WO2015199170A1 - Switching element, switching circuit, and alarm circuit - Google Patents

Abstract

To reduce size and speedily switch supply of power to an external circuit without using linkage of physical mechanical elements. Provided is a switching element. The present invention has a first fusible conductor (21) connected across first and second electrodes (11, 12), third and fourth electrodes (13, 14) arranged nearby, a second fusible conductor (22) mounted on the third electrode (13), and a heat-emitting conductor (15) having a melting point higher than that of the first and second fusible conductors (21, 22). Heat generated by an overcurrent equal to or greater than the rated current flowing through the heat-emitting conductor (15) melts the first fusible conductor (21) and cuts off the first and second electrodes (11, 12) from each other, and melts the second fusible conductor (22) and causes a short-circuit between the third and fourth electrodes (13, 14).

Description

Switch element, switch circuit and alarm circuit

The present invention relates to a switch element and a switch circuit, and more particularly to a switch element, a switch circuit, and an alarm circuit that can be reduced in size and can be easily incorporated into a circuit that is operated by surface mounting.
This application claims priority on the basis of Japanese Patent Application No. 2014-132929 filed on June 27, 2014 in Japan. This application is incorporated herein by reference. Incorporated.

An alarm fuse is generally used as a switch element for operating an alarm device. An example of the alarm fuse is shown in FIG. 18. As shown in FIG. 18, a pair of alarm contacts that are connected to alarm circuits 105 for operating the alarm devices and are spaced apart from each other in the fuse holder 100. 101, 102, a spring 103 for contacting the alarm contacts 101, 102, and a fuse wire 104 for holding the spring 103 in a state of being biased to a position separated from the alarm contact 102.

The alarm contacts 101 and 102 actuate the alarm circuit 105 when they come into contact with each other, and are formed of a conductive material having elasticity such as a leaf spring and are arranged close to each other. The alarm circuit 105 operates, for example, an alarm system by operating a buzzer or a lamp, driving a thyristor or a relay circuit, or the like.

The spring 103 is held in a state of being biased to a position separated from the alarm contact 102 by the fuse wire 104. Then, the spring 103 is elastically restored when the fuse wire 104 is melted, and presses the alarm contact 102 to contact the alarm contact 101.

The fuse wire 104 is held in a state where the spring 103 is elastically displaced, and is fused by self-heating in response to an overcurrent exceeding the rated current flowing through the fuse wire 104 to open the spring 103.

JP 2001-76610 A

In the conventional alarm fuse, the spring 103 is held in an elastically displaced state by the fuse wire 104, and the alarm contact 102 is physically pressed by fusing the fuse wire 104 to release the stress of the spring 103. Thus, a configuration in which the alarm contacts 101 and 102 are short-circuited is used. Such an alarm fuse uses a configuration in which an alarm circuit is activated by physical interlocking of mechanical elements. Therefore, the alarm fuse has a large configuration such as securing the movable range of the alarm contacts 101 and 102 and the spring 103. Therefore, it is difficult to use for a narrowed circuit, and the manufacturing cost is high.

Also, since the fuse wire 104 must be blown to short-circuit the alarm contacts 101 and 102, the alarm circuit cannot be operated unless the current exceeding the rating is continuously supplied and the fuse wire 104 is blown.

Further, since the conventional alarm fuse operates the alarm circuit by short-circuiting the alarm contacts 101 and 102 that are normally open, for example, the pilot lamp that is lit in the normal state is turned off in the abnormal state. It cannot be used for alarm operation.

The detection of the cut-off state is also possible by detecting one cut-off end potential of the fuse. In particular, when an alarm signal is output to a signal system line separated from the power system power line where the fuse is arranged, it occurs at the time of the cut-off. Large power supply noise becomes a problem, and a circuit for countermeasures against the noise is required separately.

Therefore, the present invention is a switch element and a switch circuit that shuts off an external circuit such as an alarm circuit in the event of an abnormality, and is designed to be downsized and quickly connected to the external circuit regardless of the interlocking of physical mechanical elements. It is an object of the present invention to provide a switch element that switches power feeding, a switch circuit, and an alarm circuit using the switch element.

In order to solve the above-described problem, a switch element according to the present invention includes a first and second electrodes, a first soluble conductor connected across the first and second electrodes, and a proximity The third and fourth electrodes, the second soluble conductor mounted on the third electrode, and the heat generating conductor having a higher melting point than the first and second soluble conductors. The first fusible conductor is melted and the first and second electrodes are cut off by the heat generated when an overcurrent exceeding the rated current flows through the heat generating conductor, and the second possible electrode is cut off. The molten conductor is melted to short-circuit the third and fourth electrodes.

The switch circuit according to the present invention includes a first fuse, a second fuse made of a material having a melting point lower than that of the first fuse, and a fusible material made of a material having a melting point lower than that of the first fuse. A switch in an open state that is short-circuited through a molten conductor of the conductor, and the second fuse is shut off by heat generated when an overcurrent greater than or equal to a rated current flows through the first fuse; The switch is short-circuited.

The alarm circuit according to the present invention includes a control circuit in which a first fuse is connected in series, a first operating circuit in which a second fuse and a first alarm are connected in series, and an open state. A second operating circuit in which a switch and a second alarm device are connected in series, and the second fuse is blown by heat generated when an overcurrent exceeding a rated current flows through the first fuse. The first operation circuit is shut off to stop the first alarm device, and the open switch is short-circuited to open the second operation circuit to operate the second alarm device. .

The redundant circuit according to the present invention includes a control circuit in which a first fuse is connected in series, a normal operation circuit in which a second fuse is connected in series, and a backup that is connected in series to an open switch. Circuit, and the heat generated by overcurrent exceeding the rated current flowing through the first fuse causes the second fuse to be blown to stop the normal operation circuit, and the open switch is short-circuited. The backup circuit is activated.

The switching method according to the present invention includes a first electrode, a second electrode, a first fusible conductor connected between the first electrode and the second electrode, and a third electrode disposed close to the first electrode. A fourth electrode; a second soluble conductor mounted on the third electrode; and a heating conductor having a melting point higher than that of the first and second soluble conductors, and the heating conductor. The first fusible conductor is melted by the heat generated by the overcurrent exceeding the rated current flowing through the first electrode, the first and second electrodes are disconnected, the second fusible conductor is melted, and the second fusible conductor is melted. 3. Short-circuit between the fourth and fourth electrodes.

According to the present invention, since it can be configured without using mechanical elements such as springs and alarm contacts and without being physically linked with the mechanical elements, it can be designed compactly in the plane of the insulating substrate. It is possible to mount even in a narrowed mounting area.

In addition, according to the present invention, the circuit that generates heat from the heat generating conductor and the circuit on which the soluble conductor is mounted are electrically independent, and the heat generating conductor generates heat to melt the soluble conductor. It is possible to detect an abnormal overcurrent without interrupting the circuit and operate the circuit, and there is no influence of noise when the heat-generating conductor is interrupted.

Furthermore, according to the present invention, the insulating substrate can be surface-mounted by reflow mounting or the like, and can be easily mounted even in a narrowed mounting area.

FIG. 1 is a diagram showing a state before operation of a switch element to which the present invention is applied, in which (A) is a plan view, (B) is a cross-sectional view taken along line A-A ′, and (C) is a circuit diagram. 2A and 2B are diagrams showing a state before the switch element to which the present invention is applied, in which FIG. 2A is a plan view, FIG. 2B is a cross-sectional view taken along line A-A ′, and FIG. FIG. 3 shows a state in which the heat generating conductor of the switch element generates heat, the first and second fusible conductors melt, the first and second electrodes are cut off, and the third and fourth electrodes are short-circuited. 4A is a plan view, FIG. 3B is a cross-sectional view along AA ′, and FIG. 3C is a circuit diagram. 4A and 4B are diagrams showing a state in which the heat generating conductor of the switch element is melted. FIG. 4A is a plan view, FIG. 4B is a cross-sectional view taken along line A-A ′, and FIG. FIG. 5 is a circuit diagram showing an alarm circuit. 6A and 6B are diagrams showing a switch element in which a heat generating conductor is connected to a first electrode and a third electrode. FIG. 6A is a plan view, FIG. 6B is a cross-sectional view along AA ′, and FIG. It is a circuit diagram. FIG. 7 is a cross-sectional view showing a switch element in which a cover portion electrode is formed at a position overlapping with the first electrode of the cover member. FIG. 8 is a cross-sectional view showing a switch element in which a cover part electrode is formed at a position where it overlaps between the tip parts of the third and fourth electrodes of the cover member. 9A and 9B are diagrams showing another switch element to which the present invention is applied. FIG. 9A is a plan view, FIG. 9B is a cross-sectional view along AA ′, and FIG. 9C is a cross-sectional view along BB ′. . FIG. 10 is a diagram showing a switch element in which a heat generating conductor, first, third, and fourth electrodes and first to third fusible conductors are superposed on the surface of an insulating substrate. Is a plan view, and (B) is an AA ′ cross section of (A). FIG. 11 shows a switch element in which a heat generating conductor is formed on the back surface of the insulating substrate and is superposed on the first, third, and fourth electrodes and the first to third soluble conductors formed on the surface of the insulating substrate. FIG. 4A is a plan view, and FIG. 3B is a cross-sectional view taken along line AA ′ in FIG. FIG. 12 is a perspective view showing a soluble conductor having a high-melting-point metal layer and a low-melting-point metal layer and having a covering structure, and (A) is a structure in which the high-melting-point metal layer is an inner layer and is covered with a low-melting-point metal layer. (B) shows a structure in which a low melting point metal layer is used as an inner layer and is covered with a high melting point metal layer. FIG. 13 is a perspective view showing a fusible conductor having a laminated structure of a high melting point metal layer and a low melting point metal layer, wherein (A) shows a two-layer structure of upper and lower layers, and (B) shows a three-layer structure of an inner layer and an outer layer. . FIG. 14 is a cross-sectional view showing a soluble conductor having a multilayer structure of a high melting point metal layer and a low melting point metal layer. FIG. 15 is a plan view showing a soluble conductor in which a linear opening is formed on the surface of the refractory metal layer and the low melting metal layer is exposed. FIG. 15A shows the opening along the longitudinal direction. The formed part (B) has an opening formed in the width direction. FIG. 16 is a plan view showing a soluble conductor in which a circular opening is formed on the surface of the high melting point metal layer and the low melting point metal layer is exposed. FIG. 17 is a plan view showing a soluble conductor in which a circular opening is formed in a refractory metal layer and a low melting point metal is filled therein. 18A and 18B are diagrams showing a conventional alarm element, where FIG. 18A is a cross-sectional view before operation, and FIG. 18B is a cross-sectional view after operation.

