JPS6347917A - Solid electrolytic capacitor - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid electrolytic capacitor with good high frequency performance.

[Conventional technology]

In general, a solid electrolytic capacitor element has an oxide film layer formed on an anode base made of a valve metal, and a semiconductor layer such as manganese dioxide or the like formed as a counter electrode on the outer surface of this oxide film layer. In order to roughly reduce contact resistance, a graphite layer is interposed, and a silver paste layer and a solder layer are successively provided to form a conductor layer.

[Problem that the invention seeks to solve]

However, since the silver paste used for the conductor layer is extremely expensive, efforts have been made to obtain an inexpensive paste. For example, copper paste and nickel paste have been developed, but they have problems with oxidation stability and conductivity of the contact base, and have not been able to replace silver paste.

As a result of intensive research to solve the above-mentioned problems, the present inventors have discovered that a solid capacitor in which a paste layer made of silver-coated copper powder and/or silver-coated nickel powder is used as a conductor layer is a solid capacitor that uses silver paste as a conductive layer. It was found that the oxidation stability and loss coefficient are equivalent to that of a powder layer, and that the high frequency performance is improved by the powder particles.

The present invention was made based on the above discovery, and aims to provide an inexpensive solid electrolytic capacitor that has oxidation stability and loss coefficient equivalent to that of a capacitor using silver paste, has good high frequency performance, and is inexpensive. purpose.

[Means for solving problems]

The present invention has been made to achieve the above object, and the gist thereof is to provide a solid electrolytic capacitor in which a dielectric oxide film, a semiconductor layer, and a conductive layer are sequentially formed on an anode substrate made of a valve metal. The conductor layer is made of silver-coated copper powder with a particle size of 15 μm or less and/or silver-coated particle size 1
It is found in solid electrolytic capacitors, which are paste layers made of nickel powder of 5 μm or less.

(Specific structure and operation of the invention) The solid electrolytic capacitor of the present invention will be explained below.

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

The oxide film layer on the surface of the anode substrate may be the oxide K.1 of the anode substrate itself provided on the surface layer portion of the anode substrate, or may be the oxide K. However, a layer made of an oxide of the anode valve metal itself is particularly desirable. In either case, a conventionally known method can be used to provide the oxide layer.

Although there are no particular limitations on the composition and manufacturing method of the semiconductor layer used in the present invention, in order to improve the performance of the capacitor, lead dioxide or lead dioxide and lead sulfate may be used as main components, and conventionally known chemical precipitation methods may be used. Preferably, it is produced by an electrochemical deposition method or an electrochemical deposition method.

Examples of the chemical precipitation method include a method of chemically precipitating from a solution containing a lead-containing compound and an oxidizing agent.

Examples of lead-containing compounds include those in which a lead atom has a coordinate bond or an ionic bond with a chelate-forming compound such as oxine, acetylacetone, pyromeconic acid, salicylic acid, alizarin, polyvinyl acetate, porphyrin compounds, crown compounds, and cribdate compounds. lead-containing compounds,
Lead citrate, lead acetate, basic lead acetate, lead chloride, lead bromide,
Examples include lead perchlorate, lead chlorate, lead sulfamate, lead silicon hexafluoride, lead bromate, lead fluoroborate, lead acetate hydrate, and lead nitrate. These lead-containing compounds IJ.

It is appropriately selected depending on the solvent used for the reaction mother liquor.

Further, two or more of these lead-containing compounds may be used in combination.

In the reaction, the concentration of the lead-containing compound in the solution is within the range of 0.05 mol/J from the concentration that gives saturated solubility, preferably within the range of 0.1 mol/J from the concentration that gives saturated solubility, and more Preferably 0.0% from the concentration giving saturation solubility.
It is in the range of 5 mol/J. When the concentration of lead-containing compounds in the reaction mother liquor is less than 0.05 mol/J, a solid with good performance is produced.
Can't get electrolytic capacitors. Further, if the concentration of the lead-containing compound in the reaction mother liquor exceeds the saturation solubility, no merit can be observed by adding an increased amount.

