JP2533911B2 - Solid electrolytic capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a solid electrolytic capacitor having a conductor layer having good high-temperature life performance and capable of taking out a cathode by soldering.

[Conventional technology]

A solid electrolytic capacitor in which a dielectric oxide film layer, a semiconductor layer, and a conductor layer are laminated on the surface of an anode substrate made of a metal having a valve action is conventionally known to use manganese dioxide as a semiconductor layer. . The cathode of such a solid electrolytic capacitor is taken out by forming a solder layer on the outer periphery of the conductor layer and further soldering the cathode lead to the solder layer. The above-mentioned conductor layer is generally a conductive paste layer composed of metal powder and resin, and the content of the metal powder is a high concentration of about 90% by weight in order to form a solder layer on the conductor layer.

[Problems to be Solved by the Invention]

However, in the above-mentioned solid electrolytic capacitor, since the types of the semiconductor layer and the conductive paste layer are extremely different, the difference in the coefficient of thermal expansion is remarkable, and as a result, the high temperature life performance, especially the temporal change of the ESR value in the high frequency band is large. Will be things. Further, since the metal powder occupying the conductive paste is a noble metal, if the content is high, the cost will be considerably increased.

[Means for solving the problem]

The present invention has been made to solve the above-mentioned problems, and is formed by sequentially forming a dielectric oxide film layer, a semiconductor layer and a conductor layer on the surface of an anode substrate made of a metal having a valve action. In the solid electrolytic capacitor, the conductor layer is a layer in which a second conductive paste layer made of metal powder and resin is laminated on a first conductive paste layer made of metal oxide powder, metal powder and resin. It is in.

The solid electrolytic capacitor of the present invention will be described below.

Examples of the valve metal substrate used as the anode of the solid electrolytic capacitor of the present invention include aluminum, tantalum,
Any metal having a valve action such as niobium, titanium and alloys having these as substrates can be used.

The oxide film layer on the surface of the anode substrate may be an oxide layer of the anode substrate itself provided on the surface layer of the anode substrate, or may be a layer of another dielectric oxide provided on the surface of the anode substrate. It may be present, but it is particularly preferable that the layer is made of an oxide of the anode valve metal itself. In any case, as a method of providing the oxide layer, a conventionally known method such as an anodizing method using an electrolytic solution can be used.

Next, the composition of the semiconductor layer used in the present invention and the manufacturing method are not particularly limited, but in order to enhance the performance of the capacitor, lead dioxide, or lead dioxide and lead sulfate as the main components, is used in the conventional chemical deposition. It is preferable to prepare by the method or the electrochemical deposition method.

Examples of the chemical deposition method include a method of chemically depositing from a reaction mother liquor containing a lead-containing compound and an oxidizing agent.

Examples of the lead-containing compound include oxine, acetyl ascent, pyromeconic acid, salicylic acid, alizarin, polyvinyl acetate, porphyrin-based compound, crown compound,
Lead-containing compounds in which lead atoms are coordinate-bonded or ionic-bonded to chelate-forming compounds such as cryptate compounds, lead citrate, lead acetate, basic lead acetate, lead chloride, lead bromide, lead perchlorate, Examples include lead chlorate, lead sulfamate, lead silicon hexafluoride, lead bromate, lead borofluoride, lead acetate hydrate, and lead nitrate. These lead-containing compounds are
It is appropriately selected depending on the solvent used for the reaction mother liquor. Water or an organic solvent is used as the solvent. Two or more lead-containing compounds may be mixed and used.

The concentration of the lead-containing compound in the reaction mother liquor is within the range of 0.05 mol / concentration from the concentration providing the saturated solubility, preferably within the range of 0.1 mol / concentration from the concentration providing the saturated solubility, more preferably the saturated solubility is imparted. The concentration ranges from 0.5 mol / mol. If the concentration of the lead-containing compound in the reaction mother liquor is less than 0.05 mol / mol, a solid electrolytic capacitor having good performance cannot be obtained. Further, when the concentration of the lead-containing compound in the reaction mother liquor exceeds the saturation solubility, the merit of increasing the addition amount is not recognized.

