Patent Publication Number: US-11657956-B2

Title: Coil device and pulse transformer

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a coil device used as, for example, a pulse transformer. 
     The coil device shown in the following Patent Document 1 is known as the coil device used such as the pulse transformer. In this conventional coil device, the end of the wire forming the coil is connected to the terminal electrode having the mounting surface by thermocompression bonding. 
     However, in the conventional coil device disclosed in the Patent Document 1, a part of the film covering the wire is likely to be left as a film residue on the mounting surface of the terminal electrodes during thermocompression bonding. As a result, when the coil device is mounted on a substrate, a void or the like may generate in a connecting member, such as solder, which connects the mounting surface of the terminal electrode to the substrate. The void is likely to crack and reduce the connection reliability. 
     In addition, the Sn layer on the mounting surface of the electrode terminal may melt and reduce due to the influence of heat when connecting by thermocompression bonding. As a result, the adhesion between the connecting member, such as solder, and the terminal electrode may deteriorate, and the bonding strength may decrease.
     Patent Document 1: JP Unexamined Patent Application No. 2018-78155   

     BRIEF SUMMARY OF INVENTION 
     The invention has been made in view of such circumstances, and an object thereof is to provide a coil device and a pulse transformer, those having a high bonding strength and a high bonding reliability. 
     In order to achieve the above object, a coil device of the invention includes 
     a core member having a winding core and a flange, 
     a wire wound around the winding core and having one end located at the flange, and 
     terminal electrodes provided on the flange, wherein 
     the terminal electrode includes 
     a wire connecting part to which the one end of the wire is connected and 
     a mounting part formed continuously to the wire connecting part and to be positioned away from an axis of the winding core with respect to the wire connecting part along an outer peripheral direction of the flange. 
     According to the coil device of the invention, the wire connecting part and the mounting part are separately provided in the terminal electrode. Thus, the film residue that may generate at the wire connecting part will unlikely to adhere to the mounting part when the one end of the wire is thermocompression bonded to the wire connecting part of the terminal electrode. As a result, when mounting the coil device on a substrate, voids and the like are unlikely to generate in the connecting members connecting the mounting surface of the terminal electrode and the substrate, suppressing generation of cracks, and improving connection reliability. 
     In addition, since the mounting part and wire connecting part are separately provided in the terminal electrode, the influence of heat when connecting by thermocompression bonding hardly affects the mounting part. Thus, the Sn layer on the surface of the mounting part, the layer improving the adhesion to the connection member such as solder, becomes less likely to melt. As a result, when the coil device is mounted on the substrate, the adhesion between the mounting part of the terminal electrode and the connecting member such as solder becomes good, and the bonding strength is improved. 
     The mounting part is formed continuously to the wire connecting part and to be positioned away from the axis of the winding core with respect to the wire connecting part along an outer peripheral direction of the flange. Thus, the wire connecting part becomes close to the winding core, and it becomes possible to shorten the length of the wire from the wire connecting part to the winding core, and the direct current internal resistance of the coil device can be lowered (reduction in DCR). 
     The mounting part is formed continuously to the wire connecting part and to be positioned away from the axis of the winding core with respect to the wire connecting part along an outer peripheral direction of the flange. Thus, the wire connecting part does not pop out to the outer side of the flange of the coil device, the side away from the axis of the winding core. Therefore, the coil device can be made compact, the coil device can be easily transported and handled, and the handling property when mounting is improved. 
     Further, the mounting part is preferably formed in proximity to the wire connecting part, in which case the DCR can be further reduced. Furthermore, as for the terminal electrodes positioned on both sides of the axis of the winding core, it is preferable that the wire connecting parts are positioned inside, the axis side, of the respective mounting parts. In this case, it is possible to carry out thermocompression bonding of the wire to each wire connecting part at once by the heater for thermocompression bonding. 
     Preferably, the wire connecting part that is disposed at a position lower than the mounting part along the height direction of the flange. By configuring in this manner, the risk of the film residue that may generate in the wire connecting part adhering to the mounting part is further reduced. In addition, the influence of heat when wire connecting by thermocompression bonding is further reduced in the mounting part. Furthermore, when the coil device is mounted on a substrate or the like, not wire connecting part but the mounting part of the terminal electrode contacts the connecting part of the substrate. Thus, the connection strength between the mounting part of the terminal electrode and the substrate improves and the connection reliability also improves. 
