JPH06168855A - Multilayer solid electrolytic capacitor and fabrication thereof - Google Patents

Abstract

PURPOSE:To provide a multilayer solid electrolytic capacitor excellent in electric characteristics, e.g. frequency characteristics of impedance and leak current characteristics, which exhibits stabilized characteristics over a wide temperature range and contributes to downsizing and high capacity. CONSTITUTION:After forming through tunnel pits 1, countless cubic pits are formed to obtain an anode base body 3 having surfaces of sponge-like pits 2. A plurality of anode base bodies 3 are then laminated to produce an anode laminate which is then subjected to formation thus forming a dielectric oxide 6 on the surface. A conductive polymeric layer 7 composed of a chemical polymerization film and an electrolytic polymerization film is formed entirely on the surface of dielectric oxide 6 and a cathode lead-out part, i.e., a conductor layer 8, is formed thereon thus obtaining a capacitor element 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated solid electrolytic capacitor using a conductive polymer as a solid electrolyte and a method for manufacturing the same.

[0002]

2. Description of the Related Art As a solid electrolytic capacitor, a valve action metal such as aluminum, tantalum or niobium is used as an anode body, and an anodic oxide film formed on the valve action metal is used as a dielectric body. There is one formed by forming an organic semiconductor composed of manganese dioxide or a TCNQ complex.

In recent years, for example, Japanese Patent Laid-Open No. 62-1814.
As typified by the technology disclosed in Japanese Patent Publication No. 15, a conductive five-membered polypyrrole, polythiophene, polyfuran, etc. obtained by polymerizing a five-membered heterocyclic compound such as pyrrole, thiophene, furan, etc. by chemical or electrochemical means. Solid electrolytic capacitors have been developed that use conductive polymers as solid electrolytes.

However, this conductive polymer has an electric conductivity of about 10 ² S / cm and manganese dioxide (10 ^-2 S / c).
m) and TCNQ complex (10S / CM) are very high and have excellent thermal stability. Therefore, by using this conductive polymer as a solid electrolyte, It is possible to obtain a solid electrolytic capacitor having excellent electrical characteristics such as impedance frequency characteristics and leakage current, and excellent temperature characteristics in a wide range.

On the other hand, as electronic components have become lighter, thinner and smaller, various methods have been proposed for laminating and integrating anode bodies for the purpose of increasing the capacity per unit volume even in solid electrolytic capacitors. That is, as one that meets such an object, there is one disclosed in, for example, Japanese Patent Laid-Open No. 63-239917.

According to the technique disclosed in this publication, a dielectric oxide film, a semiconductor layer, and a conductor layer are sequentially formed on one side of a metal substrate distinguished by forming an insulating layer on a predetermined portion of a valve action metal plate. A plurality of the above-mentioned capacitor substrates are laminated and fixed with a conductive paste, and the exposed portion of the other metal substrate is pressure-integrated, and then a laminated body is formed by electric welding.

Further, as disclosed in JP-A-61-30020, after connecting an anode lead to a laminated and integrated anode substrate having through-type tunnel pits, an oxide film layer, a semiconductor There is a technique of sequentially forming a layer and a conductor layer.

However, in the former technique, after the capacitor substrates are laminated, the exposed portion of the metal substrate is pressure-integrated, so that stress on the portions where the dielectric oxide film, the semiconductor layer, and the conductor layer are formed is prevented. However, there is a defect that defects occur in the dielectric oxide film, the leakage current increases, and a short circuit defect occurs.

Further, in the latter technique, since the anodic oxide film layer, the semiconductor layer and the conductor layer are formed on the previously formed laminated body, there is no leakage current defect or short circuit defect, and there is no penetration tunnel. Since the pits are formed on the anode substrate that constitutes the laminated body, there is an advantage that the semiconductor layer and the conductor layer are formed on the entire laminated body. However, generally, the surface area of the anode substrate is increased by the through tunnel pit. Less
There was a limit in increasing the capacity per unit volume, and the purpose could not be satisfied.

