Abstract:
A secondary battery and a manufacturing method thereof, the secondary battery including a bare cell having an electrode terminal connected thereto; a protection circuit board (PCB) substrate; and a metal tab to connect the PCB substrate to the electrode terminal, disposed in an accommodating groove of the PCP substrate. The metal tab includes wing portions laid across the accommodating groove, a terminal contact portion that comes in contact with the electrode terminal, and curved portions disposed between the terminal contact portion and the wing portions.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2009-0128888, filed on Dec. 22, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein, by reference. 
     BACKGROUND 
     1. Field 
     An aspect of the present disclosure relates to a metal tab and a secondary battery including the same. 
     2. Description of the Related Art 
     In general, secondary batteries are rechargeable batteries that can be manufactured in a compact size or a large size. As portable wireless devices, such as mobile phones, PDAs, and notebook computers have become smaller and more functional, many studies have recently been conducted to develop secondary batteries for such portable wireless devices. 
     A secondary battery includes a bare cell, a protection circuit board, and a connection tab electrically connecting the protection circuit board to an electrode terminal of the bare cell. However, during the manufacturing the protection circuit board, the electrode terminal and the connection tab may not be closely adhered to each other by welding, due to fabrication errors, and therefore, a contact failure may occur. 
     SUMMARY 
     In one exemplary embodiment, there is provided a secondary battery and a manufacturing method thereof, in which a welding failure between an electrode terminal and a metal tab does not occur, so that the electrode terminal and the metal tab are not easily separated from each other, by an external impact. 
     In another exemplary embodiment, there is provided a secondary battery and a manufacturing method thereof, in which a metal tab is prevented from coming off from an upper portion of a protection circuit module, during the welding of an electrode terminal and the metal tab, so that a bare cell and the protection circuit module can be firmly connected to each other. 
     According to an aspect of the present disclosure, there is provided a metal tab connected to an electrode terminal of a bare cell, through an accommodating groove formed in a protection circuit board (PCB) substrate, the metal tab including a terminal contact portion connected to the electrode terminal; sidewalls vertically extended from the terminal contact portion, along the inner walls of the accommodating groove; wing portions respectively extended from the sidewalls, which are seated on the upper surface of the PCB substrate; and bent portions formed to protrude upward along the boundary between the sidewalls and the wing portions. 
     According to various embodiments, the bent portions have a rounded shape. 
     According to various embodiments, the metal tab may be formed into a single body. 
     According to various embodiments, notches may be formed where the terminal contact portion contacts the sidewalls. 
     According to various embodiments, the notches may be respectively formed at positions opposite to each other, with the terminal contact portion interposed therebetween. 
     According to various embodiments, the notches may be formed through a punching process. 
     According to various embodiments, the notches may be formed throughout the terminal contact portion and the sidewalls. 
     According to another aspect of the present disclosure, there is provided a secondary battery including: a bare cell having an electrode terminal formed at one end thereof; a PCB substrate having an accommodating groove corresponding to the position of the electrode terminal, the PCB substrate being electrically connected to the bare cell; and a metal tab connecting the PCB substrate to the electrode terminal, through the accommodating groove. The metal tab includes: a terminal contact portion connected to the electrode terminal; sidewalls vertically extended along the inner wall of the accommodating groove, from the terminal contact portion; wing portions respectively extended from the sidewalls, seated on the upper surface of the PCB substrate; and bent portions formed to protrude upward along the boundaries between the sidewalls and the wing portions. The bent portions are formed so that the sidewalls are extended, as the bent portions are deformed, during press welding of the terminal contact portion to the electrode terminal of the bare cell. 
     According to various embodiments, the bent portions may be formed to protrude in a rounded shape and then deformed so that the sidewalls are extended. 
     According to various embodiments, the metal tab may be formed into a single body. 
     According to various embodiments, notches may be formed in a region at which the terminal contact portion comes in contact with the sidewalls. 
     According to various embodiments, the notches may be respectively formed at positions opposite to each other, with the terminal contact portion interposed therebetween. 
