JP6266355B2 - Switch element, switch circuit, and alarm circuit - Google Patents

Description

  The present invention relates to a switch element and a switch circuit, and more particularly to a switch element and a switch circuit that can be reduced in size and can be easily incorporated into a circuit that is operated by surface mounting.

  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. 15. As shown in FIG. 15, 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 position biased to a position separated from the alarm contact 102.

  The alarm contacts 101 and 102 actuate the alarm circuit 105 by being in 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 in which 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, thereby opening 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.

  In addition, since the fuse wire 104 is indispensable for short-circuiting 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.

  Therefore, the present invention provides a switch element and a switch circuit that shuts off an external circuit such as an alarm circuit in the event of an abnormality. The switch element and the switch circuit can be miniaturized and can quickly supply power to the circuit regardless of the interlocking of physical mechanical elements. An object of the present invention is to provide a switch element and a switch circuit for stopping the alarm, and an alarm circuit using the same.

  In order to solve the above-described problem, a switch element according to the present invention includes an insulating substrate, first and second electrodes formed on the insulating substrate, and straddling between the first and second electrodes. Due to the heat generated due to overcurrent exceeding the rated current flowing in the high melting point metal body, the fusible conductor having a melting point higher than the soluble conductor formed on the insulating substrate and having a higher melting point than the soluble conductor. The refractory metal body is melted after the fusible conductor is melted and the first and second electrodes are cut off.

  The switch circuit according to the present invention includes first and second electrodes that are connected by mounting the first fuse and connected to an external circuit, and the first and second electrodes are connected to each other. A switch part that stops power supply to the external circuit by opening and a functional circuit that has a melting point higher than the melting point of the first fuse and is electrically independent of the switch part. A second fuse that melts the first fuse and interrupts the first and second electrodes by heat generated by an overcurrent that exceeds the rated current flowing through the second fuse. The power supply to the circuit is stopped.

  In addition, the alarm circuit according to the present invention has first and second electrodes that are connected to each other by being mounted with a first fuse, and the first and second electrodes are opened. An operation circuit for stopping power supply to the alarm device, a second fuse formed electrically independent of the operation circuit and having a melting point higher than that of the first fuse, and the second And a control circuit having a functional circuit connected in series with a power source, and the first fuse is melted by heat generated by overcurrent exceeding the rated current flowing in the second fuse when the functional circuit is abnormal. In this way, the first and second electrodes are disconnected from each other and the power supply to the alarm device is stopped.

  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.

  Further, according to the present invention, the circuit that generates heat from the refractory metal body and the circuit on which the soluble conductor is mounted are electrically independent, and the soluble conductor is blown by heat generation from the refractory metal body. Therefore, it is possible to detect an abnormal overcurrent without operating the refractory metal body and to operate the circuit, and there is no influence of noise when the refractory metal body 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.

1A and 1B are diagrams showing a state before operation of a switch element to which the present invention is applied, in which FIG. 1A is a plan view, FIG. 1B is a cross-sectional view taken along line A-A ′, and FIG. FIG. 2 is a view showing a state in which the refractory metal body of the switch element generates heat, the melted conductor of the fusible conductor is melted, and the first and second electrodes are cut off, and (A) is a plan view. ) Is a cross-sectional view along the line AA ′, and (C) is a circuit diagram. 3A and 3B are diagrams showing a state where the refractory metal body of the switch element is melted, wherein FIG. 3A is a plan view, FIG. 3B is a cross-sectional view taken along line A-A ′, and FIG. FIG. 4 is a circuit diagram showing an alarm circuit. 5A and 5B are diagrams showing a switch element in which a refractory metal body and a first electrode are connected, where FIG. 5A is a plan view, FIG. 5B is a cross-sectional view along AA ′, and FIG. 5C is a circuit diagram. is there. FIG. 6 is a cross-sectional view showing a switch element in which a cover part electrode is formed on a cover member. FIG. 7 is a diagram showing a switch element in which a refractory metal body, a first electrode, and a soluble conductor are superimposed on the surface of an insulating substrate, (A) is a plan view, and (B) is (A). It is an AA 'cross section. FIG. 8 is a diagram showing a switch element in which a refractory metal body is formed on the back surface of an insulating substrate and the first electrode and a soluble conductor formed on the surface of the insulating substrate are overlapped, and FIG. (B) is the AA 'cross section of (A). FIG. 9 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. 10 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, where (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. 11 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. 12 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 point metal layer is exposed, and (A) shows the opening along the longitudinal direction. The formed part (B) has an opening formed in the width direction. FIG. 13 is a plan view showing a soluble conductor in which a circular opening is formed on the surface of the refractory metal layer and the low melting point metal layer is exposed. FIG. 14 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. 15A and 15B are diagrams showing a conventional alarm element, where FIG. 15A is a cross-sectional view before operation, and FIG. 15B 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. 11 and 12, and a high-melting point metal body 15 formed on the insulating substrate 10 and having a higher melting point than the soluble conductor 13. 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.

