JP6027456B2 - Secondary battery pack having a protection circuit - Google Patents

Description

  The present invention relates to a secondary battery pack in which a protection circuit is connected to a secondary battery, and more particularly, to a secondary battery pack with reduced impedance to facilitate rapid charging with a high current.

  The battery pack is provided in a state in which it can be energized from the external output terminal connected to the positive and negative electrodes of the built-in secondary battery. Further, in order to protect the secondary battery from abnormal states such as overcharge, overdischarge, excessive current, and abnormal temperature rise, it has a protection function that performs control to stop charging and discharging when an abnormal state occurs. That is, a charge / discharge control switch is interposed between the external output terminal and the secondary battery, and the charge / discharge control switch is controlled by the protection circuit. When overcharge, overdischarge, or the like is detected, the protection circuit performs control to turn off the charge / discharge control switch to cut off the charge / discharge path, thereby protecting the secondary battery.

  FIG. 11 shows a conventional example of a secondary battery pack having such a protection function. This battery pack includes a secondary battery 1 and a protection circuit 2. The protection circuit 2 is connected to the cell positive terminal 3 and the cell negative terminal 4 of the secondary battery 1, and discharges from the secondary battery 1 to an external load or from the outside via the positive output terminal 5 and the negative output terminal 6. The secondary battery 1 is charged.

  A PTC element 7 and a charge / discharge control switch 8 are inserted in the charge / discharge path on the negative electrode side connecting the cell negative electrode terminal 4 and the negative electrode output terminal 6. The PTC element 7 is used as a temperature protection element to limit or cut off the current flowing through the charging / discharging path by changing the resistance value according to the temperature rise due to heat generation of the secondary battery 1.

  The charge / discharge control switch 8 is constituted by two switch circuits 8a and 8b connected in parallel. Each of the switch circuits 8a and 8b is configured by connecting a discharge control FET 9a made of a MOSFET and a charge control FET 10a in series. The discharge control FET 9a is connected so that the parasitic diode 9b existing between the drain and the source is in a forward direction with respect to the charging current flowing from the positive electrode output terminal 5 toward the secondary battery 1. The charge control FET 10a is connected such that the parasitic diode 10b is in the forward direction with respect to the discharge current.

  In the voltage monitoring unit configured by the protection IC 11, the power supply voltage is supplied from the secondary battery 1 to the power supply terminal VDD via the resistor R <b> 1 and the capacitor C. The reference potential terminal VSS is connected to the secondary battery 1 side of the charge / discharge control switch 8. The overcurrent detection terminal V− is connected to the negative output terminal 6 side of the charge / discharge control switch 8 via a resistor R2.

  Control signals DO and CO from the protection IC 11 are supplied to the gates of the discharge control FET 9a and the charge control FET 10a, respectively. In normal charging and discharging operations, the control signals DO and CO are set to the high level, and the discharge control FET 9a and the charge control FET 10a are controlled to be in the ON state.

  The protection IC 11 detects a voltage between the reference potential terminal VSS and the overcurrent detection terminal V-, and detects a current that equivalently flows in the charge / discharge path from the detected voltage. That is, the current is equivalently detected based on the voltage drop caused by the ON resistance of the discharge control FET 9a and the charge control FET 10a. When a current exceeding a specified current value (that is, overcurrent) flows, the discharge control FET 9a or the charge control FET 10a is turned off to cut off the current.

  An improvement that facilitates quick charging of the secondary battery is desired for the secondary battery pack having the above-described configuration. In particular, as the functionality of mobile phones and the like increases, lithium secondary batteries are required to have a higher capacity. Be longer than that. In order to avoid this, it is required to reduce the time required for charging by enabling charging with a larger current value. In order to enable charging with a large current, it is necessary to reduce the impedance of the secondary battery pack. In order to reduce the impedance of the secondary battery pack, reduction of the specific resistance of the protection circuit 2, the PTC element 7 (temperature protection element), and the wiring material is an improvement target.

