JPH03276621A - Manufacture of solid-state electrolytic capacitor - Google Patents

Abstract

PURPOSE:To easily manufacture a capacitor at a low cost which is free from characteristics deterioration such as the decrease of capacitance and the increase of leak current, by keeping a solid-state electrolytic capacitor using conductive polymer in a hollow state and sealing it. CONSTITUTION:A capacitor element is constituted by arranging solid-state electrolyte 3 on a dielectric film 2 formed on the surface of an anode 1 composed of valve metal like aluminum, tantalum and titanium. Said element is kept in a hollow state without being in contact with a sheath 4 and sealed. From the viewpoint of facilitating manufacture, thermoplastic resin is desirable for sealing seath material. In particular, polyphenylene sulfide is excellent in barrier properties of water content and oxygen, and further in heat resistance. As the sealing means, any means are applicable if only hermetic properties can be obtained practically, but ultrasonic welding capable of highly reliable sealing in a short time is especially suitable.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to solid electrolytic capacitors that have excellent capacitor characteristics, particularly frequency characteristics, and reliability characteristics under high temperature and high humidity conditions, and in particular solid electrolytic capacitors that use conductive polymers as the solid electrolyte. The present invention relates to a method for manufacturing a capacitor.

2. Description of the Related Art In recent years, with the digitalization of electrical equipment, capacitors are required to be small, large in capacity, and have low impedance in the high frequency range. Traditionally, capacitors used in the high frequency range include plastic capacitors, mica capacitors,
There are multilayer ceramic capacitors, but these capacitors have a large shape and are difficult to increase capacity. On the other hand, examples of large capacity capacitors include electrolytic capacitors such as aluminum dry electrolytic capacitors and aluminum or tantalum solid electrolytic capacitors. Since the electrolyte (liquid electrolyte or solid manganese dioxide) used in these capacitors has a high resistance, it is not possible to obtain sufficiently low impedance in the high frequency range.

In contrast, recently, organic semiconductors with high conductivity and excellent anodic oxidation properties have been used as solid electrolytes instead of manganese dioxide. It has been proposed to use -tetracyanoquinodimethane combresox salt (hereinafter abbreviated as rTCNQ salt).

Invention by the same applicant (Japanese Patent Publication No. 56-10777) and invention by Shin Niwa (Japanese Patent Publication No. 58-1977)
As published in Publication No. 609, such TC
In aluminum solid electrolytic capacitors using NQ salt,
Frequency and temperature characteristics have been significantly improved, and low leakage current characteristics have been achieved. In addition, TCNQ salt has excellent thermal stability as an organic conductive material.
The high-temperature lifespan of the resulting capacitor is said to far exceed that of conventional dry electrolytic capacitors. Furthermore, in recent years,
By electrolytically polymerizing heterocyclic monomers such as pyrrole and thiophene using a supporting electrolyte, a highly conductive polymer containing the anion of the supporting electrolyte as a dopant is formed on the anode body, and this is a solid that is used as an electrolyte. Electrolytic capacitors have been proposed (Japanese Patent Application Laid-Open No. 60-3711.4
(Japanese Patent Application Laid-open No. 60233017).

Problems to be Solved by the Invention However, capacitors using solid electrolytes generally have a low ability to repair damaged parts of the dielectric film caused by the electrolyte.
Further, there are problems such as weak adhesion between the electrolyte and the dielectric film. This tendency is particularly noticeable when a conductive polymer is used as an electrolyte.

In general, solid electronic devices are used with a resin exterior to prevent mechanical damage or deterioration from outside air such as humidity and oxidation. However, when a solid electrolytic capacitor that uses a conductive polymer as an electrolyte is coated with resin, shrinkage stress generated during the curing or cooling process can cause undesirable phenomena such as peeling of the electrolyte from the dielectric film or damage to the dielectric film. There has been a problem in that capacitor characteristics deteriorate, such as a decrease in capacity or an increase in leakage current. The increase in leakage current characteristics was caused by the low ability of the electrolyte to repair the film, and it was difficult to repair it even with subsequent aging. For this reason, attempts have been made to reduce stress by using resins with rubber-like elasticity, but
Even in this case, the above-mentioned problems would occur if the capacitor was exposed to rapid temperature changes, and similar deterioration of the capacitor characteristics could not be avoided.

The present invention solves the above problems, and is a method for easily and inexpensively manufacturing a capacitor with no deterioration in characteristics by preventing the solid electrolyte from peeling off from the anode dielectric surface and preventing damage to the dielectric film. The purpose is to provide the following.

