HK1208758A1

HK1208758A1 - Protective element and battery pack

Info

Publication number: HK1208758A1
Application number: HK15109301.8A
Authority: HK
Inventors: 木村武雄
Original assignee: Dexerials Corporation
Priority date: 2012-08-01
Filing date: 2013-07-24
Publication date: 2016-03-11
Also published as: CN104508784A; TW201419349A; CN104508784B; KR101946105B1; WO2014021155A1; JP2014032768A; KR20150040953A; TWI585800B; JP5952673B2

Abstract

In order to obtain a protective element that can be easily made to fuse and that maintains current capacity during overcurrent protection, a protective element (10) is provided with: an insulating substrate (11); a heating element (14) that is layered on the insulating substrate (11) and that is covered by an insulating member (15); electrodes (12)(A1) and (12)(A2) that are formed on both ends of the insulating substrate (11); a heating element-drawing electrode (16) that is layered on the insulating member (15) so as to overlap with the heating element (14); and a fusible conductor (13), both ends of which are connected to the electrodes (12)(A1) and (12)(A2) and the central section of which is connected to the heating element-drawing electrode (16). The fusible conductor (13) comprises, for example, a thick section (13a) that has a round linear shape and measures 1.6 mmphi, and a thin section (13b) that is molded to be thinner than the thick section (13a) such that the thickness is substantially uniform at a position at which the section that faces the heating element (14) overlaps with the heating element (14). The thickness of the thin section (13b) may be, for example, 1/2 the thickness of the thick section (13a).

Description

Protection element and battery pack

Technical Field

The present invention relates to a protection element for protecting a circuit connected to a current path by blowing the current path. This application claims priority based on Japanese patent application No. 2012-171332 filed on 8/1/2012, which is incorporated herein by reference.

Background

Most of the rechargeable batteries that can be recycled after charging are processed into battery packs and provided to users. In particular, in a lithium ion secondary battery having a high weight energy density, in order to secure safety of users and electronic devices, it is common to incorporate several protection circuits such as overcharge protection and overdischarge protection in a battery pack, and to have a function of cutting off an output of the battery pack under a predetermined condition.

In most electronic devices using lithium ion secondary batteries, an FET switch incorporated in a battery pack turns ON/OFF (ON/OFF) an output, thereby performing overcharge protection or overdischarge protection of the battery pack. However, when the FET switch is short-circuited for some reason, a large instantaneous current flows due to the application of a lightning surge or the like, or when the output voltage abnormally decreases or an excessive abnormal voltage is output due to the life of the battery cell, it is necessary to protect the battery pack and the electronic device from accidents such as fire. Therefore, in order to safely cut off the output of the battery cell in any abnormal state that can be assumed in this way, a protection element is employed that is configured by a fuse element having a function of cutting off a current path in accordance with a signal from the outside.

As a protection element for a protection circuit of such a lithium ion secondary battery or the like, as described in patent document 1, a structure is generally adopted in which a heating element is provided inside the protection element, and a fusible conductor on a current path is fused by heat generation of the heating element.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2010-3665.

Disclosure of Invention

Problems to be solved by the invention

In the protection device described in patent document 1, the fusible conductor (fuse) has a maximum current capacity of about 15A for use in applications with a low current capacity such as a cellular phone and a notebook computer. In recent years, the use of lithium ion secondary batteries has been expanding, and the use of lithium ion secondary batteries for higher currents has been studied, and the use of lithium ion secondary batteries has been partially adopted, for example, in electric tools such as electric drives, and transportation equipment such as hybrid vehicles, electric vehicles, and electric power assisted bicycles. In these applications, a large current exceeding 10A to 100A may flow particularly at the time of startup or the like. It is desirable to realize a protection element corresponding to such a large current capacity.

In order to realize a protection element corresponding to a large current, the sectional area of the fusible conductor may be increased. When a wire-shaped Sn/Ag/Cu solder having a diameter of 1.6mm is used, a current capacity of about 50A can be obtained. However, the protection element is required to detect an overvoltage state of the battery cell, to cause a current to flow through a heating element formed of a resistor, and to cut off the soluble conductor by the heat generation, in addition to the case where the protection element is fused by an overcurrent state. However, in the case of the "thick" fusible conductor, there is a problem that heat conduction from the heating element is reduced, and it is difficult to stably fuse the fusible conductor.

