Fuse element and protection device

Abstract

To provide a fuse element and a protection device that can prevent deformation of the fuse element due to external heat.SOLUTION: A fuse element 20 has a laminate 40 having an inner layer as a low melting point metal part 41 and an outer layer as a high melting point metal part 42. The ratio of the high melting point metal part 42 to the laminate 40 is larger on end sides ES than a center side CS of the fuse element 20.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a fuse element and a protection device. [Background technology]

[0002] Conventionally, there are fuse elements that generate heat and melt to interrupt the current path when a current exceeding the rated value flows through the current path. Protective devices (fuse elements) equipped with fuse elements are used in a wide range of fields, from home appliances to electric vehicles.

[0003] For example, lithium-ion batteries are used in a wide range of applications, from mobile devices to electric vehicles (EVs) and storage batteries, and their capacity is increasing. As the capacity of lithium-ion batteries increases, the risk of them catching fire or other problems increases. For this reason, in order to ensure product safety, a method is generally adopted in which a protection circuit using a protection element is incorporated.

[0004] For example, Patent Document 1 discloses a protective element having a fusible conductor with a laminated structure in which an inner layer is a low-melting-point metal layer and an outer layer is a high-melting-point metal layer. The fusible conductor is connected to an electrode on a circuit board via solder. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-92892 Summary of the Invention [Problem to be solved by the invention]

[0006] Conventional solder connection techniques have the following problems. When a fuse element is used in which a low-melting-point metal is coated with a laminate of a high-melting-point metal, the cut surface of the fuse element (the end surface where the low-melting-point metal is exposed) comes into contact with the solder paste used for connection. This causes the heat from the solder to melt the low-melting-point metal in the fuse element's inner layer, potentially leading to deformation of the fuse element. Deformation of the fuse element is undesirable because it not only increases the variation in fuse resistance but also reduces the cross-sectional area and rated current.

[0007] The present invention has been made in view of the above circumstances, and has an object to provide a fuse element and a protection element that can suppress deformation of the fuse element due to external heat. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides the following means.

[0009] [1] A fuse element having a laminated body with an inner layer made of a low-melting-point metal part and an outer layer made of a high-melting-point metal part, wherein the proportion of the high-melting-point metal part to the laminate is greater at the end portions of the fuse element than at the center.

[0010] [2] The fuse element according to [1], wherein the fuse element has a longitudinal direction in the direction of current flow, and the end side of the fuse element is in a range of 1 / 3 or less from the outermost end of the total length of the fuse element in the longitudinal direction.

[0011] [3] The fuse element according to [2], wherein the low melting point metal portion has an uneven shape including concave and convex portions on the end side in the longitudinal direction.

[0012] [4] The fuse element according to [3], wherein the recess is recessed inward in the longitudinal direction from the outer end surface of the low melting point metal portion and is filled with at least a portion of the high melting point metal portion.

[0013] [5] The fuse element according to [3] or [4], wherein the recess is recessed in the thickness direction from the surface of the low melting point metal portion and is filled with at least a portion of the high melting point metal portion.

[0014] [6] A fuse element according to any one of [3] to [5], wherein the recess is recessed from the surface of the low melting point metal portion in a direction perpendicular to each of the longitudinal direction and thickness direction, and is filled with at least a portion of the high melting point metal portion.

[0015] [7] A fuse element according to any one of [2] to [6], wherein the low melting point metal portion has a hole formed at the end side in the longitudinal direction that penetrates the low melting point metal portion.

[0016] [8] The fuse element according to [7], wherein the hole penetrates from the surface of the low melting point metal portion in the thickness direction and is filled with at least a portion of the high melting point metal portion.

[0017] [9] A fuse element described in any one of [2] to [8], wherein, in a cross-sectional view perpendicular to the longitudinal direction, the low-melting-point metal portion has a uniform cross-sectional area in the longitudinal direction, and, in the cross-sectional view, the high-melting-point metal portion has a larger cross-sectional area at the end side in the longitudinal direction than at the center side.

[0018]

[10] A fuse element described in any one of [2] to [9], wherein the low melting point metal portion has a surface-treated portion on the end side in the longitudinal direction, which has been subjected to at least one of surface treatments selected from the group consisting of graining, embossing, and unevenness, and the high melting point metal portion covers the surface-treated portion.

[0019]

[11] A protection element comprising: an insulating substrate; a first electrode and a second electrode provided at a distance from each other on the insulating substrate; and a fuse element provided so as to straddle the first electrode and the second electrode and fixed to the first electrode and the second electrode via a conductive fixing member, the fuse element having a laminate having an inner layer made of a low-melting-point metal portion and an outer layer made of a high-melting-point metal portion, wherein the proportion of the high-melting-point metal portion in the laminate is greater in a portion of the fuse element that does not overlap with the insulating substrate than in a portion of the fuse element that overlaps with the insulating substrate in a plan view.

[0020]

[12] The protection element according to

[11] , further comprising a heating resistor provided on the insulating substrate, wherein the fuse element melts when heated by the heating resistor to a predetermined temperature or higher, and the proportion of the high-melting point metal portion in the laminate is greater in a portion of the fuse element not overlapping with the heating resistor in a plan view than in a portion of the fuse element overlapping with the heating resistor. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a fuse element and a protection element that can suppress deformation of the fuse element due to external heat. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a circuit diagram of a battery pack according to a first embodiment. [Figure 2] FIG. 2 is a plan view showing a protection element according to the first embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 2. [Figure 5] 1 is a plan view showing a state in which a part of the case is removed in the protection element according to the first embodiment. [Figure 6] FIG. 1 is a plan view showing a fuse element according to a first embodiment. [Figure 7] FIG. 1 is a perspective view showing a fuse element according to a first embodiment. [Figure 8] FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7. [Figure 9] 9 is a cross-sectional view taken along line IX-IX in FIG. 7. [Figure 10] FIG. 2 is a diagram showing an example of a circuit diagram of the battery pack according to the first embodiment, illustrating a state before a thermostat serving as a heat-sensitive element is heated. [Figure 11] FIG. 2 is a diagram showing the thermostat when heated and the fuse element is melted. [Figure 12] FIG. 2 is a diagram showing an example of a circuit diagram of the battery pack according to the first embodiment, in which a protection IC and a switch are mounted. [Figure 13] FIG. 10 is a plan view showing a first modified example of the fuse element. [Figure 14] FIG. 10 is a perspective view showing a first modified example of the fuse element. [Figure 15] 15 is a cross-sectional view taken along the line XV-XV in FIG. 14. [Figure 16] 16 is a cross-sectional view taken along the line XVI-XVI of FIG. 14. [Figure 17] FIG. 10 is a plan view showing a second modified example of the fuse element. [Figure 18] FIG. 10 is a perspective view showing a second modified example of the fuse element. [Figure 19] 19 is a cross-sectional view taken along the line XIX-XIX in FIG. 18. [Figure 20] 19 is a cross-sectional view taken along the line XX-XX in FIG. 18. [Figure 21] FIG. 10 is a plan view showing a third modified example of the fuse element. [Figure 22] FIG. 10 is a side view showing a third modified example of the fuse element. [Figure 23] 23 is a cross-sectional view taken along the line XXIII-XXIII in FIG. 21. [Figure 24] FIG. 10 is a plan view showing a fourth modified example of the fuse element. [Figure 25] FIG. 10 is a side view showing a fourth modified example of the fuse element. [Figure 26]26 is a cross-sectional view taken along line XXVI-XXVI of FIG. 24. [Figure 27] FIG. 10 is a plan view showing a fifth modified example of the fuse element, a first electrode, and a second electrode. [Figure 28] 28 is a cross-sectional view taken along the line XXVIII-XXVIII in FIG. 27. [Figure 29] 30. FIG. 31 is a plan view showing a sixth modified example of the fuse element, a first electrode, and a second electrode, the view including a cross section taken along the line XXIX-XXIX in FIG. [Figure 30] FIG. 30 is a cross-sectional view taken along the line XXX-XXX in FIG. 29. [Figure 31] FIG. 10 is a cross-sectional view of a protection element according to a second embodiment. [Figure 32] FIG. 10 is a cross-sectional view of a protection element according to a third embodiment. [Figure 33] FIG. 10 is a cross-sectional view of a protection element according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, the embodiments will be described in detail with reference to the drawings as appropriate. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate changes can be made within the scope of the effects of the present invention.

[0024] (First embodiment) First, a battery pack and a protection circuit including a protection element according to one embodiment of the present invention will be described with reference to Fig. 1. The battery pack according to this embodiment constitutes a part of a high-voltage, high-current (100V / 100A or more) electric circuit that uses, for example, a lithium-ion secondary battery. The battery pack is mounted, for example, in an electric vehicle (EV).

[0025] As shown in FIG. 1, the battery pack 10 includes, for example, a battery stack 15 consisting of a plurality of lithium ion secondary battery cells 15a (see FIG. 10), a protection element 11 connected in series with the battery stack 15, and a thermal sensitive element 12 that controls the operation of the protection element 11.

[0026] The protection element 11 cuts off the charge / discharge path of the battery stack 15 when an abnormality occurs in the battery pack 10. The electrical characteristics of the heat-sensitive element 12, such as on / off conduction, resistance value, and output voltage, fluctuate due to heat. The heat-sensitive element 12 activates the protection element 11 when heated to a temperature above a predetermined temperature. The operation of the protection element 11 in the battery pack 10 is controlled according to the fluctuations in the electrical characteristics of the heat-sensitive element 12.

[0027] The battery stack 15 includes battery cells 15a (see FIG. 10) that require control to protect against overvoltage, overcurrent, and the like. The battery cells 15a are connected in series and / or parallel. The battery stack 15 is detachably connected to a charging device 13 via a positive terminal 10a and a negative terminal 10b of the battery pack 10. A charging voltage from the charging device 13 is applied to the battery stack 15 via the positive terminal 10a and the negative terminal 10b of the battery pack 10. The battery pack 10 charged by the charging device 13 can operate an electronic device by connecting the positive terminal 10a and the negative terminal 10b to the electronic device.

