JP2001155963A - Capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light capacitor having a high breakdown voltage, without reducing the capacitance. SOLUTION: In this capacitor comprising two electrodes and a dielectric interposed between the two electrodes, at least one electrode of the two electrodes is made of a valve metal or an alloy thereof and the lead out lead wire connected with the electrode is made of a partly nitrized niobium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor, and more particularly, to a capacitor using a metal of a new material for an electrode lead wire.

[0002]

2. Description of the Related Art A conventional capacitor is composed of two electrodes and a dielectric material interposed between the electrodes. One of the electrodes of such a capacitor is, for example, a valve metal such as tantalum, aluminum, niobium, or the like. Electrodes made of one selected from titanium and alloys of these metals are known. One end of a lead wire is connected to the electrode to make an electrical connection to the outside. Generally, the lead wire is a thin wire made of tantalum or aluminum. When manufacturing a capacitor having a final package in a commercially available state, for example, the following is performed. A structure in which the other end of the lead wire not connected to the electrode is electrically connected to one end of an external terminal separately prepared for taking an electrical connection from the inside of the exterior to the outside. That is, a state in which one of the above-described electrodes and the external terminal are connected to each other may be employed.

[0003]

Further, for the above-described capacitors, capacitors used in recent electronic devices are required to be smaller, lighter, and larger in capacity. On the other hand, the oxide of the material of the lead wire is also formed as a part of the dielectric layer formed between the electrodes on a part of the surface of the lead wire connected to the electrode described above. Is a part which is unstable in terms of structural stress, the dielectric layer formed near the connection part including a part of the lead wire becomes unstable in terms of structural stress. In order to improve this point, a method of increasing the thickness of the dielectric layer formed on the surface of a part of the lead wire and the electrode to which the lead wire is connected can be used. However, the capacity of the capacitor manufactured by this method is small, and the demand for large capacity cannot be satisfied. This is because the thickness of the dielectric is increased. However, when a lead wire made of niobium is used, even if the dielectric layer (niobium oxide) near the lead wire connecting portion is thickened to avoid structural stress instability,
Since the dielectric constant of niobium oxide is large, it is possible to satisfy a large capacity, and since niobium is a lighter element than conventional tantalum, it is also possible to simultaneously reduce the weight. However, the withstand voltage value of a capacitor manufactured using a lead wire made of niobium is lower than that of a conventional capacitor using a lead wire made of tantalum, and is insufficient.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a lightweight capacitor having a high withstand voltage without lowering the capacitance.

[0005]

Means for Solving the Problems The present inventors diligently studied, developed a lead wire having a high withstand voltage value while suppressing a decrease in capacity, and completed the present invention. 1) A first invention for solving the above problems is a capacitor comprising two electrodes and a dielectric material interposed between the electrodes, wherein at least one of the electrodes is made of a valve metal or an alloy thereof, and A lead wire connected to the capacitor is made of niobium partially nitrided. 2) According to a second aspect of the present invention for solving the above-mentioned problem, the nitrogen content of partially nitrided niobium, which is the material of the lead wire, is 10 to 10.
It is 150,000 mass ppm, The capacitor as described in 1) above. 3) A third invention for solving the above-mentioned problem is characterized in that the electrode to which the lead wire partially nitrided is connected is made of one selected from tantalum, tantalum alloy, niobium, and niobium alloy. The capacitor described in 1) or 2) above. 4) According to a fourth aspect of the present invention, the electrode to which the lead wire partially nitrided is connected is one selected from tantalum, a tantalum alloy, niobium, and a niobium alloy, and The capacitor according to the above 1) or 2), wherein the capacitor is partially nitrided. 5) A fifth aspect of the present invention for solving the above-mentioned problem is that the structure of the electrode to which the lead wire partially nitrided is connected is a sintered body and the CV value is at least 50,000 [CV / g] or more. The capacitor according to any one of the above 1) to 4), which is a feature.

