Protection element

Abstract

To provide a protection element which can quickly and reliably cut off a current path and can be manufactured by a simple process by using a fusible conductor having a high-melting-point metal layer and a low-melting-point metal layer.SOLUTION: A protection element 1 includes an insulating substrate 2, a heating element 5, first and second electrodes 3 and 4, a heating element extraction electrode 6, and a fusible conductor 7 that melts by self-heating due to an application of an overcurrent exceeding the rated current and / or heat generation of the heating element 5 and cuts off a current path. The fusible conductor 7 has a laminated structure of a high melting point metal layer 10 and a second low melting point metal layer 12. The fusible conductor 7 is connected to the first electrode 3, the second electrode 4, and the heating element extraction electrode 6 via the second low melting point metal layer 12 in a direction in which the second low melting point metal layer 12 faces the insulating substrate 2. At least a part of the second low melting point metal layer 12 is in direct or indirect contact with the insulating substrate 2 between the first electrode 3 and the heating element extraction electrode 6 and between the second electrode 4 and the heating element extraction electrode 6.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present technology relates to a protection element that is mounted on a circuit board and cuts off current to at least a part of the circuit board when an abnormality occurs in the circuit board. [Background technology]

[0002] Many rechargeable and reusable secondary batteries are provided to users as battery packs. For example, lithium-ion secondary batteries, which have a high weight energy density, generally have several built-in protection circuits, such as overcharge protection and overdischarge protection, to ensure the safety of users and electronic devices, and have the function of cutting off the output of the battery pack in specified cases.

[0003] For example, a battery pack protection mechanism may use a built-in FET switch to turn the output on and off to protect the battery pack from overcharging or overdischarging. However, if the FET switch is short-circuited for some reason, if a lightning surge or other event causes a momentary large current to flow, or if the output voltage of a battery cell drops abnormally due to its lifespan or, conversely, if an excessively large voltage is output, the battery pack and electronic devices must be protected from accidents such as fire. Therefore, to safely shut off the output of the battery cell in any of these possible abnormal conditions, a protection element consisting of a fuse element that has the function of interrupting the current path in response to an external signal is used.

[0004] As a protection element for such a protection circuit for a lithium-ion secondary battery or the like, as described in Patent Document 1, a structure is generally used in which a heating element is provided inside the protection element, and this heating element melts a fusible conductor on the current path.

[0005] In the protective element described in Patent Document 1, when reflow mounting is used, a high-melting-point solder containing Pb, with a melting point of 300°C or higher, is generally used for the fusible conductor to prevent it from melting due to the heat of reflow. However, the RoHS Directive and other regulations only permit the use of Pb-containing solder in limited cases, and it is expected that demand for Pb-free solders will increase in the future. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-170801 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-185960 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-003878 Summary of the Invention [Problem to be solved by the invention]

[0007] Here, "solder erosion" and "corrosion phenomenon" have long been well known as the phenomenon in which gold or silver plating on electronic components dissolves in molten solder. Patent Document 2 describes a protective element compatible with Pb-free solder materials that utilizes this phenomenon. However, as described in Patent Document 2, in a structure in which a high-melting-point metal film is adhered to an insulating layer, the high-melting-point metal film only melts the low-melting-point metal film, causing a corrosion phenomenon (also called a dissolution phenomenon), which can result in incomplete circuit interruption. Furthermore, to ensure that the fusible conductor melts, it is preferable to form slits and thickness steps in the high-melting-point metal layer, but this increases the number of steps required to form the slits and thickness steps (see, for example, Patent Document 3).

[0008] Therefore, the present technology aims to provide a protective element that can quickly and reliably interrupt a current path using a fusible conductor having a high-melting point metal layer and a low-melting point metal layer, and can be manufactured using a simple process. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the protection element according to the present technology includes an insulating substrate, a heating element provided on the insulating substrate, a first electrode and a second electrode provided on the insulating substrate, a heating element lead electrode electrically connected to the heating element on a current path between the first electrode and the second electrode, and a fusible conductor connected across the first electrode, the heating element lead electrode, and the second electrode, which melts between the first electrode and the second electrode due to self-heating caused by the passage of an overcurrent exceeding a rated current and / or heat generation by the heating element, thereby interrupting the current path, and the fusible conductor includes a high-melting point metal layer, The soluble conductor has a laminated structure of a second low-melting point metal layer composed of an alloy of a high-melting point metal constituting the high-melting point metal layer and a first low-melting point metal having a melting point lower than that of the high-melting point metal, and the soluble conductor is connected to the first electrode, the second electrode, and the heating element extraction electrode via the second low-melting point metal layer with the second low-melting point metal layer facing the insulating substrate, and at least a portion of the second low-melting point metal layer of the soluble conductor is in direct or indirect contact with the insulating substrate between the first electrode and the heating element extraction electrode and between the second electrode and the heating element extraction electrode.

[0010] Further, a protective element according to the present technology includes an insulating substrate, a heating element provided on the insulating substrate, first and second electrodes provided on the insulating substrate, a heating element lead electrode electrically connected to the heating element on a current path between the first and second electrodes, and a fusible conductor connected across the first electrode, the heating element lead electrode, and the second electrode, which melts between the first and second electrodes and cuts off the current path due to self-heating caused by the passage of an overcurrent exceeding a rated current and / or heat generated by the heating element, and which has a coating structure in which both sides of a low-melting-point metal layer are coated with a high-melting-point metal layer having a melting point higher than that of the low-melting-point metal layer, and the fusible conductor is connected to each of the first electrode, the second electrode, and the heating element lead electrode via a conductive connecting material, and at least a portion of the fusible conductor is in direct or indirect contact with the insulating substrate between the first electrode and the heating element lead electrode and between the second electrode and the heating element lead electrode.

[0011] Further, a manufacturing method of a protection element according to the present technology includes a mounting step of mounting a laminate including a heating element, a first electrode, a second electrode, and an insulating substrate provided with a heating element lead electrode electrically connected to the heating element on a current path between the first electrode and the second electrode, the laminate including a high-melting-point metal layer and a first low-melting-point metal layer made of a first low-melting-point metal having a melting point lower than that of the high-melting-point metal constituting the high-melting-point metal layer, over the first electrode, the heating element lead electrode, and the second electrode formed on the insulating substrate, in an orientation in which the first low-melting-point metal layer, the first electrode, the heating element lead electrode, and the second electrode are in contact with each other; The method includes a heating step of heating the insulating substrate at a mounting temperature equal to or higher than the eutectic temperature of an alloy of the high-melting point metal and the first low-melting point metal, a melting step of forming a second low-melting point metal layer composed of an alloy of the high-melting point metal and the first low-melting point metal and having a solidus temperature lower than the mounting temperature by mutual diffusion and / or melting of a part of the high-melting point metal and the first low-melting point metal, and a connection step of connecting the soluble conductor to the first electrode, the heating element lead-out electrode, and the second electrode via the second low-melting point metal layer of the soluble conductor in which the second low-melting point metal layer solidified with the high-melting point metal layer is laminated by cooling the molten second low-melting point metal layer.

[0012] Further, a manufacturing method of a protection element according to the present technology includes a heating element, a first electrode, a second electrode, and an insulating substrate provided with a heating element lead electrode electrically connected to the heating element on a current path between the first electrode and the second electrode, and includes a conductive connecting material forming step of providing a conductive connecting material on the first electrode, the heating element lead electrode, and the second electrode formed on the insulating substrate, and between the first electrode and the heating element lead electrode and between the second electrode and the heating element lead electrode; and a low-melting point insulating material forming step of providing a conductive connecting material on the first electrode, the heating element lead electrode, and the second electrode via the conductive connecting material. The method includes a mounting process for mounting a fusible conductor having a coated structure in which both sides of a low-melting-point metal layer are coated with a high-melting-point metal layer having a melting point higher than that of the low-melting-point metal layer; a heating and melting process for heating and melting the conductive connecting material at a temperature higher than the solidus temperature of the conductive connecting material; and a connecting process for connecting the fusible conductor with the first electrode, the heating element extraction electrode, and the second electrode by cooling the melted conductive connecting material, wherein at least a portion of the fusible conductor is in direct or indirect contact with the insulating substrate between the first electrode and the heating element extraction electrode and between the second electrode and the heating element extraction electrode. [Effects of the Invention]

[0013] According to this technology, a protective element can be realized that can quickly and reliably interrupt a current path using a fusible conductor having a high-melting point metal layer and a low-melting point metal layer, and can be manufactured using a simple process.

[0014] In a protective element according to one aspect of the present technology, the low-melting-point metal layer of the soluble conductor is closely attached to the insulating substrate, thereby avoiding the problem of the circuit not being able to be completely shut off due to residual corrosion of the high-melting-point metal layer in a structure in which a high-melting-point metal layer is closely attached to an insulating layer, as described in Patent Document 2.

[0015] In a protective element according to one aspect of the present technology, the heat generated by the heating element heats the low-melting point metal layer through the heating element extraction electrode, and also directly heats the low-melting point metal layer that is at least partially in close contact with or in contact with the insulating substrate through the insulating substrate, causing a wide range of the low-melting point metal layer to melt in a short period of time, thereby efficiently melting the high-melting point metal layer and improving the fusing characteristics of the fusible conductor.

[0016] In a protective element according to one aspect of the present technology, in an overcurrent state, the low-melting-point metal layer of the fusible conductor between the electrodes is in close contact with or in contact with the insulating substrate, so that the heat generated by the fusible conductor is dissipated directly to the insulating substrate, thereby improving the current rating of the protective element.

[0017] In a protective element according to one aspect of the present technology, a first electrode, a second electrode, and a heating element lead electrode on an insulating substrate are connected to a soluble conductor using a low-melting point metal layer whose thickness has been controlled in advance, thereby realizing a protective element that does not require precise control of the solder paste.

[0018] Therefore, this technology makes it possible to achieve both fuse characteristics, which are in a trade-off relationship, namely stable connection of the fusible conductor, efficient melting of the fusible conductor by heating the heating element, and improvement of the rated current. [Brief explanation of the drawings]

[0019] [Figure 1] Figure 1 shows an example of the configuration of a protective element to which the present technology is applied, where (A) is a plan view showing the cover member omitted, (B) is a cross-sectional view of the fusible conductor in the direction of current flow, and (C) is a bottom view. [Figure 2] FIG. 2 is a plan view showing a state in which the fusible conductor is fused. [Figure 3] FIG. 3 is a circuit diagram showing an example of the configuration of a battery pack. [Figure 4] FIG. 4 is a circuit diagram of the protection element. [Figure 5] Figure 5 shows an example of the configuration of a protective element having a surface heater structure, where (A) is a plan view showing the cover member omitted, (B) is a cross-sectional view of the fusible conductor in the direction of current flow, and (C) is a bottom view. [Figure 6] FIG. 6 is a cross-sectional view showing an example of the configuration of a protection element in which an insulating substrate has a layer structure of upper and lower layers, and a heating element is formed between the upper and lower layers. [Figure 7] Figure 7 shows an example of a manufacturing process for a protective element, where (A) and (B) are cross-sectional views showing the process of mounting a fusible conductor, (C) is a cross-sectional view showing the process of heating, melting, and connecting the fusible conductor, (D) is a cross-sectional view showing the state in which a coating flux has been applied to the fusible conductor and a cover member has been provided, and (E) is a cross-sectional view showing the process of mounting the protective element on a circuit board. [Figure 8] FIG. 8 is a diagram showing a schematic diagram of interdiffusion of different metal atoms at the interface between layers of different metals. [Figure 9] FIG. 9 is a binary alloy phase diagram of silver (Ag) and tin (Sn). [Figure 10] FIG. 10 is a binary alloy phase diagram of lead (Pb) and tin (Sn). [Figure 11] FIG. 11 is a cross-sectional view schematically showing the change in state of the laminate during the heating, melting and connecting steps. [Figure 12] FIG. 12 is a cross-sectional view that schematically shows a case where the second low-melting point metal layer has a laminated structure of an alloy of a high-melting point metal and a first low-melting point metal, and the first low-melting point metal layer. [Figure 13] FIG. 13 is a cross-sectional view schematically showing the change in state of the laminate during the heating, melting and connecting steps. [Figure 14] FIG. 14 is a cross-sectional view that schematically shows a case where the second low-melting point metal layer has a laminated structure of an alloy of a high-melting point metal and a first low-melting point metal, and the first low-melting point metal layer. [Figure 15] Figure 15 is a diagram showing a schematic diagram of the process of heating and pressing the laminate using a heating head, where (A) is a cross-sectional view showing the state in which the laminate is mounted, (B) is a cross-sectional view showing the process of heating and pressing the laminate using a heating head, and (C) is a cross-sectional view showing the state in which the fusible conductor is mounted. [Figure 16]Figure 16 is a diagram showing a schematic diagram of the process of mounting a fusible conductor while pressing the laminate with a weight, where (A) is a cross-sectional view showing the state in which the laminate is mounted, (B) is a cross-sectional view showing the process of heating the laminate while pressing with a weight, and (C) is a cross-sectional view showing the state in which the fusible conductor is mounted. [Figure 17] FIG. 17 is a cross-sectional view showing a protection element in which a restriction wall is provided on the inner surface of the cover member to hold down the portion where the second low-melting point metal layer of the fusible conductor comes into contact with the insulating substrate. [Figure 18] Figure 18 shows the manufacturing process of a protection element in which a second low-melting point metal layer is in contact with an insulating layer, where (A) is a cross-sectional view showing the mounting process of the laminate, (B) is a cross-sectional view showing the state in which the first low-melting point metal layer has melted and the liquid phase is in contact with the insulating layer, and (C) is a cross-sectional view showing the protection element in which the second low-melting point metal layer is in close contact with the insulating layer. [Figure 19] Figure 19 shows the manufacturing process of a protective element in which the film thickness of the insulating layer is thicker than the sum of the film thickness of the heating element extraction electrode and the film thickness of the first low-melting point metal layer, where (A) is a cross-sectional view showing the mounting process of the laminate, (B) is a cross-sectional view showing the state in which the first low-melting point metal layer has melted and the liquid phase has come into contact with the insulating layer, and (C) is a cross-sectional view showing a protective element in which the second low-melting point metal layer has adhered to the insulating layer. [Figure 20] Figure 20 shows the manufacturing process of a protection element in which the second low-melting point metal layer is in contact with the convex portion, where (A) is a cross-sectional view showing the mounting process of the laminate, (B) is a cross-sectional view showing the state in which the first low-melting point metal layer has melted and the liquid phase is in contact with the convex portion, and (C) is a cross-sectional view showing the protection element in which the second low-melting point metal layer is in contact with the convex portion. [Figure 21] Figure 21 shows the manufacturing process of a protective element in which the height of the convex portion is made higher than the sum of the film thickness of the heating element extraction electrode and the film thickness of the first low-melting point metal layer, where (A) is a cross-sectional view showing the mounting process of the laminate, (B) is a cross-sectional view showing the state in which the first low-melting point metal layer has melted and the liquid phase has come into contact with the convex portion, and (C) is a cross-sectional view showing a protective element in which the second low-melting point metal layer has adhered to the convex portion. [Figure 22]Figure 22 shows a protective element according to a modified example, where (A) is a plan view showing the cover member omitted, (B) is a cross-sectional view in the direction of current flow of the soluble conductor, and (C) is a bottom view. [Figure 23] FIG. 23 is a cross-sectional view of a fusible conductor according to a modified example. [Figure 24] Figure 24 is a diagram showing an example of a manufacturing process for a protective element relating to a modified example, where (A) is a cross-sectional view showing the conductive connecting material formation process, (B) is a cross-sectional view showing the fusible conductor mounting process, (C) is a cross-sectional view showing the conductive connecting material heating and melting process and the fusible conductor connecting process, (D) is a cross-sectional view showing the state in which coated flux is applied to the fusible conductor and a cover member is provided, and (E) is a cross-sectional view showing the process of mounting the protective element on a circuit board. [Figure 25] FIG. 25 is a cross-sectional view showing a protection element in which a restriction wall is provided on the inner surface of a cover member, for pressing a portion where a fusible conductor contacts an insulating substrate via a conductive connecting material. [Figure 26] Figure 26 is a diagram showing the manufacturing process of a protective element in which a fusible conductor is indirectly in contact with an insulating substrate via an insulating layer, where (A) is a cross-sectional view showing the mounting process of the fusible conductor, (B) is a cross-sectional view showing the state in which the conductive connecting material has melted and the fusible conductor has come into contact with the insulating layer, and (C) is a cross-sectional view showing a protective element in which the fusible conductor has come into contact with the insulating layer. [Figure 27] Figure 27 shows the manufacturing process of a protective element in which the film thickness of the insulating layer is more than twice the film thickness of the heating element extraction electrode, where (A) is a cross-sectional view showing the mounting process of the fusible conductor, (B) is a cross-sectional view showing the state in which the conductive connecting material has melted and the fusible conductor has come into contact with the insulating layer, and (C) is a cross-sectional view showing the protective element in which the fusible conductor has come into contact with the insulating layer. [Figure 28] Figure 28 is a diagram showing the manufacturing process of a protective element in which a fusible conductor contacts a convex portion via a conductive connecting material, where (A) is a cross-sectional view showing the mounting process of the fusible conductor, (B) is a cross-sectional view showing the state in which the fusible conductor contacts a convex portion via a conductive connecting material, and (C) is a cross-sectional view showing a protective element in which the fusible conductor contacts a convex portion via a conductive connecting material. [Figure 29]Figure 29 shows the manufacturing process of a protective element in which the height of the convex portion is made higher than twice the film thickness of the heating element extraction electrode, where (A) is a cross-sectional view showing the mounting process of the soluble conductor, (B) is a cross-sectional view showing the state in which the soluble conductor is in contact with the convex portion via the conductive connecting material, and (C) is a cross-sectional view showing the protective element in which the soluble conductor is in contact with the convex portion via the conductive connecting material. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, a protection element to which the present technology is applied will be described in detail with reference to the drawings. It should be noted that the present technology is not limited to the following embodiments, and various modifications are possible within the scope of the present technology. Furthermore, the drawings are schematic, and the ratios of the dimensions may differ from the actual dimensions. Specific dimensions should be determined with reference to the following explanation. It should be noted that the drawings may also include portions with different dimensional relationships and ratios. Furthermore, although this specification describes multiple protection elements and their manufacturing processes, the same components and processes as those in the previously described protection elements and their manufacturing processes may be designated by the same reference numerals, and their details may be omitted.

