KR20150040955A - Protective element and battery pack - Google Patents

Abstract

The protective element 10 has an insulating substrate 11 and an insulating substrate 11 which is laminated on the insulating substrate 11 and is covered with the insulating member 15 so as to be able to be easily melted and to reliably separate the molten solder. A heating element lead-out electrode 16 laminated so as to overlap the heating element 14 on the insulating member 15 and a heating element lead-out electrode 16 laminated so as to overlap the electrode 12 (A1 A1 and 12 (A2), and a central portion thereof is connected to the heating-element lead-out electrode 16 having the protective film 8. The usable conductor 13 includes a thick portion 13a and a thin and flatly formed thin portion 13b. The shape of the heating element lead-out electrode 16 stretched in the direction perpendicular to the longitudinal direction of the usable conductor 13 is larger than the area at the connection position of the thinner portion 13b of the usable conductor 13 with respect to the heating element 14 ) On the electrode 18a (P1) side is increased.

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. The present application claims priority based on Japanese Patent Application No. 2012-171334, filed on August 1, 2012 in Japan, which is hereby incorporated by reference in its entirety.

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, Even in such a 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 device corresponding to such 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-based solder molded into a line 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 resistance heating element of the protection element, and to cut the usable conductor by the heat generation. As a result, there is a problem in that, in the "thick" usable conductor, the heat conduction from the heating element is lowered, and it becomes difficult to cut the usable conductor. Further, there is a problem in that, in the case of melting the "thick" usable conductor, the circuit can not be cut unless the molten solder is surely divided.

Therefore, it is an object of the present invention to provide a protection device which can easily fuse by heat generated by a heating element while securing the current capacity at the time of overcurrent protection, and to divide molten solder reliably to cut off the circuit.

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 one terminal of the heating element, And an available conductor which is connected across the first and second electrodes and which fuses the current path between the first electrode and the second electrode by heating. The heating-element lead-out electrode is disposed so as to extend in a direction different from the longitudinal direction of the usable conductor, and the area of the heating-element lead-out electrode is larger than the area at the connection position of the heating-element lead-out electrode and the usable conductor.

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, A heating-element lead-out electrode electrically connected to a current path between the first and second electrodes and to one terminal of the heating-element and electrically connected to the external circuit; and a heating-element lead-out electrode connected to the first and second electrodes from the heating- And a heating conductor for heating the current conductor between the first electrode and the second electrode, wherein the heating conductor lead electrode is arranged to extend in a direction different from the longitudinal direction of the usable conductor, The area of the side where the heating-element lead-out electrode extends is larger than the area at the connecting position.

The present invention is characterized in that the shape of the heating-element lead-out electrode is arranged so as to extend in a direction different from the longitudinal direction of the usable conductor, and the area on the side where the heating-element lead-out electrode extends is larger than the area at the connection position of the heating- , The molten solder is pulled close to the side having a large area, whereby the molten solder can be stably divided.

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

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]

In the protection device according to the present invention, the shape of the heating-element lead-out electrode to be described below was studied in order to separate the molten solder and reliably cut off the circuit.

1A and 1B, the protection element 10 includes an insulating substrate 11, a heat generating element 14 laminated on the insulating substrate 11, covered with the insulating member 15, and an insulating substrate 11 Electrodes 12 (A1 (A1) and 12 (A2) formed on both ends of the electrode 12 (A1 ) And 12 (A2), respectively. 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 preferably has a thicker portion 13a of a round wire of 1.6 mmφ and a thicker and thinner portion 13a which is thinner and thicker than the thicker portion 13a so that the thickness is almost uniform at a position overlapping the heating element 14. [ (13b). The thickness of the thin portion 13b is, for example, 1/2 of the thickness (thickness) of the thick portion 13a. It is preferable that the cross-sectional area or the current capacity of the thick portion 13a and the thin portion 13b are substantially the same. The thin-walled portion 13b of the usable conductor 13 is electrically connected to the heating-element lead-out electrode 16.

By making the thin conductor 13b thinner at the position where the conductor 13 is superimposed on the heating element 14, thermal conduction in the thickness direction of the thin portion 13b is improved and the conductor 13 can be easily It can be fused. In addition, by forming the thin portion 13b flat, it is possible to increase the contact area with the overlap portion of the heat generating element 14, efficiently transmit the heat from the heat generating body 14, have. When the cross-sectional areas of the thick portion 13a and the thin portion 13b are substantially the same, the current capacity of the usable conductor 13 becomes the same, so that the cross-sectional area of the usable conductor 13 in the current- 13) can be made to flow in accordance with the material (resistivity).

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.

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

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

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.

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.

The supporting member 3 is formed on the electrode 2 formed on the insulating substrate 11 in order to support the usable conductor 13 against the insulating substrate 11 and to improve the mechanical strength of the usable conductor 13. [ And the usable conductor 13 may be connected to the support member 3. [

In the protection device according to the present invention, a "thick" usable conductor 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 necessary to consider the treatment of the molten solder in order to secure the division of the molten solder and cut off the circuit.

1A, the heating element lead-out electrode 16 is elongated in a direction different from the longitudinal direction of the usable conductor 13, for example, in a direction perpendicular to the longitudinal direction of the usable conductor 13, One side is connected to the thin portion 13b of the usable conductor 13 and the other side is connected to the electrode 18a (P1) for the heating element 14 formed on the insulating member 15 . The shape of the heating element lead-out electrode 16 is set so that the area of the heating element 14 on the electrode 18a (P1) side is larger than the area of the heating conductor 14 at the connection position with the thinner portion 13b of the usable conductor 13, And the electrode 18a (P1) side on the extended side is set as the bottom side, as shown in Fig.