  This switch element 1 has first and second electrodes 11 and 12 connected to an alarm device 31 comprising a buzzer, a lamp, an alarm system or the like, and generates heat due to overcurrent exceeding the rated current flowing through the refractory metal body 15. By melting the fusible conductor 13, the power supply to the alarm device 31 is stopped, for example, the first and second electrodes 11 and 12 are disconnected and the pilot lamp is turned off. In addition, the switch element 1 stops heat generation when the refractory metal body 15 is melted after the first and second electrodes 11 and 12 are cut off.

[Insulated substrate]
The insulating substrate 10 is formed using an insulating member such as alumina, glass ceramics, mullite, zirconia, and the like. Since the switch element 1 transfers the heat of the refractory metal body 15 to the first and second electrodes and the soluble conductor 13 through the insulating substrate 10, the insulating substrate 10 has a heat resistance such as a ceramic substrate. It is preferably formed of a material that is excellent and has high thermal conductivity. 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 attention should be paid to the temperature when the refractory metal body 15 or the soluble conductor 13 is blown. There is a need to.

[First and second 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 fusible conductor 13 described later is mounted between 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 fusible conductor 13, and when the refractory metal body 15 generates heat when energized, it is heated by this heat to melt the molten conductor 13. Is released.

  The first and second electrodes 11 and 12 can be made to easily aggregate the molten conductor of the soluble conductor 13 by being heated by the refractory metal body 15.

  The first and second electrodes 11 and 12 are provided with external connection terminals 11a and 12a 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 alarm device 31 via these external connection terminals 11a and 12a, and the power supply to the alarm device 31 is cut off when the switch element 1 operates.

  The first and second electrodes 11 and 12 can be formed using a general electrode material such as Cu or Ag. In addition, a coating such as Ni / Au plating, Ni / Pd plating, or Ni / Pd / Au plating is coated on the surfaces of the first and second electrodes 11 and 12 by a known method such as plating. Preferably it is. Thereby, the switch element 1 can prevent the first and second electrodes 11 and 12 from being oxidized, and can reliably hold the molten conductor of the soluble conductor 13. In addition, when the switch element 1 is reflow-mounted, the first and second electrodes 11 and 12 are formed by melting the connecting solder for connecting the soluble conductor 13 or the low melting point metal forming the outer layer of the soluble conductor 13. Can be prevented from being eroded.

[High melting point metal]
The refractory metal body 15 is a conductive member that generates heat when energized, and is made of, for example, W, Mo, Ru, Cu, Ag, or an alloy containing these as main components. The refractory metal body 15 is formed by mixing powders of these alloys, compositions, or compounds with a resin binder, etc., forming a paste using a screen printing technique, firing, and the like. can do.

  The refractory metal body 15 is arranged alongside the first and second electrodes 11 and 12 on the surface 10 a of the insulating substrate 10. Thereby, the refractory metal body 15 can melt the soluble conductor 13 mounted on the first and second electrodes 11 and 12 when it generates heat upon energization.

  The refractory metal body 15 is provided with external connection terminals 15 a on the side edges 10 b and 10 c of the insulating substrate 10. The refractory metal body 15 is connected to the functional circuit 32 that triggers the operation of the alarm device 31 via the external connection terminal 15a, and generates heat to a high temperature due to an overcurrent exceeding the rating due to the abnormality of the functional circuit 32. The soluble conductor 13 is melted. For example, the refractory metal body 15 has a power design that generates heat at about 300 ° C. when 20 to 30 W of power is applied.

  In addition, the refractory metal body 15 is relatively thin at a position close to the fusible conductor 13, and a heat generating portion 15b that generates heat locally at a high temperature is formed by the concentration of current. By providing the heat generating part 15b at a position close to the fusible conductor 13, the refractory metal body 15 efficiently melts the fusible conductor 13 and quickly shuts off the first and second electrodes 11 and 12. Can do.

  Further, the switch element 1 is positioned close to one of the first or second electrodes 11 and 12, for example, as shown in FIG. 1, the tip 11b on which the soluble conductor 13 of the first electrode 11 is mounted. It is preferable that the heat generating portion 15b of the refractory metal body 15 is formed. By providing the heat generating portion 15b at a position close to the tip portion 11b on which the soluble conductor 13 of the first electrode 11 is mounted, the refractory metal body 15 can be efficiently passed through the insulating substrate 10 and the tip portion 11b. Heat can be transferred to the fusible conductor 13 to melt it, and the first and second electrodes 11 and 12 can be quickly cut off.