[0028] The battery pack 10 includes a charge / discharge control circuit 16 that controls charging and discharging of the battery stack 15. The charge / discharge control circuit 16 includes two current control elements 17 and 18 connected in series to a current path that flows from the battery stack 15 to the charging device 13, and a control unit 19 that controls the operation of these current control elements 17 and 18.

[0029] The current control elements 17 and 18 are configured, for example, with field effect transistors (hereinafter also referred to as "FETs"). The current control elements 17 and 18 control the conduction and interruption of the current path of the battery stack 15 in the charge direction and / or discharge direction by controlling the gate voltage with the control unit 19. The control unit 19 operates by receiving power supply from the charging device 13. The control unit 19 determines whether the battery stack 15 is over-discharged or over-charged based on the detection result of a detection circuit (not shown) that detects the voltage of each battery cell 15a. When the control unit 19 determines that the battery stack 15 is over-discharged or over-charged, it controls the operation of the current control elements 17 and 18 to interrupt the current path.

[0030] (protective element) The protection element 11 is connected, for example, on a charge / discharge current path between the battery stack 15 and the charge / discharge control circuit 16. The operation of the protection element 11 is controlled by the heat-sensitive element 12. Referring also to FIGS. 2 to 5, the protection element 11 includes an insulating substrate 26, a first electrode 22 and a second electrode 23 spaced apart from each other on the insulating substrate 26, a fuse element 20 provided so as to straddle the first electrode 22 and the second electrode 23 and fixed to the first electrode 22 and the second electrode 23 via a conductive fixing member 28, and having a laminate 40 (see FIG. 8) having a low-melting-point metal portion 41 as an inner layer and a high-melting-point metal portion 42 as an outer layer, and a heating resistor 24 provided on the insulating substrate 26.

[0031] Specifically, the protection element 11 comprises an insulating substrate 26, first and second electrodes 22, 23 functioning as fuse terminals, a third electrode 25 functioning as a heater terminal, a heating resistor 24 formed on the surface of the insulating substrate 26, an insulating layer 27 covering the heating resistor 24, a heating element lead electrode 21 stacked on the insulating layer 27 and connected to the heating resistor 24, a fuse element 20 mounted across the first electrode 22, the heating element lead electrode 21 and the second electrode 23 via fixing solder 28 (corresponding to fixing member 28), an island electrode 33, and a case 60.

[0032] The first and second electrodes 22, 23 are arranged spaced apart from each other in a predetermined direction. The first and second electrodes 22, 23 are connected to both ends of the fuse element 20 in the current-carrying direction. The case 60 houses the fuse element 20 and portions of the first and second electrodes 22, 23. The insulating substrate 26 is arranged between the first and second electrodes 22, 23 that face each other in the current-carrying direction in a plan view, and is housed in the case 60.

[0033] In the following, an XYZ Cartesian coordinate system (three-dimensional Cartesian coordinate system) may be set appropriately in each drawing, and each configuration may be explained. The predetermined direction in which the first electrode 22 and the second electrode 23 are aligned is called the front-rear direction. The front-rear direction corresponds to the X-axis direction in each drawing. In the X-axis direction, the -X side is called the front side, and the +X side is called the rear side. Note that the front-rear direction is the direction connecting the first electrode 22 and the second electrode 23, and is also the direction in which electricity flows when the protection element 11 is in use, so it may also be called the current flow direction.

[0034] The direction in which the plate surfaces of the first electrode 22 and the second electrode 23 face is called the up-down direction. The up-down direction is a direction perpendicular to the front-rear direction and corresponds to the Z-axis direction in each drawing. In the up-down direction, the upper side corresponds to the +Z side, and the lower side corresponds to the -Z side. The up-down direction may also be referred to as the thickness direction of the fuse element 20, etc.

[0035] The direction perpendicular to the front-rear direction and the up-down direction is called the left-right direction. The left-right direction corresponds to the Y-axis direction in each drawing. In the left-right direction, the left side corresponds to the -Y side, and the right side corresponds to the +Y side. Specifically, the -Y side is the left side when the protection element 11 is viewed from the rear (+X side), and the +Y side is the right side when the protection element 11 is viewed from the rear. The left-right direction may also be referred to as the width direction. In this case, for example, one side in the width direction corresponds to the -Y side, and the other side in the width direction corresponds to the +Y side.

[0036] In this embodiment, the terms "front side," "rear side," "upper side," "lower side," "left side," and "right side" are convenient names for clearly explaining the relative positional relationships of each component, and the actual positional relationships may be other than those indicated by these names.

[0037] The first and second electrodes 22 and 23 are terminals connected to the charge / discharge path of the battery cell 15a. The first and second electrodes 22 and 23 are each formed in a plate shape extending in a plane direction (XY plane direction) perpendicular to the up-down direction. Specifically, the first and second electrodes 22 and 23 are formed in a substantially rectangular plate shape.

[0038] The rear end (+X end) of the first electrode 22 is connected to the front end (-X end) of the fuse element 20. The front end of the first electrode 22 is exposed to the outside of the protection element 11 from the front side of the protection element 11. The front end of the second electrode 23 is connected to the rear end of the fuse element 20. The rear end of the second electrode 23 is exposed to the outside of the protection element 11 from the rear side of the protection element 11.

[0039] 1, the heating resistor 24 is connected to a third electrode 25. The heating resistor 24 is connected to the heat-sensitive element 12 via the third electrode 25. The heating resistor 24 is connected to the fuse element 20 and the charge / discharge path of the battery stack 15 by electrically connecting the heating element lead-out electrode 21 to the fuse element 20.

[0040] The insulating substrate 26 is formed of an insulating material such as alumina, glass ceramics, mullite, or zirconia. Referring to FIGS. 3 to 5, the insulating substrate 26 is formed, for example, in a substantially rectangular shape. The insulating substrate 26 may also be formed of a material used for printed wiring boards, such as a glass epoxy board or a phenolic board. For example, the configuration of the insulating substrate 26 can be changed according to design specifications.

[0041] First and second electrodes 22, 23 are formed on both opposing ends of insulating substrate 26 (specifically, the front and rear ends of insulating substrate 26). First and second electrodes 22, 23 are formed of conductive patterns of Ag, Cu, or the like. First and second electrodes 22, 23 are connected to connection electrodes provided on an external circuit board on which protection element 11 is mounted. As a result, fuse element 20 is incorporated into part of a current path formed on the external circuit board.

[0042] The heating resistor 24 is a conductive member with a relatively high resistance that generates heat when current is passed through it. The heating resistor 24 is made of, for example, nichrome, W, Mo, Ru, or a material containing any of these. The heating resistor 24 can be formed by mixing a powder of these alloys, compositions, or compounds with a resin binder or the like to form a paste, which is then patterned on the insulating substrate 26 using a screen printing technique and then fired.

[0043] The heating resistor 24 is thermally connected to the fuse element 20 by being superimposed thereon. When the heating resistor 24 generates heat due to the passage of current, it melts the fuse element 20. One end of the heating resistor 24 is connected to the heat-sensitive element 12, so that the current and heat generation of the heating resistor 24 are constantly limited. The amount of heat generated by the heating resistor 24 increases as the current increases due to the passage of current through the heat-sensitive element 12 or a decrease in electrical resistance. The increased amount of heat generated by the heating resistor 24 can melt the fuse element 20. The heating resistor 24 is also electrically connected to the fuse element 20.

[0044] The fuse element 20 is connected across the first electrode 22 and the second electrode 23 by fixing solder 28. When viewed from the top and bottom, the fuse element 20 has a shape with its longitudinal axis in the front-to-back direction (direction of current flow). During normal use, the fuse element 20 provides electrical continuity between the first and second electrodes 22, 23, and constitutes part of the current path of the external circuit in which the protection device 11 is incorporated.

[0045] The fuse element 20 melts due to self-heating (Joule heat) when a current exceeding the rated current is passed through it. The fuse element 20 melts when heated to a predetermined temperature or higher by the heating resistor 24. The fuse element 20 melts due to the heat generated by the heating resistor 24, and cuts off the connection between the first and second electrodes 22, 23. The fuse element 20 has a predetermined rated current value, and melts quickly due to the heat generated by the heating resistor 24 or due to self-heating when a current exceeding the rated current value is passed through it.

[0046] The heat-sensitive element 12 may be an electronic component whose electrical characteristics are temperature-dependent. Referring to both FIGS. 1 and 10, the heat-sensitive element 12 may be a thermostat 12a that opens and closes a circuit in response to changes in the ambient temperature. For example, the heat-sensitive element 12 may be disposed in close proximity to or in contact with the battery stack 15 and thermally connected to the battery stack 15. In this case, the heat-sensitive element 12 is heated by abnormal heat generation in the battery stack 15. This causes changes in the electrical characteristics of the heat-sensitive element 12, such as its resistance value and output voltage.

[0047] For example, if a thermostat 12a is used as the heat-sensitive element 12, one end of the thermostat 12a is connected to the open end of the battery stack 15. The other end of the thermostat 12a is connected to the heating resistor 24 of the protection element 11. The thermostat 12a always opens the current path from the battery stack 15 to the heating resistor 24. When the thermostat 12a in the battery pack 10 heats up due to abnormal heat generation in the battery stack 15 or the like, the thermostat 12a is displaced so as to close the current path from the battery stack 15 to the heating resistor 24. As a result, sufficient power from the battery stack 15 to melt the fuse element 20 is passed through the heating resistor 24.