Means for Solving the Problems The present invention achieves the above object, and its technical means includes an electrolytic capacitor element in which a solid electrolyte made of a conductive polymer is provided on a valve metal surface provided with a dielectric film. By keeping it in a hollow state and sealing it so that it does not come into direct contact with the exterior resin, stress from the exterior resin is prevented.

According to the present invention, a solid electrolytic capacitor without characteristic deterioration due to peeling of the solid electrolyte and dielectric and damage to the dielectric film can be easily obtained by the above manufacturing method.

The sealing material may be any material as long as it can substantially block moisture and oxygen, but thermoplastics are preferably used, and polyphenylene sulfide (PPS), which has low moisture permeability, is more preferably used. is used. Although any means for sealing may be used, it is preferable to use welding, and more preferably, ultrasonic welding is used to facilitate manufacturing. As the conductive polymer solid electrolyte, a conductive polymer having a repeating unit of a heterocyclic compound and doped with an anion is preferably used. More preferably, pyrrole, thiophene, furan or derivatives thereof are used as the heterocyclic compound. Methods for forming conductive polymer electrolytes include chemical oxidative polymerization and electrolytic polymerization. In the latter case, the dielectric surface may be coated with a thin conductive layer such as manganese dioxide. , the present invention can be similarly applied to such cases.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a basic configuration example of a solid electrolytic capacitor according to the present invention. A capacitor element consisting of a solid electrolyte 3 provided on a dielectric film 2 formed on the surface of an anode 1 made of a valve metal such as aluminum, tantalum, titanium, etc. is held in a hollow state without contacting an exterior 4 and sealed. O5 is a graphite layer, 6 is a silver paint layer, and 7 is a graphite layer.
．． 8 are an anode lead and a cathode lead, respectively. In the solid electrolytic capacitor according to this embodiment, since the element portion does not contact the exterior, there is no peeling of the solid electrolyte from the anode dielectric surface and no damage to the dielectric film due to stress on the exterior resin. Therefore, a solid electrolytic capacitor without deterioration of characteristics such as a decrease in capacity and an increase in leakage current characteristics can be easily manufactured. Any material can be used as the packaging material used for sealing as long as it is substantially airtight, but thermoplastic resins are preferred from the viewpoint of facilitating the manufacturing process, and polyphenylene sulfide is particularly preferred. It is suitable because it has excellent moisture and oxygen barrier properties and also has excellent heat resistance. Although any means for sealing may be used as long as it can substantially maintain airtightness, ultrasonic welding is preferable because it enables highly reliable sealing in a short time even during welding. Note that, due to dimensional accuracy, it may be difficult to hermetically seal the cathode/anode lead extraction portions by ordinary welding alone, so they may be sealed by appropriate means such as pouring epoxy resin after welding.

Next, embodiments of the present invention will be described in more detail.

<Example 1> An anode lead was attached to an 8x10 mm aluminum etched foil, and an aqueous solution of ammonium thiadibate was used.
After forming a dielectric film by anodic oxidation by applying 35V at about 70°C, it was immersed in a 30% manganese nitrate aqueous solution and further heated to 250°C.
An anode was prepared by heating at ℃ for 10 minutes to adhere pyrolytic manganese dioxide to the surface. A stainless steel auxiliary electrode is brought into contact with this anode foil, immersed in an electrolytic solution consisting of pyrrole (0.3M), ri-sodium toluenesulfonate (0.15M), and naphthalene sulfonate applied to polypyrrole via the auxiliary electrode. An electrolytic polymer film doped with acid anions was formed, washed with water and dried, then carbon paste and silver paste were applied to the electrolytic polymer film, the cathode lead was removed, and a capacitor element was completed. As shown in FIG. 2, this element 11 was placed in an exterior case 12 made of polyphenylene sulfide, covered with an exterior lid 13 made of the same material, held without contacting the exterior material, and sealed by ultrasonic welding. 14 indicates an ultrasonic welding part. Then negative/anode lead 8
．． Five capacitors were completed by filling the gap between the extraction parts of 7 with epoxy resin 15. After aging at 13V, the initial capacity at 120 Hz, loss factor, and average value of leakage current after 2 minutes of application of 10V are shown in Table 1.

Comparative example 1 shown in Table 1 in the margin below> Using a silicone rubber mold so that the external dimensions are the same,
A case made by pressing in the same manner as in Example 1, except that it was cast and exteriorized with an epoxy resin containing a stoichiometric mixture of the main agent Nipico) #828 (manufactured by Yuka Shell Epoxy) and the curing agent diaminodiphenylmethane (manufactured by Odugaya Chemical). Table 1 shows the characteristics of the capacitor. It is clear that Example 1 has a larger capacity and a smaller leakage current, demonstrating that the solid electrolytic capacitor according to the present invention has extremely excellent characteristics.

<Example 2> Pyrrole and N-methylpyrrole were used in place of pyrrole.
A capacitor was produced in the same manner as in Example 1 except that a mixture containing 15M each was used. The results are shown in Table 1.

<Comparative Example 2> A capacitor was produced in the same manner as in Example 2, except that the exterior was made in the same manner as in Comparative Example 1, and the same characteristics were measured. The results are shown in Table 1. It is clear that Example 2 has a larger capacity and a smaller leakage current, proving that the solid electrolytic capacitor according to the present invention has extremely excellent characteristics.

Example 3 A capacitor was produced in the same manner as in Example 1, except that acetonitrile was used as the solvent, tetraethylammonium perchlorate was used as the supporting electrolyte, and thiophene was used instead of pyrrole. The results are shown in Table 1.

Comparative Example 3 A capacitor was produced in the same manner as in Example 3, except that the exterior was made in the same manner as in Comparative Example 1, and the same characteristics were measured. The results are shown in Table 1. It is clear that Example 3 has a larger capacity and a smaller leakage current, proving that the solid electrolytic capacitor according to the present invention has extremely excellent characteristics.

<Example 4> After embossing, the temperature was about 90°C using a 10-thiphosphoric acid aqueous solution.
A capacitor was produced in the same manner as in Example 1, except that a tantalum foil that had been anodized to which 35 V was applied was used, and the same characteristics were measured. The results are shown in Table 1.

Comparative Example 4 A capacitor was produced in the same manner as in Example 4, except that the exterior was made in the same manner as in Comparative Example 1, and the same characteristics were measured. The results are shown in Table 1. It is clear that Example 4 has a larger capacity and a smaller leakage current, demonstrating that the solid electrolytic capacitor according to the present invention has extremely excellent characteristics.

In addition, in the examples, only the case where an electrolytic polymer formed via a manganese dioxide layer is used as an electrolyte is described, but a conductive layer other than manganese dioxide may also be used, and a method other than the electrolytic polymerization may be used. The present invention is also applicable to the case where a conductive polymer electrolyte polymerized by is used. Note that the capacitor according to the present invention is not limited to the shape and dimensions of the case as long as the element is kept in a substantially hollow state.

Effects of the Invention In short, the present invention has a solid electrolytic capacitor element using a conductive polymer that is held in a hollow state and sealed. It has the advantage that it prevents peeling from the surface and damage to the dielectric film, making it possible to easily manufacture a capacitor at low cost without deterioration of characteristics such as a decrease in capacitance or an increase in leakage current.

4

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a solid electrolytic capacitor showing the basic structure of the present invention, and FIG. 2 is a sectional view illustrating a method for embodying the manufacturing method of the present invention. 1 Anode, 2-Dielectric film, 3. Solid electrolyte, 4. Exterior, 5. Graphite layer, 6.. Senbait layer, 7..-
Anode lead, 8. Cathode lead, 11. Capacitor element, 12. Exterior case, 13. Exterior lid, 14. Ultrasonic welding part, 15. Epoxy resin.

Claims (9)

[Claims] (1) A solid electrolytic capacitor in which an electrolytic capacitor element is formed by providing a conductive polymer solid electrolyte layer on the surface of a valve metal with a dielectric film formed thereon, and is sealed with an exterior material so as to be held in a substantially hollow state. Production method. (2) The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the exterior material to be sealed is a thermoplastic resin. (3) The method for manufacturing a solid electrolytic capacitor according to claim 1 or 2, wherein the encapsulating material is made of a material containing polyphenylene sulfide as a main component. (4) The method for manufacturing a solid electrolytic capacitor according to any one of claims 1 to 3, wherein the sealing is performed by welding. (5) The method for manufacturing a solid electrolytic capacitor according to any one of claims 1 to 3, wherein the sealing is performed by ultrasonic welding. (6) The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the solid electrolyte layer is made of a conductive polymer containing at least one type of compound selected from heterocyclic compounds as a repeating unit and at least one type of anion as a dopant. (7) Manufacturing the solid electrolytic capacitor according to claim 1, wherein the solid electrolyte layer is composed of a conductive polymer containing at least one type of compound selected from heterocyclic compounds as a repeating unit and at least one type of anion as a dopant, and manganese dioxide. Method. (8) The method for manufacturing a solid electrolytic capacitor according to claim 7, wherein the heterocyclic compound is pyrrole, thiophene, or a derivative thereof. (9) The method for manufacturing a solid electrolytic capacitor according to claim 1, wherein the valve metal is one selected from aluminum, tantalum, and titanium.