WO2014021157A1

WO2014021157A1 - Protective element and battery pack

Info

Publication number: WO2014021157A1
Application number: PCT/JP2013/069996
Authority: WO
Inventors: 武雄木村; 後藤　一夫; 吉弘米田; 佐藤　浩二
Original assignee: デクセリアルズ株式会社
Priority date: 2012-08-01
Filing date: 2013-07-24
Publication date: 2014-02-06
Also published as: TW201419351A; CN104508789B; JP6081096B2; KR101946106B1; HK1208759A1; CN104508789A; JP2014032770A; TWI585801B; KR20150040955A

Abstract

In order to obtain a protective element that can be easily made to fuse and that is capable of reliably dividing molten solder, a protective element (10) is provided with: an insulating substrate (11), a heating element (14) that is layered on the insulating substrate (11) and covered by an insulating member (15); electrodes (12)(A1) and (12)(A2); 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), said heating element-drawing electrode (16) being provided with a protective layer (8). The fusible conductor (13) comprises a thick section (13a) and a thin section (13b) that is molded so as to be thin and flat. The form of the heating element-drawing electrode (16) that is extended in the lengthwise direction of the fusible conductor (13) and in the direction that is perpendicular to said lengthwise direction is set so that the area of the electrode (18a)(P1) side of the heating element (14) is larger than the area at the connecting position of the heating element-drawing electrode (16) and the thin section (13b) of the fusible conductor (13).

Description

Protective element and battery pack

The present invention relates to a protective element that protects a circuit connected on a current path by fusing the current path. This application claims priority on the basis of Japanese Patent Application No. 2012-171334 filed in Japan on August 1, 2012, and is incorporated herein by reference. Is done.

Most of the rechargeable batteries that can be charged and used repeatedly are processed into battery packs and provided to users. In particular, in lithium ion secondary batteries with high weight energy density, in order to ensure the safety of users and electronic devices, in general, several protection circuits such as overcharge protection and overdischarge protection are built in the battery pack, It has a function of shutting off the output of the battery pack in a predetermined case.

In many electronic devices using lithium ion secondary batteries, an overcharge protection or an overdischarge protection operation of the battery pack is performed by turning on / off the output using an FET switch built in the battery pack. However, when the FET switch is short-circuited for some reason, a lightning surge or the like is applied, and an instantaneous large current flows, or the output voltage drops abnormally due to the life of the battery cell. The battery pack and the electronic device must be protected from accidents such as ignition even when the is output. Accordingly, in order to safely shut off the output of the battery cell in any possible abnormal state, a protection element made of a fuse element having a function of cutting off the current path by an external signal is used.

As a protection element of such a protection circuit for a lithium ion secondary battery or the like, as described in Patent Document 1, a heating element is provided inside the protection element. A structure that melts a molten conductor is generally used.

JP 2010-3665 A

In the protective element described in Patent Document 1, the fusible conductor (fuse) has a current capacity of about 15 A at the maximum because it is used for applications having a relatively low current capacity such as a mobile phone or a notebook computer. is doing. Applications of lithium ion secondary batteries have been expanding in recent years, and their use in higher current applications such as electric tools such as electric drivers, transportation equipment such as hybrid cars, electric vehicles, and electric power assisted bicycles has been studied. Part recruitment has begun. In these applications, a large current exceeding several tens of A to 100 A may flow particularly at startup. Realization of a protection element corresponding to such a current capacity is desired.

In order to realize a protective element corresponding to a large current, the cross-sectional area of the soluble conductor may be increased. When Sn / Ag / Cu solder molded into a 1.6 mmφ line is used, a current capacity of about 50 A can be obtained. However, the protection element needs to detect the overvoltage state of the battery cell, flow current through the resistance heating element of the protection element, and cut the soluble conductor by the heat generation, in addition to the case where the protection element is melted by an overcurrent state. is there. For this reason, the “thick” soluble conductor has a problem that heat conduction from the heating element is lowered and it is difficult to cut the soluble conductor. Further, when the “thick” fusible conductor is blown, there is a problem that the circuit cannot be cut off unless the melted solder is surely cut.

