JPH10283891A - Thermal fuse material and electronic part using thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen the restrictions of selecting and producing conditions of a plating liquid, lower the cost, and miniaturize an electronic part by preventing a reaction of a glass powder even in the case a strongly acidic or a strongly alkaline plating liquid is used for forming a metal film by coating the surface of the glass powder with a resin film and then further with a metal film. SOLUTION: At first a silicone resin film 2 which can stand a strongly acidic or a strongly alkaline plating liquid is formed on the surface of a low melting point glass powder 1 having a composition consisting of 85 wt.% of PbO, 10 wt.% of B2 O3 , and 5 wt.% of SiO2 . After that, a Cu film 3 is formed on the surface of the silicone resin film 2 by a chemical plating method and further a Sn film 4 is formed by a substitution plating method to complete a thermal fuse material. Consequently, at the time when a Cu film 3 is formed on the low melting point glass powder 1, the restriction conditions of the plating are lessened and production is made easy. An electronic part produced by using such a material does not require any separate electronic part for a thermal fuse and the cost is lowered and the size can be miniaturized.

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]

In order to achieve this object, the present invention covers the surface of a glass powder with a resin film, and further applies a thermal fuse material having a metal film formed on the surface to the electrode surface of an electronic component. To form. When the temperature of the thermal fuse material reaches a temperature at which the glass powder melts, the resin film covering the surface thereof is thermally decomposed or decomposed by reaction with the glass component. The molten glass then reacts further with the metal film on its surface, breaking the conductivity of the metal film, thereby substantially insulating the thermal fuse material. Therefore, the energization of the electronic component thereafter is cut off, and the electronic component becomes safe.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is a thermal fuse material in which the surface of a glass powder is covered with a resin film and then the surface is further covered with a metal film. The surface of the glass powder is covered with a resin film because the surface of the glass powder is covered with a resin so that it can react with the glass powder even when a strong acid or strong alkaline plating solution is used to form a metal film on the surface. Therefore, the selection of the plating solution and the restrictions on the forming conditions can be reduced.

According to a second aspect of the present invention, the resin film component formed on the surface of the glass powder is a silicon resin. Silicon resin is excellent in acid resistance and alkali resistance and can be diluted with a solvent or the like, so that a thin film having a required thickness can be easily formed on the surface of glass powder.

According to a third aspect of the present invention, there is provided an electronic component in which a temperature fuse layer is formed on an electrode of the electronic component by using the thermal fuse material according to any one of the first and second aspects.
According to this configuration, under normal circumstances, sufficient conductivity is ensured by the metal film on the surface of the glass powder. However, when the electronic component is exposed to an abnormally high temperature at which the glass powder melts, the resin film on the surface thereof thermally decomposes or reacts with the molten glass, and the resin film is destroyed. Next, the melted glass further reacts with the metal film on the surface thereof to insulate the metal film, so that the energization of the electronic component can be cut off thereafter to enhance the safety.

(Embodiment 1) An embodiment of the present invention will be described below.

FIG. 1 is a view showing a cross section of a thermal fuse material of the present invention. In FIG. 1, 1 is 85% by weight of PbO,
B ₂ O ₃ is a low melting glass powder having a composition of 10 wt% and SiO ₂ of 5 wt%, and the surface thereof is covered with a silicon resin film 2, a Cu film 3 and a Sn film 4 in a layered manner.

The low-melting glass powder 1 generally elutes into a strong acid or strong alkaline solution. Therefore, in the plating step of forming the Cu film 3, if a plating solution having a pH of 8 to 9 is used, the Cu film 3 can be formed on the glass surface. Takes time. On the other hand, when the concentration of the plating solution is increased and a strongly alkaline plating solution having a pH of 12 to 13 is used, the Cu film 3 having a predetermined thickness can be formed in a short time, but the surface of the low melting point glass powder 1 is eluted. As a result, the Cu film 3 cannot be formed.

Therefore, in this embodiment, PbO is 85 wt.
%, B ₂ O ₃ is 10 wt%, and SiO ₂ is 5 wt%. On the surface of the low melting point glass powder 1, first, a silicon resin film 2 which can withstand a strong acid and a strongly alkaline plating solution is formed, and then the surface is formed. Then, a Cu film 3 was formed by a chemical plating method, and a Sn film 4 was further formed by displacement plating to complete a thermal fuse material.

Next, an electronic component using the thermal fuse material will be described. FIG. 2 is a cross-sectional view of the electronic component of the present invention. In FIG. 2, reference numeral 5 denotes a varistor element containing ZnO as a main component and Bi ₂ O ₃ , Co ₂ O ₃ , MnO _{2 and the} like as subcomponents. Electrodes 6a and 6b are provided on both main planes of the varistor element 5. After rosin and flux components are mixed with the temperature fuse material and applied on the electrodes 6a in a paste form, the mixture is heated to a temperature of about 250 ° C. The Sn film 4 formed on the surface of the low melting point glass is melted and the temperature fuse layer 7 is formed.
Was formed. Next, after connecting the terminal 8 to the surface of the thermal fuse layer 7 on the electrode 6b with solder 9, the entire electronic component was further covered with an epoxy resin 10 to produce an electronic component.

The varistor element 5 deteriorates and generates heat due to an abnormally high voltage or the like, and the melting temperature of the low melting
C., the low-melting glass powder 1 is melted, first destroying the inner silicon resin film 2, and then reacting with the Cu film 3.
Subsequently, it reacts with the Sn film 4 already in a molten state to cut off the conductivity. Thereby, the thermal fuse layer 7 formed on the electrode 6a is insulated. Therefore, thereafter, the current of the deteriorated varistor element 5 is cut off, and it becomes safe.

Although the thermal fuse layer 7 is formed on the surface of the electrode 6a in this embodiment, it may be provided on both surfaces of the electrodes 6a and 6b. Further, the metal film of the thermal fuse material is C
Not limited to u and Sn, but Pb, Ni, Pd, A
A metal such as g or Co may be used.

[0015]

As described above, as shown in the present invention, by covering the surface of the low-melting glass powder with the resin layer, it is possible to reduce the restrictions such as plating when forming a metal film on the surface of the low-melting glass powder. And the thermal fuse material can be easily produced. Further, since the electronic component using the thermal fuse material of the present invention does not need to separately connect the electronic component for thermal fuse, it is possible to manufacture an inexpensive and small-sized electronic component with thermal fuse.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a thermal fuse material according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of an electronic component using the thermal fuse material according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Low melting glass powder 2 Silicon resin film 3 Cu film 4 Sn film 5 Varistor element 6a electrode 6b electrode 7 Thermal fuse layer 8 Terminal 9 Solder 10 Epoxy resin

Claims (3)

[Claims] 1. A thermal fuse material in which the surface of a glass powder is covered with a resin and then the surface is further covered with a metal film. 2. The thermal fuse material according to claim 1, wherein the resin is a silicone resin. 3. An electronic component having the temperature fuse material according to claim 1, provided on an electrode of the electronic component.