  As shown in FIG. 11, configuring the charge / discharge control switch 8 by two switch circuits 8 a and 8 b connected in parallel is proposed as a measure for reducing the resistance of the protection circuit 2. That is, the charge / discharge control switch 8 can basically be constituted by one switch circuit. On the other hand, if the configuration in which the two switch circuits 8a and 8b are connected in parallel is used, the on-resistance of the charge / discharge control switch 8 can be reduced.

  However, when a current flows through the charge / discharge control switch 8 configured as described above, a voltage drop caused by the on-resistance of each of the discharge control FET 9a and the charge control FET 10a is reduced. Therefore, the value that is equivalently detected as the current flowing in the charging / discharging path becomes small, and the level at which an excessive current can be detected has to be increased. That is, since the general minimum value of the overcurrent detection value of the protection IC is 0.05 V, a current value that can be detected as an overcurrent when the on-resistance of the charge / discharge control switch 8 is reduced to, for example, 0.003Ω. Becomes 0.05V ÷ 0.003Ω = 16.6A.

  Therefore, in the capacity band (2Ah-3Ah) of lithium ion batteries used for general mobile devices, the overcurrent protection operation will not work unless a current of 5.5 times to 8.3 times flows. There is concern about a decrease in safety. Therefore, it is desirable that the resistance values of the discharge control FET 9a and the charge control FET 10a be about 8 mΩ to 10 mΩ (protection current value setting about 3 times the 1C capacitance value). From the viewpoint of cost and mounting area, it is desirable that only two MOSFETs are connected in parallel.

  Further, since the resistance value of the PTC element 7 is about 0.005Ω, it is generally possible to reduce the resistance of the element portion by using a breaker (about 2.5 mΩ) instead of the PTC element. Are known. Therefore, in order to further reduce the impedance of the secondary battery pack, it has been left to reduce the resistance of the wiring material connecting the secondary battery and the protection circuit, the secondary battery and the breaker, and the breaker and the protection circuit. It is cited as an issue. Conventionally, pure Ni is used for the wiring material from the viewpoint of weldability. On the other hand, it is known to reduce the impedance of the wiring material using a Cu material. However, when a Cu material is used, the conductivity is improved as compared with conventional Ni, so that welding is difficult.

  Therefore, Patent Document 1 discloses a battery lead material having a two-layer structure in which a weld layer made of Ni, Ni alloy or Fe alloy for welding connection to an electrode and a base layer made of Cu or a heat-resistant Cu alloy are clad ( Wiring material) is disclosed. The battery lead material is disposed between the battery electrode and the external terminal of the battery pack, and the weld layer is fixedly connected to the electrode by resistance welding. As a result, the electrical resistance can be reduced by about half compared to the conventional lead material using pure nickel, and the corrosion resistance and weldability are also excellent.

  Patent Document 2 discloses a battery pack in which positive and negative terminals of a battery and a protection circuit board are connected to each other by a wiring material. As the wiring material, it is described that a clad plate made of a dissimilar metal obtained by bonding an aluminum plate having a bonding property to a battery terminal and a nickel plate having a bonding property to a protective circuit board is described. Thereby, since the protective circuit board can be connected with a short wiring material disposed on the same side surface of the battery, the length of the wiring material can be shortened, the cost of the battery pack can be reduced, and the manufacturing process can be simplified. It is said that. Furthermore, if one of the metal plates is made of a low-resistance metal such as aluminum or copper as a dissimilar metal clad, the impedance of the wiring material can be lowered.

JP 11-297300 A JP 2002-289160 A

  As a clad material for connecting the secondary battery, the protection circuit, and the breaker to each other, it is desirable to use a Cu—Ni clad material composed of a Ni layer and a Cu layer or a Cu alloy layer from the viewpoint of low resistance. In this regard, Patent Document 1 discloses a structure in which a Cu-Ni clad material is used and a Ni layer suitable for welding is welded to a battery electrode and a protection circuit electrode.

