JPH05144685A - Electrolytic capacitor - Google Patents

Abstract

PURPOSE:To protect solid electrolyte from mechanical stress caused by the contraction of a resin sheath body, in a chip type solid electrolytic capacitor. CONSTITUTION:In a capacitor element, solid electrolyte 4 composed of manganese dioxide is formed on a sintered pellet 1 of valve action metal powder, and a carbon layer 5 and a silver layer 6 are formed in order around the solid electrolyte 4. In the solid electrolyte capacitor having the above element, the carbon layer 5 has a thickness of 0.1-0.3mm.

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 having good impedance characteristics.

[0002]

2. Description of the Related Art In FIG. 1, a capacitor element made of tantalum is shown with a part thereof in cross section. The manufacturing process will be described with reference to the figure. First, a suitable binder is mixed with tantalum powder to form, for example, a cylindrical shape, and the anode lead 2 is planted in the cylindrical body and then sintered. To obtain a sintered pellet 1 of tantalum.

After forming an oxide film as a dielectric on the sintered pellet 1, a solid electrolyte 4 is formed around the sintered pellet.

The solid electrolyte 4 is manganese dioxide (Mn
O ₂ ), the anode lead 2 will be described.
After inserting the solid electrolyte creeping-up prevention plate 3 into the above, the sintered pellet 1 is immersed in a manganese nitrate aqueous solution to be impregnated with manganese nitrate, and then pulled up for thermal decomposition. The concentration of the manganese nitrate aqueous solution is gradually increased and this is repeated several times. Further, the re-formation process is repeated several times for the purpose of repairing the oxide film damaged by the thermal decomposition process.

Thereafter, the sintered pellet 1 is immersed in a carbon liquid, pulled up and baked at about 150 ° C. to form a carbon layer 5 on the solid electrolyte. Then, the silver layer 6 is formed on the carbon layer 5.

The capacitor element is manufactured in this manner. When this is a chip type, a lead frame is prepared, the anode lead 2 of the capacitor element is welded to the anode terminal plate of the frame, and the silver layer is formed. 6 is attached to the cathode terminal plate of the same frame via a conductive adhesive (for example, adhesive silver), and then placed in a molding die to form a resin exterior body around the capacitor element by a resin molding method. .

[0007]

By the way, in the above-mentioned conventional example, the thickness of the carbon layer 5 is about 0.01 to 0.03.
mm, and the thickness of the silver layer 6 is about 0.01 to 0.05 mm.

For this reason, the stress due to the shrinkage of the resin sheathing produced after the molding is directly applied to the solid electrolyte 4, which causes the solid electrolyte 4 to be destroyed.
Impedance was occurring frequently.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances, and its structural feature is that a solid electrolyte made of manganese dioxide is formed on a sintered pellet of valve action metal powder. In the solid electrolytic capacitor having a capacitor element in which a carbon layer and a silver layer are sequentially formed around the solid electrolyte, the carbon layer is formed to have a thickness of 0.1 to 0.3 mm.

If the thickness of the carbon layer is 0.1 mm or less, the effect as a buffer layer cannot be expected so much, while on the other hand,
It is not preferable to set the thickness to 0.3 mm or more because peeling may occur due to a decrease in adhesion of the carbon layer.

[0011]

Since the carbon layer is about 10 times thicker than the conventional one, the stress due to the contraction of the resin outer package is buffered by the carbon layer, and the solid electrolyte is prevented from being broken.

[0012]

Example 1 A dielectric oxide film was formed on a sintered pellet of tantalum powder, and then manganese dioxide as a solid electrolyte was formed in the same manner as in the prior art. Next, using Aqua Duck (trade name) manufactured by Nippon Acheson Co., Ltd. as carbon, the sintered pellets were immersed in a 1 wt% suspension thereof, pulled up and heated at 150 ° C. for 15 minutes to bake the carbon layer. . At this time, the thickness of the carbon layer is 0.10.
It was mm. After that, a silver layer is formed in the same manner as the conventional method, and the rated voltage is 4V10 according to the conventional assembly process.
1000 μF chip type tantalum solid electrolytic capacitor
As a result of trial production, the impedance (| Z |) defect rate was 1.0% and the leakage current (LC) defect rate was 2.7%. The yield was 96.3%.

