JPH0992577A - Manufacture of chip-type solid-state electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a chip-type solid-state electrolytic capacitor which is prevented from deteriorating in reliability due to a welding failure in a capacitor element and enhanced in reliability. SOLUTION: After the tip 5 of a lead wire 1 led out from a capacitor element 3 is welded to an anode outer electrode 4A, the welded part is fused again and solidified so as to improve the anode lead wire 1 and an outer electrode 4 in welding reliability between them in a manufacturing process where a chip- type solid-state electrolytic capacitor is formed.

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 chip type solid electrolytic capacitor.

[0002]

2. Description of the Related Art As shown in FIG. 3, an anode lead wire 1 is embedded in a fine metal powder, and a pellet obtained by compressing the fine metal powder by a press is sintered to oxidize a surface of a porous pellet 2 which is a dielectric substance. A porous pellet 2 that forms a film and that forms an oxide film that is a dielectric is dipped in a manganese nitrate solution, and then heat is applied to the porous pellet 2 to which the manganese nitrate solution adheres to thermally decompose the manganese nitrate solution. The manganese dioxide layer 8 is deposited. Immerse the manganese nitrate solution in the porous pellet 2 →
The process of thermal decomposition of manganese nitrate → precipitation of the manganese dioxide layer is repeated several times.

Next, a carbon paste is applied to the surface of the manganese dioxide layer 8 deposited on the surface of the porous pellet 2 and then dried to form a carbon layer 9. Next, a silver paste is applied to the surface of the carbon layer 9 to form a silver paste layer 10 to form the capacitor element 3. After cutting out the necessary part of the anode lead-out wire 1 led out from the capacitor element 3, an external terminal 4 which is a lead frame made of nickel silver is resistance-welded by resistance welding 7 to the anode lead-out wire of the capacitor element 3 as shown in FIG. 1
It is attached to the tip portion 5 of and is used as the anode external electrode 4A.

Next, the external terminal 4 is attached to the capacitor element 3 by soldering to form a cathode external electrode 4B. Then, the outer casing 11 is formed by a mold resin made of an epoxy resin in a transformer mold, the lead frame other than those used as the external terminals 4 is cut, and then the lead frame which is the external electrode 4 is formed along the outer casing 10 to form a chip. Type solid electrolytic capacitor is manufactured.

[0005]

As shown in FIG. 2, a conventional resistance welding method is used to attach the anode lead wire 1 derived from the anode external electrode 4A and the capacitor element 3 and the tip portion 5 to each other. However, the attachment of the anode lead wire 1 to the tip 5 is
There are welding defects or pseudo welding due to variations in welding position, adhesion of manganese dioxide to the anode lead wire 1, wear of the welding electrode, and the like.

Recently, there is a tendency to downsize the capacitor element 3 due to downsizing of the capacitor, and the dimension 6 of the anode lead wire 1 is also shortened. Has become an obstacle. Poor welding or pseudo-welding between the anode lead wire 1 and the welded portion 7 of the tip portion 5 may cause post-process or open defects of the capacitor, which may lead to increase in process defects and external defects, thus improving product reliability. It was a big obstacle above.

[0007]

In order to solve the above problems, the present invention uses a capacitor element 3 which is caused by variations in welding position, adhesion of manganese dioxide to the anode lead wire 1 and wear of the welding electrode. In order to prevent welding failure and pseudo-welding between the leading end portion 5 of the led out anode lead wire 1 and the anode outer electrode 4A, a welded portion 7 between the leading end portion 5 of the anode lead wire 1 and the anode outer electrode 4A, which are resistance-welded, is formed. Is again melted and condensed by a laser or the like to improve the reliability of the welded portion 7.

Also, in terms of downsizing of the capacitor, the reliability of the welded portion 7 between the tip 5 of the anode lead wire 1 and the anode external electrode 4A is improved, so that the dimension 6 of the anode lead wire 1 is 1.0 mm in the conventional case.
What has been described above can be shortened to 0.15-0.3 mm, and the capacitor can be made smaller.

[0009]

The present invention improves the reliability of the anode lead-out wire 1 led out from the capacitor element 3 and the anode external electrode 4A which is the external electrode 4, and thus causes the reliability of welding of the conventional welded portion 7 to be impaired. The present invention eliminates welding defects and pseudo welding due to variations in welding position, adhesion of manganese dioxide to the anode lead wire, wear of the welding electrode, and the like.