  Of the tip portions 11b and 12b on which the soluble conductor 13 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, and the other electrode It is preferable to hold more soluble conductors 13 than. For example, as shown in FIG. 1, when the heating element 15 b of the refractory metal body 15 and the tip 11 b of the first electrode 11 are brought close to each other, the switch element 1 moves the tip 11 b of the first electrode 11 to the first. It is preferable that the second electrode 12 is formed wider than the distal end portion 12 b and more soluble conductors 13 are mounted on the distal end portion 11 b side of the first electrode 11.

  Since the tip portion 11b of the first electrode 11 is close to the heat generating portion 15b, more heat from the refractory metal body 15 is transmitted, and the soluble conductor 13 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 soluble conductor 13 more quickly and melted. The two electrodes 11 and 12 can be blocked.

  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 it is heated to a higher temperature and holds most of the molten soluble conductor 13. be able to.

  As shown in FIG. 1, when the functional circuit 32 is operating normally, the refractory metal body 15 is supplied with an appropriate current within the rating. The refractory metal body 15 generates heat to a high temperature when an overcurrent exceeding the rating flows due to an abnormality in the functional circuit 32, and melts the fusible conductor 13 as shown in FIG. 11 and 12 are blocked. After that, the refractory metal body 15 continues to generate heat and is melted by its own Joule heat as shown in FIG. As a result, the refractory metal body 15 is cut off from overcurrent due to an abnormality in the functional circuit 32, shuts off the functional circuit 32, and stops its own heat generation. That is, the refractory metal body 15 functions as a fuse that melts the fusible conductor 13 and interrupts its power supply path by self-heating.

  Further, the refractory metal body 15 is fused at the heat generating portion 15b by providing the heat generating portion 15b that is locally high in temperature. At this time, since the refractory metal body 15 has the heat generating portion 15b formed relatively thin, the arc discharge generated at the time of fusing is also small, and together with the covering effect of the insulating layer 16 described later, the molten conductor Can be prevented.

  In addition to forming the pattern by printing the above-described conductive paste, the refractory metal body 15 uses a refractory metal foil such as a copper foil or a silver foil, or a refractory metal wire such as a copper wire or a silver wire. May be formed. Further, when the refractory metal body 15 is configured using a refractory metal foil or a refractory metal wire, a ceramic substrate that is excellent in thermal conductivity and can rapidly melt the soluble conductor 13 is used as the insulating substrate 10. However, the problem of leakage of the molten conductor after the melting of the refractory metal body 15 is less than that of the conductive pattern.

[Insulation layer]
The first and second electrodes 11, 12 and the refractory metal body 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 and second electrodes 11 and 12 and the refractory metal body 15, and to suppress arc discharge when the refractory metal body 15 is melted. Consists of layers.

  As shown in FIGS. 1 to 3, the insulating layer 16 covers the heat generating portion 15 b of the refractory metal body 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. Has been. That is, the first and second electrodes 11 and 12 have tips 11b and 12b exposed from the insulating layer 16 so that a soluble conductor 13 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 refractory metal body 15 transmitted through the insulating substrate 10 is dissipated. The tip portions 11b and 12b can be efficiently heated and the heat can be transmitted to the soluble conductor 13. Further, the first and second electrodes 11 and 12 are provided with an insulating layer 16 between the tip portions 11b and 12b and the external connection electrodes 11a and 12a, so that the melted soluble conductor 13 can be connected to the external connection electrode 11a. , 12a, and the situation where the solder for connection with the circuit board on which the switch element 1 is mounted is melted can be prevented.

  In the switch element 1, an insulating layer 16 made of glass or the like may be formed between the refractory metal body 15 and the insulating substrate 10. Thereby, the switch element 1 can prevent leakage due to adhesion of the molten conductor to the surface of the insulating substrate 10 after the refractory metal body 15 is cut off, and can increase the insulation resistance. Furthermore, the insulating layer 16 formed between the refractory metal body 15 and the insulating substrate 10 is partially formed only in the vicinity of the center of the heat generating portion 15b, thereby ensuring heat transfer to the fusible conductor 13 and after blocking. It is possible to ensure insulation resistance.

[Soluble conductor]
The fusible conductor 13 mounted on the first and second electrodes 11 and 12 via the insulating layer 16 can use any metal that is rapidly melted by the heat generated by the refractory metal body 15. 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.

