JP3443553B2 - Electrode for electrolytic capacitor and method for manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrode in which a porous body of valve metal having pores is bonded to a valve metal foil, the electrode forming a dielectric film on the inner surface of the pore and BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for an electrolytic capacitor that is filled with an electrolyte and used for an electrolytic capacitor, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Currently, electrolytic capacitors are required to have a small size and a large capacity. For example, in an application where an electrolytic capacitor is used on the secondary side of a power supply smoothing circuit and used around the CPU of a personal computer, the electrolytic capacitor is
It is also required to have excellent high-frequency characteristics and to be able to flow a large current.

In order to meet the demand for smaller size and larger capacity, various ideas have been made for capacitor electrodes used in electrolytic capacitors. For example, an aluminum electrolytic capacitor normally uses an aluminum foil that has been subjected to surface area enlargement treatment by etching as an electrode, but by increasing the etching rate, a metal foil with finer pores is used as an electrode. Is proposed. When a dielectric film is formed on such an electrode, the dielectric film is formed even on the surface of the pores, and the area of the dielectric film can be increased. Therefore, the capacitance of the capacitor increases.

Further, the tantalum electrolytic capacitor uses a valve metal porous body obtained by sintering fine powder of tantalum as an electrode.
Since the valve metal porous body has pores, the specific surface area of the valve metal porous body is large. When a dielectric film is formed on such an electrode, the dielectric film is formed even in the pores,
A large-area dielectric film is formed. In this way, the capacitance of the capacitor has been increased by ensuring the capacitance on the surface of the pores.

Tantalum, aluminum, titanium, niobium, etc. are known as valve metals for electrodes, and electrodes for capacitors formed from fine powders of these metals are disclosed, for example, in Japanese Patent Laid-Open No. 63-283012. Kai 57-1
38330, Japanese Utility Model Laid-Open No. 58-187136,
It is disclosed in Japanese Utility Model Publication No. 59-187129. As shown in FIG. 5, an example of the structure of the capacitor electrode disclosed in these publications is such that the lead wire 16 is embedded in the anode of the lump-shaped sintered body 12 to stand upright.
One end of 6 is embedded in a fine powder of valve metal to form a molded body,
The molded body is sintered into a sintered body.

A general method for producing a tantalum electrolytic capacitor is, for example, that tantalum metal fine powder having a specific surface area corresponding to an electrostatic capacity of 30,000 μF · V / g is used, and this fine metal powder is compression molded to a predetermined size. Then, the molded body is fired to form a valve metal porous body anode, a dielectric film is formed on the anode, and an electrolyte is filled. At this time, a dielectric film is also formed on the inner surfaces of the pores of the valve metal porous body, and subsequently, the electrolyte is coated. Then, the negative electrode is brought into contact with the electrolyte and attached by a known method to obtain a tantalum electrolytic capacitor.

Further, in order to make a capacitor having a smaller size and a larger capacity, 50000 μF · V / g of tantalum metal is used.
It is expected that a tantalum electrolytic capacitor having a larger capacity can be obtained by using a fine powder having a considerable specific surface area to form a positive electrode having the same size as the positive electrode described above and using manganese dioxide as an electrolyte.

[0008]

However, even if a capacitor electrode is assembled using tantalum fine powder of 50,000 μF · V / g as described above, the capacitance of the tantalum electrolytic capacitor assembled from this electrode is Even if the fine powder having a large capacity was used, the powder did not become large, the high-frequency characteristics were poor, and it was not preferable to flow a large current.

The above problems of the conventional electrolytic capacitor electrodes were considered to be due to the following causes. (1) The conventional electrode is that the pores of the valve metal porous body, which is the positive electrode, are not sufficiently filled with the electrolyte.
That is, the dielectric film coated on the inner surface of the pores is not sufficiently coated with the electrolyte that plays the role of the negative electrode, and the dielectric film in this case is not used for forming the capacitor, so that it does not contribute to the capacitance. I don't get it. Therefore, it was not possible to obtain a desired capacitance as the entire capacitor.

(2) The contact resistance between each layer and the volume resistance in each layer are small because the joint area to be in contact with the electrolyte which is the cathode and the cathode extraction electrode (usually the carbon layer and the silver conductive resin) is small. In other words, the surface area of the porous body that determines the size of the contact area is not sufficient, and the entire surface area of the pores is not used effectively, so the equivalent series resistance of the capacitor increases and the high frequency characteristics deteriorate. Was becoming. In order to overcome the above drawbacks, it is necessary to sufficiently fill the pores of the valve metal porous body with an electrolyte, increase the surface area of the valve metal porous body, and sufficiently utilize it for the contact surface with the cathode. Is.