     The stepped part prevents a lateral shift of the end (the lead) of the wire when winding starts or ends on the winding core, and the ends of the wires can be appropriately connected to the wire connecting part. In addition, the presence of the stepped part further reduces the possibility that the film residue that may be generated in the wire connecting part adheres to the mounting part. 
     The flange may have a first region in which the wire connecting part is disposed and a second region in which the mounting part is disposed. A stepped part may be formed according to the stepped part formed on the terminal electrode between the first region and the second region. Alternatively, a gap space larger than the gap between the wire connecting part of the terminal electrode and the first region may be formed between the mounting part of the terminal electrode and the second region. In addition, the first region and the wire connecting part are preferably not attached, and the second region and the mounting part are preferably not attached. 
     The terminal electrode preferably further includes an installation part continuously formed to the mounting part at a position different from the connection part between the wire connecting part and the mounting part. And the installation part is preferably fixed by such as an adhesive on the outer surface of the flange. With this configuration, there is no need to fix the wire connecting part and the mounting part of the terminal electrode to the flange, and such as a heat and impact resistance of the coil device after mounting improves. 
     In the terminal electrode, an area of the wire connecting part is preferably smaller than an area of the mounting part in the terminal electrode. With this configuration, the heat capacity of the wire connecting part can be relatively reduced, and the influence of the heat when thermocompression bonding of the wire on the mounting part can be reduced. 
     The width of the wire connecting part may be narrower than the width of the mounting part along the axis direction of the winding core. With this configuration, the area of the wire connecting part can be made smaller than the area of the mounting part. Preferably, the wire connecting part is formed continuously to an edge of the mounting part close to the winding core. With this configuration, the wire connecting part becomes close to the winding core, and it becomes possible to shorten the length of the wire from the wire connecting part to the winding core, and it is possible to further reduce DCR. 
     Preferably, an exposed surface, where the outer surface of the flange is exposed, is formed between the edge of the wire connecting part close to the winding core and the inner side face of the flange close to the winding core. More preferably, the exposed surface is chamfered. With this configuration, it is possible to increase the angle at which the end of the wire contacts the edge of the winding core side of the wire connecting part, and to reduce a damage to the end of the wire. 
     One of the pluralities of terminal electrodes provided in the flange has a wide wire connecting part wider than the wire connecting part of the other terminal electrodes. The ends of two or more wires may be connected to the wide wire connecting part side by side along the outer circumferential direction of the flanges. 
     The pulse transformer of the invention includes any one of the coil devices described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of the coil device according to an embodiment of the invention. 
         FIG.  2    is a partial perspective view of the coil device shown in  FIG.  1    and an enlarged view of the part II in  FIG.  1   . 
         FIG.  3    is a plan view of the coil device shown in  FIG.  1     
         FIG.  4    is a cross-sectional view of the coil device shown in  FIG.  1   , taken along IV-IV. 
         FIG.  5 A  is a perspective view showing a first terminal member of the coil device shown in  FIG.  1   . 
         FIG.  5 B  is a perspective view showing a second terminal member of the coil device shown in  FIG.  1   . 
         FIG.  6 A  is a first view illustrating a state in which a wire end is thermocompression bonded in the coil device of  FIG.  1   . 
         FIG.  6 B  is a second view illustrating a state in which a wire end is thermocompression bonded in the coil device of  FIG.  1   . 
     
    
    
     Hereinafter, the invention will be described based on embodiments shown in the drawings. 
     As shown in  FIG.  1   , the coil device  1  is a surface mount type coil component used such as a pulse transformer. The coil device  1  has a drum core  10 , a coil part  30 , and terminal electrodes  51  to  56  as drum-shaped core members. 
     In the coil device  1 , the upper surface in the Z-axis direction in  FIG.  1    is the mounting surface, when the coil device  1  is mounted on such as a substrate. In the following description, X-axis is parallel to the winding axis of the coil part  30  of the coil device  1 , Z-axis is parallel to the height direction of the coil device  1 , and Y axis is substantially vertical to the X-axis and the Z-axis. 
     The external size of the coil device  1  is not particularly limited, and the X-axis length may be 3.0 to 6.0 mm, the Y-axis width may be 3.0 to 6.0 mm, and the Z-axis height may be 1.5 to 4.0 mm. 
