JP2641746B2 - Molded chip tantalum solid electrolytic capacitor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded chip tantalum solid electrolytic capacitor in which a capacitor element and a cathode element are connected via a fuse and packaged with a mold resin.

[Conventional technology]

Conventionally, a tantalum solid electrolytic capacitor has been used in which a tantalum metal is used as an anode body, an oxide film is formed on the surface by anodic oxidation to form a dielectric, and a solid electrolyte is closely contacted with the oxide film as a cathode. . Such a tantalum solid electrolytic capacitor is sometimes provided as a chip capacitor that is provided with a molding resin, has a terminal structure suitable for face bonding, and is incorporated in a hybrid IC circuit.

In such a molded chip tantalum solid electrolytic capacitor, the capacitor element and the cathode terminal led out are connected via a fuse, and if a short circuit occurs due to reverse insertion into the set or overvoltage, the peripheral circuit There have been proposed ones that prevent burnout and the like and have improved safety. The present inventor has made several proposals for such a molded chip tantalum solid electrolytic capacitor.

FIG. 4 shows a basic configuration of a molded chip tantalum solid electrolytic capacitor (hereinafter, referred to as a “chip capacitor”) proposed by the present inventor earlier.

The chip capacitor includes a capacitor element 1, an anode lead 2 derived from the capacitor element 1, an anode terminal 3 connected to the anode lead 2, and a conductive bonding material 4 on the cathode layer surface of the capacitor element 1. And a cathode terminal 7 connected to the fuse 5 by a conductive bonding material 6 similar to the conductive bonding material 4 such that the anode terminal 3 and the cathode terminal 7 are led out. It is configured to be provided with an exterior and housed in the mold resin 8. An insulating plate 9 made of Teflon or the like is provided near the lead-out portion of the anode lead-out line 2 of the capacitor element 1.

The capacitor element 1 is formed by forming an oxide film on a tantalum powder molded and fired in a vacuum to form a dielectric,
An electrolyte such as manganese dioxide is formed on the surface of the oxide film, and a carbon layer and a cathode layer are further laminated. The anode lead 2 led out from the capacitor element 1 is made of tantalum metal. . The anode terminal 3 is made of nickel, nickel silver, 42 alloy, stainless steel, or the like, and subjected to solder plating under copper. The fuse 5 is made of a plate-like or linear low-melting alloy material, and the mold resin 8 is made of an epoxy resin or a silicone resin. Further, the conductive bonding materials 4 and 6 are, for example, a conductive adhesive or solder (including cream solder).

In the cathode layer on the surface of the capacitor element 1, an insulating coating layer 10 is formed at least at a portion facing the fuse 5 by dipping, coating, or pasting a sheet.

When the chip capacitor fails due to, for example, a short circuit in the capacitor element 1, a large current flows through the fuse 5 and the fuse 5 is blown. This prevents burning of other circuit components and the like when a short circuit occurs in the capacitor element 1 or the like. When the temperature of the capacitor element 1 rises to an undesired level,
The amount of heat from the capacitor element 1 is conducted to the fuse 5, whereby the fuse 5 is blown. In this manner, the fuse 5 also plays a role as a so-called thermal fuse, and prevents the capacitor element 1 from being burned out.

The above-mentioned insulating coating layer 10 is provided between the portion other than the end of the fuse 5 connected to the capacitor element 1 and the
It is provided to insulate from the surface and to secure the length of the effective portion of the fuse 5 necessary for obtaining the desired fusing characteristics. That is, when the fuse 5 comes into contact with the surface of the capacitor element 1, a current flows through the contact portion, so that the characteristics of the chip capacitor such as a change in capacitance and the fusing characteristics of the fuse 5 change. Therefore, when the insulating coating layer 10 is not provided, the characteristics of the chip capacitor and the fusing characteristics of the fuse 5 become unstable.

[Problems to be solved by the invention]

However, in the above-described chip capacitor, the fuse 5 is easily deformed. When the fuse 5 is connected to the capacitor element 1 and the cathode terminal 7, both ends thereof are securely connected to the capacitor element 1 and the cathode terminal 7. It is relatively difficult to locate parts. For this reason, workability at the time of manufacturing the chip capacitor cannot be improved, and the connection between the fuse 5 and the capacitor element 1 and the cathode terminal 7 cannot be made reliably and firmly. there were. Further, the connection between the fuse 5 and the capacitor element 1 by the conductive bonding material 4 is performed in a relatively small area, and therefore, the efficiency of transferring the heat from the capacitor element 1 to the fuse 5 is poor.
This fuse 5 could not reliably function as the above-mentioned thermal fuse.

Furthermore, since the insulating coating layer 10 is formed on the surface of the capacitor element 1, steps such as drying and curing of the insulating coating layer 10 are required during manufacturing.
There were problems such as an increase in man-hours.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned technical problems, improve workability during manufacturing, reduce the number of manufacturing steps, and prevent a defective connection of a molded chip tantalum solid electrolyte. The purpose is to provide a capacitor.

