JP2009231319A - Solid electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor for exhibiting the flame retardant operation of a flame retarder effectively by a method without poorly affecting an oxide film on the surface of a sintered body since flame retardant powder is added into a collector layer in a solid electrolytic capacitor, where the oxide film is formed on the sintered body made of a valve operation metal and a solid electrolyte layer and the collector layer are successively laminated on the oxide film. <P>SOLUTION: In the solid electrolytic capacitor, where the oxide film is formed on the sintered body made of a valve operation metal and the solid electrolyte layer and the collector layer are successively laminated on the oxide film, the fire retardant powder is added into the collector layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solid electrolytic capacitor. In particular, it relates to a solid electrolytic capacitor having high flame retardancy.

  For example, the solid electrolytic capacitor is manufactured by the following method. That is, first, one end of an anode lead wire made of valve action metal such as tantalum or niobium is embedded in advance, and a powder obtained by mixing a binder with a fine powder of valve action metal such as tantalum, niobium or aluminum is press-press molded. To do. After molding, it is heated and sintered at a high temperature in a vacuum to form a sintered body. Next, this sintered body is immersed in a chemical conversion solution and subjected to chemical conversion treatment to form an oxide film. After forming the oxide film, a solid electrolyte layer made of a conductive polymer such as polypyrrole or polyaniline, or manganese dioxide is formed. Thereafter, a carbon layer and a silver layer are sequentially formed to form a current collector layer. The anode terminal is connected to the anode lead wire, and the cathode terminal is connected to the current collector layer. Further, the capacitor element after the current collector layer is formed and a part of the anode terminal and the cathode terminal are covered with an exterior made of an insulating resin or the like to obtain a solid electrolytic capacitor.

By the way, this type of solid electrolytic capacitor, unlike an aluminum electrolytic capacitor using an electrolytic solution or a film capacitor, has a demand for flame resistance because the capacitor generates heat when there is an incorrect connection or failure. In particular, when a tantalum sintered body is used as the sintered body and manganese dioxide is used as the solid electrolyte layer, the manganese dioxide may decompose and release oxygen due to heat generated by the tantalum powder.
Therefore, conventionally, an inorganic binder is provided on the current collector layer of this type of solid electrolytic capacitor to impart flame retardancy (Patent Document 1). Moreover, the digestive substance layer was provided between the layers of a multilayer outer resin, and the digestive function was provided (patent document 2).
JP-A-1-194410 Kaihei 8-45794

By the way, in the method of Patent Document 1 in which a binder made of an inorganic material is provided on the current collector layer, the current collector layer is merely flame retardant, and the flame retardancy of the entire capacitor may not be sufficient.
Further, in the method of Patent Document 2 in which a digestible substance layer is provided between layers of the multilayer outer layer resin to provide a digestive function, the digestive function may be difficult to act because it is far from a sintered body that generates heat.

  The present invention has been made in view of the above problems, in a solid electrolytic capacitor in which an oxide film is formed on a sintered body made of a valve action metal, and a solid electrolyte layer and a current collector layer are sequentially laminated on the oxide film. Since the flame retardant powder is added to the current collector layer, the flame retardant effectively exhibits the flame retardant action in a way that does not adversely affect the oxide film on the surface of the sintered body. An object of the present invention is to provide a solid electrolytic capacitor capable of satisfying the requirements.

In order to solve the above-mentioned problems, the present invention provides a current collector in a solid electrolytic capacitor in which an oxide film is formed on a sintered body made of a valve action metal, and a solid electrolyte layer and a current collector layer are sequentially laminated on the oxide film. A solid electrolytic capacitor in which a flame retardant powder is added to a body layer is provided.
Further, in a solid electrolytic capacitor in which an oxide film is formed on a sintered body made of a valve action metal, and a solid electrolyte layer, and a cathode paste layer made up of a carbon paste layer and a silver paste layer are sequentially laminated on the oxide film. A solid electrolytic capacitor in which a flame retardant powder is added to at least one of a carbon paste layer and a silver paste layer is provided.