     The drum core  10  has a rod-like part (winding core  11  shown in  FIG.  4   ) around which the coil part  30  is wound, and a pair of flanges  12 ,  12  provided at both axial ends of the winding core  11 . As shown in  FIG.  4   , the cross-sectional shape of the winding core  11  is a substantial square in the embodiment, however it is not particularly limited and may have a shape of polygon, circle, ellipse, etc. As shown in  FIG.  1   , although the external shape of the two flanges  12 ,  12  have a substantially rectangular parallelepiped of the same shape, both may mutually differ in shape or size. 
     The drum core  10  is made of a magnetic material including for example, a magnetic material having a relatively high permeability such as a Ni—Zn based ferrite and a Mn—Zn based ferrite, or a magnetic powder such as a metal magnetic material. 
     As shown in  FIG.  3   , the two flanges  12 ,  12  are arranged substantially parallel to each other at a predetermined interval in the X-axis direction. Both ends of the winding core  11  in X-axis direction are connected to the central parts of each inner surface  13 ,  13  in Y-axis direction facing the pair of flanges  12 ,  12 . 
     In each of the flanges  12 ,  12 , three of the first to the third terminal electrodes  51  to  53  are formed on the mounting face  20  of one of the flanges  12 , three of the first to the third terminal electrodes  51  to  53  are disposed on the mounting face  20  of one flange  12 , and three of the forth to the sixth terminal electrodes  54  to  56  are disposed on the mounting face  20  of the other flange  12 . 
     A coil part  30  is formed on the winding core  11  of the drum core  10 . According to the embodiment, the coil part  30  has four wires  31  to  34  wound around the winding core  11 . The first wire  31  and the second wire  32  constitute a primary coil as the pulse transformer, and the third wire  33  and the fourth wire  34  constitute a secondary coil as the pulse transformer. The first wire  31  and the second wire  32  forming the primary coil are wound in opposite directions, and the third wire  33  and the fourth wire  34  forming the secondary coil are wound in the opposite direction. 
     As shown in  FIG.  3   , the respective end  31   a  to  34   a  and  31   b  to  34   b  of the four wires  31  to  34  wound around in this manner is connected by such as thermocompression bonding to the flanges  12 ,  12  of the drum core  10 . 
     Specifically, one end  31   a  of the first wire  31  is connected to the first terminal electrode  51 , one end  32   a  of the second wire  32  is connected to the second terminal electrode  52 , and one ends  33   a ,  34   a  respectively of the third wire  33  and the fourth wire  34  are both connected to the third terminal electrode  53 . 
     Further, the other ends  31   b ,  32   b  of the first wire  31  and the second wire  32  are both connected to the sixth terminal electrode  56 , the other end  33   b  of the third wire  33  is connected to the fifth terminal electrode  55 , and the other end  34   b  of the forth wire  34  is connected to the forth terminal electrode  54 . 
     The wires  31  to  34  are wound in such configuration and connect to the terminal electrodes  51  to  56 . Therefore, the first terminal electrode  51  and the second terminal electrode  52  form a primary coil side terminal, an input side terminal. And the fourth terminal electrode  54  and the fifth terminal electrode  55  form a secondary coil side terminal, an output side terminal. The third terminal electrode  53  and the sixth terminal electrode  56  are center taps on the primary coil side (input side) and the secondary coil side (output side), respectively. 
     Each wire  31  to  34  is made by a covered conductive wire. For example, a core material made of a good conductor having high conductivity such as copper (Cu) is covered with an insulating material made of an imide modified polyurethane, and further the outermost surface is covered with a thin resin film such as polyester. However, the material of the core material or the film material of the wires  31  to  34  are not limited thereto. 
     Further, the wire diameter, the number of turns, the method for winding, the number of layers of the wire wound around coil  30 , etc. of each wire  31  to  34  in the coil part  30  may be determined according to the properties of the obtained coil device  1 . In the embodiment, the wire diameter and the number of turns in each wire  31  to  34  are the same. Each pair of wires  31 ,  33  (or  32 ,  34 ) wound in the same direction is wound together. For example, as shown in  FIG.  4   , four wires are wound in two layers on the coil part  30 . 
     As shown in  FIGS.  5 A and  5 B , the terminal electrodes  51  to  56  are formed integrally by bending metallic plate terminal members  61 ,  62 , respectively. The terminal members  61 ,  62  are made of, for example, a metal such as copper or copper alloy, or another conductive plates. 
