JPH05234828A - Manufacture of solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To enhance the breakdown strength of the title capacitor, to reduce an irregularity in the leakage current of the title capacitor and to enhance the reliability of the title capacitor by a method wherein an anode lead wire is heated and melted without exerting a pressure and, after that, it is solidified and it is connected to a metal frame. CONSTITUTION:An anode lead wire 2 for a capacitor element 1 is arranged in a recessed part 4 formed in a metal frame 3. After it has been arranged, the tip of the anode lead wire 2 is irradiated with a YAG laser at 20 W for one second, and the anode lead wire is melted. When the anode lead wire 2 is melted, it is made spherical due to surface tension. Consequently, the anode lead wire 2 comes into contact with the metal frame 2; it is solidified in this state; it is connected to the metal frame 3. A cathode layer for the capacitor element 2 is connected to the metal frame by using a conductive adhesive. After it has been connected, a transfer molding operation is executed by using an epoxy resin, and an outer package is formed. After the outer package has been formed, an aging operation is performed, terminals are formed, and a chip-shaped capacitor is formed. Since no pressure is exerted on the anode lead wire in this manner, the breakdown strength of the title capacitor can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid electrolytic capacitor.

[0002]

2. Description of the Related Art A capacitor such as a tantalum solid electrolytic capacitor is manufactured, for example, as follows. That is, first, a sintered body made of fine tantalum powder, in which an anode lead wire of tantalum or the like is drawn out, is formed. Next, this sintered body is anodized to form an oxide film, and then a manganese dioxide layer and a cathode layer are sequentially formed to form a capacitor element. Then, the anode lead wire is resistance-welded to the metal frame, and the cathode layer is connected to the metal frame by a conductive adhesive. After the capacitor element is connected to the metal frame, transfer molding is performed to form an exterior.

[0003]

However, in order to connect the anode lead wire to the metal frame by resistance welding, pressure must be applied to the contact point between the anode lead wire and the metal frame. Therefore, this pressure applies stress to the portion of the anode lead wire in the sintered body. The stress causes the oxide film to deteriorate or break. As a result, there is a drawback that the withstand voltage of the capacitor element is lowered, and the variation of the leakage current is increased, so that the reliability is lowered.

An object of the present invention is to provide a method for manufacturing a solid electrolytic capacitor which has improved reliability, improved breakdown voltage, reduced leakage current variation, and high reliability.

[0005]

In order to achieve the above object, the present invention provides a method for manufacturing a solid electrolytic capacitor, in which a capacitor element from which an anode lead wire is drawn is connected to a metal frame to form an outer package, and an anode is provided. It is intended to provide a method for producing a solid electrolytic capacitor, characterized in that a lead wire is heated and melted without applying pressure and then solidified and connected to a metal frame.

To heat and melt the anode lead wire without applying pressure, a laser or arc discharge method is used.

[0007]

[Function] The anode lead wire of the capacitor element is heated and melted without applying pressure using a laser or the like and solidified to be connected to the metal frame, so that no stress is applied to the anode lead wire at the time of connection, and an oxide film is formed. Will not be deteriorated or damaged at all.

[0008]

EXAMPLES The present invention will be described below based on examples. Example 1: First, an anode lead wire made of tantalum wire is pulled out to form a sintered body made of fine tantalum powder. Next, this sintered body is anodized to form an oxide film. After forming the oxide film, it is impregnated with a manganese nitrate solution and thermally decomposed to form a manganese dioxide layer. afterwards,
Colloidal carbon is adhered to form a carbon layer and the cathode is pulled out, and silver paste is applied to the surface to form a cathode layer. After forming the cathode layer, as shown in FIG. 1A, the anode lead wire 2 of the capacitor element 1 is arranged in the recess 4 formed in the metal frame 3. After the arrangement, the tip of the anode lead wire 2 is irradiated with a YAG laser at 20 W for 1 second to melt it. When the anode lead wire 2 is melted, it becomes spherical due to surface tension. Therefore, as shown in FIG. 1B, the anode lead wire 2 contacts the metal frame 3, is solidified in that state, and is connected to the metal frame 3.
The cathode layer of the capacitor element 1 is connected to the metal frame with a conductive adhesive. After connection, transfer molding is performed with an epoxy resin to form an exterior. After forming the outer package, it is aged to form terminals to form a chip-type capacitor.

Example 2 In Example 1, connection was made under the same conditions except that the anode lead wire was connected to a metal frame as follows. That is, as shown in FIG. 2A, the bent portion 6 is formed on the metal frame 5. Then, the anode lead wire 9 of the capacitor element 8 is formed in the concave portion 7 provided in the bent portion 6.
To place. Next, a YAG laser is irradiated under the same conditions as in Example 1, and the anode lead wire 9 is connected to the metal frame 5 as shown in FIG.

Conventional Example: Manufacturing is performed under the same conditions as in Example 1, except that the anode lead wire is connected to the metal frame by the resistance welding method as follows. That is, FIG.
The anode lead wire 11 is placed on the flat surface of the metal frame 12, as shown in FIG. Then, resistance welding is performed by applying a pressure of 3 kg / 8 mm ² , and the anode lead wire 11 is connected as shown in FIG.

Next, in order to compare the breakdown voltage defects, a rating of 1
A voltage of 20 V was applied to the tantalum solid electrolytic capacitors having the structures of Example 1 and Example 2 of 6 V and 2.2 μF and the conventional example. And what short-circuited was made into a defect, and the number was measured. The number of samples is 1000 each. As a result of the measurement, in Example 1 and Example 2, the number was 0.
The conventional example had two defects.

The leakage current of the tantalum solid electrolytic capacitor having the same rating as above was measured and shown in FIG.
As a result, Example 1 and Example 2 showed almost the same variation. However, in the conventional example, the maximum value is increased by one digit,
The variation was very large.

[0013]

As described above, according to the manufacturing method of the present invention, the anode lead wire is heated and melted without applying pressure by laser or arc discharge and solidified to be connected to the metal frame. And the leakage current variation can be reduced, and a highly reliable solid electrolytic capacitor can be obtained.

[Brief description of drawings]

FIG. 1 shows perspective views before and after connecting a capacitor element of an embodiment of the present invention to a metal frame.

FIG. 2 shows perspective views before and after connecting a capacitor element of another embodiment of the present invention to a metal frame.

FIG. 3 shows perspective views before and after connecting a conventional capacitor element to a metal frame.

FIG. 4 shows a graph of leakage current.

[Explanation of symbols]

1, 8 ... Capacitor element, 2, 9 ... Anode lead wire,
3, 5 ... Metal frame.

Claims (1)

[Claims] 1. A method for manufacturing a solid electrolytic capacitor in which a capacitor element from which an anode lead wire is drawn out is connected to a metal frame to form an exterior, the anode lead wire is heated and melted without applying pressure, and then solidified to be a metal. A method for manufacturing a solid electrolytic capacitor, which comprises connecting to a frame.