Based on the above findings, the present invention is intended to provide an electrode which is excellent in high frequency characteristics and which can be used for a large capacity electrolytic capacitor capable of flowing a large current. Further, the present invention seeks to provide a method of manufacturing an electrode capable of exhibiting such characteristics.

[0012]

An electrode for an electrolytic capacitor according to the present invention is bonded to a valve metal foil by using a valve metal porous body having pores as an anode to form an electrode, and a dielectric film is formed in the pores of the electrode. It is used for capacitors filled with electrolyte, but the feature is that it uses a sintered body that is formed by laminating a plurality of compacts formed from valve metal powder and then sintered as an electrode. The sintered body has a structure in which sintered layers corresponding to the respective molded bodies are laminated.

In the electrode of the present invention, the density of the bonding interface area between two adjacent sintered layers in the sintered body is lower than that of the inside of the sintered layer, that is, the pores in the bonding interface area are The diameter is made larger than the diameter of the pores inside the sintered layer. At the time of filling the electrolyte, the electrolyte easily penetrates into the bonding interface region along the large-sized pores in the bonding interface region continuous with the outer surface of the laminate, and then in the bonding interface region between the respective sintered layers. The permeated electrolyte can further permeate into the sintered layer through the small pore diameter. In this way, the electrolyte can be sufficiently filled even in the relatively small pores inside the sintered layer, and the capacity efficiency of the capacitor can be improved. This allows the electrode to utilize the specific surface area of the sintered layer having pores for the function of the capacitor as effectively as possible.

As described above, the electrolytic capacitor electrode of the present invention facilitates the filling of the electrolyte pores by forming one valve metal porous body in a multi-layer structure and providing a large pore portion between the layer boundaries. In addition, the capacity extraction efficiency is improved.

In the present invention, the sintered body of the electrode is further processed into two kinds of sintered layers (that is, a first sintered layer and a second sintered layer) in which the size of pores in the sintered layer is changed. It is preferable to form a laminated body in which tie layers and) are alternately laminated. Since the sintered layer having a large pore size (for example, the first sintered layer) has large pores, it is easy to fill and permeate the electrolyte from the surface of the sintered body into the pores.
Even if the sintered layer adjacent to the second sintered layer (for example, the second sintered layer) has small pores, the first sintered layer penetrates into the second sintered layer and penetrates into the pores. Is relatively easy to occur due to its short permeation distance, thus increasing the filling rate of the electrolyte into the pores.

The electrode manufacturing method of the present invention comprises a step of laminating a plurality of compacts formed from valve metal powder to form a laminate, and sintering the laminate to form a valve metal porous body. And a sintering process.

Adjacent green bodies of the laminate are subjected to a sintering process,
Although they are integrally joined to form a sintered layer, the density of the joint interface area between the molded bodies becomes lower than that of the inside of the molded body during the sintering process, and the diameter of the pores in the joint interface area is smaller than that of the sintered body. The diameter is larger than the diameter of the pores inside the layer. So, as mentioned above,
During the filling of the electrolyte, the electrolyte propagates through the large-sized pore group in the bonding interface region continuous with the outer surface of the laminate, and further,
It is possible to penetrate the inside of the sintered body through the small pore diameter inside the sintered layer.

Further, in the sintering step, when a plurality of compacts are laminated and sintered, the compacts are sintered on the surface of the valve metal porous body in the vicinity of the joint interface between adjacent compacts. Due to the difference in shrinkage ratio, a large number of concaves and convexes are generated (although it varies depending on conditions such as sintering temperature, sintering time, powder grade and molding density). These streaky irregularities increase the surface area (joint area with the negative electrode) of the valve metal porous body and reduce the equivalent series resistance of the capacitor, so that high frequency characteristics are improved.

The present invention is further advanced to classify a plurality of molded bodies to be laminated on one molded body into two or more kinds, and to form a first molded body and a second molded body having different pore sizes. By alternately stacking and, it is possible to form a first sintered layer and a second sintered layer having different pore sizes after sintering. As described above, at the time of filling the electrolyte, from the sintered layer having a large pore size (for example, the first sintered layer) to the small sintered layer having a small pore size adjacent thereto (for example, The electrolyte solution easily permeates into the second sintered layer) to increase the electric capacity.