Examples of the oxidant include quinone, chloranil, pyridine-N-oxide, dimethylflufoxide, chromic acid, potassium permanganate, selenium oxide, mercury acetate, vanadium oxide, sodium chlorate, ferric chloride,
Examples thereof include hydrogen peroxide, coconut powder, and benzoyl peroxide. These oxidizing agents may be appropriately selected depending on the solvent used in the reaction mother liquor. Also, two or more oxidizing agents may be mixed and used.

The amount of the oxidizing agent used is 0.1 of the molar amount of the lead-containing compound used.
It is preferably within a range of 5 to 5 times mol. When the proportion of the oxidizing agent used is more than 5 times the mole amount of the lead compound used, there is no cost advantage, and when it is less than 0.1 times the mole amount, a solid electrolytic capacitor having good performance cannot be obtained.

As a method of forming a semiconductor layer containing lead dioxide as a main component, for example, a reaction mother liquor is prepared by mixing a solution in which a lead-containing compound is dissolved and a solution in which an oxidizing agent is dissolved, and then the reaction mother liquor is coated with the above-described oxide film. A method of immersing the provided anode substrate and chemically precipitating it can be mentioned.

On the other hand, as the electrochemical deposition method, for example, a method previously proposed by the present inventors to deposit lead dioxide by electrolytic oxidation in an electrolytic solution containing a high-concentration lead-containing compound can be mentioned (Japanese Patent Laid-open Publication No. Sho. 62-185307).

Further, when the semiconductor layer is composed of lead dioxide which originally functions as a semiconductor and a layer containing lead sulfate which is an insulating material as a main component, the leakage current of the capacitor can be reduced by mixing lead sulfate. On the other hand, the compounding of lead sulfate lowers the electric conductivity of the semiconductor layer and increases the loss coefficient, but a high level of performance can be maintained and expressed even when compared with conventional solid electrolytic capacitors. Therefore, the semiconductor layer is
If it is composed of a mixture of lead dioxide and lead sulfate,
Good capacitor performance can be maintained and expressed in a wide range of compositions of 90 parts by weight or less of lead sulfate with respect to 10 parts by weight or more and less than 100 parts by weight, but lead sulfate is preferably used for 20 to 50 parts by weight of lead dioxide. A good balance between the leakage current and the loss coefficient is achieved in the range of 80 to 50 parts by weight, more preferably 25 to 35 parts by weight of lead dioxide and 75 to 65 parts by weight of lead sulfate. If the amount of lead dioxide is less than 10 parts by weight, the conductivity is deteriorated, the loss factor increases, and the capacity does not appear sufficiently.

The semiconductor layer containing lead dioxide and lead sulfate as main components can be formed by chemical deposition using, for example, an aqueous solution containing lead ions and persulfate ions as a reaction mother liquor. Also, a suitable oxidizing agent containing no persulfate ion may be added.

The lead ion concentration in the mother liquor is within the range of 0.05 mol / concentration from the concentration giving the saturated solubility, preferably 0.1 mol / percent from the concentration giving the saturated solubility, and more preferably 0.5 mol / percent from the concentration giving the saturated solubility. If the concentration of lead ions is higher than the saturation solubility, there is no merit by increasing the amount. If the concentration of lead ions is lower than 0.05 mol / mol, the lead ions in the mother liquor are too thin, and the number of times of coating must be increased.

On the other hand, the concentration of persulfate ions in the mother liquor is in the range of 5 to 0.05 in terms of molar ratio with respect to lead ions. If the concentration of persulfate ion is more than 5 with respect to the lead ion, unreacted persulfate ion remains, resulting in higher cost, and the concentration of persulfate ion is less than 0.05 with respect to the lead ion. If so, unreacted lead ions remain and the conductivity deteriorates, which is not preferable.

Examples of compounds that give lead ion species include lead citrate, lead perchlorate, lead nitrate, lead acetate, basic lead acetate, lead chlorate, lead sulfamate, lead hexafluoride, lead bromate, and lead chloride. , Lead bromide and the like. Two or more kinds of compounds that give these lead ion species may be mixed and used.

On the other hand, examples of the compound that provides the persulfate ion species include potassium persulfate, sodium persulfate, and ammonium persulfate. Two or more kinds of these compounds giving the persulfate ion species may be mixed and used.

