Patent Publication Number: US-8112872-B2

Title: Method of manufacturing a coil component

Description:
TECHNICAL FIELD 
     The present invention relates to a coil component and method for producing the coil component. 
     BACKGROUND 
     One type of coil component well known in the art has a core including a winding portion and a pair of flanges, and a winding wound over the winding portion. Japanese Patent Application Publication No. H07-302719 discloses a technique for protecting the wound portion of the winding with an insulating resin. More specifically, a resin coating is formed over the wound area of the winding by injecting a liquid resin thereon. 
     In addition, the coil component is conventionally provided with terminal electrodes electrically connected to each end of the winding. The terminal electrodes are provided on the surface-mounting side of the coil component to be electrically connected to electrodes formed on a circuit board when the coil component is mounted on the circuit board. In order to ensure reliable contact between the terminal electrodes and the electrodes on the circuit board, the coil component must be mounted in a precise orientation onto a precise position of the circuit board. 
     As technological advances are made to increase the performance and reduce the size of electronic devices employing coil components, such as mobile telephones, there has been increasing demand to reduce the size and increase the mounting density of the coil components themselves. To meet this demand, coil components are now being manufactured with a core size of a few millimeters. However, reducing the core size also reduces the size of the winding in the wound area, making it more difficult to fill this wound area with resin. 
     Further, the reduced size of the coil component has made it more difficult to visually determine the position and orientation of the coil component being mounted on the circuit board, often leading to mounting errors. Changing the shape of the core or adding a marker or the like to the core has helped confirm the correct orientation of the coil component, but increases the difficulty of the manufacturing process with additional steps to change the core shape and apply a marker. 
     SUMMARY 
     Therefore, it is an object of the present invention to provide a coil component having an easily discernible orientation, and to provide a method of manufacturing such a coil component that facilitates the injection of resin. 
     This and other object of the present invention will be attained by a coil component including a core, terminal electrodes, a winding, an insulating resin, and a marker. The core includes a winding portion having a first end and a second end, a first flange disposed at the first end and having an outer peripheral surface, and a second flange disposed at the second end and having an outer peripheral surface. A winding accommodating region is defined by the winding portion and the first and second flanges. The terminal electrodes are disposed on at least one of the first flange and the second flange. The winding is wound about the winding portion to provide a wound portion and is connected to the terminal electrodes. The insulating resin layer covers the wound portion of the winding within the winding accommodating region. The marker is formed of a material the same as that of the insulating resin layer and is deposited on a part of the outer peripheral surface on the first flange and the second flange. 
     In another aspect of the invention, there is provided a method of producing a coil component including a core having a winding portion, a pair of flanges having an outer peripheral surface and providing a winding accommodating region defined by the winding portion and the pair of flanges; terminal electrodes disposed on at least one of the pair of flanges; and a winding wound about the winding portion and connected to the terminal electrodes. The method includes (a) wrapping the winding about the winding portion in layers within the winding accommodating region to provide a wound portion, (b) connecting ends of the winding to the terminal electrodes, and (c) immersing a portion of the outer peripheral surface of the pair of flanges in a liquid resin bath to form a resin coating over the wound portion of the winding within the winding accommodating region, and simultaneously forming a marker made from the liquid resin on the immersed portion of the outer peripheral surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a coil component according to one embodiment of the present invention; 
         FIG. 2  is a rear view of a core in the coil component according to the embodiment; 
         FIG. 3  is a bottom view of the coil component according to the embodiment; 
         FIG. 4  is a front view of the coil component according to the embodiment; and 
         FIG. 5  is a schematic diagram illustrating a method of manufacturing the coil component according to the embodiment, where; 
         FIG. 5(   a ) shows the core prior to immersion in a liquid resin bath; 
         FIG. 5(   b ) shows the core immersed in the liquid resin bath; 
         FIG. 5(   c ) shows the liquid resin rising due to the capillary effect; and 
         FIG. 5(   d ) shows the winding covered with liquid resin; and 
         FIG. 5(   e ) shows the core after being lifted out of the liquid resin bath. 
