Protection element and battery pack

Abstract

The present invention provides a protective element that prevents fuse elements from breaking and can also cope with high current, and a battery pack using the same. The protective element of the present invention comprises: a substrate 2 having a first electrode 3 and a second electrode 4 connected to an external circuit; a fusible conductor 5 having one side 5a supported on the substrate 2 and connected to the first electrode 3 and the second electrode 4; and a substrate 7 with a heating element having a heating element 6 that melts the fusible conductor 5 by heating; the other side 5b of the fusible conductor 5 is at a contact point with the substrate 7 with the heating element.

Description

Technical Field

[0001] This technology relates to a protective element that protects a circuit connected in a current path by melting the current path, and a battery pack using the same. Prior Technology

[0002] Most rechargeable and reusable batteries are manufactured into battery packs and then provided to users. Especially in lithium-ion batteries with high energy density, in order to ensure the safety of users and electronic devices, several protection circuits such as overcharge protection and over-discharge protection are generally built into the battery pack, which can cut off the output of the battery pack under certain circumstances.

[0003] As a protection element for protection circuits of lithium-ion batteries, etc., the following structure is used: a heating element is provided inside the protection element, and the fusible conductor in the current path is melted by the heating of the heating element.

[0004] The applications of lithium-ion batteries have been expanding in recent years, extending to higher current applications such as power tools like electric screwdrivers, and transportation vehicles like hybrids, electric cars, and electric-assisted bicycles. These applications involve situations, particularly during startup, where currents exceeding tens to hundreds of A are required. The industry has long sought protective components to handle such high current capacities. Furthermore, with the increasing adoption of various applications, there is a growing demand for components with smaller size and lower profile, reducing layout constraints.

[0005] In order to realize a protective element to cope with such a large current, a protective element is proposed that uses a fusible conductor with an increased cross-sectional area and connects the fusible conductor to the surface of an insulating substrate on which a heating element is formed.

[0006] Figure 13 is a diagram showing one example of the configuration of the previous protective element. (A) is a top view with the cover member omitted, and (B) is a cross-sectional view along A-A'. The protective element 100 shown in Figure 13 includes: an insulating substrate 101; first and second electrodes 102 and 103, which are connected to the current path of an external circuit via first and second external connecting electrodes 102a and 103a formed on the front and back sides of the insulating substrate 101; a heating element 104 formed on the front side of the insulating substrate 101, which heats up when energized; an insulating layer 105 covering the heating element 104; a heating element lead-out electrode 106 deposited on the insulating layer 105 and connected to the heating element 104; and a fuse element 107 mounted across the first electrode 102, the heating element lead-out electrode 106, and the second electrode 103 via a connecting solder.

[0007] The heating element 104 is connected to a heating element power supply electrode 108 formed on the front side of the insulating substrate 101. The heating element power supply electrode 108 is connected to a third external connection electrode (not shown) formed on the back side of the insulating substrate 101 via a toothed structure. The heating element 104 is connected to an external power supply provided in an external circuit via the third external connection electrode. Furthermore, the heating element 104 continuously controls the current and heat generation by means of a switching element (not shown).

[0008] The heating element 104 is covered by an insulating layer 105 including a glass layer, and overlaps with the heating element lead-out electrode 106 formed on the insulating layer 105 through the insulating layer 105. The insulating layer 105 is formed, for example, by printing and firing glass paste. Furthermore, a fuse element 107 is connected to the heating element lead-out electrode 106, spanning between the first and second electrodes 102 and 103.

[0009] The fuse element 107 is thermally connected to the heating element 104 by overlapping the insulating layer 105 and the heating element 104. Once the heating element 104 heats up due to the power supply, it will melt.

[0010] The fuse element 107 is formed of a low-melting-point metal such as Pb-free solder, or has a multilayer structure in which a low-melting-point metal is coated with a high-melting-point metal. Furthermore, the fuse element 107 forms part of the current path of the external circuit in which the protection element 100 is assembled, by connecting the first electrode 102 to the second electrode 103 via the lead-out electrode 106 from the heating element 104. Moreover, the fuse element 107 breaks by self-heating (Joule heating) when a current exceeding its rated value flows, or by melting due to the heating element 104, thus blocking the connection between the first and second electrodes 102 and 103.

[0011] Furthermore, if the protection element 100 needs to cut off the current path of the external circuit, it energizes the heating element 104 via a switching element. The heating element 104 then heats up to a high temperature, causing the fuse element 107 assembled on the current path of the external circuit to melt. The molten conductor of the fuse element 107 is attracted by the more wettable heating element lead-out electrode 106 and the first and second electrodes 102 and 103. Thus, the fuse element 107 melts between the first electrode 102, the heating element lead-out electrode 106, and the second electrode 103, thus cutting off the current path of the external circuit. [Previous Technical Documents] [Patent Literature]

[0012] [Patent Document 1] Japanese Patent No. 6030431 [Patent Document 2] Japanese Patent Application Publication No. 2016-225090 [Patent Document 3] Japanese Patent Application Publication No. 2015-228302 Summary of the Invention

[0013] [The problem the invention aims to solve]

[0014] The low-melting-point metal constituting the fuse element 107 has a melting point of about 300°C, and the heating element 104, which is melted from it, is required to be able to heat up to about 1000°C. Furthermore, the insulating substrate 101 on which the heating element 104 is mounted is also required to withstand the heat intensity generated by the heating element 104, and a ceramic substrate or the like is used.

[0015] Furthermore, since it is positioned in the power path, the fuse element 107, which is a conductor, must be connected at least two of the first and second electrodes 102 and 103.

