JPH01294303A - Conductive paste and solid-state electrolytic capacitor - Google Patents

Abstract

PURPOSE:To prevent the deterioration in stability of the solid-state electrolytic capacitor in the title to a high temperature over a long period of time, by using as a conductive layer conductive paste having its excellent adhesion to an object of its application. CONSTITUTION:A conductive layer is formed out of conductive paste consisting of the mixture of a conductive high polymer, metal dust and a resin. A semiconductor whose conductivity is within 10<-5>S.cm<-1> and 10<4>S.cm<-1> is intended for the conductive high polymer application and then used generally in the form of dust. Materials serving as the metal dust, are referred to for example, silver dust, gold dust, palladium dust, nickel dust, silver-clad nickel dust, silver-clad copper dust, each dust of these alloys and the like. The ratio by weight of using the conductive high polymer to the metal dust ranges from 1/6 to 6 times the weight of the metal dust. Any resin on the market can be also used for the resin. This makes it possible to obtain a solid-state electrolytic capacitor of a low cost, being excellent in stability against a high temperature.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a conductive paste with excellent adhesion, low cost, and low resistance, and a solid electrolyte with good performance using the conductive paste as an S conductor layer. Concerning capacitors.

(Prior Art) Conventionally, a conductive paste is a mixture of metal powder whose main component is a negative metal such as gold, silver, or platinum, and a binder resin that integrates the metal powder.

In addition, in conventional solid electrolytic capacitors, an oxide film layer is formed on an anode base made of a valve metal, a semiconductor layer such as manganese dioxide is formed as a counter electrode on the outer surface of this oxide film layer, and a layer of semiconductor such as manganese dioxide is formed on the outer surface of this oxide film layer. A conductive layer is formed to reduce contact resistance.

[Problem to be solved by the invention]

However, if the metal powder in the conductive paste is noble metal, it is expensive, and because it has a higher specific gravity than the resin, it is likely to separate from the resin during storage, resulting in partial non-uniformity during use and poor workability. On the other hand, when the metal powder is a base metal such as copper or nickel, although it is inexpensive, the above-mentioned non-uniformity appears and there are problems with high temperature stability. Furthermore, due to the difference in coefficient of thermal expansion between the metal powder and the object to which the conductive paste made of resin is applied, there is a drawback that adhesion deteriorates when left at high temperatures. Particularly, when the conductive paste is used in the conductor layer of a solid electrolytic capacitor, the solid electrolytic capacitor has the disadvantage that the loss factor is degraded over time when subjected to a high temperature long-term life test.

In view of the above circumstances, the present invention provides an inexpensive conductive paste with excellent adhesion to an object to be coated, and a solid electrolytic capacitor whose high temperature stability does not deteriorate over a long period of time, using the conductive paste in a conductive layer. The purpose is to

[Means for solving problems]

In order to achieve the above object, the present invention includes:
In a solid electrolytic capacitor in which a dielectric oxide film layer, a semiconductor layer and a conductor layer are sequentially formed on an anode substrate made of a conductive paste which is a U compound of a neutral polymer, a metal powder and a resin, and a valve metal. , the conductor R4 is formed of the conductive paste.

[Specific structure and operation of the invention]

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

The conductive polymer used in the conductive paste of the present invention has an electrical conductivity of 10 → 8 cm-' to 10'S cm'.
It is a semiconductor between the two, and is generally used in powder form.

Conductive island molecules are obtained by doping a polymer compound having a conjugated double bond in its main chain with a dopant. Typical examples of polymer compounds with conjugated double bonds in the main chain include polydiophene, acetylene polymer, polypyrrole, vorinolane, polyaniline, polyquinoline, polyparaphenylene, boria-1-nylene sulfide, polyparaphenylene oxide, boriacene, and polypropylene. Examples include carbazole, polyphenothiazine, polyviridine 1cum, polybenzopyridine, polyviroline, polypyrrolenin, poly(paraphenylenethienylene), and copolymers thereof. Methods for producing these polymer compounds include methods previously proposed by the present inventors, for example, in JP-A-59-210914.
, JP 61-2728, JP 61-224, JP I
N? 61-64729, JP-A [61-854411,
: The method described or J, P011711. s(1:i
, POIVllll, Lett, [d, 189 (198
0), J, Electroanal, Chem, 1
35173 (1982).

Hakromol, Chem, Rapid, Commu
m, 2551 (1981), J.

