JP4329800B2 - Solid electrolytic capacitor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a solid electrolytic capacitor and a method for manufacturing the same, and in particular, in order to reduce equivalent series resistance (hereinafter referred to as ESR) and to enable downsizing of the capacitor, the improvement is made to improve the capacity appearance rate. The present invention relates to an applied solid electrolytic capacitor and a manufacturing method thereof.

  An electrolytic capacitor using a metal having a valve action such as tantalum or aluminum is obtained by expanding the dielectric by making the valve action metal as the anode-side counter electrode into the shape of a sintered body or an etching foil. Since it is small and a large capacity can be obtained, it is widely used. In particular, a solid electrolytic capacitor using a solid electrolyte as an electrolyte has features such as small size, large capacity, low equivalent series resistance, easy to chip, and suitable for surface mounting. It is indispensable for miniaturization, high functionality and low cost of electronic equipment.

  In this type of solid electrolytic capacitor, as a small-sized and large-capacity application, an anode foil and a cathode foil made of a valve metal such as aluminum are generally wound with a separator interposed therebetween to form a capacitor element. It is impregnated with a driving electrolyte, and has a sealed structure in which a capacitor element is housed in a metal case such as aluminum or a case made of synthetic resin. As the anode material, aluminum, tantalum, niobium, titanium and the like are used, and as the cathode material, the same kind of metal as the anode material is used.

  By the way, in order to increase the capacitance of the electrolytic capacitor, it is important to improve the capacitance of the cathode material together with the anode material. The capacitance of each electrode in an electrolytic capacitor depends on the type and thickness of the insulating film formed thinly on the electrode surface, the surface area of the electrode, etc., and the dielectric constant of the insulating film is ε and the thickness of the insulating film When the thickness is t and the surface area of the electrode is A, the capacitance C is expressed by the following equation.

C = ε (A / t)
As is apparent from this equation, in order to increase the capacitance, it is effective to increase the electrode surface area, select an insulating film material having a high dielectric constant, and reduce the thickness of the insulating film. Of these, it is not preferable to simply use a large electrode in order to increase the electrode surface area, because it only increases the size of the electrolytic capacitor. Therefore, conventionally, the surface area of the aluminum foil that is the base material of the electrode material is etched to form irregularities, thereby increasing the substantial surface area.

  Further, Patent Document 1 discloses a cathode material obtained by forming a metal film on the surface of a base material by using a metal vapor deposition technique as an alternative to the above etching process. According to this technique, it is said that by selecting the film forming conditions, fine irregularities can be formed on the surface of the film to increase the surface area and to obtain a large capacitance. In addition, if a metal such as Ti, which shows a high dielectric constant when it becomes an oxide, is used as the metal film, the dielectric constant of the insulating film formed on the surface of the cathode material is increased to obtain a larger capacitance. It has been shown that it can.

Further, in Patent Document 2 filed earlier by the present applicant, the capacitance of the electrolytic capacitor is a combined capacitance in which the anode side capacitance and the cathode side capacitance are connected in series. In view of this, in order to increase the capacitance value on the cathode side, a technique of forming a vapor deposition layer made of titanium nitride on a high-purity aluminum surface used for a cathode electrode by a cathode arc vapor deposition method is shown.
JP 59-167209 A JP-A-3-150825

  However, the solid electrolytic capacitor using the cathode foil formed by the conventional technique as described above has the following problems. That is, in the conventional solid electrolytic capacitor, in order to increase the capacitance of the electrolytic capacitor, the surface of the aluminum foil that is the base material of the electrode material is subjected to etching treatment. The increase in the capacitance of the electrode material by the etching technique has a limit because the dissolution proceeds simultaneously and the increase in the area expansion rate is hindered.

  Conventionally, manganese dioxide formed mainly by thermal decomposition of manganese nitrate has been used as the solid electrolyte of the solid electrolytic capacitor. However, since this manganese dioxide has a relatively high conductivity, There was a limit to the reduction. Furthermore, in the step of forming manganese dioxide, heat treatment at 200 to 300 ° C. must be performed several times, so that an oxide film is formed on the surface of the film made of metal nitride formed on the surface of the cathode foil. As a result, the electrostatic capacity of the electrolytic capacitor is reduced, and as a result, the electrostatic capacity of the electrolytic capacitor is reduced.

