Protective element and battery pack

Abstract

Provided are: a protective element capable of improving insulation properties after a fuse element has melted; and a battery pack using the protective element.　The protective element comprises a case 2, a fuse element 3, a pair of fuse terminals 4a, 4b connected to the fuse element 3, and a melting member 5 that is connected to at least one surface of the fuse element 3 and configured to melt the fuse element 3. The melting member 5 is provided with an insulating substrate 6 and an intermediate electrode 7 that is provided on a surface 6a of the insulating substrate 6 that contacts the fuse element 3 and is connected to the fuse element 3. Between the insulating substrate 6 and at least one of the pair of fuse terminals 4a, 4b, there are spaces 10 above and below the fuse element 3, and in the area where the fuse element 3 and the insulating substrate 6 overlap, there are spaces 11 above and below the fuse element 3 and the insulating substrate 6.

Description

Protection elements and battery packs

[0001] This technology relates to a protection element that interrupts a current path, and a battery pack using the same. This application claims priority based on Japanese Patent Application No. 2023-096557, filed in Japan on June 12, 2023, which is incorporated herein by reference.

[0002] In recent years, lithium-ion batteries have expanded from their use in mobile devices to applications such as electric vehicles (EVs) and storage batteries, resulting in an increase in current capacity. Because these batteries pose a risk of fire in the event of an abnormality, the mainstream approach to ensure product safety as capacity increases is to incorporate protection circuits using protective elements.

[0003] There are two types of protective elements: current fuses that protect against overcurrent, and fuses that protect against both overcurrent and overvoltage. Current fuses that protect against overcurrent are connected in series to electrical circuits and immediately cut off the current path when an overcurrent occurs due to an electrical short circuit or other event within the equipment, protecting the wires and equipment that make up the circuit from accidents such as fire. Overcurrent protection fuses have a relatively simple structure, and when an overcurrent flows, the fusible conductor element of the fuse, which has a small cross-sectional area, reaches its melting point due to Joule heat and melts, cutting off the current path.

[0004] Overcurrent protection fuses include, for example, glass tube fuses, blade fuses, slow-blow fuses, and EV fuses. Glass tube fuses are used, for example, to protect against overcurrent when the engine is ignited. Blade fuses have a simpler structure than glass tube fuses and, like glass tube fuses, are used, for example, as fuses for automobiles. Slow-blow fuses are used to protect against overcurrent in motor parts used in power windows, automatic wipers, air conditioners, and other components installed in automobiles. EV fuses are used to protect against overcurrent in the electrical systems of hybrid and electric vehicles, which, unlike gasoline-powered automobiles, operate at high voltages.

[0005] The mainstream fuses that function as overvoltage protection in addition to overcurrent protection fuses are equipped with a heating element that melts when heated. Specifically, when an IC that monitors the voltage and temperature of a lithium-ion battery detects an abnormality, it sends a signal to an FET that functions as an ON / OFF switch. When the FET is in the ON state, current begins to flow to the heating element, and the heat generated by the current melts the fuse, cutting off the current path.

[0006] In both overcurrent and overvoltage protection devices, if an abnormality is detected, a quick circuit interruption is required for safety. In addition, the protection device generally comprises a thick-film printed circuit board and a fuse element (see, for example, Patent Document 1).

[0007] JP 2015-053260 A

[0008] As mentioned above, lithium-ion batteries and other batteries are expanding from their use in mobile devices to applications such as EVs and storage batteries, and as a result, protective elements are also being required to accommodate higher rated voltages and larger current capacities.

[0009] However, increasing the rated voltage of the current makes it easier for sparks (discharges) to occur between the electrodes after the fuse element has blown, and repeated sparks can cause tracking, which can impede the fuse element from blowing or lead to it not being cut, thereby deteriorating the insulation properties of the fuse element after it has blown.

[0010] Furthermore, increasing the rated voltage can be achieved by increasing the size of the components, but expanding the internal space of the case not only increases the size of the components, but also increases costs and makes it less user-friendly.

[0011] Increasing the volume of the fuse element or the thickness of the conductor on the insulating substrate is one possible way to increase the current capacity, but as the volume of the fuse element increases or the conductor thickness increases, the impact when the fuse element blows becomes more severe, and there is a risk that the insulation properties after blowing will deteriorate due to the adhesion of molten debris, etc. Furthermore, tracking via the molten debris is more likely to occur after the fuse element blows.

[0012] 30 shows an example of a conventional protection element 100 compatible with high voltages, where (A) is a plan view, (B) is a cross-sectional view taken along the line D-D' of (A), and (C) is a cross-sectional view taken along the line P-P' of (A). Fig. 31 is a plan view of the protection element 100 with the upper case omitted, where (A) is a schematic diagram showing the state before operation, (B) is a state in which an interruption has occurred due to self-heating caused by an overcurrent, and (C) is a state after the interruption.

[0013] 30 and 31 , the protective element 100 includes a pair of upper and lower cases 101, a fuse element 102 made of a fusible conductor, and a fusing member 103 that fuses the fuse element 102. The fusing member 103 includes an insulating substrate 104, an intermediate electrode 105 connected to the fuse element 102, and a heating element 106 that generates heat when energized and fuses the fuse element 102. The lower case 101a has a pair of fuse terminals 107 and 108 connected to the fuse element 102 and a heating element terminal 109 connected to the heating element 106 mounted on its side edges, and the insulating substrate 104 mounted in its center. One end of the heating element 106 is connected to the intermediate electrode 105, and the other end is connected to an external power source via the heating element terminal 109.

[0014] The fuse element 102 is connected to the fuse terminals 107, 108 and the intermediate electrode 105 by a conductive material such as solder. The fuse element 102 is superimposed on the heating element 106 via an insulating layer and the intermediate electrode 105. The fuse terminals 107, 108 of the protective element 100 are connected to terminals of an external circuit, so that the fuse element 102 is incorporated into the current path of the external circuit. When current is applied to the heating element 106 from an external power source, the heat from the heating element 106 melts the fuse element 102. When an abnormal current flows through the external circuit, the fuse element 102 melts due to self-heating (Joule heat), thereby interrupting the current path of the external circuit.

[0015] Here, conventional protective elements that can withstand high voltages have a rated voltage limit of about 80 V, and at voltages higher than this, for example, 100 V or higher, the blowout impact of fuse element 102 also becomes greater, causing soot-like debris 102a from melted fuse element 102 to adhere to the inner surface of the case or the surface of the insulating substrate (see FIG. 31(C)). As a result, after fuse element 102 blows, a spark (discharge) occurs between fuse terminal 107, insulating substrate 104, and fuse terminal 108, with the risk of subsequent tracking occurring.

[0016] Therefore, an object of the present technology is to provide a protection element that can improve insulation after a fuse element has blown, and a battery pack using the same.

[0017] In order to solve the above-mentioned problems, the protection element according to the present technology includes a case, a fuse element housed in the case, a pair of fuse terminals spaced apart in the current-carrying direction of the fuse element and supported on a side surface of the case and connected to the fuse element, and a fusing member connected to at least one surface of the fuse element between the pair of fuse terminals and fusing the fuse element, wherein the fusing member includes an insulating substrate and an intermediate electrode provided on a surface of the insulating substrate that contacts the fuse element and is connected to the fuse element, and between the insulating substrate and at least one of the pair of fuse terminals, there is a space above and below the fuse element, and in a region where the fuse element and the insulating substrate overlap, there is a space above and below the fuse element and the insulating substrate.

[0018] In addition, the battery pack according to the present technology includes one or more battery cells and a protection element connected to a charge / discharge path of the battery cell and blocking the charge / discharge path, and the protection element is the protection element described above.

[0019] According to this technology, because there is space between the fuse terminal and the insulating substrate, Joule heat from the fuse element is less likely to dissipate between the fuse terminal and the intermediate electrode. Furthermore, because there are spaces above and below the fuse element and the insulating substrate, the fuse element expands spherically on the surface of the insulating substrate when melted, causing the molten conductor to aggregate on the intermediate electrode and fuse terminal, making it less likely for Joule heat from the fuse element to dissipate. This allows the fuse element to be heated over a wide area, dispersing and mitigating the explosive thermal shock that occurs when the fuse element reaches its melting point and melts. Therefore, this technology allows for safe interruption even in cases of self-heating due to overcurrent at high voltages, and also prevents degradation of insulation due to molten debris.

