JPH10162714A - Chip fuse element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably fuse it by an abnormal current, restrain sensitivity to a rush current, and eliminate a fusing action by laying and forming a heating conductor film heated by abnormal current input and a fusible conductor film fused by heating of the heating conductor film at a melting point lower than this, on an insulating substrate. SOLUTION: Terminal electrodes are arranged on both ends of a cermaic substrate 1 where a glass glaze layer 2 is formed on a main surface, and a heating conductor film 3 using tungsten, molybdenum, silver or the like independently or using a high melting point metallic material of its alloy on the glass glaze layer 2 and a fusible conductor film 4 of a metallic material having a melting point lower than this, are connected in series to each other, and are laid. Selection and a shape of these materials are decided by fuse rating by considering heat conductivity of the glass glaze layer 2. For example, the shape is set so that it does not reach a melting point or more even if it is transmitted to the fusible conductor film 4 by heating of the heating conductor film 3 in a rush current not more than a rated current, and that the fusible conductor film 4 is reliably fused by being transmitted to the fusible conductor film 4 when the heating conductor film 3 is heated in a rated current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for
Chip fuses that are not easily blown by a large current generated instantaneously (hereinafter referred to as an inrush current) and stably blown by an overcurrent (hereinafter referred to as an abnormal current) lasting about 1/10 to 1 second. It is about structure.

[0002]

2. Description of the Related Art In a chip fuse element, a glass glaze layer is formed on a main surface of an insulating substrate, and terminal electrodes are formed on both ends in the longitudinal direction of the insulating substrate. A fuse conductor thin film made of a metal material such as aluminum is applied therebetween, and a protective glass layer is formed on the blown conductor film.

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

However, in such a chip fuse element in which the fuse conductor thin film between the terminal electrodes generates heat and blows out, the fuse blows normally with respect to an abnormal current and blows with an inrush current generated when the power is turned on. In order not to work, the metal material of the fuse conductor thin film,
It must be achieved by combining various conditions such as thickness and conductor pattern, and its control is very difficult.

Accordingly, the present applicant has firstly provided a heating conductor film which generates heat by the input of an abnormal current between two terminal electrodes;
A fusing conductor wire formed of a metal material having a melting point lower than the melting point of the heating conductor film and being blown by the heat of the heating conductor film was connected in series, and the fusing conductor wire was laid on the heating conductor film. A chip fuse element was proposed.

[0006] According to this structure, the conductor film (heating conductor film) which generates heat and the conductor wire (fusing conductor wire) which generates fusing action are separately provided, so that abnormal current and inrush current can be reduced. The corresponding heat generation characteristics can be easily controlled, and the fusing characteristics of the fusing conductor that is blown off by this heat generation can be easily controlled. It is possible to easily configure a chip fuse element to be blown.

However, even if a conductor film that generates heat and a conductor wire that generates a fusing function are separately formed, the fusing conductor is formed by a thin wire bonding wire such as aluminum. To do
There was a problem that the assembly process became complicated.

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, reduce sensitivity to an inrush current, and reduce the inrush current. An object of the present invention is to provide a chip fuse element that does not melt and has a simplified manufacturing method and structure.

[0009]

According to the present invention, there is provided a heating conductor film which generates heat by input of an abnormal current on an insulating substrate;
A fusing conductor film formed of a metal material having a melting point lower than the melting point of the heating conductor film, which is blown off by the heat generated by the heating conductor film, is adhered and formed, and the conductor film of the invention and the fusing conductor film are provided on an insulating substrate. And a chip fuse element connected in series between the two terminal electrodes.

[0010]

In the chip fuse element of the present invention, a conductor film that generates heat (heat-generating conductor film) and a conductor film that generates fusing (fused conductor film) are connected in series. In addition, the fusing of the fusing conductor film is performed by fusing when the heat of the fusing conductor film generated by the heat generating conductor film is higher than the melting point of the fusing conductor film from the heating conductor film to the fusing conductor film and from the substrate to the fusing conductor film. become. That is, in a very short time such as an inrush current, for example, a current generated between 0 and 0.5 μsec, even if heat is generated by the heating conductor film, it does not reach the point where the fusing conductor film is blown during that time. For an abnormal current flowing for a longer time, for example, for more than 0.1 to 1 second, heat is transmitted from the heating conductor film to the fusing conductor film, and the fusing conductor film can be fusing. Therefore,
Since a rush current or an abnormal current has occurred in the blown conductor film of the chip fuse element, the temperature rise characteristic due to the heat transmitted from the heating conductor film can be a downwardly convex curve.

Thus, it is possible to easily configure a chip fuse element that does not blow for an inrush current but blows for an abnormal current.

Further, since the heat-generating conductor film and the fusing conductor film are respectively adhered to the surface of the substrate, the bonding operation using an aluminum wire as in the prior art is not required, and the heat-generating conductor film and the fusing conductor film are formed in series. In addition, the manufacturing method and structure can be greatly simplified because the heating conductor film and the fusing conductor film can be directly covered like a normal chip fuse. become.

