Abstract:
A surface mount pulse transformer has a drum type core including a core and first and second flanges disposed on both ends of the core and installed on a substrate and a primary winding wire and a secondary winding wire wound around the core and provided with an intermediate tap, respectively, wherein first and second terminal electrodes being connected to each of both ends of the primary winding wire and a third terminal electrode for connecting being connected to the intermediate tap of the secondary winding wire are disposed on the surface of the first flange and a fourth terminal electrode being connected to the intermediate tap of the primary winding wire and fifth and sixth terminal electrodes being connected to each of both ends of the secondary winding wire are disposed on the surface of the second flange.

Description:
TECHNICAL FIELD 
     The invention relates to a surface mount pulse transformer and a method and an apparatus for manufacturing the same. 
     BACKGROUND OF THE INVENTION 
     When equipment such as a personal computer and the like are connected to networks such as a LAN, a phone network, and the like, it is necessary to protect the equipment from an ESD (Electrostatic Discharge) and a high voltage which intrude therein through a cable. To cope with the above problem, a pulse transformer is used for a connector constituting a connection point of the cable and the equipment. 
     A conventionally used pulse transformer is composed of a doughnut-shaped core (toroidal core) and a primary coil and a secondary coil wound around the core (refer to, for example, Japanese Patent Application Laid-Open No. 7-161535) and has a property for transmitting only the alternating component (pulses) of a voltage applied to the primary coil to the secondary coil. Since a direct current component is not transmitted to the secondary coil, the pulse transformer can shut off the ESD and the high voltage. 
     Recently, since it is also required to make a pulse transformer compact and surface mountable, examples that use a drum core in place of a toroidal core have been proposed. They are called a surface mount pulse transformer. 
       FIG. 15  shows a typical arrangement example of the surface mount pulse transformer.  FIG. 16  is a view showing an equivalent circuit of the surface mount pulse transformer  1  shown in  FIG. 15 . 
     As shown in  FIG. 15 , the surface mount pulse transformer  1  has a drum type core  2  which includes a core  2   a , around which wires are wound, and flanges  2   b ,  2   c  disposed on both the ends of the core  2   a . Three terminal electrodes P 1  to P 3  and P 4  to P 6  are disposed on the upper surfaces of the flanges  2   b ,  2   c , respectively. 
     As shown in  FIGS. 15 and 16 , wires S 1  to S 4  are wound around the core  2   a , and both the ends S 1   a , S 1   b  of the wire S 1  are connected to the terminal electrodes P 1 , P 2 , both the ends S 2   a , S 2   b  of the wire S 2  are connected to the terminal electrodes P 2 , P 3 , both the ends S 3   a , S 3   b  of the wire S 3  are connected to the terminal electrodes P 4 , P 5 , and both the ends S 4   a , S 4   b  of the wire S 4  are connected to the terminal electrodes P 5 , P 6 , respectively. 
     The surface mount pulse transformer  1  is a circuit of a balanced input and output. As shown in  FIG. 16 , the terminal electrodes P 1  and P 3  act as a plus side terminal IN+ and a minus side terminal IN− of a balanced input, respectively. The terminal electrodes P 4  and P 6  act as a plus side terminal OUT+ and a minus side terminal OUT− of a balanced output, respectively. The respective wires are wound around the core  2   a  so that an induced current flows from the terminal OUT+ to the terminal OUT− when a current flows from the terminal IN+ to the terminal IN−. The terminal electrodes P 2 , P 5  act as intermediate taps CT on an input side and an output side, respectively. 
       FIGS. 17A to 17H  are views showing a winding process of the surface mount pulse transformer  1 . As shown in  FIGS. 17A to 17H , the winding process is divided into winding steps shown  FIGS. 17A to 17D  of a first layer and winding steps shown  FIGS. 17E to 17H  of a second layer. 
     The wires S 1  and  54  are bifilar wound in the winding steps of the first layer. Specifically, the end S 1   a  of the wire S 1  is connected to the terminal electrode P 1  first ( FIG. 17A ), and then the end S 4   a  of the wire S 4  is connected to the terminal electrode P 5  ( FIG. 17B ). The wires S 1  and S 4  start to be wound together around the core  2   a  from one end side thereof counterclockwise when viewed from the one end side. When the wires S 1  and S 4  have been wound, the end S 1   b  of the wire S 1  is connected to the terminal electrode P 2  ( FIG. 17C ), and then the end S 4   b  of the wire  54  is connected to the terminal electrode P 4  ( FIG. 17D ). 
