Tungsten Powder Application in Electrolytic Capacitor

A capacitor which made of tungsten powder has good leakage current (LC) performance

A tungsten powder which has tungsten silicide (such as W5Si3) on the surfaces of particles and has a silicon content of 0.05-7% by mass; a positive electrode body for capacitors; an electrolytic capacitor; a method for producing a tungsten powder; and a method for producing a positive electrode body for capacitors. The tungsten powder has an average primary particle diameter of 0.1-1 μm, and tungsten silicide is localized within 50 nm from the surface of each particle. The tungsten powder contains at least one of tungsten nitride, tungsten carbide and tungsten boride in a part of the surface of each particle. It is preferable for the tungsten powder that the content of phosphorus element is 1-500 ppm by mass, the oxygen content is 0.05-8% by mass, and the content of elements other than tungsten, silicon, nitrogen, carbon, boron, oxygen and phosphorus is 0.1% by mass or less. It is also preferable that the tungsten granulated powder has an average particle diameter of 50-200 μm and a specific surface area of 0.2-20 m2/g. According to the present invention, a tungsten capacitor which has good leakage current (LC) performance can be provided.The present invention relates to: a tungsten powder which has tungsten silicide (such as W5Si3) on the surfaces of particles and has a silicon content of 0.05-7% by mass; a positive electrode body for capacitors; an electrolytic capacitor; a method for producing a tungsten powder; and a method for producing a positive electrode body for capacitors. The tungsten powder has an average primary particle diameter of 0.1-1 μm, and tungsten silicide is localized within 50 nm from the surface of each particle. The tungsten powder contains at least one of tungsten nitride, tungsten carbide and tungsten boride in a part of the surface of each particle. It is preferable for the tungsten powder that the content of phosphorus element is 1-500 ppm by mass, the oxygen content is 0.05-8% by mass, and the content of elements other than tungsten, silicon, nitrogen, carbon, boron, oxygen and phosphorus is 0.1% by mass or less. It is also preferable that the tungsten granulated powder has an average particle diameter of 50-200 μm and a specific surface area of 0.2-20 m2/g. According to the present invention, a tungsten capacitor which has good leakage current (LC) performance can be provided.

The present invention is tungsten powder, the anode body of a capacitor using the same, and to an electrolytic capacitor using the anode.

Size of the shape of the electronic devices such as mobile phones and personal computers, high speed, with the weight reduction, the capacitors used in these electronic devices, lightly smaller, larger capacity, the lower the ESR is sought there.

As such a capacitor, an anode body of a capacitor made of a sintered body of valve metal powder such as that can be anodized tantalum was anodized to form a dielectric layer made of these metal oxides on the surface thereof is the electrolytic capacitor has been proposed.

Tungsten is used as the valve metal, electrolytic capacitors with sintered tungsten powder to the anode body, the volume of the anode body using a tantalum powder of the same particle size, compared to the electrolytic capacitor is obtained in the same formation voltage , it is possible to obtain a large capacitance, leakage current (LC) was not subjected to practical use as a large electrolytic capacitor. To improve this, tungsten and other alloys capacitor is considered that have been but the leakage current with the metal is not sufficient for those improved somewhat.

An object of the present invention, a tungsten powder can be solved the problem of leakage current (LC) in the electrolytic capacitor of the sintered body of tungsten powder and anode as a valve metal, anode body of a capacitor using the same, and an anode The present invention is to provide an electrolytic capacitor using the body as an electrode.

The present inventors have found that the silicon content can be solved the above problems by a sintered body of tungsten powder part was tungsten silicide on the surface so that the specific range is used as the anode body , and the present invention  has been completed .

According to the tungsten powder of the present invention, and conventional tungsten powder, as compared to the tungsten alloy powder in a volume equivalent or more, it is possible that the LC characteristics per volume producing a good electrolytic capacitor.

Tungsten powder used in the present invention (raw tungsten powder) is commercially available. Smaller tungsten powder particle size, for example, tungsten trioxide powder was triturated under a hydrogen atmosphere or a tungstic acid or tungsten halide by using a reducing agent such as hydrogen or sodium, selecting the reducing conditions appropriate It can be obtained by.

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