JPS62271412A - Solid electrolytic capacitor - Google Patents

Abstract

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

Description

[Detailed description of the invention] 3. Detailed description of the invention Industrial applications The present invention relates to solid electrolytic capacitors.

A conventional solid electrolytic capacitor is constructed by forming an oxide layer, which is a dielectric, on the surface of a valve metal base constituting an anode, and sequentially laminating a semiconductor layer and a conductor layer on the oxide layer.

As the valve metal constituting the anode, metals having a valve action such as aluminum, mental, niobium, and titanium are used, and among these, aluminum and tantalum are often used. The shape of the anode valve metal base is porous sintered body,
Capacitors can be made of plates (foils), wires, etc. Among these, capacitors of the type where plates (foils) are spirally wound can be made into small capacitors with large capacitance.

However, even with this spirally wound type capacitor,
Electrolytic capacitors using conventional electrolytes and 1980-1
Like the capacitor using TCNQ salt described in Publication No. 7609, a type capacitor in which two electrode foils are rolled up with a separator paper in between has a limit in reducing the volume due to the structure.

Further, when an electrolytic solution or TCNQ@ was used, the electrical conductivity was as low as 10 8.3 or less, and did not have a good effect on the performance such as the loss coefficient (mδ) or the in-beam characteristics of the capacitor.

Problems to be Solved by the Invention An object of the present invention is to solve the conventional problems and provide a solid electrolytic capacitor that can be made smaller and smaller in volume than conventional products, and has good capacitor performance. .

Means for Solving the Problems The present invention provides a solid electrolytic capacitor that can achieve the above objects.

That is, in the present invention, a semiconductor layer and a conductor layer mainly composed of lead dioxide and lead sulfate are sequentially formed on the oxide layer of a spirally wound anode valve metal base having an oxide layer on one surface. The present invention relates to a solid electrolytic capacitor characterized in that:

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

As the valve metal substrate used as the anode, any metal having a valve action may be used, such as aluminum, tantalum, niobium, titanium, and alloys using these as substrates. Of these, it is advantageous to use aluminum. The shape of the anode substrate before being formed into a spiral shape is usually a plate shape (including foil, recon, etc.).

The oxide 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 another dielectric oxide layer provided on the surface of the anode substrate. It's okay. Among these, a layer made of an oxide of the anode valve metal itself is preferable. In either case, a conventionally known method can be used to provide the oxide layer.

For example, when using aluminum foil as the anode substrate,
If the surface of the aluminum foil is electrochemically etched and then electrolytically treated in an aqueous solution of boric acid and ammonium borate, an oxide layer consisting of an alumina dielectric is formed on the aluminum foil, which is the anode substrate. Ru. Note that an anode lead wire is connected to the anode valve metal base by caulking, high-frequency bonding, or the like before and after providing the -oxide layer.

In order to form the anode valve metal base into a spiral shape, a method such as winding only the anode is used in the method of manufacturing a wound element consisting of cathode and anode foils used in conventional electrolytic capacitors using an electrolytic solution. For example, it has a spiral shape as shown in FIG. The number of windings, winding diameter, winding pitch, etc. can be determined as desired and are not particularly limited. Among these, it is preferable to wind the anode valve metal base with the spacing taken into consideration in advance so that the semiconductor layer and the conductor layer can be properly formed on the oxide layer.

In addition, in the case where cracks occur in the oxide layer provided in advance during molding, reformation can be performed. The reconstitution method may be any conventionally known method. For example, electrochemical treatment of aluminum foil in an aqueous solution of boric acid and ammonium borate as described above is applied.

The semiconductor layer used in the present invention is composed of a layer containing lead dioxide and lead sulfate as main components.

When the semiconductor layer is composed of a layer whose main components are lead dioxide, which originally plays the role of a semiconductor, and lead sulfate, which is an insulating material, the leakage current value of the capacitor can be reduced depending on the blend of lead sulfate. On the other hand, since the electrical conductivity of the semiconductor layer decreases due to the addition of lead sulfate, for example, the loss factor (-δ)
Although it gets bigger.

