JP2010206117A - Chip-type solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chip-type solid electrolytic capacitor whose reliability of a capacitor characteristic is improved by preventing peeling between a plating layer and electrolytic layer and by preventing a crack produced on the electrolytic layer or plating layer due to thermal stress by means of an improvement of an electrolytic layer of a conductive high polymer. <P>SOLUTION: The chip-type solid electrolytic capacitor is formed in a manner such that a dielectric oxide film and the conductive high polymer being as a solid electrolyte are laminated in order on a surface of an anode body being as a rectangular porous body and an anode lead is introduced from one edge of the anode body, and on the surface side of the conductive high polymer, the conductive high polymer coated with a conductive polymer solution paste or a diffusion liquid paste of a conductive polymer is provided, and the plating layer is prepared on it. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a chip-type solid electrolytic capacitor using a conductive polymer as a solid electrolyte. In particular, the present invention relates to a chip-type solid electrolytic capacitor using a conductive polymer as a sintered solid electrolyte.

  Solid electrolytic capacitors, especially sintered type capacitors, were formed by chemical conversion treatment on the anode body in which one end of the anode lead was embedded by expanding the surface area of tantalum or niobium as a porous sintered body. A dielectric oxide film, a solid electrolyte layer, and a cathode current collector layer formed of a conductive paste have capacitor elements sequentially provided, and the outermost cathode current collector layer is formed of a conductive paste. The cathode terminal plate is connected via a connection body such as a conductive adhesive, and the anode terminal plate is connected to the anode lead by welding or the like. And it coat | covers by methods, such as a shaping | molding metal mold | die by the exterior which consists of insulating resins, etc., and the anode terminal plate and the cathode terminal plate are pulled out from the exterior.

  Recently, as a solid electrolyte layer, a solid electrolytic capacitor using a conductive polymer having higher conductivity than manganese dioxide and excellent heat resistance, such as polypyrrole, polyaniline, polythiophene, etc., is being developed. .

In order to use these conductive polymers as an electrolyte layer, conventionally, an anode body of a porous sintered body is immersed in a conductive monomer solution, and an oxidizing agent is formed on the surface of the oxide film on the surface of the anode body that is an insulator. The method of depositing and conducting as a polymer by chemical oxidative polymerization by the method, then thickening the electrolyte layer by methods such as electrolytic polymerization, and the method of thickening the electrolyte layer by repeating the chemical polymerization several times It was.
As a cathode current collector layer formed on the surface of these electrolyte layers, a method of providing a plating layer instead of providing a conventional conductive paste layer has been proposed in order to prevent internal diffusion of oxygen, moisture, etc. (For example, Patent Document 1).

Japanese Patent Laid-Open No. 05-021279

  As a cathode current collector layer, instead of providing a layer made of conductive paste, a method of providing a plating layer is difficult because a metal plating layer is hardened due to thermal stress during manufacturing or installation of the capacitor and thermal stress due to environmental high temperature load. Peeling occurs between the polymer electrolyte layer and the electrolyte layer, and the electrolyte layer is cracked. As a result, the oxide film on the anode body surface is damaged, or the plating layer is cracked. As a result, the reliability of the capacitor characteristics was not sufficient.

The object of the present invention is to improve the reliability of the capacitor characteristics by improving the electrolyte layer of the conductive polymer and preventing the occurrence of peeling between the plating layer and the electrolyte layer or cracking in the electrolyte layer or the plating layer due to thermal stress. It is to provide a chip-type solid electrolytic capacitor with improved performance.

In order to solve the above problems, the present invention sequentially forms a dielectric oxide film, a conductive polymer layer as a solid electrolyte, and a plating layer as a current collector on the surface of the anode body of the porous sintered body. In a chip-type solid electrolytic capacitor that is laminated and has an anode lead led out from one end face of the anode body, a conductive polymer solution paste or a conductive material is provided on the side of the conductive polymer layer that contacts the plating layer. Provided is a chip-type solid electrolytic capacitor characterized in that a conductive polymer coated with a polymer dispersion paste is provided.
Further, a dielectric oxide film, a conductive polymer layer as a solid electrolyte, and a plating layer as a current collector are sequentially laminated on the surface of the anode body of the porous sintered body, and one end face of the anode body In the chip-type solid electrolytic capacitor having an anode lead derived from the conductive polymer layer, a conductive polymer obtained by chemically oxidatively polymerizing a conductive monomer inside the porous body is formed on the inner surface of the anode body. Provided is a chip-type solid electrolytic capacitor characterized in that a conductive polymer solution paste or a conductive polymer coated with a conductive polymer dispersion paste is provided on the outer surface of the anode body.

