Protective element and method for manufacturing protective element

Abstract

The invention provides a protection element capable of reducing the use amount of electrode forming materials, maintaining conductivity and connectivity, and coping with large current. A heating element 3 provided on the insulating substrate 2; a first electrode 4 and a second electrode 5 provided on the insulating substrate 2; a heating element extraction electrode 6 disposed between the first electrode 4 and the second electrode 5 and electrically connected to one end side of the heating element 3; and a fusible conductor 7. And a fusible conductor (7) that is disposed on the surfaces of the first electrode (4), the second electrode (5), and the heating element extraction electrode (6) and electrically connects the first electrode (4) and the heating element extraction electrode (6) and the second electrode (5) and the heating element extraction electrode (6). The first electrode (4), the second electrode (5), and a connection portion (8) of the heating element extraction electrode (6), which is connected to the fusible conductor (7), are formed thicker than the other portions of the first electrode (4), the second electrode (5), and the heating element extraction electrode (6).

Description

Technical Field

[0001] The present technology relates to a protection element, which is installed on a current path and, when a current exceeding a rated value flows, melts a fusible conductor by heating a heating element, thereby cutting off the current path. This application is an application claiming priority based on Japanese patent application No. 2022-100560 filed in Japan on June 22, 2022, which is cited in this application by reference. Background Art

[0002] Lithium-ion secondary batteries (LiB) are high-output, high-energy-density batteries that are suitable for a variety of applications while improving battery performance. However, LiBs are batteries that have the risk of emitting smoke and catching fire when they become overcharged due to certain influences, such as failures of ICs and FETs that control charging and discharging. As a secondary protection measure, protection elements with heating elements are used. As LiB-mounted applications expand, the number of LiBs produced has also increased, and the demand for protection elements to protect LiBs has also increased.

[0003] like Fig.12 As shown, a general protection element 100 with a heating element comprises an insulating substrate 101, a first and a second electrode 102, 103 formed on a surface 101a of the insulating substrate 101 and connected to a protection circuit, a heating element 105 formed on a back surface 101b of the insulating substrate 101 and energized and heated based on an external signal, a heating element lead-out electrode 106 electrically connected to the heating element 105, and a fusible conductor 107 connected between the first and the second electrodes 102, 103.

[0004] The first and second electrodes 102, 103 and the heating element lead-out electrode 106 are formed by applying silver paste on the surface 101a of the insulating substrate 101 and firing it. Therefore, the electrodes 102, 103, 106 have the same thickness as a whole. The soluble conductor 107 is connected to the first and second electrodes 102, 103 and the heating element lead-out electrode 106 by connecting solder or other connecting materials.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2017-174592 Summary of the invention

[0008] Problems to be solved by the invention

[0009] With the expansion of LiB-mounted applications in recent years, the demand for further high-current and low-price protection elements is increasing. The silver paste that constitutes the first and second electrodes and the heating element lead-out electrode is expensive, and the reduction of its usage has been studied. However, if the electrode thickness is made thinner (for example, less than 10μm), the glass component contained as a component for sintering and fixing will precipitate on the electrode surface during sintering, which may damage the conductivity with the fusible conductor and the connectivity with the insulating substrate and the fusible conductor. In addition, by making the electrode thickness thinner, the conductor resistance also increases, which may also become an obstacle to high current. Furthermore, when the electrode area is reduced in order to reduce the use of silver paste, the fusible conductor also needs to be miniaturized, which makes it difficult to cope with high current.

[0010] The present technology aims to provide a protection element and a method for manufacturing the protection element, which can reduce the amount of electrode forming material used, maintain conductivity and connectivity, and can cope with a large current.

[0011] Methods for solving problems

[0012] In order to solve the above-mentioned problems, the protection element of the present technology is characterized in that it comprises an insulating substrate, a heating element arranged on the insulating substrate, a first electrode and a second electrode arranged on the insulating substrate, a heating element lead-out electrode arranged between the first electrode and the second electrode and electrically connected to one end side of the heating element, and a soluble conductor, wherein the soluble conductor is arranged on the surfaces of the first electrode, the second electrode and the heating element lead-out electrode, electrically connects the first electrode and the heating element lead-out electrode and the second electrode and the heating element lead-out electrode, and the thickness of the connection portion of the first electrode, the second electrode and the heating element lead-out electrode connected to the soluble conductor is formed to be thicker than the thickness of other portions.

[0013] In order to solve the above-mentioned problems, the protection element of the present technology is characterized in that it comprises an insulating substrate, a heating element arranged on the back side of the insulating substrate, a first electrode and a second electrode arranged on the insulating substrate, and a soluble conductor, wherein the soluble conductor is arranged on the surface of the first electrode and the second electrode to electrically connect the first electrode and the second electrode, and the thickness of the connection part of the first electrode and the second electrode connected to the soluble conductor is formed to be thicker than the thickness of other parts.

[0014] In addition, the manufacturing method of the protection element of the present technology includes a process of forming a first electrode, a second electrode and a heat generating body lead-out electrode arranged between the first electrode and the second electrode by printing a conductive paste on an insulating substrate and firing the paste, and a process of forming a connecting electrode connected to a fusible conductor by printing a conductive paste on the first electrode, the second electrode and the heat generating body lead-out electrode and firing the paste. The fusible conductor connects the first electrode and the heat generating body lead-out electrode and the second electrode and the heat generating body lead-out electrode. The thickness of the connecting portion of the first electrode, the second electrode and the heat generating body lead-out electrode connected to the fusible conductor is formed to be thicker than the thickness of other portions.

