JP2000340473A - Solid electrolytic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolytic capacitor which improves the connection performance of a fuse wire to a capacitor element and enables the capacity increase. SOLUTION: A metal layer 9 formed on a capacitor element 1 is electrically connected to a cathode side lead frame 5 via a fuse wire 4. The capacitor element 1, the fuse wire 4 and a part of the cathode side lead frame 5 are covered with a resin-molded package 6 to compose a capacitor. With this constitution, the fuse wire 4 is connected to the metal layer 9 at a plurality of points.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid electrolytic capacitor, and more particularly to a solid electrolytic capacitor with a fuse wire in which a capacitor element is connected to a lead frame via a fuse wire.

[0002]

2. Description of the Related Art Conventionally, capacitors have been widely used in electronic circuits. Among capacitors, electrolytic capacitors are often used for power circuits and the like because of their relatively small size and large capacity. Typical electrolytic capacitors include aluminum electrolytic capacitors and tantalum electrolytic capacitors.Tantalum electrolytic capacitors, which are excellent in terms of leakage current characteristics, frequency characteristics, and temperature characteristics, need these characteristics It is often used for noise limiter circuits and filter circuits.

FIG. 12 is a diagram showing an example of the structure of a tantalum solid electrolytic capacitor (hereinafter, simply referred to as "solid electrolytic capacitor"). In this solid electrolytic capacitor, a metal wire 2 as an anode extending from a capacitor element 1 is electrically connected to an anode-side lead frame 3. Further, a metal layer 9 as a cathode formed on the capacitor element 1 is electrically connected to the cathode side lead frame 5 via the fuse wire 4. Then, the capacitor element 1, the metal wire 2, the fuse wire 4, and a part of each of the lead frames 3 and 5 are molded with an epoxy resin or the like to form a resin package 6.

[0004] The fuse wire 4 functions as a thermal fuse that conducts the metal layer 9 of the capacitor element 1 to the cathode side lead frame 5 and blows off due to abnormal heat generation of the capacitor element 1.

[0005] One end of the fuse wire 4 is bonded to and connected to the cathode side lead frame 5. The other end is bonded and connected to the surface of the metal layer 9. For example, a method of thermocompression bonding is used for bonding the fuse wire 4. However, in some cases, the bonding is insufficient, so that the fuse wire 4 is opened and the function as the fuse wire 4 cannot be performed.

[0006] In recent years, there has been an increasing need for higher capacity of solid electrolytic capacitors. FIG. 13 is a diagram showing an equivalent circuit of the solid electrolytic capacitor. In this equivalent circuit of the solid electrolytic capacitor, the resistance Rc of the capacitor element 1 and the resistance Rf of the fuse wire 4 are connected in series. These are called equivalent series resistances (hereinafter, referred to as “ESR”) of the capacitor element 1. Normally, the resistance Rf of the fuse wire 4 is set to a value sufficiently smaller than the resistance Rc of the capacitor element 1.

Here, in the characteristics of the solid electrolytic capacitor, when the capacitance C of the solid electrolytic capacitor increases, the resistance Rc of the capacitor element 1 tends to decrease. For this reason, the value of ESR also decreases, but when the capacitance C of the solid electrolytic capacitor is increased, the ratio of the resistance Rf of the fuse wire 4 in the ESR becomes so large that it cannot be ignored, which adversely affects the characteristics of the solid electrolytic capacitor. There are cases.

The present invention was conceived in view of the above circumstances, and has as its object to provide a solid electrolytic capacitor capable of improving the bonding property of a fuse wire to a capacitor element and increasing the capacity. , The subject.

[0009]

DISCLOSURE OF THE INVENTION In order to solve the above problems, the present invention employs the following technical means.

According to the solid electrolytic capacitor according to the first aspect of the present invention, the metal layer formed on the capacitor element and the lead frame are electrically connected via the fuse body, and the capacitor element, the fuse body and the lead are provided. A solid electrolytic capacitor in which a part of a frame is housed in a resin mold package, wherein a fuse body is connected to a metal layer at a plurality of locations.

More specifically, the fuse body is made of a fuse wire, and one end of the fuse wire is connected to an end face of the capacitor element having a substantially rectangular shape, and is connected to a lead frame. Is connected to the side surface of the capacitor element.

According to the present invention, since the fuse wire as the fuse body is connected to the metal layer at a plurality of locations, the fuse wire for the capacitor element is compared with the conventional configuration where the fuse wire is connected at only one location. Bondability can be further improved.

