JPH0695492B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a solid electrolytic capacitor, and more particularly to a method for manufacturing a solid electrolytic capacitor having excellent high temperature life characteristics after encapsulation.

[Prior Art] Generally, in an element of a solid electrolytic capacitor, an oxide film layer is formed on an anode substrate made of a valve metal, and a semiconductor layer such as manganese dioxide is formed as an opposite electrode on the outer surface of the oxide film layer. Further, in order to reduce the contact resistance, a silver paste layer is provided to form a conductor layer. The solid electrolytic capacitor element thus manufactured is sealed with thermosetting resin or the like.

[Problems to be Solved by the Invention] However, when the solid electrolytic capacitor element formed up to the conductor layer is directly sealed with a thermosetting resin or the like,
The high temperature life characteristics of the produced solid electrolytic capacitor were sometimes significantly deteriorated.

In view of the above circumstances, it is an object of the present invention to provide a method for manufacturing a solid electrolytic capacitor having excellent high temperature life characteristics after sealing.

[Means for Solving the Problems] The inventors of the present invention have, as a result of intensive studies to solve the above-mentioned problems, surprisingly, after forming the conductor layer, heat the solid electrolytic capacitor element at a high temperature. By doing so, it was found that the above-mentioned object can be effectively achieved, and a solid electrolytic capacitor with good performance can be obtained, and the present invention has been completed. That is, according to the present invention, in the method for producing 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, After forming the body layer, apply this solid electrolytic capacitor element to 100 ℃ -260 ℃
In the method for manufacturing a solid electrolytic capacitor, the solid electrolytic capacitor is sealed after being heated at the temperature. In order to improve the performance of the solid electrolytic capacitor, the semiconductor layer is preferably a layer containing lead dioxide as a main component or a layer containing a mixture containing lead dioxide and lead sulfate as a main component.

[Specific Configuration and Action of the Invention] Hereinafter, a method for manufacturing the solid electrolytic capacitor of the present invention will be described.

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 substrate itself, or may be a layer of another dielectric oxide provided on the surface of the substrate. Preferably, it is a layer consisting of the oxide of the valve metal itself.

In any case, a conventionally known method can be used as a method for providing the oxide layer.

Next, there is no particular limitation on the composition of the semiconductor layer used in the present invention and the manufacturing method, but in order to improve the performance of the capacitor, lead dioxide or lead dioxide and lead sulfate is used as a main component, and a conventionally known chemical deposition method is used. It is preferable to manufacture by the method or the electrochemical deposition method.

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

As the lead-containing compound, for example, oxine, acetylacetone, 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 thereof 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. Moreover, you may use these lead-containing compounds in mixture of 2 or more types.

The concentration of the lead-containing compound in the reaction mother liquor is in the range of 0.05 mol / l from the concentration giving the saturated solubility, preferably in the range of 0.1 mol / l from the concentration giving the saturated solubility, more preferably the saturated solubility. It is in the range of 0.5 mol / l from the given concentration. The concentration of lead-containing compound in the reaction mother liquor is 0.05 mol
If it is less than / l, a solid electrolytic capacitor with 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.

As the oxidizing agent, for example, quinone, chloranil, pyridine-N-oxide, dimethyl sulfoxide, chromic acid, potassium permanganate, selenium oxide, mercury acetate,
Examples thereof include vanadium oxide, sodium chlorate, ferric chloride, hydrogen peroxide, benzoyl peroxide, calcium hypochlorite, calcium chlorite, calcium chlorate, calcium perchlorate and the like. These oxidizing agents may be appropriately selected depending on the solvent used. Also, two or more oxidizing agents may be mixed and used.

The proportion of the oxidizing agent used is 5 to 5 times the molar amount of the lead-containing compound used.
It is preferably in the range of 0.1 times by mole. If 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 if it is less than 0.1 times the mole amount, a solid electrolytic capacitor with good performance cannot be obtained.

As a method for 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 oxidant is dissolved, and then the above-mentioned oxide film is formed on the reaction mother liquor. There is a method of immersing a chemical conversion foil having a to chemically deposit.

On the other hand, as the electrochemical deposition method, for example, a method proposed by the present inventors to deposit lead dioxide by electrolytic oxidation in an electrolytic solution containing high-concentration lead ions can be cited (Japanese Patent Application No. Sho. 61-26952).

Further, when the semiconductor layer is composed of a layer containing lead dioxide which originally functions as a semiconductor and lead sulfate which is an insulating material as a main component, the leakage current value of the capacitor can be reduced by blending lead sulfate. On the other hand, the compounding of lead sulfate lowers the electric conductivity of the semiconductor layer and thus increases the loss coefficient value, but a high level of performance can be maintained and expressed even when compared with the conventional solid electrolytic capacitor. Therefore, the semiconductor layer is
If it is composed of a mixture of lead dioxide and lead sulfate,
It is possible to maintain and develop good capacitor performance in a wide range of composition 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 preferably 20 to 20 parts by weight of lead dioxide.
The balance between the leakage current value and the loss coefficient value is particularly good in the range of 80 to 50 parts by weight of lead sulfate to 50 parts by weight, more preferably 75 to 65 parts by weight of lead sulfate to 25 to 35 parts by weight of lead dioxide. Become. If the amount of lead dioxide is less than 10 parts by weight, the electroconductivity deteriorates, the loss factor value increases, and the capacity does not appear sufficiently.

The semiconductor layer mainly composed of lead dioxide and lead sulfate is, for example,
An aqueous solution containing lead ions and persulfate ions can be formed as a reaction mother liquor by chemical deposition. or,
A suitable oxidizing agent that does not contain persulfate ions may be added.

The concentration of lead ion in the mother liquor is determined from the concentration that gives saturated solubility.
0.05 mol / l, preferably from a concentration giving a saturated solubility of 0.
1 mol / l, more preferably from a concentration that gives saturated solubility
Within the range of 0.5 mol / l. If the concentration of lead ions is higher than the saturation solubility, there is no merit by increasing the amount.
When the concentration of lead ions is lower than 0.05 mol / l,
Since the lead ion concentration in the mother liquor is too low, the number of semiconductor depositions 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 giving lead ion species include lead citrate, lead perchlorate, lead nitrate, lead acetate, basic lead acetate, lead chlorate, lead sulfamate, lead hexafluoride, lead bromate, and chloride. Examples thereof include lead and lead bromide. 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 gives a 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.

On the other hand, examples of the oxidizing agent include hydrogen peroxide, calcium hypochlorite, calcium chlorite, calcium chlorate, calcium perchlorate, and the like.

Next, a conductor layer is formed by forming a metal layer or a carbon layer on the semiconductor layer formed as described above, or by forming a metal layer on the carbon layer. . The method of forming the carbon layer on the semiconductor layer is not particularly limited, and a conventionally known method, for example, a method of applying a carbon paste is adopted. As a method for providing a metal layer on the carbon layer, for example, a method of applying a paste containing silver, nickel, copper, silver-coated copper or the like, or a method already proposed by the present inventors (Japanese Patent Application No. 61
-266092), or a method of plating or vapor depositing silver, nickel, copper or the like.

The solid electrolytic capacitor element thus manufactured is heated at a high temperature of 100 ° C. to 260 ° C. and then sealed. The temperature and time of heating cannot be unconditionally specified because they vary depending on the type of solid electrolytic capacitor element, the type of semiconductor layer, the type of conductor layer, composition, etc., but find the approximate conditions as follows. be able to.
That is, leave the solid electrolytic capacitor element that is not pre-sealed for several hours at several temperatures, measure the ESR value at high frequency, the time when the ESR value stabilizes, and the temperature at that time as a guide for heating. can do. When the heating temperature is low, the heating time becomes long to improve the high temperature life characteristics, and conversely, when the heating temperature exceeds 260 ° C, the performance of the solid electrolytic capacitor itself deteriorates.

The solid electrolytic capacitor element heated at high temperature is sealed with a thermosetting resin such as epoxy resin, phenol resin, urethane resin, alkyd resin. The sealing method in this case may be a dipping method, a potting method, or sealing with a photocurable resin, or
A sealing method in which both the thermosetting resin and the photocurable resin are used in two steps may be used.

[Examples] Hereinafter, the present invention will be described in more detail 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, the surface of the foil was electrochemically etched by an alternating current, and then an anode terminal was caulked to the etched aluminum foil, and an anode lead wire was connected. Then, it was electrochemically treated in an aqueous solution of boric acid and ammonium borate to form an oxide film of alumina to obtain a low-pressure etched aluminum chemical conversion foil (about 10 μF / cm ² ). After winding this formed foil, the lead foil trihydrate 1.0
It was immersed in a mol / l aqueous solution. This formed foil was used as the anode side and a normal, non-etched aluminum foil was used as the cathode side, and electrolytic oxidation was performed at 15V. After 1 hour, the semiconductor layer made of lead dioxide formed on the chemical conversion foil was washed with water to remove unreacted materials, and then dried. Next, a conductor layer was formed on the semiconductor layer with a conductive paste composed of 30% by weight of silver powder, 60% by weight of lead dioxide powder, and 10% by weight of acrylic resin. After taking out the cathode, it was heated at 140 ° C. for 100 hours. Then, the element was housed in an aluminum can, and the housing port was sealed with an epoxy resin.

Example 2 The same formed foil as in Example 1 was mixed with lead acetate trihydrate 2.4 mol / l.
The mixture was immersed in a mixed solution of the aqueous solution of 4 and an aqueous solution of ammonium persulfate of 4 mol / l and reacted at 80 ° C. for 30 minutes. The generated semiconductor layer was washed with water to remove unreacted materials and dried. Then, a conductor layer was formed in the same manner as in Example 1. 150 after removing the cathode
Heat at 80 ° C. for 80 hours. Then, it was sealed with an epoxy resin in the same manner as in Example 1.

The semiconductor layer contains about 25% by weight lead dioxide and about 75% lead sulfate.
It was confirmed to consist of wt% by X-ray analysis and infrared spectroscopic analysis.

Example 3 A solid electrolytic capacitor element which had been heated up in the same manner as in Example 2 was dipped in an epoxy acrylate resin and photo-cured, then again dipped in the epoxy resin, thermally cured and sealed.

Comparative Example 1 A solid electrolytic capacitor was prepared by sealing in the same manner as in Example 1 except that the conductor was formed in Example 1 and heating was not performed after taking out the cathode.

Comparative Example 2 A solid electrolytic capacitor was produced by sealing in the same manner as in Example 2 except that the conductor was formed in Example 2 and heating was not performed after taking out the cathode.

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

[Effects of the Invention] As described above, according to the present invention, after forming the conductor layer, the solid electrolytic capacitor element is heated to a high temperature of 100 ° C to 260 ° C and then sealed. A solid electrolytic capacitor having excellent life characteristics can be manufactured.

Claims (3)

[Claims] 1. A method for manufacturing a solid electrolytic capacitor comprising a dielectric oxide film layer, a semiconductor layer, and a conductor layer sequentially formed on the surface of an anode substrate made of a metal having a valve action. After the formation, the solid electrolytic capacitor element is heated at a temperature of 100 ° C. to 260 ° C. and then sealed, and a method for manufacturing a solid electrolytic capacitor. 2. The method for producing a solid electrolytic capacitor according to claim 1, wherein the semiconductor layer is a layer containing lead dioxide as a main component. 3. The method for producing a solid electrolytic capacitor according to claim 1, wherein the semiconductor layer is a layer containing lead dioxide and lead sulfate as main components.