Specifically, in order to adjust the pore size and diameter of the sintered layer, the two types of compacts (that is, the first compact and the second compact) are composed of valve metal powder during sintering. Can be a molded product having a different heat shrinkage ratio, a molded product having a different molded product density, a molded product made of a valve metal powder having a different specific surface area, or a molded product made of a valve metal powder having a different physical strength.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The electrode of the present invention is characterized by laminating two or more sintered layers of valve metal into a porous body having an integral structure. , High-melting-point metals such as Ti can be used, and a thin-walled porous compact is formed from powder of these metals, and the compacts are laminated and sintered,
The sintered body includes a sintered layer formed by sintering each molded body.

In the electrode of the present invention, in order to change the pore size, it is possible to utilize a plurality of the above-mentioned sintered layers which are composed of a first sintered layer and a second sintered layer having different densities. . That is, the valve metal porous body formed by stacking the sintered layers having different sintering densities has a region of low density and a region of high density in layers. Large pores are formed adjacent to the low-density region, so that the pores in this sintered layer region can be sufficiently filled with the electrolyte.

In general, the first and second sintered layers having different densities have a density ratio that is lower than that of the sintered layers having a lower density.
The density ratio of the sintered layer having a high density is preferably about 1.1 to 3.

The sintering density differs depending on the type of metal, but for example, in the case of a tantalum electrode, if one of the low-density sintered layers has a density of 2.5 to 5.5 g / cm ^3. On the other hand, the other high-density sintered layer is 5.
A range of 5 to 7.5 g / cm ³ can be adopted.

Further, the other electrode for the electrolytic capacitor of the present invention comprises a first sintered layer and a second sintered layer having different specific surface areas (total area including pore inner area per unit weight of powder. The same applies hereinafter). Those consisting of slabs are available.

The sintered layer specific surface area smaller (e.g., the first sintered layer), since the pores are large, it is easy to fill penetration of the electrolyte from the surface of the sintered body into the pores, the first Even if the second sintered layer adjacent to the sintered layer has small pores, permeation from the first sintered layer to the second sintered layer is relatively likely to occur, so that the electrolyte in the pores can be prevented. The filling rate is also high.

In such a porous body, the valve metal porous body is bonded to the valve metal foil so that the sintered layer and the valve metal foil are substantially parallel to each other to form an electrode. Further, as a sintered layer is substantially perpendicular to the valve metal foil <br/>, it may be bonded to the valve metal porous body to the valve metal foil.

The electrode of the present invention is manufactured by laminating a plurality of porous compacts formed from valve metal powder into a laminate by a laminating step, and sintering the laminate by a sintering step. The valve is made of a porous metal. The porous body of valve metal having pores is further bonded to a valve metal foil to form an electrode, a dielectric film is formed in the pores of the electrode, and an electrolyte is filled therein to be used in an electrolytic capacitor.

The molded body is thinly molded from fine valve metal particles, and the molding method includes compression molding, for example,
It is molded into a plate or sheet by press molding or roll molding from powder. In addition, the molded body contains valve metal particles.
Steaming to adjust the slurry or paste, to form a film with a desired thickness on a release plate, creating a thin film may be a green sheet was peeled off the same.

In the valve metal powder, individual powder fine particles themselves are
It is equipped with a large number of protrusions or projections, and by molding it, the molded body becomes a large number of metal aggregates, is porous, and has a wide range of pore diameter distribution and a large specific surface area. ing. A plurality of, in particular, a large number of these compacts are laminated to form a laminate, which is heated in a furnace to a high temperature equal to or higher than the sintering temperature and sintered to be integrated into a porous sintered body. That is, a porous body is obtained.

The thickness of one molded body is 50 to 500 μm.
However, this dimension is a thickness required to quickly fill one sintered layer to an adjacent sintered layer with an electrolytic solution, and can be adjusted by the pore size to be filled. The dimension of this compact can be approximately the thickness of the sintered layer.

As described above, the molded body can be a laminated body by laminating a plurality of molded bodies having substantially the same pore size. Further, the sintered body of the electrode is preferably a laminate of two or more kinds of molded bodies having different pore sizes.
This allows the sintered layers adjacent to each other to have different pore sizes.

As an example of the pore size, a compact having a small pore size has a pore size distribution with a median diameter distribution of 0.05 to 0.6 μm.
A distribution of 0.3-1.5 μm is available. The pore diameter is represented by the peak value of the pore diameter distribution of the sintered layer, and the pore diameter is
Evaluate with the peak value by mercury penetration method,
The ratio of the peak pore diameter of the large pore diameter molded body ( first molded body) to the peak pore diameter of the small pore diameter molded body (referred to as the second molded body) is 1.2 to 5. About 0 can be adopted.

