JPS6048091B2 - solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a solid electrolytic capacitor with excellent moisture resistance.

Generally, Ag alone or Ag dispersed in an organic solvent is mainly used for electrodes of electronic components including solid electrolytic capacitors because of its excellent electrical conductivity and excellent solderability. .

However, since such Ag is easily oxidized and reduced and easily becomes ions, it is likely to cause a phenomenon called migration. Therefore, the inventors of the present invention have made the discovery as a result of studies focusing on using a conductive material instead of Ag as an electrode material for a solid electrolytic capacitor.

Table 1 shows a commercially available capacitor using Ag conductive paint #4922 (trade name) manufactured by DuPont in the United States, and A-type, which was prototyped in the laboratory using A$, which is a stable metal that does not cause migration. This figure shows a comparison of the results of a humidity life test on capacitors using electrical paint.

The test capacitor used a Ta sintered body, on which a dielectric oxide film was formed using a general method, and then a manganese dioxide layer created by thermal decomposition of manganese nitrate and a carbon layer were successively laminated on top of this. Formed rated i25V) 4.7μF
This device was divided into two, coated with the two types of conductive paints, dried at 100° C., and then a solder layer was formed thereon. Also, the test is 55
25 V was applied under the conditions of high humidity of 90% RH and 90% RH, and the number of short circuit failures that occurred over time was investigated. Table 1 ) 5 - As can be seen from Table 1, although there are some variations depending on the rod, there is less deterioration when using Au conductive paint, and the general concept of Ag migration phenomenon is different for solid electrolytic capacitors. It turns out not to be.

The present invention has been made in view of these results, and the solid electrolytic capacitor according to the present invention will be described below.
The figure shows a solid electrolytic capacitor according to an embodiment of the present invention, and in the figure, 1 is an anode lead wire 1 made of tantalum.
This anode body 1 is constructed by forming a dielectric oxide film on the surface of a sintered body of tantalum powder. 2 is a manganese dioxide layer as a semiconductor metal oxide formed on this anode body 1, 3 is a carbon layer formed on this manganese dioxide layer 2, and 4 is an Ag-free conductive layer formed on this carbon layer 3. paint layer,
5 is a conductive paint layer containing Ag formed on the conductive paint layer 4, 6 is a solder layer for connecting the cathode lead wire 7 to the conductive paint layer 5, and 8 is the anode lead wire 1a. The L-shaped anode lead wire 9 is connected by welding, and 9 is an exterior resin such as epoxy resin for covering the entire capacitor element by dipping or the like.

Here, the above A
As the conductive paint layer 4 that does not contain g, there is an Au conductive paint, but it is expensive. Therefore, this A
As a substitute for 4-electroconductive paint, we conducted three different studies from the viewpoints of electrical conductivity, stability, possibility of pulverization, price, and possibility of turning it into paint, and found that In. ．． Li. ．． Na etc. are soft and difficult to make into fine powder, A1, Fe etc. are also very easily oxidized, and Si. ．． Bi,. Mn and other metals have poor electrical conductivity and are often unsuitable metals, but Ni. ．． Cul
Sn. ．． Pb,. Zn,. Hf. ．． Ti,. Zr,,T
a. ．． Be,. Cr,. COL4. Mg,. M.O. ．． W
was a substance that relatively satisfied the above conditions. In addition, intermetallic compounds and carbides with similar properties to these intermetallic compounds, such as TaC, . HfClMOC,. TiC, HfN as a nitride. ．． TiNlZrN. ．． IrlN had high electrical conductivity and was a substance that relatively satisfied the above conditions.
In addition, Mn2O5, Mn2p2, SiB3, SiB
6, In2O3, SnO2, V2O3, BeO,. Bi
2O3 can also be used. Moreover, as a single metal, Cu. ．． Ni. ．． Table 2 shows the results of experiments on pulverization and coating of TiN as Bel metal carbide and TaCl metal nitride, as well as the application to solid electrolytic capacitors. In addition, each fine powder has approximately 20
In order to reduce the powder to less than μ and make it into a powder that can be made into paint, it must be shaped into flakes, that is, flattened.
It was flattened by crushing it in an agate mortar. Then, the flat powder was made into a paint using methacrylic resin as a binder and butyl acetate solution as a solvent. The blending ratio of the binder to the conductive paint was 3 to 40% by weight, and a solvent was added as appropriate to adjust the viscosity. Then, after applying such conductive paint to the surface of the carbon layer of a capacitor element with a rating of 25μF and 4.7μF and thoroughly drying it, the characteristics were measured by contacting both ends of the anode and cathode with Au contact pins. I went to

Table 2 also shows #4922 (product name) from DuPont, USA.
The characteristics when using the Ag conductive paint are also shown for comparison. As is clear from this table, A? Although the Tan δ is slightly higher than that of electro-conductive paints, it can be used satisfactorily for practical purposes.

