US-20260128237-A1 - SOLID ELECTROLYTIC CAPACITOR

Abstract

A solid electrolytic capacitor with both low ESR and high withstand voltage is provided. The solid electrolytic capacitor includes a capacitor element having anode foil, a cathode body, and an electrolyte. A surface of the anode foil is enlarged by tunnel-shaped etching pits and has dielectric film. The cathode body faces the anode foil. The electrolyte includes a solid electrolyte layer containing a conductive polymer. A weight of the conductive polymer is 11 mg/cm 3 or less per unit volume of the capacitor element.

Inventors

• Kenta Sato
• Kenji Machida
• Katsumi MOGAKI
• Kyohei YOSHIOKA

Assignees

• NIPPON CHEMI-CON CORPORATION

Dates

Publication Date

20260507

Application Date

20230814

Priority Date

20220929

Claims (13)

1. 1 . A solid electrolytic capacitor comprising a capacitor element having anode foil, cathode body, and an electrolyte, wherein: a surface of the anode foil is enlarged by tunnel-shaped etching pits and has dielectric film, the cathode body faces the anode foil, the electrolyte includes a solid electrolyte layer containing a conductive polymer, and a weight of the conductive polymer is 11 mg/cm 3 or less per unit volume of the capacitor element.
2. 2 . The solid electrolytic capacitor according to claim 1 , wherein the weight of the conductive polymer is 2 mg/cm 3 to 11 mg/cm 3 per unit volume of the capacitor element.
3. 3 . The solid electrolytic capacitor according to claim 1 , wherein the weight of the conductive polymer is 6.2 mg/cm 3 to 9.0 mg/cm 3 per unit volume of the capacitor element.
4. 4 . The solid electrolytic capacitor according to claim 1 , comprising a liquid component filled in voids of the capacitor element.
5. 5 . The solid electrolytic capacitor according to claim 1 , wherein the solid electrolyte layer is formed by containing a part or all of the conductive polymers and a solvent in conductive polymer solution in which the conductive polymer is dispersed or dissolved.
6. 6 . The solid electrolytic capacitor according to claim 5 , wherein the solid electrolyte layer includes a compound with a hydroxy group.
7. 7 . The solid electrolytic capacitor according to claim 3 , comprising a liquid component filled in voids of the capacitor element.
8. 8 . The solid electrolytic capacitor according to claim 7 , wherein the solid electrolyte layer is formed by containing a part or all of the conductive polymer and a solvent in conductive polymer solution in which the conductive polymer is dispersed or dissolved.
9. 9 . The solid electrolytic capacitor according to claim 8 , wherein the solid electrolyte layer includes a compound with a hydroxy group.
10. 10 . The solid electrolytic capacitor according to claim 3 , wherein the solid electrolyte layer is formed by containing a part or all of the conductive polymer and a solvent in conductive polymer solution in which the conductive polymer is dispersed or dissolved.
11. 11 . The solid electrolytic capacitor according to claim 10 , wherein the solid electrolyte layer includes a compound with a hydroxy group.
12. 12 . A manufacturing method of a solid electrolytic capacitor, comprising: an anode foil formation process of enlarging a surface of anode foil by tunnel-shaped etching pits and forming dielectric film on the surface of the anode foil; an element formation process of forming a capacitor element by making the anode foil and a cathode body to face each other; and a solid electrolyte formation process of forming a solid electrolyte layer containing a conductive polymer in the capacitor element in a ratio of 11 mg/cm 3 or less per unit volume of the capacitor element.
13. 13 . The manufacturing method of the solid electrolytic capacitor according to claim 12 , comprising a filling process of filling a liquid component in voids of the capacitor element.