It has been found that the present invention maintains and exhibits a high level of performance compared to conventional solid electrolytic capacitors. Therefore, when the semiconductor layer is composed of a mixture of lead dioxide and lead sulfate, the content of lead dioxide in the semiconductor layer is 1'O% by weight or more.
Within the range of less than 0.00 weight i, preferably lead dioxide 1
Good capacitor performance can be maintained and achieved over a wide range of compositions, such as 0 to 95% by weight of lead sulfate and 90 to 5% by weight of lead sulfate; ~50% by weight, even lead dioxide 25-3
In the range of 75 to 65% by weight of lead sulfate relative to 5% by weight, the balance between leakage current value and loss coefficient is particularly good. If the amount of lead dioxide is less than 10% by weight, conductivity becomes poor, resulting in a large loss factor and insufficient capacity. If the lead dioxide content is 100% by weight, the leakage current value becomes large), and a large amount of time is required for post-chemical formation or aging after capacitor production, which is disadvantageous in terms of cost.

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.

The concentration of lead ions in the reaction mother liquor is 0.1 mol/! to a concentration that gives saturated solubility, preferably 0.5 mol/!
to the concentration that gives saturated solubility. If the concentration of lead ions is higher than the concentration that gives saturation solubility, no benefit can be seen by adding an increased amount.

Furthermore, when the concentration of lead ions is lower than 0.1 mol μ, there is a problem that the number of applications must be increased because the concentration of lead ions in the reaction mother liquor is too low. On the other hand, the concentration of persulfate ions in the reaction mother liquor is within the range of 0.05 to 5 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 will remain, resulting in high costs. If it is less than 0.05, unreacted lead ions remain and the conductivity deteriorates, which is not preferable.

In the present invention, other oxidizing agents that do not contain persulfate ions may be added to the reaction mother liquor. The amount of the oxidizing agent to be mixed is determined through preliminary experiments in order to maintain a good balance between the leakage current value and the loss coefficient value of the manufactured capacitor.

Typical examples of compounds that provide lead ion species include lead citrate, lead perchlorate, lead nitrate, lead acetate, basic lead acetate, lead chlorate, lead sulfamate, lead silicon hexafluoride, and lead bromate. , lead chloride, lead bromide, etc. Two or more of these compounds providing lead ion species may be used in combination. On the other hand, representative examples of compounds that provide peracid ions S include potassium persulfate, sodium persulfate, ammonium persulfate, and the like. Two or more of these compounds that provide persulfate ion species may be used as a mixture. Examples of oxidizing agents include hydrogen peroxide, calcium hypochlorite, calcium chlorite, calcium chlorate, and perchlorate. Examples include calcium acid.

The conductor layer provided on the semiconductor layer can be formed by, for example, solidifying a conductive paste, plating, metal vapor deposition, forming a heat-resistant conductive resin film, or the like. As conductive paste, silver paste, copper 4-st, aluminum 4-st,
Carden paste, Sentsukeru paste, etc. are preferred, but
These may be used alone or in combination of two or more. When two or more types are used, they may be mixed and layered, or may be stacked as separate layers. After applying the conductive paste, it is left in the air or heated to solidify.

Examples of plating include nickel plating and copper plating. Further, examples of vapor-deposited metals include aluminum, copper, and the like.

The end terminal can be attached to the conductive layer using, for example, a conductive paste, or soldered thereon after the conductive paste has solidified.

The solid electrolytic capacitor of the present invention constructed as described above can be used as a general-purpose capacitor product for various exterior applications such as a resin mold, a resin case, a gold 84 exterior case, resin dipping, and a laminated film exterior. I can do it.

Effects of the Invention The solid electrolytic capacitor of the present invention can be made smaller and smaller in volume than conventional electrolytic capacitors, and has good capacitor performance.

EXAMPLES Hereinafter, the present invention will be explained in more detail by showing 5AM flJ. Note that the characteristic values of the solid electrolytic capacitors in each row are shown in Table 1.

Example 1 An aluminum foil with a length of 10 m and a width of 0.53 was used as an anode,
The surface of the foil was electrochemically etched using alternating current. Next, the anode terminal was caulked to the etched aluminum foil, and the anode lead wire was connected.

Subsequently, an alumina oxide layer was formed by electrochemical treatment in an aqueous solution of boric acid and ammonium borate to obtain a low-pressure etched aluminum chemical foil (approximately 1, OpF10n2). Next, after winding this chemically formed foil, it was completely re-formed in the aqueous solution of boric acid and ammonium borate described above.

The concentration of lead acetate trihydrate is 3.8 mol/! The concentration of lead acetate trihydrate aqueous solution and ammonium persulfate is 4.0 mol/!
An aqueous ammonium persulfate solution was mixed to obtain a reaction mother liquor. The above-mentioned rolled foil was immersed in this reaction mother liquor and heated to 80℃ for 20 minutes.
I left it for a minute. The semiconductor layer deposited on the winding circuit was thoroughly washed with water to remove unreacted substances, and then dried under reduced pressure at 100° C. for 1 hour. The resulting semiconductor layer is made of lead dioxide and lead sulfate.
It was confirmed by mass spectrometry, X-ray analysis, and infrared spectroscopy that it contained about 25% by weight of lead dioxide.