Hereinafter, a switch element, a switch circuit, and an alarm circuit to which the present invention is applied will be described in detail with reference to the drawings. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made without departing from the scope of the present invention. Further, the drawings are schematic, and the ratio of each dimension may be different from the actual one. Specific dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

As shown in FIG. 1, the switch element 1 to which the present invention is applied includes an insulating substrate 10, first and second electrodes 11 and 12 formed on the insulating substrate 10, and first and second electrodes. 1st soluble conductor 21 connected across 11 and 12, 3rd and 4th electrodes 13 and 14 arrange | positioned adjacent to the insulated substrate 10, and the 3rd electrode are mounted. The second soluble conductor 22 and the heat generating conductor 15 formed on the insulating substrate 10 and having a melting point higher than those of the first and second soluble conductors 21 and 22 are provided. 1A is a plan view showing the switch element 1 excluding the cover member 20, FIG. 1B is a cross-sectional view taken along line A-A ', and FIG. 1C is a circuit diagram.

In the switch element 1, the first and second electrodes 11 and 12 are connected in series with the first external circuit, and the third and fourth electrodes 13 and 14 are connected in series with the second external circuit. The first fusible conductor 21 is melted by the heat generated by the heat generating conductor 15, the first and second electrodes 11, 12 are fused to cut off the first external circuit, and the second fusible conductor 22 is melted. Thus, the third and fourth electrodes 13 and 14 are short-circuited to open the second external circuit.

For example, in the switch element 1, the first and second electrodes 11 and 12 are connected to a first alarm 31 (see FIG. 5) made of a pilot lamp or the like, and the third and fourth electrodes 13 and 14 are buzzers. The first and second fusible conductors 21 and 22 are connected to a second alarm device 32 (see FIG. 5) composed of a lamp, an alarm system, or the like, and generate heat due to overcurrent exceeding the rated current flowing through the heat conductor 15. Is melted, the power supply to the alarm device 31 is stopped, for example, the first and second electrodes 11 and 12 are melted and the pilot lamp is turned off, and the molten conductor 22a of the second fusible conductor 22 is stopped. The third and fourth electrodes 13 and 14 are short-circuited via the switch to activate a buzzer, a lamp and other alarm systems. Further, the switch element 1 includes the heat generating conductor 15 made of a refractory metal, and after the interruption between the first and second electrodes 11 and 12 and the short circuit between the third and fourth electrodes 13 and 14, the heat generating conductor. Heat generation is stopped by fusing 15 by self-heating.

[Insulated substrate]
The insulating substrate 10 is formed using an insulating member such as alumina, glass ceramics, mullite, zirconia, and the like. The switch element 1 is used as an insulating substrate 10 to transmit heat of the heat generating conductor 15 to the first to fourth electrodes 11 to 14 and the first and second fusible conductors 21 and 22 through the insulating substrate 10. Is preferably made of a material having excellent heat resistance and high thermal conductivity, such as a ceramic substrate. In addition, the insulating substrate 10 may be made of a material used for a printed wiring board such as a glass epoxy board or a phenol board, but the heating conductor 15 and the first and second soluble conductors 21 and 22 may be used. It is necessary to pay attention to the temperature at the time of fusing.

In the switch element 1, the first to fourth electrodes 11 to 14 and the heating conductor 15 are formed on the same surface of the insulating substrate 10, and the first and second electrodes 11 and 12 are formed on one side of the heating conductor 15. Is arranged, and the third and fourth electrodes 13 and 14 are arranged on the other side of the heating conductor 15.

[First to fourth electrodes]
The first and second electrodes 11 and 12 are disposed on the surface 10a of the insulating substrate 10 so as to face each other and be separated from each other. In addition, a first soluble conductor 21 described later is mounted across the front end portions 11b and 12b of the first and second electrodes 11 and 12 facing each other. The first and second electrodes 11 and 12 are electrically connected via the first fusible conductor 21, and when the heat generating conductor 15 generates heat when energized, it is heated by this heat, and the first fusible conductor 15 is heated. The conductor 21 is opened by fusing.

The third and fourth electrodes 13 and 14 are also arranged close to each other on the surface 10a of the insulating substrate 10 and opened by being separated from each other. In addition, a second soluble conductor 22 described later is mounted on the tip portion 13 b of the third electrode 13 facing the fourth electrode 4. When the heat generating conductor 15 generates heat as the current is applied to the third and fourth electrodes 13 and 14, the second soluble conductor 22 heated and melted by this heat is interposed between the third and fourth electrodes 13 and 14. A switch 2 that is electrically short-circuited is formed by aggregating across the two.

Further, as shown in FIG. 2, the switch element 1 may have the third soluble conductor 23 mounted on the tip portion 14 b of the fourth electrode 14 facing the third electrode 4. In the switch element 1, by providing the second and third fusible conductors 22 and 23, more molten conductors 22a and 23a are aggregated between the third and fourth electrodes 13 and 14, and more quickly and While short-circuiting between the 3rd, 4th electrodes 13 and 14 more reliably, the short circuit resistance after a short circuit can be reduced. Hereinafter, the configuration of the switch element 1 shown in FIG. 2 in which the second soluble conductor 22 is mounted on the third electrode 13 and the third soluble conductor 23 is mounted on the fourth electrode 14 will be described as an example. Explained.

In addition, the 3rd, 4th electrodes 13 and 14 can make the molten conductor 22a of the 2nd soluble conductor 22 easy to aggregate by being heated by the heat generating conductor 15. FIG.

The first to fourth electrodes 11 to 14 are provided with external connection terminals 11a to 14a on the side edges 10b and 10c of the insulating substrate 10, respectively. The first and second electrodes 11 and 12 are always connected to the first alarm device 31 via these external connection terminals 11a and 12a, and the switch element 1 operates to move to the first alarm device 31. Shut off the power supply. In addition, the third and fourth electrodes 13 and 14 are connected to the second alarm device 32 via the external connection terminals 13a and 14a, and the switch device 1 operates, so that the second alarm device 32 is connected. Can be fed.

The first to fourth electrodes 11 to 14 can be formed using a general electrode material such as silver or copper, or a refractory metal containing silver or copper as a main component. The first to fourth electrodes 11 to 14 can be formed by patterning these electrode materials in the form of a paste on the surface 10a of the insulating substrate 10 using a screen printing technique, and firing the pattern. .

The first to fourth electrodes 11 to 14 are coated with a coating such as Ni / Au plating, Ni / Pd plating, or Ni / Pd / Au plating by a known technique such as plating. Preferably it is. As a result, the switch element 1 can prevent the first to fourth electrodes 11 to 14 from being oxidized and can reliably hold the molten conductors 21a to 23a of the first to third soluble conductors 21 to 23. . In addition, when the switch element 1 is mounted by reflow soldering, a low melting point that forms connection solder for connecting the first to third soluble conductors 21 to 23 or an outer layer of the first to third soluble conductors 21 to 23 It is possible to prevent the first to fourth electrodes 11 to 14 from being eroded (soldered) by melting the metal.

[Heat conductor]
The heating conductor 15 that heats and melts the first and second soluble conductors 21 and 22 is a conductive material that generates heat when energized. For example, Nichrome, W, Mo, Ru, Cu, Ag, or the like A refractory metal material containing can be preferably used. The heat generating conductor 15 is formed by mixing a powdered material of these alloys, compositions, or compounds with a resin binder or the like, patterning the paste using a screen printing technique, and firing the paste. Can do.

The heating conductor 15 is arranged on the surface 10 a of the insulating substrate 10 along with the first and second electrodes 11 and 12 and the third and fourth electrodes 13 and 14. As a result, when the heat generating conductor 15 generates heat upon energization, the first to third soluble conductors 21 to 23 mounted on the first to fourth electrodes 11 to 14 can be melted.

The heating conductor 15 is provided with fifth and sixth external connection terminals 15 a ₁ and 15 a ₂ on the side edges 10 b and 10 c of the insulating substrate 10. The heat generating conductor 15 is connected to a control circuit 34 (see FIG. 5) that triggers the operation of the first alarm device 31 via the fifth and sixth external connection terminals 15a ₁ and 15a ₂ and is controlled in the event of an abnormality. The overcurrent exceeding the rating applied from the circuit 34 generates heat to a high temperature, and the first to third fusible conductors 21 to 23 are fused. For example, the heat conductor 15 is designed so that it generates heat at about 300 ° C. when 20 to 30 W of power is applied.