[0021] [Protection element 1] 1 is a diagram showing a protection element 1 to which the present technology is applied, (A) is a plan view, (B) is a cross-sectional view in the direction of current flow of the fusible conductor, and (C) is a bottom view. As shown in Fig. 1, the protection element 1 includes an insulating substrate 2, a heating element 5 provided on the insulating substrate 2, a first electrode 3 and a second electrode 4 provided on the insulating substrate 2, a heating element lead electrode 6 electrically connected to the heating element 5 on the current path between the first electrode 3 and the second electrode 4, and a fusible conductor 7 connected across the first electrode 3, the heating element lead electrode 6, and the second electrode 4, which fuses between the first electrode 3 and the second electrode 4 due to self-heating and / or heat generation of the heating element 5 caused by the passage of an overcurrent exceeding the rated current, thereby interrupting the current path.

[0022] The soluble conductor 7 is a laminate of a high-melting point metal layer 10 and a second low-melting point metal layer 12 composed of an alloy of a high-melting point metal 10a constituting the high-melting point metal layer 10 and a first low-melting point metal 12b having a melting point lower than that of the high-melting point metal 10a, or a laminate of an alloy of the high-melting point metal 10a and the first low-melting point metal 12b and the first low-melting point metal layer 11 of the laminate 35 described later, and is connected to the first electrode 3, the second electrode 4 and the heating element extraction electrode 6 via the second low-melting point metal layer 12 with the second low-melting point metal layer 12 facing the insulating substrate 2.

[0023] Furthermore, in the soluble conductor 7, at least a portion of the second low-melting point metal layer 12 is in direct contact with the insulating substrate 2 between the first electrode 3 and the heating element extraction electrode 6 and between the second electrode 4 and the heating element extraction electrode 6.

[0024] When the second low-melting point metal layer 12 melts due to heat generated by the heating element 5 or self-heating caused by overcurrent, the soluble conductor 7 causes a dissolution phenomenon (corrosion) in which the high-melting point metal layer 10 dissolves into the molten second low-melting point metal layer 12, and is drawn to the first electrode 3, the second electrode 4, and the heating element lead electrode 6, which have high wettability to the molten metal. At this time, according to the protective element 1, at least a portion of the second low-melting point metal layer 12, which has a relatively low melting point, is in contact with the insulating substrate 2 between the first electrode 3 and the heating element lead electrode 6 and between the second electrode 4 and the heating element lead electrode 6, so that the current paths between the first electrode 3 and the heating element lead electrode 6 and between the second electrode 4 and the heating element lead electrode 6 can be reliably interrupted.

[0025] That is, in a conventional configuration in which a high-melting-point metal film is in contact with an insulating substrate, there is a problem in that the current path is not completely blocked due to the etched residue of the high-melting-point metal film. However, in the protection element 1, the second low-melting-point metal layer 12, which has a relatively low melting point, is in contact with the insulating substrate 2, so that the molten second low-melting-point metal layer 12 is prevented from remaining on the insulating substrate 2, and is instead drawn to the heating element lead electrode 6 and the first and second electrodes 3 and 4 while the high-melting-point metal layer 10 is dissolving.

[0026] Furthermore, when the fusible conductor 7 is melted by the heat of the heating element 5, the heat generated by the heating element 5 heats the second low melting point metal layer 12 via the heating element lead electrode 6, and also directly heats the second low melting point metal layer 12, at least a portion of which is in contact with the insulating substrate 2, via the insulating substrate 2. As a result, a wide range of the second low melting point metal layer 12 melts in a short time, which efficiently melts the high melting point metal layer 10 and improves the fast melting characteristics of the fusible conductor 7.

[0027] Furthermore, in the case where the soluble conductor 7 melts due to self-heating caused by an overcurrent, the second low-melting point metal layer 12 between the first electrode 3 and the heating element extraction electrode 6 and between the second electrode 4 and the heating element extraction electrode 6 comes into contact with the insulating substrate 2, so that the heat generated by the self-heating of the soluble conductor 7 is dissipated directly to the insulating substrate 2, thereby improving the current rating of the protection element 1.

[0028] In addition, since the soluble conductor 7 is connected to the first electrode 3, the second electrode 4, and the heating element extraction electrode 6 via the second low-melting point metal layer 12 whose thickness has been controlled in advance, precise control of the solder paste is not required.

[0029] Therefore, the protective element 1 can achieve a balance between the fuse characteristics that are in a trade-off relationship: "stable connection of the fusible conductor," "efficient melting of the fusible conductor by heating the heating element," and "improvement of the rated current."

[0030] Each component of the protection element 1 will be described in detail below.

[0031] [Insulating substrate] The insulating substrate 2 is formed of an insulating material such as alumina, glass ceramics, mullite, zirconia, etc. Alternatively, the insulating substrate 2 may be made of a material used for printed wiring boards such as a glass epoxy board or a phenol board.

[0032] [First and second electrodes] First and second electrodes 3 and 4 are formed on opposite ends of the insulating substrate 2. The first and second electrodes 3 and 4 are each formed of a conductive pattern of Ag, Cu, or the like. The surfaces of the first and second electrodes 3 and 4 may be coated with a film such as Ni / Au plating, Ni / Pd plating, or Ni / Pd / Au plating by a known method such as plating. This prevents oxidation of the first and second electrodes 3 and 4, and prevents fluctuations in rating due to an increase in conduction resistance. Furthermore, when the protective element 1 is reflow-mounted, the second low-melting-point metal layer 12 connecting the fusible conductor 7 melts, preventing the first and second electrodes 3 and 4 from being corroded (soldered).

[0033] The first electrode 3 is connected to a first external connection electrode 13 formed on the back surface 2b of the insulating substrate 2 via a castellation (not shown). The second electrode 4 is connected to a second external connection electrode 14 formed on the back surface 2b of the insulating substrate 2 via a castellation (not shown). When the protection element 1 is mounted on an external circuit board, the first and second external connection electrodes 13, 14 are connected to connection electrodes provided on the external circuit board, and the fusible conductor 7 is incorporated into a part of the current path formed on the external circuit board.

[0034] The first and second electrodes 3, 4 are electrically connected to each other via the fusible conductor 7. As shown in Fig. 2, the first and second electrodes 3, 4 are disconnected when a large current exceeding the rated current flows through the protective element 1, causing the fusible conductor 7 to melt due to self-heating (Joule heat), or when the heating element 5 generates heat as current flows, causing the fusible conductor 7 to melt.

[0035] [Heater] The heating element 5 is a conductive material with a relatively high resistance that generates heat when current is applied, such as nichrome, W, Mo, Ru, or a material containing these. The heating element 5 can be formed by mixing a powder of these alloys, compositions, or compounds with a resin binder or the like to form a paste, forming a pattern on the insulating substrate 2 using a screen printing technique, and firing the paste. For example, the heating element 5 can be formed by adjusting a mixed paste of ruthenium oxide paste, silver, and glass paste according to a predetermined voltage, forming a film of a predetermined area at a predetermined position on the back surface 2b of the insulating substrate 2, and then firing the film under appropriate conditions. The shape of the heating element 5 can be designed as desired, but a roughly rectangular shape corresponding to the shape of the insulating substrate 2, as shown in Figure 1(C), is preferred to maximize the heating area.

[0036] Furthermore, one end 5a of the heating element 5 is connected to the first extraction electrode 15, and the other end 5b is connected to the second extraction electrode 16. The first extraction electrode 15 is formed by being extracted from the heating element electrode 17 along one end 5a of the heating element 5, and in the protection element 1 shown in FIG. 1, it extends along one side edge of the heating element 5, which is formed in a substantially rectangular shape, and overlaps one side edge of the heating element 5. Similarly, the second extraction electrode 16 is formed by being extracted from the back surface-side intermediate electrode 18b along the other end 5b of the heating element 5, and in the protection element 1 shown in FIG. 1, it extends along the other side edge of the heating element 5, which is formed in a substantially rectangular shape, and overlaps the other side edge of the heating element 5.

[0037] The heating element electrode 17 and the back-side intermediate electrode 18b are formed on opposing side edges of the insulating substrate 2 that are different from the side edges on which the first and second external connection electrodes 13, 14 are provided. The heating element electrode 17 is a power supply electrode to the heating element 5, and is connected to one end 5a of the heating element 5 via the first extraction electrode 15.

[0038] The first and second extraction electrodes 15, 16, the heating element electrode 17, and the back-side intermediate electrode 18b can be formed by printing and firing a conductive paste of Ag, Cu, or the like, similar to the first and second electrodes 3, 4. Furthermore, by making each of these electrodes formed on the back surface 2b of the insulating substrate 2 from the same material, they can be formed in a single printing and firing process.

[0039] The heating element electrode 17 may be connected to a resistance measurement electrode (not shown) formed on the surface 2a of the insulating substrate 2 via a castellation. The first and second electrodes 3, 4 may be provided with a restricting wall to prevent the connection solder provided on the electrodes of the circuit board 34 connected to the first and second external connection electrodes 13, 14 from melting during reflow mounting or the like, creeping up onto the first and second electrodes 3, 4 via the castellation, and spreading onto the first and second electrodes 3, 4. The resistance measurement electrodes may also be provided with a restricting wall. The restricting wall can be formed using an insulating material that is not wettable by solder, such as glass, solder resist, or an insulating adhesive, and can be formed on the first and second electrodes 3, 4 by printing or the like. The restricting wall prevents the molten connection solder from spreading to the first and second electrodes 3, 4 and the resistance measurement electrodes, thereby maintaining the connectivity between the protection element 1 and the circuit board 34.

[0040] The intermediate electrode 18 is an electrode provided between the heating element 5 and the heating element extraction electrode 6 formed on the front surface 2a of the insulating substrate 2, and includes a front surface-side intermediate electrode 18a formed on the front surface 2a of the insulating substrate 2 and a back surface-side intermediate electrode 18b formed on the back surface 2b of the insulating substrate 2, which are connected via castellations. The front surface-side intermediate electrode 18a is connected to the heating element extraction electrode 6. The back surface-side intermediate electrode 18b is connected to the other end 5b of the heating element 5 via the second extraction electrode 16.

[0041] [Insulating protective layer] 1(B) and 1(C), the heating element 5, the first extraction electrode 15, and the second extraction electrode 16 are covered with an insulating protective layer 8. The insulating protective layer 8 is provided to protect and insulate the heating element 5, and is made of an insulating material such as glass that is heat resistant to the heat generation temperature of the heating element 5. Examples of glass raw materials that make up the insulating material include silica-based glass overcoat glass paste and insulating glass paste.

[0042] The insulating protective layer 8 can be formed by applying, for example, a glass-based paste by screen printing or the like, followed by baking. The thickness of the insulating protective layer 8 is set in consideration of the applicability of the glass paste or the like, and is, for example, greater than 10 μm and equal to or less than 40 μm, and preferably equal to or greater than 20 μm and equal to or less than 40 μm.

[0043] [Heater element extraction electrode] The heating element extraction electrode 6 formed on the surface 2a of the insulating substrate 2 has one end connected to the surface-side intermediate electrode 18a, and is connected to the soluble conductor 7 between the first and second electrodes 3 and 4 via the second low-melting point metal layer 12. In addition, the heating element extraction electrode 6 overlaps with the heating element 5 via the insulating substrate 2.

[0044] The heater lead electrode 6 can be formed by printing and firing a conductive paste of Ag, Cu, or the like, similar to the first and second electrodes 3 and 4. The surface of the heater lead electrode 6 may be coated with a film such as Ni / Au plating, Ni / Pd plating, or Ni / Pd / Au plating by a known method such as plating.