According to the present invention, in a solid electrolytic capacitor in which an oxide film is formed on a sintered body made of a valve metal, and a solid electrolyte layer and a current collector layer are sequentially laminated on the oxide film, Since the flame retardant of the flame retardant is added, since the flame retardant is a solid at a short distance from the sintered body that is the source of ignition, it does not bleed into the solid electrolyte layer, affecting the capacitor characteristics. It is possible to provide a solid electrolytic capacitor capable of effectively exhibiting the flame retarding action of the flame retardant without giving it.

  The solid electrolyte layer described in the present invention is a solid layer provided on the surface of a sintered body made of a valve action metal provided with an oxide film and capable of moving ions from an externally applied electric field. Consists of conductive polymers such as polypyrrole and polyaniline, or manganese dioxide.

The current collector layer described in the present invention is an electrode layer for the purpose of collecting current of the solid electrolyte layer, and specifically, a silver paste having high conductivity is generally used. Sometimes solder paste is provided. Since silver has migration, a carbon paste layer is generally provided between the solid electrolyte layer and the silver paste. The paste is a liquid material mainly containing a dispersing agent such as a polymer resin and a dispersion medium such as an organic solvent or pure water in addition to the above powder. Moreover, in order to process into a paste form, it can obtain easily by kneading | mixing or disperse | distributing uniformly using a normal stirrer, a raking machine, a 3 roll, a roll mill, etc.
In the current collector layer described in the present invention, a flame retardant is added to a part or the whole of a paste component that is usually used composed of a conductive powder, an organic component, an organic solvent, and the like. The addition amount is used by adding 1 wt% to 20 wt% with respect to the total weight of the current collector layer. When a flame retardant is added only to the silver paste, a problem is not likely to occur in silver-resistant migration of the underlying carbon paste layer, but the conductivity of the silver paste layer may be lowered. When a flame retardant is added to the underlying carbon paste layer, silver migration may be reduced, but there are few problems that the conductivity of the silver paste layer is reduced.

The flame retardant described in the present invention is a powdery flame retardant and is hardly soluble in water. The particle size is about 0.01 μm to 20 μm, and specifically, at least one of metal hydroxides such as aluminum hydroxide, aluminum hydroxide oxide, aluminum magnesium hydroxide, magnesium hydroxide, or antimony trioxide can be used. These are sparingly soluble in water and organic solvents. Therefore, they are used as powders, and are mixed and used in a silver paste or a carbon paste that becomes a current collector layer.
In particular, since the particle size of antimony trioxide is relatively large from 0.3 μm to 10 μm, the antimony trioxide particles are coated with antimony pentoxide particles having a particle size of about 0.005 μm to 0.1 μm, A composite of antimony trioxide particles and silica particles can be used. Thus, by coating antimony pentoxide particles on antimony trioxide particles, or by combining antimony trioxide particles with silica particles or the like, it is easy to disperse in the solution and long-term stability can be obtained.
In addition, since antimony trioxide reacts with halogen and exhibits superior flame retardancy, halogen-based flame retardants can be mixed with silver paste and carbon paste in the current collector layer, as long as they can be used. A halogen-containing substance (halogenated substance) may be used as a constituent material of the paste.
In the case of metal hydroxides, in addition to single addition, calcium flame retardant and ethylenediamine zinc phosphate are used in combination and added within the above ratio range. By performing the surface treatment, the water resistance is greatly improved.

Capacitor characteristics because the flame retardant is added in the current collector layer at a short distance from the sintered body that is the source of ignition, and because the flame retardant is solid, it does not bleed into the solid electrolyte layer. It will not affect Further, since it does not ooze out to the outer layer resin that is in contact with the outside air, moisture, contaminated air, or the like does not enter from the infiltrated portion and does not affect corrosion or the like.

