Electrolytic capacitor having reduced equivalent series resistance (ESR) and production method for same

A method for producing an electrolytic capacitor comprising:

• a first step of preparing an electrode foil;
• a second step of obtaining a lead member that includes a lead wire and a plate-shaped tab portion that is provided at one end portion of the lead wire and has a surface with an arithmetic average roughness Ra of 4 μm or more;
• and
• a third step of placing the electrode foil on a surface of the tab portion to form an overlapping portion in which the tab portion and the electrode foil overlap each other, perforating the tab portion in the overlapping portion at a predetermined position, and crimping the electrode foil and the tab portion to connect the electrode foil and the lead member to each other,
• wherein in the first step, the electrode foil that includes a metal foil that includes a porous portion in a surface thereof and a dielectric layer that covers the porous portion is prepared as an anode foil, and
• in the second step, the lead member is obtained as an anode lead member,
• the method further including:
• a step of cutting the anode foil into a predetermined size prior to the third step;
• and
• a step of subjecting an end face of the anode foil cut into the predetermined size to a first chemical conversion treatment at a first chemical conversion voltage after the third step,
• wherein, in the second step, the surface of the tab portion is subjected to a second chemical conversion treatment at a second chemical conversion voltage, and
• the second chemical conversion voltage is larger than the first chemical conversion voltage.

A method for producing an electrolytic capacitor comprising:

• a first step of preparing an electrode foil;
• a second step of obtaining a lead member that includes a lead wire and a plate-shaped tab portion that is provided at one end portion of the lead wire and has a surface with an arithmetic average roughness Ra of 4 μm or more;
• and
• a third step of placing the electrode foil on a surface of the tab portion to form an overlapping portion in which the tab portion and the electrode foil overlap each other, perforating the tab portion in the overlapping portion at a predetermined position, and crimping the electrode foil and the tab portion to connect the electrode foil and the lead member to each other,
• wherein in the first step, the electrode foil that includes a metal foil that includes a porous portion in a surface thereof and a dielectric layer that covers the porous portion is prepared as an anode foil, and
• in the second step, the lead member is obtained as an anode lead member,
• the method further including:
• a step of cutting the anode foil into a predetermined size prior to the third step;
• and
• a step of subjecting an end face of the anode foil cut into the predetermined size to a first chemical conversion treatment at a first chemical conversion voltage after the third step,
• wherein, in the second step, the surface of the tab portion is subjected to a second chemical conversion treatment at a second chemical conversion voltage,
• a first oxide coating film that covers the end face of the anode foil is formed through the first chemical conversion treatment,
• a second oxide coating film that covers the surface of the tab portion is formed through the second chemical conversion treatment, and
• the second oxide coating film is thicker than the first oxide coating film.