Therefore, an object is to obtain a protection element capable of securing a current capacity at the time of overcurrent protection and stably fusing off even if a heat generating element generates heat.

Means for solving the problems

As a means for solving the above problems, a protection element according to the present invention includes: an insulating substrate; a heating element laminated on the insulating substrate; an insulating member laminated on the insulating substrate so as to cover at least the heating element; 1 st and 2 nd electrodes; a heating element lead-out electrode laminated on the insulating member so as to overlap the heating element and electrically connected to a current path between the 1 st and 2 nd electrodes and one terminal of the heating element; and a fusible conductor which is laminated from the heating element extraction electrode to the 1 st and 2 nd electrodes and fuses a current path between the 1 st electrode and the 2 nd electrode by heating. In addition, the fusible conductor has a portion overlapping and located on the heating element, which is a thin portion having a concave shape and a thin thickness, and the other portion is a thick portion having a thickness larger than that of the thin portion and having substantially the same current capacity as that of the thin portion, and the thin portion can be easily fused by heat generation of the heating element.

Preferably, the protective element according to the present invention further includes a support member disposed to support at least a part of the thick portion close to the thin portion with respect to the insulating substrate, the support member having a metal layer at least on a surface thereof, and the support member being thermally insulated from the insulating substrate.

Preferably, the protective element according to the present invention further includes: a molten solder discharge electrode which is in contact with the thin-walled portion of the fusible conductor and which reaches the insulating substrate through the insulating member; and a receiving electrode formed on the insulating substrate and connected to the molten solder discharging electrode.

The battery pack according to the present invention includes: 1 or more battery cells; a protection element connected to cut off a current flowing in the battery cell; and a current control element that detects respective voltage values of the battery cells and controls a current of the heating protection element. Further, the protection element has: an insulating substrate; a heating element laminated on the insulating substrate; an insulating member laminated on the insulating substrate so as to cover at least the heating element; 1 st and 2 nd electrodes; a heating element lead-out electrode laminated on the insulating member so as to overlap the heating element and electrically connected to a current path between the 1 st and 2 nd electrodes and one terminal of the heating element; and a fusible conductor laminated from the heating element extraction electrode to the 1 st and 2 nd electrodes and fusing a current path between the 1 st electrode and the 2 nd electrode by heating, wherein the fusible conductor includes a thick portion and a thin portion, and the thin portion is formed by flat molding in a concave shape with a thin thickness in a portion overlapping and located on the heating element.

In the present invention, the portion of the soluble conductor that is overlapped with the heating element is a thin portion having a concave shape and a thin thickness, and the other portion is a thick portion having a thickness larger than the thin portion and having substantially the same current capacity as the thin portion.

Further, since the heat generating element is provided with the support member having the metal layer at least on the surface thereof and thermally insulating the insulating substrate, the heat generated by the heat generating element is concentrated on the thin portion of the soluble conductor to promote the fusion of the soluble conductor, and the solder melted by the heat generation of the heat generating element is guided by the wettability of the support member and contained, so that stable fusion characteristics can be realized.

Further, the solder melted by the heat generation of the heating element can be guided by the wettability of the molten solder discharging electrode and accommodated in the accommodating electrode, and therefore, stable fusing characteristics can be realized.

Drawings

In fig. 1, fig. 1 (a) is a plan view of a protective member to which the present invention is applied; FIG. 1 (B) is a cross-sectional view taken along line AA' of FIG. 1 (A); fig. 1 (C) is a sectional view showing a state after the fusible conductor is fused.

Fig. 2 is a block diagram showing an application example of a protection element to which the present invention is applied.

Fig. 3 is a diagram showing an example of a circuit configuration of a protection element to which the present invention is applied.

In fig. 4, fig. 4 (a) is a plan view of a protective member of other embodiments of the present invention; FIG. 4 (B) is a cross-sectional view taken along line AA' of FIG. 4 (A); fig. 4 (C) is a sectional view showing a state in which the fusible conductor is melted.

In fig. 5, fig. 5 (a) to (C) are plan views for explaining a process of manufacturing a protective element according to another embodiment of the present invention.