     
    
    
     EMBODIMENT 
     Next, a coil component and a method for producing the coil component according to one embodiment of the present invention will be described with reference to  FIGS. 1 through 5 . A coil component  1  shown in  FIG. 1  primarily includes a core  2 , a single winding  6 , terminal electrodes  7 , and a resin coating  8 . 
     As shown in  FIG. 2 , the core  2  is a few millimeters by a few millimeters wide with a height of about 1 millimeter. The core  2  is basically made from magnetic material such as ferrite and includes a substantially cylindrical winding portion  3 , and a first flange  4  and a second flange  5  disposed one on either end of the winding portion  3 . A winding accommodating region  2 A for accommodating the winding  6  is defined between the first and second flanges  4  and  5  around the winding portion  3 . Since the first and second flanges  4  and  5  are symmetrical in shape, only the second flange  5  will be described below. 
     The second flange  5  is a plate member having a prescribed thickness. The second flange  5  has a bottom surface  5 A ( FIG. 3 ) that is substantially octagonal in shape and serves as the mounting surface when mounting the coil component  1  on a circuit board (not shown). As shown in  FIGS. 2 through 4 , the second flange  5  has a first peripheral surface  51 , a second peripheral surface  52 , a first omitted peripheral surface  53 , a second omitted peripheral surface  54 , a third peripheral surface  55 , a fourth peripheral surface  56 , a third omitted peripheral surface  57 , and a fourth omitted peripheral surface  58  all extending from the peripheral edge of the bottom surface  5 A toward the first flange  4 . 
     The first and second peripheral surfaces  51  and  52  are parallel surfaces, the first and second omitted peripheral surfaces  53  and  54  are disposed on one side of the first and second peripheral surfaces  51  and  52 , and the third and fourth omitted peripheral surfaces  57  and  58  are disposed on the other side of the first and second peripheral surfaces  51  and  52 . The third peripheral surface  55  is provided between the first and second omitted peripheral surfaces  53  and  54 , and the fourth peripheral surface  56  is provided between the third and fourth omitted peripheral surfaces  57  and  58 . The third and fourth peripheral surfaces  55  and  56  are substantially parallel. These peripheral surfaces  51 - 58  constitute the outer peripheral surface of the second flange  5 . 
     When the coil component  1  is mounted on a circuit board, the first, second, third, and fourth peripheral surfaces  51 ,  52 ,  55 , and  56  are substantially in contact with or in close proximity to the electronic parts of other neighboring coil components. When viewing the bottom surface  5 A along the direction of a line connecting the first and second flanges  4  and  5 , the first, second, third, and fourth omitted peripheral surfaces  53 ,  54 ,  57 , and  58  constitute the chamfered four corners of an imaginary square constructed by extending each of the first, second, third, and fourth peripheral surfaces  51 ,  52 ,  55 , and  56 . This configuration inhibits the first, second, third, and fourth omitted peripheral surfaces  53 ,  54 ,  57 , and  58  from substantially coming into contact with other electronic parts. 
     As shown in  FIGS. 2 and 4 , a top surface  4 A is provided on the first flange  4  on the opposite side of the core  2  from the bottom surface  5 A. The first flange  4  has a first peripheral surface  41 , a second peripheral surface  42 , a first omitted peripheral surface  43 , a second omitted peripheral surface  44 , a third peripheral surface  45 , a fourth peripheral surface  46 , a third omitted peripheral surface  47 , and a fourth omitted peripheral surface  48  those corresponding to the outer peripheral surface of the second flange  5 . 
     The winding  6  is a copper wire having an insulating coating and is wound about the winding portion  3  ( FIG. 2 ). As shown in  FIG. 4 , the winding  6  is accommodated in the winding accommodating region  2 A. The winding  6  has a first end  6 A and a second end  6 B electrically connected to the terminal electrodes  7 . 
     The terminal electrodes  7  include a first terminal electrode  7 A and a second terminal electrode  7 B. As shown in  FIGS. 2-4 , the first terminal electrode  7 A is provided across the first omitted peripheral surface  53 , a portion of the bottom surface  5 A, and the third omitted peripheral surface  57 . The second terminal electrode  7 B is provided across the second omitted peripheral surface  54 , a portion of the bottom surface  5 A separated from the first terminal electrode  7 A, and the fourth omitted peripheral surface  58 . The first end  6 A of the winding  6  is electrically connected to the first terminal electrode  7 A at a portion of the first omitted peripheral surface  53 , while the second end  6 B of the winding  6  is electrically connected to the second terminal electrode  7 B at a portion of the second omitted peripheral surface  54 . 