Examples of the oxidizing agent include hydrogen peroxide, hypochlorite, chlorite, chlorate, perchlorate and the like.

Next, the conductor layer provided on the semiconductor layer formed as described above includes a first conductive paste layer made of metal oxide powder, metal powder and resin, and a first conductive paste layer made of metal powder and resin on the first conductive paste layer. It is a layer in which two conductive paste layers are laminated.

Examples of the metal oxide powder include manganese dioxide, tin dioxide, tungsten dioxide, lead dioxide, copper monoxide, zinc monoxide, nickel monoxide, cobalt monoxide, titanium dioxide, iron sesquioxide, barium titanate, tantalum oxide, Vanadium trioxide, tungsten trioxide and the like,
It is desirable to use a metal oxide powder for forming a semiconductor layer, but lead dioxide is particularly preferable from the viewpoint of good conductivity. Examples of the metal powder include silver powder, gold powder, palladium powder, copper powder, nickel powder, silver-copper alloy powder, silver-nickel alloy powder, silver-coated copper powder, silver-coated nickel powder, and silver-coated carbon powder. And alloy powders thereof.

The metal powder is preferably in the shape of flakes or corals in order to improve the conductivity of the conductive paste, but may be in the shape of a normal sphere or a shape similar to a sphere.

Further, the content ratio of the metal oxide powder in the paste to the metal powder in the paste is preferably in the range of 1/6 to 6 times the weight of the metal powder. If the ratio of the mixture of metal oxide powder is less than 1/6 times that of the metal powder, the high temperature stability of the manufactured solid electrolytic capacitor may be insufficient, and if it exceeds 6 times that of the metal powder, the electrical conductivity becomes poor. It may be insufficient.

The action of the metal powder and the metal oxide powder is presumed as follows. That is, the conductivity of the metal oxide powder is about 1/100 to 1/1000 compared to the conductivity of the metal powder, but when dispersed together with the metal powder in the paste, only the metal powder is dispersed. The conductivity is not so deteriorated as compared with the case of On the other hand, regarding high-temperature stability, it is considered that the coefficient of thermal expansion of the resin that is the paste component is large and it is important to reduce this coefficient in order to prevent thermal stress. It seems to have the effect of reducing the coefficient.

On the other hand, as the resin used for the conductive paste, the resin used for known conductive paste is used, for example, acrylic resin, alkyd resin, fluororesin, vinyl resin, silicone resin, epoxy resin, urethane resin, phenol resin, etc. Is mentioned. The resin components in the first and second conductive paste layers are preferably the same in order to have the same coefficient of thermal expansion.

The ratio of the metal powder and the metal oxide powder (hereinafter collectively referred to as powder) in the first conductive paste layer is 35 to 95% by weight, and particularly preferably 55 to 95% by weight. If the content of the powder is less than 35% by weight, the conductivity of the paste is insufficient, and if it exceeds 95% by weight, the adhesiveness of the paste is insufficient, and the performance of the solid electrolytic capacitor is deteriorated.

The proportion of the metal powder in the second conductive paste layer is such that solder can be attached when the cathode lead described later is connected by solder, and generally 75 to 95% by weight is preferable. If the proportion of the metal powder is less than 75% by weight, it becomes difficult to attach the solder, and if it exceeds 95% by weight, the adhesiveness of the paste becomes insufficient.

It is important that the first conductive paste layer described above is formed on the entire surface of the semiconductor layer, and if formed on only a part of the semiconductor layer, the ESR value of the manufactured solid electrolytic capacitor will be poor.

On the other hand, it suffices to stack the second conductive paste layer on a part of the first conductive paste layer, and generally the second conductive paste layer is formed on the portion to which the solder for connecting the cathode lead is attached. It should be a part.

Next, for example, a cathode lead formed by plating tin on copper is connected to the second conductive paste layer by soldering.

The solid electrolytic capacitor of the present invention thus configured can be used as a general-purpose capacitor product for various purposes by, for example, resin molding, a resin case, a metal outer case, resin dipping, and a laminated film outer case.

〔Example〕

 Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.

