Abstract:
A battery pack that enhances the reliability and coupling force of a connection member electrically connecting two protective circuit boards is disclosed. The battery pack includes: a secondary battery including a positive electrode and a negative electrode; a first protective circuit board electrically connected to the battery; a second protective circuit board electrically connected to the first protective circuit board; and at least one conductive plate coupled to one surface of the first protective circuit board and one surface of the second protective circuit board.

Description:
CLAIM FOR PRIORITY 
     This application is based on and claims priority to Korean Patent Application No. 10-2008-0030049 filed on Mar. 31, 2008 in the Korean Intellectual Property Office (KIPO), the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a battery pack, and more particularly to, a battery pack that enables protective circuit boards coupled to a battery to have structures of high reliability and strong coupling forces. 
     2. Description of the Related Art 
     In recent years, compact and light portable electric and electronic appliances such as cellular phones, laptop computers, and camcorders are being actively developed and produced. Such portable electric and electronic appliances have embedded battery packs to allow operation even in places where there is no separate power source. Battery packs are currently employ chargeable and dischargeable batteries as they are more economical. Representative batteries include nickel-cadmium (Ni—Cd) batteries, Nickel-metal hydride (Ni-MH) batteries, lithium batteries, and lithium ion secondary batteries. 
     In particular, lithium ion batteries have operational voltages around three times higher than those of nickel-cadmium batteries or nickel-metal hydride batteries and are widely used as power sources for portable electronic appliances. In addition, lithium ion batteries are also widely used due to their relatively high energy density per weight. 
     In a lithium ion secondary battery used in a laptop computer, a plurality of battery cells are connected in series or in parallel in view of the increased power consumption and use time. 
     In this case, the lithium ion secondary battery for a laptop computer may be realized by a battery pack attachable to and detachable from the laptop computer. 
     Battery packs have various shapes according to the sizes and efficiencies of laptop computers with which the battery packs are used Since the laptop computers generally have very thin shape, the battery packs are also formed such that they have thicknesses within the thicknesses of the laptop computer. 
     Further, the battery packs that are detachably mounted to the laptop computers have protective circuits controlling the flows of currents of the batteries as the batteries become overheated, overcurrented, overcharged, overdischarged, or otherwise deteriorated. 
     In particular, a battery pack for a laptop computer generally employs a plurality of lithium ion secondary batteries, which has an increased possibility of danger. Accordingly, a smart protective circuit having more functions than a general protective circuit controlling one lithium ion secondary battery is mounted to such a battery pack. As the smart protective circuit has diversified functions, its mounting area becomes larger, in which case it occupies a considerable volume inside the battery pack. 
     In particular, a large amount of current flows through a connector of a battery pack that is connected to a contact portion of a battery of a laptop computer. The connector occupies a considerable space inside the battery pack. 
     Accordingly, a smart protective circuit is separated onto a board to which a connector is attached and a board to which a protective circuit is attached, in order to more efficiently utilize the interior space of a battery pack. 
     The separated boards are electrically connected to each other by an electric wire, and a current of up to several tens of Amperes flows through a portion of the electric wire to form a high current path between a positive electrode and a negative electrode of a battery. 
     However, if the electric wire is not big enough to allow sufficient current to flow, its resistance increases potentially causing overheating of the lithium ion secondary battery due to the obstructed current flow, which can cause explosion or deterioration of the battery. In addition, the coating of the electric wire may be melted by emission of heat, causing a short circuit with other signal wires. In this case, the protective circuit malfunctions or suffers damage, causing decrease of the reliability of the battery pack. 
     Moreover, the electric wire connecting the separated boards needs to have a sufficient coupling force so as not to be separated from the boards even when the boards are bent or the like in the process of assembling the battery pack. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above problems, and the present invention provides a battery pack that improves the reliability of a connection member electrically connecting two protective circuit boards to each other. 
     The present invention also provides a battery pack that improves the coupling force of a connection member electrically connecting two protective circuit boards to each other. 
