Patent Publication Number: US-11037726-B2

Title: Method for manufacturing common-mode choke coil

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. national stage application of the PCT international application No. PCT/JP2017/040176 filed on Nov. 8, 2017, which claims the benefit of foreign priority of Japanese patent application No. 2017-033085 filed on Feb. 24, 2017, the contents all of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a method for manufacturing a common-mode choke coil, including a magnetic core and wire, used in a range of electronic devices. 
     BACKGROUND ART 
     A winding-type common-mode choke coil is known to be used for suppressing unwanted radiation noise of power supply lines and common-mode noise of radio frequency signals. 
     The common-mode choke coil includes a ferrite magnetic core with flanges on both sides of a winding core, a wire formed of multiple insulation-coated conductive wires wound about the winding core of the magnetic core for several to several tens of turns typically by bifilar winding, and a magnetic plate bonded with adhesive to both flanges of the magnetic core. The magnetic plate has almost the same magnetic permeability as the magnetic core. The magnetic core and the magnetic plate are made by baking pressed ferrite powder mixed with binder. Multiple electrodes are formed on at least one flange, and a winding-start end and winding-finish end of the wire are soldered or thermally compressed onto these electrodes to establish conductive connection. This type of common-mode choke coil achieves a predetermined impedance value by setting appropriate number of turns of the wire wound about the winding core of the magnetic core. In this case, the insulation-coated conductive wire needs to be wound about each of the magnetic cores, resulting in poor productivity. In this regard, a proposal is made for winding the insulation-coated conductive wire in the state the magnetic core is bonded to the lead frame. 
     For example, PTL 1 discloses a conventional method for manufacturing a common-mode choke coil similar to the above common-mode choke coil. 
     CITATION LIST 
     Patent Literature 
     PTL1: Japanese Patent Laid-Open Publication No. 7-161563 
     SUMMARY 
     A magnetic core includes a winding core and first and second flanges connected to the winding core. First and second terminal electrodes are connected to a lead frame. The first flange is bonded to the first and second terminal electrodes. Third and fourth terminal electrodes are bonded to the second flange. First and second insulation-coated conductive wires are wound about the winding core. The first and second insulation-coated conductive wires are connected to the first and second terminal electrodes and the third and fourth terminal electrodes. The lead frame is bent so as to rotate the magnetic core by 90 degrees with respect to the lead frame. A magnetic plate is bonded to the magnetic core. The magnetic core is removed from the lead frame by removing the first and second terminal electrodes from the lead frame, thereby providing a common-mode choke coil. 
     The common-mode choke coil having stable electrical performance is produced efficiently by the above method. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1A  is a side view of a common-mode choke coil in accordance with an exemplary embodiment. 
         FIG. 1B  is a circuit diagram of the common-mode choke coil in accordance with the embodiment. 
         FIG. 2  is a perspective view of a magnetic core of the common-mode choke coil in accordance with the embodiment. 
         FIG. 3  is a perspective view of the common-mode choke coil in accordance with the embodiment for illustrating a method of manufacturing the common-mode choke coil. 
         FIG. 4  is a perspective view of the common-mode choke coil in accordance with the embodiment for illustrating the method of manufacturing the common-mode choke coil. 
         FIG. 5  is a perspective view of the common-mode choke coil in accordance with the embodiment for illustrating the method of manufacturing the common-mode choke coil. 
         FIG. 6  is a perspective view of the common-mode choke coil in accordance with the embodiment for illustrating the method of manufacturing the common-mode choke coil. 
         FIG. 7  is a perspective view of the common-mode choke coil in accordance with the embodiment for illustrating the method of manufacturing the common-mode choke coil. 
         FIG. 8  is a perspective view of the common-mode choke coil in accordance with the embodiment for illustrating the method of manufacturing the common-mode choke coil. 
         FIG. 9  is a perspective view of the common-mode choke coil in accordance with the embodiment for illustrating the method of manufacturing the common-mode choke coil. 
         FIG. 10  is a perspective view illustrating the method for manufacturing the common-mode choke coil in accordance with the exemplary embodiment. 