[0016] Furthermore, it has also been proposed that: a structure in which a heating element is built into a cover member covering the fuse element for the purpose of assisting the heating element of the insulating substrate (Patent Document 1); a structure in which a conductive elastic member is placed between the fuse element and the constituent members on the housing side for the purpose of protecting the fuse element from thermal shock, thereby dispersing and mitigating stress (Patent Document 2); and a structure in which external electrode terminals are prepared and the fuse element is formed to support only the surface electrode of the insulating substrate on which the heating element is provided, thereby dispersing stress (Patent Document 3).

[0017] The inventions described in patent documents 1-3 listed above can provide protective elements with very simple construction and extremely high safety. However, their construction involves connecting a fuse element containing a low-melting-point metal (mainly a solder alloy of tin or lead) to a heat-resistant insulating substrate (mainly a ceramic substrate) that is resistant to heat. When these ceramic substrates and fuse elements are exposed to thermal cycles, mechanical stress will be generated due to the difference in their coefficients of linear expansion. This stress may cause the fuse element, which has lower mechanical strength than the ceramic substrate, to gradually tear.

[0018] Especially when the cross-sectional area of ​​low-melting-point metals is increased to cope with high current, the stress caused by linear expansion increases, which tends to shorten the time until the fuse element breaks.

[0019] Although the inventions described in Patent Documents 2-3 are constructed using conductive elastic components or external electrodes, they also have some problems, such as the increase in conductor resistance due to the addition of conductive components, making them unsuitable for high current applications; and the increase in size or manufacturing steps and cost due to the addition of external electrodes.

[0020] Therefore, the purpose of this technology is to provide a protective element that prevents fuse elements from breaking and can also cope with high current, as well as a battery pack using it. [Technical means to solve the problem]

[0021] To solve the above problems, the protective element of this technology includes: a substrate having a first electrode and a second electrode connected to an external circuit; a fusible conductor having one side supported on the substrate and connected to the first electrode and the second electrode; and a substrate with a heating element having a heating element that melts the fusible conductor by heating; and the other side of the fusible conductor having a contact point with the substrate with the heating element at one point.

[0022] Furthermore, the battery pack of this technology includes: one or more battery cells; a protection element connected to the charging and discharging path of the battery cells and blocking the charging and discharging path; and a current control element that detects the voltage value of the battery cells and controls the energization of the protection element; the protection element includes: a substrate having a first electrode and a second electrode connected to an external circuit; a fusible conductor having one side supported on the substrate and connected to the first electrode and the second electrode; and a substrate with a heating element having a heating element that melts the fusible conductor by heating; and the other side of the fusible conductor has a contact point with the substrate with the heating element at one location. [Effects of the Invention]

[0023] According to this technology, since the connection point between the fusible conductor and the substrate carrying the heating element is only one point, the fusible conductor will not suffer damage such as deformation or breakage due to internal stress even when repeatedly exposed to high-temperature and low-temperature environments, thus exhibiting stability in shape or size. Therefore, the resistance value of the fusible conductor in the protective components and battery pack of this technology is stable and can maintain a high rated value. Simple Explanation of the Diagram

[0024] Figure 1 shows a protective element using this technology. (A) is a top view, (B) is a cross-sectional view along line B-B', and (C) is a cross-sectional view along line A-A'. Figure 2 is a top view of the substrate 2. Figure 3 is a cross-sectional view showing the molten state of a fusible conductor. Figure 4 shows a cross-sectional perspective view of a fusible conductor. Figure 5 is a diagram showing the circuit configuration of the protection element. Figure 6 is a cross-sectional view showing a variation of the protective element. Figure 7 is a diagram showing the circuit configuration of the protective element in a variation example. Figure 8 is a cross-sectional view showing a variation of the protective element. Figure 9 is a cross-sectional view showing a variation of the protective element. Figure 10 is a cross-sectional view showing a variation of the protective element. Figure 11 is a cross-sectional view showing a variation of the protective element. Figure 12 is a circuit diagram showing an example of a battery pack configuration. Figure 13 is a diagram showing one example of the configuration of the previous protective element. (A) is a top view with the cover component omitted, and (B) is a cross-sectional view along A-A'. Implementation

[0025] The following description, with reference to the drawings, details the protective element incorporating this technology and the battery pack using it. Furthermore, this technology is not limited to the embodiments described below; various modifications can be made without departing from the spirit of this technology. Also, the drawings are schematic diagrams, and sometimes the proportions of dimensions may differ from the actual object. Specific dimensions should be determined by referring to the following explanation. Furthermore, the drawings also include portions with different dimensional relationships or proportions.

[0026] As shown in Figure 1, the protective element 1 using this technology includes: a substrate 2 having a first electrode 3 and a second electrode 4 connected to an external circuit; a fusible conductor 5 having one side 5a supported on the substrate 2 and connected to the first electrode 3 and the second electrode 4; and a substrate 7 with a heating element 6 provided thereon, which melts the fusible conductor 5 by heating.

[0027] Furthermore, the fusible conductor 5 has one contact point with the substrate 7 containing the heating element on its other side 5b. Here, as described below, the substrate 7 containing the heating element 6 is designed to withstand the heat generated by the heating element 6, and therefore uses a ceramic substrate or the like. On the other hand, the fusible conductor 5 is mainly composed of a low-melting-point metal that can be melted by the heat generated by the heating element 6. Therefore, there is a difference in the coefficient of linear expansion between the fusible conductor 5 and the substrate 7 containing the heating element. If there are multiple contact points between the fusible conductor 5 supported on the base substrate 2 and the substrate 7 containing the heating element, when repeatedly exposed to high-temperature and low-temperature environments due to reflow installation or the usage environment of the installed product, the difference in the coefficient of linear expansion between the fusible conductor 5 and the ceramic substrate may cause internal stress, potentially resulting in deformation or breakage.

