Abstract:
A mold for a battery, such as a secondary battery, and a method of molding a battery, such as a secondary battery, using the mold, uses a minimum amount of a molding substance, such as a resin, has its molding time shortened, and has a safety vent of a can being prevented from being fractured by high pressure during a molding process. Runners, through which a resin flows, are arranged parallel to cavities and the safety vent of the can is positioned closest to the gates, into which a resin is injected after the can and a protective circuit board are seated in the cavities. Due to the structure of the runners of the mold and the location of the safety vent of the can, the amount of resin used and the molding time are reduced. A fracture of the safety vent is avoided since a lower pressure occurs at the location closest to the gates during a resin filling process.

Description:
CLAIM OF PRIORITY 
     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from applications for MOLD FOR SECONDARY BATTERY and METHOD FOR MOLDING SECONDARY BATTERY earlier filed in the Korean Intellectual Property Office on 15 Mar. 2004 and 30 Mar. 2004 and there duly assigned Serial No. 2004-17436 and 20046-21423. Furthermore, this application is a divisional of Applicants&#39; Ser. No. 11/065,581 filed in the U.S. Patent &amp; Trademark Office on 25 Feb. 2005, and assigned to the assignee of the present invention. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to molding a battery, and more particularly, the present invention relates to a mold for a battery and a method of molding a battery, such as a secondary battery, using the mold, wherein a minimum amount of a molding substance, such as a resin, is used to retain a board, such as a protective circuit board, on the battery, resulting in the molding time using the resin being shortened and a safety vent of a battery can being prevented from being fractured by high pressure during a molding process. 
     2. Description of the Prior Art 
     As generally known in the art, a secondary battery, particularly a square-type lithium ion secondary battery electrically connects a protective circuit board to the positive and negative terminals of a can (battery sheath), in order to protect the battery from overcharging, over-discharging, an over-current, a short due to an external load, and the like. The can has a safety vent, which has a smaller wall thickness than that of the remainder of the can, formed on a side of the negative terminal so that if abnormal pressure occurs, the safety vent is fractured and internal gas is discharged to the exterior. 
     Both the can and the protective circuit board are contained in a sheath cover, which is composed of an upper cover and a lower cover, and are shipped as a product, in order to enhance the mechanical coupling strength between the can and the protective circuit board and protect them from external environments. 
     Recently, a method has been used wherein the gap between the can and the protective circuit board is filled with a resin or wherein the can and the protective circuit board are completely coated with a resin, in order to reduce the number of parts and improve the productivity. For example, upper and lower molds are provided with cavities, in which cans and protective circuit boards are to be contained, and gates and runners, which are connected to the cavities and act as channels for the resin during filling. Both the cans and the protective circuit boards are then seated on the cavities of the upper and lower molds and a resin, which has high temperature and high pressure, is injected toward the cavities through the runners and the gates, which are in communication with the runners. As a result, the cans and protective circuit boards are firmly mechanically retained by the resin. 
     However, such molds have a problem in that the runners, which act as channels for the resin, are formed a great distance away from the cavities and the amount of resin, which remains in the runners and the gates, is larger than that which is used to fill the gap between the cans and the protective circuit boards. This wastes the resin. In particular, after the resin molding is completed and the batteries are removed from the molds, the resin, which remains in the runners and the gates of the molds, is in a hardened state. Consequently, the expensive resin, which cannot be reused, must be removed from the runners and gates and disposed of. 
     In addition, it takes a long time for the resin to reach the cavities, because the runners are positioned away from the cavities and are very long. This prolongs the filling time. It is also likely that the cavities, in particular, the gap between the cans and the protective circuit boards, are not completely filled with the resin and the process ends in that state. This results in a poor molding of the secondary battery. 
     Conventional resin molding methods also have a problem in that, since the safety vent of the can is positioned farther from the gate into which the resin is injected, the safety vent is vulnerable to fracture due to the resin filling pressure. This is because the farther from the gate into which the resin flows, the higher the air pressure due to the resin filling becomes, and the safety vent, which has a smaller wall thickness than that of the remainder of the can, can be fractured toward the interior of the can by such high pressure. 
