JPH1050184A - Chip fuse element - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To stably operate a fusing operation for an abnormal current and at the same time reduce sensitivity to an inrush current.
An object of the present invention is to provide a chip fuse element that is not blown by an inrush current. A heating conductor film (3) that generates heat due to an abnormal current input between a terminal electrode (2) and a metal material having a melting point lower than the melting point of the heating conductor film (3). This is a chip fuse element in which a fusing conductor 4 to be blown is connected and arranged, and the fusing conductor 4 is bridged on the heating conductor film 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip fuse element for protecting a circuit against abnormal current of a predetermined circuit.

[0002]

2. Description of the Related Art In a chip fuse element, a glaze layer is formed on a main surface of an insulating substrate, and terminal electrodes are formed at opposite ends of the insulating substrate at the same time. And a protective glass film is formed on the fusing conductor film.

In a chip fuse element, an abnormal current applied between terminal electrodes causes a fusing conductor film to generate heat. At this time, the thermal conductivity of the glaze layer was appropriately set so that the generated heat did not excessively escape to the insulating substrate side. Then, due to this heat generation, the fusing conductor film itself is disconnected, and acts as a fuse. Further, the fusing portion was filled with a protective glass film softened by heat generation to maintain high insulation after fusing.

For this reason, the calorific value of the fusing conductor film is appropriately controlled from the material and the conductor pattern, and the glaze layer,
It was necessary to appropriately control the properties of the protective glass film.

[0005]

However, in the conventional chip fuse element, the conductor between the terminal electrodes performs a heating action and a fusing action. It is very difficult to form a stable fuse element that operates and does not blow under the inrush current generated when the switching of the predetermined circuit is turned ON only by controlling the metal material, the conductor thickness, and the conductor pattern of the blown conductor film. Was difficult.

The present invention has been devised in view of the above-mentioned problems, and has as its object to stably operate a fusing operation for an abnormal current and at the same time reduce the sensitivity to an inrush current. Another object of the present invention is to provide a chip fuse element that is not blown by an inrush current.

[0007]

According to the present invention, a heat-generating conductor film that generates heat by the input of an abnormal current and a metal material having a melting point lower than the melting point of the heat-generating conductor film are provided between two terminal electrodes. A chip fuse element in which a fusing conductor that is blown by the heat of the heat generating conductor film is connected in series, and the fusing conductor is laid on the heat generating conductor film.

[0008]

In the chip fuse element of the present invention, a conductor film generating heat (heat generating conductor film) and a conductor generating fusing (fused conductor) are separately provided.
The heat generation characteristics with respect to the abnormal current and the inrush current can be easily controlled, and the fusing characteristics of the fusing conductor that is melted by the heat can be easily controlled. , It is possible to easily configure a chip fuse element that blows.

Generally, an inrush current has a steep current characteristic, and the time during which the current flows is instantaneous. For example, 50
It is about μsec. In comparison, the abnormal current is a current that flows for a longer time.

Therefore, if the resistance value (heat generation) of the heating conductor film is set so as not to blow the fusing conductor in consideration of the allowable rush current (current of a very short time),
Although heat is generated by the heating conductor against inrush current,
It is possible to prevent the heat generated by fusing the fusing conductor from being achieved.

Conversely, abnormal current (current for a relatively long time)
Then, heat is generated in the heating conductor film, and the fusing conductor can be blown.

At this time, if the melting point of the heat-generating conductor film is set to be higher than the melting point of the fusing conductor, the above-described control becomes very simple, the sensitivity to the inrush current is reduced, and a stable chip that operates only with the abnormal current is used. A fuse element can be achieved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a chip fuse element of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing a state in which a protective cover of the present invention is omitted, and FIG. 2 is a sectional structural view.

In the figure, 1 is an insulating substrate, 2 is a terminal electrode, 3 is a heating conductor film, 4 is a fusing conductor, and 5 is a protective cover.

The insulating substrate 1 is a ceramic substrate such as alumina. A glass glaze layer 11 having a low thermal conductivity is formed on a portion where the heat generating conductor film 3 is formed as required. Further, terminal electrodes 2 are formed at opposite ends of the insulating substrate 1.

The terminal electrode 2 is formed by baking a base metal conductor film 21 made of an Ag-based conductor on the insulating substrate 1, and is coated with a surface plating layer 22 such as Ni plating or solder plating on the base conductor film 21. Is being worn. One end of the heating conductor film 3 is connected to one terminal electrode 2,
One end of the fusing conductor 4 is connected to the other terminal electrode 2.

The heat-generating conductor film 3 is made of a material having a melting point higher than the melting point of the fusing conductor 4 and, in consideration of the amount of heat generated by the current characteristics of the rush current (current value / input time), its metal material is used. The pattern of the conductor film is determined. For example, using an Ag material, photolithography technology (deposition of an Ag thin film, application of a photoresist film, selective exposure, selective development of a photoresist film, selective etching of an Ag thin film, peeling of a photoresist film) Thereby, a pattern is formed in a predetermined shape.

As described above, one end of the heating conductor film 3 is connected to one terminal electrode 2, and the other end of the heating conductor film 3 is connected to the other end of the fusing conductor 4.