[0020] FIG. 1 is a top view of a protection element to which the present technology is applied. FIG. 2 is a plan view of the protection element, omitting the upper case. FIG. 3 is a cross-sectional view taken along the line D-D' in FIG. 1. FIG. 4 is a cross-sectional view taken along the line P-P' in FIG. 1. FIG. 5 is a diagram showing an upper case and a lower case, where (A) is a plan view of the upper case, (B) is a plan view of the lower case, and (C) is a cross-section showing the upper and lower cases butted together. FIG. 6 is a diagram showing a fusing member, where (A) is a plan view and (B) is a bottom view. FIG. 7 is a cross-sectional view showing an example of a fuse element. FIG. 8 is a cross-sectional view showing the protection element shown in FIG. 3 in a state where the fuse element has melted. FIG. 9 is a circuit diagram showing an example configuration of a battery pack. FIG. 10 is a circuit diagram of a protection element. FIG. 11 is a cross-sectional view showing a protection element in which a heating element is formed on the back surface of an insulating substrate. FIG. 12 is a plan view of the protection element shown in FIG. 11, omitting the upper case. 13 is a diagram showing an insulating substrate of the protection element shown in FIG. 11 , where (A) is a plan view and (B) is a bottom view. FIG. 14 is a cross-sectional view showing a protection element in which a holding electrode is formed on the back surface of the insulating substrate. FIG. 15 is a plan view showing the protection element shown in FIG. 14 , with the upper case omitted. FIG. 16 is a diagram showing the insulating substrate of the protection element shown in FIG. 14 , where (A) is a plan view and (B) is a bottom view. FIG. 17 is a cross-sectional view showing the protection element shown in FIG. 14 in a state in which the fuse element has melted. FIG. 18 is a circuit diagram of the protection element shown in FIG. 14 . FIG. 19 is a cross-sectional view showing a protection element in which a heating element, an insulating layer, and a holding electrode are formed on the back surface of the insulating substrate. FIG. 20 is a plan view showing the protection element shown in FIG. 19 , with the upper case omitted. FIG. 21 is a diagram showing the insulating substrate of the protection element shown in FIG. 19 , where (A) is a plan view and (B) is a bottom view. FIG. 22 is a cross-sectional view showing the protection element shown in FIG. 19 in a state in which the fuse element has melted. Fig. 23 is a cross-sectional view showing a protection element in which a fusing member having a heating element formed on the surface of an insulating substrate is connected to one side and the other side of a fuse element. Fig. 24 is a plan view showing the protection element shown in Fig. 23 with the upper case omitted. Fig. 25 is a circuit diagram of the protection element shown in Fig. 23. Fig. 26 is a cross-sectional view showing the protection element shown in Fig. 23 in a state in which the fuse element has been blown.Fig. 27 is a cross-sectional view showing a protection element in which a fusing member having a heating element formed on the back surface of an insulating substrate is connected to one side and the other side of a fuse element. Fig. 28 is a plan view showing the protection element shown in Fig. 27 , omitting the upper case. Fig. 29 is a cross-sectional view showing the protection element shown in Fig. 27 in a state in which the fuse element has fused. Fig. 30 is a diagram showing an example of a conventional high-voltage protection element 100, where (A) is a plan view and (B) is a cross-sectional view taken along the line D-D' of (A). Fig. 31 is a plan view showing the protection element 100, omitting the upper case, schematically showing (A) the state before operation, (B) the state in which an interruption has occurred due to self-heating caused by an overcurrent, and (C) the state after interruption.

[0021] A protection element and a battery pack to which the present technology is applied will be described in detail below 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. 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 description. It should be noted that the drawings may also include portions in which the dimensional relationships and ratios differ.

[0022] [Protective element] FIG. 1 is a top view of a protective element 1 to which the present technology is applied, FIG. 2 is a plan view showing the protective element 1 with the upper case thereof omitted, FIG. 3 is a cross-sectional view taken along the line DD' in FIG. 1, and FIG. 4 is a cross-sectional view taken along the line PP' in FIG. 1.

[0023] 1 to 4 , a protective element 1 to which the present invention is applied includes a case 2, a fuse element 3 housed in the case 2, a pair of fuse terminals 4 a, 4 b supported on the side surfaces of the case 2 and spaced apart in the current-carrying direction of the fuse element 3 and connected to the fuse element 3, and a fusing member 5 connected to at least one surface of the fuse element 3 between the pair of fuse terminals 4 a, 4 b and fusing the fuse element 3. The fusing member 5 includes an insulating substrate 6 and an intermediate electrode 7 provided on a surface 6 a of the insulating substrate 6 that contacts the fuse element 3 and is connected to the fuse element 3. The protective element 1 has spaces 10 above and below the fuse element 3 between the insulating substrate 6 and at least one of the pair of fuse terminals 4 a, 4 b, and spaces 11 above and below the fuse element 3 and the insulating substrate 6 in a region where the fuse element 3 and the insulating substrate 6 overlap.

[0024] The fuse element 3 is connected to the intermediate electrode 7 and the pair of fuse terminals 4a, 4b by a joining material such as connection solder 13. The fuse terminals 4a, 4b are connected to terminals on the current path of an external circuit, and the fuse element 3 is incorporated into part of the current path of the external circuit. The fuse element 3 will not melt even due to self-heating (Joule heat) while a predetermined rated current is flowing. When a current higher than the rated current flows, the fuse element 3 melts due to self-heating, thereby interrupting the current path between the fuse terminals 4a, 4b.

[0025] In this protective element 1, because there is a space 10 between the fuse terminals 4a, 4b and the insulating substrate 6, it becomes difficult for Joule heat of the fuse element 3 to be dissipated between the fuse terminals 4a, 4b and the intermediate electrode 7. Furthermore, because there are spaces 11 above and below the fuse element 3 and the insulating substrate 6, the fuse element 3 expands spherically on the surface 6a of the insulating substrate 6 when melted, and the molten conductor aggregates on the intermediate electrode 7 and the fuse terminals, making it difficult for Joule heat of the fuse element 3 to be dissipated.

[0026] This allows the fuse element 3 to be heated over a wide area, dispersing and mitigating the explosive thermal shock that occurs when the fuse element 3 reaches its melting point and melts. Therefore, the protection device 1 can safely interrupt power even in the event of self-heating caused by a high-voltage overcurrent, and can also prevent deterioration of insulation due to molten debris.

[0027] The case 2, fuse element 3, fuse terminals 4a and 4b, and fusing member 5 that constitute the protective device 1 will be described in detail below.

[0028] [Case] ​​The case 2 can be formed using insulating materials such as various engineering plastics, thermoplastic plastics, ceramics, and glass epoxy boards. The case 2 houses the fuse element 3 and the fusing member 5, and supports the fuse terminals 4a, 4b and the heating element terminal 15, allowing them to extend inside and outside the case. The case 2 also has sufficient internal space to allow the molten conductor 3a to expand spherically when the fuse element 3 melts and to condense on the intermediate electrode 7 and the fuse terminals 4a, 4b.

[0029] As shown in Figures 3 and 4, the case 2 is formed by combining an upper case 21 and a lower case 22. Figure 5 shows the upper case 21 and the lower case 22, with (A) being a plan view of the upper case 21, (B) being a plan view of the lower case 22, and (C) being a cross-section showing the upper case 21 and the lower case 22 butted together. The upper case 21 has mating recesses 23 formed on the lower surface of its side wall. The lower case 22 has mating protrusions 24 formed on the upper surface of its side wall that mate with the mating recesses 23. The upper and lower cases 21, 22 are combined by mating the mating protrusions 24 with the mating recesses 23, and are fixed together with adhesive 25 provided on the upper and lower surfaces of the side walls.