In fig. 6, fig. 6 (a) is a plan view of a protective member combining two embodiments of the present invention; FIG. 6 (B) is a sectional view taken along line AA' of FIG. 6 (A).

In fig. 7, fig. 7 (a) is a plan view of a protection element according to a modification of the present invention; FIG. 7 (B) is a cross-sectional view taken along line AA' of FIG. 7 (A).

Fig. 8 is a cross-sectional view conceptually showing a case where the fusible conductor of the protection element of the modification of the present invention is blown; fig. 8 (a) shows a state where the thin portion of the fusible conductor starts to melt, and is a diagram showing a case where the melted solder flows in an arrow direction; fig. 8 (B) is a diagram showing a state where the thin-walled portion is fused.

In fig. 9, (a) to (C) are sectional views for explaining a procedure of manufacturing the fusible conductor used in the protection element according to the modification of the present invention.

Detailed Description

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments, and various modifications can be made without departing from the scope of the present invention.

[ Structure of protective element ]

As shown in fig. 1 (a) and 1 (B), the protection element 10 includes: an insulating substrate 11; a heating element 14 laminated on the insulating substrate 11 and covering the insulating member 15; electrodes 12 (a 1), 12 (a 2) formed at both ends of the insulating substrate 11; a heating element-drawing electrode 16 laminated on the insulating member 15 so as to overlap the heating element 14; and a fusible conductor 13 having both ends connected to the electrodes 12 (a 1) and 12 (a 2) and a central portion connected to the heating element-drawing electrode 16. Heating element electrodes 18 (P1) and 18 (P2) connected to a power supply are connected to both ends of the heating element 14 so that the heating element generates heat by flowing an electric current. The fusible conductor 13 includes: a thick portion 13a in the shape of a circular line of, for example, 1.6mm phi; and a thin portion 13b formed to be thinner than the thick portion 13a and flat so that the thickness of a portion facing the heating element 14 is substantially uniform at a position overlapping the heating element 14. The thickness of the thin portion 13b is, for example, 1/2 equal to the thickness (thickness) of the thick portion 13 a. It is preferable that the cross-sectional areas of the thick portion 13a and the thin portion 13b are substantially the same. The thin portion 13b of the soluble conductor 13 is electrically connected to the heating element-drawing electrode 16.

In this way, by making the position of the soluble conductor 13 overlapping the heating element 14 a thin-walled portion 13b, the heat conduction in the thickness direction in the thin-walled portion 13b is increased, and therefore the soluble conductor 13 can be easily fused by the heat generation of the heating element 14. Further, by forming the thin portion 13b flat, the contact area of the overlapping portion with the heating element 14 can be increased, and heat from the heating element 14 can be efficiently transmitted, so that stable fusing characteristics can be realized. In addition, when the cross-sectional areas of the thick portion 13a and the thin portion 13b are substantially the same, the current capacity of the soluble conductor 13 is not changed, and a current corresponding to the cross-sectional area in the current flowing direction of the soluble conductor 13 and the material (resistivity) of the soluble conductor 13 can be passed.

The insulating substrate 11 is formed of a member having insulating properties such as alumina, glass ceramic, mullite, zirconia, or the like. Further, a material for a printed wiring board such as a glass epoxy board or a phenol resin board may be used, but it is necessary to keep track of the temperature at which the fuse is blown.

The fusible conductor 13 is connected to the two electrodes 12 (a 1) and 12 (a 2) inside the protective element 10, and is connected to an external circuit via the two electrodes 12 (a 1) and 12 (a 2). The two electrodes 12 (a 1), 12 (a 2) may be formed on the insulating substrate 11, or may be formed as an insulating material made of epoxy resin or the like integrated with the insulating substrate 11.

The heating element 14 is a conductive member having a high relative resistance value and generating heat when energized, and is made of, for example, W, Mo, Ru, or the like. A powder of these alloys, compositions, and compounds is mixed with a resin binder or the like, a paste pattern is formed on the insulating substrate 11 by a screen printing technique, and the mixture is fired or the like.

An insulating member 15 is disposed so as to cover the heating element 14, and a heating element extraction electrode 16 is disposed so as to face the heating element 14 via the insulating member 15. Obviously, the insulating member 15 may be a laminated substrate in which the heating elements 14 are integrally laminated.