  The present invention has been proposed in order to solve the above-described problems of the prior art, and its object is to reduce the ESR and to improve the capacity appearance rate and to produce the same. It is to provide a method.

  In order to solve the above-mentioned problems, the present inventor has intensively studied a solid electrolytic capacitor capable of reducing ESR and improving the capacity appearance rate and a method for manufacturing the same, and has completed the present invention. Is. That is, in a winding type solid electrolytic capacitor using a conductive polymer or lead dioxide as an electrolyte layer, a chemical conversion film is formed on the surface of the cathode foil, and a film made of a metal nitride is formed thereon by vapor deposition. Thus, it has been found that the ESR can be reduced and the capacity appearance rate can be improved.

  First, the present inventor has disclosed various types of wound solid electrolytic capacitors using a conductive polymer that has been attracting attention in recent years as an electrolyte layer and has high conductivity and good adhesion to a dielectric film. Study was carried out. Typical examples of the conductive polymer include polyethylene dioxythiophene (hereinafter referred to as PEDT), polypyrrole, polyaniline, TCNQ (7,7,8,8-tetracyanoquinodimethane), or dielectrics thereof. It has been known. Furthermore, various studies were also conducted on a wound-type solid electrolytic capacitor using lead dioxide, which is known as an inorganic conductive compound.

上式より明らかなように、Ｃc が値を持つ（陰極箔が容量を持つ）限り、コンデンサの容量Ｃは陽極側の静電容量Ｃa より小さくなる。言い換えれば、本発明のように陰極箔表面に蒸着したＴｉＮと陰極箔金属とが導通して陰極箔の容量Ｃcが無限大となった場合には、陰極箔の容量成分がなくなり、陽極箔と陰極箔の直列接続の合成容量であるコンデンサの容量Ｃは陽極側の静電容量Ｃa と等しくなって、最大となる。 In addition, the present inventor forms a conversion film on the cathode foil under various conversion voltages, further deposits TiN on the cathode foil, and uses this cathode foil to produce a capacitor under the conditions described later, When the capacity of the foil alone was measured, the capacity was infinite. That is, it was found that TiN formed on the chemical conversion film removed a part of the chemical conversion film formed on the surface of the cathode foil, and that TiN and the cathode foil metal were conductive. By the way, the fact that the electrostatic capacity C of the electrolytic capacitor becomes a combined capacity in which the anode-side electrostatic capacity Ca and the cathode-side electrostatic capacity Cc are connected in series is expressed by the following equation.

As is apparent from the above equation, as long as Cc has a value (the cathode foil has a capacitance), the capacitance C of the capacitor is smaller than the capacitance Ca on the anode side. In other words, when TiN deposited on the surface of the cathode foil and the cathode foil metal are conducted as in the present invention and the capacity Cc of the cathode foil becomes infinite, the capacity component of the cathode foil disappears, and the anode foil and The capacitance C of the capacitor, which is the combined capacitance of the cathode foils connected in series, becomes equal to the capacitance Ca on the anode side and becomes the maximum.

  As the metal nitride, TiN, ZrN, TaN, NbN, or the like that is difficult to form an oxide film on the surface can be used. The film formed on the surface of the cathode is not limited to a metal nitride, and any other material may be used as long as it can form a film and does not oxidize. For example, Ti, Zr, Ta, Nb, etc. can be used.

In addition, as a method for forming a film made of metal nitride on the cathode made of valve metal, the vapor deposition method is preferable in consideration of the strength of the formed film, adhesion to the cathode, control of film forming conditions, etc. However, the cathodic arc plasma deposition method is more preferable. The application conditions of this cathodic arc plasma deposition method are as follows. That is, the current value is 80 to 300 A, and the voltage value is 15 to 20V. In the case of metal nitride, the cathode made of the valve metal is heated to 200 to 450 ° C., and the total pressure including nitrogen is 1 × 10 ⁻¹ to 1 × 10 ⁻⁴ Torr.

