JP2006278851A - Manufacturing method of solid electrolytic capacitor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a solid electrolytic capacitor element in which the flow nature of valve action metal powder is improved and a property variation is little and the wear of a forming metallic mold is little at the time of forming. <P>SOLUTION: The method of manufacturing the solid electrolytic capacitor element comprises steps of mixing the valve action metal powder and an additive, carrying out forming and sintering to form a sintered body, and forming an oxide film and a cathode layer on the sintered body. In the manufacturing method, a straight chain version saturated fatty acid is dissolved into an organic solvent, used as the additive, mixed with the valve action metal powder, and dried. The straight chain version saturated fatty acid is a stearic acid and a palmitic acid, and moreover an addition amount is 0.05 to 15.0 wt.% in a valve action metal weight ratio. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a solid electrolytic capacitor element using a valve action metal such as tantalum or niobium.

  Conventionally, an element used in a solid electrolytic capacitor has a valve action metal powder mixed with a liquid binder to granulate the valve action metal powder, which is molded by compression molding, and further, an anode lead is formed on the molded body. The planted material is made by sintering at high temperature and high vacuum.

This conventional method for producing a solid electrolytic capacitor element is to granulate valve action metal powder and reduce the amount of fine particles in the valve action metal powder, thereby improving the flowability of the powder, supplying it to the molding die, and compressing it. Molding is in progress. For example, in granulation of tantalum powder using a fluid granulator, primary granulation is performed by spraying a liquid inorganic binder such as water or phosphoric acid as a liquid binder, followed by a liquid organic binder such as PVA. The method of spraying and final granulation is used (for example, refer patent document 1).
Moreover, in order to further improve the flowability of the valve-action metal granulated powder after mixing the additive, a technique for regulating the particle size in the range of 20 to 400 μm is also used (for example, see Patent Document 2).
JP-A-5-65502 JP-A-4-136102

  As described above, when a liquid binder for granulation is used as an additive, the particle size distribution of the valve action metal powder after mixing the additive is shifted to a larger particle size side, and the molding die is increased by increasing the average particle size. In the case of molding with an ultra-small molding machine, there is a problem that the molding density varies.

  Further, as granulating binders such as the above additives, camphor, benzoic acid, polyvinyl alcohol, polyvinyl acetal, polymethyl methacrylate, acrylic resin, polyester resin, vinyl chloride resin, formal resin, polyamide resin, polyurethane resin, When using polysulfone resin, styrene resin, polycarbonate resin, ether resin, silicon resin, formaldehyde resin, urea resin, epoxy resin, melamine resin, alkyd resin, cellulose resin, nitrocellulose resin, natural resin, phenol resin, etc. Since the mold releasability between the molding die and the compression molded body is poor, there is a problem that the molding die is heavily worn and the die is frequently damaged.

  Because of the above problems, there has been a demand for a method for producing a solid electrolytic capacitor element that has little variation in molding density and can reduce wear and breakage of a molding die during molding.

The present invention solves the above-mentioned problem. After mixing the valve action metal powder and the additive, it is molded and sintered to form a sintered body, and an oxide film and a cathode layer are formed on the sintered body. In the method for producing a solid electrolytic capacitor element,
A method for producing a solid electrolytic capacitor element, wherein the additive is a linear saturated fatty acid dissolved in an organic solvent.

  Further, the present invention provides a method for producing a solid electrolytic capacitor element, wherein the linear saturated fatty acid is stearic acid or palmitic acid.

  Furthermore, it is a manufacturing method of the solid electrolytic capacitor element characterized by the addition amount of the said linear saturated fatty acid being 0.05-15.0 wt% by valve action metal weight ratio.

  By using linear saturated fatty acid dissolved in an organic solvent as an additive to the valve action metal powder, and molding after drying, the valve action metal powder is in a state of thin film coating with the linear action saturated fatty acid, Since the powder particles are not entangled and slippery, the flowability is improved, and the additive has no granulating action, and the particle size distribution of the valve metal powder after mixing is almost the same as the particle size distribution before mixing. Therefore, density variation during molding can be reduced even when the molding die size is very small.

  In addition, since the linear saturated fatty acid has good slipperiness, the releasability between the molding die and the compression molding is improved, the molding die wear is small, and the molding die wear can be reduced.

[Example 1]
Below, the manufacturing method of the solid electrolytic capacitor element by this invention is demonstrated. First, after mixing 500 g of tantalum powder having a particle size distribution of about 1 to 400 μm and 100 ml of a solution in which 0.01 wt% of stearic acid as an additive in a weight ratio of valve action metal in ethanol of 20 ± 5 ° C. was mixed, It dried in a 40 ± 5 degreeC thermostat.

  Next, using the powder, an anode lead was planted and compression molded to form a molded body element.

[Examples 2 to 7]
Example 1 except that the amount of stearic acid added was 0.05 wt%, 0.10 wt%, 1.0 wt%, 10.0 wt%, 15.0 wt%, 20.0 wt% in terms of the weight ratio of the valve action metal A molded body element was formed by the method described above.

(Conventional example)
A tantalum powder having a particle size distribution of about 1 to 400 μm similar to that in Example 1 and a polyvinyl butyral having a valve action metal weight ratio of 1.0 wt% as a liquid binder mixed in ethanol at 20 ± 5 ° C. Then, it was dried in a constant temperature bath of 40 ± 5 ° C.

