JPH0676728A - Circuit protective element - Google Patents

Abstract

PURPOSE:To surely assure insulation after fusion of a metal wire. CONSTITUTION:This circuit protective element comprises a pair of electrodes 1, a metal wire 2 stretchingly connected between the electrodes l, a low melting point glass body 3 for covering the metal wire 2, synthetic resin 4 for covering the external surface of the low melting point glass body 3 and a molding resin body 5. The low melting point glass body 3 is formed of the power of inorganic components including low melting point glass or a powder aggregate. Since carbide is hardly produced with heat generation at the time of fusion of the metal wire 2, the state of insulation can be surely maintained without any residual resistance generated. The combustion fusion of a metal wire is surely performed with residual air contained within the powder of low melting point glass body or a powder aggregate. Synthetic resin to cover the low melting point glass protects the low melting point glass and the metal wire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit protection device for preventing overcurrent breakdown of a circuit.

[0002]

2. Description of the Related Art Conventionally, as a circuit protection element, a structure in which a flexible resin is coated on the outer periphery of a metal wire is known, as described in, for example, Japanese Utility Model Publication No. 58-38988.

[0003]

In the conventional circuit protection element having a structure in which a flexible resin is coated around the metal wire, insulation after fusing may be uncertain. The reason is that even if the metal wire is melted, the flexible resin around the melted part of the metal wire burns and carbonizes, and due to this carbide, etc., the insulation after melting cannot be sufficiently guaranteed. There is.

The present invention has been made in view of the above-mentioned problems, and a circuit in which carbonization does not occur around the metal wire when the metal wire is melted and the insulation of the metal wire after fusing can be surely guaranteed. A protective element is provided.

[0005]

A circuit protection element of the present invention is a circuit protection element for preventing an overcurrent of a circuit,
A pair of electrodes, a metal wire stretched and connected between predetermined positions of the electrode, and an inorganic component containing at least a low-melting glass that covers the outer periphery of the metal wire and at least the connection portion with the metal wire of the electrode. A low melting point glass body of powder or a powder aggregate, a synthetic resin covering the outer surface of the low melting point glass body on the side where the metal wire is stretched and connected to the electrode, the electrode, the metal wire, and the low melting point glass body, and And a molded resin body obtained by molding the synthetic resin and leading out the ends of the both electrodes.

[0006]

In the circuit protection element of the present invention, the low melting point glass body covering the entire outer periphery of the metal wire and at least the connection portion of the electrode with the metal wire is a powder or a powder aggregate in a rugged or dry state. Alternatively, a gap is formed between the powder aggregates, and the low melting point glass body is a powder or a powder aggregate and is porous, so that the burnout of the metal wire is ensured by the residual air or residual oxygen.

Further, since the low melting point glass body is an inorganic material, there is almost no carbide due to heat generation when the metal wire is melted, residual resistance does not occur, and insulation after melting of the metal wire can be ensured. .

Further, the synthetic resin covering the low melting glass buffer-protects the low melting glass and the metal wire.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the circuit protection device of the present invention will be described with reference to the drawings.

In FIGS. 1 and 2, reference numerals 1 and 1 denote a pair of electrodes formed of a conductive metal or the like for mounting a circuit protection element between circuits to be protected from overcurrent. 1, a metal wire 2 is stretched at a predetermined position of the electrodes 1, 1 between the tips, for example, by bending an intermediate portion in an arc shape and both ends of the metal wire 2 are connected to the electrodes 1, 1. . This metal wire 2 is a thin metal wire that melts with a predetermined current and has a wire diameter
An aluminum wire having a thickness of 10 μm to 50 μm, for example, 20 μm is wire-bonded by an ultrasonic bonder to the electrode 1,
Connected to 1. The metal wire 2 is not limited to an aluminum wire, and a metal thin wire capable of wire bonding, such as gold (Au), silver (Ag), or copper (Cu), may be used depending on the fusing current. it can.

Further, the outer periphery of the metal wire 2 and at least the connecting portion of the electrodes 1, 1 with the metal wire 2 are covered with a low melting point glass body 3. The low-melting glass body 3 is a powder or powder aggregate of an inorganic component containing at least low-melting glass, and the low-melting glass body 3 is a low-melting glass body having a lower melting point than the metal wire 2. And this low melting point glass body 3
When the paste is heated, it loses its viscosity due to the evaporation or volatilization of the solvent, and becomes a so-called completely dry or dry powder or powder aggregate.

The low melting point glass body 3 is formed, for example, by applying a paste containing lead-based low melting point glass, silica particles and a binder resin.

The silica particles have a thickening action in the SiO ₂ main component system known as Aerosil, for example. By virtue of this thickening effect, that is, the silica particles have silanol groups (SiOH) on their surface and tend to bond to each other by hydrogen bonds, which are relatively weak bonds and are separated again when a small external force is applied. , When the viscosity decreases and the state becomes stationary, a chemical bond is generated again, and this phenomenon causes a thixotropic effect. When this synthetic resin 4 is applied to the outer circumference of the metal wire 2, the metal wire 2 of both electrodes 1, 1 It does not spread from the connection portion to the outside, and the control adjustment of the application region of the low melting point glass body 3 becomes easy.

The binder resin is, for example, butyl carbinol of 93 to 98% by weight and ethyl cellulose of 2 to 3.
7% by weight are mixed and mixed with a stirrer for 4 hours under heating at 50 ° C. and kneading.

The low melting point glass paste is prepared by mixing 85% by weight of low melting point glass, 10% by weight of silica particles and 5% by weight of a binder resin with 30 to 40 g of butylcarbinol.

Further, the outer periphery of the low melting point glass body 3 on which the metal wire 2 is stretched in an arc shape and bulges is covered with a synthetic resin 4 in the form of a film or a layer. This synthetic resin is
For example, a solventless polyester resin is used. As the synthetic resin 4, a solventless epoxy resin, a solventless silicone resin, or the like may be used as long as it achieves the purpose of protecting the low melting point glass body 3 of powder or powder aggregate. However, it is necessary to adjust the synthetic resin 4 so that it does not penetrate into the powder of the low melting point glass body 3 or the inside of the powder aggregate.

The electrodes 1, 1, the metal wire 2, the low melting point glass body 3 and the synthetic resin 4 are covered with a mold resin body 5 made of a thermosetting resin such as an epoxy resin. The mold resin body 5 is not limited to the thermosetting resin as long as it has a heat resistance of about 230 ° C. or more and can withstand the soldering temperature during mounting, and can be made of any resin such as a thermoplastic resin. The electrodes 1, 1 projecting from the vicinity of the bottoms of both ends of the mold resin body 5 are arranged along both end faces of the mold resin body 5, and the other ends are opposed to each other on the upper surface of the mold resin body 5. It

Next, a method of manufacturing the circuit protection element 6 of the above embodiment will be described.

First, both ends of the metal wire 2 are welded by ultrasonic bonding between one ends of the pair of electrodes 1 and 1 having a desired shape formed on a lead frame (not shown). Next, a low melting point glass paste is applied to at least the entire outer circumference of the metal wire 2 and the connection portion of the electrodes 1 and 1 with the metal wire 2. Next, the outer periphery of the low melting point glass paste of the metal wire 2 is covered with a synthetic resin 4 such as a solventless polyester resin.
Cover with.

Then, the synthetic resin 4 is dried by heating or heating at a curing temperature of, for example, 150 ° C. for 1 hour. At the curing temperature of this synthetic resin 4, the viscosity of the low-melting glass paste is lost, and the low-melting glass body 3 becomes a so-called blunt or dry powder or powder aggregate, and a part of the outer periphery of the low-melting glass body 3 The synthetic resin 4 covering the resin is also cured to form a layer or film (FIG. 2).

Next, a mold resin body 5 is formed by molding with a thermosetting resin such as an epoxy resin so that the other ends of the electrodes 1 and 1 are led out to the outside. In this case, since the hardened synthetic resin 4 absorbs the pressure when the mold resin body 5 is injected, it does not affect the low melting point glass body 3 and the metal wire 2.

Then, the other ends (not shown) of the electrodes 1 and 1 are cut off at desired positions of a lead frame (not shown), and the other ends of the electrodes 1 and 1 are side surfaces of the molded resin body 5. It is in a state of being led to the outside. Then this electrode 1,
The other end portions (not shown) of 1 are bent and arranged along both end surfaces of the molded resin body 5 so that the other end portions face each other on the upper surface of the molded resin body 5. The surface mount type chip configuration shown in FIG. 1 is used. As described above, the surface-mounting type circuit protection element 6 of this embodiment can be manufactured.

Next, the operation of this embodiment will be described.

In the circuit protection element 6 of this embodiment, the synthetic resin 4 covering the low melting point glass body 3 buffer-protects the low melting point glass body 3 and the metal wire 2.

When an overcurrent flows between the electrodes 1 and 1,
The metal wire 2 is exothermicly melted and cut. At this time, the metal wire 2
Since the low-melting-point glass body 3 exists in the outer periphery of the metal wire 2 and at least the connection portion of the electrodes 1, 1 with the metal wire 2, the heat generated when the metal wire 2 is melted melts the substantially peripheral portion of the metal wire 2,
The low-melting glass body 3 enters the space portion 7 generated by fusing shown in FIG. 3, and the powder or the powder aggregate of the low-melting glass body 3 falls due to the tension releasing action of the metal wire 2.

Since the low melting point glass body 3 is an inorganic substance due to the heat generated when the metal wire 2 is melted, it melts in the vicinity of the melting area, but does not burn and does not form conductive carbide. Therefore, the metal wires 2a, 2a after fusing do not come into contact with each other, and further, since no carbide is generated, insulation after fusing can be completely guaranteed,
By mounting the circuit protection element 6 of the embodiment on, for example, a power supply line of a semiconductor device or a driver line through which a large current flows, an overcurrent in this device reacts reliably and accurately to cut off the current supply. It is possible to hold the cutoff state more reliably.

Next, another embodiment will be described.

