JP5994410B2 - Protective element - Google Patents

Description

  The present invention relates to a protection element that protects an element or the like connected to a subsequent stage by fusing a path with heat of the overcurrent when an overcurrent flows.

  In general, a fuse that protects a circuit element from an overcurrent is known which is melted by heat generated by the overcurrent and interrupts an energization path. Patent Document 1 discloses a fusing fuse using a low melting point metal. FIG. 5 is a schematic diagram showing the configuration of the fuse disclosed in Patent Document 1. As shown in FIG.

  In Patent Document 1, a film resistor 101 is formed on an insulating substrate 100, and two portions of the film resistor 101 are exposed, and an insulating layer 102 is provided on the film resistor 101. A heater electrode 103 is provided on one of the two exposed portions, and a heater / fuse composite electrode 104 is provided on the other. The heater / fuse composite electrode 104 partially extends on the insulating layer 102. In addition, two fuse electrodes 105a and 105b are provided in a non-conducting state with the membrane resistor 101, respectively, and an extended portion (heater electrode portion 104a) of the heater / fuse composite electrode 104 and two A low-melting-point metal fuse 106 is connected between each of the two fuse electrodes 105a and 105b. When the circuit abnormality detection circuit element detects a circuit abnormality, the film resistor 101 is energized to generate heat, and the fuse 106 is melted by the generated heat.

JP 2001-57139 A

  However, in the case of Patent Document 1, it is difficult to reduce costs because a circuit abnormality detection circuit element is required to blow the fuse 106, and further, a process of providing the insulating layer 102 and the like is required. May increase. Further, since the heater electrode is provided, the heater electrode is enlarged by the area of the heater electrode, which is an obstacle to miniaturization.

  Accordingly, an object of the present invention is to provide an inexpensive and small protective element without requiring a separate element such as a heater for interrupting the current path.

  The protection element according to the present invention includes an insulator substrate, a first conductive pattern, a second conductive pattern, and a third conductive pattern that are formed in a non-connected manner on the surface of the insulator substrate, A conductive path between the first conductive pattern and the second conductive pattern, the first path metal being melted at a predetermined temperature, and the first path metal and the third conductive pattern. A second path metal that is electrically conductive and melts at a predetermined temperature.

  In this configuration, when an overcurrent flows through the first path metal that conducts between the first conductive pattern and the second conductive pattern, the temperature rises and the first path metal melts. . In addition, when an overcurrent flows through the second path metal that conducts between the first path metal and the third conductive pattern, the temperature rises and the second path metal melts. When one of the first path metal and the second path metal is melted, the other is also melted by heat conduction. When the path metal is thus melted, the path metal is divided by the surface tension. Therefore, the protection element according to the present invention controls two currents by controlling the amount of current in one of the current path formed by the first path metal and the current path formed by the second path metal. Both paths can be blocked. That is, the interruption of the two current paths can be controlled without requiring an element such as a heater, and the protection element can be reduced in size and cost.

  In the protection element according to the present invention, the second path metal may have a narrower width than the first path metal.

  In this configuration, if the melting temperature of the first path metal is the same as the melting temperature of the second path metal, the second path metal is narrower than the first path metal. The second path metal has a higher resistance than the first path metal. Therefore, the current value at which the current path is blocked can be made different between the first path metal and the second path metal. That is, the second path metal can be melted at a low current value.

  In the protection element according to the present invention, the melting temperature of the second path metal may be higher than the melting temperature of the first path metal.

  In this configuration, since the melting temperature of the second path metal is higher than the melting temperature of the first path metal, the second path metal is melted first before the first path metal is melted. This can be prevented, and when the second path metal is melted, the first path metal can be reliably melted.

  In the protection element according to the present invention, it is preferable that the first path metal and the second path metal are configured in a T shape when viewed from the normal direction of the surface of the insulator substrate.

  In this configuration, the length of the second path metal can be shortened, so that cost reduction can be realized and pattern formation can be facilitated.