[0015] In addition, the manufacturing method of the protection element of the present technology includes a process of forming a first electrode and a second electrode by printing a conductive paste on an insulating substrate and firing the conductive paste, and a process of forming a connecting electrode connected to a fusible conductor by printing a conductive paste on the first electrode and the second electrode and firing the conductive paste. The fusible conductor connects the first electrode and the second electrode, and the thickness of the connecting portion of the first electrode and the second electrode connected to the fusible conductor is formed to be thicker than the thickness of other portions.

[0016] Effects of the Invention

[0017] According to the present technology, it is possible to reduce the amount of electrode forming material used, maintain conductivity and connectivity, and cope with a larger current. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] [ Figure 1 ] Figure 1 1 and 2 are diagrams showing a protection element to which the present technology is applied, wherein (A) is a top view showing the protection element with a housing omitted, (B) is a bottom view, and (C) is a cross-sectional view.

[0019] [ Figure 2 ] Figure 2 It is a plan view showing a state where the fusible conductor is melted.

[0020] [ Figure 3 ] Figure 3 is a cross-sectional view showing a connection portion of a first electrode.

[0021] [ Figure 4 ] Figure 4 This is a plan view showing a configuration in which the connection portion is formed slightly inside the inner edges of the first electrode and the second electrode.

[0022] [ Figure 5 ] Figure 5 is a cross-sectional view of a fusible conductor.

[0023] [ Figure 6 ] Figure 6 This is a circuit diagram showing a configuration example of a battery pack.

[0024] [ Figure 7 ] Figure 7 This is a circuit diagram of a protection element to which this technology is applied.

[0025] [ Figure 8 ] Figure 8 1 and 2 are diagrams showing a protective element according to a modified example, wherein (A) is a top view showing the protective element without a housing, (B) is a bottom view, and (C) is a cross-sectional view.

[0026] [ Fig. 9 ] Fig. 9 This is a plan view showing a protection element according to a modified example with the case, the heat generating element lead-out electrode, and the soluble conductor omitted.

[0027] [ Fig.10 ] Fig.10 1 and 2 are diagrams showing a protection element according to another modified example, wherein (A) is a top view showing the protection element without omitting a housing, (B) is a bottom view, and (C) is a cross-sectional view.

[0028] [ Fig.11 ] Fig.11 It is a diagram showing a circuit configuration of a protection element according to another modified example.

[0029] [ Fig.12 ] Fig.12 The figures show a protective element with a heating element, (A) is a top view showing the protective element without a casing, (B) is a bottom view, and (C) is a cross-sectional view. DETAILED DESCRIPTION

[0030] Hereinafter, a protective element and a method for manufacturing a protective element to which the present technology is applied are described in detail with reference to the accompanying drawings. It should be noted that the present technology is not limited to the following embodiments, and various changes can be made without departing from the main purpose of the present technology. In addition, the accompanying drawings are schematic, and the ratios of various dimensions are sometimes different from reality. Specific dimensions should be determined by referring to the following description. In addition, the drawings also include parts with different dimensional relationships and ratios.

[0031] like Figure 1As shown in (A) to (C), a protection element 1 to which the present technology is applied includes an insulating substrate 2, a heating element 3 provided on the insulating substrate 2, a first electrode 4 and a second electrode 5 provided on the insulating substrate 2, a heating element lead-out electrode 6 disposed between the first electrode 4 and the second electrode 5 and electrically connected to one end of the heating element 3, and a soluble conductor 7 disposed on the surfaces of the first electrode 4, the second electrode 5, and the heating element lead-out electrode 6 to electrically connect the first electrode 4 and the heating element lead-out electrode 6 and the second electrode 5 and the heating element lead-out electrode 6. In addition, in the protection element 1, the thickness of a connection portion 8 of the first electrode 4, the second electrode 5, and the heating element lead-out electrode 6 to which the soluble conductor 7 is connected is formed to be thicker than the thickness of other portions.

[0032] In the first electrode 4, the second electrode 5 and the heating element lead-out electrode 6, the connecting portion 8 connected to the soluble conductor 7 is formed to be thicker than the thickness of the other portions, that is, the thickness of the portions other than the connecting portion 8 can be formed to be thinner, so compared with the case where the entire surface is formed with a uniform thickness, the amount of electrode forming material used to form the first electrode 4, the second electrode 5 and the heating element lead-out electrode 6 can be reduced.

[0033] In addition, the electrode forming material contains a glass component as a component for sintering and fixing with the insulating substrate 2. If the electrode thickness is made extremely thin, the glass component will precipitate on the electrode surface, which may damage the conductivity and connectivity with the soluble conductor 7. However, the protection element 1 has a sufficient thickness in the connection portion 8 connected to the soluble conductor 7, so there is no precipitation of the glass component, and the conductivity and connectivity with the soluble conductor 7 can be maintained. In addition, by making the connection portion 8 have a sufficient thickness, the on-resistance does not increase. Therefore, it is possible to reduce the amount of electrode forming material used, maintain conductivity and connectivity, and cope with large currents.

[0034] Such a protection element 1 is assembled into an external circuit, and the fusible conductor 7 constitutes a part of the current path of the external circuit. The fusible conductor 7 is melted by the heat of the heating element 3 or the overcurrent exceeding the rated value, thereby cutting off the current path (see Figure 2 ). Hereinafter, each structure of the protection element 1 will be described in detail.

[0035] [Insulating substrate]

[0036] The insulating substrate 2 is formed of an insulating member such as alumina, glass ceramics, mullite, zirconia, etc. In addition, the insulating substrate 2 may also use a material used for a printed wiring board such as a glass epoxy substrate or a phenol substrate. It should be noted that in this specification, the surface of the insulating substrate 2 on which the soluble conductor 7 is mounted is referred to as the front surface 2a, and the surface opposite to the surface on which the soluble conductor 7 is mounted is referred to as the back surface 2b.