However, the various paints mentioned above cannot be soldered, resulting in poor productivity when connecting the cathode lead wire. In the present invention, in consideration of this point, a solderable Ag conductive paint is applied onto a conductive paint that does not contain Ag. Table 3 shows that an Ag conductive paint layer (#4922 (trade name) manufactured by DuPont, USA) is formed on the various conductive paint layers shown in Table 2 above.
This figure shows the results of a humidity life test when a capacitor like the one shown in the figure was made.

The test was carried out at 55°C and 90% RH for 20
The number of short-circuit failures was investigated by applying 25V for 00 hours. As is clear from Table 3, in the present invention, A? A conductive paint layer that does not contain Ag exists between the conductive paint layer and the carbon layer, and the average distance to the surface of the dielectric oxide film becomes considerably long, and the porous manganese dioxide layer Since the micropores in the carbon layer are filled with a conductive paint that does not contain Ag, the migration of Ag in the short recesses shortens the distance to the surface of the oxide film, and the conductive paint does not contain Ag. Since the paint is a dense layer containing a large amount of binder, it becomes a major hindrance when Ag migration occurs, and the occurrence of short circuit defects can be reduced.

In addition, A? When forming the electrolytic paint, it is necessary to prevent it from protruding, and it is best to form it in as small an area as possible. Here, in the above embodiment, Ni. ．． Cu,. Be. ．． ZnlTaC. ．． Ti
C,. TiN. ．． Although only Zr has been explained, in addition to these, there are CO. ．． C
r,. Zr. , Ta also shows excellent properties, Be and its oxide BeO also show excellent properties, and Hf
N. ．． HfC. ．． In2O3, SnO2, etc. also exhibit excellent properties. Similar excellent results were also obtained with a conductive paint made by pressure-welding and mixing several types of conductive materials. Table 4 shows the results. In addition, what is shown in this Table 4 is approximately 3
Mix 10y of 0μ Zn fine powder, mix well in an agate mortar, add 3y of methacrylic resin as a binder and 10mL of butyl acetate, mix well to make a conductive paint, and use this as a conductive paint for capacitor elements. It was coated on a carbon layer and dried at 100° C. for 3 minutes, and the formation of the Ag conductive paint layer, the drawing out of the leads, and the exterior were performed in the same manner as described above. In addition, a humidity life test was conducted in the same manner as described above, and the number of short-circuit failures was investigated. As described above, according to the present invention, a solid electrolytic capacitor with excellent moisture resistance can be obtained at low cost.

[Brief explanation of drawings]

FIG. 3 is a sectional view showing a solid electrolytic capacitor according to an embodiment of the present invention. 1... Anode body, 1a... Anode lead wire,
2... Manganese dioxide layer, 3... Carbon layer, 4, 5... Conductive paint layer, 6... Solder layer.

Claims (1)

[Claims] 1. A semiconductor metal oxide layer, a carbon layer,
In a solid electrolytic capacitor formed by sequentially laminating cathode conductive layers, the cathode conductive layer includes an Ag-free conductive paint layer in direct contact with the carbon layer, and an Ag-containing conductive paint layer formed on the conductive paint layer. A solid electrolytic capacitor characterized by comprising a paint layer. 2 The conductive paint that does not contain Ag contains Ni, Cu, Sn,
Pb, Zn, Hf, Ti, Zr, Ta, Be, Cr, C
o, Mg, Mo, W, TaC, HfC, MoC, TiC
, HfN, TiN, ZrN, InN, Mn_2O_5,
Mn_2P_2, SiB_3, SiB_6, In_2O
_3, SnO_2, V_2O_3, Bi_2O_3, B
The solid electrolytic capacitor according to claim 1, wherein the solid electrolytic capacitor is a conductive paint containing at least one type of eO.