Next, a molded body element was formed by the same method as in Example 1 using the powder.
The valve action metal powders of Examples 1 to 7 and the conventional example were each measured for particle size distribution, flowability, friction force for extruding the molded body from the molding die during molding, and variation in the weight of the molded body. The measurement results are shown in FIGS.

Further, the molded body element is sintered in a high-temperature and high-vacuum atmosphere, the sintered body is formed in a phosphoric acid solution, a tantalum oxide film is formed, a manganese dioxide layer as a solid electrolyte layer, and a cathode lead A carbon layer and a silver paste layer were sequentially formed as layers to obtain a tantalum solid electrolytic capacitor element.
Then, the anode lead of the capacitor element is connected to the anode terminal by welding, and the cathode layer is connected to the cathode terminal by a conductive paint, and then an exterior resin is applied to give a rating of 10 V
A −10 μF chip-shaped solid electrolytic capacitor was produced.
About the capacitor element of each condition, the leakage current value after 1 minute when a capacitance value at 120 Hz, a tan δ value, and a rated voltage are applied is shown in FIGS.

[Comparison of particle size distribution]
As is clear from FIG. 1, the particle size distribution of the valve metal powder after mixing in which stearic acid was added to the valve metal powder in an amount of 0.05 to 15.0 wt% (Examples 2 to 6) was compared with that before the mixing. In the case of 20.0 wt% (Example 7), the particle size distribution shifted to a slightly larger particle size side. Further, the conventional example was shifted to the particle size side where the particle size distribution was large as compared with Example 7.

[Comparison of flowability of valve action metal powder]
Further, as apparent from FIG. 2, the flowability of the valve action metal powder improved as the amount of stearic acid added increased (Examples 1 to 7). This is because the particles of the valve action metal powder are not easily entangled with each other and become easy to slip. However, when the addition amount is as small as 0.01 wt% (Example 1), improvement in flowability is not observed as compared with the conventional example.

[Comparison of frictional force between molding die and compression molded body]
In addition, as is clear from FIG. 3, in Examples 2 to 7, the frictional force between the molding die and the compression molded body decreased as the amount of stearic acid added increased as compared with the conventional example. This is because stearic acid has good slipperiness between the molding die and the valve action metal powder, and has improved mold releasability. However, when the addition amount was 0.01 wt% (Example 1), the flowability of the powder was poor, and it was not possible to sufficiently supply it into the mold, so that molding was impossible.

[Comparison of weight variation of compacts]
As is clear from FIG. 4, Examples 2 to 6 have a smaller weight variation of the molded body than the conventional example, but when the addition amount is 20.0 wt% (Example 7), the weight of the molded body. The variation became large.

[Comparison of electrical characteristics of products]
Further, as is apparent from FIGS. 5 to 7, in Examples 2 to 6, variations in product capacitance value, tan δ value, and leakage current value were smaller than those in the conventional example. This is because the weight variation of the molded body is reduced as described above.
However, when the addition amount was 20.0 wt% (Example 7), the variation was large.
From the above, the addition range of stearic acid is desirably 0.05 to 15.0 wt%. If it is less than 0.05 wt%, the flowability of the powder becomes poor, so that molding becomes impossible, and if it exceeds 20.0 wt%, the weight variation of the molded product increases.

  Although stearic acid was used as an additive in Examples 1 to 7, the same effect can be obtained by using palmitic acid.

  Moreover, although tantalum was used as the valve action metal powder of Examples 1 to 7, the same effect can be obtained even when niobium, aluminum, titanium or the like is used.

  Furthermore, although manganese dioxide was used as the solid electrolyte of Examples 1 to 7, the same effect can be obtained even when a conductive polymer such as polythiophene, polypyrrole or polyaniline is used.

It is the figure which compared the particle size distribution of the valve action metal powder after Examples 1-7 and the additive mixing in a prior art example. It is the figure which compared the flowability of the valve action metal powder after Examples 1-7 and the additive mixing in a prior art example. It is the figure which compared the frictional force at the time of extruding from the metal mold | die after compression molding of the valve action metal powder after the additive mixing in Examples 1-7 and a prior art example. It is the figure which compared the weight variation of the molded object when compression molding the valve action metal powder after the additive mixing in Examples 1-7 and a prior art example. It is the figure which compared the capacitance value of the solid electrolytic capacitor in Examples 1-7 and a prior art example. It is the figure which compared the tan-delta value of the solid electrolytic capacitor in Examples 1-7 and a prior art example. It is the figure which compared the leakage current value of Examples 1-7 and the solid electrolytic capacitor in a prior art example.

Claims (3)

In the method for producing a solid electrolytic capacitor element in which a valve action metal powder and an additive are mixed, then molded and sintered to form a sintered body, and an oxide film and a cathode layer are formed on the sintered body.
A method for producing a solid electrolytic capacitor element, wherein the additive is a linear saturated fatty acid dissolved in an organic solvent.   The method for producing a solid electrolytic capacitor element, wherein the linear saturated fatty acid according to claim 1 is stearic acid or palmitic acid.   The method for producing a solid electrolytic capacitor element, wherein the addition amount of the linear saturated fatty acid according to claim 1 is 0.05 to 15.0 wt% in terms of the weight ratio of the valve action metal.

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