[0037] [First Electrode and Second Electrode]

[0038] The first electrode 4 and the second electrode 5 are formed at opposite ends of the surface 2a of the insulating substrate 2. The first electrode 4 and the second electrode 5 are respectively formed of a conductive pattern of Ag, Cu or an alloy thereof. The first electrode 4 and the second electrode 5 can be formed by, for example, printing Ag paste in a predetermined pattern by screen printing and then firing at a predetermined temperature.

[0039] The first electrode 4 is continuous with the first external connection electrode 11 formed on the back surface 2b via the castellations from the front surface 2a of the insulating substrate 2. In addition, the second electrode 5 is continuous with the second external connection electrode 12 formed on the back surface 2b via the castellations from the front surface 2a of the insulating substrate 2. When the protection element 1 is mounted on an external circuit substrate, the first external connection electrode 11 and the second external connection electrode 12 are connected to the connection electrodes provided on the external circuit substrate, so that the soluble conductor 7 is assembled in a part of the current path formed on the external circuit substrate.

[0040] The first and second electrodes 4 and 5 are electrically connected to each other by mounting the fusible conductor 7 on the connection portion 8 via a conductive connection material such as solder. Figure 2 As shown, the first and second electrodes 4 and 5 are disconnected when the heating element 3 generates heat and the fusible conductor 7 melts, or when a large current exceeding the rated value flows through the protection element 1 and the fusible conductor 7 melts due to self-heating (Joule heat).

[0041] [Heat-generating element lead-out electrode]

[0042] The heat generating body lead-out electrode 6 is provided in a region between the first electrode 4 and the second electrode 5, and one end thereof is connected to an intermediate electrode 14 described later. The heat generating body lead-out electrode 6 is connected to a soluble conductor 7 between the first and second electrodes 4 and 5 via a bonding material such as solder.

[0043] [Connection]

[0044] The first electrode 4 , the second electrode 5 , and the heat-generating body lead-out electrode 6 form a connection portion 8 to which the soluble conductor 7 is connected. Figure 3 4 is a cross-sectional view showing the connection portion 8 of the first electrode 4. Figure 1 , Figure 3 As shown, the connection portion 8 is formed by laminating the connection electrode 10 along the portion where the soluble conductor 7 is connected to the first electrode 4 and the second electrode 5, for example, the inner edges of the first and second electrodes 4 and 5, and in the center of the heating element lead-out electrode 6. The soluble conductor 7 is connected to the connection electrode 10 via a connection material such as a connection solder.

[0045] The connection electrode 10 is preferably formed of the same component as the first and second electrodes 4, 5, and the heating element extraction electrode 6. For example, the connection electrode 10 is formed by printing Ag paste in a predetermined pattern by screen printing and then firing at a predetermined temperature, so that the molten glass component contained in the Ag paste is laminated and integrated with the previously formed first and second electrodes 4, 5, and the heating element extraction electrode 6. As a result, the connection portion 8 has a sufficient thickness, so that the glass component will not precipitate, and the conductivity and connectivity with the fusible conductor 7 can be maintained.

[0046] In addition, the connection portion 8 is formed thicker than the thickness of other portions, and the connection electrode 10 protrudes on the first and second electrodes 4 and 5 and the heat-generating body lead-out electrode 6. As a result, heat and pressure from the outside can be effectively transmitted to the connection electrode 10 that is the connection portion with the soluble conductor 7. Therefore, for example, when the soluble conductor 7 is mounted on the connection electrode 10 with a soldering iron, the heat and pressure will not spread to the entire first and second electrodes 4 and 5, and can be efficiently supplied to the connection electrode 10.

[0047] In addition, since the connection portion 8 is formed thicker than other portions, it is possible to prevent the molten body of the connection solder or the like that connects the soluble conductor 7 from agglomerating at the connection portion 8 and flowing out to the outer edge side of the first and second electrodes 4 and 5 when the soluble conductor 7 is mounted. Thus, it is possible to prevent the molten body of the connection solder or the like from wetting and spreading to the first and second external connection electrodes 11 and 12, and it is possible to maintain the connection of the soluble conductor 7 and the connection between the protection element 1 and the external circuit board.

[0048] like Figure 1 As shown, the connection portion 8 preferably has an area substantially equal to that of the soluble conductor 7 on the first and second electrodes 4 and 5. If the connection portion 8 is too small compared to the soluble conductor 7, there is a possibility that the on-resistance increases. In addition, even if the area of ​​the connection portion 8 is too large compared to the soluble conductor 7, the effect of reducing the amount of electrode material used is reduced. Therefore, with respect to the size of the connection portion 8, it is preferred that when the soluble conductor 7 is arranged, the connection portion 8 is formed so that the overlapping area ratio of the soluble conductor 7 on the first and second electrodes 4 and 5 to the connection portion 8 is 90% to 110%.

[0049] The thickness of the connecting portion 8 (i.e., the total thickness of the first electrode 4 and the connecting electrode 10, the total thickness of the second electrode 5 and the connecting electrode 10, and the total thickness of the heating element lead-out electrode 6 and the connecting electrode 10) is preferably 20 μm or more. Thus, during the formation process of the connecting electrode 10 and the installation process of the fusible conductor 7, the precipitation of glass components on the surface of the connecting electrode 10 can be suppressed, and the conductivity and mechanical connection reliability of the fusible conductor 7 can be ensured.