[0045] [Fusible conductor] Next, we will explain the fusible conductor 7. The fusible conductor 7 is mounted between the first and second electrodes 3, 4, and melts down due to heat generated by the passage of current through the heating element 5 or due to self-heating (Joule heat) when a current exceeding the rated current is passed through it, thereby interrupting the current path between the first electrode 3 and the second electrode 4.

[0046] The fusible conductor 7 is a laminated structure consisting of an upper layer and a lower layer, with a high-melting-point metal layer 10 as the upper layer and a second low-melting-point metal layer 12 as the lower layer, and in the protective element 1, it forms a rectangular plate shape in a plan view. High-melting-point metals and low-melting-point metals are metals that have a difference in melting point and can melt. A metal with a relatively low melting point is a "low-melting-point metal," and a metal with a relatively high melting point that dissolves into the molten low-melting-point metal is a "high-melting-point metal." In this specification, the high-melting-point metal constituting the high-melting-point metal layer 10 is referred to as "high-melting-point metal 10a," and the low-melting-point metal contained in the high-melting-point metal layer 10 is referred to as "low-melting-point metal 10b." The high-melting-point metal contained in the second low-melting-point metal layer 12 is referred to as "high-melting-point metal 12a," and the low-melting-point metal constituting the second low-melting-point metal layer 12 is referred to as "low-melting-point metal 12b." Furthermore, the high-melting-point metal contained in the first low-melting-point metal layer 11 of the laminate 35 described below is referred to as the "high-melting-point metal 11a," and the low-melting-point metal constituting the first low-melting-point metal layer 11 is referred to as the "low-melting-point metal 11b." This definition is an example based on a binary alloy, but in the case of a multi-component alloy such as a ternary alloy or more, each component is defined in the same way.

[0047] The high-melting point metal 10a constituting the high-melting point metal layer 10 is, for example, Ag or Cu, or a metal containing either of these as its main component, and has a high melting point that prevents it from melting even when the first and second electrodes 3, 4 and the heating element extraction electrode 6 are connected to the soluble conductor 7 or when the protective element 1 is mounted on the circuit board 34 by reflow.

[0048] The second low-melting-point metal layer 12 is composed of an alloy of a high-melting-point metal 12a, which is the high-melting-point metal 10a constituting the high-melting-point metal layer 10, and a first low-melting-point metal 12b, which has a melting point lower than that of the high-melting-point metal 12a. The second low-melting-point metal layer 12 is formed by mutual diffusion and / or dissolution of part of the high-melting-point metal layer 10 and the metals of the first low-melting-point metal layer 11 when a laminate 35, having the high-melting-point metal layer 10 as an upper layer and the first low-melting-point metal layer 11 composed of the first low-melting-point metal 11b as a lower layer, is connected across the first electrode 3, the heating element lead electrode 6, and the second electrode 4 by heating, such as by reflow mounting (see FIGS. 7 and 11). In addition, the second low melting point metal layer 12 may have a laminated structure of an alloy of the high melting point metal 12a and the first low melting point metal 12b and the first low melting point metal layer 11, because the first low melting point metal layer 11 of the laminate 35 is not completely melted and remains. The soluble conductor 7 is connected to the first electrode 3, the heating element lead electrode 6, and the second electrode 4 by this second low melting point metal layer 12.

[0049] The first low-melting-point metal 12b is preferably a solder or a metal containing Sn as a main component, which is a material commonly called “Pb-free solder.” The melting point of the first low-melting-point metal 12b does not necessarily have to be higher than the reflow temperature, and may melt at, for example, about 200°C.

[0050] The melting point of the first low-melting-point metal 12b may be higher than the reflow temperature for mounting the fusible conductor 7. As will be described later, in the laminate 35, at the lamination interface between the high-melting-point metal layer 10 and the first low-melting-point metal layer 11, atoms 10aA of the high-melting-point metal 10a and atoms 11bA of the first low-melting-point metal 11b interdiffuse to form the second low-melting-point metal layer 12. The melting point of the second low-melting-point metal layer 12 decreases as the diffusion progresses, approaching the eutectic temperature. Therefore, even if the melting point of the first low-melting-point metal 11b is higher than the reflow temperature, if the eutectic line of the second low-melting-point metal layer 12 is lower than the reflow temperature, the second low-melting-point metal layer 12 will be in a liquid phase, or at least in a state where a solid phase and a liquid phase are mixed. Thereafter, the second low-melting point metal layer 12 cools, forming a soluble conductor 7 consisting of a laminate of the high-melting point metal layer 10 and the second low-melting point metal layer 12, and the soluble conductor 7 is connected to the first and second electrodes 3, 4 and the heating element extraction electrode 6 via the second low-melting point metal layer 12.

[0051] The second low-melting point metal layer 12 is formed by interdiffusion and / or dissolution of a portion of the high-melting point metal layer 10 and the first low-melting point metal layer 11. However, if the thickness of the first low-melting point metal layer 11 is less than 1 / 10 of the thickness of the high-melting point metal layer 10 (this ratio varies depending on the material) or if the reflow mounting temperature is higher than the liquidus temperature of the first low-melting point metal layer 11, at some point during the process from mounting the fusible conductor 7 on each electrode to mounting the protective element 1 on the circuit board 34, the temperature rise due to reflow mounting causes interdiffusion and / or dissolution of a portion of the high-melting point metal layer 10 and the entire first low-melting point metal layer 11, forming an alloy of the high-melting point metal layer 10 and the first low-melting point metal layer 11.

[0052] The soluble conductor 7 is connected to the first electrode 3, the second electrode 4, and the heating element lead electrode 6 via the second low-melting point metal layer 12, with the second low-melting point metal layer 12 facing the insulating substrate 2. Therefore, the protective element 1 does not require precise control of the film thickness of the solder paste, the reflow temperature, etc., which is necessary to connect the soluble conductor 7 and each electrode via the solder paste.

[0053] Furthermore, in the soluble conductor 7, at least a portion of the second low-melting point metal layer 12 is in direct contact with the insulating substrate 2 between the first electrode 3 and the heating element lead electrode 6 and between the second electrode 4 and the heating element lead electrode 6. Therefore, when the soluble conductor 7 is to be blown by the heat of the heating element 5, the heat generated by the heating element 5 heats the second low-melting point metal layer 12 through the heating element lead electrode 6 and also directly heats the second low-melting point metal layer 12, at least a portion of which is in contact with the insulating substrate 2, through the insulating substrate 2. As a result, between the first electrode 3 and the heating element lead electrode 6 that need to be blown and between the second electrode 4 and the heating element lead electrode 6, the second low-melting point metal layer 12 melts over a wide area in a short time, thereby efficiently melting the high-melting point metal layer 10 and improving the fast-fusing characteristics of the soluble conductor 7. Furthermore, by directly heating the heating element lead electrode 6 by the heating element 5, the molten conductor 7a of the fusible conductor 7 can be more easily coagulated.

[0054] In addition, in the case where the soluble conductor 7 melts due to self-heating caused by an overcurrent, the second low-melting point metal layer 12 between the first electrode 3 and the heating element extraction electrode 6 and between the second electrode 4 and the heating element extraction electrode 6 comes into contact with the insulating substrate 2, so that the heat generated by self-heating due to the passage of current through the soluble conductor 7 is dissipated directly to the insulating substrate 2, thereby improving the current rating of the protection element 1.

[0055] Therefore, the protective element 1 can achieve the fuse characteristics, which are in a trade-off relationship between "stable connection of the fusible conductor," "efficient melting of the fusible conductor by heating of the heating element," and "improvement of the rated current." The process of contacting the second low-melting point metal layer 12 with the insulating substrate 2 between the first and second electrodes 3, 4 and the heating element lead electrode 6 will be described in detail later.

[0056] Here, the manner in which the second low-melting point metal layer 12 is in contact with the insulating substrate 2 between the first and second electrodes 3, 4 and the heating element lead electrode 6 may include a manner in which the second low-melting point metal layer 12 is in complete contact with the surface of the insulating substrate 2, as well as a manner in which there is a gap of several μm to several tens of μm. When the second low-melting point metal layer 12 is cooled from a state in which it is in close contact with the surface 2a of the insulating substrate 2, it may undergo hardening shrinkage or may develop cracks, which may create a gap of several μm to several tens of μm from the surface 2a of the insulating substrate 2. In this case, a heat transfer path is formed between the heating element 5 and the second low-melting point metal layer 12 via radiant heat, thereby achieving the same effect as when they are in contact.

[0057] [Liquidus point of second low melting point metal layer] The protection element 1 is mounted on a circuit board 34 and cuts off current to at least a portion of the circuit board 34 when an abnormality occurs in the circuit board 34. The protection element 1 can be mounted efficiently on the circuit board 34 by reflow soldering. Here, the liquidus point of the second low-melting point metal layer 12 is preferably higher than the mounting temperature of the protection element 1 on the circuit board 34.

[0058] Since the liquidus point of the second low-melting point metal layer 12 is higher than the mounting temperature on the circuit board 34, the second low-melting point metal layer 12 melts when mounted on the circuit board, and gaps are prevented from occurring between the second low-melting point metal layer 12 and the insulating substrate 2 between the first and second electrodes 3, 4 and the heating element extraction electrode 6.

[0059] [Contact area between the second low-melting-point metal layer and the insulating substrate] The contact area between the second low melting point metal layer 12 and the insulating substrate 2 is preferably 50% or more of the area between the first electrode 3 overlapping the soluble conductor 7 and the heating element lead electrode 6, and 50% or more of the area between the second electrode 4 overlapping the soluble conductor 7 and the heating element lead electrode 6. This allows the above-mentioned effect of the contact between the second low melting point metal layer 12 and the insulating substrate 2 to be more effectively exhibited.

[0060] [Layer thickness] In addition, the thickness of the high melting point metal layer 10 in the stacking direction is preferably thicker than the thickness of the second low melting point metal layer 12 in the stacking direction. By using a metal with low resistance such as Ag as the high melting point metal layer 10, the increase in the internal resistance of the soluble conductor 7 can be suppressed, and the rating can be improved while suppressing the increase in size of the protective element 1.

[0061] The fusible conductor 7 can improve resistance to surges (pulse resistance) in which an abnormally high voltage is instantaneously applied to an electrical system incorporating the protective element 1. In other words, the fusible conductor 7 must not melt even when a current of, for example, 100 A flows for several milliseconds. Since large currents that flow in an extremely short time flow through the surface layer of the conductor (skin effect), the fusible conductor 7 has a low-resistance, high-melting-point metal layer 10, such as Ag, as its upper layer. This allows the current applied by a surge to flow easily, preventing melting due to self-heating. Therefore, the fusible conductor 7 can significantly improve surge resistance compared to fuses made of conventional solder alloys.

[0062] The fusible conductor 7 is coated with a coating flux 9 to prevent oxidation and improve wettability during fusing. The inside of the protective element 1 is protected by covering the insulating substrate 2 with a cover member 19. The cover member 19 can be formed using insulating materials such as various engineering plastics, thermoplastic plastics, ceramics, and glass epoxy boards. The cover member 19 also has an internal space on the surface 2a of the insulating substrate 2 that is sufficient to allow the fusible conductor 7a to expand spherically when the fusible conductor 7 melts, and to aggregate on the heating element lead electrode 6 and the first and second electrodes 3 and 4.

[0063] [Circuit configuration example] Such a protection device 1 is used by being incorporated into a circuit in a battery pack 20 of, for example, a lithium ion secondary battery. As shown in Fig. 3, the battery pack 20 has a battery stack 25 made up of, for example, a total of four battery cells 21a to 21d of lithium ion secondary batteries.

[0064] The battery pack 20 includes a battery stack 25, a charge / discharge control circuit 26 that controls the charging and discharging of the battery stack 25, a protection element 1 to which the present invention is applied that cuts off the charge / discharge path when an abnormality occurs in the battery stack 25, a detection circuit 27 that detects the voltage of each battery cell 21a to 21d, and a current control element 28 that serves as a switch element that controls the operation of the protection element 1 in accordance with the detection result of the detection circuit 27.

[0065] The battery stack 25 is a series connection of battery cells 21a to 21d that require control to protect against overcharge and overdischarge, and is detachably connected to a charging device 22 via the positive terminal 20a and negative terminal 20b of the battery pack 20, and a charging voltage is applied from the charging device 22. The battery pack 20 charged by the charging device 22 can be used to operate an electronic device that runs on a battery by connecting the positive terminal 20a and negative terminal 20b to the electronic device.

[0066] The charge / discharge control circuit 26 includes two current control elements 23a, 23b connected in series to a current path between the battery stack 25 and the charging device 22, and a control unit 24 that controls the operation of these current control elements 23a, 23b. The current control elements 23a, 23b are configured, for example, by field-effect transistors (hereinafter referred to as FETs), and the control unit 24 controls the gate voltage to control conduction and interruption of the current path of the battery stack 25 in the charging and / or discharging directions. Depending on the detection result by the detection circuit 27, when the battery stack 25 is over-discharged or over-charged, the control unit 24 controls the operation of the current control elements 23a, 23b to interrupt the current path.

[0067] The protection element 1 is connected, for example, on a charge / discharge current path between the battery stack 25 and the charge / discharge control circuit 26, and its operation is controlled by the current control element .

[0068] The detection circuit 27 is connected to each of the battery cells 21a to 21d, detects the voltage value of each of the battery cells 21a to 21d, and supplies each voltage value to the control unit 24 of the charge / discharge control circuit 26. The detection circuit 27 also outputs a control signal for controlling the current control element 28 when any one of the battery cells 21a to 21d reaches an overcharge voltage or an overdischarge voltage.

[0069] The current control element 28 is configured, for example, by a FET, and when the detection signal output from the detection circuit 27 indicates that the voltage value of the battery cells 21a to 21d exceeds a predetermined over-discharge or over-charge state, it activates the protection element 1 and controls the charge / discharge current path of the battery stack 25 to be cut off regardless of the switch operation of the current control elements 23a and 23b.

[0070] The protective element 1 to which the present invention is applied and used in the battery pack 20 configured as described above has a circuit configuration as shown in FIG. 4. That is, the protective element 1 has the first external connection electrode 13 connected to the battery stack 25 side and the second external connection electrode 14 connected to the positive terminal 20a side, thereby connecting the soluble conductor 7 in series to the charge / discharge path of the battery stack 25. Furthermore, the protective element 1 has the heating element 5 connected to the current control element 28 via the heating element electrode 17, and the heating element 5 is connected to one end of the battery stack 25. In this way, one end of the heating element 5 is connected to the soluble conductor 7 and one end of the battery stack 25 via the heating element lead-out electrode 6, and the other end is connected to the current control element 28 and the other end of the battery stack 25 via the heating element electrode 17. This forms a power supply path to the heating element 5, the current supply of which can be controlled by the current control element 28.