     In the winding steps of the second layer, the wires S 2  and S 3  are bifilar wound. Note that the wires S 1 , S 4  of the first layer are omitted in  FIGS. 17E to 17H . Specifically, the end S 3   a  of the wire S 3  is connected to the terminal electrode P 4  first ( FIG. 17E ), and then the end S 2   a  of the wire S 2  is connected to the terminal electrode P 2  ( FIG. 17F ). The wires S 2  and S 3  start to be wound together around the core  2   a  from one end side thereof counterclockwise when viewed from the one end side. When the wires S 2  and S 3  have been wound, the end Sib of the wire S 3  is connected to the terminal electrode P 5  ( FIG. 17G ), and then the end S 2   b  of the wire  2  is connected to the terminal electrode P 3  ( FIG. 17H ). 
     SUMMARY OF THE INVENTION 
     However, in the conventional surface mount pulse transformer, since the wires are alternately connected to the flanges  2   b ,  2   c  as shown in  FIGS. 17A to 17H , the conventional surface mount pulse transformer has a problem in that when a winding job is performed using an automatic winder which performs a winding job only to one of the flanges at a time, a long time is required for the winding job, which causes increase of manufacturing cost. 
     Accordingly, an object of the invention is to provide a surface mount pulse transformer capable of reducing a winding job time when a winding job is performed using an automatic winder which performs the winding job only to one of flanges at a time and a manufacturing method and a manufacturing apparatus of the same. 
     A surface mount pulse transformer according to the invention for achieving the above object is characterized by having a drum type core including a core and first and second flanges disposed on both ends of the core and installed onto a substrate and a primary winding wire and a secondary winding wire wound around the core and provided with an intermediate tap, respectively, wherein first and second terminal electrodes being connected to each of both ends of the primary winding wire and a third terminal electrode being connected to the intermediate tap of the secondary winding wire are disposed on the surface of the first flange and a fourth terminal electrode being connected to the intermediate tap of the primary winding wire and fifth and sixth terminal electrodes being connected to each of both ends of the secondary winding wire are disposed on the surface of the second flange. 
     According to the invention, both the two terminal electrodes which are connected at the same timing (the first terminal electrode and the third terminal electrode, the fourth terminal electrode and the sixth terminal electrode, the second terminal electrode and the third terminal electrode, and the fourth terminal electrode and the fifth terminal electrode) are located on the one flange. As a result, a winding job time can be reduced when a winding job is performed using an automatic winder capable of performing a wire connection job of only one of flanges at a time. 
     In the surface mount pulse transformer, the third terminal electrode may be disposed nearer to one end or the other end of the substrate confronting surface of the first flange in a first direction vertical to a magnetic core direction in the substrate surface, and the fourth terminal electrode may be disposed nearer to one end or the other end of the substrate confronting surface of the second flange in the first direction. According to the arrangement, since the first and second terminal electrodes can be disposed away from the third terminal electrode and the fifth and sixth terminal electrodes can be disposed away from the fourth terminal electrode, the primary winding wires can be securely insulated from the secondary winding wires. Further, an increase in size of the surface mount pulse transformer can be suppressed. 
     In the surface mount pulse transformer, the first and second terminal electrodes may be disposed nearer to one end of the substrate confronting surface of the first flange in the first direction, the third terminal electrode may be disposed nearer to the other end of the substrate confronting surface of the first flange in the first direction, the fourth terminal electrode may be disposed nearer to one end of the substrate confronting surface of the second flange in the first direction, and the fifth and sixth terminal electrodes may be disposed nearer to the other end of the substrate confronting surface of the second flange in the first direction. According to the arrangement, the terminal electrodes relating to the primary winding wires (the first, second, and fourth terminal electrodes) can be disposed away from the terminal electrode relating to the secondary winding wires (the third, fifth, and sixth terminal electrodes) on both the sides of the surface mount pulse transformer in the first direction. As a result, the primary winding wires can be more securely insulated from the secondary winding wires. 
     In the surface mount pulse transformer, the separation distances between the third terminal electrode and each of the first and second terminal electrodes are longer than the separation distance between the first terminal electrode and the second terminal electrode, and the separation distances between the fourth terminal electrode and each of the fifth and sixth terminal electrodes are longer than the separation distance between the fifth terminal electrode and the sixth terminal electrode. According to the above arrangement, the primary wires can be more securely insulated from the secondary winding wires. 
     In the surface mount pulse transformer, the primary winding wire may be composed of a first wire connecting between the first terminal electrode and the fourth terminal electrode and a second wire connecting between the fourth terminal electrode and the second terminal electrode, the secondary winding wire may be composed of a third wire connecting between the fifth terminal electrode and the third terminal electrode and a fourth wire connecting between the third terminal electrode and the sixth terminal electrode, and the winding direction of the first and fourth wires may be opposite to the winding direction of the second and third wires when the winding direction from the first flange toward the second flange is viewed from the first flange. According to the above arrangement, when winding of the wires starts and ends, the wires need not be extended from one end to the other end of the core. 