[0028] However, since the connection point between the fusible conductor 5 and the substrate 7 carrying the heating element is at one point, the fusible conductor 5 will not suffer damage such as deformation or breakage due to internal stress when repeatedly exposed to high-temperature and low-temperature environments, thus exhibiting stability in shape or size. Therefore, the resistance value of the fusible conductor 5 of the protective element 1 is stable and can maintain a high rated value.

[0029] Furthermore, when there are multiple contacts with the substrate 7 containing the heating element, if the cross-sectional area of ​​the fusible conductor 5 is increased to cope with the large current, the stress caused by the difference in the coefficients of linear expansion between the conductor and the substrate 7 containing the heating element will increase, and the time until breakage will tend to become shorter. However, since the protective element 1 prevents the generation and damage of internal stress caused by the difference in the coefficients of linear expansion between the conductor and the substrate 7 containing the heating element, it can also cope with the large current caused by the increased cross-sectional area of ​​the fusible conductor 5.

[0030] Furthermore, the fusible conductor 5 and the first, second electrodes 3, 4 and other constituent elements of the substrate 2 have multiple contact points, but the substrate 2 does not have a heating element 6. It can use a material with low heat resistance and a small difference in the coefficient of linear expansion. Therefore, there will be basically no breakage or deformation caused by internal stress due to the difference in the coefficient of linear expansion between the conductor 5 and the substrate 2.

[0031] That is, the protective element 1 is constructed to mitigate the thermal shock to the fusible conductor 5. The detailed structure of the protective element 1 will be described below.

[0032] [Substrate] The substrate 2 is formed of insulating components such as glass epoxy board or phenolic substrate.

[0033] As shown in Figure 2, first and second electrodes 3 and 4 are formed at opposite ends of the substrate 2. The first and second electrodes 3 and 4 are formed from conductive patterns such as Ag or Cu. Preferably, a Ni / Au plating layer, a Ni / Pd plating layer, or a Ni / Pd / Au plating layer is coated on the front surface of the first and second electrodes 3 and 4 using known methods such as plating. This prevents oxidation of the first and second electrodes 3 and 4 and prevents changes in rated values ​​associated with increased on-resistance. Furthermore, during reflow soldering of the protective element 1, melting the solder connecting the fusible conductor 5 prevents molten corrosion (solder corrosion) of the first and second electrodes 3 and 4.

[0034] The first electrode 3 extends from the front side 2a of the substrate 2 through a conductive via 10 penetrating the substrate 2 and is continuous with the first external connection electrode 11 formed on the back side 2b. Similarly, the second electrode 4 extends from the front side 2a of the substrate 2 through the conductive via 10 and is continuous with the second external connection electrode 12 formed on the back side 2b. If the protection element 1 is mounted on an external circuit board, the first and second external connection electrodes 11 and 12 are connected to the connection electrodes disposed on the external circuit board, thereby assembling the fusible conductor 5 into a portion of the current path formed on the external circuit board. Furthermore, the connection between the first and second electrodes 3 and 4 and the first and second external connection electrodes 11 and 12 can also be achieved through a toothed structure formed on the side edge of the substrate 2.

[0035] The first and second electrodes 3 and 4 are electrically connected via a fusible conductor 5 mounted on a conductive connecting material 9 such as solder. Furthermore, as shown in Figure 3, the first and second electrodes 3 and 4 may be disconnected by the fusible conductor 5 melting due to self-heating (Joule heating) caused by the flow of a large current exceeding the rated value through the protection element 1, or by the heating element 6 heating up during energization, causing the fusible conductor 5 to melt.

[0036] Furthermore, a holding portion 8 for holding the fusible conductor 5c is provided between the first electrode 3 and the second electrode 4 on the substrate 2. The holding portion 8 is formed of a material with excellent wettability relative to the fusible conductor 5c, such as a conductive pattern made of Ag or Cu. Alternatively, the holding portion 8 can be formed of the same material as the first and second electrodes 3 and 4, thereby allowing it to be formed simultaneously in the same forming process. The fusible conductor 5 is connected to the holding portion 8 via a connecting material with excellent thermal conductivity, such as a conductive connecting material 9.

[0037] Furthermore, the conductive connecting material 9 can be any metal bonding material with a melting point lower than that of the metal constituting the fusible conductor 5. Examples of such metal bonding materials include tin-based alloys such as Sn-Ag, Sn-Ag-Cu, Sn-Bi, and Sn-Bi-Sb; lead-based alloys such as Pb-Sn and Pb-Au; and indium-based alloys such as Pb-In and In-Sn. Additionally, the substrate 2 can also be configured with solder resist for the purpose of insulation or position control of the fusible conductor 5.

[0038] Unlike the insulating substrate in the previous protective element, the base substrate 2 does not have a heating element 6. Therefore, the base substrate 2 does not require high heat resistance, and a substrate with lower heat resistance can be used. Therefore, the substrate used as the base substrate 2 can have a smaller difference in the coefficient of linear expansion with the fusible conductor 5.

[0039] In this way, when the protective element 1 is repeatedly exposed to high temperature and low temperature environments, the substrate 2 can suppress the generation of large internal stress between it and the fusible conductor 5, prevent the fusible conductor 5 from being damaged by deformation or breakage due to internal stress, and maintain the stability of its shape or size.

[0040] [Fusible conductor] Next, the fusible conductor 5 will be described. The fusible conductor 5 is installed across the first and second electrodes 3 and 4, and is melted by the heating element 6 due to the heat generated by the current, or melted by self-heating (Joule heating) due to the current flowing through it, thus blocking the current path between the first electrode 3 and the second electrode 4.

[0041] The fusible conductor 5 can be any low-melting-point metal material that has the conductivity to melt when heated by the heating element 6 due to the heat generated by the current or in 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. can be used.