[Operation] The operation of the present invention is not necessarily clear, but can be estimated as follows. The above-described dielectric layer formed between the electrodes is also formed on a part of the lead wire connected to the electrode, but when niobium is used as the material of the lead wire, niobium has a higher oxygen affinity than tantalum, so the lead layer is drawn. Niobium has a large tendency to extract oxygen contained in the dielectric layer formed on the lead wire. Therefore, it is considered that the insulating property of the dielectric layer formed in the vicinity of the connection part including a part of the lead wire decreases, and as a result, the withstand voltage decreases. According to the present invention, since niobium, which is a material of the lead wire, is made of partially nitrided niobium, niobium is already bonded to nitrogen, so that it can be estimated that the tendency of oxygen to be extracted from the dielectric layer is reduced. As a result, it can be estimated that deterioration of the withstand voltage value of the finally manufactured capacitor can be suppressed.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment for obtaining a capacitor of the present invention will be described. As the material of one electrode used in the present invention, one selected from valve metals such as tantalum, niobium, and aluminum and alloys containing these as a main component can be used. The shape of the electrode can be plate-like, foil-like, rod-like, sintered, or the like. The size can be arbitrarily determined in consideration of the capacity of the capacitor to be manufactured.
In the case of a foil shape or a rod shape, the surface area per unit volume may be increased by bending, winding, or etching the surface. After the case of producing a sintered body obtained by pressure molding a powder of a material described above for example (10 ^{0 -} 10
^-6 ) 500 to 2000 ° C. under the condition of × 133 [Pa],
It is possible to use a method of standing for several minutes to several hours.

The partially nitrided niobium used as the lead wire in the present invention can be in the form of a plate, foil, or rod, and is generally smaller in size than the electrodes described above. Used. For connection between one end of the lead wire and the electrode, a method of electrically connecting by welding, conductive paste, caulking, crimping, or the like can be used. When the shape of the electrode is a sintered body, for example, a part of the lead wire is inserted when metal powder is pressed and then sintered together to form a sintered body of the electrode and the lead wire. The wires may be electrically connected. Further, the number of lead wires connected to each electrode may be one or more.

The partially nitrided niobium lead wire of the present invention is obtained by nitriding a part of niobium. For example, it is obtained by nitriding a niobium lead wire in a nitrogen gas atmosphere. In this case, the amount of nitrogen is 10
It is preferable to set it to １５０150,000 mass ppm. From the viewpoint of reducing the leakage current value of the dielectric composed of niobium oxide, it is preferably 100 to 10000 ppm by mass. More preferably, it is 500 to 7000 mass ppm. In addition, as the nitriding method, any one of liquid nitriding, ionic nitriding, gas nitriding, and the like, or a combination thereof can be used. The gas nitriding treatment in a nitrogen gas atmosphere is preferable because the apparatus is simple and the operation is easy.

[0010] Nitrogenation is performed at a temperature of 2000 ° C. or less and the time is within several tens of hours. A partially nitrided niobium lead wire having a desired amount of nitrogen can be obtained. You can get a quantity.
If niobium is allowed to stand in a nitrogen atmosphere for several tens of hours even at room temperature, a partially nitrided lead wire having a nitrogen content of several tens of ppm by mass can be obtained.

As another method for obtaining a partially nitrided niobium lead wire of the present invention, a long or / and wide partially nitrided niobium lead wire precursor is prepared and described above. When connecting to the electrode or when the electrode is a sintered body, for example, when inserting the lead wire before press-molding the metal powder to give the electrode, an appropriate length or / and
Alternatively, the lead wire of niobium, which is partially nitrided, may be obtained by cutting into niobium.

The lead used for the partially nitrided niobium may be connected after the electrode used in the present invention is a partially nitrided electrode. As an example of a method of manufacturing a partially nitrided electrode, the above-described nitriding treatment method used when partially nitriding the lead wire of niobium can be given. The nitriding method can be implemented by any one of liquid nitriding, ion nitriding, gas nitriding, etc., or a combination thereof. The gas nitriding treatment in a nitrogen gas atmosphere is preferable because the apparatus is simple and the operation is easy.

As the dielectric of the capacitor, for example, a polymer material such as tantalum oxide, aluminum oxide, titanium oxide, and polyparaxylene, and a ceramic compound such as barium titanate can be used.

