Provided is a solid electrolytic capacitor having large capacitance, low ESR, and superior high-frequency characteristics and high-temperature endurance. The solid electrolytic capacitor is provided with: a cathode 10 having a cathode substrate 11 made of a valve metal and having an etching pit 11a; an oxide layer 12 made of an oxide of the valve metal provided on a surface of the cathode substrate 11, and a carbon coating layer 13 provided on a surface of the oxide layer 12, the carbon coating layer 13 including carbon particles and having an entry area 13a that enters the etching pit 11a and a penetration area 13b that penetrates through the oxide layer 12 and conducts with the cathode substrate 11; an anode having an anode substrate made of a valve metal, and a dielectric layer provided on a surface of the anode substrate and made of an oxide of the valve metal that composes the anode substrate; and a solid electrolyte layer including a conductive polymer provided between the carbon coating layer of the cathode and the dielectric layer of the anode.

An electrolytic capacitor includes a capacitor element, a liquid component, a case housing the capacitor element and the liquid component, and a sealing member sealing the case. the capacitor element includes a porous sintered body including a dielectric layer, a cathode foil facing at least a part of the porous sintered body, and a conductive polymer covering at least a part of a surface of the dielectric layer. The conductive polymer is in contact with the cathode foil. And a void in the capacitor element is impregnated with the liquid component.

A capacitor element includes an anode body, a dielectric layer disposed on a surface of the anode body, a solid electrolyte layer covering at least a part of the dielectric layer, and a cathode lead-out layer covering at least a part of the solid electrolyte layer. An insulating member is disposed from an outermost surface of the cathode lead-out layer to a depth of more than or equal to 0.001 μm.

An electrolytic capacitor including a capacitor element. The capacitor element includes an anode body, a dielectric layer covering at least a part of the anode body, a solid electrolyte layer covering at least a part of the dielectric layer, and a cathode lead-out layer covering at least a part of the solid electrolyte layer. The cathode lead-out layer includes a conductive layer. An oxygen permeability of the conductive layer at a thickness of 10 μm is less than or equal to 7 cc/m.sup.2.Math.day.Math.atm.

A disclosed capacitor element includes: a first electrode; a dielectric layer covering at least a portion of the first electrode; and a second electrode covering at least a portion of the dielectric layer. The second electrode includes a solid electrolyte layer, a conductive carbon layer covering at least a portion of the solid electrolyte layer, and a metal paste layer covering at least a portion of the carbon layer. The carbon layer includes flake carbon particles and spherical carbon particles. A particle diameter of the spherical carbon particles is less than an average major diameter of the flake carbon particles, or greater than or equal to the average major diameter of the flake carbon particles.

An electrode foil for an electrolytic capacitor includes: an anode body that includes a core part and a porous part disposed on a surface of the core part, and contains a first metal; a first dielectric layer that covers at least a part of the porous part; and a second dielectric layer that covers at least a part of the first dielectric layer. The second dielectric layer contains an oxide of a second metal. The first dielectric layer includes a first part having a thickness T.sub.1 and a second part having a thickness T.sub.2 smaller than the thickness T.sub.1.

An electrode foil for an electrolytic capacitor includes: an anode body that includes a core part and a porous part disposed on a surface of the core part, and contains a first metal; a first dielectric layer that covers at least a part of the porous part; and a second dielectric layer that covers at least a part of the first dielectric layer. The second dielectric layer contains an oxide of a second metal. The first dielectric layer includes a first part having a thickness T.sub.1 and a second part having a thickness T.sub.2 smaller than the thickness T.sub.1.

A chemical etch is performed on a sheet of material. An electrochemical etch is performed on the sheet of material after the chemical etch is performed on the sheet of material. A capacitor is fabricated such that an electrode included in the capacitor includes material from the sheet of material after the electrochemical etch was performed on the sheet of material. In some instances, the chemical etch included at least partially immersing the sheet of material in an etch bath that includes molybdenum. Additionally or alternately, the chemical etch can be performed for a period of time less than 60 s.

A chemical etch is performed on a sheet of material. An electrochemical etch is performed on the sheet of material after the chemical etch is performed on the sheet of material. A capacitor is fabricated such that an electrode included in the capacitor includes material from the sheet of material after the electrochemical etch was performed on the sheet of material. In some instances, the chemical etch included at least partially immersing the sheet of material in an etch bath that includes molybdenum. Additionally or alternately, the chemical etch can be performed for a period of time less than 60 s.

An electrolytic capacitor includes a capacitor element, an exterior body , a first external electrode, and a second external electrode. The capacitor element includes an anode body that is electrically connected to the first external electrode and has a porous part on a surface thereof, a dielectric layer that is disposed on a surface of at least a part of the porous part, and a solid electrolyte layer that covers at least a part of the dielectric layer, and is electrically connected to the second external electrode. The exterior body has a first principal surface, a second principal surface intersecting the first principal surface, a third principal surface opposite to the first principal surface, and a fourth principal surface opposite to the second principal surface. The first external electrode and the second external electrode are disposed along the first principal surface of the exterior body to be separated from each other.