C, S Chem, Commun, 854 (1979
), J. Polym, Sci.

Polym, Lett, Ed, 20187 (19
82), J, EI electroanal.

Chem, 135173 (1982), J.C.
hca+, Phys, 711506 (1979)
, Bull, Chen, Soc, Japan 512
091 (1978).

J, POlym, SCi, Pollllllll, Che.
m, [:6. 12357 (1974), J.

^pp1. Polym, sci, 202541
(1976), HakromolChem, Yu26
130 (1969), J.A.C.S., 824
669 (1960) and the like.

These polymer compounds contain 12, Br2, SO
3.

or by doping with dopants such as AsFs, SbFs, etc. using chemical methods.

By doping with anions such as C, JO4-, PF4-, As Fs-, etc. using an electrochemical method, a conductive polymer having an electrical conductivity of 10-5 to 104S-CIll-1 can be obtained.

Any commercially available metal powder can be used as the metal powder used in the conductive paste of the present invention, such as silver powder, gold powder, palladium powder, copper powder, nickel powder, silver coated nickel powder, silver coated copper powder, and Examples include alloy powders of these.

The ratio of the conductive polymer to these metal powders ranges from 176 times to 6 times the weight of the metal powders.

If the ratio of conductive polymer is less than 176 times that of metal powder, the high temperature stability of the prepared conductive paste will be insufficient, and if the ratio of conductive polymer exceeds 6 times that of metal powder, conductivity will be insufficient. Become.

Any commercially available resin can be used as the resin used in the S-electrode paste of the present invention, but in order to optimize workability, a solvent may be added to adjust the viscosity.

In addition, by appropriately adjusting the ratio of the conductive polymer and metal powder mixture to the resin, a conductive paste with arbitrary conductivity can be obtained. The content ratio is preferably 35 to 95%,
In particular, 5% of 55 to 95 weight is preferable. If the total ratio of the conductive polymer and metal powder is less than 35% by weight, the paste will have insufficient electrical conductivity, and if it exceeds 95% by weight, the paste will have insufficient adhesiveness.

In the solid electrolytic capacitor of the present invention in which a conductive layer is formed using the above-mentioned conductive paste, the valve metal RM body used as the anode is made of a material having valve action, such as aluminum, tantalum, niobium, titanium, or an alloy containing these as a substrate. Any metal 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 another dielectric oxide layer provided on the surface of the anode substrate. However, it is particularly desirable that the layer be made of an oxide of the anode valve metal itself. In either case, the method of providing the oxide layer is II! using an electrolyte. Conventionally known methods such as polarization method can be used.

Furthermore, 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, conductive polymers, lead dioxide, or materials containing lead dioxide and lead sulfate as main components are recommended. It is preferable to produce lead dioxide, or one whose main components are lead dioxide and lead sulfate, by a conventionally known chemical precipitation method or electrochemical precipitation method.

When the semiconductor layer is made of a conductive polymer, the types and formation methods of the semiconductor layer include those previously proposed by the present inventors, such as JP-A-60-17909, JP-A-60-22311, and JP-A-60-37114. , JP-A-60-37115, JP-A-6
1-22613, Special 1;
85813, JP-A-61-89619, JP-A-61-9
1912, JP-A-61-91913, JP-A-62-43
12, JP-A-62-29124, JP-A-62-4710
The types and forming methods described in No. 9 etc. are employed.

In addition, a method for forming a semiconductor layer when the semiconductor layer is a layer mainly composed of lead dioxide or lead dioxide and sulfur RWa is described by the present inventors, for example, in JP-A-62-185307, 1 ft.
! The method described in Sho 63-51621 etc. can be used.

It is important to use a conductive paste made of the above-mentioned 8 conductive molecules, metal powder, and resin for the conductor layer of the solid electrolytic capacitor of the present invention. By using this conductive paste, a solid electrolytic capacitor with good high temperature stability can be manufactured. The reason for this is that the high-temperature stability of solid electrolytic capacitors can generally be solved by reducing the difference in thermal expansion coefficient between the semiconductor layer and the conductive layer and maintaining adhesion, but the 1wi polymer in the conductive paste is This is because it has the effect of reducing the difference in thermal expansion coefficient between the semiconductor layer and the conductor layer.

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.