The wound foil with the semiconductor layer made of lead dioxide and lead sulfate was then immersed in a silver paste bath, pulled out, and air-dried. A solidified silver paste layer was formed on the semiconductor layer of the wound foil. A copper wire was used as a cathode lead, connected to a wound foil using silver paste, and then sealed with resin to produce a solid electrolytic capacitor.

Example 2 In Example 1, the concentration of ammonium persulfate when forming the semiconductor layer was 0.4 mol/! A solid electrolytic capacitor was produced in the same manner as in Example 1 except that It was confirmed that the semiconductor layer at this time was composed of lead dioxide and lead sulfate, and contained about 35% by weight of lead dioxide.

Example 3 In Example 1, when forming the semiconductor layer, 0.05 mol/! of hydrogen peroxide was added to the reaction mother liquor. A solid electrolytic capacitor was produced in the same manner as in Example 1 except for the addition of the following. 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.

Example 4 When forming the semiconductor layer in Example 1, 0.2 mol/! of hydrogen peroxide solution was added to the reaction mother liquor. A solid electrolytic capacitor was produced in the same manner as in Example 1 except for the addition of the following.

It was confirmed that the semiconductor layer at this time was composed of lead dioxide and lead sulfate, and contained about 94% by weight of lead dioxide.

Comparative Example 1 Using the same etched aluminum foil as in Example 1, an electrolytic capacitor was fabricated using a stain removal solution by a method known in the art. That is, a wound element consisting of an anode foil (etched aluminum foil), a cathode foil, and a separator each having a terminal is impregnated with an ethylene glycol ammonium adipate electrolyte, and the element is placed inside an aluminum exterior case. The capacitor was stored and the opening was closed with a rubber sealing member to produce an electrolytic capacitor.

Comparative Example 2 Using the same etched aluminum foil as in Example 1, a solid electrolytic capacitor with a conductor layer made of TCNQ salt was produced according to the method described in Japanese Patent Application Laid-Open No. 17609/1983. That is, a complex salt of isopropylisoquinoline and TCNQ was placed in an aluminum exterior case and melted by heating. Next, a wound element consisting of an anode foil, a cathode foil, and a separator each having a terminal was preheated and impregnated into the above-mentioned molten TCNQ complex salt, and rapidly cooled and solidified. An electrolytic capacitor was produced by closing the opening with a rubber sealing body.

Comparative Example 3 In Example 1, the concentration of lead acetate trihydrate was 3.8 mol/! When using an aqueous solution, the concentration of lead citric acid was 0.7 mol/
! A solid electrolytic capacitor was produced in the same manner as in Example 1, except that an aqueous lead citrate solution was used and a reaction mother liquor containing ammonium persulfate at a concentration of 4.8 mol/l/l was used. It was confirmed that the semiconductor layer at this time was made of a composition consisting of lead dioxide and lead sulfate, and contained about 5% by weight of lead dioxide.

Table 1 *Value at 120Hz Book*10kHz N Material *Value at 20v Relative comparison value with Comparative Example 1 as 1

[Brief explanation of drawings]

FIG. 1 is a perspective view of a spirally wound anode valve metal base. 1...Anode valve metal base, 2...Anode lead terminal.

Claims (4)

[Claims] (1) A semiconductor layer and a conductor layer containing lead dioxide and lead sulfate as main components are sequentially formed on the oxide layer of a spirally wound anode valve metal base having an oxide layer on its surface. A solid electrolytic capacitor characterized by: (2) The solid electrolyte according to claim (1), wherein the semiconductor layer containing lead dioxide and lead sulfate as main components is a layer chemically precipitated from a reaction mother liquor containing lead ions and persulfate ions. capacitor. (3) The concentration of lead ions in the reaction mother liquor ranges from 0.1 mol/l to the concentration that provides saturation solubility, and the persulfate ions range from 0.05 mol to 5 mol per mol of lead ions. The solid electrolytic capacitor according to claim (2), which is within the range. (4) 10% by weight or more of lead dioxide in the semiconductor layer
The solid electrolytic capacitor according to claim 1, wherein the solid electrolytic capacitor is contained in a range of less than % by weight.