When tantalum oxide is used as a dielectric,
Tantalum oxide is formed by forming one electrode of tantalum or a tantalum alloy or a partially nitrided one in an electrolytic solution, or attaching a tantalum-containing complex such as an alkoxy complex or an acetylacetonate complex to the electrode. After that, they can be produced by hydrolyzing and / or pyrolyzing them.

When niobium oxide is used as the dielectric, niobium oxide is formed by forming one electrode of niobium or a niobium alloy or a partially nitrided one in an electrolytic solution, or a niobium-containing complex such as an alkoxy. After attaching a complex, an acetylacetonate complex and the like to the electrode, they can be produced by subjecting them to water decomposition and / or thermal decomposition.

When aluminum oxide is used as the dielectric, aluminum oxide can also be produced by forming one electrode, aluminum or an aluminum alloy, or a partially nitrided one in an electrolytic solution.

When titanium oxide is used as the dielectric, titanium oxide can also be produced by forming titanium or titanium alloy, which is one of the electrodes, or a partially nitrided one thereof in an electrolytic solution.

When the dielectric is obtained by forming in an electrolytic solution, the capacitor of the present invention becomes an electrolytic capacitor and the formed electrode side becomes an anode.
When the complex is obtained by decomposition, the electrode to which the complex is attached has no theoretical polarity and can be used as an anode or a cathode.

As a method for forming a polymer substance and a ceramic compound as a dielectric, the methods described in JP-B-7-63045 and JP-B-7-85461 can be used. A film of a polymer substance or a film of a ceramic compound can be formed on one electrode by a reaction or the like.

Among these dielectric layers and the method of forming the dielectric layer, an electrode made of tantalum, a tantalum alloy, or a partially nitrided one thereof is formed in an electrolytic solution to form a tantalum oxide on the electrode. Is a method of forming niobium oxide as a dielectric on the electrode by forming an electrode made of niobium, a niobium alloy or a partially nitrided one in an electrolytic solution, and forming niobium oxide on the electrode as a dielectric. Is preferable, and the capacity of the produced capacitor is large. It is preferable to use a nitrided one because the leakage current value is small and the reliability is good.

Further, when the structure of the electrode is a sintered body,
A sintered body is prepared using tantalum, a tantalum alloy, or a partially nitrided powder thereof, and a CV value (a value obtained by dividing a product of a capacity and an applied voltage at the time of electrolytic oxidation by an electrode weight) is at least 50,000. [CV / g] or more is preferable because a large-capacity capacitor can be obtained. For example, the CV value can be obtained by using a powder having an average particle size of 0.6 to 1 [μm]. Furthermore, a larger CV value can be obtained by reducing the average particle size of the powder shape for producing the sintered body. 60000-14000
To obtain 0 [CV / g], for example, 0.2 to 0.5
[Μm], a further 150,000 [CV
/ G] or more, for example, by setting it to less than 0.2 [μm], it is possible to obtain a sintered body having a larger CV value required for obtaining a capacitor having a larger capacity.

Further, when the structure of the electrode is a sintered body,
A sintered body is manufactured using niobium, a niobium alloy, or a powder partially nitrided thereof, and has a CV value (a value obtained by dividing a product of a capacity and an applied voltage during electrolytic oxidation by an electrode weight) of at least 50,000. [CV / g] or more is preferable because a large-capacity capacitor can be obtained. For example, the CV value can be obtained by using powder having an average particle diameter of 3 to 5 [μm]. Furthermore, a larger CV value can be obtained by reducing the average particle size of the powder shape for producing the sintered body. In order to obtain 100000 [CV / g] or more, for example, 0.3 to 2 [μm], and to obtain 600,000 [CV / g] or more, for example, 0.2 [μm] or less. Accordingly, a sintered body having a larger CV value required for obtaining a capacitor having a larger capacity can be obtained.

Tantalum powder having such an average particle size can be obtained, for example, by a method of reducing potassium fluoride tantalate with sodium, a method of grinding and dehydrogenating a hydride of a tantalum ingot, a method of reducing tantalum chloride with carbon or metal, and the like. Can be obtained by For example, when obtained from a method by sodium reduction of potassium fluoride tantalate,
By adjusting the concentration of the raw material and the concentration of the sodium salt of the catalyst to be used, a tantalum powder having a desired average particle size can be obtained.