Further, the heat generating conductor 15 becomes relatively thin at positions close to the first to third fusible conductors 21 to 23, and a heat generating portion 15b that generates heat locally to a high temperature is formed by the concentration of current. ing. By providing the heat generating portion 15b at a position close to the first to third soluble conductors 21 to 23, the heat generating conductor 15 efficiently melts the first to third soluble conductors 21 to 23 and quickly The first and second electrodes 11 and 12 can be blocked, and the third and fourth electrodes 13 and 14 can be short-circuited.

Further, the switch element 1 includes one of the first and second electrodes 11 and 12, for example, as shown in FIG. 2, a tip portion 11b on which the first soluble conductor 21 of the first electrode 11 is mounted. It is preferable that the heat generating conductor 15 is formed so as to be close to the heat generating portion 15b. By providing the heat generating portion 15b at a position close to the tip portion 11b on which the first fusible conductor 21 of the first electrode 11 is mounted, the heat generating conductor 15 is efficient through the insulating substrate 10 and the tip portion 11b. It is possible to transfer heat to the first fusible conductor 21 and melt it so that the first and second electrodes 11 and 12 can be quickly cut off.

In addition, of the tip portions 11b and 12b on which the first soluble conductor 21 of the first or second electrode 11 or 12 is mounted, one area close to the heat generating portion 15b is wider than the other area. It is preferable to hold more first soluble conductors 21 than the other electrode. For example, as shown in FIG. 2, when the heat generating portion 15 b of the heat generating conductor 15 and the tip portion 11 b of the first electrode 11 are brought close to each other, the switch element 1 causes the tip portion 11 b of the first electrode 11 to It is preferable that the electrode 12 is formed wider than the tip portion 12 b and the first soluble conductor 21 is mounted on the tip portion 11 b side of the first electrode 11 more.

Since the tip portion 11b of the first electrode 11 is close to the heat generating portion 15b, more heat is transmitted from the heat generating conductor 15, and the first soluble conductor 21 can be efficiently melted. Therefore, the tip 11b of the first electrode 11 has a relatively large area and holds more soluble conductors, so that heat can be transferred to the first soluble conductor 21 more quickly and melted. It is possible to block between the first and second electrodes 11 and 12.

Further, the tip portion 11b of the first electrode 11 is close to the heat generating portion 15b and is formed in a relatively large area, so that most of the first soluble conductor 21 heated to a higher temperature and melted. Can be held.

The switch element 1 is preferably formed so that the tip portion 13b of the third electrode 13 on which the second soluble conductor 22 is mounted and the heat generating portion 15b are close to each other. By providing the tip portion 13b on which the second soluble conductor 22 of the third electrode 13 is mounted and the heat generating portion 15b in a close position, the heat generating conductor 15 passes through the insulating substrate 10 and the tip portion 13b. Heat can be efficiently transferred to the second soluble conductor 22 and melted, and the third and fourth electrodes 13 and 14 can be quickly short-circuited. The third soluble conductor 23 may be mounted on the fourth electrode 14 and the tip portion 14b and the heat generating portion 15b of the fourth electrode 14 may be brought close to each other.

As shown in FIG. 2, when the control circuit 34 is operating normally, the heating conductor 15 is supplied with an appropriate current within the rating. The heat generating conductor 15 generates heat when the overcurrent exceeding the rating flows when the control circuit 34 detects an abnormality or due to the abnormality of the control circuit 34. As shown in FIG. The three fusible conductors 21 to 23 are blown, the first and second electrodes 11 and 12 are cut off, and the third and fourth electrodes 13 and 14 are short-circuited. After that, the heat generating conductor 15 continues to generate heat, so that it is melted by its own Joule heat as shown in FIG. As a result, the switch element 1 cuts off the power supply path from the control circuit 34 to the heating conductor 15 and stops the heat generation of the heating conductor 15. In other words, the heat generating conductor 15 functions as a fuse that melts the first to third fusible conductors 21 to 23 and interrupts its own power supply path by self-heating.

Also, the heat generating conductor 15 is fused at the heat generating portion 15b by providing the heat generating portion 15b that is locally hot. At this time, since the heat generating conductor 15 has the heat generating portion 15b formed relatively thin, arc discharge generated at the time of fusing can be reduced to a small scale, and the effect of covering the insulating layer 16 to be described later can be dispersed. Can be prevented.

In addition to forming the pattern by printing the above-mentioned conductive paste, the heat conductor 15 is not limited to Ag, Cu, W, Mo, Ru, Nichrome, or a foil, plate-like body, wire, or other material made of these materials. You may form using a mounting body. Further, when the heating conductor 15 is configured using these mounting bodies, a ceramic substrate that is excellent in thermal conductivity and can quickly melt the first to third soluble conductors 21 to 23 is used as the insulating substrate 10. However, the problem of leakage of the molten conductor after fusing of the heat generating conductor 15 is less than that of the conductive pattern.

[Insulation layer]
The first to fourth electrodes 11 to 14 and the heat generating conductor 15 are covered with an insulating layer 16 on the surface 10 a of the insulating substrate 10. The insulating layer 16 is provided to protect and insulate the first to fourth electrodes 11 to 14 and the heating conductor 15, and to suppress arc discharge when the heating conductor 15 is melted. For example, a glass layer or glass is used. It is a layer made of a material having a main component.

As shown in FIGS. 1 to 4, the insulating layer 16 covers the heat generating portion 15 b of the heat generating conductor 15 and is formed on a region excluding the tip portions 11 b and 12 b of the first and second electrodes 11 and 12. Yes. That is, the first and second electrodes 11 and 12 have the tip portions 11b and 12b exposed from the insulating layer 16, and a first soluble conductor 21 described later can be mounted.

Further, by forming the insulating layer 16 on the region excluding the tip portions 11b and 12b of the first and second electrodes 11 and 12, the heat of the heat generating conductor 15 transmitted through the insulating substrate 10 is dissipated. , The tip portions 11b and 12b can be efficiently heated, and heat can be transferred to the first soluble conductor 21. The first and second electrodes 11 and 12 are provided with an insulating layer 16 between the tip end portions 11b and 12b and the external connection electrodes 11a and 12a, so that the melted first soluble conductor 21 is external. It is possible to prevent a situation where the solder for connection to the circuit board on which the switch element 1 is mounted flows out to the connection electrodes 11a and 12a side and is melted.

Also, as shown in FIGS. 1 to 4, the insulating layer 16 is formed on a region excluding the tip portions 13b and 13b of the third and fourth electrodes 13 and 14. That is, the tip portions 13b and 14b of the third and fourth electrodes 13 and 14 are exposed from the insulating layer 16, and second and third soluble conductors 22 and 23 described later can be aggregated and combined. .

Further, in the third and fourth electrodes 13 and 14, the support portion 17 is exposed to the outside from an opening portion 16 a formed in a part of the insulating layer 16. The third and fourth electrodes 13 and 14 are provided with connecting solder at the tip portions 13b and 14b and the support portion 17, and the connecting solder extends between the tip portions 13b and 14b and the support portion 17. The second and third fusible conductors 22 and 23 are supported on the insulating layer 16.

In the switch element 1, the insulating layer 16 made of glass or the like may be formed between the heat generating conductor 15 and the insulating substrate 10, and the heat generating conductor 15 may be formed inside the insulating layer 16. Thereby, the switch element 1 can prevent leakage due to the molten conductor adhering to the surface of the insulating substrate 10 after the heat-generating conductor 15 is cut off, and can increase the insulation resistance. Further, the insulating layer 16 formed between the heat generating conductor 15 and the insulating substrate 10 is partially formed only in the vicinity of the center of the heat generating portion 15b, so that it is transmitted to the first and second fusible conductors 21 and 22. It is possible to ensure both heat resistance and insulation resistance after interruption.

[Soluble conductor]
As the first to third soluble conductors 21 to 23 mounted on the first to fourth electrodes 11 to 14, any metal that can be quickly melted by the heat generated by the heating conductor 15 can be used. A low-melting-point metal such as solder or solder that does not melt at the time of 260 ° C. reflow mounting mainly containing Pb can be used.

The first to third soluble conductors 21 to 23 may contain a low melting point metal and a high melting point metal. As the low melting point metal, it is preferable to use solder, Pb-free solder containing Sn as a main component, and as the high melting point metal, it is preferable to use Ag, Cu or an alloy containing these as main components. By containing the high melting point metal and the low melting point metal, even when the reflow temperature exceeds the melting temperature of the low melting point metal and the low melting point metal melts when the switch element 1 is reflow mounted, Outflow to the outside can be suppressed, and the shapes of the first to third soluble conductors 21 to 23 can be maintained. In addition, even during melting, the low melting point metal melts, so that the high melting point metal is eroded (soldered), so that it can be rapidly melted at a temperature lower than the melting point of the high melting point metal. The first to third fusible conductors 21 to 23 can be formed by various configurations as will be described later.

The first to third soluble conductors 21 to 23 are preferably coated with a flux 28 on a part or all of the surface in order to prevent oxidation and improve wettability.

[Switch circuit / alarm circuit]
The switch element 1 as described above has a circuit configuration as shown in FIG. That is, in the switch element 1, the first electrode 11 and the second electrode 12 are normally connected via the first soluble conductor 21 (FIG. 2C), and the first heat generation conductor 15 generates heat to generate the first electrode 11 and the second electrode 12. When one soluble conductor 21 is melted, it is opened. (FIG. 3C). The switch element 1 is opened when the third electrode 13 and the fourth electrode 14 are normal (FIG. 2C), and the second and third fusible conductors 22, When 23 is melted, the switch 2 is configured to be short-circuited via the molten conductors 22a and 23a (FIG. 3C). The external connection terminals 13 a and 14 a of the third and fourth electrodes 13 and 14 constitute both terminals of the switch 2.

