JPH0774054A - Solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To improve characteristics of a solid electrolytic capacitor, manufacture it easily, reduce manufacturing cost, and prevent connection failure for a printed circuit board etc. CONSTITUTION:In a method for manufacturing a solid electrolytic capacitor which is covered with an armor by successively forming a dielectric covering 3, an anode oxide covering 4, and cathode layers 5 and 6 at an anode body 1 where a lead wire 2 for anode is led out and which consists of a metal for valve operation, an armor 8 which is provided by exposing the lead wire 2 for anode and the cathode layer 6 and electrodes 9 and 10 which are laminated at each exposed part of the lead wire 2 for anode and the above cathode layer 6 and mainly consist of copper particles where silver is applied to the surface are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip-shaped solid electrolytic capacitor.

[0002]

2. Description of the Related Art Small electronic components tend to be made into chips in order to miniaturize electronic devices and improve the density of mounting electronic components on a wiring board.

The solid electrolytic capacitor is being made into a chip as a kind of electronic component, and at the same time, it is necessary to further reduce the size and increase the capacity that can be stored in the same volume.

To meet this requirement, for example, a conventional solid electrolytic capacitor has a structure as shown in FIG. That is, reference numeral 21 denotes an anode body formed by sintering fine powder of valve action metal such as tantalum, and leads out an anode lead wire 22 made of tantalum or the like. Then, a dielectric film 23, a solid electrolyte layer 24 such as manganese dioxide, and a first cathode layer 25 made of corodile carbon and silver paste are sequentially formed on the anode body 21. A resin layer 26 for preventing the solid electrolyte from climbing up is provided at the root of the anode lead wire 22. Further, a second cathode layer 27 made of silver paste is provided on the surface of the first cathode layer 25, which is the surface opposite to the lead-out surface of the anode lead wire 22. Then, a part of the anode lead wire 22 and the second cathode layer 27 is exposed, and an exterior 28 made of resin is provided. On the exposed portions of the anode lead wire 22 and the second cathode layer 27, silver paste and first electrode layers 29 and 30 in which iron or copper is mixed with this silver paste are provided. Further, the second electrode layers 31 and 32 to which the solderable metal such as nickel or copper is attached by the electroless plating treatment are attached to the surfaces of the first electrode layers 29 and 30.
Is provided. Solder layers 33 and 34 are provided on the surfaces of the second electrode layers 31 and 32, respectively.

[0005]

However, when performing electroless plating, acid or alkali cleaning and degreasing are required as pretreatment. The processing liquid used at this time is the first electrode layer 29, the second cathode layer 27, and the first cathode layer 2.
5 permeates or remains in 5 to deteriorate the first cathode layer 25 and the like. Further, this liquid passes through the gap around the anode lead wire 22 and deteriorates the solid electrolyte layer 24 and the dielectric film 23. Therefore, the conventional capacitor has a drawback that characteristics such as leakage current (hereinafter abbreviated as LC) and tan δ are deteriorated.
Further, the electroless plating treatment has problems such as a working environment and wastewater treatment, which makes it difficult to manufacture and has a drawback of increasing manufacturing cost.

Therefore, in the conventional example of FIG. 2, the second electrode layer 31 and the like formed by electroless plating are omitted,
It is also possible to directly provide the solder layer 33 or the like on the first electrode layer 29 or the like. However, in this configuration, when the first electrode layer 29 and the like are made of silver paste, silver melts into the molten solder. The first electrode layer 29 and the like cover the end portion of the exterior 28 made of resin. Therefore, when the silver melts in the solder, the portion of the outer package 28 is covered with the silver melted solder. By the way, the solder has a property that it is difficult to adhere to the resin. Therefore, the first electrode layer 2
9 is peeled off at the exterior 28. As a result, even if the capacitor 35 is soldered to a printed circuit board or the like, it is easily peeled off when vibration is applied. Also, the first
When the electrode layer 29 or the like is made of a material in which iron or copper is mixed in silver paste, the copper or the like is easily oxidized, so that the solder leak property is deteriorated and it is difficult to solder the capacitor 35 to a printed circuit board or the like. There is a drawback.

An object of the present invention is to provide a solid electrolytic capacitor which is capable of improving the above-mentioned drawbacks, improving characteristics, being easily manufactured, reducing the manufacturing cost, and preventing defective connection to a printed circuit board or the like. is there.

[0008]

In order to achieve the above object, the present invention provides an anode body made of a valve metal with a dielectric coating, a solid electrolyte layer and a cathode layer, from which an anode lead wire is drawn out. In the solid electrolytic capacitor which is formed and covers the exterior, the exterior provided with the lead wire for the anode and the cathode layer provided, and the exposed lead wire for the anode and the cathode layer are laminated on the surface, and silver is provided on the surface. The present invention provides a solid electrolytic capacitor having an electrode mainly composed of coated copper particles.

The package is formed by immersing the anode body after forming the cathode layer in powder resin or liquid resin, or by transfer molding the powder resin.

The electrode is formed by applying a paste-like substance obtained by adding a binder such as an epoxy type, a cellulosic type, or a polyamide type to silver particles whose surface is coated with silver, and applying the paste.

Note that solder may be applied to the surfaces of the electrodes.

[0012]

According to the present invention, since the electrode is formed of a substance whose main component is copper particles whose surface is coated with silver, and the electroless plating treatment is not performed, the treatment liquid can form a cathode or a dielectric film. It does not deteriorate, so that it is possible to prevent the deterioration of the characteristics, and to improve the manufacturing defects.