  However, as a result of conducting resistance welding by using a Cu-Ni clad material and contacting an electrode with a Ni layer suitable for welding, the Cu material is burned or cracked in the resistance welding series welding. It was found that the function as a wiring material deteriorates. Patent Document 1 does not describe a connection form between the battery electrode and the protection circuit board.

  On the other hand, Patent Document 2 discloses using a clad plate made of a dissimilar metal as a wiring material for connecting a battery electrode and a protection circuit board. That is, a clad plate is used in which a first metal plate having bonding properties to battery electrodes and a second metal plate having bonding properties to terminals of the protection circuit board are bonded together. Further, it is disclosed that as a clad material using Cu, Cu is used as a first metal plate and Al is used as a second metal plate.

  However, Patent Document 2 uses a clad plate obtained by bonding a first metal plate having bonding properties to battery electrodes and a second metal plate having bonding properties to terminals of the protection circuit board. Different metal layers are welded to the electrode of the battery and the terminal of the protection circuit board. Therefore, in the case of the clad material using Cu, the Cu material becomes the surface on one side of the welded portion, and there arises a problem that burns and cracks occur due to series welding.

  Moreover, the wiring material specifically described as an embodiment in Patent Document 2 is an Al—Ni clad material. For this reason, there is no description regarding the problem recognition and the solution to the problem of burning and cracks generated in the Cu layer when the Cu—Ni clad material is used.

  Therefore, the present invention provides a secondary battery pack in which resistance is reduced by using a Cu-Ni clad material as a wiring material between a battery electrode and a protection circuit board, and a problem of burning the Cu material associated therewith is eliminated. The purpose is to do.

  The secondary battery pack of the present invention includes, as a basic configuration, a secondary battery, and a protection circuit disposed in a charge / discharge path between a pair of cell electrode terminals of the secondary battery and an external output terminal, The protection circuit includes a charge / discharge control switch inserted in series in the charge / discharge path, and a current detection unit that detects a current flowing through the charge / discharge path, and a detection value of the current detection unit reaches an overcurrent region. When this is done, the charge / discharge control switch is configured to be turned off, and a protection circuit board on which the protection circuit is mounted is mounted to face the cell electrode terminal of the secondary battery.

In order to solve the above problems, the secondary battery pack of the present invention includes a Ni layer as a wiring material for connecting between each of the pair of cell electrode terminals of the secondary battery and the circuit terminals of the protection circuit board. When, Cu layer or Cu-Ni clad material composed of Cu alloy layer is used, the wiring member is bordered resistor soluble by contacting the Cu layer side with respect to the cell electrode terminals and the circuit terminals It is characterized by being.

  According to the secondary battery pack having the above configuration, the resistance of the wiring portion of the secondary battery pack can be reduced by using the Cu—Ni clad material as the wiring material. In addition, since the wiring material is bonded by resistance welding with the Cu electrode side being brought into contact with the cell electrode terminal and the circuit terminal, the problem of burning of the Cu material is avoided, and the connection portion by resistance welding is avoided. It is possible to further reduce the resistance of the wiring part of the secondary battery pack without deteriorating the bonding strength. As a result, it is possible to improve the ease of rapid charging at a high current for a secondary battery pack having a configuration in which a protection circuit is connected to the secondary battery.

