JPS58200523A - 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 a process for forming an electrode lead layer by electroless nickel plating, in which characteristic deterioration is caused by undesired penetration of a processing liquid into a capacitor element. This is related to the improvement of

In general, this type of solid electrolytic capacitor is made by, for example, press-molding metal powder having a valve action into a cylindrical shape and sintering it.A metal wire having a valve action is installed in advance as the #j electrode lead on a capacitor element, and the anode A first external lead member is welded to the lead-out portion of the lead, and a second external lead member is welded to the circumferential surface of the capacitor element with an oxide layer, a semiconductor layer,
It is constructed by covering the entire circumferential surface of a capacitor element with a soldering poppy and a capacitor element on an electrode lead-out layer formed through a graphite layer.

By the way, in the electrode lead layer of the capacitor element, the graphite layer shows almost no wettability to the solder material.
In view of the fact that it is almost impossible to solder the second external lead member to the graphite layer, the conductive member has excellent electrical and mechanical connectivity to the graphite layer and also has excellent corrosion resistance to the solder member. It is formed in

This conductive member is widely used, for example, containing silver powder with an average particle size of 2 to 3 μm and a resin, and in which the ratio 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 constructed as a conductive suspension consisting of a resin and a solvent, and the electrode lead layer is formed by immersing a capacitor element in this conductive suspension, pulling it up, and then subjecting it to heat treatment. 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 exhibits a migration phenomenon.

For this reason, the leakage current characteristics are impaired due to the migration of silver to the graphite layer, the semiconductor layer, and the oxide layer.

Such migration phenomenon depends on the ambient conditions,! l! ′
Although it is influenced by the operating conditions, it is especially noticeable when no DC voltage is applied to the first and second external lead members and when the humidity is high, and the leakage current characteristics are also significantly improved. There is a tendency to become more popular.

Therefore, the present applicant first developed a method for manufacturing a solid-state decomposed capacitor in which an oxide layer, a semiconductor layer, and a graphite layer are formed on a capacitor element, and an electrode lead layer is formed on the graphite layer by electroless nickel plating. Proposed.

According to this method, it is possible to completely prevent the migration of the drawing member of the electrode drawing layer into the capacitor element, thereby significantly improving the leakage current characteristics, and also improving the quality of the capacitor.

By the way, this electrode lead layer formed by electroless nickel plating is made by immersing the capacitor element in an activation processing solution to the extent that the top surface of the capacitor element is not immersed, and then immersing it in an electroless nickel plating bath at the same level as the immersion level of the processing solution. It is formed by dipping it to a level.

However, if there are no fluctuations in the level of immersion of the capacitor element in the activation treatment solution, excellent effects can be expected as described above, but there are also problems such as variations in dimensional accuracy, especially when batch processing is performed. Therefore, it is extremely difficult to maintain a constant immersion level for each capacitor element, and in some cases, the top surface of the capacitor element is immersed in the processing liquid.

In particular, if a processing liquid containing chlorine permeates into the -H capacitor element, it is difficult to remove it without adversely affecting the capacitor characteristics. For this reason, when hydrochloric acid is generated by combining with residual salt due to moisture infiltration after commercialization, the oxidized layer is damaged by its strong etching and action, resulting in significantly deteriorated leakage current characteristics and voltage resistance characteristics. There is a problem of damage.

In view of these points, the present invention provides a method for manufacturing a solid electrolytic capacitor that can reduce undesired infiltration of a processing liquid into a capacitor element in an electroless plating process even if there is some variation in dimensional accuracy. One manufacturing method will be described below with reference to FIGS. 1 to 4.

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. Then, an oxide layer, a semiconductor layer, and a graphite layer are formed on the capacitor element (1), and base metal powders such as nickel, tin, copper, iron, and carbon are added on the graphite layer.

The first electrode lead layer 3 is formed by depositing a conductive member containing resin. Next, as shown in FIG. 2, the capacitor element 1 is immersed in an activation treatment solution so that the upper part (anode IJ side) of the first electrode pull-out noodle 3 is not immersed. After pulling up, the second electrode lead layer 4 made of electroless nickel plating is formed by roughly immersing it in an electroless nickel plating bath at almost the same level as the immersion level in the activation treatment. be done. Next, as shown in FIG. 3, the first external lead member 5 is welded to the anode lead 2, and the second external lead member 6 is welded to the second electrode lead layer 4. 7
)do. After that, as shown in Figure 4, Nifnden 2nd
Since the electrode drawer brass 3 and 4 are made of base metal, the migration of the constituent members of the electrode drawer into the capacitor element is completely prevented even if the electrode drawer brass 3 and 4 are left in a high humidity atmosphere for a long time under direct load conditions. IJ2 can do it. Therefore, characteristic deterioration caused by silver migration can be completely eliminated, and a high quality capacitor can be obtained.