The plurality of molded products are preferably composed of a first molded product and a second molded product having different heat shrinkage rates of the molded product. In the laminating step, the first molded body and the second molded body are laminated alternately, for example, to form a laminated body. During the sintering process, due to the difference in shrinkage between the first compact and the second compact, unevenness due to the difference in shrinkage is formed in a streak or layer on the outer surface of the sintered compact. However, the junction area with the negative electrode can be increased, the equivalent series resistance of the capacitor can be reduced, and the high frequency characteristics can be improved.

In the method for producing an electrode of the present invention, the plurality of molded bodies include two types of molded bodies, which are a first molded body and a second molded body having different molded body densities from each other. It is preferable that the first molded body and the second molded body are laminated, for example, alternately to form a laminated body.

The region of the compact having a low density of the compact has a large shrinkage due to the progress of sintering by sintering at a high temperature. Therefore, a concave portion is layered on the outer surface of the valve metal porous body near the bonding interface. Occurs and the surface area of the valve metal porous body increases. This reduces the equivalent series resistance of the capacitor and improves the high frequency characteristics. On the contrary, when sintered at a low temperature, a convex portion is generated, but the effect is the same.

Further, the method for producing an electrode for an electrolytic capacitor according to the present invention comprises at least a first molded body and a second molded body made of valve metal powders having different specific surface areas per unit weight.
It is preferable to include two or more kinds of molded products of the above-mentioned molded product and to laminate the first molded product and the second molded product alternately in the laminating step to obtain a laminated product.

A molded body made of a powder having a small specific surface area (for example, a first molded body) is less likely to be sintered than a molded body made of a powder having a large specific surface area (for example, a second molded body). The thermal contraction rate due to binding is small, and thus large pores are left in the sintered layer, and convex portions are formed on the outer surface. Since the compact having a small specific surface area becomes a sintered layer having large pores, it is easy to fill and permeate the electrolyte from the surface of the sintered body into the pores,
Even if the second sintered layer adjacent to the first sintered layer has small pores, the filling rate of the electrolyte into the pores is high.

Therefore, it is possible to facilitate the filling of the electrolyte from the molded products having different specific surface areas and to improve the capacity drawing efficiency.
In addition, the surface of the porous valve metal body can be provided with unevenness, and the low equivalent series resistance can be achieved by increasing the bonding area with the negative electrode.

In addition, the production of the electrode of the present invention includes two or more kinds of molded bodies, which are a first molded body and a second molded body made of valve metal powders having different physical strengths of agglomerated powders. In the laminating step, the first molded body and the second molded body may be alternately laminated to form a laminated body. In the tantalum powder, the primary particles have an irregular shape having a large number of minute protrusions, and a large number of minute primary particles aggregate with each other to form secondary particles. When the strength is high, the shape is less likely to collapse in the press molding when forming a molded body, so that relatively large pores remain, on the other hand, the powder having secondary particles of low strength is likely to collapse due to compression of the secondary particles. The molded body has relatively small pores.

Therefore, when a compact made of a powder of secondary particles having a high strength is sintered, it is more difficult to sinter than a sintered layer of a compact of a powder having a weak strength. Therefore, the sintered layer is formed by sintering. The shrinkage rate is small, has large pores, and becomes a convex portion on the side surface of the porous body, and the sintered layer from the compact having low strength has a large shrinkage rate due to sintering and has small pores. It becomes a recess on the side surface of the porous body. In this way, by using a large portion of the fine pores in the valve metal porous body as pores for efficiently drawing out the capacity, and by providing the surface area of the valve metal porous body with unevenness, A low equivalent series resistance can be achieved by increasing the contact area with the negative electrode.

Further, in the method for producing an electrode of the present invention, as described above, the molded body is formed into a plate shape or a sheet shape, and in the laminating step, the molded body is laminated on the valve metal foil to form a laminated body. preferable. Alternatively, the molded body may be formed into a plate shape or a sheet shape, and the laminated body may be sintered into a valve metal porous body in the sintering step, and then the valve metal porous body may be bonded to the valve metal foil. In this case, the molded body and the valve metal foil can also be bonded so as to be substantially parallel or perpendicular to each other.

(First Embodiment) The electrolytic capacitor electrode of the first embodiment is manufactured as follows. First, a fine powder of valve metal is compression-molded to form a plurality of plate-shaped compacts, for example, 10 compacts. Next, the surface of the valve metal foil is polished to form the electrode metal foil 3 having fine irregularities on the surface.
Further, these 10 molded bodies are laminated on the electrode metal foil 3 to form a laminated body. Finally, the laminated body is sintered under predetermined conditions to form the valve metal porous body 2, whereby the electrode 20 for the electrolytic capacitor shown in FIG. 1 is completed.

