JPH0141244B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for manufacturing a solid electrolytic capacitor, and more particularly to a method for preventing a semiconductor layer from creeping up onto an anode lead led out from a capacitor element.

[Background technology]

In general, this type of solid electrolytic capacitor is made of a capacitor element made by press-molding metal powder with valve action, such as tantalum, titanium, aluminum, etc., into a cylindrical shape and sintering it, and a metal wire with valve action is attached in advance to the anode lead. A first external lead member is welded to the lead-out portion of the anode lead, and a second external lead member is attached to an electrode lead-out layer formed on the circumferential surface of the capacitor element via an oxide layer and a semiconductor layer. The entire circumferential surface of the capacitor element is covered with a resin material.

By the way, before welding the first external lead member to the anode lead led out from the capacitor element of this capacitor, an oxide layer is formed on the surface of the anode lead and the capacitor element is further coated with a sufficient amount of semiconductor mother liquor. After being impregnated with oxide, a thermal decomposition reaction is caused in a high temperature atmosphere, and a semiconductor layer is formed on the oxide layer.

However, since there are many die scratches in the axial direction on the surface of the anode lead, the semiconductor mother liquid impregnated in the capacitor element passes through these die scratches and reaches the part of the anode lead leading out from the capacitor element. It adheres and is thermally decomposed, resulting in so-called creep-up of the semiconductor layer. Normally, the impregnation and thermal decomposition operation of the semiconductor mother liquor is repeated several times or more in view of the porous nature of the capacitor element, and the creeping-up of the semiconductor layer tends to progress further.

Therefore, when welding the first external lead member to the lead-out portion of the anode lead, the first external lead member and the semiconductor layer that has climbed up may come into contact, increasing leakage current, and sometimes the cathode and anode may There is a problem in that the capacitor becomes short-circuited and cannot function as a capacitor.

Therefore, before forming the semiconductor layer on the capacitor element, the applicant prevents the formation of the semiconductor layer by forming a water-repellent coating only on the anode lead portion led out from the surface of the capacitor element. We proposed a manufacturing method for this purpose.

According to this method, even if a die scratch is formed on the anode lead, it is possible to reliably prevent the semiconductor mother liquor from creeping up due to the water-repellent effect of the water-repellent coating. It is possible to prevent the formation of a semiconductor layer on the anode lead portion to which the member is welded, and it is possible to reduce deterioration of leakage current characteristics.

However, the formation of a water-repellent coating on the anode lead is performed by, for example, immersing the capacitor element and the anode lead in a water-repellent material in the form of a solution, and then washing and removing the water-repellent material that adheres only to the capacitor element. However, the water repellent material impregnated deep into the capacitor element cannot be removed by simple cleaning. Therefore, since it has to be immersed in the cleaning liquid for a long time, workability is significantly impaired, making it difficult to apply to mass production processes.

[Disclosure of the invention]

In view of these points, the present invention is capable of suppressing the formation of a semiconductor layer creeping up to the anode lead portion led out from the surface of the capacitor element by the water-repellent member, and also prevents the water-repellent member from forming in the deep part of the capacitor element. The purpose is to provide a method for manufacturing a solid electrolytic capacitor that can prevent seepage, and specifically, a capacitor made of metal powder that has a valve action, and from which a metal wire that has a valve action is derived as an anode lead. Prior to forming a semiconductor layer on the element, a paste-like water-repellent material formed by emulsion polymerization is applied to the portion of the anode lead extending from the surface of the capacitor element.

According to this invention, since the paste-like water-repellent material formed by emulsion polymerization is applied to the anode lead portion, it is possible to prevent the water-repellent material from seeping into the capacitor element. For this reason, cleaning and removal of the soaked water-repellent member as in the method proposed by the present applicant described above can be omitted, work efficiency can be significantly improved, and the influence on capacitor characteristics can also be avoided.

In particular, since the water-repellent member is formed by emulsion polymerization, the product shape is not spherical but tends to be fibrous. For this reason, separation of solid content is less likely to occur during adhesion to the anode lead, allowing for stable adhesion work and sufficient resistance to mechanical impact after heat treatment.

[Best mode for carrying out the invention]

Next, FIGS. 1 to 3 will explain one embodiment of the present invention.
This will be explained with reference to the figures.

First, as shown in Figure 1, add 1 portion of tantalum powder.
A tantalum wire of 0.25 mm is installed in advance as an anode lead 2 on a capacitor element 1 which is formed by pressure forming and sintering into a cylindrical shape of 1 mm. Next, as shown in FIG. 2, a water-repellent member 3 made of Polyflon Paste P-9001 (fluorine-based resin) manufactured by Daikin Corporation is applied to the part of the anode lead 2 extending from the capacitor element surface 1a at a rate of 0.05%. mg deposited at 240℃
Heat for 10 minutes. Note that this water-repellent member 3 is made of polytetrafluoroethylene (PTFE), surfactant,
Contains water, is composed of emulsion polymerization, and has a molecular weight of 1600~
It has a viscosity of 2200 poise. Then, an electrode lead layer 4 is formed on the circumferential surface of the capacitor element 1 via an oxide layer and a semiconductor layer. Next, as shown in FIG. 3, an L-shaped first external lead member 5 is welded to the lead-out portion of the anode lead 2 so as to intersect at a substantially right angle, and a straight second external lead member 6 is welded to the lead-out portion of the anode lead 2. is soldered to the electrode lead layer 4. After that,
A solid electrolytic capacitor is obtained by covering the entire circumferential surface of the capacitor element 1 with a resin material 7.

According to this embodiment, the creeping up of the semiconductor layer onto the anode lead 2 is significantly reduced, and the incidence of defects in leakage current characteristics caused by welding the first external lead member 5 to the anode lead 2 is reduced to 1% or less. can be improved.

In addition, since the water-repellent member 3 is emulsion polymerized and has a paste-like structure, it has excellent dispersibility compared to suspension polymerization, and the product shape is not spherical.
It tends to become fibrous. Therefore, the work of adhering the anode lead 2 to the anode lead 2 can be performed stably, and seepage into the capacitor element can be effectively prevented, and the cleaning operation can be completely omitted.

Furthermore, the welding position of the first external lead member 5 to the anode lead 2 can be further adjusted to the capacitor element in order to prevent the semiconductor layer (for example, manganese dioxide) from creeping up by using the paste-like water-repellent member 3 produced by emulsion polymerization. It can be brought close to surface 1a. For this reason, the exterior form of the resin material 7 can be made smaller.

In addition, in the present invention, the capacitor element may be composed of a single metal powder having a valve action, or a composite or alloy powder. Alternatively, the anode lead can be welded to the capacitor element. Furthermore, the water-repellent material that is emulsion polymerized and is in the form of a paste is not limited to only fluorine-based materials. Furthermore, the forms of the external lead member and the exterior resin material may be changed as appropriate, or they may be omitted.

[Brief explanation of drawings]

The figures are explanatory diagrams of the method of the present invention, in which Fig. 1 is a side sectional view of a capacitor element, Fig. 2 is a side sectional view showing a state in which a paste-like water-repellent material is coated on an anode lead, and Fig. 3 is a side sectional view of a capacitor element. is a side sectional view showing the completed state. In the figure, 1 is a capacitor element, 1a is a capacitor element surface, 2 is an anode lead, and 3 is a water repellent member.

Claims (1)

[Claims] 1. Prior to forming a semiconductor layer on a capacitor element made of a metal powder having a valve action and from which a metal wire having a valve action is led out as an anode lead, the part of the anode lead led out from the surface of the capacitor element is A method for manufacturing a solid electrolytic capacitor, which comprises applying a paste-like water-repellent material by emulsion polymerization.