Example 2 After forming a dielectric oxide film on a sintered pellet of tantalum powder, manganese dioxide as a solid electrolyte was formed in the same manner as in the conventional method. Next, using Aqua Duck (trade name) manufactured by Nippon Acheson Co., Ltd. as carbon, immersing the sintered pellets in the 3 wt% suspension,
The carbon layer was baked by pulling up and heating at 150 ° C. for 15 minutes. At this time, the thickness of the carbon layer is 0.1
It was 3 mm. After that, a silver layer is formed in the same manner as the conventional method, and the rated voltage is 4V1 according to the conventional assembly process.
100 μF of 0 μF chip type tantalum solid electrolytic capacitor
When 0 prototypes were manufactured, the impedance (| Z |) defect rate was 0.9% and the leakage current (LC) defect rate was 1.9%. The yield was 97.2%.

Example 3 A dielectric oxide film was formed on a sintered pellet of tantalum powder, and then manganese dioxide as a solid electrolyte was formed in the same manner as in the prior art. Next, by using Aqua Duck (trade name) manufactured by Nippon Acheson Co., Ltd. as carbon, the sintered pellets are immersed in a 5 wt% suspension thereof,
The carbon layer was baked by pulling up and heating at 150 ° C. for 15 minutes. At this time, the thickness of the carbon layer is 0.1
It was 6 mm. After that, a silver layer is formed in the same manner as the conventional method, and the rated voltage is 4V1 according to the conventional assembly process.
100 μF of 0 μF chip type tantalum solid electrolytic capacitor
When 0 prototypes were manufactured, the impedance (| Z |) defect rate was 0.6% and the leakage current (LC) defect rate was 1.8%. The yield was 97.6%.

Example 4 A dielectric oxide film was formed on a sintered pellet of tantalum powder, and then manganese dioxide as a solid electrolyte was formed in the same manner as in the prior art. Next, using Aqua Duck (trade name) manufactured by Nippon Acheson Co., Ltd. as carbon, the sintered pellets were immersed in a 10 wt% suspension of the carbon, pulled up and heated at 150 ° C. for 15 minutes to bake the carbon layer. .. At this time, the thickness of the carbon layer was 0.20 mm. After that, a silver layer was formed in the same manner as the conventional method, and 1000 chip tantalum solid electrolytic capacitors with a rating of 4V and 10 μF were prototyped according to the conventional assembly process, and the impedance (| Z
|) The defective rate was 0.5% and the leakage current (LC) defective rate was 1.8%. The yield was 97.7%.

Comparative Example 1 After forming a dielectric oxide film on a sintered pellet of tantalum powder, manganese dioxide as a solid electrolyte was formed in a conventional manner. Next, using Aqua Duck (trade name) manufactured by Nippon Acheson Co., Ltd. as the carbon, the sintered pellets are immersed in a 0.5 wt% suspension of the carbon, pulled up and heated at 150 ° C. for 15 minutes to bake the carbon layer. I did. At this time, the thickness of the carbon layer was 0.05 mm. After that, a silver layer was formed in the same manner as the conventional method, and 1000 chip tantalum solid electrolytic capacitors with a rating of 4V and 10 μF were prototyped according to the conventional assembly process, and the impedance (| Z
|) The defective rate was 1.2% and the leakage current (LC) defective rate was 3.1%. The yield was 95.7%.

Example 5 A dielectric oxide film was formed on a sintered pellet of tantalum powder, and then manganese dioxide as a solid electrolyte was formed in the same manner as in the prior art. Next, using T-602 (trade name) manufactured by Nippon Graphite Co., Ltd. as carbon,
The sintered pellet was immersed in the 50 wt% suspension, pulled up and heated at 190 ° C. for 15 minutes to bake the carbon layer. The thickness of the carbon layer at this time is 0.15 m
It was m. After that, a silver layer is formed in the same manner as the conventional method, and the rated voltage is 4V10 according to the conventional assembly process.
1000 μF chip type tantalum solid electrolytic capacitor
As a result of trial production, the impedance (| Z |) defect rate was 0.7%, and the leakage current (LC) defect rate was 2.7%. The yield was 96.6%.