The niobium powder having such an average particle size is as follows:
For example, it can be obtained by a method of pulverizing sodium reduced product of potassium fluoroniobate, a method of pulverizing and dehydrogenating a hydride of niobium ingot, a method of reducing niobium oxide by carbon, and the like. For example, in the case of a method obtained by grinding and dehydrogenation of a hydride of a niobium ingot, a niobium powder having a desired average particle size can be obtained by adjusting the hydrogenation amount and the grinding time of the niobium ingot, a grinding device, and the like. .

When a part of the powder for a capacitor is nitrided, its nitrogen content is from several hundred ppm by mass to several thousand ppm.
0 mass ppm, preferably 500 mass ppm to 7000 mass ppm. When the amount of nitrogen is within this range, the leakage current value (LC value) of the sintered body produced from the powder for a capacitor shows a better value without lowering the capacity. A capacitor with a small value can be obtained.

Here, the amount of nitrogen in the powder for a capacitor such as tantalum or niobium is not a state of being adsorbed to these materials, but a value which is surely bonded and nitrided.

A partially nitrided electrode can also be obtained by using a method of nitriding after producing a sintered body. For example, after molding and sintering niobium powder, the sintered body can be nitrided using the above-described nitriding treatment method. In this case, the lead wire connected to the electrode can be nitrided together, and the process can be simplified.

On the other hand, the other electrode of the capacitor of the present invention is not particularly limited, and examples thereof include at least one compound selected from an electrolytic solution, an organic semiconductor and an inorganic semiconductor known in the aluminum electrolytic capacitor industry. Can be Specific examples of the electrolyte include a mixed solution of dimethylformamide and ethylene glycol in which 5% by weight of isobutyltripropylammonium borotetrafluoride electrolyte is dissolved, and a mixture of propylene carbonate and ethylene glycol in which 7% by weight of tetraethylammonium borotetrafluoride is dissolved. Solution and the like. Specific examples of the organic semiconductor include an organic semiconductor composed of benzopyrroline tetramer and chloranil, an organic semiconductor composed mainly of tetrathiotetracene, an organic semiconductor composed mainly of tetracyanoquinodimethane, and the following general formula (1) Alternatively, an organic semiconductor mainly composed of a conductive polymer obtained by doping the polymer represented by (2) with a dopant may be used. Specific examples of the inorganic semiconductor include an inorganic semiconductor containing lead dioxide or manganese dioxide as a main component and an inorganic semiconductor made of triiron tetroxide. Such semiconductors may be used alone or in combination of two or more.

[0029]

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[0030]

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In the formulas (1) and (2), R1 to R
4 is hydrogen, an alkyl group having 1 to 6 carbon atoms or 1 to carbon atoms.
6, which may be the same or different, X represents an oxygen, sulfur or nitrogen atom, and R5 is present only when X is a nitrogen atom, And R1 and R2 and R3 and R4 may be bonded to each other to form a ring.
Examples of the polymer represented by the formula (1) or (2) include polyaniline, polyoxyphenylene, polyphenylene sulfide, polythiophene, polyfuran, polypyrrole, polymethylpyrrole, and derivatives of these polymers.

As the above organic semiconductor and inorganic semiconductor,
When a capacitor having a conductivity in the range of 10 ⁻² S · cm ⁻¹ to 10 ³ S · cm ⁻¹ is used, the impedance value of the manufactured capacitor becomes smaller, and the capacitance at a high frequency can be further increased.

Next, when the other electrode is solid, for example, a carbon paste layer and a silver paste layer are sequentially laminated on the other electrode, and one end of the other lead wire is connected thereon. Further, the other end can be connected to an external terminal prepared for the other electrode, and then sealed with a material such as epoxy resin to form a capacitor. At this time, in order to establish an electrical connection from the inside of the epoxy resin to the outside, the other end of the lead line of niobium partially nitrided (one end is connected to one electrode) is, for example, partially nitrided. One end of the external terminal prepared for the drawn niobium lead wire may be electrically connected to the inside of the exterior. That is, a partially nitrided niobium lead wire may be connected between the one electrode and the external terminal.