  Moreover, the soluble conductor 13 may contain a low melting metal and a high melting 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 shape of the soluble conductor 13 can be maintained. In addition, even when fusing, the low melting point metal melts, and the high melting point metal is eroded (soldered), so that the fusing can be quickly performed at a temperature lower than the melting point of the high melting point metal. In addition, the soluble conductor 13 can be formed by various structures so that it may demonstrate later.

  The soluble conductor 13 is preferably coated with a flux 18 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 soluble conductor 13 (FIG. 1C) and are soluble by the heat generation of the refractory metal body 15. When the conductor 13 melts, it is opened. (FIG. 2 (C)).

  The switch element 1 is used by being incorporated in an alarm circuit 30, for example. FIG. 4 is a diagram showing an example of the circuit configuration of the alarm circuit 30. As shown in FIG. The alarm circuit 30 is formed by an operation circuit 33 for operating the alarm device 31 by a first fuse 35 made of the fusible conductor 13 of the switch element 1 and electrically independent of the operation circuit 33. And a control circuit 34 having a functional circuit in which a second fuse 36 made of a refractory metal body 15 having a high melting point is connected in series to a power source.

  As shown in FIG. 4, the switch element 1 has an alarm that both external connection terminals 11a and 12a of the first fuse 35 (the fusible conductor 13) are energized when normal, such as a pilot lamp, and are de-energized when abnormal. Connected to the device 31. In the switch element 1, both external connection terminals 15 a of the second fuse 36 (the refractory metal body 15) are connected to the functional circuit 32.

  The switch element 1 having such a configuration has a fusible conductor 13 due to heat generation of the refractory metal body 15 formed adjacent to the first and second electrodes 11 and 12 that operate the alarm device 31. Is melted, and the first and second electrodes 11 and 12 are blocked. That is, the switch element 1 is configured such that the refractory metal body 15 and the first and second electrodes 11 and 12 are physically and electrically independent, and the soluble conductor 13 is heated by the heat of the refractory metal body 15. It cuts off by melting, so to speak, it has a configuration that works together by connecting thermally.

  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, since the refractory metal body 15 and the first and second electrodes 11 and 12 are configured physically and electrically independently, for example, the refractory metal body that functions as a fuse is used. When the alarm signal is output to the signal system line separated from the power system power line in which the circuit 15 is disposed, there is no influence of the power supply noise when the refractory metal body 15 is cut off, and no noise countermeasure circuit is required. A high alarm circuit can be constructed.

  In actual use, an overcurrent exceeding the rating flows through the refractory metal body 15 due to the malfunction of the functional circuit 32 in the switch element 1. Then, as shown in FIG. 2 (A), the refractory metal body 15 generates heat, and heat is applied to the soluble conductor 13 through the insulating substrate 10 and the tip portions 11b, 12b of the first and second electrodes 11, 12. As a result, the soluble conductor 13 is melted. The molten conductor of the fusible conductor 13 agglomerates on the tip portions 11 b and 12 b of the first and second electrodes 11 and 12 heated by the refractory metal body 15. Thereby, the switch element 1 can interrupt between the 1st, 2nd electrodes 11 and 12 and can stop the electricity supply to the alarm device 31 of the operating circuit 33 (FIG.2 (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.

  At this time, the switch element 1 is provided with a thin heat generating portion 15b in the vicinity of the soluble conductor 13 of the refractory metal body 15, so that the high resistance heat generating portion 15b becomes high temperature and the soluble conductor 13 is efficiently formed. And the first and second electrodes 11 and 12 can be quickly short-circuited. In the refractory metal body 15, the high resistance heat generating portion 15b is only locally heated, and both the external connection terminals 15a facing the side edges are kept at a relatively low temperature due to the heat dissipation effect. Therefore, the switch element 1 does not melt the solder for mounting the external connection terminal 15a.

  As shown in FIG. 3, the refractory metal body 15 continues to generate heat even after the first and second electrodes 11 and 12 are cut off, and cut off by its own Joule heat (FIGS. 3A and 3B). As a result, the switch element 1 is cut off from energization of the refractory metal body 15 by the functional circuit 32 and stops generating heat (FIG. 3C). At this time, since the high melting point metal body 15 is covered with the insulating layer 16, the switch element 1 can suppress arc discharge and suppress explosive scattering of the molten conductor. Further, by providing the heat generating portion 15b that is thinly formed on the refractory metal body 15, the fusing part is narrowed, and the amount of the molten conductor scattered can be reduced.