Since the chip-type solid electrolytic capacitor of the present invention is provided with a conductive polymer coated with a conductive polymer solution paste or a conductive polymer dispersion paste as a base layer of the plating layer, It is possible to provide a chip-type solid electrolytic capacitor with improved reliability of capacitor characteristics by preventing peeling between the electrolyte layer and cracking in the electrolyte layer or the plating layer.

1 shows a chip-type solid electrolytic capacitor according to the present invention. 3 shows another chip-type solid electrolytic capacitor according to the present invention.

The plating layer described in the present invention is generally a layer formed by a plating method in a liquid or in a vacuum, and is made of a metal except for impurities and additives taken in a trace amount. The metal can be selected from copper, nickel, cobalt, tin, zinc or an alloy containing at least one of them, which can be plated in liquid or can be deposited in vacuum. The thickness of the plating layer is such that no pinholes remain in the plating layer, and is about 1 μm to 50 μm, preferably about 10 μm to 20 μm. If it is thin, pinholes are likely to remain in the plating layer, moisture resistance tends to deteriorate, and electrical resistance tends to increase. On the other hand, if it is thick, it will not be easily deformed, and it will be difficult to absorb thermal stress between materials.
As the submerged plating, electroless plating, electrolytic plating, or electroless plating can be used on the surface without particular limitation, such as electrolytic plating.
For example, as electroless copper plating, first, a catalyst nucleus is provided. A palladium ion catalyst or a palladium colloid catalyst is used for imparting the catalyst nucleus. Adsorption to the conductive on a polymer of the palladium catalyst in the present invention is in the range of 0.03~0.6μg / cm ^2, and more preferably in the range of 0.05~0.3μg / cm ² . The treatment temperature for adsorbing the palladium catalyst is preferably 10 to 40 ° C. By controlling the treatment time, the adsorption amount of the palladium catalyst onto the conductive polymer can be controlled.
Moreover, a commercially available electroless copper plating can be used for the electroless copper plating layer. These electroless copper platings are mainly composed of copper sulfate, formalin, complexing agent and sodium hydroxide. When electroplating is performed on the plating, the thickness is in the range of 0.1 to 5 μm.
Next, an electrolytic copper plating layer is provided on the surface of the electroless copper plating layer. Only electrolytic copper plating may be provided from the beginning. For example, if a copper sulfate-based solution is used, the conditions are copper 50 to 80 g / l, sulfuric acid 50 to 150 g / l, liquid temperature 40 to 50 ° C., and current density 10 to 50 A / dm ^2. .
As an electrolytic plating apparatus, the cathode electrode may be connected to the conductive polymer layer side, and the cathode electrode may be connected to the anode lead in addition to a method using a copper plate as the anode electrode.

  The anode body described in the present invention is a molded sponge-like sintered body. For example, one end of an anode lead is embedded into a fine powder having an average particle diameter of about 1 μm of valve action metal such as tantalum, niobium or aluminum. It is a sponge-like sintered body formed by press-pressing a powder mixed with a binder such as acrylic resin or camphor, and then sintering in vacuum.