[0013]

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

FIG. 1 is a sectional view of a chip fuse for explaining an embodiment of the present invention, and FIG. 2 is a plan view of the chip fuse in a state where a terminal electrode and a protective overcoat layer are omitted. In the figure, 1 is an insulating substrate, 2 is a glass glaze layer, 3 is a heating conductor film, 4 is a fusing conductor film, 5, 5
Is a terminal electrode, and 6 is a protective overcoat layer.

The insulating substrate 1 can be exemplified by an alumina ceramic substrate or a glass-ceramic substrate, and has a substantially rectangular parallelepiped shape. On the surface of the insulating substrate 1, a glass glaze layer 2 for controlling thermal conductivity is formed. In addition, terminal electrodes 5 and 5 are formed at opposite ends of the insulating substrate 1. The terminal electrodes 5 and 5 are formed by laminating an Ag-based base metal conductive film formed by baking on the insulating substrate 1 and a surface plating layer such as Ni or solder applied on the base conductive film.

On the surface of the insulating substrate 1, two terminal electrodes 5,
The heating conductor film 3 and the fusing conductor film 4 are disposed between the five. Specifically, a fusing conductor film 4 on the surface of the insulating substrate 1 is adhered and formed, and one end thereof is connected to one terminal electrode 5 via an electrode pad 3c. Also,
The other end of the fusing conductor film 4 is connected to, for example, an electrode pad 3b which is also one end of the heating conductor film 3 in an overlapping manner. Also,
The electrode pad 3 a, which is the other end of the heating conductor film 3, is connected to the other terminal electrode 5. That is, between the terminal electrodes 5 and 5,
The electrode pad 3a, the fusing conductor film 4, and the heating conductor film 3 (electrode pads 3b, 3c) are arranged in a state of being respectively connected in series.

Here, the heating conductor film 3 is made of, for example, a high melting point metal material such as tungsten or its alloy, molybdenum or its alloy, Ag or its alloy, or the like.

The melting conductor film 4 has a melting point of the heating conductor film 3.
A material that is lower than the melting point of
For example, it is made of aluminum or the like.

Each of the conductor films 3 and 4 is formed by a resistance heating method,
It is formed using a thin film technique such as a sputtering method.
Further, the predetermined shape is achieved by using a mask or by a photolithography technique.

The selection of the material of the heating conductor film 3 and the fusing conductor film 4 and the shape thereof are determined variously based on the rating of the fuse in consideration of the thermal conductivity of the glass glaze layer 2. When the inrush current is equal to or less than the current, heat is generated from the heating conductor film 3 and the heat is transmitted to the fusing conductor film 4.
In order not to reach the melting point of the fusing conductor film 4 or more, and at the rated current, heat is generated from the heating conductor film 3 and the heat is transmitted to the fusing conductor film 4 so that the fusing conductor film 4 is surely blown. What is necessary is just to set a shape.

The heating conductor film 3 and the fusing conductor film 4 are covered with a protective overcoat layer 6. The protective overcoat layer 6 has, for example, a laminated structure of a low melting point glass layer and a moisture resistant resin layer covering the surface thereof. The low-melting-point glass layer is softened by the heat-generating action of the heat-generating conductor film 3, and when the fusing conductor film 4 is blown, the fusing portion is filled with a glass component to ensure high insulation after fusing.

According to the above configuration, the two terminal electrodes 5,
When a normal current flows between the wires 5, the flow of the current is allowed through the heating conductor film 3 and the fusing conductor film 4.

When a rush current generated when the power is turned on flows between the two terminal electrodes 5, 5, the heating conductor film 3
Is very short, for example, 0.5 μsec, and even if this heat is transmitted to the fusing conductor film 4 side, the temperature does not rise to such an extent that fusing occurs in the fusing conductor film 4. Allow current flow.

Further, when an abnormal current of about 0.1 to 1.0 second flows, heat is generated in the heat generating conductor film 3, and the heat is directly transmitted to the fusing conductor film 4 side, and further, through the glass glaze layer 2. As a result, the temperature becomes equal to or higher than the melting point of the fusing conductor film 4 and the fusing conductor film 4 is blown, whereby the flow of the current is interrupted.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventor conducted an experiment in order to confirm the effect of the chip fuse element having the above-described structure based on the finite element method.

