JPH07120610B2 - Method for manufacturing solid electrolytic capacitor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a solid electrolytic capacitor having excellent high temperature life characteristics.

[Prior Art] Generally, in an element of a solid electrolytic capacitor, an oxide film layer is formed on the surface of 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. Furthermore, in order to reduce the contact resistance, a silver paste layer is provided to form a conductor layer.

[Problems to be Solved by the Invention] However, the capacitor element thus formed has a high thermal expansion coefficient due to the difference in thermal expansion coefficient between the semiconductor layer such as manganese dioxide and the conductor layer of silver paste. There was a phenomenon that peeling of both layers occurs when left to stand. In particular, it was necessary to improve this phenomenon because this phenomenon appears prominently in the life test at high temperature.

In view of the above circumstances, the present invention improves the contact between the semiconductor layer and the conductor layer by maintaining the anode substrate and / or the conductive paste at a predetermined temperature when forming the conductor layer, An object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor having excellent high temperature life characteristics of the device.

[Means for Solving the Problems] The present invention has been made in order to achieve the above-mentioned object, and the gist thereof is an oxide film on the surface of an anode substrate made of a metal having a valve action, and an oxide film on the oxide film. In the method for producing a solid electrolytic capacitor, wherein a semiconductor layer is formed on the semiconductor layer, and a conductor layer made of a conductive paste is formed on the semiconductor layer, an anode substrate on which the semiconductor layer is formed when the conductor layer is formed, / Or holding the conductive paste at a predetermined temperature in the range of 60 ~ 200 ℃, contact the anode base on which the semiconductor layer is formed and the conductive paste at the temperature, the conductive paste to the semiconductor In the method for producing a solid electrolytic capacitor, which is brought into contact with a layer, 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. Arbitrariness.

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

As the valve metal substrate used as the anode of the solid electrolytic capacitor of the present invention, any metal having a valve action such as aluminum, tantalum, 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, a conventionally known method can be used as a method for providing the oxide layer.

The composition of the semiconductor layer used in the present invention and the method for producing the semiconductor layer are not particularly limited, but in order to improve the performance of the capacitor, lead dioxide or lead dioxide and lead sulfate are used as the main components, and conventionally known chemical deposition is performed. 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 solution containing a lead-containing compound and an oxidizing agent.

As the lead-containing compound, for example, an atom of lead is coordinate-bonded or ion-bonded to a chelate-forming compound such as oxine, acetylacetone, pyromeconic acid, salicylic acid, alizarin, polyvinyl acetate, porphyrin compounds, crown compounds, and cryptate compounds. Lead-containing compounds,
Lead citrate, acetate, basic lead acetate, lead chloride, lead bromide,
Examples thereof include lead perchlorate, lead chlorate, lead sulfamate, lead hexafluoride, lead bromate, lead borofluoride, lead acetate hydrate, and lead nitrate. These lead-containing compounds are appropriately selected depending on the solvent used in 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 / from the concentration giving the saturated solubility, preferably in the range of 0.1 mol / from the concentration giving the saturated solubility,
More preferably from the concentration giving a saturated solubility of 0.5 mol /
Is the range. The concentration of lead-containing compounds in the reaction mother liquor is 0.
If it is less than 05 mol / mol, 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,
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 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 provided anode substrate to chemically deposit it.

On the other hand, examples of the electrochemical deposition method include a method previously proposed by the present inventors to deposit lead dioxide by electrolytic oxidation in an electrolytic solution containing a high concentration of lead ions.
(Japanese Patent Application No. 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,
Good capacitor performance can be maintained and expressed 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 lead sulfate is preferably used for 20 to 50 parts by weight of lead dioxide. 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 provide a good balance between the leakage current value and the loss coefficient value. 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 concentration of lead ion in the mother liquor is determined from the concentration that gives saturated solubility.
0.05 mol / percent, preferably a concentration that gives a saturated solubility
It is within the range of 0.1 mol / percent, and more preferably 0.5 mol / percent from the concentration providing 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 giving lead ion species include lead citrate, lead perchlorate, lead sulfate, 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 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.

Further, the conductive paste used as the conductor of the present invention, a conventionally known one is used, for example, Ag, Pd, Au, Pt.
Noble metal powders such as those mixed with a binder organic resin or an organic solvent are available.

In the present invention, the method for forming the conductor layer is formed by keeping the anode substrate and / or the conductive paste on which the semiconductor layer is formed at a high temperature and bringing them into contact with each other.
The temperature it holds is higher than room temperature,
It ranges from 60 ° C to 200 ° C.

If it is lower than 60 ° C, the high temperature life characteristics are poor, and
If the temperature is higher than 200 ° C, the semiconductor layer and the conductive paste itself are deteriorated, which is not preferable.

