JPH0896694A - Chip type current fuse - Google Patents

Abstract

PURPOSE: To improve a fusing characteristic and a manufacturing yield by arranging a cover member made of heat resistant insulating material at the joining portion of a fuse element so as to touch it or be close to it. CONSTITUTION: A fuse element 4 is temporarily fitted between spare electrodes 10A, 10A of both ends 7 on the hollow recessed portion 6 of an insulating base 1 so as to be suspended. A cover member 15 is, for instance, a square member of an alumina insulator same as the base 1, and is provided with the recessed portion 6, and its both ends 17 are respectively joined to the ends 7 of a main body. The member 15 is arranged on a joining portion of the element 4 and the electrode 10A so that its surface touches the electrode 10A. That is, the fine wire-like element 4 is suspended on the portion 6 of the square base 1 having the portion 6, and the member 15 made of heat resistant insulating material is arranged at the element joining portion so as to touch it or be close to it. Thereby, the heat generation of the fuse element joining portion escapes to the member 15 so that the heat generation of the joining portion is suppressed, characteristics in short circuit shutdown, rated fusion, and the like become stable and a manufacturing yield can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip type current fuse, and more particularly to a microminiature chip type fuse which can be surface-mounted on a printed wiring board or the like.

[0002]

2. Description of the Related Art Actual Kaihei No. 5-69847, Actual Fair 1-3
Japanese Patent Publication No. 0779 discloses an example of the above-mentioned chip-type fuse. This fuse is configured by forming a recess in the upper surface of a rectangular insulating base, filling the recess with an organic insulating material having a low melting point, and disposing a wide fuse element along the organic insulating material. There is. According to such a fuse, a chip-type fuse without an end cap is realized. However, since a wide metal resistance coating layer is continuously provided on the surface of the organic insulating material layer, its structure is slightly complicated, and its fusing property is complicated because the metal resistance coating is involved.

On the other hand, the applicant of the present invention has proposed a chip-type fuse having the structure shown in FIG.
No. 258, Japanese Utility Model Application No. 5-40259, utility model registration application, etc.). 5A is a vertical sectional view, and FIG. 5B is a side sectional view. The insulating substrate 1 is a heat-resistant insulator such as an alumina insulator having a small size and having a recess 6. An upper surface electrode 10, a lower surface electrode 13, and a side surface electrode 11 are formed on both ends 7, 7 of the recess 6 in the vertical direction.

The fuse element 4 is suspended between the upper surface electrodes 10 at both ends 7 on the hollow recess 6 of the insulating base 1. The cover member 15 of the insulating base 1 is fitted on the upper surface of the insulating base 1 on which the fuse element 4 is arranged. As described above, since the fuse element 4 is a thin metal wire suspended in the hollow portion similar to the conventional tubular fuse, when a constant current corresponding to each diameter flows, the fuse element 4 is melted in the atmosphere and its melting capacity, The fusing characteristic is similar to that of the tubular fuse.

[0005]

However, in such a structure in which the fuse element and the terminal joint portion thereof are on the same plane, heat is generated at the joint portion due to a current such as short circuit interruption, short circuit interruption, rated fusing, etc. In some cases, stable characteristics may not be obtained.

The present invention has been made in view of the above circumstances, and is a chip-type fuse in which a fuse element and its terminal joint portion are on the same plane, and by improving the heat dissipation of the terminal joint portion, the fusing characteristics and An object of the present invention is to provide a chip-type fuse that can improve the manufacturing yield.

[0007]

In the chip-type current fuse of the present invention, a recess is provided in an intermediate portion of a rectangular insulating base, and electrodes communicating with terminal electrodes are provided at both ends of the recess. A fuse element made of a thin metal wire is suspended between the electrodes at both ends, and both ends of the fuse element form a joint with the electrode, and a heat-resistant insulator so as to come into contact with or come close to the joint of the fuse element. A cover member made of is arranged.

[0008]

Since the cover member made of a heat-resistant insulator is arranged in contact with or close to the joint portion of the fuse element, the heat generated at the joint portion can be effectively released to the cover member. Therefore, the temperature rise at the joint portion when the fusing current is applied is suppressed, and the fuse element is surely blown at the central portion which should be blown.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1A is a vertical sectional view of an insulating base body portion of a first embodiment of the present invention, and FIG. 1B is a side sectional view thereof. The insulating substrate 1 is a heat-resistant insulating material such as a microminiature rectangular ceramic having a concave portion 6, and an alumina insulator is used in this embodiment. A preliminary electrode 10A, a lower surface electrode 13, and a side surface electrode 11 are formed on both ends 7 of the recess 6 in the vertical direction by metal caps.

The fuse element 4 is temporarily fixed and suspended between the preliminary electrodes 10A, 10A at both ends 7 on the hollow recess 6 of the insulating substrate 1. The fuse element 4 is
For example, it is an ultrafine wire with a diameter of several tens of μm, and is composed of, for example, a Cu wire whose surface is coated with an Ag plating film, or an Ag wire alone. As described above, since the fuse element 4 is a thin metal wire suspended in the hollow portion similar to the conventional tubular fuse, when a constant current corresponding to each diameter flows, the fuse element 4 is melted in the atmosphere and its melting capacity, The fusing characteristic is similar to that of the tubular fuse.