[0010]

As described above, in the conventionally disclosed laminated solid electrolytic capacitor technology,
Due to the stress applied during the manufacturing process, defects occur in the dielectric oxide film, resulting in the problem of impairing various electrical characteristics.Also, through-type tunnel pits are formed in the anode substrate that constitutes the laminate. Even if it does, it is impossible to achieve the desired increase in the surface area of the anode substrate, and there is a problem to be solved.

The present invention has been made to solve the above problems, and its purpose is to provide excellent electrical characteristics such as impedance frequency characteristics and leakage current characteristics, and various characteristics over a wide temperature range. The present invention provides a laminated solid electrolytic capacitor that contributes to the stable miniaturization and large capacity of the solid electrolytic capacitor.

[0012]

The laminated solid electrolytic capacitor of the present invention has a sponge-like surface formed by a through-hole tunnel pit formed in a valve metal foil and a cubic pit formed by AC etching. An anode laminate formed by laminating a plurality of anode bases obtained by roughening the pits, a dielectric oxide film formed on the entire surface of the anode base forming the anode laminate, and a dielectric oxide film formed on the dielectric oxide film. It is characterized by comprising the formed conductive polymer layer and a conductor layer formed on the conductive polymer layer.

Further, as means for obtaining the above-mentioned laminated solid electrolytic capacitor, through-hole type tunnel pits are formed in the valve metal foil, and then an infinite number of cubic pits are formed by AC etching so that the surface has a sponge-like shape. A step of obtaining a roughened anode substrate in pits, a step of laminating a plurality of the anode substrates to obtain an anode laminate, and a dielectric oxide film by chemical conversion treatment on the entire surface of each anode substrate constituting the anode laminate. And a step of forming a conductive polymer layer on the dielectric oxide film, and a step of forming a conductive layer on the conductive polymer layer. is there.

[0014]

According to the present invention, the preformed anode laminate is subjected to chemical conversion treatment to form the dielectric oxide film on the entire surface of each of the anode substrates constituting the anode laminate, so that the dielectric oxide film is formed during the manufacturing process. In addition, there is no factor that induces a defective portion due to mechanical stress, or there is no stress on the conductor layer including the conductive polymer layer, and various factors that deteriorate characteristics can be eliminated.

Further, since penetration type tunnel pits are formed in the anode base body which constitutes the anode laminate, and the surface is roughened into spongy pits by cubic pits formed by AC etching. A conductive polymer layer with high electrical conductivity and excellent thermal stability is formed uniformly over the entire surface of the dielectric oxide film with an expanded surface area, including the inside of the anode substrate laminate, with a necessary and sufficient thickness. You can

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, as shown in FIG. 2, Miller index (1
The aluminum foil having a occupancy of the (00) surface of 90% or more is used, and the solution is mainly in a solution containing chloride ions at 80 ° C.
After forming the penetration type tunnel pit 1 by performing direct current DC electrolysis, forming an infinite number of cubic pits by performing AC electrolysis for 5 minutes in an aqueous solution containing mainly chlorine ions and sulfate ions for 10 minutes. Thus, an anode substrate 3 having a spongy pit 2 on the surface is obtained.

Next, as shown in FIG.
Are laminated and punched to a required size, and the anode lead wire 4 is fixed to an arbitrary place by welding or the like to form the anode laminate 5.

As shown in FIGS. 1 (A) and 1 (B), however, this anode laminate 5 is subjected to a chemical conversion treatment in a chemical conversion liquid at a voltage suitable for the rated voltage of the product, and a dielectric material is applied to the surface thereof. The oxide film 6 is formed, and then, immersed in a 2M-pyrrole / ethanol solution for 5 minutes, and further immersed in a 0.5M-ammonium persulfate aqueous solution for 5 minutes to perform chemical oxidative polymerization, and the surface of the dielectric oxide film 6 is formed. A chemically polymerized film made of polypyrrole is formed on the entire surface.