         FIG. 11  is a circuit diagram of another common-mode choke coil in accordance with the embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 1A  is a side view of common-mode choke coil  1001  in accordance with an exemplary embodiment.  FIG. 1B  is a circuit diagram of common-mode choke coil  1001 . Common-mode choke coil  1001  includes magnetic core  11 , insulation-coated conductive wires  18 A and  18 B wound about magnetic core  11 , and terminal electrodes  16 A,  16 B,  17 A, and  17 B bonded to magnetic core  11 . One end  118 A of insulation-coated conductive wire  18 A is connected to terminal electrode  16 A, and another end  218 A of insulation-coated conductive wire  18 A is connected to terminal electrode  16 B. One end  118 B of insulation-coated conductive wire  18 B is connected to terminal electrode  17 A, and another end  218 B of insulation coated conductive wire  18 B is connected to terminal electrode  17 B. Insulation-coated conductive wires  18 A and  18 B are magnetically coupled to each other. 
     A method for manufacturing common-mode choke coil  1001  will be described below with reference to drawings.  FIGS. 2 to 10  are perspective views of common-mode choke coil  1001  for illustrating the method of manufacturing common-mode choke coil  1001 . 
     First, magnetic core  11  is prepared.  FIG. 2  shows magnetic core  11 . Magnetic core  11  includes winding core  12  having ends  12 A and  12 B opposite to each other in longitudinal direction D 12 , flange  13  connected to end  12 A of winding core  12 , and flange  14  connected to end  12 B of winding core  12 . Width  13 W of flanges  13  and  14  in the longitudinal direction is about 3.2 mm Outer dimension  13 D of flanges  13  and  14  is about 4.5 mm Height  13 H of flanges  13  and  14  is about 2.2 mm Magnetic core  11  is obtained by pressing ferrite powder mixed with binder and then baking the pressed ferrite powder. 
     Flange  13  has surface  213  connected to winding core  12 , surface  113  opposite to surface  213  in longitudinal direction D 12 , and end surfaces  313 ,  413 ,  513 , and  613  connected to surfaces  113  and  213 . End surfaces  313  and  413  are opposite to each other, and end surfaces  513  and  613  are opposite to each other. Surface  113  has substantially a rectangular shape surrounded by four sides  113 A to  113 D. Four sides  113 A to  113 D thus constitute outer peripheral edge  113 P of surface  113 . End surfaces  313  to  613  are connected to surface  113  at sides  113 A to  113 D, respectively. Side  113 A and  113 B are parallel to each other. Sides  113 C and  113 D are parallel to each other and perpendicular to sides  113 A and  113 B. Similarly, flange  14  has surface  214  connected to winding core  12 , surface  114  opposite to surface  214  in longitudinal direction D 12 , and end surfaces  314 ,  414 ,  514 , and  614  connected to surfaces  114  and  214 . End surfaces  314  and  414  are opposite to each other, and end surfaces  514  and  614  are opposite to each other. 
     Next, lead frame  15  having a hoop shape shown in  FIG. 3  is prepared. Lead frame  15  includes plural frames  15 A connected to form the hoop shape. Terminal electrodes  16 A and  16 B are connected to lead frame  15 . More specifically, lead frame  15  further includes portions  116 A,  116 B,  216 A, and  216 B. Portions  116 A and  216 A extend from each frame  15 A, and are connected to terminal electrode  16 A. Portions  116 B and  216 B extend from each frame  15 A and are connected to terminal electrode  16 B. Lead frame  15  to which terminal electrodes  16 A and  16 B are connected is obtained by punching and bending a metal sheet made of phosphor bronze and having a thickness of about 0.1 mm. Terminal electrodes  16 A and  16 B are disposed on flanges  13  and  14  of magnetic core  11 , respectively. Terminal electrode  16 A is connected to lead frame  15  via two portions  116 A and  216 A, and terminal electrode  16 B is connected to lead frame  15  via two portions  116 B and  216 B. 
     Next, as shown in  FIG. 4 , adhesive is applied to portions of flange  13  of magnetic core  11  where terminal electrodes  16 A and  16 B are to be disposed thereon. Magnetic core  11  is placed such that flange  13  of magnetic core  11  is bonded to terminal electrodes  16 A and  16 B. Magnetic core  11  is tentatively fixed onto lead frame  15  via terminal electrodes  16 A and  16 B by heating at a temperature of 150° C. for about 1 minute. Magnetic core  11  is thus supported by four portions  116 A,  116 B,  216 A, and  216 B of lead frame  15 . 