[0042] Furthermore, the fusible conductor 5 can also be a structure containing both a high-melting-point metal and a low-melting-point metal. For example, as shown in FIG4, the fusible conductor 5 is a laminated structure comprising an inner layer and an outer layer, wherein the inner layer has a low-melting-point metal layer 18, and the outer layer of the laminated structure has a high-melting-point metal layer 19. The fusible conductor 5 is connected to the first and second electrodes 3 and 4 and the holding portion 8 via a conductive bonding material 9 such as solder.

[0043] The low-melting-point metal layer 18 is preferably solder or a metal with Sn as its main component, which is generally referred to as "Pb-free solder". The melting point of the low-melting-point metal layer 18 does not necessarily need to be higher than the reflow oven temperature, and it can melt at around 200°C. The high-melting-point metal layer 19 is a metal layer deposited on the surface of the low-melting-point metal layer 18, such as Ag or Cu or a metal with any of these as its main component, and has a high melting point that will not melt when the connection or protection element 1 of the first and second electrodes 3 and 4 and the holding part 8 to the fusible conductor 5 is installed on the external circuit board by reflow soldering.

[0044] This fusible conductor 5 can be formed by depositing a high-melting-point metal layer onto a low-melting-point metal foil using a plating technique, or it can be formed using other well-known lamination techniques or film formation techniques. In this case, the fusible conductor 5 can be formed such that the entire surface of the low-melting-point metal layer 18 is covered by the high-melting-point metal layer 19, or it can be formed such that only one pair of opposite sides are covered. Furthermore, the fusible conductor 5 can be constructed with the high-melting-point metal layer 19 as the inner layer and the low-melting-point metal layer 18 as the outer layer, or it can be formed by various configurations, such as a multilayer structure consisting of three or more layers formed by alternating lamination of the low-melting-point metal layer 18 and the high-melting-point metal layer 19, with an opening in a portion of the outer layer to expose a portion of the inner layer, etc.

[0045] The fusible conductor 5 is formed by layering a high-melting-point metal layer 19 on top of a low-melting-point metal layer 18 as the inner layer. Even when the reflow temperature exceeds the melting temperature of the low-melting-point metal layer 18, the fusible conductor 5 can maintain its shape and not melt. Therefore, the first and second electrodes 3 and 4 and the holding part 8 can be efficiently connected to the fusible conductor 5 through reflow, or the protective element 1 can be mounted on an external circuit board. Furthermore, during reflow, the resistance value will not locally increase or decrease due to the deformation of the fusible conductor 5, thus preventing melting at a specific temperature, or preventing changes in melting characteristics such as melting before reaching a specific temperature.

[0046] Furthermore, the fusible conductor 5 will not melt even if it self-heats while carrying a specific rated current. Moreover, if a current higher than the rated value is carried, it will melt due to self-heating, thus blocking the current path between the first and second electrodes 3 and 4. Also, the heating element 6 will melt due to heating, thus blocking the current path between the first and second electrodes 3 and 4.

[0047] At this time, the fusible conductor 5 is etched by the molten low-melting-point metal layer 18 to the high-melting-point metal layer 19 (solder etching), and the high-melting-point metal layer 19 melts at a temperature lower than the melting temperature. Therefore, the fusible conductor 5 can be melted in a short time by the etching effect of the low-melting-point metal layer 18 on the high-melting-point metal layer 19. Furthermore, the molten conductor 5c of the fusible conductor 5 is broken by the physical pull-in action of the holding part 8 and the first and second electrodes 3 and 4, so the current path between the first and second electrodes 3 and 4 can be quickly and reliably cut off (Fig. 3).

[0048] Furthermore, the fusible conductor 5 is preferably formed with a volume greater than that of the high-melting-point metal layer 19 than the low-melting-point metal layer 18. The fusible conductor 5 is heated by self-heating due to overcurrent or by the heating element 6, and the high-melting-point metal is melted and corroded by the melting of the low-melting-point metal, thereby rapidly melting and breaking off. Therefore, by forming a volume greater than that of the high-melting-point metal layer 19 than the low-melting-point metal layer 18, the fusible conductor 5 can promote this melting and corrosion process, rapidly breaking off the connection between the first and second electrodes 3 and 4.

[0049] Furthermore, the fusible conductor 5 is constructed by layering a high-melting-point metal layer 19 onto a low-melting-point metal layer 18, which forms the inner layer. This significantly reduces the fusing temperature compared to previous chip fuses containing high-melting-point metals. Therefore, compared to chip fuses of the same size, the fusible conductor 5 allows for a larger cross-sectional area, resulting in a substantial increase in current rating. Moreover, compared to previous chip fuses with the same current rating, miniaturization and thinning are possible, along with superior fast-blow fusing performance.

[0050] Furthermore, the fusible conductor 5 improves the withstandability (pulse withstand) against surges that instantaneously apply abnormally high voltages to an electrical system equipped with the protective element 1. That is, the fusible conductor 5 will not melt within a few milliseconds of current flow, for example, 100 A. In this regard, a large current flowing for an extremely short time will flow through the surface layer of the conductor (skin effect). Therefore, the fusible conductor 5 is provided with a high-melting-point metal layer 19, such as an Ag plating layer with low resistance, as an outer layer, thereby facilitating the flow of current applied by a surge and preventing melting due to self-heating. Therefore, the fusible conductor 5 significantly improves surge withstand compared to previous fuses containing solder alloys.

[0051] This fusible conductor 5 is in contact with the substrate 7 containing the heating element, on the opposite side of one side 5a of the first and second electrodes and the holding part 8. Moreover, the protective element 1 is at the contact point between the other side 5b of the fusible conductor 5 and the substrate 7 containing the heating element.

[0052] [Baseboard with heating element] The substrate 7 with a heating element has an insulating substrate 13 and a heating element 6 formed on the insulating substrate 13 and which melts the fusible conductor 5 by heating.

[0053] [Insulating substrate] The insulating substrate 13 is formed of a substrate that is insulating and resistant to the heat generated by the heating element 6, such as alumina, glass ceramic, mullite, or zirconium oxide. Among these, a ceramic substrate with excellent heat resistance to the high-temperature heat generated by the heating element 6 is particularly suitable.

[0054] As shown in Figure 1, an insulating substrate 13 has a heating element 6 formed on its front side 13a and an intermediate electrode 31 formed on its back side 13b, which is connected to the other side 5b of the fusible conductor 5. The intermediate electrode 31 is connected to the other side 5b of the fusible conductor 5 by means of a conductive connecting material 9 such as solder. Moreover, when the fusible conductor 5 melts, the intermediate electrode 31, together with the holding portion 8 formed on the substrate 2, condenses and holds the molten conductor 5c.

[0055] [Heat source] The heating element 6 is a conductive component with relatively high resistance that heats up when energized, and is made of materials such as nickel-chromium alloy, W, Mo, Ru, or materials containing these alloys. The heating element 6 can be formed by mixing powdered alloys or compositions / compounds with resin binders to form a slurry, and then applying the slurry to an insulating substrate 13 using screen printing technology to form a pattern, followed by firing. For example, the heating element 6 can be formed by adjusting a mixture of ruthenium oxide slurry, silver, and glass slurry according to a specific voltage, applying a film of a specific area at a specific location on the front side 13a of the insulating substrate 13, and then firing it under appropriate conditions. Furthermore, the shape of the heating element 6 can be appropriately designed; as shown in Figure 1, forming it into a roughly rectangular shape according to the shape of the insulating substrate 13 is preferable in terms of maximizing the heating area.

[0056] Furthermore, on the front side 13a of the insulating substrate 13 where the heating element 6 is formed, first and second heating element electrodes 14 and 15 constituting a power supply path to the heating element 6 are formed. The first heating element electrode 14 is formed on one side edge of the front side 13a of the insulating substrate 13, and the second heating element electrode 15 is formed on the other side edge opposite to the one side edge. The heating element 6 is connected to the first heating element electrode 14 at one end by overlapping, and to the second heating element electrode 15 at the other end by overlapping.

[0057] The first heating element electrode 14 and the second heating element electrode 15 serve as electrodes for power supply terminals of the heating element 6. The first heating element electrode 14 is connected to the first heating element power supply electrode 33 disposed on the back side 13b of the insulating substrate 13 via a toothed structure, and the second heating element electrode 15 is connected to the second heating element power supply electrode 34 disposed on the back side 13b of the insulating substrate 13 via a toothed structure. The first heating element power supply electrode 33 and the second heating element power supply electrode 34 are connected to the third electrode 35 and the fourth electrode 36 formed on the front side 2a of the substrate 2 via conductive connection material 9, etc.

[0058] The third electrode 35 extends from the front side 2a of the substrate 2 through a conductive via 10 penetrating the substrate 2 and is continuous with the third external connection electrode 37 formed on the back side 2b. Similarly, the fourth electrode 36 extends from the front side 2a of the substrate 2 through a conductive via 10 and is continuous with the fourth external connection electrode 38 formed on the back side 2b. If the protection element 1 is mounted on an external circuit board, the third and fourth external connection electrodes 37 and 38 are assembled into a portion of the power supply path for supplying power to the heating element 6 by connecting to the connection electrodes disposed on the external circuit board. As shown in FIG. 5, the power supply path for the heating element 6 and the current path for the fusible conductor 5 are formed independently. Furthermore, the connection between the third and fourth electrodes 35 and 36 and the third and fourth external connection electrodes 37 and 38 can also be achieved through a toothed structure formed on the side edge of the substrate 2.

[0059] Furthermore, as shown in Figures 6 and 7, the protection element 1 can also connect the power supply path to the heating element 6 with the current path of the fusible conductor 5. In this case, the second heating element power supply electrode 34 is connected to the intermediate electrode 31 formed on the back surface 13b of the insulating substrate 13, and the fourth external connection electrode 38 is not provided. Thus, when the protection element 1 is assembled into the battery pack 20 described below (see Figure 12), the heating element 6 is powered by the battery stack 25, and the heating stops by cutting off the power supply path through the melting of the fusible conductor 5. Furthermore, the second heating element electrode 15 can also be connected to the intermediate electrode 31 through a conductive via (not shown) provided on the insulating substrate 13.

[0060] The first and second heating element electrodes 14 and 15, the first and second heating element power supply electrodes 33 and 34, and the intermediate electrode 31 can be formed by printing and firing conductive paste such as Ag or Cu. Furthermore, by using the same material to form the electrodes on the front side 13a or back side 13b of the insulating substrate 13, they can be formed in a single printing and firing process.

[0061] The heating element 6 is protected and insulated by being covered with an insulating layer 32, including a glass layer. The insulating layer 32 can be formed, for example, by coating and firing a glass-based paste. Furthermore, the insulating substrate 13 can also be provided with a solder resist for the purpose of insulation.

[0062] The first and second heating element power supply electrodes 33 and 34, formed on the back side 13b of the heating element substrate 7, are connected to the third and fourth electrodes formed on the front side 2a of the substrate 2 via conductive connecting material 9. Furthermore, the intermediate electrode 31, formed on the back side 13b of the heating element substrate 7, is connected to the other side 5b of the fusible conductor 5 via conductive connecting material 9. Thus, the heating element substrate 7 is connected to the substrate 2. At this time, the contact point between the fusible conductor 5 and the heating element substrate 7 is at point 1, and the heating element 6 is formed on the opposite side of the heating element substrate 7 to the side that contacts the fusible conductor 5.

