KR101946105B1 - Protective element and battery pack - Google Patents

Abstract

The protection element 10 includes an insulating substrate 11 and a heating element 11 which is laminated on the insulating substrate 11 and is covered with the insulating member 15, Electrodes 12 (A1) and 12 (A2) formed on both ends of the insulating substrate 11 and a heating element lead-out electrode 16 laminated on the insulating member 15 so as to overlap the heating element 14, And a usable conductor 13 whose both ends are connected to the electrodes 12 (A1) and 12 (A2) and whose center portion is connected to the heating-element lead-out electrode 16. The usable conductor 13 has a thicker portion 13a of a round wire of, for example, 1.6 mm? And a thicker portion 13a so as to have a substantially uniform thickness at a position where the portion facing the heating element 14 overlaps the heating element 14. [ And a thin-walled portion 13b formed thinner than the thin-walled portion 13b. The thickness of the thin portion 13b is, for example, 1/2 of the thickness (thickness) of the thick portion 13a.

Description

[0001] PROTECTIVE ELEMENT AND BATTERY PACK [0002]

The present invention relates to a protection device for protecting a circuit connected on an electric current path by fusing an electric current path. This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-171332, filed on August 1, 2012, the entirety of which is incorporated herein by reference.

Most of the secondary batteries that can be charged and used repeatedly are processed into battery packs and provided to the user. Particularly, in a lithium ion secondary battery having a high weight energy density, in order to secure the safety of the user and the electronic equipment, generally, some protection circuit such as overcharge protection and over discharge protection is built in the battery pack, It has a function to block the output of the pack.

BACKGROUND ART [0002] In an electronic device using most lithium ion secondary batteries, an output is turned ON / OFF using an FET switch incorporated in a battery pack to perform overcharge protection or over-discharge protection operation of the battery pack. However, when the FET switch is short-circuited for some reason, a momentary large current flows due to a lightning surge or the like, or the output voltage greatly decreases due to the life of the battery cell, In either case, the battery pack or the electronic device must be protected from accidents such as ignition. Therefore, in order to safely shut off the output of the battery cell in any such abnormal state that can be assumed, a protection element including a fuse element having a function of cutting off the current path by an external signal is used.

As a protection element for a protection circuit suitable for such a lithium ion secondary battery, as disclosed in Patent Document 1, a structure is known in which a heating element is provided inside a protective element and the usable conductor on the current path is fused by heat generation of the heating element. .

Japanese Patent Application Laid-Open No. 2010-3665

In the protection device described in Patent Document 1, the usable conductor (fuse) has a current capacity of about 15 A at the maximum for use in applications where the current capacity is comparatively low such as a cellular phone or a notebook computer. The use of lithium ion secondary batteries has recently been expanded, and applications for larger currents, such as electric power tools such as electric drivers, and hybrid electric vehicles, electric vehicles, electric bicycles, and the like, . In these applications, large currents exceeding several tens of amperes to 100 amperes may flow, particularly at startup. It is desired to realize a protection element corresponding to such a large current capacity.

In order to realize a protection element corresponding to a large current, it is sufficient to increase the cross-sectional area of the usable conductor. When a Sn / Ag / Cu solder formed into a linear shape of 1.6 mm? Is used, a current capacity of about 50 A can be obtained. However, in addition to the case where the protection element is fused by the overcurrent state, it is necessary to detect the overvoltage state of the battery cell, to supply current to the heating element formed of the resistor, and to cut the usable conductor by the heat generation. However, in the case of the " coarse " usable conductor, the heat conduction from the exothermic body is lowered, which makes it difficult to stably melt the usable conductor.

It is therefore an object of the present invention to provide a protection device capable of stably fusing even by heat generated by a heating element while securing current capacity at the time of overcurrent protection.

According to an aspect of the present invention, there is provided a protection 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; A heating element lead-out electrode laminated on the insulating member so as to overlap with the heating element and electrically connected to a current path between the first and second electrodes and to one terminal of the heating element; And an available conductor which fuses a current path between the first electrode and the second electrode by heating. The permissible conductor is a thick portion having a thickness thinner in thickness than the thin portion and having a current capacity substantially equal to that of the thin portion, the portion overlapping with the heat generating element being concave, Can be easily fused by the heat generated by the heating element.

Preferably, the protection element according to the present invention further comprises a support member having at least a surface metal layer disposed to support at least a part of the thick portion close to the thin portion against the insulating substrate, And is thermally insulated from the insulating substrate.