More specifically, the electrolytic capacitor electrode 20 is formed by joining the valve metal porous body 2 to the electrode metal foil 3, and the valve metal porous body 2 includes ten layered sintered layers 1. Are laminated and integrated, each sintered layer 1 is formed by sintering a molded body, and one sintered body corresponds to one sintered layer 1. . The sinter layer 1 is sinter-bonded to the sinter layers 1 disposed above and below it.
The density of the bonding interface region 7 near the bonding surface 6 where the sintered layer 1 contacts the upper and lower sintered layers 1 is smaller than the density of the regions other than the bonding interface region 7, and is formed in the bonding interface region 7. The size of the formed pores is larger than the size of the pores formed in the region other than the bonding interface region 7. Furthermore, as shown in FIG. 3, since the edge of the sintered layer 1 is rounded, a concave portion is formed near the joint surface 6 on the side surface of the valve metal porous body 1.

Regarding the mechanism of forming the concave portion on the side surface of the valve metal porous body 2 and the mechanism of increasing the size of the pores in the joint interface region 7, when the molded bodies are laminated to form a laminated body as described above. , The density of the portion of the laminated body sandwiched between the two molded bodies becomes sparse. Therefore, the density of the portion between the two sintered layers 1 of the valve metal porous body 2 obtained by sintering this laminated body, that is, the vicinity of the bonding interface region 7 becomes sparse. Bonding interface area 7
Since the density is low, the size of the pores formed in the bonding interface region 7 becomes large. Further, since the portion sandwiched between the two compacts has a low density, the shrinkage due to sintering is large, and the shrinkage forms a recess near the joint surface 6 on the side surface of the valve metal porous body 1.

[Example 1] As a specific example, 70000μ
Fine tantalum powder equivalent to F / V / g, size 1.0 mm
It is compression-molded to × 3.0 mm × 0.44 mm to obtain a molded body, and the molded body is laminated on the metal foil for electrode in order of 10 sheets, and 1
Vacuum sintering was performed at 350 ° C. to prepare an electrode 10 for an electrolytic capacitor.

Next, the electrolytic capacitor electrode 10 is replaced with about 8
A dielectric film was formed by chemical conversion in a phosphoric acid solution at 5 ° C. with an applied voltage of 20 V, and then the electrolyte was filled with manganese dioxide. Furthermore, after providing a cathode extraction electrode composed of a carbon layer and a silver conductive resin layer, an external anode and an external cathode terminal were joined, and an electrolytic capacitor was produced by resin molding. The theoretical capacitance of the electrolytic capacitor thus manufactured is about 350 μF. Hereinafter, this electrolytic capacitor is referred to as Example 1.

As a comparative example, fine tantalum powder was compression molded into a block having a size of 1.0 mm × 3.0 mm × 4.4 mm to obtain a valve metal porous body. A valve metal foil having surface irregularities formed by polishing was joined to the block and sintered to form an electrode for an electrolytic capacitor. Hereinafter, this capacitor electrode is referred to as a comparative electrode 1. The density of the valve metal porous body of the comparative electrode 1 is substantially equal to the density of the valve metal porous body 2 of the electrolytic capacitor electrode 10.

Further, in the same manner as that used in Example 1, the theoretical capacitance from the comparative electrode 1 was 350 μF.
A comparative electrolytic capacitor was prepared.

Capacitance when a voltage of frequency 120 Hz was applied to Example 1 and the comparative capacitor, frequency 10
Table 1 below shows the capacitance when a voltage of 0 kHz is applied and the equivalent series resistance when a voltage of frequency 1 MHz, which is the resonance point, is applied.

[0051]

[Table 1]

It can be seen from Table 1 that the capacitance of Example 1 is larger than the capacitance of the comparative capacitor and is close to the theoretical capacitance. In addition, the decrease in electrostatic capacitance that occurs when the applied voltage is high frequency is smaller in the first embodiment than in the comparative capacitor. Further, it can be seen that the equivalent series resistance of Example 1 is superior. Example 1
Has excellent high-frequency characteristics and can carry a large ripple current.

The large capacity of Example 1 is that large pores are formed in the joint interface region of the valve metal porous body 2 of the electrode 10 for the electrolytic capacitor, and the large pores have dielectric properties. This is because the capacitance can be efficiently obtained in the pores by forming the film and further filling the electrolyte.

Further, the high frequency characteristics of Example 1 are excellent because, as described above, since the concave portion is formed on the surface of the valve metal porous body and the surface area of the valve metal porous body becomes large, Example 1 This is because the equivalent series resistance of is reduced.