     Next, as shown in  FIG. 5 , two terminal electrodes  17 A and  17 B are bonded adhesive to flange  14  of magnetic core  11  with the adhesive. When the metal sheet is punched to form lead frame  15 , a portion of the metal sheet to be punched is punched to have shapes of terminal electrodes  17 A and  17 B to be utilized as terminal electrodes  17 A and  17 B. This configuration reduces a material loss of the metal sheet. Then, similarly, terminal electrodes  17 A and  17 B are tentatively fixed onto flange  14  by heating at a temperature of about 150° C. for about 1 minute. 
     Then, as shown in  FIG. 6 , a pair of insulation-coated conductive wires  18 A and  18 B are wound about winding core  12  of magnetic core  11 . Ends  118 A and  218 A of insulation-coated conductive wire  18 A are connected to terminal electrodes  16 A and  16 B, respectively. Ends  118 B and  218 B (see  FIG. 1B ) of insulation-coated conductive wire  18 B are connected to terminal electrodes  17 A and  17 B, respectively. While the pair of insulation-coated conductive wires  18 A and  18 B are wound about winding core  12 , magnetic core  11  shown in  FIG. 2  is connected to lead frame  15  at three sides  113 A,  113 C, and  113 D of outer peripheral edge  113 P of surface  113  of flange  13  that are not on a single straight line, thereby allowing insulation-coated conductive wires  18 A and  18 B to be reliably wound about winding core  12 . 
     Next, as shown in  FIG. 7 , portions  216 A and  216 B of lead frame  15  connected to terminal electrodes  16 A and  16 B are cut at cut positions  19 A and  19 B. Portions  216 A and  216 B of lead frame  15  are cut such that terminal electrodes  16 A and  16 B protrude from end surface  413  (see  FIG. 2 ) of flange  13 . In accordance with the embodiment, terminal electrodes  16 A and  16 B protrude from end surface  413  of flange  13  by about 0.1 mm. 
     Next, as shown in  FIG. 8 , lead frame  15  is bent at bent positions  21 A and  21 B of portions  116 A and  116 B so as to rotate magnetic core  11  fixed onto lead frame  15  by 90 degrees with respect to lead frame  15  in predetermined rotation direction R 1 . Here, the rotation by 90 degrees is not necessarily mean a rotation exactly by 90 degrees. This means that plane P 1001  (see  FIG. 1A ) including end surfaces  413  and  414  of flanges  13  and  14  becomes almost horizontal as a result of the rotation. 
     Next, as shown in  FIG. 9 , adhesive is applied to end surfaces  413  and  414  of flanges  13  and  14 , and magnetic plate  23  is attached and heated at about a temperature of 150° C. for about 1 minute to tentatively fix magnetic plate  23 . Since terminal electrodes  16 A and  16 B protrude from end surface  413  of flange  13  by about 0.1 mm, magnetic plate  23  is easily positioned with respect to magnetic core  11 . In this case, terminal electrodes  17 A and  17 B (see  FIG. 5 ) preferably do not protrude from end surface  414  of flange  14 . This configuration allows magnetic plate  23  to be easily aligned even though the size of magnetic plate  23  varies. End surfaces  413  and  414  of flanges  13  and  14  thus function as bonding surfaces to be bonded onto magnetic plate  23  with adhesive.  FIG. 1A  shows adhesives  413 A and  414 A applied to end surfaces  413  and  414  (bonding surfaces) of flanges  13  and  14  of magnetic core  11  and adhering to magnetic plate  23 . Adhesive  413 A reaches respective portions of terminal electrodes  16 A and  16 B protruding from plane P 1001  including end surface  413  of flange  13 . This configuration further increase the bonding strength between magnetic core  11  and magnetic plate  23 . 
     Next, as shown in  FIG. 10 , magnetic core  11  fixed onto lead frame  15  is rotated back by 90 degrees with respect to lead frame  15 . More specifically, lead frame  15  is bent at bent positions  22 A and  22 B of portions  116 A and  116 B of lead frame  15  so as to rotate magnetic core  11  in rotation direction R 2  opposite to rotation direction R 1 . 
     Next, lead frame  15  having the hoop shape is cut by predetermined lengths, stored in a stocker, and heated at a temperature of about 150° C. for about 30 minutes to cure the adhesive tentatively fixing terminal electrodes  16 A,  16 B,  17 A, and  17 B onto magnetic core  11 . 