The solid electrolytic capacitor manufactured by the method described above can be made into a general-purpose capacitor product for various applications by, for example, a resin mold, a resin case, a metal outer case, a resin dipping laminated film outer case, or the like.

[Examples] 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 1 cm was used as an anode, and the surface of the foil was electrochemically etched by an alternating current. 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, and a low-pressure etched aluminum chemical conversion foil (about 0.5 μF / cm ² ) was obtained. Furthermore, the portion of the chemical conversion foil other than the lead wire for the anode terminal was immersed in 1.0 mol of lead acetate trihydrate / aqueous solution, and a diluted aqueous solution of 0.5 times the molar amount of lead acetate trihydrate was added, After leaving for 1 hour, a semiconductor layer composed of a lead dioxide layer was formed on the dielectric film layer, the lead dioxide layer was washed with water to remove unreacted substances, and then dried under reduced pressure. Subsequently, the anode substrate having the semiconductor layer formed thereon was kept at 130 ° C. and further immersed in a silver paste bath kept at 80 ° C.
Subsequently, a cathode lead wire was connected with solder and resin-sealed to produce a solid electrolytic capacitor.

Example 2 A chemical conversion foil similar to that in Example 1 was prepared by mixing lead acetate trihydrate with 2.4 mol / mol.
It was immersed in a mixed solution of an aqueous solution of 4 mol / mol of ammonium persulfate and reacted at 80 ° C. for 30 minutes. The resulting semiconductor layer was washed with water to remove unreacted materials, and then dried under reduced pressure. Subsequently, while keeping the anode substrate having the semiconductor layer formed thereon at 130 ° C., it was immersed in a silver-coded copper powder paste bath left at room temperature. Then, a solid electrolytic capacitor was produced in the same manner as in Example 1. The semiconductor layer contains about 25% by weight of lead dioxide,
It was confirmed by X-ray analysis and infrared spectroscopic analysis that lead sulfate consisted of about 75% by weight.

Examples 3 to 4 The temperatures for holding the anode substrate in Example 2 were 85 ° C. and 160, respectively.
A solid electrolytic capacitor was produced in the same manner as in Example 2 except that the temperature was changed to ° C.

Example 5 In Example 2, 0.05 mol / hydrogen peroxide solution was added to the mixed solution used for forming the semiconductor layer to form the semiconductor layer, and then the anode substrate was kept at room temperature, and the conductive paste was added to 90%.
A conductor layer was formed in the same manner as in Example 2 except that the temperature was kept at 0 ° C. to prepare a solid electrolytic capacitor. The semiconductor layer is a composition of lead dioxide and lead sulfate, and
It was confirmed that the content was 50% by weight.

Comparative Example 1 Example 1 is the same as Example 1 except that the conductor layer was formed at room temperature without heating the anode substrate and the silver paste to a predetermined temperature.
A solid electrolytic capacitor was produced in the same manner as in.

Table 1 collectively shows the no-load life characteristic values of the solid electrolytic capacitors produced in Examples 1 to 5 and Comparative Example 1 at a temperature of 125 ° C.

As is clear from Table 1, when forming the conductor layer,
It can be seen that the high temperature life characteristics of the solid electrolytic capacitor produced by holding the anode substrate at a high temperature are improved.

[Advantages of the Invention] The present invention provides a method for producing a solid electrolytic capacitor by sequentially forming an oxide film, a semiconductor layer, and a conductor layer made of a conductive paste on the surface of an anode substrate made of a metal having a valve action. By maintaining the anode base and / or the conductive paste at a high temperature of 60 to 200 ° C. when forming the conductor layer on the semiconductor layer, the adhesion between the semiconductor layer and the conductor layer becomes good, It is possible to manufacture a capacitor element in which the layer peeling phenomenon is prevented and which has excellent life characteristics at high temperature.

Claims (3)

[Claims] 1. A solid electrolytic capacitor comprising an anode substrate made of a metal having a valve action, an oxide film on the surface, a semiconductor layer on the oxide film, and a conductor layer made of a conductive paste on the semiconductor layer. In the manufacturing method, when the conductor layer is formed, the semiconductor substrate-formed anode substrate and / or the conductive paste is held at a predetermined temperature in the range of 60 to 200 ° C., and the semiconductor is kept at that temperature. A method for producing a solid electrolytic capacitor, characterized in that an anode substrate having a layer formed thereon is brought into contact with the conductive paste, and the conductive paste is adhered onto the semiconductor layer. 2. The method for producing a solid electrolytic capacitor according to claim 1, wherein the semiconductor layer contains 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 mixture containing lead dioxide and lead sulfate as main components.