The block diagram which shows the circuit structure of the secondary battery pack in one embodiment of this invention Sectional drawing which shows the structure of the breaker which is an element of the secondary battery pack The perspective view which shows the external appearance of the secondary battery pack Sectional drawing principal part which shows notionally the structure of the mounting part of the protection circuit board with respect to the secondary battery 1 4 is a partial cross-sectional view showing an enlarged connection portion between the cell positive electrode terminal 3 and the protection circuit 2 of the secondary battery 1 when viewed from the right side in FIG. 4 is an enlarged partial cross-sectional view of the connection portion between the cell negative electrode terminal 4 and the breaker 12 of the secondary battery 1 as viewed from the front in FIG. 4 is a partial cross-sectional view showing an enlarged connection portion between the breaker 12 and the protection circuit 2 when viewed from the left side in FIG. Sectional drawing which shows an effect | action at the time of carrying out series welding of the positive electrode terminal 3 and the wiring material 15 Sectional drawing which shows an effect | action at the time of carrying out the direct welding of the lead terminal 19 and the wiring material 16 Sectional drawing which shows the problem at the time of carrying out series welding by making Ni layer 15b contact | abut to the cell positive / negative electrode terminal 3 Block diagram showing a conventional secondary battery pack

  The secondary battery pack of the present invention can take the following aspects based on the above configuration.

  That is, the wiring member connecting between the circuit terminal and the cell electrode terminal is bent at an angle of 180 degrees in a U shape with the Ni layer inside, forming upper and lower bent pieces. Then, the upper bent piece and the lower bent piece can be configured such that the Cu layer faces the circuit terminal and the cell electrode terminal, respectively.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Embodiment>
FIG. 1 is a block diagram showing a circuit configuration of a secondary battery pack according to an embodiment of the present invention. Constituent elements similar to those in the conventional example shown in FIG.

  The secondary battery pack includes a secondary battery 1 such as a lithium ion battery. A protection circuit 2 is connected to the secondary battery 1, and discharging to an external load or charging from the outside is performed via a positive electrode (external) output terminal 5 and a negative electrode (external) output terminal 6 of the protection circuit 2. Is called.

  In the charge / discharge path on the negative electrode side between the cell negative electrode terminal 4 and the negative electrode output terminal 6 of the secondary battery 1, a charge / discharge control switch 8 comprising a breaker 12 and two switch circuits 8a, 8b connected in parallel. Are connected in series. The breaker 12 has a configuration in which a bimetal and a PTC element are combined, and a specific structure and operation thereof will be described later, but is used in place of the PTC element 7 in the conventional example shown in FIG.

  FIG. 1 shows a wiring material 15 that connects the cell positive terminal 3 of the secondary battery 1 and the circuit terminal 13 of the protection circuit 2, a wiring material 16 that connects the cell negative terminal 4 of the secondary battery 1 and the breaker 12, and a breaker. The wiring material 17 which connects 12 and the circuit terminal 14 of the protection circuit 2 is shown. In the present embodiment, a Cu—Ni clad material (having a Ni layer only on one side) made of a Ni layer and a Cu layer or a Cu alloy layer is used as the wiring material 15, the wiring material 16, and the wiring material 17. .

  The feature of this embodiment is that the Cu layer side of the Cu—Ni clad material of the wiring materials 15 to 17 is joined to the cell positive and negative electrode terminals 3 and 4 and the circuit terminals 13 and 14 by resistance welding. It is. Details and effects of this configuration will be described later.

  The breaker 12 has a structure shown in a sectional view in FIG. That is, the PTC element 21 and the bimetal 22 are interposed between the lead terminals 19 and 20 supported by the frame body 18. The outer ends of the lead terminals 19 and 20 protruding outside the frame 18 are connected to the charge / discharge path as shown in FIG.

  In the frame 18, the lead terminal 19 is disposed at the bottom, the lead terminal 20 is disposed at the top and faces vertically, and a PTC element 21 and a bimetal 22 are disposed between the two, and the lead terminal according to temperature. It is comprised so that the conduction | electrical_connection form between 19 and 20 may change. A bent portion 23 is formed at the end of the lead terminal 20 in the frame 18, and a terminal protrusion 24 is provided at the tip thereof. When the terminal protrusion 24 contacts the lead terminal 19, a first conduction state in which the lead terminals 19 and 20 are directly conducted is formed.