[0063] Furthermore, the protective element 1 is protected by being covered internally by a housing (not shown). The housing may be formed from insulating materials such as various engineering plastics, thermoplastics, ceramics, or glass epoxy boards.

[0064] According to this protective element 1, since the connection between the fusible conductor 5 and the substrate 7 with the heating element is a single point, damage such as deformation or breakage caused by the internal stress of the fusible conductor 5 can be suppressed even when repeatedly exposed to high-temperature and low-temperature environments. Furthermore, the insulating substrate 13 of the substrate 7 with the heating element can also be made of a ceramic substrate or the like with excellent heat resistance without considering the difference in the coefficient of linear expansion relative to the fusible conductor 5. This provides a protective element that can improve heat resistance and achieve the desired heating temperature of the heating element 6 in the element structure, increase the cross-sectional area of ​​the fusible conductor 5 to achieve high ratings, and has excellent fast melting performance.

[0065] Furthermore, the substrate 2 supporting the fusible conductor 5 can be made of a material with a smaller difference in the coefficient of linear expansion of the fusible conductor 5. Since a greater difference in the coefficient of linear expansion between materials results in greater stress, reducing the difference in the coefficient of linear expansion improves durability against thermal shock. For example, the coefficient of linear expansion of a ceramic substrate is 7.2 (ppm / ℃), while that of a glass epoxy substrate is 14 (ppm / ℃). Also, the coefficient of linear expansion of tin, which becomes the material of the fusible conductor 5, is 26.9 (ppm / ℃), and that of lead is 29.1 (ppm / ℃).

[0066] Since the difference in the coefficient of linear expansion between the ceramic substrate and tin is approximately 20, and the difference is approximately 13, by changing the substrate 2 from a ceramic substrate to a glass epoxy substrate, the difference in the coefficient of linear expansion is reduced by about 40%. Therefore, the resulting stress can also be reduced by 40%. Thus, by using a substrate 2 with a smaller difference in the coefficient of linear expansion relative to the fusible conductor 5 compared to the insulating substrate 13 of the substrate 7 containing the heating element, the heat resistance of the fusible conductor 5 to repeated thermal cycling under high and low temperature conditions can be improved.

[0067] Furthermore, regarding the conductor resistance of the substrate 2, since the conductor resistance values ​​of the materials used in the first and second electrodes 3 and 4 are the same as those of the ceramic substrate, a resistance value equal to or higher than that of the ceramic substrate can be achieved.

[0068] Furthermore, when using glass epoxy material as the substrate 2, the first and second external connection electrodes 11 and 12 can be formed in the same way as the ceramic substrate to form a protective element that can be surface mounted, and even without the use of external electrode terminals, the structure can be made small.

[0069] [Example 1 of the variation] Next, variations of the protective element using this technology will be described. Furthermore, in the following description, components identical to those in the protective element 1 described above will be labeled with the same symbols, and their details will be omitted. The protective element using this technology may also have a plurality of fusible conductors. The protective element 40 shown in FIG8 has two fusible conductors 5A and 5B provided on the substrate 2. Fusible conductor 5A is provided between the first electrode 3 and the holding portion 8, and fusible conductor 5B is provided between the second electrode 4 and the holding portion 8. Furthermore, the intermediate electrode 31 of the substrate 7 with the heating element has a number of contacts corresponding to the number of fusible conductors 5 provided on the substrate 2, and the protective element 40 shown in FIG8 is connected to each of the fusible conductors 5A and 5B at two of these contacts.

[0070] In the protective element 40, the fusible conductor also has a contact point with the substrate containing the heating element at another point. That is, the fusible conductor 5A and the intermediate electrode 31 are in contact at one point, and the fusible conductor 5B is also in contact with the intermediate electrode 31 at one point. Therefore, when the protective element 40 is repeatedly exposed to high temperature and low temperature environments, it can also prevent damage such as internal stress, deformation or breakage of the fusible conductors 5A and 5B due to the difference in the coefficient of linear expansion between them and the insulating substrate 13.

[0071] Furthermore, more than three fusible conductors 5 can be provided. Also, when viewed from above the substrate 2, multiple fusible conductors 5 can be provided by arranging them side by side across the first and second electrodes 3 and 4 and the holding part 8. The size, structure, material, resistance value or thermal conductivity and other physical properties of the multiple fusible conductors 5 can be the same or different.

[0072] Alternatively, the number of intermediate electrodes 31 and fusible conductors 5 can correspond to form a plurality, with each intermediate electrode 31 and each fusible conductor 5 having a connection point of 1.

[0073] [Variation Example 2] Furthermore, the protective element using this technology can also be configured with multiple heating elements. As shown in Figure 9, the protective element 50 has two heating elements 6A and 6B arranged side-by-side on a substrate 7 with heating elements. Heating elements 6A and 6B are connected at one end to the first heating element electrode 14 by overlapping, and at the other end to the second heating element electrode 15 by overlapping. The power supply path to the heating element 6 from the first heating element electrode 14 and the second heating element electrode 15 is the same as that of the protective element 1 described above.

[0074] In the protective element 50, the fusible conductor is also in contact with the substrate with the heating element at one point on its other side. That is, the fusible conductor 5 is in contact with the intermediate electrode 31 at one point. Therefore, when the protective element 50 is repeatedly exposed to high temperature and low temperature environments, it can also prevent damage such as internal stress, deformation or breakage of the fusible conductor 5 due to the difference in the coefficient of linear expansion between it and the insulating substrate 13.

[0075] [Variation Example 3] Furthermore, the protective element using this technology can also have a heating element formed on the side of the substrate with the heating element that is in contact with the fusible conductor. The protective element 60 shown in Figure 10 has a heating element 6 disposed on the back side 13b of the insulating substrate 13 of the substrate 7 with the heating element. The heating element 6 is protected and insulated by being covered by an insulating layer 32. Additionally, an intermediate electrode 31 connected to the second heating element electrode 15 is superimposed on the insulating layer 32.