[0071] [Protection element operation] When the detection circuit 27 detects an abnormal voltage in any of the battery cells 21a to 21d, it outputs a cutoff signal to the current control element 28. The current control element 28 then controls the current to energize the heating element 5. In the protection element 1, current flows from the battery stack 25 to the heating element 5, causing the heating element 5 to start generating heat. In the protection element 1, heat from the heating element 5 is transferred to the fusible conductor 7 via the intermediate electrode 18 and the heating element lead electrode 6, which have excellent thermal conductivity, and via the insulating substrate 2, causing the fusible conductor 7 to melt and cut off the charge / discharge path of the battery stack 25. Furthermore, in the protection element 1, the fusible conductor 7 is formed by stacking the high-melting-point metal layer 10 and the second low-melting-point metal layer 12. Therefore, the second low-melting-point metal layer 12 melts before the high-melting-point metal layer 10 melts, and the melted second low-melting-point metal layer 12 melts the high-melting-point metal layer 10, allowing the fusible conductor 7 to melt in a short time by utilizing the melting action of the high-melting-point metal layer 10.

[0072] When the fusible conductor 7 melts, the protection element 1 also cuts off the power supply path to the heating element 5, and the heating element 5 stops generating heat.

[0073] In addition, even when an overcurrent exceeding the rated current flows through the battery pack 20, the protective element 1 can cut off the charge / discharge path of the battery pack 20 by melting the fusible conductor 7 due to self-heating.

[0074] In this way, the fusible conductor 7 of the protective element 1 melts due to heat generated by the passage of current through the heating element 5 or due to self-heating of the fusible conductor 7 caused by an overcurrent. As described above, the protective element 1 has a structure in which the second low-melting point metal layer 12 is laminated on the high-melting point metal layer 10, so deformation of the fusible conductor 7 is suppressed even when the protective element 1 is reflow-mounted on the circuit board 34 or when the circuit board 34 on which the protective element 1 is mounted is further exposed to a high-temperature environment such as reflow heating. Therefore, fluctuations in the fusing characteristics due to fluctuations in resistance value caused by deformation of the fusible conductor 7 are prevented, and the fusible conductor 7 can be quickly melted by a predetermined overcurrent or heat generated by the heating element 5.

[0075] The protection device 1 according to the present invention is not limited to use in a battery pack for lithium ion secondary batteries, and can of course be applied to various uses that require the interruption of a current path by an electrical signal.

[0076] [Surface heater structure] The heating element 5 described above may be formed on the surface 2a of the insulating substrate 2. FIG. 5 is a diagram showing a protection element 30 to which the present technology is applied, where (A) is a plan view, (B) is a cross-sectional view in the current-carrying direction of the fusible conductor, and (C) is a bottom view. In the protection element 30 shown in FIG. 5, the heating element 5 is formed on the surface 2a of the insulating substrate 2. Accordingly, the insulating protective layer 8, the first extraction electrode 15, the second extraction electrode 16, the heating element electrode 17, and the intermediate electrode 18 are also formed on the surface 2a of the insulating substrate 2. Note that, unlike the protection element 1, the intermediate electrode 18 is only formed on the surface 2a of the insulating substrate 2, and the second extraction electrode 16 and the heating element extraction electrode 6 are connected thereto.

[0077] The heating element electrode 17 and the intermediate electrode 18 are provided on one and the other of a pair of side edges perpendicular to the pair of side edges on which the first electrode 3 and the second electrode 4 are provided. The heating element electrode 17 is connected from the front surface 2a of the insulating substrate 2 to a third external connection electrode 31 formed on the back surface 2b via a castellation. The heating element 5 of the protection element 30 is connected to the current control element 28 via the heating element electrode 17 and the third external connection electrode 31, and the heating element 5 is connected to one end of the battery stack 25. The intermediate electrode 18 may be connected from the front surface 2a of the insulating substrate 2 to a fourth external connection electrode (not shown) formed on the back surface 2b via a castellation, and serving as an electrode for mounting on a circuit board 34.

[0078] The heating element lead electrode 6 is formed on the insulating protective layer 8, so that one end is connected to the intermediate electrode 18 and overlaps with the heating element 5 via the insulating protective layer 8. In the protective element 30, the heating element 5 and the fusible conductor 7 are thermally connected by overlapping them via the insulating protective layer 8 and the heating element lead electrode 6, and the heat of the heating element 5 is transferred to the fusible conductor 7 also via the insulating protective layer 8 and the heating element lead electrode 6, allowing for faster meltdown.

[0079] [Internal heater structure] The heating element 5 may also be provided inside the insulating substrate 2. In the protective element 40 shown in FIG. 6, the insulating substrate 2 has a two-layer structure consisting of an upper layer and a lower layer, and the heating element 5, a first extraction electrode 15, and a second extraction electrode 16 are formed between the upper and lower layers. The first extraction electrode 15 is connected to a heating element electrode 17 provided on the front surface 2a or the back surface 2b of the insulating substrate 2 via a castellation or a conductive through-hole (not shown). The second extraction electrode 16 is connected to an intermediate electrode 18 provided on the front surface 2a or the back surface 2b of the insulating substrate 2 via a castellation or a conductive through-hole (not shown).

[0080] [Protection element 1 manufacturing process] Next, we will explain the manufacturing process of the protection element 1. As shown in Fig. 7, the manufacturing process of the protection element 1 includes a mounting process of the laminate 35, a heating process of heating the laminate 35, a melting process of melting the first low melting point metal layer 11, and a connecting process of forming the soluble conductor 7 and connecting it to the electrode.

[0081] [Mounting process] 7(A)(B) are cross-sectional views showing the mounting process of the soluble conductor 7. Prior to the mounting process, the first electrode 3, the second electrode 4, the heating element lead electrode 6, and the front-side intermediate electrode 18a are formed on the front surface 2a of the insulating substrate 2, and the heating element 5, the first external connection electrode 13, the second external connection electrode 14, the first lead electrode 15, the second lead electrode 16, the heating element electrode 17, the back-side intermediate electrode 18b, and the insulating protective layer 8 are formed on the back surface 2b of the insulating substrate 2 to form an element body 1A. It is preferable that a connection flux 29 is applied in advance to the first electrode 3, the second electrode 4, the heating element lead electrode 6, and between these electrodes. Next, a laminate 35 is formed on the insulating substrate 2 over the first electrode 3, the heating element extraction electrode 6, and the second electrode 4, and is composed of a high-melting point metal layer 10 and a first low-melting point metal layer 11 composed of a first low-melting point metal 11b having a melting point lower than that of the high-melting point metal 10a constituting the high-melting point metal layer 10, such that the first low-melting point metal layer 11 contacts the first electrode 3, the heating element extraction electrode 6, and the second electrode 4.

[0082] The laminate 35 is formed by laminating a high melting point metal layer 10 and a first low melting point metal layer 11. As a lamination method, for example, a known lamination method such as rolling, pressure bonding, plating coating, etc. can be used.

[0083] [Heating process] 7(C) is a cross-sectional view showing the heating, melting, and connection process of the soluble conductor 7. The soluble conductor 7 can be efficiently connected to each electrode by reflow mounting. In the heating process, the insulating substrate 2 on which the laminate 35 is mounted is heated at a mounting temperature equal to or higher than the eutectic temperature of the alloy of the high-melting-point metal 10a and the first low-melting-point metal 11b. Note that heating may also be performed at a temperature lower than the solidus temperature of the first low-melting-point metal 11b.

[0084] [Melting process] In the melting step, a second low melting point metal layer 12 is formed by interdiffusion and / or melting of a part of the high melting point metal layer 10 and the first low melting point metal layer 11 .

[0085] [Connection process] In the connection process, the molten second low-melting point metal layer 12 cools, connecting the soluble conductor 7 to the first electrode 3, the heating element extraction electrode 6, and the second electrode 4 via the second low-melting point metal layer 12 of the soluble conductor 7, which is laminated with the high-melting point metal layer 10 and the solidified second low-melting point metal layer 12.

[0086] Here, the heating temperature for mounting the fusible conductor 7 (reflow temperature in the case of reflow mounting) is equal to or higher than the solidus temperature of the alloy of the high melting point metal layer 10 and the first low melting point metal layer 11. In the laminate 35, at the lamination interface between the high melting point metal layer 10 and the first low melting point metal layer 11, atoms 10aA of the high melting point metal 10a and atoms 11bA of the first low melting point metal 11b interdiffuse to form the second low melting point metal layer 12. The liquidus temperature of the second low melting point metal layer 12 decreases as the diffusion progresses, and approaches the eutectic point to become liquid.

[0087] 8 is a diagram showing the interdiffusion of dissimilar metal atoms at the interface between different metal layers. As shown in FIG. 8, when a laminate of dissimilar metals is heated, dissimilar metal atoms (e.g., high-melting-point metal atoms 10aA and first low-melting-point metal atoms 11bA) interdiffuse at the interface between the dissimilar metal layers, forming an alloy layer (e.g., second low-melting-point metal layer 12) between the dissimilar metals. When the ratio of the dissimilar metals exceeds a predetermined ratio (atomic %) and the liquidus of the alloy with that ratio falls below the heating temperature, the alloy becomes liquid, and the high-melting-point metal 10a dissolves in the liquid alloy, further lowering the liquidus.

[0088] 9 is a binary alloy phase diagram of silver (Ag) and tin (Sn). Assuming that tin (Sn) is used as the first low-melting-point metal 11b, the solidus and liquidus of the first low-melting-point metal 11b (Sn) are 232°C (231.9681°C). The eutectic line of the alloy of the high-melting-point metal 10a (Ag) and the first low-melting-point metal 11b (Sn) is 221°C. When a reflow temperature lower than 232°C and equal to or higher than 221°C is applied, interdiffusion of the high-melting-point metal 10a (Ag) and the first low-melting-point metal 11b (Sn) progresses at the lamination interface between the high-melting-point metal layer 10 and the first low-melting-point metal layer 11, causing the solidus of the second low-melting-point metal layer 12 to drop and become liquid. Then, the high melting point metal 10a dissolves (dissolves) in the liquid Ag—Sn alloy, and the liquidus line further drops, approaching the eutectic line (221° C.). Note that the diffusion coefficient in the solid is approximately 10 times that of the liquid. -4 Since the diffusion rate is about twice as fast as that of the first low melting point metal 11b, the dissolution (melting) of the molten Ag—Sn alloy into the high melting point metal 10a proceeds faster than the diffusion of the first low melting point metal 11b into the high melting point metal layer 10.

[0089] 10 is a binary alloy phase diagram of lead (Pb) and tin (Sn). When tin (Sn) is assumed as the first low-melting-point metal 11b, the solidus and liquidus of the first low-melting-point metal 11b (Sn) are 232°C (231.9681°C). In addition, the eutectic line of the alloy of the high-melting-point metal 10a (Pb) and the first low-melting-point metal 11b (Sn) is 183°C.

[0090] When a reflow temperature of less than 232°C and equal to or greater than 183°C is applied, the high melting point metal 10a (Pb) and the first low melting point metal 11b (Sn) mutually diffuse at the lamination interface between the high melting point metal layer 10 and the first low melting point metal layer 11, causing the solidus of the second low melting point metal layer 12 to drop and become liquid. Then, the high melting point metal 10a dissolves (melts) in the liquid Pb-Sn alloy, further lowering the liquidus and approaching the eutectic line (183°C). Note that the diffusion coefficient in the solid is approximately 10 times that of the liquid. -4 Since the diffusion rate is about twice as fast as that of the first low melting point metal 11b, the dissolution (melting) of the molten Pb—Sn alloy into the high melting point metal 10a proceeds faster than the diffusion of the first low melting point metal 11b into the high melting point metal layer 10.

[0091] 11A and 11B are cross-sectional views schematically illustrating the state changes of a laminate 35 during the heating, melting, and bonding steps. The laminate 35 is a laminate of a high-melting-point metal layer 10, which is a single-layer alloy (Sn—Ag alloy) of a high-melting-point metal 10a (e.g., Ag) and a first low-melting-point metal 10b (e.g., Sn), and a first low-melting-point metal layer 11, which is made of a first low-melting-point metal 11b (e.g., 100% Sn) (FIG. 11A). The high-melting-point metal layer 10 is phase-separated into a phase (solid phase) of the high-melting-point metal 10a and a phase (solid phase) of the first low-melting-point metal 10b, which are mixed together.

[0092] The laminate 35 has a first low-melting-point metal layer 11 mounted on each electrode. In the early stage of reflow heating, the two types of metals form an alloy at the interface between the layers (see FIG. 8), and the liquidus of the high-melting-point metal layer 10 and the first low-melting-point metal layer 11 becomes lower than the liquidus of each of them alone, forming a liquid phase 35L at the interface between the high-melting-point metal layer 10 and the first low-melting-point metal layer 11 (FIG. 11(B)).

[0093] In the later stage of reflow heating, the liquid phase 35L formed at the interface between the high-melting-point metal layer 10 and the first low-melting-point metal layer 11 dissolves part of the high-melting-point metal layer 10 and almost all of the first low-melting-point metal layer 11, wetting and spreading over the surface of each electrode. However, because the liquid phase 35L continues to dissolve the high-melting-point metal layer 10 and the first low-melting-point metal layer 11 on and between the electrodes during reflow heating, the liquid phase 35L is not drawn toward each electrode to the extent that it disappears completely, but remains below the high-melting-point metal layer 10 between the electrodes (FIG. 11(C)).

[0094] After cooling, when the liquid phase 35L drops below the eutectic line, it separates into a solid phase α (high-melting point metal 10a: Ag-rich) and a solid phase β (first low-melting point metal 12b: Sn-rich) through a eutectic reaction, forming a second low-melting point metal layer 12 with a eutectic structure that forms a marbled pattern (Figure 11(D)).

[0095] In this way, even if the liquidus temperature of the first low-melting-point metal 11b is higher than the mounting temperature (reflow temperature), if the eutectic line of the second low-melting-point metal layer 12 is lower than the mounting temperature (reflow temperature), the high-melting-point metal 10a (Ag) and the first low-melting-point metal 11b (Sn) will coexist in a liquid phase, and the liquid phase region will expand as the melting proceeds. By cooling from this state and solidifying, the high-melting-point metal 10a (Ag) and the first low-melting-point metal 12b (Sn) will precipitate and form a stable second low-melting-point metal layer 12 with a eutectic composition.

[0096] The second low-melting-point metal layer 12, which has a eutectic composition of the high-melting-point metal 10a and the first low-melting-point metal 12b, can also be formed by setting the mounting temperature (reflow temperature) below the solidus temperature of the first low-melting-point metal 11b, as long as the mounting temperature (reflow temperature) is equal to or higher than the eutectic temperature of the alloy of the high-melting-point metal and the first low-melting-point metal. Therefore, in the heating step, the insulating substrate 2 on which the laminate 35 is mounted may be heated at a mounting temperature that is lower than the solidus temperature of the first low-melting-point metal 11b and equal to or higher than the eutectic temperature of the alloy of the high-melting-point metal 10a and the first low-melting-point metal 11b. Of course, the mounting temperature may also be equal to or higher than the solidus temperature of the first low-melting-point metal 11b.