[0030] As shown in FIG. 5B , the lower case 22 is formed in a substantially rectangular shape and has side edge portions 22a that form mating protrusions 24 and support fuse terminals 4a, 4b and heating element terminals 15 (described later), and a hollow portion 22b that is surrounded by the side edge portion 22a and in which a fusing member 5 connected to the fuse element 3 is located. The side edge portion 22a is formed to protrude around the entire inner surface of the lower case 22, on which the fuse terminals 4a, 4b and heating element terminal 15 are placed, supporting the case 2 from both inside and outside. As shown in FIGS. 3 and 4 , the fuse terminals 4a, 4b and heating element terminal 15 are supported so that their respective tip surfaces are flush with the inner end of the side edge portion 22a. The hollow portion 22b is where the fusing member 5 connected to the fuse element 3 is located, and has an internal space below the fusing member 5, allowing the fusing member 5 to be held in a hollow space.

[0031] 5A, the upper case 21 is formed in a substantially rectangular shape like the lower case 22, and is butt-joined to the lower case 22 to cover the fuse element 3 and the fusing member 5 connected to the fuse element 3. The upper case 21 also has an internal space above the fuse element 3 where the molten conductor 3a can wet, spread, and condense over the fuse terminals 4a, 4b and the intermediate electrode 7.

[0032] [Fuse Terminals] The fuse terminals 4 a, 4 b can be formed using known terminal materials such as pure copper, copper alloy, etc. The fuse terminals 4 a, 4 b are, for example, rectangular plate-shaped, spaced apart in the direction of current flow through the fuse element 3, supported by the side edge 22 a of the lower case 22, and led out from inside the case 2 to the outside.

[0033] The fuse terminals 4a, 4b have screw holes 14 at their tips extending outside the case 2, allowing them to be connected by screws or the like to connection electrodes provided on an external circuit. The fuse terminals 4a, 4b are connected to the ends of the fuse element 3 using a joining material such as connection solder 13. Note that connection may also be made using connection solder or the like without the screw holes 14.

[0034] As a result, the fuse terminals 4a and 4b are electrically connected via the fuse element 3. When the fuse element 3 is blown, the connection is broken.

[0035] [Fusing Member] The fusing member 5 is connected to at least one surface of the fuse element 3 between the pair of fuse terminals 4 a and 4 b and serves to fuse the fuse element 3 .

[0036] [Insulating Substrate] The fusing member 5 includes an insulating substrate 6. The insulating substrate 6 is formed of an insulating material such as alumina, glass ceramics, mullite, or zirconia. Alternatively, the insulating substrate 6 may be made of a material used for printed wiring boards, such as a glass epoxy board or a phenol board. An intermediate electrode 7 connected to the fuse element 3 is formed on a surface 6a of the insulating substrate 6.

[0037] The insulating substrate 6 is physically connected to the fuse element 3 via an intermediate electrode 7 formed on a surface 6 a. In the insulating substrate 6 according to the present technology, as shown in FIGS. 2 to 4 , the surface on which the intermediate electrode 7 connected to the fuse element 3 is formed is referred to as the surface 6 a, and the surface opposite to the surface 6 a is referred to as the back surface 6 b.

[0038] [Intermediate Electrode] The intermediate electrode 7 is formed of a conductive pattern of Ag, Cu, etc. Preferably, the surface of the intermediate electrode 7 is coated with a film such as Ni / Au plating, Ni / Pd plating, or Ni / Pd / Au plating by a known method such as plating.

[0039] [Heater / Insulating Layer] A protective element to which the present technology is applied preferably includes, on an insulating substrate 6, a heater 8 that melts the fuse element 3 by generating heat, and an insulating layer 9 that covers the heater 8. In the protective element 1 shown in Figures 2 to 4, the heater 8 and the insulating layer 9 are provided on the surface 6a of the insulating substrate 6.

[0040] The heating element 8 is a conductive member with a relatively high resistance that generates heat when electricity is passed through it, and is made of, for example, nichrome, W, Mo, Ru, etc., or a material containing these. The heating element 8 can be formed by mixing a powder of these alloys, compositions, or compounds with a resin binder or the like to form a paste, which is then patterned on the insulating substrate 6 using a screen printing technique, and then fired.

[0041] 6, one end of the heating element 8 is connected to a heating element power supply electrode 16, and the other end is connected to a heating element electrode 17. The heating element power supply electrode 16 is an electrode connected to one end of the heating element 8 and serves as a power supply terminal to the heating element 8, and is connected to a heating element terminal 15 via connection solder 13 (see FIGS. 2 and 4). The heating element 8 is covered with an insulating layer 9, and an intermediate electrode 7 formed on the insulating layer 9 is superimposed thereon.

[0042] Heating element terminal 15 is made of the same material and has the same shape as fuse terminals 4a and 4b described above, and like fuse terminals 4a and 4b, is supported by side edge 22a of lower case 22 and extends from inside case 2 to the outside. Heating element terminal 15 has a screw hole 14 at the tip that extends outside case 2, so that it can be connected by screwing or the like to a connection electrode provided on an external circuit.

[0043] 4, the heating element terminals 15 and the insulating substrate 6 are provided at approximately the same height, and the side surfaces of the heating element terminals 15 and the insulating substrate 6 are tightly attached via connection solder 13. As a result, the insulating substrate 6 is held in the hollow portion 22b by the connection solder 13 applied from the heating element power supply electrodes 16 to the heating element terminals 15. In other words, the insulating substrate 6 is held in a hollow state in the hollow portion 22b, except for being connected to the case 2 via the heating element terminals 15.

[0044] The heater power supply electrode 16 is connected to the heater terminal 15, which is connected to an external circuit, and is thereby connected to a power source provided in the external circuit, making it possible to supply power to the heater 8. The heater electrode 17 is also connected to the intermediate electrode 7 described above. As a result, the intermediate electrode 7 functions as a heater lead electrode connected to the heater 8 via the heater electrode 17.

[0045] The heating element power supply electrodes 16 and the heating element electrodes 17 are each formed of a conductive pattern of Ag, Cu, or the like. Preferably, the surfaces of the heating element power supply electrodes 16 and the heating element electrodes 17 are 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 allows the protective element 1 to prevent oxidation of the heating element power supply electrodes 16 and the heating element electrodes 17 and to prevent fluctuations in rating due to an increase in conduction resistance.

[0046] The insulating layer 9 is made of, for example, a glass layer, and is provided to protect and insulate the heating element 8. The insulating layer 9 is formed to be thin, for example, 10 to 40 μm in thickness. The insulating layer 9 may also be formed between the surface 6 a of the insulating substrate 6 and the heating element 8.

[0047] [Auxiliary Electrode] An auxiliary electrode 18 is provided on the surface 6a of the insulating substrate 6. The auxiliary electrode 18, together with the intermediate electrode 7, is connected to the fuse element 3 by a bonding material such as connection solder 13, and holds the molten conductor 3a. The auxiliary electrodes 18 are formed on both side edges of the insulating substrate 6 in the extension direction of the fuse element 3, sandwiching the intermediate electrode 7 therebetween.

[0048] [Process for Forming Fusing Member] The fusing member 5 is formed by forming the heating element power supply electrode 16, the heating element electrode 17, and the auxiliary electrode 18 on the surface 6a of the insulating substrate 6, all using a known forming method such as screen printing, followed by forming the heating element 8 and laminating the insulating layer 9. Next, the intermediate electrode 7 is formed. The fusing member 5 has the intermediate electrode 7 and auxiliary electrode 18 connected to the fuse element 3 by connecting solder 13. The fuse element 3, to which the fusing member 5 is connected, is connected by connecting solder 13 to fuse terminals 4a, 4b supported on the side edge 22a of the lower case 22. In addition, the heating element power supply electrode 16 of the insulating substrate 6 is connected by connecting solder 13 to the heating element terminal 15 supported on the side edge 22a of the lower case 22.

