JPH0213808B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a solid electrolytic capacitor that is inexpensive and has excellent characteristics. Currently, the cathode conductive layer of solid electrolytic capacitors has
Ag conductive paint has excellent electrical conductivity and solderability.
It is commonly used because it is easy to make into paint. However, recently the price of precious metals such as Ag and Au has increased significantly, and at 1 o'clock, the price had soared to 230,000 yen/Kg.
Solid electrolytic capacitors are also being forced to raise product prices. On the other hand, although Ag conductive paint has excellent solderability, it causes a "silver crack" phenomenon when soldering at high temperatures and for long periods of time, resulting in an increase in tanδ of the capacitor and poor soldering heat resistance. There was a drawback that it was stored away. Therefore, recently there has been a demand for a conductive material to replace the Ag conductive paint. The present invention has been made in view of the current situation, and the content of the present invention will be explained below. As an alternative to the conventional Ag conductive paint, there is a Cu conductive paint, but this Cu conductive paint cannot be soldered and cannot be used in applications that require soldering. In addition to this Cu conductive paint, Ni powder, which has relatively good electrical conductivity,
Conductive paint was made using Sn powder, Zn powder, etc.
I couldn't solder any of them. Therefore, since soldering is possible with Ag conductive paint, we thought that by mixing some Ag powder with the metal powder, we could impart solderability. Based on this idea, we added Ag powder to Ni powder. As a result of adding and mixing to form a conductive paint, the desired results of the present invention were obtained. The figure shows the main parts of a solid electrolytic capacitor according to an embodiment of the present invention. In the figure, 1 is an anode body equipped with an anode lead wire 1a such as a tantalum wire, and this anode body 1 is made of sintered tantalum powder. It is constructed by forming a dielectric oxide film 1b on the surface of the body. 2 is a manganese dioxide layer as a semiconductor layer formed on this anode body 1, 3 is a carbon layer formed on this manganese dioxide layer 2, 4 is a cathode conductive layer formed on this carbon layer 3,
This cathode conductive layer 4 is made of conductive fine powder other than Ag.
It is composed of conductive paint containing conductive powder made of Ag fine powder. 5 is a solder layer formed on this cathode conductive layer 4. Next, specific examples of the present invention will be described. Based on approximately 99.9% pure Ni powder with a particle size of 4 to 7μ, this has a spherical or flattened particle shape and a particle size of 0.1 to 1μ, 1 to 5μ, 5 to 20μ, 20
~50μ and 50~100μ of 99.5% purity Ag powder were mixed, and a conductive paint was obtained using methacrylic resin as a binder and butyl acetate as a solvent. The mixing method is to weigh out a certain amount of the Ni powder, add Ag powder under various conditions to it, stir well in an agate mortar to mix, and then add acetic acid in advance to the well-mixed state. A solution of methacrylic resin dissolved in butyl was added and kneaded. At this time, the amount of binder was 10% by weight based on the total weight of the conductive powder, and an appropriate amount of butyl acetate as a solvent was added to adjust the viscosity. In order to test whether the conductive paint obtained in this way has solderability and electrical resistance as a cathode conductive layer of a capacitor, a capacitor element with a rating of 35 V and 1 μF (as shown in the figure) was prepared in advance. (Structure shown) coated on the carbon layer and heated at 100℃.
After drying for 30 minutes, flux was applied and the solderability was examined by immersing it in a 200°C solder bath. In addition, as a substitute for measuring the electrical resistance of conductive paint, we measured the tan δ of the capacitor at 120 Hz. The results are shown in Table 1.

【table】

[Table] As is clear from Table 1, when it comes to the shape of the Ag powder mixed with the Ni powder, a flat shape is more effective in terms of solderability than a spherical shape. This is considered to be because the surface area of the entire Ag powder is small in the case of a spherical shape. Further, even if the particle is spherical, if the particle size becomes large, solder can be applied partially, but this is not practical. Furthermore, even if the particle is flat, if the particle size is very small, soldering will not be possible, so it is necessary to set the particle size to an appropriate value. Furthermore, tanδ is a conventional Ag conductive paint, such as #4922 (trade name) from DuPont, USA.
Although it was slightly larger than the one using , it is not a problem for general products. Next, flat Ag powder with a particle size of 5 to 20 μm was prepared.
Solderability when changing the amount of Ni powder mixed
I investigated tanδ. The samples used in the test were obtained in the same manner as above. The results are shown in Table 2.

[Table] As is clear from Table 2, solderability and tanδ characteristics improve by increasing the amount of Ag powder mixed, but as the amount of Ag mixed increases, the price increases accordingly. It becomes less effective. Considering the results of these experiments, it is clear that the particle size is 3~
Adding 15 to 50% by weight of 50μ Ag powder is good in terms of price, solderability, and tanδ characteristics. Here, in the present invention, in addition to Ni powder,
Ti, Zr, Ta, Cu, Co, Cr, Sn, Pb, Zn, Be,
Mo, W, TaC, HfC, MoC, TiC, HfN,
A similar effect can be obtained by mixing TiN, ZrN, InN, and SnO ₃ with Ag powder, and a similar effect can be obtained by mixing not only one type but two or more of them with Ag powder. can get. As described above, according to the present invention, it is possible to obtain the product at a lower cost compared to the conventional products, and the problem that occurs due to high temperature soldering or long time soldering.
This makes it possible to eliminate the increase in tanδ.

[Brief explanation of drawings]

The figure is a sectional view showing essential parts of a solid electrolytic capacitor according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Anode body, 1a... Anode lead wire, 1b... Dielectric oxide film, 2... Manganese dioxide layer, 3... Carbon layer, 4... Cathode conductive layer, 5... Solder layer.

Claims (1)

[Claims] 1 A semiconductor layer, a carbon layer,
In solid electrolytic capacitors formed by sequentially laminating cathode conductive layers, Ti, Zr, Ta, Ni, Cu, Co,
Cr, Sn, Pb, Zn, Be, Mo, W, TaC, HfC,
Conductive fine powder of at least one of MoC, TiC, HfN, TiN, ZrN, InN, SnO ₂ and a particle size of 3
The cathode conductive layer is formed with a conductive paint containing conductive powder consisting of ~50μ flat-shaped Ag fine powder, and 15~50 μm of Ag fine powder is added to the conductive fine powder.
A solid electrolytic capacitor characterized by a 50% mixture by weight.