JPH10144191A - Thermal fuse material and electronic component using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To break current-carrying so as to secure the safety of an electronic component by breaking metal conductivity so as to be insulative when thermal fuse material formed by coating the outer surface of glass powder through metal film is fused so as to react with the metal film. SOLUTION: A varistor 1 is a sintered body composed of ZnO, as a main component, and Bi2 O3 , or the like, as a sub-component, electrodes 2a, 2b are provided on its surface. A terminal 4 is attached onto the electrode 2a via a thermal fuse layer, and is coated by resin 6. When the varistor 1 is deteriorated and heated by abnormal high voltage or the like, glass powder is low melting point lead glass powder so as to fuse at about 400 deg.C. The same reacts with the Cu metal film 8 of an inner layer, and further reacts with a Sn metal film 9 in a fused state so as to break its conductivity, and the thermal fuse layer 3 becomes insulative substantially. Thereafter, no current flows in the deteriorated varistor 1 so as to be safe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal fuse material and an electronic component using the same.

[0002]

2. Description of the Related Art In a conventional electronic component, there has been a problem that when an overcurrent flows through the electronic component, a temperature rise occurs, and it is necessary to cut off the power supply in a safe state.

[0003]

Conventionally, measures have been taken such as connecting a thermal fuse component to the electronic component separately in series. However, the use of a separate thermal fuse component is expensive and large. There was a problem that would be. Therefore, an object of the present invention is to solve these problems, that is, problems of becoming expensive and increasing in size.

[0004]

SUMMARY OF THE INVENTION To achieve this object, the present invention is to form a thermal fuse material by covering the outer surface of glass powder with a metal film. The thermal fuse material is provided on the electrodes of the electronic component to constitute the electronic component.

[0005]

DETAILED DESCRIPTION OF THE INVENTION The invention according to claim 1 of the present invention is a thermal fuse material in which the outer surface of a glass powder is covered with a metal film, and when the temperature becomes high and the glass powder is melted, the metal on the outer surface is melted. It reacts with the film, thereby cutting off the conductivity of the metal film and substantially insulating the metal film, so that the current is cut off thereafter, and the device is safe.

According to a second aspect of the present invention, the glass powder is formed of a low melting point glass,
Since the glass powder is made of low melting point glass, it can be melted at a low temperature and operated in a more secure state.

According to a third aspect of the present invention, the melting temperature of the glass powder is set to 700 ° C. or less, and the safety is ensured by operating at 700 ° C. or less to insulate the glass powder. It can be enhanced.

According to a fourth aspect of the present invention, the glass powder is formed of a lead-based glass or a bismuth-based glass.
The thermal fuse material according to any one of (1) to (3), which is a lead-based glass or a bismuth-based glass, reacts very well with the metal on the outer surface by melting, and reduces its conductivity. Insulation is smoothly performed.

According to a fifth aspect of the present invention, the metal film is made of Pb,
The method according to claim 1, comprising at least one of Sn, Ni, Cu, Pd, and Ag,
By covering the outer surface of the metal film with such a metal film, sufficient conductivity at normal times is ensured.

According to a sixth aspect of the present invention, in the case where the metal film has a multilayer structure, a metal film made of at least one of Pb, Sn, and Ag is formed as the outermost layer. It allows for soldering to the surface of the thermal fuse material.

According to a seventh aspect of the present invention, there is provided an electronic component provided with the thermal fuse material according to any one of the first to sixth aspects on an electrode of the electronic component. Sufficient conductivity is ensured by the metal film on the surface of the glass powder, and at high temperatures, the glass powder melts and reacts with the metal film to insulate it, preventing further energization and enhancing safety. Things.

According to an eighth aspect of the present invention, there is provided the electronic component according to the seventh aspect, wherein a terminal is provided on the thermal fuse material, wherein the thermal fuse material is interposed between the electrode and the terminal of the electronic component. By doing so, it is possible to ensure safety when the electronic component is heated.

(Embodiment 1) In the following, an embodiment of the present invention will be described with reference to the accompanying drawings. In FIG. 1, reference numeral 1 denotes a varistor (voltage non-linear resistance element), which contains ZnO as a main component and a sub-component as a varistor. It is a sintered body containing Bi ₂ O ₃ , Co ₂ O ₃ , MnO _{2 and the} like. Electrodes 2 a and 2 b are provided on the surface of the varistor 1, and a terminal 4 is attached on the electrode 2 a via a thermal fuse layer 3 by solder 5.
They are covered with a resin 6.

