JPH03132011A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve high-frequency characteristics of a solid electrolytic capacitor by a method wherein polythiophene precursor is melted and applied to a dielectric oxide film layer and polymerized by oxidizing agent to form a conductive polymer layer whose main component is polythiophene. CONSTITUTION:Thiophene is treated with Lewis acid such as AlCl3 to obtain polythiophene precursor which is thiophene oligomer having a nonconjugate part on a part of its skeleton. A valve action metal is immersed into the molten precursor to form a coating on a dielectric oxide film. The valve action metal is made of Al, Ta, Ti, etc., or alloy having such metal as substrate. The adhering film is polymerized by oxidizing agent. If I or the like is added at that time, the conductivity of the coating is improved, and high-frequency characteristics of a solid capacitor are improved. A carbon paste cathode layer is provided on the obtained semiconductor layer and sealed to complete a product. With this constitution, oxidative polymerization can be completed within a short time and, further, a sufficient capacitance can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a method for manufacturing a solid electrolytic capacitor with good high frequency performance.

[Prior Art] A solid electrolytic capacitor has a structure in which a semiconductor layer is attached to a valve metal such as aluminum, tantalum, or niobium, which has a dielectric acid film layer on its surface. In addition, the shape of the valve metal has a complicated shape in order to increase the surface area.

Conventionally, manganese dioxide, which is mainly formed by thermal decomposition of manganese nitrate, has been used for the semiconductor layer of this type of solid electrolytic capacitor. However, due to the high heat required during this thermal decomposition and the oxidizing effect of the NO□ gas generated, aluminum is a dielectric material.

There are major drawbacks such as damage to the dielectric oxide skin such as tantalum, resulting in lower withstand voltage, increased leakage current, and deterioration of dielectric properties.

In addition, the process of reconstitution is required several times.

In order to compensate for these drawbacks, attempts have been made to form a semiconductor layer without applying high heat, that is, to form a semiconductor layer using a highly conductive polymeric semiconductor material. An example of such a solid electrolytic capacitor is a solid electrolytic capacitor in which the conductive layer is made of a conductive polymer compound obtained by doping a dopant into a polymer compound obtained by polymerizing a polymer expressed by the following general formula. ing.

In addition, this type of solid electrolytic capacitor whose semiconductor layer is an ri conductive polymer compound is also available! The general formula (
1) A method of forming a semiconductor layer by electrolytically polymerizing in a solution containing a monomer represented by the general formula (1).
) A method is known in which a semiconductor layer is formed by reacting on a dielectric oxide film layer using an oxidizing agent prepared separately.

[Problem to be Solved by the Invention 1] However, with the method using electrolytic polymerization described above, not only does it take a long time to form a semiconductor layer, but also when the valve metal has an extremely deep shape (i.e., the unit area Valve metals (with a large capacity per unit) have the disadvantage of not being able to draw out sufficient capacity. In addition, in the method of reacting monomers on a dielectric oxide film layer, it is necessary to dehydrogenate the monomers with an oxidizing agent in order to turn them into polymers.
In the case of a valve metal having an extremely convoluted shape as described above, dehydrogenation does not proceed sufficiently, and as a result, there is a problem in that the high frequency performance of the produced solid electrolytic capacitor is still insufficient.

[Means for Solving the Problems 1] The present invention has been made in order to solve the problems mentioned above, in which a dielectric oxide film layer and a polythiophene layer are sequentially applied to the surface of a metal having a valve action. In the manufacturing method of a solid electrolytic capacitor having a semiconductor layer and a conductor layer formed of conductive molecules, the 2F conductor layer is formed by melting the polythiophene precursor to form the dielectric oxide film layer.
The present invention provides a method for manufacturing a solid electrolytic capacitor, which is formed by attaching the polythiophene precursor to L and oxidatively polymerizing the polythiophene precursor with an oxidizing agent to form a conductive polymer containing polythiophene as a main component.

The present invention will be explained in detail below.

As the valve metal used as the anode of the solid electrolytic capacitor in the present invention, any metal having a valve effect can be used, such as aluminum, tantalum, niobium, titanium, and alloys using these as substrates.

The dielectric oxide film provided on the surface of the valve metal may be an oxide layer of the valve metal itself provided on the surface portion of the valve metal (or an oxide layer provided on the surface of the valve metal. Although the layer may be made of another dielectric oxide, it is particularly preferable to use a layer made of the oxide of the valve metal itself.In either case, the method of providing the oxide layer is to use an electrolytic solution. Conventionally known methods such as the anodization method used can be used.

The semiconductor layer according to the present invention includes the dielectric oxide film layer described above.
(l) melting the polythiophene precursor and depositing it on the dielectric oxide film layer; and (2) oxidatively polymerizing the polythiophene precursor with an oxidizing agent to form a conductive polymer mainly composed of polythiophene. It is important to form it by the process of making it.

The polythiophene precursor in the present invention is a thiophene oligomer having a non-conjugated portion in a part of its skeleton, and has a melting point in the range of 240 to 280°C. Such a polythiophene precursor can be prepared by, for example, treating thiophene with a Lewis acid such as AlCl1 or CuC1□.

The aforementioned polythiophene precursor is deposited on the dielectric oxide layer 19 by melting the polythiophene precursor, immersing the valve metal in the melt, and then pulling the valve metal.

Further, in the present invention, an oxidizing agent, which will be described later, is introduced into the polythiophene precursor and oxidatively polymerized, thereby forming a conductive polymer containing polythiophene as a main component and converting it into a semiconductor.