     In the surface mount pulse transformer, the first to fourth wires may be wound so that the wire-diameter-direction distance between the first wire and the third wire, the wire-diameter-direction distance between the first wire and the fourth wire, the wire-diameter-direction distance between the second wire and the third wire, and the wire-diameter-direction distance between the second wire and the fourth wire are equal to each other in the same turn. According to this arrangement, there can be obtained a surface mount pulse transformer which has good magnetic coupling efficiency and frequency characteristics. 
     A method of manufacturing a surface mount pulse transformer according to the invention having a drum type core including a core and first and second flanges disposed on both ends of the core and installed on a substrate, and a primary winding wire and a secondary winding wire wound around the core and provided with an intermediate tap, respectively, wherein first and second terminal electrodes being connected to each of both ends of the primary winding wire and a third terminal electrode being connected to the intermediate tap of the secondary winding wire are disposed on the surface of the first flange, and a fourth terminal electrode being connected to the intermediate tap of the primary winding wire and fifth and sixth terminal electrodes being connected to each of both ends of the secondary winding wire are disposed on the surface of the second flange, the manufacturing method being characterized by having the steps of simultaneously connecting a plus side end of the primary winding wire to the first terminal electrode and the intermediate tap of the secondary winding wire to the third terminal electrode, simultaneously connecting the intermediate tap of the primary winding wire to the fourth terminal electrode and a minus side end of the secondary winding wire to the sixth terminal electrode, simultaneously connecting a minus side end of the primary winding wire to the second terminal electrode and the intermediate tap of the secondary winding wire to the third terminal electrode, and simultaneously connecting the intermediate tap of the primary winding wire to the fourth terminal electrode and a plus side end of the secondary winding wire to the fifth terminal electrode. 
     According to the above arrangement, connecting jobs of the two ends which are connected at the same timing (the plus side end of the primary winding wire and the intermediate tap of the secondary winding wire, the intermediate tap of the primary winding wire and the minus side end of the secondary winding wire, the minus side end of the primary winding wire and the intermediate tap of the secondary winding wire, and the intermediate tap of the primary winding wire and the plus side end of the secondary winding wire) can be simultaneously preformed. As a result, the winding job time can be reduced when the winding job is performed using the automatic winder capable of performing the wire connection job of only one of flanges at a time. 
     Further, an apparatus for manufacturing a surface mount pulse transformer according to the invention includes a drum type core including a core and first and second flanges disposed on both ends of the core and installed on a substrate and a primary winding wire and a secondary winding wire wound around the core and provided with an intermediate tap, respectively. In the manufacturing apparatus, first and second terminal electrodes being connected to each of both ends of the primary winding wire, and a third terminal electrode being connected to the intermediate tap of the secondary winding wire are disposed on the surface of the first flange, and a fourth terminal electrode being connected to the intermediate tap of the primary winding wire and fifth and sixth terminal electrodes being connected to each of both ends of the secondary winding wire are disposed on the surface of the second flange. The manufacturing apparatus simultaneously connects the plus side end of the primary winding wire to the first terminal electrode and the intermediate tap of the secondary winding wire to the third terminal electrode, simultaneously connects the intermediate tap of the primary winding wire to the fourth terminal electrode and the minus side end of the secondary winding wire to the sixth terminal electrode, simultaneously connects the minus side end of the primary winding wire to the second terminal electrode and the intermediate tap of the secondary winding wire to the third terminal electrode, and simultaneously connects the intermediate tap of the primary winding wire to the fourth terminal electrode and the plus side end of the secondary winding wire to the fifth terminal electrode. 