[0050] The first and second electrodes 4 and 5 and the heat generating body lead-out electrode 6 preferably have a thickness of 10 μm or more. This can suppress precipitation of glass components in regions other than the connection portion 8 and ensure mechanical connection reliability with the insulating substrate 2.

[0051] The thickness of the connection portion 8 is preferably at least twice the thickness of the portion other than the connection portion 8 of the first and second electrodes 4, 5, and the heating element lead electrode 6. By increasing the number of printing times in the connection portion 8, the thickness of the connection portion 8 becomes thicker than the thickness of the portion other than the connection portion, thereby improving the wettability of the bonding material such as the connection solder used to connect the soluble conductor 5. In addition, the printing and firing of the conductive paste forming the first and second electrodes 4, 5, the heating element lead electrode 6, and the connection electrode 10 can be formed with a desired thickness by repeating the printing and firing multiple times.

[0052] In addition, if Figure 4 As shown, the connection portion 8 may be formed slightly inside the inner edge of the first electrode 4 and the second electrode 5. The connection portion 8 is formed thicker than other portions and protrudes, so when the fusible conductor 7 is melted, tension is actively applied to the first and second electrodes 4 and 5, so that the molten conductor 7a is aggregated on the connection portion 8, and the first electrode 4 and the heating element lead-out electrode 6 and the second electrode 5 and the heating element lead-out electrode 6 can be melted more quickly. At this time, the connection portion 8 is formed slightly inside the inner edge of the first electrode 4 and the second electrode 5, so that the molten conductor 7a aggregated on each connection portion 8 after melting can be prevented from contacting, thereby improving insulation reliability.

[0053] It should be noted that it is preferable to apply a coating such as Ni / Au plating, Ni / Pd plating, or Ni / Pd / Au plating on the surfaces of the first and second electrodes 4 and 5 and the connecting portion 8 by a known method such as plating. As a result, the protection element 1 can prevent oxidation of the first and second electrodes 4 and 5 and the connecting portion 8, and prevent a change in the rated value associated with an increase in the on-resistance. In addition, when the protection element 1 is reflow mounted, it is possible to prevent the connecting solder for connecting the fusible conductor 7 from melting and corroding the connecting portion 8 (solder erosion).

[0054] It should be noted that the first and second electrodes 4 and 5 may also be provided with a limiting wall, which prevents the connection solder provided on the electrodes of the external circuit substrate connected to the first and second external connection electrodes 11 and 12 from melting during reflow mounting, climbing up to the first and second electrodes 4 and 5 through the castellations, and wetting and spreading. The limiting wall can be formed using an insulating material that does not have wettability to solder, such as glass, solder resist, and insulating adhesive, and can be formed on the first and second electrodes 4 and 5 by printing, etc. By providing the limiting wall, the molten connection solder can be prevented from wetting and spreading to the first and second electrodes 4 and 5, and the connectivity between the protection element 1 and the external circuit substrate can be maintained.

[0055] [Heat generating element]

[0056] like Figure 1 As shown in (B), a heating element 3 is formed on the back side 2b of the insulating substrate 2. The heating element 3 is a conductive component having a relatively high resistance value and generating heat when electricity is applied, and is made of, for example, nickel-chromium alloy, W, Mo, Ru, etc., or a material containing them. The heating element 3 can be formed by mixing powders of these alloys or compositions or compounds with a resin binder, etc. to form a paste, and then forming a pattern on the insulating substrate 2 using a screen printing technique, and performing firing, etc. As an example, the heating element 3 can be formed as follows: a mixed paste of ruthenium oxide paste, silver and glass paste is modulated according to a specified voltage, and a film is formed at a specified position and area on the back side 2b of the insulating substrate 2, and then a firing treatment is performed under appropriate conditions. In addition, the shape of the heating element 3 can be appropriately designed, but as Figure 1 As shown in (B), in order to maximize the heat generation area, it is preferable to set it in a substantially rectangular shape according to the shape of the insulating substrate 2.

[0057] In addition, one end 3a of the heating element 3 is connected to the first extraction electrode 15, and the other end 3b is connected to the second extraction electrode 16. The first extraction electrode 15 is formed by being drawn out from the heating element electrode 17 along the one end 3a of the heating element 3. Figure 1 In the protection element 1 shown in FIG. 1 , the second lead electrode 16 extends along one side edge of the heating element 3 formed in a substantially rectangular shape and overlaps with one side edge of the heating element 3. Similarly, the second lead electrode 16 is formed by leading from the intermediate electrode 14 along the other end 3b of the heating element 3. Figure 1 In the illustrated protection element 1 , the protection element 1 extends along the other side edge of the heat generating element 3 formed in a substantially rectangular shape and overlaps with the other side edge of the heat generating element 3 .

[0058] The heating element electrode 17 and the intermediate electrode 14 are formed on the side edges of the insulating substrate 2 that are opposite to the side edges on which the first and second electrodes 4 and 5 are provided. The heating element electrode 17 is a power supply electrode for supplying power to the heating element 3, is connected to one end portion 3a of the heating element 3 via the first lead-out electrode 15, and functions as an external connection electrode when the protection element 1 is connected to an external circuit.

[0059] The heating element electrode 17, the first lead electrode 15, the second lead electrode 16 and the intermediate electrode 14 can be formed by printing and firing a conductive paste such as Ag, Cu or an alloy thereof, similarly to the first electrode 4 and the second electrode 5. In addition, by making these electrodes formed on the back surface 2b of the insulating substrate 2 from the same material, they can be formed by a single printing and firing process.