2A, the thin-walled portion 13b of the usable conductor 13 is heated by the heating of the heating element 14, and the heating element 14 is heated by the heating element 14. As a result, The portion that overlaps with the first portion starts to melt. The melted solder has a property that it is larger in area and moves to the higher wettability side, so that the thin portion 13b is pulled close to the direction of the arrow in Fig. 2B. Then, as shown in Fig. 2C, since the molten solder tries to flow on the large-area side of the heating-element lead-out electrode 16, that is, the bottom side of the isosceles triangle, the solder is more quickly divided by the force of the molten solder . Thereby, the usable conductor 13 is divided and the circuit can be stably intercepted.

Further, by using a well-known pattern forming technique, such an isosceles triangular electrode can be formed directly on the insulating member 15. [ Alternatively, it may be formed by providing an insulating protective layer having an opening in the shape of an isosceles triangle on the surface of the substantially rectangular heating element lead-out electrode 16.

[How to use the protection device]

As shown in Fig. 3, 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 by being embedded 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 battery cell 21 to 24 and the control circuit 10 for controlling 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 by receiving the power supply from the charging device 35 and controls the current control 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 devices 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, for example, a circuit configuration as shown in Fig. 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 protection element 10 including such a circuit configuration can reliably melt the usable conductor 13 on the current path by heat generation of the heating element 14 while realizing a low profile.

[Modifications]

The shape of the heating element lead-out 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 usable conductor 13 becomes wider as it is spaced apart from this position However, the isosceles triangle (Fig. 5A) described above or the two sides of the isosceles triangle may be wedge-shaped, which is a curve, as shown in Fig. 5B. Further, as shown in Figs. 5C and 5D, the connecting portion of the thin portion 13b of the usable conductor 13 may have a portion having a large area on both sides.

On the other hand, the heating-element lead-out electrode 16 is usually patterned by Cu or Ag (Ag paste or the like). This metal (or an alloy mainly composed of these metals) is a solder dissolution phenomenon which is dissolved in molten solder Is known. In the conventional protection device having the current capacity up to about 15 A, since the amount of the usable conductor (solder) is smaller than the amount of the metal used for the heating element lead-out electrode, there is no need to consider the phenomenon of solder dissolution. Here, when "thick" solder is used as the usable conductor 13 due to the large current capacity of the protective element, the solderability becomes significant during the operation of the protective element 10, The electrode 16 disappears, the power supply to the heating element 14 is stopped, and the fusing operation is stopped in some cases. In order to prevent this, as shown in Figs. 6A and 6B, a protective film 8 which is resistant to solder is formed on the surface of the heating-element lead-out electrode 16. By connecting the usable conductor 13 through the protective film 8, the solder of the usable conductor 13 does not corrode the heating element lead-out electrode 16, and the heating element 14 can continue to receive power supply, The usable conductor 13 can be fused stably. As the protective film 8, any material can be used depending on resistance to soldering and easiness of manufacturing. For example, Ni / Au plating is preferably used.

2: Electrode
3: Support member, opening
8: Shield
10: Protection element
11: insulating substrate
12 (A1), 12 (A2): electrode
13: Available conductor
13a: thickening
13b: Thin wall
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 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

Claims (10)

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-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 one terminal of the heating element,
And an available conductor which is connected to the first and second electrodes from the heating element lead-out electrode and fuses a current path between the first electrode and the second electrode by heating,
Wherein the heating-element lead-out electrode is arranged to extend in a direction different from a longitudinal direction of the usable conductor, and an area of a side on which the heating-element lead-out electrode is drawn is larger than an area at a connecting position of the heating-element lead-out electrode and the usable conductor Wherein the protection element is a protection element. The protection device according to claim 1, wherein the heating-element lead-out electrode is arranged to extend in a direction perpendicular to a longitudinal direction of the usable conductor. The protection device according to claim 1, wherein the heating-element lead-out electrode is a triangle having a shape at a side connected to the usable conductor and forming a bottom at a side where the heating-element lead-out electrode is extended. 4. The protective device according to claim 3, wherein the heating element lead-out electrode is elongated to a line-symmetrical position with the longitudinal direction of the usable conductor as a symmetrical axis. The protective device according to claim 1, wherein the heating-element lead-out electrode comprises a metal containing Ag or Ag as a main component or a metal containing Cu or Cu as a main component. The protection device according to claim 5, wherein the heating-element lead-out electrode has a protective layer on its surface. The protective device according to claim 6, wherein the protective layer is Ni / Au plating. The protection device according to claim 1, wherein the usable conductor includes a thick portion and a thin portion formed in a concave shape and thinly formed and flatly formed in a portion overlapping the heating element. The protective device according to claim 8, wherein the permissible conductor has substantially the same cross sectional area in the thick portion and the thin portion. 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-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 one terminal of the heating element,
And an available conductor which is connected to the first and second electrodes from the heating element lead-out electrode and which fuses a current path between the first electrode and the second electrode by heating,
Wherein the heating-element lead-out electrode is arranged to extend in a direction different from a longitudinal direction of the usable conductor, and an area of a side on which the heating-element lead-out electrode is drawn is larger than an area at a connecting position of the heating-element lead-out electrode and the usable conductor And a battery pack.

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