JPH0727851B2 - 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 aging a solid electrolytic capacitor element having a semiconductor layer made of lead dioxide or lead dioxide and lead sulfate.

[Prior Art] Generally, in a solid electrolytic capacitor element, 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, a conductor layer is provided to reduce the contact resistance. Since lead dioxide, which is a semiconductor other than manganese dioxide described above, has a relatively high electric conductivity, it was expected to produce a high-performance solid electrolytic capacitor, but none was realized. In such a situation, the present inventors have
Japanese Patent Application No. 61-26952, Japanese Patent Application No. 61-93451, etc. discloses a solid electrolytic capacitor or a solid electrolytic capacitor which has a semiconductor layer of lead dioxide or lead dioxide and lead sulfate and has good performance and which can be industrially realized. Proposed manufacturing method. further,
As a method for aging this type of solid electrolytic capacitor, it has been proposed in Japanese Patent Application Nos. 61-120192 and 61-121230 to perform chemical conversion treatment after forming a conductor layer.

[Problems to be solved by the invention]

However, from an industrial point of view, there has been a demand for a method in which the leakage current is further smaller than that of the above-described aging method and the aging can be performed in a short time.

[Means for solving problems]

The present invention has been made to achieve the above object. According to the present invention, a dielectric oxide film layer, lead dioxide or lead dioxide and lead sulfate are formed on the surface of an anode substrate made of a metal having a valve action. In a method for manufacturing a solid electrolytic capacitor, which is formed by sequentially forming a semiconductor layer having a main component and a conductor layer,
A method for producing a solid electrolytic capacitor, comprising aging the solid electrolytic capacitor element at a temperature of 100 ° C. to 260 ° C. after encapsulation after forming the semiconductor layer.

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, the semiconductor layer used in the present invention is preferably made of lead dioxide or lead dioxide and lead sulfate as main components by a conventionally known chemical deposition method or 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).

Examples of the lead-containing compound include oxine, acetylacetone, pyromeconic acid, salicylic acid, alizarin, polyvinyl acetate, porphyrin compounds, crown compounds,
Lead-containing compounds in which lead atoms are coordinate-bonded or ionic-bonded to chelate-forming compounds such as criplatate 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. From the concentration giving 0.5 mol / l. If the concentration of the lead-containing compound in the reaction mother liquor is less than 0.05 mol / 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.

Examples of the oxidizing agent include quinone, chloranil, pyridine-N-oxide, dimethylsulfoxide, chromic acid, potassium permanganate, selenium oxide, mercury acetate, vanadium oxide, sodium chlorate, ferric chloride,
Examples thereof include hydrogen peroxide, benzoyl peroxide, calcium hypochlorite, calcium perchlorate, calcium chlorate, calcium perchlorate and the like. These oxidizing agents may be appropriately selected depending on the solvent used. The oxidant is
You may mix and use 2 or more types.

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 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. There is a method of immersing the formed chemical foil and chemically depositing it.

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 by chemical precipitation as a reaction mother liquor. Also,
A suitable oxidizing agent that does not contain persulfate ions may be added.

The concentration of lead ion in the mother liquor is calculated from
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,
The lead ion concentration in the mother liquor is too low, so that 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 that give iron 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, on the semiconductor layer formed as described above,
The conductor layer is formed by forming the metal layer or the carbon layer, or by forming the 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 paste containing silver, nickel, copper, silver-coated copper, or the like, or a paste already proposed by the present inventors in Japanese Patent Application No. 61-266092 is applied. Or a method of plating or vapor depositing silver, nickel, copper or the like. The solid electrolytic capacitor element thus manufactured is housed in a resin case or a metal case, or is resin-molded and sealed with a phenol resin or an epoxy resin.

The solid electrolytic capacitor element manufactured by the method described above is aged at a predetermined voltage and time at a temperature of 100 to 260 ° C. before sealing. The aging time varies depending on the capacity of the solid electrolytic capacitor element, but is generally within 1 hour. Aging under this temperature condition can greatly reduce the leakage current, but this is due to the Joule heat generated by the current concentrated in the defective portion of the oxide film layer due to energization and the presence in the solid electrolytic capacitor element. The ambient temperature of the solid electrolytic capacitor element can be controlled when a defective portion is repaired by a small amount of water.
It is considered that the temperature of 100 to 260 ° C. activates the above-mentioned repair reaction. Further, if the ambient temperature during aging is less than 100 ° C, the aging time becomes long, which is industrially disadvantageous. On the contrary, if it exceeds 260 ° C, the performance of the solid electrolytic capacitor deteriorates due to aging.

On the other hand, as an aging method for this solid electrolytic capacitor element, first, the solid electrolytic capacitor element is set at an ambient temperature of 80
The first aging is performed under the conditions of ℃ or more and less than 100 ℃ and relative humidity of 75% to 100%, and then the second aging is performed by raising the ambient temperature and at the temperature of 100 ℃ or more and 260 ℃ or less. You can also In this method, the aging step is performed twice, but a solid electrolytic capacitor with a small leakage current can be manufactured.

〔Example〕

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 silver paste, and the cathode was taken out. Then, aging was performed at an ambient temperature of 125 ° C. and a voltage of 15 V for 30 minutes. Then, sealing was performed to produce a solid electrolytic capacitor.

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 above aqueous solution of 4 mol / l of ammonium persulfate and reacted at 80 ° C. for 30 minutes. The generated semiconductor layer was washed with water to remove unreacted materials, and then a conductor layer was formed in the same manner as in Example 1. Ambient temperature 150 after removing the cathode
Aging was performed for 20 minutes at a temperature of 15 V and a temperature of 15 ° C. Then, sealing was performed to produce a solid electrolytic capacitor. It was confirmed by X-ray analysis and infrared spectroscopic analysis that the semiconductor layer consisted of about 25 wt% lead dioxide and about 75 wt% lead sulfate.

Example 3 A solid electrolytic capacitor was produced in the same manner as in Example 2 except that aging was carried out at an ambient temperature of 100 ° C. and a voltage of 15 V for 2 hours.

Example 4 A solid electrolytic capacitor was produced in the same manner as in Example 2 except that aging was performed in Example 2 at an ambient temperature of 260 ° C. and a voltage of 15 V for 3 minutes.

Example 5 In Example 2, first, aging was performed at a voltage of 15 V for 5 minutes under the conditions of an ambient temperature of 90 ° C. and a relative humidity of 90%, and the temperature was further raised to aging at an ambient temperature of 125 ° C. and a voltage of 15 V for 15 minutes. A solid electrolytic capacitor was produced in the same manner as in Example 2 except that the above procedure was performed.

Comparative Example 1 A solid electrolytic capacitor was produced in the same manner as in Example 1 except that aging was performed in Example 1 at an ambient temperature of 80 ° C. and a voltage of 15 V for 5 hours.

Comparative Example 2 A solid electrolytic capacitor was produced in the same manner as in Example 1 except that aging was performed in Example 1 at an ambient temperature of 270 ° C. and a voltage of 15 V for 3 minutes.

Comparative Example 3 In Example 2, first, aging was performed at a voltage of 15 V for 5 minutes under the conditions of an ambient temperature of 60 ° C. and a relative humidity of 90%, and the temperature was further raised to an ambient temperature of 80 ° C., a relative humidity of 10% and a voltage of 15 V. A solid electrolytic capacitor was produced in the same manner as in Example 2 except that aging was performed for 5 hours.

Comparative Example 4 In Example 2, first, aging was performed at a voltage of 15 V for 5 minutes under the conditions of an ambient temperature of 60 ° C. and a relative humidity of 90%, and the temperature was further raised to aging at an ambient temperature of 270 ° C. and a voltage of 15 V for 3 minutes. A solid electrolytic capacitor was produced in the same manner as in Example 2 except that the steps were performed.

Table 1 collectively shows the characteristic values of the solid electrolytic capacitors produced in Examples 1 to 5 and Comparative Examples 1 to 4.

[Effects of the Invention] As described above, according to the present invention, a solid electrolytic capacitor element encapsulation front opening having a semiconductor layer containing lead dioxide or lead dioxide and lead sulfate as a main component after forming a conductor layer. Aging at a temperature of 100 ° C. to 260 ° C. makes it possible to manufacture a solid electrolytic capacitor with a very small leakage current, and since the time required for aging is short, it has great industrial utility value.

Claims (1)

[Claims] 1. A dielectric oxide film layer, a lead dioxide or a semiconductor layer containing lead dioxide and lead sulfate as main components, and a conductor layer are sequentially formed on the surface of an anode substrate made of a metal having a valve action. In the method of manufacturing a solid electrolytic capacitor,
A method for manufacturing a solid electrolytic capacitor, comprising aging the solid electrolytic capacitor element at a temperature of 100 ° C. to 260 ° C. after forming the conductor layer and before sealing.