As means for this, after the resistance welding between the anode external electrode 4A and the tip portion 5 of the anode lead wire 1, the welded portion 7 is melted and condensed again to improve the reliability of the welded portion 7.
The size 6 of the anode lead wire 1 is set to 0.
It was possible to make it as short as 15 to 0.3 mm, and the capacitor could be made smaller.

[0011]

Embodiments of the present invention will be described by taking a chip type tantalum solid electrolytic capacitor as an example. A tantalum metal fine powder having an average particle diameter of 3 μm and a secondary particle diameter of about 100 μm is put into a press machine with a tantalum wire having a diameter of 0.25 mm protruding, and the tantalum metal fine powder is compressed by the press machine to obtain 0.75 × 1.02. ×
1. Make 10mm tantalum pellets. Next, the tantalum pellets are sintered in a vacuum at a temperature of about 2000 ° C. to produce porous tantalum pellets 2 as shown in FIGS.

After the porous tantalum pellets 2 are immersed in a phosphoric acid solution, a voltage is applied between the anode lead wire 1 and the phosphoric acid solution to carry out chemical formation to form a tantalum oxide film as a dielectric. Next, when the formation of the tantalum oxide film is completed, the porous tantalum pellets 2 are immersed in a manganese nitrate solution, and then the porous tantalum pellets 2 are taken out from the manganese nitrate solution and subjected to heat decomposition to be repeated 3 to 5 times. A manganese dioxide layer 8 is formed on the surface of the tantalum pellet 2.

Next, the porous tantalum pellet 2 having the manganese dioxide layer 8 formed thereon is dipped in a carbon paste and then dried by heating to form a carbon layer 9. Next, a silver paste is applied to the surface of the carbon layer 9 and dried by heating to form a silver paste layer 10 to form a capacitor element 3.

Next, the anode lead wire 1 embedded in the capacitor element 3 is cut while leaving a required length. Next, after the anode outer electrode 4A made of a lead frame is resistance-welded to the tip portion 5 of the anode lead wire 1, the welded portion 7 of the tip portion 5 of the anode lead wire 1 and the anode external electrode 4A made of the lead frame is irradiated with a yag razor. After melting and condensing, the cathode external electrode 4
The lead frame B is attached to the silver paste layer 10 with solder.

Next, the outer casing 11 of the capacitor element 3 to which the lead frame which is the external electrode 3 is attached is formed by transfer molding of a molding resin made of epoxy resin.
In order to downsize the capacitor, the size 6 of the anode lead wire 1 may be shortened by 0.13 to 0.5 mm and attached to the anode external electrode 4A.

[0016]

Since the chip type solid electrolytic capacitor of the present invention is manufactured as described above, it has the following unique effects. Regarding welding defects and pseudo-welding of the welded portion 7 of the tip portion 5 of the anode lead-out wire 1 caused by variations in the welding position, adhesion of manganese dioxide to the anode lead-out wire 1 and wear of the welding electrode, 4% was generated, but it was completely eliminated by the present invention.

The dimension 6 of the anode lead wire 1 is 1.0
The volume of the capacitor can be reduced by 10% by being able to shorten from 0.15 mm to 0.15 to 0.3 mm.

[Brief description of drawings]

FIG. 1 shows a perspective view of a product of the present invention.

FIG. 2 shows a perspective view of a conventional product.

FIG. 3 shows a sectional view of a conventional product.

FIG. 4 shows a sectional view of the product of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Anode lead wire, 2 ... Porous pellet, 3 ... Capacitor element, 4 ... External electrode, 4A ... Anode external electrode, 4
B ... Cathode external electrode, 5 ... Tip part, 6 ... Anode lead wire size, 7 ... Welded part, 8 ... Manganese dioxide layer, 9 ... Carbon layer, 10 ... Silver paste layer, 11 ... Exterior

Claims (2)

[Claims] 1. A capacitor element in which an oxide film is formed on a porous pellet obtained by burying an anode lead wire in a fine metal powder and press-pressing the pellet, and forming a cathode such as manganese dioxide on the surface of the porous pellet. In (1), after attaching the tip of the anode lead wire and the external electrode by resistance welding, the tip of the anode lead wire and the external electrode attachment part are melted and condensed again with a laser to attach the anode lead wire and the external electrode. A method of manufacturing a chip type solid electrolytic capacitor characterized by the above. 2. The method for manufacturing a chip-type solid electrolytic capacitor according to claim 1, wherein the distance between the tip of the anode lead wire and the porous chip is 0.15 to 0.3 mm.