     As described above, according to the invention, a winding job time can be reduced when a winding job of a surface mount pulse transformer is performed using an automatic winder capable of performing a wire connection job of only one of flanges at a time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view showing an external appearance structure of a surface mount pulse transformer according to a preferred embodiment of the invention; 
         FIGS. 2A and 2B  are plan views of the surface mount pulse transformer according to the preferred embodiment of the invention, wherein  FIG. 2A  shows only wires of a first layer, and  FIG. 2B  shows also wires of a second layer; 
         FIG. 3  is a sectional view taken along the line A-A′ of  FIG. 1  and shows a winding structure of the respective wires in detail; 
         FIG. 4  is a view showing an equivalent circuit of the surface mount pulse transformer according to the preferred embodiment of the invention; 
         FIG. 5  is a plan view of a print substrate on which the surface mount pulse transformer according to the preferred embodiment of the invention is mounted; 
         FIG. 6  is a view showing an arrangement of an automatic winder for performing a wire winding job of the surface mount pulse transformer according to the preferred embodiment of the invention and steps of the winding job performed by the automatic winder; 
         FIG. 7  is a view showing the arrangement of the automatic winder for performing the wire winding job of the surface mount pulse transformer according to the preferred embodiment of the invention and steps of the winding job performed by the automatic winder; 
         FIG. 8  is a view showing the arrangement of the automatic winder for performing the wire winding job of the surface mount pulse transformer according to the preferred embodiment of the invention and steps of the winding job performed by the automatic winder; 
         FIG. 9  is a view showing the arrangement of the automatic winder for performing the wire winding job of the surface mount pulse transformer according to the preferred embodiment of the invention and steps of the winding job performed by the automatic winder; 
         FIG. 10  is a view showing the arrangement of the automatic winder for performing the wire winding job of the surface mount pulse transformer according to the preferred embodiment of the invention and steps of the winding job performed by the automatic winder; 
         FIG. 11  is a view showing the arrangement of the automatic winder for performing the wire winding job of the surface mount pulse transformer according to the preferred embodiment of the invention and steps of the winding job performed by the automatic winder; 
         FIG. 12  is a view showing the arrangement of the automatic winder for performing the wire winding job of the surface mount pulse transformer according to the preferred embodiment of the invention and steps of the winding job performed by the automatic winder; 
         FIG. 13  is a view showing the arrangement of the automatic winder for performing the wire winding job of the surface mount pulse transformer according to the preferred embodiment of the invention and steps of the winding job performed by the automatic winder; 
         FIG. 14  is a plan view of the surface mount pulse transformer according to the preferred embodiment of the invention; 
         FIG. 15  is a schematic perspective view showing an external appearance structure of a surface mount pulse transformer according to a background art of the invention; 
         FIG. 16  is a view showing an equivalent circuit of the surface mount pulse transformer according to the background art of the invention; and 
         FIGS. 17A to 17H  are views showing a wire winding process of the surface mount pulse transformer according to the background art of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A preferred embodiment of the invention will be described below in detail with reference to the accompanying drawings. 
       FIG. 1  is a schematic perspective view showing an external appearance structure of a surface mount pulse transformer  10  according to a preferred embodiment of the invention.  FIGS. 2A and 2B  are plan views of the surface mount pulse transformer  10 .  FIG. 2A  shows only wires of a first layer, and  FIG. 2B  shows also wires of a second layer.  FIG. 3  is a sectional view taken along the line A-A′ of  FIG. 1  and shows a winding structure of the respective wires in detail. An arrangement of the surface mount pulse transformer  10  will be described below with reference to the drawings. 
     As shown in  FIGS. 1 ,  2 A and  2 B, the surface mount pulse transformer  10  has a drum core  11 , a sheet-shaped core  12  attached to the drum core  11 , and wires S 1  to S 4  wound around the drum core  11 . 
     The drum core  11  has a rod-shaped core  11   a  and flanges  11   b ,  11   c  disposed to both ends of the core  11   a  and they are integrated with each other in the structure of the drum core  11 . The drum core  11  is placed on a substrate (to be described later) for use and bonded on the substrate with the upper surfaces  11   bs ,  11   cs  of the flanges  11   b ,  11   c  facing the substrate. The sheet-shaped core  12  is securely attached to the lower surfaces (surfaces opposite to the upper surfaces  11   bs ,  11   cs ) of the flanges  11   b ,  11   c.    
     Note that the drum core  11  and the sheet-shaped core  12  are made of a magnetic material having relatively higher magnetic permeability, for example, a sintered body of Ni—Zn ferrite and Mn—Zn ferrite. Note that the magnetic material having the high magnetic permeability such as the Mn—Zn ferrite and the like ordinarily has a low specific resistance and conductivity. 
     Three terminal electrodes E 1  to E 3  are formed on the upper surface  11   bs  of the flange  11   b , and three terminal electrodes E 4  to E 6  are formed on the upper surface  11   cs  of the flange  11   c . The terminal electrodes E 1  to E 3  are disposed in this order from one end side in an x-direction (direction perpendicular to a magnetic core direction (a y-direction) in a substrate plane) shown in  FIG. 1 . Likewise, the terminal electrodes E 4  to E 6  are also disposed in this order from the one end side of the x-direction. The ends of the wires S 1  to S 4  are connected to the terminal electrodes E 1  to E 6  by heat compression bonding. 
     Note that, as apparent from  FIGS. 1 ,  2 A and  2 B, the terminal electrode E 3  is disposed slightly away from the terminal electrodes E 1 , E 2 . The terminal electrode E 4  is disposed slightly away from the terminal electrodes E 5 , E 6  likewise. This is for the purpose of securing a withstand voltage between a primary winding wire and a secondary winding wire. This point will be described later in detail again. 