  Thus, in the switch element 1, the refractory metal body 15 having a melting point higher than that of the fusible conductor 13 generates heat, so that the fusible conductor 13 is reliably melted before the refractory metal body 15. The second electrodes 11 and 12 can be blocked. That is, in the switch element 1, the fusing of the refractory metal body 15 is not a condition for blocking the first and second electrodes 11 and 12. Thus, the switch element 1 can be used as an alarm element that reports that an overcurrent exceeding the rating of the refractory metal body 15 has flowed due to an abnormality of the functional circuit 32. Therefore, according to the alarm circuit 30 in which the switch element 1 is incorporated, an abnormality of the functional circuit 32 can be quickly detected according to the operation of the alarm device 31 such as turning off the pilot lamp, and before the functional circuit 32 completely fails. Therefore, it is possible to prevent the function circuit 32 from being stopped and to operate the backup circuit.

  The refractory metal body 15 automatically stops heat generation 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 functional circuit 32, can stop the heat generation of the refractory metal body 15 with a simple configuration, and can reduce the size of the entire element. .

  Further, the switch element 1 may connect the refractory metal body 15 with one of the first or second electrodes 11 and 12 close to the heat generating portion 15 b of the refractory metal body 15. For example, as shown in FIG. 5, when the heating element 15 b of the refractory metal body 15 and the tip 11 b of the first electrode 11 are close to each other, the switch element 1 includes the refractory metal body 15 and the first electrode. 11 may be formed. The connection portion 19 can be provided by patterning in the same process as the refractory metal body 15 and the first electrode 11 using the same conductive material as that of the refractory metal body 15 and the first electrode 11, for example. .

  By connecting the refractory metal body 15 and the first electrode 11, the switch element 1 can also be heated through the connection portion 19 and the first electrode 11 when the refractory metal body 15 generates heat when energized. It is transmitted to the molten conductor 13 and can be melted more quickly. Therefore, it is preferable to form the connection part 19 with metal materials, such as Ag and Cu, which are excellent in thermal conductivity.

  The connecting portion 19 is provided at a position slightly away from the center of the heat generating portion 15 of the refractory metal body 15. Since the refractory metal body 15 is provided with the connecting portion 19 and its resistance value is lowered and the temperature does not easily rise, the heat generating portion 15b generates heat at a high temperature and is connected to the center of the heat generating portion 15b in order to shut off by self-heating. This is because it needs to be provided at a position separated from the portion 19.

[Cover member]
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 21 that constitutes a side surface of the switch element 1 and a top surface portion 22 that constitutes an upper surface of the switch element 1, and the side wall 21 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.

  As shown in FIG. 6, the cover member 20 may have a cover portion electrode 23 formed on the inner surface side of the top surface portion 22. The cover part electrode 23 is formed at a position overlapping one of the first electrode 11 and the second electrode 12. More preferably, the cover electrode 23 is overlapped with the tip portion 11b of the first electrode 11 which is close to the heat generating portion 15b of the refractory metal body 15 and has a relatively large area. As a result, when the high melting point metal body 15 generates heat and the soluble conductor 13 is melted, the cover conductor electrode 23 comes into contact with the molten conductor aggregated on the tip portion 11b of the first electrode 11 and spreads wet. As a result, the allowable amount for holding the molten conductor can be increased, and the first and second electrodes 11 and 12 can be blocked more reliably.

[Modification 1]
In the switch element to which the present invention is applied, the refractory metal body and the first electrode or the second electrode may be overlapped on the surface of the insulating substrate. 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. In the switch element 40, as shown in FIG. 7, a refractory metal body 15 is formed between the opposing 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 are formed on opposite side edges 10 b and 10 c of the surface 10 a of the insulating substrate 10.

  The refractory metal body 15 is covered with a first insulating layer 41 at a substantially central portion of the insulating substrate 10. The refractory metal body 15 has external connection terminals 15 a formed on the side edges 10 d and 10 e of the insulating substrate 10. Further, the refractory metal body 15 is formed with a heat generating portion 15b that generates heat at a high temperature by forming an intermediate portion thinner than both end portions.

  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.

  As for the 1st, 2nd electrodes 11 and 12, the solder | pewter for a connection is provided in the front-end | tip parts 11b and 12b, and the soluble conductor 13 is mounted ranging over the front-end | tip parts 11b and 12b by this connection solder. In addition, the switch element 40 includes one of the first and second electrodes 11 and 12, for example, as shown in FIG. 7, the distal end portion 11 b of the first electrode 11 formed in a relatively large area, and the distal end A part of the soluble conductor 13 mounted on the part 11 b is superimposed on the heat generating part 15 b of the refractory metal body 15. A flux 18 is applied on the soluble conductor 13 to prevent oxidation and improve wettability.

