JP2013178939A - Current fuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current fuse in which energy loss can be suppressed.SOLUTION: A current fuse 10 includes a fuse element 2, two first wiring conductors 3, 3 having one ends connected, respectively, with both ends of the fuse element 2, and two second wiring conductors 4, 4 provided continuously to the other ends of the two first wiring conductors 3, 3, respectively, and composed of a material having a resistance and a resistance temperature coefficient larger than those of the first wiring conductor 3. Consequently, heating at a high resistance part can be suppressed during normal use where an overcurrent is not flowing. As a result, energy loss of the current fuse 10 can be suppressed during normal time, while maintaining inrush resistance.

Description

  The present invention relates to a current fuse.

  A current fuse is known as a component for protecting an electric circuit when an overcurrent flows. Examples of the current fuse include a fuse disclosed in Patent Document 1. The fuse includes two metal terminals having a high resistance portion and a low resistance portion, and a fusible alloy positioned between the metal terminals. In the fuse disclosed in Patent Document 1, a fusible alloy and a high resistance portion that generates a large amount of heat are arranged apart from each other via a low resistance portion. Thereby, in order for the heat of the high resistance portion to be conducted to the fusible alloy, it is necessary that an overcurrent flows through the fuse for a certain period of time. Thus, this fuse has improved inrush resistance.

JP 2010-251045 A

  However, in the fuse disclosed in Patent Document 1, the high resistance portion is provided at a position away from the fusible alloy. Thereby, in order to transmit heat to the fusible alloy when an overcurrent flows, high heat generation is required in the high resistance portion. For this reason, the resistance value of the high resistance portion has to be set large. Along with this, heat generation may occur in the high resistance portion even during normal use where no overcurrent flows. As a result, there is a problem that energy loss due to the current fuse increases.

  The present invention has been made in view of such problems, and an object thereof is to provide a current fuse capable of suppressing energy loss.

  The current fuse of one aspect of the present invention includes a fuse element, two first wiring conductors having one end connected to each of both ends of the fuse element, and continuous to the other end of each of the two first wiring conductors. And two second wiring conductors made of a material having a resistance value and a temperature coefficient of resistance larger than those of the first wiring conductors.

  According to the current fuse of one aspect of the present invention, the resistance temperature coefficient of the second wiring conductor is larger than the resistance temperature coefficient of the first wiring conductor. Thereby, when an overcurrent flows, the resistance value of a 2nd wiring conductor can be raised favorably. Therefore, compared with the fuse disclosed in Patent Document 1, the resistance value of the second wiring conductor during normal use can be set low. In connection with this, the heat_generation | fever which arises in a high resistance part can be suppressed at the time of normal use when the overcurrent does not flow. As a result, with respect to the current fuse, it is possible to suppress normal energy loss while maintaining inrush resistance.

It is a perspective view which shows the example of the current fuse of one Embodiment of this invention. FIG. 2 is a cross-sectional view taken along the line X-X ′ in the current fuse shown in FIG. 1. 10 is a cross-sectional view showing a current fuse according to Modification Example 1. FIG. 10 is a cross-sectional view showing a current fuse according to Modification 2. FIG. 10 is a cross-sectional view showing a current fuse according to Modification 3. FIG. 10 is a plan view showing a current fuse according to Modification 4. FIG. 10 is a plan view showing a current fuse according to Modification 5. FIG.

  Hereinafter, a current fuse 10 according to an embodiment of the present invention will be described with reference to the drawings.

<Configuration of current fuse 10>
As shown in FIGS. 1 and 2, a current fuse 10 according to an embodiment of the present invention is connected to an insulating substrate 1, a fuse element 2 provided on the upper surface of the insulating substrate 1, and both ends of the fuse element 2. The first wiring conductor 3, the second wiring conductor 4 provided continuously to the first wiring conductor 3, and the sealing member 5 that covers the fuse element 2 are provided.

  The current fuse 10 is a component for protecting an external circuit when an overcurrent flows. Specifically, the current fuse 10 is installed inside an external circuit and normally functions as a conductor. When an overcurrent flows through the external circuit, the current fuse 10 blocks the current flowing through the external circuit by blowing the fuse element 2.

  The insulating substrate 1 is an insulating substrate. The insulating substrate 1 has a quadrangular shape when viewed in plan. The insulating substrate 1 is a member for mounting the fuse element 2. The insulating substrate 1 is made of, for example, a ceramic material such as alumina, mullite, or aluminum nitride, or a glass ceramic material. Note that the thickness of the insulating substrate 1 is set to, for example, 0.2 mm or more and 1 mm or less.