     If the safety vent is fractured in this way, a secondary problem can occur, i.e., the resin at a high pressure can penetrate into the can, and the electrolyte can easily leak to the exterior along the interface between the can and the resin during use of the battery. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a mold for a battery, such as a secondary battery, that minimizes the waste of a molding substance, such as a resin, used to retain a board, such as a protective circuit board, in a battery can. 
     Another object of the present invention is to provide a mold for a battery that minimizes the molding time using a resin. 
     Still another object of the present invention is to provide a method of molding a battery that prevents the fracture of a safety vent of a can due to high pressure during a process of molding a can and a protective circuit board in a mold using a resin. 
     In order to accomplish these and other objects, a mold is provided comprising: a lower mold including a first runner arranged on an upper surface thereof, the first runner having a predetermined depth and extending linearly a predetermined length, the first runner arranged to have a resin injected therein and to pass therethrough; at least one first gate having a predetermined depth and connected to the first runner, the at least one first gate arranged to guide the resin along a direction, the first gate having a first cavity formed on a side of the first runner and having a predetermined depth, the cavity arranged to accommodate a can and a protective circuit board therein, the can and the protective circuit board arranged to have a predetermined gap defined therebetween while being electrically connected to each other; and an upper mold having a second runner, a second gate, and a second cavity arranged on a lower surface thereof, the second runner having the same shape and arranged at a location corresponding to that of the first runner, the second gate having the same shape and arranged at a location corresponding to that of the first gate, and the second cavity having the same shape and arranged at a location corresponding to that of the first cavity. 
     The first and second cavities are preferably each of a rectangular shape having short and long sides, and wherein the first and second gates are arranged to be in communication with the gap with an angle of between 10° to 80° at a location of the long side of their respective cavity corresponding to the gap. 
     The first and second runners are preferably arranged parallel to the long side of their respective cavity. 
     The first and second gates preferably have slant surfaces arranged such that the closer to the gap between the can and the protective circuit board, the smaller the cross-sectional area through which the resin passes after passing through the first and second gates becomes. 
     In order to further accomplish these and other objects, a method is provided comprising: arranging a can to have a positive terminal on a front surface thereof, a negative terminal next to a side of the positive terminal, and a safety vent next to a side of the negative terminal; electrically connecting the positive and negative terminals of the can to a protective circuit board; arranging a mold to have a cavity of a predetermined depth, the cavity being arranged to integrally seat the can and the protective circuit board thereon to have a gate next to a side of the cavity to guide a flow of resin through a gap between the can and the protective circuit board and to have a runner to be in communication with the gate to guide the flow of resin; seating the can and the protective circuit board on the cavity of the mold to position the gate of the mold at a lateral portion of the gap between the can and the protective circuit board; and injecting a resin into the runner such that the resin passes through the gate and is injected into the gap between the can and the protective circuit board seated inside the cavity. 
     The method preferably further comprises positioning the safety vent of the can between the negative terminal and the gate. 
     The method preferably further comprises arranging a distance between the safety vent of the can and the gate to be smaller than a distance between the negative terminal and the gate. 
     The method preferably further comprises positioning the safety vent of the can adjacent to the gate. 
     The method preferably further comprising injecting the resin to pass through the safety vent of the can, the negative and positive terminals successively, the resin adhering to the safety vent of the can, the negative and positive terminals and filling the gap. 
     A resin injection trace preferably remains on a portion of the resin adjacent to the gate after injecting the resin. 
     A resin injection trace preferably remains on the lateral portion of the resin adjacent to the safety vent after injecting the resin. 
     The method preferably further comprises interposing an insulating sheet between the safety vent of the can and the protective circuit board. 