     As shown in  FIG.  5 A , each of the terminal electrodes  51 ,  52 ,  54 , and  55  has the same size and the same shape, and includes the wire connecting part  63   a , the mounting part  65 , and the installation part  66 . The connecting part  63   a  is continuously formed proximity to one end of the mounting part  65  in the X-axis direction so as to extend in the Y-axis direction via the stepped portion  64 . The installation part  66  is continuously formed and bent from the other end of the mounting part  65  in the X-axis direction toward the lower side of the Z-axis, at a position different from that of the wire connecting part  63   a.    
     The height z1 of the installation part  66  in the Z-axis direction is preferably equal to or shorter than the height z0 in the Z-axis direction of the flange  12  shown in  FIG.  4   , and z1/z0 is preferably 0.1 to 1. As shown in  FIG.  5 A , the width of the installation part  66  in the Y-axis direction is preferably equal to or larger than the width y2 of the mounting part  65  in the axial direction, but it may be smaller. The width y1 of the wire connecting part  63   a  in the Y-axis direction is substantially the same as the width y2 of the mounting part  65  in the Y-axis direction, and y1/y2 is preferably within 0.1 to 1.5. 
     The width x2 of the wire connecting part  63   a  in the X-axis direction is preferably shorter than the width x1 of the mounting part  65  in the X-axis direction. x2/x1 is preferably ¼ to ¾, and further preferably ⅓ to ⅔. Moreover, a not shown area s1 of the wire connecting part  63   a  is smaller than a not shown area s2 of the mounting part  65 . s1/s2 is preferably ¼ to ¾, and more preferably ⅓ to ⅔. 
     The length x1 of the mounting part  65  in the X-axis direction is preferably equal to or less than, and more preferably less than the width x0 of the mounting face  20  of the flange  12  as shown in  FIG.  3   . In order to form exposed surfaces  23   a  to  23   b  in which a part of the mounting face  20  (a part of the outer surface of the flange  12 ) is exposed between the edge  67  of the wire connecting parts  63   a ,  63   b  of the terminal electrode close to the winding core and the inner side face  13  of the flange  12  close to the winding core. The exposed surfaces  23   a  to  23   b  are preferably chamfered, including a rounding process, at the intersection between the inner side face  13  and the mounting face  20 . 
     As shown in  FIG.  5 A , it is preferable that the width of the step part  64  in the Y-axis direction is either the same as the plate thickness t1 of the metallic plate terminal members  61  or is approximately 1 to 2 times the plate thickness t1. The stepped part  64  is formed between the wire connecting part  63   a  and the mounting part  65 . Thus, the mounting part  65  is placed higher than the wire connecting part  63   a  in the Z-axis direction by a step height z2 of the stepped part  64  in the Z-axis direction. The step height z2 of the step part  64  in the Z-axis direction is preferably about the same as the plate thickness t1 of the terminal member  61  or is approximately 1.0 to 3.0 times the plate thickness t1. The thickness t1 is not particularly limited, but preferably 50 to 150 μm. 
     As shown in  FIG.  5 B , the terminal electrodes  53 ,  56  respectively has the same size and shape, and includes a wire connecting part  63   b , the mounting part  65 , and an installation part  66 . The wire connecting part  63   b  is formed in proximity to one end part of the mounting part  65  in the X-axis direction so as to extend in the Y-axis direction via the stepped part  64 . The installation part  66  is continuously formed and bent from the other end of the mounting part  65  in the X-axis direction toward the lower side of the Z-axis, at a position different from that of the wire connecting part  63   b.    
     The height z1 of the installation part  66  in the Z-axis direction shown in  FIG.  5 B  is preferably the same as the height z1 of the installation part  66  in the Z-axis direction shown in  FIG.  5 A , but they may be different. The width of the installation part  66  in the Y-axis direction shown in  FIG.  5 B  is preferably the same as the width of the installation part  66  in the Y-axis direction shown in  FIG.  5 A , but may be different. Furthermore, the mounting part  65  and the step part  64  shown in  FIG.  5 B  are also preferably similar to the mounting part  65  and the step part  64  shown in  FIG.  5 A , but may be different. The stepped part  64  is formed between the wire connecting part  63   b  and the mounting part  65 . Thus, the mounting part  65  is placed higher than the wire connecting part  63   b  in the Z-axis direction by a step height z2 of the stepped part  64  in the Z-axis direction. 