[0048] Although not shown, the heat-sensitive element 12 may be a thermostat 12a or a negative temperature coefficient thermistor (NTC thermistor, CTR thermistor) whose resistance decreases with an increase in the ambient temperature. The heat-sensitive element 12 may also be a diode whose voltage changes when the temperature exceeds a threshold value. Other examples of the heat-sensitive element 12 include a Peltier element, a thermocouple, a bimetal, and a temperature sensor. For example, the configuration of the heat-sensitive element 12 may be changed according to design specifications.

[0049] 3 to 5, the case 60 includes a first holding member 61 and a second holding member 62 that are stacked in the vertical direction. The first holding member 61 is a generally rectangular cylindrical member with a closed top and an open bottom. Recesses (not shown) may be formed at each of the four corners of the first holding member 61. The second holding member 62 has a substantially rectangular shape in plan view that has the same outer shape as the first holding member 61, and has a concave shape that opens upward in the center in cross section. Each corner (four corners) of the second holding member 62 may be provided with a convex portion (not shown) that can fit into a concave portion formed in the first holding member 61.

[0050] The recessed portions formed in the first holding member 61 and the protruding portions provided on the second holding member 62 may constitute a positioning structure for the case 60. For example, first, an adhesive is applied to at least one of the lower surface of the first holding member 61 and the upper surface of the second holding member 62. Next, the lower surface of the first holding member 61 and the upper surface of the second holding member 62 are aligned so that the first holding member 61 and the second holding member 62 overlap in a plan view, thereby fitting the protruding portions into the recessed portions. In this way, the first holding member 61 and the second holding member 62 may be fixed together with the adhesive.

[0051] Note that the present invention is not limited to forming recesses at each corner of the first holding member 61 and providing protrusions at each corner of the second holding member 62. For example, protrusions may be provided at each corner of the first holding member 61 and recesses may be provided at each corner of the second holding member 62. For example, the manner in which the protrusions are provided and the manner in which the recesses are formed can be changed according to design specifications.

[0052] The rear end (+X end) of the first electrode 22 is connected to the front end (-X end) of the fuse element 20. The front end of the first electrode 22 protrudes from the front side of the case 60 to the outside of the case 60 and is exposed. The front end of the second electrode 23 is connected to the rear end of the fuse element 20. The rear end of the second electrode 23 protrudes from the rear side of the case 60 to the outside of the case 60 and is exposed. The right end of the third electrode 25 is connected to the left end of the heat generating element lead electrode 21. The left end of the third electrode 25 protrudes from the left side of the case 60 to the outside of the case 60 and is exposed.

[0053] The protective element 11 of this embodiment is of a screw type. Specifically, the protective element 11 is connected to wiring by passing a screw through the holes (holes of each terminal) of the electrodes 22, 23, and 25 protruding outside the case 60.

[0054] The island-shaped electrodes 33 are formed on both ends of the surface of the insulating substrate 26. The island-shaped electrodes 33 on one end of the insulating substrate 26 and the island-shaped electrodes 33 on the other end are spaced apart in the front-to-rear direction via the heating resistor 24, etc. When the fuse element 20 melts, the island-shaped electrodes 33 hold a portion of the molten conductor of the fuse element 20 apart from the first and second electrodes 22, 23 due to their wettability.

[0055] (protection circuit) 1 and 10, the protection element 11 has a circuit configuration including a fuse element 20 connected in series across first and second electrodes 22, 23, and a heating resistor 24 that melts the fuse element 20 by passing current through the connection point of the fuse element 20 to generate heat. The protection element 11 has a current path from the heat-sensitive element 12, the third electrode 25, the heating resistor 24, and the fuse element 20 to the heating resistor 24, and the current flow to the heating resistor 24 is controlled by the heat-sensitive element 12.

[0056] The protection element 11 is connected to one open end of the battery stack 15 via a first electrode 22. The protection element 11 is connected to the positive terminal 10a of the battery pack 10 via a second electrode 23. As a result, the fuse element 20 is connected in series to the charge / discharge current path of the battery pack 10 via the first and second electrodes 22, 23.

[0057] The third electrode 25 of the protection element 11 is connected to one open end of the battery stack 15 that energizes the heating resistor 24, and the heat-sensitive element 12 (e.g., thermostat 12a) limits the current flow to the heating resistor 24. Therefore, the fuse element 20 does not melt due to heat generated by the heating resistor 24, and the charge / discharge current path of the battery pack 10 is allowed to pass current.

[0058] The battery pack 10 may need to interrupt its current path due to abnormal heat generation caused by an overvoltage of the battery cell 15a or abnormal overheating of the surrounding temperature caused by a fire or the like. In this case, the battery pack 10 closes the current path to the heating resistor 24 when the heat-sensitive element 12 heats up and exceeds a predetermined threshold. This allows current to flow from the battery stack 15 to the heating resistor 24. As a result, the protective element 11 causes the heating resistor 24 to heat up to a high temperature, melting the fuse element 20 incorporated in the current path of the battery pack 10. The molten conductor of the fuse element 20 is attracted to the heating element lead electrode 21 and the first and second electrodes 22 and 23, which have high wettability, thereby melting the fuse element 20. Therefore, the battery pack 10 melts the area between the first electrode 22, the heating element lead electrode 21, and the second electrode 23, thereby interrupting the current path of the battery stack 15 (see FIG. 11).

[0059] Such a battery pack 10 can cut off the charge / discharge current path of the battery stack 15 by activating the protection element 11 with the heat-sensitive element 12. Therefore, regardless of the switch operation of the current control elements 17 and 18 or the control IC that controls the protection element 11, the charge / discharge current path of the battery stack 15 can be cut off without the risk of malfunction even when exposed to a high-temperature environment.

[0060] The protective element 11 forms part of the current path to the heating resistor 24 by connecting the fuse element 20 to the heating resistor 24. Therefore, when the fuse element 20 melts and the connection to the external circuit is cut off, the current path to the heating resistor 24 is also cut off, so that the protective element 11 can stop heat generation.

[0061] 12, the battery pack 10 may include a switch circuit 50 in addition to the heat-sensitive element 12 (thermistor 12b in the figure). The switch circuit 50 has a function of detecting an abnormal voltage of the entire battery stack 15 and / or an abnormal voltage of each battery cell 15a, and activating the protection element 11 by operating a switch. For example, the switch circuit 50 includes a protection IC 51 that monitors the voltage of the entire battery stack 15 and / or the voltage of each battery cell 15a, and a switch 52 that is operated by the protection IC 51.

[0062] The switch 52 is, for example, a FET. One end of the switch 52 is connected to one open end of the battery stack 15 or the battery cell 15a. The other end of the switch 52 is connected to the heating resistor 24 of the protection element 11. This connects the switch 52 in parallel with the heat-sensitive element 12 (thermistor 12b in the figure). The switch 52 is controlled by the protection IC 51 to switch between an on state and an off state.

[0063] The Protection IC 51 is connected to, for example, both open ends of the battery stack 15 and each battery cell 15 a. The Protection IC 51, for example, constantly monitors the voltage of the entire battery stack 15 and / or the voltage of each battery cell 15 a, and turns on the switch 52 to energize the heating resistor 24 when an abnormal voltage is detected.

[0064] Specifically, the Protection IC 51 determines whether or not an overvoltage exists based on the voltage across the battery stack 15 and / or the battery cell 15a. For example, if the voltage of the battery cell 15a exceeds a predetermined threshold during charging, the Protection IC 51 determines that the voltage of the battery stack 15 or the battery cell 15a is an overvoltage. If the Protection IC 51 determines that an overvoltage exists, it controls the switch 52 to change from an OFF state to an ON state. This activates the protection element 11, which melts the fuse element 20, thereby interrupting the charge / discharge current path of the battery stack 15.

[0065] In the protection circuit described above, the heat-sensitive element 12 is provided in parallel with the charge / discharge path of the battery stack 15, but this is not limiting. For example, the heat-sensitive element 12 may be provided on a path electrically independent of the charge / discharge path of the battery stack 15, and power may be supplied from a separately provided power source. Furthermore, the battery pack of the present invention is not limited to use in the battery pack 10 of lithium-ion secondary batteries, and can be applied to various uses that require the current path to be cut off in the event of abnormal overheating.

[0066] (Connection with fuse elements, etc.) 3 to 5, the fuse element 20 of this embodiment is provided so as to straddle the first electrode 22 and the second electrode 23. The fuse element 20 is fixed to the first electrode 22, the second electrode 22, and the heating element lead electrode 21 via fixing solder 28 (hereinafter simply referred to as "solder 28"). The fixing solder 28 is an example of a fixing member having electrical conductivity.

[0067] For example, the solder 28 is a Pb-free solder. For example, the material of the solder 28 can be a metal material such as Sn, an Sn-Cu alloy, an Sn-Bi alloy, or an Sn-Ag alloy. For example, the material of the solder 28 can be a mixture of low-melting-point metal particles (Bi) and high-melting-point metal particles (Sn, Ag, Cu, etc.), or a material in which a coating layer of low-melting-point metal particles is formed on the surface of high-melting-point metal particles. For example, the material of the solder 28 is not limited to the above and can be changed according to design specifications.

[0068] For example, the fuse element 20 may be joined to the electrodes 22, 23 by a fixing solder 28 supplemented by an epoxy-based flux 29. The epoxy-based flux 29 contains an epoxy resin, a carboxylic acid, and a solvent. The epoxy-based flux 29 may further contain other components as needed.

[0069] The fixing solder 28 and the epoxy-based flux 29 may or may not be integrated. For example, the fuse element 20 may be joined to the electrodes 22, 23 by the fixing solder 28 formed on the epoxy-based flux 29 formed on the electrodes 22, 23. For example, the arrangement of the fixing solder 28 and the epoxy-based flux 29 can be changed depending on the design specifications.