     In order to yet further accomplish these and other objects, a mold is provided comprising: a lower mold including a first runner arranged on an upper surface thereof, the first runner having a predetermined depth and extending linearly a predetermined length, the first runner arranged to have a molding substance injected therein and to pass therethrough; at least one first gate having a predetermined depth and connected to the first runner, the at least one first gate arranged to guide the molding substance along a direction, the first gate having a first cavity formed on a side of the first runner and having a predetermined depth, the cavity arranged to accommodate a can and a board therein, the can and the board arranged to have a predetermined gap defined therebetween while being electrically connected to each other; and an upper mold having a second runner, a second gate, and a second cavity arranged on a lower surface thereof, the second runner having the same shape and arranged at a location corresponding to that of the first runner, the second gate having the same shape and arranged at a location corresponding to that of the first gate, and the second cavity having the same shape and arranged at a location corresponding to that of the first cavity. 
     The first and second cavities are preferably each of a rectangular shape having short and long sides, and wherein the first and second gates are arranged to be in communication with the gap with an angle of between 10° to 80° at a location of the long side of their respective cavity corresponding to the gap. 
     The first and second runners are preferably arranged parallel to the long side of their respective cavity. 
     The first and second gates preferably have slant surfaces arranged such that the closer to the gap between the can and the protective circuit board, the smaller the cross-sectional area through which the molding substance passes after passing through the first and second gates becomes. 
     In order to yet further accomplish these and other objects, a method is provided comprising: arranging a can to have a first terminal on a front surface thereof, a second terminal next to a side of the first terminal, and a safety vent next to a side of the second terminal; electrically connecting the first and second terminals of the can to a board; arranging a mold to have a cavity of a predetermined depth, the cavity being arranged to integrally seat the can and the board thereon; arranging a gate next to a side of the cavity to guide a flow of a molding substance through a gap between the can and the board and arranging a runner to be in communication with the gate to guide the flow of a molding substance; seating the can and the board on the cavity of the mold to position the gate of the mold at a lateral portion of the gap between the can and the board; and injecting a molding substance into the runner such that the molding substance passes through the gate and is injected into the gap between the can and the board seated inside the cavity. 
     The method preferably further comprises positioning the safety vent of the can between the second terminal and the gate. 
     The method preferably further comprises arranging a distance between the safety vent of the can and the gate to be smaller than a distance between the second terminal and the gate. 
     The method preferably further comprises positioning the safety vent of the can adjacent to the gate. 
     The method preferably further comprises injecting the molding substance to pass through the safety vent of the can, the second and first terminals successively, the molding substance adhering to the safety vent of the can, the second and first terminals, and filling the gap. 
     A molding substance injection trace preferably remains on a portion of the molding substance adjacent to the gate after injecting the molding substance. 
     A molding substance injection trace preferably remains on the lateral portion of the molding substance adjacent to the safety vent after injecting the molding substance. 
     The method preferably further comprises interposing an insulating paper between the safety vent of the can and the board. 
     According to the mold for a battery of the present invention, as mentioned above, the runners, through which the resin is injected and passes, are formed parallel to the direction of the long sides of the cavities so that the resin travels the shortest path and the waste of the resin is minimized. 
     It is also possible to minimize the molding time using the resin, because the resin travels along the lateral portions of the cavities and then fills the gap between the can and the protective circuit board. 
     According to the method of molding a battery of the present invention, the safety vent of the can is not fractured by high pressure during a molding process, because the safety vent is positioned closest to the gate, the pressure of which is lower during the molding process. 
     Consequently, the safety vent can still work normally even after the completion of resin molding. This prevents the resin from being injected to the interior through the safety vent of the can or any electrolyte from leaking to the exterior. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the present invention, and many of the attendant advantages thereof, will be readily apparent as the present invention becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
         FIG. 1A  is an exploded perspective view of a mold for a secondary battery according to an embodiment of the present invention; 
         FIG. 1B  is a perspective view of a can and a protective circuit board seated on the mold of  FIG. 1 ; 
         FIG. 2A  is an exploded perspective view of a can and a protective circuit board which are to be molded by a mold for a secondary battery according to an embodiment of the present invention; 
         FIG. 2B  is a perspective view of the rear side of a protective circuit board; 
         FIG. 3A  is a perspective view of seating a can and a protective circuit board on a mold during a method of molding a secondary battery according to an embodiment of the present invention; 
         FIG. 3B  is a top view of a can and a protective circuit board seated on a lower mold with an upper mold omitted; 
         FIG. 3C  is a top view magnifying an area  1  of  FIG. 3B ; 
         FIG. 3D  is a sectional view taken along line  2 - 2  of  FIG. 3B ; 
         FIG. 4A  is a top view of the gap between a can and a protective circuit board being filled with a resin during a method of molding a secondary battery according to an embodiment of the present invention; 
         FIG. 4B  is a sectional view taken along line  3 - 3  of  FIG. 4A ; and 
         FIG. 5  is a perspective view of a secondary battery which has been molded according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In the following description and drawings, the same reference numerals are used to designate the same or similar components, and a repetition of the description of the same or similar components has been omitted. 