     In accordance with an exemplary embodiment of the present invention, there is provided a battery pack comprising: a secondary battery including a positive electrode and a negative electrode; a first protective circuit board electrically connected to the battery; a second protective circuit board electrically connected to the first protective circuit board; and at least one conductive plate coupled to one surface of the first protective circuit board and one surface of the second protective circuit board. 
     The conductive plate may include a body having bending regions, and a soldering portion for coupling the first protective circuit board and the second protective circuit to each other by soldering at least portions of the bending region to the first protective circuit board and the second protective circuit. 
     The at least one conductive plate may be a first conductive plate coupled to the first protective circuit board and the second protective circuit board and a second conductive plate coupled to the first protective circuit board and the second protective circuit board and spaced apart from the first conductive plate. 
     The first conductive plate may be electrically connected to the positive electrode of the battery and the second conductive plate may be electrically connected to the negative electrode of the battery. 
     The battery pack may further include a flexible printed circuit board (FPCB) formed between the first conductive plate and the second conductive plate to electrically connect the first protective circuit board and the second protective circuit board to each other. The flexible printed circuit board may be bent in shapes corresponding to the bending regions of the first conductive plate and the second conductive plate. 
     The conductive plate may have a first electrical connection region in contact with the first protective circuit board, a first bending region extending from the first electrical connection region, a connection region extending from the first bending region, a second bending region extending from the connection region, and a second electrical connection region extending from the second bending region and being in contact with the second protective circuit board. 
     The soldering portion may include a first soldering portion formed between the first bending region and the first protective circuit board and a second soldering portion formed between the second bending region and the second protective circuit board. 
     The first electrical connection region may have a shape corresponding to that of the second electrical connection region and is opposite to the second electrical connection region with respect to the center of the connection region, and the first bending region has a shape corresponding to that of the second bending region and is opposite to the second bending region with respect to the center of the connection region. 
     A central portion of the connection region may be bent so as to maintain the angle between the first protective circuit board and the second protective circuit board by 80 to 100 degrees. 
     A portion of the first electrical connection region that makes contact with the first protective circuit board may have a rectangular shape, and the soldering portion may have a box-like shape around the portion of the first electrical connection region that makes contact with the first protective circuit board. 
     The first bending region may have a first bending portion bent from the first electrical connection region and a second bending portion bent in a direction opposite to that of the first bending portion. 
     The soldering portion corresponding to the first protective circuit board may have a coupling area securing region formed between the first protective circuit board and the first bending portion and a coupling force reinforcing region connected to the coupling area securing region and being formed between the first protective circuit board and the second bending portion. 
     A distance between a first imaginary tangential line tangential to a full curve point of the first bending portion and a second imaginary tangential line tangential to a full curve point of the second bending portion may be within a range of 3 to 15% of the thickness of the conductive plate. 
     A distance from the lower surface of each conductive plate and the upper surface of the conductive plate spaced apart from the lower surface by the existence of the bending regions may be within a range of 150 to 250% of the thickness of the conductive plate. The thickness of the conductive plate may be 0.35 mm to 1.1 mm. 
     The first protective circuit board may include a first insulation substrate, a first printed circuit pattern coupled to the first insulation substrate, and a protective circuit electrically connected to the first printed circuit pattern, and the second protective circuit board includes a second insulation substrate, a second printed circuit pattern coupled to the second insulation substrate, and a protective circuit coupled to the second insulation substrate. The conductive plate may electrically connect the connector and the protective circuit to each other. 
     An area of one surface of each conductive plate that makes contact with the printed circuit board may be within a range of 70 to 90% of that of the printed circuit board. 
     The conductive plate may have soldering recesses around its surface making contact with the first protective circuit board and the second protective circuit board respectively. 
     The connection region is bendable so as to allow the second protective circuit to be mounted so as to extend in a direction that intersects the first protective circuit board. 
     The conductive plate has a first and a second electrical connection region that couples to the first and second protective circuit board and a connecting region that extends between the first and second electrical connection region, wherein the conductive plate is shaped so that the connection region is spaced from the electrical connection region to thereby permit greater access to the electrical connection regions at the place where the electrical connection regions are coupled to the first and second protective circuit boards for welding therebetween. 