  For 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 switching element 1 described above.

  According to such a switch element 40, since many of the front-end | tip part 11b of the 1st electrode 11 and the soluble conductor 13 are arrange | positioned so that it may overlap with the heat generating part 15b of the refractory metal body 15, the heat generating part 15b The soluble conductor 13 can be quickly melted by heat generation, and the first and second electrodes 11 and 12 can be shut off. At this time, in the switch element 40, the heat generating portion 15b, the first electrode 11, and the soluble conductor 13 are continuously laminated via the first insulating layer 41 made of glass or the like. Of heat can be transferred efficiently.

[Modification 2]
In addition, the switch element to which the present invention is applied has the first and second electrodes formed on the surface of the insulating substrate, and the refractory metal body is formed on the back surface of the insulating substrate. The electrode or the second electrode 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. In the switch element 50, as shown in FIG. 8, the refractory metal body 15 is formed between the opposite side edges 10d and 10e of the back surface 10f of the insulating substrate 10. In the switch element 50, the first and second electrodes 11 and 12 are formed on opposite side edges 10 b and 10 c of the surface 10 a of the insulating substrate 10.

  The refractory metal body 15 is covered with a first insulating layer 51 at a substantially central portion of the insulating substrate 10. The refractory metal body 15 has external connection terminals 15 a formed on the side edges 10 d and 10 e of the insulating substrate 10. Further, the refractory metal body 15 is formed with a heat generating portion 15b that generates heat at a high temperature by forming an intermediate portion where the first electrode 11 or the second electrode 12 overlaps to be thinner than both end portions.

  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.

  As for the 1st, 2nd electrodes 11 and 12, the solder | pewter for a connection is provided in the front-end | tip parts 11b and 12b, and the soluble conductor 13 is mounted ranging over the front-end | tip parts 11b and 12b by this connection solder. Further, the switch element 50 includes one of the first and second electrodes 11 and 12, for example, as shown in FIG. 8, a distal end portion 11 b of the first electrode 11 formed in a relatively large area, and a distal end A part of the soluble conductor 13 mounted on the part 11 b is superimposed on the heat generating part 15 b of the refractory metal body 15. A flux 18 is applied on the soluble conductor 13 to prevent oxidation and improve wettability.

  For the first and second insulating layers 51 and 52, 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 50, since most of the tip portion 11b of the first electrode 11 and the soluble conductor 13 are disposed so as to overlap the heat generating portion 15b of the refractory metal body 15, the heat generating portion 15b The soluble conductor 13 can be quickly melted by heat generation, and the first and second electrodes 11 and 12 can be shut off. At this time, the switch element 50 is formed of the refractory metal body 15 on the same surface as the surface on which the soluble conductor 13 is provided by using the insulating substrate 10 having excellent thermal conductivity such as a ceramic substrate. This is preferable because it can be heated as much as the case.

[Modified example of soluble conductor]
As described above, any or all of the soluble conductor 13 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. 9A, the soluble conductor 13 may be a soluble conductor in which a high melting point metal layer 60 is provided as an inner layer and a low melting point metal layer 61 is provided as an outer layer. In this case, the soluble conductor 13 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, or may have a structure in which a pair of opposite side surfaces are covered. 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.

  As shown in FIG. 9B, the soluble conductor 13 may be a soluble conductor 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. Also in this case, the soluble conductor 13 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, or a structure in which the soluble conductor 13 is covered except for a pair of opposing side surfaces.

  Further, the soluble conductor 13 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, as shown in FIG. 10A, the soluble conductor 13 has a two-layer structure composed of a lower layer supported by the first and second electrodes 11 and 12 and an upper layer stacked on the lower layer. The low melting point metal layer 61 that is the upper layer may be laminated on the upper surface of the lower melting point metal layer 60 that is formed, and conversely, the upper melting point metal layer 60 that is the upper layer on the lower melting point metal layer 61 that is the lower layer. May be laminated. Alternatively, the soluble conductor 13 may be formed as a three-layer structure including an inner layer and an outer layer laminated on the upper and lower surfaces of the inner layer, as shown in FIG. 10 (B), and the refractory metal layer 60 serving as the inner layer. The low melting point metal layer 61 serving as the outer layer may be stacked on the upper and lower surfaces of the upper layer, and the high melting point metal layer 60 serving as the outer layer may be stacked on the upper and lower surfaces of the low melting point metal layer 61 serving as the inner layer.