[0049] 3 , in the protection device 1 to which the present technology is applied, the intermediate electrode 7 is connected to the fuse element 3, and the heating element power supply electrode 16 is connected to the heating element terminal 15, thereby holding the fusing member 5 in the air within the case 2. As a result, spaces 10 are formed above and below the fuse element 3 between the insulating substrate 6 and at least one, preferably both, of the pair of fuse terminals 4 a, 4 b, and spaces 11 are formed above and below the fuse element 3 and the insulating substrate 6 in the region where the fuse element 3 and the insulating substrate 6 overlap.

[0050] In such a protection device 1, when an abnormal current flows through the fuse element 3, there is a space 10 between the fuse terminals 4a, 4b and the insulating substrate 6, making it difficult for the Joule heat of the fuse element 3 to be dissipated between the fuse terminals 4a, 4b and the intermediate electrode 7. Furthermore, there are spaces 11 above and below the fuse element 3 and the insulating substrate 6, so that when the fuse element 3 melts, it expands spherically on the surface 6a of the insulating substrate 6, and the molten conductor aggregates on the intermediate electrode 7 and the fuse terminals, making it difficult for the Joule heat of the fuse element 3 to be dissipated.

[0051] This allows the fuse element 3 to be heated over a wide area, dispersing and mitigating the explosive thermal shock that occurs when the fuse element 3 reaches its melting point and melts. Therefore, the protection device 1 can safely shut off the fuse even in the event of self-heating caused by an overcurrent at a high voltage. Furthermore, sparks and tracking caused by molten debris are prevented, minimizing deterioration of insulation properties.

[0052] [D3≧7 mm] In the protective element 1, the greater the distance D3 between the pair of fuse terminals 4a, 4b in the cross-sectional view of the fuse element 3 in the extension direction shown in FIG. 3 , the more preferable, and D3 of 7 mm or more is particularly preferable. That is, from the standpoint of suppressing Joule heat dissipation from the fuse element 3, the greater the distance D3 between the pair of fuse terminals 4a, 4b is, the more preferable. However, the greater the distance between the fuse terminals 4a, 4b, the higher the resistance between the terminals. Therefore, in order to increase the current, it becomes necessary to increase the volume of the fuse element 3. Setting the distance D3 between the fuse terminals 4a, 4b to 7 mm or more is preferable for achieving a larger current rating and higher voltage while miniaturizing the component.

[0053] 3 , the protective element 1 preferably has a distance D1 of 1 mm or more between one fuse terminal 4a and one side edge of the insulating substrate 6 facing the fuse terminal 4a. The protective element 1 has a space 10 above and below the fuse element between the insulating substrate 6 and one fuse terminal 4a, and the distance of the space 10 is defined as the distance D1 between the fuse terminal 4a and the side edge of the insulating substrate 6 in the cross-sectional view of the fuse element 3 in the extension direction.

[0054] That is, the protective element 1 does not have a configuration in which the fuse terminal 4a overlaps the insulating substrate 6 (D1<0 mm) or a configuration in which the fuse terminal 4a contacts the insulating substrate 6 (D1=0 mm).

[0055] The protective element 1 can further effectively suppress heat dissipation from the fuse element 3 by making the distance D1 1 mm or more, and more preferably, by making it greater than 1 mm.

[0056] For the same reason, in the protective element 1, it is preferable that the distance D2 between the other fuse terminal 4b and the other side edge of the insulating substrate 6 facing the fuse terminal 4b be 1 mm or more in a cross-sectional view of the fuse element 3 in the extension direction shown in Fig. 3. In other words, the protective element 1 does not have a configuration in which the fuse terminal 4b overlaps the insulating substrate 6 (D2 < 0 mm) or a configuration in which the fuse terminal 4b contacts the insulating substrate 6 (D2 = 0 mm).

[0057] [W<D3] In addition, in the cross-sectional view of the protection element 1 in the extension direction of the fuse element 3 shown in Figure 3, the width W of the insulating substrate 6 in the direction between the pair of fuse terminals 4a, 4b is smaller than the distance D3 between the pair of fuse terminals 4a, 4b. This allows the protection element 1 to provide spaces 10 above and below the fuse element between the insulating substrate 6 and the fuse terminals 4a, 4b.

[0058] [D3 - W < 2 mm / W < 5 mm] In order to ensure that the distance D1 between the fuse terminal 4a and the side edge of the insulating substrate 6 and the distance D2 between the fuse terminal 4b and the side edge of the insulating substrate 6 are 1 mm or more, the protective element 1 preferably satisfies the following conditions: W < 5 mm D3 - W < 2 mm W: Width of the insulating substrate 6 in the direction between the pair of fuse terminals 4a, 4b D3: Distance between the pair of fuse terminals 4a, 4b

[0059] [Fuse Element] Next, we will explain the fuse element 3. The fuse element 3 is mounted between the fuse terminals 4 a and 4 b, and melts down due to heat generated by the passage of current through the heating element 8 or due to self-heating (Joule heat) caused by the passage of a current exceeding the rated value, thereby interrupting the current path between the fuse terminals 4 a and 4 b.

[0060] The fuse element 3 may be made of any conductive material that melts when heated by the passage of current through the heating element 8 or when an overcurrent occurs. For example, in addition to SnAgCu-based Pb-free solder, BiPbSn alloys, BiPb alloys, BiSn alloys, SnPb alloys, PbIn alloys, ZnAl alloys, InSn alloys, PbAgSn alloys, etc. may be used.

[0061] 7 , the fuse element 3 is a laminated structure including an inner layer and an outer layer, with a low-melting-point metal layer 26 as the inner layer and a high-melting-point metal layer 27 as the outer layer laminated on the low-melting-point metal layer 26. The fuse element 3 is connected to the fuse terminals 4 a, 4 b, the intermediate electrode 7, and the auxiliary electrode 18 via a bonding material such as a connection solder 13.

[0062] The low-melting-point metal layer 26 is preferably a solder or a metal containing Sn as its main component, a material commonly referred to as "Pb-free solder." The melting point of the low-melting-point metal layer 26 does not necessarily need to be higher than the temperature of the reflow furnace; it may melt at approximately 200°C. The high-melting-point metal layer 27 is a metal layer laminated on the surface of the low-melting-point metal layer 26, and is, for example, Ag or Cu, or a metal containing either of these as its main component. It has a high melting point that prevents it from melting even when the fuse terminals 4a, 4b, the intermediate electrode 7, and the auxiliary electrode 18 are connected to the fuse element 3 by reflow.

[0063] Such a fuse element 3 can be formed by depositing a high-melting-point metal layer on a low-melting-point metal foil using a plating technique, or by using other well-known lamination or film-forming techniques. The fuse element 3 may have a structure in which the entire surface of the low-melting-point metal layer 26 is covered with the high-melting-point metal layer 27, or a structure in which only a pair of opposing side surfaces are covered. The fuse element 3 may also have a coated structure in which the high-melting-point metal layer 27 is an inner layer and the low-melting-point metal layer 26 is an outer layer. Furthermore, in addition to the coated structure, various other structures can be formed, such as a two-layer structure in which the low-melting-point metal layer 26 is a lower layer and the high-melting-point metal layer 27 is an upper layer, a multilayer structure in which low-melting-point metal layers and high-melting-point metal layers are alternately stacked, or a structure in which an opening is provided in part of the outer layer to expose part of the inner layer.

[0064] The fuse element 3 has a coating structure or laminated structure of the low-melting-point metal layer 26 and the high-melting-point metal layer 27, so that the fuse element 3 can maintain its shape and not blow even when the reflow temperature exceeds the melting temperature of the low-melting-point metal layer 26. Therefore, the fuse terminals 4a, 4b, the intermediate electrode 7, and the auxiliary electrode 18 can be efficiently connected to the fuse element 3 by reflow. Furthermore, even when the fuse element 3 is deformed by reflow, the resistance value can be locally increased or decreased, preventing variations in the fusing characteristics, such as not blowing at a predetermined temperature or blowing below the predetermined temperature. Therefore, the protective device 1 can quickly blow the fuse element 3 by heat generation from the heating element 8 ( FIG. 8 ).

