Abstract:
Disclosed herein is a method of manufacturing a coil, including: preparing a mold having vertically movable fixing pins disposed therein and slidable left and right sidewalls; seating a magnetic plate on an inner bottom of the mold; loading the coil on the magnetic plate so that lead parts of the coil are disposed between the fixing pins and the sidewalls of the mold; sliding the left and right sidewalls of the mold into the mold to closely adhere the lead parts of the coil to the fixing pins; filling a magnetic slurry in the mold and primarily pressing the magnetic slurry; and lowering the fixing pins to perform secondary pressing, in order to prevent deformation or position deviation of the coil at the time of molding the coil.

Description:
CROSS REFERENCE(S) TO RELATED APPLICATIONS 
       [0001]    This application claims the foreign priority benefit under 35 U.S.C. Section 119 of Korean Application No. 10-2012-0148430, entitled “Method of Manufacturing Coil” filed on Dec. 18, 2012, which is hereby incorporated by reference in its entirety into this application. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a method of manufacturing a coil, and more particularly, to a method of manufacturing a coil by molding. 
         [0004]    2. Description of the Related Art 
         [0005]    Recently, as a portable information communication device has been continuously miniaturized, various components configuring the portable information communication device have also been demanded to be ultra-thinned. Particularly, a surface mounting type coil included in a power supply circuit should have a thickness that is ultra-thinned to 1.0 mm or less in order to satisfy a design condition required by the portable information communication device. 
         [0006]    Since slimness, electrical characteristics, and mechanical strength are important in the surface mounting type coil as described above, a complex technology is required in order to implement a method of designing and manufacturing the surface mounting type coil. 
         [0007]    A general method of manufacturing the surface mounting type coil according to the related art will be described. After a coil wound around a ferrite core is disposed in an internal space of a mold, the internal space is sealed by a magnetic slurry in a melted state to manufacture a molded product or an air core coil is disposed in the internal space of the mold as it is and is then sealed (Korean Patent Laid-Open Publication No. 10-2008-0022679). 
         [0008]    However, at the time of sealing the internal space by the magnetic slurry, the coil disposed in the mold may be deformed depending on a charging pressure of the magnetic slurry. Alternatively, the coil may be biased or inclined toward any one side in the internal space of the mold. Therefore, the coil may be molded in the state in which it deviates from a predetermined position. 
         [0009]    The deformation or the position deviation of the coil as described above may cause an appearance defect and have a bad effect on electrical characteristics such as an inductance value, direct current (DC) overlapping characteristics, or the like. Therefore, a technology of preventing the deformation or the position deviation of the coil at the time of molding the coil has emerged. 
       RELATED ART DOCUMENT 
     Patent Document 
       [0010]    (Patent Document 1) Korean Patent Laid-Open Publication No. 10-2008-0022679 
       SUMMARY OF THE INVENTION 
       [0011]    An object of the present invention is to provide a method of manufacturing a coil capable of securing reliability by preventing a coil in a mold from being deformed or deviating from a predetermined position at the time of molding the coil. 
         [0012]    According to an exemplary embodiment of the present invention, there is provided a method of manufacturing a coil, including: preparing a mold having vertically movable fixing pins disposed therein and slidable left and right sidewalls; seating a magnetic plate on an inner bottom of the mold; loading the coil on the magnetic plate so that lead parts of the coil are disposed between the fixing pins and the sidewalls of the mold; sliding the left and right sidewalls of the mold into the mold to closely adhere the lead parts of the coil to the fixing pins; filling a magnetic slurry in the mold and primarily pressing the magnetic slurry; and lowering the fixing pins to perform secondary pressing. 
         [0013]    The magnetic plate may have a convex shape. 
         [0014]    In the seating of the magnetic plate in the inner bottom of the mold, a convex part may be positioned between the fixing pins. 
         [0015]    In the lowering of the fixing pins, the fixing pins may stop when upper distal ends of the fixing pins and an inner bottom surface of the mold are positioned on the same plane. 
         [0016]    The method may further include sintering a molded product obtained after the performing of the secondary pressing. 
         [0017]    The coil may be an air core coil including a winding part formed by winding a conducting wire in a spiral shape and two lead parts extended from both ends of the winding part and protruding outward. 
         [0018]    The magnetic plate and the magnetic slurry may be made of at least one selected from a group consisting of a Fe based material, a Fe—Si based material, a Fe—Al based material, a Fe—Ni based material, and a Fe—Al—Si based material. 
         [0019]    The primary pressing and the secondary pressing may be performed by positioning a press plate in an opening part of an upper portion of the mold and pressing the press plate downward, and a compression strength of the primary pressing may be set to be lower than that of the secondary pressing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIGS. 1A to 6B  are views sequentially showing processes of a method of manufacturing a coil according to an exemplary embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0021]    Various advantages and features of the present invention and methods accomplishing thereof will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. However, the present invention may be modified in many different forms and it should not be limited to exemplary embodiments set forth herein. These exemplary embodiments may be provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals throughout the description denote like elements. 
