JPH0315332B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a solid electrolytic capacitor.

Conventional solid electrolytic capacitors that use valve metals such as aluminum and tantalum as anode materials generally form an element body by molding and sintering the powder material, and then attach a manganese nitrate solution to the anodized anode element. After heat treatment to form a solid electrolyte layer made of manganese dioxide, a cathode layer made of colloidal carbon etc. is formed on the outer circumferential surface, and a cathode lead-out part is provided by soldering etc. to form a capacitor element. This is what I did.

Therefore, the dielectric is an anodic oxide film produced by anodic oxidation, and nitric acid gas generated during heat treatment to form a manganese dioxide layer used as an electrolyte is heated to the anode by thermal stress. The oxide film is easily destroyed.

As a result, a large margin is required between the anodizing voltage and the rated voltage of the finished product. In reality, it is not possible to obtain the expected CV product compared to the value of It had the major drawback of being prone to cracking.

Dielectric materials used in electrolytic capacitors are generally mostly metal oxides such as aluminum and tantalum, or composite metal oxides such as barium titanate.

Electrolytic capacitors using sintered anode elements are
Like foil-wound electrolytic capacitors, they have been produced electrochemically in solutions of ammonium borate, ammonium carbonate, phosphoric acid, sulfuric acid, oxalic acid, etc. to obtain a dielectric film, usually by anodizing. For this reason, these solutions are adsorbed and trapped in the anodized film, or water molecules remain, leaving voids or voids after thermal decomposition due to heat treatment during the anodizing process. When a load is applied to the product after it has been commercialized, it induces an electronic avalanche over time, adversely affecting the lifespan and reliability of the product, and the quality is still not satisfactory.

Furthermore, during the production process of the manganese dioxide layer used as the electrolyte, the dielectric film is partially eroded by the heat treatment as described above, resulting in more defects on the dielectric film.

One of the major factors is considered to be that the anodic oxide film used as the dielectric is generated in a solution, so a metal oxide in a perfect crystalline state cannot be obtained.

In view of the above points, the present invention is based on a new idea of not forming an electrolyte layer such as manganese dioxide on a metal oxide used as a dielectric, but instead forming a dielectric film on a solid electrolyte layer. It is.

That is, a solid electrolyte layer made of manganese dioxide or the like is formed on the surface of the cathode electrode body, and a liquid made of Al ₂ O ₃ , TiO ₂ , Ta ₂ O ₅ , etc. alone or in combination is formed on the surface of the solid electrolyte layer. Alternatively, a paste-like dielectric film-forming material is applied, and this is heat-treated by a coating pyrolysis method to form a dielectric film layer made of a metal oxide, and then a dielectric film layer made of a metal oxide is formed on the surface of the dielectric film layer. This is a method for manufacturing a solid electrolytic capacitor, characterized in that an anode electrode body is connected and packaged via a conductive layer such as a conductive adhesive.

The present invention will be described in detail below based on examples.

Various thin film processing technologies using metal oxides have been studied in the past, and in recent years, PVD methods such as thermal evaporation, sputtering, and ion plating, and CVD methods using chemical vapor deposition have been used to develop optoelectronics. It is mainly used as a technology for producing transparent thin films in the field. However, these PVD
Many of the equipment used in the CVD method or CVD method are extremely expensive, their maintenance is difficult, and there are many unstable factors in the quality of the obtained products, so the manufacturing cost must also be extremely high. I didn't get it.

In order to solve these problems, paints containing organic metals have recently been devised. A membrane pyrolysis method was developed.

According to the above method, a metal oxide film produced by anodic oxidation of a conventional valve metal is used as a dielectric,
Electrolytic capacitors, in which a solid electrolyte such as manganese dioxide is thermally decomposed on the dielectric material, have been manufactured with an upper limit of operating voltage of about 1/4 to 1/5 compared to the anodic oxidation voltage. According to the present invention, a metal oxide film serving as a dielectric can be obtained by a coating film pyrolysis method on a solid electrolyte layer produced by pyrolysis on a cathode electrode body.

Therefore, when firing manganese dioxide, Al ₂ O ₃ is easily destroyed by the nitric acid gas generated from manganese nitrate, so most solid electrolytic capacitors use expensive raw materials such as tantalum as the anode electrode material. However, according to the present invention, aluminum can be easily used and the cost of the material can be significantly reduced.

FIG. 1 shows an embodiment of a solid electrolytic capacitor manufactured according to the present invention, in which a manganese nitrate solution is deposited on a cathode electrode body 1 made of aluminum, etc.
On the manganese dioxide layer 2 generated by heat treatment
A metal alcoholate (alkoxide) containing Al ₂ O ₃ is applied and fired to form an oxide film layer 3 of Al ₂ O ₃ . In this case, the metal alcoholate is heated to 350 to 500℃ or 800 to 800℃ depending on the state of formation of the desired film.
It is fired in an atmosphere of 900℃. After that, the anode electrode body 4 having the anode lead 14 that can be soldered is electrically connected to the dielectric layer 3 via the conductive adhesive layer 5 made of carbon, silver, etc. After being housed in an exterior metal case 11 having a cathode lead 12 via an insulating shielding material 15 such as ethylene fluoride, it is hermetically sealed by a method such as hermetically tightening or winding. The metal oxide film layer 3 serving as a dielectric contains Al, Ti,
Although a benzene solution of a monometal alkoxide such as Ta was used, a quick-drying solvent such as an ester may also be used.

Good results were obtained using methylate, ethylate, or butylate as the alkoxide.

Figure 2 is a load test characteristic diagram when a voltage is applied in an atmosphere of 85°C comparing an aluminum solid electrolytic capacitor manufactured using the above method with a rating of 25V and 1μF of the present invention and a conventional product with the same rating. .

According to the present invention, unlike conventional methods, deterioration of the dielectric film during electrolyte generation does not occur, and therefore extremely stable characteristics are exhibited.

As mentioned above, the present invention is based on an idea that is completely opposite to the conventional method in which electrolytes were manufactured sequentially from the anode side to the cathode side, and a dielectric layer is formed on the electrolyte by a metal alkoxide film pyrolysis method. This makes it possible to manufacture solid electrolytic capacitors with excellent reliability, which has high industrial and practical value.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a solid electrolytic capacitor according to an embodiment of the present invention, and FIG. 2 is a high-temperature load characteristic diagram of a solid electrolytic capacitor comparing a product of the present invention and a conventional product. 1... Electrode body for cathode, 2... Solid electrolyte layer, 3
...Dielectric film layer, 4... Electrode body for anode, 5...
conductive layer.

Claims (1)

[Claims] 1 Forming a solid electrolyte layer on the surface of the cathode electrode body,
A liquid or pasty dielectric film-forming material made of single or mixed components is applied to the surface of the solid electrolyte layer, and this is heat-treated by a coating film pyrolysis method to remove metal oxides. 1. A method for manufacturing a solid electrolytic capacitor, comprising: forming a dielectric film layer, and connecting and packaging an anode electrode body on the surface of the dielectric film layer via a conductive layer.