[Means for solving the problem]

In the molded chip tantalum solid electrolytic capacitor of the present invention, the fuse is folded back so that a heat-resistant insulating plate is sandwiched between both ends of the fuse, and one end of the fuse is connected to a capacitor element on one surface side of the heat-resistant insulating plate. The fuse is connected to the front surface, and the other end of the fuse is connected to the cathode terminal on the other surface side.

[Action]

According to the configuration of the present invention, the fuse is folded so that both ends are located on different surface sides of the heat-resistant insulating plate. Thus, the heat-resistant insulating plate is sandwiched between both ends of the fuse. One end of the fuse is connected to the surface of the capacitor element on one surface of the heat-resistant insulating plate, and the other end is connected to the cathode terminal on the other surface of the heat-resistant insulating plate. This allows the capacitor element and the cathode terminal to be connected via the fuse in a state in which both ends of the fuse and the heat-resistant insulating plate are laminated between the capacitor element and the cathode terminal. Become.

Therefore, when making connections at both ends of the fuse, a force is applied between the capacitor element and the cathode terminal in a direction approaching each other, so that a force is applied between the capacitor element surface and the one end of the fuse. Further, since the cathode terminal and the other end of the fuse can be brought into close contact with each other, each connection at both ends of the fuse can be made firmly and reliably.

Also, as a result of the above-described connection, the connection area between the capacitor element and the one end of the fuse can be made relatively large, so that the heat generated in the capacitor element is efficiently transmitted to the fuse. . This ensures that the fuse is blown not only when a large current flows through the fuse due to a short circuit of the capacitor element, but also when the capacitor element generates an undesired amount of heat. . The heat-resistant insulating plate prevents a short circuit between both ends of the fuse when the fuse becomes hot and melts.

Furthermore, since the fuse can secure a sufficient effective length to obtain a desired fusing characteristic on the other surface side of the heat-resistant insulating plate, it is not necessary to form an insulating coating layer or the like on the surface of the capacitor element. The number of manufacturing steps can be reduced.

〔Example〕

FIG. 1 is a sectional view showing a basic configuration of a molded chip tantalum solid electrolytic capacitor (hereinafter, referred to as a "chip capacitor") according to an embodiment of the present invention. FIG. 2 is an exploded perspective view thereof. FIG. 3 is a perspective view showing a state before applying a mold exterior. This chip capacitor is formed by forming an oxide film on a tantalum powder molded and baked in a vacuum to make it a dielectric, forming an electrolyte such as manganese dioxide on the surface of this oxide film, and further forming a carbon layer and a cathode. It has a capacitor element 11 formed by stacking layers. An anode lead wire 12 made of tantalum metal is led out of the capacitor element 11, and an anode terminal 13 is welded to the anode lead wire 12. The anode terminal 13 is obtained by plating nickel, nickel silver, 42 alloy, stainless steel, or the like with copper under solder. An insulating plate 14 made of Teflon or the like is provided near the lead-out portion of the anode lead-out wire 12 of the capacitor element 11.

The cathode layer on the surface of the capacitor element 11 has a fuse 15 made of a low melting point alloy material, for example, in the form of a plate having a thickness of 30 to 70 μm.
Are connected by a conductive bonding material 16. The conductive bonding material 16 is a conductive adhesive or solder (including cream solder). The fuse 15 is folded back so that both end portions 15a and 15b are located on different surfaces of a heat-resistant insulating plate 17 made of a resin material such as polyimide, polyamide, fluorine, silicone, or epoxy. Have been to be. In this manner, the heat-resistant insulating plate 17 is sandwiched between both ends 15a and 15b of the fuse 15, so that one end 15a of the fuse 15 is connected to the capacitor on one surface side of the heat-resistant insulating plate 17. This means that it is connected to the surface of the element 11.

On the other surface side of the heat-resistant insulating plate 17, the fuse
The other end 15b of 15 is connected to the cathode terminal 18 by a conductive bonding material 19 similar to the conductive bonding material 16. In this manner, both ends 15a and 15b of the fuse 15 and the heat-resistant insulating plate 17 are laminated between the capacitor element 11 and the cathode element 18, and in such a state, the cathode terminal 18 is connected to the capacitor element.
11 is connected to the surface via a fuse 15. In connection with the bent portion 15c of the fuse 15, a hot melt material mainly composed of polypropylene, ethylene vinyl acetate (EVA), polyamide nylon, or the like, or a low-temperature molten polymer material 20 such as a thermoplastic resin is disposed. You. This low-temperature molten polymer material 20 softens at 140-220 ° C.
It is desirable to liquefy at ~ 290 ° C.

FIG. 3 shows a state in which the above-described respective connections have been made. From this state shown in FIG. 3, a mold exterior with a molding resin 21 such as an epoxy resin or a silicone resin is applied. At this time, the anode terminal 13 and the cathode terminal 18 are led out of the mold resin 21. The temperature conditions required for the low-temperature molten polymer material 20 are set in consideration of the temperature of the mold resin 21 at the time of this mold exterior, the melting temperature of the fuse 15, and the like.

In the above-described chip capacitor, for example, when a short circuit occurs in the capacitor element 11, a large current flows through the fuse 15, and the heat generated at this time causes the fuse 15 to start melting from the bent portion 15c. At this time, the low-temperature molten polymer material 20 disposed in relation to the bent portion 15c also melts and liquefies.
The melted fuse 15 is generated by an electric current flowing through the fuse 15, and is eluted and dispersed in the liquefied low-temperature molten polymer material 22 by electromagnetic force or the like acting on the bent portion 15c. Fusing is achieved.
In this way, it is possible to prevent the peripheral circuit components from being burned out, so that the safety is remarkably improved. Since the heat-resistant insulating plate 17 is disposed between both ends 15a and 15b of the fuse 15, when the fuse 15 becomes high temperature and melts, short-circuiting between both ends 15a and 15b of the fuse 15 is prevented. Absent.

In assembling the above-described chip capacitor, the fuse 15 is wound around a heat-resistant insulating plate 17 and fixed with, for example, an adhesive (not shown), and then both ends 15a and 15b of the fuse 15 and the surface of the capacitor element 11 And the respective connections with the cathode terminal 18 are made. At the time of this connection, a force in a direction approaching each other is applied to the capacitor element 11 and the cathode terminal 18 by using, for example, a pair of elastic bodies (not shown).
The one end 15a of the fuse 15 and the capacitor element 11 and the other end 15b and the cathode terminal 18 are in close contact with each other. In this way, each connection at both end portions 15a and 15b of the fuse 15 can be made firmly and securely, and the fuse 15 can be connected during the connection work.
Therefore, each connection can be made with good workability.

Further, since the surface of the capacitor element 11 and the one end 15a of the fuse 15 are in close contact with each other, the connection area between them can be increased, so that the amount of heat from the capacitor element 11 is efficiently transmitted to the fuse 15. Will be able to do it. Thus, when the capacitor element 11 generates an undesired amount of heat, the fuse 15 can be surely blown to prevent the capacitor element 11 from burning out. That is, in this chip capacitor, the fuse 15 can sufficiently serve as a so-called thermal fuse.

Furthermore, in the chip capacitor of this embodiment, the portion on the other surface side of the heat-resistant insulating plate 17 of the fuse 15 is insulated from the surface of the capacitor element 11, so that the desired portion of the effective portion of the fuse 15 on the other surface side is desired. The required length for obtaining the required fusing characteristics can be secured. As a result, it is not necessary to form an insulating coating layer on the surface of the capacitor element as in the conventional chip capacitor shown in FIG. 4, so that the number of manufacturing steps can be reduced.

〔The invention's effect〕

According to the molded chip tantalum solid electrolytic capacitor of the present invention, both ends of the fuse and the heat-resistant insulating plate around which the fuse is wound are between the capacitor element and the cathode terminal. The connection to the cathode terminal is established via the fuse. Therefore, when making connections at both ends of the fuse, a force is applied between the capacitor element and the cathode terminal in a direction approaching each other, so that a force is applied between the capacitor element surface and the one end of the fuse. Further, since the cathode terminal and the other end of the fuse can be brought into close contact with each other, each connection at both ends of the fuse can be made firmly and reliably. Moreover, the fuse is not deformed at the time of this connection, and the connection of the fuse can be performed with good workability.

Further, as a result of the above-described connection, the connection area between the capacitor element and the one end of the fuse can be made relatively large, so that the heat generated by blocking the capacitor is efficiently transmitted to the fuse. . As a result, not only when a large current flows through the fuse due to a short circuit of the capacitor element, but also when the capacitor element generates an undesired amount of heat, the fuse is reliably blown and the capacitor element is heated. Burning can be prevented.

Furthermore, since the fuse can secure a sufficient effective length to obtain a desired fusing characteristic on the other surface side of the heat resistant insulating plate, it is necessary to form an insulating coating layer or the like on the surface of the capacitor element. Therefore, the number of manufacturing steps can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a basic structure of a molded chip tantalum solid electrolytic capacitor according to one embodiment of the present invention.
FIG. 3 is an exploded perspective view, FIG. 3 is a perspective view showing a state before applying a mold package, and FIG. 4 is a cross-sectional view showing a basic configuration of a molded chip tantalum solid electrolytic capacitor previously proposed by the present inventors. It is. 11 ... Capacitor element, 15 ... Fuse, 15a ... One end, 15b ... Other end, 17 ... Heat resistant insulating plate, 18
… Cathode terminal, 20… Low temperature molten polymer material, 21… Mold resin

Claims (1)

(57) [Claims] 1. A molded chip tantalum solid electrolytic capacitor having a capacitor element and a cathode terminal connected via a fuse and covered with a mold resin, wherein the fuse is folded back and a heat-resistant insulating plate is sandwiched between both ends of the fuse. Wherein one end of the fuse is connected to the surface of the capacitor element on one surface side of the heat-resistant insulating plate, and the other end of the fuse is connected to the cathode terminal on the other surface side. Chip tantalum solid electrolytic capacitor.