[0060] The intermediate electrode 14 is an electrode provided between the heating element 3 and the heating element lead-out electrode 6 provided on the surface 2a of the insulating substrate 2, and is connected to the other end 3b of the heating element 3 and is connected to the heating element lead-out electrode 6 formed on the surface 2a of the insulating substrate 2 via the castellations. The heating element lead-out electrode 6 overlaps with the heating element 3 via the insulating substrate 2 and is connected to the fusible conductor 7.

[0061] [Insulation protective layer]

[0062] In addition, the heating element 3, the first extraction electrode 15, and the second extraction electrode 16 may also be covered by an insulating protective layer 9. The insulating protective layer 9 is provided to protect and insulate the heating element 3, and is composed of an insulating material such as glass that is heat-resistant to the heating temperature of the heating element 3. Examples of glass raw materials constituting the insulating material 9 include glass paste for outer coating of silica-based glass and glass paste for insulation.

[0063] The insulating protective layer 9 can be formed by applying and firing the glass-based paste using screen printing or the like. Figure 1 In the protection element 1 shown, the insulating protection layer 9 is formed so as to cover the heating element 3 , the first extraction electrode 15 , and the second extraction electrode 16 formed on the back surface 2 b of the insulating substrate 2 .

[0064] The thickness of the insulating protective layer 9 is set from the viewpoint of the coating property of the glass paste or the like and the cutting time of the fusible conductor 7. That is, the thickness of the insulating protective layer 9 is appropriately set according to the coating property of the glass paste or the like and the required cutting time of the fusible conductor 7, and is, for example, 10 μm or more and 40 μm or less, preferably 20 μm or more and 40 μm or less.

[0065] [Fusible conductor]

[0066] Next, the soluble conductor 7 is described. The soluble conductor 7 is installed across the first and second electrodes 4 and 5, and is melted by heat generated by the energization of the heating element 3, or melted by self-heating (Joule heat) due to the energization of a current exceeding the rated value, thereby cutting off the current path between the first electrode 4 and the second electrode 5. The soluble conductor 7 is connected to the first and second electrodes 4 and 5 and the heating element lead-out electrode 6 via a bonding material such as a connecting solder.

[0067] The fusible conductor 7 can be any conductive material that melts due to the heat generated by the energization of the heating element 3 or an overcurrent state, for example, SnAgCu-based Pb-free solder, BiPbSn alloy, BiPb alloy, BiSn alloy, SnPb alloy, PbIn alloy, ZnAl alloy, InSn alloy, PbAgSn alloy, etc.

[0068] In addition, the fusible conductor 7 may also be a structure containing a high melting point metal and a low melting point metal. Figure 5 As shown, the soluble conductor 7 is a laminated structure composed of an inner layer and an outer layer, and has a low melting point metal layer 18 as the inner layer and a high melting point metal layer 19 as the outer layer laminated on the low melting point metal layer 18 .

[0069] The low melting point metal layer 18 is preferably solder or a metal with Sn as the main component, which is a material generally called Pb-free solder. The melting point of the low melting point metal layer 18 does not necessarily need to be higher than the reflow temperature, and it can also melt at around 200°C. The high melting point metal layer 19 is a metal layer stacked on the surface of the low melting point metal layer 18, such as Ag or Cu or a metal with any of them as the main component, and has a high melting point that does not melt even when the first and second electrodes 4, 5 and the heating element lead-out electrode 6 are connected to the soluble conductor 7 by reflow, and the protection element 1 is installed on the external circuit substrate.

[0070] Such a soluble conductor 7 can be formed by forming a high melting point metal layer on a low melting point metal foil using a plating technique, or can also be formed using other well-known lamination techniques or film formation techniques. In addition, the soluble conductor 7 may be a structure in which the entire surface of the low melting point metal layer 18 is covered by the high melting point metal layer 19, or a structure in which the surface is covered except for a pair of opposing side surfaces. It should be noted that the soluble conductor 7 may also be configured with the high melting point metal layer 19 as an inner layer and the low melting point metal layer 18 as an outer layer, or may be formed by a multilayer structure of three or more layers in which the low melting point metal layer 18 and the high melting point metal layer 19 are alternately laminated, or by providing an opening in a part of the outer layer to expose a part of the inner layer, etc.

[0071] The soluble conductor 7 is formed by laminating the high melting point metal layer 19 as an outer layer on the low melting point metal layer 18 as an inner layer, so that the shape of the soluble conductor 7 can be maintained and it will not be melted even when the reflow temperature exceeds the melting temperature of the low melting point metal layer 18. Therefore, the first and second electrodes 4, 5 and the heating element lead electrode 6 can be efficiently connected to the soluble conductor 7 by reflow, and the protection element 1 can be mounted on the external circuit board. In addition, even by reflow, it is possible to prevent the melting characteristics from changing, such as not melting at a predetermined temperature or melting at a temperature lower than a predetermined temperature, due to the resistance value locally increasing or decreasing due to deformation of the soluble conductor 7.

[0072] The fusible conductor 7 does not melt due to self-heating while a predetermined rated current flows. When a current higher than the rated value flows, the fusible conductor 7 melts due to self-heating, thereby cutting off the current path between the first and second electrodes 4 and 5. The heating element 3 heats up and melts due to power-on, thereby cutting off the current path between the first and second electrodes 4 and 5.

[0073] At this time, in the fusible conductor 7, the molten low melting point metal layer 18 dissolves (solder erodes) the high melting point metal layer 19, so that the high melting point metal layer 19 melts at a temperature lower than the melting temperature. Therefore, the fusible conductor 7 can be melted in a short time by the erosion of the high melting point metal layer 19 by the low melting point metal layer 18. In addition, the molten conductor 7a of the fusible conductor 7 is cut off by the physical attraction of the connecting portion 8 provided on the heating element lead-out electrode 6 and the first and second electrodes 4 and 5, so that the current path between the first and second electrodes 4 and 5 can be quickly and reliably cut off ( Figure 2 ).