[0065] Furthermore, the fuse element 3 will not melt due to self-heating while a predetermined rated current is flowing. When a current higher than the rated current flows, the fuse element 3 melts due to self-heating (Joule heat), interrupting the current path between the fuse terminals 4a and 4b. As described above, the protective element 1 provides the space 10 between the fuse terminals 4a and 4b and the insulating substrate 6, and the spaces 11 above and below the fuse element 3 and the insulating substrate 6. This makes it difficult for the Joule heat of the fuse element 3 to dissipate, and the fuse element 3 is heated over a wide area, dispersing and mitigating the explosive thermal shock that occurs when the fuse element 3 melts after reaching its melting point. Therefore, the protective element 1 can safely interrupt a current caused by self-heating due to an overcurrent at a high voltage. Furthermore, the protective element 1 prevents sparks and tracking caused by molten debris, thereby suppressing a decrease in insulation performance.

[0066] Furthermore, when the fuse element 3 self-heats due to heat generation by the heating element 8 or an overcurrent, the low-melting-point metal layer 26, which melts first, corrodes (eats the solder from) the high-melting-point metal layer 27, causing the high-melting-point metal layer 27 to melt at a temperature lower than its melting point. Therefore, the fuse element 3 can be blown in a short time by utilizing the corrosion of the high-melting-point metal layer 27 by the low-melting-point metal layer 26. Furthermore, the fuse element 3 is divided by the physical pulling action of the molten conductor 3a by the intermediate electrode 7 and the auxiliary electrode 18, so that the current path between the fuse terminals 4a, 4b can be quickly and reliably interrupted.

[0067] Furthermore, the fuse element 3 may be configured so that the volume of the low-melting-point metal layer 26 is greater than the volume of the high-melting-point metal layer 27. When the fuse element 3 is heated by self-heating due to an overcurrent or by heat generated by the heating element 8, the low-melting-point metal melts and corrodes the high-melting-point metal, thereby enabling the fuse element 3 to melt and blow quickly. Therefore, by configuring the volume of the low-melting-point metal layer 26 to be greater than the volume of the high-melting-point metal layer 27, the fuse element 3 can promote this corrosion action and quickly cut off the connection between the fuse terminals 4 a, 4 b.

[0068] Furthermore, in the fuse element 3, which is constructed by laminating a high-melting-point metal layer 27 on a low-melting-point metal layer 26 as an inner layer, the fusing temperature can be significantly reduced compared to conventional chip fuses made of high-melting-point metals. Therefore, the fuse element 3 can have a larger cross-sectional area and a significantly higher current rating than chip fuses of the same size. Furthermore, it can be made smaller and thinner than conventional chip fuses with the same current rating, and has excellent fast-fusing properties.

[0069] Furthermore, the fuse element 3 can improve its resistance (pulse resistance) to surges, which are instantaneous applications of abnormally high voltage to an electrical system incorporating the protective device 1. That is, the fuse element 3 must not blow even when a current of, for example, 100 A flows for several milliseconds. Because a large current that flows in an extremely short time flows through the surface layer of the conductor (skin effect), a fuse element 3 having a low-resistance, high-melting-point metal layer 27 such as Ag plating as an outer layer can easily pass the current applied by a surge and prevent blowout due to self-heating. Therefore, the fuse element 3 can significantly improve its resistance to surges compared to fuses made of conventional solder alloys.

[0070] The fuse element 3 may be coated with flux (not shown) to prevent oxidation and improve wettability during melting.

[0071] [Circuit Configuration Example] Such a protection device 1 is used by being incorporated into a circuit in a battery pack 40 of, for example, a lithium ion secondary battery, as shown in Fig. 9. The battery pack 40 has a battery stack 45 consisting of, for example, a total of four battery cells 41a to 41d of lithium ion secondary batteries.

[0072] The battery pack 40 includes a battery stack 45, a charge / discharge control circuit 46 that controls the charging and discharging of the battery stack 45, 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 45, a detection circuit 47 that detects the voltage of each battery cell 41a to 41d, and a current control element 48 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 47.

[0073] The battery stack 45 is a series connection of battery cells 41a to 41d that require control to protect against overcharge and overdischarge, and is detachably connected to a charging device 42 via the positive terminal 40a and negative terminal 40b of the battery pack 40, and is applied with a charging voltage from the charging device 42. The battery pack 40 charged by the charging device 42 can be used to operate an electronic device that is powered by a battery by connecting the positive terminal 40a and negative terminal 40b to the electronic device.

[0074] The charge / discharge control circuit 46 includes two current control elements 43a, 43b connected in series in a current path between the battery stack 45 and the charging device 42, and a control unit 44 that controls the operation of these current control elements 43a, 43b. The current control elements 43a, 43b are configured, for example, by field-effect transistors (hereinafter referred to as FETs), and the control unit 44 controls the gate voltage to control conduction and interruption of the current path of the battery stack 45 in the charging and / or discharging directions. The control unit 44 operates by receiving power supply from the charging device 42, and controls the operation of the current control elements 43a, 43b to interrupt the current path when the battery stack 45 is overcharged or overdischarged, depending on the detection result by the detection circuit 47.

[0075] The protection element 1 is connected, for example, on a charge / discharge current path between a battery stack 45 and a charge / discharge control circuit 46 , and its operation is controlled by a current control element 48 .

[0076] The detection circuit 47 is connected to each of the battery cells 41a to 41d, detects the voltage value of each of the battery cells 41a to 41d, and supplies each voltage value to the control unit 44 of the charge / discharge control circuit 46. The detection circuit 47 also outputs a control signal for controlling the current control element 48 when any one of the battery cells 41a to 41d reaches an overcharge voltage or an overdischarge voltage.

[0077] The current control element 48 is composed of, for example, a FET, and when the detection signal output from the detection circuit 47 indicates that the voltage value of the battery cells 41a to 41d 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 45 to be cut off regardless of the switch operation of the current control elements 43a and 43b.

[0078] The protective element 1 to which the present invention is applied and used in the battery pack 40 configured as described above has a circuit configuration as shown in FIG. 10 . That is, in the protective element 1, the fuse terminal 4a is connected to the battery stack 45 and the fuse terminal 4b is connected to the positive terminal 40a, thereby connecting the fuse element 3 in series to the charge / discharge path of the battery stack 45. In addition, in the protective element 1, the heating element 8 is connected to the current control element 48 via the heating element power supply electrode 16 and the heating element terminal 15, and the heating element 8 is also connected to the battery stack 45. As a result, one end of the heating element 8 is connected to the fuse element 3 and one end of the battery stack 45 via the heating element electrode 17 and the intermediate electrode 7, and the other end is connected to the current control element 48 and the other end of the battery stack 45 via the heating element terminal 15. This forms a power supply path to the heating element 8, the current supply path to which is controlled by the current control element 48.

[0079] [Operation of the Protection Element] With the protection element 1 mounted on the external circuit board, the heating element 8 is connected to the current control element 48 and other elements formed in the external circuit via the heating element terminals 15, and current flow and heat generation are regulated under normal conditions. When the detection circuit 47 detects an abnormal voltage in any of the battery cells 41a to 41d, it outputs a cut-off signal to the current control element 48. The current control element 48 then controls the current to flow through the heating element 8. When current flows from the battery stack 45, the heating element 8 begins to generate heat.

[0080] Heat from the heating element 8 is transferred to the fuse element 3 via the heating element electrode 17 and intermediate electrode 7, and also from the insulating substrate 6 via the intermediate electrode 7 and auxiliary electrode 18 to the fuse element 3, melting the fuse element 3. In the fuse element 3, the molten conductor 3a aggregates on the intermediate electrode 7 and auxiliary electrode 18, and is melted between the fuse terminals 4a and 4b (FIG. 8). This cuts off the charge / discharge path of the battery pack 40.

[0081] Furthermore, even if an overcurrent exceeding the rated current flows through the fuse element 3, the fuse element 3 melts due to self-heating and is blown between the fuse terminals 4 a and 4 b of the protection device 1. This allows the charge / discharge path of the battery pack 40 to be cut off.

[0082] Furthermore, by forming the fuse element 3 of the protective element 1 so that it contains a high-melting point metal and a low-melting point metal, the low-melting point metal melts before the high-melting point metal melts, and the molten low-melting point metal corrodes the high-melting point metal, allowing the fuse element 3 to melt in a short time.