Further, the copper particles are hard to melt into the solder and have good leakability with the solder. However, copper has higher conductivity than silver and is more likely to be oxidized, and in this state, the leaking property with respect to solder is reduced. In the present invention, since the copper particles are coated with silver, oxidation can be prevented, and the leakability with solder will not be reduced. Further, when a solder layer is provided on the electrode or soldered to a printed circuit board or the like, the copper particles remain even if the silver coated with the copper particles melts in the solder. Therefore, it is possible to prevent defective soldering on a printed circuit board or the like.

[0014]

EXAMPLES The present invention will be described below based on examples.
Reference numeral 1 is an anode body obtained by sintering fine powder of tantalum. Reference numeral 2 denotes a tantalum anode lead wire having one end inside the anode body 1 and the other end drawn out. Reference numeral 3 is a dielectric film formed on the surface of the anode body 1. Reference numeral 4 is a solid electrolyte layer made of manganese dioxide formed on the surface of the dielectric film 3. Reference numeral 5 is a first cathode layer formed on the surface of the solid electrolyte layer 4 and made of colloidal carbon and silver paste.
Reference numeral 6 denotes a second cathode layer made of silver paste, which is formed on the surface of the first cathode layer 5 on the side opposite to the lead-out surface of the anode lead wire 2. The cathode layer is formed by the first cathode layer 5 and the second cathode layer 6. Reference numeral 7 is an insulating washer made of Teflon attached to the root of the anode lead wire 2. 8 is
The exterior is made of resin and covers the entire anode body 1 except for the tip portion of the anode lead wire 2 and the central portion of the second cathode layer 6. Reference numerals 9 and 10 are electrodes made of a paste obtained by adding a binder such as an epoxy type to copper particles coated with silver on the surface. The electrode 9 is in contact with the exposed portion of the center of the second cathode layer 6 and is laminated up to the outer casing 8 in the vicinity thereof.
The electrode 10 is in contact with the exposed portion of the tip of the anode lead wire 2 and is laminated up to the exterior 8 in the vicinity. 11 and 12
Are solder layers laminated on the electrodes 9 and 10, respectively.

Next, the manufacturing method of the above embodiment will be described. First, fine powder of tantalum is formed into a cylindrical shape and sintered to form the anode body 1. In addition, the lead wire 2 for the anode
Is to be inserted at one end when molding tantalum. Next, insulate the washer 7 at the root of the anode lead wire 2.
Put on. After that, a dielectric film 3 and the like are formed on the surfaces of the anode body 1 and the anode lead wire 2 by an electrolytic oxidation method. After forming the dielectric film 3, the solid electrolyte layer 4 is formed on the surface of the dielectric film 3 provided on the anode body 1 by a thermal decomposition method. After forming the solid electrolyte layer 4, the anode body 1 is sequentially dipped in colloidal carbon and silver paste to form the first cathode layer 5. After forming the first cathode layer 5, the anode body 1 is immersed in silver paste to form the second cathode layer 6. After forming the second cathode layer 6, the outer casing 8 is formed by a dipping method or a transfer molding method. At this time, the tip portion of the lead wire 2 for the anode and the central portion of the second cathode layer 6 may be exposed to form the outer package 8, or after the resin is applied by immersion or the like. Alternatively, the resin on the surface of the exposed portion may be removed by polishing or the like. Then, the dielectric film on the surface of the anode lead wire 2 is removed by polishing. After forming the outer casing 8, the electrodes 9 and 10 are formed by immersing the outer casing 8 in a paste obtained by adding a binder such as an epoxy to copper particles coated with silver. Electrodes 9 and 1
After forming 0, it is dipped in solder and solder layers 11 and 12 are formed.
To form.

Further, with respect to the tantalum chip type solid electrolytic capacitors having the structures of the above-mentioned embodiment and the conventional example of FIG. 2, the initial characteristics of three types of ratings are measured and shown in Table 1. In the conventional example of FIG. 2, the first electrode layers 29 and 30 are made of silver paste. And the number of samples is 3 each
The number is 0. The margin below.

[0017]

[Table 1]

As is clear from Table 1, when the same ratings are compared, the LCs of Examples 1 to 3 are 15% to about 17% lower than those of Conventional Examples 1 to 3, and tan δ
Of 80% to about 86.7%.

[0019]

As described above, according to the present invention, since the electrode is formed by the substance whose main component is the copper particles coated with silver on the surface and the electroless plating layer is not provided, the characteristics such as LC and tan δ are improved. It is possible to obtain a solid electrolytic capacitor which can be improved in manufacturing cost, can be easily manufactured, can be manufactured at low cost, and can prevent connection failure to a printed circuit board or the like.

[Brief description of drawings]

FIG. 1 shows a cross-sectional view of an embodiment of the present invention.

FIG. 2 shows a cross-sectional view of a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Anode body, 2 ... Anode lead wire, 3 ... Dielectric film, 4 ... Solid electrolyte layer, 5 ... 1st cathode layer, 6 ... 2nd cathode layer, 8 ... Exterior, 9 and 10 ... Electrode.

Claims (1)

[Claims] 1. A solid electrolytic capacitor in which a dielectric film, a solid electrolyte layer and a cathode layer are formed on an anode body made of a valve metal, from which a lead wire for an anode is drawn, and an exterior is covered, and a lead wire for an anode is used. A cathode layer and an exterior provided to expose, laminated on each exposed portion of the lead wire for the anode and the cathode layer, characterized in that it has an electrode mainly composed of copper particles coated with silver on the surface, Solid electrolytic capacitor.