As the oxidizing agent, ecla, AsF s, Pl:5,
S03, FNIl, l 2S20. , N21zS2
0e, 2S20-1 KklnO,, lI □0
2. 1 m chloric acid, 1 m hypochlorous acid, perchlorate, SbF
5.11F3, [1C13BBr, F2520S, 1I
Conventionally known oxidizing agents such as NO3 can be used, and one or more of each oxidizing agent may be used. The oxidizing agent can be introduced into the polythiophene precursor by applying a solution of the oxidizing agent dissolved in a suitable solvent or, in the case of a gaseous oxidizing agent, by contacting it in the gas phase. Can be done. In addition, in the present invention, an oxidizing agent is first deposited on the dielectric oxide film layer, and then the polythiophene precursor is melted and oxidized and polymerized at the same time as it is deposited on the dielectric oxide film layer, so that polythiophene is the main component. A semiconductor layer made of a conductive polymer may be formed.

The oxidizing agent used in the present invention itself is a substance that becomes a dolphant for the polythiophene formed by oxidative polymerization and imparts electrical conductivity. A dopant other than the conventionally known oxidizing agent may be doped before or after or together with the oxidizing agent.

Examples of such dopants include iodine, arsenic fluoride, sulfuric acid, AsFa, etc.
Examples thereof include dopants described in Japanese Patent Application Laid-Open No. 58-54554.

Further, such a dopant can be doped using a chemical method or an electrochemical method.

The semiconductor used in the present invention has an electrical conductivity of lO°~to2s・c
m-' order is obtained, and the higher the conductivity, the better the high frequency characteristics of the produced solid electrolytic capacitor.

The solid electrolytic capacitor produced by the method of the present invention is made into a product by removing the cathode layer from the above-mentioned semiconductor layer using carbon paste or/and silver paste, etc., and then sealing it with a resin, a case, etc. using a conventionally known method. Ru.

[Effect 1] When a polythiophene precursor is melted and deposited on a dielectric oxide film layer and oxidatively polymerized with an oxidizing agent to form a semiconductor layer consisting of a conductive polymer mainly composed of polythiophene, the polythiophene precursor Since it is a material that has already been partially oxidatively polymerized, fewer mice need to be oxidatively polymerized than when oxidatively polymerizing a thiophene monomer to form polythiophene. As a result, there is less dehydrogenation required to obtain a polymer that achieves the desired electrical conductivity.
Compared to the electrolytic method, oxidative polymerization not only completes in a short time, but also allows sufficient capacity to be extracted because the polythiophene precursor is melted and deposited on the dielectric oxide film layer.

[Example j Examples and comparative examples will be shown and explained below.

Example 1 The polythiophene 111 precursor was obtained by adding aluminum chloride to a thiophene monomer, reacting at 0° C. for 2 hours, washing thoroughly, and confirming that there was no hydrochloric acid residue using a 6i1 acid silver test.

It was dark yellow and had a melting point of 240-280°C.

On the other hand, a separately prepared Ta pellet (3 mm x 2 mrrI
, 0.5 mm thick, CV 20,000/g) in a phosphoric acid aqueous solution to form a dielectric oxide film layer of Ta 2 (] 5 on the surface at 7°C. Such elements were used for 30 points. Heshi,
The sample was immersed in the melt of the polythiophene precursor described above, pulled up, and further immersed in a 20% ammonium persulfate aqueous solution. Thereafter, the Ta pellets were washed with water and then dried.

Carbon paste and silver paste were sequentially deposited on the thus formed conductor layer made of a conductive polymer containing polythiophene as a main component to form a conductor layer.

The solid electrolytic capacitor was then sealed with resin.

Example 2 A solid electrolytic capacitor was produced in the same manner as in Example 1 except that 5% potassium permanganate aqueous solution was used instead of the 20% ammonium persulfate aqueous solution in Example 1.

Example 3 A solid electrolytic capacitor was produced in the same manner as in Example 1, except that a 10% iron chloride alcohol solution was used in place of the 20% ammonium persulfate aqueous solution in Example 1, and the capacitor was washed with alcohol.

Comparative Example 1 A Ta pellet similar to that used in Example 1 was used as an anode, a separately prepared Ta foil was used as a cathode, and as an electrolyte, 0.1 mol of thiophene, 0.1 mol of BunN, and 0.1 mol of C were dissolved.
Electrolytic polymerization was carried out for 2 hours using an Il, CN solution to obtain an element whose semiconductor layer was a conductive polymer in which bothyliophene was doped with BF and an anion. Furthermore, a conductive layer was formed and sealed in the same manner as in Example 1 to produce a solid electrolytic capacitor.

Comparative Example 2 A solid electrolytic capacitor was produced in the same manner as in Example 1, except that a thiophene monomer was deposited on the dielectric oxide film layer of the Ta pellet instead of the polythiophene precursor in Example 1.

Table 1 summarizes the performance of the solid electrolytic capacitors fabricated on each side.

(Leaving space below) Table 1 Umbrella Price reference at 12011z Direction at 10KIIz [Effects of the invention J According to the present invention, the polythiophene precursor is melted and deposited on the dielectric oxide film layer, and the oxidizing agent is Since the solid electrolytic capacitor (11) is oxidatively polymerized to form a semiconductor layer made of a conductive polymer containing polythiophene as its main component, the solid electrolytic capacitor (11) has sufficient Furukawa performance and also has good high frequency performance.

Claims (1)

[Claims] 1. A method for manufacturing a solid electrolytic capacitor in which a dielectric oxide film layer, a semiconductor layer made of a conductive polymer containing polythiophene as a main component, and a conductor layer are sequentially formed on the surface of a metal having a valve action. , a step of melting a polythiophene precursor and depositing it on the dielectric oxide film layer, and a step of oxidatively polymerizing the polythiophene precursor with an oxidizing agent to form a conductive polymer mainly composed of polythiophene. Features: Manufacturing method of solid electrolytic capacitors.