JP2008244400A - Method for manufacturing solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the leakage current characteristic of a solid electrolytic capacitor by improving the adhesiveness of a dielectric film and a solid electrolytic layer. <P>SOLUTION: A method for manufacturing the solid electrolytic capacitor has a process of forming a dielectric film on the surface of an anode body; a process of forming the solid electrolytic layer on the dielectric film; and a process of performing surface treatment to the anode body in which the dielectric film is formed arranged between the process of forming the dielectric film and the process of forming the solid electrolytic layer, wherein the surface treatment has a step of radiating ultraviolet rays. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a solid electrolytic capacitor using a conductive polymer as a solid electrolyte.

In recent years, with the miniaturization and weight reduction of electronic components, a small-sized and high-capacity high-frequency capacitor has been demanded. As such a capacitor, a solid electrolyte in which a solid electrolyte layer is formed using a conductive polymer compound. Capacitors have been proposed.

  In the solid electrolytic capacitor, a dielectric film which is an inorganic layer formed by oxidizing the surface of an anode body formed of a sintered body of a valve action metal such as tantalum, niobium, titanium or aluminum, and the dielectric Increased leakage current due to reduced adhesion to the solid electrolyte layer, which is an organic material layer (conductive polymer layer) formed into a film, and reliability due to increased ESR (Equivalent Series Resistance) There is a problem of decline.

  For this reason, when a conductive polymer compound is formed on a dielectric film, generally a conductive precoat layer is formed in advance, and then the entire surface of the dielectric film is coated by electrolytic oxidation polymerization. Forming a polymer compound has been performed. However, even when the conductive polymer is formed by such a method, the adhesion between the dielectric film and the solid electrolyte layer (conductive polymer layer) is not sufficient.

In order to solve the above problems, a method of performing surface treatment using a silane coupling agent after forming a dielectric film (for example, Patent Document 1), a method of mixing a silane coupling agent in a polymerization solution (for example, Patent Document 2), etc. Thus, it has been proposed to improve the adhesion between the dielectric film and the solid electrolyte layer.
Japanese Patent Laid-Open No. 02-74021 JP 11-329900 A

  However, in the above method, the number of hydroxyl groups on the dielectric film is limited, and it is difficult to say that the adhesion between the dielectric film and the solid electrolyte layer is sufficiently improved. In particular, when no hydroxyl group is formed in the defect part of the dielectric film, the silane coupling agent is not attached, so the adhesion strength of the conductive polymer to the defect part is weak and easy to peel off. There has been a problem of increasing the leakage current.

  In view of the above problems, the present invention provides a method for producing a solid electrolytic capacitor comprising a step of forming a dielectric film on the surface of an anode body and a step of forming a solid electrolyte layer on the dielectric film. Between the step of forming a film and the step of forming the solid electrolyte layer includes a step of performing a surface treatment on the anode body on which the dielectric film is formed, and the step of performing the surface treatment includes And a step of irradiating with ultraviolet rays.

  The step of performing the surface treatment includes a step of irradiating with ultraviolet rays and a step of surface treatment with a silane coupling agent.

  The present invention also provides a solid electrolytic capacitor comprising a step of forming a dielectric film on the surface of the anode foil, and a step of winding the anode foil and the cathode foil on which the dielectric film is formed via a separator. In the manufacturing method, between the step of forming a dielectric film on the surface of the anode foil and the step of winding, there is a step of surface-treating the anode foil on which the dielectric is formed, and the surface treatment The process includes the step of irradiating with ultraviolet rays.

  By irradiating the dielectric film with ultraviolet rays, the bond between water vapor and / or oxygen on the dielectric film and in the air is cut, and a large number of hydroxyl groups are formed on the surface of the dielectric film, so there is more silane coupling agent. It adheres and the adhesiveness with a solid electrolyte layer can be improved. As a result, the adhesion strength of the conductive polymer is improved even in the defective portion of the dielectric film, and repair by aging is possible, so that the leakage current characteristic of the manufactured solid electrolytic capacitor is improved.

Embodiments of the present invention will be described.
(Embodiment 1)
A dielectric film is formed on the peripheral surface of the anode body made of the valve metal in which the anode lead is implanted. Here, the anode lead is preferably made of a valve metal and is made of the same material as the anode body.

  The dielectric film is formed by a known method. That is, a dielectric film is formed on the surface of the anode body by applying a voltage to an acid aqueous solution such as phosphoric acid to perform electrolytic oxidation.

