JPS58197714A - Method of producing solid electrolytic condenser - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a solid electrolytic capacitor, and in particular to improvement of characteristic deterioration caused by migration of a metal member constituting an electrode lead layer into a capacitor element.

In general, this Kusunoki solid electrolytic capacitor is made by press-molding metal powder with a valve action, such as tantalum, niobium, or aluminum, into a cylindrical shape and sintering the capacitor element. An L-shaped first external lead member is welded to the lead-out portion of the anode lead, and an oxide layer is formed on the circumferential surface of the straight-shaped second external lead member.

It is constructed by soldering to an electrode lead layer formed through a semiconductor layer and a graphite layer, and covering the entire circumferential surface of the capacitor element with a resin material.

By the way, in view of the fact that the graphite layer of the electrode lead layer in the capacitor element shows almost no wettability to the solder member, it is almost impossible to solder the second external lead member to the graphite layer. It is made of a conductive material that has excellent electrical and mechanical connectivity with the graphite layer and excellent n-th property with respect to the solder material.

This conductive member is widely used, for example, containing silver powder with an average particle size of 2 to 3 microns and a resin, and in which the proportion of the silver powder to the whole is set to 70% by weight. The conductive material is usually silver powder or inorganic material.

It is composed of a conductive suspension consisting of a resin and a solvent, and the electrode lead layer is formed by dipping the capacitor element in this conductive suspension, pulling it up, and then heating it to about 150"C. The silver powder is fixed to the circumferential surface of the capacitor element by thermosetting the resin, and good electrical connection between the silver powder and the graphite layer is maintained.

However, when such a solid electrolytic capacitor is used in a humid atmosphere, the silver constituting the electrode lead layer is ionized by the presence of moisture, and a migration phenomenon occurs.

For this reason, the migration of silver into the graphite layer, semiconductor layer, and oxide layer may impair leakage current characteristics.

This migration phenomenon is affected by ambient conditions, operating conditions, etc., but it appears particularly when no DC voltage is applied to the first and second external lead members and when the humidity is high. However, the leakage current characteristics also tend to be significantly impaired.

Therefore, there is a problem in that the use of this method is severely restricted for highly reliable equipment such as precision foot measuring equipment and industrial equipment that requires a stable and small leakage current value over a long period of time.

In view of these points, the present invention can prevent the migration of the constituent members of the electrode extraction layer to the semiconductor layer and oxide layer without being affected by the surrounding conditions and operating conditions, and can significantly improve the leakage current characteristics. It provides a method for manufacturing solid electrolytic capacitors, and the following is the first part of the manufacturing method.
This will be explained with reference to FIGS.

First, as shown in FIG. 1, a metal wire having a valve function is installed in advance as an anode lead 2 on a capacitor element 1 which is formed by press-forming metal powder having a valve function into a cylindrical shape and sintering it. Note that the capacitor element 1 can be configured not only in a cylindrical shape but also in a prismatic or flat shape.
can also be derived by welding to the circumferential surface of the capacitor element 1. Next, as shown in FIG. 2, an oxide layer, a semiconductor layer, and a graphite layer 3 are sequentially formed on the capacitor element 1. Then, a paste-like conductive member containing base metal powder such as copper, nickel, aluminum, and resin is applied onto the graphite layer 3 and heat-treated.
A first electrode extraction layer 4 is formed. Next, as shown in FIG.
i14. A second electrode lead layer 5 is formed by h&j electroless nickel plating. Next, as shown in Figure 4,
An L-shaped first external lead member 6 is welded to the anode lead 2, and a straight second external lead member 7 is soldered to the second electrode lead layer 5 (8).

A solid electrolytic capacitor is then obtained by covering the entire circumferential surface of the capacitor element 1 with the resin material 9.

Since the second electrode lead layer 5 of the capacitor element l is formed by electroless nickel plating, even if it is operated in a humid atmosphere or left unused, the electrode lead layer constituent members will remain intact. Migration to the semiconductor layer and the # layer can be completely prevented. Therefore, deterioration of leakage current characteristics can be prevented, and application to equipment requiring high reliability is possible.