One end of the heating element-drawing electrode 16 is connected to the heating element electrode 18 (P1) and one end of the heating element 14. The other end of the heating element 14 is connected to the other heating element electrode 18 (P2).

The soluble conductor 13 may be a conductive material that melts and fuses due to an overcurrent state and heat generation of the heating element 14, and for example, a BiPb alloy, a BiSn alloy, a SnPb alloy, a PbIn alloy, a ZnAl alloy, an InSn alloy, a PbAgSn alloy, or the like may be used in addition to the SnAgCu-based lead-free solder.

The soluble conductor 13 may be a laminate of a high-melting-point metal made of Ag or Cu or a metal mainly composed of Ag or Cu and a low-melting-point metal such as lead-free solder mainly composed of Sn.

In the protection element according to the present invention, a fusible conductor having a large cross-sectional area is used because of a large current capacity. In the case where the fusible conductor is fused, since the amount of the melted solder is large, it is difficult to reliably interrupt the circuit, and therefore it is necessary to lead to a space capable of accommodating the melted solder. Further, since the thin portion 13b is provided in the fusible conductor 13, stress is likely to concentrate at the boundary between the thick portion 13a and the thin portion 13b, and mechanical damage is likely to occur.

Therefore, as shown in fig. 1 (a) to (C), the metal support member 3 is formed on the individual electrode 2 insulated from the other part of the insulating substrate 11 like a thermal circuit. The supporting member 3 is connected to support the soluble conductor 13 near the connection portion between the thick portion 13a and the thin portion 13b of the soluble conductor 13.

As shown in fig. 1 (C), when the fusible conductor 13 is melted, the solder melted is drawn in the direction of the arrow in fig. 1 (C) because the solder wettability of the support member 3 is larger than that of the insulating member 15 and the insulating substrate 11. Since the space 8 is present between the lower portion of the soluble conductor 13 and the insulating member 15 and the insulating substrate 11, the supporting member 3 and the individual electrode 2 are disposed in the space 8, and a large amount of the molten solder can be accommodated. Further, by disposing the support member 3 in the vicinity of the boundary between the thin portion 13b and the thick portion 13a of the soluble conductor 13 where stress is likely to concentrate, the portion with weak mechanical strength is supported, and the strength of the soluble conductor 13 is increased. In particular, damage to the fusible conductor 13 can be prevented during the production of the protection element 10, which can contribute to an increase in the production yield of the protection element 10. The individual electrodes 2 are formed by patterning using, for example, Cu or Ag paste, but the individual electrodes 2 are not connected to other circuits so as to be insulated from other portions like the thermal circuit of the support member 3. Further, the support member 3 and the housing electrode 4 have a certain heat capacity, and therefore a heat storage effect can be expected. When the soluble conductor 13 melts, the heat generated by the heating element 14 reaches the thin portion 13b of the soluble conductor 13 via the insulating member 15. The heat generated by the support member 3 and the individual electrode 2 flows into the support member 3 side due to the heat storage effect, and the heat is prevented from flowing out to the thick portion 13a connected to the thin portion 13 b. Therefore, the heat generated by the heating element 14 can be concentrated on the thin portion 13b of the soluble conductor 13, and this can contribute to stabilization of the fusion-cutting of the soluble conductor 13.

The metal support member 3 may be a metal that is easily wettable by solder, and may be formed integrally with the individual electrode 2 by Cu, Ag, Ni, or the like. The support member 3 uses solder having a lower melting point than the fusible conductor 13, and can be easily manufactured. That is, the individual electrodes 2 and the other electrodes are simultaneously patterned with Ag paste on the insulating substrate 11 by a general alignment process, and the insulating members 15 are disposed and connected. Subsequently, the support member 3 made of the low melting point solder is formed on the individual electrode 2, and can be easily connected to the soluble conductor 13 through the reflow process.

[ method of Using protective Member ]

As shown in fig. 2, the protection element 10 described above is used for a circuit in a battery pack of a lithium ion secondary battery.

For example, the protection element 10 is used by being incorporated into a battery pack 20 having a battery stack 25 composed of battery cells 21 to 24 of 4 lithium ion secondary batteries in total.