(Second Embodiment) Next, an electrolytic capacitor electrode according to a second embodiment of the present invention will be described.
The electrolytic capacitor electrode of the present embodiment is manufactured as follows. First, the valve metal fine powder is molded to form two kinds of molded bodies having different molded body densities. In the following examples, the compact having a lower density is referred to as a first compact, and the compact having a higher density is referred to as a second compact. Next, the first molded body and the second molded body are alternately laminated on the metal foil for electrode to form a laminated body. By sintering this laminated body to form a valve metal porous body, the electrolytic capacitor electrode of the present embodiment is completed.

With reference to FIGS. 2 and 4, the electrolytic capacitor electrode 20 according to the present embodiment will be described in detail. As shown in FIG. 2, the electrolytic capacitor electrode 20 is
This is a structure in which the valve metal porous body 2a is bonded to the electrode metal foil 3. The valve metal porous body 2a has a 10-layer structure in which plate-shaped first sintered layers 4 and plate-shaped second sintered layers 5 are alternately laminated. The first sintered layer 4 and the second sintered layer 5 are obtained by sintering the first molded body and the second molded body, respectively. The first sintered layer 4 and the second sintered layer 5 which are adjacent to each other are sintered and joined.

In this example, the size of the pores (not shown) present in the second sintered layer 5 is smaller than the size of the pores (not shown) present in the first sintered layer 4. Further, as shown in FIG. 4, the side surface of the first sintered layer 4 sandwiched between the upper and lower second sintered layers 5 has a concave shape.

The mechanism by which the size of the pores formed in the first sintered layer 4 increases and the mechanism by which the side surface of the first sintered layer 4 becomes concave will be described below. As described above, the first compact having a low density and the second compact having a high density are alternately laminated to form a laminated body and sintered to form the valve metal porous body 2a. Therefore, the density of the first sintered layer 4 formed by sintering the first molded body is smaller than the density of the second sintered layer 4 formed by sintering the second molded body,
Under the conditions of this embodiment, the size of the pores formed in the first sintered layer 4 is larger than the size of the pores formed in the second sintered layer 5, and the first molding is performed. The body has a higher heat shrinkage rate than the second molded body, and during sintering, the first molded body shrinks more than the second molded body.
The side surface of the first sintered layer 4 has a concave shape.

[Embodiment 2] Similar to Embodiment 1, the electrode 2 for electrolytic capacitor is used.
An electrolytic capacitor with a theoretical capacitance of 370 μF is made from 0. First, 70000 μF · V / g tantalum fine powder was compression-molded into a thin plate of 1.0 mm × 3.0 mm × 0.44 mm to obtain a plate-shaped first plate with a density of 4.4 mg / cm ³ .
5 molded articles were prepared. Similarly, 70,000 μF · V /
g tantalum fine powder size 1.0mm × 3.0mm ×
It is molded to 0.44 mm and five second molded bodies are formed on a thin plate with a density of 6.0 mg / cm ³ . The 1st molded object and the 2nd molded object were laminated | stacked by turns on the metal foil for electrodes, and the laminated body of 10 layer structure was formed in the metal foil for electrodes. By sintering this laminated body to form a valve metal porous body, the electrolytic capacitor electrode of the present embodiment is completed. The manufacturing method of the electrode metal foil and the conditions for sintering the laminate are the same as those in the first embodiment.

As Comparative Example 2, tantalum fine powder having a size of 1.0 mm × 3.0 mm × 4.4 mm and a density of 5.2 mg was used.
/ Cm ³ in a block shape by compression molding and sintering to make a valve metal porous body.
A capacitor electrode for comparison was made by bonding and sintering the same metal foil for electrodes as that used for the electrodes of. The sintering conditions at this time are the same as the conditions for sintering the valve metal porous body of the electrolytic capacitor electrode 20.

From this comparative capacitor electrode, a theoretical capacitance of 37 is obtained in the same manner as the capacitor of Example 2.
A 0 μF comparative electrolytic capacitor was made.

The capacitance of the capacitor of Example 2 and the capacitor of the comparative example when a voltage of 120 Hz was applied, the capacitance when a voltage of 100 kHz was applied, and the voltage of a resonance frequency of 1 MHz. Table 2 below shows the equivalent series resistance when a voltage is applied.

[0063]

[Table 2]

Table 2 shows that the capacitance of the capacitor of Example 2 is larger than the capacitance of the comparative capacitor and close to the theoretical capacitance. The decrease in electrostatic capacitance that occurs when the applied voltage is high frequency is also smaller in the capacitor of the second embodiment than in the comparative capacitor. further,
It can be seen that the capacitor of Example 2 is also superior in equivalent series resistance. That is, the capacitor according to the second embodiment is excellent in high frequency characteristics and can flow a large ripple current.