The conductive polymer solution paste described in the present invention mainly comprises a conductive polymer, a binder, and a solvent, and other additives that are added as necessary.
As the conductive polymer, a conductive polymer such as polyaniline, polypyrrole, polythiophene, polyparaphenylene, polyacetylene or the like that can be dissolved in a solvent is selected.
Examples of the binder include polyisoprene, polystyrene, polyethylene, polyvinyl pyrrolidone, polyvinyl alcohol, polymethyl methacrylate, polyacrylonitrile, polyester, polyamide, polyurethane, polycarbonate, cellulose, and elastomers thereof.
Examples of the additive include a crosslinking agent and a flow modifier.
Examples of the crosslinking agent include functional silanes such as functional silanes such as tetraalkoxysilane and crosslinkable polymers.
Examples of the flow control agent include synthetic quartz, fused silica, manganese dioxide, tin oxide, vanadium oxide, indium oxide, iron oxide, aluminum oxide, cerium oxide, glass powder and other inorganic oxide fillers, silicon nitride, boron nitride, and aluminum nitride. Inorganic oxide fillers such as carbide fillers such as silicon carbide and boron carbide, conductive fillers such as carbon and non-solvent conductive polymers, and the like are used.
The average particle diameter of the filler is preferably in the range of 0.1 μm to 50 μm, and particularly preferably in the range of 0.5 μm to 10 μm. When the average particle size is smaller than 0.1 μm, the fluidity of the conductive polymer solution is difficult to be improved when the blending amount is small. Further, the blending amount of the filler in the conductive polymer solution is preferably in the range of 0.01% to 30% by volume with respect to the conductive polymer. In particular, since the inorganic filler has a conductivity that is one to several orders of magnitude lower than that of the conductive polymer, the impedance characteristics of the solid electrolytic capacitor are likely to deteriorate if the blending amount exceeds the above range.
As the solvent, water or an organic solvent is used. Examples of the organic solvent include ketones, esters, alcohols, aromatic hydrocarbons, nitriles, cellosolves, nitrogen-containing compounds, and the like.

The conductive polymer dispersion paste described in the present invention mainly comprises conductive polymer particles, a binder, a dispersant and a solvent, and other additives which are added as necessary. These materials can also be selected from the materials for the conductive polymer solution paste. In some cases, the binder and the dispersant are also used.
As the solvent, in addition to the above organic solvent, water, alcohol, or a mixture thereof is used.
The conductive polymer particles are selected in a state insoluble in the solvent for the conductive polymer.
In addition to the above binders such as polyvinyl alcohol, the dispersant is alkyl glycoxide, polyethylene glycol, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, fatty acid sorbitan ester, alkyl polyglucoside, fatty acid diethanolamide, alkyl monoglyceryl ether, etc. Or the like.

  The layer formed from the conductive polymer solution paste or conductive polymer dispersion paste described in the present invention is more plastic and tougher than the layer formed from the conductive polymer by adding a paste agent. In addition to physical properties such as properties, it is easy to improve the adhesion between the front and back layers.

  The external surface described in the present invention refers to the surface forming the outer shape of the anode body.

  The internal surface described in the present invention refers to a porous internal surface other than the surface forming the outer shape of the anode body.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 shows a chip-type solid electrolytic capacitor according to the present invention.
The anode lead 1 is made of a valve metal such as tantalum, niobium, or aluminum, which has a linear shape with a diameter of about 0.1 mm to 0.5 mm, or a strip shape with a thickness of about 0.1 mm to 0.5 mm.
Capacitor element 2 is formed by embedding one end of anode lead 1 and pressing a powder obtained by mixing a binder, such as acrylic or camphor, with a fine powder having an average particle diameter of about 1 μm, such as tantalum, niobium or aluminum. Sponge-shaped porous rectangular anode body 3 formed by pressure forming and then sintered in vacuum, anodized film (not shown) on this anode body 3, and a solid electrolyte layer of a conductive polymer 4 and a cathode current collector layer 5 as a plating layer.
The anode body 3 is a molded sponge-like sintered body. One end of the anode lead 1 is embedded, and a powder obtained by mixing a fine powder of valve action metal with a binder such as acrylic resin or camphor is press-press molded. Then, a sponge-like sintered body formed by sintering in vacuum.
The solid electrolyte layer 4 includes a chemically oxidized polymerized conductive polymer provided on the surface of the anodized film of the porous molded body or a solid electrolyte lower layer 4a of the polymerized conductive polymer provided on the surface thereof, and It comprises a solid electrolyte upper layer portion 4b coated with a conductive polymer solution paste or conductive polymer dispersion paste provided on the surface of the solid electrolyte lower layer portion 4a.
Reference numeral 6 denotes a cathode terminal plate, which is connected to the cathode current collector layer 5 of the plating layer by a connection body 7 such as a conductive adhesive or solder.
Reference numeral 8 denotes an anode terminal plate which is connected to the anode lead 1 by welding such as resistance welding or laser welding or a conductive adhesive.
Reference numeral 9 denotes an exterior which seals the capacitor element 2 and the like with a sealing resin such as an epoxy resin. The cathode terminal plate 6 and the anode terminal plate 8 are exposed from the side to the bottom of the exterior 9 in FIG.