     The wires S 1  to S 4  are insulated conductive wires and wound around the core  11   a  in a double-layered structure. That is, as shown in  FIGS. 2A and 2B  and  FIG. 3 , a first layer is arranged by bifilar winding the wires S 1 , S 4  (alternately winding the two wires side by side in a single layer), and the wires S 2 , S 3  arrange a second layer by the bifilar winding. The wires S 1  to S 4  have the same number of turns. 
     Note that, as shown in  FIGS. 2A and 2B , the winding direction of the first layer of the wires S 1  to S 4  is different from that of the second layer thereof. More specifically, when a winding direction from, for example, the flange  11   b  toward the flange  11   c  is viewed from the flange  11   b , the wires S 1 , S 4  are wound in a clockwise direction, whereas the wires S 2 , S 3  are wound in a counterclockwise direction, that is, the wires S 1 , S 4  and the wires S 2 , S 3  are wound in an opposite direction. This is for the purpose of making it not necessary to extend the respective wires from one end of the core  11   a  to the other end thereof when the winding of them starts and ends, the details of which will be described later. 
     How the wires S 1  to S 4  are connected to the terminal electrodes E 1  to E 6  will be described. As shown in  FIG. 2A , one end S 1   a  and the other end S 1   b  of the wire S 1  are connected to the terminal electrodes E 1 , E 4 , respectively, and one end S 4   a  and the other end S 4   b  of the wire S 4  are connected to the terminal electrodes E 3 , E 6 , respectively. As shown in  FIG. 2B , one end S 2   a  and the other end S 2   b  of the wire S 2  are connected to the terminal electrodes E 4 , E 2 , respectively. Further, one end S 1   a  and the other end S 3   b  of the wire S 3  are connected to the terminal electrodes E 5 , E 3 , respectively. 
       FIG. 4  is an equivalent circuit of the surface mount pulse transformer  10  realized by the arrangement described above. 
     As shown in  FIG. 4 , the terminal electrodes E 1 , E 2  act as a plus side terminal IN+ and a minus side terminal IN− of a balanced input, respectively. Further, the terminal electrode E 5 , E 6  act as a plus side terminal OUT+ and a minus side terminal OUT− of a balanced output, respectively. The terminal electrodes E 3 , E 4  act as intermediate taps CT on an input side and an output side, respectively. The wires S 1 , S 2  constitute the primary winding wire of the surface mount pulse transformer  10 , and the wires S 3 , S 4  constitute the secondary winding wire of the surface mount pulse transformer  10 . Further, the drum core  11  and the sheet-shaped core  12  constitute a closed magnetic path of the surface mount pulse transformer  10 . 
     The operation of the surface mount pulse transformer  10  will be described in more detail again with reference to  FIG. 2B .  FIG. 2B  shows a balanced input current i 1  and a balanced output current i 2  of the surface mount pulse transformer  10  and also a magnetic field m generated in the core  11   a  in operation. As shown in  FIG. 2B , when the balanced input current i 1  flows to the terminal electrodes E 1 , E 2 , the magnetic field m is generated in the core  11   a  around which the wires S 1 , S 2  are wound, the magnetic field m having an S-pole on the flange  11   b  side and an N-pole on the flange  11   c  side. The magnetic field m causes the wires S 3 , S 4  to generate an induced current which becomes the balanced output current i 2 . Accordingly, the equivalent circuit shown in  FIG. 4  is realized. 
     As described above, the winding direction of the wires S 1 , S 4  is opposite to that of the wires S 2 , S 3 . With this arrangement, it is possible to start and end the winding of the respective wires at the positions nearest to the flanges where they are connected. That is, when it is assumed that the winding direction of the wires S 1 , S 4  is the same as that of the wires S 2 , S 3 , it is necessary to extend the wires S 2 , S 3  to the flange  11   c  side and to start winding of them after they are connected to the terminal electrode E 2 , E 3  and to extend them from the flange  11   b  side to the terminal electrodes E 4 , E 5  and to connect them when the winding of them is ended in order to cause the surface mount pulse transformer  10  to perform the above operation (in particular, to generate the balanced output current i 2  by the magnetic field m). However, the extension of the wires is not necessary in the surface mount pulse transformer  10 . 
       FIG. 5  is a plan view of a print substrate  50  on which the surface mount pulse transformer  10  is mounted. 
     A region  51  on the print substrate  50  shown in  FIG. 5  is a region on which the surface mount pulse transformer  10  is mounted. As shown in  FIG. 5 , six land patterns  52  to  57  are disposed on the mounting region  51 . The land patterns  52 ,  53  are patterns connected to a pair of balanced transmission lines STL 1 , SBL 1  and connected to the terminal electrodes E 1 , E 2  of the surface mount pulse transformer  10 . The land patterns  56 ,  57  are patterns connected to a pair of balanced transmission lines STL 2 , STL 2  and connected to the terminal electrodes E 5 , E 6  of the surface mount pulse transformer  10 . The land patterns  54 ,  55  are patterns connected to intermediate tap lines CTL 2 , CTL 1  of the secondary winding wire (wires S 3 , S 4 ) and the primary winding wire (wires S 1 , S 2 ) of the surface mount pulse transformer  10 , respectively and connected to the terminal electrodes E 3 , E 4  of the surface mount pulse transformer  10 . 