The switch element 1 is used by being incorporated in the alarm circuit 30, for example. FIG. 5 is a diagram illustrating an example of a circuit configuration of the alarm circuit 30. The alarm circuit 30 includes a control circuit 34 in which a first fuse 33 (heating conductor 15) made of a refractory metal body having a higher melting point than the first to third fusible conductors 21 to 23 is connected in series to a power source. The first operating circuit 36 for operating the first alarm 31 via the second fuse 35 made of the first fusible conductor 21 and the molten conductors of the second and third fusible conductors 22 and 23 And a second operating circuit 37 for operating the second alarm device 32 by the switch 2 that is short-circuited via 22a and 23a. The control circuit 34 and the first and second operating circuits 36 and 37 are electrically connected. It was formed independently.

As shown in FIG. 5, in the switch element 1, both external connection terminals 11a and 12a of the second fuse 35 (first fusible conductor 21) are energized at normal times, such as pilot lamps, and energized at abnormal times. Connected to the first alarm device 31. In addition, the switch element 1 is connected to a second alarm device 31 composed of a buzzer, a lamp, an alarm system, or the like in which both external connection terminals 13a and 14a of the switch 2 are opened when normal and are energized when abnormal. Further, in the switch element 1, the fifth and sixth external connection terminals 15 a ₁ and 15 a _{2 of} the first fuse 33 (heating conductor 15) are connected to the control circuit 34.

The switch element 1 having such a configuration is configured such that the first heat generating conductor 15 formed adjacent to the first and second electrodes 11 and 12 that operate the first alarm device 31 generates heat. The fusible conductor 21 is melted, and the first and second electrodes 11 and 12 are blocked. That is, the switch element 1 is configured such that the heat generating conductor 15 and the first and second electrodes 11 and 12 are physically and electrically independent, and the first soluble conductor 21 is melted by the heat of the heat generating conductor 15. It cuts off by doing, so to speak, it takes the structure linked by thermally connecting.

Similarly, the switch element 1 is the first by the heat generation of the heat generating conductor 15 formed adjacent to the third and fourth electrodes 13 and 14 constituting the switch 2 that operates the second alarm device 32. 2. The third soluble conductors 22 and 23 are melted and short-circuited through the molten conductors 22a and 23a. That is, the switch element 1 is configured so that the heat generating conductor 15 and the third and fourth electrodes 13 and 14 are physically and electrically independent, and the second and third soluble conductors are heated by the heat of the heat generating conductor 15. A short circuit occurs when the materials 22 and 23 are melted.

Therefore, since the switch element 1 can be configured without using mechanical elements such as springs and alarm contacts and without being physically linked with the mechanical elements, the switch element 1 should be designed to be compact in the plane of the insulating substrate 10. Can be mounted in a narrowed mounting area. Further, the switch element 1 can reduce the number of parts and the number of manufacturing steps, and can reduce the cost. Furthermore, the switch element 1 can be mounted on the surface of the insulating substrate 10 by reflow mounting or the like, and can be easily mounted even in a narrowed mounting region.

In the switch element 1, the heat generating conductor 15 and the first to fourth electrodes 11 to 14 are physically and electrically independent, and the heat generating conductor 15 functioning as the first fuse 33 is cut off. First, the first alarm device 31 is shut off and the second alarm device 32 is operated. Therefore, for example, when an alarm signal is output to a signal system line separated from the power system power line in which the heat generating conductor 15 functioning as a fuse is arranged, there is no influence of power supply noise when the heat generating conductor 15 is cut off, and for noise countermeasures A circuit is also unnecessary, and a highly reliable alarm circuit can be configured.

In actual use, when an abnormality occurs in the control circuit 34 in the switch element 1, an overcurrent exceeding the rating flows through the heating conductor 15. Then, as shown in FIG. 3A, the heat generating conductor 15 generates heat, and heat is applied to the first soluble conductor 21 through the insulating substrate 10 and the tip portions 11b, 12b of the first and second electrodes 11, 12. As a result, the first soluble conductor 21 is melted. The molten conductor 21a of the first fusible conductor 21 aggregates on the tip portions 11b and 12b of the first and second electrodes 11 and 12 heated by the heating conductor 15. Thereby, the switch element 1 interrupts | blocks between the 1st, 2nd electrodes 11 and 12, and can stop the electricity supply to the 1st alarm device 31 of the 1st operation circuit 36 (FIG.3 (C )). The alarm circuit 30 can notify the abnormality, for example, the pilot lamp is turned off when the energization to the alarm device 31 is stopped.

In the switching element 1, when the heat generating conductor 15 generates heat, the second and third soluble conductors 22 and 23 are melted. The molten conductors 22a and 23a of the second and third fusible conductors 22 and 23 have a larger area than the support portion 17 exposed from the opening 16a and are heated by the heating conductor 15 in the third and fourth. The electrodes 13 and 14 are agglomerated and bonded onto the respective tip portions 13b and 14b. Thereby, the switch element 1 can short-circuit between the 3rd, 4th electrodes 13 and 14, and can operate the 2nd alarm device 32. FIG. That is, in the switch element 1, the switch 2 is turned on (FIG. 3C). In the alarm circuit 30, when the switch 2 of the switch element 1 is turned on, the second alarm circuit 32 is operated by the second operation circuit 37.

At this time, the switch element 1 includes the heat generating portion 15 b of the heat generating conductor 15, the tip end portion 11 b on which the first fusible conductor 21 of the first electrode 11 is mounted, and the second possible portion of the third electrode 13. By disposing the tip portion 13b on which the molten conductor 22 is mounted close to the heat generating portion 15b which is thin and has a high resistance, the first and second soluble conductors 21 and 22 are efficiently melted. Thus, the first and second electrodes 11 and 12 can be quickly cut off, and the third and fourth electrodes 13 and 14 can be short-circuited. Further, the heat generating conductor 15 is such that the high-resistance heat generating portion 15b is only locally heated, and the fifth and sixth external connection terminals 15a ₁ and 15a ₂ facing the side edges are relatively low in temperature due to the heat dissipation effect. To be kept. Therefore, in the switch element 1, the mounting solder for the fifth and sixth external connection terminals 15a ₁ and 15a ₂ is not melted.

As shown in FIG. 4, the heat-generating conductor 15 continues to generate heat after being interrupted between the first and second electrodes 11 and 12 and the third and fourth electrodes 13 and 14 are short-circuited, and is interrupted by its own Joule heat. (FIGS. 4A and 4B). As a result, the switch element 1 is cut off from energization to the heat generating conductor 15 by the control circuit 34 and stops generating heat (FIG. 4C). At this time, since the heat generating conductor 15 is covered with the insulating layer 16, the switch element 1 can suppress large-scale arc discharge and suppress explosive scattering of the molten conductor. In addition, by providing the heat generating portion 15b that is thinly formed on the heat generating conductor 15, the fusing portion is narrowed, and the amount of the molten conductor that is scattered can be reduced.

In this way, the switch element 1 reliably generates the first to third soluble conductors 21 to 23 by the heat generation conductor 15 having a higher melting point than the first to third soluble conductors 21 to 23 generating heat. It melts before the heat generating conductor 15, the first and second electrodes 11 and 12 can be cut off, and the third and fourth electrodes 13 and 14 can be short-circuited. That is, in the switch element 1, the fusing of the heat generating conductor 15 is not a condition for cutting off the first and second electrodes 11 and 12 and short-circuiting the third and fourth electrodes 13 and 14.

Thus, the switch element 1 can be used as an alarm element that shuts off the first alarm device 31 and activates the second alarm device 32 when the control circuit 34 is abnormal. Therefore, according to the alarm circuit 30 in which the switch element 1 is incorporated, the first alarm device 31 is shut off such as turning off the pilot lamp, and the alarm buzzer, the alarm lamp, or the energization of the function circuit corresponding to the abnormality is second. By operating the alarm device 32, the abnormality of the control circuit 34 can be dealt with.

The alarm circuit in which the switch element 1 is incorporated can be used as an alarm element that transmits the abnormality even when an overcurrent exceeding the rating of the heating conductor 15 flows due to the abnormality detection of the control circuit 34. The alarm element can quickly detect abnormality detection by the control circuit 34 in accordance with the operation of the first and second alarm devices 31 and 32, such as turning off the pilot lamp and operating the alarm buzzer, and stops the control circuit 34 proactively. In addition, it is possible to take measures such as operating the backup circuit.

In addition to applying to the alarm circuit, the switch element 1 is always connected by being connected to the first and second electrodes 11 and 12 instead of the first and second alarm circuits 31 and 32. Applied to any redundant circuit with a backup function, including a normal operation circuit that is connected to the third and fourth electrodes 13 and 14, and a backup circuit that operates at the time of abnormality of the normal operation circuit. You can also

Also, the heat generating conductor 15 automatically stops generating heat by being cut off by its own Joule heat. Therefore, the switch element 1 does not need to be provided with a mechanism for restricting the power supply by the control circuit 34, can stop the heat generation of the heat generating conductor 15 with a simple configuration, and can reduce the size of the entire element.

[Connection]
Further, the switch element 1 may connect one of the first or second electrodes 11 and 12 close to the heat generating portion 15 b of the heat generating conductor 15 and the heat generating conductor 15. For example, as shown in FIG. 6, when the heating element 15 b of the heating conductor 15 and the tip 11 b of the first electrode 11 are close to each other, the switch element 1 A first connection portion 18 that connects the electrode 11 may be formed.