       FIG. 1A  is an exploded perspective view of a mold for a secondary battery according to an embodiment of the present invention and referring to  FIG. 1B  is a view of the can and the protective circuit board seated on the mold of  FIG. 1A . 
     A mold for a secondary battery according to an embodiment of the present invention includes a lower mold  100 , on which a can  10  and a protective circuit board  17  are seated with a gap  27  defined between them, and an upper mold  200 , which is fastened on top of the lower mold  100  so that a resin can be injected to fill the gap  27 . 
     The lower mold  100  has a first runner  110  formed on its upper surface  101 , which extends linearly a predetermined length and which has a predetermined depth, so that a resin can be injected and flow through it. At least one first gate  120  is formed to be in communication with the first runner  110  and to guide the resin along a direction which is angled relative to that of the runner  110 . A first cavity  130  is formed next to a side of the first runner  110 , which has a predetermined depth and is in communication with the first gate  120  so that a can  10  and a protective circuit board  17  can be seated thereon with a predetermined gap  27  defined between them while they are electrically connected to each other. 
     The first cavity  130  can be of a substantially rectangular shape having short and long sides  131  and  132 . The first gate  120  is in communication with the long side  132  with an angle of 10° to 80° at a location corresponding to that of the gap  27 . In other words, the first gate  120  is in communication with the gap  27  between the can  10  and the protective circuit board  27 . Accordingly, a resin can be directly injected into the gap  27  after passing through the first gate  120 . Of course, the first cavity  130  can also be of a regular square shape, instead of a rectangular shape, and the shape of the first cavity  130  is not limited in the present invention. 
     The first runner  110  can be formed parallel to the long side  132  of the first cavity  130  for minimized length. This arrangement makes it possible to minimize the amount of resin remaining in the first runner  110  and the first gate  120  after completion of molding, and to shorten the time for injecting a resin. Even when the first cavity  130  is of a substantially regular square shape, the first runner  110  can, of course, still be formed parallel to a side thereof. 
     The upper mold  200  has the same shape as the lower mold  100 . In particular, the upper mold  200  has a second runner  210  formed on its lower surface  201 , which is fastened on the upper surface  101  of the lower mold  100 , in the same shape at a location corresponding to that of the first runner  110 . The upper mold  200  also has a second gate  220  formed in the same shape at a location corresponding to that of the first gate  120  and a second cavity  230  formed in the same shape at a location corresponding to that of the first cavity  130 . The second cavity  230  can, of course, be of a rectangular shape having short and long sides  231  and  232 . 
     The resin flows into the gap  27  between the cap  10  and the protective circuit board  17  along a direction as marked by a solid arrow in the drawing. 
     According to another aspect of the present invention, a method of molding a secondary battery includes: electrically connecting a can and a protective circuit board to each other; providing a mold; seating the can and the protective circuit board on the mold, and filling the mold with a resin. 
     Electrically connecting a can and a protective circuit board to each other is described below with reference to  FIGS. 2A and 2B . 
