JPH0268917A - tantalum solid electrolytic capacitor - Google Patents

Abstract

PURPOSE:To obtain a mold chip type solid tantalum capacitor with a fuse which is superior in reliability by mounting in advance an island like solder layer in a part of the surface of an electrolytic element, thereby connecting the fuse to the solder layer. CONSTITUTION:An electrolytic element 1 is constructed by laminating a semiconductor metal oxide layer and a cathode layer in order on an anode equipped with an anode deriving wire 4 and having a dielectric oxide film on the surface. An island like solder layer 8 is provided in advance on the cathode layer located on the surface of the electrolytic element 1 and a fuse 6 is connected between the solder layer 8 and a cathode terminal 3b. For example, the foregoing solder layer 8 consists of a low melting point alloy material which is Pb system alloy having a fusing point of 225 deg.C or more and is regarded as a material having a relatively high fusing point. After coating its layer with creamy solder, this device allows only a part of creamy solder to be maintained at a high temperature of 280-300 deg.C in 0.1-0.4sec by a hot air gun, infrared ray irradiation, and the like and then, its layer is formed by melting above solder. Both the solder layer 8 and fuse material 6 are joined with solder or a conductive bonding agent having a melting point which is equal to or lower than those of above two materials.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a molded tantalum solid electrolytic capacitor which has a built-in fuse to provide high safety.

BACKGROUND OF THE INVENTION Recently, with the increasing use of chips in the field of industrial equipment, there has been a demand for high reliability with added safety. In particular, the tantalum solid electrolytic capacitor may be short-circuited due to reverse insertion into a tantalum solid electrolytic capacitor set, overvoltage trouble, etc. In order to prevent circuit burnout that occurs at this time, molded chip tantalum solid electrolytic capacitors with built-in fuses and parallel type and axial type molded tantalum solid electrolytic capacitors with round wire leads are increasingly being used.

A conventional molded chip mental solid electrolytic capacitor with a fuse and a molded tantalum solid electrolytic capacitor with a fuse will be described below.

FIG. 3 is an assembled perspective view of a conventional molded chip mental solid electrolytic capacitor with a fuse, and FIG. 4 is an assembled perspective view of a conventional molded tantalum solid electrolytic capacitor with a fuse.

In each case, 1 is a capacitor element, 2 is an insulating plate made of Teflon, 4 is a tantalum wire as an anode lead wire, and 6 is a conductive bonding material made of cream solder, conductive adhesive, or the like. Reference numeral 6 indicates a fuse material, and 9 indicates a full-coverage solder, which is a Pb alloy material having a melting point of 266°C or higher.

Furthermore, 32L in Figure 4 is the external anode terminal, which is made of nickel.

It is constructed by processing a thin plate of iron, nickel silver, 42 alloy, stainless steel, etc. with copper under-solder plating.

3b is an external cathode terminal, and the material is the same as that of the external anode terminal 3a. 7 is an insulating coating material made of epoxy resin or silicone resin.

Also, 3 in Figure 6 is the external cathode terminal, which is made of nickel.

It is a round wire made of iron, nickel silver, 4270I, stainless steel, etc. with copper under solder plating.

The functions of the molded chip tantalum solid electrolytic capacitor with a fuse and the molded tantalum solid electrolytic capacitor with a fuse constructed as described above will be explained below.

-1f, when the capacitor element 1 is short-circuited, a current flows through the fuse material 6, and when the current exceeds the fusing current, the fuse material 6 is blown out. Furthermore, even if the temperature of the capacitor element 1 rises, the current is cut off due to the destruction of the fuse connection or the melting of the fuse, thereby preventing the capacitor element 1 from burning out.

Problems to be Solved by the Invention However, in the above-mentioned conventional configuration, the entire surface of the capacitor element coated with a cathode layer such as silver paint is coated with solder at an optimum working temperature of 280"C or higher, so the silver paint layer is exposed to high-temperature solder. The problem was that it was eroded in the bath, resulting in peeling and severe wear and tear.

In addition, due to the heat stress during solder coating, leakage current,
There was a problem that Tan δ etc. became large.

Further, by soldering the capacitor element, the shape of the capacitor element becomes large, exposure and resin cracking occur, and a large amount of solder is used, which is disadvantageous in terms of cost.

Note that in order to simultaneously melt the cream-like high-temperature solder and join the fuse material 6 without using the full-coverage solder 9 on the capacitor element 1, it is necessary to hold the fuse material 6 at high temperature for a long time. 6 was deformed and there was a great risk of it being cut.

Furthermore, since the optimum working temperature is high and narrowly limited, there is also the problem of strict management conditions.

The present invention solves the above conventional problems, and aims to provide a highly reliable molded chip tantalum solid electrolytic capacitor with a fuse and a molded chip tantalum capacitor with a fuse.

