capacitor with low impedance and stable characteristics is provided.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a tantalum pellet on which a solid electrolyte is formed.

FIG. 2 is a partially enlarged sectional view of a tantalum pellet for explaining the first step of forming a carbon layer.

FIG. 3 is a partially enlarged sectional view of a tantalum pellet for explaining a second step of forming a carbon layer.

FIG. 4 is a partially enlarged sectional view of a tantalum pellet for explaining the third step of forming a carbon layer.

[Explanation of symbols]

1 Tantalum pellets 2 Anode lead 3 Solid electrolyte creep prevention plate 4 Solid electrolyte 5 Carbon 6,7 Carbon layer

Claims (1)

[Claims] Claim 1: Solid electrolysis in which a dielectric oxide film is formed on a sintered pellet of valve action metal powder, a solid electrolyte is formed, and a carbon layer and a silver layer are sequentially formed on the solid electrolyte to form a cathode layer. In the capacitor manufacturing method, when forming the carbon layer, the sintered pellets are first immersed in a low concentration carbon suspension and dried, and then immersed in a high concentration carbon suspension and dried. A method for manufacturing a solid electrolytic capacitor, which is characterized in that the capacitor is then dipped in a low-concentration carbon suspension again and dried.