JPS5950209B2 - solid electrolytic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention primarily relates to improvements in chip-type solid electrolytic capacitors.

In general, this type of solid electrolytic capacitor is made of a capacitor element A made by pressure-forming metal powder having a valve action such as tantalum, niobium, aluminum, etc. into a rectangular parallelepiped and sintering it, as shown in Figure 1. A functional metal wire is planted as an anode lead B, and a Z-shaped external lead member C is welded to the protruding part of this anode lead B.
A solder layer E as a terminal (external lead member) is formed on the electrode lead layer on the circumferential surface of the capacitor element A, and then the connection portion between the anode lead B and the external lead member C is formed with a resin material F. It is constructed by covering.

By the way, this capacitor is placed on a printed board G as shown in FIG. 2, and by heating the printed board G, the external lead member C1 is attached to the printed conductor.
It is mounted by soldering each solder layer E, but since the solder layer E is in contact with the printed circuit board G over a wide area, the temperature of the capacitor element A is high during soldering. There is a tendency to

Normally, an oxide layer as a dielectric layer and a semiconductor layer are sequentially formed on the circumferential surface of the capacitor element A before forming the electrode lead layer, but the oxide layer is easily deteriorated thermally. For example, when the temperature exceeds 200℃, it starts to deteriorate.
The higher the temperature, the more the deterioration tends to be accelerated.

However, when mounting the capacitor element A on the printed board G as described above, the capacitor element A is in contact with the printed board G over a wide area via the solder layer E. It has a wide heat receiving area and can be heated to a high temperature in a short time.

Particularly recently, in order to improve workability in soldering, the heating temperature is much higher than the melting temperature of the solder, e.g. 260-270°C.
℃, the capacitor element A is also heated to a higher temperature.

For this reason, the capacitor element A has a drawback in that its characteristics as a capacitor, such as leakage current, are significantly impaired due to deterioration of the oxide layer.

In view of these points, the present invention provides a solid electrolytic capacitor that can alleviate the thermal influence on the capacitor element when mounted on a printed board etc. and can effectively improve the characteristics and reliability. Let's discuss an example.

In FIG. 3, reference numeral 1 denotes a capacitor element constructed by press-forming metal powder having a valve action into a rectangular parallelepiped and sintering it.

2 is an anode lead made of a metal wire having a valve action and derived from a capacitor Niremen 1-1,
In the illustrated example, the metal powder is implanted in the center of the metal powder prior to pressure molding, but it can also be welded to the circumferential surface of the capacitor element 1 and derived.

Reference numeral 3 denotes an electrode lead layer formed on the circumferential surface of the capacitor element 1 via an oxide layer and a semiconductor layer, and is constructed by, for example, polymerizing a silver paste layer on a graphite layer. It can also be configured as follows.

Note that the electrode lead layer (cathode) 3 is formed on the circumferential surface of the capacitor element so as not to come into contact with the anode lead 2.

Reference numeral 4 denotes a heat shielding member which is adhered onto the electrode lead-out layer 3 of the capacitor element 1 so as to cover most of it, and is preferably made of a resin material such as epoxy resin or phenol resin.

Note that this heat shielding member 4 may be appropriately used as long as it has lower thermal conductivity than the electrode lead layer 3, the solder member, etc., and does not have an adverse effect on the capacitor element 1.

5 is an electrode extraction layer 3 in the condenser element 1
The uncoated portion 3a and the heat shielding member 4 by the heat shielding member 4
The solder applied thereon is preferably an electrically conductive material, for example silver paste.

Reference numeral 6 denotes a solder layer formed on the conductive member 5, and is formed, for example, by dipping it in a molten solder tank and pulling it up.

7 is an external lead member configured in a Z shape, for example,
The upper new curved portion is overlapped and welded to the protruding portion 2a of the anode lead 2.

Note that the lower bent portion is designed to be substantially flush with the electrode lead layer 3 or the solder layer 6.

A resin material 8 is applied to the peripheral surface of the capacitor element 1 on the outlet side of the anode lead 2 so as to cover the welded part between the protrusion 2a of the anode lead 2 and the external lead member 7. In addition to the method, the packaging can also be done by a dipping method or a molding method.

Next, a method for manufacturing this capacitor will be explained with reference to FIG.

First, as shown in FIG.
A metal wire having a valve action is installed in advance as the anode lead 2.

Then, the electrode lead layer 3 is formed on the circumferential surface of the capacitor element 10 via an oxide layer and a semiconductor layer.

Next, as shown in the figure, the capacitor element 1 is immersed in a liquid heat shielding member 4' so that the upper part 3a of the electrode lead layer 3 is not immersed.

When the capacitor element 1 is pulled up, most of the electrode lead layer 3 is covered with the heat shielding member 4, as shown in FIG.

Incidentally, when a thermosetting resin such as an epoxy resin is used as the heat shielding member 4, it is desirable to perform a heat treatment after pulling it out of the liquid bath.

Next, as shown in Figure d, the condenser element 1.
is immersed in the liquid conductive member 5' so that the uncoated portion 3a of the electrode extraction layer 3 and the heat shielding member 4 are completely immersed.

When the condenser element 1 is pulled up, the conductive member 5 is deposited on the portion 3a of the electrode extraction layer 3 not covered by the heat shielding member 4 and on the heat shielding member 4, as shown in FIG.