  The bimetal 22 is curved so as to protrude upward as shown in the drawing at room temperature. On the other hand, when the temperature rises, the degree of bending becomes small (the curvature becomes small) and the end portion is displaced upward, so that the bent portion 23 of the lead terminal 20 is pushed up. Accordingly, the terminal protrusion 24 is separated from the lead terminal 19 and the current path through the terminal protrusion 24 is interrupted. As a result, the current path between the lead terminals 19 and 20 is in a second conduction state in which the current path is indirectly conducted via the PTC element 21 and the bimetal 22. In this state, the resistance is extremely high, and the current is substantially cut off, but some current flows.

  As is clear from the above operation, in the first conduction state, current flows by direct conduction between the lead terminals 19 and 20, so the breaker 12 is in a very low resistance state. Since the breaker 12 has a mechanical contact structure, there is no resistance fluctuation in the temperature range until the bimetal is reversed. That is, the resistance value does not depend on temperature, and a low resistance can be realized as compared with the PTC element 7 whose resistance value varies depending on the temperature. In rapid charging in which charging is performed with a large current, the heat generation of the cell increases. Therefore, a breaker that is not subjected to a resistance change due to the heat generation of the cell during charging is an element advantageous in reducing the resistance.

  However, even if the present invention is applied to a case where other temperature protection elements such as a thermal fuse are used instead of the breaker 12, it is possible to obtain a corresponding effect. The temperature protection element means an element having a function of limiting the current flowing through the charge / discharge path according to the temperature rise due to heat generation of the secondary battery 1.

  In addition, it is not essential to employ the charge / discharge control switch 8 including the two switch circuits 8a and 8b connected in parallel. That is, even if the present invention is applied to the case where the charge / discharge control switch 8 is configured by a series circuit of a single discharge control FET 9a and a charge control FET 10a, a corresponding effect can be obtained.

  Next, an example of an application structure of the wiring members 15 to 17 in the secondary battery pack of the present embodiment will be described with reference to FIGS. FIG. 3 is a perspective view showing an appearance of the secondary battery pack according to the present embodiment.

  As shown in FIG. 3, a cap frame 25 is attached to the upper part of the secondary battery 1, and a protective circuit board is attached to the upper part of the cap, but since it is covered with a cover material, FIG. Does not appear. A protection circuit 2 including a protection IC 11 and the like is mounted on the protection circuit board. An output terminal 26 for external connection is exposed from the upper end surface of the cap frame 25. The output terminal 26 is attached to the protection circuit board and includes the positive output terminal 5 and the negative output terminal 6 of FIG.

  FIG. 4 is a cross-sectional view of an essential part conceptually showing the configuration of the mounting portion of the protection circuit board for the secondary battery 1. FIG. 4 shows a cross-sectional structure of the secondary battery pack from which the cover material is removed from the state of FIG. The secondary battery 1 is configured by incorporating a unit cell inside an outer can 27 made of, for example, aluminum or an aluminum alloy. Since the internal configuration of the outer can 27 is general, the illustration is omitted. The cell positive electrode terminal 3 and the cell negative electrode terminal 4 arranged on the upper surface portion of the outer can 27 are electrically connected to the positive electrode and the negative electrode of the unit cell, respectively. The cell positive electrode terminal 3 may be composed of a clad plate.

  The cap frame 25 is mounted on the upper portion of the outer can 27 and forms a space between the upper surface of the outer can 27. A protection circuit board 28 on which the protection circuit 2 is mounted is mounted so as to be positioned above the space. The circuit terminal 13 provided on the lower surface of the protection circuit board 28 is connected to the cell positive electrode terminal 3. Similarly provided circuit terminal 14 is connected to cell negative electrode terminal 4 with breaker 12 interposed.