[0070] (Configuration of fuse element) 6 to 9, the fuse element 20 has a laminate 40 in which an inner layer is a low-melting-point metal portion 41 and an outer layer is a high-melting-point metal portion 42. The proportion of the high-melting-point metal portion 42 in the laminate 40 is greater on the end side ES than on the center side CS of the fuse element 20. The relationship of the proportion of the high-melting-point metal portion 42 in the laminate 40 satisfies the following formula (1).

[0071] 42VE / 40VE>42VC / 40VC Formula (1)

[0072] In formula (1), 40VE represents the volume of the laminate 40 at the end side ES of the fuse element 20, 40VC represents the volume of the laminate 40 at the center side CS of the fuse element 20, 42VE represents the volume of the high-melting-point metal portion 42 at the end side ES of the fuse element 20, and 42VC represents the volume of the high-melting-point metal portion 42 at the end side ES of the fuse element 20. Note that the volume of the laminate 40 refers to the volume of the entire laminate 40 (the total volume of the low-melting-point metal portion 41 and the high-melting-point metal portion 42), and the volume of the "···" at the end side ES of the fuse element 20 refers to the volume of the "···" on one end side (one side) of the fuse element 20.

[0073] The fuse element 20 has a longitudinal direction in the current flow direction (X direction). The end side ES of the fuse element 20 is in a range (range indicated by an arrow in the X direction) of 1 / 3 or less from the outermost end (the outermost end in the X direction) of the total length of the fuse element 20 in the longitudinal direction (total length in the X direction). Note that the end side ES of the fuse element 20 may be in a range of 1 / 4 or less, or 1 / 5 or less, from the outermost end of the total length of the fuse element 20 in the longitudinal direction. The range of the end side ES of the fuse element 20 is not limited to the above and can be changed according to design specifications.

[0074] 5 and 9 together, the proportion of the high-melting point metal portion 42 in the laminate 40 is greater in a portion where the fuse element 20 does not overlap with the insulating substrate 26 (substrate non-overlapping region NA1 shown in FIG. 5) than in a portion where the fuse element 20 overlaps with the insulating substrate 26 in a plan view (substrate overlapping region SA1 shown in FIG. 5). The proportion of the high-melting point metal portion 42 in the laminate 40 is greater in a portion where the fuse element 20 does not overlap with the heating resistor 24 (resistor non-overlapping region NA2 shown in FIG. 5) than in a portion where the fuse element 20 overlaps with the heating resistor 24 in a plan view (resistor overlapping region SA2 shown in FIG. 5).

[0075] 6 to 9, the low-melting-point metal portion 41 has an uneven shape 70 including recesses 71 and protrusions 72 on an end side ES in the longitudinal direction. The recesses 71 are recessed inward in the longitudinal direction from the outer end surface of the low-melting-point metal portion 41. When the outermost surface (outermost end surface) in the longitudinal direction of the low-melting-point metal portion 41 is used as a reference, the recesses 71 are portions recessed inward in the longitudinal direction (inward in the X direction) from the outermost end surface of the low-melting-point metal portion 41. A protrusion 72 that protrudes in the longitudinal direction is formed between two recesses 71 adjacent in the width direction of the low-melting-point metal portion 41. When the bottom surface (innermost surface in the X direction) of the recesses 71 formed in the low-melting-point metal portion 41 is used as a reference, the protrusion 72 is a portion that protrudes outward in the longitudinal direction (outer in the X direction) from the bottom surface of the recess 71.

[0076] The uneven shape 70 is formed on both ends in the X direction of the low-melting-point metal portion 41. The uneven shape 70 is formed in the portions where the low-melting-point metal portion 41 overlaps with the first electrode 22 and the second electrode 23 in plan view (see FIG. 5).

[0077] 9, the recess 71 is formed in a U-shape that is convex inward in the X direction in plan view. Note that the recess 71 is not limited to the above, and may be formed in a U-shape in plan view. The planar shape of the recess 71 can be changed according to design specifications.

[0078] The recesses 71 are formed linearly when viewed in the longitudinal direction (YZ side view). The recesses 71 are formed linearly across the entire thickness direction at both ends in the X direction of the low-melting-point metal portion 41. A plurality of recesses 71 are formed. The plurality of recesses 71 are regularly arranged at predetermined intervals in the width direction (Y direction).

[0079] 9, three recesses 71 are formed on one side in the X direction of the low melting point metal portion 41. The three recesses 71 include one recess 71 formed in the center in the Y direction at the outer end portion in the X direction of the low melting point metal portion 41, and two recesses 71 formed toward the outer sides in the Y direction. Note that the formation mode of the recesses 71 (number, arrangement location, etc.) is not limited to the above and can be changed according to design specifications.

[0080] The recess 71 is filled with at least a portion of the high-melting-point metal portion 42. For example, it is more preferable that the high-melting-point metal portion 42 fill at least half of the recess 71, and even more preferable that the high-melting-point metal portion 42 fill at least two-thirds of the recess 71. The manner in which the high-melting-point metal portion 42 fills the recess 71 is not limited to the above and can be changed according to design specifications.

[0081] (Method of manufacturing a fuse element) For example, the fuse element 20 may be manufactured using a plating technique. In the fuse element 20, the high melting point metal portion 42 that covers the low melting point metal portion 41 may be formed by plating. Plating methods can be broadly classified into two types: (1) wet plating and (2) dry plating.

[0082] (1) Wet plating Wet plating, also known as the wet process, is a plating method that utilizes oxidation-reduction reactions in an aqueous solution. (1-1) Electroplating Electroplating is a plating method that uses electricity to generate an oxidation-reduction reaction. This method makes it easy to control the film thickness and allows for inexpensive processing. The main classifications of electroplating are as follows: (1-1-1) Rack plating Hook plating is a plating method in which the object to be plated is hooked onto a jig and immersed in a plating solution. Since this method requires the object to be shaped like a part, it is preferable that the object be of a certain size. (1-1-2) Barrel plating Barrel plating is a method in which a barrel containing the object to be plated is placed in a plating solution and plated while the barrel is rotated. With this method, the object is shaped into a part, and many parts can be plated at once, so if the parts are small, mass plating can be easily performed. (1-1-3) Continuous plating Continuous plating is a method of plating metal strips called wires or hoops, which allows for low-cost mass plating. (1-1-4) Brush plating Brush plating, also known as brush plating, is a technique in which an electric current is passed between a brush and the object to be plated, and the brush is soaked in plating solution, plating the area where the brush touches the object. This technique is suitable for partial plating.

[0083] (1-2) Electroless plating Electroless plating is a plating method that does not use electricity, and is a method that mainly uses chemical reactions to deposit plating. The main classifications of electroless plating are as follows: (1-2-1) Substitution plating Immersion plating is a technique in which plating ions receive electrons generated when the metal to be plated dissolves and ionizes, resulting in the deposition of plating. (1-2-2) Chemical reduction plating Chemical reduction plating is a technique that uses a chemical reducing agent to generate electron exchange in the plating solution, even if the object to be plated is not metal.

[0084] (2) Dry plating Dry plating, also known as a dry process, is a plating method that uses a material and the metal to be plated in a high vacuum without using an aqueous solution. The main classifications of dry plating are as follows: (2-1) Vacuum deposition Vacuum deposition is a technique in which the metal to be plated is heated and evaporated in a vacuum container, and then brought into contact with the object to be plated, depositing the plating. (2-2) Ion plating Ion plating is a technique in which a gas consisting of separated ions and electrons, called gas plasma, is generated in a high-vacuum container, and the metal to be plated is irradiated with an electron beam to deposit a plating on the object to be plated. (2-3) Sputtering Sputtering is a method of depositing plating by injecting an inert gas such as argon into a high vacuum and applying a high DC voltage between the object to be plated and the metal to be coated.

[0085] For example, the fuse element 20 may be configured such that the high melting point metal portion 42 covering the low melting point metal portion 41 includes multiple layers (two or more layers). In the example of Fig. 8, the high melting point metal portion 42 includes a first high melting point metal layer 42A and a second high melting point metal layer 42B.

[0086] For example, metal materials such as Sn or an alloy mainly composed of Sn can be used for the low melting point metal portion 41. For example, metal materials such as Cu or an alloy mainly composed of Cu can be used for the first high melting point metal layer 42A. For example, metal materials such as Ag or an alloy mainly composed of Ag can be used for the second high melting point metal layer 42B. The term "main component" refers to a component that accounts for 50 wt% or more of the total mass of the material.

[0087] The first high-melting point metal layer 42A protects the low-melting point metal portion 41 from changes in state (suppressing melting of the metal components) and also serves to improve adhesion with the second high-melting point metal layer 42B. The first high-melting point metal layer 42A may cover the entire surface of the low-melting point metal portion 41 with a uniform thickness. For example, the first high-melting point metal layer 42A may be formed with Cu plating to a thickness of 1 μm or less so as to uniformly cover the entire surface of the low-melting point metal portion 41. For example, in the fuse element 20, the first high-melting point metal layer 42A covering the low-melting point metal portion 41 may be formed with barrel plating.

[0088] The second high-melting point metal layer 42B serves to prevent contact between the connecting solder (corresponding to the fixing solder 28) and the low-melting point metal portion 41. The second high-melting point metal layer 42B may cover the entire surface of the first high-melting point metal layer 42A with a uniform thickness. For example, the second high-melting point metal layer 42B may be formed with Ag plating to a thickness of 5 μm or more so as to uniformly cover the entire surface of the first high-melting point metal layer 42A that covers the low-melting point metal portion 41. For example, in the fuse element 20, the second high-melting point metal layer 42B that covers the first high-melting point metal layer 42A may be formed with barrel plating.

[0089] The fuse element 20 is not limited to the above, and may have a two-layer laminate structure of a low-melting-point metal portion 41 and a high-melting-point metal portion 42 covering the low-melting-point metal portion 41. In this case, for example, the low-melting-point metal portion 41 may be made of a metal material such as Sn, an Sn-Cu alloy, an Sn-Bi alloy, or an Sn-Ag alloy. For example, the high-melting-point metal portion 42 may be made of Ag, Cu, or an alloy containing Ag or Cu as a main component. For example, the high-melting-point metal portion 42 may have a high melting point that does not melt even when the fuse element 20 is heated in a reflow furnace.