Similarly, the switch element 1 includes a heating conductor 15 and a third electrode 13 on which the second soluble conductor 22 is mounted or a fourth electrode 14 on which the third soluble conductor 23 is mounted. You may form the 2nd connection part 19 to connect. For example, the switch element 1 connects the vicinity of the heat generating portion 15b of the heat generating conductor 15 and the third electrode 13 when the heat generating portion 15b of the heat generating conductor 15 and the tip portion 13b of the third electrode 13 are close to each other. The second connection portion 19 may be formed.

The first and second connecting portions 18 and 19 are made of the same conductive material as that of the heat conductor 15 and the first to fourth electrodes 11 to 14, for example, and the heat conductor 15 and the first to fourth electrodes 11 to 14 are used. Can be provided by forming a pattern in the same process.

By connecting the heat generating conductor 15 and the first and third electrodes 11, 13, the switch element 1 can be connected via the first connecting portion 18 and the first electrode 11 when the heat generating conductor 15 generates heat when energized. The heat is transferred to the first soluble conductor 21 and can be melted more rapidly. Similarly, when the heat generating conductor 15 generates heat by energization, the heat is transmitted to the second soluble conductor 22 via the second connecting portion 19 and the third electrode 13 and can be melted more rapidly. For this reason, it is preferable to form the 1st, 2nd connection parts 18 and 19 with metal materials, such as Ag and Cu which are excellent in heat conductivity.

Note that the first and second connecting portions 18 and 19 are provided at positions slightly away from the center of the heat generating portion 15b of the heat generating conductor 15. Since the heating conductor 15 is provided with the first and second connection portions 18 and 19 so that the resistance value decreases and the temperature does not easily rise. This is because the center of the portion 15b and the first and second connecting portions 18 and 19 need to be provided at positions separated from each other.

[Cover electrode]
In the switch element 1, a cover member 20 that protects the inside is attached on an insulating substrate 10. The inside of the switch element 1 is protected by covering the insulating substrate 10 with the cover member 20. The cover member 20 includes a side wall 24 that constitutes a side surface of the switch element 1 and a top surface portion 25 that constitutes an upper surface of the switch element 1, and the side wall 24 is connected to the insulating substrate 10. It becomes a lid that closes the inside of the. The cover member 20 is formed using an insulating member such as a thermoplastic plastic, ceramics, or a glass epoxy substrate.

Further, as shown in FIG. 7, the cover member 20 may have a first cover electrode 26 formed on the inner surface side of the top surface portion 25. The first cover part electrode 26 is formed at a position overlapping with one of the first electrode 11 and the second electrode 12. As shown in FIG. 7, the first cover part electrode 26 is close to the heat generating part 15b of the heat generating conductor 15, and overlaps with the tip part 11b of the first electrode 11 formed in a relatively large area. It is more preferable. As a result, when the heat generating conductor 15 generates heat and the first fusible conductor 21 is melted, the first cover electrode 26 has the molten conductor 21a aggregated on the front end portion 11b of the first electrode 11. By contacting and spreading, the allowable amount for holding the molten conductor 21a can be increased, and the first and second electrodes 11 and 12 can be blocked more reliably.

Further, as shown in FIG. 8, the cover member 20 may have a second cover portion electrode 27 formed on the inner surface side of the top surface portion 25. The second cover part electrode 27 is formed at a position that overlaps between the tip parts 13 b and 14 b of the third and fourth electrodes 13 and 14. The second cover part electrode 27 is formed by melting the third and fourth electrodes 13 and 14 when the heat generating conductor 15 generates heat and the second and third fusible conductors 22 and 23 are melted. When the conductors 22a and 23a come into contact with each other to spread out, the allowable amount for holding the molten conductors 22a and 23a can be increased, and the third and fourth electrodes 13 and 14 can be short-circuited more reliably.

[Projection support of second soluble conductor]
Further, in the switch element to which the present invention is applied, as shown in FIG. 9, the third soluble conductor 23 is not provided on the fourth electrode 14, and the second soluble conductor 22 is replaced with the third electrode 13. May be supported by projecting to the fourth electrode 14 side. In the following description, the same components as those of the above-described switch element 1 are denoted by the same reference numerals and the details thereof are omitted. The switch element 5 shown in FIG. 9 is melted when the second soluble conductor 22 supported by the third electrode 13 protrudes toward the fourth electrode 14 and is melted by the heat generated by the heat conductor 15. The conductor aggregates and bonds onto the tip portions 13b and 14b of the third and fourth electrodes 13 and 14, respectively. As a result, the switch element 5 is short-circuited between the third and fourth electrodes 13 and 14. FIG. 9B is a cross-sectional view taken along the line AA ′ in FIG. 9A, and FIG. 9C is a cross-sectional view taken along the line BB ′ in FIG.

The second soluble conductor 22 is exposed from the support portion 17 exposed from the opening portion 16 a opened in the insulating layer 16 laminated on the third and fourth electrodes 13 and 14, and exposed from the insulating layer 16. The third electrode 13 is supported on the third electrode 13 by connecting solder provided at the tip portion 13 b of the third electrode 13. Further, as shown in FIG. 9C, the second fusible conductor 22 extends on the insulating layer 16 laminated on the fourth electrode 14 by projecting to the fourth electrode 14 side. This overlaps with the fourth electrode 14. The second fusible conductor 22 extends on the insulating layer 16 so as to be separated from the tip end portion 14b exposed from the insulating layer 16, whereby the third and fourth electrodes 13, 14 are separated from each other. It is open.

Then, when the second fusible conductor 22 is melted by the heat generated by the heat generating conductor 15, the second conductive conductor 22 also comes into contact with the tip portion 14 b of the fourth electrode 14 in the process of agglomerating on the third electrode 13, 3. Aggregate between the tip portions 13b, 14b of the fourth electrodes 13, 14.

In FIG. 9, the second soluble conductor 22 supported by the third electrode 13 is protruded toward the fourth electrode side. On the contrary, the second soluble conductor 22 is connected to the third electrode 13. The third soluble conductor 23 may be supported by projecting from the fourth electrode 14 to the third electrode 13 side.

In the switch element 1 described above, as in the switch element 5, the third soluble conductor 23 is not provided on the fourth electrode 14, and the second soluble conductor 22 is connected to the third electrode 13 from the third electrode 13. 4 may protrude and be supported on the electrode 14 side.

[Fifth and sixth external connection terminals]
Further, as shown in FIG. 9, the switch element to which the present invention is applied becomes a connection terminal for an external circuit on the surface 10a of the insulating substrate 10 on which the first to fourth electrodes 11 to 14 are formed. The first to fourth external connection terminals 11a to 14a may be provided. In addition, the switch element to which the present invention is applied has fifth and sixth external connection terminals 15a ₁ and 15a _{2 serving} as connection terminals for external circuits on the surface 10a of the insulating substrate 10 on which the heat generating conductor 15 is formed. May be provided. In the switch element 5 shown in FIG. 9, the surface 10a side of the insulating substrate 10 on which the first to fourth electrodes 11 to 14 and the heat generating conductor 15 are provided is a mounting surface.

The first to sixth external connection terminals 11a to 14a, 15a ₁ and 15a ₂ are connection terminals for mounting on a substrate constituting an external circuit, and are formed using, for example, metal bumps or metal posts. The shape of the metal bump or the metal post is not limited. Further, the first to sixth external connection terminals 11a to 14a, 15a ₁ and 15a ₂ have a height protruding from the cover member 10 provided on the insulating substrate 2, as shown in FIG. 9C. And can be mounted on the substrate side that is the mounting target of the short-circuit element 25.

As described above, the switch element 5 does not include the external connection terminals 11a to 14a, 15a ₁ and 15a ₂ continuous to the back surface of the insulating substrate 10 through the conductive through holes, but the first to fourth electrodes 11 to External connection terminals 11a to 14a, 15a ₁ and 15a ₂ are formed on the same surface as 14 and the heating conductor 15. The external connection terminals 11a to 14a, 15a ₁ and 15a ₂ are provided on the first to fourth electrodes and the heat generating conductor 15, and have a high degree of freedom in shape and size and have a low conduction resistance. Can be easily provided. Thereby, the switch element 5 has the third and fourth electrodes 13 and 14 as compared with the case where the third and fourth external connection terminals 13a and 14a drawn to the back surface through the conductive through holes are used. It is possible to easily improve the rating when short-circuiting and opening an external circuit, and to handle a large current.

Note that the switch element 5 is connected to the third external connection terminal 13a and the conductive resistance between the third and fourth electrodes 13 and 14 when the third electrode 13 and the fourth electrode 14 are short-circuited. It is preferable that the combined resistance with the fourth external connection terminal 14a is low. Thereby, the switch element 5 can prevent the improvement of the rating of the external circuit opened by the third and fourth external connection terminals 13a and 14a from being hindered.

The first to sixth external connection terminals 11a to 14a, 15a ₁ and 15a ₂ may be formed by providing a low melting point metal layer on the surface of the high melting point metal to be the core. As the metal constituting the low melting point metal layer, a solder such as Pb-free solder containing Sn as a main component can be suitably used. As the high melting point metal, Cu or Ag or an alloy containing these as a main component can be used. It can be used suitably.

By providing the low melting point metal layer on the surface of the high melting point metal, even when the reflow temperature exceeds the melting temperature of the low melting point metal layer when the switch element 5 is reflow mounted, It is possible to prevent the sixth external connection terminals 11a to 14a, 15a ₁ and 15a _{2 from} melting. The first to sixth external connection terminals 11a to 14a, 15a ₁ and 15a ₂ are connected to the first to fourth electrodes 11 to 14 and the heating conductor 15 by using a low melting point metal constituting the outer layer. be able to.