FIG. 2 shows a chip-type solid electrolytic capacitor according to the present invention in which the solid electrolyte layer has a different configuration.
The solid electrolyte layer 4 includes an internal solid electrolyte layer 4c obtained by chemically oxidizing and polymerizing a conductive monomer provided on the inner surface of the porous molded body, and a conductive polymer provided on the outer surface of the porous molded body. The outer solid electrolyte layer 4d is coated with a solution paste or a conductive polymer dispersion paste.
Further, the configuration other than the solid electrolyte layer 4 is the same as that shown in FIG.

The anode body 3 is impregnated with an oxidizing agent solution and dried, then impregnated with a conductive monomer solution, and then subjected to chemical oxidative polymerization.
Thereafter, a washing process such as washing with water or a liquid removal process is provided, and the inner surface of the anode body 3 is electrically conductive by drying at a high temperature at 100 to 160 ° C. after removing the monomer and the oxidant solution on the outer surface of the anode body 3 as much as possible. As a result, a conductive polymer obtained by chemically oxidatively polymerizing the conductive monomer inside the porous body is formed, and it is difficult to form a conductive polymer obtained by chemical oxidative polymerization on the outer surface of the anode body 3. Further, it is preferable to increase the density of the outer surface of the anode body 3 to reduce the pore diameter, so that the conductive monomer solution or the oxidizing agent solution tends to stay inside the anode body 3 even after washing.
By the above method or the like, it is possible to directly or directly provide the outer surface of the anode body 3 with a conductive polymer solution paste or a conductive polymer dispersion paste coated with a conductive polymer dispersion paste. The area can be increased, and the conductive polymer coated with the conductive polymer solution paste or the conductive polymer dispersion paste is firmly connected to the dielectric oxide film on the outer surface of the anode body 3. Is possible.

A method of manufacturing a tantalum chip type solid electrolytic capacitor having a rating of 10 V and 100 μF will be described. A fine powder of tantalum is used as the valve action metal, and a fine powder obtained by adding an acrylic resin as a binder to the fine powder is compression-molded by a press machine with one end of a tantalum anode lead wire embedded. The molded body was heat-treated in vacuum and sintered to form a rectangular parallelepiped sintered body having a width of 3 mm, a thickness of 1.5 mm, and a length of 4 mm.
Next, the sintered body was immersed in a diluted phosphoric acid solution, and a DC voltage of 30 V was applied to form a dielectric film. After forming the dielectric film, a 0.1 mol / l thiophene monomer aqueous methanol solution and an 0.1 mol / l ferric dodecylbenzenesulfonic acid methanol aqueous solution as an oxidizing agent solution were prepared.
Next, the anode body was impregnated with an oxidizing agent solution and dried at room temperature for 20 minutes. Thereafter, the thiophene monomer solution was impregnated and kept at room temperature for 60 minutes for chemical oxidative polymerization, followed by washing with water and drying. This series of operations was repeated 10 times to provide a conductive polymer layer chemically oxidized and polymerized on the inner surface of the anode body.
Next, thiophene polymer powder: 20% by mass, polyvinyl alcohol as a binder dissolved in 1% by mass of N-methyl-2-pyrrolidone is used. The application of the functional polymer was repeated twice. Thereafter, it was dried by heating.
Next, a cathode current collector layer having a plating layer thickness of 15 μm was formed. The plating was performed using an electrolytic copper sulfate solution under the conditions of a copper concentration of 60 g / l, sulfuric acid 60 g / l, a liquid temperature of 45 ° C., and a current density of 20 A / dm ² .
Next, the cathode current collector layer of the element was connected to the cathode terminal portion of the lead frame having a thickness of 0.1 mm with a silver conductive paste, and the anode lead wire was welded to the anode terminal portion of the lead frame to be fired. The ligature was attached to a lead frame. After the element was attached to the lead frame, an exterior was formed by transfer molding using epoxy resin. After forming the exterior, aging treatment was performed, the lead frame was cut and removed, the cathode terminal and the anode terminal were formed, and a chip-type solid electrolytic capacitor was obtained.