  Further, the soluble conductor 13 may have a multilayer structure of four or more layers in which the high melting point metal layers 60 and the low melting point metal layers 61 are alternately laminated as shown in FIG. In this case, the soluble conductor 13 may have a structure in which the entire surface or a pair of opposite side surfaces are covered with a metal layer constituting the outermost layer.

  In the soluble conductor 13, the high melting point 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. 12 is a plan view of the fusible conductor 13.

  The soluble conductor 13 shown in FIG. 12A has a longitudinal direction by forming a plurality of linear refractory metal layers 60 in the longitudinal direction at predetermined intervals in the width direction on the surface of the low melting point metal layer 61. A linear opening 62 is formed along the opening, and the low melting point metal layer 61 is exposed from the opening 62. The fusible conductor 13 exposes the low melting point metal layer 61 from the opening 62, thereby increasing the contact area between the melted low melting point metal and the high melting point metal and further promoting the erosion action of the high melting point metal layer 60. The fusing property can be improved. 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. 12B, the soluble conductor 13 is formed by forming a plurality of linear refractory metal layers 60 in the width direction on the surface of the low melting point metal layer 61 at predetermined intervals in the longitudinal direction. Thus, the linear opening 62 may be formed along the width direction.

  Further, as shown in FIG. 13, the soluble conductor 13 forms a refractory metal layer 60 on the surface of the low melting point metal layer 61, and a circular opening 63 is formed over the entire surface of the refractory metal layer 60. 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.

  The fusible conductor 13 is exposed to the low melting point metal layer 61 through the opening 63, thereby increasing the contact area between the molten low melting point metal and the high melting point metal, further promoting the erosion action of the high melting point metal and fusing. Can be improved.

  Further, as shown in FIG. 14, the soluble conductor 13 has a large number of openings 64 formed in the refractory metal layer 60 serving as an inner layer, and the refractory metal layer 60 is formed with a low melting point metal using a plating technique or the like. The layer 61 may be formed and filled in the opening 64. As a result, the soluble conductor 13 increases the area where the molten low melting point metal contacts the high melting point metal, so that the low melting point metal can corrode the high melting point metal in a shorter time.

  Further, it is preferable that the soluble conductor 13 is formed so 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 soluble conductor 13 is heated by the refractory metal body 15, so that the refractory metal is melted by melting the refractory metal, and can thereby be melted and blown quickly. Therefore, the soluble conductor 13 promotes this erosion 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 prompts the first and second electrodes 11. , 12 can be blocked.

1, 40, 50 switch element, 10 insulating substrate, 10a surface, 10f back surface, 11 first electrode, 12 second electrode, 13 soluble conductor, 15 refractory metal body, 16 insulating layer, 18 flux, 19 connection Part, 20 cover member, 21 side wall, 22 top surface part, 23 cover part electrode, 30 alarm circuit, 31 alarm device, 32 function circuit, 35 first fuse, 36 second fuse

Claims (37)