[0074] In addition, the soluble conductor 7 is preferably formed so that the volume of the low melting point metal layer 18 is larger than the volume of the high melting point metal layer 19. The soluble conductor 7 is heated by self-heating caused by overcurrent or heating of the heating element 3, and the low melting point metal melts and corrodes the high melting point metal, thereby being able to melt and fuse quickly. Therefore, by forming the soluble conductor 7 so that the volume of the low melting point metal layer 18 is larger than the volume of the high melting point metal layer 19, the corrosion effect can be promoted and the first and second electrodes 4 and 5 can be quickly cut off.

[0075] In addition, the fusible conductor 7 is composed of a high melting point metal layer 19 stacked on a low melting point metal layer 18 as an inner layer, so the melting temperature can be greatly reduced compared to conventional chip fuses composed of high melting point metals. Therefore, the fusible conductor 7 can increase the cross-sectional area and greatly increase the current rating compared to chip fuses of the same size. In addition, compared to existing chip fuses with the same current rating, it can be miniaturized and thinned, and has excellent rapid melting properties.

[0076] In addition, the fusible conductor 7 can improve the resistance (pulse resistance) to surges of abnormally high voltages applied instantaneously to the electrical system in which the protection element 1 is assembled. That is, the fusible conductor 7 will not melt even if a current of, for example, 100A flows for several milliseconds. In this regard, since a large current flowing in a very short time flows through the surface layer of the conductor (skin effect), the fusible conductor 7 is provided with a high melting point metal layer 19 such as an Ag plating layer with a low resistance value as an outer layer, so that the current applied by the surge easily flows, and melting due to self-heating can be prevented. Therefore, the fusible conductor 7 can greatly improve the resistance to surges compared to conventional fuses made of solder alloys.

[0077] It should be noted that, in order to resist oxidation and improve wettability during melting, the fusible conductor 7 may also be coated with flux (not shown). In addition, the protection element 1 is covered by the housing 30 through the insulating substrate 2 to protect its interior. The housing 30 can be formed using insulating components such as various engineering plastics, thermoplastics, ceramics, and glass epoxy substrates. In addition, the housing 30 has an internal space sufficient for the fusible conductor 7 to expand into a spherical shape when melted on the surface 2a of the insulating substrate 2, and for the molten conductor 7a to condense on the heating element lead-out electrode 6, the first and second electrodes 4, 5.

[0078] [Circuit Configuration Example]

[0079] Such a protection element 1 is used by being incorporated into a circuit in a battery pack 20 of a lithium-ion secondary battery. The battery pack 20 has a plurality of battery stacks 25, for example, Figure 6 As shown, the battery stack 25 is composed of a total of four lithium-ion secondary battery cells 21 a to 21 d.

[0080] The battery pack 20 includes a battery stack 25, a charge and discharge control circuit 26 for controlling the charge and discharge of the battery stack 25, a protection element 1 applying the present invention for cutting off the charge and discharge path when an abnormality occurs in the battery stack 25, a detection circuit 27 for detecting the voltage of each battery cell 21a to 21d, and a current control element 28 as a switching element for controlling the operation of the protection element 1 according to the detection result of the detection circuit 27.

[0081] The battery stack 25 is formed by connecting in series the battery cells 21a to 21d that need to be controlled to be protected from overcharge and overdischarge, and the battery stack 25 is detachably connected to the charging device 22 via the positive terminal 20a and the negative terminal 20b of the battery pack 20, and is applied with a charging voltage from the charging device 22. The battery pack 20 charged by the charging device 22 can be operated by connecting the positive terminal 20a and the negative terminal 20b to an electronic device that uses the battery to operate.

[0082] The charge and discharge control circuit 26 includes two current control elements 23a and 23b connected in series on the 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 and 23b. The current control elements 23a and 23b are composed of, for example, field effect transistors (hereinafter referred to as FETs), and the control unit 24 controls the gate voltage to control the conduction and disconnection of the current path to the battery stack 25 in the charging direction and / or the discharging direction. The control unit 24 operates by receiving power supply from the charging device 22, and controls the operation of the current control elements 23a and 23b to disconnect the current path when the battery stack 25 is over-discharged or over-charged according to the detection result of the detection circuit 27.

[0083] The protection element 1 is connected to, for example, a charge and discharge current path between the battery stack 25 and the charge and discharge control circuit 26 , and its operation is controlled by a current control element 28 .

[0084] The detection circuit 27 is connected to each battery cell 21a to 21d, detects the voltage value of each battery cell 21a to 21d, and provides each voltage value to the control unit 24 of the charge and discharge control circuit 26. In addition, the detection circuit 27 outputs a control signal for controlling the current control element 28 when any of the battery cells 21a to 21d reaches an overcharge voltage or an overdischarge voltage.

[0085] The current control element 28 is composed of, for example, a FET, and when the voltage value of the battery cells 21a to 21d exceeds the voltage of a specified over-discharge or over-charge state based on the detection signal output from the detection circuit 27, control is performed to activate the protection element 1, thereby cutting off the charge and discharge current path of the battery stack 25 regardless of the switching operation of the current control elements 23a and 23b.