First, the structure of the chip fuse element has a width of 1.
A substrate 1 made of alumina ceramic having a thickness of 25 mm, a length of 2.0 mm and a thickness of 0.49 mm (thermal conductivity 16 W / m · K, specific heat 0.8 J / g · k,
On the surface of density 3.6g / cm3), width 1.0mm, length 1.3mm, thickness
Glaze glass layer 2 of 0.013mm (thermal conductivity 0.5W / m · K,
A specific heat of 1.2 J / g · k and a density of 4.0 g / cm 3) were formed, and a heat-generating conductive film 3 made of tungsten metallization having a thickness of 10 μm was formed on the surface thereof. More specifically, a substantially rectangular electrode pad of 0.4 mm in the longitudinal direction and 0.6 mm in the width direction made of Ag or the like is formed at three positions at both ends and the center in the longitudinal direction of the substrate 1. And a pad having a width of 0.2 mm. After that, between the center pad and the other pad, 0.2mm width, 0.6mm length, 2.7μ thickness
Then, a fusing conductor film 4 made of aluminum is formed by vapor deposition. Thus, the heating conductor film 3 and the fusing conductor film 4 are connected in series via the pads. The pads at both ends of the surface of the substrate 1 become the terminal electrodes 5 and 5 formed at both ends of the substrate 1.

Thereafter, a protective overcoat layer 6 made of low-melting glass having a thickness of 10 μm is formed on the heating conductor film 3 and the fusing conductor film 4. Finally, end face electrodes 5 and 5 mainly composed of silver were formed at both ends in the longitudinal direction of the substrate 1 so as to be connected to pads at both ends.

The current fuse and the duration thereof are changed from 0.1 second to 2 seconds by using a current source between the terminal electrodes 5 and 5 of the chip fuse element having the above-described structure.
The conditions under which fusing occurs in the test were determined. As a result, when the duration was 2 seconds, the fusing occurred at 2A, whereas the fusing occurred at 2A.
In 1 second, no fusing occurred even at 10A.

The above-mentioned reason becomes clear by the transient heat conduction analysis using the finite element method. In the analysis, the calculated value of the current was 2 A.

As a result, as shown in FIG. 3, it can be understood that the temperature rise curve of the fused conductor film 4 made of aluminum draws a downwardly convex curve. In a conventional chip fuse that uses a fuse conductor film that also serves as a normal heat-generating action and a fusing action, the temperature-rise curve draws a sharply rising and convex curve,
If a sudden large current is applied irrespective of an inrush current or an abnormal current, there is a danger that the temperature will rapidly rise in the initial stage and fusing will occur. However, even if heat is generated abruptly on the heat-generating conductor film 3 side as in the above-described structure, the initial temperature rise becomes gentle on the fusing conductor film 4 side due to the time required for heat transmission and the like. Furthermore, the possibility of instantaneous fusing is low.

By arranging the heating conductor film 3 and the fusing conductor film 4 at a certain distance in this manner, it is difficult to blow against an inrush current at the time of turning on the power, and it is possible to reduce the fusing current.
A chip fuse that stably blows against an abnormal current that lasts for about / 10 to 1 second.

Further, structurally, a heat generating means for generating heat and a fusing means for fusing are provided on the glass glaze layer 2 of the insulating substrate 1 by using a thin film technique. The conductive film 4 is directly formed by deposition.
For this reason, the control of the conductivity of the heat transmitted from the heating conductor film 3 to the fusing conductor film 4 can be controlled by the material and thickness of the glass glaze layer, so that a chip fuse that meets the rating of the chip pues can be easily achieved.

Further, since a low-melting glass layer for covering and protecting the heating conductor film 3 and the fusing conductor film 4 can be formed collectively and easily by using a known film-forming technique, the size and the size of the low-melting glass layer can be reduced. The height and the manufacturing method can be simplified. Also,
In terms of characteristics, the fusing groove formed by fusing of the fusing conductor film 4 is filled with the low-melting glass component, so that after fusing, stable insulating properties are obtained and sparks and the like may occur. In addition, for example, there is little alteration such as oxidation of aluminum of the fused conductor film 4 and a highly practical chip fuse element capable of maintaining stable characteristics for a long period of time.

[0034]

As described above, according to the present invention, a chip which has a low sensitivity to an inrush current when the power is turned on and can stably cut off an abnormal current which lasts for a predetermined time or more. It becomes a fuse element, and furthermore, it becomes a highly practical chip fuse element having a small size, a low profile, stable characteristics, and stable characteristics, in which the temperature rise control of the fusing conductor film can be performed relatively easily.

[Brief description of the drawings]

FIG. 1 is a sectional view of a chip fuse element of the present invention.

FIG. 2 is a partial plan view of the chip fuse element of the present invention.

FIG. 3 is a characteristic diagram showing a temperature rise characteristic of a fused conductor film of the present invention obtained by a finite element analysis.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ceramic substrate 2 ... Glass glaze layer 3 ... Heat generation conductor film 4 ... Fusing conductor film 5 ... Terminal electrode 6 ... Protection overcoat layer

Claims (1)

[Claims] 1. A heat-generating conductor film that generates heat by the input of an abnormal current on an insulating substrate, and a fusing conductor film that is formed of a metal material having a melting point lower than the melting point of the heat-generating conductor film, and is blown by the heat generation of the heat-generating conductor film. Wherein the conductor film and the fusing conductor film of the present invention are connected in series between two terminal electrodes provided on an insulating substrate.