JP3305824B2 - Circuit protection element - Google Patents

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 a circuit from being damaged by overcurrent.

[0002]

2. Description of the Related Art Conventionally, this kind of circuit protection element has a structure in which one fuse element element is connected between a pair of electrodes.

In this type of circuit protection element, since both ends of the fuse element are welded to the electrodes by a thin wire bonding machine, for example, a circuit protection element having a large current capacity using a fuse element having a wire diameter larger than 50 μmφ is used. Cannot be used, the same bonding machine cannot be used, and it is not easy to increase the current capacity using a fuse element having a large wire diameter.

[0004]

In a circuit protection element having a conventional structure, fuse elements having different wire diameters cannot be connected by the same bonding machine. Therefore, it is necessary to increase the current capacity by changing the wire diameter of the fuse element. There was a problem that was not easy.

The present invention has been made in view of the above problems, and provides a circuit protection element that can easily increase the current capacity.

[0006]

According to the present invention, there is provided a circuit protection element comprising: a pair of electrodes; a fuse element in which a plurality of electrodes are connected in parallel between the pair of electrodes; an outer periphery of the fuse element and the electrodes ; and the gel-like mixed layer porous made of a low melting inorganic powder and synthetic resin covering the connection portion of the fuse element, one outer periphery of the mixed layer
An elastic and non-permeable synthetic resin layer formed on the portion,
It comprises a mixed resin layer and a mold resin body covering the synthetic resin layer .

[0007]

The circuit protection element according to the present invention is the same element ,
The Fuse elements can increase the current capacity by connecting a plurality of parallel, also can be connected to the fuse element between the electrodes using the same bonding machine.

Further, when soldering to a circuit board or the like, even if an external stress or a thermal stress acts on the circuit protection element, it is mixed.
The synthetic resin layer covering the composite layer is elastically deformed and the mixed layer and fuse
Gel mixture layer bullet while cushioning protection elements
The fuse element can be prevented from breaking due to a change in characteristics . Further, when an overcurrent flows between the electrodes and the fuse element is heated and melted and cut, the heat generated when the fuse element is blown causes a substantial peripheral portion of the fuse element to be cut off. The low-melting inorganic powder in the mixed layer of the above melts, and the low-melting inorganic material that has melted penetrates into the space created between the tips due to the fusing of the fuse element, and the fused fuse element becomes spherical due to surface tension. The pores between the particles of the low melting point inorganic powder and the gaps generated by the melting of the low melting point inorganic powder flow into the gaps, so that conduction is not established between the cut ends of the fuse element, and the cutoff state of the fuse element is reliably maintained.

Further , since the synthetic resin layer is made impermeable,
Infiltration into pores between particles of low melting point inorganic powder in the mixed layer
No melting, low melting element
The pores between the particles of the point inorganic powder are not blocked.

Further, when molding a molded resin body,
The pressure generated by shrinkage during curing of the synthetic resin
Absorbs and affects mixed layers and fuse elements.
I can't.

[0011]

Next, the configuration of an embodiment of the circuit protection element of the present invention will be described with reference to FIGS.

In FIG. 2, reference numeral 1 denotes a circuit protection element body. The circuit protection element body 1 is a pair formed by, for example, a conductive metal plate material which is soldered to be mounted on a circuit to be protected from overcurrent. The electrodes 2 and 2 are provided to face each other.

As shown in FIG. 1, an intermediate portion is curved between the electrodes 2 and 2 at a predetermined position of the electrodes 2 and 2, for example, between the front ends facing each other with a gap therebetween. A plurality of, for example, two fuse elements 3, 3 whose parts are connected are stretched in parallel. Each of the fuse elements 3 and 3 is a thin metal wire that is blown by a predetermined current, and is an aluminum wire containing a small amount of silicon (Si) having a wire diameter of 10 μm to 500 μm, for example, 45 μm φ, or gold ( A thin metal wire such as Au), silver (Ag), copper (Cu) or the like that can be wire-bonded is connected to the electrodes 2 and 2 by wire bonding using an ultrasonic bonder machine (not shown).

Further, a mixed layer 5 made of a low melting point inorganic powder and a synthetic resin is formed on the outer periphery of the fuse elements 3 and 3 and the connection between the electrodes 2 and 2 with the fuse elements 3 and 3. The low-melting inorganic powder is mainly composed of, for example, a lead-based low-melting glass powder and an alumina powder, and the synthetic resin is, for example, a low-viscosity liquid silicone resin (JIS-3181). The silicone resin is mixed at a volume ratio of 1 to the low-melting inorganic powder so as to be 3 or more, and the silicone resin is present between the particle contacts so as to connect the particles of the low-melting inorganic powder. It is formed in a gel form.