     Accordingly, the battery pack of the present invention improves reliability by separating a conductive plate, i.e. a connection member electrically connecting two protective circuit boards to each other from a flexible printed circuit board. 
     Furthermore, the battery pack of the present invention improves coupling force by allowing a conductive plate, i.e. a connection member electrically connecting two protective circuit boards to each other, to strongly couple two protective circuit boards to each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects, features and advantages of the present invention will be more apparent from the following detailed description in conjunction with the accompanying drawings, in which: 
         FIG. 1A  is a top view illustrating a battery pack according to an embodiment of the present invention; 
         FIG. 1B  is a front view of the battery pack illustrated in  FIG. 1A ; 
         FIG. 1C  is a top view of  FIG. 1A  with a multi-cell battery of the battery pack being removed; 
         FIG. 1D  is a top view of  FIG. 1C  with a first protective circuit board of  FIG. 1A  being deployed in the direction of an arrow; 
         FIG. 1E  is a bottom view of  FIG. 1D  with  FIG. 1D  being viewed from the bottom; 
         FIG. 1F  is a partially cross-sectional view taken along line I-I of  FIG. 1E ; 
         FIG. 1G  is a perspective view of a conductive plate illustrated in  FIG. 1E ; 
         FIG. 1H  is a partial bottom view obtained by enlarging a region  1   h  illustrated in  FIG. 1E ; 
         FIG. 1I  is a partially cross-sectional view obtained by enlarging a region  1   i  illustrated in  FIG. 1E ; and 
         FIG. 2  is a perspective view of a conductive plate of a battery pack according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same reference numerals are used throughout the drawings to refer to the same or like elements, and descriptions of the same elements may not be repeated. Furthermore, detailed descriptions of the same or similar effects and operations of the embodiments incorporated herein may be omitted to avoid obscuring the subject matter of the present invention. 
       FIG. 1A  is a top view illustrating a battery pack according to an embodiment of the present invention.  FIG. 1B  is a front view of the battery pack illustrated in  FIG. 1A .  FIG. 1C  is a top view of  FIG. 1A  with a multi-cell battery of the battery pack being removed.  FIG. 1D  is a top view in which a first protective circuit board and a second protective circuit board are in parallel to each other by deploying the first circuit board illustrated in  FIG. 1   a  in the direction of an arrow.  FIG. 1E  is a bottom view of  FIG. 1D  with  FIG. 1D  being viewed from the bottom.  FIG. 1F  is a partially cross-sectional view taken along line I-I of  FIG. 1E .  FIG. 1G  is a perspective view of a conductive plate illustrated in  FIG. 1E .  FIG. 1H  is a partial bottom view obtained by enlarging a region  1   h  illustrated in  FIG. 1E .  FIG. 1I  is a partially cross-sectional view obtained by enlarging a region  1   i  illustrated in  FIG. 1E . 
     As illustrated in  FIGS. 1A to 1I , the battery pack  10  according to an embodiment of the present invention includes a multi-cell battery  100 , a first protective circuit board  200 , a second protective circuit board  300 , a pair of conductive plates  400 , and a pair of soldering portions  500 . The battery pack  10  further includes a flexible printed circuit board  600 . 
     The multi-cell battery  100  includes a plurality of battery cells  101 . In this case, the battery  100  is a rechargeable lithium ion battery and has a positive electrode  110  and a negative electrode  120 . The battery cells  101  are connected in series or in parallel to each other to form the battery  100  having the positive electrode  110  and the negative electrode  120 . The battery cells  101  are electrically connected to each other through lead tabs. In the embodiment of the present invention, the plurality of battery cells  101  form a battery but one battery cell may form a battery. 
     The first protective circuit board  200  includes a first insulation substrate  210 , a first printed circuit pattern  220 , and a protective circuit  230 . 
     The first insulation substrate  210  is formed of a resin such as epoxy resin or bakelite. A plurality of layers may be compressed in the first insulation substrate  210 , and a via hole passing through the upper and lower surfaces of the first insulation substrate  210  may be formed in the first insulation substrate  210 . 