Further, since the first electrode lead layer 3 is formed of a conductive material with excellent conductivity under the second electrode lead L P, Q 4, the second external lead member 6 is connected. Even if the second electrode extension layer 4 is formed only in the portions other than the upper portion 1a, the capacitor characteristics will not be impaired. For this reason, the level at which the capacitor element 1 is immersed in the activation treatment liquid can be made sufficiently shallow, which significantly reduces the characteristic deterioration caused by the treatment liquid seeping into the capacitor element from the top surface. Ru.

Next, specific examples will be described.

Example 1 A capacitor element made by press-molding tantalum powder into a 3.5φ x 4M column and sintering it is pre-marked with ○. A tantalum wire of 5φ■ is installed as an anode lead.

Then, an oxide layer, a semiconductor layer, and a graphite layer are formed on the capacitor element. Next, a capacitor element was placed in a conductive member made of copper powder, resin, and solvent, and the proportion of copper powder in the total amount was set to 70% by weight, and the part 0.1 wm below the top surface of the conductive member was set at the immersion level. By immersing the capacitor element in this manner, a first electrode extension layer is formed on the side peripheral surface and bottom surface of the capacitor element. Next, the capacitor element is immersed for 1 to 2 seconds so that the center portion of the side circumferential surface thereof is at the immersion level for activation treatment. The capacitor element is then immersed in a nickel sulfate bath for 25 minutes to the same level of immersion as the palladium chloride bath. Raise it, wash and dry. This allows the first f[i? A second 'i4L pole extraction layer was formed by electroless nickel plating on the 1. peak portion of the extraction layer. Note that the thickness of the nickel plating layer was 2 to 3 μm. A tantalum solid electrolytic capacitor is manufactured using the following conventional method.

This capacitor was left unloaded in an atmosphere with a temperature of 65°C and a relative humidity of 95%, and the leakage current was measured after charging at a DC voltage of 46 V for 3 minutes at specific time intervals. When we investigated the ratio, we obtained the results shown in the table below.

As is clear from the above table, no difference was observed in the initial characteristics of leakage current between the product of the present invention and the conventional product.

Although no significant difference was observed in the defect rate until 500 hours had elapsed, at 1000 hours, the inventive product had 10% defects, while the conventional product had 60% defects, which was significant. A significant difference was noted. This is considered to be because no silver was used in the electrode lead layer of the product of the present invention.

In addition, when the 11 products of the present invention were disassembled and the presence or absence of residual salt in the capacitor element was investigated, no salt was detected at all.

Example a Example 1. In this example, the same effect as in Example 1 was obtained by replacing the copper powder with nickel powder as the metal powder constituting the first electrode extraction layer. Moreover, the first electrode lead layer of the second electrode extraction layer
The adhesion to the electrode lead layer was slightly improved.

In the present invention, the capacitor element may have a prismatic shape or a flat shape in addition to a cylindrical shape. Furthermore, a treatment solution other than those in the embodiments may be used in the electroless nickel plating process. Furthermore, it can also be applied in chip form.

As described above, according to the present invention, even if there is some variation in dimensional accuracy, it is possible to reduce the undesired infiltration of the processing liquid into the capacitor element during the thermal electrolytic nickel plating step E, and the undesirable infiltration of the treatment liquid into the capacitor element due to the residual It is possible to improve the deterioration of characteristics caused by

[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 capacitor element, s 2nd ntrz, 2nd degree, a side sectional view showing the formation state of the electrode extraction layer, and Fig. 3 is a side sectional view showing the state of formation of the electrode extraction layer. FIG. 4 is a side sectional view showing the completed state. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A capacitor element made of a metal powder having a valve action, from which a metal wire having a valve action is led out as an anode lead, and an oxide layer, a semiconductor layer, and a graphite layer are formed on the capacitor element. process and base metal powder onto the graphite layer of the capacitor element. A step of forming a first electrode lead-out rib by applying a conductive member containing resin, and a second electrode lead-out formed by electroless nickel plating on the first electric lead-out layer excluding the upper part of the capacitor element. A method for manufacturing a solid electrolytic capacitor, comprising the step of forming a layer.