The first to sixth external connection terminals 11a to 14a, 15a ₁ and 15a ₂ can be formed by forming a low melting point metal on a high melting point metal by using a plating technique, and other well-known laminated layers. It can also be formed by using a technique or a film forming technique.

The first to sixth external connection terminals 11a to 14a, 15a ₁ and 15a ₂ are formed by applying a conductive plating layer or a conductive paste in addition to using metal bumps or metal posts. Alternatively, the conductive layer may be formed.

Further, the first to sixth external connection terminals 11a to 14a, 15a ₁ and 15a ₂ are provided in advance on the mounting object side such as a substrate on which the switch element 5 is mounted, and in the mounting body on which the short-circuit element is mounted, It may be connected to the first to fourth electrodes 11 to 14 and the heat generating conductor 15.

Also in the switch element 1 described above, similarly to the switch element 5, a connection terminal for an external circuit is formed on the surface 10a of the insulating substrate 10 on which the first to fourth electrodes 11 to 14 and the heating conductor 15 are formed. The first to sixth external connection terminals 11a to 14a, 15a ₁ and 15a ₂ may be provided.

[Modification 1]
Note that the switch element to which the present invention is applied includes the first electrode 11 and / or the second electrode 12 and the third electrode on the surface 10a of the insulating substrate 10 via the insulating layer on the heating conductor. 13 or the third electrode 13 and the fourth electrode 14 may be overlapped, and the first and second soluble conductors 21 and 22 or the first to third soluble conductors 21 to 23 may be overlapped. Good. In the following description, the same components as those of the above-described switch element 1 are denoted by the same reference numerals and the details thereof are omitted. As shown in FIG. 10, in the switch element 40, a heat generating conductor 15 is formed between the opposite side edges 10d and 10e of the surface 10a of the insulating substrate 10. In the switch element 40, the first and second electrodes 11 and 12 and the third and fourth electrodes 13 and 14 are formed on opposite side edges 10 b and 10 c of the surface 10 a of the insulating substrate 10, respectively. .

The heat generating conductor 15 is covered with a first insulating layer 41 at a substantially central portion of the insulating substrate 10. The heating conductor 15 has fifth and sixth external connection terminals 15a ₁ and 15a ₂ formed on the side edges 10d and 10e of the insulating substrate 10, respectively. Further, the heat generating conductor 15 is formed with a heat generating portion 15b that generates heat at a high temperature by forming an intermediate portion narrower than both end portions. The heat generating portion 15b overlaps with the tip portion 11b of the first electrode 11 and / or the tip portion 12b of the second electrode 12, and the first soluble conductor 21 mounted between the tip portions 11b and 12b. It can be heated efficiently. Similarly, the heat generating portion 15b is superposed on the tip portion 13b of the third electrode 13, and can efficiently heat the second soluble conductor 22 mounted on the tip portion 13b. The heat generating portion 15b can also efficiently heat the third soluble conductor 23 mounted on the tip portion 14b by overlapping with the tip portion 14b of the fourth electrode 14.

The first and second electrodes 11 and 12 have external connection terminals 11a and 12a formed on the side edges 10b and 10c of the insulating substrate 10, respectively. The first and second electrodes 11 and 12 are formed from the side edges 10 b and 10 c to the upper surface of the first insulating layer 41, and the tip portions 11 b and 12 b are close to each other on the upper surface of the first insulating layer 41. And opened by being separated. The first and second electrodes 11 and 12 are covered with a second insulating layer 42 except for the tip portions 11b and 12b.

The first and second electrodes 11 and 12 are provided with connecting solder at the tip portions 11b and 12b, and the first soluble conductor 21 is mounted across the tip portions 11b and 12b by the connecting solder. Yes. In addition, the switch element 40 includes one of the first and second electrodes 11 and 12, for example, as shown in FIG. A part of the first fusible conductor 21 mounted on the part 11 b is superimposed on the heat generating part 15 b of the heat generating conductor 15. On the first soluble conductor 21, a flux 28 is applied to a part or all of the surface for preventing oxidation and improving wettability.

The third and fourth electrodes 13 and 14 have external connection terminals 13a and 14a formed on the side edges 10b and 10c of the insulating substrate 10, respectively. The third and fourth electrodes 13 and 14 are formed from the side edges 10b and 10c to the upper surface of the first insulating layer 41, and the tip portions 13b and 14b are close to each other on the upper surface of the first insulating layer 41. And opened by being separated. The third and fourth electrodes 13 and 14 are covered with the second insulating layer 42 except for the tip portions 13b and 14b.

In the second insulating layer 42, an opening 42a is partially formed. The third and fourth electrodes 13 and 14 are provided with connecting solder on the support portion 17 exposed outward from the tip end portions 13b and 14b and the opening 42a. The second and third fusible conductors 22 and 23 are supported on the second insulating layer 42 between 14 b and the support portion 17. Thereby, the front-end | tip part 13b of the 3rd electrode 13, and the 2nd soluble conductor 22, or the front-end | tip parts 13b, 14b of the 3rd, 4th electrodes 13 and 14, and the 2nd, 3rd soluble conductor 22, 23 is at least partially overlapped with the heat generating portion 15 b of the heat generating conductor 15. On the second and third soluble conductors 22 and 23, a flux 28 is applied to a part or all of the surface for preventing oxidation, improving wettability, and the like.

As the first and second insulating layers 41 and 42, an insulating material such as glass can be suitably used, as with the insulating layer 16 of the switch element 1 described above.

According to such a switch element 40, since the front end portion 11b of the first electrode 11 and the first fusible conductor 21 are arranged so as to overlap the heat generating portion 15b of the heat generating conductor 15, the heat generating portion 15b The first soluble conductor 21 can be quickly melted by heat generation, and the first and second electrodes 11 and 12 can be blocked. At this time, the switch element 40 has the heat generating portion 15b, the first electrode 11, and the first soluble conductor 21 continuously laminated via the first insulating layer 41 made of glass or the like. The heat of the heat generating part 15b can be transmitted efficiently.

Further, according to the switch element 40, the third electrode 13 and the second fusible conductor 22, or the third and fourth electrodes 13 and 14, the second, Since the third fusible conductors 22 and 23 are disposed, the second fusible conductor 22 or the second and third fusible conductors 22 and 23 are quickly melted by the heat generated by the heat generating portion 15b, and the third The fourth electrodes 13 and 14 can be short-circuited. At this time, the switch element 40 has the heat generating portion 15b, the third and fourth electrodes 13, 14 and the second and third fusible elements through the first and second insulating layers 41 and 42 made of glass or the like. Since the conductors 22 and 23 are continuously laminated, the heat of the heat generating portion 15b can be efficiently conducted.

In the switch element 40 as well as the switch element 5, the third soluble conductor 23 is not provided on the fourth electrode 14, and the second soluble conductor 22 is connected to the fourth electrode 13 from the third electrode 13. You may support by protruding to the electrode 14 side. Also in the switch element 40, similarly to the switch element 5, it becomes a connection terminal for an external circuit on the surface 10 a on which the first to fourth electrodes 11 to 14 and the heat generating conductor 15 of the insulating substrate 10 are formed. The first to sixth external connection terminals 11a to 14a, 15a ₁ and 15a ₂ may be provided.

[Modification 2]
In addition, the switch element to which the present invention is applied is formed on the refractory metal body by forming the first to fourth electrodes on the surface 10a of the insulating substrate 10 and forming the refractory metal body on the back surface of the insulating substrate. The first electrode 11 and / or the second electrode 12 and the third electrode 13 or the third electrode 13 and the fourth electrode 14 are superimposed on each other, and the first and second soluble conductors 21 , 22 or the first to third fusible conductors 21 to 23 may be overlapped. In the following description, the same components as those of the above-described switch element 1 are denoted by the same reference numerals and the details thereof are omitted. As shown in FIG. 11, in the switch element 50, the heat generating conductor 15 is formed between the opposing side edges 10d and 10e of the back surface 10f of the insulating substrate 10. The switch element 50 includes first and second electrodes 11 and 12 and third and fourth electrodes 13 and 14 formed on opposite side edges 10b and 10c of the surface 10a of the insulating substrate 10, respectively. Yes.

The heat generating conductor 15 is covered with a first insulating layer 51 at a substantially central portion of the insulating substrate 10. The heating conductor 15 has fifth and sixth external connection terminals 15a ₁ and 15a ₂ formed on the side edges 10d and 10e of the insulating substrate 10, respectively. Further, the heat generating conductor 15 is formed with a heat generating portion 15b that generates heat at a high temperature by forming an intermediate portion narrower than both end portions. The heat generating portion 15b overlaps with the tip portion 11b of the first electrode 11 and / or the tip portion 12b of the second electrode 12, and the first soluble conductor 21 mounted between the tip portions 11b and 12b. It can be heated efficiently. Similarly, the heat generating portion 15b is superposed on the tip portion 13b of the third electrode 13, and can efficiently heat the second soluble conductor 22 mounted on the tip portion 13b. The heat generating portion 15b can also efficiently heat the third soluble conductor 23 mounted on the tip portion 14b by overlapping with the tip portion 14b of the fourth electrode 14.