The capacitance of the capacitor of Example 2 is large because large pores are formed in the first sintered layer of the valve metal porous body provided in the electrode 20 for the electrolytic capacitor. Is. That is, by filling the electrolyte in the large pores of this size, the capacitance was efficiently obtained in the pores.

Further, the equivalent series resistance of the capacitor of Example 2 was small because the side surface of the first sintered layer was concave as described above, and the surface area of the valve metal porous body was large. This is because By reducing the equivalent series resistance, the high frequency characteristics of the capacitor of the second embodiment are improved. Further, the physical strength with the negative electrode is increased, and the reliability such as prevention of peeling is improved.

Further, in the above-described embodiment, the same tantalum powder is used to form compacts having different densities, which are then sintered,
Partial coarseness, pore size, different valve metal porous body with different shrinkage, etc. are made, and further, the primary particle diameter of tantalum powder or the degree of aggregation of secondary particles is adjusted, the powder diameter of tantalum powder or By adjusting the bulk density to 2 levels or more,
A plurality of molded bodies having different densities or heat shrinkage rates may be prepared, and the molded bodies may be laminated and sintered to form the valve metal porous body. Further, a molded body may be formed by using two or more kinds of valve metal powders having different densities or heat shrinkage rates.

[0068]

The electrode for an electrolytic capacitor of the present invention comprises a valve metal porous body obtained by laminating and sintering a plurality of molded bodies, and the valve metal porous body has a low density region and a high density region. However, since pores with large dimensions are formed in the region of low density, if an electrolytic capacitor is made using this electrode, it is possible to sufficiently fill the pores with large dimensions with electrolyte. An electrolytic capacitor having a capacity can be obtained.

Further, since the region of low density has a large heat shrinkage, a concave region is formed in the valve metal porous body. As a result, the surface area of the valve metal porous body is increased, the junction resistance with the negative electrode is reduced, the equivalent series resistance of the electrolytic capacitor is reduced, and the high frequency characteristics are improved.

In the electrolytic capacitor electrode of the present invention,
By using a valve metal porous body obtained by laminating and sintering a plurality of molded bodies having different molding densities, the surface area of the valve metal porous body can be further increased.

In the electrolytic capacitor electrode of the present invention,
The surface area of the valve metal porous body can be further increased by forming a plurality of molded bodies from powders of valve metals having different heat shrinkage rates, and using the porous valve metal body formed by stacking and sintering the molded bodies. .

[Brief description of drawings]

FIG. 1 shows a sectional view of an electrode for an electrolytic capacitor according to an embodiment of the present invention.

FIG. 2 shows a cross-sectional view of an electrode for an electrolytic capacitor according to an embodiment of the present invention.

FIG. 3 shows an enlarged sectional view of an electrode for an electrolytic capacitor according to an embodiment of the present invention.

FIG. 4 shows an enlarged sectional view of an electrode for an electrolytic capacitor according to an embodiment of the present invention.

FIG. 5 shows a perspective view of a conventional electrode for an electrolytic capacitor.

[Explanation of symbols]

1 Sintered layer 2 valve metal porous body 2a Valve metal porous body Metallic foil for 3 electrodes 4 First sintered layer 5 Second sintered layer 20 Electrolytic capacitor electrode.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshihiro Higuchi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-50-36951 (JP, A) JP-A-10- 233347 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01G 9/052 H01G 9/04 H01G 9/00

Claims (17)