Preferably, the protection element according to the present invention comprises: a molten solder discharge electrode contacting the thin portion of a usable conductor and passing through an insulating member and reaching an insulating substrate; a solder discharge electrode formed on the insulating substrate and connected to the molten solder discharge electrode, Respectively.

A battery pack according to the present invention includes at least one battery cell, a protection element connected to cut off a current flowing in the battery cell, and a current control element for detecting a voltage value of each battery cell, Respectively. The protection element 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, first and second electrodes, and an insulating member A current path between the first and second electrodes, and a heating-element lead-out electrode electrically connected to one terminal of the heating-current lead, and a heating-element lead-out electrode which is laminated from the heating-element lead-out electrode to the first and second electrodes, And a usable conductor for melting a current path between the two electrodes. The usable conductor includes a thick portion and a thin portion that is formed in a concave shape and thinly formed and flattened, the portion overlapping the heat element.

The present invention is characterized in that the usable conductor is a thick thin portion having a concave shape in which the portion where the usable conductor overlaps with the heating body is thick and the other portion is thicker than the thin portion and has a thick- The usable conductor can be easily fused by the heat generation of the heating element without lowering the current capacity of the usable conductor.

Further, since the supporting member having at least a metal layer on its surface and being thermally insulated from the insulating substrate is further provided, the heat generated by the heating element is concentrated on the thin portion of the usable conductor to promote the fusing of the usable conductor, The solder melted by the heat of the support member is introduced and accommodated by the wettability of the support member, so that stable stable solder characteristics can be realized.

Further, the solder melted by the heat generated by the heating element can be guided by the wettability of the molten solder discharge electrode, and can be accommodated in the receiving electrode, so that the stable melting characteristic can be realized.

1A is a plan view of a protection device to which the present invention is applied. 1B is a cross-sectional view taken along the line AA 'in FIG. 1A. 1C is a cross-sectional view showing a state in which the usable conductor is fused.
2 is a block diagram showing an application example of a protection device to which the present invention is applied.
3 is a diagram showing an example of the circuit configuration of a protection device to which the present invention is applied.
4A is a plan view of a protection device according to another embodiment of the present invention. 4B is a cross-sectional view taken along line AA 'of FIG. 4A. 4C is a cross-sectional view showing a state in which the usable conductor is being melted.
5A to 5C are plan views for explaining a manufacturing process of a protection device according to another embodiment of the present invention.
6A is a plan view of a protection device in which two embodiments are combined with the present invention. 6B is a cross-sectional view taken along line AA 'of Fig. 6A.
7A is a plan view of a protection device according to a modification of the present invention. FIG. 7B is a cross-sectional view taken along line AA 'of FIG. 7A.
8 is a cross-sectional view conceptually showing a state in which a usable conductor of a protective element of the modification of the present invention is fused. Fig. 8A shows a state in which the thin portion of the usable conductor starts to melt, and Fig. 8B shows a state in which molten solder flows in the arrow direction. Fig. 8B shows a state in which the thin portion is fused.
9A to 9C are cross-sectional views for explaining a procedure for manufacturing an available conductor used in a protection device according to a modification of the present invention.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. It is needless to say that the present invention is not limited to the following embodiments, and various modifications can be made within the scope not departing from the gist of the present invention.

[Configuration of Protection Device]

1A and 1B, the protection element 10 includes an insulating substrate 11, a heat generating element 14 laminated on the insulating substrate 11 and covered with the insulating member 15, an insulating substrate 11, Electrodes 12 (A1) and 12 (A2) formed at both ends of the electrode 12 (A1) and 12 (A2) formed on both ends of the insulating member 15, a heating element lead-out electrode 16 laminated so as to overlap the heating element 14 on the insulating member 15, , 12 (A2), and a central portion thereof is connected to the heating-element lead-out electrode 16. At both ends of the heat generating element 14, heating element electrodes 18 (P1) and 18 (P2) for connecting a power source are connected so as to generate current by flowing a current to the heating element. The usable conductor 13 has a thick portion 13a of 1.6 mm in diameter and a portion facing the heating element 14 so as to be substantially uniform in thickness at a position overlapping the heating element 14, And a thin-walled portion 13b thinner and flat than the wall 13a. The thickness of the thin portion 13b is, for example, 1/2 of the thickness (thickness) of the thick portion 13a. The cross-sectional areas of the thick portion 13a and the thin portion 13b are preferably substantially the same. The thin-walled portion 13b of the usable conductor 13 is electrically connected to the heating-element lead-out electrode 16.