The first and second electrodes 11 and 12 have external connection terminals 11a and 12a formed on the side edges 10b and 10c of the insulating substrate 10, respectively. Further, the first and second electrodes 11 and 12 are opened when the front end portions 11b and 12b are brought close to and separated from the side edges 10b and 10c at the substantially central portion of the surface 10a of the insulating substrate 10. ing. The first and second electrodes 11 and 12 are covered with a second insulating layer 52 except for the tip portions 11b and 12b.

The first and second electrodes 11 and 12 are provided with connecting solder at the tip portions 11b and 12b, and the first soluble conductor 21 is mounted across the tip portions 11b and 12b by the connecting solder. Yes. In addition, the switch element 50 includes one of the first and second electrodes 11 and 12, for example, as shown in FIG. 11, a tip portion 11b of the first electrode 11 formed in a relatively large area, and a tip. A part of the first fusible conductor 21 mounted on the part 11 b is superimposed on the heat generating part 15 b of the heat generating conductor 15. On the first soluble conductor 21, a flux 28 is applied to a part or all of the surface for preventing oxidation and improving wettability.

The third and fourth electrodes 13 and 14 have external connection terminals 13a and 14a formed on the side edges 10b and 10c of the insulating substrate 10, respectively. In addition, the third and fourth electrodes 13 and 14 are opened when the front end portions 13b and 14b are brought close to and separated from the side edges 10b and 10c at the substantially central portion of the surface 10a of the insulating substrate 10. ing. The third and fourth electrodes 13 and 14 are covered with the second insulating layer 52 except for the tip portions 13b and 14b.

In the second insulating layer 52, an opening 52a is formed in part. The third and fourth electrodes 13 and 14 are provided with connecting solder on the support portion 17 exposed outward from the tip end portions 13b and 14b and the opening 52a. The second and third fusible conductors 22 and 23 are supported on the second insulating layer 52 between 14 b and the support portion 17. Thereby, the front-end | tip part 13b of the 3rd electrode 13, and the 2nd soluble conductor 22, or the front-end | tip parts 13b, 14b of the 3rd, 4th electrodes 13 and 14, and the 2nd, 3rd soluble conductor 22, 23 is at least partially overlapped with the heat generating portion 15 b of the heat generating conductor 15. On the second and third soluble conductors 22 and 23, a flux 28 is applied to a part or all of the surface for preventing oxidation, improving wettability, and the like.

As for the first and second insulating layers 51 and 52, an insulating material such as glass can be suitably used, as in the case of the insulating layer 16 of the switch element 1 described above.

According to such a switch element 50, since the tip portion 11b of the first electrode 11 and the first fusible conductor 21 are arranged so as to overlap the heat generating portion 15b of the heat generating conductor 15, the heat generation of the heat generating portion 15b. Thus, the first soluble conductor 21 can be quickly melted, and the first and second electrodes 11 and 12 can be blocked.

Further, according to the switch element 50, the third electrode 13 and the second fusible conductor 22, or the third and fourth electrodes 13 and 14, the second, Since the third fusible conductors 22 and 23 are disposed, the second fusible conductor 22 or the second and third fusible conductors 22 and 23 are quickly melted by the heat generated by the heat generating portion 15b, and the third The fourth electrodes 13 and 14 can be short-circuited.

At this time, the switch element 50 is a surface on which the heat generating conductor 15 is provided with the first to third soluble conductors 21 to 23 by using an insulating substrate 10 having excellent thermal conductivity such as a ceramic substrate. It is preferable because it can be heated in the same manner as when formed on the same surface.

In the switch element 50, as in the switch element 5, the third soluble conductor 23 is not provided on the fourth electrode 14, and the second soluble conductor 22 is connected to the fourth electrode 13 from the third electrode 13. You may support by protruding to the electrode 14 side.

[Modified example of soluble conductor]
As described above, any or all of the first to third soluble conductors 21 to 23 may contain a low melting point metal and a high melting point metal. The refractory metal layer 60 is made of Ag, Cu or an alloy containing these as a main component, and the low melting metal layer 61 is made of solder, Pb-free solder containing Sn as a main component, or the like. At this time, as shown in FIG. 12A, the first to third fusible conductors 21 to 23 may be provided with a high melting point metal layer 60 as an inner layer and a low melting point metal layer 61 as an outer layer. A molten conductor may be used. In this case, the first to third fusible conductors 21 to 23 may have a structure in which the entire surface of the high melting point metal layer 60 is covered with the low melting point metal layer 61 and is covered except for a pair of opposite side surfaces. It may be a structure. The covering structure with the high melting point metal layer 60 and the low melting point metal layer 61 can be formed using a known film forming technique such as plating.

Further, as shown in FIG. 12B, the first to third soluble conductors 21 to 23 are soluble in which a low melting point metal layer 61 is provided as an inner layer and a high melting point metal layer 60 is provided as an outer layer. A conductor may be used. Also in this case, the first to third fusible conductors 21 to 23 may have a structure in which the entire surface of the low melting point metal layer 61 is covered with the high melting point metal layer 60, and is covered except for a pair of opposing side surfaces. The structure may be different.

Further, the first to third fusible conductors 21 to 23 may have a laminated structure in which a high melting point metal layer 60 and a low melting point metal layer 61 are laminated as shown in FIG.

In this case, the first to third fusible conductors 21 to 23 are laminated on the lower layer supported by the first to fourth electrodes 11 to 14 and on the lower layer, as shown in FIG. The upper refractory metal layer 60 may be laminated on the upper surface of the lower melting point metal layer 61, or the upper layer of the refractory metal layer 60 serving as the lower layer. A low melting point metal layer 61 as an upper layer may be laminated. Alternatively, as shown in FIG. 13B, the first to third soluble conductors 21 to 23 may be formed as a three-layer structure including an inner layer and an outer layer stacked on the upper and lower surfaces of the inner layer. The refractory metal layer 60 serving as the outer layer may be laminated on the upper and lower surfaces of the low melting point metal layer 61 serving as the inner layer, and the low melting point metal layer 61 serving as the outer layer may be disposed on the upper and lower surfaces of the refractory metal layer 60 serving as the inner layer. You may laminate.

Further, as shown in FIG. 14, the first to third soluble conductors 21 to 23 may have a multilayer structure of four or more layers in which high melting point metal layers 60 and low melting point metal layers 61 are alternately laminated. . In this case, the first to third fusible conductors 21 to 23 may be structured so as to be covered with the metal layer constituting the outermost layer except for the entire surface or a pair of opposite side surfaces.

In the first to third soluble conductors 21 to 23, the refractory metal layer 60 may be partially laminated in a stripe shape on the surface of the low melting point metal layer 61 constituting the inner layer. FIG. 15 is a plan view of the first to third fusible conductors 21 to 23.

The first to third fusible conductors 21 to 23 shown in FIG. 15A have a plurality of linear refractory metal layers 60 in the longitudinal direction on the surface of the low melting point metal layer 61 at predetermined intervals in the width direction. By being formed, a linear opening 62 is formed along the longitudinal direction, and the low melting point metal layer 61 is exposed from the opening 62. In the first to third fusible conductors 21 to 23, the low melting point metal layer 61 is exposed from the opening 62, thereby increasing the contact area between the molten low melting point metal and the high melting point metal. It is possible to further improve the fusing property by further promoting the erosion action of. The opening 62 can be formed, for example, by subjecting the low melting point metal layer 61 to partial plating of a metal constituting the high melting point metal layer 60.

Further, as shown in FIG. 15B, the first to third soluble conductors 21 to 23 are formed on the surface of the low melting point metal layer 61 at a predetermined interval in the longitudinal direction at the linear refractory metal layer 60. By forming a plurality of holes in the width direction, the linear openings 62 may be formed along the width direction.

Further, as shown in FIG. 16, the first to third fusible conductors 21 to 23 form a refractory metal layer 60 on the surface of the low melting point metal layer 61 and extend over the entire surface of the refractory metal layer 60. Alternatively, a circular or rectangular opening 63 may be formed, and the low melting point metal layer 61 may be exposed from the opening 63. The opening 63 can be formed, for example, by subjecting the low melting point metal layer 61 to partial plating of a metal constituting the high melting point metal layer 60.

In the first to third fusible conductors 21 to 23, when the low melting point metal layer 61 is exposed from the opening 63, the contact area between the molten low melting point metal and the high melting point metal increases, and the melting point of the high melting point metal is increased. The phagocytosis can be further promoted to improve the fusing property.

In addition, as shown in FIG. 17, the first to third soluble conductors 21 to 23 are formed with a large number of openings 64 in the refractory metal layer 60 serving as the inner layer, and the refractory metal layer 60 is plated. The low melting point metal layer 61 may be formed using a technique or the like and filled in the opening 64. Thereby, in the first to third soluble conductors 21 to 23, the area where the low-melting-point metal that is melted contacts the high-melting-point metal increases. Will be able to.

The first to third soluble conductors 21 to 23 are preferably formed such that the volume of the low melting point metal layer 61 is larger than the volume of the high melting point metal layer 60. The first to third fusible conductors 21 to 23 are heated by the heat generating conductor 15 to melt the low melting point metal and thereby melt the high melting point metal, thereby quickly melting and fusing. . Therefore, the first to third soluble conductors 21 to 23 promote this corrosion action by forming the volume of the low melting point metal layer 61 larger than the volume of the high melting point metal layer 60, and promptly. Blocking between the first and second electrodes 11 and 12 and short-circuiting between the third and fourth electrodes 13 and 14 can be performed.