[0083] When the fuse element 3 melts, the charge / discharge path of the battery stack 45 is cut off between the fuse terminals 4a and 4b. When the fuse element 3 melts, the power supply path to the heating element 8 is also cut off, and the heating element 8 stops generating heat.

[0084] The protective element 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.

[0085] [Variation 1] Next, a variation of a protection element to which the present technology is applied will be described. Note that in the following description, the same components as those in the protection element 1 described above will be assigned the same reference numerals, and their details may be omitted. As shown in FIG. 11 , a protection element to which the present technology is applied may have a heating element 8 formed on the rear surface 6b of an insulating substrate 6. FIG. 11 is a cross-sectional view showing a protection element 50 in which a heating element 8 is formed on the rear surface 6b of an insulating substrate 6. FIG. 12 is a plan view showing the protection element 50 with the upper case 21 omitted. FIG. 13 is a view showing the insulating substrate 6 of the protection element 50, with (A) being a plan view and (B) being a bottom view.

[0086] The insulating substrate 6 has an intermediate electrode 7 and an auxiliary electrode 18 formed on its front surface 6a, and a heating element 8 and an insulating layer 9 formed on its back surface 6b. The insulating substrate 6 also has heating element power supply electrodes 16 formed on one side edge of the front surface 6a and back surface 6b. The heating element power supply electrode 16a formed on the front surface 6a and the heating element power supply electrode 16b formed on the back surface 6b are continuous via castellations. The back surface heating element power supply electrode 16b is connected to the heating element 8. The front surface heating element power supply electrode 16a is connected to the heating element terminal 15.

[0087] Similarly, heating element electrodes 17 are formed on the other side edges of the front surface 6a and the back surface 6b, respectively. The heating element electrode 17a formed on the front surface 6a and the heating element electrode 17b formed on the back surface 6b are continuous via a conductive through-hole. The back surface heating element electrode 17b is connected to the heating element 8. The front surface heating element electrode 17a is connected to the intermediate electrode 7.

[0088] [Process for Forming Fusing Member] The fusing member 5 for the protective element 50 is formed by forming the front-side heating element power supply electrode 16a, the front-side heating element electrode 17a, and the auxiliary electrode 18 on the front surface 6a of the insulating substrate 6, which has half-through holes for castellations formed on its side surfaces, using a known forming method such as screen printing, and then forming the intermediate electrode 7. The back-side heating element power supply electrode 16b and the back-side heating element electrode 17b are also formed on the back surface 6b of the insulating substrate 6 using a known forming method such as screen printing. Next, the heating element 8 is formed, and the insulating layer 9 is laminated. After that, through-holes are formed using a drill or the like to connect the heating element electrodes 17a and 17b. Next, the castellations connecting the front and back-side heating element power supply electrodes 16a and 16b and the through-holes connecting the front and back-side heating element electrodes 17a and 17b are electrically connected by plating or the like. The fusing member 5 includes the intermediate electrode 7, the auxiliary electrode 18, and the fuse element 3 connected by connection solder 13. The fuse element 3, to which the fusing member 5 is connected, is connected by connecting solder 13 to fuse terminals 4a and 4b supported on the side edge 22a of the lower case 22. Also, the front-side heating element power supply electrode 16a of the insulating substrate 6 is connected by connecting solder 13 to a heating element terminal 15 supported on the side edge 22a of the lower case 22.

[0089] [Variation 2] Next, another variation of the protection element to which the present technology is applied will be described. Note that in the following description, the same components as those in the protection elements 1 and 50 described above will be assigned the same reference numerals, and their details may be omitted. In a protection element 60 shown in Fig. 14, a holding electrode 61 that holds the molten conductor 3a of the fuse element 3 when the fuse element 3 blows is formed on the back surface 6b of the insulating substrate 6. The holding electrode 61 is connected to an intermediate electrode 7 formed on the front surface 6a of the insulating substrate 6 by a through hole 62 that penetrates the insulating substrate 6.

[0090] Fig. 14 is a cross-sectional view showing a protection element 60 in which a holding electrode 61 is formed on the rear surface 6b of an insulating substrate 6. Fig. 15 is a plan view showing the protection element 60 without the upper case 21. Fig. 16 is a diagram showing the insulating substrate 6 of the protection element 60, where (A) is a plan view and (B) is a bottom view.

[0091] The insulating substrate 6 has a heating element 8, an insulating layer 9 covering the heating element 8, an intermediate electrode 7 laminated on the insulating layer 9, and an auxiliary electrode 18 formed on its front surface 6a. The insulating substrate 6 also has a holding electrode 61 formed on its back surface 6b. The intermediate electrode 7 and the holding electrode 61 are connected by a through hole 62 that penetrates the insulating substrate 6.

[0092] 14, two heating elements 8 are formed in parallel on the surface 6a of the insulating substrate 6. One end of each heating element 8 is connected to a heating element power supply electrode 16, and the other end is connected to a heating element electrode 17. Note that the protective element 60 may be provided with one heating element 8 or three or more heating elements 8.

[0093] [Retention Electrode] The retention electrode 61 formed on the back surface 6b of the insulating substrate 6 is located opposite the intermediate electrode 7 formed in the approximate center of the front surface 6a, with the insulating substrate 6 interposed therebetween. The retention electrode 61 is also connected to the intermediate electrode 7 via a through hole 62 that penetrates from the surface of the retention electrode 61 to the surface of the intermediate electrode 7. This allows the molten conductor 3a of the molten fuse element 3 to be attracted toward the retention electrode 61 via the through hole 62.

[0094] The holding electrode 61 can be formed by a known method such as screen printing using a known electrode material such as Ag, Cu, or an alloy material containing Ag or Cu as a main component.

[0095] When the fuse element 3 melts, the through-hole 62 draws in the molten conductor 3a of the fuse element 3 by capillary action, thereby reducing the volume of the molten conductor 3a held on the intermediate electrode 7. As a result, even if the fuse element 3 becomes larger due to higher ratings and higher capacities of the protective device 60, resulting in an increased amount of melting, a large amount of molten conductor 3a can be held by the holding electrode 61, intermediate electrode 7, and auxiliary electrode 18, as shown in Fig. 17 , and the fuse element 3 can be reliably melted.

[0096] The through holes 62 are formed in areas of the insulating substrate 6 where no heating elements 8 are formed. In the fusing member 5 shown in Figures 14 to 16, the through holes 62 are formed in areas between the heating elements 8 arranged in parallel.

[0097] A conductive layer 64 is formed on the inner surface of the through hole 62. The conductive layer 64 is continuous with the holding electrode 61 and the intermediate electrode 7. This electrically connects the holding electrode 61 and the intermediate electrode 7 via the conductive layer 64. Furthermore, by forming the conductive layer 64, heat from the heating element 8 is also conducted to the holding electrode 61 via the intermediate electrode 7 and the through hole 62.

[0098] Furthermore, since the molten conductor 3a aggregates on the intermediate electrode 7 when it is blown, the continuity between the intermediate electrode 7 and the conductive layer 64 makes it easier to guide the molten conductor 3a into the through hole 62. The molten conductor 3a also spreads and is held by the holding electrode 61, which is continuous with the conductive layer 64 ( FIG. 17 ). Therefore, more molten conductor 3a can be attracted and held by the through hole 62 and the holding electrode 61, reducing the volume of the molten conductor 3a held by the intermediate electrode 7 and the auxiliary electrode 18, ensuring reliable blown-out.

[0099] The conductive layer 64 is formed of, for example, one of copper, silver, gold, iron, nickel, palladium, lead, or tin, or an alloy containing any of these as a main component, and can be formed on the inner surface of the through hole 62 by a known method such as electrolytic plating or printing with a conductive paste. Alternatively, the conductive layer 64 may be formed by inserting a plurality of metal wires or an aggregate of conductive ribbons into the through hole 62.