Since the thick conductor 13b of the conductor 13 is thinned at the position overlapping the heating element 14, the thermal conductivity in the thickness direction of the thin portion 13b is improved, The usable conductor 13 can be readily fused by heat generation. Further, by forming the thin portion 13b flat, the contact area with the overlap portion of the heat generating element 14 can be increased, the heat from the heat generating body 14 can be efficiently transmitted, and stable stable melting characteristics can be realized . The current capacity of the usable conductor 13 does not change and the sectional area of the usable conductor 13 in the current carrying direction and the cross sectional area of the usable conductor 13 do not change, A current according to the material (resistivity) of the resistor can be passed.

The insulating substrate 11 is formed of a member having an insulating property such as alumina, glass ceramics, mullite, zirconia, or the like. Other materials used for a printed wiring board such as a glass epoxy substrate and a phenol substrate can be used, but it is necessary to pay attention to the temperature at the time of fusing.

The two electrodes 12 (A1) and 12 (A2) connect the usable conductors 13 in the inside of the protective element 10 and are connected to the outside through the two electrodes 12 (A1) and 12 Circuit. The two electrodes 12 (A1) and 12 (A2) may be formed on the insulating substrate 11 or may be formed of an insulating material including an epoxy resin or the like integrated with the insulating substrate 11 have.

The heat generating element 14 is a member having a relatively high resistance value and having conductivity to generate heat when energized, and includes, for example, W, Mo, Ru, and the like. The alloy, the composition, and the compound powder are mixed with a resin binder or the like to form a paste, and the paste is formed on the insulating substrate 11 by patterning and firing using a screen printing technique.

An insulating member 15 is disposed so as to cover the heating element 14 and a heating element lead-out electrode 16 is disposed so as to face the heating element 14 via the insulating member 15. It goes without saying that the insulating member 15 may be a laminated substrate in which the heating elements 14 are integrally laminated.

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

The usable conductor 13 may be any conductive material that melts and fuses by the overcurrent state and the heat generated by the heating element 14. For example, in addition to SnAgCu-based Pb-free solder, BiPbSn alloy, BiPb alloy, BiSn alloy, SnPb Alloy, PbIn alloy, ZnAl alloy, InSn alloy, PbAgSn alloy and the like can be used.

The usable conductor 13 may be a laminate of a refractory metal containing Ag or Cu or a metal mainly composed of Ag or Cu and a refractory metal such as Pb-free solder containing Sn as a main component.

In the protection device according to the present invention, an available conductor having a large cross-sectional area is used in order to cope with a large current capacity. In the case where the usable conductor is fused, since the amount of the solder to be melted is large, it is difficult to surely cut off the circuit, and therefore it is necessary to induce a space capable of accommodating the molten solder. In addition, by providing the thin portion 13b on the usable conductor 13, the stress tends to concentrate at the boundary position between the thick portion 13a and the thin portion 13b, and mechanical damage is likely to occur.

Thus, as shown in Figs. 1A to 1C, a metal supporting member 3 is formed on the independent electrode 2, which is thermally insulated from the other part of the insulating substrate 11. The support member 3 is connected to support the usable conductor 13 in the vicinity of the connection portion between the thick portion 13a and the thin portion 13b of the usable conductor 13. [

1C, since the solder wettability of the support member 3 is larger than that of the insulating member 15 and the insulating substrate 11 at the time of melting the usable conductor 13, It is drawn in the direction of the arrow. A space 8 is provided between the lower portion of the usable conductor 13 and the insulating member 15 and the insulating substrate 11. By arranging the supporting member 3 and the independent electrode 2 in this space 8, Of the molten solder. The support member 3 can be disposed in the vicinity of the boundary between the thin portion 13b and the thick portion 13a of the usable conductor 13 where the stress can easily concentrate, The strength of the conductor 13 is improved. In particular, it is possible to prevent damage to the usable conductor 13 at the time of manufacturing the protection element 10, thereby contributing to improvement of the production yield of the protection element 10. [ The independent electrode 2 is formed by patterning, for example, with Cu or Ag paste, but the independent electrode 2 is not connected to other circuits so that the support member 3 is thermally isolated from other parts. In addition, since the supporting member 3 and the receiving electrode 4 have a constant heat capacity, a heat storage effect can be expected. The heat generated by the heating element 14 reaches the thin portion 13b of the usable conductor 13 through the insulating member 15 when the usable conductor 13 is melted. Heat generated by the support member 3 and the independent electrode 2 is introduced into the side of the support member 3 to prevent the heat from flowing to the thick portion 13a connected to the thin portion 13b . Therefore, the heat generated by the heating element 14 can be concentrated on the thin portion 13b of the usable conductor 13, contributing to stabilization of the melting point of the usable conductor 13. [

The support member 3 made of metal may be a metal that can easily wet the solder, and may be integrally formed with the independent electrode 2 using Cu, Ag, Ni or the like. The support member 3 can be easily manufactured by using solder having a melting point lower than that of the usable conductor 13. That is, the independent electrodes 2 are patterned on the insulating substrate 11 by Ag paste at the same time as the other electrodes by using a normal alignment process, and the insulating member 15 is arranged and connected. Thereafter, the support member 3 including the low melting point solder is formed on the independent electrode 2, and the solder can be easily connected to the usable conductor 13 through the reflow process.

[How to use the protection device]

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

For example, the protection element 10 is used in a battery pack 20 having a battery stack 25 including battery cells 21 to 24 of a total of four lithium ion secondary batteries.

The battery pack 20 includes a battery stack 25, a charge / discharge control circuit 30 for controlling charge / discharge of the battery stack 25, The detection circuit 26 for detecting the voltage of each of the battery cells 21 to 24 and the operation of the protection element 10 in accordance with the detection result of the detection circuit 26 And a current control element 27 are provided.

The battery stacks 25 are connected in series to the battery cells 21 to 24 that require control to protect the overcharged and overdischarged states and are connected in series between the positive terminal 20a and the negative terminal 20b of the battery pack 20, And the charging voltage from the charging device 35 is applied. The electronic device can be operated by connecting the positive electrode terminal 20a and the negative electrode terminal 20b of the battery pack 20 charged by the charging device 35 to an electronic device that operates as a battery.

The charge / discharge control circuit 30 includes two current control elements 31 and 32 connected in series to the current path from the battery stack 25 to the charging device 35, and the operation of the current control elements 31 and 32 And a control section 33 for controlling the control section 33. The current control elements 31 and 32 are constituted by, for example, a field effect transistor (hereinafter referred to as an FET) and control the gate voltage by the control unit 33 to conduct the current path of the battery stack 25 And blocking. The control unit 33 operates in response to the power supplied from the charging device 35 and controls the current control so as to block the current path when the battery stack 25 is overdischarged or overcharged in accordance with the detection result by the detection circuit 26 Thereby controlling the operation of the elements 31 and 32.

The protection element 10 is connected, for example, on the charging / discharging current path between the battery stack 25 and the charging / discharging control circuit 30, 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 and detects the voltage value of each battery cell 21 to 24 and supplies each voltage value to the control section 33 of the charge / discharge control circuit 30 Supply. Further, 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 is turned on when the voltage value of the battery cells 21 to 24 becomes a voltage exceeding a predetermined overdischarge or overcharge state by the detection signal outputted from the detection circuit 26, To control the charging / discharging current path of the battery stack 25 to be interrupted without depending on the switching operation of the current control elements 31 and 32. [

The configuration of the protection device 10 in the battery pack 20 including the above configuration will be described in detail.

First, the protection device 10 to which the present invention is applied has a circuit configuration as shown in Fig. 3, for example. That is, the protection element 10 is connected to the heating conductor 14, which is connected in series via the heating element lead-out electrode 16, with the heating element 14 ). In the protection element 10, for example, the usable conductor 13 is connected in series on the charging / discharging current path, and the heating element 14 is connected to the current control element 27. One of the two electrodes 12 and 12 is connected to the protection element 10, and the other is connected to the protection element A2. Further, the heating-element lead-out 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.

The protective element 10 including such a circuit configuration can reliably fuse the usable conductor 13 on the current path by the heat generated by the heating element 14 while realizing a reduction in height.

[Other Embodiments]

4A and 4B, the protective element 10 of the present invention includes a molten solder discharge electrode 5 formed on the insulating member 15 so as to be close to the thin-walled portion 13b, 11 may be provided with a receiving electrode 4 for receiving the molten solder induced by the molten solder discharge electrode 5. By providing the molten solder discharge electrode 5 and the receiving electrode 4, a large amount of molten solder of the usable conductor using the " coarse " solder for coping with a large current is induced to contribute to the reliable division of the usable conductor 13 can do.