The low-melting glass body 3 contains low-melting glass powder, for example, 60 to 65% by weight, preferably 63% by weight, and silica powder, for example, 3.5 to 7% by weight, preferably 7% by weight.
Is mixed with 25 to 35% by weight, preferably 30% by weight, of butyl carbinol as a solvent. Since silica has a thickening effect, a paste having viscosity and easy to apply can be formed without adding a binder.

The other structure is the same as that of the above embodiment.

Also in this embodiment, similarly to the structure of FIG. 1 of the previous embodiment, the curing temperature of the synthetic resin 4 (for example, 15
Heat at 0 ° C. for 60 minutes). As a result, when the outer peripheral synthetic resin 4 hardens, the inner butylcarbinol evaporates or volatilizes out of the system and loses its low melting point glass and silica viscosity, resulting in a so-called blunt or dry powder or powder aggregate. The low melting point glass body 3a has a body state.

As shown in FIG. 4, when the low-melting glass body 3 is enlarged about 3,000 times, the fine silica grains 11 are filled in the gaps between the large angular glass grains 10, and the glass grains 10 Voids 12 are formed between the silica grains 11. In this state, when the section immersed in the covering liquid, for example, an oxalate alcohol solution, is seen, the covering liquid has penetrated as shown in 10 minutes (Fig. 5) to 1 hour (Fig. 6). It is clear that this is because the low melting point glass body 3 becomes a powder or a powder aggregate, and voids are formed, which contributes to heat dissipation during melting of the metal wire 2.

Next, the experimental results of the circuit protection device of this embodiment will be described.

As a result of passing an overcurrent of 2.5 times the rated current through this circuit protection element, all of the 500 circuit protection elements of each rating are reliably cut off within 1 second by melting the metal wire 2. It showed the characteristics that There are some types of rated current from 0.4 A to 2 A. For example, 0.4 A causes 2.5 times the current of 1 A to cause fusing.

FIG. 7 shows a state in which the metal wire 2 is blown.
FIG. 8 is a side cross-section enlarged about 215 times, and FIG. 8 shows a trace pore 14 in which the metal wire 2 instantaneously burns due to high temperature heat generation. This means that the inside of the low-melting-point glass body 3 is porous, air remains in the pores thereof, and acts on the combustion of the metal wire 2, and the metal wire 2 is gasified and enters the holes 15. Presumed.

Further, as shown in FIG. 8, since the low melting point glass powder and the silica powder exist around the fusing part of the metal wire 2, and the void of the melted metal wire 2 does not remain, the powder collapses. I know what I did.

Further, when a cross section of the metal wire 2 in a melted state is viewed with an electron microscope photograph, it is confirmed that a residual mass of the metal wire (aluminum) 2 is present at the melted end of the metal wire 2, and the metal wire 2 is It was confirmed that the combustion spreads around the combustion point and stops when the combustion progresses to a temperature below the combustion temperature.

Further, in the case of the aluminum metal wire 2, it is considered that the fusing part is oxidized to improve the electric insulation property.

[0038]

According to the present invention, since the low-melting glass body is an inorganic material, there is almost no carbide due to heat generation when the metal wire is melted, no residual resistance is generated, and the low-melting glass body is powder or powder. Since the aggregate is porous, combustion blowout of the metal wire is ensured by residual air or residual oxygen, and further, the synthetic resin covering the low melting point glass protects the low melting point glass and the metal wire, and with a simple structure, The metal wire is surely blown by an overcurrent, and the blown state is surely maintained, so that the insulated state can be surely maintained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a circuit protection element showing an embodiment of the present invention.

FIG. 2 is a longitudinal cross-sectional explanatory view of a main part for explaining a state before melting of the circuit protection element of the same.

FIG. 3 is a longitudinal cross-sectional explanatory view of relevant parts for explaining a state after the circuit protection element has been fused.

FIG. 4 is an enlarged cross-sectional explanatory view of the low melting point glass body of the above.

FIG. 5 is an explanatory diagram 10 minutes after the low melting glass body is covered with a covering liquid.

FIG. 6 is an explanatory view one hour after the low melting glass body was covered with the immersion liquid.

FIG. 7 is an enlarged vertical cross-sectional explanatory view showing a melting state of the same metal wire.

FIG. 8 is an enlarged vertical cross-sectional explanatory view showing a melting state of the metal wire of the above.

[Explanation of symbols]

 1 electrode 2 metal wire 3 low melting point glass body 4 synthetic resin 5 mold resin body

Claims (1)

[Claims] 1. A circuit protection element for preventing an overcurrent of a circuit, comprising a pair of electrodes, a metal wire stretched and connected between predetermined positions of the electrodes, an outer periphery of the metal wire and at least the electrode. And a low melting point glass body of an inorganic component powder or a powder aggregate containing at least a low melting point glass for covering the connection portion with the metal wire, and an outer surface of the low melting point glass body on the side where the metal wire is stretched and connected to the electrode. And a synthetic resin covering the electrode, the metal wire, the low melting point glass body and the synthetic resin, and a molded resin body in which both ends of the both electrodes are led out. Element.