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

The ratio of the oxidizing agent used is 5 to
It is preferably within the range of 0.1 times the mole. If the proportion of the oxidizing agent used is more than 5 times the mole of the lead compound used, there is no cost advantage, and if it is less than 0 or 1 times the mole of the lead compound used, a solid Ti decomposition condenser with good performance cannot be obtained. do not have.

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 containing a lead-containing compound and a solution containing an oxidizing agent, and then the above-mentioned oxide film is added to the reaction mother liquor. A method of chemically depositing the anode by immersing the provided anode substrate can be mentioned.

On the other hand, examples of electrochemical deposition methods include a method previously proposed by the present inventors in which lead dioxide is deposited by electrolytic oxidation in an electrolytic solution containing a high concentration of lead ions (
Patent application Sho 6l-26952).

Further, if the semiconductor layer is composed of a layer whose main components are lead dioxide, which plays the role of a semiconductor, and lead sulfate, which is an insulating material, the leakage current value of the capacitor can be reduced by adding lead sulfate. On the other hand, the present invention has found that although the addition of lead sulfate lowers the electrical conductivity of the semiconductor layer and increases the loss factor, it maintains and exhibits a high level of performance compared to conventional solid electrolytic capacitors. It was done. Therefore, when the semiconductor layer is composed of a mixture of lead dioxide and lead sulfate, good capacitor performance can be obtained over a wide range of compositions in which lead dioxide is contained in 10 m nodes or more and less than 100 parts by weight, and lead sulfate is contained in 90 parts by weight or less. Although it is possible to maintain the expression, it is preferable to use 20 to 50 lead dioxide in the suspended part and 80 to 80 to lead sulfate in the can part.
A good balance between the leakage current value and the loss factor value can be achieved in a range of 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, the conductivity will be poor, the loss factor will be large, and the capacity ω will not be sufficiently expressed.

A semiconductor layer containing lead dioxide and lead sulfate as main components can be formed by chemical precipitation using, for example, an aqueous solution containing lead ions and persulfate ions as a reaction mother liquid. Also, ``A
A suitable oxidizing agent that does not contain sulfate ions may also be added.

The lead ion QB in the mother liquor is preferably 0.05 mol/J1 from the concentration that gives saturated solubility, preferably 0.1 mol/J1 from the concentration that gives saturated solubility, more preferably 0.5 mol/J from the concentration that gives saturated solubility. Within range. When the concentration of lead ions is higher than the saturation solubility, there is no benefit from adding r.

Furthermore, when the concentration of lead ions is lower than 0.05 mol/J, there is a problem that the number of applications must be increased because the lead ions in the mother liquor become concentrated.

On the other hand, the concentration of persulfate ions in the mother liquor is within the range of 5 to 0.05 in molar ratio to lead ions.

If the concentration of persulfate ions is more than 5 in molar ratio to lead ions, unreacted persulfate ions remain, resulting in high costs, and the concentration of persulfate ions is 0.05 in molar ratio to lead ions. If the amount is less, unreacted lead ions remain and conductivity deteriorates, which is not preferable.

Examples of compounds that provide lead ion species include lead citrate, lead perchlorate, lead nitrate, lead acetate, basic lead acetate, lead chlorate, lead sulfamate, silicon hexafluoride, lead bromate, and lead chloride. , lead bromide, etc. Two or more of these compounds providing lead ion species may be used in combination. On the other hand, examples of compounds that provide persulfate ion species include persulfate, sodium persulfate, and ammonium persulfate. Two or more of these compounds that provide persulfate ion species may be used in combination.

On the other hand, examples of oxidizing agents include hydrogen peroxide, calcium hypochlorite, calcium chlorite, calcium chlorate,
Examples include calcium perchlorate.