Then, in an electrolytic oxidation polymerization solution containing 0.05 mol / liter of alkylnaphthalene sulfonate as a supporting electrolyte and 0.2 mol / liter of pyrrole monomer, the chemically polymerized film formed in the previous step was used as an anode, Constant current electrolytic oxidation polymerization (1mA)
/ Cm ² , 2 h) to form an electropolymerized film made of polypyrrole, and a conductive polymer layer 7 made of a chemically polymerized film and an electropolymerized film is formed on the entire surface of the dielectric oxide film 6 formed on the anode substrate 3. Then, a graphite layer and a silver paste layer are sequentially formed on the conductive polymer layer 7 to form a conductor layer 8 as a cathode lead-out portion to form a capacitor element 9.

Next, as shown in FIG. 4, an anode external terminal 10 is connected and fixed to the anode lead wire 4 and a cathode external terminal 11 is connected and fixed to the conductor layer 8, respectively, and a resin sheath 12 is formed by transfer molding, for example. Giving capacitor body 1
3 is formed, and the anode external terminal 10 and the cathode external terminal 11 led out from the side surface of the capacitor body 13 are bent along the side surface of the capacitor body 13 to reach the bottom surface, thereby forming a finished product. .

According to the laminated solid electrolytic capacitor having the above-mentioned structure, the anode base body 3 constituting the anode laminated body 5 is formed.
A through-type tunnel pit 1 is formed in the inner surface of the anode laminated body 5 because the surface is roughened into spongy pits 2 by forming a number of cubic pits formed by AC etching. Conductive polymer layer 7 consisting of a chemically polymerized film and an electrolytic polymerized film, which have high electrical conductivity and excellent thermal stability, on the entire surface of the dielectric oxide film 6 having an expanded surface area including
Then, the conductor layer 8 can be uniformly formed thereon with a necessary and sufficient thickness.

Therefore, the electrical characteristics such as the frequency characteristic of impedance can be improved and the characteristics can be stabilized in a wide temperature range, and the size and capacity can be reduced.

Further, since the formation of the dielectric oxide film 6 on the anode substrate 3 is performed in a state where the anode substrate 3 is laminated in advance to form the anode laminate 5, there is no stress on the dielectric oxide film 6 and therefore the dielectric oxide film is formed. The film 6 is not damaged, and it also has an effect of contributing to the improvement of the leakage current characteristic and the drastic reduction of short circuit defects.

Next, in order to further clarify the superiority of the present invention, a characteristic comparison between the embodiment according to the present invention and the comparative examples A and B according to the prior art will be described.

That is, the capacitance, tan δ, leakage current and equivalent series resistance (ESR) initial characteristics at a frequency of 100 KHz of the following examples and Comparative Examples A and B were examined, and the results are shown in Table 1. Became. In addition, the impedance of each of the examples and the comparative examples A and B-
As a result of examining the frequency characteristic, the result is as shown in FIG. The number of samples is 100 each.

(Embodiment) With the technical contents described in the above embodiment, the rated voltage 1 formed by using an anode laminate having a size of 3 mm × 3 mm formed by laminating four sheets
Chip type multilayer solid electrolytic capacitor with 0V and nominal capacitance of 4.7μF.

(Comparative Example A) The surface was roughened into sponge-like pits by forming an infinite number of cubic pits by AC electrolysis for 5 A for 10 minutes in an aqueous solution containing mainly chlorine ions and sulfate ions, Thereafter, the aluminum foil having a dielectric oxide film formed on its surface by chemical conversion treatment is divided into an anode resin side and an anode lead side and a cathode side having a size of 3 mm x 3 mm, and the cathode side of the anode substrate is obtained. In addition, by forming a conductive polymer layer made of polypyrrole in the same manner as in the above embodiment, further forming a graphite layer and a silver paste layer on the conductive polymer layer in this order to form a conductor layer. To form a capacitor base plate,
Four sheets are laminated so that the anode lead-out portion and the cathode formation side correspond to each other, then the cathode formation side is fixed with a silver adhesive, and the anode lead-out portion is put together by electric welding to form a capacitor element.
A rated voltage of 10 is obtained as a finished product by taking the same means as in the above embodiment.
Chip type multilayer solid electrolytic capacitor with V and nominal capacitance of 4.7 μF.