The battery pack 20 includes: a battery stack 25; a charge/discharge control circuit 30 for controlling charge/discharge of the battery stack 25; a protection element 10 to which the present invention is applied, which protects the battery stack 25 and the charge and discharge control circuit 30; a detection circuit 26 for detecting the voltage of each of the battery cells 21 to 24; and a current control element 27 for controlling the operation of the protection element 10 based on the detection result of the detection circuit 26.

The battery stack 25 is connected in series with battery cells 21 to 24 that need to be controlled to protect the overcharge and overdischarge states, is detachably connected to the charging device 35 via a positive electrode terminal 20a and a negative electrode terminal 20b of the battery pack 20, and is applied with a charging voltage from the charging device 35. The battery pack 20 charged by the charging device 35 is connected to the positive electrode terminal 20a, and the negative electrode terminal 20b is connected to an electronic device operated by the battery, so that the electronic device can be operated.

The charge and discharge control circuit 30 includes: two current control elements 31, 32 connected in series on a current path flowing from the battery stack 25 into the charging device 35; and a control unit 33 for controlling the operations of the current control elements 31 and 32. The current control elements 31 and 32 are formed of, for example, field effect transistors (hereinafter, referred to as FETs), and control the on/off of the current path of the cell stack 25 by controlling the gate voltage by the control unit 33. The control unit 33 operates by receiving power supply from the charging device 35, and controls the operation of the current control elements 31 and 32 so as to block the current path when the battery stack 25 is overdischarged or overcharged based on the detection result of the detection circuit 26.

The protection element 10 is connected to a charge/discharge current path between the battery stack 25 and the charge/discharge control circuit 30, for example, and its operation is controlled by the current control element 27.

The detection circuit 26 is connected to each of the battery cells 21 to 24, detects the voltage value of each of the battery cells 21 to 24, and supplies each voltage value to the control unit 33 of the charge/discharge control circuit 30. The detection circuit 26 outputs a control signal for controlling the current control element 27 when any one of the battery cells 21 to 24 becomes an overcharge voltage or an overdischarge voltage.

The current control element 27 operates the protection element 10 to interrupt the charge/discharge current path of the battery stack 25 independently of the switching operation of the current control elements 31 and 32 when the voltage values of the battery cells 21 to 24 become a voltage exceeding a predetermined over-discharge or over-charge state based on the detection signal output from the detection circuit 26.

In the battery pack 20 configured as described above, the configuration of the protection element 10 will be described in detail.

First, the protection element 10 to which the present invention is applied has a circuit configuration as shown in fig. 3, for example. That is, the circuit configuration of the protection element 10 includes: a fusible conductor 13 connected in series via a heating element lead-out electrode 16; and a heating element 14 that generates heat by being energized through the connection point of the soluble conductor 13 to melt the soluble conductor 13. In the protective element 10, for example, the soluble conductor 13 is connected in series to the charge/discharge current path, and the heating element 14 is connected to the current control element 27. Of the 2 electrodes 12, 12 of the protection element 10, one is connected to a1, and the other is connected to a 2. The heating element-drawing electrode 16 and the heating element electrode 18 connected thereto are connected to P1, and the other heating element electrode 18 is connected to P2.

In the protection element 10 having such a circuit configuration, the fusible conductor 13 on the current path can be reliably fused by heat generation of the heating element 14 while achieving a reduction in height.

[ other embodiments ]

As shown in fig. 4 (a) and 4 (B), the protection element 10 of the present invention may include: a molten solder discharge electrode 5 formed on the insulating member 15 so as to be close to the thin-walled portion 13 b; and a containing electrode 4 for containing the molten solder guided by the molten solder discharge electrode 5 on the insulating substrate 11. By providing the molten solder discharge electrode 5 and the receiving electrode 4, a large amount of molten solder using a fusible conductor of "thick" solder for a large current can be guided, which can contribute to reliable separation of the fusible conductor 13.

The molten solder discharging electrode 5 is formed on the same surface as the heating element-drawing electrode 16 formed on the insulating member 15. The molten solder discharging electrode 5 is arranged along the longitudinal direction of the fusible conductor 13, is connected to the thin portion 13b on the insulating member 15, and is connected to the storage electrode 4 formed on the insulating substrate 11 through a side surface (side surface electrode) of the insulating member 15. The molten solder discharging electrode 5 may be configured by forming a through-hole electrode so as to face the rear surface side from the upper surface of the insulating member 15. The lower surface and the side surface of the side surface electrode of the insulating member 15 are connected to the housing electrode 4 by solder. Then, the surfaces of the molten solder discharging electrode 5 and the receiving electrode 4 are subjected to soldering treatment to form a fillet.

As shown in fig. 4 (C), when the thin portion 13b of the soluble conductor 13 melts, capillary inflow occurs in the gap between the thin portion 13b of the soluble conductor 13 and the insulating member 15, and the molten solder moves along the molten solder discharge electrode 5 forming the fillet and is guided in the direction of accommodating the electrode 4. If the area of the housing electrode 4 is set to be large to some extent, the molten solder is housed in the housing electrode 4 in accordance with the wettability of the housing electrode 4. By providing the path and the receiving portion for guiding the melted solder in this way, even in the case of the large-current fusible conductor 13 using a large amount of solder, the melted solder can be separated and the circuit can be reliably interrupted.

As shown in fig. 5 (a) to (C), the path for accommodating the molten solder in this embodiment can be easily formed by patterning a metal by, for example, a printing technique.

As shown in FIG. 5A, heating element electrodes 18 (P1) and 18 (P2) for supplying electric power to the heating element 14 are formed on an insulating substrate 11, and a storage electrode 4 is formed. These electrodes may be formed in a Cu pattern or may be formed using Ag paste. As shown in fig. 5B, an insulating member (laminated substrate) 15 of the laminated heating element 14 is welded to an electrode pattern formed on the insulating substrate 11. Electrodes 18a (P1), 18a (P2) for supplying power to the heating element 14 are formed on one pair of opposing sides of the rectangular insulating member 15, and molten solder discharging electrodes 5, 5 are formed on the other pair of opposing sides. As shown in fig. 5 (C), on the insulating member 15 mounted, the fusible conductor 13 is carried. The heating element-drawing electrode 16 and the molten solder-discharging electrode 5 are disposed so as to be connected to the thin portion 13b when the fusible conductor 13 is mounted.

This embodiment can be combined with the embodiment described with reference to fig. 1 to form a protective element. That is, as shown in fig. 6 (a) and 6 (B), the support member 3 is formed on the individual electrode 2 formed on the insulating substrate 11, and the molten solder discharge electrode 5 is provided on the insulating member 15 and connected to the receiving electrode 4 formed on the insulating substrate 11. Here, if the storage electrode 4 is formed in a ring shape and the individual electrode 2 is patterned so as to be disposed at the center of the ring, the limited area on the insulating substrate 11 can be effectively used. The pattern of the electrode is not limited to this, and can be set arbitrarily.

[ modified examples ]

In the case of a protection element that is compatible with a large current, ensuring a space for accommodating a large amount of molten solder is the biggest problem, and a modification for this will be described.

As shown in fig. 7 a and 7B, a space (recess) for accommodating the insulating member 15 mounted on the insulating substrate 11 is present in the thin portion 13B of the soluble conductor 13, and the molten solder can be accommodated more easily by enlarging the space as viewed from the insulating member 15 side. That is, as shown in fig. 7 (B), the thin portion 13B of the soluble conductor 13 is bent in a shape such that the central portion 13d, which is located at a substantially equal distance from the boundary position 13c between the thin portion 13B and the thick portion 13a, is connected to the heating element-drawing electrode 16. Further, the center portion 13d is bent upward toward the boundary position 13c, so that the distance in the vertical direction between the boundary position 13c and the insulating member 15 can be increased.

As shown in fig. 8 (a), when the heating element 14 is energized, the thin portion 13b of the soluble conductor 13 melts, and the melted solder is guided to the side of the support member 3 having high solder wettability by the space of the boundary position 13c and the insulating member 15. As shown in fig. 8 (B), the molten solder is drawn to one side of the support member 3 on both sides and is contained, while also being contained on the heating element-drawing electrode 16.

The fusible conductor 13 having the thin portion 13b formed in the "M" shape in cross section can be manufactured, for example, as follows.

As shown in fig. 9 (a), the pressing pin 40 is disposed at a predetermined position where the thin portion 13b of the soluble conductor 13 is to be formed, and is moved in the arrow direction. As shown in fig. 9 (B), when the pressing pin 40 is pressed against the soluble conductor 13 at a predetermined pressure, both ends of the soluble conductor 13 are bent to the side receiving the pressure even if the thin portion 13B is linear due to the ductility and rigidity of the metal when the pressing pin 40 is removed. As shown in fig. 9 (C), when pressure is applied in the arrow direction to both ends of the bent soluble conductor 13 so that the thick portions 13a on both sides are linear, the thin portion 13b has a substantially M-shape. The longitudinal cross-sectional shape of the soluble conductor 13 of the thin portion 13b is not limited to the "M" shape, and any similar shape may be used to expand the accommodating space for the molten solder in the direction along the thick portion 13a of the soluble conductor 13.

This modification can be used in combination with the support member 3 and/or the molten solder discharging electrode 5, and thus a further mechanism for discharging molten solder can be ensured, and stable fusing characteristics can be achieved.

Description of the reference symbols

2 individual electrodes, 3 support members, 4 accommodating electrodes, 5 molten solder discharge electrodes, 8 spaces, 10 protective elements, 11 insulating substrates, 12 (a 1), 12 (a 2) electrodes, 13 fusible conductors, 13a thick-walled portions, 13b thin-walled portions, 13c boundary positions, 13d central portions, 14 heating elements, 15 insulating members, 16 heating element lead-out electrodes, 17 solder, 18 (P1), 18 (P2) heating element electrodes, 18a (P1), 18a (P2) electrodes, 20 battery packs, 20a positive electrode terminals, 20b negative electrode terminals, 21 to 24 battery cells, 25 battery stacks, 26 detection circuits, 27, 31, 32 current control elements, 30 charge and discharge control circuits, 33 control portions, 35 charging devices, 40 press pins.

Claims

1. A protective element, comprising:

an insulating substrate;

a heating element laminated on the insulating substrate;

an insulating member laminated on the insulating substrate so as to cover at least the heating element;

1 st and 2 nd electrodes;

a heating element-drawing electrode laminated on the insulating member so as to overlap the heating element, and electrically connected to a current path between the 1 st and 2 nd electrodes and one terminal of the heating element; and

a fusible conductor laminated from the heating element extraction electrode to the 1 st and 2 nd electrodes, and fusing a current path between the 1 st electrode and the 2 nd electrode by heating,

the fusible conductor includes a thick portion and a thin portion, and the thin portion is formed by a thin and flat concave shape of a portion overlapping and located on the heating element.

2. The protective element of claim 1,

the thin portion is formed by a thin portion formed on the insulating substrate, and the thick portion is formed by a thick portion formed on the insulating substrate and a thin portion formed on the thin portion.

3. The protective element according to claim 2,

the support member is thermally insulated from the insulating substrate.

4. The protective element of claim 1,

the solder-melting apparatus further includes a molten solder discharge electrode that is located near the thin portion of the fusible conductor and reaches the insulating substrate through the insulating member.

5. The protective element according to claim 4,

the solder-melting apparatus further comprises a storage electrode formed on the insulating substrate and connected to the molten solder discharge electrode.

6. The protective element according to claim 1,

the fusible conductor is connected to the heating element-drawing electrode at an intermediate portion of the thin portion, and a path through which the molten solder flows from the connected portion toward a boundary position between the thin portion and the thick portion is formed.

7. The protective element according to claim 6,

the thin-walled fusible conductor has an M-shaped cross section in the longitudinal direction and the stacking direction.

8. Protection element according to claim 2 or 3,

the support member has a metal material having a melting point lower than that of the fusible conductor at least on a surface thereof.

9. The protective element according to claim 8,

the low-melting-point metal material is a low-melting-point solder.

10. The protective element according to claim 1,

the thin portion and the thick portion have substantially the same cross-sectional area.

11. A battery pack, comprising:

1 or more battery cells;

a protection element connected to interrupt a current flowing through the battery cell; and

a current control element for detecting the voltage value of each battery unit and controlling the current for heating the protection element,

the protection element includes:

an insulating substrate;

a heating element laminated on the insulating substrate;

1 st and 2 nd electrodes;