  The fuse element 2 is a member for electrically insulating the two first wiring conductors 3 and 3 when an overcurrent flows through the current fuse 10. The fuse element 2 is a member that blows when the temperature of the fuse element 2 becomes a specific temperature or higher. The fuse element 2 is a plate-like member. The fuse element 2 is mounted on the upper surface of the insulating substrate 1. Each of both ends of the fuse element 2 is connected to one end of each of the two first wiring conductors 3. Both end portions of the fuse element 2 are joined to the first wiring conductor 3. For the joining, for example, a brazing material such as solder is used. Moreover, you may join using ultrasonic surface joining. The fuse element 2 is made of, for example, a metal material such as indium, bismuth, or tin, or an alloy thereof. The melting point at which the fuse element 2 is melted is set to, for example, 80 ° C. or higher and 180 ° C. or lower. The thickness of the fuse element 2 is set to 0.05 mm or more and 0.5 mm or less, for example.

  The fuse element 2 is made of a material having a resistance value and a resistance temperature coefficient smaller than those of the first wiring conductor 3. As a result, the heat generated in the fuse element 2 when an overcurrent flows through the current fuse 10 can be reduced. Therefore, the possibility that the fuse element 2 is melted by heat generated in the fuse element 2 can be suppressed. As a result, the inrush resistance of the current fuse 10 can be improved.

  The first wiring conductors 3 are formed at two positions on the upper surface of the insulating substrate 1 so as to be separated from each other. One end of the first wiring conductor 3 is connected to each of both end portions of the fuse element 2. The first wiring conductor 3 is a member for electrically connecting the fuse element 2 and the second wiring conductor 4. The first wiring conductor 3 is also a member for transferring heat generated in the second wiring conductor 4 to the fuse element 2.

  The first wiring conductor 3 is made of a material having a smaller resistance value and resistance temperature coefficient than the second wiring conductor 4. Thereby, when an overcurrent flows through the current fuse 10, the heat generated in the first wiring conductor 3 can be reduced. Therefore, the possibility that the fuse element 2 is melted by heat generated in the first wiring conductor 3 can be suppressed. As a result, the inrush resistance of the current fuse 10 can be improved. The 1st wiring conductor 3 consists of metal materials, such as copper, silver, or tungsten, or these alloys, for example. The first wiring conductor 3 is formed on the upper surface of the insulating substrate 1 by, for example, a screen printing method.

  The second wiring conductor 4 is formed at two locations over the upper surface, side surface and lower surface of the insulating substrate 1. The two second wiring conductors 4 and 4 are located away from each other. The two second wiring conductors 4, 4 are continuous with the other end of each of the two first wiring conductors 3, 3 on the upper surface of the insulating substrate 1. Specifically, in this example, the first wiring conductor 3 and the second wiring conductor 4 form a wiring pattern that connects the fuse element 2 and an external circuit. The second wiring conductor 4 is connected to an external circuit on the lower surface of the insulating substrate 1. It is preferable that the first wiring conductor 3 and the second wiring conductor 4 overlap each other.

  The second wiring conductor 4 is a member for generating heat when an overcurrent flows through the current fuse 10. The heat generated by the second wiring conductor 4 is transmitted to the fuse element 2 through the first wiring conductor 3. The heat transferred from the second wiring conductor 4 to the fuse element 2 melts the fuse element 2. In this way, the current fuse 10 is electrically insulated when an overcurrent flows.

  Since the second wiring conductor 4 is a member for generating heat when an overcurrent flows, the second wiring conductor 4 is made of a material having a resistance value larger than that of the first wiring conductor 3. Further, the second wiring conductor 4 according to this example is made of a material having a resistance temperature coefficient larger than that of the first wiring conductor 3.

  The second wiring conductor 4 generates heat when an overcurrent flows. Since the second wiring conductor 4 has a large temperature coefficient of resistance, the resistance increases with this heat generation. When the overcurrent further flows through the second wiring conductor 4 having increased resistance, the second wiring conductor 4 can generate further heat.

  As described above, the second wiring conductor 4 generates heat while increasing its own resistance when an overcurrent flows for a certain period of time. Therefore, the resistance value of the second wiring conductor 4 during normal use can be set low. In connection with this, the heat_generation | fever which arises in a high resistance part at the time of normal use can be suppressed. As a result, the current fuse 10 can be kept small in energy loss during normal operation while maintaining inrush resistance.