[0086] The protection element 1 to which the present invention is applied and used in the battery pack 20 having the above-mentioned structure has Figure 7 The circuit configuration is as shown. That is, in the protection element 1, the first external connection electrode 11 is connected to the battery stack 25 side, and the second external connection electrode 12 is connected to the positive terminal 20a side, so that the soluble conductor 7 is connected in series to the charge and discharge path of the battery stack 25. In addition, the heating element 3 of the protection element 1 is connected to the current control element 28 via the heating element electrode 17, and the heating element 3 is connected to the battery stack 25. In this way, one end of the heating element 3 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. Thus, a power supply path to the heating element 3 is formed, in which power supply can be controlled by the current control element 28.

[0087] [Operation of protection element]

[0088] When the detection circuit 27 detects an abnormal voltage in any of the battery cells 21a to 21d, a cutoff signal is output to the current control element 28. Then, the current control element 28 controls the current to energize the heating element 3. In the protection element 1, the current flows from the battery stack 25 to the heating element 3, whereby the heating element 3 starts to generate heat. The protection element 1 causes the fusible conductor 7 to melt due to the heat generated by the heating element 3, thereby cutting off the charge and discharge path of the battery stack 25. In addition, the protection element 1 is formed by making the fusible conductor 7 contain a high melting point metal and a low melting point metal, so that the low melting point metal melts before the high melting point metal melts, and the fusible conductor 7 can be melted in a short time by utilizing the corrosion effect of the molten low melting point metal on the high melting point metal.

[0089] The molten conductor 7a of the fusible conductor 7 is aggregated at the connection portion 8 formed between the first electrode 4, the second electrode 5 and the heating element lead-out electrode 6, and the electrodes are cut off. Since the connection electrode 10 protrudes from the connection portion 8, the tension is actively applied to the first and second electrodes 4 and 5 to aggregate the molten conductor 7a at the connection portion 8, and the connection between the first electrode 4 and the heating element lead-out electrode 6 and the connection between the second electrode 5 and the heating element lead-out electrode 6 can be more quickly cut off. In addition, the fusible conductor 7 can be quickly cut off, so that the heating element 3 can be prevented from being damaged before the fusible conductor 7 is cut off, and the current path can be cut off safely and quickly.

[0090] The protection element 1 is melted by the fusible conductor 7 , and the power supply path to the heating element 3 is also cut off, so that the heating element 3 stops generating heat.

[0091] It should be noted that, even when an overcurrent exceeding the rated value flows through the battery pack 20 of the protection element 1 , the soluble conductor 7 melts due to self-heating, and the charge and discharge path of the battery pack 20 can be cut off.

[0092] In this way, the protection element 1 melts the fusible conductor 7 by the heat generated by the energization of the heating element 3 or the self-heating of the fusible conductor 7 caused by the overcurrent. As described above, even when the protection element 1 is mounted on the circuit board during reflow, and the circuit board on which the protection element 1 is mounted is further exposed to a high temperature environment such as reflow heating, the deformation of the fusible conductor 7 is suppressed by having a structure in which the low melting point metal is covered by the high melting point metal. Therefore, the change in the fusing characteristics caused by the change in the resistance value caused by the deformation of the fusible conductor 7 can be prevented, and the fusible conductor 7 can be quickly melted by a predetermined overcurrent or the heat generated by the heating element 3.

[0093] The protection element 1 of the present invention is not limited to being used in a battery pack of a lithium-ion secondary battery, but can be applied to various uses that require interruption of a current path using an electric signal.

[0094] [Modification 1]

[0095] A modification of the protection element to which the present technology is applied will be described. In the following description, the same reference numerals may be given to the same components as those of the protection element 1 described above, and detailed description thereof may be omitted. Figure 8 The protection element 40 shown has a heating element 3 , a first extraction electrode 15 , a second extraction electrode 16 , a heating element electrode 17 , and an insulating protection layer 9 formed on a surface 2 a of an insulating substrate 2 , and other structures are the same as those of the protection element 1 described above.

[0096] Fig. 9 This is a top view showing the protective element 40 with the housing 30, the heating element lead-out electrode 6, and the soluble conductor 7 omitted. The heating element electrode 17 and the intermediate electrode 14 are formed on the side edges of the surface 2a of the insulating substrate 2 that are opposite to the side edges where the first and second electrodes 4 and 5 are provided. The heating element electrode 17 is continuous with the third external connection electrode 13 formed on the back surface 2b of the insulating substrate 2 via the castellations. The third external connection electrode 13 is connected to the current control element 28 by mounting the protective element 40 on an external circuit.

[0097] It should be noted that the heating element electrode 17, like the first and second electrodes 4 and 5, can also be provided with a limiting wall, which prevents the connecting solder provided on the electrode of the external circuit substrate connected to the third external connection electrode 13 from melting during reflow installation, climbing up the heating element electrode 17 through the castellations, and wetting and spreading on the heating element electrode 17.

[0098] The heating element 3, the first lead electrode 15, and the second lead electrode 16 are formed in the region between the first electrode 4 and the second electrode 5, and are covered by the insulating protective layer 9. In addition, one end of the heating element lead electrode 6 is connected to the intermediate electrode 14 and is formed on the insulating protective layer 9, thereby overlapping with the heating element 3 via the insulating protective layer 9.

[0099] In the protection element 40 , since the heat generating element 3 is formed on the surface 2 a of the insulating substrate 2 similarly to the soluble conductor 7 , the heat of the heat generating element 3 is easily transferred to the soluble conductor 7 .

[0100] [Modification 2]

[0101] Next, other modified examples of the protection element to which the present technology is applied are described. In the following description, the same reference numerals are sometimes used to denote the same components as the above-mentioned protection elements 1 and 40, and their detailed description is omitted. Fig.10 As shown, the protection element 50 applicable to the present technology omits the heating element lead-out electrode 6, and separates the current path of the soluble conductor 7 and the current path of the heating element 3. One end of the heating element 3 provided on the back surface 2b of the insulating substrate 2 is connected to the heating element electrode 17 via the first lead-out electrode 15, and the other end is connected to the intermediate electrode 14 via the second lead-out electrode 16.