Next, the anode body on which the dielectric film is formed is irradiated with ultraviolet rays. Irradiation with ultraviolet rays breaks the bond between the anode body and water vapor or oxygen contained in the air, and as a result, hydroxyl groups adhere to the surface of the dielectric film. The hydroxyl group can also adhere to the dielectric film defect portion.
After UV irradiation, silane coupling agent treatment is performed. Specifically, the anode body is immersed in a silane coupling agent solution, or the silane coupling agent solution is applied to the surface of the dielectric film. Conventionally known silane coupling agents can be used. The silane coupling agent solution preferably contains water as a solvent. The silane coupling agent has a hydroxyl group at the terminal by hydrolysis. The hydroxyl group is hydrogen bonded to the hydroxyl group protruding on the surface of the dielectric film. Thereafter, heat treatment is performed, and the hydroxyl group adhering to the surface of the dielectric film and the hydroxyl group of the silane coupling agent are dehydrated and condensed so that the dielectric film and the silane coupling agent are in close contact with each other.
After performing the surface treatment as described above, a solid electrolyte layer is formed on the surface of the dielectric film. The solid electrolyte layer is made of a conductive polymer. Specifically, the conductive polymer means a conductive polymer among polymers obtained by polymerizing a heterocyclic compound such as pyrrole or thiophene, an aromatic compound such as aniline, and derivatives thereof. The method for forming the solid electrolyte layer may be arbitrarily selected from conventionally known methods such as chemical oxidative polymerization and / or electrolytic oxidative polymerization.

  Since the dielectric film to which the silane coupling agent is attached has an organic functional group on the surface, the adhesion with the organic matter is improved. Since the solid electrolyte layer formed by the above-mentioned method is an organic substance, the dielectric film and the solid electrolyte layer can be firmly adhered via a silane coupling agent.

A cathode lead layer is formed on the solid electrolyte layer formed as described above to produce a capacitor element. Further, the anode lead of the capacitor element is connected to an anode lead frame, a part of the cathode lead layer is connected to the cathode lead frame, and the capacitor element is covered with an exterior resin to produce a solid electrolytic capacitor.
(Embodiment 2)
A dielectric film is formed on the surface of the anode foil made of aluminum foil or the like. The dielectric film is formed by immersing the anode foil in an acid aqueous solution and applying a voltage. Next, the anode foil on which the dielectric film is formed is irradiated with ultraviolet rays. By irradiating with ultraviolet rays, water vapor and oxygen in the dielectric film and in the air are decomposed, and hydroxyl groups adhere to the surface of the dielectric film formed on the surface of the anode foil. In addition, the hydroxyl group can be attached to a defect portion of the dielectric film.

Next, treatment with a silane coupling agent solution is performed. Specifically, a silane coupling agent solution is applied to the anode foil. The said silane coupling agent can be used arbitrarily from well-known things. Moreover, it is preferable that the solvent of the said solution contains water. The silane coupling agent is hydrolyzed in a solution containing water and has a hydroxyl group at the terminal group. Then, by performing heat treatment, the hydroxyl group on the surface of the dielectric film and the hydroxyl group of the silane coupling agent are dehydrated and condensed, and the dielectric film and the silane coupling agent adhere.
A cathode foil made of the anode foil and aluminum foil on which the dielectric film is formed is wound through a separator to produce a capacitor element.

  A solid electrolyte containing a conductive polymer is formed on the capacitor element. The solid electrolyte is formed by a well-known method. That is, it is formed by immersing the capacitor element in a solution containing at least a monomer and an oxidizing agent. The solid electrolyte layer and the dielectric film to which the silane coupling agent is adhered are fixed as in the first embodiment. Therefore, the dielectric film and the solid electrolyte are in close contact via the silane coupling agent.

The capacitor element on which the solid electrolyte is formed as described above is housed in an aluminum case and sealed and processed to complete a solid electrolytic capacitor.
The above embodiments are merely for explaining the present invention, and should not be construed as limiting the invention described in the claims. The present invention can be freely modified within the scope of the claims and the scope of equivalent meanings. For example, in Embodiment 1, the anode lead and the anode lead frame may be connected via a conductive member.

Claims (5)

In a method for producing a solid electrolytic capacitor comprising a step of forming a dielectric film on the surface of an anode body, and a step of forming a solid electrolyte layer on the dielectric film,
A solid electrolytic capacitor comprising a step of performing a surface treatment including a step of irradiating the surface of the dielectric coating with ultraviolet light between the step of forming the dielectric coating and the step of forming the solid electrolyte layer. Manufacturing method.   The step of performing the surface treatment includes a step of irradiating the surface of the dielectric film formed on the surface of the anode body with ultraviolet light, and a step of applying a silane coupling agent solution to the surface of the dielectric film or silane coupling. The method for producing a solid electrolytic capacitor according to claim 1, further comprising a step of immersing the anode body having the dielectric film formed on the surface thereof in an agent solution. In a method for producing a solid electrolytic capacitor comprising a step of forming a dielectric film on the surface of the anode foil, and a step of winding the anode foil and the cathode foil on which the dielectric film is formed via a separator,
Solid electrolytic process comprising a step of performing a surface treatment on the anode foil including a step of irradiating ultraviolet rays between the step of forming a dielectric film on the surface of the anode foil and the step of winding. Capacitor manufacturing method.   The step of performing the surface treatment on the anode foil includes the steps of irradiating the anode foil on which the dielectric film is formed with ultraviolet irradiation and the step of applying a silane coupling agent solution to the anode foil or the silane coupling agent solution. The method for manufacturing a solid electrolytic capacitor according to claim 3, further comprising a step of immersing the anode foil. A solid electrolytic capacitor produced by the production method according to claim 1.