Therefore, an object is to obtain a protective element that can be easily blown by heat generated by a heating element while ensuring a current capacity at the time of overcurrent protection, and can reliably cut off a circuit by dividing molten solder. And

As means for solving the above-described problems, a protection element according to the present invention includes an insulating substrate, a heating element stacked on the insulating substrate, and an insulating member stacked on the insulating substrate so as to cover at least the heating element. The first and second electrodes are stacked on the insulating member so as to overlap the heating element, and are electrically connected to the current path between the first and second electrodes and one terminal of the heating element. And a heating element extraction electrode that is electrically connected to an external circuit, and is connected across the first and second electrodes from the heating element extraction electrode, and is heated between the first electrode and the second electrode. And a soluble conductor that melts the current path. The heating element extraction electrode is arranged to extend in a direction different from the longitudinal direction of the soluble conductor, and the heating element extraction electrode extends more than the area at the connection position between the heating element extraction electrode and the soluble conductor. The side area is larger.

The battery pack according to the present invention includes one or more battery cells, a protection element connected to cut off a current flowing through the battery cell, and a current for detecting the voltage value of each battery cell and heating the protection element. A current control element to be controlled. The protective element includes an insulating substrate, a heating element stacked on the insulating substrate, an insulating member stacked on the insulating substrate so as to cover at least the heating element, first and second electrodes, and a heating element. Are stacked on the insulating member so as to overlap with each other, and are electrically connected to the current path between the first and second electrodes and one terminal of the heating element to make electrical connection with an external circuit. A body lead electrode and a soluble conductor connected from the heating element lead electrode to the first and second electrodes, and by heating, melts a current path between the first electrode and the second electrode; The heating element extraction electrode is arranged so as to extend in a direction different from the longitudinal direction of the soluble conductor, and the heating element extraction electrode is on the side where the heating element extraction electrode extends than the area at the connection position of the heating element extraction electrode and the soluble conductor The area is larger.

The present invention is arranged such that the shape of the heating element extraction electrode extends in a direction different from the longitudinal direction of the soluble conductor, and the heating element extraction is more than the area at the connection position of the heating element extraction electrode and the soluble conductor. Since the area on the side where the electrode extends is larger, the molten solder can be stably divided by drawing the molten solder toward the larger area.

FIG. 1A is a plan view of a protection element to which the present invention is applied. FIG. 1B is a cross-sectional view taken along line AA ′ in FIG. 2A to 2C are plan views for explaining the fusing operation of the protection element to which the present invention is applied. FIG. 3 is a block diagram showing an application example of a protection element to which the present invention is applied. FIG. 4 is a diagram showing a circuit configuration example of a protection element to which the present invention is applied. 5A to 5D are plan views showing variations in the shape of the heating element extraction electrode of the protection element to which the present invention is applied. FIG. 6A is a plan view of a heating element extraction electrode according to a modification of the present invention. FIG. 6B is a cross-sectional view taken along the line AA ′ in FIG.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited only to the following embodiment, Of course, a various change is possible in the range which does not deviate from the summary of this invention.

[Configuration of protection element]
In the protection element according to the present invention, the shape of the heating element extraction electrode described below has been devised in order to divide the molten solder to ensure circuit interruption.

As shown in FIGS. 1A and 1B, the protection element 10 includes an insulating substrate 11, a heating element 14 laminated on the insulating substrate 11 and covered with an insulating member 15, and both ends of the insulating substrate 11. Electrodes 12 (A1) and 12 (A2) formed on the heating member 14 and the heating element lead electrode 16 laminated on the insulating member 15 so as to overlap the heating element 14, and both ends of the electrodes 12 (A1) and 12 (A2). And a soluble conductor 13 connected to (). At both ends of the heating element 14, heating element electrodes 18 (P1) and 18 (P2) are connected to which a power source is connected in order to cause the heating element to generate current and generate heat. The fusible conductor 13 is preferably formed to be thinner and flatter than the thick portion 13a so that the thickness is substantially uniform at the position where it overlaps with the heating element 14 and the round wire-like thick portion 13a of 1.6 mmφ. The thin portion 13b. The thickness of the thin portion 13b is, for example, 1/2 of the thickness (thickness) of the thick portion 13a. In addition, it is preferable that the cross-sectional area or electric current capacity of the thick part 13a and the thin part 13b is substantially the same. The thin portion 13 b of the soluble conductor 13 is electrically connected to the heating element extraction electrode 16.