  Moreover, it is desirable that the conversion voltage applied to form a conversion coating on the surface of the cathode foil is 10 V or less. The reason is that if the conversion voltage is 10 V or more, the thickness of the conversion coating formed on the surface of the cathode foil increases, the capacitance of the cathode foil decreases, and the capacitance of the capacitor, which is the combined capacity of the anode foil and the cathode foil, This is because the capacity decreases.

  Further, as a chemical conversion solution for the cathode foil, a phosphoric acid type chemical conversion solution such as ammonium dihydrogen phosphate and diammonium hydrogen phosphate, a boric acid type chemical conversion solution such as ammonium borate, an adipic acid type such as ammonium adipate, etc. However, it is desirable to use ammonium dihydrogen phosphate. In addition, 0.005-3% is suitable for the density | concentration of the aqueous solution of ammonium dihydrogen phosphate.

  In addition, as described above, as the conductive polymer, PEDT, polypyrrole, polyaniline, TCNQ, or a dielectric thereof that does not require high-temperature treatment in the capacitor production process can be used. In the winding type capacitor, PEDT can be polymerized at around 100 ° C., temperature control is easy in the capacitor manufacturing process, heat resistance is excellent, and PEDT having the largest capacitance per unit volume is used. It is desirable.

  Then, the manufacturing method of the winding type solid electrolytic capacitor using a conductive polymer as an electrolyte layer is demonstrated. As the anode foil, one obtained by subjecting the surface of an etched aluminum foil to a chemical conversion treatment by a conventionally used method to form a dielectric film is used. This anode foil is wound together with a cathode foil and a separator to form a capacitor element, impregnated with ethylenedioxythiophene (hereinafter referred to as EDT), and further made of 40-60% ferric paratoluenesulfonate. Impregnated with butanol solution and heated at 20 to 180 ° C. for 30 minutes or more. Thereafter, the surface of the capacitor element is covered with a resin, and aging is performed.

  Here, an EDT monomer can be used as the EDT impregnated in the capacitor element, but a monomer solution in which EDT and a volatile solvent are mixed at a volume ratio of 1: 1 to 1: 3 can also be used. As the volatile solvent, hydrocarbons such as pentane, ethers such as tetrahydrofuran, esters such as ethyl formate, ketones such as acetone, alcohols such as methanol, nitrogen compounds such as acetonitrile, etc. may be used. Of these, methanol, ethanol, acetone and the like are preferable. As the oxidizing agent, ferric paratoluenesulfonate dissolved in butanol is used. In this case, the ratio of butanol and ferric paratoluenesulfonate may be arbitrary, but in the present invention, a 40 to 60% solution is used. The mixing ratio of EDT and oxidizing agent is preferably in the range of 1: 3 to 1: 6.

  In addition, as with the conductive polymer described above, various studies were also conducted on a wound solid electrolytic capacitor using lead dioxide that can form a semiconductor layer at a low temperature. As a result, an electrolyte layer made of a conductive polymer was obtained. As in the case of the solid electrolytic capacitor having the above, it was found that the withstand voltage characteristics, the leakage current characteristics, etc. are good, the ESR can be reduced, and a high capacity appearance rate can be obtained. Since this lead dioxide forms a highly conductive semiconductor layer, a solid electrolytic capacitor having low ESR characteristics can be formed. In addition, since the semiconductor layer using lead dioxide can be formed by oxidizing lead acetate with an oxidizing agent such as ammonium persulfate at room temperature, the anodized film is less damaged than manganese dioxide formed at high temperature. It is considered that withstand voltage characteristics, leakage current characteristics, etc. are good, and characteristics equivalent to those of a conductive polymer can be obtained.

  However, lead dioxide has a drawback that the rated voltage is lower than the formation voltage of the anode foil, compared to the PEDT. Therefore, in order to obtain the same rated voltage as that of PEDT, the conversion voltage of the anode foil must be increased, and accordingly, the thickness of the conversion film of the anode foil increases and the capacitance of the anode foil decreases. The capacitance of the capacitor, which is the combined capacitance of the anode foil capacitance and the cathode foil capacitance, is reduced.