According to the above configuration, the resistance of the fuse wire is connected in parallel with the capacitor element, and the resistance of the fuse wire can be reduced. Therefore, even if the resistance of the capacitor element decreases with the increase in the capacity of the solid electrolytic capacitor, the ratio of the resistance of the fuse wire in the ESR can be suppressed, which may adversely affect the characteristics of the solid electrolytic capacitor. Absent.

According to a preferred embodiment of the present invention,
An insulating layer having electrical insulation for preventing contact between the lead frame and the metal layer is formed on the lead frame. Thus, when the solid electrolytic capacitor is manufactured, the lead frame can be brought into contact with the metal layer of the capacitor element via the insulating layer, so that the positioning of the capacitor element is facilitated and the workability can be improved.

[0015] Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings.

FIG. 1 is a view showing the structure of a solid electrolytic capacitor according to the present invention. This solid electrolytic capacitor is
A substantially rectangular capacitor element 1 integrally formed with a metal wire 2, an anode-side lead frame 3 electrically connected to the capacitor element 1 via the metal wire 2, and a fuse wire 4 as a fuse body And a cathode lead frame 5 electrically connected to the capacitor element 1.

The capacitor element 1, the metal wire 2, the fuse wire 4, and a part of each lead frame 3, 5
The resin package 6 is formed by molding with a thermosetting resin such as an epoxy resin or a phenol resin.
A portion of each of the lead frames 3 and 5 exposed from the resin package 6 is bent, and a horizontal surface 7 is formed at a tip portion thereof, so that the solid electrolytic capacitor can be surface-mounted on a printed circuit board or the like.

The capacitor element 1 is made of a porous sintered body 8 formed by compressing and sintering a powder made of a metal such as tantalum.
On the other hand, the base end of the above-described metal wire 2 is embedded and integrated, an oxide film as a dielectric is formed, and a semiconductor layer, a graphite layer (neither is shown),
And a metal layer 9 are laminated.

The metal wire 2 functions as an anode, and is formed of the same kind of metal as the porous sintered body 8, such as tantalum. The metal wire 2 extends from one end face 10 of the capacitor element 1 via a Teflon ring 11, and its tip is welded and connected to the anode-side lead frame 3.

The metal layer 9 of the capacitor element 1 functions as a cathode, and is formed on the outer surface 12 and the other end surface 13 of the capacitor element 1 by, for example, silver paste.

On the end face of the cathode-side lead frame 5, that is, on the face facing the capacitor element 1, the capacitor element 1
An insulating layer 14 for preventing contact between the metal layer 9 and the cathode-side lead frame 5 is formed. The insulating layer 14
It is formed by applying a resin having an electrical insulation property such as a polyimide resin, whereby the metal layer 9 of the capacitor element 1 and the cathode side lead frame 5 are directly
No more contact.

The fuse wire 4 is made of a high melting point solder having a melting point of about 300 ° C. One end of the fuse wire 4 is bonded and connected to the cathode side lead frame 5, and the other end of the capacitor element 1. 13
In contact with the metal layer 9 formed on the substrate. The other end is bonded to and connected to the surface of the metal layer 9 formed on the outer surface 12 of the capacitor element 1.

The fuse wire 4 has a function as a thermal fuse that conducts the capacitor element 1 and the cathode side lead frame 5 and blows off due to abnormal heat generation of the capacitor element 1.

For example, when a large current flows through the capacitor element 1 and a short circuit occurs inside the capacitor element 1 to generate heat, the temperature of the fuse wire 4 connected thereto rises. Then, when the capacitor element 1 or the fuse wire 4 reaches a predetermined temperature or higher, the high melting point solder of the fuse wire 4 is melted. At this time, the fuse wire 4
It melts at both of the plurality of locations connected to the capacitor element 1 and cuts off the current to open the circuit. Therefore, the fuse wire 4 can prevent adverse effects on other circuits due to heat generation of the capacitor element 1 beforehand.

Here, according to the above configuration, one end of the fuse wire 4 is connected to the other end surface 13 of the capacitor element 1, and the other end is connected to the outer surface 12 of the capacitor element 1. That is, since the fuse wires 4 are connected to the metal layer 9 of the capacitor element 1 at a plurality of locations, the number of connection locations of the fuse wires 4 is smaller than that of a conventional solid electrolytic capacitor connected at only one location. And the reliability of the joining of the fuse wire 4 to the capacitor element 1 can be improved.