  The 2nd wiring conductor 4 consists of metal materials, such as copper, silver, or tungsten, or these alloys, for example. The second wiring conductor 4 is formed on the upper surface of the insulating substrate 1 by, for example, a screen printing method.

  As a method for adjusting the temperature coefficient of resistance and the resistance value of the second wiring conductor 4, the following method can be used. Specifically, for example, when tungsten is used as the main material, the temperature coefficient of resistance and the resistance value can be adjusted by adjusting the type and amount of the additive, for example. Specifically, 20% by mass of alumina fine particles may be added to tungsten used for the second wiring conductor 4. Thus, the temperature coefficient of resistance can be set to 4400 ppm / ° C., and the sheet resistance value when the thickness is 20 μm can be set to 0.18 Ω / sq. Moreover, it is preferable to add 40% by mass of molybdenum to tungsten used for the first wiring conductor 3. As a result, the temperature coefficient of resistance can be 3000 ppm / ° C., and the sheet resistance value when the thickness is 20 μm can be 0.008 Ω / sq.

  The sealing member 5 is a member for improving the environmental resistance of the fuse element 2. The sealing member 5 is provided on the upper surface of the insulating substrate 1 so as to cover the fuse element 2. Further, the sealing member 5 covers a part of the first wiring conductor 3. The current fuse 10 has improved long-term reliability because the fuse element 2 is covered with the sealing member 5. The sealing member 5 is made of, for example, a flux containing rosin or the like.

  In addition, this invention is not limited to the above-mentioned embodiment, A various change, improvement, etc. are possible in the range which does not deviate from the summary of this invention. For example, in this example, the insulating substrate 1 has a quadrangular shape when viewed in plan, but is not limited thereto. Specifically, it may be circular or polygonal.

  In this example, two first wiring conductors 3 and two second wiring conductors 4 are provided, but the present invention is not limited to this. Specifically, two or more first wiring conductors 3 and two second wiring conductors 4 may be provided.

  Further, in this example, the second wiring conductor 4 is formed on the upper surface, the side surface, and the lower surface of the insulating substrate 1, but is not limited thereto. Specifically, the second wiring conductor 4 may be formed only on the side surface and the lower surface of the insulating substrate 1. In this case, the first wiring conductor 3 is formed up to the end of the upper surface of the insulating substrate 1, and the first wiring conductor 3 and the second wiring conductor are formed at the corner formed by the upper surface and the side surface of the insulating substrate 1. 4 are connected. The first wiring conductor 3 may be formed on the upper surface and the side surface of the insulating substrate 1, and the first wiring conductor 3 and the second wiring conductor 4 may be connected on the side surface of the insulating substrate 1.

  Similarly, the second wiring conductor 4 may be formed only on the lower surface of the insulating substrate 1. In this case, the first wiring conductor 3 is formed on the upper surface and the side surface of the insulating substrate 1, and the first wiring conductor 3 and the second wiring conductor 4 are formed at corners formed by the lower surface and the side surface of the insulating substrate 1. And are connected. The first wiring conductor 3 may be formed on the upper surface, the side surface, and the lower surface of the insulating substrate 1, and the first wiring conductor 3 and the second wiring conductor 4 may be connected on the lower surface of the insulating substrate 1.

  Moreover, in this example, although the 1st wiring conductor 3 and the 2nd wiring conductor 4 are each exposed outside, it is not restricted to this. Specifically, a plating layer that covers the first wiring conductor 3 and the second wiring conductor 4 may be provided. By providing the plating layer covering the first wiring conductor 3 and the second wiring conductor 4, the environmental resistance of the first wiring conductor 3 and the second wiring conductor 4 can be improved. A nickel plating layer can be used as the plating layer.

<Modification 1>
Modification 1 of the current fuse 10 will be described. In addition, in each structure of this example, about the member which has the structure and function similar to the above-mentioned current fuse 10, the same referential mark is attached | subjected and the detailed description is abbreviate | omitted.

  In the current fuse 10 shown in FIGS. 1 and 2, the second wiring conductor 4 is formed on the upper surface, side surface, and lower surface of the insulating substrate 1, but is not limited thereto. For example, as shown in FIG. 3, the insulating substrate 1 has a through-hole penetrating between the upper surface and the lower surface, and the second wiring conductor 4 is formed on the upper surface of the insulating substrate 1, the inside of the through-hole, and the lower surface. Also good.