Moreover, since the graphite layer 3F has the first electrode lead layer 4 mainly composed of base metal powder, the second electrode lead layer 5 formed by electroless nickel plating is formed on the first electrode lead layer 4. can be selectively formed on the surface. This eliminates the need for a mask at the base of the @Kariichi 12, improving workability.

In addition, since the first electrode drawing layer 4 as a base layer is formed prior to the formation of the second electrode drawing layer 5, the second electrode drawing layer 5 is formed as a base layer.
No. 1! The adhesion strength of the pole extraction layer 5 to the capacitor element 1 is improved. For this reason, 1. When the second external lead member 7 is soldered to the second electrode lead layer 5, peeling of the electrode lead layer at the bottom of the capacitor element can be prevented.0 Furthermore, high reliability is usually required. Although solid electrolytic capacitors packaged in metal cases are relatively often used in equipment such as the There is a problem with doing so. However, by configuring as described above, reliability can be improved, so a simple exterior type can be applied.

This, together with avoiding the use of silver, can effectively reduce the price.

Next, specific examples will be described. An oxide layer, a semiconductor layer, and a graphite layer are formed on a capacitor element made by press-molding tantalum powder into a cylindrical shape of 3.5φX 4 as and sintering it. Then, the conductive element was immersed in a paste-like conductive material made of copper powder, resin, and solvent, and the proportion of the copper powder in the whole was set to 70% by weight, making sure that the top surface was not immersed. The first electrode drawing layer is formed by carrying out a post-drawing heat treatment.

Next, this capacitor element is immersed in a 70°C nickel sulfate bath for 25 minutes so that the immersion level is 0.5 degrees above the top surface. After lifting, wash and dry.

As a result, a thickness of 2 to 3 μm is formed on the first electrode lead layer.
A second electrode lead layer consisting of an electroless nickel plating layer of m was formed. As described above, a tantalum solid electrolytic capacitor is manufactured by the usual method.

This capacitor was left unloaded in an atmosphere with a temperature of 65°C and a relative humidity of 95%, and every 500 and 1000 hours, it was charged at a DC voltage of 46 V for 3 minutes and the leakage current was measured. When we investigated the defectiveness rate, we obtained the results shown in the table below.

As is clear from the above table, there was no significant difference in initial leakage current between the product of the present invention and the conventional product. However, although no significant difference was observed in the failure rate at 500 hours, no significant difference was observed at 100 hours. This is considered to be because the electrode σ1 output layer of the product of the present invention is made of a metal other than silver that does not migrate.

In addition, in the present invention, an appropriate plating solution other than nickel sulfate can be used as the electroless nickel plating solution.

Furthermore, depending on the plating solution, activation treatment may be performed prior to plating treatment.

Furthermore, it can also be applied in the form of a chip.

As described above, according to the present invention, by configuring the first electrode lead layer with a conductive material mainly composed of base metal powder and the second electrode lead layer with electroless nickel plating, silver migration can be prevented. In addition to preventing characteristic deterioration,
Costs can also be effectively reduced.

[Brief explanation of the drawing]

The figures are explanatory diagrams of the method of the present invention, in which Fig. 1 is a side sectional view of a 4''i capacitor element, and Fig. 2 is a side view showing a state in which the first 11-pole extraction layer is formed on the graphite layer of the capacitor element. Cross-sectional view: FIG. 3 is a side sectional view showing a state in which a second 111-pole extraction layer is formed on the first electrode extraction layer, and FIG. 4 is a side sectional view showing the completed state. is the capacitor element, 2 is the anode lead, 3
is a graphite layer, 4 is a first electrode extraction layer, and 5 is a second electrode layer.
This is the electrode extraction layer. Figure 1 Figure 2 Figure 4

Claims (1)

[Claims] A step of sequentially forming an oxide layer, a semiconductor layer, and a graphite layer on a capacitor element made of a metal powder having a valve action, and a step of depositing a conductive member containing a base metal powder and a resin on the graphite layer of the capacitor element. First
manufacturing a solid electrolytic capacitor, comprising the steps of: forming an 11-electrode lead layer; and forming a second electrode lead layer by electroless nickel plating on the first tm lead layer of a capacitor element. Method.