     Next, as shown in  FIG. 10 , portions  116 A and  116 B of lead frame  15  connected to terminal electrodes  16 A and  16 B are cut at cut positions  20 A and  20 B to provide individual pieces of common-mode choke coil  1001 . As shown in  FIG. 10 , since lead frame  15  is bent at bent positions  22 A and  22 B on portions  116 A and  116 B of lead frame  15  so as to rotate magnetic core  11  in rotation direction R 2 , portions  116 A and  116 B are easily cut at cut positions  20 A and  20 B in a direction same as the cutting direction of lead frame  15  at cut positions  19 A and  19 B (see  FIG. 7 ) of lead frame  15 . 
     In the method of manufacturing common-mode choke coil disclosed in PTL1, the insulation-coated conductive wire is wound while only the bottom surface of one flange is bonded to the lead frame. Therefore, the magnetic core are movable, and prevents the wire from being wound reliably, resulting in unstable electrical performance. As the diameter of the insulation-coated conductive wire is larger in order to reduce a direct-current resistance, the wire is accordingly prevented from being wound reliably. 
     In the method of manufacturing common-mode choke coil  1001  in accordance with the embodiment, as shown in  FIG. 2 , magnetic core  11  is bonded to lead frame  15  shown in  FIG. 6  at three sides  113 A,  113 C, and  113 D of surface  113  of flange  13  that are not on a single straight line, thereby allowing insulation-coated conductive wires  18 A and  18 B to be reliably wound about winding core  12 . Accordingly, common-mode choke coil  1001  having stable electrical performance can be manufactured efficiently. 
       FIG. 11  is a circuit diagram of another common-mode choke coil  1002  in accordance with the embodiment. In  FIG. 11 , components identical to those of common-mode choke coil  1001  shown in  FIGS. 1A to 10  are denoted by the same reference numerals. Common-mode choke coil  1002  in  FIG. 11  is different from common-mode choke coil  1001  shown in  FIGS. 1A to 10  in connection between insulation-coated conductive wire  18 A and terminal electrodes  16 A,  16 B,  17 A, and  17 B. More specifically, in common-mode choke coil  1002  shown in  FIG. 11 , one end  118 A of insulation-coated conductive wire  18 A is connected to terminal electrode  16 A, and another end  218 A of insulation-coated conductive wire  18 A is connected to terminal electrode  17 A. One end  118 B of insulation-coated conductive wire  18 B is connected to terminal electrode  16 B, and another end  218 B of insulation-coated conductive wire  18 B is connected to terminal electrode  17 B. Insulation-coated conductive wires  18 A and  18 B are magnetically coupled to each other. Common-mode choke coil  1002  shown in  FIG. 11  has stable electrical characteristics as well as common-mode choke coil  1001  shown in  FIGS. 1A to 10 . 
     As described above, in common-mode choke coil  1001  in accordance with the embodiment, insulation-coated conductive wire  18 A is connected to terminal electrode  16 A and one terminal electrode  16 B of terminal electrodes  16 B and  17 A, and is connected to none of terminal electrode  17 B and another terminal electrode  17 A of terminal electrodes  16 B and  17 A. Insulation-coated conductive wire  18 B is connected to terminal electrode  17 B and another terminal electrode  17 A of terminal electrode  16 B and  17 A and terminal electrode  17 B, and is connected to none of terminal electrode  16 A and one terminal electrode  16 B of terminal electrodes  16 B and  17 A. 
     In common-mode choke coil  1002  in accordance with the embodiment, insulation-coated conductive wire  18 A is connected to terminal electrode  16 A and one terminal electrode  17 A of terminal electrodes  16 B and  17 A, and is connected to none of terminal electrode  17 B and another terminal electrode  16 B of terminal electrodes  16 B and  17 A. Insulation-coated conductive wire  18 B is connected to terminal electrode  17 B and another terminal electrode  16 B of terminal electrodes  16 B and  17 A, and is connected to none of terminal electrode  16 A and one terminal electrode  17 A of terminal electrodes  16 B and  17 A. 
     REFERENCE MARKS IN THE DRAWINGS 
     
         
           11  magnetic core 
           12  winding core 
           13  flange (first flange) 
           14  flange (second flange) 
           15  lead frame 
           16 A terminal electrode (first terminal electrode) 
           16 B terminal electrode (second terminal electrode) 
           17 A terminal electrode (third terminal electrode) 
           17 B terminal electrode (fourth terminal electrode) 
           18 A insulation-coated conductive wire (first insulation-coated conductive wire) 
           18 B insulation-coated conductive wire (first insulation-coated conductive wire) 
           19 A,  19 B cut position 
           20 A,  20 B cut position 
           21 A,  21 B bent position 
           22 A,  22 B bent position 
           23  magnetic plate