The molten solder discharge electrode 5 is formed on the same plane as the heating-element lead-out electrode 16 formed on the insulating member 15. The molten solder discharge electrode 5 is disposed along the longitudinal direction of the usable conductor 13 and connected to the thin portion 13b on the insulating member 15 and connected to the side surface of the insulating member 15 And is connected to the receiving electrode 4 formed on the insulating substrate 11 through the through- The molten solder discharge electrode 5 may be formed by forming a through-hole electrode from the upper surface of the insulating member 15 to the back surface side. The lower surface and the side surface of the side electrode of the insulating member 15 and the receiving electrode 4 are connected by solder. Then, the surfaces of the molten solder discharge electrode 5 and the receiving electrode 4 are soldered to form a solder fillet.

When the thin portion 13b of the usable conductor 13 is melted as shown in Fig. 4C, the capillary flows into the gap between the thin portion 13b of the usable conductor 13 and the insulating member 15, The molten solder moves along the molten solder discharge electrode 5 formed, and is guided in the direction of the receiving electrode 4. The molten solder is accommodated on the receiving electrode 4 in accordance with the wettability of the receiving electrode 4 if the area in which the receiving electrode 4 is disposed is taken to be somewhat large. By disposing the path where the molten solder is guided and the accommodating portion, the molten solder can be divided and the circuit can be surely blocked even in the case of the usable conductor 13 for a large current using a large amount of solder.

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

5A, heating electrode 18 (P1), 18 (P2) for supplying power to the heating element 14 is formed on the insulating substrate 11, and at the same time, the receiving electrode 4 is formed . This electrode may form a Cu pattern or may be formed of Ag paste. As shown in Fig. 5B, an insulating member (laminated substrate) 15 in which a heating element 14 is laminated is connected to an electrode pattern formed on the insulating substrate 11 by soldering. Electrodes 18a (P1) and 18a (P2) for power supply of the heating element 14 are formed on a pair of opposite sides of the insulating member 15 formed in a rectangular shape, and on the other pair of opposite sides, Solder discharge electrodes 5 and 5 are formed. As shown in Fig. 5C, the usable conductor 13 is mounted on the insulating member 15 mounted. When the usable conductor 13 is mounted, the heating element lead-out electrode 16 and the molten solder discharge electrode 5 are connected to the thin portion 13b.

In this embodiment, a protection element may be formed by combining the embodiments described in Fig. 6A and 6B, the supporting member 3 is formed on the independent electrode 2 formed on the insulating substrate 11 and the molten solder discharge electrode 5 And is connected to the receiving electrode 4 formed on the insulating substrate 11. [ Here, if the receiving electrode 4 is formed in an annular shape and the independent electrode 2 is arranged at the center of the ring, a limited area on the insulating substrate 11 can be effectively utilized. It is needless to say that the patterning of the electrode is not limited to this and can be arbitrarily set.

[Modifications]

In the case of the protection element corresponding to a large current, securing a space for accommodating a large amount of molten solder is the greatest problem, and a modification will be described.

7A and 7B, a space (concave portion) in which the insulating member 15 mounted on the insulating substrate 11 is accommodated exists in the thin-walled portion 13b of the usable conductor 13, By expanding the space from the side of the insulating member 15, it becomes possible to more easily accommodate the molten solder. 7B, the shape of the thin portion 13b of the usable conductor 13 is substantially the same as the center portion (that is, substantially the same distance from the boundary position 13c between the thin portion 13b and the thick portion 13a) 13d are bent to be connected to the heating-element lead-out electrode 16. The distance between the boundary position 13c and the insulating member 15 in the vertical direction can be increased by bending upward from the central portion 13d toward the boundary position 13c.

As shown in Fig. 8A, when the heating element 14 is energized, the thin portion 13b of the usable conductor 13 melts and the solder is melted and the distance between the boundary position 13c and the insulating member 15 becomes vacant The solder wettability is induced on the side of the support member 3 having a large wettability. As shown in Fig. 8B, the melted solder is also received on the heating member lead-out electrode 16 while being drawn into the support members 3 on both sides and accommodated.

