JPS6142848B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a solid electrolytic capacitor. Electrolytic capacitors, which are generally manufactured using elements formed by sintering metal powders having a valve action such as tantalum, aluminum, or niobium, are widely used as small-sized, large-capacity capacitors. In addition, in order to further increase the size and capacity of electrolytic capacitors, attempts have been made to manufacture electrolytic capacitors by spraying valve metal powder of the same material as the base material onto a base material such as a foil, plate, or wire made of valve metal. There is. However, the adhesion strength of the metal layer deposited by the above-mentioned thermal spraying to the base material is weak, and since thermal spraying is performed in a high-temperature atmosphere, oxygen and impurities in the electrode metal (copper, etc.) may react with the sprayed metal. A deposited metal layer is formed on the base material in a mixed state. Furthermore, distortion may occur inside this deposited metal layer. For this reason, there are drawbacks such as an adverse effect on the anodic oxidation for forming the dielectric layer performed in the next step, making it impossible to obtain good characteristics. In order to eliminate these drawbacks, the following methods have conventionally been applied: (a) The base material is previously subjected to surface-enlarging treatment in order to strengthen the adhesion strength between the deposited metal layer and the base material. (b) Acid or alkali cleaning is performed to remove a large amount of impurities that have reacted with the deposited metal layer. (c) An annealing treatment is performed to remove internal strain between the deposited metal layer and the base material. etc. were taken. However, these conventional methods are not sufficient to eliminate the defects and require too many extra man-hours for post-processing, making them unsuitable for mass production. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor that eliminates the drawbacks of these conventional methods and has particularly improved anodization characteristics. That is, according to the present invention, there is obtained a method for manufacturing a solid electrolytic capacitor, which is characterized in that a capacitor element is obtained by thermally spraying a valve metal powder onto a valve metal base material and then performing high-temperature vacuum sintering. In particular, the method for producing a solid electrolytic capacitor according to the present invention involves spraying valve metal powder of the same material as the base material onto the surface of a base material such as a foil, plate, or wire made of a valve metal such as tantalum aluminum or nib, and then spraying the valve metal powder of the same material as the base material. The method is also characterized in that it includes a step of sintering the metal sprayed base material in a high-temperature vacuum to form an anodized film on the surface of the deposited metal layer. Next, the present invention will be explained in detail. First, an anode lead wire made of the same material as the base material is connected to a base material such as a foil, plate, or wire made of a valve metal such as tantalum, aluminum, or niobium by a method such as welding or caulking. Next, this base material is degreased and cleaned using a cleaning liquid such as alcohol or trichlorethylene, and then a valve metal powder made of the same material as the base material is thermally sprayed onto the surface of the base material. Thermal spraying is performed by plasma spraying, acetylene spraying, propane spraying, etc., so the valve metal powder is molten or semi-molten and impinges on the surface of the base material to instantly solidify and adhere to the base material, reducing the porosity. Forms a high metal layer. Next, the base material obtained by thermal spraying is sintered in a vacuum heat treatment furnace, and this thermal spraying causes distortion of the adhered metal layer, poor bonding of powder particles, and poor adhesion between the metal layer and the base material. and remove defects such as increased impurities. Vacuum degree if the valve metal is tantalum
1500℃~ in a 10 ^-6 Torr high vacuum heat treatment furnace
Sintering is performed at a sintering temperature of 1800°C for a sintering time of about 30 minutes. It is preferable to carry out sintering under conditions that match the sintering characteristics of the valve metal sprayed in this manner. Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. First, as shown in FIG. 1, tantalum anode lead wires 2 with a diameter of 0.17 mmφ and a length of 8 mm are connected to a tantalum substrate 1 with a width of 3 mm, a length of 90 mm, and a thickness of 0.2 mm at a pitch of 3 mm by resistance welding. Next, this substrate 1 is degreased and cleaned using a trichlorethylene cleaning solution, and then tantalum powder is sprayed onto both sides of the substrate 1 by plasma spraying, as shown in FIG. The thermal spraying conditions at this time were that the internal temperature of the thermal spray gun was approximately 20,000℃;
The temperature near the tip of the thermal spray nozzle is 5000°C to 10000°C, the distance between the thermal spraying nozzle and the substrate 1 is approximately 10 cm, and the amount of tantalum powder supplied is approximately 30 g/min.
If the thermal spraying time is about 1 second, a deposited metal layer 3 with a thickness of about 200 μm is formed on the surface of the substrate 1. Next, the substrate 1 on which the deposited metal layer 3 has been formed is sintered in a vacuum heat treatment furnace at a vacuum level of 10 ^-6 Torr and a sintering temperature of 1500° C. for 30 minutes. Thereafter, as shown in FIG. 3, the substrate 1 is cut into required dimensions to obtain the capacitor element 4. Next, according to the well-known manufacturing method of solid electrolytic capacitors, the chemical voltage is 70V.
A dielectric layer was formed on the surface by anodic oxidation, and a cathode layer was sequentially formed by baking a semiconductor layer, baking graphite, and baking silver paste. Table 1 shows the electrical characteristics of the solid electrolytic capacitor manufactured by the method of the present invention compared with the solid electrolytic capacitor manufactured by the conventional method.

[Table] In this embodiment, a tantalum plate as shown in FIG. 1 is used, but the outer shape may be a foil as shown in FIG. 4a or a line as shown in FIG. 4b. As described above, the present invention has the effect of providing a solid electrolytic capacitor with low leakage current value and high withstand voltage performance. Furthermore, small-sized, large-capacity capacitors can be mass-produced more easily than conventional methods.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a substrate according to an embodiment of the present invention, FIG. 2 is a side sectional view of the substrate after metal powder spraying according to the present invention, FIG. 3 is a perspective view of a capacitor element according to the present invention, and FIG. Figures a and b are perspective views of other embodiment substrates according to the present invention. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Anode lead wire, 3...Deposited metal layer, 4...Capacitor element.

Claims (1)

[Claims] 1. The step of thermally spraying a valve metal powder of the same material as the base material onto the surface of a base material made of a valve metal, and then sintering the metal sprayed base material in a vacuum heat treatment furnace. A method for manufacturing an electrolytic capacitor, comprising the step of removing defects such as poor adhesion between a base material and sprayed metal and increased impurities, and then forming an anodized film on the surface of the sprayed metal.