First and second electrodes;
A soluble conductor connected across the first and second electrodes;
A high melting point metal body having a melting point higher than that of the soluble conductor,
A switch element that melts the soluble conductor by heat generated by overcurrent exceeding the rated current flowing in the refractory metal body.   2. The switch element according to claim 1, wherein the refractory metal body is melted by self-heating (joule heat) accompanying an overcurrent exceeding a rated current after the first and second electrodes are interrupted.   The switch element according to claim 1 or 2, wherein the refractory metal body and the first and second electrodes are electrode patterns laminated on a surface of an insulating substrate.   4. The switch element according to claim 3, wherein the refractory metal body and the first and second electrodes are formed by patterning silver, copper, or a refractory metal mainly composed of silver or copper.   The electrode pattern of the refractory metal body is formed with a heat generating portion that locally becomes heated to a high temperature when the current is concentrated because the position close to the soluble conductor is relatively narrow. The switch element as described in.   The switch element according to claim 5, wherein one of the distal end portions of the first or second electrode on which the soluble conductor is mounted and the heat generating portion are close to each other.   Of the tip portion of the first or second electrode on which the soluble conductor is mounted, one area close to the heat generating portion is wider than the other area and more soluble than the other electrode. The switch element according to claim 6 which holds a conductor.   8. The switch element according to claim 6, wherein, of the first and second electrodes, one of the electrodes adjacent to the heat generating portion is connected to the refractory metal body.   The switch element according to claim 1, wherein the refractory metal body is covered with an insulating layer.   The switch element according to claim 3, wherein an insulating layer is formed between the refractory metal body and the insulating substrate.   The switch element according to any one of claims 1 to 10, wherein the first and second electrodes are covered with an insulating layer except for a front end portion on which the soluble conductor is mounted.   The switch element according to claim 9, wherein the insulating layer is made of glass or an insulating material containing glass as a main component.   The switch element according to claim 1, wherein the refractory metal body is a foil or a wire mainly composed of copper or silver.   The switch element according to claim 1, wherein the first and second electrodes and the refractory metal body are arranged side by side on the same plane of the insulating substrate.   On one surface of the insulating substrate, one of the first electrode or the second electrode and the soluble conductor mounted on the one electrode are placed on the refractory metal body via an insulating layer. The switch element according to claim 3, wherein the switch element is laminated.   The first and second electrodes are disposed on one surface of the insulating substrate, the refractory metal body is disposed on the other surface of the insulating substrate, and the refractory metal body and the first electrode or The switch element according to any one of claims 3 to 7, which is superimposed on one of the second electrodes and the soluble conductor mounted on the one electrode.   The switch element according to claim 15 or 16, wherein an insulating layer is formed between the refractory metal body and the insulating substrate.   The switch element according to any one of claims 15 to 17, wherein the first and second electrodes are covered with the insulating layer except for a tip portion on which the soluble conductor is mounted.   The switch element according to claim 15, wherein the insulating layer is made of glass or an insulating material containing glass as a main component.   The switch element according to claim 3, wherein the insulating substrate is a ceramic substrate.   The switch element according to claim 1, wherein the soluble conductor is solder. The soluble conductor contains a low melting point metal and a high melting point metal,
The switch element according to any one of claims 1 to 20, wherein the low-melting-point metal melts due to heat generation of the high-melting-point metal body and erodes the high-melting-point metal. The low melting point metal is solder,
The switch element according to claim 22, wherein the refractory metal is Ag, Cu, or an alloy containing Ag or Cu as a main component.   24. The switch element according to claim 22 or 23, wherein the soluble conductor has a coating structure in which an inner layer is a high melting point metal and an outer layer is a low melting point metal.   The switch element according to claim 22 or 23, wherein the soluble conductor has an inner layer made of a low melting point metal and an outer layer made of a high melting point metal.   The switch element according to claim 22 or 23, wherein the soluble conductor has a laminated structure in which a low melting point metal and a high melting point metal are laminated.   The switch element according to claim 22 or 23, wherein the soluble conductor has a multilayer structure of four or more layers in which a low melting point metal and a high melting point metal are alternately laminated.   The switch element according to claim 22 or 23, wherein the soluble conductor is provided with an opening in a high melting point metal formed on a surface of the low melting point metal constituting the inner layer.   The soluble conductor has a high melting point metal layer having a number of openings and a low melting point metal layer formed on the high melting point metal layer, and the opening is filled with a low melting point metal. Item 24. The switch element according to item 22 or 23.   The switch element according to any one of claims 22 to 29, wherein the soluble conductor has a volume of a low-melting-point metal larger than a volume of a high-melting-point metal.   The switch element according to any one of claims 1 to 30, wherein a flux is coated on the soluble conductor.   The switch element according to any one of claims 1 to 31, wherein the first and second electrode surfaces are coated with any of Ni / Au plating, Ni / Pd plating, and Ni / Pd / Au plating. . A cover member provided on the insulating substrate for protecting the inside;
The switch element according to any one of claims 3 to 32, wherein the cover member is provided with a cover portion electrode at a position overlapping with any one of the first and second electrodes. A first fuse is connected to the external circuit and the first and second electrodes are connected to the external circuit, and the first and second electrodes are opened to supply power to the external circuit. A switch part for stopping
A second fuse having a melting point higher than the melting point of the first fuse and connected to a functional circuit formed electrically independent of the switch portion;
A switch circuit that melts the first fuse and interrupts the first and second electrodes to stop the power supply to the external circuit due to heat generated by overcurrent exceeding the rated current flowing in the second fuse. .   35. The switch circuit according to claim 34, wherein the second fuse is blown by self-heating (Joule heat) accompanying an overcurrent exceeding a rated current after the first fuse is cut off. The first and second electrodes are connected to each other by being opened, and the power supply to the alarm is stopped by opening the first and second electrodes. An operating circuit to
A second fuse formed electrically independent of the operating circuit and having a melting point higher than the melting point of the first fuse; and a control circuit having a functional circuit in which the second fuse is connected in series to a power source; With
When the functional circuit is abnormal, the first fuse is melted and the first and second electrodes are disconnected by the heat generated by the overcurrent exceeding the rated current flowing through the second fuse. Alarm circuit that stops power supply.   The alarm circuit according to claim 36, wherein the second fuse is blown by self-heating (Joule heat) accompanying an overcurrent exceeding a rated current after the first fuse is cut off.