  The protection element according to the present invention may be configured to further include sealing means for sealing the first path metal and the second path metal to the insulator substrate.

  In this configuration, since the first path metal, the second path metal, and the like are sealed, deterioration such as oxidation over time can be reduced, and the reliability of protection can be prevented from being lowered.

  According to the present invention, both current paths are cut off by controlling the amount of current in one of the current path formed by the first path metal and the current path formed by the second path metal. Can be made. That is, the interruption of the two current paths can be controlled without requiring an element such as a heater, and the protection element can be reduced in size and cost.

Schematic of the protection element according to the first embodiment Schematic diagram showing the protection element when the solder alloy melts Schematic of the protection element according to the second embodiment Schematic diagram showing the protection element when the solder alloy melts Schematic diagram showing the configuration of the fuse disclosed in Patent Document 1

<< First Embodiment >>
FIG. 1 is a schematic diagram of a protection element according to the first embodiment. 1A is a top view, FIG. 1B is a cross-sectional view taken along line I-I shown in FIG. 1A, and FIG. 1C is in FIG. It is sectional drawing in the II-II line shown in FIG. For convenience of explanation, in FIG. 1A, the solder alloy (first path metal) 15 and the solder alloy (second path metal) 16 are transmitted and shown by dotted lines.

  The protection element 1 according to the present embodiment includes a printed board (insulator board) 10 made of a glass cloth base epoxy resin. The printed circuit board 10 has a rectangular parallelepiped shape having a rectangular front and back surfaces having a long side and a short side when viewed from above, and three conductive wiring patterns (first first) made of, for example, thin copper foil are formed on the surface thereof. ), A wiring pattern (second conductive pattern) 12 and a wiring pattern (third conductive pattern) 13 are formed.

  Each of the wiring patterns 11 and 12 has a rectangular shape with long sides and short sides as viewed from above, the long sides are parallel to the short sides of the printed circuit board 10 and along the longitudinal direction of the printed circuit board 10. Located on a straight line. Furthermore, the wiring patterns 11 and 12 are positioned symmetrically about the line segment orthogonal to the long side at the center of the long side of the printed circuit board 10.

  On the printed board 10, a solder alloy 15 is formed for electrical connection between the wiring pattern 11 and the wiring pattern 12. The solder alloy 15 has a width of the same length as the long sides of the wiring patterns 11 and 12 and constitutes a linear current path (hereinafter referred to as a first current path) parallel to the long sides of the printed circuit board 10. ing. This solder alloy 15 is made of a low melting point metal that does not melt at the time of reflow but melts at a predetermined temperature.

  The wiring pattern 13 is similar to the wiring patterns 11 and 12 when viewed from above, and is smaller than the wiring patterns 11 and 12. The wiring pattern 13 is formed at a position where the long side is parallel to the long side of the printed circuit board 10 and at the approximate center between the wiring patterns 11 and 12 and away from the solder alloy 15. On the printed circuit board 10, a solder alloy 16 is formed for electrical connection between the wiring pattern 13 and the solder alloy 15.

  The solder alloy 16 is made of a low melting point metal similar to the solder alloy 15. The solder alloy 16 is connected to the solder alloy 15 substantially vertically so as to form an integral T-shaped member together with the solder alloy 15 in a top view. That is, the solder alloys 15 and 16 constitute a current path (hereinafter referred to as a second current path) that connects the wiring pattern 13 and the wiring patterns 11 and 12. Further, the solder alloy 16 has the same width as the long side of the wiring pattern 13. That is, it has a narrower width than the solder alloy 15.

  As a method of forming the solder alloys 15 and 16 on the surface of the printed circuit board 10, a solder paste is applied to the surface of the printed circuit board 10, and the solder alloys 15 and 16 are mounted thereon. The solder alloys 15 and 16 do not melt, but the solder paste reflows at a melting temperature. Thereafter, cleaning is performed with a flux cleaning solution at 70 ° C. for 10 min to remove the flux. The solder alloys 15 and 16 may be formed separately.