Means for Solving the Problems In order to achieve this object, the present invention provides an island-shaped solder layer in advance on a part of the surface of a capacitor element, and connects a fuse to the solder layer.

Effect: This configuration reduces the thermal stress on the capacitor element, stabilizes the fuse connection, and prevents deformation.

The risk of cutting can be prevented and miniaturization is possible, which is advantageous in terms of cost and work.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows an assembled perspective view of a chip tantalum solid electrolytic capacitor with a fuse in one embodiment of the present invention.

In FIG. 2, 1 is a capacitor element, and 2 is an insulating plate made of Teflon. 31L is an external anode terminal, and 3b is an external cathode terminal, both of which are made of nickel, iron, nickel silver, 4270 steel, or stainless steel with at least a copper base.
It is a processed thin plate with a thickness of about 0.1 that has been subjected to solder plating. 4 is an anode lead-out wire, which is made of tantalum wire. 6 is a conductive bonding material, and 6 is a fuse material made of an alloy material having a relatively high melting point. Reference numeral 7 denotes an insulating coating material made of epoxy or silicone type, and 8 denotes an island-shaped solder layer, which is made of a Pb type alloy material with a relatively high melting point and a relatively high melting point of 266° C. or higher.

The operation of the fuse-equipped chip tantalum solid electrolytic capacitor of this embodiment constructed as described above will be described below. First, the capacitor element 1 is made by molding tantalum powder and firing it in a vacuum to form a dielectric oxide film, further forming an electrolyte such as manganese dioxide on the surface, and then laminating a carbon layer and a cathode layer. The anode lead wire 4 of this capacitor element 1 is welded to the external anode terminal 31L. One end of the fuse material 6 is connected to the external cathode terminal 3b by a bonding material, spot welding, or the like.

The other end of the fuse material 6 is joined to a solder layer 8 previously provided on a portion of the surface of the capacitor element 1.

The island-shaped solder layer 8 is a coating layer that has a metallic luster and is made by applying creamy solder and melting it by heating.

Heating can be performed by using a hot air gun, infrared irradiation, laser beam irradiation, heater chip heating, etc.

To form this solder layer 8, only the cream solder portion is held at a high temperature of 280'C to 360C for 0.1 to 0.4 seconds, so that the entire capacitor element 1 is not subjected to thermal stress. The solder layer 8 and the fuse material are equivalent to each other,
Alternatively, they are bonded using a bonding material having a lower melting point, such as solder or conductive adhesive. The product is further packaged with an epoxy or silicone mold resin.

In the solid electrolytic capacitor with a fuse made in this way, the capacitor element 1 may be short-circuited and a large current may flow, or the fuse material 6 may be caused by heat generation in the capacitor element 1.
The operation to prevent the circuit from being burnt out due to melting is the same as in the conventional example.

As described above, according to this embodiment, the fuse connection to the cathode layer coated on the capacitor element is stabilized, and the leakage current and
There is no change in characteristics such as T2Lnδ, it is possible to prevent appearance defects such as exposure and resin cracking, and it is also possible to increase the capacity. Furthermore, improvements can be made in terms of cost and work.

FIG. 2 shows a perspective view of a molded tantalum solid electrolytic capacitor with a fuse in another embodiment of the present invention, and corresponds to FIG. 4.

Effects of the Invention As described above, the present invention achieves
The cathode layer on the capacitor element is not eroded, and the connection strength is increased and stabilized. Moreover, since the capacitor element is not subjected to thermal stress, high-quality products with no characteristic deterioration can be produced. In addition, there is no exposure or resin cracking, and the appearance is improved.

In addition, the amount of solder can be saved, which is advantageous in terms of cost, and it has better heat conduction than cream-like solder simultaneous melting assembly, does not cause fuse deformation, and stabilizes working conditions.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a chip tantalum solid electrolytic capacitor according to an embodiment of the present invention, FIG. 2 is a perspective view of a molded tantalum solid electrolytic capacitor according to another embodiment of the present invention,
FIG. 3 is a perspective view of a conventional chip tantalum solid electrolytic capacitor with a fuse, and FIG. 4 is a perspective view of a conventional molded tantalum solid electrolytic capacitor. 1... Capacitor element, 32L... External anode terminal, 3b... External cathode terminal, 3...
... External cathode terminal, 4 ... Anode lead wire, 6.
... Fuse material, 8 ... Solder layer. Name of agent: Patent attorney Shigetaka Awano and 1 other person 1st
Figure 2

Claims (1)

[Claims] A capacitor element is constructed by sequentially laminating a semiconductor metal oxide layer and a cathode layer on an anode equipped with an anode lead wire and having a dielectric oxide film on the surface, and an island is formed in advance on the cathode layer on the surface of the capacitor element. A tantalum solid electrolytic capacitor with a shaped solder layer and a fuse connected between the solder layer and the cathode terminal.