Example 1 An aluminum foil having a length of 2 cm and a width of 0.5 cm was used as an anode, and the surface of the foil was electrochemically etched by an alternating current.
Crim the anode terminal to the etched aluminum foil,
The anode terminal was connected. Then, it was electrochemically treated in an aqueous solution of phosphoric acid and ammonium phosphate to form an oxide film of alumina, and a low-voltage etched aluminum conversion foil (about 10 μF / cm ² ) was obtained. Then, it was immersed in 1 mol of lead acetate trihydrate / water solution except for the anode terminal. On the other hand, an aluminum foil prepared separately was used as a negative electrode, and an anode terminal was used as a positive electrode to carry out an electrochemical reaction at 15V. The lead dioxide semiconductor layer formed on the chemical conversion foil was thoroughly washed with water and then dried under reduced pressure at 120 ° C. Then, a first conductive paste layer consisting of 55% by weight of tungsten trioxide powder, 35% by weight of silver powder and 10% by weight of butadiene resin was applied and formed on the entire surface of the semiconductor layer. Second, consisting of 90% by weight of silver powder and 10% by weight of butadiene resin
Was formed on a part of the first conductive paste layer. Thereafter, a tin-plated copper cathode lead was connected to the above-mentioned second conductive paste layer by soldering. Subsequently, the resin was sealed to produce a solid electrolytic capacitor.

Example 2 A portion of a chemical conversion foil similar to that of Example 1 other than the anode terminal was immersed in a mixed solution (reaction mother liquor) of an aqueous solution of lead acetate trihydrate (2.4 mol / mol) and ammonium persulfate (4 mol / mol).
After reacting at 80 ° C for 30 minutes, a semiconductor layer made of lead dioxide and lead sulfate was formed on the dielectric oxide film layer. The produced semiconductor layer was composed of lead dioxide and lead sulfate, and it was confirmed by mass spectrometry, X-ray analysis and infrared spectroscopy that lead dioxide was contained in an amount of about 25% by weight.

Then, a first conductive paste layer composed of 30% by weight of silver powder, 60% by weight of lead dioxide powder and 10% by weight of acrylic resin was formed on the entire surface of the semiconductor layer. Then, in the same manner as in Example 1 except that the resin component was changed to acrylic resin, the second
A conductive paste layer and a cathode lead were formed, connected, and sealed to produce a solid electrolytic capacitor.

Example 3 After a semiconductor layer made of lead dioxide and lead sulfate was formed in the same manner as described in Example 2, 25% by weight of silver powder, 65% by weight of lead dioxide powder, and 10% by weight of urethane resin were used as the first conductive material. A paste layer is formed on the entire surface of the semiconductor layer and gold powder 90
A second conductive paste layer composed of 10% by weight of urethane resin and 10% by weight of urethane resin was formed on a part of the first conductive paste layer.
Then, the cathode lead was connected to the above-mentioned second conductive paste layer by soldering. Subsequently, the resin was sealed to produce a solid electrolytic capacitor.

Comparative Examples 1-2 In Examples 1 and 2, except that the first conductive paste layer was not formed and the second conductive paste layer was formed over the entire surface of the semiconductor layer, respectively. A solid electrolytic capacitor was produced in the same manner as in.

Table 1 collectively shows the characteristic values of the solid electrolytic capacitors produced in Examples 1 to 3 and Comparative Examples 1 and 2.

[Advantages of the Invention] As described above, in the solid electrolytic capacitor according to the present invention, the conductor layer has a part of the metal powder on the first conductive paste layer made of metal oxide powder, metal powder and resin. Since it is a layer in which a second conductive paste layer made of a resin and is laminated, it has excellent high-temperature stability in the high-frequency band, and the cathode lead can be taken out with solder, and workability is good. It is a solid electrolytic capacitor that can be industrially advantageously manufactured because the total amount of metal powder used is small.

Claims (2)

(57) [Claims] 1. A solid electrolytic capacitor in which a dielectric oxide film layer, a semiconductor layer and a conductor layer are sequentially formed on the surface of an anode substrate made of a metal having a valve action, wherein the conductor layer is a metal oxide. A solid electrolytic capacitor, which is a layer in which a second conductive paste layer made of metal powder and resin is laminated on a first conductive paste layer made of powder, metal powder and resin. 2. The solid electrolytic capacitor according to claim 1, wherein the semiconductor layer is lead dioxide or a layer containing lead dioxide and lead sulfate as main components.