         [0022]    Terms used in the present specification are for explaining exemplary embodiments rather than limiting the present invention. Unless explicitly described to the contrary, a singular form includes a plural form in the present specification. The word “comprise” and variations such as “comprises” or “comprising,” will be understood to imply the inclusion of stated constituents, steps, operations and/or elements but not the exclusion of any other constituents, steps, operations and/or elements. 
         [0023]      FIGS. 1A to 6B  are views sequentially showing processes of a method of manufacturing a coil according to an exemplary embodiment of the present invention. Here, each of the accompanying drawings includes A, which is a cross-sectional view, and B, which is a plan view. Additionally, components shown in the accompanying drawings are not necessarily shown to scale. For example, sizes of some components shown in the accompanying drawings may be exaggerated as compared with other components in order to assist in the understanding of the exemplary embodiments of the present invention. 
         [0024]    In the method of manufacturing a coil according to the exemplary embodiment of the present invention, a mold  100  having two fixing pins  110  disposed therein is first prepared, as shown in  FIGS. 1A and 1B . 
         [0025]    Here, the fixing pin  110  may be designed so as to be vertically movable to the outside of the mold  100 . That is, the fixing pin  110  is disposed in the mold  100  as shown in  FIGS. 1A and 1B  before the subsequent process is performed and is lowered vertically by mechanical driving when the subsequent process is performed. 
         [0026]    More specifically, the two fixing pins  110  may be spaced apart from each other by a predetermined interval and be disposed at the same position on a straight line. This structure may depend on a structure of a coil  220  that is subsequently loaded in the mold  100 . This structure of the coil  220  will be described below in detail. 
         [0027]    Left and right sidewalls  120  of the mold  100  may be designed so as to be slidable horizontally. Therefore, the mold  100  has a structure in which each of the left and right sidewalls  120  is horizontally slid in a body part  130  in which a lower surface portion and front and rear surface portions are connected integrally with each other. 
         [0028]    The left and right sidewalls  120  of the mold  100  are disposed at a position at which it is slightly pushed outward as shown in  FIGS. 1A  and  1 B before the coil  220  is loaded in the mold  100  and are slid to an inner portion of the mold  100  by mechanical movement when the coil  220  is loaded in the mold  100 . 
         [0029]    When the left and right sidewalls  120  are slid to the inner portion of the mold  100 , the left and right sidewalls  120  are integrated with the body part  130  of the mold  100 , such that a molding frame of which only an upper portion is opened is completed. An inner size of the molding frame having the form as described above, that is, the mold  100  having the left and right sidewalls  120  slid to the inner portion thereof coincides with a specification of the finally completed coil. 
         [0030]    When the mold  100  as described above is prepared, a magnetic plate  211  is seated on an inner bottom of the mold  100 , as shown in  FIGS. 2A and 2B . 
         [0031]    The magnetic plate  211  may be formed of a flat plate that does not have a thickness deviation so that the coil  220  may be loaded without being inclined and have a convex shape as shown in  FIG. 2B . Therefore, in the case in which the magnetic plate  211  is seated in the mold  100 , a convex part is positioned between the two fixing pins  110 . 
         [0032]    The magnetic plate  211  may be made of, for example, known ferrite having high magnetic permeability and a soft magnetic metal material. More specifically, the magnetic plate  211  may be made of at least one selected from a group consisting of a Fe based material, a Fe—Si based material, a Fe—Al based material, a Fe—Ni based material, and a Fe—Al—Si based material. 
         [0033]    When the magnetic plate  211  is seated on the inner bottom of the mold  100 , the coil  220  is loaded on the magnetic plate  211  as shown in  FIGS. 3A and 3B . 
         [0034]    Here, the coil  220  may be an air core coil. Therefore, the coil  220  may include a winding part  221  formed by winding a conducting wire in a spiral shape and two lead parts  222  extended from both ends of the winding part  221  and protruding outward. 
         [0035]    Since the lead parts  222  protruding outward are bent at a predetermined angle, when the coil  220  is loaded on the magnetic plate  211  in the state in which the lead parts  222  are directed toward the fixing pins  110 , a left lead part  222  is disposed between a left fixing pin  110  and the left sidewall  120  and a right lead part  222  is disposed between a right fixing pin  110  and the right sidewall  120 , as shown in  FIGS. 3A and 3B . However, since the lead part  222  has predetermined elasticity, a distal end  222   a  of the lead part  222  is disposed to be spaced apart from the fixing pin  110 . 
         [0036]    When the coil  220  is loaded on the magnetic plate  211 , the left and right sidewalls  120  are slid to the inner portion of the mold  100 , as shown in  FIGS. 4A and 4B . 