     As shown in  FIG. 4 , the resin coating  8  is injected into the winding accommodating region  2 A over the wound portion of the winding  6  to protect the winding  6 . Further, a marker  8 A projects from the third peripheral surfaces  45  and  55 . The marker  8 A is formed integrally with the resin coating  8  and is made from a material the same as that of the resin coating  8 . The first and second terminal electrodes  7 A and  7 B serving as positions for connecting the ends of the winding  6  are formed in the first omitted peripheral surface  53  and second omitted peripheral surface  54  disposed on both sides of the third peripheral surface  55  of the second flange  5 . Accordingly, the positions of the terminal electrodes  7  relative to the bottom surface  5 A, i.e., the mounting surface, can be determined based on the marker  8 A. Therefore, mounting errors can be reduced by always maintaining the coil component  1  in a given orientation such that an imaginary line from the center of the coil component  1  to the marker  8 A is in a fixed direction when mounting the coil component  1  on the circuit board. 
     When manufacturing the coil component  1 , the winding  6  is wound about the winding portion  3  within the winding accommodating region  2 A to provide a multilayer windings (winding step), and subsequently the first and second ends  6 A and  6 B of the wound winding  6  are connected to the terminal electrodes  7  (wire connecting step). 
     For forming the resin coating  8  over the winding  6 , as shown in  FIG. 5(   a ), the core  2  is held above a liquid resin bath W filled with liquid resin such that the third peripheral surfaces  45  and  55  are facing downward. From this state, the core  2  is moved to and held in a position at which the third peripheral surfaces  45  and  55  contact the surface of the liquid resin ( FIG. 5(   b )). Since the height of the core  2  is approximately 1 mm, the distance between the first and second flanges  4  and  5  is approximately 0.4 mm. Hence, when the third peripheral surfaces  45  and  55  are immersed in the liquid resin of the liquid resin bath W, the liquid resin penetrates the winding accommodating region  2 A between the first and second flanges  4  and  5  due to the capillary effect ( FIG. 5(   c )). Since the winding  6  is tightly wound within the winding accommodating region  2 A, gaps within the winding  6  are small. Since the degree to which liquid rises due to capillary action is inversely proportional to the diameter of the tube, a force acts to draw up the liquid resin in the narrow gaps formed in the wound portion of the winding  6 , resulting in the liquid resin penetrating the wound portion of the winding  6  across the entire portion ( FIG. 5(   d )). After the resin coating  8  has been formed and the core  2  lifted out of the liquid resin bath W ( FIG. 5(   e )), the liquid resin remains deposited on the third peripheral surfaces  45  and  55 , which were the surfaces that contacted the liquid resin in the liquid resin bath W. This concludes the step of immersing the core  2  into the liquid resin bath W (resin immersion step). Subsequent hardening of the resin completes formation of the resin coating  8  and marker  8 A. 
     As a modification, while the marker  8 A is provided in a location where the terminal electrodes  7  are not formed in the above description, the marker  8 A may be provided on the outer peripheral surface at the location of the terminal electrodes  7 . With this configuration, the terminal electrodes  7  are protected by resin, reducing the chances of short-circuiting. Accordingly, this configuration suppresses the occurrence of short-circuiting between neighboring coil components  1 , even when coil components  1  are mounted very densely. Further, the resin coating  8  and marker  8 A may be formed of a resin with insulating properties, or a resin containing ferrite powder, for example. The properties of the coil component  1  can be varied by controlling the ratio of the ferrite powder in the resin. Further, the resin need not be applied using the liquid resin bath W, but may be supplied with a resin supplying apparatus having an aperture whose diameter corresponds to the distance between the first and second flanges  4  and  5 . 
     While the invention has been described in detail with reference to the specific embodiment thereof, it would be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention.