JPS5910570B2 - Manufacturing method of electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in the manufacturing method of electrolytic capacitors, primarily solid electrolytic capacitors.

In general, solid electrolytic capacitors have a capacitor element A that has a valve action in advance, as shown in Figure 1, which is made by press-molding metal powder such as tantalum, niobium, aluminum, etc., into a cylindrical shape and sintering it. A metal wire is planted as an anode lead B, a first external lead member C which can be soldered is welded to the protruding part of this anode lead B, and a second external lead member D is attached to the capacitor element A.
The capacitor element l-
The entire circumferential surface of A is covered with a resin material F.

By the way, before welding the first external lead member C to the anode lead B extending from the surface of the capacitor element A, the capacitor element A is suspended from a band-shaped metal plate G as shown in FIG. An oxidized layer is formed by immersion in a chemical conversion solution H and chemical conversion treatment, and further immersed in a semiconductor mother liquor, followed by thermal decomposition in a high-temperature atmosphere furnace to form a semiconductor layer on the oxidized layer.

Normally, the liquid temperature of the chemical liquid H is set at around 90°C, which is higher than the working efficiency and characteristics, so that vapor from the chemical liquid H, bubbles from the condenser element 1-A, etc. A conductive path is formed together with the chemical atmosphere.

Therefore, in such an atmosphere, the first external lead member C
If there is, the first external lead member C will be corroded by the chemical conversion treatment, making it difficult to solder it and making it impossible to easily incorporate it into a printed circuit board, etc., as well as corrosive substances mixed into the chemical liquid H. A problem arises in that its lifespan is significantly shortened.

For this reason, welding of the first external lead member C to the anode lead B must be performed after the chemical conversion treatment process of the capacitor element A.

However, the work efficiency decreases due to the complexity of the work process, and the electrode lead layer E is not formed on the top surface of the anode lead B of the capacitor element A on the lead-out side, so it is oxidized by welding sparks, etc. The drawback is that the leakage current characteristics are significantly impaired due to damage to the semiconductor layer.

In view of these points, the present invention provides a method for manufacturing an electrolytic capacitor in which properties and workability can be improved by chemical conversion treatment of a solderable external lead member welded to an anode lead extending from a capacitor element. Examples will be described below.

In FIG. 3, reference numeral 1 denotes a capacitor element made of a metal member having a valve action, and the illustrated example is made by press-molding metal powder having a valve action into a cylindrical shape and sintering it, but for example, It can also be constructed by simply crushing a metal wire or press-molding a thin wire into a desired shape.

Reference numeral 2 denotes an anode lead made of a metal member having a valve function and extending from the capacitor element 1. Although the anode lead 2 is installed on the capacitor element 1 in the illustrated example, it can also be welded, for example, to the circumferential surface of the anode lead.

Reference numeral 3 denotes a solderable external lead member made of nickel, iron, nickel-iron, copper, etc., one end of which is bent into an L shape, for example, and is welded to cross over the protruding portion of the anode lead 2.

4 is a band-shaped metal plate, on one side of which is an external lead member 3.
The other end is welded at a constant pitch.

5 is chemical liquid TEAL. First, the external lead member 3 is attached to the metal plate 4.
10 to 4 capacitor elements 1 suspended via
The bent portion 3 of the external lead member 3 is placed in the chemical liquid 5 whose liquid temperature is controlled to a relatively low temperature of 0°C, preferably about 30°C.
A is immersed so as not to be immersed, and chemically converted for, for example, 2 to 8 hours until a predetermined capacity is obtained.

At this time, the formation voltage V and the formation current (2) change, for example, as shown in FIG. 4, but until time t1, the formation voltage V increases and the formation current (2) maintains a substantially constant value.

During this chemical formation, the liquid temperature is as low as 40°C or less, so
The generation of vapor from the chemical liquid 5 is almost negligible, and the generation of bubbles from the condenser element 1 is active.
They do not form a chemical conversion atmosphere layer on the liquid surface.

Therefore, the external lead member 3 will not be corroded.

Next, these capacitor elements 1 are immersed in a chemical conversion liquid whose temperature is controlled at a high temperature of 41 to 90°C, preferably about 80°C, so that the bent part 3a of the external lead member 3 is not immersed, and the above-mentioned low-temperature chemical formation is performed. Formation voltage of 50-9
A 0% voltage is applied and the chemical conversion treatment is performed for, for example, 30 minutes to 2 hours.

This high-temperature chemical formation corresponds to after t1 in Figure 4, so the formation voltage V is almost constant, while the formation current ■ is gradually decreasing, so although steam is generated from the chemical liquid, the capacitor Since the generation of bubbles from the element 1 is extremely small due to the decrease in the chemical formation current, a sufficient chemical formation atmosphere cannot be formed above the liquid surface.

For this reason, the external lead member 3 is slightly corroded, but this does not pose any practical problem.

Hereinafter, an electrolytic capacitor is obtained by a usual method.

As described above, since the solderable external lead member 3 is welded to the anode lead 2 extending from the capacitor element 1 prior to its chemical conversion treatment, work efficiency in the assembly process can be significantly improved.

Specifically, welding of the external lead member to the anode lead is performed by welding the anode lead B, which extends sufficiently longer than the capacitor element A, to the metal plate G, as shown in FIG. This is done by forming an electrode lead layer, and then cutting the anode lead B from a desired part and holding it with a chuck. However, when the capacitor element is chucked, mechanical stress is applied to the oxide layer and the semiconductor layer. This tends to cause characteristics to deteriorate.

However, according to the present invention, since the anode lead is welded to the anode lead before chemical formation without any oxide layer or semiconductor layer being formed, even if the external lead member is welded using a chuck, the characteristics will not deteriorate.

For this reason, work efficiency can be improved since the work can be done without paying special attention.

Moreover, the first chemical conversion treatment of capacitor element 1 is 4
Because the process is carried out in a chemical solution with a relatively low liquid temperature of 0°C or less, even if a material that is corroded by the chemical solution is used as an external lead member, it will be corroded to the extent that it becomes a practical problem. Never.

In addition, chemical conversion treatment is divided into two stages: low-temperature chemical formation and high-temperature chemical formation, and low-temperature chemical conversion is performed for a relatively long time, and high-temperature chemical conversion is performed for a shorter time than low-temperature chemical conversion, so as mentioned above, the external lead member may be corroded to the point where it becomes a practical problem. Not only is this not possible, but the deterioration in leakage current characteristics caused by low-temperature chemical formation can be compensated for by high-temperature chemical formation in a relatively short period of time without significantly reducing the capacitance value.

In particular, it is important to set the applied voltage lower during high-temperature formation than during low-temperature formation; at the same voltage level, even if leakage current characteristics can be compensated for, the formation of an oxide layer will proceed and the capacitance will decrease. Therefore, it is desirable to select the voltage according to the purpose.

In addition, since welding of the external lead member to the anode lead is performed before forming the capacitor element, not only will there be no deterioration of characteristics due to sparks during welding, but there will also be no damage to the surface of the capacitor element due to sparks.
Even if it is damaged by the chuck, it can be healed by the chemical conversion operation, so that there is no adverse effect on the properties.

Furthermore, the metal plate G shown in FIG. 2 can be completely omitted, and
Since the material of the metal plate 4 is not limited to an expensive metal member having a valve action, the cost of the capacitor can be reduced.

In the present invention, the anode lead can be led out in a state longer than the capacitor element and then cut to a predetermined length, or alternatively, it can be led out in a state shorter than the initial length.

Further, the external lead member can be welded to the anode lead by not only lap welding but also butt welding.

As described above, according to the present invention, the solderable external lead member can be welded to the anode lead before forming by combining low-temperature forming and high-temperature forming, thereby improving work efficiency and characteristics and reducing capacitor costs. can be reduced.

[Brief explanation of drawings]

Fig. 1 is a front cross-sectional view of a conventional capacitor, Fig. 2 is an explanatory diagram of the chemical formation method of the capacitor element in Fig. 1, and Fig. 3 is a front sectional view of a conventional capacitor.
The figure is a sectional view of a main part for explaining the method of the present invention, and FIG. 4 is a characteristic diagram of changes in voltage and current in a chemically formed state. 44

Claims (1)

[Claims] 1 After welding the solderable external lead member to the anode lead extending from the capacitor element made of a metal material with valve action, welded the capacitor element to a chemical compound with a liquid temperature set at a relatively low temperature of 10 to 40°C. It is characterized by being immersed in a liquid for chemical conversion treatment, and then being immersed in a chemical conversion liquid whose liquid temperature is set at 41 to 90°C, and then subjected to chemical conversion treatment by applying a voltage of 50 to 90% of the chemical conversion voltage during low-temperature chemical formation. A method for manufacturing an electrolytic capacitor.