     A front surface of the can  10  is provided with a safety vent  11 , a negative terminal  13  surrounded by an insulator  12 , and a positive terminal  14 . The negative terminal  13  is coupled to a negative lead  15  and the positive terminal  14  is coupled to a positive lead  16 . The can  10  has a substantially rectangular-shaped protective circuit board  17  positioned in front of the can  10  to protect the battery from overcharging, over-discharging, an over-current, a short due to external load, and the like. A front surface of the protective circuit board  17  is provided with a type determination terminal  19 , an external negative terminal  20 , and an external positive terminal  21 . The protective circuit board  17  also has a number of round protrusions  22   a  and  22   b  formed on the upper and lower portions thereof, which protrude to the exterior and are to be interlocked with a resin later. An insulating paper  26  can be additionally interposed between the protective circuit board  17  and the can  10  to prevent the negative lead  15  from contacting the positive region of the can  10  and the safety vent  11  fractured by high pressure during resin filling. 
     A rear surface of the protective circuit board  17  is provided with a protective circuit portion  23 , a negative connection terminal  24  to which the negative lead  15  is connected, and a positive connection terminal  25  to which the positive lead  16  is connected. 
     Seating the can and the protective circuit board on the mold is described below with reference to  FIGS. 3A to 3E . 
       FIG. 3A  is a perspective view of the can and the protective circuit board seated on the mold.  FIG. 3B  is a top view of the can and the protective circuit board seated on a lower mold without an upper mold.  FIG. 3C  is a top view magnifying area  1  of  FIG. 3B  and  FIG. 3D  is a sectional view taken along line  2 - 2  of  FIG. 3B . 
     The can  10  and the protective circuit board  17  are seated between the first cavity  130 , which is formed on the upper surface  101  of the lower mold  100 , and the second cavity  230 , which is formed on the lower surface  201  of the upper mold  200 . 
     The gap  27  between the can  10  and the protective circuit board  17  is positioned in such a manner that it faces the first and second gates  120  and  220 . In particular, the safety vent  11 , which is formed on the can  10  with a smaller wall thickness than that of the remainder of the can  10 , is positioned closest to the first and second gates  120  and  220 . Specifically, the safety vent  11  is positioned between the negative terminal  13  and the first and second gates  120  and  220 . In other words, the distance between the safety vent  11  and the first and second gates  120  and  220  is smaller than that between the negative terminal  13  and the first and second gates  120  and  220 . More particularly, the safety vent  11  of the can  10 , the negative lead  15 , and the positive lead  16  are positioned successively from the first and second gates  120  and  220 . The safety vent  11  is positioned at the right ends of the first and second cavities  130  and  230 , which are closest to the first and second gates  120  and  220 , the negative lead  15  is positioned near the center of the first and second cavities  130  and  230 , and the positive lead  16  is positioned at the left ends of the first and second cavities  130  and  230 , as shown in  FIG. 3C . Of course, the location of the gap  27  between the can  10  and the protective circuit board  17  can be identical to that of the first and second gates  120  and  220 , as mentioned above. As a result, the gap  27  can easily be filled with the resin, which has passed through the first and second runners  110  and  210  and the first and second gates  120  and  220 . The first and second gates  120  and  220  can have slant surfaces  121  and  221  of a smaller width so that the closer to the gap  27  between the can  10  and the protective circuit board  17 , the smaller the cross-sectional area, through which the resin passes after passing through the first and second gates  120  and  220 , becomes. 
       FIG. 4A  is a view of the gap  27  between the can  10  and the protective circuit board  17  being filled with a resin during the method for molding a secondary battery according to an embodiment of the present invention and  FIG. 4B  is a sectional view taken along line  3 - 3  of  FIG. 4A . 
     After the can  10  and the protective circuit board  17  are seated, a resin  18  of high temperature and high pressure (temperature: about 200-300 degrees, pressure: about 0.5-1.0 MPa) is injected through the first and second runners  110  and  120 . The injected resin  18  then passes through the first and second gates  120  and  220 , which are formed in the shape of a tree together with the first and second runners  110  and  210 , and is moved toward the first and second cavities  130  and  230  for filling. In particular, the resin  18  fills the gap  27  between the can  10  and the protective circuit board  17 . As mentioned above, the resin  18  adheres successively to the safety vent  11  of the can  10 , the negative and positive leads  15  and  16 . Finally, the resin  18  completely retains the can  10  and the protective circuit board  17  in a mechanical fashion. 
