JPS625628A - Solid electrolytic capacitor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to solid electrolytic capacitors, and more specifically to improving the moisture resistance of resin-clad tantalum solid electrolytic capacitors.

Conventional technology Conventional resin-clad tantalum solid electrolytic capacitors, such as dipmental solid electrolytic capacitors.

The configuration is as shown in FIG. That is, a dielectric oxide film is formed by molding and sintering tantalum powder and anodizing it, and on the other hand, manganese dioxide as an electrolyte, carbon as a cathode current collector, and a silver paint layer.

A capacitor element 1 formed by sequentially laminating solder layers is completed by first applying a first outer covering using a synthetic resin 2 having a low viscosity, and then applying a main outer covering using a zero synthetic resin 3 on the other side. 4 is a lead wire. Furthermore, the main parts of the dip tantalum solid electrolytic capacitor are shown in FIG. 5 is tantalum metal, on which a dielectric oxide film 6 is formed by anodic oxidation. Furthermore, manganese dioxide 7, which is an electrolyte, is laminated.

A cathode current collector 8 made of a carbon layer, a silver paint layer, etc. is formed. Note that the exterior resin layer was omitted.

Problems to be Solved by the Invention If such a conventional tantalum solid electrolytic capacitor is left unloaded in a high temperature and high humidity atmosphere, and then a rated voltage of ``'C is applied in a normal temperature and humidity atmosphere, short circuit failures and leakage currents may occur. A defect had occurred.

The reason is that the core of tantalum solid electrolytic capacitors is made of extremely fine powder, and it is impossible for the solid electrolyte, manganese dioxide, to adhere to the entire area of the dielectric oxide film. , a portion of the dielectric oxide film that is not covered by the manganese dioxide layer (referred to as a non-solidified region) occurs. When a tantalum solid electrolytic capacitor is left unloaded for a long time in a high-temperature, high-humidity atmosphere, the silver powder in the silver paint layer moves and adheres to the non-solidified area, resulting in a short circuit.

The present invention is intended to solve these problems, and aims to provide a solid electrolytic capacitor that does not suffer from short-circuit defects even after being left unloaded in a high-temperature, high-humidity atmosphere.

Means for Solving the Problems The present invention (1) is intended to solve the above problems,
After shaping and sintering tantalum powder to form a dielectric oxide film, and then forming a solid electrolyte layer such as manganese dioxide, a carbon layer, and silver paint e, it is impregnated with an organometallic compound and dried.

Effect The present invention has the above-described structure, so that the silver powder of the silver paint layer and the silane coupling agent are bonded together with a chemical bond.
Since the movement of silver powder is prevented, short-circuit failures will not occur even after solid electrolytic capacitors are left unloaded in high temperature and high humidity environments. The reaction mechanism between the silver powder and the silane subbing agent will be explained in detail below.

The organometallic compound used in the present invention is a so-called silane coupling agent.

As shown in the basic chemical structural formula (1), it is an organosilicon compound having silicon as the central element and two or more different reactive groups within the molecule.

R-3i2IR'), ・・・・・・・・・
(1) Of the two types of reactive groups, R is a functional group that can chemically bond with organic materials (such as various synthetic resins).

These include vinyl, epoxy, and acrylic groups.

Examples include adno group and mercapto group. In addition, the other reactive group R' [inorganic material (e.g., metal, metal oxide,
(glass, ceramic, inorganic filler, etc.); for example, a methoxy group.

These include ethoxy groups and halogens. In other words, a silane coupling agent has both a functional group that selectively chemically bonds with an organic substance and a functional group that selectively chemically bonds with an inorganic substance in a single molecule, and this silane coupling agent It has the property of chemically bonding an organic substance and an inorganic substance through the flapping agent.

Next, the reaction mechanism when using a silane coupling agent will be explained. That is, the functional group R' that selectively chemically bonds with an inorganic substance is hydrolyzed and converted into silanol. The silanol produced here is present on the metal surface and τ
It undergoes a dehydration reaction with the hydroxyl group present, and chemically bonds with the metal via the oxygen atom.

Lipophilic group, that is, a functional group that selectively chemically bonds with an organic substance.As mentioned above, a vinyl group or an epoxy group.

Since it is an acrylic group, it binds to the end group of the other polymer by converting a double bond into a single bond or opening an epoxy ring. Tsumashi.

As shown in Figure 1, a chemical bond occurs between a metal and an organic substance as shown in (metal-〇-3i-R-organic substance), and the metal and organic substance are chemically bonded via a silane coupling agent. be.

In this way, due to the silane coupling agent, which is reactive with both metals and organic substances, the silver powder and the silane coupling agent form a τ bond with a chemical bond, and the silane coupling agent also chemically bonds with the polymer of the silver paint. Since no movement of silver powder occurs, no short-circuit failure occurs even if the product is left unloaded in a high-temperature, high-humidity atmosphere because there is no movement of silver.

EXAMPLE A 10 V, 10 μF di-imbutantalum solid electrolytic capacitor will be described below as an example of the present invention.

The conventional product was manufactured by the usual method. That is, a dielectric oxide film was formed by molding and sintering Ta powder and chemical conversion, a solid electrolyte was formed by thermal decomposition of an aqueous manganese nitrate solution, and then a silver paint layer was formed and an exterior was applied to produce a finished product.

On the other hand, in one product of the present invention, a silver paint layer was formed using the same method as the conventional method, impregnated with a silane coupling agent, and covered with a finished product.

The conventional product and the product of the present invention were left unloaded in an atmosphere of 85°C and 984RH for 600 hours.

2 times the rated voltage for 1000 hours, i.e. 1
A short circuit test was performed by applying 2V. The results are shown in the table below.

(Margin below) As is clear from this table, the conventional product (/i: 1
After 000 hours, a total of 7 short-circuit defects occurred. On the other hand, in one product of the present invention, only two short-circuit defects occurred after 100 Q hours had passed.

As described in detail, according to the present invention, the silane coupling agent binds to both the silver powder and the synthetic resin with a chemical bond, so it is possible to prevent the movement of the silver powder, and it is possible to prevent the silver powder from moving in a high temperature and high humidity atmosphere. A solid electrolytic capacitor that does not cause short-circuit defects even when left unloaded can be obtained, and its industrial value is great.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the reaction mechanism of the silane coupling agent according to the present invention, FIG. 2 is a sectional view of a conventional dip tantalum solid electrolytic capacitor, and FIG. 3 is a sectional view showing the main parts of a capacitor element. 1...Capacitor element, 5...Tantalum metal. 6... Dielectric oxide film, 7... Manganese dioxide layer. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
α in the figure

Claims (4)

[Claims] (1) After shaping and sintering tantalum powder to form a dielectric oxide film, and sequentially forming a solid electrolyte layer such as manganese dioxide, a carbon layer, and a silver paint layer, it was impregnated with an organometallic compound and dried. A solid electrolytic capacitor featuring: (2) The solid electrolytic capacitor according to claim 1, wherein the metal element of the organometallic compound is Si. (3) The organometallic compound has the general formula, R-Si≡(R')_
3. The solid electrolytic capacitor according to claim 2, which is represented by 3. (4) R is one selected from vinyl group, epoxy group, acrylic group, amino group, and mercapto group, and R'
4. The solid electrolytic capacitor according to claim 3, wherein is one selected from a methoxy group, an ethoxy group, and a halogen.