  Although omitted in FIG. 1, a liquid flux is applied to the surface of the mounted solder alloy 15 by printing.

  As described above, the printed circuit board 10 on which the wiring patterns 11, 12, 13 and the solder alloys 15, 16 are formed is housed in a case 20 made of metal or resin. The printed circuit board 10 and the case 20 are fixed with an adhesive, for example. By accommodating the printed circuit board 10 in the case 20, it is possible to prevent foreign matter from adhering to the flux applied to the surface of the solder alloy 15.

  The printed circuit board 10 on which the wiring patterns 11, 12, 13 and the solder alloys 15 and 16 are formed is preferably sealed with a resin. In this case, since the wiring patterns 11, 12, 13 and the solder alloys 15, 16 are embedded in the resin, deterioration such as oxidation with the passage of time can be reduced, and the reliability of protection can be prevented from being lowered.

  The protection element 1 configured as described above is, for example, solder-mounted on a circuit board or the like on which an element or the like is mounted, and the wiring pattern on the circuit board is connected to the wiring patterns 11, 12, and 13. When an overcurrent exceeding a certain level flows in the solder alloys 15 and 16, the solder alloys 15 and 16 are self-heated and melt, so that the first current path and the second current path are interrupted.

  FIG. 2 is a schematic diagram showing the protection element 1 when the solder alloys 15 and 16 are melted. In the first embodiment, the solder alloys 15 and 16 are made of a material having the same melting temperature, and the solder alloy 16 having a narrow path width has a higher resistivity than the solder alloy 15. Therefore, when the current supply to the solder alloy 16 is controlled to cause the solder alloy 16 to self-heat and melt, the solder alloy 16 is melted before the solder alloy 15. Then, the heat generated by the solder alloy 16 is transferred to the solder alloy 15, and the solder alloy 15 is also melted. Since the melted solder alloy 16 and solder alloy 15 try to be spheroidized by surface tension while being wetted to the wiring patterns 11, 12, 13, the solder alloy 15, 16 is divided to form metal blocks 15A, 15B, 16A. Thereby, the first current path and the second current path are interrupted.

  Thus, the protection element 1 can interrupt the first current path by controlling the energization of the second current path without requiring a heater or the like. Therefore, it is possible to reduce the size and cost compared to the case where a heater or the like is provided.

<< Second Embodiment >>
FIG. 3 is a schematic view of the protective element according to the second embodiment viewed from above. The protection element 21 according to the second embodiment includes a printed board 30 having wiring patterns 31, 32, and 33 formed on the surface thereof, as in the first embodiment. Further, unlike the first embodiment, a conductive wiring pattern (fourth conductive pattern) 34 is further formed on the surface of the printed board 30.

  The wiring pattern 34 has a rectangular shape having a long side and a short side when viewed from above, the long side has the same length as the long sides of the wiring patterns 31 and 32, and the short side is the long side of the wiring pattern 33. It is getting longer. The wiring pattern 34 is located substantially at the center between the wiring patterns 31 and 32, and the long side faces the long side of the wiring patterns 31 and 32, and the short side faces the long side of the wiring pattern 33. At this time, the wiring pattern 34 is formed so as to protrude from the wiring patterns 31 and 32 toward the wiring pattern 33.

  The printed circuit board 30 is formed with a linear solder alloy 35 that conducts the wiring patterns 31, 34, and 32. The solder alloy 35 is a linear current path having the same length as the long sides of the wiring patterns 31 and 32 and parallel to the long side of the printed circuit board 30. The solder alloy 35 forms a current path between the wiring patterns 31 and 34 (hereinafter referred to as a third current path) and a current path between the wiring patterns 32 and 34 (hereinafter referred to as a fourth current path). . The solder alloy 35 is formed of a low melting point metal that does not melt at the time of reflow and melts at a temperature T1.