     The width x2 of the wire connecting part  63   b  in the X-axis direction shown in  FIG.  5 B  is preferably the same as the width x2 of the wire connecting part  63   a  in the X-axis direction shown in  FIG.  5 A , but may be different. According to the embodiment, the width y1a of the wire connecting part (a wide wire connecting part)  63   b  shown in  FIG.  5 B  is larger than the width y1 of the wire connecting part  63   a  in the Y-axis direction shown in  FIG.  5 A . y1a/y1 is preferably 1.2 to 3, more preferably 1.5 to 2.5. As shown in  FIG.  1   , ends of two or more wires are connected side by side in the outer peripheral direction of the flange  12  to the wide wire connecting part  63   b.    
     As shown in  FIG.  4   , the wire connecting part  63   a  shown in  FIG.  5 A  is disposed in close contact with the first regions  21   a ,  21   b  formed on the mounting face  20  of the flange  12 , but it is not necessary to be adhered, and there may be a gap. Further, as shown in  FIG.  4   , the mounting part  65  shown in  FIG.  5 A  is disposed in close contact with the second regions  22   a ,  22   b  formed on the mounting face  20  of the flange  12 , but it is not necessary to be adhered, and there may be a gap. 
     According to the embodiment, a core step part is formed between the first region  21   a  ( 21   b ) and the second region  22   a  ( 22   b ) formed on the mounting face  20  of the flange  12 , and the second region  22   a  ( 22   b ) is disposed at a position higher than the first region  21   a  ( 21   b ) in the Z-axis direction. It is preferable that the stepped part  64  of the terminal member  61  is disposed on the core stepped part, and the step height of the core stepped part is substantially the same as or smaller than the stepped height z2 of the stepped part  64  shown in  FIG.  5 A . 
     That is, the gap between the mounting part  65  and the second region  22   a  ( 22   b ) is preferably larger than the gap between the wire connecting part  63   a  and the first region  21   a  ( 21   b ). The wire connecting part  63   a  and the first region  21   a  ( 21   b ) are preferably in close contact with each other, since the end of the wire  32  ( 31 ) is thermocompression bonded to the wire connecting part  63   a  in a later step, however, there is no problem even if there is a gap between the mounting part  65  and the second region  22   a  ( 22   b ). Rather, by the presence of the gap, the resilient deformation range of the mounting part  65  is increased and the heat and/or impact resistance after mounting on the substrate of the coil device  1  may be improved. 
     As shown in  FIG.  4   , the wire connecting part  63   b  shown in  FIG.  5 B  is disposed in close contact with the first region  21   c  formed on the mounting face  20  of the flange  12 , but it is not necessary to be adhered, and there may be a gap. Further, as shown in  FIG.  4   , the mounting part  65  shown in  FIG.  5 B  is disposed in close contact with the second regions  22   c  formed on the mounting face  20  of the flange  12 , but it is not necessary to be adhered, and there may be a gap. 
     According to the embodiment, a core step part is formed between the first region  21   c  and the second region  22   c  formed on the mounting face  20  of the flange  12 , and the second region  22   c  is disposed at a position higher than the first region  21   c  in the Z-axis direction. It is preferable that the stepped part  64  of the terminal member  62  is disposed on the core stepped part, and the step height of the core stepped part is substantially the same as or smaller than the stepped height z2 of the stepped part  64  shown in  FIG.  5 B . 
     That is, the gap between the mounting part  65  and the second region  22   c  is preferably larger than the gap between the wire connecting part  63   b  and the first region  21   c  shown in  FIG.  4   . The end of the wires  33 ,  34  are thermocompression bonded to the wire connecting part  63   b  in a later step. Thus, the wire connecting part  63   b  and the first region  21   c  are preferably in close contact with each other, however, there is no problem even if there is a gap between the mounting part  65  and the second region  22   c . Rather, by the presence of the gap, the resilient deformation range of the mounting part  65  is increased and the heat and/or impact resistance after mounting on the substrate of the coil device  1  may be improved. 
     As shown in  FIG.  1   , the installation part  66  of the terminal members  61 ,  62  shown in  FIGS.  5 A and  5 B  are respectively bonded to the outer side faces  14 ,  14  of the flanges  12 ,  12  by such as an adhesion. The mounting part  65 , the step part  64  and the wire connecting part  63   a  of terminal members  61 ,  62  shown in  FIGS.  5 A and  5 B  are preferably not adhered to the mounting face  20  which is the upper surface of the flange  12  in the Z-axis direction shown in  FIG.  1   , and they are preferably freely movable. 
     The coplanarity (flatness) of the mounting face of the coil device  1  is improved by not adhering and fixing the wire connecting parts  63   a ,  63   b  and the mounting part  65  of the terminal electrodes  51  to  56  to the mounting faces  20 ,  20  of the flanges  12 ,  12 , respectively. Further, the resistance to distortion or vibration of the substrate when the coil device  1  is mounted on the substrate or the like can be improved, and the mounting reliability can be improved. 
     As shown in  FIG.  3   , when the terminal members  61 ,  62  are attached to the flange  12 , wire connecting parts  63   a  ( 63   b ) and the mounting part  65  are displaced along the outer peripheral direction (the Y-axis direction in the embodiment) of the flange  12 . And the wire connecting part  63   a  ( 63   b ) is disposed in a position closer to the axial direction A of the winding core  11  than the mounting part  65 . In particular, the terminal electrodes  52 ,  53  ( 55 ,  56 ) located on both sides of the axis A of the winding core  11  are provided with wire connecting part  63   a ,  63   b  on the inner side (axis A side) of the mounting part  65 , respectively. 
     When producing the coil device  1  having such configuration, terminal parts  51  to  56  are installed on the drum core  10  at first. The first terminal part  61  and the second terminal part  62 , corresponding to each terminal electrodes  51  to  56 , are formed by disposing the wire connecting parts  63   a ,  63   b  on the first regions  21   a  to  21   c  of the mounting faces  20 ,  20  of the flanges  12 ,  12 , disposing the second regions  22   a  to  22   c  on the mounting part  65 , and adhering the installation part  66  to the outer side faces  14 ,  14  of the flanges  12 ,  12  with the adhesive. 
     In addition, the method of forming the terminal electrodes  51  to  56  is not limited to the installation method of the terminal members  61 ,  62 , and may be formed by the baking method of the print or coated conductive film, the plating method, etc. Even with those method, the terminal electrode having the wire connecting parts  63   a ,  63   b , the step part  64 , and the mounting part  65 , similar to the embodiment, can be formed on the mounting faces  20 ,  20 , and the exposed surfaces  23   a  to  23   c  can also be formed to the mounting faces  20 ,  20 . 
     After the terminal electrodes  51  to  53  and  54  to  56  are attached to the respective flange of the drum core  10 , the drum core  10  is then set in a winding machine, and the wires  31  to  34  are wound around the winding core  11  of the drum core  10  in a predetermined order. 
     Next, the ends  31   a  to  34   a  and  31   b  to  34   b  of the wound wires  31  to  34  are fixed to the wire connecting parts  63   a ,  63   b  of the terminal electrodes  51  to  56  by thermocompression bonding. For example, in the connection of the end parts  33   a ,  34   a  of the third wire  33  and the fourth wire  34  to the wire connecting part  63   b  of the third terminal electrode, as shown in  FIG.  6 A , the heater H is pressed against the wires  33 ,  34  and the wire connecting part  63   b  from above and heated in the state in which a middle of the wires  33 ,  34  pulled out by a not shown winding machine are disposed at the wire connecting part  63   b  of the third terminal electrode  53 . The thermocompression bonding of the wire  33  to the wire connecting part  63   b  and the thermocompression bonding of the wire  34  to the wire connecting part  63   b  may be performed in separate steps. 
     By the thermocompression bonding, the film material of the wire  33 ,  34  is melted or peeled. The core material of the wire  33 ,  34 , the conductor, is exposed and the wire  33 ,  34  is compressed and electrically connected to the wire connecting part  63   b  of the terminal electrode  53 . 
     In the coil device  1  of the embodiment, the wire connecting parts  63   a ,  63   b  of the terminal electrodes  51  to  56  are disposed closer to the axis A side of the coil part  30  than the mounting part  65 . According to the flanges  12 ,  12  in which three terminal electrodes  51  to  53  or  54  to  56  are disposed, as shown in  FIG.  6 B , two heaters H 1  and H 2  may be used for the thermocompression bonding or a single heater may be used for the thermocompression bonding of four wires  31  to  34  by changing the positions to be thermo-bonded. 
     According to the embodiment, for example, since the wire connecting part  63   a  of the second terminal electrode  52  and the wire connecting part  63   b  of the third terminal electrode  53  are both arranged on the inner side, ends of the wires  32 ,  34  wound around in the same direction can be simultaneously thermocompression bonded by one wide heater H 2 . Therefore, in the coil device  1 , the producing process of thermocompression bonding the terminal electrodes  51  to  56  to the ends  31   a  to  34   a  and  31   b  to  34   b  of the wires  31  to  34  can be simplified, and the producing apparatus can be simplified. 
     After the thermocompression bonding of the both ends  31   a  to  34   a  and  31   b  to  34   b  of the wires  31  to  34  to the terminal electrodes  51  to  56  is completed, the wires are cut ahead from the wire connecting parts of the wire ends  31   a  to  34   a ,  31   b  to  34   b.    
     In the coil device  1  of the embodiment, the wire connecting part  63   a  ( 63   b ) and the mounting part  65  are separately provided to the terminal electrodes  51  to  56 . Thus, the possibility that the coating film residue that may generate in the wire connecting part  63   a  ( 63   b ) adheres to the mounting part  65  is reduced when thermocompression bonding the one end of the wires  31  to  34  to the wire connecting part  63   a  ( 63   b ) of the terminal electrodes  51  to  56 . As a result, when mounting the coil device on a not shown circuit substrate, voids and the like are not likely to generate in the connecting members, such as solder, connecting the mounting face of the terminal electrodes  51  to  56  and the substrate. Thus, the generation of cracks is suppressing, and connection reliability is improving. 
     Further, since the wire connecting part  63   a  ( 63   b ) and the mounting part  65  are separately provided to the terminal electrodes  51  to  56 , heat when connecting wire by thermocompression bonding hardly affects the mounting part  65 . And the Sn layer on the surface of the mounting part  65 , improving adhesion with the connection member such as solder, becomes less likely to melt. As a result, when the coil device  1  is mounted on such as a substrate, the adhesion between the mounting parts of the terminal electrodes  51  to  56  and the connecting member such as solder becomes good, and the bonding strength is improved. 
     Furthermore, since the mounting part  65  is continuously formed on the wire connecting part  63   a ( 63   b ) so as to be displaced from the wire connecting part along the outer peripheral direction (the Y-axis direction according to the embodiment) of the flange in a direction away from the axis A of the winding core  11 , the wire connecting part  63   a ( 63   b ) becomes close to the winding core  11 , and it becomes possible to shorten a length of the pulled-out wire from the wire connecting part  63   a ( 63   b ) to the winding core  11 , and the direct current internal resistance of the coil device  1  can be lowered (a reduction of DCR). 
     Moreover, in the embodiment, since the wire connecting part  63   a  ( 63   b ) is continuously formed to the edge of the mounting part  65  close to the winding core  11 , the wire connecting part  63   a ( 63   b ) becomes more closer to the winding core  11 , and it becomes possible to shorten a length of the pulled-out wires  31  to  34  from the wire connecting part  63   a ( 63   b ) to the winding core  11 , and further reduction of DCR can be realized. 
     The mounting part  65  is formed continuously to the wire connecting part  63   a ( 63   b ) and to be positioned away from the axis A of the winding core  11  with respect to the wire connecting part  63   a ( 63   b ) along an outer peripheral direction of the flange  12 . Thus, the wire connecting part  63   a ( 63   b ) does not pop out to the outer side of the flange  12  of the coil device  1 , the side away from the axis A of the winding core  11 . Therefore, the coil device  1  can be made compact, transport and handling of the coil device  1  can be facilitated, and the handleability at the time of mounting can be improved. 
     Further, the mounting part  65  is preferably formed in proximity to the wire connecting part  63   a ( 63   b ) via the step part  64 , in which case the DCR can be further reduced. Furthermore, along the height direction (the Z-axis direction) of the flange  12 , the wire connecting part  63   a  ( 63   b ) is disposed at a lower position than the mounting part  65 . For this reason, the film residue that may generate at the wire connecting part  63   a ( 63   b ) will more unlikely to adhere to the mounting part  65 . In addition, the influence of heat when connecting by thermocompression bonding is further reduced in the mounting part  65 . Furthermore, when the coil device  1  is mounted on such as the substrate, the connecting part of the substrate firstly contacts the mounting part  65  and not the wire connecting part  63   a ( 63   b ) of the terminal electrode. Thus, the connection strength between the mounting part  65  of the terminal electrodes  51  to  56  and the substrate improves, and the connection reliability also improves. 