     The first printed circuit pattern  220  is compressed and is adhered to the first insulation substrate  210 . The first printed circuit pattern  220  is formed on the upper and lower surfaces of the first insulation substrate  210 . The first printed circuit pattern  220  is inserted into an intermediate layer of the first insulation substrate  210 . 
     The protective circuit  230  is electrically connected to the first printed circuit pattern  220 . The protective circuit  230  is positioned on the first insulation substrate  210 . The protective circuit  230  controls electrical connection for charge and discharge of the battery  100  according to the voltage of the battery  100 . More particularly, the protective circuit  230  includes a passive device, a charge field effect transistor (FET), a discharge FET, a temperature device, and a control circuit. In this case, the control circuit turns on or off the charge FET and the discharge FET during charge of the battery  100  to charge or discharge the battery  100 . When the temperature device detects that the temperature of the battery  100  is above a predetermined value, the control circuit turns off the charge FET and the discharge FET to prevent the battery  100  from being overheated. The control circuit detects the voltage of the battery  100 , and recognizes an overcharge or overdischarge state of the battery  100  according to the detected voltage. In this case, the control circuit turns off the charge FET to prevent a charge operation of the battery  100  or turns off the discharge FET to prevent a discharge operation of the battery  100 . When an over-current flows through the battery  100 , the control circuit protects the battery  100  by turning off the charge FET and the discharge battery. The control circuit calculates the charge/discharge cycle of the battery  100 , and extends the lifespan of the battery by controlling charge current according to the calculated charge/discharge cycle. 
     The second protective circuit board  300  includes a second insulation substrate  310 , a second printed circuit pattern  320 , and a connector  330  and also includes a second protective circuit. When the mounting space of the first protective circuit board  200  is narrow, the elements of the protective circuit  230  may be selectively mounted to the second protective circuit board  300 . In this case, the second protective circuit board  300  is electrically connected to the first protective circuit board  200  through the protective plates  400  and a flexible printed circuit board  600 . 
     The second insulation substrate  310  has the same or similar shape and material as those of the first insulation substrate  210 , and detailed descriptions thereof will be omitted. 
     The second printed circuit pattern  320  is formed on the upper and lower surfaces and an intermediate layer of the second insulation substrate  310 . The second printed circuit pattern  320  is formed in a via hole of the second insulation substrate  310 . The second printed circuit pattern  320  is formed of the same conductive metal, such as copper, as that of the first printed circuit pattern  220 . 
     The connector  330  is coupled to one surface of the second insulation substrate  310 . The connector  330  includes a plurality of contact terminals and a case surrounding the contact terminals. The connector  330  is adapted to supply a high current of the positive electrode  110  and the negative electrode  120  of the battery  100  that flows through the first conductive plate  410  and the second conductive plate  420  to portable electronic appliances such as laptop computers. In this case, the conductive plates  400  electrically connect the connector  330  and the protective circuit  230  to each other to allow the protective circuit  230  to function as an electrical passage for protecting the battery  100 . 
     The second protective circuit board  300  to which the connector  330  is mounted is separated from the first protective circuit board  200 , in which case the position of the connector  330  in contact with contact terminals of a battery of a portable electronic device may be easily secured during manufacturing of a battery pack. The conductive plates  400  electrically connect the first protective circuit board  200  and the second protective circuit board  300  to each other and firmly couple the two boards to each other, enabling manufacturing of a battery pack having a stable structure. 
     The conductive plates  400  are a first conductive plate  410  and a second conductive plate  420 . In this case, the first conductive plate  410  is electrically connected to the positive electrode  110  of the battery  100  and the second conductive plate  420  is electrically connected to the negative electrode  120  of the battery  100 . In other words, the conductive plates  400  correspond to a charge/discharge high current path of the battery  100 . The conductive plates  400  are formed of nickel or a nickel alloy to enhance conductivity and the coupling forces between the conductive plates  400  and the soldering portions  500  during its coupling to the printed circuit pattern. 