  Thereby, the possibility that the heat generated by the second wiring conductor 4 is radiated to the outside of the current fuse 10 can be suppressed.

<Modification 2>
A modification 2 of the current fuse 10 will be described. In addition, in each structure of this example, about the member which has the structure and function similar to the above-mentioned current fuse 10, the same referential mark is attached | subjected and the detailed description is abbreviate | omitted.

  In the current fuse 10 shown in FIG. 3, the second wiring conductor 4 is formed in the vertical direction inside the insulating substrate 1, but is not limited thereto. For example, as shown in FIG. 4, the second wiring conductor 4 is formed in a direction parallel to the main surface of the insulating substrate 1 inside the insulating substrate 1, and a part thereof is located directly below the fuse element 2. It may be.

  Thereby, the heat generated by the second wiring conductor 4 can be transmitted to the fuse element 2 not only via the first wiring conductor 3 but also via the insulating substrate 1. Thereby, heat can be transmitted over a wide range of the fuse element 2.

<Modification 3>
A modification 3 of the current fuse 10 will be described. In addition, in each structure of this example, about the member which has the structure and function similar to the above-mentioned current fuse 10, the same referential mark is attached | subjected and the detailed description is abbreviate | omitted.

  In the current fuse 10 shown in FIGS. 1 and 2, the sealing member 5 covers only a part of the fuse element 2 and the first wiring conductor 3, but is not limited thereto. For example, as shown in FIG. 5, the sealing member 5 may be formed so as to cover a part of the second wiring conductor 4.

  As described above, the configuration in which a part of the second wiring conductor 4 is not exposed to the outside can suppress the possibility that the heat generated by the second wiring conductor 4 is radiated to the outside of the current fuse 10. .

  In FIG. 5, the sealing member 5 covers a part of the second wiring conductor 4, but is not limited thereto. Specifically, the sealing member 5 may cover the entire second wiring conductor 4.

<Modification 4>
A modification 4 of the current fuse 10 will be described. In addition, in each structure of this example, about the member which has the structure and function similar to the above-mentioned current fuse 10, the same referential mark is attached | subjected and the detailed description is abbreviate | omitted.

  In the current fuse 10 shown in FIGS. 1 and 2, the width of the first wiring conductor 3 and the width of the second wiring conductor 4 in the direction perpendicular to the direction of current flow are the same, but this is not limitative. Absent. For example, as shown in FIG. 6, the width of the second wiring conductor 4 may be smaller than the width of the first wiring conductor 3.

  Thereby, the resistance of the second wiring conductor 4 can be further increased. Therefore, the heat generated in the second wiring conductor 4 can be further increased.

<Modification 5>
Modification 5 of the current fuse 10 will be described. In addition, in each structure of this example, about the member which has the structure and function similar to the above-mentioned current fuse 10, the same referential mark is attached | subjected and the detailed description is abbreviate | omitted.

  In the current fuse 10 shown in FIGS. 1 and 2, the fuse element 2, the first wiring conductor 3, and the second wiring conductor 4 are formed in a straight line, but the present invention is not limited thereto. For example, as shown in FIG. 7, the second wiring conductor 4 and the fuse element 2 may be provided side by side.

  Thereby, the heat generated by the second wiring conductor 4 can be transmitted to the fuse element 2 not only via the first wiring conductor 3 but also via the insulating substrate 1. Thereby, heat can be transmitted over a wide range of the fuse element 2.

  Further, in the current fuse 10 shown in FIG. 7, the two second wiring conductors 4 and 4 are positioned with the fuse element 2 interposed therebetween. Thereby, heat can be transmitted over a wider range of the fuse element 2.

1: Insulating substrate 2: Fuse element 3: First wiring conductor 4: Second wiring conductor 5: Sealing member 10: Current fuse

Claims (2)

A fuse element;
Two first wiring conductors having one end connected to each of both ends of the fuse element;
And two second wiring conductors made of a material having a resistance value and a temperature coefficient of resistance larger than those of the first wiring conductors, which are continuously provided at the other ends of the two first wiring conductors. Features current fuse.   2. The current fuse according to claim 1, wherein a resistance value and a resistance temperature coefficient of the fuse element are smaller than a resistance value and a resistance temperature coefficient of the first wiring conductor.

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