[0076] The intermediate electrode 31 overlaps with the heating element 6 through the insulating layer 32. Furthermore, the intermediate electrode 31 is connected to the other side 5b of the fusible conductor 5 via a conductive connecting material 9. That is, the protective element 60 is formed on the side of the substrate 7 with the heating element that contacts the fusible conductor 5.

[0077] Furthermore, the first and second heating element electrodes 14 and 15 are also formed on the back side 13b of the insulating substrate 13, so there is no need to form the first and second heating element energizing electrodes 33 and 34, which are connected to the third and fourth electrodes 35 and 36 formed on the substrate 2. The intermediate electrode 31 is formed from the second heating element electrode 15 onto the insulating layer 32.

[0078] In the protective element 60, the fusible conductor also has one contact point with the substrate containing the heating element. That is, the fusible conductor 5 is in contact with the intermediate electrode 31 at one point. Therefore, when the protective element 60 is repeatedly exposed to high-temperature and low-temperature environments, it can prevent damage such as internal stress, deformation, or breakage of the fusible conductor 5 due to the difference in the coefficient of linear expansion between the fusible conductor 6 and the insulating substrate 13. Furthermore, since the heating element 6 is in contact with the fusible conductor 5 through the insulating layer 32 and the intermediate electrode 31, the heat from the heating element 6 is more easily transferred to the fusible conductor 5, resulting in excellent rapid melting performance.

[0079] Furthermore, as a variation of the protective element 40, a plurality of heating elements 6 may be formed on the substrate 7 with the heating element, similar to the protective element 50 (see Figure 11). Also, as a variation of the protective element 60, a plurality of fusible conductors 5 may be formed on the substrate 2, similar to the protective element 40, or a plurality of heating elements 6 may be formed on the substrate 7 with the heating element, similar to the protective element 50.

[0080] [Battery Pack] These protective elements 1, 40, 50, and 60 are used, for example, in the circuitry of a lithium-ion battery pack 20. Figure 12 is a circuit diagram showing an example of the configuration of a battery pack using protective element 1. As shown in Figure 12, the battery pack 20 has, for example, a battery stack 25 containing a total of four lithium-ion battery cells 21a to 21d.

[0081] The battery pack 20 includes: a battery stack 25; a charge / discharge control circuit 26 that controls the charge and discharge of the battery stack 25; a protection element 1 that incorporates the present invention to cut off the charge / discharge path when the battery stack 25 is abnormal; a detection circuit 27 that detects the voltage of each battery cell 21a to 21d; and a current control element 28 that acts as a switching element that controls the operation of the protection element 1 based on the detection result of the detection circuit 27.

[0082] The battery stack 25 is formed by connecting battery cells 21a-21d in series to control over overcharging and over-discharging conditions. It is detachably connected to the charging device 22 via the positive terminal 20a and negative terminal 20b of the battery stack 25, and is charged by the charging device 22. The battery stack 20, charged by the charging device 22, can be operated by connecting the positive terminal 20a and negative terminal 20b to a battery-operated electronic device.

[0083] The charge / discharge control circuit 26 includes two current control elements 23a and 23b connected in series in 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, for example, field-effect transistors (FETs). By controlling the gate voltage using the control unit 24, the control unit controls the conduction and / or disconnection of the battery stack 25 in the charging and / or discharging direction of the current path. The control unit 24 operates upon receiving power from the charging device 22. Based on the detection results of the detection circuit 27, when the battery stack 25 is over-discharged or over-charged, it controls the operation of the current control elements 23a and 23b by disconnecting the current path.

[0084] The protection element 1 is connected, for example, to the charging and discharging current path between the battery stack 25 and the charging and discharging control circuit 26, and its operation is controlled by the current control element 28.

[0085] The detection circuit 27 is connected to each battery cell 21a-21d, detects the voltage value of each battery cell 21a-21d, and supplies each voltage value to the control unit 24 of the charge / discharge control circuit 26. Furthermore, when any of the battery cells 21a-21d reaches an overcharge voltage or an over-discharge voltage, the detection circuit 27 outputs a control signal to the control current control element 28.

[0086] The current control element 28 is, for example, composed of a FET. By means of the detection signal output by the self-detection circuit 27, when the voltage value of the battery cells 21a~21d exceeds the voltage of a specific over-discharge or over-charge state, the protection element 1 is activated, so as to control the charging and discharging current path of the battery stack 25 regardless of the switching action of the current control elements 23a and 23b.

[0087] The protective element 1 of the present invention, used in a battery pack 20 comprising the configuration described above, has the circuit configuration shown in FIG7. Specifically, the protective element 1 is connected to the battery stack 25 side via a first external connection electrode 11 and to the positive terminal 20a side via a second external connection electrode 12, thereby connecting the fusible conductor 5 in series in the charging / discharging path of the battery stack 25. Furthermore, the protective element 1's heating element 6 is connected to the current control element 28 via a first heating element electrode 14 to a third external connection electrode 37, and the heating element 6 is connected to the open end of the battery stack 25. Thus, one end of the heating element 6 is connected to the fusible conductor 5 and one open end of the battery stack 25 via an intermediate electrode 31, and the other end is connected to the current control element 28 and the other open end of the battery stack 25 via a third external connection electrode 33. This forms a power supply path to the heating element 6 that can be controlled by the current control element 28.