     The first conductive plate  410  includes a first electrical connection region  411 , a first bending region  412 , a connection region  413 , a second bending region  414 , and a second electrical connection region  415 . 
     The first electrical connection region  411  is electrically connected to the first protective circuit board  200 . In this case, as illustrated in  FIG. 1H , a portion of the first electrical connection region  411  that makes contact with the first protective circuit board  200  has a rectangular shape, and the soldering portion  500  has a box-like shape around the portion of the first electrical connection region  411  that makes contact with the first protective circuit board  200 . Accordingly, the first conductive plate  410  improves the coupling force between the first conductive plate  410  and the first protective circuit board  200 , thereby providing a stable structure. The rectangular edges of the first connection region  411  may be chamfered so as to be rounded. 
     The area of one surface of each conductive plate  400  that makes contact with the second printed circuit pattern  320  is made to be more than 70% of that of the second printed circuit pattern  320  to improve the conductivity between the conductive plate  400  and the second printed circuit pattern  320 . Further, the area of one surface of each conductive plate  400  that makes contact with the second printed circuit pattern  320  is made to be less than 90% of that of the second printed circuit pattern  320  to provide a coupling space in which the soldering portion  500  is soldered. 
     The first bending region  412  includes a first bending portion  412   a  and a second bending portion  412   b.    
     The first bending portion  412   a  extends from the first electrical connection region  411 , and is bent from the end of the first electrical connection region  411 . The first bending portion  412   a  is bent counterclockwise at the first electrical connection region  411  to form an arc shape. Accordingly, an area where the soldering portion  500  can be soldered increases between the first protective circuit board  200  and the first bending portion  412   a , thereby increasing the coupling force between the conductive plate  400  and the first protective circuit board  200 . 
     The second bending portion  412   b  extends from the first bending portion  412   a . The second bending portion  412   b  is bent clockwise to form an arc shape. The second bending portion  412   b  is bent in the direction opposite to the first bending portion  412 , so that the first electrical connection region  411  and the connection region  413  are substantially parallel to each other. 
     The distance D 10  between a first imaginary tangential line D 11  tangential to a full curve point of the first bending portion  412   a  and a second imaginary tangential line D 12  tangential to a full curve point of the second bending portion  412   b  is within a range of 3 to 15% of the thickness of the conductive plate  400 . In other words, when the distance D 10  is above 3% of the thickness of the conductive plate  400 , the first bending portion  412   a  and the second bending portion  412   b  may be sufficiently bent to increase the coupling area between the conductive plate  400  and the soldering portion  500 . On the other hand, if the distance D 10  between the first tangential line D 11  and the second tangential line D 12  is above 15% of the thickness of the conductive plate  400 , when the first bending portion  412   a  and the second bending portion  412  are excessively bent, the coupling area between the conductive plate  400  and the soldering portion  500  decreases, weakening the coupling force between the conductive plate  400  and the soldering portion  500 . Accordingly, the distance D 10  needs to be within a range between 3 to 15% to maintain the coupling force of the soldering portion  500 . 
     The connection region  413  extends from the second bending portion  412   b . In addition, the connection region  413  is parallel to the first electrical connection region  411 . 
     A central portion of the connection region is bent to maintain the angle between the first protective circuit board  200  and the second protective circuit board  300  within a range of 80 to 100 degrees. The conductive plate  400  is bent as illustrated in  FIG. 1   b . Accordingly, the first protective circuit board  200  having the protective circuit and the second protective circuit board  300  having the connector  330  may be easily mounted longitudinally and transversely inside the battery pack. 
     The second bending region  414  extends from the connection region  413  and includes bending portions  414   a  and  414   b . The bending portions  414   a  and  414   b  have shapes corresponding to those of the first bending portion  412   a  and the second bending portion  412   b  of the first bending region  412 . In other words, each conductive plate  400  is symmetrical with respect to a reference line vertical to the length of the conductive plate  400 , the reference line being positioned at the center of the connection region  413 . Accordingly, detailed descriptions of the bending portions of the second bending region  414  will be omitted. 