The usable conductor 13 having the thin-walled portion 13b having the cross-sectional shape of " M " shape can be manufactured, for example, as follows.

9A, the pressing pin 40 is disposed at a predetermined position at which the thin portion 13b of the usable conductor 13 should be formed, and is moved in the direction of the arrow. 9B, when the pressing pin 40 is pressed against the usable conductor 13 at a predetermined pressure, when the pressing pin 40 is removed due to the ductility and rigidity of the metal, the thin portion 13b Are both in a straight line, both ends of the usable conductor 13 are bent toward the side where the pressure is applied. As shown in Fig. 9C, when the both ends of the bent flexible conductor 13 are pressed in the direction of the arrow so that the thick portions 13a on both sides are linear, the shape of the thin portion 13b is almost "M" Shape. The sectional shape in the longitudinal direction of the usable conductor 13 of the thin portion 13b is not limited to the above-described "M" shape but may be a shape of the solder in the direction of the thick portion 13a of the usable conductor 13 Needless to say, depending on the intention of enlarging the space, it may be any similar shape.

This modified example can be used in combination with the above-described support member 3 and / or the molten solder discharge electrode 5, and further, a discharging mechanism of molten solder is ensured, and stable stable soldering characteristics can be realized It becomes.

2: independent electrode
3: Support member
4: receiving electrode
5: Melted solder discharge electrode
8: Space
10: Protection element
11: insulating substrate
12 (A1), 12 (A2): electrode
13: Available conductor
13a: thickening
13b: Thin wall
13c: Boundary position
13d:
14: Heating element
15: Insulation member
16: Heating element extraction electrode
17: Flux
18 (P1), 18 (P2): Heating element electrode
18a (P1), 18a (P2): electrode
20: Battery pack
20a: Positive electrode terminal
20b: negative terminal
21 to 24: Battery cell
25: Battery stack
26: Detection circuit
27, 31, 32: current control element
30: charge / discharge control circuit
33:
35: Charging device
40:

Claims (11)

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;
First and second electrodes,
A heating element lead electrode laminated on the insulating member so as to overlap with the heating element and electrically connected to a current path between the first and second electrodes and one terminal of the heating element;
And an usable conductor which is laminated from the heating element lead-out electrode to the first and second electrodes and which fuses a current path between the first electrode and the second electrode by heating,
Wherein the flexible conductor comprises a thick portion and a thin portion which is concave and has a thinner thickness than that of the thick portion and overlaps with the heating element. 2. The flexible printed circuit board according to claim 1, wherein at least a part of the thick portion close to the thin portion is arranged so as to be spaced from the insulating substrate and to accommodate the melted available conductor between the usable conductor and the insulating substrate Further comprising a support member having at least a metal layer on its surface. The protection device according to claim 2, wherein the support member is thermally insulated from the insulating substrate. The protective device according to claim 1, further comprising a molten solder discharge electrode which is close to a thin portion of the usable conductor and reaches the insulating substrate through the insulating member. The protection device according to claim 4, further comprising an accommodation electrode formed on the insulating substrate and connected to the molten solder discharge electrode. 2. The semiconductor device according to claim 1, wherein the flexible conductor is connected to the heating-element lead-out electrode at an intermediate portion of the thin-wall portion, and from the connected portion toward a boundary position between the thin- And a flow path is formed. 7. The protective device according to claim 6, wherein the thin portion is formed in a M-shaped cross-sectional shape in the stacking direction with respect to the longitudinal direction of the usable conductor. The protection device according to claim 2 or 3, wherein the support member has a metal material having a melting point lower than that of the usable conductor at least on its surface. The protective device according to claim 8, wherein the metal material is solder having a melting point lower than that of the usable conductor. The protection device according to claim 1, wherein a cross-sectional area of the thin portion and that of the thick portion are the same. At least one battery cell,
A protection element connected to cut off a current flowing in the battery cell,
And a current control element for detecting a voltage value of each of the battery cells and controlling a current for heating the protection element,
The protection device 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;
First and second electrodes,
A heating element lead electrode laminated on the insulating member so as to overlap with the heating element and electrically connected to a current path between the first and second electrodes and one terminal of the heating element;
And an available conductor which is laminated from the heating element lead-out electrode to the first and second electrodes and fuses a current path between the first electrode and the second electrode by heating,
Wherein the usable conductor includes a thick portion and a thin portion formed in a concave shape and thinner than the thick portion and overlapped with the heating element and formed flat.

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