  Then, the manufacturing method of the winding type solid electrolytic capacitor using lead dioxide as an electrolyte layer is demonstrated. That is, as the anode foil, one obtained by subjecting the surface of an etched aluminum foil to a chemical conversion treatment by a conventionally used method to form a dielectric film is used. This anode foil is wound together with a cathode foil and a separator to form a capacitor element, and this capacitor element is immersed in a lead acetate aqueous solution in a range from 0.05 mol / liter to a concentration that gives saturated solubility, and acetic acid is added thereto. An aqueous solution of ammonium persulfate in the range of 0.1 to 5 mol per 1 mol of lead is added and left at room temperature for 30 minutes to 2 hours to form a lead dioxide layer on the dielectric layer. Next, the capacitor element is washed with water and dried, and then sealed with a resin to form a solid electrolytic capacitor.

  Even if the cathode foil according to the present invention is used for an electrolytic capacitor using a normal electrolytic solution, an electric double layer capacitor is formed at the interface between the electrolytic solution and the cathode foil and becomes a capacitive component, so that the capacitance of the cathode foil is zero. The maximum capacity as in the present invention cannot be obtained.

  According to the present invention, a chemical conversion film is formed on the surface of the cathode foil by forming a chemical conversion film on the surface of the cathode foil and further forming a film made of the metal nitride thereon. The metal nitride and the cathode foil metal are electrically connected. As a result, the capacity of the cathode foil becomes infinite, and the capacitance component on the surface of the cathode foil disappears. As a result, the capacitance of the capacitor, which is the combined capacity of the anode foil and the cathode foil, is equal to the capacitance of only the anode foil. Become the maximum. Further, since the capacity component of the cathode foil is eliminated, the dielectric loss is also eliminated, and tan δ is also reduced. Therefore, according to the present invention, it is possible to provide a solid electrolytic capacitor capable of reducing ESR and improving the capacity appearance rate, and a method for manufacturing the same.

(1) First Embodiment Hereinafter, a first embodiment of the present invention will be specifically described with reference to Table 1.

  The present embodiment relates to a winding type solid electrolytic capacitor using a conductive polymer as an electrolyte layer. In addition, the cathode foil which formed the chemical conversion film on the surface based on this invention, and also formed the film | membrane which consists of metal nitride on it was created like the following Example 1. FIG. Further, as Comparative Example 1, a cathode foil in which only a chemical conversion film was formed on the cathode surface at the same conversion voltage as in Example 1 was used, and as Conventional Example 1, a normal cathode foil was used.

Example 1
A high-purity aluminum foil (purity 99%, thickness 50 μm) cut to 4 mm × 30 mm is used as a material to be treated, and after etching, an aqueous solution of 0.15% ammonium dihydrogen phosphate at a formation voltage of 2 V Then, a TiN film was formed on the surface by a cathodic arc plasma deposition method. The conditions of the cathodic arc plasma deposition method were as follows: a Ti target was used in a nitrogen atmosphere, a high-purity aluminum foil was heated to 200 ° C., and 5 × 10 ⁻³ Torr, 300 A, 20 V. Then, the cathode foil is wound together with the anode foil and the separator to form a capacitor element having an element shape of 4φ × 7 L. The capacitor element is impregnated with EDT monomer, and further 45% paratoluenesulfonic acid is used as an oxidant solution. Impregnated with ferric butanol solution and heated at 100 ° C. for 1 hour. Thereafter, the surface of the capacitor element was covered with a resin, and aging was performed to form a solid electrolytic capacitor. This solid electrolytic capacitor has a rated voltage of 6.3 WV and a rated capacity of 33 μF.

(Comparative Example 1)
The same material as in Example 1 was used as the material to be treated. After the etching treatment, a cathode foil was prepared by chemical conversion with an aqueous solution of 0.15% ammonium dihydrogen phosphate at a conversion voltage of 2V. Then, using this cathode foil, a solid electrolytic capacitor was formed in the same manner as in Example 1.

(Conventional example 1)
The same material as in Example 1 was used as the material to be treated, and the cathode foil with no chemical conversion film and metal nitride film formed thereon was used. Then, using this cathode foil, a solid electrolytic capacitor was formed in the same manner as in Example 1.

[Comparison result]
Table 1 shows the electrical characteristics of the solid electrolytic capacitors of Example 1, Comparative Example 1, and Conventional Example 1 obtained by the above method.