1, 40, 50 switch element, 10 insulating substrate, 10a front surface, 10f back surface, 11 first electrode, 12 second electrode, 13 third electrode, 14 fourth electrode, 15 heating conductor, 16 insulating layer, 18 1st connection part, 19 2nd connection part, 20 Cover member, 21 1st soluble conductor, 22 2nd soluble conductor, 23 3rd soluble conductor, 24 Side wall, 25 Top surface part, 26 1st cover part electrode, 27 2nd cover part electrode, 28 flux, 30 alarm circuit, 31 1st alarm device, 32 2nd alarm device, 33 1st fuse, 34 control circuit, 35 2nd Fuse, 36 first operating circuit, 37 second operating circuit, 41 first insulating layer, 42 second insulating layer

Claims (45)

1. First and second electrodes;
   A first soluble conductor connected across the first and second electrodes;
   Third and fourth electrodes arranged in close proximity;
   A second soluble conductor mounted on the third electrode;
   A heating conductor having a higher melting point than the first and second soluble conductors,
   The first fusible conductor is melted and the first and second electrodes are cut off by melting the second fusible conductor due to heat generated when an overcurrent exceeding the rated current flows through the heating conductor. And a switch element for short-circuiting the third and fourth electrodes.
2. 2. The switch according to claim 1, wherein the heating conductor is made of a refractory metal, and is cut off by self-heating (Joule heat) accompanying overcurrent exceeding a rated current after the first and second electrodes are cut off. element.
3. 3. The switch element according to claim 1, wherein the second soluble conductor is supported by protruding from the third electrode toward the fourth electrode.
4. The switch element according to claim 1 or 2, wherein a third soluble conductor is mounted on the fourth electrode.
5. 3. The switch element according to claim 1, wherein the heating conductor and the first to fourth electrodes are made of silver, copper, or a refractory metal mainly composed of silver or copper.
6. The switch element according to claim 1, wherein the heating conductor and the first to fourth electrodes are provided on a surface of an insulating substrate.
7. The switch element according to claim 6, wherein the heating conductor and the first to fourth electrodes are electrode patterns laminated on a surface of an insulating substrate.
8. 2. The heat generating conductor is formed such that a position close to the first and second fusible conductors is relatively thin, and a heat generating portion that generates heat locally is formed by current concentration. 2. The switch element according to 2.
9. The switch element according to claim 8, wherein one of the tip portions of the first or second electrode on which the first soluble conductor is mounted and the heat generating portion are close to each other.
10. 10. The switch element according to claim 9, wherein one of the first and second electrodes whose tip is close to the heat generating part is connected to the vicinity of the heat generating part.
11. 10. The switch element according to claim 9, wherein, of the tip portions of the first or second electrode on which the first soluble conductor is mounted, one area close to the heat generating portion is wider than the other area.
12. The switch element according to claim 8, wherein a tip portion of the third electrode on which the second fusible conductor is mounted and the heat generating portion are close to each other.
13. The switch element according to claim 12, wherein the third electrode and the vicinity of the heat generating portion are connected.
14. The switch element according to claim 1, wherein the heating conductor is covered with an insulating layer.
15. The switch element according to claim 1, wherein the heat generating conductor is formed inside an insulating layer.
16. The switch element according to claim 1, wherein the first and second electrodes are laminated with an insulating layer, and a front end portion on which the first soluble conductor is mounted is exposed to the outside.
17. In the third and fourth electrodes, an insulating layer is laminated, and a front end portion facing each other and a support portion that is separated from the front end portion via the insulating layer are exposed to the outside. The switch element according to claim 1, wherein the second soluble conductor is supported by a support portion.
18. The switch element according to any one of claims 14 to 17, wherein the insulating layer is made of glass or an insulating material containing glass as a main component.
19. 3. The switch element according to claim 1, wherein the heating conductor is a pattern or a mounting body made of Ag, Cu, W, Mo, Ru, nichrome, or a material containing these.
20. The first to fourth electrodes and the heat generating conductor are formed on the same surface of the insulating substrate, the first and second electrodes are disposed on one side of the heat generating conductor, and the other of the heat generating conductors The switch element according to claim 6, wherein the third and fourth electrodes are arranged on the side of the switch.
21. On one surface of the insulating substrate, the first soluble conductor mounted between the first and second electrodes, and the second soluble conductor supported by the third electrode; Is overlaid on the heating conductor via an insulating layer.
22. The first to fourth electrodes are disposed on one surface of the insulating substrate, and the heating conductor is disposed on the other surface of the insulating substrate.
    The heating conductor is mounted on one of the first or second electrode and the first soluble conductor mounted on the one electrode, and the third electrode and the third electrode. The switch element according to claim 6, wherein the switch element is superimposed on the second soluble conductor via the insulating substrate.
23. The switch element according to any one of claims 6, 7, and 20 to 22, wherein the insulating substrate is a ceramic substrate.
24. 3. The switch element according to claim 1, wherein the first and second soluble conductors are solder.
25. The first and second soluble conductors contain a low melting point metal and a high melting point metal,
    The switch element according to claim 1, wherein the low-melting-point metal is melted by the heat generated by the heat-generating conductor and erodes the high-melting-point metal.
26. The low melting point metal is solder,
    26. The switch element according to claim 25, wherein the refractory metal is Ag, Cu, or an alloy mainly composed of Ag or Cu.
27. 27. The switch element according to claim 25 or 26, wherein the first and second soluble conductors have a coating structure in which an inner layer is a high melting point metal and an outer layer is a low melting point metal.
28. 27. The switch element according to claim 25 or 26, wherein the first and second soluble conductors have a coating structure in which an inner layer is a low melting point metal and an outer layer is a high melting point metal.
29. 27. The switch element according to claim 25 or 26, wherein the first and second soluble conductors have a laminated structure in which a low melting point metal and a high melting point metal are laminated.
30. 27. The switch element according to claim 25, wherein the first and second soluble conductors have a multilayer structure of four or more layers in which a low melting point metal and a high melting point metal are alternately laminated.
31. 27. The switch element according to claim 25 or 26, wherein the first and second soluble conductors are provided with openings in a high melting point metal formed on a surface of a low melting point metal constituting the inner layer.
32. The first and second soluble conductors have a high melting point metal layer having a large number of openings and a low melting point metal layer formed on the high melting point metal layer, and the low melting point metal is formed in the openings. 27. The switch element according to claim 25 or 26, wherein:
33. 27. The switch element according to claim 25 or 26, wherein the first and second soluble conductors have a volume of a low melting point metal larger than a volume of a high melting point metal.
34. 27. The switch element according to claim 25 or 26, wherein a flux is coated on a part or all of the surfaces of the first and second soluble conductors.
35. The surface of the first to fourth electrodes is coated with any one of Ni / Au plating, Ni / Pd plating, and Ni / Pd / Au plating. 27. The switch element according to any one of -22, 25, and 26.
36. A cover member provided on the insulating substrate for protecting the inside;
    23. The cover member according to claim 6, wherein a first cover part electrode is provided at a position overlapping with any one of the first and second electrodes. Switch element.
37. A cover member provided on the insulating substrate for protecting the inside;
    The cover member according to any one of claims 6, 7, and 20 to 22, wherein the cover member is provided with a second cover part electrode at a position overlapping between the tip parts of the third and fourth electrodes. The switch element according to item.
38. On the surface of the insulating substrate on which the first to fourth electrodes are disposed, the first to fourth external connection terminals that are continuous with the first to fourth electrodes and the ends of the heat generating conductor are continuous. The switch element according to any one of claims 6, 7, and 20 to 22, further comprising fifth and sixth external connection terminals.
39. A first fuse;
    A second fuse made of a material having a melting point lower than that of the first fuse;
    A switch in an open state that short-circuits through a molten conductor of a fusible conductor made of a material having a melting point lower than that of the first fuse;
    A switch circuit that shuts off the second fuse and short-circuits the open switch due to heat generated when an overcurrent greater than or equal to a rated current flows through the first fuse.
40. 40. The switch circuit according to claim 39, wherein the first fuse is blown by self-heating (Joule heat) accompanying overcurrent exceeding a rated current after the second fuse is cut off and the switch is short-circuited.
41. A control circuit having a first fuse connected in series;
    A first operating circuit in which a second fuse and a first alarm are connected in series;
    An open switch and a second operating circuit with a second alarm connected in series;
    The heat generated by the overcurrent exceeding the rated current flowing through the first fuse causes the second fuse to blow, shuts off the first operating circuit, stops the first alarm device, and opens. An alarm circuit for operating the second alarm device by short-circuiting the switch in a state to open the second operation circuit;
42. 42. The alarm circuit according to claim 41, wherein the first fuse is blown by self-heating (Joule heat) accompanying overcurrent exceeding a rated current after the second fuse is blown and the switch is short-circuited.
43. A control circuit having a first fuse connected in series;
    A normal operating circuit with a second fuse connected in series;
    A backup circuit connected in series to the open switch,
    Due to the heat generated when overcurrent exceeding the rated current flows through the first fuse, the second fuse is blown to stop the normal operation circuit, and the open switch is short-circuited to short-circuit the backup circuit. Redundant circuit to operate.
44. 44. The redundant circuit according to claim 43, wherein the first fuse is blown by self-heating (Joule heat) accompanying overcurrent exceeding a rated current after the second fuse is blown and the backup circuit is activated.
45. First and second electrodes;
    A first soluble conductor connected across the first and second electrodes;
    Third and fourth electrodes arranged in close proximity;
    A second soluble conductor mounted on the third electrode;
    A heating conductor having a higher melting point than the first and second soluble conductors,
    The first fusible conductor is melted and the first and second electrodes are cut off by melting the second fusible conductor due to heat generated when an overcurrent exceeding the rated current flows through the heating conductor. A switch method for short-circuiting the third and fourth electrodes.

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