[0100] The fusing member 5 may have a plurality of through holes 62. This increases the number of paths for attracting the molten conductor 3 a of the fuse element 3, and allows a larger amount of the molten conductor 3 a to be attracted quickly, thereby reducing the volume of the molten conductor 3 a held by the intermediate electrode 7 and the auxiliary electrode 18.

[0101] [Process for Forming Fusing Member] The fusing member 5 for the protective element 60 is formed by forming the heating element power supply electrode 16, the heating element electrode 17, and the auxiliary electrode 18 on the front surface 6a of the insulating substrate 6 using a known forming method such as screen printing, followed by forming the heating element 8 and laminating the insulating layer 9. Next, the intermediate electrode 7 is formed. A holding electrode 61 is also formed on the back surface 6b of the insulating substrate 6 using a known forming method such as screen printing. After that, a through hole 62 is formed using a drill or the like, and a conductive layer 64 is formed by plating or the like to complete the fusing member 5. The intermediate electrode 7 and auxiliary electrode 18 are connected to the fuse element 3 by connecting solder 13. The fuse element 3 connected to the fusing member 5 is connected to the fuse terminals 4a and 4b supported on the side edge 22a of the lower case 22 by connecting solder 13. The heating element power supply electrode 16 of the insulating substrate 6 is also connected to the heating element terminal 15 supported on the side edge 22a of the lower case 22 by connecting solder 13.

[0102] 18 is a circuit diagram of the protection element 60. In the fusing member 5 connected to the fuse element 3, one end of each heating element 8 formed on the surface 6a of the insulating substrate 6 is connected to the fuse element 3 via the heating element electrode 17 and the intermediate electrode 7. In addition, in the fusing member 5, the heating element power supply electrode 16 connected to the other end of each heating element 8 is connected to the heating element terminal 15 via a connecting material such as connection solder 13. As a result, in the fusing member 5, each heating element 8 is connected to a power source provided in an external circuit via the heating element terminal 15, and each heating element 8 is able to generate heat.

[0103] [Variation 3] Next, another variation of the protective element to which the present technology is applied will be described. In the following description, the same components as those in the protective elements 1, 50, and 60 described above will be denoted by the same reference numerals, and detailed descriptions thereof may be omitted. A protective element 70 shown in Fig. 19 has a heating element 8, an insulating layer 9 covering the heating element 8, and a holding electrode 61 that holds the molten conductor 3a of the fuse element 3 when the fuse element 3 melts, formed on the back surface 6b of the insulating substrate 6. The holding electrode 61 is connected to an intermediate electrode 7 formed on the front surface 6a of the insulating substrate 6 by a through hole 62 that penetrates the insulating substrate 6.

[0104] Fig. 19 is a cross-sectional view showing a protection element 70 in which a heating element 8, an insulating layer 9, and a holding electrode 61 are formed on the rear surface 6b of an insulating substrate 6. Fig. 20 is a plan view showing the protection element 70 without the upper case 21. Fig. 21 is a view showing the insulating substrate 6 of the protection element 70, where (A) is a plan view and (B) is a bottom view.

[0105] The insulating substrate 6 has an intermediate electrode 7 and an auxiliary electrode 18 formed on its front surface 6a, and a heating element 8, an insulating layer 9, and a holding electrode 61 formed on its back surface 6b. The insulating substrate 6 also has heating element power supply electrodes 16 formed on one side edge of the front surface 6a and back surface 6b. The heating element power supply electrode 16a formed on the front surface 6a and the heating element power supply electrode 16b formed on the back surface 6b are continuous via castellations. The back surface heating element power supply electrode 16b is connected to the heating element 8. The front surface heating element power supply electrode 16a is connected to the heating element terminal 15.

[0106] The insulating substrate 6 also has a heating element electrode 17 formed on the other edge of the rear surface 6b of the insulating substrate 6. The heating element electrode 17 is connected to the heating element 8 and also to a holding electrode 61 laminated on the insulating layer 9.

[0107] The holding electrode 61 is laminated on the insulating layer 9 and is formed at a position facing the intermediate electrode 7 formed at approximately the center of the surface 6 a via the insulating substrate 6 .

[0108] The through-holes 62 are formed in areas of the insulating substrate 6 where no heating elements 8 are formed. In the fusing member 5 shown in Fig. 19, the through-holes 62 are formed in areas between the parallel heating elements 8. Furthermore, the through-holes 62 have conductive layers 64 formed on their inner surfaces that are continuous with the holding electrodes 61 and the intermediate electrodes 7.

[0109] As a result, the intermediate electrode 7 formed on the front surface 6 a of the insulating substrate 6 and the heating element 8 formed on the back surface 6 b are continuous via the heating element electrode 17 , the holding electrode 61 and the through-hole 62 .

[0110] 19, two heating elements 8 are formed in parallel on the rear surface 6b of the insulating substrate 6. One end of each heating element 8 is connected to the rear surface heating element power supply electrode 16b, and the other end is connected to the heating element electrode 17. Note that the protective element 70 may also be provided with one heating element 8 or three or more heating elements 8.

[0111] When the molten conductor 3a aggregates on the intermediate electrode 7 when the fuse element 3 melts, the protective element 70 guides the molten conductor 3a into the through hole 62, where it spreads and is held by the holding electrode 61 that is continuous with the conductive layer 64 (see FIG. 22 ). Therefore, more molten conductor 3a can be attracted and held by the through hole 62 and the holding electrode 61, reducing the volume of the molten conductor 3a held by the intermediate electrode 7 and the auxiliary electrode 18, ensuring reliable melting.

[0112] It is also preferable to form a plurality of through holes 62 in the protective element 70. This increases the number of paths for attracting the molten conductor 3 a of the fuse element 3, and allows a larger amount of the molten conductor 3 a to be attracted quickly, thereby reducing the volume of the molten conductor 3 a held by the intermediate electrode 7 and auxiliary electrode 18.

[0113] [Variation 4] Next, another variation of the protection element to which the present technology is applied will be described. Note that in the following description, the same components as those of the protection elements 1, 50, 60, and 70 described above will be assigned the same reference numerals, and their details may be omitted. The protection element 80 shown in Fig. 23 is a protection element 60 having a heating element 8 provided on the surface 6a of an insulating substrate 6, in which the fusing member 5 is connected to one surface of the fuse element 3 and the other surface opposite to the one surface. That is, in the protection element 80, the fuse element 3 is sandwiched between multiple fusing members 5.

[0114] Fig. 23 is a cross-sectional view showing a protective element 80 in which a fusing member 5 having a heating element 8 formed on the surface 6a of an insulating substrate 6 is connected to one side and the other side of a fuse element 3. Fig. 24 is a plan view showing the protective element 80 with the upper case 21 omitted.

[0115] 25 is a circuit diagram of a protection element 80. Each fusing member 5 connected to one surface and the other surface of the fuse element 3 has one end of a heating element 8 formed on the surface 6a of each insulating substrate 6 connected to the fuse element 3 via a heating element electrode 17 and an intermediate electrode 7. Each fusing member 5 faces a heating element power supply electrode 16 connected to the other end of the heating element 8, and is connected to each heating element terminal 15 via a connecting material such as connecting solder 13. As a result, each fusing member 5 is connected via the heating element terminal 15 to a power source for generating heat from the heating element 8 provided in an external circuit.

[0116] 26 , when the protective element 80 melts the fuse element 3 due to heat generated by the heating element 8, the heating elements 8 of the fusing members 5, 5 connected to both sides of the fuse element 3 generate heat, heating the fuse element 3 from both sides. Therefore, the protective element 80 can quickly heat and melt the fuse element 3 even when the cross-sectional area of ​​the fuse element 3 is increased to accommodate large current applications.

[0117] Furthermore, the protective element 80 draws the molten conductor 3a from both sides of the fuse element 3 into each through-hole 62 formed in each fusing member 5 and holds it with the holding electrodes 61. Therefore, even when the cross-sectional area of ​​the fuse element 3 is increased to accommodate high-current applications and a large amount of molten conductor 3a is generated, the protective element 80 can reliably draw in the molten conductor 3a using the multiple fusing members 5 and melt the fuse element 3. Furthermore, by drawing in the molten conductor 3a using the multiple fusing members 5, the protective element 80 can more quickly melt the fuse element 3.