  As is apparent from Table 1, in Conventional Example 1 in which neither the chemical conversion film nor the metal nitride film is formed on the surface of the cathode foil, the electrostatic capacity (Cap) is "30. The equivalent series resistance (ESR) was as high as “49” and tan δ was as high as “0.120”. On the other hand, in Example 1, Cap increases to “46.8”, which is approximately 1.55 times that of Conventional Example 1, and tan δ increases to “0.020”, which is approximately 16.7% of Conventional Example 1. Declined. Further, the ESR was “35”, which was about 71.4% of the conventional example 1.

  On the other hand, in Comparative Example 1 in which only the chemical conversion film is formed on the surface of the cathode foil, Cap rises to “32.1”, which is about 1.06 times that of Conventional Example 1, and tan δ is “0.088”. 1 to about 73.3%. Further, the ESR was “35”, which was about 71.4% of the conventional example 1.

  The reason why such a result was obtained is considered to be as follows. That is, in Example 1, a film made of a metal nitride is formed by a vapor deposition method on the chemical conversion film formed on the surface of the cathode foil, and this metal nitride is formed on the surface of the cathode foil. A part of the film is removed, and the metal nitride and the cathode foil metal become conductive. Furthermore, in this embodiment, since a conductive polymer is used as the electrolyte, it is not necessary to perform a high temperature treatment in the process of producing the capacitor, so that an oxide film is not formed on the surface of the metal nitride.

  Thus, according to Example 1, the metal nitride deposited on the surface of the cathode foil and the cathode foil metal are electrically connected, the capacity of the cathode foil becomes infinite, the capacity component on the surface of the cathode foil disappears, and as a result, the anode The capacitance of the capacitor, which is the combined capacitance of the foil and the cathode foil, increases to be equal to the capacitance of the anode foil alone. Further, since the capacity component of the cathode foil is eliminated, the dielectric loss is also eliminated, and tan δ is also reduced.

  Furthermore, since the metal nitride formed on the surface of the cathode foil is formed by the vapor deposition method, the metal nitride is not formed on the side surface of the recessed portion of the etched cathode foil surface. Therefore, although the conductive polymer and the cathode foil are in direct contact with each other in this portion, since the chemical conversion film is formed in advance on the surface of the cathode foil, the adhesion between the cathode foil and the conductive polymer is improved. , ESR and tan δ are considered to be reduced.

  On the other hand, in Comparative Example 1 in which only the chemical conversion film was formed on the surface of the cathode foil, the rate of increase in Cap was not large compared to Example 1, but tan δ was about 73.3% of Conventional Example 1, and ESR. Decreased to about 71.4% of Conventional Example 1. This is presumably because the formation of a chemical conversion film on the surface of the cathode foil with a predetermined conversion voltage improved the adhesion between the cathode foil and the conductive polymer, and reduced ESR and tan δ.

  According to the first embodiment having the above-described configuration, in a solid electrolytic capacitor using a cathode foil in which a chemical conversion film is formed on the surface and a film made of a metal nitride is further formed thereon, ESR and tan δ It has become clear that the capacity appearance rate can be significantly improved.

(2) Second Embodiment The present embodiment relates to a winding type solid electrolytic capacitor using lead dioxide as an electrolyte layer. In addition, the cathode foil which formed the chemical conversion film on the surface which concerns on this invention, and also formed the film | membrane which consists of metal nitride on it was created like the following Example 2. FIG. Further, as Comparative Example 2, a cathode foil in which only a chemical conversion film was formed on the cathode surface at the same conversion voltage as in Example 2 was used. As Conventional Example 2, a normal cathode foil was used.

(Example 2)
A high-purity aluminum foil (purity 99%, thickness 50 μm) cut to 4 mm × 30 mm is used as a material to be treated, and after etching, an aqueous solution of 0.15% ammonium dihydrogen phosphate at a formation voltage of 2 V Then, a TiN film was formed on the surface by a cathodic arc plasma deposition method. The conditions of the cathodic arc plasma deposition method were as follows: a Ti target was used in a nitrogen atmosphere, a high-purity aluminum foil was heated to 200 ° C., and 5 × 10 ⁻³ Torr, 300 A, 20 V. And this cathode foil was wound with the anode foil and the separator, and the capacitor | condenser element whose element shape is 4phi * 7L was formed. This capacitor element was immersed in a 3 mol / liter lead acetate aqueous solution, and the same amount of 3 mol / liter ammonium persulfate aqueous solution was added thereto and left at room temperature for 1 hour. Next, the capacitor element was washed with water and dried, and then a solid electrolytic capacitor having a rated voltage of 6.3 WV and a rated capacity of 22 μF was formed in the same manner as in Example 1.