By making the soluble conductor 13 a thin portion 13b where the position overlapping the heating element 14 is thinned, the heat conduction in the thickness direction of the thin portion 13b is improved, and the soluble conductor 13 can be easily blown. it can. Further, by molding the thin wall portion 13b into a flat shape, the contact area with the overlapping portion of the heating element 14 can be increased, heat from the heating element 14 can be efficiently transmitted, and stable fusing characteristics. Can be realized. When the cross-sectional areas of the thick portion 13a and the thin portion 13b are substantially the same, the current capacity of the fusible conductor 13 is the same. A current corresponding to the material (specific resistance) can be passed.

The two electrodes 12 (A1) and 12 (A2) connect the fusible conductor 13 inside the protective element 10, and are connected to an external circuit through the two electrodes 12 (A1) and 12 (A2). To do. The two electrodes 12 (A 1) and 12 (A 2) may be formed on the insulating substrate 11, or may be formed on an insulating material made of an epoxy resin or the like integrated with the insulating substrate 11.

One end of the heating element extraction 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 insulating substrate 11 is formed of an insulating member such as alumina, glass ceramics, mullite, zirconia, or the like. In addition, although the material used for printed wiring boards, such as a glass epoxy board | substrate and a phenol board | substrate, may be used, it is necessary to pay attention to the temperature at the time of fuse blowing.

The heating element 14 is a conductive member that has a relatively high resistance value and generates heat when energized, and is made of, for example, W, Mo, Ru, or the like. These alloys, compositions, or compound powders are mixed with a resin binder or the like to form a paste on the insulating substrate 11 by patterning using a screen printing technique and firing.

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 through the insulating member 15. Of course, the insulating member 15 may be a laminated substrate in which the heating elements 14 are integrally laminated.

The fusible conductor 13 may be any conductive material that melts and melts due to 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 An alloy, SnPb alloy, PbIn alloy, ZnAl alloy, InSn alloy, PbAgSn alloy, or the like can be used.

Further, the soluble conductor 13 may be a laminate of a high melting point metal made of a metal mainly composed of Ag or Cu or Ag or Cu and a low melting point metal such as Pb-free solder mainly composed of Sn. Good.

In order to support the fusible conductor 13 with respect to the insulating substrate 11 and improve the mechanical strength of the fusible conductor 13, the support member 3 is formed on the electrode 2 formed on the insulating substrate 11. The fusible conductor 13 may be connected to the support member 3.

In the protective element according to the present invention, a “thick” soluble conductor is used to cope with a large current capacity. When the soluble conductor is melted, the amount of solder to be melted is large. Therefore, it is necessary to consider the treatment of the melted solder in order to ensure that the melted solder is divided and to shut off the circuit.

Therefore, as shown in FIG. 1A, the heating element extraction electrode 16 is stretched in a direction different from the longitudinal direction of the fusible conductor 13, for example, in a direction perpendicular to the longitudinal direction of the fusible conductor 13. One side is connected to the thin portion 13 b of the fusible conductor 13, and the other extended side is connected to the electrode 18 a (P 1) for the heating element 14 formed on the insulating member 15. The shape of the heating element extraction electrode 16 is, for example, such that the area on the electrode 18a (P1) side of the heating element 14 is larger than the area at the connection position of the fusible conductor 13 with the thin portion 13b. The shape of the isosceles triangle is set such that the side of the connecting position is the apex and the extended side of the electrode 18a (P1) is the base.

Thus, when the shape of the heating element extraction electrode 16 is an isosceles triangle, as shown in FIG. 2A, the thin portion 13b of the soluble conductor 13 is heated to the heating element 14 by heating the heating element 14. The overlapping part begins to melt. Since the molten solder has a property of moving to a wider area and higher wettability, the thin portion 13b is drawn in the direction of the arrow in FIG. As shown in FIG. 2 (C), since the molten solder tends to flow on the wide side of the heating element extraction electrode 16, that is, on the bottom side of the isosceles triangle, the force that the molten solder flows is used. As a result, it is possible to divide the solder more quickly. As a result, the soluble conductor 13 is divided and the circuit can be stably shut off.