FIG. 2A is a view in which a cover member 15 made of a heat resistant insulator is fitted on the insulating substrate 1, and FIG.
[Fig. 4] is a sectional view taken along line BB in (A). The cover member 15 is, for example, an alumina insulator rectangular member similar to the insulating base 1, and is provided with a recess 6, and both ends 17 thereof are respectively joined to both ends 7 of the main body.
The fuse element 4 is arranged on the joint with the preliminary electrode 10A so that the surface of the cover member 15 contacts the electrode. By fitting the cover member 15 of the chip-type current fuse on the insulating substrate 1, a box-type (chip-type) current fuse as shown in the drawing is formed.

FIG. 3A is a vertical sectional view of the second embodiment of the present invention, and FIG. 3B is a side sectional view taken along the line BB. Figure 4
(A) and (B) show the state in which the cover member is fitted. Also in this embodiment, the concave portion 6 is provided in the middle portion of the rectangular insulating substrate 1, and the upper surfaces of both end portions 7 of the concave portion 6 are
The upper surface electrode 10 communicating with the lower surface electrode 13 and the side surface electrode 11 is formed by a metal cap. Top electrodes 10, 1
A fuse element 4 made of a thin metal wire is suspended between 0, and both ends of the fuse element 4 are connected to the upper surface electrodes 10,
10 is joined by, for example, spot welding to form a joint.

In this embodiment, caps 15 made of a heat resistant insulator (eg, alumina insulator) are fitted so as to wrap both ends of the fuse element 4. The cap 15 also has a recess 6 in the middle thereof, and both ends 17 thereof are arranged so as to come into contact with or be close to the joint of the fuse element 4.

As described above, since the concave portion is provided in the intermediate portion of the rectangular insulating substrate and the fuse element is suspended on the electrode portion between both ends of the concave portion, the fuse element is blown in the air. Therefore, the fusing characteristic of the fuse element is the same as that of a normal tubular fuse. Since the terminal electrodes at both ends of the insulating base are provided with the terminal electrodes communicating with the joints, the chip-type surface-mountable ultra-small circuit breaker element is obtained.

Next, the operation of the chip-type current fuse of each of the above-mentioned embodiments will be described. The fuse element melts when a current of a certain value or more flows.However, the fuse element and its joint are on the same plane, and a heat-resistant insulator such as ceramic should be placed in contact with or close to the joint. When arranged, the heat generated at the joint is diffused into the heat resistant insulator. This amount of heat of diffusion is caused by the fact that the heat conductivity of the heat-resistant insulator is higher than that of an ordinary plastic case or the like. Also, as in the first embodiment of FIG.
It is more effective to bring the cover of the heat-resistant insulator into contact with the joint via the metal electrode.

If the heat generated in the joint portion when the fusing current of the fuse element is passed can be released to the cover, heat generation of the joint portion, that is, temperature rise can be suppressed. Therefore, the heat generated in the central portion of the fuse element 4 becomes large, and the fuse element 4 can be surely blown. Therefore, stable fusing characteristics can be obtained by short-circuit breaking, rated fusing, and the like. In addition, the fuse element 4
When an overcurrent flows to the fuse element 4, the fuse element 4 is blown in the air of the base body 1 and the hollow portions 6 and 6 of the cover.
Its fusing characteristics are exactly the same as a normal tube fuse,
Very stable fusing characteristics can be obtained.

[0018]

As described above, according to the chip type current fuse of the present invention, a thin wire-shaped fuse element is suspended above a concave portion of a rectangular insulating base having a concave portion and is made of an insulating material having heat resistance. The cover member is arranged so as to be in contact with or close to the fuse element joint portion. Therefore, the heat generated at the fuse element joint portion escapes to the cover member, the heat generated at the joint portion is suppressed, and stable characteristics such as short circuit interruption and rated fusing can be obtained. Therefore, according to the present invention, it is possible to stabilize the fusing characteristics of the microminiature chip-type fuse, reduce the defective rate in mass production, and improve the manufacturing yield.

[Brief description of drawings]

FIG. 1A is a vertical sectional view of an insulating substrate of a chip type current fuse according to a first embodiment of the present invention, and FIG. 1B is a side sectional view taken along the line BB.

2A is a vertical sectional view showing a state in which a cover member is fitted in the upper diagram, and FIG. 2B is a side sectional view thereof.

FIG. 3A is a vertical sectional view of an insulating substrate of a chip-type current fuse according to a second embodiment of the present invention, and FIG. 3B is a side sectional view taken along the line BB.

4A is a vertical sectional view showing a state in which a cover member is fitted in the upper diagram, and FIG. 4B is a side sectional view thereof.

5A is a longitudinal sectional view of an insulating substrate of a conventional chip-type current fuse, and FIG. 5B is a side sectional view thereof.

[Explanation of symbols]

 1 Insulating Substrate (Alumina Insulator) 4 Fuse Element 6 Recesses 7, 17 Both Ends 10 Top Surface Electrode 10A Spare Electrode 11, 12, 13 Electrode 15 Cover Member

Claims (1)

[Claims] 1. A fuse element comprising a rectangular insulating substrate provided with a concave portion at an intermediate portion thereof, electrodes provided at both ends of the concave portion communicating with terminal electrodes, and a metal thin wire provided between electrodes at both ends of the concave portion. A chip, wherein both ends of the fuse element form a joint with the electrode, and a cover member made of a heat-resistant insulator is arranged so as to come into contact with or close to the joint of the fuse element. Type current fuse.