  In Example 2, compared with Example 1 using PEDT, the rated capacity is as small as 22 μF. The reason is as follows. That is, lead dioxide has a lower rated voltage of the capacitor with respect to the formation voltage of the anode foil than PEDT. Therefore, in the case of lead dioxide at the same rated voltage, the formation voltage of the anode foil must be increased. Therefore, the thickness of the anode foil is increased, the capacitance of the anode foil is decreased, and the capacitance of the capacitor, which is the combined capacitance of the capacitance of the anode foil and the capacitance of the cathode foil, is decreased.

(Comparative Example 2)
The same material as in Example 2 was used as the material to be treated. After the etching treatment, a cathode foil was prepared by chemical conversion with an aqueous solution of 0.15% ammonium dihydrogen phosphate at a conversion voltage of 2V. Then, using this cathode foil, a solid electrolytic capacitor was formed in the same manner as in Example 2.

(Conventional example 2)
The same material as in Example 2 was used as the material to be treated, and a cathode foil that did not have a chemical conversion film and a metal nitride film formed thereon was used. Then, using this cathode foil, a solid electrolytic capacitor was formed in the same manner as in Example 2.

[Comparison result]
Table 2 shows the electrical characteristics of the solid electrolytic capacitors of Example 2, Comparative Example 2 and Conventional Example 2 obtained by the above method.

  As is apparent from Table 2, in the conventional example 2 in which neither the chemical conversion film nor the metal nitride film is formed on the surface of the cathode foil, the capacitance (Cap) is "22. As low as 0, the equivalent series resistance (ESR) was as high as “157” and tan δ was as high as “0.129”. On the other hand, in Example 2, Cap was “24.9”, which was about 13% higher than that of Conventional Example 2, and tan δ was “0.033”, which was about 26% of that of Conventional Example 2. Further, the ESR was “136”, which was about 87% of the conventional example 2.

  On the other hand, in Comparative Example 2 in which only the chemical conversion film is formed on the surface of the cathode foil, Cap is “23.1”, which is about 5% higher than Conventional Example 2, and tan δ is “0.092”, which is about the same as that of Conventional Example 2. It decreased to 71%. Further, the ESR was “138”, which was about 88% of the conventional example 2.

  The reason why such a result was obtained is considered to be as follows. That is, in Example 2, a film made of a metal nitride is formed by a vapor deposition method on the chemical conversion film formed on the surface of the cathode foil, and this metal nitride is formed on the surface of the cathode foil. A part of the film is removed, and the metal nitride and the cathode foil metal become conductive. Furthermore, in this embodiment, since lead dioxide is used as the electrolyte, it is not necessary to perform high-temperature treatment in the process of producing the capacitor, so that an oxide film is not formed on the surface of the metal nitride.

  As described above, according to Example 2, the metal nitride deposited on the surface of the cathode foil and the cathode foil metal are electrically connected, the capacity of the cathode foil becomes infinite, and the capacity component on the surface of the cathode foil is eliminated. The capacitance of the capacitor, which is the combined capacitance of the foil and the cathode foil, increases to be equal to the capacitance of the anode foil alone. Further, since the capacity component of the cathode foil is eliminated, the dielectric loss is also eliminated, and tan δ is also reduced.

  Furthermore, since the metal nitride formed on the surface of the cathode foil is formed by the vapor deposition method, the metal nitride is not formed on the side surface of the recessed portion of the etched cathode foil surface. Therefore, lead dioxide and the cathode foil are in direct contact with each other in this portion, but since the chemical conversion film is previously formed on the surface of the cathode foil, the adhesion between the cathode foil and the lead dioxide is improved, and ESR. And tan δ are considered to be reduced.