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.
Reference numeral 1 denotes an anode lead, which is made of a valve metal such as tantalum, niobium, or aluminum having a diameter of about 0.1 mm to 0.5 mm, or a strip-shaped plate having a thickness of about 0.1 mm to 0.5 mm. Become.
2 is a capacitor element, in which one end of the anode lead 1 is embedded, and 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 of a valve metal such as tantalum, niobium or aluminum is pressed. A sponge-like anode sintered body formed by pressure molding and then sintered in vacuum, an anodized film, a solid electrolyte layer 3 of manganese dioxide, and a flame retardant powder are added to the sintered body. The carbon layer and the silver current collector layer 4 are sequentially provided.
A cathode terminal plate 5 is connected to the current collector layer 4 with a conductive adhesive or the like.
Reference numeral 6 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. The lead-out portions of the cathode terminal plate 5 and the anode terminal plate 6 are folded along the capacitor body in FIG. 1, but conversely, they may spread from the lower side to the outside.
Reference numeral 7 denotes an exterior that seals the capacitor element and the like with a sealing resin such as an epoxy resin. The cathode terminal plate 5 and the anode terminal plate 6 are exposed from the end surface portion of the exterior 7. The cathode terminal plate 5 or the anode terminal plate 6 may be exposed to the outside instead of the bottom surface side of the outer casing 7, or may be extended to the bottom surface side along the side surface of the capacitor body.

FIG. 2 shows a part of a cross-sectional view of the capacitor element of the chip-type solid electrolytic capacitor according to the present invention.
2A shows a state in which the carbon paste layer 8 contains the flame retardant powder 9, and FIG. 2B shows a state in which the silver paste layer 10 contains the flame retardant powder 9. Is shown.
FIG. 2C shows a state where the current collector layer 4 of the carbon paste layer 8 and the silver paste layer 10 contains the flame retardant powder 9.
More specifically, FIG. 2 (a) shows a case where the sintered body 11 on which the anodized film is formed is immersed in an aqueous manganese nitrate solution and thermally decomposed to obtain manganese dioxide, or contains a monomer for a conductive polymer. It is immersed in a solution and polymerized to form a solid electrolyte layer 3, and then immersed in a paste in which a flame retardant powder 9 is mixed in a carbon paste and solidified to form a carbon paste layer 8. The state which provided the silver paste layer 10 on the surface is shown. The carbon paste layer 8 may be heated to about 250 ° C. and fired to release organic substances to some extent.
In FIG. 2 (b), after obtaining the solid electrolyte layer 3 on the sintered body 11 as in FIG. 2 (a), the carbon paste layer 8 was provided, and then the flame retardant powder 9 was mixed in the silver paste. A state is shown in which the silver paste layer 10 is formed by dipping in a paste and solidifying. The carbon paste layer 8 may be heated to about 250 ° C. and fired to release organic substances to some extent.
FIG. 2 (c) shows the solid electrolyte layer 3 obtained on the sintered body 11 in the same manner as FIG. 2 (a), and then immersed in a paste in which a flame retardant powder 9 is mixed in a carbon paste and solidified. The carbon paste layer 8 is provided, and then immersed in a paste in which a flame retardant powder 9 is mixed in the silver paste and solidified to form a silver paste layer 10. The carbon paste layer 8 may be heated to about 250 ° C. and fired to release organic substances to some extent.

Example 1
Tantalum powder having an average particle size of 0.5 μm is put in a tantalum container and heated in a vacuum atmosphere at a temperature of 1400 ° C. for 1 hour. The heat-treated tantalum powder is bonded to each other. The tantalum powder is taken out from the container and lightly crushed, and is made into a sintered granulated powder of a predetermined size by a sieving method, a wind method or the like. Next, the crushed tantalum powder is compression-molded to a size of 1.1 × 1.5 × 0.8 mm and fired in vacuum to produce a tantalum sintered body. Note that an anode lead wire made of a tantalum wire having a diameter of 0.25 mm is implanted into the sintered body and the tip thereof is drawn out during compression molding. Then, this sintered body is immersed in a nitric acid solution having a concentration of 0.1% and anodized at a voltage of 26 V for 120 minutes to form an oxide film. Next, the sintered body is impregnated with an aqueous manganese nitrate solution having a concentration of 20%, and then thermally decomposed at a temperature of 260 ° C. to obtain a solid electrolyte layer of manganese dioxide.
Next, it is immersed in a paste in which 10 wt% of antimony trioxide powder is mixed in carbon paste and solidified to form a carbon paste layer, and a silver paste layer is provided on the surface.
Next, after forming a silver paste layer, a cathode terminal is connected to the silver paste layer with a silver conductive paste, and the anode terminal is welded to the anode lead wire. Then, an epoxy resin is transfer-molded to form an exterior, and then subjected to an aging process.
(Example 2)