When the other electrode is liquid, for example, a capacitor composed of both electrodes and a dielectric can be electrically connected to the other electrode in a can (if necessary, an external terminal for the other electrode). (One end is connected) to form a capacitor. In this case, the electrode side to which one end of the lead wire made of partially nitrided niobium is connected leads the lead wire of partially nitrided niobium to the outside from the can, and at the same time, leads the lead wire of partially nitrided niobium. Is designed to be electrically insulated from other electrodes and cans, for example, by using insulating rubber or the like. Alternatively, after cutting the lead wire of the partially nitrided niobium connected to the electrode at an appropriate position,
The terminal may be designed so as to be connected to one end of an external terminal prepared for a lead wire made of partially niobium niobium and to lead the external terminal to the outside.

Instead of using the external terminals, the other end of each lead wire not connected to the electrode can be directly drawn out of the exterior. Alternatively, an external terminal may be directly connected to the other electrode without using a lead wire.

In an electrolytic capacitor using aluminum or an aluminum alloy as a foil electrode, a niobium lead wire partially nitrided can be used as a lead wire connected to at least one electrode.

The capacitor of the present invention in which a capacitor is manufactured using a lead wire of niobium partially nitrided according to the above description has a good withstand voltage without reducing the capacity of the capacitor. Alternatively, the leakage current value can be suppressed low. Therefore, a highly reliable capacitor can be obtained. Examples Hereinafter, specific examples of the present invention will be described in more detail. The nitriding amount of the niobium lead wire and the nitriding amount of the powder were measured as follows. The nitrogen amount of the niobium lead wire and the nitrogen amount of the powder were obtained using an oxygen nitrogen amount measuring device manufactured by LECO, which obtained the nitrogen amount from the thermal conductivity, and the ratio to the separately measured powder mass was determined as the nitriding amount. .

The capacity of the sintered body was measured as follows. At room temperature, the capacity at 120 Hz measured by connecting an HP LCR measuring instrument between a sintered body immersed in 30% sulfuric acid and an electrode of a tantalum material immersed in a sulfuric acid solution is defined as the capacity of the sintered body. did.

The leakage current value (LC value) of the sintered body was measured as follows. At room temperature, a DC voltage of 70% of the formation voltage at the time of forming the dielectric was continuously applied for 3 minutes between the sintered body immersed in the 20% phosphoric acid aqueous solution and the electrode placed in the phosphoric acid aqueous solution. The current value measured later was defined as the leakage current value of the sintered body. In the present invention, a voltage of 14 [V] was applied.

The capacitance of the capacitor processed into a chip was measured as follows. At room temperature, 120 Hz was measured by connecting an HP LCR measuring instrument between the terminals of the fabricated chip.
The capacitance at was taken as the capacitance of the capacitor processed into a chip.

The leakage current of the capacitor processed into a chip was measured as follows. Rated voltage value (2.5 [V], 4
[V], 6.3 [V], 10 [V], 16 [V], 25
[V] etc.) of about 1/3 of the formation voltage during dielectric production
A DC voltage close to about 1/4 was continuously applied between the terminals of the manufactured chip at room temperature for one minute, and the current value measured was taken as the leakage current value of the capacitor processed into the chip.
In the present invention, a voltage of 6.3 [V] was applied.

Test Examples 1 to 10 A plurality of niobium thin wires having a thickness of 0.25 mmφ and a length of 10 mm were prepared, and a portion of the niobium of the niobium thin wires was nitrided under the conditions of Test Examples 1 to 10 shown in Table 1. Thus, a lead wire of niobium partially nitrided was produced. Separately, a niobium powder composed of tantalum powder (average particle size 0.7 μm) and partially nitrided niobium powder (average particle size 1 μm.
It was obtained by leaving it in a nitrogen gas atmosphere at 00 ° C. for 2 hours. 2000 mass ppm combined nitrogen. ) Was prepared. In the electrode types of Test Examples 1 to 10 shown in Table 1, 0.14 g of tantalum powder and 0.09 g of niobium powder composed of partially nitrided niobium were weighed.
Each of these powders was molded together with the partially nitrided niobium lead wire described above to a size of 3.5 × 1.8.
× 4.1mm molded body (the lead wire is about 2m
m embedded in the molded body. ) Was prepared. afterwards,
The molded bodies of Test Examples 1 to 10 were sintered at the temperatures shown in Table 1. Each of the resulting sintered bodies to which the partially nitrided niobium lead wire was connected was immersed in a 0.1% aqueous phosphoric acid solution together with a part of the lead wire connected to the sintered body. In this state, these sintered bodies were used as an anode and platinum foil was used as a counter electrode, and at a temperature of 80 ° C., a forming voltage of 20 V was applied to form a chemical for 200 minutes. A dielectric oxide film layer was formed on the surface of a part of the lead wire. Table 2 shows the capacity of each sintered body thus obtained. In addition,
The numerical values in Table 2 are average values of 10 samples.

