JP2748490B2 - Solid electrolytic capacitor and method of manufacturing the same - Google Patents

Description

The present invention relates to a solid electrolytic capacitor and a method for manufacturing the same.

[Conventional technology]

As shown in FIG. 2, a conventional solid electrolytic capacitor has an anode body 11 formed by pressing metal powder having a valve action.
A metal wire 12 having a valve action is implanted in advance as an anode lead and sintered in a vacuum, and the anode body is formed by anodizing.
An oxide film layer is formed on the outer peripheral surface of 11, a semiconductor layer such as manganese dioxide is formed on the outer peripheral surface of the oxide film layer as a counter electrode, and a graphite layer 13 for further reducing contact resistance.
A silver paste layer 14 is applied via the metal layer to form a cathode conductor layer, thereby forming a capacitor element.

[Problems to be solved by the invention]

In the conventional capacitor element described above, the organic binder in the silver paste is decomposed by the heat at the time of forming the solder layer, and silver particles are diffused into the solder bath. There is a disadvantage that the dielectric loss increases. As a solution to this, there has been proposed a method of forming a plating layer of copper, nickel or the like by an electroless plating method after forming a graphite layer without interposing a silver paste which causes a silver erosion phenomenon. However, this electroless plating method can be batch-processed and is more suitable for mass production than the plasma jet method or the sputtering method.However, the hydrogen generated during the plating reaction causes the area around the anode lead not covered with the graphite layer to be covered by the hydrogen. The manganese dioxide and the oxide film are reduced and decomposed, resulting in increased dielectric loss and increased leakage current.

An object of the present invention is to provide a method for forming a silver layer in a humid atmosphere without decomposing an organic binder in a silver paste due to heat at the time of forming a solder layer and diffusing silver particles into a solder bath. It is an object of the present invention to provide a solid electrolytic capacitor which is excellent in quality and easy to manufacture, and which can protect an oxide film and manganese dioxide from a gas at the time of a plating reaction in the manufacture without causing migration, and which is easy to manufacture.

[Means for solving the problem]

The solid electrolytic capacitor of the present invention comprises a dielectric oxide film layer, a semiconductor oxide layer, a first graphite layer, a second graphite layer, and electroless plating on an anode body made of a valve metal having an anode lead implanted thereon. A solid electrolytic capacitor having a cathode layer in which a base metal layer is sequentially formed, comprising: a first resin layer made of a resin containing a substance whose magnetization remains after application of a magnetic field on the anode lead planting surface; and a ferromagnetic particle. And a second resin layer made of a powder resin.

The effect can be exhibited by forming the second graphite layer as a layer composed of graphite powder, silver / palladium alloy powder, inorganic filler and resin. Further, the method for manufacturing a solid electrolytic capacitor of the present invention includes a step of forming an anode body made of a valve metal implanted with an anode lead, and a step of forming a dielectric oxide film layer on the anode body, A step of sequentially forming a semiconductor oxide layer, a first graphite layer, a second graphite layer, and a base metal layer of electroless plating on a body oxide film layer to form a cathode layer, and connecting an external cathode terminal on the cathode layer And a step of connecting an external anode terminal to the anode lead, and a step of molding and covering with an exterior insulating resin. Forming a first resin layer by applying a resin containing magnetic particles on the anode lead planting surface and then heating and curing the resin, and applying a magnetic field to the first resin layer before forming the base metal layer. mark Immersing the anode body in a powdered resin exhibiting ferromagnetism after being magnetized, thereby adhering the powdered resin only on the first resin layer on which magnetic attraction acts, followed by heat curing. Forming a second resin layer by
Forming a base metal layer by electroless plating.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view of one embodiment of a resin-molded solid electrolytic capacitor manufactured by the method for manufacturing a solid electrolytic capacitor of the present invention.

An anode lead 2 made of a tantalum material is erected on a pressure-molded and vacuum-sintered anode body 1 of tantalum powder, which is one of metals having a valve action. After the first resin layer 5a is formed on the anode lead planting surface, an oxide film layer and a manganese dioxide layer (not shown) are formed on the outer peripheral surface of the anode body 1,
A first graphite layer 4 and a second graphite layer 6 containing a silver-palladium alloy powder are sequentially formed on the outside thereof except for the anode lead planting surface. A powdery resin is adhered on the first resin layer 5a and heated to form the second resin layer 5b.
On the other hand, a base metal layer 7 of electroless plating made of nickel or the like is formed on the second graphite layer 6. Anode lead 2
The external anode terminal 3 is welded to the tip of the base member, and the external cathode terminal 9 is connected to the base metal layer 7 made of nickel or the like by a solder layer 8, so that the entire capacitor element is made of an exterior insulating resin layer 10 made of a thermosetting resin. To form a resin mold type solid electrolytic capacitor.

Next, a process of manufacturing the resin-molded tantalum solid electrolytic capacitor having such a configuration will be described in detail.

Pressure molded tantalum powder is vacuum sintered at high temperature,
A solution obtained by diluting a mixture of nickel powder and Teflon with pure water is applied to the anode lead setting surface of the anode body 1 having the tantalum anode lead 2 set thereon by a dispenser.
The first resin layer is formed by being cured in an atmosphere at a temperature of ° C. Anode body 1 is anodized in a phosphoric acid aqueous solution at a formation voltage of 100 V to form a tantalum oxide film on the entire outer peripheral surface. To form a manganese dioxide layer.
This dipping and pyrolysis is performed several times to obtain a uniform manganese dioxide layer. Next, the anode body 1 on which the manganese dioxide layer has been formed is immersed in a graphite solution in which graphite powder is suspended in an aqueous solution of a water-soluble polymer material.
The first graphite layer 4 is formed by drying in an atmosphere of 00 ° C.