         [0037]    As described above, since the distal ends  222   a  of the lead parts  222  of the coil  220  are disposed between the fixing pins  110  and the sidewalls  120  in the state in which they are spaced apart from the fixing pins  110 , when the left and right sidewalls  120  are slid to the inner portion of the mold  100  to be thereby closely adhered to the fixing pins  110 , the distal ends  222   a  of the lead parts  222  are stably fixed between the fixing pins  110  and the sidewalls  120 , as shown in  FIGS. 4A and 4B . 
         [0038]    Therefore, since the coil  220  may be stably loaded on the magnetic plate  211 , even though a magnetic slurry is filled in the mold  100  in the subsequent process, a defect such as deformation of the coil, deviation of the coil from a predetermined position, or the like, due to a charging pressure of the magnetic slurry may be prevented. 
         [0039]    After the left and right sidewalls  120  are slid, the magnetic slurry  212  are filled in the mold  100  and is then pressed primarily, as shown in  FIGS. 5A and 5B . 
         [0040]    The magnetic slurry  212  is made of the same material as that of the magnetic plate  211 . More specifically, the magnetic slurry  212  may be prepared by an organic binder, a plasticizer, and the like, to powders of at least one selected from a group consisting of a Fe based material, a Fe—Si based material, a Fe—Al based material, a Fe—Ni based material, and a Fe—Al—Si based material and wet-mixing them with each other by a mixing method such as a ball mill method, a basket mill method, or the like. If necessary, a volatile solvent for adjusting a viscosity may be mixed. 
         [0041]    The magnetic slurry  212  prepared as described above is filled in the mold  100 . In this case, it is important to fill a sufficient amount of magnetic slurry  212  in consideration that the fixing pins  110  are discharged to the outside of the mold  100  in the subsequent process. Otherwise, due to insufficiency of the magnetic slurry  212 , a defect that an upper portion of the coil  220  is exposed to the outside may occur after the coil  220  is finally completed. 
         [0042]    A press plate  300  is positioned in an opening part of an upper portion of the mold  100  and is then pressed downward at a predetermined pressure condition, for example, a compression strength of 5 Kgf for 20 seconds. Therefore, the magnetic slurry  212  to which a predetermined pressure is applied buries the coil  220  therein in the state in which it maintains a predetermined viscosity or more. 
         [0043]    Then, as shown in  FIGS. 6A and 6B , the fixing pins  110  is lowered vertically to perform secondary pressing. In this case, the fixing pins  110  are not completely discharged to the outside of the mold  100 , but stop as soon as upper distal ends of the fixing pins  110  and the bottom surface of the mold  100  are positioned on the same plane. This may be controlled by movement of a motor connected to the fixing pins  110 . 
         [0044]    When the secondary pressing performed using the press plate  300  in the state in which the fixing pins  110  are lowered vertically as described above, the magnetic slurry  212  is filled in a space occupied by the fixing pins  110  to completely seal the coil  220 . 
         [0045]    Here, it is to notice that a compression strength of the primary pressing is set to be lower than that of the secondary pressing. The secondary pressing is performed by pressing the press plate  300  at a compression strength of, for example, 10 Kgf for 20 seconds. As a result, the magnetic slurry  212  is solidified in a semi-hardened state. Therefore, when the compression strength of the primary pressing is set to be higher than that of the secondary pressing, the magnetic slurry  212  is solidified, such that it may not be filled in the space occupied by the fixing pins  110  in the secondary pressing. 
         [0046]    When the secondary pressing ends as described above, finally, the left and right sidewalls  120  are opened to discharge a molded product, and the discharged molded product is sintered under a predetermined condition to completely harden the magnetic plate  211  and the magnetic slurry  212  integrally with each other, thereby finally completing the coil according to the exemplary embodiment of the present invention. 
         [0047]    According to the exemplary embodiment of the present invention, the left and right sidewalls of the mold are slid to stably fix the coil in the mold, thereby making it possible to prevent the coil from being deformed or deviating from a predetermined position at the time of molding the coil. Therefore, reliability of a product may be significantly improved. 
         [0048]    The present invention has been described in connection with what is presently considered to be practical exemplary embodiments. Although the exemplary embodiments of the present invention have been described, the present invention may be also used in various other combinations, modifications and environments. In other words, the present invention may be changed or modified within the range of concept of the invention disclosed in the specification, the range equivalent to the disclosure and/or the range of the technology or knowledge in the field to which the present invention pertains. The exemplary embodiments described above have been provided to explain the best state in carrying out the present invention. Therefore, they may be carried out in other states known to the field to which the present invention pertains in using other inventions such as the present invention and also be modified in various forms required in specific application fields and usages of the invention. Therefore, it is to be understood that the invention is not limited to the disclosed embodiments. It is to be understood that other embodiments are also included within the spirit and scope of the appended claims.