     With this layout, the balanced transmission lines STL 1 , SBL 1  and the balanced transmission lines STL 2 , STL 2  can be linearly formed in parallel with each other. As a result, since it is not necessary to bypass wiring patterns on the print substrate, an area occupied by the wiring patterns does not increase more than necessary and moreover symmetry of the wiring patterns can be secured. Accordingly, reduction in size of the overall surface mount pulse transformer can be compatible with an improvement of signal quality. 
     Note that the intermediate tap lines CTL 1 , CTL 2  are individually disposed in  FIG. 5 . However, when the intermediate taps are simply connected to the ground, the one intermediate tap line CTL may be connected to both the land patterns  54 ,  55 . 
     Next, a manufacturing apparatus (automatic winder) and a manufacturing method of the surface mount pulse transformer  10  will be described. 
       FIGS. 6 to 13  are views showing an arrangement of the automatic winder  70  for performing a wire winding job of the surface mount pulse transformer  10  and the respective steps of a winding job performed by the automatic winder  70 . 
     First, the arrangement of the automatic winder  70  will be described. As shown in  FIGS. 6 and 7 , the automatic winder  70  has a base  71  for fixing the drum core  11  by the flange  11   b , three fixing units  72   a  to  72   c  for temporarily fixing wires, three guide pins  73   a  to  73   c  disposed on one side of the drum core  11 , two nozzles  74   a ,  74   b  for drawing wires fed out from bobbins which are not shown, a heater  75  ( FIG. 6  shows only a shape of the contact surface of the heater in contact with the flange by a dotted line), and a cutter  76  ( FIG. 7  shows only a cross sectional shape of the cutter by a dotted line). 
     Note that since the automatic winder  70  has only each one set of the heater  75  and the cutter  76  for performing the connection job, it cannot perform the connection job in both the two flanges at a time. 
     As shown in  FIG. 6 , the automatic winder  70  first fixes the wires fed out from the nozzles  74   a ,  74   b  to the fixing units  72   a ,  72   c , respectively. Note that the wires fed out from the nozzles  74   a ,  74   b  at the time become the wires S 1 , S 4 , respectively. 
     Next, the automatic winder  70  moves the nozzles  74   a ,  74   b  to the vicinity of the flange  11   c  through the guide pins  73   a ,  73   c , respectively. With this operation, the wires S 1 , S 4  pass above the terminal electrodes E 1 , E 3 , respectively. 
     The automatic winder  70  moves the heater  75  above the flange  11   b  in the state that the wires S 1 , S 4  are located above the terminal electrodes E 1 , E 3  and further lowers the heater  75  so that the heater  75  comes into contact with the surface of the flange  11   b . With this operation, the wires S 1 , S 4  are thermo-compression bonded to the terminal electrodes E 1 , E 3 , and the thermo-compression bonded portions of the wires S 1 , S 4  become the ends S 1   a , S 4   a , respectively. 
     On the completion of thermo-compression bonding, the automatic winder  70  moves the heater  75 , next lowers the cutter  76  along the end of the flange  11   b  opposite to the core  11   a  of the flange  11   b  as shown in  FIG. 7 , and the wires S 1 , S 4  are cut by the cutter  76 . 
     Next, as shown in  FIG. 7 , the automatic winder  70  moves the nozzles  74   a ,  74   b  to the vicinity of the flange  11   b  and disposes them adjacent to each other so that the nozzle  74   a  is located on the flange  11   b  side when viewed from the nozzle  74   b . Then, the nozzles  74   a ,  74   b  are moved from the positions along a direction B shown in  FIG. 7 . At the same time, the drum core  11  is rotated in a direction R 1  shown in  FIG. 7  about a magnetic core direction. With these operations, the wires S 1 , S 4  are bifilar wound around the core  11   a  as shown in  FIG. 8 . Note that the automatic winder  70  controls the rotation speed of the drum core  11  and the operation of the nozzles  74   a ,  74   b  so that the respective wires have a positional relationship shown in  FIG. 3 . 
     When the wires S 1 , S 4  have been wound for a necessary number of turns, the automatic winder  70  draws the wires S 1 , S 4  above the terminal electrodes E 4 , E 6  by moving the nozzles  74   a ,  74   b  across above the terminal electrodes E 4 , E 6 , respectively and further moves the heater  75  above the flange  11   c  and lowers it so that it comes into contact with the surface of the flange  11   c . With this operation, the wires S 1 , S 4  are thermo-compression bonded to the terminal electrodes E 4 , E 6 , and the thermo-compression bonded portions of them become the ends S 1   b , S 4   b , respectively. 
     On the completion of thermo-compression bonding, the automatic winder  70  moves the heater  75 , next lowers the cutter  76  along the end of the flange  11   c  opposite to the core  11   a  as shown in  FIG. 9 , and the wires S 1 , S 4  are cut by the cutter  76 . In this manner, the winding job of the first layer is completed. 
     In the second layer, the automatic winder  70  first fixes the wires fed out from the nozzles  74   a ,  74   b  to the fixing units  72   b ,  72   c , respectively as shown in  FIG. 10 . Note that the wires fed out from the nozzles  74   a ,  74   b  at the time become the wires S 2 , S 3 , respectively. 
     Next, the automatic winder  70  moves the nozzles  74   a ,  74   b  to the vicinity of the flange  11   c  through the guide pins  73   b ,  73   c , respectively. With this operation, the wires S 2 , S 3  pass above the terminal electrodes E 2 , E 3 , respectively. The nozzle  74   b  is preferably moved from the guide pin  73   c  to the flange  11   c  slightly obliquely to the magnetic core direction so that the wire S 3  does not overlap with the wire S 4  on the terminal electrode E 3 . 
     The automatic winder  70  moves the heater  75  above the flange  11   b  with the wires S 2 , S 3  being located above the terminal electrodes E 2 , E 3 , and further lowers the heater  75  so as to be in contact with the surface of the flange  11   b . With this operation, the wires S 2 , S 3  are thermo-compression bonded to the terminal electrodes E 2 , E 3 , and the thermo-compression bonded portions of the wires S 2  and S 3  become the ends S 2   b , S 3   b , respectively. 
     On the completion of thermo-compression bonding, the automatic winder  70  moves the heater  75 , next lowers the cutter  76  along the end of the flange  11   b  opposite to the core  11   a  as shown in  FIG. 11 , and the wires S 2 , S 3  are cut by the cutter  76 . 
     Next, as shown in  FIG. 11 , the automatic winder  70  moves the nozzles  74   a ,  74   b  to the vicinity of the flange  11   b  and disposes them adjacent to each other so that the nozzle  74   b  is disposed to the flange  11   b  side when viewed from the nozzle  74   a . Then, the nozzles  74   a ,  74   b  are moved from the positions along a direction B shown in  FIG. 11 . At the same time, the drum core  11  is rotated in a direction R 2  shown in  FIG. 11  about the magnetic core direction. The direction R 2  is opposite to the direction R 1  described above. With these operations, the wires S 2 , S 3  are bifilar wound on the wires S 1 , S 2  already wound around the core  11   a  as shown in  FIG. 12 . Note that the automatic winder  70  controls the rotation speed of the drum core  11  and the operation of the nozzles  74   a ,  74   b  so that the respective wires have the positional relationship shown in  FIG. 3 . 
     When the wires S 2 , S 3  have been wound for a necessary number of turns, the automatic winder  70  draws the wires S 2 , S 3  above the terminal electrodes E 4 , E 5  by moving the nozzles  74   a ,  74   b  across above the terminal electrodes E 4 , E 5 , respectively and further moves the heater  75  above the flange  11   c  and lowers the heater  75  so as to be in contact with the surface of the flange  11   c . With this operation, the wires S 2 , S 3  are thermo-compression bonded to the terminal electrodes E 4 , E 5 , and the thermo-compression bonded portions of the wires S 2  and S 3  become the ends S 2   a , S 1   a , respectively. 
     On the completion of thermo-compression bonding, the automatic winder  70  moves the heater  75 , next lowers the cutter  76  along the end of the flange  11   c  opposite to the core  11   a  as shown in  FIG. 13 , and the wires S 2 , S 3  are cut by the cutter  76 . In this manner, the winding job of the second layer is completed. 
     As described above, the automatic winder  70  simultaneously performs the connection job (thermo-compression bonding by the heater  75  and the cutting by the cutter  76 ) of the two ends (the ends S 1   a  and S 4   a , the ends S 1   b  and S 4   b , the ends S 2   b  and S 3   b , and the ends S 2   a  and S 3   a ) to be connected at the same timing, respectively. Accordingly, a winding job time is greatly reduced in comparison with the winding job time of the background Art ( FIG. 17 ) in which each two ends of the wires are independently connected. Specifically, 44 seconds were required by a winding job in the surface mount pulse transformer  1  performed by the background art using the automatic winder. However, a winding job in the surface mount pulse transformer  10  using the automatic winder  70  can be finished in 18 seconds. 