  In Example 2, the increase rate of capacitance (about 13%) is smaller than the increase rate (about 55%) in Example 1 using PEDT for the following reason. It is thought that. That is, as described above, in Example 2, when the same rated voltage as that in Example 1 is used, the formation voltage of the anode foil must be increased, so that the thickness of the anode foil increases and the capacitance of the anode foil increases. Becomes smaller. Therefore, even if the capacitance of the cathode foil becomes infinite by depositing TiN, the contribution to the capacitance of the capacitor, which is the combined capacitance of the capacitance of the anode foil and the capacitance of the cathode foil, is PEDT. This is considered to be because it becomes smaller than Example 1 using.

  On the other hand, in Comparative Example 2 in which only the chemical conversion film was formed on the surface of the cathode foil, the rate of increase in Cap was not large compared to Example 2, but tan δ was about 71.3% of Conventional Example 2 and ESR. Decreased to about 87.9% of Conventional Example 2. This is presumably because the formation of a chemical conversion film on the surface of the cathode foil with a predetermined conversion voltage improved the adhesion between the cathode foil and lead dioxide and reduced ESR and tan δ.

  According to the second embodiment having such a configuration, in a solid electrolytic capacitor using a cathode foil in which a chemical conversion film is formed on the surface and a film made of a metal nitride is further formed thereon, lead dioxide is used as an electrolyte. Even when used, it has become clear that ESR and tan δ can be reduced and the capacity appearance rate can be greatly improved, as in the case of a solid electrolytic capacitor having an electrolyte layer made of a conductive polymer.

Claims (8)

A cathode foil made of a valve metal and an anode foil made of a valve metal having an oxide film formed on the surface thereof are wound through a separator to form a capacitor element, and is made of a conductive polymer between the cathode foil and the anode foil. In a solid electrolytic capacitor in which an electrolyte layer is formed,
A chemical conversion film was formed on the surface of the cathode foil, and a vapor deposition layer made of a metal nitride was formed thereon by vapor deposition so as to remove a part of the chemical conversion film thereon, and the vapor deposition layer and the cathode foil were made conductive. Solid electrolytic capacitor characterized by A cathode foil made of a valve metal and an anode foil made of a valve metal having an oxide film formed on the surface thereof are wound through a separator to form a capacitor element, and an electrolyte made of lead dioxide between the cathode foil and the anode foil In a solid electrolytic capacitor with a layer formed,
A chemical conversion film was formed on the surface of the cathode foil, and a vapor deposition layer made of a metal nitride was formed thereon by vapor deposition so as to remove a part of the chemical conversion film thereon, and the vapor deposition layer and the cathode foil were made conductive. Solid electrolytic capacitor characterized by   The solid electrolytic capacitor according to claim 1, wherein the conductive polymer is polyethylene dioxythiophene. The solid electrolytic capacitor according to any one of claims 1 to 3 , wherein the valve metal is aluminum. 3. The solid electrolytic capacitor according to claim 1 , wherein the metal nitride is any one of TiN, ZrN, TaN, and NbN. The solid electrolytic capacitor according to claim 1 , wherein the vapor deposition method is a cathodic arc plasma vapor deposition method. A cathode foil made of a valve metal and an anode foil made of a valve metal having an oxide film formed on the surface thereof are wound through a separator to form a capacitor element, and is made of a conductive polymer between the cathode foil and the anode foil. In the manufacturing method of the solid electrolytic capacitor for forming the electrolyte layer,
Forming a chemical conversion film on the surface of the cathode foil, and further forming a vapor deposition layer made of a metal nitride by vapor deposition so as to remove a part of the chemical conversion film on the surface, and electrically connecting the vapor deposition layer and the cathode foil; A method for producing a solid electrolytic capacitor. A cathode foil made of a valve metal and an anode foil made of a valve metal having an oxide film formed on the surface thereof are wound through a separator to form a capacitor element, and an electrolyte made of lead dioxide between the cathode foil and the anode foil In the method of manufacturing a solid electrolytic capacitor for forming a layer,
Forming a chemical conversion film on the surface of the cathode foil, and further forming a vapor deposition layer made of a metal nitride by vapor deposition so as to remove a part of the chemical conversion film on the surface, and electrically connecting the vapor deposition layer and the cathode foil; A method for producing a solid electrolytic capacitor.