(Comparative Example B) Mainly, four aluminum foils having through-type tunnel pits were laminated by carrying out direct current electrolysis at 80 ° C. for 10 minutes in an aqueous solution containing chloride ions to form a laminated body. The body was punched into a size of 3 mm × 3 mm, and after the anodic oxide coating process, the same means as in the above example was taken to obtain a finished product with a rated voltage of 10 V and a nominal capacitance of 4.
7μF chip type multilayer solid electrolytic capacitor.

[0029]

[Table 1]

As is clear from Table 1 and FIG. 5, in Comparative Example A, the leakage current characteristics, ESR characteristics, and impedance characteristics were deteriorated, and in Comparative Example B, the electrostatic capacity was lower than that of the Examples. Extremely small, about 1/4, and tan δ, E
While the SR characteristics are greatly deteriorated and both are not practical,
The examples showed stable results in all characteristics, and the excellent action and effect of the present invention were confirmed.

The reason for this is that in the case of Comparative Example A,
This is because the dielectric oxide film was damaged by the stress at the time of putting the capacitor base plates together, and the conductive polymer layer and the semiconductor layer were also cracked, and the resistance value increased, and in the case of Comparative Example B, aluminum was used. It is considered that the pits formed on the foil are only penetration type tunnel pits and the foil magnification does not increase.

Further, the present invention is not limited to the above-mentioned embodiments, but in addition to aluminum foil, tantalum,
It is also possible to use titanium, niobium foil, etc. Further, in the above-mentioned embodiment, the chip-shaped terminal is used, and the chip structure having the exterior by transfer molding is described as an example. It is also possible to use a CP wire or the like to form a lead wire structure by applying an exterior by a fluid immersion method, a dip method, or the like, and further, the method of forming the conductive polymer layer and the conductor layer, etc. can be appropriately selected. Of course.

[0033]

According to the present invention, the entire surface of the dielectric oxide film whose surface area is greatly expanded, including the inside of the capacitor element,
By forming a conductive polymer layer as a solid electrolyte uniformly with a necessary and sufficient desired thickness, including impedance frequency characteristics, excellent other electrical characteristics, stable characteristics over a wide temperature range, It is possible to obtain a small-sized and large-capacity laminated solid electrolytic capacitor and a manufacturing method thereof.

[Brief description of drawings]

FIG. 1 shows a capacitor element that constitutes a laminated solid electrolytic capacitor according to an embodiment of the present invention, where (A) is an enlarged cross-sectional view of the entire capacitor element, and (B) is an enlarged view of part (a) of (A). Fig.

FIG. 2 is an enlarged imitation view showing an aluminum foil forming the capacitor element shown in FIG.

FIG. 3 is a front view showing an anode laminate according to an example of the present invention.

FIG. 4 is a sectional view showing a laminated solid electrolytic capacitor according to an embodiment of the present invention.

FIG. 5 is an impedance characteristic curve diagram with respect to frequency.

[Explanation of reference numerals] 1 through tunnel pit 2 sponge-like pit 3 anode substrate 4 anode lead wire 5 anode laminate 6 dielectric oxide film 7 conductive polymer layer 8 conductive layer 9 capacitor element

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01G 9/24 C 7924-5E

Claims (2)

[Claims] 1. A plurality of anode substrates obtained by roughening the surface into sponge-like pits with through-type tunnel pits formed in a valve metal foil and cubic pits formed by AC etching. Anode laminate formed by laminating, dielectric oxide film formed on the entire surface of the anode substrate constituting the anode laminate, conductive polymer layer formed on the dielectric oxide film, and the conductive polymer A laminated solid electrolytic capacitor, comprising: a conductor layer formed on the layer. 2. A step of forming a through-hole tunnel pit in a valve metal foil and then forming an infinite number of cubic pits by AC etching to obtain an anode substrate having a surface roughened into spongy pits. And a step of laminating a plurality of the anode substrates to obtain an anode laminate, a step of forming a dielectric oxide film by chemical conversion treatment on the entire surface of each of the anode substrates constituting the anode laminate, and the dielectric oxide film. A method for producing a laminated solid electrolytic capacitor, which comprises sequentially performing a step of forming a conductive polymer layer thereon and a step of forming a conductor layer on the conductive polymer layer.