Further, the outer periphery of the swelled mixed layer 5 in which the fuse elements 3 and 3 are stretched in an arc shape is coated with, for example, an elastic jelly-like synthetic resin layer 6 in a film form. The synthetic resin layer 6 is made of, for example, a non-solvent polyester resin. In addition, this synthetic resin layer 6
Is to achieve the purpose of protecting the mixed layer 5,
Solventless epoxy resins, solventless silicone resins, and the like are used.

However, it is necessary to adjust the synthetic resin layer 6 so as not to penetrate into pores such as between particles of the low melting point inorganic powder of the mixed layer 5. In addition, the synthetic resin layer 6 may be provided not only in a film shape but also in a layer shape.

The electrodes 2 and 2, the fuse elements 3 and 3, the mixed layer 5 and the synthetic resin layer 6 are covered with a mold resin body 7 made of a thermosetting resin such as an epoxy resin. The mold resin body 7 has a heat resistance of 230.
The resin is not limited to the thermosetting resin as long as it can withstand the soldering temperature at the time of mounting of about ° C. or more, and can be made of any resin such as a thermoplastic resin.

The two electrodes 2 and 2 projecting from the vicinity of the upper ends of both ends of the molded resin body 7 are bent along both end surfaces of the molded resin body 7, and the bent end is connected to the bottom surface of the molded resin body 7. Are arranged facing each other.

Next, a method of manufacturing the circuit protection element body 1 of the above embodiment will be described.

First, both ends of the fuse elements 3 and 3 are ultrasonically bonded to a lead frame (not shown) between the front ends thereof opposed to each other via a gap between the pair of electrodes 2 and 2 formed by punching or the like. Welding. Next, the mixed layer 5 is applied to the entire outer periphery of the fuse elements 3 and 3 and the connection between the electrodes 2 and 2 and the fuse elements 3 and 3. Further, the outer periphery of the mixed layer 5 is coated with a synthetic resin such as a solventless polyester resin to form a synthetic resin layer 6.

Next, the mixed layer 5 and the synthetic resin layer 6 are dried by heating or heating at, for example, 160 ° C. for 3 hours.

Then, for example, a molded resin body 7 is formed with a thermosetting resin such as an epoxy resin so that the other ends of the electrodes 2 and 2 are led out. In this case, since the dried synthetic resin layer 6 absorbs the pressure generated when the molding resin body 7 is injected and molded, it does not affect the mixed layer 5 and the fuse elements 3 and 3.

Next, the base ends of the electrodes 2 and 2 protruding outward from the side surfaces of the molded resin body 7 on the lead frame side are cut off, and the cut ends of the electrodes 2 and 2 are separated from the molded resin body 7. The circuit protection element body 1 having a chip configuration of a surface mounting type is formed by bending and arranging along both end faces and making the tip portions face each other on the bottom surface of the mold resin body 7.

Next, the operation of this embodiment will be described.

First, the electrodes 2 and 2 facing the bottom surface of the molded resin body 7 are soldered to a circuit board on which a circuit (not shown) is mounted, and the circuit protection element body 1 is surface-mounted.

At the time of this soldering, when an external stress is applied to the electrodes 2 and 2 by the soldering iron or the like coming into contact with the electrodes 2 and 2 or by carrying the circuit protection element body 1 by pinching,
When the electrodes 2 and 2 are thermally expanded by the heat of soldering,
Stress is applied to the mixed layer 5 and the fuse elements 3 and 3. At this time, the synthetic resin layer 6 covering the mixed layer 5 is elastically deformed to cushion and protect the mixed layer 5 and the fuse elements 3, 3, and the mixed layer 5 is elastically deformed to prevent disconnection of the fuse elements 3, 3. it can.

On the other hand, when an overcurrent flows between the electrodes 2 and 2, a plurality of fuse elements 3 and 3 are melted by heating and cut. In this case, the mixed layer 5 exists on the outer periphery of the fuse elements 3 and 3 and at least the connection between the electrodes 2 and the fuse elements 3 and 3. Therefore, heat generated when the fuse elements 3 and 3 are blown is
The low-melting-point inorganic powder in the mixed layer 5 substantially at the periphery of the fuse elements 3 and 3 is dissolved.

The melted low-melting inorganic glass penetrates into the space created between the tips of the fuse elements 3 and 3 due to melting, and the melted fuse elements 3 and 3 are rounded by the surface tension. While flowing into pores between particles of the low-melting inorganic powder and gaps generated by melting of the low-melting inorganic powder.