[0088] [Action of protection components] If the detection circuit 27 detects an abnormal voltage in any of the battery cells 21a-21d, it outputs a shutdown signal to the current control element 28. The current control element 28 then controls the current by energizing the heating element 6. The protection element 1 flows current from the battery stack 25 to the heating element 6, thereby causing the heating element 6 to heat up. The protection element 1 uses the heat from the heating element 6 to melt the fusible conductor 5, thus interrupting the charging and discharging path of the battery stack 25. Furthermore, the protection element 1 is formed by containing both a high-melting-point metal and a low-melting-point metal in the fusible conductor 5. Before the high-melting-point metal melts, the low-melting-point metal is melted, and the molten low-melting-point metal corrodes the high-melting-point metal, causing the fusible conductor 5 to melt in a short time.

[0089] Here, the protective element 1 is supported at the contact point between the fusible conductor 5 on the substrate 2 and the substrate 7 with the heating element. Therefore, since the insulating substrate 13 of the substrate 7 with the heating element, which requires high thermal strength, is made of a ceramic substrate or the like, even if the difference in the coefficient of linear expansion between the fusible conductor 5 and the substrate 7 increases, the fusible conductor 5 will not suffer damage such as deformation or breakage due to internal stress when repeatedly exposed to high and low temperature environments due to reflow installation or the usage environment of the product, thus exhibiting stability in shape or size. In this way, the fusible conductor 5 can prevent changes in fusing characteristics caused by changes in resistance value due to deformation, and while maintaining a high rated value, it can quickly melt and break due to the heating of the heating element 6.

[0090] The protective element 1 cuts off the power supply path to the heating element 6 by melting the fusible conductor 5, thus stopping the heating of the heating element 6.

[0091] Furthermore, when the overcurrent exceeding the rated value flows through the battery pack 20, the fusible conductor 5 can also melt due to self-heating, thus blocking the charging and discharging path of the battery pack 20.

[0092] Thus, the protective element 1 causes the fusible conductor 5 to melt due to the heat generated by the heating element 6 when energized, or due to the self-heating of the fusible conductor 5 caused by overcurrent. At this time, when the protective element 1 is installed on the circuit board during reflow soldering, or when the circuit board with the protective element 1 is exposed to high-temperature environments such as reflow heating, the deformation of the fusible conductor 5 can be suppressed by the structure of a low-melting-point metal coated with a high-melting-point metal. Therefore, changes in melting characteristics caused by resistance changes due to deformation of the fusible conductor 5 can be prevented, and the conductor can be quickly melted by a specific overcurrent or the heating element 6.

[0093] The protective element 1 of the present invention is not limited to use in lithium-ion battery packs, but can also be applied to various applications that require the interruption of current paths based on electrical signals.

[0094] 1: Protective components 2: Substrate 2a: Front 2b: Back 3: First electrode 4: Second electrode 5: Fusible conductor 5a: A face 5A: Fusible conductor 5b: The Other Side 5B: Fusible conductor 6: Heating element 6A, 6B: Heating element 7: Substrate with heating element 8: Maintaining section 9: Conductive connection materials 10: Conductive via 11: First external connection electrode 12: Second external connection electrode 13: Insulating substrate 13a: Front 13b: Reverse side 14: First heating element electrode 15: Second heating element electrode 16: First lead electrode 17: Second lead electrode 18: Low melting point metal layer 19: High melting point metal layer 20: Battery Pack 20a: Positive extreme particle 20b: Negative extreme component 21: Battery Unit 21a~21d: Battery cells 22: Charging device 23: Current control element 23a, 23b: Current control elements 24: Control Department 25: Battery Stack 26: Charge and discharge control circuit 27: Detection Circuit 28: Current control element 31: Intermediate electrode 32: Insulation layer 33: Third external connection electrode 34: Fourth external connection electrode 35: Third electrode 36: Fourth electrode 37: Third external connection electrode 38: Fourth external connection electrode 40: Protective Components 50: Protective Components 60: Protective Components 100: Protective Components 101: Insulating substrate 102: First electrode 102a: First external connection electrode 103: Second electrode 103a: Second external connection electrode 104: Fever Element 105: Insulation layer 106: Heating element lead-out electrode 107: Fuse element

Claims

1. A protective element comprising: a substrate having a first electrode and a second electrode connected to an external circuit; a fusible conductor having one side supported on the substrate and connected to the first electrode and the second electrode; and a substrate with a heating element having a heating element that melts the fusible conductor by heating; the other side of the fusible conductor having a contact point with the substrate with the heating element at one location; and the substrate with the heating element being a ceramic substrate.

2. The protective element as claimed in claim 1, wherein the heating element is formed on the side opposite to the surface of the substrate with the heating element that is in contact with the fusible conductor.

3. The protective element as claimed in claim 1, wherein the heating element is formed on the side of the substrate with the heating element that is in contact with the fusible conductor.

4. The protective element of any one of claims 1 to 3 has a plurality of the aforementioned fusible conductors, and each of the aforementioned fusible conductors has one contact point with the aforementioned substrate carrying the heating element.

5. The protective element of any one of claims 1 to 3, wherein the difference in the coefficient of linear expansion between the substrate and the fusible conductor is smaller than that between the substrate with the heating element and the substrate with the heating element.

6. The protective element of any one of claims 1 to 3, wherein the substrate with the heating element is formed with a plurality of the heating elements.

7. A battery pack comprising: one or more battery cells; a protection element connected to a charge / discharge path of the battery cells and blocking the charge / discharge path; and a current control element that detects the voltage value of the battery cells and controls the energization of the protection element; wherein the protection element comprises: a substrate having a first electrode and a second electrode connected to an external circuit; a fusible conductor having one side supported on the substrate and connected to the first electrode and the second electrode; and a substrate with a heating element having a heating element that melts the fusible conductor by heating; wherein the other side of the fusible conductor has a contact point with the substrate with the heating element; and the substrate with the heating element is a ceramic substrate.

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