Further, as the conductor layer provided on the semiconductor layer, a paste layer made of silver-coated copper powder and/or silver-coated nickel powder is used. Examples of the method for producing silver-coated copper powder and/or silver-coated nickel powder include a method in which copper powder or nickel powder is electrolessly plated with silver. The amount of silver in the powder is less than 50% by weight, preferably less than 20% by weight and less than 1% by weight. silver ji
Even if lt exceeds 50% by weight, there is no benefit from increasing the amount.

In this way, when copper or nickel is coated with silver,
・The amount of expensive silver used is significantly reduced, the manufacturing cost of the paste for forming the conductor layer is low, and its electrical properties are equivalent to those using pure silver powder.

The above copper powder or nickel powder has a particle size of 15
It is important that the thickness be less than μm. In addition, copper powder and nickel powder are desirably flaky in order to have good respectability when used as a conductive paste, that is, to improve contact between the powders in the paste. .

A method for producing a paste made of silver-coated copper powder or a paste made of silver-coated nickel powder is to mix silver-coated copper powder or nickel powder, an appropriate polymer or oligomer, and a solvent. It will be done.

As the above-mentioned polymer or oligomer, polymers or oligomers used in known conductive pastes are used, such as acrylic resin, alkyd resin, fluororesin, cellulose resin, vinyl resin, silicone resin, epoxy resin, urethane resin, novolac resin, etc. , resol, etc., but it goes without saying that the material is not limited to these.

Further, the solvent used may be any known solvent as long as it dissolves these polymers or oligomers. This solvent scatters during drying of the conductor layer and does not remain in the paste layer of the solid capacitor. Further, when the polymer or oligomer is liquid, it is not necessary to use a solvent. In the case of roughly thermosetting polymers or oligomers,
A known curing agent may be added, or a liquid containing a curing agent may be prepared separately and mixed at the time of use.

The proportion of powder in the paste is 35 to 95% by weight, preferably 65 to 95 r,u; 11%. When the proportion of powder is less than 35% by weight, the conductivity of the paste is insufficient, and when it is greater than 95% by weight, the adhesiveness of the paste is insufficient, and the performance of the solid electrolytic capacitor deteriorates in both cases.

The solid electrolytic capacitor of the present invention configured as described above can be made of, for example, a resin mold, a resin case, a metal exterior case,
It can be made into a general-purpose capacitor product for various uses by resin dipping and laminate film exterior.

〔Example〕

Hereinafter, the present invention will be explained by showing Examples and Comparative Examples.

Example 1 An aluminum foil with a length of 2 cm and a width of 1 cm was used as an anode, and after the surface of the foil was electrochemically etched using alternating current, the 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 on the aluminum, turning the low-pressure etched aluminum chemical foil (approximately 0.5 μF/ci) blue. Roughly, the parts of this chemically formed foil other than the anode terminal lead wire were immersed in a 1.0 mol/J aqueous solution of lead acetate trihydrate, and 0.5 times the molar excess of lead acetate trihydrate. A dilute aqueous solution of hydrogen oxide was added, and the mixture was left to stand for 1 hour to form a semiconductor layer consisting of a lead dioxide layer on the dielectric film layer.The lead dioxide layer was washed with water to remove unreacted materials, and then dried under reduced pressure.

In addition, a t-butanol solution in which polymethyl methacrylate was dissolved was added to a silver-coated copper powder containing 10% by weight of silver plated with electroless silver plating on copper powder with a particle size between 4 μm and 7 μm. 20 heavy electric 1%,
A paste consisting of silver coated copper powder is prepared by mixing the silver coat powder to 80% by weight (R)%, and this is applied to the chemically formed foil on which the lead dioxide layer is formed on the dielectric film layer and dried. did.

Furthermore, a cathode terminal was connected to this base 1~, and a solid electrolytic capacitor was fabricated using resin.