Incidentally, when using a silver paste made of silver powder, resin, and solvent, for example, as the conductive member 5, it is desirable to heat it.

Next, as shown in FIG. 5F, a solder layer 6 is formed on the conductive member 5 by dipping the capacitor element 1 into a molten solder tank (not shown) and pulling it up.

After that, the external lead member 7 is attached to the protrusion 2a of the anode lead 2.
A resin material 8 is applied to the circumferential surface of the capacitor element 10 on the outlet side of the anode lead 2 so as to cover the welded portion and cured to obtain the solid electrolytic capacitor shown in FIG.

This capacitor is mounted on a printed board G, for example, as shown in FIG.

That is, the capacitor is placed on the printed board G so that the solder layer 6 and the external lead member 7 are located at predetermined positions of the printed conductor, and then the solder layer 6 and the external lead member are heated by heating the printed board G. Element 7 is soldered to the printed conductor.

At this time, the capacitor element 1 is heated by conductive heat from the printed board G, but the electrode lead layer 3
Most of the area is covered with the heat shielding member 4, so the heat conduction path from the printed board G to the capacitor element 1 is almost entirely covered by the heat shielding member 4 of the electrode extraction layer 3.
It is constrained by a.

For this reason, the printed board G of capacitor element 1
The heat receiving area from the capacitor element 1 becomes smaller.
temperature rise can be suppressed to a low level, and deterioration of leakage current characteristics due to deterioration of the oxide layer can be prevented.

Furthermore, by reducing the heat receiving area of the capacitor element 1 from the printed board G, even if the heating temperature of the printed board G is further increased, the thermal influence on the capacitor element 1 can be suppressed, and workability can be further improved. .

In this regard, the present inventor manufactured a capacitor element by press-molding tantalum powder into a rectangular parallelepiped of 2 x 2 x 4 mm and sintering it, and applied epoxy resin on the electrode lead layer so that an uncoated part of 1 mm was formed at one end. A solid electrolytic capacitor having the structure shown in Fig. 3 was manufactured by immersing the capacitor in the water, and then forming a silver paste and a solder layer thereon.The solid electrolytic capacitor was placed on a printed board with a thickness of 1.5 tmm and heated to 260 to 270°C. The soldering process was carried out by placing it on the set heating element, and after that, the characteristics were measured, and the following results were obtained.

Regarding leakage current, the average leakage current was 2 nA in the product of the present invention, whereas it was 6 nA in the conventional product.

Further, regarding the dielectric loss, the average loss in the product of the present invention was 3%, whereas it was 4.5% in the conventional product.

Such a significant difference in characteristics is considered to be due to the fact that the thermal influence upon mounting the capacitor element 1 on the printed board G is relaxed.

FIG. 6 shows another embodiment of the present invention, in which a protrusion 2a of an anode lead 2 led out from a capacitor element 1 is bent into a substantially Z-shape as an external lead member 7'.

A metal layer 9, for example, a gold plating layer, which has excellent compatibility with the solder member, is formed on at least the surface of the lower bent portion.

According to this embodiment, there is no need to weld the Z-shaped external lead member 7 as shown in FIG. Damage to the oxide layer and semiconductor layer on the surface of the capacitor element can be prevented, and leakage current characteristics can be improved.

FIG. 7 shows a further different embodiment of the present invention, in which the end face of the protruding part of the anode lead 2 is exposed from the resin material 8, and a metal layer with excellent solderability is applied to the surface thereof. is attached as an external lead member 72.

According to this embodiment, the same effects as the embodiment shown in FIG. 6 can be expected, and the end surface of the protruding portion of the anode lead 2 is
Since the terminal is substantially flush with the surface of the resin material 8, the terminal can be constructed simply by forming a conductive layer on the surface of the resin material 8, and workability can be significantly improved.

It should be noted that the present invention is not limited to the above-mentioned embodiments; for example, the capacitor element can be formed into any suitable shape such as a rectangular parallelepiped or a columnar shape.

Further, the solder layer on the conductive member can also be omitted.

Furthermore, a separate external lead member (terminal) electrically connected to the electrode lead layer may be provided.

As described above, according to the present invention, the thermal influence on the capacitor element during mounting on a printed board or the like can be alleviated, and the characteristics and reliability can be significantly improved.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of a conventional example, Fig. 2 is a side sectional view showing the mounting state on a printed board, Fig. 3 is a side sectional view showing an embodiment of the present invention, and Fig. 4 is a manufacturing method. A side sectional view for explanation, FIG. 5 is a side sectional view showing the mounting state on a printed board,
6 and 7 are side sectional views showing other different embodiments of the present invention. In the figure, 1 is a capacitor element, 2 is an anode lead, 3
3 is an electrode extraction layer, 3a is an uncoated part, 4 is a heat shielding member, and 5
is a conductive member.

Claims (1)

[Claims] 1. An electrode lead layer is formed on the circumferential surface of a capacitor element made of metal powder having a valve action, and a metal wire having a valve action is led out as an anode lead through an oxide layer and a semiconductor layer, and an anode lead. At the same time, a heat shielding member is applied on the electrode lead-out layer so that a part thereof is not covered, and the heat shielding member and the electrode lead-out layer not covered by the heat shielding member are soldered. A solid electrolytic capacitor characterized in that it is coated with a conductive material that can be used.