(57) [Claims] 1. An electrode comprising a valve metal porous body having pores bonded to a valve metal foil, wherein the electrode forms a dielectric film on the inner surface of the pores and fills the pores with an electrolyte. In an electrode for an electrolytic capacitor used in an electrolytic capacitor, the valve metal porous body is a sintered body formed by laminating a plurality of porous sintered layers formed from valve metal powder. An electrode for an electrolytic capacitor, characterized in that a laminated interface region of adjacent sintered layers has pores having a diameter larger than the pores inside the sintered layers in the bound body. 2. The electrolysis according to claim 1, wherein in the plurality of sintered layers, the first sintered layer and the second sintered layer adjacent thereto have different pore sizes. Electrodes for capacitors. 3. The plurality of sintered layers according to claim 1, wherein the first sintered layer and the second sintered layer adjacent thereto have different sintering densities. Electrode for electrolytic capacitor. 4. The plurality of sintered layers according to claim 1, wherein the first sintered layer and the second sintered layer adjacent thereto have different specific surface areas from each other. Electrode for electrolytic capacitor. 5. A sintered body formed by laminating a plurality of sintered layers, wherein the first sintered layer and the second sintered layer are laminated at least once or more. 5. The electrode for an electrolytic capacitor according to any one of 1 to 4. 6. A sintered body formed by laminating a plurality of sintered layers, wherein first sintered layers and second sintered layers are alternately laminated. 4. The electrode for an electrolytic capacitor according to any one of 4 above. 7. The valve metal porous body is bonded to the valve metal foil so that the sintered layer and the valve metal foil are substantially parallel to each other. The electrode for an electrolytic capacitor as described in any one. 8. The valve metal porous body is bonded to the valve metal foil such that the sintered layer is substantially perpendicular to the valve metal foil. The electrode for an electrolytic capacitor as described in. 9. An electrolytic capacitor used as an electrolytic capacitor by bonding a porous body of valve metal having pores to a valve metal foil to form an electrode, forming a dielectric film in the pores of the electrode and filling an electrolyte. A method for manufacturing the electrode for use in a method, comprising: a first molded body and a second molded body which are a plurality of porous molded bodies molded from valve metal powder and have different heat shrinkage rates during sintering. Two or more types of molded bodies consisting of
A laminating step of laminating so as to be bonded to each other into a laminated body, and a sintering step of sintering the laminated body into a porous body of valve metal,
A method of manufacturing an electrode for an electrolytic capacitor, comprising: a porous body of the valve metal, which is formed by laminating a plurality of porous sintered layers. 10. An electrolytic capacitor which is used as an electrolytic capacitor by bonding a porous body of valve metal having pores to a valve metal foil to form an electrode, forming a dielectric film in the pores of the electrode and filling an electrolyte with the electrolyte. A method for producing the electrode for use in a method, comprising: a plurality of porous compacts molded from valve metal powder, and two or more kinds of first compacts and second compacts having different compact densities. A step of laminating the molded articles of 1 above so as to be bonded to each other to form a laminated body; a sintering step of sintering the laminated body to form a porous body of valve metal;
A method of manufacturing an electrode for an electrolytic capacitor, comprising: a porous body of the valve metal, which is formed by laminating a plurality of porous sintered layers. 11. An electrolytic capacitor which is used as an electrolytic capacitor by bonding a porous body of a valve metal having pores to a valve metal foil to form an electrode, forming a dielectric film in the pores of the electrode and filling an electrolyte. A method for manufacturing the electrode for use in a method, comprising: a first molded body and a second molded body, which are a plurality of porous molded bodies molded from valve metal powder, and made of valve metal powders having different specific surface areas. A step of laminating two or more kinds of molded bodies consisting of the above so as to be bonded to each other to form a laminated body, and a sintering step of sintering the laminated body to form a porous body of valve metal,
A method of manufacturing an electrode for an electrolytic capacitor, comprising: a porous body of the valve metal, which is formed by laminating a plurality of porous sintered layers. 12. An electrolytic capacitor which is used as an electrolytic capacitor by joining a porous body of valve metal having pores with a valve metal foil to form an electrode, forming a dielectric film in the pores of the electrode and filling an electrolyte. A method for manufacturing the electrode for use in a method, comprising: a plurality of porous compacts formed from valve metal powder, and a first compact and a second compact made of valve metal powders having different physical strengths from each other. A laminating step of laminating two or more types of shaped bodies made of shaped bodies so as to be bonded to each other into a laminated body; and a sintering step of sintering the laminated body into a porous body of valve metal,
A method of manufacturing an electrode for an electrolytic capacitor, comprising: a porous body of the valve metal, which is formed by laminating a plurality of porous sintered layers. 13. The method for producing an electrode for an electrolytic capacitor according to claim 9, wherein the laminating step comprises alternately laminating the first molded body and the second molded body. 14. The electrode for an electrolytic capacitor according to claim 9, wherein the laminating step repeats laminating the first molded body and the second molded body at least once or more. Production method. 15. The molded body is plate-shaped or sheet-shaped, and in the laminating step, the molded body is laminated on the valve metal foil to form a laminated body. A method for manufacturing an electrode for an electrolytic capacitor as described in 1. 16. The molded body is plate-shaped or sheet-shaped, and after the sintering step, the sintered layer formed by sintering the molded body is substantially parallel to the valve metal foil, The method for manufacturing an electrode for an electrolytic capacitor according to claim 9, wherein the valve metal porous body is bonded to the valve metal foil. 17. A valve metal porous body, wherein the molded body is plate-shaped or sheet-shaped, and after the sintering step, the sintered layer formed by sintering the molded body is substantially perpendicular to the valve metal foil. The method for manufacturing an electrode for an electrolytic capacitor according to claim 9, wherein the body is joined to the valve metal foil.