[0090] For example, the fuse element 20 may be configured such that the entire surface of the inner-layer low-melting-point metal portion 41 is covered with the outer-layer high-melting-point metal portion 42. With this configuration, even if a low-melting-point metal with a melting point lower than the reflow temperature is used, the outflow of the inner-layer low-melting-point metal to the outside during reflow mounting can be prevented. Furthermore, when the fuse element 20 blows, the melting of the inner-layer low-melting-point metal corrodes (solder-eats) the outer-layer high-melting-point metal, allowing it to melt quickly.

[0091] (Protection element manufacturing method) The method for manufacturing the protection element 11 of this embodiment includes a step of connecting the fuse element 20 to the electrodes 21, 22, and 23 via fixing solder 28. An example of the method for manufacturing the protection element 11 of this embodiment will be described below.

[0092] First, fixing solder 28 is applied to the heating element lead electrode 21 and the electrodes 22, 23. Then, the fuse element 20 is connected to the heating element lead electrode 21 and the electrodes 22, 23 via the fixing solder 28. For example, a solder paste containing a Sn—Bi based solder material is used as the fixing solder 28. Note that an adhesive-type Sn—Bi solder paste may also be used as the fixing solder 28.

[0093] Next, reflow heating is performed using a reflow furnace (reflow device) not shown, and the fuse element 20 is solder-connected to the heating element lead electrode 21 and the electrodes 22, 23. In this embodiment, by using a Sn-Bi solder material as the fixing solder 28, reflow heating can be performed at a temperature of less than 150°C. The reflow heating melts the fixing solder 28, and alloys the base metal and the fuse element 20. This electrically connects and fixes the fuse element 20 to the heating element lead electrode 21 and the electrodes 22, 23. Note that the heating method used for soldering is not limited to the above, and a hot plate using a heater as a heat source may also be used.

[0094] (Effects of this embodiment) The fuse element 20 of the present embodiment described above has a laminate 40 in which the inner layer is a low-melting-point metal portion 41 and the outer layer is a high-melting-point metal portion 42. The proportion of the high-melting-point metal portion 42 in the laminate 40 is greater on the end side ES of the fuse element 20 than on the center side CS. With this configuration, even when external heat (such as heat from the fixing solder 28) is applied to the end side ES of the fuse element 20, the high melting point metal portion 42 of the outer layer, which accounts for a larger proportion than the center side CS, can prevent the external heat from promoting melting of the low melting point metal portion 41 of the inner layer. Therefore, the inner layer is not guided to the fixing solder 28. Therefore, deformation of the fuse element 20 due to external heat can be prevented.

[0095] In this embodiment, the fuse element 20 has a longitudinal direction in the current flow direction. The end side ES of the fuse element 20 is in a range of 1 / 3 or less from the outermost end with respect to the entire length of the fuse element 20 in the longitudinal direction. With this configuration, even when external heat is applied to an area of ​​the fuse element 20 that is one-third or less from the outermost end, the high-melting-point metal portion 42 of the outer layer, which accounts for a larger proportion than the central side CS, can prevent the external heat from promoting melting of the low-melting-point metal portion 41 of the inner layer. Therefore, deformation of the fuse element 20 due to external heat can be more effectively prevented.

[0096] In this embodiment, the low melting point metal portion 41 has an uneven shape 70 including recesses 71 and protrusions 72 on the end side ES in the longitudinal direction. With this configuration, the surface area is increased by the uneven shape 70 of the low-melting-point metal portion 41, so the proportion of the high-melting-point metal portion 42 in the outer layer can be more effectively increased. Therefore, deformation of the fuse element 20 due to external heat can be more effectively suppressed.

[0097] In this embodiment, the recess 71 is recessed inward in the longitudinal direction from the outer end surface of the low melting point metal portion 41. The recess 71 is filled with at least a portion of the high melting point metal portion . With this configuration, a portion of the high-melting-point metal portion 42 enters the recess 71 that recesses longitudinally inward from the outer end surface of the low-melting-point metal portion 41, thereby more effectively increasing the proportion of the high-melting-point metal portion 42 in the outer layer. Therefore, deformation of the fuse element 20 due to external heat can be more effectively suppressed.

[0098] The protection element 11 of this embodiment includes an insulating substrate 26, a first electrode 22 and a second electrode 23 that are spaced apart from each other on the insulating substrate 26, and a fuse element 20 that is provided so as to straddle the first electrode 22 and the second electrode 23 and is fixed to the first electrode 22 and the second electrode 23 via a conductive fixing member 28, and that has a laminate 40 that has a low-melting-point metal portion 41 as an inner layer and a high-melting-point metal portion 42 as an outer layer. The proportion of the high-melting-point metal portion 42 to the laminate 40 is greater in a portion of the fuse element 20 that does not overlap with the insulating substrate 26 than in a portion of the fuse element 20 that overlaps with the insulating substrate 26 in a plan view. With this configuration, the proportion of the high-melting-point metal portion 42 in the outer layer can be more effectively increased outside the region where the fuse element 20 melts. Therefore, deformation of the fuse element 20 due to external heat can be more effectively suppressed. Meanwhile, the proportion of the high-melting-point metal portion 42 in the outer layer can be reduced within the region where the fuse element 20 melts. Therefore, the melting point of the fuse element 20 can be concentrated in a thin portion, and the current path can be cut off more safely.

[0099] In this embodiment, the fuse element 20 further includes a heating resistor 24 provided on the insulating substrate 26. The fuse element 20 melts when heated to a predetermined temperature or higher by the heating resistor 24. The proportion of the high-melting point metal portion 42 in the laminate 40 is greater in the portion of the fuse element 20 that does not overlap with the heating resistor 24 in a plan view than in the portion that overlaps with the heating resistor 24. This configuration makes it possible to more effectively increase the proportion of the high-melting-point metal portion 42 in the outer layer outside the region of the fuse element 20 that melts when heated by the heating resistor 24. This makes it possible to more effectively prevent deformation of the fuse element 20 due to external heat. On the other hand, it is possible to reduce the proportion of the high-melting-point metal portion 42 in the outer layer within the region that melts when heated by the heating resistor 24. This allows the melting point of the fuse element 20 to be concentrated in a thin portion, making it possible to more safely cut off the current path.

[0100] However, due to the recent increase in current capacity, the cross-sectional area of ​​fuse elements has become larger, so the conventional method of cutting element films requires dedicated equipment, making it difficult to reduce costs. In contrast, in this embodiment, the fuse element has a laminate with a low-melting-point metal portion as the inner layer and a high-melting-point metal portion as the outer layer, and the high-melting-point metal portion is disposed over the entire surface. This configuration achieves a structure in which the cut surface (the end surface where the low-melting-point metal is exposed) does not come into contact with solder. In addition, the ratio of the high-melting-point metal portion to the laminate is greater at the end side of the fuse element than at the center side. This suppresses thermal deformation of the fuse element even when external heat is applied, such as during reflow soldering, and provides a protection element with a stable fuse resistance value. Furthermore, in terms of cost, the elimination of the need for dedicated processing equipment contributes to cost reduction.

[0101] Furthermore, in this embodiment, the low-melting-point metal portion has an uneven shape on both outer longitudinal ends, and the fuse element has an uneven shape on both outer longitudinal ends (direction of current flow) of the fuse element. When both end faces that form the current path for the rated current have an uneven shape, capillary action along the uneven shape facilitates the formation of fillets (rounded corners) of the connecting solder at the connection portions with the electrodes. This is therefore more suitable for strengthening the solder connection.

[0102] In addition, in this embodiment, the proportion of the high-melting-point metal portion in the laminate is greater in the portion above the electrode (the portion overlapping the electrode in plan view) than in the center portion (the portion not overlapping the electrode in plan view). This configuration creates a difference in heat capacity to limit the portion of the fuse element that is desired to be activated, and allows for the formation of a portion that is more likely to melt. Therefore, the melting point of the fuse element can be concentrated in a thin portion, allowing for a safer interruption of the current path.

[0103] Although various methods can be used to coat the high-melting-point metal portion, barrel plating is preferred because it is easy to process. In this embodiment, the fuse element is a component through which electricity can flow, and barrel plating allows the plating process to be performed while the component is rotating, making it excellent for coating the entire surface of the component and allowing for processing of a large amount at once, making it more suitable.

[0104] The present invention is not limited to the above-described embodiment, and the configuration may be modified within the scope of the present invention, as described below. In the illustrations of other embodiments and modifications, the same components as those in the above-described embodiment are denoted by the same reference numerals, and the following mainly describes the differences.

[0105] In the above embodiment, the fuse element has a longitudinal direction in the current flow direction, and the end side of the fuse element is within a range of 1 / 3 or less from the outermost end of the total length of the fuse element in the longitudinal direction. However, this is not limited to this. For example, the fuse element may have a longitudinal direction in a direction intersecting the current flow direction. For example, the end side of the fuse element may be set based on the total length of the fuse element in the current flow direction. The shape of the fuse element and / or the extent of the end side of the fuse element can be changed depending on the design specifications.

[0106] In the above embodiment, the low-melting-point metal portion has an uneven shape including recesses and protrusions at its longitudinal end, but this is not limited thereto. For example, the low-melting-point metal portion may have holes formed at its longitudinal end that penetrate the low-melting-point metal portion. For example, the low-melting-point metal portion may have both an uneven shape and holes formed at its longitudinal end. The formation of the uneven shape and / or holes can be changed according to design specifications.

[0107] In the above embodiment, the protective element includes an insulating substrate housed in a case and a heating resistor provided on the insulating substrate, but this is not limiting. For example, the protective element does not need to include an insulating substrate and a heating resistor. The installation mode of the insulating substrate and / or the heating resistor can be changed according to design specifications.

[0108] In the above embodiment, the low-melting-point metal portion has an uneven shape including recesses and protrusions at its longitudinal end portions, the recesses recessed inward in the longitudinal direction from the outer end surface of the low-melting-point metal portion, the recesses recessed inward in the longitudinal direction (inward in the X direction) from the outermost end surface of the low-melting-point metal portion when the outermost surface (outermost end surface) in the longitudinal direction of the low-melting-point metal portion is used as a reference, and a protrusion protruding in the longitudinal direction is formed between two adjacent recesses in the width direction of the low-melting-point metal portion, and the protrusions protruding outward in the longitudinal direction (outward in the X direction) from the bottom surface (innermost surface in the X direction) of the recess formed in the low-melting-point metal portion when the bottom surface (innermost surface in the X direction) of the recess formed in the low-melting-point metal portion is used as a reference. However, this is not limited to this. For example, when a predetermined plane in the longitudinal direction of the low-melting-point metal portion is used as a reference, recesses recessed inward in the longitudinal direction (inward in the X direction) from the predetermined plane or protrusions protruding outward in the longitudinal direction (outward in the X direction) from the predetermined plane may be formed. For example, the manner in which the recesses or protrusions are formed can be changed according to design specifications.

[0109] In the above embodiment, the recesses are formed linearly when viewed from the longitudinal direction (YZ side view), but this is not limiting. For example, the recesses may be formed in a wavy or dashed line shape when viewed from the YZ side. For example, the shape of the recesses can be changed depending on the design specifications.

[0110] In the above embodiment, the recesses are formed linearly across the entire thickness direction at both ends of the low-melting-point metal portion in the X direction, but this is not limiting. For example, the recesses may be formed only partially across the thickness direction at both ends of the low-melting-point metal portion in the X direction. For example, the formation of the recesses can be changed according to design specifications.

[0111] In the above embodiment, an example has been described in which a plurality of recesses are formed and the recesses are regularly arranged at predetermined intervals in the width direction (Y direction), but this is not limiting. For example, the recesses may be irregularly arranged at predetermined intervals in the width direction (Y direction). For example, the arrangement of the recesses can be changed according to design specifications.

[0112] (Other variations) Another modified example according to the embodiment of the present invention will be described with reference to Figures 13 to 30. In each figure of this modified example, components that are similar or substantially similar (substantially the same) to those in the first embodiment may be denoted by the same reference numerals or names, and descriptions thereof may be omitted.

[0113] In the above embodiment, an example has been described in which the recesses are recessed inward in the longitudinal direction from the outer end surfaces of the low-melting-point metal portion 41, but this is not limiting. For example, referring to FIGS. 13 to 16, the recesses 71A may be recessed in the thickness direction from the surface of the low-melting-point metal portion 41. In the example of FIG. 15, the recesses 71A are recessed inward in the Z direction from both outer Z-direction surfaces of the low-melting-point metal portion 41. In the example of FIG. 15, the recesses 71A are formed in a U-shape that is convex inward in the Z direction when viewed from the width direction (in an XZ side view). Note that the recesses 71A are not limited to the above, and may be formed in a U-shape when viewed from the XZ side. The side view shape of the recesses 71A can be changed according to design specifications.

[0114] The recesses 71A are formed linearly in a plan view (XY side view). The recesses 71A are formed linearly across the entire width direction at both ends in the X direction of the low-melting-point metal portion 41. In the example of FIG. 15, one recess 71A is formed on each outer surface in the Z direction on one side in the X direction of the low-melting-point metal portion 41. Note that the formation mode of the recesses 71A (number, location, etc.) is not limited to the above and can be changed according to design specifications.

[0115] The recess 71A is filled with at least a portion of the high-melting-point metal portion 42. In the example of Fig. 15, the high-melting-point metal portion 42 extends so as to fill the entire recess 71A. However, the high-melting-point metal portion 42 is not limited to the above, and may extend so as to fill only a portion of the recess 71A. The manner in which the high-melting-point metal portion 42 extends into the recess 71A is not limited to the above, and can be changed according to design specifications.

[0116] In this modification, the recess 71A is recessed in the thickness direction from the surface of the low melting point metal portion 41. At least a portion of the high melting point metal portion 42 is filled in the recess 71A. With this configuration, a portion of the high-melting-point metal portion 42 enters the recess 71A recessed in the thickness direction from the surface of the low-melting-point metal portion 41, thereby more effectively increasing the proportion of the high-melting-point metal portion 42 in the outer layer. Therefore, deformation of the fuse element 20A due to external heat can be more effectively suppressed.

[0117] For example, referring to FIGS. 17 to 20 , the recess 71B may be recessed from the surface of the low-melting-point metal portion 41 in a direction (corresponding to the width direction) perpendicular to both the longitudinal direction and the thickness direction. In the examples of FIGS. 19 and 20 , the recess 71B is recessed inward in the Z direction from both outer Z-direction surfaces of the low-melting-point metal portion 41 and recessed inward in the Y direction from both Y-direction side surfaces. In the example of FIG. 19 , the Z-direction outer portion of the recess 71B is formed in a U-shape that is convex inward in the Z direction when viewed from the width direction (in an X-Z side view). In the example of FIG. 20 , the Y-direction outer portion of the recess 71B is formed in a U-shape that is convex inward in the Y direction when viewed from above (in an X-Y side view). The recess 71B is not limited to the above, and may be formed in a U-shape when viewed from each side. The side view shape of the recess 71B can be changed according to design specifications.

[0118] The recess 71B is formed linearly in a plan view (XY side view) and also linearly when viewed in the width direction (XZ side view). The recess 71B is formed in a closed ring shape around the entire periphery of the low melting point metal portion 41 at both ends of the low melting point metal portion 41 in the X direction. In the example of FIGS. 19 and 20, one continuous recess 71B (one closed ring-shaped recess 71B) is formed on one side of the low melting point metal portion 41 in the X direction. Note that the formation mode of the recess 71B (number, arrangement location, etc.) is not limited to the above and can be changed according to design specifications.

[0119] The recess 71B is filled with at least a portion of the high-melting-point metal portion 42. In the examples of Figures 19 and 20, the high-melting-point metal portion 42 extends to fill the entire recess 71B. However, the high-melting-point metal portion 42 is not limited to the above, and may extend to fill only a portion of the recess 71B. The manner in which the high-melting-point metal portion 42 extends into the recess 71B is not limited to the above, and can be changed according to design specifications.

[0120] In this modification, the recess 71B is recessed in directions perpendicular to both the longitudinal direction and the thickness direction from the surface of the low melting point metal portion 41. At least a portion of the high melting point metal portion 42 is filled in the recess 71B. With this configuration, a portion of the high-melting-point metal portion 42 enters the recess 71B that is recessed from the surface of the low-melting-point metal portion 41 in directions perpendicular to both the longitudinal direction and the thickness direction, so that the proportion of the high-melting-point metal portion 42 in the outer layer can be more effectively increased, thereby more effectively suppressing deformation of the fuse element 20B due to external heat.

[0121] 21 to 23, the recess 71C may be formed in a curved shape (arc shape) that is convex inward in the X direction in a plan view. In the example of FIG. 23, one recess 71C is formed on one side of the low melting point metal portion 41 in the X direction. The recess 71C is formed in the center in the Y direction at the outer end of the low melting point metal portion 41 in the X direction. Note that the formation mode of the recesses 71C (number, location, etc.) is not limited to the above and can be changed according to design specifications.

[0122] The recess 71C is filled with at least a portion of the high-melting-point metal portion 42. In the example of Fig. 23, the high-melting-point metal portion 42 enters the recess 71C so as to partially fill it. The high-melting-point metal portion 42 is not limited to the above, and may enter the recess 71C so as to fill the entire recess 71C. The manner in which the high-melting-point metal portion 42 enters the recess 71C is not limited to the above, and can be changed according to design specifications.

[0123] In this modification, the recess 71C is recessed inward in the longitudinal direction from the outer end surface of the low melting point metal portion 41. At least a portion of the high melting point metal portion 42 is filled in the recess 71C. With this configuration, a portion of the high-melting-point metal portion 42 enters the recess 71C that recesses longitudinally inward from the outer end surface of the low-melting-point metal portion 41, thereby more effectively increasing the proportion of the high-melting-point metal portion 42 in the outer layer. Therefore, deformation of the fuse element 20C due to external heat can be more effectively suppressed.

[0124] For example, referring to FIGS. 24 to 26, the low-melting-point metal portion 41 may have a hole 73 formed at the end side in the longitudinal direction, penetrating the low-melting-point metal portion 41. In the example of FIG. 26, the hole 73 penetrates the low-melting-point metal portion 41 from the surface in the thickness direction. In the example of FIG. 24, the hole 73 is formed in a circular shape (near circle) in plan view (in XY side view). Note that the hole 73 is not limited to the above, and may be formed in an elongated hole shape, an elliptical shape, or a rectangular shape in plan view. The planar shape of the hole 73 can be changed according to design specifications.

[0125] In the example of FIG. 26 , one hole 73 is formed on one side of the low melting point metal portion 41 in the X direction. Note that a plurality of holes 73 may be formed on one side of the low melting point metal portion 41 in the X direction. For example, the hole 73 may penetrate from the outer surface of the low melting point metal portion 41 in a direction intersecting the thickness direction (for example, from the outer surface in the Y direction to the Y direction). The hole 73 is not limited to penetrating in the vertical direction (Z direction), but may also penetrate in the horizontal direction (X direction or Y direction). The formation mode of the hole 73 (number, arrangement location, etc.) is not limited to the above and can be changed according to design specifications.