Next, epoxy resin 20-40%, graphite powder 20-30
%, Inorganic filler 5-10%, silver-palladium powder 1-10
% Is mixed in a weight ratio and immersed in a mixture diluted with butyl cellosolve, and thermally cured in an atmosphere at 150 to 200 ° C. to form a second graphite layer 6. The silver-palladium alloy powder in the second graphite layer serves as a plating catalyst, and the inorganic filler has an effect of forming irregularities on the surface and increasing the adhesion of the plating film by an anchor effect. The silver-palladium alloy used had a weight ratio of silver to palladium of 8: 2.

Next, a magnetic field of about 3KOe is applied to the anode body 1 to saturate the nickel powder in the first resin layer and then remove the magnetic field.
At this time, the first resin is in a magnetized state even after the removal of the magnetic field due to the residual magnetization of the nickel powder contained therein. When the anode body 1 is immersed in a tank in which a powdery epoxy resin containing nickel powder flows, the powdery epoxy resin adheres to the first resin layer 5a by magnetic attraction. Then, the resin is cured in an atmosphere at 150 to 200 ° C. to form the second resin layer 5b.

Next, after cleaning with pure water, electroless plating is performed. Since the anode body 1 is covered with the second graphite layer 6 and the second resin layer 5b, the manganese dioxide layer and the oxide film are protected from gas during the reaction. As the plating solution, for example, an electroless nickel plating solution using dimethylaminoborane as a reducing agent (pH = 6.7 at room temperature) is used, plating is performed at 65 ° C. for 60 minutes, and a nickel plating layer 7 of about 4 to 5 μm is formed. Is done. After the plating is completed, the whole is sufficiently washed with water, and moisture is evaporated in an atmosphere at 120 to 150 ° C.

Further, the external anode terminal 3 made of a solderable material is welded to the anode lead 2 and the external cathode terminal 9 is placed on the nickel plating layer 7 via a solder paste. The solder paste is formed as the solder layer 8 by performing infrared reflow, and the nickel plating layer 7 and the external cathode terminal 9 are electrically connected.

Finally, the capacitor element is molded with an exterior insulating resin layer 10 made of a thermosetting resin, and the external anode terminal 3 is formed.
And the external cathode terminal 9 is bent to form a resin-molded solid electrolytic capacitor.

In this embodiment, nickel powder is contained in the first resin layer and the second resin layer. However, since this material may be ferromagnetic particles, three kinds of metals, iron, chromium, and nickel, may be used. And a binary or ternary alloy thereof, or a multi-element alloy powder with another metal.

In addition, powdered epoxy resin was used as a material for the second resin layer, but since this material is used to protect the oxide film and the manganese dioxide layer from hydrogen generated during the plating reaction, Resins such as acryl, polyester, polyvinyl chloride, polypropylene and the like and mixed resins thereof may be used.

〔The invention's effect〕

As described above, the present invention has the following effects by using no silver paste for the cathode layer and forming the first and second resin layers on the anode lead planting surface.

(1) Since no expensive silver paste is used at all, product cost can be greatly reduced, and there is no migration of silver in a humid atmosphere, so that the quality of the solid electrolytic capacitor is improved.

(2) Since the first and second resin layers are formed on the anode lead planting surface, the oxide film and manganese dioxide are protected from gas during the plating reaction, so that the quality of the solid electrolytic capacitor is improved.

(3) Batch processing of the formation of the second resin layer becomes possible, and man-hours can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a resin-molded tantalum solid electrolytic capacitor manufactured by a manufacturing method of one embodiment to explain one embodiment of the present invention, and FIG. 2 is an example of a conventional tantalum solid electrolytic capacitor. It is a longitudinal cross-sectional view. DESCRIPTION OF SYMBOLS 1 ... Anode body, 2 ... Anode lead, 3 ... External anode terminal, 4 ... First graphite layer, 5a ... First resin layer, 5b ... Second resin layer, 6 ... 2, graphite layer 7, base metal layer 8, solder layer 9, external cathode terminal 10, exterior insulating resin layer 11, anode body 12, anode lead 13, graphite layer 13, 14 ... Silver paste layer.

Claims (2)

(57) [Claims] 1. A dielectric oxide film layer and a semiconductor oxide layer on an anode body made of a valve metal having an anode lead implanted thereon.
A solid electrolytic capacitor having a cathode layer in which a graphite layer, a second graphite layer, and a base metal layer of electroless plating are sequentially formed, comprising a resin containing a substance whose magnetization remains after the application of a magnetic field on the anode lead planting surface. A solid electrolytic capacitor comprising: a first resin layer; and a second resin layer formed of a powder resin containing ferromagnetic particles on the first resin layer. A step of forming an anode body made of a valve metal having an anode lead implanted thereon, forming a dielectric oxide film layer on the anode body, and forming a semiconductor oxide film on the dielectric oxide film layer. Layer, a first graphite layer, a second graphite layer,
A step of sequentially forming a base metal layer of electroless plating to form a cathode layer, a step of connecting an external cathode terminal on the cathode layer, a step of connecting an external anode terminal to the anode lead, and a mold packaging with an outer insulating resin. Applying a resin containing magnetic particles on the anode lead planting surface on the anode body before forming the dielectric oxide film layer, followed by heating and curing. Forming a first resin layer by applying a magnetic field to the first resin layer before forming the base metal layer, magnetizing the first resin layer, and then immersing the anode body in a powdery resin exhibiting ferromagnetism. The powdery resin is adhered only to the first resin layer on which magnetic attraction acts by heating, and then is cured by heating.
Forming a resin layer and forming a base metal layer by electroless plating.