Description

FIELD OF INVENTION The present disclosure relates to a solid electrolytic capacitor in which an electrolyte is a solid electrolyte layer or a solid electrolyte layer and a liquid component. BACKGROUND Electrolytic capacitors include valve action metal, such as tantalum or aluminum, as anode foil and cathode foil. A surface of the anode foil is enlarged by making the valve action metal into a sintered body or a shape such as etching foil, and the enlarged surface has dielectric film by a process such as anode oxidation. An electrolyte intervenes between the anode foil and the cathode foil. The specific surface area of this electrolytic capacitor can be enlarged by enlarging the surface of the anode foil, which is advantageous to achieve the capacitance larger than other types of capacitors. Furthermore, the electrolytic capacitor includes the electrolyte in a state of electrolytic solution. An area of the dielectric film of the anode foil that contacts the electrolytic solution increases. Therefore, the capacitance of the electrolytic capacitor can be further increased easily. However, the electrolytic solution evaporates and volatilizes to the outside over time, and the capacitance of the electrolytic capacitor decreases and the dissipation factor of the electrolytic capacitor increases over time, and the electrolytic capacitor dries up. Accordingly, a solid electrolytic capacitor using a solid electrolyte is getting attention among the electrolytic capacitors. Manganese dioxide and 7,7,8,8-tetracyanoquinodimethane (TCNQ) complex are known as a solid electrolyte. In recent years, the conductive polymer derived from monomers having π-conjugated double bonds, such as poly(3,4-ethylenedioxythiophene) (PEDOT) with slow reaction speed and excellent adhesion to the dielectric film, are rapidly becoming popular. The conductive polymer has acid compounds such as polyanions are used as a dopant or have a substructure that acts as a dopant in the monomer molecule, exhibiting high conductivity. Therefore, the solid electrolytic capacitor is advantageous in that the equivalent series resistance (ESR) is low. The solid electrolytic capacitor is less effective in repairing defects in the oxide film of the anode that is a dielectric than a liquid-type electrolytic capacitor in which a capacitor element is impregnated with electrolytic solution, and the leakage current may be increased. Therefore, a so-called hybrid-type solid electrolytic capacitor in which a solid electrolyte layer is formed on a capacitor element formed by facing the anode foil and the cathode foil via a separator, and voids of the capacitor element are impregnated with electrolytic solution for driving is proposed. PRIOR ART DOCUMENT Patent Document Patent Document 1: JP2008-109068APatent Document 2: JP4536625B SUMMARY OF INVENTION Problems to be Solved by Invention Capacitors are used in various application. For example, in the field of power electronics, a power supply circuit, which converts AC power into DC power by a converter circuit and converts said DC power into desired AC power by an inverter circuit, is provided with a smoothing capacitor to suppress pulsation of DC output from the converter circuit, smooth the suppressed DC, and then input the smoothed DC to the inverter circuit. Furthermore, for the stable operation and noise removal of a semi-conductor switching element such as gallium nitride, a decoupling capacitor is provided near said semi-conductor switching element. Along with higher power demand in recent years, higher withstand voltage is required for the solid electrolytic capacitor. For example, in the field such as power electronics, a capacitor with high withstand voltage of at least above 200 V is expected. However, it is not easy to maintain low ESR, which is the advantage of the solid electrolytic capacitor, while achieving high withstand voltage. The present disclosure is proposed to address the above problems, and the objective to provide a solid electrolytic capacitor with both low ESR and high withstand voltage. Means to Solve the Problem To address the above problem, a solid electrolytic capacitor of the present embodiment includes: a capacitor element having anode foil, cathode body, and an electrolyte, in which a surface of the anode foil is enlarged by tunnel-shaped etching pits and has dielectric film, the cathode body faces the anode foil, the electrolyte includes a solid electrolyte layer containing a conductive polymer, and a weight of the conductive polymer is 11 mg/cm3 or less per unit volume of the capacitor element. The weight of the conductive polymer may be 2 mg/cm3 to 11 mg/cm3 per unit volume of the capacitor element. The weight of the conductive polymer may be 6.2 mg/cm3 to 9.0 mg/cm3 per unit volume of the capacitor element. The solid electrolytic capacitor may include a liquid component filled in voids of the capacitor element. The solid electrolyte layer may be formed by containing a part or all of t