  The printed circuit board 30 is formed with a linear solder alloy 36 that conducts the wiring patterns 33 and 34. The solder alloy 36 is configured as a T-shaped member integrated with the solder alloy 35 in a top view. The solder alloy 36 serves as a current path (hereinafter referred to as a fifth current path) that connects the wiring pattern 33 and the wiring pattern 34. The solder alloy 36 has the same width as the long side of the wiring pattern 33. That is, the solder alloy 36 has a narrower width than the solder alloy 35. The solder alloy 36 is made of a low melting point metal that does not melt during reflow but melts at a temperature T2 (> T1).

  Although the solder alloy 36 is narrower than the solder alloy 35, the widths of the solder alloys 35 and 36 are adjusted so that the solder alloy 35 is melted before the solder alloy 36 when an overcurrent flows. Has been.

  The formation method of the solder alloys 35 and 36 is the same as that of the first embodiment. The solder alloys 35 and 36 are coated with a liquid flux on the surface. Furthermore, although not shown, the protective element 21 according to the second embodiment is housed in a metal or resin case as in the first embodiment.

  The protective element 21 configured as described above is solder-mounted, for example, on a circuit board or the like, as in the first embodiment, and the wiring pattern on the circuit board is connected to the wiring patterns 31, 32, 33, and 34. . When an overcurrent exceeding a certain level flows in the solder alloys 35, 36, the solder alloys 35, 36 are self-heated and melt, so that the current path between the wiring patterns 31, 32, 33, 34 is cut off.

  FIG. 4 is a schematic diagram showing the protection element 21 when the solder alloys 35 and 36 are melted. In the second embodiment, when an overcurrent flows, the solder alloy 35 is melted prior to the solder alloy 36 due to heat transfer from the solder alloy 36 to form metal masses 35A and 35B. As described above, the melting of the solder alloy 35 before the solder alloy 36 reduces the possibility that the third current path and the fourth current path will not be blocked without melting the solder alloy 35. it can. In addition, even if the third current path and the fourth current path are interrupted, the fifth current path remains, so that the necessary current path (fifth current path) remains while another path (third Wiring design capable of reliably interrupting the current path and the fourth current path).

  It should be noted that the specific configuration and the like of the protection element can be appropriately changed in design, and the actions and effects described in the above-described embodiments are merely a list of the most preferable actions and effects that arise from the present invention, and the present invention. The functions and effects of are not limited to those described in the above-described embodiments.

DESCRIPTION OF SYMBOLS 1,21 ... Protection element 10, 30 ... Printed circuit board 11, 12, 13, 31, 32, 33, 34 ... Wiring pattern 15, 16, 35, 36 ... Solder alloy 15A, 15B, 16A, 35A, 35B ... Metal lump 20 ... Case

Claims (5)

An insulator substrate;
A first conductive pattern, a second conductive pattern, and a third conductive pattern formed in a non-connected manner on the surface of the insulator substrate;
A first path metal which is electrically connected between the first conductive pattern and the second conductive pattern and generates heat by a flowing current and melts at a predetermined temperature;
A second path metal that is electrically connected between the third conductive pattern and the first path metal and that generates heat by a flowing current and melts at a predetermined temperature;
Equipped with a,
The protective element according to claim 1, wherein the first path metal and the second path metal are integrally formed . The second path metal is formed to be narrower than the first path metal.
The protective element according to claim 1. The melting temperature of the second path metal is higher than the melting temperature of the first path metal;
The protective element according to claim 1 or claim 2, wherein The first path metal and the second path metal are:
A T-shape is formed when viewed from the normal direction of the surface of the insulator substrate.
The protective element according to any one of claims 1 to 3, wherein A sealing means for sealing the first path metal and the second path metal to the insulator substrate;
The protective element according to any one of claims 1 to 4, wherein

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