     The stepped part  64  is formed between the wire connecting parts  63   a ( 63   b ) and the mounting part  65 . The stepped part  64  prevents a lateral shift of the end (the lead) of the wires  31  to  34  when winding wires  31  to  34  start or end on the winding core  11 , and the ends of the wires  31  to  34  can be appropriately connected to the wire connecting parts  63   a ( 63   b ). In addition, the presence of the stepped part  64  further reduces the possibility that the film residue that may be generated in the wire connecting part  63   a ( 63   b ) adheres to the mounting part  65 . 
     Furthermore, on the terminal electrodes  51  to  56  of the embodiment, the area of the wire connecting part  63   a ( 63   b ) is smaller than the area of the mounting part  65 . With the configuration, the heat capacity of wire connecting part  63   a ( 63   b ) can be relatively reduced, and the influence of the heat at the time of thermocompression bonding of the wires  31  to  34  on the mounting part  65  can be reduced. 
     Moreover, according to the embodiment, the exposed surfaces  23   a  to  23   c , in which the outer surface of the flange  12  is exposed, is formed between the edge  67  of the wire connecting part  63   a  ( 63   b ) close to the winding core  11  and the inner side face  13  of the flange  12  close to the winding core  11 . The exposed surfaces  23   a  to  23   c  are chamfered. By this configuration, it becomes possible to increase the angle at which the end of the wires  31  to  34  contact the edge  67  of the winding core  11  side of the wire connecting part  63   a ( 63   b ), and to reduce a damage to the pulled-out ends (leads) of the wires  31  to  34 . 
     The invention is not limited to the above embodiments and modifications may be made in various aspects within a scope of the invention. 
     For example, in the embodiment described above, the mounting faces  20 ,  20  may be configured as flat surfaces without unevenness. That is, the second regions  22   a  to  22   c  higher than the first regions  21   a  to  21   c  may not be formed on the mounting faces  20 ,  20 . When the second regions  22   a  to  22   c  are not formed, a space is provided between each mounting part  65  of the terminal electrodes  51  to  56  and the mounting face  20 . However, also in this case, the terminal members  61 ,  62  are maintained in the shapes shown in  FIGS.  5 A and  5 B . 
     Furthermore, in the embodiment described above, a plate-like core that magnetically communicates these flanges  12 ,  12  is not connected to the faces opposite to the mounting faces  20 ,  20  of the pair of flanges  12 ,  12 . The plate-like cores may connect to the faces by such as adhesion. 
     Further, in the above embodiment, the third terminal electrode  53  and the sixth terminal electrode  56  are formed as the center taps on the input side and the output side, but the center taps may be omitted depending on the application. In that case, the third terminal electrode  53  and the sixth terminal electrode  56  become unnecessary, and the coil device (a pulse transformer) can be made by two wires. 
     In the above embodiment, the invention has been described as a device suitable as a pulse transformer used for transmitting a pulse signal through such as a LAN cable, but the application of the invention is not limited thereto. The invention is also applicable to other coil devices such as common mode filters, and is applicable to all electronic parts in which wire leads are connected to terminal electrodes by thermocompression bonding or the methods other than thermocompression bonding. 
     DESCRIPTION OF REFERENCE NUMERAL 
     
         
           1  . . . coil device 
           10  . . . drum core (core member) 
           11  . . . winding core 
           12  . . . flange 
           13  . . . inner side face 
           14  . . . outer side face 
           20  . . . mounting face
         21   a  to  21   c  . . . the first area     22   a  to  22   c  . . . the second area     23   a  to  23   c  . . . the exposed surface   
     
           30  . . . coil part 
           31  to  34  . . . wires
         31   a  to  34   a ,  31   b  to  34   b  . . . end part (lead)   
     
           51  to  56  . . . terminal electrode 
           61 ,  62  . . . terminal members 
           63   a ,  63   b  . . . wire connecting part 
           64  . . . step part 
           65  . . . mounting part 
           66  . . . installation part 
           67  . . . edge of the connecting wire