     According to various embodiments, the notches may be formed through a punching process. 
     According to various embodiments, the notches may be formed throughout the terminal contact portion and the sidewalls. 
     In a secondary battery and a manufacturing method thereof, according to various embodiments, a welding failure between a metal tab and an electrode terminal does not occur. Accordingly, the metal tab and the electrode terminal are not easily separated from each other, by an external impact. Further, the metal tab is prevented from coming off from a PCB substrate, so that the PCB substrate and a bare cell can be firmly connected to each other. 
     Additional aspects and/or advantages of the present disclosure will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the present disclosure will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings, of which: 
         FIG. 1  is a perspective view of a secondary battery, according to an exemplary embodiment of the present disclosure; 
         FIG. 2A  is a perspective view illustrating the structure of a metal tab employed in the secondary battery of  FIG. 1 ; 
         FIG. 2B  is a plan view illustrating the structure of the metal tab; 
         FIG. 3A  is a view illustrating the state before resistance-welding the metal tab; and 
         FIG. 3B  is a view illustrating the state after resistance-welding the metal tab. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the exemplary embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The exemplary embodiments are described below, in order to explain the aspects of the present disclosure, by referring to the figures. 
     In addition, when an element is referred to as being “on” another element, it can be directly on another element or be indirectly on the other element, with one or more intervening elements interposed therebetween. Also, when an element is referred to as being “connected to” another element, it can be directly connected to another element or be indirectly connected to the other element, with one or more intervening elements interposed therebetween. 
       FIG. 1  is a perspective view of a secondary battery, according to an exemplary embodiment of the present disclosure. Referring to  FIG. 1 , the secondary battery  50  includes a bare cell  100  and a protection circuit module  200 . 
     The bare cell  100  includes an electrode assembly (not shown) and a metal can  120 . The electrode assembly is formed by stacking a positive electrode plate, a separator, and a negative electrode plate. The charging/discharging of the electrode assembly is performed through positive and negative electrode terminals respectively connected to the positive and negative electrode plates. The electrode assembly is mounted, together with an electrolyte, in the metal can  120 , The metal can  120  is connected to one of the positive and negative electrode plates of the electrode assembly, so as to have a positive or negative polarity. A can plate  140  is formed at the top of the metal can  120 , so that an electrode terminal  110  having an opposite polarity to the metal can  120  can be exposed. An insulating layer  130  is formed between the can plate  140  and the electrode terminal  110 , so that the can plate  140  and the electrode terminal  110  are isolated from each other. An electrolyte injection hole  150  is formed in the can plate  140 , through which the electrolyte is injected. After the injection of the electrolyte is finished, the electrolyte injection hole  150  is covered by a stopper or the like, so as to prevent the electrolyte from being discharged from the metal can  120 . 
     The protection circuit module  200  includes a printed circuit board (PCB) substrate  210 , a protection circuit  220 , and a metal tab  230 . The protection circuit  220  is formed on the PCB substrate  210 . The metal tab  230  is inserted into an accommodating groove  231  formed in the PCB substrate  210 , so as to come in contact with the electrode terminal  110 , which is exposed through the can plate  140 . The protection circuit module  200  operates to prevent the overcharging and overdischarging of the bare cell  100 . The protection circuit module  200  is formed by attaching a plurality of semiconductor elements to the protection circuit  220 . The metal tab  230  may be formed of a metal, such as nickel or the like. 
     The secondary battery is shown in  FIG. 1  as being a prismatic-type secondary battery. However, the secondary battery may be a pouch-type secondary battery, according to some aspects. 
       FIG. 2A  is a perspective view illustrating the structure of the metal tab  230 .  FIG. 2B  is a plan view illustrating the structure of the metal tab  230 . Referring to  FIGS. 2A and 2B , the metal tab  230  includes: a terminal contact portion  233  that comes into contact with the electrode terminal  110 , through the accommodating groove  231  of the protection circuit module  200 ; sidewalls  234  extending vertically from the terminal contact portion  233 , along the inner walls of the accommodating groove  231 ; and wing portions  235  extending horizontally from the sidewalls  234 , so as to be seated on the upper surface of the PCB substrate  210 . 