  After obtaining a solid electrolyte layer on the sintered body in the same manner as in Example 1, a carbon paste layer was provided, and then immersed in a paste in which 10 wt% of antimony trioxide powder was mixed in a silver paste, solidified and silver A paste layer was formed. Next, after forming a silver paste layer, a cathode terminal is connected to the silver paste layer with a silver conductive paste, and the anode terminal is welded to the anode lead wire. Then, an epoxy resin is transfer-molded to form an exterior, and then subjected to aging treatment.

(Example 3)
After obtaining a solid electrolyte layer on the sintered body in the same manner as in Example 1, it was immersed in a paste in which 5 wt% of a flame retardant powder was mixed in a carbon paste, solidified to form a carbon paste layer, and then silver The paste was immersed in a paste in which 5 wt% of antimony trioxide powder was mixed and solidified to form a silver paste layer. Next, after forming a silver paste layer, a cathode terminal is connected to the silver paste layer with a silver conductive paste, and the anode terminal is welded to the anode lead wire. Then, an epoxy resin is transfer-molded to form an exterior, and then subjected to an aging process.

Example 4
A solid electrolytic capacitor was obtained in the same manner as in Example 1 except that the antimony trioxide powder was changed to aluminum hydroxide powder.

(Example 5)
A solid electrolytic capacitor was obtained in the same manner as in Example 2 except that the antimony trioxide powder was changed to aluminum hydroxide powder.

(Example 6-9)
A solid electrolytic capacitor was obtained in the same manner as in Example 3, except that the antimony trioxide powder was changed to aluminum hydroxide, aluminum hydroxide oxide, aluminum magnesium hydroxide or magnesium hydroxide powder.

The above examples and those in which the powder of the flame retardant was not added to the current collector layer were set as Comparative Example 1, and the capacity, leakage current and flame retardancy were measured (n = 20), and the results shown in Table 1 were obtained. . The method for measuring the leakage current was 10 V and the value when applied for 1 minute. The evaluation method of flame retardancy uses an electrical short circuit, and performs an overvoltage test to induce combustion by increasing current by 0.5 A every 15 minutes. The surface temperature was measured and the average value was recorded.
From the above results, it can be seen that neither the capacity nor the leakage current is affected by the addition of the flame retardant powder, and the addition of the flame retardant powder suppresses the rise in the capacitor surface temperature due to the overvoltage test of the example. It could be confirmed.

It is a cross-sectional view of the chip-type solid electrolytic capacitor according to the present invention. The part of the cross-sectional view of a capacitor | condenser element of the chip-type solid electrolytic capacitor which concerns on this invention is shown.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Lead for anode 2 ... Capacitor element 3 ... Solid electrolyte layer 4 ... Current collector layer 5 ... Cathode terminal board 6 ... Anode terminal board 7 ... Exterior 8 ... Carbon paste layer 9 ... Flame retardant powder 10 ... Silver paste layer 11 ... sintered body.

Claims (2)

  In a solid electrolytic capacitor in which an oxide film is formed on a sintered body made of a valve metal and a solid electrolyte layer and a current collector layer are sequentially laminated on this oxide film, a flame retardant powder is added to the current collector layer. Solid electrolytic capacitor.   In a solid electrolytic capacitor in which an oxide film is formed on a sintered body made of a valve action metal, and a solid electrolyte layer and a cathode paste layer composed of a carbon paste layer and a silver paste layer are sequentially laminated on the oxide film, A solid electrolytic capacitor in which a flame retardant powder is added to at least one of a paste layer and a silver paste layer.

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