[0043]

[Table 1]

[0044]

[Table 2]

Test Examples 11 to 30 Next, the sintered bodies obtained in the same manner as in Test Examples 1 to 10
0 were prepared. A dielectric oxide film layer was formed on the surface of the immersed sintered body and a part of the immersed lead wire in the same manner as in Test Examples 1 to 10, except that the formation time was changed to 500 minutes. Then, using 30 of the 60 electrodes after each chemical formation, a polopyrrole layer was formed on the surface of the dielectric oxide film layer as the other electrode of the capacitor. These were designated as Test Examples 11 to 20, respectively. A manganese dioxide layer was formed on the surface of the dielectric oxide film layer as the other electrode of the capacitor, using 30 of the 60 electrodes after each chemical conversion. These were each tested in Test Example 21.
To 30.

Next, a carbon paste layer and a silver paste layer were sequentially laminated on the other electrode described above. External terminals (lead frame) prepared separately for the other electrode
Of the other electrode was connected with a silver paste. The partially nitrided niobium lead wire was cut at an appropriate position and connected to one end of an external terminal prepared for the partially nitrided niobium lead wire by welding. Thereafter, a portion other than the other end (the side not connected) of each external terminal was epoxy-sealed together with an electrode, a dielectric, and a lead wire to produce a capacitor. Table 3 shows the capacitances and withstand voltage values of these manufactured capacitors.

The withstand voltage value was such that the number of short-circuited capacitors exceeded five when the voltage applied to each of the 30 capacitors in each test example was sequentially increased by 1 V.

[0048]

[Table 3]

Test Examples 11 to 13 and Test Examples 14 and 1 in Table 3
5, and Test Examples 16 to 18 and Test Examples 19 and 20, and Test Examples 21 to 23 and Test Examples 24 and 25, and Test Examples 26 to 28 and Test Examples 29 and 30, respectively, to partially nitride. It can be seen that the capacitor using the niobium lead wire as the lead wire has a higher withstand voltage value than the conventional capacitor using niobium as the lead wire without lowering the capacitance.

[0050]

As described above, the capacitor of the present invention is lighter and has a higher withstand voltage value. Further, according to the present invention, a capacitor having a large withstand voltage and a large capacity can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of one electrode of a capacitor having a lead wire made of partially nitrided niobium according to the present invention.

[Explanation of symbols]

 1 One electrode 2 Lead wire made of partially nitrided niobium

Claims (5)

[Claims] In a capacitor comprising two electrodes and a dielectric material interposed between the electrodes, at least one of the electrodes is made of a valve metal or an alloy thereof, and a lead wire connected to the electrodes is provided. A capacitor made of partially nitrided niobium. 2. The capacitor according to claim 1, wherein the nitrogen content of the partially nitrided niobium, which is a material of the lead wire, is 10 to 150,000 ppm by mass. 3. An electrode to which a lead wire partially nitrided is connected is made of one selected from tantalum, tantalum alloy, niobium, and niobium alloy. 3. The capacitor according to 2. 4. An electrode to which a lead wire partially nitrided is connected is one selected from tantalum, a tantalum alloy, niobium, and a niobium alloy, and is partially nitrided. The capacitor according to claim 1 or 2, wherein 5. The structure of an electrode to which a lead wire partially nitrided is connected is a sintered body and has a CV value of at least 50,000 [CV / g] or more. The capacitor according to any one of the preceding claims.