Further, since the fuse wires 4 are connected at a plurality of locations, as shown in FIG. 2, the equivalent circuit of the solid electrolytic capacitor substantially divides the resistance of the fuse wires 4 and Rf1 and Rf2 are connected in parallel. Therefore, the resistance value of the fuse wire 4 can be significantly reduced as compared with the conventional equivalent circuit (see FIG. 13). Therefore, when the capacitance of the solid electrolytic capacitor is increased, even if the value of ESR becomes smaller, the fuse wire 4 is smaller than the resistance Rc of the capacitor element 1.
Can be suppressed sufficiently low, so that the characteristics of the solid electrolytic capacitor are not adversely affected, and the capacity of the solid electrolytic capacitor can be increased without any trouble.

Next, a method for manufacturing the solid electrolytic capacitor will be described. First, after manufacturing the capacitor element 1 as a single unit, an insulating resin 14 such as a polyimide resin is applied to the tip of the cathode-side lead frame 5 to form an insulating layer 14.

Next, the tip of the metal wire 2 of the capacitor element 1 is placed on the anode-side lead frame 3 and fixed by welding. At this time, a minute gap may be provided between the other end surface 13 of the capacitor element 1 and the cathode-side lead frame 5.

Subsequently, one end of the fuse wire 4 is bonded to the cathode side lead frame 5. Specifically, as shown in FIG. 3, the fuse wire 4 is passed through a jig called a capillary 15, and one end of the fuse wire 4 is projected from the tip of the capillary 15. At this time, one end is formed in a ball shape, but has a larger diameter than usual.

Then, as shown in FIG.
By moving the tip 5 downward, the tip of the fuse wire 4 is pressed against the bonding pad formed on the cathode lead frame 5, so that one end of the fuse wire 4 is thermocompression-bonded on the cathode lead frame 5. At this time, since one end of the fuse wire 4 is formed in a ball shape having a diameter larger than usual, it is protruded outside from the cathode side lead frame 5 and is thermocompression-bonded so as to contact the other end surface 13 of the capacitor element 1. You.

Subsequently, as shown in FIG. 5, the fuse wire 4 is cut at a predetermined position, and the cut portion is formed in a ball shape. Then, as shown in FIG.
The ball-shaped cut portion is thermocompression-bonded onto the outer surface 12 of the capacitor element 1 while being twisted so as to bend.

Thereafter, the periphery of the capacitor element 1, the fuse wire 4 and a part of each of the lead frames 3 and 5 are molded with a thermosetting resin such as an epoxy resin using a predetermined mold to form a resin package 6. Form. Then, unnecessary portions of the lead frames 3 and 5 on the surface of the resin package 6 are removed, and a predetermined forming is performed to obtain a solid electrolytic capacitor as shown in FIG.

As described above, in the method for manufacturing a solid electrolytic capacitor, when one end of the fuse wire 4 is thermocompression-bonded to the cathode side lead frame 5, one end of the fuse wire 4 is also connected to the other end surface 13 of the capacitor element 1. Since they can be connected, they can be manufactured without changing the conventional manufacturing process. Therefore, since a conventional production line can be used as it is, there is no need to change the production equipment and increase the production cost.

In the above manufacturing method, as shown in FIG. 7, when the metal wire 2 of the capacitor element 1 is welded to the anode-side lead frame 3, the other end surface 13 of the capacitor element 1 and the cathode-side lead frame 5 are connected. The insulating layer 14 may be contacted. By doing so, there is an advantage that the positioning of the capacitor element 1 is facilitated, so that the equipment cost involved is reduced and the operation can be simplified.

Further, in order to obtain a high capacity in a solid electrolytic capacitor, it is necessary to increase the size of the capacitor element 1 itself, but on the other hand, it is necessary to maintain the size of the resin package 6. There is.
In such a case, if the positioning of the capacitor element 1 is reliably performed as described above, the capacitor element 1 itself can be enlarged while maintaining the size of the resin package 6, and thus the solid electrolytic capacitor can be obtained. Can be increased.

Further, when the other end surface 13 of the capacitor element 1 is brought into contact with the insulating layer 14 of the cathode side lead frame 5, when one end of the fuse wire 4 is thermocompression-bonded to the cathode side lead frame 5, Since one end of the fuse wire 4 does not have to be forced out of the cathode side lead frame 5, workability is improved. At this time, one end of the fuse wire 4 may be thermocompression-bonded to the cathode lead frame 5 before the metal wire 2 of the capacitor element 1 is welded to the anode lead frame 3.

Another method for connecting one end of the fuse wire 4 to the other end 13 of the capacitor element 1 is as follows. That is, as shown in FIG. 8, after the metal wire 2 of the capacitor element 1 is connected to the anode-side lead frame 3, the capacitor element 1 is pushed down from above within the elastic limit of the anode-side lead frame 3 (FIG. 8, white arrow). A), and maintain a constant posture.

When thermocompression bonding to the cathode side lead frame 5 is performed, as shown in FIG. 9, when the capacitor element 1 is returned to the original position, one end of the fuse wire 4 is connected to the other end face of the capacitor element 1. 13 and thermocompression bonded. Therefore, the other end surface 1 of the capacitor element 1
3, the bonding area of the fuse wire 4 becomes larger,
The joining reliability can be further improved.

Further, as described below, a method in which the shapes of the capacitor element 1 and the capillary 15 are devised can be applied.

For example, as shown in FIG. 10, in the shape of the capacitor element 1, the other end surface 13 may be formed so as to expand in a curved shape. This is the capacitor element 1
Can be easily formed by increasing the amount of the silver paste of the metal layer 9 at the time of manufacture of a single unit. According to the above configuration, when one end of the fuse wire 4 is thermocompression-bonded to the cathode lead frame 5, the metal wire 9 protrudes toward the cathode lead frame 5. The thermocompression bonding can be performed by contacting the other end surface 13 of the substrate. Further, according to this configuration, one end of the fuse wire 4 does not need to be formed in a ball shape larger than usual. Note that the shape of the other end surface 13 is not limited to the shape that expands in a curved shape as long as the shape protrudes toward the cathode-side lead frame 5 side.

FIGS. 11A and 11B are views showing a modification of the capillary 15, wherein FIG. 11A is a sectional view and FIG. 11B is a bottom view. As shown in the figure, the shape of the tip of the capillary 15 may be a shape provided with a groove 17 extending in one direction from the center hole 16. Thus, when the one end of the fuse wire 4 is thermocompression-bonded to the cathode side lead frame 5, if the capillary 15 is arranged so that the groove 17 faces the capacitor element 1, the one end of the fuse wire 4 will extend along the groove 17. As a result, it is easy to protrude to the outside of the cathode side lead frame 5, and it is easy to make contact with the other end surface 13 of the capacitor element 1.
Therefore, one end of the fuse wire 4 is easily connected to the other end surface 13, and workability is improved.

Of course, the scope of the present invention is not limited to the above embodiment. For example, in the above embodiment, a tantalum solid electrolytic capacitor using tantalum as an anode metal has been described. However, the above-described configuration may be applied to a solid electrolytic capacitor using aluminum, niobium, or the like as an anode metal.

In the above-described embodiment, the number of connection points of the fuse wire 4 to the capacitor element 1 is two, but the number is not limited to two.

[Brief description of the drawings]

FIG. 1 is a view showing a structure of a solid electrolytic capacitor according to the present invention.

FIG. 2 is a diagram showing an equivalent circuit of the solid electrolytic capacitor shown in FIG.

FIG. 3 is a diagram for explaining a manufacturing process of the solid electrolytic capacitor.

FIG. 4 is a diagram for explaining a manufacturing process of the solid electrolytic capacitor.

FIG. 5 is a diagram for explaining a manufacturing process of the solid electrolytic capacitor.

FIG. 6 is a diagram for explaining a manufacturing process of the solid electrolytic capacitor.

FIG. 7 is a diagram showing a modification of the solid electrolytic capacitor.

FIG. 8 is a diagram for explaining another manufacturing process of the solid electrolytic capacitor.

FIG. 9 is a diagram for explaining another manufacturing process of the solid electrolytic capacitor.

FIG. 10 is a diagram showing a modification of the capacitor element.

FIG. 11 is a diagram showing a modification of the capillary.

FIG. 12 is a diagram showing a structure of a conventional solid electrolytic capacitor.

13 is a diagram showing an equivalent circuit of the solid electrolytic capacitor shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Capacitor element 2 Metal wire 3 Anode side lead frame 4 Fuse wire 5 Cathode side lead frame 6 Resin package 9 Metal layer 12 Outer side 13 Other end 14 Insulating layer

Claims (3)

[Claims] 1. A metal layer formed on a capacitor element and a lead frame are electrically connected via a fuse body, and the capacitor element, the fuse body, and a part of the lead frame are housed in a resin mold package. A solid electrolytic capacitor according to claim 1, wherein the fuse body is connected to the metal layer at a plurality of locations. 2. A fuse body comprising a fuse wire, wherein one end of the fuse wire is connected to an end face of the capacitor element having a substantially rectangular shape and is connected to the lead frame, and the other end of the fuse wire is provided. The solid electrolytic capacitor according to claim 1, wherein is connected to a side surface of the capacitor element. 3. The solid electrolytic capacitor according to claim 1, wherein an insulating layer having an electrical insulating property for preventing contact between the lead frame and the metal layer is formed on the lead frame.