  5 to 7 are partial cross-sectional views showing enlarged connection portions of the wiring members 15 to 17. FIG. 5 is a view as seen from the right side of FIG. 4 and shows a connection portion between the cell positive terminal 3 of the secondary battery 1 and the circuit terminal 13 of the protection circuit 2. FIG. 6 is a view as seen from the front of FIG. 4 and shows a connection portion between the cell negative electrode terminal 4 of the secondary battery 1 and the lead terminal 20 of the breaker 12. FIG. 7 is a view seen from the left side of FIG. 4 and shows a connection portion between the circuit terminal 14 of the protection circuit 2 and the lead terminal 19 of the breaker 12. However, since FIG. 4 is conceptually shown for easy viewing, it does not correspond to the dimensions of each part of FIGS.

  The secondary battery 1, the breaker 12, and the protection circuit board 28 in this configuration are connected as follows by welding with the wiring members 15 to 17. That is, as shown in FIG. 5, one end of the wiring member 15 and the circuit terminal 13 of the protection circuit board 28, and the other end of the wiring member 15 and the cell positive electrode terminal 3 of the secondary battery 1 are joined by welding. Yes. The wiring material 15 is a clad material composed of a Cu layer 15a and a Ni layer 15b, and is bent in a U-shape, that is, at an angle of 180 degrees with the Ni layer 15b on the inside. Accordingly, the wiring member 15 forms upper and lower bent pieces, and the Cu layer 15a faces upward in the upper bent piece, and the Cu layer 15a faces downward in the lower bent piece. Thus, the wiring member 15 is welded with the Cu layer 15a facing both the cell positive electrode terminal 3 and the circuit terminal 13.

  Moreover, as shown in FIG. 6, the one end part of the wiring material 16 and the lead terminal 20 of the breaker 12, and the other end part of the wiring material 16 and the cell negative electrode terminal 4 of the secondary battery 1 are joined by welding. The wiring material 16 is also a clad material composed of the Cu layer 16a and the Ni layer 16b, and is resistance-welded with the Cu layer 16a facing the cell negative electrode terminal 4 by placing the Cu layer 16a on the lower side. On the other hand, although the Cu layer 16a is opposed to the lead terminal 20, the Ni layer 16b may be opposed to the lead terminal 20 as described later.

  Further, as shown in FIG. 7, one end of the wiring member 17 and the circuit terminal 14 of the protection circuit board 28, and the other end of the wiring member 17 and the lead terminal 19 of the breaker 12 are joined by welding. The wiring material 17 is also a clad material composed of the Cu layer 17a and the Ni layer 17b, and is bent in a U shape with the Ni layer 17b inside, that is, at an angle of 180 degrees. As a result, the circuit layer 14 is welded with the Cu layer 17a facing the circuit terminal 14. Although the Cu layer 16a is also opposed to the lead terminal 19, the Ni layer 16b may be opposed to the lead terminal 20 as in the case of the lead terminal 20.

  In this way, the wiring members 15 to 17 are resistance-welded to the cell positive and negative terminals 3 and 4 and the circuit terminals 13 and 14 with the Cu layers 15a to 17a facing each other. Thereby, even if the joining using the conventional resistance welding technique is applied, it is possible to avoid the Cu material from being burned and the Cu material from being cracked. Therefore, the resistance of the wiring part of the secondary battery pack can be further reduced without deteriorating the characteristics of the connection part by welding. As a result, it is possible to improve the ease of rapid charging at a high current for a secondary battery pack having a configuration in which a protection circuit is connected to the secondary battery.

  The reason why such an effect is obtained will be described below. In resistance welding, generally two types of methods are used: series welding and direct welding. In the case of the secondary battery pack having the above configuration, series welding is used for welding the wiring members 15 to 17 to the cell positive and negative terminals 3 and 4 and the circuit terminals 13 and 14 for the reason described later. On the other hand, direct welding is used for welding the wiring members 16 and 17 to the lead terminals 19 and 20 of the breaker 12.

  The action accompanying series welding is shown in FIG. 8 by taking the case of the cell positive terminal 3 and the wiring member 15 as an example. FIG. 9 shows the effects of direct welding in the case of the lead terminal 19 and the wiring member 16 as an example. In the series welding, as shown in FIG. 8, two electrode rods 29 are pressed against the same plane on the upper part of the wiring member 15 brought into contact with the cell positive and negative electrode terminals 3 to energize. On the other hand, in direct welding, as shown in FIG. 9, the electrode rod 29 is pressed against the lower surface of the lead terminal 19 and the upper surface of the wiring member 16 in an opposing direction to energize.

  However, as can be seen from FIG. 9, the application of direct welding is based on the premise that the welding target member is sandwiched between the electrode rods 29. Therefore, in the case of the lead terminals 19 and 20 of the breaker 12, it is possible to apply direct welding, but in the case of the cell positive and negative terminals 3 and 4 and the circuit terminals 13 and 14, the electrode terminals 29 are sandwiched. Because it is a structure that is impossible, series welding must be used.

  In series welding, as shown in FIG. 8, a welding point 30 is formed between the cell positive / negative terminal 3 and the wiring member 15 by the effective current Ie. On the other hand, reactive currents In and Ic that flow through the Ni layer 15b and the Cu layer 15a and do not contribute to welding are also generated. This causes burns because the current flows in a different location from the point where you want to weld. However, since the Ni layer 15b is disposed on the upper portion, the reactive current on the surface layer is suppressed, and the influence of burning or the like is small.

  In order to explain the problems associated with series welding, FIG. 10 shows the effect when series welding is performed with the Ni layer 15b in contact with the cell positive and negative electrode terminals 3 unlike the present embodiment. In this case, the reactive current Ic flowing through the Cu layer 15a with which the electrode rod 29 abuts is large. Therefore, heat may be generated even between the electrode rod 29 and the Cu layer 15a, and an unnecessary welded portion 32 of the electrode rod 29 to the Cu layer 15a may be formed. When the electrode rod 29 was forcibly separated in this state, a situation occurred in which the meat of the Cu layer 15a adhered to the electrode rod 29 and peeled off. As a result, the Cu layer 15a becomes thin, and as a result, cracks occur.

  On the other hand, in this embodiment, the Cu layer 15a is brought into contact with the cell positive electrode terminal 3, and accordingly, the reactive current on the surface layer is suppressed by the arrangement in which the electrode rod 29 is in contact with the Ni layer 15b. 29 joints can be reduced. Furthermore, since the Ni layer is harder than the Cu layer, even if the electrode rods are joined, the Ni meat does not easily adhere to the electrode rods and peel off.

  On the other hand, in the case of direct welding, as shown in FIG. 9, the current flowing between the upper and lower electrode rods 29 effectively acts on the joining of the welding points 31, and the reactive current can be ignored on the basis of the welding principle. For this reason, it is not necessary to consider burning and cracking. Accordingly, FIG. 9 shows a structure in which the Cu layer 15a is in contact with the lead terminal 19, but there is no problem if resistance welding is performed with the Ni layer 15b in contact.

  As the Cu—Ni clad material of the wiring materials 15 to 17, for example, the thickness ratio Cu: Ni = 3: 1 of the Cu layer (or Cu alloy layer) and the Ni layer, and the total thickness t = 0 of the clad material Good characteristics can be obtained by using one having a thickness of 1 mm.

  The connection process among the secondary battery 1, the breaker 12, and the protection circuit board 28 in this configuration can be performed as follows as an example. The wiring members 15 and 17 are bent in a U shape in a later process, but are initially used in a flat state. First, the Cu layer 17a or Ni layer 17a at one end of the wiring member 17 is brought into contact with the lead terminal 19 of the breaker 12, and the Cu layer 16a or Ni layer 16a at one end of the wiring member 16 is brought into the lead terminal 20 of the breaker 12. They are brought into contact with each other and joined by direct welding.

  Next, the protective circuit board 28 is placed in an upside down position with respect to the state shown in FIG. 4, and the Cu layer 15 a at one end of the wiring member 15 is formed on the upper surface of the circuit terminal 13 positioned at the upper end thereof. Similarly, the Cu layer 17a at the other end of the wiring member 17 is brought into contact with the upper surface of the circuit terminal 14 located at the upper end and joined by series welding.

  Next, the upper end surface (the lower end surface in FIG. 4) of the protection circuit board 28 that is vertically inverted as described above and the upper end surface of the secondary battery 1 are aligned. Thereby, the circuit terminals 13 and 14 of the protection circuit board 28, and the cell positive terminal 3 and the cell negative terminal 4 of the secondary battery 1 are aligned on the same plane.

  In this state, the Cu layer 15a at the other end of the wiring member 15 is brought into contact with the cell positive terminal 3 of the secondary battery 1, and the Cu layer 16a at the other end of the wiring member 16 is brought into contact with the cell negative terminal 4. And each is joined by series welding. Thereafter, the wiring members 15 and 17 are bent by 180 degrees at the center as shown in FIGS. 5 and 7, so that the protective circuit board 28 is mounted on the outer can 27 as shown in FIG. State. By holding this state, the mounting is completed.

  Thereafter, the cap frame 25 and the outer can 27 are integrated by injecting an integrally molded resin into the space between the cap frame 25 and the outer can 27, and the secondary battery 1 is completed.

  In addition, in order to integrate a protective circuit etc. in an exterior can and form a battery pack, other means can also be taken. For example, a means for forming the cap frame itself from an integrally molded resin, a means for forming a secondary battery by mounting a protection circuit or the like on the inner frame and covering it with the cap frame may be used.

  The secondary battery pack of the present invention can reduce the impedance of the secondary battery pack by using a Cu—Ni clad material as a wiring material, and can avoid the occurrence of problems associated with welding. It is useful as a battery pack used for a device such as a telephone that is required to be rapidly rechargeable.

DESCRIPTION OF SYMBOLS 1 Secondary battery 2 Protection circuit 3 Cell positive electrode terminal 4 Cell negative electrode terminal 5 Positive electrode output terminal 6 Negative electrode output terminal 7, 21 PTC element 8 Charge / discharge control switch 8a, 8b Switch circuit 9a Discharge control FET
9b Parasitic diode 10a Charge control FET
10b Parasitic diode 11 Protection IC
12 circuit breakers 13 and 14 circuit terminals 15 to 17 wiring material 18 frame 19 and 20 lead terminal 22 bimetal 23 bent portion 24 terminal projection 25 cap frame 26 output terminal 27 outer can 28 protective circuit board 29 electrode rods 30 and 31 welding point 32 Unnecessary weld

Claims (2)

A secondary battery, and a protection circuit disposed in a charge / discharge path between a pair of cell electrode terminals of the secondary battery and an external output terminal;
The protection circuit includes a charge / discharge control switch inserted in series in the charge / discharge path, and a current detection unit that detects a current flowing through the charge / discharge path, and a detection value of the current detection unit is in an overcurrent region. Configured to control the charge / discharge control switch to turn off when
In the secondary battery pack in which the protection circuit board on which the protection circuit is mounted is mounted facing the cell electrode terminal of the secondary battery,
As a wiring material for connecting each of the pair of cell electrode terminals of the secondary battery and the circuit terminals of the protection circuit board, a Cu-Ni clad material made of a Ni layer and a Cu layer or a Cu alloy layer is used. Used,
The wiring material, a secondary battery pack characterized in that it bordered resistor soluble by contacting the Cu layer side with respect to the cell electrode terminals and the circuit terminals.   The wiring member that connects between the circuit terminal and the cell electrode terminal is bent at an angle of 180 degrees in a U shape with the Ni layer inside, forming upper and lower bent pieces, The secondary battery pack according to claim 1, wherein the upper bent piece and the lower bent piece respectively oppose the Cu layer to the circuit terminal and the cell electrode terminal.

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