Note that such an isosceles triangular electrode can be formed directly on the insulating member 15 by using a known pattern molding technique. Alternatively, an insulating protective layer having an isosceles triangular opening may be provided on the surface of the substantially rectangular heating element extraction electrode 16.
[How to use protection elements]

As shown in FIG. 3, the protection element 10 described above is used in a circuit in a battery pack of a lithium ion secondary battery.

For example, the protective element 10 is used by being incorporated in a battery pack 20 having a battery stack 25 composed of 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 that controls charge / discharge of the battery stack 25, a protection element 10 to which the present invention that protects the battery stack 25 and the charge / discharge control circuit 30 is applied, A detection circuit 26 that detects the voltages of the battery cells 21 to 24 and a current control element 27 that controls the operation of the protection element 10 according to the detection result of the detection circuit 26 are provided.

The battery stack 25 includes battery cells 21 to 24 that need to be controlled to protect overcharge and overdischarge states. The battery stack 25 is detachable via the positive electrode terminal 20a and the negative electrode terminal 20b of the battery pack 20. Are connected to the charging device 35, and a charging voltage from the charging device 35 is applied thereto. The electronic device can be operated by connecting the battery pack 20 charged by the charging device 35 to the positive terminal 20a and the negative terminal 20b to the electronic device that is operated by the battery.

The charge / discharge control circuit 30 includes two

current control elements

31 and 32 connected in series to a current path flowing from the battery stack 25 to the charging device 35, and a control unit 33 that controls operations of the

current control elements

31 and 32. Is provided. The

current control elements

31 and 32 are configured by, for example, field effect transistors (hereinafter referred to as FETs), and control the gate voltage by the control unit 33 to control conduction and interruption of the current path of the battery stack 25. . The control unit 33 operates by receiving power supply from the charging device 35, and according to the detection result by the detection circuit 26, when the battery stack 25 is overdischarged or overcharged, current control is performed so as to cut off the current path. The operation of the

elements

31 and 32 is controlled.

Protective element 10 is connected, for example, on a charge / discharge current path between battery stack 25 and charge / discharge control circuit 30, and its operation is controlled by 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 the 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 when the voltage value of the battery cells 21 to 24 exceeds a predetermined overdischarge or overcharge state by the detection signal output from the detection circuit 26, Control is performed so that the charging / discharging current path of the battery stack 25 is cut off regardless of the switching operation of the

current control elements

31 and 32.

In the battery pack 20 having the above configuration, the configuration of the protection element 10 will be specifically described.

First, the protection element 10 to which the present invention is applied has a circuit configuration as shown in FIG. That is, the protective element 10 generates heat by melting the soluble conductor 13 by causing the soluble conductor 13 connected in series via the heating element lead electrode 16 and the connection point of the soluble conductor 13 to generate heat. This is a circuit configuration comprising the body 14. In the protection element 10, for example, the fusible conductor 13 is connected in series on the charge / discharge current path, and the heating element 14 is connected to the current control element 27. Of the two

electrodes

12 and 12 of the protective element 10, one is connected to A1, and the other is connected to A2. Further, the heating element extraction 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 protection element 10 having such a circuit configuration can surely melt the soluble conductor 13 on the current path by the heat generation of the heating element 14 while realizing a low profile.
[Modification]

The shape of the heating element extraction electrode 16 on the insulating member 15 may be any shape as long as the area at the connection position with the thin portion 13b of the fusible conductor 13 increases as the distance from the position increases. As shown in the above-mentioned isosceles triangle (FIG. 5 (A)) and FIG. 5 (B), the two sides of the isosceles triangle may have a curved wedge shape. Moreover, it is good also as a shape which has a part with a large area on both sides with respect to the connection position of the soluble conductor 13 thin part 13b like FIG.5 (C) and FIG.5 (D).