[0097] 12 is a cross-sectional view schematically showing a case where the second low-melting-point metal layer 12 has a laminated structure of an alloy of a high-melting-point metal 12a and a first low-melting-point metal 12b, and the first low-melting-point metal layer 11. As shown in FIG. 12(C), in the later stage of reflow heating, the first low-melting-point metal layer 11 of the laminate 35 may not be completely melted and may remain. As a result, after cooling, the second low-melting-point metal layer 12 has a laminated structure of the alloy of a high-melting-point metal 12a and a first low-melting-point metal 12b, and the first low-melting-point metal layer 11 (FIG. 12(D)).

[0098] Figure 13 is also a cross-sectional view schematically showing the state changes of the laminate 35 during the heating, melting, and bonding steps, but the configuration of the laminate 35 is different from that shown in Figures 11(A) and 12(A). In the laminate 35 shown in Figure 13, the high-melting-point metal layer 10 is composed almost entirely of high-melting-point metal 10a with a small amount of first low-melting-point metal 10b mixed in, and the first low-melting-point metal layer 11 is composed almost entirely of first low-melting-point metal 11b. In Figure 13, the first low-melting-point metal layer 11 is completely melted, and the second low-melting-point metal layer 12 is formed.

[0099] Figure 14 is a cross-sectional view that schematically shows a case in which, in the configuration shown in Figure 13, the first low-melting point metal layer 11 of the laminate 35 is not completely melted and remains, and the second low-melting point metal layer 12 has a laminated structure of an alloy of a high-melting point metal 12a and the first low-melting point metal 12b and the first low-melting point metal layer 11.

[0100] In the configurations shown in FIGS. 11 to 14, the first low-melting-point metal layer 11 may contain a small amount of high-melting-point metal 11a, although this is not shown.

[0101] [Mounting on circuit board] As shown in Fig. 7(D), the protective element 1 connected to the fusible conductor 7 is protected from the inside by applying a coating flux 9 to the fusible conductor 7 and then providing a cover member 19 on the surface 2a of the insulating substrate 2. Next, as shown in Fig. 7(E), the protective element 1 is mounted on a circuit board 34, and cuts off at least a portion of the current flow within the circuit board 34 when an abnormality occurs in the circuit board 34.

[0102] There are no particular limitations on the method for mounting the protection element 1 on the circuit board 34, but it can be efficiently performed by reflow. A connection material such as solder paste is applied to multiple terminals 34a provided on the circuit board 34, and the first and second external connection electrodes 13, 14 and the heating element electrode 17 provided on the back surface 2b of the insulating substrate 2 are mounted, and then reflow heating is performed. As a result, the fusible conductor 7 is connected in series to the current path formed on the circuit board 34, and the heating element 5 is connected to the current control element 28 via the heating element electrode 17, and the heating element 5 is connected to one end of the battery stack 25 via the current control element 28.

[0103] At this time, as described above, by making the liquidus point of the second low-melting point metal layer 12 higher than the mounting temperature (reflow temperature) of the protection element 1 on the circuit board 34, the second low-melting point metal layer 12 melts when mounted on the circuit board 34, and this prevents gaps from forming between the second low-melting point metal layer 12 and the insulating substrate 2 between the first and second electrodes 3, 4 and the heating element extraction electrode 6.

[0104] In addition, due to the heating during mounting on the circuit board 34, the second low melting point metal layer 12 of the soluble conductor 7 begins to melt again, and by melting the high melting point metal layer 10, the area of ​​the second low melting point metal layer 12 spreads to the upper layer side. Even at this time, on the electrodes and between the electrodes during heating, the high melting point metal layer 10 continues to melt due to the liquefied second low melting point metal layer 12. Therefore, the second low melting point metal layer 12 is not attracted to each electrode side so that it disappears completely, but remains below the high melting point metal layer 10 between the electrodes, and the laminated structure is maintained (see FIG. 11(C)).

[0105] Furthermore, if the liquidized second low-melting point metal layer 12 completely dissolves the high-melting point metal layer 10, that is, if the entire soluble conductor 7 becomes liquid, the soluble conductor 7a will condense on the first and second electrodes 3, 4 and the heating element lead electrode 6 as shown in Figure 2, causing the soluble conductor 7 to melt and no longer function as a protective element 1. Therefore, by selecting appropriate materials for the high-melting point metal layer 10 and the low-melting point metal layer 11 and controlling their respective thicknesses, the high-melting point metal layer 10 will not be completely dissolved, and the laminated structure of the high-melting point metal layer 10 and the second low-melting point metal layer 12 will be maintained.

[0106] In addition, the laminate 35 mounted on the insulating substrate 2 is designed to take into account the heating during reflow mounting on the circuit board 34, with the metals of the high melting point metal layer 10 and the first low melting point metal layer 11 and the thickness of the first low melting point metal layer 11. That is, since the protective element 1 is used in a state mounted on the circuit board 34, when the fusing conditions such as the applied voltage (for example, 4 V), the resistance value of the heating element 5 (for example, 2.5 Ω), the heat generation temperature (for example, 300 ° C to 400 ° C), and the fusing time after heat generation (for example, fusing within 5 seconds) are set, in the case of Sn-Pb solder, by referring to the Sn-Pb binary phase diagram, it is possible to design the configuration of the fusible conductor 7 that matches this (the volume ratio of the high melting point metal layer 10 / the second low melting point metal layer 12). From this viewpoint, it is preferable that the protective element 1 is designed so that, when the soluble conductor 7 is mounted, the thickness of the high melting point metal layer 10 in the stacking direction is thicker than the thickness of the second low melting point metal layer 12 in the stacking direction.

[0107] [Pressure mounting] 7(C), in the manufacturing process of the protection element 1, it is preferable to pressurize the upper part of the high-melting point metal layer 10 toward the insulating substrate 2 between the heating step and the connecting step. This allows at least a part of the second low-melting point metal layer 12 to be in direct contact with the insulating substrate 2 between the first electrode 3 and the heater lead electrode 6 and between the second electrode 4 and the heater lead electrode 6.

[0108] 15 shows an example of a method for applying pressure to the high-melting-point metal layer 10. The heating head 36 preferably has a pressing surface that is larger than or equal to the surface area of ​​the laminate 35, and heats and presses the entire surface of the laminate 35. The heating head 36 heats and presses the laminate 35 at a predetermined temperature, for example, a mounting temperature that is lower than the solidus temperature of the first low-melting-point metal 11a and higher than the eutectic temperature of the alloy of the high-melting-point metal 10a and the first low-melting-point metal 11a.

[0109] After the mounting process of the laminate 35, the heating head 36 heats and presses the laminate 35 from above the high-melting-point metal layer 10 at a predetermined temperature, pressure, and time. As a result, through the process of melting the first low-melting-point metal layer 11 and melting a portion of the high-melting-point metal layer 10 in the reflow mounting described above (see FIG. 11), a soluble conductor 7 is formed, which is a laminate of the high-melting-point metal layer 10 and the second low-melting-point metal layer 12, and the soluble conductor 7 is connected to the first and second electrodes 3 and 4 and the heating element lead electrode 6 via the second low-melting-point metal layer 12. In addition, the second low-melting-point metal layer 12 can be brought into contact with the insulating substrate 2 between the first electrode 3 and the heating element lead electrode 6 and between the second electrode 4 and the heating element lead electrode 6.

[0110] It is preferable that the heating head 36 continues to press the second low-melting point metal layer 12 until it is cooled and solidified, thereby allowing the solidified second low-melting point metal layer 12 to come into contact with the insulating substrate 2 over a wider area between the first electrode 3 and the heater lead electrode 6 and between the second electrode 4 and the heater lead electrode 6.

[0111] In addition, in the heating and pressing process using the heating head 36, the laminate 35 may be heated and pressed at a mounting temperature that is equal to or higher than the solidus temperature of the first low-melting point metal 11a and equal to or higher than the eutectic temperature of the alloy of the high-melting point metal 10a and the first low-melting point metal 11a.

[0112] 16, the high-melting-point metal layer 10 may be pressed by a weight 37. The weight 37 preferably has a pressing surface that is at least as large as the surface area of ​​the laminate 35 and presses the entire surface of the laminate 35. After the mounting step of the laminate 35, the weight 37 is placed on the high-melting-point metal layer 10, and in this state is subjected to the reflow step.

[0113] As a result, through the process of melting the first low melting point metal layer 11 and part of the high melting point metal layer 10 in the reflow mounting described above (see FIG. 11), a soluble conductor 7 is formed, which is a laminate of the high melting point metal layer 10 and the second low melting point metal layer 12, and the soluble conductor 7 is connected to the first and second electrodes 3 and 4 and the heating element lead electrode 6 via the second low melting point metal layer 12. In addition, the second low melting point metal layer 12 can be brought into contact with the insulating substrate 2 between the first electrode 3 and the heating element lead electrode 6 and between the second electrode 4 and the heating element lead electrode 6.

[0114] It is preferable that the weight 37 is left on the second low-melting point metal layer 12 until the second low-melting point metal layer 12 is cooled and solidified, thereby allowing the solidified second low-melting point metal layer 12 to come into contact with the insulating substrate 2 over a wider area between the first electrode 3 and the heater lead electrode 6 and between the second electrode 4 and the heater lead electrode 6.

[0115] [Regulatory barriers] As shown in FIG. 17, the protective element 1 may have a restricting wall 39 on the inner surface of the cover member 19, which restricts the portion where the second low-melting point metal layer 12 of the fusible conductor 7 contacts the insulating substrate 2. The restricting wall 39 is provided at a position facing the first electrode 3 of the insulating substrate 2 and the heating element lead electrode 6, and the second electrode 4 and the heating element lead electrode 6. The restricting wall 39 may be integrally formed with the cover member 19, or may be formed separately and connected by adhesion, welding, or the like. The restricting wall 39 only needs to have heat resistance to the reflow temperature equivalent to that of the cover member 19, and may be formed from the same material as the cover member 19 or a different material.

[0116] Even if the second low-melting point metal layer 12 of the soluble conductor 7 melts due to heating when the protective element 1 is mounted on the circuit board 34, the regulating wall 39 prevents the soluble conductor 7 from floating, and prevents gaps from occurring between the second low-melting point metal layer 12 and the insulating substrate 2 between the first electrode 3 of the insulating substrate 2 and the heating element extraction electrode 6, and between the second electrode 4 and the heating element extraction electrode 6.

[0117] [Insulating layer] An insulating layer 51 having a thickness greater than that of any of the first and second electrodes 3, 4 and the heater lead electrode 6 may be formed between the first electrode 3 and the heater lead electrode 6 on the insulating substrate 2 and between the second electrode 4 and the heater lead electrode 6. The protection element 50 shown in FIG. 18 is in indirect contact with the insulating substrate 2 as the second low-melting point metal layer 12 is in contact with the insulating layer 51.

[0118] The insulating layer 51 can be formed of an insulating material such as glass or ceramic. The insulating layer 51 can be formed by a known method such as printing and firing a glass paste, or bonding ceramic. After the insulating substrate 2 provided with the insulating layer 51 has a connection flux 29 applied to each of the first electrode 3, the second electrode 4, and the heating element lead electrode 6, the insulating substrate 2 is subjected to a mounting process of the laminate 35, a heating process of heating the laminate 35, a melting process of melting the first low-melting point metal layer 11, and a connecting process of forming a fusible conductor 7 and connecting it to the electrode, thereby forming the protective element 50 (FIG. 18(C)).

[0119] Since the thickness of the insulating layer 51 is greater than the thickness of any of the first and second electrodes 3, 4 and the heating element lead electrode 6, the insulating layer 51 and the first low-melting point metal layer 11 of the laminate 35 come into contact with each other in the mounting process, as shown in Fig. 18(A). When the laminate 35 is heated in this state by reflow or the like and the first low-melting point metal layer 11 melts, the liquid phase 35L comes into contact with the insulating layer 51 regardless of the tension. When the laminate 35 is then cooled, the second low-melting point metal layer 12 contracts in volume as it cools, causing it to adhere to the insulating layer 51, as shown in Fig. 18(B).

[0120] This allows the second low-melting point metal layer 12 to be indirectly in contact with the insulating substrate 2 via the insulating layer 51 between the first electrode 3 and the heater lead electrode 6 and between the second electrode 4 and the heater lead electrode 6. By forming the insulating layer 51 using an insulating material with excellent thermal conductivity, the protective element 50 achieves the same effect as the protective element 1 in which the second low-melting point metal layer 12 is in direct contact with the insulating substrate 2.

[0121] Insulation layer thickness 19, the thickness of the insulating layer may be greater than the sum of the thickness of the heater lead electrode 6 and the thickness of the first low-melting point metal layer 11. In the protective element 60 shown in FIG. 19, a thick insulating layer 61 is provided between the first electrode 3 of the insulating substrate 2 and the heater lead electrode 6 and between the second electrode 4 and the heater lead electrode 6.

[0122] The thick insulating layer 61 can be formed, for example, by printing and baking an insulating material such as glass paste. The insulating material may be printed in multiple steps to increase the thickness. In the formation process, the insulating layer 61 is formed to have an arc-shaped cross section due to the tension of the insulating material. As a result, in the process of mounting the fusible conductor 7 and the process of mounting the protective element 60 on the circuit board 34, the molten second low-melting point metal layer 12 is brought into close contact with the periphery of the insulating layer 61 due to volumetric contraction caused by cooling (FIG. 19(B)).

[0123] In addition, the thickness of the insulating layer 61 is formed to be thicker than the sum of the thickness of the heating element lead electrode 6 and the thickness of the first low melting point metal layer 11. Therefore, the area of ​​the liquid phase 35L expands while dissolving the high melting point metal layer 10, and covers the insulating layer 61, and due to the volume contraction caused by the cooling of the second low melting point metal layer 12, it adheres to the insulating layer 61. By widening the contact area in this way, the force of the soluble conductor 7 toward the insulating substrate 2 side further increases, so that it can be adhered without gaps.

[0124] In addition, the insulating layer 61 has no corners because it is formed in an arc shape. Therefore, no voids are formed near the corners due to the tension of the liquid phase 35L, and the soluble conductor 7 can be tightly attached to the insulating layer 61 without any gaps.

[0125] [Convex part of insulating substrate] Furthermore, protrusions 71 having a height greater than the thickness of any of the first and second electrodes 3, 4 and the heater lead electrode 6 may be formed on the insulating substrate 2 between the first electrode 3 and the heater lead electrode 6 and between the second electrode 4 and the heater lead electrode 6. The protection element 70 shown in FIG. 20 is in direct contact with the insulating substrate 2 as the second low-melting point metal layer 12 contacts the protrusions 71.

[0126] The convex portion 71 is a portion formed on the insulating substrate 2. After the connecting flux 29 is applied to each of the first electrode 3, the second electrode 4, and the heating element lead electrode 6, the insulating substrate 2 provided with the convex portion 71 undergoes a mounting process of the laminate 35, a heating process of heating the laminate 35, a melting process of melting the first low-melting point metal layer 11, and a connecting process of forming the fusible conductor 7 and connecting it to the electrodes, thereby forming the protective element 70 (FIG. 20(C)).

[0127] The height of the protrusion 71 is greater than the thickness of any of the first and second electrodes 3 and 4 and the heating element lead electrode 6, so the protrusion 71 protrudes from the other electrodes, and as shown in FIG. 20(A), the protrusion 71 comes into contact with the first low-melting point metal layer 11 of the laminate 35 in the mounting process. When the first low-melting point metal layer 11 is melted by heating in this state by reflow or the like, the liquid phase 35L comes into contact with the protrusion 71 regardless of the tension. When the first low-melting point metal layer 11 is then cooled, the liquid phase 35L comes into contact with the protrusion 71 due to volumetric contraction caused by cooling of the second low-melting point metal layer 12, as shown in FIG. 20(B).

[0128] This allows the second low-melting point metal layer 12 to be in direct contact with the insulating substrate 2 via the protrusions 71 between the first electrode 3 and the heater lead electrode 6 and between the second electrode 4 and the heater lead electrode 6. The protective element 70 has the same effect as the protective element 1 in which the second low-melting point metal layer 12 is in direct contact with the insulating substrate 2 between the first electrode 3 and the heater lead electrode 6 and between the second electrode 4 and the heater lead electrode 6.

[0129] [Convex height] 21, the height of the convex portion may be greater than the sum of the thickness of the heating element lead electrode 6 and the thickness of the first low-melting point metal layer 11. In the protection element 80 shown in FIG. 21, tall convex portions 81 are formed between the first electrode 3 of the insulating substrate 2 and the heating element lead electrode 6, and between the second electrode 4 and the heating element lead electrode 6.

[0130] The convex portion 81 is a portion formed on the insulating substrate 2. The convex portion 81 is preferably formed to have an arc-shaped cross section. As a result, in the process of mounting the fusible conductor 7 or the process of mounting the protective element 80 on the circuit board 34, the molten second low-melting point metal layer 12 adheres to the periphery of the convex portion 81 due to volumetric contraction accompanying cooling (FIG. 21(B)). By widening the contact area in this way, the force of the fusible conductor 7 toward the insulating substrate 2 further increases, allowing for close contact without gaps.

[0131] In addition, the film thickness of the convex portion 81 is formed to be thicker than the sum of the thickness of the heating element lead electrode 6 and the thickness of the first low melting point metal layer 11. Therefore, the area of ​​the liquid phase 35L expands while dissolving the high melting point metal layer 10, and covers the convex portion 81, and due to volume contraction caused by cooling of the second low melting point metal layer 12, it adheres to the convex portion 81. By widening the contact area in this way, the force of the soluble conductor 7 toward the insulating substrate 2 side further increases, so that it can be adhered without gaps.

[0132] In addition, the convex portion 81 is formed in an arc shape and does not have corners. For this reason, no voids are formed near the corners due to the tension of the liquid phase 35L, and the soluble conductor 7 can be tightly attached to the convex portion 81 without any gaps.

[0133] In the above-described protective elements 50, 60, 70, and 80, the heating element 5 is formed on the back surface 2b of the insulating substrate 2. However, as with the protective element 1 shown in FIG. 5, the heating element 5, the insulating protective layer 8, the first extraction electrode 15, the second extraction electrode 16, the heating element electrode 17, and the intermediate electrode 18 may be formed on the front surface 2a of the insulating substrate 2. Also, as with the protective element 1 shown in FIG. 6, the protective elements 50, 60, 70, and 80 may have an insulating substrate 2 with a two-layer structure of an upper layer and a lower layer, and the heating element 5, the first extraction electrode 15, and the second extraction electrode 16 may be formed between the upper and lower layers. Furthermore, in the protective elements 50, 60, 70, and 80, as with the protective element 1 shown in FIG. 17, a restricting wall 39 may be provided on the inner surface of the cover member 19 to hold down the portion where the second low-melting point metal layer 12 of the fusible conductor 7 contacts the insulating substrate 2.

[0134] [Protection element 100] Next, a modified example of a protection element to which the present technology is applied will be described. Fig. 22 shows a protection element 100 according to a modified example, where (A) is a plan view, (B) is a cross-sectional view in the current-carrying direction of the fusible conductor, and (C) is a bottom view. As shown in Fig. 22, the protection element 100 differs from the protection element 1 described above in the configuration of the fusible conductor and the connection form of the fusible conductor. Furthermore, like the protection element 1, the protection element 100 is used as a protection element for a battery pack 20 and other electronic devices.

[0135] The protective element 100 comprises an insulating substrate 2, a heating element 5 provided on the insulating substrate 2, a first electrode 3 and a second electrode 4 provided on the insulating substrate 2, a heating element lead-out electrode 6 electrically connected to the heating element 5 on the current path between the first electrode 3 and the second electrode 4, and a fusible conductor 101 connected across the first electrode 3, the heating element lead-out electrode 6, and the second electrode 4, which melts between the first electrode 3 and the second electrode 4 due to self-heating caused by the passage of an overcurrent exceeding the rated current and / or heat generation by the heating element 5, thereby interrupting the current path.

[0136] The soluble conductor 101 has a coating structure in which both sides of a low-melting-point metal layer 102 are coated with a high-melting-point metal layer 103 having a melting point higher than that of the low-melting-point metal layer 102, and is connected to each of the first electrode 3, the second electrode 4, and the heating element extraction electrode 6 via a conductive connecting material 105 such as solder.

[0137] Furthermore, at least a portion of the soluble conductor 101 is in indirect contact with the insulating substrate 2 via the conductive connecting material 105 between the first electrode 3 and the heating element extraction electrode 6 and between the second electrode 4 and the heating element extraction electrode 6.

[0138] In the protection element 100, the insulating substrate 2, the heating element 5, the insulating protective layer 8, the first electrode 3, the second electrode 4, the heating element extraction electrode 6, the first external connection electrode 13, the second external connection electrode 14, the first extraction electrode 15, the second extraction electrode 16, the heating element electrode 17, the intermediate electrode 18, and the cover member 19 have the same configuration as the protection element 1 described above, so details will be omitted.

[0139] [Fusible conductor] Like the fusible conductor 7, the fusible conductor 101 is implemented between the first and second electrodes 3, 4, and melts due to heat generated by the passage of current through the heating element 5 or due to self-heating (Joule heat) when a current exceeding the rated current is passed through it, thereby interrupting the current path between the first electrode 3 and the second electrode 4.

[0140] As shown in Figure 23, the soluble conductor 101 has a coating structure in which both sides of the low-melting-point metal layer 102 are coated with a high-melting-point metal layer 103 having a melting point higher than that of the low-melting-point metal layer 102, and in the protective element 100, it has a rectangular plate shape in plan view. The high-melting-point metal constituting the high-melting-point metal layer 103 and the low-melting-point metal constituting the low-melting-point metal layer 102 are metals that have a melting point difference and can melt, and a metal with a relatively low melting point is a "low-melting-point metal", and a metal with a relatively high melting point that dissolves into the molten low-melting-point metal is a "high-melting-point metal".

[0141] The high-melting point metal constituting the soluble conductor 101 can be the same as the high-melting point metal 10a in the above-mentioned protection element 1, and the low-melting point metal can be the same as the first low-melting point metal 11b in the above-mentioned protection element 1.

[0142] Such a soluble conductor 101 can be formed, for example, by forming a high-melting point metal layer on a low-melting point metal foil using a plating technique, or can be formed using other well-known lamination techniques or film formation techniques. The soluble conductor 101 may have a structure in which the entire surface of the low-melting point metal layer 102 is covered with a high-melting point metal layer 103, or may have a structure in which only a pair of opposing side surfaces of the low-melting point metal layer 102 are covered. The soluble conductor 101 can be formed in various configurations, such as a multilayer structure of three or more layers in which the low-melting point metal layer 102 and the high-melting point metal layer 103 are alternately stacked, or an opening is provided in part of the outer layer to expose part of the inner layer.

[0143] The soluble conductor 101 is coated with a low-melting-point metal layer 102 as an inner layer and a high-melting-point metal layer 103 as an outer layer, so that even if the mounting temperature, such as the reflow temperature, exceeds the melting temperature of the low-melting-point metal layer 102, the soluble conductor 101 can maintain its shape and will not melt. Therefore, the connection between the first and second electrodes 3, 4 and the heating element lead electrode 6 and the soluble conductor 101, and the mounting of the protective element 100 on the circuit board 34 can be efficiently performed by reflow. In addition, even if the soluble conductor 101 is deformed by reflow, the resistance value becomes locally high or low. This can prevent fluctuations in fusing characteristics, such as not melting at a predetermined temperature or melting at a temperature lower than the predetermined temperature.

[0144] In addition, the soluble conductor 101 will not melt even if it generates heat while a predetermined rated current is flowing. When a current higher than the rated current flows, it melts due to self-heating, cutting off the current path between the first and second electrodes 3 and 4. When the heating element 5 is energized and generates heat, it melts and cuts off the current path between the first and second electrodes 3 and 4.

[0145] At this time, the molten low-melting point metal layer 102 corrodes (solder-eats) the high-melting point metal layer 103, so that the soluble conductor 101 melts at a temperature lower than the melting temperature of the high-melting point metal layer 103. Therefore, the soluble conductor 101 can be melted in a short time by utilizing the melting action of the low-melting point metal layer 102 on the high-melting point metal layer 103. In addition, the molten conductor 101a of the soluble conductor 101 is divided by the physical pulling action of the heating element lead electrode 6 and the first and second electrodes 3, 4, so that the current path between the first and second electrodes 3, 4 can be quickly and reliably interrupted.

[0146] In addition, it is preferable that the soluble conductor 101 has a volume of the low-melting point metal layer 102 greater than the volume of the high-melting point metal layer 103. The soluble conductor 101 is heated by self-heating due to overcurrent or by heat generation from the heating element 5, and the low-melting point metal melts, corroding the high-melting point metal, thereby quickly melting and fusing. Therefore, by forming the volume of the low-melting point metal layer 102 of the soluble conductor 101 to be greater than the volume of the high-melting point metal layer 103, this dissolution action is promoted and the first and second electrodes 3, 4 can be quickly disconnected.

[0147] In addition, since the fusible conductor 101 is configured such that the inner layer, a low-melting-point metal layer 102, is coated with a high-melting-point metal layer 103, the fusing temperature can be significantly reduced compared to conventional chip fuses made of high-melting-point metals. Therefore, the fusible conductor 101 can have a larger cross-sectional area and a significantly improved current rating compared to chip fuses of the same size. In addition, it can be made smaller and thinner than conventional chip fuses with the same current rating, and has excellent fast-fusing properties.

[0148] Furthermore, the soluble conductor 101 can improve resistance (pulse resistance) to surges, which are instantaneous applications of abnormally high voltage to an electrical system incorporating the protective element 100. In other words, the soluble conductor 101 must not melt even when, for example, a 100A current flows for several milliseconds. Since a large current that flows in an extremely short time flows through the surface layer of the conductor (skin effect), the soluble conductor 101 has a low-resistance, high-melting-point metal layer 103, such as Ag plating, as its outer layer. This allows the current applied by a surge to flow easily, preventing melting due to self-heating. Therefore, the soluble conductor 101 can significantly improve resistance to surges compared to fuses made of conventional solder alloys.

[0149] The fusible conductor 101 is coated with a coating flux 9 to prevent oxidation and improve wettability during melting. The inside of the protective element 100 is protected by covering the insulating substrate 2 with a cover member 19.

[0150] Here, at least a portion of the soluble conductor 101 is in indirect contact with the insulating substrate 2 between the first electrode 3 and the heating element lead electrode 6 and between the second electrode 4 and the heating element lead electrode 6. In the protection element 100 shown in FIG. 22, the soluble conductor 101 is in contact with the insulating substrate 2 via the conductive connecting material 105.

[0151] When the soluble conductor 101 melts due to heat generated by the heating element 5 or self-heating due to overcurrent, it causes a dissolution phenomenon (corrosion) in which the high melting point metal layer 103 dissolves into the molten low melting point metal layer 102, and is attracted to the first electrode 3, the second electrode 4, and the heating element lead electrode 6, which have high wettability to the molten metal. At this time, according to the protective element 100, between the first electrode 3 and the heating element lead electrode 6 and between the second electrode 4 and the heating element lead electrode 6, at least a part of the soluble conductor 101 is in indirect contact with the insulating substrate 2, so that the current paths between the first electrode 3 and the heating element lead electrode 6 and between the second electrode 4 and the heating element lead electrode 6 can be reliably blocked.

[0152] That is, in a conventional configuration in which a high-melting-point metal film is in contact with an insulating substrate, the problem occurs that the current path is not completely blocked due to the erosion residue of the high-melting-point metal film. However, in the protective element 100, the soluble conductor 101 is in direct or indirect contact with the insulating substrate 2 via a conductive connecting material 105 such as solder, or via an insulating layer or a protrusion as described below, so that the molten high-melting-point metal layer 10 is prevented from remaining undissolved on the insulating substrate 2, and is attracted to the heating element lead electrode 6 and the first and second electrodes 3 and 4 while the high-melting-point metal layer 10 is dissolving.

[0153] Furthermore, when the soluble conductor 101 is melted by the heat of the heating element 5, the heat generated by the heating element 5 heats the soluble conductor 101 via the heating element lead electrode 6, and also directly heats the soluble conductor 101 that is at least partially in contact with the insulating substrate 2 via the insulating substrate 2. As a result, a wide range of the soluble conductor 101 melts in a short time, which efficiently melts the high-melting point metal layer 103 and improves the fast-melting characteristics of the soluble conductor 101.

[0154] Furthermore, in the case where the soluble conductor 101 melts due to self-heating caused by an overcurrent, the soluble conductor 101 between the first electrode 3 and the heating element extraction electrode 6 and between the second electrode 4 and the heating element extraction electrode 6 comes into direct or indirect contact with the insulating substrate 2, so that the heat generated by the self-heating of the soluble conductor 101 is dissipated directly to the insulating substrate 2, thereby improving the current rating of the protective element 100.

[0155] In addition, since the soluble conductor 101 is connected to the first electrode 3, the second electrode 4, and the heating element lead electrode 6 via the conductive connecting material 105, precise control of the solder paste is not required.

[0156] Therefore, the protective element 100 can achieve a balance between the fuse characteristics that are in a trade-off relationship: "stable connection of the fusible conductor," "efficient melting of the fusible conductor by heating the heating element," and "improvement of the rated current."

[0157] [Liquidus point of conductive interconnect material] The protection element 100 is mounted on the circuit board 34 and cuts off electrical current in at least a portion of the circuit board 34 when an abnormality occurs in the circuit board 34. The protection element 100 can be mounted efficiently on the circuit board 34 by reflow. Here, the liquidus point of the conductive connecting material 105 is preferably higher than the mounting temperature of the protection element 100 on the circuit board 34.

[0158] As shown in Figure 22, in the protective element 100, the conductive connecting material 105 is in contact with the insulating substrate 2 between the first electrode 3 and the heating element extraction electrode 6 and between the second electrode 4 and the heating element extraction electrode 6, and the soluble conductor 101 is in contact with the insulating substrate 2 via the conductive connecting material 105.

[0159] Since the liquidus point of the conductive connecting material 105 is higher than the mounting temperature on the circuit board 34, the conductive connecting material 105 melts when mounted on the circuit board, which prevents gaps from forming between the conductive connecting material 105 and the insulating substrate 2 between the first and second electrodes 3, 4 and the heating element extraction electrode 6.

[0160] [Contact area between fusible conductor and insulating substrate] Between the first electrode 3 and the heating element extraction electrode 6 and between the second electrode 4 and the heating element extraction electrode 6, the contact area between the soluble conductor 101 and the insulating substrate 2 is preferably 50% or more of the area between the first electrode 3 overlapping with the soluble conductor 101 and the heating element extraction electrode 6, and 50% or more of the area between the second electrode 4 overlapping with the soluble conductor 101 and the heating element extraction electrode 6. This allows the effect of the contact between the soluble conductor 101 and the insulating substrate 2 to be more effectively exerted.

[0161] The protection device 100, like the protection device 1, is incorporated into a circuit or the like in a battery pack 20 of a lithium ion secondary battery (see FIG. 3).

[0162] [Manufacturing process of the protection element 100] Next, we will explain the manufacturing process of the protection element 100. As shown in Fig. 24, the manufacturing process of the protection element 100 includes a conductive connecting material forming process of providing a conductive connecting material 105, a mounting process of the soluble conductor 101, a heating and melting process of heating and melting the conductive connecting material 105, and a connecting process of connecting the soluble conductor 7 onto each electrode.

[0163] [Conductive connecting material formation process] 24(A) is a cross-sectional view illustrating the conductive connecting material forming step. Prior to the conductive connecting material forming step, a first electrode 3, a second electrode 4, a heater element lead electrode 6, and a front-side intermediate electrode 18a are formed on the front surface 2a of an insulating substrate 2, and a heater element 5, a first external connection electrode 13, a second external connection electrode 14, a first lead electrode 15, a second lead electrode 16, a heater element electrode 17, a back-side intermediate electrode 18b, and an insulating protective layer 8 are formed on the rear surface 2b of the insulating substrate 2 to form an element body 100A. An uncured conductive connecting material 105 is provided on the first electrode 3, the heater element lead electrode 6, and the second electrode 4 formed on the insulating substrate 2, as well as between the first electrode 3 and the heater element lead electrode 6 and between the second electrode 4 and the heater element lead electrode 6. The conductive connecting material 105 can be provided by a known method, such as screen printing or application using a dispenser.

[0164] 24(B) is a cross-sectional view showing the mounting process of the soluble conductor 101. In the mounting process, the soluble conductor 101 is mounted on the first electrode 3 formed on the insulating substrate 2, on the heating element lead electrode 6, and on the second electrode 4 via the conductive connecting material 105.

[0165] [Heating and melting process] 24(C) is a cross-sectional view showing the heating and melting step of the conductive connecting material 105 and the connecting step of the soluble conductor 101. The soluble conductor 101 can be efficiently connected to each electrode by reflow mounting. In the heating and melting step, the insulating substrate 2 on which the soluble conductor 101 is mounted is heated to a mounting temperature higher than the solidus temperature of the conductive connecting material 105, preferably at a mounting temperature higher than the liquidus temperature, to melt it.

[0166] [Connection process] In the connection process, the molten conductive connecting material 105 cools, and the soluble conductor 101 is connected to the first electrode 3, the heating element lead electrode 6, and the second electrode 4 via the conductive connecting material 105.

[0167] [Mounting on circuit board] As shown in Fig. 24(D), the protective element 100 to which the fusible conductor 101 is connected is protected inside by applying a coating flux 9 onto the fusible conductor 101 and then providing a cover member 19 on the surface 2a of the insulating substrate 2. Next, as shown in Fig. 24(E), the protective element 100 is mounted on the circuit board 34 and cuts off at least part of the current flow within the circuit board 34 when an abnormality occurs in the circuit board 34.

[0168] The protective element 100 can be mounted efficiently on the circuit board 34 by reflow. A connection material such as solder paste is applied to a plurality of terminals 34a provided on the circuit board 34, and the first and second external connection electrodes 13, 14 and the heating element electrode 17 provided on the rear surface 2b of the insulating substrate 2 are mounted thereon, followed by reflow heating. As a result, the soluble conductor 101 is connected in series to the current path formed on the circuit board 34, and the heating element 5 is connected to the current control element 28 via the heating element electrode 17, and the heating element 5 is connected to one end of the battery stack 25 via the current control element 28.

[0169] In this case, as described above, by setting the liquidus point of the conductive connecting material 105 higher than the reflow temperature of the protection element 100 onto the circuit board 34, the conductive connecting material 105 melts during reflow mounting onto the circuit board 34, and gaps can be prevented from occurring between the conductive connecting material 105 and the insulating substrate 2 between the first and second electrodes 3, 4 and the heating element extraction electrode 6.

[0170] Furthermore, even if the low melting point metal layer 102 of the soluble conductor 101 melts due to heating during reflow mounting on the circuit board 34, the high melting point metal layer 103 covering the low melting point metal layer 102 will not be completely melted and the entire soluble conductor 101 will not become liquid, and the soluble conductor 101 will not melt and the covering structure will be maintained.

[0171] [Pressure mounting] Also, in the manufacturing process of the protection element 100, similarly to the manufacturing process of the protection element 1, it is preferable to pressurize the upper part of the soluble conductor 101 toward the insulating substrate 2 between the heating / melting process and the connecting process. This allows at least a part of the soluble conductor 101 to contact the insulating substrate 2 via the conductive connecting material 105 between the first electrode 3 and the heating element lead electrode 6 and between the second electrode 4 and the heating element lead electrode 6.

[0172] As a means for applying pressure to the fusible conductor 101, the above-mentioned method of heating and pressing with the heating head 36 (see FIG. 15) or the method of applying pressure with the weight 37 and heating by reflow or the like (see FIG. 16) can be used. The pressure mounting method using the heating head 36 and the weight 37 has been described above, so a description thereof will be omitted.

[0173] [Regulatory barriers] As shown in FIG. 25, the protection element 100 may have a restriction wall 39 on the inner surface of the cover member 19 that holds down the portion where the soluble conductor 101 contacts the insulating substrate 2 via the conductive connecting material 105.

[0174] Even when the conductive connecting material 105 connecting the soluble conductor 101 melts due to heating when the protective element 100 is mounted on the circuit board 34, the regulating wall 39 prevents the soluble conductor 101 from floating, and prevents gaps from occurring between the conductive connecting material 105 and the insulating substrate 2 between the first electrode 3 and the heating element extraction electrode 6 of the insulating substrate 2, and between the second electrode 4 and the heating element extraction electrode 6, thereby maintaining contact of the soluble conductor 101 with the insulating substrate 2 via the conductive connecting material 105.

[0175] [Insulating layer] An insulating layer 51 having a thickness greater than the thickness of any of the first and second electrodes 3, 4 and the heating element extraction electrode 6 may be formed between the first electrode 3 and the heating element extraction electrode 6 of the insulating substrate 2 and between the second electrode 4 and the heating element extraction electrode 6. In the protective element 110 shown in FIG. 26, the conductive connecting material 105 contacts the soluble conductor 101 and the insulating layer 51, and the soluble conductor 101 indirectly contacts the insulating substrate 2 via the insulating layer 51.

[0176] After the step of forming the conductive connecting material 105, the insulating substrate 2 provided with the insulating layer 51 undergoes the step of mounting the soluble conductor 101, the step of heating the conductive connecting material 105, and the step of connecting the soluble conductor 101, to form the protective element 110 (Figure 26(C)).

[0177] Since the thickness of the insulating layer 51 is thicker than the thickness of any of the first and second electrodes 3, 4 and the heating element lead electrode 6, as shown in FIG. 26(A), the insulating layer 51 and the conductive connecting material 105 come into contact with each other in the conductive connecting material forming step. After the soluble conductor 101 is mounted, it is heated by reflow or the like, and when the conductive connecting material 105 melts, the soluble conductor 101 comes into contact with the insulating layer 51 regardless of the tension. After that, when it is cooled, as shown in FIG. 26(B), the conductive connecting material 105 solidifies with the soluble conductor 101 in contact with the insulating layer 51.

[0178] This allows the soluble conductor 101 to be indirectly in contact with the insulating substrate 2 via the insulating layer 51 between the first electrode 3 and the heating element extraction electrode 6 and between the second electrode 4 and the heating element extraction electrode 6. The protective element 110 has an insulating layer 51 formed using an insulating material with excellent thermal conductivity, thereby achieving the same effect as the protective element 1 in which the second low-melting point metal layer 12 is in direct contact with the insulating substrate 2.

[0179] Insulation layer thickness 27, the thickness of the insulating layer may be more than twice the thickness of the heating element extraction electrode 6. In the protection element 120 shown in FIG. 27, a thick insulating layer 61 is provided between the first electrode 3 of the insulating substrate 2 and the heating element extraction electrode 6, and between the second electrode 4 and the heating element extraction electrode 6. As a result, in the mounting process of the fusible conductor 101 and the mounting process of the protection element 120 on the circuit board 34, the molten conductive connecting material 105 is brought into close contact with the periphery of the arc-shaped insulating layer 61 due to volumetric contraction accompanying cooling.

[0180] In addition, the thickness of the insulating layer 61 is formed to be more than twice the thickness of the heating element extraction electrode 6. Therefore, the molten conductive connecting material 105 covers the insulating layer 61, and due to volumetric shrinkage caused by cooling, it adheres to the insulating layer 61. By widening the contact area in this way, the force of the soluble conductor 101 toward the insulating substrate 2 increases, so that the soluble conductor 101 and the insulating substrate 2 can be adhered to each other without any gaps via the insulating layer 61 (FIG. 27(B)).

[0181] The insulating layer 61 is formed in an arc-shaped cross section without corners, so that no voids are formed near the corners due to the tension of the molten conductive connecting material 105, and the fusible conductor 101 can adhere to the insulating layer 61 without any gaps.

[0182] [Convex part of insulating substrate] Furthermore, a convex portion 71 having a height greater than the thickness of any of the first and second electrodes 3, 4 and the heater extracting electrode 6 may be formed on the insulating substrate 2 between the first electrode 3 and the heater extracting electrode 6 and between the second electrode 4 and the heater extracting electrode 6. In the protection element 130 shown in FIG. 28, the conductive connecting material 105 comes into contact with the convex portion 71, so that the soluble conductor 101 comes into indirect contact with the insulating substrate 2 via the conductive connecting material 105.

[0183] The convex portion 71 is a portion formed on the insulating substrate 2. The height of the convex portion 71 is greater than the thickness of any of the first and second electrodes 3, 4 and the heating element lead electrode 6. After the step of forming the conductive connecting material 105, the insulating substrate 2 provided with the convex portion 71 undergoes a step of mounting the soluble conductor 101, a step of heating the conductive connecting material 105, and a step of connecting the soluble conductor 101, thereby forming the protective element 130 (FIG. 28(C)).

[0184] As shown in FIG. 28(A), in the mounting process, the soluble conductor 101 is mounted over the first and second electrodes 3 and 4, the heating element lead electrode 6, and the protrusion 71 via the conductive connecting material 105. After the soluble conductor 101 is mounted, it is heated by reflow or the like, so that the soluble conductor 101 is connected to the first and second electrodes 3 and 4 and the heating element lead electrode 6 via the molten conductive connecting material 105, and the conductive connecting material 105 comes into contact with the protrusion 71. The soluble conductor 101 is indirectly brought into contact with the protrusion 71 of the insulating substrate 2 via the conductive connecting material 105 that has solidified upon cooling. Thereafter, as shown in FIG. 28(C), a coating flux 9 is applied to the soluble conductor 101, and a cover member 19 is provided.

[0185] This allows the soluble conductor 101 to be in contact with the insulating substrate 2 via the conductive connecting material 105 between the first electrode 3 and the heating element extraction electrode 6 and between the second electrode 4 and the heating element extraction electrode 6. The protective element 130 uses an insulating substrate 2 on which a convex portion 71 is provided using an insulating material with excellent thermal conductivity, thereby achieving the same effect as the protective element 1 in which the second low-melting point metal layer 12 is in direct contact with the insulating substrate 2.

[0186] [Convex height] 29, the height of the convex portion may be greater than twice the film thickness of the heater lead electrode 6. In the protection element 140 shown in FIG. 29, tall convex portions 81 are formed between the first electrode 3 of the insulating substrate 2 and the heater lead electrode 6, and between the second electrode 4 and the heater lead electrode 6.

[0187] The convex portion 81 is a portion formed on the insulating substrate 2. The convex portion 81 is preferably formed to have an arc-shaped cross section. As a result, in the mounting process of the fusible conductor 101 and the mounting process of the protection element 140 on the circuit board 34, the molten conductive connecting material 105 covers the convex portion 81 and adheres to the periphery of the arc-shaped convex portion 81 due to volumetric contraction accompanying cooling (FIG. 29(B)).

[0188] Furthermore, since the convex portion 81 is formed in an arc shape without corners, no voids are formed near the corners due to the tension of the molten conductive connecting material 105, and the soluble conductor 101 can be tightly attached to the convex portion 81 without any gaps.

[0189] In addition, the above-mentioned protection elements 100, 110, 120, 130, and 140 have the heating element 5 formed on the back surface 2b of the insulating substrate 2, but as with the protection element 1 shown in FIG. 5, the heating element 5, the insulating protective layer 8, the first extraction electrode 15, the second extraction electrode 16, the heating element electrode 17, and the intermediate electrode 18 may be formed on the front surface 2a of the insulating substrate 2. Also, as with the protection element 1 shown in FIG. 6, the protection elements 100, 110, 120, 130, and 140 may have an insulating substrate 2 with a two-layer structure of an upper layer and a lower layer, and the heating element 5, the first extraction electrode 15, and the second extraction electrode 16 may be formed between the upper and lower layers. Furthermore, in the protection elements 100, 110, 120, 130, and 140, as with the protection element 1 shown in FIG. 17, a restricting wall 39 that holds the portion where the soluble conductor 101 contacts the insulating substrate 2 may be provided on the inner surface of the cover member 19. [Explanation of symbols]

[0190] 1 protective element, 1A element body, 2 insulating substrate, 2a front surface, 2b rear surface, 3 first electrode, 4 second electrode, 5 heating element, 5a one end, 5b other end, 6 heating element lead electrode, 7 fusible conductor, 7a molten conductor, 8 insulating protective layer, 9 coating flux, 10 high melting point metal layer, 10a high melting point metal, 10b low melting point metal, 11 first low melting point metal layer, 11a first high melting point metal, 11b first low melting point metal, 12 second low melting point metal layer, 12a high melting point metal, 12b low melting point metal, 13 first external connection electrode, 14 second external connection electrode, 15 first lead electrode, 16 second lead electrode, 17 heating element electrode, 18a front surface side intermediate electrode, 18b rear surface side intermediate electrode, 19 cover member, 20 Battery pack, 20a positive terminal, 20b negative terminal, 21 battery cell, 22 charging device, 23 current control element, 24 control unit, 25 battery stack, 26 charge / discharge control circuit, 27 detection circuit, 28 current control element, 29 connection flux, 30 protection element, 31 third external connection electrode, 34 circuit board, 34a terminal, 35 laminate, 36 heating head, 37 weight, 39 regulating wall, 40 protection element, 50 protection element, 51 insulating layer, 60 protection element, 61 insulating layer, 70 protection element, 71 convex portion, 80 protection element, 81 convex portion, 100 protection element, 100A element body, 101 fusible conductor, 101a fusible conductor, 102 low melting point metal layer, 103 high melting point metal layer, 105 conductive connecting material, 110 Protection element, 120 protection element, 130 protection element, 140 protection element

Claims

1. an insulating substrate; a heating element provided on the insulating substrate; a first electrode and a second electrode provided on the insulating substrate; a heating element extraction electrode electrically connected to the heating element on a current path between the first electrode and the second electrode; A fusible conductor is connected across the first electrode, the heating element extraction electrode, and the second electrode, and melts between the first electrode and the second electrode due to self-heating caused by the passage of an overcurrent exceeding a rated current and / or heat generation by the heating element, thereby interrupting the current path. The fusible conductor has a laminated structure of a high-melting point metal layer and a second low-melting point metal layer composed of an alloy of a high-melting point metal constituting the high-melting point metal layer and a first low-melting point metal having a melting point lower than that of the high-melting point metal, The soluble conductor is connected to the first electrode, the second electrode, and the heating element lead electrode via the second low-melting point metal layer in a direction in which the second low-melting point metal layer faces the insulating substrate, Between the first electrode and the heating element extraction electrode and between the second electrode and the heating element extraction electrode, at least a part of the second low melting point metal layer of the soluble conductor is in direct or indirect contact with the insulating substrate, Protection element.