The fusing conductor 4 is made of a metal material having a melting point lower than at least the melting point (about 960 ° in the case of Ag) of the heat generating conductor film 3, for example, aluminum (melting point, eg, 600
° C). In addition, it is preferable to use an aluminum thin wire that is frequently used in wire bonding or the like so that the heat of the heat generating conductor film 3 can directly influence and complete insulation characteristics can be obtained after fusing.

One end of the fusing conductor 4 is connected to the other terminal electrode 2, and the other end is connected to the other end of the heating conductor film 3.

As a result, between the terminal electrodes 2 and 2, there is a conductor portion in which the heating conductor film 3 and the fusing conductor 4 are connected in series. In addition, the fusing conductor 4 has a wire shape and is arranged so as to bridge the upper portion of the heating conductor film 3.

The heating conductor film 3 and the fusing conductor 4 are
It is covered by a protective cover 5. The protective cover 5 has a housing shape with one side open to maintain a space around the fusing conductor 4, and the material and structure of the protective cover may be appropriately set.

In the present invention, the abnormal current of the circuit includes:
It operates stably as a fuse element, and the circuit switch O
The inrush current generated at the time of N needs to be set so as not to operate. Note that the characteristic of the inrush current is a current that sharply occurs in a very short time as compared with the abnormal current. For example, the time for determining the rated current of the chip fuse element is usually 1
In seconds, the inrush current is about 50 μsec.

Considering the difference between the characteristics of the two currents, the heat generation of the heat-generating conductor film 3 may be set so as not to reach at least the melting point of the fusing conductor 4 when an inrush current is applied. More specifically, the relationship between the thermal conductivity (heat storage characteristics) of the glass glaze layer 11 and the resistance value and pattern of the heating conductor film 3 is appropriately controlled to set the Joule heat in the heating conductor film 3 to a predetermined value. I just need.

Specifically, a borosilicate glass glaze layer 11 having a thermal conductivity of 0.836 W / m · K and a thickness of 20 μm is formed on the glass glaze layer 11, and the heating conductor film 3 is made of Ag. The conductor was set to have a thickness of 1.0 μm, the width of the conductor was set to 0.3 mm and the length of 2.5 mm.
mm, a fine wire diameter of 30 μm, and a maximum space of 0.5 mm on the heating conductor film 4.

Although this is one combination, the heat storage characteristics of the glass glaze layer 11 depend on the allowable rush current setting (without fusing) of the chip fuse element, the rated current of the abnormal current, and the rated fusing determination time. The heat-generating characteristics of the heat-generating conductor film 3 and the fusing characteristics of the fusing conductor 4 may be appropriately designed.

In this way, the blown conductor 4 blown only by the abnormal current is in the form of a wire, so that once blown, it is possible to maintain very high insulation properties.

In the conventional chip fuse element, the fuse element performs a heating operation and, at the same time, blows when the heat exceeds the melting point, that is, with one conductor,
Since both heat generation and fusing were performed, the sensitivity to inrush current was low, and it was very difficult to set the fuse element so that fusing characteristics could be stably obtained for abnormal current. On the other hand, in the present invention, as described above, since the conductor films (conductors) for the heat generation action and the fusing action are separately provided, the heat generation characteristic with respect to an inrush current or an abnormal current,
The control of the fusing characteristics becomes very simple, and as a result, a chip fuse element exhibiting extremely stable characteristics can be obtained.

FIGS. 3 and 4 show the tendency of the characteristics of the conventional chip fuse element and the chip fuse element of the present invention to be improved.

As is clear from FIGS. 3 and 4, when the energizing current is large, the fusing time is longer than in the conventional case (FIG. 3). In the region where the fusing time is relatively short, the Joule integral ( (The product of the square of the current and the input time of the current) (FIG. 4). this is,
It shows that the sensitivity becomes dull in a region where the fusing time is relatively short, which indicates that the inrush current can be tolerated.

Since the fusing conductor 4 is formed by using the wire bonding fine wire technique, a fusing conductor connection pad 31 is formed on the other end of the heating conductor film 3 to improve the wire bonding bonding property. It is important to achieve a stable connection of the conductor 4.

[0033]

As described above, in the chip fuse element of the present invention, the fuse operation, that is, the heating operation and the fusing operation due to the heating are configured by separate conductor films or conductors, respectively, so that the sensitivity to the inrush current is reduced. A chip fuse element that is low and can operate stably as a fuse against an abnormal current can be easily configured.

[Brief description of the drawings]

FIG. 1 is a perspective view of a chip fuse element of the present invention in a state where a protective cover is omitted.

FIG. 2 is a sectional structural view of a chip fuse element of the present invention.

FIG. 3 is a characteristic diagram showing a relationship between a flowing current and a fusing time of a chip fuse element of the present invention and a conventional chip fuse element.

FIG. 4 is a characteristic diagram showing a relationship between a blow time and a Joule integral of a chip fuse element of the present invention and a conventional chip fuse element.

[Description of Signs] 1 ... Insulating substrate 11 ... Glaze layer 2 ... Terminal electrode 3 ... Heating conductor film 31 ... ..Connection pads 4... Fusing conductors 5... Protective cover

Claims (1)

[Claims] 1. A heating conductor film which generates heat by the input of an abnormal current between two terminal electrodes and a metal material having a melting point lower than the melting point of the heating conductor film, and is cut off by the heat generation of the heating conductor film. A chip fuse element comprising: a fusing conductor connected in series; and the fusing conductor being laid on the heating conductor film.