On the other hand, the heating element extraction electrode 16 is usually patterned by Cu or Ag (Ag paste or the like), but these metals (or alloys containing them as a main component) are in the molten solder when the solder melts. Solder corrosion phenomenon that dissolves in is known. In the conventional protective element having a current capacity of up to about 15 A, the amount of soluble conductor (solder) is smaller than the amount of metal used for the heating element extraction electrode, so there is no need to consider the solder corrosion phenomenon. . Here, when the “thick” solder is used as the soluble conductor 13 along with the increase in the current capacity of the protection element, solder corrosion becomes noticeable during the operation of the protection element 10, and a heating element is generated during the operation of the protection element. The extraction electrode 16 may disappear, the power supply to the heating element 14 may stop, and the fusing operation may stop. In order to prevent this, as shown in FIGS. 6A and 6B, a protective film 8 that resists solder corrosion is formed on the surface of the heating element extraction electrode 16. By connecting the fusible conductor 13 via the protective film 8, the solder of the fusible conductor 13 can continue to receive the supply of power without eroding the heating element lead electrode 16, The soluble conductor 13 can be blown stably. Any material can be used for the protective film 8 depending on resistance to solder corrosion, ease of manufacture, and the like. For example, Ni / Au plating is preferably used.

2 electrode, 3 support member, opening, 8 protective film, 10 protective element, 11 insulating substrate, 12 (A1), 12 (A2) electrode, 13 soluble conductor, 13a thick part, 13b thin part, 14 heating element, 15 insulation member, 16 heating element extraction electrode, 18 (P1), 18 (P2) heating element electrode, 18a (P1), 18a (P2) electrode, 20 battery pack, 20a positive terminal, 20b negative terminal, 21-24 battery Cell, 25 battery stack, 26 detection circuit, 27, 31, 32 current control element, 30 charge / discharge control circuit, 33 control unit, 35 charging device

Claims

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;
Laminated on the insulating member so as to overlap with the heating element, and electrically connected to the current path between the first and second electrodes and one terminal of the heating element; A heating element extraction electrode for electrical connection;
A soluble conductor that is connected from the heating element extraction electrode to the first and second electrodes and that melts a current path between the first electrode and the second electrode by heating;
The heating element extraction electrode is disposed so as to extend in a direction different from the longitudinal direction of the soluble conductor, and the heating element extraction electrode is larger than the area at the connection position of the heating element extraction electrode and the soluble conductor. A protective element characterized by having a larger area on the side where the film extends.
2. The protective element according to claim 1, wherein the heating element extraction electrode is arranged so as to extend in a direction perpendicular to the longitudinal direction of the soluble conductor.
2. The heating element extraction electrode according to claim 1, wherein the shape of the heating element extraction electrode is a triangle having a vertex on a side connected to the soluble conductor and forming a base on the side on which the heating element extraction electrode is extended. Protection element.
4. The protective element according to claim 3, wherein the heating element extraction electrode is extended to a line-symmetrical position with the longitudinal direction of the soluble conductor as the axis of symmetry.
2. The protective element according to claim 1, wherein the heating element extraction electrode is made of Ag or a metal containing Ag as a main component, or a metal containing Cu or Cu as a main component.
The protective element according to claim 5, wherein the heating element extraction electrode has a protective layer on a surface thereof.
The protective element according to claim 6, wherein the protective layer is Ni / Au plated.
2. The protection element according to claim 1, wherein the soluble conductor includes a thick portion and a thin portion formed in a concave shape with a portion located so as to overlap the heating element being thin and flat. .
The protective element according to claim 8, wherein the soluble conductor has substantially the same cross-sectional area in the thick part and the thin part.
One or more battery cells;
A protective element connected to cut off the current flowing through the battery cell;
A current control element that detects a voltage value of each of the battery cells and controls a current for heating the protection element;
The protective element is
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;
Laminated on the insulating member so as to overlap with the heating element, and electrically connected to the current path between the first and second electrodes and one terminal of the heating element; A heating element extraction electrode for electrical connection;
A soluble conductor which is connected from the heating element extraction electrode to the first and second electrodes and melts a current path between the first electrode and the second electrode by heating;
The heating element extraction electrode is disposed so as to extend in a direction different from the longitudinal direction of the soluble conductor, and the heating element extraction electrode is larger than the area at the connection position of the heating element extraction electrode and the soluble conductor. The battery pack is characterized in that the area on the side where the wire extends is larger.