The heat generated when the fuse elements 3 and 3 are blown causes the silicone resin between the particles of the low-melting inorganic powder to burn and partially carbonize. However, since the carbon content is small, the blown fuse element is used. There is no continuity between the three ends.

For this reason, since the fuse elements 3 and 3 after blowing do not contact each other and do not conduct, the insulation after blowing can be completely guaranteed, and a plurality of fuse elements 3 and 3 are connected in parallel. Since the connection is made, the current capacity increases, and the circuit protection element body 1 is attached to, for example, a power supply line of a semiconductor device or a driver line through which a large current flows. In response, the current supply can be interrupted, and the interrupted state can be maintained more reliably.

The fuse elements 3 and 3 can be connected to the electrodes 2 and 2 using the same bonding machine.

[0032] Also, the electrodes 2, 2 is not limited to the conductive metal plate may be a suitable Yibin electrode.

Next, the circuit protection element body 1 shown in the above embodiment will be described.
The experimental results will be described.

FIG. 3 shows an element body in which both ends of a single fuse element 3 having a wire diameter of 45 μmφ and a length of about 1 mm are joined to opposing electrodes 2 and 2 having a gap between the tips of about 0.2 mm. As shown in FIG. 3, in the element body in which the applied current is about 5 A and the fuse is blown in about 0.1 second and the both ends of one fuse element 3 having a length of about 0.3 mm to 0.4 mm are joined, FIG. Fused within the range indicated by.

In the element body in which two fuse elements 3 and 3 having a wire diameter of 45 μmφ and a length of about 1 mm are joined to opposite electrodes 2 and 2 having a gap between the tips of about 0.2 mm, Fusing within the range indicated by the iii characteristic line in FIG.
In the element body in which both end portions of the two fuse elements 3 and 3 having a diameter of 0.4 mm to 0.4 mm were melted within the range indicated by the iv characteristic line in FIG.

Therefore, in the case of one fuse element 3 having a length of about 0.3 mm to 0.4 mm, a fusing current of 9.5 mm
Although it was about A, it was confirmed that the fusing current of the two fuse elements 3 and 3 was about twice as large at about 18 A.

[0037]

According to the present invention, the current capacity can be increased by connecting a plurality of fuse elements in parallel in the same element, and the same fuse element is used for the plurality of fuse elements. As a result, the fuse element can be connected between the electrodes using the same bonding machine, and a circuit protection element having a large current capacity can be obtained easily and inexpensively, and the circuit protection element is soldered to a circuit board such as a surface mount. The synthetic resin layer covers the mixed layer even when external stress or thermal stress acts.
Elastically deforms and cushions the mixed layer and fuse element
At the same time, the gel-like mixed layer buffers and protects the fuse element, preventing the fuse element from breaking. Furthermore, when an overcurrent flows between the electrodes and the fuse element is heated and melted and cut, the fuse element is blown. Due to the heat generated at this time, the low-melting inorganic powder in the mixed layer substantially at the periphery of the fuse element dissolves, and the low-melting inorganic material that has melted penetrates into the space created between the tips due to fusing of the fuse element, and melts. fuse element becomes spherical due to surface tension, flow into the gap caused by the melting of the pores and a low-melting inorganic powder between the low-melting inorganic powder particles, without having to conduct between the cut end of the fuse element, the fuse element The shut-off state is reliably maintained.

Further , since the synthetic resin layer is impermeable,
Infiltration into pores between particles of low melting point inorganic powder in the mixed layer
No melting, low melting element
The pores between the inorganic powder particles are not blocked,
Open fuse element between particles of low melting point inorganic powder
Of the fuse element
Conduction between them can be prevented.

Further, when molding the molded resin body,
The pressure generated by shrinkage during curing of the synthetic resin
Absorbs and affects mixed layers and fuse elements.
I can't.

[Brief description of the drawings]

FIG. 1 is a plan view of a connection portion between a fuse element and an electrode of a circuit protection element according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of the circuit protection element.

FIG. 3 is a characteristic diagram of a conventional circuit protection element and an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Circuit protection element body 2 Electrode 3 Fuse element 5 Mixed layer 6 Synthetic resin layer 7 Mold resin body

Claims (1)

(57) [Claims] A pair of electrodes, a fuse element in which a plurality of electrodes are connected in parallel between the pair of electrodes, an outer periphery of the fuse element, and a connection portion between the electrode and the fuse element. and the gel-like mixed layer porous consisting of coated low melting inorganic powder and synthetic resin, impermeable resiliently quality formed on a part of the outer periphery of the mixed layer
Synthetic resin layer, and a mold resin body covering the mixed layer and the film-like synthetic resin layer
Circuit protection device characterized by comprising and.