[0126] At least a portion of the high-melting-point metal portion 42 is filled in the hole 73. In the example of FIG. 26, the high-melting-point metal portion 42 enters the hole 73 so as to partially fill it. In the example of FIG. 26, the high-melting-point metal portion 42 is formed so as to fit along the inner circumferential surface of the hole 73. The high-melting-point metal portion 42 is not limited to the above, and may enter the hole 73 so as to fill the entire hole 73. The manner in which the high-melting-point metal portion 42 enters the hole 73 is not limited to the above, and can be changed according to design specifications.

[0127] In this modification, the low melting point metal portion 41 has a hole 73 formed on the end side in the longitudinal direction, which penetrates the low melting point metal portion 41 . With this configuration, the surface area is increased by the holes 73 in the low-melting-point metal portion 41, so that the proportion of the high-melting-point metal portion 42 in the outer layer can be more effectively increased. Therefore, deformation of the fuse element 20D due to external heat can be more effectively suppressed.

[0128] In this modification, the holes 73 penetrate from the surface of the low melting point metal portion 41 in the thickness direction. The holes 73 are filled with at least a portion of the high melting point metal portion . With this configuration, a portion of the high-melting-point metal portion 42 enters the hole 73 that penetrates from the surface of the low-melting-point metal portion 41 in the thickness direction, so the proportion of the high-melting-point metal portion 42 in the outer layer can be more effectively increased, and deformation of the fuse element 20D due to external heat can therefore be more effectively suppressed.

[0129] 27 and 28, in a cross-sectional view perpendicular to the longitudinal direction, the low-melting-point metal portion 41 may have a uniform cross-sectional area in the longitudinal direction, and the high-melting-point metal portion 42 may have a cross-sectional area larger at the longitudinal end portions than at the center portion in the cross-sectional view. In the example of FIG. 28, the high-melting-point metal portion 42 is formed so that the portions on the electrodes 22, 23 (portions overlapping with the electrodes 22, 23 in a plan view) are thicker than the center portion (portions not overlapping with the electrodes 22, 23 in a plan view). In the example of FIG. 28, the high-melting-point metal portion 42 has thick portions 74 on the electrodes 22, 23.

[0130] For example, the low-melting-point metal portion 41 may be formed in the shape of a rectangular parallelepiped with its longitudinal axis in the X direction. For example, the high-melting-point metal portion 42 may be formed such that the plating on the electrodes 22, 23 is 2 μm or more thicker than the center. For example, the thick portion 74 may have a thickness of 2 μm or more. For example, the high-melting-point metal portion 42 may be formed by barrel plating followed by dip plating on one side.

[0131] In this modification, in a cross section perpendicular to the longitudinal direction, the low-melting-point metal portion 41 has a uniform cross-sectional area in the longitudinal direction. In the cross-sectional view, the high-melting-point metal portion 42 has a larger cross-sectional area at the end portions in the longitudinal direction than at the center portion. This configuration makes it possible to more effectively increase the proportion of the high-melting-point metal portion 42 in the outer layer at the longitudinal end portions, thereby more effectively suppressing deformation of the fuse element 20D due to external heat.

[0132] Furthermore, the thinly plated portions of fuse element 20D (portions toward the center in the X direction) have high resistance and are prone to heat generation, so the melting point begins in those portions. Therefore, the melting point of fuse element 20D can be concentrated in the thin portions, allowing the current path to be cut off more safely.

[0133] 29 and 30, the low melting point metal portion 41 may have, on its longitudinal end side, a surface-treated portion 75 that has been subjected to at least one of surface treatments of graining, embossing, and unevenness, and the high melting point metal portion 42 may cover the surface-treated portion 75. In the example of Figures 29 and 30, the low melting point metal portion 41 has the surface-treated portion 75 in a portion located on the electrodes 22, 23 (a portion that overlaps with the electrodes 22, 23 in a plan view).

[0134] 29 and 30, the proportion of the high-melting-point metal portion 42 in the laminate 40 is greater in the portion on the electrodes 22, 23 (portion overlapping with the electrodes 22, 23 in plan view) than in the central portion (portion not overlapping with the electrodes 22, 23 in plan view). In the surface-processed portion 75, the plating of the high-melting-point metal portion 42 may be formed to be thicker than the central portion by a predetermined amount.

[0135] In this modification, the low-melting-point metal portion 41 has a surface-treated portion 75 on the longitudinal end side, which has been subjected to at least one of surface treatments selected from the group consisting of graining, embossing, and textured. The high-melting-point metal portion 42 covers the surface-treated portion 75. With this configuration, the surface area of ​​the low-melting-point metal portion 41 is increased by the surface-treated portion 75, which more effectively increases the proportion of the high-melting-point metal portion 42 in the outer layer. Therefore, deformation of the fuse element 20E due to external heat can be more effectively suppressed.

[0136] (Protection element (second embodiment)) A protective element 211 according to a second embodiment of the present invention will be described with reference to Fig. 31. The protective element 211 of the second embodiment differs from the first embodiment described above mainly in that a heating resistor is provided on the rear surface (back surface) of the insulating substrate (a rear heater is provided). Note that in each drawing of this embodiment, components that are the same or substantially the same as those in the first embodiment may be denoted by the same reference numerals or names, and descriptions thereof may be omitted.

[0137] 31 , the protection element 211 includes an insulating substrate 26, first and second electrodes 22 and 23 functioning as fuse terminals, a third electrode 25 functioning as a heater terminal, a heating resistor 24 formed on the back surface of the insulating substrate 26 (the surface opposite to the fuse element 20), an insulating layer 27 covering the heating resistor 24, a heating element lead electrode 21 stacked on the insulating layer 27 via the insulating substrate 26 and connected to the heating resistor 24, a fuse element 20 mounted across the first electrode 22, the heating element lead electrode 21, and the second electrode 23 via fixing solder 28, an island electrode 33, and a case 60. The fuse element 20 is joined to the electrodes 22 and 23 by the solder 28.

[0138] In the protection element 211 according to the second embodiment, the proportion of the high-melting-point metal portion 42 in the laminate 40 is also greater in the portion of the fuse element 20 that does not overlap with the heating resistor 24 in a plan view than in the portion of the laminate 40 that overlaps with the heating resistor 24. This makes it possible to more effectively increase the proportion of the high-melting-point metal portion 42 in the outer layer outside the region of the fuse element 20 that is melted by heating from the heating resistor 24. This makes it possible to more effectively suppress deformation of the fuse element 20 due to external heat. On the other hand, the proportion of the high-melting-point metal portion 42 in the outer layer can be reduced within the region that is melted by heating from the heating resistor 24. This allows the high-melting-point metal portion 42 to be concentrated in a thin portion at the melting point of the fuse element 20, making it possible to more safely interrupt the current path.

[0139] (Protection element (third embodiment)) A protection element 311 according to a third embodiment of the present invention will be described with reference to Fig. 32. The protection element 311 of the third embodiment differs from the first embodiment described above mainly in that the heating resistor 324 is located on insulating substrates 326A and 326B, sandwiching the fuse element 20. Note that in the drawings of this embodiment, components that are the same or substantially the same as those in the first and second embodiments may be given the same reference numerals or names, and descriptions thereof may be omitted.

[0140] 32 , the protection element 311 includes first and second insulating substrates 326A and 326B, first and second electrodes 22 and 23, a heating resistor 324 provided on the surfaces of the insulating substrates 326A and 326B, an insulating layer 327 covering the heating resistor 324, a heating element lead electrode 321 stacked on the insulating layer 327 and connected to the heating resistor 324, a fuse element 20 mounted across the first electrode 22, the heating element lead electrode 321, and the second electrode 23 via fixing solder 28, a surface electrode 371, a conductive layer 372, a back electrode 373, an island electrode 333, and a case 60. The fuse element 20 is joined to the electrodes 22 and 23, etc., by the solder 28.

[0141] The insulating substrates 326A and 326B are disposed between the first and second electrodes 22 and 23. The insulating substrates 326A and 326B are spaced apart from each other in the vertical direction. One insulating substrate 326A is disposed above the fuse element 20. The other insulating substrate 326B is disposed below the fuse element 20. The insulating substrates 326A and 326B are formed with through-holes 326h that penetrate the insulating substrates 326A and 326B in the thickness direction.

[0142] The surface electrode 371 is formed on the surface of the insulating substrates 326A and 326B (on the surface on the fuse element 20 side). The surface electrode 371 is disposed between the fuse element 20 and the insulating layer 327. The surface electrode 371 is connected to a part of the fuse element 20 via solder or the like.

[0143] When the fuse element 20 melts due to the heat generated by the heating resistor 324, the melted fuse element 20 (hereinafter also referred to as the "molten conductor") aggregates on the surface electrode 371. As a result, the molten conductor aggregated on the surface electrode 371 can be drawn into the through-hole 326h by capillary action. As a result, even when the cross-sectional area of ​​the fuse element 20 is increased to accommodate high-current applications, the protection device 311 can reliably interrupt the current path between the first and second electrodes 22, 23 without the molten conductor excessively agglomerating on the surfaces of the insulating substrates 326A, 326B.

[0144] The conductive layer 372 is formed on the inner circumferential surface of the through-hole 326h of the insulating substrates 326A and 326B. The conductive layer 372 is continuous with the surface electrode 371. The conductive layer 372 is formed, for example, from a metal material that allows a molten conductor to spread thereon. The conductive layer 372 is formed, for example, by a paste process, a plating process, or the like.

[0145] Since the conductive layer 372 is continuous with the surface electrode 371, the protective element 311 can easily draw the molten conductor that has aggregated on the surface electrode 371 into the through-hole 326h. This allows a larger amount of the molten conductor to be drawn into the through-hole 326h.

[0146] The back electrode 373 is formed on the back surface of the insulating substrates 326A, 326B (the surface opposite to the fuse element 20). The back electrode 373 is formed on the opposite side of the insulating substrates 326A, 326B from the front electrode 371. The back electrode 373 is continuous with the conductive layer 372.

[0147] Because the back electrode 373 is continuous with the conductive layer 372, the molten conductor that has traveled along the conductive layer 372 and been drawn into the through-hole 326h is concentrated on the back electrode 373. This allows even more molten conductor to be drawn in.

[0148] The island electrodes 333 are formed on the edges of the surfaces of the insulating substrates 326A and 326B. The island electrodes 333 are spaced apart from the outer surface electrodes 371 in the front-to-rear direction. When the fuse element 20 melts, the island electrodes 333 retain a portion of the molten conductor at a distance from the surface electrodes 371 and the first and second electrodes 22 and 23 due to their wettability.

[0149] The through-hole 326h may be filled with preliminary solder 375 having a melting point lower than that of the fuse element 20. With this configuration, when the heating resistor 324 generates heat, the preliminary solder 375 melts before the fuse element 20, and the molten conductor can be drawn into the through-hole 326h. This allows the molten conductor to be efficiently drawn from the front side to the back side of the insulating substrates 326A and 326B, and the current path between the first electrode 22 and the second electrode 23 can be reliably interrupted regardless of the position.

[0150] For example, at least a portion of through-hole 326h may be filled with flux together with or instead of pre-solder 375. This configuration also improves the wettability of fuse element 20, allowing the molten conductor to be efficiently drawn into through-hole 326h.

[0151] In this embodiment, a plurality of heating resistors 324 are arranged on both sides of the fuse element 20 in the vertical direction. One end of each heating resistor 324 is connected to the fuse element 20 via a heating element lead electrode 321. The other end of each heating resistor 324 is connected to a power source for generating heat from the heating resistor 324 via an external connection electrode (not shown).

[0152] When the protective element 311 melts the fuse element 20, each heating resistor 324 generates heat and draws the molten conductor into each through-hole 326h. Therefore, even when the cross-sectional area of ​​the fuse element 20 is increased to accommodate large current applications and a large amount of molten conductor is generated, the protective element 311 can draw the molten conductor from both the top and bottom directions and reliably melt the fuse element 20. Furthermore, by drawing the molten conductor from both the top and bottom directions, the protective element 311 can melt the fuse element 20 more quickly.

[0153] The protective element 311 can quickly blow the fuse element 20 even when the fuse element 20 has a coating structure in which a low-melting-point metal constituting the inner layer is coated with a high-melting-point metal. A fuse element 20 coated with a high-melting-point metal requires time to heat up to a temperature at which the high-melting-point metal in the outer layer melts, even when the heating resistor 324 generates heat. The protective element 311 includes multiple heating resistors 324, and by simultaneously heating each heating resistor 324, the high-melting-point metal in the outer layer can be quickly heated to its melting temperature. Therefore, the protective element 311 allows the thickness of the high-melting-point metal layer constituting the outer layer to be increased, thereby achieving a higher rating and maintaining fast-fusing characteristics.

[0154] The protective element 311 is preferably connected to the fuse element 20 with a pair of heating resistors 324 facing each other. This allows the protective element 311 to simultaneously heat the same location on the fuse element 20 from both sides with the pair of heating resistors 324 and to attract molten conductor from both above and below. This allows the fuse element 20 to be heated and blown more quickly.

[0155] In the protection element 311 according to the third embodiment, the proportion of the high-melting-point metal portion 42 in the laminate 40 is also greater in the portion of the fuse element 20 that does not overlap with the heating resistor 324 in a plan view than in the portion of the laminate 40 that overlaps with the heating resistor 324. This makes it possible to more effectively increase the proportion of the high-melting-point metal portion 42 in the outer layer outside the region of the fuse element 20 that is melted by heating from the heating resistor 324. This makes it possible to more effectively suppress deformation of the fuse element 20 due to external heat. On the other hand, the proportion of the high-melting-point metal portion 42 in the outer layer can be reduced within the region that is melted by heating from the heating resistor 324. This allows the high-melting-point metal portion 42 to be concentrated in a thin portion at the melting point of the fuse element 20, making it possible to more safely interrupt the current path.

[0156] (Protection element (fourth embodiment)) A protective element 411 according to a fourth embodiment of the present invention will be described with reference to Fig. 33. The protective element 411 of the fourth embodiment differs from the third embodiment described above mainly in that a heating resistor is provided on the rear surface (back surface) of the insulating substrate (a rear heater is provided). Note that in the drawings of this embodiment, components that are the same or substantially the same as those of the first to third embodiments may be given the same reference numerals or names and descriptions thereof may be omitted.

[0157] 33 , the protection element 411 includes first and second insulating substrates 326A and 326B, first and second electrodes 22 and 23, a heating resistor 324 provided on the back surfaces of the insulating substrates 326A and 326B (the surfaces opposite to the fuse element 20), an insulating layer 327 covering the heating resistor 324, a heating element lead electrode 321 stacked on the insulating layer 327 and connected to the heating resistor 324, the fuse element 20 mounted across the first electrode 22, the heating element lead electrode 321, and the second electrode 23 via fixing solder 28, a surface electrode 371, a conductive layer 372, a back electrode 373, an island electrode 333, and a case 60. The fuse element 20 is joined to the electrodes 22 and 23 by the solder 28.

[0158] In the protection element 411 according to the fourth embodiment, the proportion of the high-melting-point metal portion 42 in the laminate 40 is also greater in the portion of the fuse element 20 that does not overlap with the heating resistor 324 in a plan view than in the portion of the laminate 40 that overlaps with the heating resistor 324. This makes it possible to more effectively increase the proportion of the high-melting-point metal portion 42 in the outer layer outside the region of the fuse element 20 that is melted by heating from the heating resistor 324. This makes it possible to more effectively suppress deformation of the fuse element 20 due to external heat. On the other hand, the proportion of the high-melting-point metal portion 42 in the outer layer can be reduced within the region that is melted by heating from the heating resistor 324. This allows the high-melting-point metal portion 42 to be concentrated in a thin portion at the melting point of the fuse element 20, making it possible to more safely interrupt the current path.

[0159] The protection element of the present invention is not limited to the above-described embodiment.

[0160] The present invention may be combined with the various configurations described in the above-described embodiments, modifications, and reference examples, and may also include additions, omissions, substitutions, and other modifications of the configurations, without departing from the spirit of the present invention. Furthermore, the present invention is not limited to the above-described embodiments, but is limited only by the claims. [Explanation of symbols]

[0161] 11,211,311,411 Protection elements 20, 20A~20E fuse element 22 First electrode 23 Second electrode 24,324 heating resistors 26, 326A, 326B Insulating substrate 28 Solder (fixing material) 40 laminate 41 Low melting point metal part 42 High melting point metal parts 70 Uneven shape 71, 71A~71C recess 72 Convex part 73 Hole 75 Surface processing section CS Center side of fuse element ES End side of fuse element

Claims

1. A fuse element having a laminated body in which an inner layer is a low melting point metal portion and an outer layer is a high melting point metal portion, a ratio of the high-melting-point metal portion to the laminate is greater on the end side of the fuse element than on the central side thereof; Fuse element.

2. The fuse element has a longitudinal direction in the current-carrying direction, The end side of the fuse element is in a range of 1 / 3 or less from the outermost end with respect to the entire length of the fuse element in the longitudinal direction. The fuse element of claim 1 .

3. The low-melting-point metal portion has an uneven shape including a recess and a protrusion on an end side in the longitudinal direction. The fuse element of claim 2 .

4. The recess is recessed inward in the longitudinal direction from the outer end surface of the low-melting-point metal portion, and is filled with at least a portion of the high-melting-point metal portion. The fuse element of claim 3 .

5. the recess is recessed in a thickness direction from a surface of the low melting point metal portion, and is filled with at least a portion of the high melting point metal portion.

5. The fuse element according to claim 3 or 4.

6. the recess is recessed from the surface of the low-melting-point metal portion in a direction perpendicular to each of the longitudinal direction and the thickness direction, and is filled with at least a portion of the high-melting-point metal portion.

5. The fuse element according to claim 3 or 4.

7. The low-melting-point metal portion has a hole formed at an end side in the longitudinal direction, the hole penetrating the low-melting-point metal portion. The fuse element of claim 2 .

8. The hole penetrates from the surface of the low-melting-point metal portion in the thickness direction and is filled with at least a portion of the high-melting-point metal portion. The fuse element of claim 7.

9. In a cross-sectional view perpendicular to the longitudinal direction, the low-melting-point metal portion has a uniform cross-sectional area in the longitudinal direction, In the cross-sectional view, the high-melting-point metal portion has a larger cross-sectional area at the end side in the longitudinal direction than at the center side. The fuse element of claim 2 .

10. the low-melting-point metal portion has a surface-treated portion on an end side in the longitudinal direction, the surface being subjected to at least one of a graining treatment, an embossing treatment, and a concavo-convex treatment, The high-melting-point metal portion covers the surface-treated portion. The fuse element of claim 2 .

11. an insulating substrate; a first electrode and a second electrode provided on the insulating substrate and spaced apart from each other; a fuse element provided so as to straddle the first electrode and the second electrode, fixed to the first electrode and the second electrode via a conductive fixing member, and having a laminated body having an inner layer made of a low-melting-point metal portion and an outer layer made of a high-melting-point metal portion; a ratio of the high-melting-point metal portion to the laminate is greater in a portion of the fuse element that does not overlap with the insulating substrate than in a portion of the fuse element that overlaps with the insulating substrate in a plan view; Protection element.

12. The insulating substrate further includes a heating resistor. The fuse element is melted when heated to a predetermined temperature or higher by the heating resistor, a ratio of the high-melting-point metal portion to the laminate is greater in a portion of the fuse element that does not overlap with the heating resistor than in a portion of the fuse element that overlaps with the heating resistor in a plan view; The protection element according to claim 11 .

Images