JPH0757615A - Electronic part for protection of resin-sealed circuit - Google Patents

Abstract

PURPOSE:To provide an electronic part having less heat generation when a fuse is melted, and having excellent melting characteristics. CONSTITUTION:Low fusing point metal is used for a fuse 3 to bridge and connect 4 lead terminals 1, 2 to each other. Around the fuse 3 comprising this low fusing point metal is insulation coated with silicone rubber 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-sealed type electronic component for circuit protection, and more particularly to a structure using a low melting point metal as a fuse for connecting terminals. It concerns excellent electronic components.

[0002]

2. Description of the Related Art In recent years, surface mounting (chip formation) is progressing in the field of electronic equipment, and as a resin-sealed type electronic component for circuit protection, there is a demand for a component that generates particularly little heat.

In a circuit protection electronic component, the fuse connecting between its lead terminals is blown by the fact that the fuse is heated and melted when an overcurrent more than a permissible amount flows to the fuse, and the fuse is broken. In this process,
The ambient temperature of the fuse is determined by the melting point of the fuse wire, heat conduction to the resin in contact with the periphery of the fuse, heat conduction from the terminals connected to the fuse, etc., but the most influential point is the melting point of the fuse. Yes, in the case of commonly used fuse wires such as aluminum and copper,
Since the melting point is close to 1000 ° C., the temperature rise of the electronic component body is large and the influence on the printed circuit board is not small.

Therefore, in the resin-sealed circuit protection electronic component, the temperature rise is avoided by limiting the range of use so that the absolute value of the current that is blown by the overcurrent is several times the rated current or more. I am trying.

[0005]

However, when the above-mentioned metal having a high melting point is used as a fuse, there is a problem that the external shape becomes large in order to suppress the temperature rise, which is against the demand for miniaturization.

The present invention has been obtained as a result of a study for the purpose of solving the problems in the conventional electronic components described above.

[0007]

That is, the present invention is characterized in that, in an electronic component for circuit protection, a low melting point metal is used as a fuse for bridging the terminals.

[0008]

The electronic component for resin-sealed type circuit protection of the present invention is
By using a low melting point metal as a fuse for bridging the terminals, the temperature rise of the fuse wire does not exceed the melting point and blows when an electric current exceeding an allowable amount flows in the electronic component, resulting in the electronic component. The temperature rise can be suppressed to a low level.

As the low melting point metal fuse wire, lead, tin,
The melting point of zinc or alloys thereof, or alloys thereof with silver, antimony, indium, etc., is 250-
The thing of about 400 degreeC is used.

[0010]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view showing an internal structure of a circuit protection electronic component of the present invention, and FIG. 2 is an explanatory view showing a state of the electronic component after a fuse is blown. In the figure,
Reference numerals 1 and 2 denote lead terminals. A fuse wire having a melting point of about 300 ° C. (for example, a diameter of 0.1) is formed between the lead terminals 1 and 2 by using an alloy of tin, lead and silver as a low melting point metal.
mm) 3 are bridge-connected 4 by welding. In addition to welding, this connection may be fixed with solder or a conductive adhesive.

Then, the liquid silicone rubber 5 was coated around the fuse wire 3 by potting to form a fuse element. After the silicone rubber 5 is cured, an insulating resin 6 made of epoxy resin or the like is insulated by means of transfer molding or the like, and the lead terminals 1 and 2 are further bent in a U-shape to form an electronic component for circuit protection. Is completed.

When a current exceeding the permissible current flows through the completed electronic component for circuit protection, the fuse wire 3 generates heat, and the outer periphery resin 6 such as a silicone rubber 5 and an epoxy resin that covers the surroundings. The heat is transmitted to the electronic component, and the temperature of the entire electronic component rises while keeping the balance between the heat generation of the fuse wire 3 and the heat radiation to the outside. However, since the fuse wire is made of a material having a low melting point, the fuse wire is blown without increasing the temperature above the melting point, and the current is surely cut off. Further, at that time, the number of cross-links of the silicone rubber 5 covering the periphery of the fuse wire 3 is lowered by heat and softens to become a liquid to cover the fuse 3, so that the blow fuse 3a as shown in FIG. In the liquid silicone rubber, the melting tip is rounded, and is fused into a substantially spherical shape by the surface tension of itself.

As described above, with respect to the electronic component A according to the present embodiment that uses the low melting point metal as the fuse wire and the conventional electronic component B that uses the aluminum wire as the fuse wire, the temperature rises until the respective fuses are blown. The result shown in FIG. 3 is obtained, which shows that the electronic component B of the conventional example has a high temperature, whereas the electronic component A of the present example has a melting temperature of the fuse wire. It is shown that the effect of the fuse wire made of a low melting point metal is great, since it has a small effect on the printed circuit board and other electronic parts during mounting.

[0014]

As described above, the electronic component of the present invention has a structure in which a low melting point metal is used for the fuse wire connected between the lead terminals, so that the temperature rise when a current more than the allowable amount flows Can be kept low.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an internal structure of a resin-sealed circuit protection electronic component of the present invention.

FIG. 2 is an explanatory diagram showing an internal state of the electronic component for resin-sealed circuit protection according to the present invention after the fuse is blown.

FIG. 3 is a diagram showing the temperature rise characteristics of the electronic component of the present invention and a conventional electronic component when the fuse is blown.

[Explanation of symbols]

 1 lead terminal 2 lead terminal 3 fuse wire 3a fused fuse 5 silicone rubber 6 exterior resin

Claims (1)

[Claims] 1. A fuse for bridging between terminals in a resin-sealed electronic component for circuit protection, which opens a circuit when a current exceeding an allowable amount flows in order to prevent overcurrent breakdown of a circuit component. An electronic component for resin-sealed circuit protection, characterized in that a low melting point metal is used as the material.