     The air pressure established in the gap  27  has the smallest value at a point of time when the resin  18  has passed through the first and second gates  120  and  220 . This is because the air remaining in the gap  27  has not yet been compressed very much by the resin  18 . In such a low-pressure state, the resin  18  goes past the safety vent  11 , particularly the insulating paper  26  fastened on the surface thereof, and the safety vent  11  is not subject to high pressure. 
     After going past the safety vent  11  and the negative lead  15 , the resin  18  approaches the positive lead  26  and greatly compresses the air. This increases the air pressure drastically. However, the can  10  is not easily fractured by such a high pressure, because the can  10 , which is connected to the positive lead  26  and the positive terminal  14 , has no thin wall region located at the high pressure area. 
     As shown in  FIG. 4B , a round protrusion  22   a  formed on the lower portion of the protective circuit board  17  is forced against the bottom surface of the cavity  130  of the lower mold  100  and a round protrusion  22   b  formed on the upper portion is forced against the bottom surface of the cavity  230  of the upper mold  200 . As a result, a predetermined gap  27   a  is formed between the protective circuit board  17  and the first cavity  130  of the lower mold  100  and a predetermined gap  27   b  is formed between the protective circuit board  17  and the second cavity  230  of the upper mold  200  by the round protrusions  22   a  and  22   b . Of course, a type determination terminal  19 , an external negative terminal  20 , and an external positive terminal  21 , which are formed on the protective circuit board  17 , are forced against the lateral wall of the first cavity  130  of the lower mold  10  and against that of the second cavity  230  of the upper mold  200 . Accordingly, when the gap  27  between the can  10  and the protective circuit board  17  is filled with a resin during a resin filling process, the space  27 ′, which is defined at the front to surface of the protective circuit board  17  by the gaps  27   a  and  27   b , is also filled with the resin simultaneously. Of course, the resin cannot reach the surfaces of the terminals  19 ,  20 , and  21 , because they are forced against the lateral surfaces of the first and second cavities  130  and  230 . 
       FIG. 5  is a perspective view of a secondary battery which has been molded according to a method of molding a secondary battery according to an embodiment of the present invention. 
     A resin  18  completely retains a protective circuit board (not shown) on a can  10  in a mechanical fashion. Of course, the above-mentioned type determination terminal  19 , external negative terminal  20 , and external positive terminal  21  are exposed from the front surface of the resin  18  for type determination and easy charging and discharging. A round protrusion (not shown) of the protective circuit board  17  is also completely surrounded by the resin  18 , so that the protective circuit board  17  is retained on the can  10  in a more stable manner. 
     After the removal of the secondary battery, any resin  18  remaining in the first runner  110  and the first gate  120  in a hardened state is removed and another resin filling process is performed successively for another can and protective circuit board. 
     Reference numeral  18 ′ refers to a remaining trace of the resin  18  which has passed through the first and second gates  120  and  220 . In particular, physical separation occurs between the resin  18  and a resin remnant, which remains in the first and second gates  120  and  220 , when the secondary battery is removed from the mold after the completion of the molding process, and the trace  18 ′ of the separation is left. Of course, a safety vent  11  is formed on the can  10 , which is closest to the trace  18 ′. 
     As mentioned above, the mold for a secondary battery according to the present invention is advantageous in that the runners, through which a resin is injected and passes, are formed parallel to the direction of the long sides of cavities so that the resin travels the shortest path and the waste of the resin is minimized. 
     It is also possible to minimize the molding time using the resin, because the resin travels along the lateral portions of the cavities and then fills the gap between the can and the protective circuit board. 
     According to the method for molding a secondary battery of the present invention, the safety vent of the can is not fractured by high pressure during a molding process, because the safety vent is positioned closest to the gate, the pressure of which is lower during the molding process. 
     Consequently, the safety vent can still work normally even after the completion of resin molding. This prevents the resin from being injected to the interior through the safety vent of the can or any electrolyte from leaking to the exterior. 
     Although exemplary embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the present invention as recited in the accompanying claims.