     The second electrical connection region  415  extends from the bending portion of the second bending region  414  and is electrically connected to the second protective circuit board  300 . The second electrical connection region  415  has a shape corresponding to that of the first electrical connection region  411 , and only the relation with which the second electrical region  415  is coupled to the second protective circuit board  300  is different from the case of the first electrical connection region  411 . Accordingly, detailed descriptions of the second electrical connection region  415  will be omitted. 
     The second conductive plate  420  is electrically connected to the negative electrode  120  of the battery  100 . In this case, the second conductive plate  420  is spaced apart from the first conductive plate  410  to prevent its short circuit with the first conductive plate  410 . The second conductive plate  420  has the same or similar shape and material as those of the first conductive plate  410 , and detailed descriptions thereof will be omitted. 
     Meanwhile, as illustrated in  FIG. 1I , the distance D 20  from the lower surface of each conductive plate  400  and the upper surface of the conductive plate  400  spaced apart from the lower surface by the existence of the bending regions  412  and  414  is within a range of 150 to 250% of the thickness T 10  of the conductive plate  400 . In the embodiment of the present invention, the thickness of each conductive plate  400  is 0.35 mm to 1.1 mm. When the distance D 20  is below 150% of the thickness T 10  of the conductive plate  400 , the space for the soldering portion  500  becomes too small, seriously decreasing the coupling force between the conductive plate  400  and the protective circuit board. On the other hand, when the distance D 20  is above 250% of the thickness T 10  of the conductive plate  400 , the bending regions  412  and  414  of the conductive plate  400  become too long, unnecessarily increasing the mounting volume of the conductive plate  400 . Meanwhile, when the thickness T 10  of each conductive plate  400  is below 0.3 mm, the strength of the conductive plate  400  becomes too weak, causing the conductive plate  400  to be bent even by a small impact and to be short-circuited. On the other hand, when the thickness T 10  of each conductive plate  400  is below 1.1 mm, it is difficult to form bending portions of the bending regions  412  and  414 , decreasing the coupling area of the soldering portion  510 , in which case the coupling force between the conductive plate  400  and the protective circuit boards  200  and  300  may be weakened. 
     Each soldering portion  500  couples at least one portion of the first bending region  412  of the first conductive plate  400  to the first protective circuit board  200  using solder. The soldering portion  500  couples at least one portion of the first bending region  412  of the first conductive plate  400  to the second protective circuit board  300  using solder. 
     As illustrated in  FIG. 1F , the soldering portions  500  are a first soldering portion  510  formed between the first bending region  412  and the first protective circuit board  200  and a second soldering portion  520  formed between the second bending region  414  and the second protective circuit board  300 . In other words, the first soldering portion  510  is coupled to the first protective circuit board  200  and the second soldering portion  520  is coupled to the second protective circuit board  300 . Accordingly, when the centers of the conductive plates  400  are bent, the conductive plates  400  have strong coupling forces so as not to be separated from coupling surfaces of the first protective circuit board  200  and the second protective circuit board  300 . 
     As illustrated in  FIG. 1I , the first soldering portion  510  includes a coupling area securing region  511  and a coupling force reinforcing region  512 . The second soldering portion  520  also includes a coupling area securing region and a coupling force reinforcing region and has a shape corresponding to that of the first soldering portion  510 , in which case detailed descriptions thereof will be omitted. 
     The coupling area securing region  511  is formed between the first protective circuit board  200  and the first bending portion  412   a . In other words, the coupling area securing region  511  is filled between the first bending portion  412   a  between the first electrical connection region  411  and the second bending portion  412   b , and the first protective circuit board  200 , maximally increasing the coupling area between the conductive plate  400  and the first protective circuit board  200 . 
     The coupling force reinforcing region  512  extends from the coupling area securing region  511  and is formed between the first protective circuit board  200  and the second bending portion  412   b . The coupling force reinforcing region  512  supports the coupling area securing region  511  for securing coupling area, further, enhancing the coupling force between the conductive plate  400  and the protective circuit board  300 . 