[0102] Fig.11 : is a diagram showing the circuit structure of the protection element 50. The protection element 50 is installed in an external circuit, so that the first external connection electrode 11 is connected to the battery stack 25 side, and the second external connection electrode 12 is connected to the positive terminal 20a side, thereby the soluble conductor 7 is connected in series to the charge and discharge path of the battery stack 25. The heating element 3 is connected to the current control element 28 via the heating element electrode 17, and is connected to the battery stack 25. In addition, the heating element 3 is connected to the ground wire (not shown) via the intermediate electrode 14. Thus, a power supply path to the heating element 3 is formed, in which the power supply can be controlled by the current control element 28. When the soluble conductor 7 is blown, the protection element 50 stops the power supply to the heating element 3 through the detection circuit 27 and the current control element 28 that detect this situation.

[0103] Description of Reference Numerals

[0104] 1: protection element, 2: insulating substrate, 3: heating element, 4: first electrode, 5: second electrode, 6: heating element lead-out electrode, 7: fusible conductor, 8: connecting part, 9: insulating protection layer, 10: connecting electrode, 11: first external connection electrode, 12: second external connection electrode, 13: third external connection electrode, 14: intermediate electrode, 15: first lead-out electrode, 16: second lead-out electrode, 17: heating element electrode, 18: low melting point metal layer, 19: high melting point metal layer, 20: battery pack, 21: battery cell, 22: charging device, 23: current control element, 24: control part, 25: battery stack, 26: charge and discharge control circuit, 27: detection circuit, 28: current control element, 30: casing, 40: protection element, 50: protection element.

Claims

1. A protection element, characterized in that: have: Insulating substrate, A heating element is disposed on the insulating substrate. The first electrode and the second electrode are disposed on the insulating substrate. a heating element lead-out electrode disposed between the first electrode and the second electrode and electrically connected to one end of the heating element, and A fusible conductor is disposed on the surfaces of the first electrode, the second electrode and the heating element lead-out electrode, and electrically connects the first electrode to the heating element lead-out electrode and the second electrode to the heating element lead-out electrode; The thickness of the connection part of the first electrode, the second electrode, and the heat generating body lead-out electrode connected to the soluble conductor is formed thicker than the thickness of other parts.

2. The protection element according to claim 1, wherein: The connecting portion is composed of a portion of each of the first electrode, the second electrode, and the heat generating body lead-out electrode where the soluble conductor is mounted, and a connecting electrode stacked on the portion.

3. The protection element according to claim 2, wherein: The connecting electrode has the same component as that of the first electrode, the second electrode, or the heat generating body lead-out electrode that are stacked respectively.

4. The protection element according to any one of claims 1 to 3, wherein: The thickness of the connecting portion is greater than 20 μm.

5. The protection element according to claim 4, wherein: The first electrode, the second electrode, and the heat generating body lead-out electrode have a thickness of 10 μm or more.

6. The protection element according to claim 1 or 2, wherein: The thickness of the connection portion is at least twice the thickness of the first electrode, the second electrode, or the heat generating body lead-out electrode that are stacked respectively, at a portion other than the connection portion.

7. The protection element according to any one of claims 1 to 3, wherein: The heating element is formed on a back surface of the insulating substrate opposite to a surface on which the soluble conductor is provided.

8. The protection element according to any one of claims 1 to 3, wherein: The heating element is formed on the surface of the insulating substrate on which the fusible conductor is provided, the protection element has an insulating protection layer covering the heating element, and the heating element lead-out electrode is provided on the insulating protection layer.

9. The protection element according to any one of claims 1 to 3, wherein: The insulating substrate is a ceramic substrate.

10. A protection element, characterized in that: have: Insulating substrate, The heating element is arranged on the back side of the insulating substrate. The first electrode and the second electrode are disposed on the insulating substrate, and A fusible conductor is disposed on the surfaces of the first electrode and the second electrode to electrically connect the first electrode and the second electrode; The thickness of the connection part of the first electrode and the second electrode connected to the soluble conductor is formed thicker than the thickness of other parts.

11. The protection element according to claim 10, wherein: The connecting portion is composed of a portion of each of the first electrode and the second electrode where the soluble conductor is mounted and a connecting electrode stacked on the portion.

12. A method for manufacturing a protection element, comprising: The process of forming a first electrode, a second electrode and a heating element lead-out electrode disposed between the first electrode and the second electrode by printing a conductive paste on an insulating substrate and firing the conductive paste, and A step of forming a connection electrode connected to a fusible conductor by printing a conductive paste on the first electrode, the second electrode and the heating element lead-out electrode and firing the conductive paste, wherein the fusible conductor connects the first electrode and the heating element lead-out electrode and the second electrode and the heating element lead-out electrode; The thickness of the connection part of the first electrode, the second electrode, and the heat generating body lead-out electrode connected to the soluble conductor is formed thicker than the thickness of other parts.

13. A method for manufacturing a protection element, comprising: The process of forming the first electrode and the second electrode by printing the conductive paste on the insulating substrate and firing it, and a step of forming a connection electrode connected to a fusible conductor by printing and firing a conductive paste on the first electrode and the second electrode, the fusible conductor connecting the first electrode and the second electrode; The thickness of the connection part of the first electrode and the second electrode connected to the soluble conductor is formed thicker than the thickness of other parts.

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