2. A protection element mounted on a circuit board, which cuts off current to at least a part of the circuit board when an abnormality occurs in the circuit board, 2. The protection element according to claim 1, wherein the liquidus point of the second low-melting-point metal layer is higher than a temperature at which the protection element is mounted on the circuit board.

3. A cover member is provided on the surface of the insulating substrate on which the soluble conductor is provided and covers the soluble conductor, The protective element according to claim 1, wherein the inner surface of the cover member has a restricting wall that holds down a portion where the second low melting point metal layer of the fusible conductor contacts the insulating substrate.

4. an insulating layer is formed on the insulating substrate between the first electrode and the heat generating element lead electrode and between the second electrode and the heat generating element lead electrode, the insulating layer having a thickness greater than the thickness of any of the first and second electrodes and the heat generating element lead electrode; The protection element according to claim 1 , wherein the second low-melting-point metal layer is in contact with the insulating layer.

5. 5. The protection element according to claim 4, wherein the insulating layer has a thickness greater than the sum of the thickness of the heating element lead electrode and the thickness of the first low-melting-point metal layer.

6. the insulating substrate has protrusions formed between the first electrode and the heat generating element lead electrode and between the second electrode and the heat generating element lead electrode, the protrusions having a height greater than the thickness of any of the first and second electrodes and the heat generating element lead electrode; The protection element according to claim 1 , wherein the second low-melting-point metal layer is in contact with the protrusion.

7. 7. The protection element according to claim 6, wherein the height of the convex portion is greater than the sum of the thickness of the heating element lead electrode and the thickness of the first low-melting point metal layer.

8. The heating element is provided on the surface on which the fusible conductor of the insulating substrate is provided, or on the back surface opposite to the surface, 8. The protection element according to claim 1, further comprising an insulating member provided on the insulating substrate so as to cover at least the heating element.

9. 8. The protection element according to claim 1, wherein the heating element is provided inside the insulating substrate.

10. The contact area between the second low melting point metal layer and the insulating substrate is 50% or more of the area between the first electrode overlapping the soluble conductor and the heating element extraction electrode, and the second electrode overlapping the soluble conductor. The protective element according to any one of claims 1 to 7, which is 50% or more of the area between the heating element extraction electrode.

11. The second low-melting point metal layer is formed by interdiffusion and / or dissolution of a portion of the high-melting point metal and all of the first low-melting point metal constituting the first low-melting point metal layer.

12. 8. The protection element according to claim 1, wherein the high melting point metal layer has a thickness in the stacking direction greater than the thickness of the second low melting point metal layer in the stacking direction.

13. A protection element described in any one of claims 1 to 7, wherein the second low-melting point metal layer has the first low-melting point metal layer of a laminate in which the high-melting point metal layer and a first low-melting point metal layer composed of the first low-melting point metal are stacked.

14. an insulating substrate; a heating element provided on the insulating substrate; a first electrode and a second electrode provided on the insulating substrate; a heating element extraction electrode electrically connected to the heating element on a current path between the first electrode and the second electrode; A fusible conductor is connected across the first electrode, the heating element extraction electrode, and the second electrode, and melts between the first electrode and the second electrode due to self-heating caused by the passage of an overcurrent exceeding a rated current and / or heat generation by the heating element, thereby interrupting the current path. The fusible conductor has a coating structure in which both surfaces of a low-melting-point metal layer are coated with a high-melting-point metal layer having a melting point higher than that of the low-melting-point metal layer, The soluble conductor is connected to each of the first electrode, the second electrode, and the heating element extraction electrode via a conductive connecting material, Between the first electrode and the heating element extraction electrode and between the second electrode and the heating element extraction electrode, at least a portion of the soluble conductor is in direct or indirect contact with the insulating substrate, Protection element.

15. A protection element mounted on a circuit board, which cuts off current to at least a part of the circuit board when an abnormality occurs in the circuit board, the conductive connecting material is in contact with the insulating substrate between the first electrode and the heating element lead electrode and between the second electrode and the heating element lead electrode; At least a portion of the fusible conductor contacts the insulating substrate via the conductive connecting material, the liquidus point of the conductive connecting material is higher than the mounting temperature of the protection element on the circuit board; The protection element according to claim 14.

16. A cover member is provided on the surface of the insulating substrate on which the soluble conductor is provided, and covers the soluble conductor, the conductive connecting material is in contact with the insulating substrate between the first electrode and the heating element lead electrode and between the second electrode and the heating element lead electrode; At least a portion of the fusible conductor contacts the insulating substrate via the conductive connecting material, The protection element according to claim 14, wherein the inner surface of the cover member has a restriction wall that holds down a portion where the soluble conductor contacts the insulating substrate via the conductive connecting material.

17. an insulating layer is formed on the insulating substrate between the first electrode and the heat generating element lead electrode and between the second electrode and the heat generating element lead electrode, the insulating layer having a thickness greater than the thickness of any of the first and second electrodes and the heat generating element lead electrode; The protection element according to claim 14, wherein the fusible conductor is in contact with the insulating layer.

18. The protection element according to claim 17 , wherein the insulating layer has a thickness greater than twice the thickness of the heater lead electrode.

19. the insulating substrate has protrusions formed between the first electrode and the heat generating element lead electrode and between the second electrode and the heat generating element lead electrode, the protrusions having a height greater than the thickness of any of the first and second electrodes and the heat generating element lead electrode; The protection element according to claim 14 , wherein the conductive connecting material is in contact with the protrusion.

20. The protection element according to claim 19 , wherein the height of the protrusion is greater than twice the thickness of the heat generating element lead electrode.

21. The heating element is provided on the surface on which the fusible conductor of the insulating substrate is provided, or on the back surface opposite to the surface, 21. The protection element according to claim 14, further comprising an insulating member provided on the insulating substrate so as to cover at least the heating element.

22. The protection element according to any one of claims 14 to 20, wherein the heating element is provided inside the insulating substrate.

23. The protection element according to any one of claims 1 to 7 and 14 to 20, wherein the high-melting-point metal layer is made of Ag or Cu or a metal mainly composed of Ag or Cu, and the first low-melting-point metal layer is made of Sn or a metal mainly composed of Sn.

24. a heating element, a first electrode, a second electrode, and an insulating substrate provided with a heating element lead electrode electrically connected to the heating element on a current path between the first electrode and the second electrode; a mounting process in which a laminate including a high-melting-point metal layer and a first low-melting-point metal layer made of a first low-melting-point metal having a melting point lower than that of the high-melting-point metal constituting the high-melting-point metal layer is laminated over the first electrode, the heating element lead electrode, and the second electrode formed on the insulating substrate, in an orientation in which the first low-melting-point metal layer contacts the first electrode, the heating element lead electrode, and the second electrode; a heating step of heating the insulating substrate on which the laminate is mounted at a mounting temperature equal to or higher than the eutectic temperature of an alloy of the high-melting-point metal and the first low-melting-point metal; a melting step of forming a second low-melting point metal layer, which is made of an alloy of the high-melting point metal and the first low-melting point metal by interdiffusion and / or dissolution of a portion of the high-melting point metal and the first low-melting point metal, and has a solidus temperature lower than the mounting temperature; The molten second low-melting point metal layer is cooled, and the second low-melting point metal layer is solidified with the high-melting point metal layer. A connection process for connecting the soluble conductor to the first electrode, the heating element lead electrode, and the second electrode through the second low-melting point metal layer of the soluble conductor in which the second low-melting point metal layer is laminated. A method for manufacturing a protective element.

25. the protection element is mounted on a circuit board and cuts off current to at least a part of the circuit board when an abnormality occurs in the circuit board; The method for manufacturing a protection element according to claim 24 , wherein the liquidus point of the second low-melting point metal layer is higher than a temperature at which the protection element is mounted on the circuit board.

26. 25. The manufacturing method of the protective element according to claim 24, wherein the second low melting point metal layer of the soluble conductor is brought into contact with the insulating substrate by pressing the upper part of the high melting point metal layer against the insulating substrate between the heating step and the connecting step.

27. an insulating layer is formed on the insulating substrate between the first electrode and the heat generating element lead electrode and between the second electrode and the heat generating element lead electrode, the insulating layer having a thickness greater than the thickness of any of the first and second electrodes and the heat generating element lead electrode; The method for manufacturing a protection element according to claim 24 , wherein the second low-melting-point metal layer is in contact with the insulating layer.

28. 28. The method for manufacturing a protection element according to claim 27, wherein the thickness of the insulating layer is greater than the sum of the thickness of the heating element lead electrode and the thickness of the first low-melting point metal layer.

29. the insulating substrate has protrusions formed between the first electrode and the heat generating element lead electrode and between the second electrode and the heat generating element lead electrode, the protrusions having a height greater than the thickness of any of the first and second electrodes and the heat generating element lead electrode; The method for manufacturing a protection element according to claim 24 , wherein the second low-melting-point metal layer is in contact with the protrusion.

30. 30. The method for manufacturing a protection element according to claim 29, wherein the height of the convex portion is greater than the sum of the thickness of the heating element lead electrode and the thickness of the first low-melting point metal layer.

31. The contact area between the second low melting point metal layer and the insulating substrate is 50% or more of the area between the first electrode overlapping the soluble conductor and the heating element lead electrode, and the second electrode overlapping the soluble conductor and the heating element lead electrode. The manufacturing method of any one of claims 24 to 30, which is 50% or more of the area between the electrode.

32. The method for manufacturing a protection element according to any one of claims 24 to 30, wherein in the melting step, a portion of the high-melting point metal and all of the first low-melting point metal melt together due to mutual diffusion at the interface between the high-melting point metal layer and the first low-melting point metal layer, thereby forming the second low-melting point metal layer.

33. 31. The method for manufacturing a protection element according to claim 24, wherein the high melting point metal layer has a thickness in a stacking direction greater than a thickness in a stacking direction of the second low melting point metal layer.

34. The method for manufacturing a protection element according to any one of claims 24 to 30, wherein in the heating step, the insulating substrate on which the laminate is mounted is heated at a mounting temperature lower than the solidus temperature of the first low-melting point metal.

35. 31. The method for manufacturing a protection element according to claim 24, wherein the second low-melting-point metal layer comprises the first low-melting-point metal layer of the laminate.

36. a heating element, a first electrode, a second electrode, and an insulating substrate provided with a heating element lead electrode electrically connected to the heating element on a current path between the first electrode and the second electrode; a conductive connecting material forming step of providing a conductive connecting material on the first electrode, the heater element lead electrode, and the second electrode formed on the insulating substrate, as well as between the first electrode and the heater element lead electrode and between the second electrode and the heater element lead electrode; A mounting process for mounting a fusible conductor having a coating structure in which both surfaces of a low-melting point metal layer are coated with a high-melting point metal layer having a melting point higher than that of the low-melting point metal layer via the conductive connecting material over the first electrode, the heating element extraction electrode, and the second electrode; a heating and melting step of heating and melting the conductive connecting material at a temperature higher than the solidus temperature of the conductive connecting material; A connecting step in which the molten conductive connecting material is cooled to connect the soluble conductor to the first electrode, the heating element lead electrode, and the second electrode, Between the first electrode and the heating element extraction electrode and between the second electrode and the heating element extraction electrode, at least a portion of the soluble conductor is in direct or indirect contact with the insulating substrate, A method for manufacturing a protective element.

37. the protection element is mounted on a circuit board and cuts off current to at least a part of the circuit board when an abnormality occurs in the circuit board; 37. The method for manufacturing a protection element according to claim 36, wherein the liquidus point of the conductive connecting material is higher than a temperature at which the protection element is mounted on the circuit board.

38. 37. The method for manufacturing a protective element according to claim 36, wherein the conductive connecting material is brought into contact with the insulating substrate by pressing the soluble conductor against the insulating substrate during the heating step and the connecting step.

39. an insulating layer is formed on the insulating substrate between the first electrode and the heat generating element lead electrode and between the second electrode and the heat generating element lead electrode, the insulating layer having a thickness greater than the thickness of any of the first and second electrodes and the heat generating element lead electrode; The method for manufacturing a protection element according to claim 36 , wherein the conductive connecting material contacts the insulating layer.

40. 40. The method for manufacturing a protection element according to claim 39, wherein the thickness of the insulating layer is more than twice the thickness of the heater lead electrode.

41. the insulating substrate has protrusions formed between the first electrode and the heat generating element lead electrode and between the second electrode and the heat generating element lead electrode, the protrusions having a height greater than the thickness of any of the first and second electrodes and the heat generating element lead electrode; The method for manufacturing a protection element according to claim 36 , wherein the conductive connecting material is in contact with the protrusion.

42. 42. The method for manufacturing a protection element according to claim 41, wherein the height of the protrusion is greater than twice the thickness of the heat generating element lead electrode.

43. The protection element according to any one of claims 24 to 30, 36 to 42, wherein the high melting point metal layer is made of Ag or Cu or a metal mainly composed of Ag or Cu, and the first low melting point metal layer is made of Sn or a metal mainly composed of Sn.

44. one or more battery cells; a protection element connected to a charge / discharge path of the battery cell and blocking the charge / discharge path; a current control element that detects a voltage value of the battery cell and controls current flow to the protection element; The protective element is a protective element according to any one of claims 1 to 7 and 14 to 20. Battery pack.

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