JPS5845806B2 - Manufacturing method of electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an electrolytic capacitor, and in particular to a method of coating the surface of an anode lead made of valve metal, which cannot be soldered, protruding from an anode body with alloy solder, which can be soldered. It's about how to do it.

Hereinafter, the case where it is used in a tantalum solid electrolytic capacitor will be explained as an example.

Conventionally, general tantalum solid electrolytic capacitors have an anode internal lead made of tantalum metal buried in tantalum metal powder, and the powder is sintered to form a porous sintered body. A dielectric oxide film is formed on the surface by anodizing to form an anode body, and a manganese dioxide layer as an electrolyte, a colloidal graphite layer as a conductive layer, and a silver paste are layered on top of this in order to form a capacitor element. Furthermore, an anode outer lead such as a nickel wire that can be soldered is connected to the anode inner lead by welding, and finally this is housed in a metal case having a cathode lead, and this gold layer case and the conductive lead are connected to each other by welding. The capacitor element was manufactured by electrically connecting the layers with solder and filling the space between the metal case and the capacitor element with resin.

Figure 1 shows its structure.

In Fig. 1, 1 is a sintered body, 2 is an anode internal lead, and 3 is a sintered body.
is a dielectric oxide film, 4 is a manganese dioxide layer, 5 is a colloidal graphite layer, 6 is a silver paste layer, T is a metal case, 8 is a cathode lead, 9 is an anode external lead, 10 is solder, 11 is resin, 12 is Shows welds.

The major features of tantalum solid electrolytic capacitors are that the dielectric oxide film has a high dielectric constant, and porous sintered bodies can be easily obtained, resulting in a high capacitance per unit volume. For this reason, it is often used in small circuits.

Currently, small-sized devices with a diameter of about 1OφX3.0 mm are being produced, and further miniaturization is required.

However, as the size becomes smaller, welding between the anode inner lead and the anode outer lead becomes extremely difficult and requires precision, which may cause a decrease in productivity and also cause problems in the welding process. The stress caused deterioration of the capacitor's characteristics, such as an increase in leakage current.

The present invention was developed to solve such conventional problems, and the present invention will be explained below.

The method for manufacturing an electrolytic capacitor of the present invention uses tantalum, niobium, titanium, tungsten, and hafnium.

The anode lead surface made of a valve metal such as zirconium has tin and lead as main components, and contains 0.05 to 30% by weight of zinc and 0.1 to 15% by weight of at least one rare earth metal. Alloy solder that can be soldered in general, such as Sansolza (trade name) manufactured by Asahi Glass Co., Ltd., at 350 to 500℃.
The anode lead surface is coated with the alloy solder by welding while applying ultrasonic vibration of 10 KN (z to 30 KHz) at a temperature of .

The conditions will be explained in more detail.

Tantalum is an alloy solder whose main components are tin and lead, and which also contains 0.05 to 30% by weight of zinc and 0.1 to 15% by weight of at least one rare earth metal.

When welding to the surface of a valve metal such as niobium, titanium, tungsten, hafnium, or zirconium, the higher the temperature of the alloy solder, the higher the frequency of the ultrasonic vibration applied to the alloy solder, the better. The longer the value, the better.

However, if high temperature and high frequency ultrasonic vibrations are applied to the anode lead of a capacitor for a long period of time, the characteristics of the capacitor will be affected and deteriorate, which is not desirable for the capacitor.

By the way, the alloy solder is tantalum or niobium.

When soldered to the surface of an anode lead made of valve metal such as titanium, zirconium, tungsten, or hafnium while applying ultrasonic vibrations of 5 fat or more at a temperature of 250°C or higher,
It can be welded in about 5 seconds, but if you solder the anode lead whose surface is coated with alloy solder to a printed circuit board using general eutectic solder without applying vibration, the anode lead will be welded in about 5 seconds. The alloy solder welded to the surface easily peels off, making it impractical.

This is called re-soldering immersion, and can be used to determine whether the alloy solder is welded to the anode lead surface.

According to the experimental results, the conditions under which the alloy solder formed on the anode and lead surfaces did not peel off even after this re-soldering immersion were performed were that the temperature was 350° C. or higher and the frequency of ultrasonic vibration was 10 KHz or higher.

In addition, the temperature is 350°C or higher and the frequency of ultrasonic vibration is 1.
As a result of experiments, the range of temperature and frequency of ultrasonic vibration that does not adversely affect the characteristics of the capacitor is 0 KHz or higher, the temperature is 350 to 500 °C, and the frequency of ultrasonic vibration is 10.
~30KHz.

That is, when the temperature exceeds 500° C. and the frequency of ultrasonic vibration exceeds 30 KHz, the characteristics of the capacitor deteriorate.