The thermal fuse layer 3 is made of a thermal fuse material as shown in FIG. That is,
The thermal fuse material is composed of 85% by weight of PbO and 1% of B ₂ O _3.
The surface of a lead-based glass powder 7 having a composition of 0% by weight and 5% by weight of SiO ₂ is chemically plated with Cu to form a Cu metal film 8, and a part of the surface is replaced with Sn to perform plating.
In this case, an n-metal film 9 is formed. The particle size of this thermal fuse material is about 10 μm. A rosin, a flux component, and the like are mixed with the temperature fuse material, applied in a paste form on the electrode 2a, and then heated to 250 ° C. to melt the Sn metal film 9 on the surface. After that, the terminal 4 is attached with the solder 5 and then covered with the epoxy resin 6 to produce the electronic component shown in FIG.

When the varistor 1 deteriorates due to abnormally high voltage and generates heat, the glass powder is a low melting point lead-based glass having a composition of 85% by weight of PbO, 10% by weight of B ₂ O _{3 and} 5% by weight of SiO _2. Since it is a powder, it melts at about 400 ° C., first reacts with the inner Cu metal film 8, and subsequently reacts with the Sn metal film 9 already in a molten state to cut off this conductivity, and substantially reduces the temperature fuse layer. 3 is insulated. Therefore, after that, no current flows through the deteriorated varistor 1 and the varistor 1 is safe.

Although the thermal fuse layer 3 is provided only on one side of the electrode 2a in the present embodiment, it may be provided on both sides.

(Embodiment 2) Next, another embodiment of the present invention will be described.

That is, another embodiment is a multilayer varistor shown in FIG. 3, in which the varistor 10 contains ZnO as a main component,
A sintered body containing Bi ₂ O ₃ , Co ₂ O ₃ , MnO _2, etc. as subcomponents, provided with an internal electrode 11 made of Ag—Pb, and an external electrode 12 made of Ag connected thereto;
The surface is covered with a thermal fuse layer 13. The thermal fuse material was produced in the same manner as in the first embodiment.

In the present embodiment, when the varistor 10 is deteriorated and generates heat after being mounted on a printed circuit board or the like,
As in the case of the first embodiment, the thermal fuse layer 13 is insulated, and thereafter, no current flows through the deteriorated varistor 10 and the varistor 10 is safe.

In this embodiment, the external electrodes 12
Although only the thermal fuse layer 13 is formed thereon, another metal layer such as Ni may be formed between the external electrode 12 and the thermal fuse layer 13. Further, another metal layer may be formed on the thermal fuse layer 13.

Although the thermal fuse layer 13 is provided on both sides of the external electrode 12 in the present embodiment, it may be provided on only one side.

[0022]

As described above, by manufacturing an electronic component using the thermal fuse material of the present invention, there is no need to separately connect a thermal fuse component, and thus an inexpensive and small-sized electronic component with a thermal fuse can be manufactured. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a sectional view of an electronic component according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the thermal fuse material.

FIG. 3 is a sectional view of an electronic component according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Varistor 2a electrode 2b electrode 3 Thermal fuse layer 4 Terminal 5 Solder 6 Resin 7 Glass powder 8 Cu metal film 9 Sn metal film 10 Varistor 11 Internal electrode 12 External electrode 13 Thermal fuse layer

Claims (8)

[Claims] 1. A thermal fuse material comprising an outer surface of glass powder covered with a metal film. 2. The thermal fuse material according to claim 1, wherein the glass powder comprises a low melting point glass. 3. The thermal fuse material according to claim 1, wherein the melting point of the glass powder is 700 ° C. or less. 4. The thermal fuse material according to claim 1, wherein the glass powder is made of lead-based glass or bismuth-based glass. 5. The metal film is made of Pb, Sn, Ni, Cu, P
5. The thermal fuse material according to claim 1, comprising at least one of d and Ag. 6. The metal film is composed of multiple layers, the inner layer is a metal film attached to the outer surface of glass powder, and the outer layer is Pb, Sn, Ag.
The thermal fuse material according to any one of claims 1 to 4, comprising at least one of the following. 7. An electronic component having an electrode provided with the thermal fuse material according to claim 1. 8. The electronic component according to claim 7, wherein terminals are provided on the thermal fuse material.