Example 6 After forming a dielectric oxide film on a sintered pellet of tantalum powder, manganese dioxide as a solid electrolyte was formed in the same manner as in the conventional method. Next, using T-602 (trade name) manufactured by Nippon Graphite Co., Ltd. as carbon,
The sintered pellet was immersed in the 50 wt% suspension, pulled up and heated at 190 ° C. for 15 minutes to bake the carbon layer. Again, the carbon layer was immersed in the same 50 wt% suspension of carbon, pulled up and heated at 190 ° C. for 15 minutes to bake the carbon layer. At this time, the thickness of the carbon layer was 0.23 mm. After that, a silver layer is formed in the same manner as the conventional method, and further according to the conventional assembly process,
When 1000 chip tantalum solid electrolytic capacitors with a rating of 4V and 10μF were prototyped, their impedance (|
The Z |) defect rate was 0.5%, and the leakage current (LC) defect rate was 2.1%. The yield was 97.4%.

Example 7 A dielectric oxide film was formed on a sintered pellet of tantalum powder, and then manganese dioxide as a solid electrolyte was formed in the same manner as in the prior art. Next, using T-602 (trade name) manufactured by Nippon Graphite Co., Ltd. as carbon,
The sintered pellet was immersed in the 100 wt% suspension, pulled up and heated at 190 ° C. for 15 minutes to bake the carbon layer. The thickness of the carbon layer at this time is 0.3 m
It was m. After that, a silver layer is formed in the same manner as the conventional method, and the rated voltage is 4V10 according to the conventional assembly process.
1000 μF chip type tantalum solid electrolytic capacitor
As a result of trial production, the impedance (| Z |) defect rate was 0.6% and the leakage current (LC) defect rate was 2.0%. The yield was 97.4%.

Comparative Example 2 After forming a dielectric oxide film on a sintered pellet of tantalum powder, manganese dioxide as a solid electrolyte was formed in the same manner as in the prior art. Next, using T-602 (trade name) manufactured by Nippon Graphite Co., Ltd. as carbon,
The sintered pellet was immersed in the 30 wt% suspension, pulled up and heated at 190 ° C. for 15 minutes to bake the carbon layer. The thickness of the carbon layer at this time is 0.07 m
It was m. After that, a silver layer is formed in the same manner as the conventional method, and the rated voltage is 4V10 according to the conventional assembly process.
1000 μF chip type tantalum solid electrolytic capacitor
As a result of trial production, the impedance (| Z |) defect rate was 0.8% and the leakage current (LC) defect rate was 2.8%. The yield was 96.4%. In order to facilitate the comparison, the characteristic defective rate and the yield of Examples 1 to 7 and Comparative Examples 1 and 2 are shown in Table 1. As can be seen from this table, according to the present invention, the characteristic defective rate and the yield are shown. The stay is greatly improved.

[0021]

[Table 1]

[0022]

As described above, according to the present invention,
By setting the thickness of the carbon layer to 0.1 to 0.3 mm, the mechanical stress due to the shrinkage of the resin outer package is buffered by the carbon layer, so that the solid electrolyte is prevented from being broken and the characteristic defect rate is reduced. Can be reduced.

[Brief description of drawings]

FIG. 1 is a front view showing a part of the capacitor element in section for explaining a configuration of a capacitor element.

[Explanation of symbols]

 1 Sintered Pellets 2 Anode Leads 3 Solid Electrolyte Crawling Prevention Plate 4 Solid Electrolyte 5 Carbon Layer 6 Silver Layer

Claims (1)

[Claims] 1. A solid electrolytic capacitor having a capacitor element in which a solid electrolyte made of manganese dioxide is formed on a sintered pellet of valve metal powder, and a carbon layer and a silver layer are sequentially formed around the solid electrolyte. A solid electrolytic capacitor, wherein the carbon layer is formed with a thickness of 0.1 to 0.3 mm.