In addition, the temperature is 350-500℃, the frequency of ultrasonic vibration is 10
When the surface of the anode lead made of valve metal was coated with alloy solder under the condition of ~30 KHz, the time required was about 5 seconds.

Hereinafter, one embodiment of the present invention will be described using the drawings of FIGS. 2 to 4.

First, the internal structure of the capacitor will be explained based on FIG.

In FIG. 2, 21 is a sintered body of tantalum metal powder,
This sintered body 21 has an anode lead 2 made of tantalum metal.
2 is buried therein, and a dielectric oxide film 23 is formed on the surface of this sintered body 21 to constitute an anode body 24.

Further, on the surface of this anode body 24, an electrolyte layer 25 such as a manganese dioxide layer, a cathode layer 26 such as a carbon layer, and a conductive layer 27 such as silver paint are sequentially laminated to constitute a capacitor element 28.

Reference numeral 29 denotes a metal case that houses and holds the capacitor element 28. This metal case 29 has a cylindrical shape with only one end open, and a cathode lead 30 that can be soldered is fixed to one end surface of the case 29. ing.

Note that this metal case 29 is
The conductive layer 27 of the capacitor element 28
and are electrically connected by solder 31.

Note that the cathode layer 26.degree. conductive layer 27. The metal case 29 constitutes a cathode.

Reference numeral 32 denotes a resin filled in the space formed by accommodating the capacitor element 28 in the metal case 29.

Note that here, 33 is a Sansolza alloy solder layer coated on the surface of the anode lead 22 that protrudes to the outside, and this alloy solder layer 33 is formed on the dielectric oxide film 23 .

Next, a specific example of coating the surface of the anode lead 22 with the alloy solder layer 33 will be described.

First, the surface of the anode lead 22 is ultrasonically cleaned using an organic solvent such as trichloride.

This is to remove dirt and the like adhering to the surface of the anode IJ-122 and to prevent a decrease in adhesive strength due to this dirt.

As shown in FIGS. 3 and 4, it has a plurality of holding holes 34 each having a through hole 34a into which one capacitor is inserted and through which the anode lead 22 protrudes, and has good thermal conductivity with a heat dissipation effect. The capacitor is held with a fixture 35 made of copper or the like.

Then, connect the anode lead 22 of this capacitor to 350~
The anode lead 22 is immersed in molten solder in an ultrasonic solder bath 36 containing melted solder at a temperature of 500° C., and ultrasonic vibrations of 10 to 301 GIz are applied using an ultrasonic vibration horn 36a to coat the surface of the anode lead 22 with solder. do.

The time is approximately 5 seconds. In this case, since the capacitor is held by the fixture 35 which has a heat dissipation effect, the influence of heat on the capacitor can be minimized.

Further, although not shown, if the fixture 35 is provided with a cooling pipe through which cold water passes, the heat dissipation effect will be even more effective.

As described above, according to the present invention, the surface of the anode lead made of valve metal can be coated with a solderable alloy solder without adversely affecting the characteristics of the capacitor, and the conventional welding process is unnecessary. In addition to being able to make capacitors smaller, it has great industrial value.

Note that although the above description has been made regarding a tank solid electrolytic capacitor, the same effect can of course be obtained with other solid electrolytic capacitors and wet electrolytic capacitors.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the internal structure of a conventional tantalum solid electrolytic capacitor, and FIG. FIG. 3 is a schematic configuration diagram showing a specific example of the method, and FIG. 4 is an external perspective view of a portion shown in FIG. 3. 22... Anode lead, 24... Anode body, 25... Electrolyte, 26... Cathode layer,
27... Conductive layer, 29... Metal case, 30... Cathode lead, 33... Alloy solder layer.

Claims (1)

[Scope of Claims] 1. Consists of an anode body having an anode lead made of a valve metal, and a cathode having an electrolyte and a cathode lead, the surface of the anode lead being coated with tin and lead as main components, and 0.05 to 100%. 05-30
An alloy solder containing 0.1% to 15% by weight of at least one rare earth metal is welded to the anode at a temperature of 350° to 500°C while applying ultrasonic vibrations of 10Kllz to 30KIIz. A method for manufacturing an electrolytic capacitor, characterized in that the lead surface is coated with the alloy solder. 2. The method for manufacturing an electrolytic capacitor according to claim 1, wherein the anode lead surface is cleaned with an organic solvent before being coated with the alloy solder. 3. The method of manufacturing an electrolytic capacitor according to claim 1, wherein the surface of the anode lead is coated with alloy solder while cooling the capacitor element consisting of the anode body, electrolyte, and cathode.