     Reduction of the winding job time is realized by the arrangement of the surface mount pulse transformer  10  and the arrangement of the automatic winder  70  corresponding to the arrangement of the surface mount pulse transformer  10  each described above. 
     First, in the surface mount pulse transformer  10 , the respective two ends (the ends S 1   a  and S 4   a , the ends S 1   b  and S 4   b , the ends S 2   b  and S 3   b , and the ends S 2   a  and S 1   a ) to be connected at the same timing are located to the one flange. With this arrangement, an automatic winder such as the automatic winder  70 , which performs a connection job only in one of the flanges at a time, can simultaneously connect two ends. 
     Next, in the automatic winder  70 , since the three guide pins  73   a  to  73   c  are disposed on the one side of the drum core  11 , the respective wires can be drawn above the terminal electrodes from the same direction by moving the nozzles  74   a ,  74   b . With this operation, when, for example, the ends S 1   a , S 4   a  are connected to the terminal electrodes E 1 , E 3 , since the wires S 1 , S 4  can be drawn above the terminal electrodes E 1 , E 3  from the same side of the drum core  11 , the two ends can be connected at the same time. 
     Conversely, in the automatic winder  70 , it is not necessary to dispose the guide pins  73   a  to  73   c  on both the sides of the drum core  11 . With this arrangement, the automatic winder can be arranged simply. 
     The other advantages achieved by the surface mount pulse transformer  10  will be described below. 
     In the surface mount pulse transformer  10 , since the terminal electrodes, to which the primary winding wire (the wires S 1 , S 2 ) are connected, and the terminal electrodes, to which the secondary winding wire are connected, are disposed on the same flange, a certain degree of a distance must be provided between the former terminal electrodes and the latter terminal electrodes to secure a withstand voltage between the primary winding wire and the secondary winding wire. Although the size of the drum core  11  is increased by the above arrangement, the surface mount pulse transformer  10  can suppress an increase of its size. This will be described below in detail. 
       FIG. 14  is a plan view of the surface mount pulse transformer  10  which is shown also in  FIG. 2B . As shown in  FIG. 14 , the terminal electrodes E 1 , E 2  are disposed nearer to one end of the substrate-confronting surface  11   bs  of the flange  11   b  in an x-direction, and the terminal electrode E 3  is disposed nearer to the other end of the substrate-confronting surface  11   bs  of the flange  11   b  in the x-direction. The separation distance D 13  between the terminal electrodes E 3  and E 1  and the separation distance D 23  between the terminal electrodes E 3  and E 2  are longer than the separation distance D 12  between the terminal electrodes E 1  and E 2 , respectively. 
     Likewise, the terminal electrode E 4  is disposed nearer to one end of the substrate-confronting surface  11   cs  of the flange  11   c  in the x-direction, and the terminal electrodes E 5 , E 6  are disposed nearer to the other end of the substrate-confronting surface  11   cs  of the flange  11   c  in the x-direction. The separation distance D 45  between the terminal electrodes E 4  and E 5  and the separation distance D 46  between the terminal electrodes E 4  and E 6  are longer than the separation distance D 56  between the terminal electrodes E 5  and E 6 , respectively. 
     As described above, in the surface mount pulse transformer  10 , the terminal electrode E 3  is separated from the terminal electrodes E 1 , E 2  on the surface of the flange  11   b , and the terminal electrode E 3  is separated from the terminal electrodes E 5 , E 6  on the surface of the flange  11   c . As a result, the size of the surface mount pulse transformer  10  can be reduced in comparison with a case where the terminal electrode E 3  is interposed between the terminal electrodes E 1 , E 2  and the terminal electrode E 4  is interposed between the terminal electrodes E 5 , E 6 . That is, the increase of the size of the surface mount pulse transformer  10  can be suppressed. 
     Note that, in the invention, it is not essential to arrange the winding structure of the respective wires as shown in  FIG. 3 . For example, the position of the wire S 2  of the second layer may be replaced with the position of the wire S 3  thereof. In this case, when the nozzles  74   a ,  74   b  are moved to vicinity of the flange  11   b  to wind the wires S 2 , S 3  by the automatic winder  70  ( FIG. 11 ), the nozzles  74   a ,  74   b  are disposed adjacent to each other so that the nozzle  74   a  is disposed to the flange  11   b  side when viewed from the nozzle  74   b  in place of that the nozzles  74   a ,  74   b  are disposed adjacent to each other so that the nozzle  74   b  is disposed to the flange  11   b  side when viewed from the nozzle  74   a . Accordingly, it is not necessary to intersect the wires S 2 , S 3  by replacing the positions of the nozzles as shown in  FIG. 11 . 
     Although the preferable embodiment of the invention has been described above, it is needless to say that the invention is by no means restricted to the embodiment and can be embodied in various modes within the scope which does not depart from the gist of the invention.