[0118] The protective element 80 can quickly blow the fuse element 3 even when the fuse element 3 has a coating structure in which a low-melting-point metal constituting the inner layer is coated with a high-melting-point metal or a laminated structure of low-melting-point metal and high-melting-point metal. That is, a fuse element 3 coated with or laminated with a high-melting-point metal requires time to heat up to the temperature at which the high-melting-point metal melts, even when the heating element 8 generates heat. Here, the protective element 80 includes multiple fusing members 5, and by simultaneously heating each heating element 8, the high-melting-point metal can be quickly heated to its melting temperature. Therefore, the protective element 80 allows the thickness of the high-melting-point metal layer constituting the outer layer to be increased, thereby achieving a higher rating and maintaining fast-fusing characteristics.

[0119] 23, the protective element 80 is preferably connected to the fuse element 3 with a pair of opposing fusing members 5. This allows the protective element 80 to heat the same location on the fuse element 3 from both sides simultaneously with the pair of fusing members 5 and to attract the molten conductor 3a, enabling the fuse element 3 to be heated and blown more quickly.

[0120] Furthermore, in the protective element 80, it is preferable that the auxiliary electrodes 18 formed on the insulating substrates 6 of the pair of fusing members 5, 5 face each other across the fuse element 3. This symmetrically connects the pair of fusing members 5, 5, which prevents the load from being imbalanced on the fuse element 3 during reflow mounting or heating of the fuse element 3, and improves resistance to deformation of the fuse element 3 and misalignment of the fusing members 5.

[0121] It is preferable to form the heating elements 8 on both sides of the through-hole 62 in order to heat the auxiliary electrode 18 and the intermediate electrode 7 and to aggregate and attract a larger amount of the molten conductor 3a.

[0122] [Variation 5] Next, another variation of the protection element to which the present technology is applied will be described. Note that in the following description, the same components as those of the protection elements 1, 50, 60, 70, and 80 described above will be assigned the same reference numerals, and their details may be omitted. The protection element 90 shown in Fig. 27 is a protection element 70 having a heating element 8 provided on the rear surface 6b of the insulating substrate 6, in which the fusing member 5 is connected to one surface and the other surface of the fuse element 3. That is, in the protection element 90, the fuse element 3 is sandwiched between multiple fusing members 5.

[0123] Fig. 27 is a cross-sectional view showing a protective element 90 in which a fusing member 5 having a heating element 8 formed on the rear surface 6b of an insulating substrate 6 is connected to one surface and the other surface of a fuse element 3. Fig. 28 is a plan view showing the protective element 90 with the upper case 21 omitted.

[0124] The protective element 90 has a circuit configuration similar to that of the protective element 80 shown in Fig. 25. In each of the fusing members 5 connected to one and the other surfaces of the fuse element 3, one end of the heating element 8 formed on the rear surface 6b of each insulating substrate 6 is connected to the fuse element 3 via an intermediate electrode 7 that is continuous with the heating element electrode 17, the holding electrode 61, and the through-hole 62. In addition, each of the fusing members 5 faces the front-side heating element power supply electrode 16a connected to the other end of the heating element 8, and is connected to each of the heating element terminals 15 via a connecting material such as connecting solder 13. As a result, each of the fusing members 5 is connected via the heating element terminal 15 to a power source for generating heat from the heating element 8 provided in an external circuit.

[0125] In the protective element 90, the fusing operation and effect caused by heat generated by the heating element 8 are the same as those of the protective element 80 described above, and heat is applied from both sides of the fuse element 3. Also, as shown in Figure 29, the protective element 90, like the protective element 80, draws the molten conductors 3a from both sides of the fuse element 3 into the through holes 62 formed in each fusing member 5 and holds them with the holding electrodes 61.

[0126] Furthermore, the protective element 90 can more quickly fuse the fuse element 3 by attracting the molten conductor 3a with the multiple fusing members 5. Furthermore, the protective element 90 includes multiple fusing members 5, and by simultaneously generating heat from each heating element 8, the high-melting-point metal can be quickly heated to its melting temperature. Therefore, the protective element 90 can increase the thickness of the high-melting-point metal layer that constitutes the outer layer, thereby achieving a higher rating while maintaining fast-fusing characteristics.

[0127] 27, in the protective element 90, it is preferable that the pair of fusing members 5, 5 are connected to the fuse element 3 so as to face each other. Also in the protective element 90, it is preferable that the auxiliary electrodes 18 formed on the insulating substrates 6 of the pair of fusing members 5, 5 face each other across the fuse element 3.

[0128] It is preferable to form the heating elements 8 on both sides of the through-hole 62 in order to heat the auxiliary electrode 18 and the intermediate electrode 7 and to aggregate and attract a larger amount of the molten conductor 3a.

[0129] REFERENCE SIGNS LIST 1 Protective element, 2 Case, 3 Fuse element, 4a, 4b Fuse terminal, 5 Fusing member, 6 Insulating substrate, 6a Surface, 6b Back surface, 7 Intermediate electrode, 8 Heating element, 9 Insulating layer, 10 Space, 11 Space, 13 Connection solder, 14 Screw hole, 15 Heating element terminal, 16 Heating element power supply electrode, 17 Heating element electrode, 18 Auxiliary electrode, 21 Upper case, 22 Lower case, 22a Side edge portion, 22b Hollow portion, 23 Fitting recess, 24 Fitting protrusion, 25 Adhesive, 26 Low melting point metal layer, 27 High melting point metal layer, 40 Battery pack, 41 Battery cell, 42 Charging device, 43 Current control element, 44 Control unit, 45 Battery stack, 46 Charge / discharge control circuit, 47 Detection circuit, 48 Current control element, 50 Protective element, 60 Protective element, 61 holding electrode, 62 through hole, 64 conductive layer, 70 protective element, 80 protective element, 90 protective element

Claims

1. A protective element comprising: a case; a fuse element housed in the case; a pair of fuse terminals supported on side surfaces of the case and spaced apart in the direction of current flow through the fuse element and connected to the fuse element; and a fusing member connected to at least one surface of the fuse element between the pair of fuse terminals and for fusing the fuse element, wherein the fusing member comprises an insulating substrate and an intermediate electrode provided on a surface of the insulating substrate that contacts the fuse element and connected to the fuse element, wherein a space is defined above and below the fuse element between the insulating substrate and at least one of the pair of fuse terminals, and wherein a space is defined above and below the fuse element and the insulating substrate in a region where the fuse element and the insulating substrate overlap.

2. The protection element according to claim 1, wherein said fusing member comprises a heating element formed on said insulating substrate, which generates heat to fuse said fuse element, and an insulating layer covering said heating element.

3. A protection element according to claim 1 or 2, wherein in a cross-sectional view, the distance D3 between the pair of fuse terminals is 7 mm or more.

4. A protective element as claimed in claim 1 or 2, wherein in a cross-sectional view, a distance D1 between one of said fuse terminals and a side edge of said insulating substrate facing said one fuse terminal is 1 mm or more.

5. A protection element as set forth in claim 4, wherein in a cross-sectional view, a distance D2 between the other fuse terminal and a side edge of the insulating substrate facing the other fuse terminal is 1 mm or more.

6. A protection element according to claim 1 or 2, wherein in a cross-sectional view, the width W of the insulating substrate in the direction between the pair of fuse terminals is smaller than the distance D3 between the pair of fuse terminals.

7. The protective element according to claim 6, which satisfies the following conditions: W<5 mm D3-W<2 mm 8. A protection element according to claim 2, wherein the heating element is provided on the front surface of the insulating substrate or on the back surface opposite to the front surface.

9. A protective element as claimed in claim 1 or 2, wherein the insulating substrate is provided with a retaining electrode on a back surface opposite to the front surface, and the intermediate electrode and the retaining electrode are connected by a through hole penetrating the insulating substrate.

10. A battery pack comprising one or more battery cells and a protection element connected to a charge / discharge path of the battery cell for blocking the charge / discharge path, the protection element being the protection element defined in claim 1 or 2.

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