Examples 1 to 3 Three types of conductive pastes having the compositions shown in Table 1 were prepared and applied to a substrate on which a polypyrrole film obtained by electrolytic polymerization, a polythiophene film, and lead dioxide powder were adhered under pressure with a load of 10 tons. and dried under reduced pressure at 100°C. These were then left at a temperature of 105° C. for 2,000 hours, but there was no change in surface resistance, indicating that there was no change in the adhesion between the paste, film, and substrate.

Table 1 Comparative Example 1 Silver powder 90% without adding polypyrrole powder to conductive paste
A conductive paste consisting only of a heavy sliding part and an acrylic resin 101 hanging part was prepared, and this conductive paste was applied to a polypyrrole film obtained using an electrolytic chassis similar to that in Example 1, and dried under reduced pressure at 100°C. When this was left at 105° C. for 2000 hours, the surface resistance increased and the adhesion between the paste and the film decreased.

Example 4 An aluminum foil with a length of 2 att and a width of 0 and 5 Crrr was used as an anode, and the surface of the foil was electrochemically etched using alternating current.The anode terminal was caulked to the etched aluminum foil, and the anode lead wire was connected. Connected.

Next, an alumina oxide film is formed by electrochemical treatment in an aqueous solution of phosphoric acid and ammonium phosphate, and etched aluminum foil for low pressure (approximately 10 μF/cM
) was obtained. Next, the chemically modified foil was immersed in an aqueous solution of 1 mol/J of vinegar Ml trihydrate, and a mixed solution of an aqueous solution of 2.4 mol/J of lead acetate trihydrate and 47 mol/J of perSM-ammonium ( reaction mother liquor) and reacted at 80°C for 30 minutes,
The semiconductor layer made of lead dioxide and lead sulfate formed on the dielectric oxide film layer was thoroughly washed with water and then dried under reduced pressure at 120°C. The produced semiconductor layer was composed of lead dioxide and lead oxide, and it was confirmed by qualitative analysis, X-ray analysis, and infrared spectroscopy that it contained about 25% by weight of lead dioxide.

Next, the chemically formed foil with the semiconductor layer formed thereon was immersed in the conductive paste bath prepared in Example 3, pulled up, and dried under reduced pressure at 100°C. A solid electrolytic capacitor was produced by connecting the cathode with the paste described above and sealing with resin.

Example 5 A chemically formed foil similar to Example 4 was mixed with 1.0 mol/lead acetate trihydrate.
It was immersed in a J aqueous solution, and an electrolytic reaction was carried out using a separately prepared stainless steel foil as a cathode to form a semiconductor layer made of lead dioxide on the chemically formed foil. Next, the conductive paste of Example 1 was used to form a Wffi body layer, and a solid electrolytic capacitor was manufactured.

Example 6 0.02 M of virol monomer was dissolved in an electrolytic solution using the same chemically modified foil as in Example 4 as a positive electrode and platinum as a negative electrode.
Electrolytic polymerization was performed using IMBu 4 N B F 4 acetonitrile solvent to form a semiconductor layer of polypyrrole doped with BF 4 - on the chemically formed foil.

Then, a conductive layer was formed in the same manner as in Example 5 to produce a solid-state capacitor.

Example 7 A solid electrolytic capacitor was produced in the same manner as in Example 6 except that diofenmo and l-mer were used instead of virol monomer and the conductive paste of Example 2 was used.

Comparative Examples 2 to 3 Solid electrolytic capacitors were produced in the same manner as in Examples 4 and 6, except that the conductive paste produced in Comparative Example 1 was used for the conductor layer.

The characteristic values of the solid electrolytic capacitors produced in Examples 4 to 7 and Comparative Examples 2 to 3 are summarized in Table 2.

Table 2 As is clear from Table 2, solid electrolytic capacitors whose conductor layer is a paste layer containing a conductive polymer, metal powder, and resin have improved high-temperature stability and exhibit good properties. There is.

〔Effect of the invention〕

As mentioned above, the conductive paste related to Mizumoto 1!11 is inexpensive and has excellent adhesion, and solid electrolytic capacitors using the conductive paste for the conductive layer are more stable at high temperatures than conventional solid electrolytic capacitors. It has advantages such as excellent performance and low cost.

Claims (2)

[Claims] (1) A conductive paste characterized by being a mixture of a conductive polymer, metal powder, and resin. (2) A solid electrolytic capacitor in which a dielectric oxide film layer, a semiconductor layer, and a conductive layer are sequentially formed on the surface of an anode substrate made of a valve metal, wherein the conductive layer is formed by forming the conductive paste according to claim 1. Solid electrolytic capacitor made of