  As a method for forming a conductive polymer dispersion paste layer on the surface of a chemically oxidatively polymerized conductive polymer layer in preparation of a solid electrolyte layer, thiophene: 0.1 mol / l, sodium naphthalene sulfonate, which is doppane, : 0.2 mol / l and an oxidizing agent of iron chloride: 0.2 mol / l in a methanol solution was chemically oxidatively polymerized to remove excess and then dried to obtain powdered polythiophene. Next, a conductive polymer is applied to the surface of the chemically oxidized polymerized conductive polymer layer by using a suspension of this powdery polythiophene: 20% by mass and polyvinylpyrrolidone: 1% by mass as a binder. The same procedure as in Example 1 was performed except that.

In preparation of the solid electrolyte layer, the anode body was impregnated with an oxidant solution and dried at room temperature for 20 minutes. Thereafter, the thiophene monomer solution was impregnated and kept at room temperature for 60 minutes for chemical oxidative polymerization, followed by washing with water and drying.
This series of operations was repeated 10 times to provide a conductive polymer obtained by chemically oxidizing and polymerizing a conductive monomer inside the porous body on the inner surface of the anode body.
Next, a thiophene polymer powder: 20% by mass, polyvinyl alcohol as a binder dissolved in 1% by mass of N-methyl-2-pyrrolidone is used, and a conductive polymer is applied to the outer surface of the anode body and dried by heating. However, this was performed in the same manner as in Example 1 except that this was performed twice.

(Comparative Example 1)
It was prepared in the same manner as in Example 1 except that a chemical oxidation polymerization film was also provided on the outer surface of the anode body.
The method of forming a chemical oxidation polymerized film on the external surface is as follows: after impregnation in a methanol solution of 0.1 mol / l thiophene monomer and holding at room temperature for 30 minutes, then 0.1 mol / l dodecylbenzenesulfonic acid as an oxidant solution After impregnating with an aqueous ferric methanol solution and holding at room temperature for 10 minutes, chemical oxidative polymerization was performed in an atmosphere of 40 ° C. and 40% for 20 minutes. Thereafter, washing and drying were performed. This series of operations was repeated 10 times.

  The initial characteristics of the chip-type solid electrolytic capacitors of Examples and Comparative Examples and the leakage current after being left in a high temperature atmosphere at 150 ° C. for 100 hours were measured. Further, ESR (equivalent series resistance) was a value at 100 KHz, and the heat cycle test was performed under conditions of a temperature of −55 ° C. to 125 ° C. and 200 cycles. The measurement is performed at each n10, and the average measurement results are shown in Table 1.

As described above, as is apparent from the results of the high temperature storage and heat cycle test in Table 1, the embodiment can provide a chip-type solid electrolytic capacitor that can improve the stability of ESR and leakage current as compared with the conventional example.

  DESCRIPTION OF SYMBOLS 1 ... Lead for anode, 2 ... Capacitor element, 3 ... Anode body, 4 ... Solid electrolyte layer, 4a ... Solid electrolyte lower layer part, 4b ... Solid electrolyte upper layer part, 4c ... Internal solid electrolyte layer, 4d ... External solid electrolyte layer, 5 ... Cathode current collector layer of plating layer, 6 ... Cathode terminal plate, 7 ... Connector, 8 ... Anode terminal plate, 9 ... Exterior.

Claims (2)

  A dielectric oxide film, a conductive polymer layer as a solid electrolyte, and a plating layer as a current collector are sequentially stacked on the surface of the anode body of the porous sintered body and derived from one end face of the anode body. In the chip-type solid electrolytic capacitor having the anode lead formed, a conductive polymer solution paste or a conductive polymer dispersion paste is applied to a side of the conductive polymer layer in contact with the plating layer. A chip-type solid electrolytic capacitor characterized by providing molecules.   A dielectric oxide film, a conductive polymer layer as a solid electrolyte, and a plating layer as a current collector are sequentially stacked on the surface of the anode body of the porous sintered body and derived from one end face of the anode body. In the chip-type solid electrolytic capacitor having an anode lead, a conductive polymer obtained by chemically oxidatively polymerizing a conductive monomer inside the porous body is provided on the inner surface of the anode body in the conductive polymer layer, A chip-type solid electrolytic capacitor characterized in that a conductive polymer solution paste or a conductive polymer dispersion paste is provided on the outer surface of the anode body.

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