Example 2 The same chemically formed foil as in Example 1 except for the anode terminal lead wire was treated with a mixed solution of an aqueous solution of lead acetate trihydrate 2.4'Nyl/L and an aqueous solution of ammonium persulfate 4'FNyl/J. (reaction mother liquor)) and reacted at 80°C for 40 minutes to form lead dioxide and lll! The A' right suspension consisting of lead I acid was thoroughly washed with water and dried under reduced pressure at 120°C. The generated semiconductor layer was composed of lead dioxide and lead sulfate, and it was confirmed by mass spectrometry, X-ray analysis, and infrared spectroscopy that it contained about 25,000 M% of lead dioxide.

Next, a paste made of silver-coated copper powder similar to that produced in Example 1 was applied onto the semiconductor layer and dried, and the cathode was taken out in the same manner as in Example 1 and sealed with resin to produce a solid electrolytic capacitor. .

Example 3 A semiconductor layer was produced in the same manner as in Example 1, except that 0.05 mol/J of hydrogen peroxide solution was further added to the reaction mother liquor during semiconductor formation in Example 2. It was confirmed that the semiconductor layer at this time was composed of lead dioxide and lead sulfate, and contained about 50% by weight of lead dioxide.

In addition, 70% by weight of silver-coated nickel powder of 115% by weight of LFF, which is made by applying electroless silver plating to nickel powder with a particle size between 8 μm and 14 μm, and 30% by weight of resol; 1%
was added to prepare a paste consisting of silver-coated nickel powder, which was applied to a chemically formed foil on which a semiconductor layer consisting of lead dioxide and lead sulfate was formed on the electrical conductor film layer, and dried at 140°C. Furthermore, connect the cathode terminal with this paste and
After drying at ℃, the capacitor was sealed with resin to produce a solid electrolytic capacitor.

Comparative Example 1 A solid electrolytic capacitor was produced in the same manner as in Example 1, using silver-coated copper powder using copper powder having a particle size between 18 μm and 30 μm.

Comparative Example 2 A solid electrolytic capacitor was produced in the same manner as in Example 2 using copper powder that was not electrolessly plated with silver.

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

Table 1: *Value at 120H7 - Value at 10V - *Value at 100KHz (Direct *Represents volume after being exposed to 125° C. for 500 hours 74).

As is clear from Table 1, the solid electrolytic capacitors using silver-coated copper powder and/or silver-coated nickel powder as the material exhibit good properties. Furthermore, those using powder having a particle size of 15 μm or less have particularly good high frequency performance.

In addition, in the present invention, after preparing a paste in which a suitable amount of silver powder was further added to silver-coated copper powder with a particle size of 15 μm or less and/or silver-coated nickel powder with a particle size of 15 μm or less, the paste was used as a conductor layer. When a solid electrolytic capacitor is manufactured, except for the cost increase due to the addition of silver powder, the performance of the solid electrolytic capacitor including high frequency performance is good, and it is clear that this is an example of application of the present invention.

〔Effect of the invention〕

As described above, the solid electrolytic capacitor according to the present invention has advantages such as superior capacitor performance, particularly excellent high frequency characteristics, and low cost compared to conventional solid electrolytic capacitors.

Claims (3)

[Claims] (1) In a solid electrolytic capacitor in which a dielectric oxide film, a semiconductor layer, and a conductive layer are sequentially formed on an anode substrate made of a valve metal, the conductive layer has a silver-coated particle size of 15
Particle size 15μ coated with copper powder and/or silver less than μm
A solid electrolytic capacitor characterized in that it is a paste layer made of nickel powder with a size of less than m. (2) The solid electrolytic capacitor according to claim 1, wherein the semiconductor layer is a layer containing lead dioxide as a main component. (3) The solid electrolytic capacitor according to claim 1, wherein the semiconductor layer is a layer containing lead dioxide and lead sulfate as main components.