     The flexible circuit board circuit board (FPCB)  600  is formed between the first conductive plate  410  and the second conductive plate  420  and electrically connects the first protective circuit board  200  and the second protective circuit board  300  to each other. The flexible printed circuit board  600  includes a plurality of copper foils and an insulation film coating the copper foils. In the flexible printed circuit board  600 , the copper foils are coated with the insulation film with them being disposed side by side in a row and are integrated with the insulation film. The flexible printed circuit board  600  functions as an electrical passage through which a signal about the voltage of the battery  100  and control signals of the protective circuits are transmitted. 
     As shown in  FIG. 1B , the flexible printed circuit board  600  is bent so as to have a shape corresponding to those of the bending regions  412  and  414  of the conductive plate  400 . When a central portion of the conductive plate  400  is bent with the flexible printed circuit board not being deflected in a shape corresponding to the conductive plate  400 , the central portion of the flexible printed circuit board  600  is excessively deflected and portions of the flexible printed circuit board  600  that are coupled to the printed circuit boards  200  and  300  may be separated. Accordingly, the flexible printed circuit board  600  is bent in a shape corresponding to the bending regions  412  and  414  of the conductive plate  400 , preventing it from being separated from the protective circuit boards  200  and  300 . 
     As mentioned above, the battery pack  10  according to the embodiment of the present invention allows the flow of a high current of the battery  100  using the conductive plates  400  and transmits only signals using the flexible printed circuit board  600 . In other words, the protective circuit boards  200  and  300  have little possibility of being melted or short-circuited by the heat of the high current path unlike existing protective circuit boards using one flexible printed circuit board for signals and a high current path, enhancing the reliability of the battery pack  10 . 
     Furthermore, the conductive plates  400  of the battery pack  10  that electrically connect the protective circuit boards  200  and  300  to each other are strongly coupled to the protective circuit boards  200  and  300 , providing a stable structure. 
       FIG. 2  is a perspective view of a conductive plate of a battery pack according to another embodiment of the present invention. 
     Referring to  FIG. 2 , the battery pack according to the embodiment of the present invention includes a multi-cell battery (not shown), a first protective circuit board (not shown), a second protective circuit board (not shown), at least one conductive plate  1400 , and soldering portions (not shown). The battery pack according to the embodiment of the present invention further includes a flexible printed circuit board (not shown). 
     In the embodiment of the present invention, the multi-cell battery (not shown), the first protective circuit board (not shown), the second protective circuit board (not shown), the soldering portions (not shown), and the flexible printed circuit board (not shown) are the same or similar as those of the former embodiment of the present invention, and detailed descriptions thereof will be omitted. In the embodiment of the present invention, a modified conductive plate  1400  will be mainly described. 
     The conductive plate  1400  includes a first electrical connection region  1410 , a first bending region  1420 , a connection region  1430 , a second bending region  1440 , and a second electrical bending region  1450 . 
     The first bending region  1420 , the connection region  1430 , and the second bending region  1440  have the same shapes as those of the former embodiment of the present invention, and detailed descriptions thereof will be omitted. 
     Soldering recesses  1460  are formed in the first electrical connection region  1410  and the second electrical connection region  1450  respectively. The soldering recesses  1460  are formed at side portions of the first electrical connection region  1410  and the second electrical connection region  1450  that make contact with the first protective circuit board and the second protective circuit board respectively. The soldering recesses  1460  increase the areas of the first electrical connection region  1410  and the second electrical region  1450 , increasing the coupling area where the soldering portions are coupled. Accordingly, the conductive plate  1400  enhances the coupling forces between the conductive plate  1400  and the first protective circuit board and the second protective circuit board. 
     As mentioned above, the battery pack according to the embodiment of the present invention has the soldering recesses  1460  in the conductive plate  1400 , enhancing the coupling forces between the conductive plate  1400  and the first protective board and the second protective circuit board. 
     Although exemplary embodiments of the present invention have been described in detail hereinabove, it should be understood that many variations and modifications of the basic inventive concept herein described, which may appear to those skilled in the art, will still fall within the spirit and scope of the exemplary embodiments of the present invention as defined by the appended claims.