     Both of the wing portions  235  are bent into a wing shape and positioned around the accommodating groove  231 , so that the wing portions  235  do not pass through the accommodating groove  231 . Bent portions  232  are formed between the wing portions  235  and the sidewalls  234 . The bent portions  232  are not bent at a right angle. Instead, the bent portions  232  are curved. The bent portions  232  are bent upward between the wing portions  235  and the sidewalls  234 , so as to facilitate the welding of the metal tab  230 . In other words, the bent portions  232  extend vertically away from the terminal contact portion  233 , so as to protrude above the planes of the sidewalls  234 . The bent portions  232  are partially unbent, so as to lengthen the sidewalls  234  of the metal tab  230 , when the terminal contact portion  233  is brought into contact with the electrode terminal  110 , during welding. 
     When the welding is performed as described above, it is less likely that the wing portions  235  will be separated or detached from the upper portion of the PCB substrate  210 . In particular, the curvature of the bent portions  232  compensates for non-uniformities of the electrode terminal  110  and/or the PCB substrate  210 . This is because a sufficient length for the welding of the metal tab  230  is secured by the extension (partial unbending) of the bent portions  232 . 
     Notches  236  are formed between the sidewalls  234  and the terminal contact portions  233  of the metal tab  230 . Two notches  236  are shown to be formed in the metal tab  230 , in a diagonal orientation. However, four notches  236  may be formed, according to some aspects. The notches  236  are formed by a punching process. The notches  236  may be formed at any one of the sidewalls  234  and the terminal contact portion  233 , or may be formed throughout the sidewalls  234  and the terminal contact portion. The notches  236  are formed as described above, so that the extension (partial unbending) of the metal tab  230  can be smoothly performed, during the welding. In the metal tab  230 , the terminal contact portion  233 , the wing portions  235 , and the sidewalls  234  may be formed as a single body. 
       FIG. 3A  is a view illustrating the metal tab  230 , before the metal tab  230  is resistance welded to the secondary battery.  FIG. 3B  is a view illustrating the metal tab  230 , after the metal tab  230  is resistance welded to the secondary battery. 
     As illustrated in  FIG. 3A , if the metal tab  230  is inserted into the accommodating groove  231  of the PCB substrate  210 , the terminal contact portion  233  is spaced apart from the electrode terminal  110 , at a predetermined interval. Once in this state, the resistance welding is then performed. During the resistance welding, a predetermined pressure is applied to the terminal contact portion  233 , using resistance welding rods  300 , so that the metal tab  230  comes into contact with the electrode terminal  110 , as illustrated in  FIG. 3B . When heat is applied through the resistance welding rods  300 , the metal tab is fixed to the electrode terminal  110 . When the thickness of the protection circuit module  200  is not uniform, due to a fabrication error or the like, or when the electrode terminal  110  is not formed parallel on the can plate  140 , the terminal contact portion  233  of the metal tab  230  does not easily come into contact with the electrode terminal  110 . If the welding is performed in this state, a welding failure may occur, between the nickel tab and the electrode terminal. 
     However, if curved surfaces are formed between the wing portions  235  and the sidewalls  234 , the terminal contact portion  233  can easily come into contact with the electrode terminal  110 , when the pressure is applied to the terminal contact portion  233  by the resistance welding rods  300 . Even if the thickness of the protection circuit module  200  is not uniform, the curved surfaces compensate for the varying thickness of the of the protection circuit module  200 , by straightening to different degrees. The formation of the bent portions  232  results in the bent portions having less rigidity than other portions of the metal tab  230 . Thus, the bent portions  232  can be more easily bent than other portions of the metal tab  230 . Accordingly, the terminal contact portion  233  can easily come into contact with the electrode terminal  110 , by the partial unbending of the bent portions  232 . 
     Although a few exemplary embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these exemplary embodiments, without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents.