Patent Publication Number: US-10763035-B2

Title: Common mode filter

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims the benefit of priority from Japanese Patent Application Serial No. 2016-252921 (filed on Dec. 27, 2016), the contents of which are hereby incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The present discloser relates to a common mode filter, and more particularly to a winding-type common mode filter. 
     BACKGROUND 
     Common mode filters have been known as one of electronic components used for high-frequency circuits. There are mainly two types of common mode filters, one is a winding type and the other is a thin film type. For high frequency circuits, winding-type common mode filters are often used. 
     A winding-type common mode filter includes a drum core, two winding wires wound around the drum core, and a plurality of terminal electrodes that are each electrically connected to ends of the two windings. The drum core has a pair of flanges and a winding core that connects the pair of flanges. Each of the two windings has a winding portion wound around an outer peripheral surface of the winding core and a lead portion that extends from each end of the winding portion to a tip of the winding. 
     Each of the two windings is electrically connected with a corresponding terminal electrode at its lead portion. The winding portion is wound around the winding core such that it contacts the outer peripheral surface of the winding core. The winding portion has more than one turn. In order to match a characteristic impedance of the winding, it is desirable that a capacitances generated between two adjacent turns in the winding portion be constant by arranging the turns at a regular interval in the winding portion. 
     Conventional winding-type common mode filters are disclosed in, for example, Japanese Patent Application Publication No. 2005-56934 (“the &#39;934 Publication”), Japanese Patent Application Publication No. 2012-29210 (“the &#39;210 Publication”), Japanese Patent Application Publication No. 2002-008931 (“the &#39;931 Publication”), and International Publication WO 2008/096487 (“the &#39;487 Publication”). In these conventional common mode filters, terminal electrodes are provided on a lower surface or an upper surface of the flange, and the lead portion of the winding is coupled to a junction portion of a terminal electrode. 
     It is desirable that the two windings of the common mode filter are formed to have the same length. This is because it is difficult to match the characteristic impedance if the two windings have different lengths. 
     However, in conventional common mode filters in which the terminal electrodes are provided on one of the lower surface or the upper surface of the flange, the geometrical arrangement of the two windings, in particular, the geometrical arrangement of the lead portions becomes asymmetric with respect to each other, and therefore it is difficult to make the lengths of the two windings equal to each other. 
     When a general-purpose drum core is used, it is particularly difficult to make the length of the lead portion of one of the two windings equal to the length of the lead portion of the other winding. For example, when a general-purpose drum core is used, to obtain a small inductance design, the number of turns of the winding around the winding core is decreased. Accordingly, referring to FIG. 3 of the &#39;487 Publication, the windings are disproportionally arranged toward one of the flanges. 
     As described in the &#39;210 Publication, when two windings are bifilar-wound, if a distance between adjacent turns of the two windings is made constant, the two windings can be each formed symmetrically with respect to the center of the winding core of the drum core in the length direction of the winding core. However, as pointed out in paragraph [0006] of the &#39;210 Publication, it is difficult to bifilar-wind the two wires such that the interval between the two windings becomes constant. 
     FIG. 5 of the &#39;931 Publication discloses a common mode filter in which a concave portion is formed on each end surface of each flange and a terminal electrode is provided in each of the concave portions. In such a configuration, it is possible to arrange the two windings geometrically symmetrical by providing the terminal electrodes on the two opposing side surfaces of each flange. 
     However, in the common mode filter described in the &#39;931 Publication, the lead portion of each winding is connected to the terminal electrode in a slack state. More specifically, the lead portion of each winding extends in a slight arc from the boundary with the winding portion to the junction portion (the conductive connecting portion E) with the terminal electrode. Therefore, the length of the lead portion changes depending on the looseness of the lead portion. Moreover, when the lead portion is slack, it may lead to variation in the intervals between adjacent turns of the winding portion. In the common mode filter described in the &#39;931 Publication, since the end portions of the windings are bonded to the flat electrode layer by welding or the like, it is difficult to keep the windings tensioned when the windings are bonded to the electrode layer. When the windings are not tensioned at the time of bonding, the windings are jointed to the terminal electrodes such that they remain in a slack state. As described above, in the common mode filter of the &#39;931 Publication, it is difficult to bond the lead and end portions of the winding to the terminal electrodes without any slack. 
     SUMMARY 
     One object of the disclosure is to provide a winding-type common mode filter in which the lengths of the two windings are made equal. More specifically, provided is a common filter in which the lengths of the two windings are made equal even when the windings are disproportionally arranged on one side. Other objects of the present invention will be made apparent through description of the specification as a whole. 
     A common mode filter according to one embodiment of the disclosure is a winding-type common mode filter that includes a drum core, and a pair of winding wires wound around the drum core. The drum core includes a winding core, a first flange provided on one end of the winding core, and a second flange provided on the other end of the winding core. The first flange has a first lower surface that faces a mounting surface of a circuit board and a pair of first end surfaces that intersect the first lower surface, and the second flange has a second lower surface that faces the mounting surface of the circuit board and a pair of second end surfaces that intersect the second lower surface. 
     The common mode filter according to the embodiment further includes a first terminal electrode, a second terminal electrode, a third terminal electrode, and a fourth terminal electrode. The first terminal electrode and the third terminal electrode are provided on the first flange, and the second terminal electrode and the fourth terminal electrode are provided on the second flange. 
     In one embodiment, the first terminal electrode includes a first securing portion for securing a first lead portion of a first winding wire, the second terminal electrode includes a second securing portion for securing a second lead portion of the first winding wire, the third terminal electrode includes a third securing portion for securing a third lead portion of a second winding wire, and the fourth terminal electrode includes a fourth securing portion for securing a fourth lead portion of the second winding wire. 
     In one embodiment, the first terminal electrode includes a first junction surface disposed on one of the pair of the first end surfaces, and a first clamping piece formed on the first junction surface. The second terminal electrode includes a second junction surface disposed on one of the pair of the second end surfaces, and a second clamping piece formed on the second junction surface. The third terminal electrode includes a third junction surface disposed on the other of the pair of the first end surfaces, and a third clamping piece formed on the third junction surface. The fourth terminal electrode includes a fourth junction surface disposed on the other of the pair of the second end surfaces, and a fourth clamping piece formed on the fourth junction surface. 
     In one embodiment, the pair of winding wires includes a first winding wire and a second winding wire. The first winding wire includes a first winding portion, a first lead portion, and a second lead portion. The first winding portion is wound around the winding core from a first winding start position to a first winding end position on the winding core. The first lead portion extends from the first winding start position and is secured by the first securing portion to be connected to the first terminal electrode. The second lead portion extends from the first winding end position and is secured by the second securing portion to be connected to the second terminal electrode. The second winding wire includes a second winding portion, a third lead portion, and a fourth lead portion. The second winding portion is wound around the winding core from a second winding start position to a second winding end position on the winding core. The third lead portion extends from the second winding start position and is secured by the third securing portion to be connected to the third terminal electrode. The fourth lead portion extends from the second winding end position and is secured by the fourth securing portion to be connected to the fourth terminal electrode. The second winding portion is wound by the same number of turns and in the same direction as the first winding wire. 
     In the above-described embodiment, the length of the winding portion (the first winding portion) of the first winding wire and the length of the winding portion (the second winding portion) of the second winding wire are equal to each other. 
     In one embodiment, the first securing portion includes a first junction surface and a first clamping piece. The second securing portion includes a second junction surface and a second clamping piece. The third securing portion includes a third junction surface and a third clamping piece. The fourth securing portion includes a fourth junction surface and a fourth clamping piece. In this embodiment, the first lead portion is clamped between the first junction surface and the first clamping piece to be connected to the first terminal electrode. The second lead portion is clamped between the second junction surface and the second clamping piece to be connected to the second terminal electrode. The third lead portion is clamped between the third junction surface and the third clamping piece to be connected to the third terminal electrode. The fourth lead portion is clamped between the fourth junction surface and the fourth clamping piece to be connected to the fourth terminal electrode. 
     In one embodiment, the first winding start position and the second winding start position are arranged at an equal distance from the first flange and arranged symmetrically to each other with respect to a center of the winding core. The first winding end position and the second winding end position are arranged at an equal distance from the second flange and arranged symmetrically to each other with respect to the center of the winding core. 
     In one embodiment, the first securing portion and the third securing portion are arranged symmetrically to each other with respect to the center of the winding core, and the second securing portion and the fourth securing portion are arranged symmetrically to each other with respect to the center of the winding core. 
     According to the above embodiment, the length of the first lead portion of the first winding wire and the length of the third lead portion of the second winding wire are equalized to each other due to the geometric symmetry between the first winding start position and the second winding start position, and the geometric symmetry between the first clamping piece and the third clamping piece. Similarly, the length of the second lead portion of the first winding wire and the length of the fourth lead portion of the second winding wire are equalized to each other due to the geometric symmetry between the first winding end position and the second winding end position, and the geometric symmetry between the second clamping piece and the fourth clamping piece. 
     In one embodiment, the first lead portion extends linearly from the first winding start position to an inner end of the first end surface on which the first securing portion is disposed. The second lead portion extends linearly from the first winding end position to an inner end of the second end surface on which the second securing portion is disposed. The third lead portion extends linearly from the second winding start position to an inner end of the first end surface on which the third securing portion is disposed. The fourth lead portion extends linearly from the second winding end position to an inner end of the second end surface on which the fourth securing portion is disposed. 
     According to the above embodiment, since the geometric symmetry between the first lead portion and the corresponding third lead portion, and the geometric symmetry between the second lead portion and the corresponding fourth lead portion are given, and each lead portion is linearly formed so that slack of each lead portion will not occur. Consequently it is possible to make the length of the first lead portion equal to the length of the third lead portion, and it is possible to make the length of the second lead portion equal to the length of the fourth lead portion. Moreover, the length of the first winding portion and the length of the second winding portion is equalized as described above. Therefore it is possible to make the length of the first winding wire equal to the length of the second winding wire. Furthermore, since each lead portion of the winding wires is clamped between the corresponding clamping piece and the corresponding junction surface, it is possible to prevent the slack of the winding wires. 
     In one embodiment, the first lead portion is arranged along a first line that connects the first winding start position and a first clamping point situated at a position closest to the first winding start position in the first clamping piece as viewed from the front. The second lead portion is arranged along a second line that connects the first winding end position and a second clamping point situated at a position closest to the first winding end position in the second clamping piece as viewed from the front. The third lead portion is arranged along a third line that connects the second winding start position and a third clamping point situated at a position closest to the second winding start position in the second clamping piece as viewed from the front. The fourth lead portion is arranged along a fourth line that connects the second winding end position and a fourth clamping point situated at a position closest to the second winding end position in the second clamping piece as viewed from the front. 
     This arrangement can be realized by applying tension to the lead portions to such an extent that the looseness does not occur when the lead portions are clamped between the corresponding clamping pieces and the corresponding junction surfaces. According to this embodiment, it is possible to prevent a difference in the lengths of the winding wires caused by the slack of the lead portions. 
     In one embodiment, the first clamping piece is folded toward the first junction surface along a first folding line. The first folding line is inclined with respect to the first line as viewed from the front. The first junction portion is bent at the first clamping point toward the first folding line. 
     According to this embodiment, since the first junction portion of the first winding wire is bent at the first clamping point toward the first folding line, even when a force is applied to the first winding wire in a direction in which the first winding wire comes off from the first clamping piece, the bent portion is caught by the clamping piece, which prevents the first junction portion of the first winding wire from coming off from the first clamping piece. 
     In one embodiment, the first clamping piece is folded toward the first junction surface along a first folding line that is arranged collinearly with the first line as viewed from the front. 
     According to this embodiment, since the direction in which the first lead portion of the first winding wire extends (the direction along the first line) is arranged collinearly with the folding line of the first clamping piece, the first lead portion can be clamped over the entire length of the clamping piece along the folding line, so that it is possible to hold the first lead portion stably. 
     According to each embodiment of the disclosure, it is possible to obtain a common mode filter in which the first winding wire and the second winding wire have the same length. Therefore, characteristic impedances of the two windings can be easily matched to a predetermined value (for example, 50Ω or 100Ω). Moreover, since the terminal electrodes are provided on the side surfaces of the flange, it is possible to obtain a thin common mode filter compared to ones that have the terminal electrodes on its upper and lower surfaces. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a common mode filter according to one embodiment of the disclosure. 
         FIG. 2  is a front view of the common mode filter of  FIG. 1  viewed from the front (viewed from the arrow F 1   a ). 
         FIG. 3  is a side view of the common mode filter of  FIG. 1  as viewed from the left side surface (as viewed from the arrow F 1   b ). 
         FIG. 4  is a side view of the common mode filter of  FIG. 1  as viewed from the right side surface (as viewed from the arrow F 1   c ). 
         FIG. 5  is an enlarged view of a portion of the common mode filter of  FIG. 1  in the vicinity of a flange  16 . 
         FIG. 6  is a schematic view of the common mode filter of  FIG. 1  showing an arrangement of windings as viewed from the left side surface. 
         FIG. 7  is a schematic view of the common mode filter of  FIG. 1  showing the arrangement of windings as viewed from the upper surface (as viewed from the arrow F 1   d ). 
         FIG. 8  is a developed view of terminal metal attachments of the common mode filter of  FIG. 1 . 
         FIGS. 9 a  to 9 c    illustrate a step of bending the terminal metal attachment of  FIG. 8 .  FIG. 9 a    illustrates one of the terminal metal attachments in  FIG. 8  before bent,  FIG. 9 b    is a front view showing the bent terminal metal attachment,  FIG. 9 c    is a side view of the terminal metal attachment of  FIG. 9 b    viewed from the direction of the arrow F 4 . 
         FIGS. 10 a  to 10 d    illustrates an example of a manufacturing process of the common mode filter of  FIG. 1 . 
         FIGS. 11 a  to 11 c    are enlarged views of a part of the terminal metal attachment of  FIG. 8 .  FIG. 11 a    illustrates the terminal metal attachment in which the winding is temporarily fixed to a clamping piece.  FIG. 11 b    illustrates the terminal metal attachment in which the clamping piece is folded.  FIG. 11 c    illustrates the terminal metal attachment in which the winding is welded. 
         FIGS. 12 a  to 12 c    illustrate a terminal metal attachment provided in a common mode filter according to another embodiment of the disclosure. 
         FIG. 13  is a schematic view of the common mode filter according to the other embodiment showing an arrangement of windings as viewed from the left side surface. 
         FIG. 14  is a schematic view of the common mode filter according to another embodiment for describing a securing mechanism for the windings. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Various embodiments of the invention will be described hereinafter with reference to the drawings. In the drawings, like elements are designated by like reference numerals throughout. It should be noted that the drawings do not necessarily appear in accurate scales, for convenience of description. 
     A common mode filter  100  according to an embodiment of the disclosure will be now described with reference to  FIGS. 1 to 4 .  FIG. 1  is a perspective view of a common mode filter  100  according to the embodiment of the disclosure,  FIG. 2  is a front view of the common mode filter  100  viewed from the front (viewed from the arrow F 1   a ), and  FIG. 3  is a side view of the common mode filter  100  viewed from a left side surface (viewed from the arrow F 1   b ), and  FIG. 4  is a side view of the common mode filter  100  viewed from a right side surface side (viewed from the arrow F 1   c ). 
     In the illustrated embodiment, the common mode filter  100  includes a drum core  12 , a winding part  30 , terminal electrodes  40 ,  42 ,  44 ,  46 , and a plate core  60 . 
     In one embodiment of the invention, the drum core  12  includes a winding core  14  that has a substantially rectangular cross section, a substantially rectangular parallelepiped flange  16  provided at one end of the winding core  14  in the axial direction, and a substantially rectangular parallelepiped flange  22  provided at the other end of the winding core  14  in the axial direction. The drum core  12  is formed of, for example, a Ni—Zn ferrite material. In one embodiment of the disclosure, the permeability (μ) of the drum core  12  is in the range of 400 to 1000, for example 500. In addition to the rectangular shape, the cross-sectional shape of the winding core  14  may be a polygon such as a hexagon or an octagon, or it may be a circle or an ellipse. The cross-sectional shape of the winding core  14  may take any shape as long as it does not contradict the gist of the invention. 
     In one embodiment of the disclosure, the common mode filter  100  is configured to have the dimension 4.5 mm (length)×3.2 mm (width)×2.8 mm (height). Here, the length of the common mode filter  100  is the dimension in an axial direction (the X direction in  FIG. 1 ) of the winding core  14  of the drum core  12 . The width of the drum core  12  is the dimension in a direction perpendicular to the X direction and parallel to a mounting surface (the Y direction in  FIG. 1 ). The height of the drum core  12  is the dimension in a direction orthogonal to the X direction and the Y direction (the Z direction in  FIG. 1 ). The winding core  14  of the drum core  12  is configured to have a width (the dimension in the Y direction in  FIG. 1 ) of 1.6 mm and a height (the dimension in the Z direction in  FIG. 1 ) of 0.8 mm. The drum core  12  is configured to have a length (the dimension in the X direction in  FIG. 1 ) of 4.3 mm, a width (the dimension in the Y direction of  FIG. 1 ) of 3.2 mm, and a height (the dimension in the Z direction in  FIG. 1 ) of 2.1 mm. 
     In one embodiment, the winding part  30  includes two winding wires  32 ,  34 . In the illustrated embodiment, the winding wire  32  is wound around the outer surface of the winding core  14 . One end of the wire  32  is electrically connected to the terminal electrode  40  and the other end of the winding wire  32  is electrically connected to the terminal electrode  46 . Like the winding wire  32 , the winding wire  34  is wound around the outer surface of the winding core  14 . One end of the wire  34  is electrically connected to the terminal electrode  42  and the other end of the wire  34  is electrically connected to the terminal electrode  44 . In one embodiment of the disclosure, AIW (polyamideimide copper wire) φ 0.05 mm can be used as the windings  32 ,  34 . 
     In one embodiment, the winding wire  32  and the winding wire  34  are wound on the outer surface of the winding core  14  in the same circumferential direction and by the same number of turns. In one embodiment, the winding wire  32  and the winding wire  34  are wound on the outer surface of the winding core  14  at the same pitch. 
     The flange  16  has a lower surface  16 A, an upper surface  16 B, an end surface  16 C, an end surface  16 D, a side surface  16 E, and a side surface  16 F. The flange  22  has a lower surface  22 A, an upper surface  22 B, an end surface  22 C, an end surface  22 D, a side surface  22 E and a side surface  22 F. The lower surface  16 A and the lower surface  22 A are surfaces that face a circuit board (not shown) when the common mode filter  100  is mounted on the circuit board. Each of the end surfaces  16 C and  16 D intersects with the lower surface  16 A at the lower end thereof and each of the end surfaces  22 C and  22 D intersects with the lower surface  22 A at its lower end. In the illustrated embodiment, chamfered portions  16 G,  22 G are formed from the upper surfaces  16 B,  22 B of the flanges  16 ,  22  toward the inner side surfaces  16 F,  22 F. The chamfered portions  16 G,  22 G are provided for securing terminal metal attachments  110 ,  110 ′,  130 ,  130 ′. 
     Grooves  18 ,  20  are formed on the end surface  16 C and the end surface  16 D of the flange  16  respectively. The grooves  18 ,  20  are formed such that they extend across the center in the upper-lower direction of the end surfaces  16 C,  16 D. In the illustrated example, the grooves  18  and  20  are formed such that the end surfaces  16 C,  16 D are each connected to the corresponding bottom portion of the groove via tapered surfaces. Consequently, the bottom surfaces of the grooves  18 ,  20  are provided at positions receding inward from the end surfaces  16 C,  16 D. The tapered surfaces of the end surfaces  16 C,  16 D are provided on each side of the corresponding bottom surface in the end surfaces  16 C,  16 D. The angle of the tapered surfaces of the end surfaces  16 C,  16 D is adequately determined according to requirements that includes the directions (lead out direction) in which the winding wires  32 ,  34  extend. In this specification, the tapered surfaces and the bottom surfaces of the grooves  18 ,  20  are regarded as a part of the end surfaces  16 C,  16 D, respectively. Like the grooves  18  and  20  formed in the flange  16 , grooves  24  and  26  are also formed in the flange  22 . 
     In one embodiment, the flanges  16 ,  22  are configured to have a thickness of 0.6 mm. Each of the grooves  18 ,  20 ,  24 ,  26  is configured such that its bottom portion has a width of 0.7 mm and a depth of 0.5 mm. 
     The terminal electrodes  40 ,  42  are provided on one flange  16 , and the terminal electrodes  44 ,  46  are provided on the other flange  22 . In the illustrated embodiment, the terminal electrode  40  includes the terminal metal attachment  110 , the terminal electrode  42  includes the terminal metal attachment  130 , the terminal electrode  44  includes the terminal metal attachment  110 ′, and the terminal electrode  46  includes the terminal metal attachment  130 ′. Each of the terminal metal attachments  110 ,  110 ′,  130 ,  130 ′ is made of, for example, a phosphor bronze plate or a copper plate. 
     The terminal metal attachment  110  is provided on the end surface  16 C of the flange  16 , and the terminal metal attachment  130  is provided on the end surface  16 D. Further, the terminal metal attachment  110 ′ is provided on the end surface  22 C of the flange  22 , and the terminal metal attachment  130 ′ is provided on the end surface  22 D. 
     The terminal metal attachment  110  will be now further described with reference to  FIG. 8 .  FIG. 8  is a developed view of the terminal metal attachment  110  and the terminal metal attachment  130 . Since the terminal metal attachment  110 ′ is formed in the same shape as the terminal metal attachment  110  and the terminal metal attachment  130 ′ is formed in the same shape as the terminal metal attachment  130 , only the terminal metal attachment  110  and the terminal metal attachment  130  are shown in  FIGS. 8 and 9 . The description of the terminal metal attachment  110 ′ and the terminal metal attachment  130 ′ will be hereunder omitted. 
     Referring to  FIGS. 8 and 9 , the terminal metal attachment  110  has a side surface portion  111 . The side surface portion  111  has a planar strip portion  112  and a wide expanded portion  113  formed so as to be continuous with the strip portion  112 . The expanded portion  113  is connected to the strip portion  112  via the side portions  113 A,  113 B which are inclined with respect to the long side of the strip portion  112 . In one embodiment of the disclosure, a junction surface  116  having a triangular shape is provided near the lower end of the strip portion  112 . On the oblique side of the junction surface  116  that faces upward, there are provided a clamping piece  118  for clamping the windings  32 ,  34  between itself and the junction surface  116 , and a fastening portion  120  where the winding wires  32 ,  34  are secured by welding. 
     The terminal metal attachment  130  has a side surface portion  131 . The side surface portion  131  has a planar strip portion  132  and a wide expanded portion  133  formed so as to be continuous with the strip portion  132 . The position of the expanded portion  133  is shifted from the strip portion  132  by being connected to the strip portion  132  via the inclined side portions  133 A,  133 B. A triangular junction surface  136  is provided on the lower side of the strip portion  132 . On the oblique side of the junction surface  136  that faces upward, there are provided a clamping piece  138  for clamping the windings  32 ,  34  between itself and the junction surface  136 , and a fastening portion  140  where the winding wires  32 ,  34  are secured by welding. 
     Next, a step of bending the terminal metal attachments will be described with reference to  FIGS. 9 a  to 9 c   .  FIGS. 9 a  to 9 c    illustrate a step of bending the terminal metal attachment  110 . Although the terminal metal attachment  110  will be described as an example illustrated in  FIGS. 9 a  to 9 c   , those skilled in the art would understand that the other terminal metal attachments  110 ′,  130 ,  130 ′ can also be bent in the same manner. 
     Referring to  FIG. 9 a   , the upper portion of the strip portion  112  of the terminal metal attachment  110  is firstly bent along the broken lines L 1  and L 2 , and an upper surface contact portion  112 A and a fitting portion  112 B are formed as shown in  FIG. 9 b   . Further, by bending the expanded portion  113  along the broken line L 3 , a mounting portion  114  is formed as shown in  FIG. 9 b   . Moreover, by bending the strip portion  112  along the broken line L 4 , the junction surface  116  as illustrated in  FIG. 9 b    is obtained. Further, by bending the junction surface  116  along the broken lines L 5  and L 6 , the clamping piece  118  and the fastening portion  120  are formed as illustrated in  FIGS. 9 b    and  9   c.    
     The terminal metal attachment  110  bent in this manner has the configuration shown in  FIG. 9 b   . The terminal metal attachment  110  bent in this way is then attached on the end surface  16 C of the flange  16 . The terminal metal attachment  110  is attached on the flange  16  such that the side surface portion  111  contacts the flange end surface  16 E, the upper surface contact portion  112 A contacts the flange upper surface  16 B, the fitting portion  112 B is fitted with the chamfered portion  16 G of the flange  16 , the mounting portion  114  contacts the flange lower surface  16 A, and the junction surface  116  contacts the bottom surface of the groove  18  in the flange  16 . In the same manner, the terminal metal attachment  110 ′ is attached on the end surface  22 C of the flange  22 . 
     The terminal metal attachment  130 ′ is also attached on the end surface  22 C of the flange  16  in the same manner. More specifically, the terminal metal attachment  130  that has been bent similarly to the terminal metal attachment  110  illustrated in  FIG. 9B  is attached on the flange  16  such that the side surface portion  131  contacts the flange end surface  16 E, the upper surface contact portion  132 A contacts the flange upper surface  16 B, the fitting portion  132 B is fitted with the chamfered portion  16 G of the flange  16 , the mounting portion  134  contacts the flange lower surface  16 A, and the junction surface  136  contacts the bottom surface of the groove  20  in the flange  16 . In the same manner, the terminal metal attachment  130 ′ is attached on the end surface  22 D of the flange  22 . 
     The plate core  60  is, for example, a plate-like member formed of a Ni—Zn ferrite material and is bonded to the upper surface  16 B of the flange  16  and the upper surface  22 B of the flange  22  with an epoxy (Tg 125° C. specification). For example, the plate core  60  is configured to have a length of 4.5 mm, a width of 3.2 mm, and a height of 0.6 mm. In one embodiment of the disclosure, the permeability (μ) of the plate core  60  is in the range of 400 to 1000, for example 500. 
     An arrangement of the winding wire  32  and the winding wire  34  with respect to the drum core  12  will be now described with reference to  FIGS. 6 and 7 .  FIG. 6  is a schematic view of the common mode filter  100  showing an arrangement of windings  32  and  34  as viewed from the left side surface (as viewed from the arrow Fib).  FIG. 7  is a schematic view of the common mode filter  100  showing an arrangement of the windings  32  and  34  as viewed from the upper surface (as viewed from the arrow F 1   d ). 
     Referring to  FIGS. 6 and 7 , the winding wire  32  includes a winding portion  32 C wound around the outer surface of the winding core  14  from a winding start position P 11  to a winding end position P 21 , a lead portion  32 A that extends from the winding start position P 11  and is connected to the terminal electrode  40 ; and a lead portion  32 B that extends from a winding end position P 21  and is connected to the terminal electrode  46 . The winding wire  34  includes a winding portion  34 C wound around the outer surface of the winding core  14  from a winding start position P 31  (see  FIG. 5 ) to a winding end position P 41 , a lead portion  34 A that extends from the winding start position P 31  and is connected to the terminal electrode  42 ; and a lead portion  34 B that extends from a winding end position P 41  and is connected to the terminal electrode  44 . As described above, the winding portion  32 C ( 34 C) is a portion that is directly or indirectly wound on the outer peripheral surface of the winding core  14 . When the winding has one winding, the winding portion of the winding is directly wound on the outer peripheral surface of the winding core  14 . Whereas when the winding is wound in twice or more over the first layer of the winding, the winding portion of the second or more layers of the winding are indirectly wound around the outer peripheral surface of the winding core  14  via the layer(s) of the winding situated thereunder. The lead portion  32 A ( 34 A) refers to a portion that extends from one end of the winding wire  32  ( 34 ) to the winding portion  32 C ( 34 C), and the lead portion  32 B ( 34 B) refers to the portion that extends from the other end of the winding wire  32  ( 34 ) to the winding portion  32 C ( 34 C). 
     In one embodiment of the disclosure, the lead portion  32 A of the winding wire  32  has a bridge portion  32 A 1  that linearly extends from the winding start position P 11  to a flange contact position P 12  at the inner end of the end surface  16 C of the flange  16 , and a junction portion  32 A 2  that extends from the flange contact position P 12  to the fastening portion  120  through the clamping piece  118 . The winding wire  32  is electrically connected to the terminal metal attachment  110  (the terminal electrode  40 ) through the junction portion  32 A 2 . The junction portion  32 A 2  linearly extends from the flange contact position P 12  to the clamping piece  118 . The winding wire  32  is secured to the terminal electrode  40  by clamping the lead portion  32 A between the junction surface  116  and the clamping piece  118 , and melting the fastening portion  120  as necessary to weld the tip of the lead portion  32 A onto the junction surface  116 . In the specification, a portion of the terminal electrode  40  on which the winding wire  32  is fixed is referred to as a securing portion of the terminal electrode  40 . The securing portion of the terminal electrode  40  includes at least one or all of the junction surface  116 , the clamping piece  118 , and the fastening portion  120 . 
     The lead portion  32 B of the winding wire  32  has a bridge portion  32 B 1  that linearly extends from the winding end position P 21  to a flange contact position P 22  at the inner end of the end surface  22 D of the flange  22 , and a junction portion  32 B 2  that extends from the flange contact position P 22  to the fastening portion  140 ′ through the clamping piece  138 ′. The winding wire  32  is electrically connected to the terminal metal attachment  130 ′ (the terminal electrode  46 ) through the junction portion  32 B 2 . The junction portion  32 B 2  linearly extends from the flange contact position P 22  to the clamping piece  138 ′. The winding wire  32  is fixed to the terminal electrode  46  by clamping the lead portion  32 B between the junction surface  136 ′ and the clamping piece  138 ′, and melting the fastening portion  140 ′ as necessary to weld the tip of the lead portion  32 B onto the junction surface  136 ′. In the specification, a portion of the terminal electrode  46  on which the winding wire  32  is fixed is referred to as a securing portion of the terminal electrode  46 . The securing portion of the terminal electrode  46  includes at least one or all of the junction surface  136 ′, the clamping piece  138 ′, and the fastening portion  140 ′. 
     In one embodiment of the disclosure, the lead portion  34 A of the winding wire  34  has a bridge portion  34 A 1  that linearly extends from the winding start position P 31  to a flange contact position P 32  at the inner end of the end surface  16 D of the flange  16 , and a junction portion  34 A 2  that extends from the flange contact position P 32  to the fastening portion  140  through the clamping piece  138 . The winding wire  34  is electrically connected to the terminal metal attachment  130  (the terminal electrode  42 ) through the junction portion  34 A 2 . The junction portion  34 A 2  linearly extends from the flange contact position P 32  to the clamping piece  138 . The winding wire  34  is fixed to the terminal electrode  42  by clamping the lead portion  34 A between the junction surface  136  and the clamping piece  138 , and melting the fastening portion  140  as necessary to weld the tip of the lead portion  34 A onto the junction surface  136 . In the specification, a portion of the terminal electrode  42  on which the winding wire  34  is fixed is referred to as a securing portion of the terminal electrode  42 . The securing portion of the terminal electrode  42  includes at least one or all of the junction surface  136 , the clamping piece  138 , and the fastening portion  140 . 
     In one embodiment of the disclosure, the lead portion  34 B of the winding wire  34  has a bridge portion  34 B 1  that linearly extends from the winding end position P 41  to a flange contact position P 42  at the inner end of the end surface  22 C of the flange  22 , and a junction portion  34 B 2  that extends from the flange contact position P 42  to the fastening portion  120 ′ through the clamping piece  118 ′. The winding wire  34  is electrically connected to the terminal metal attachment  110 ′ (the terminal electrode  44 ) through the junction portion  34 B 2 . The junction portion  34 B 2  linearly extends from the flange contact position P 42  to the clamping piece  118 ′. The winding wire  34  is fixed to the terminal electrode  44  by clamping the lead portion  34 B between the junction surface  116 ′ and the clamping piece  118 ′, and melting the fastening portion  120 ′ as necessary to weld the tip of the lead portion  34 B onto the junction surface  116 ′. In the specification, a portion of the terminal electrode  44  on which the winding wire  34  is fixed is referred to as a securing portion of the terminal electrode  44 . The securing portion of the terminal electrode  44  includes at least one or all of the junction surface  116 ′, the clamping piece  118 ′, and the fastening portion  120 ′. 
     As can be seen in  FIG. 6 , in one embodiment of the disclosure, the winding start position P 11  and the winding start position P 31  are situated at positions symmetrical to each other with respect to the center C 1  of the winding core  14 . The center C 1  of the winding core  14  refers to, for example, the center of gravity of the cross section of the winding core  14  (a cross section obtained by cutting the winding core  14  in a plane perpendicular to its axis). For example, when the winding core  14  is formed in a rectangular section as shown in  FIG. 6 , the intersection point of the diagonal lines is the center C 1  of the winding core  14 . Similarly, the winding end position P 21  and the winding end position P 41  are situated at positions symmetrical to each other with respect to the center C 1  of the winding core  14 . 
     In one embodiment of the disclosure, the flange contact position P 12  and the flange contact position P 32  may also be situated symmetrical to each other with respect to the center C 1  of the winding core  14 . In addition, the flange contact position P 22  and the flange contact position P 42  may also be arranged symmetrical to each other with respect to the center C 1  of the winding core  14 . 
     As can be seen in  FIG. 7 , in one embodiment of the disclosure, both the winding start position P 11  and the winding start position P 31  are situated in a virtual plane  51  that is parallel to the inner side surface  16 F of the flange  16 . With this arrangement, the distance from the winding start position P 11  to the flange  16  (the length of a perpendicular line drawn from the winding start position P 11  to the side surface  16 F of the flange  16 ) and the distance from the winding start position P 31  to the flange  16  (the length of the perpendicular line drawn from the winding start position P 31  to the side surface  16 F of the flange  16 ) are made equal to each other. Similarly, both the winding end position P 21  and the winding end position P 41  are situated in a virtual plane S 2  that is parallel to the inner side surface  22 F of the flange  22 . With this arrangement, the distance from the winding end position P 21  to the flange  22  (the length of a perpendicular line drawn from the winding end position P 21  to the side surface  22 F of the flange  22 ) and the distance from the winding end position P 41  to the flange  22  (the length of the perpendicular line drawn from the winding end position P 41  to the side surface  22 F of the flange  22 ) are made equal to each other. 
     In one embodiment of the disclosure, the securing portion of the terminal electrode  40  and the securing portion of the terminal electrode  42  described above are arranged symmetrically to each other with respect to the center C 1  of the winding core  14 . The securing portion of the terminal electrode  44  and the securing portion of the terminal electrode  46  described above are arranged symmetrically to each other with respect to the center C 1 . For example, in the embodiment illustrated in  FIG. 6 , in one embodiment of the disclosure, the clamping piece  118  for clamping the junction portion  32 A 2  of the winding wire  32  and the clamping piece  138  for clamping the joint portion  34 A 2  of the winding wire  34  are arranged symmetrically to each other with respect to the center C 1  of the winding core  14 . Further, the clamping piece  138 ′ for clamping the junction portion  32 B 2  of the winding wire  32  and the clamping piece  118 ′ for clamping the junction portion  34 B 2  of the winding wire  34  are arranged symmetrically to each other with respect to the center C 1  of the winding core  14 . 
     According to the arrangement of the winding wire  32  and the winding wire  34  described above, the length of the bridge portion  32 A 1  of the winding wire  32  and the length of the bridge portion  34 A 1  of the winding wire  34  are made equal to each other so that the length of the bridge portion  32 B 1  of the winding wire  32  and the length of the bridge portion  34 B 1  of the winding wire  34  are made equal to each other. The length of the junction portion  32 A 2  of the winding wire  32  and the length of the junction portion  34 A 2  of the winding wire  34  are made equal to each other so that the length of the junction portion  32 B 2  of the winding wire  32  is made equal to the length of the junction portion  34 B 2  of the winding wire  34 . 
     As described above, according to the embodiment, the length of the lead portion  32 A of the winding wire  32  is equal to the length of the lead portion  34 A of the winding wire  34 , the length of the lead portion  32 B of the winding wire  32  is equal to the length of the lead portion  34 B of the winding wire  34 , the length of the winding portion  32 C of the winding wire  32  is equal to the length of the winding portion  34 C of the winding wire  34 . Therefore, the length of the winding wire  32  and the length of the winding wire  34  are made equal to each other. 
     In the embodiment of the disclosure, referring to  FIG. 5 , the lead portion  32 A is arranged along an imaginary line VL 1  that connects the winding start position P 11  and a clamping point P 13  situated at a position closest to the winding start position P 11  in the clamping piece  118  as viewed from the front. Although not shown, the lead portions  32 B,  34 A,  34 B are arranged in the same manner. For instance, the lead portion  32 A is arranged along an imaginary line that connects the winding start position P 31  and a clamping point situated at a position closest to the winding start position P 31  in the clamping piece  138  as viewed from the front. In such an arrangement, when the lead portions  32 A,  32 B,  34 A,  34 B are clamped by the corresponding clamping pieces  118 ,  138 ′,  138 ,  118 ′, tension is applied to the lead portions to such an extent that the looseness does not occur. 
     Next, an example of a manufacturing process of the common mode filter  100  will be described with reference to  FIGS. 10 a  to 10 d    First, the drum core  12  is formed. Specifically, a Ni—Zn ferrite material is mixed with a binder, and the mixture material is compression molded using a molding die to obtain a drum-shaped molded body. Deburring may be carried out for this molded body if necessary. By sintering the molded body at a predetermined firing temperature, the drum core  12  that has the shaft portion  14  and the flanges  16 ,  22  is obtained. 
     A plate core  60  is also formed. To obtain the plate core  60 , a Ni—Zn ferrite material is mixed with a binder, and the mixture material is compression molded using a molding die to obtain a plate-like molded body. By sintering this molded body, the plate core  60  is obtained. 
     Also, the bent terminal metal attachments  110 ,  110 ′,  130 ,  130 ′ shown in  FIG. 9 b    are prepared. 
     Subsequently, as illustrated in  FIG. 10 a   , the terminal metal attachments  110 ,  110 ′ are attached to the end surface  16 C of the flange  16  and the end surface  22 C of the flange  22 , respectively. The terminal metal attachments  130 ,  130 ′ are attached on the end surface  22 D of the flange  22  and the end surface  16 D of the flange  16 . At this point, adhesive may be applied to either or both of an end-surface junction position  150  and a side-surface adhesive position  152  in order to enhance the junction and alignment of the attached terminal metal attachments  110 ,  110 ′,  130 ,  130 ′ at predetermined positions in the outer end surfaces  16 E,  22 E of the flanges  16 ,  22 . The end-surface junction position  150  is situated above the center in the height direction of the flanges  16 ,  22 . 
     Next, referring to  FIG. 10 b   , the winding wire  32  is wound around the outer peripheral surface of the shaft portion  14  as many times as necessary, and then the winding wire  34  is wound around the outer peripheral surface of the shaft portion  14 . The winding wire  34  is wound adjacently to the winding wire  32  and wound the same number of times in the same circumferential direction as the winding wire  32 . 
     Next, referring to  FIG. 10 c   , the temporarily fastened lead portions  32 A,  32 B,  34 A,  34 B are fixed by welding. More specifically, the fastening portions  120 ,  140  are melted by using a YAG laser to weld the lead portions  32 A,  32 B,  34 A,  34 B so as to fix them. 
     Subsequently, referring to  FIG. 10 d   , an adhesive is applied to the upper surface junction positions  154  of the upper surface  16 B of the flange  16  and the upper surface  22 B of the flange  22 , and the plate core  60  is then bonded to the upper surface  16 B and the upper surface  22 B. When the plate core  60  is adhered, the plate core  60  is aligned with the flange  16  and the flange  22  such that the recesses  62 A,  62 B,  62 C,  62 D face the upper contact portions  112 A,  132 A of the terminal metal attachments  110 ,  130 . The common mode filter  100  obtained as described above is mounted on an electronic component or the like by soldering the mounting portions  114 ,  134  of the terminal metal attachments  110 ,  110 ′,  130 ,  130 ′. 
     More specifically, the winding wire  32  is temporarily fastened to the junction surface  116  by clamping the lead portion  32 A with the junction surface  116  and the clamping piece  118 . Subsequently, the fastening portion  120  is melted by using a YAG laser, so that the tip of the lead portion  32 A where is exposed from the clamping piece  118  is welded to the junction surface  116 . Thus, one end of the winding wire  32  is secured to the terminal metal attachment  110 . Next, the winding wire  32  is extended from the clamping piece  118  to the winding start position P 11  via the flange contact position P 12 . And the winding wire  32  is wound on the outer surface of the winding core  14  from the winding start position P 11  to the winding end position P 21 . Subsequently, the lead portion  32 B of the winding wire  32  is extended from the winding end position P 21  via the flange contact position P 22  to the clamping piece  138 ′, and the lead portion  32 B is clamped between the junction surface  136 ′ and the clamping piece  138 ′ to temporarily fasten the winding wire  32  to the junction surface  136 ′. The fastening portion  140  is then melted by using a YAG laser, so that the tip of the lead portion  32 B where is exposed from the clamping piece  138 ′ is welded to the junction surface  136 ′. The winding wire  34  is wound around the winding core  14  in the same manner. By this junction procedure, since the winding wire  32  is temporarily fastened by the clamping piece  138 ′ at the time of welding so that it is possible to prevent the winding wire  32  from being loosened during the welding. 
     A terminal metal attachment provided in a common mode filter according to another embodiment of the disclosure will be now described with reference to  FIG. 12 .  FIG. 12 a    illustrates the above-described terminal metal attachment  110  again for comparison. The terminal metal attachment  110  has a fitting portion  112 B that is formed by bending a tip of the upper surface contact portion  112 A and engages with a chamfered portion  16 G provided on the flange upper surface  16 B side. In the terminal metal attachment  110 A shown in  FIG. 12B , a fitting portion  115  is formed by bending the lower side of the end surface portion  112 , that is, the tip of the mounting portion  114 . The fitting portion  115  is engaged with the chamfered portion  16 H provided on the flange lower surface  16 A. Accordingly, in the terminal metal attachment  110 A, the fitting portions  112 B,  115  can be engaged with the chamfered portions  16 G,  16 H provided in the upper and lower portions of the flange. In the terminal metal attachment  110 B shown in  FIG. 12C , a protrusion  122  is provided on the inner side of the upper surface contact portion  112 A, and an upper surface groove  161  to which the protrusion  122  is engaged is provided on the flange upper surface  16 B. 
     The terminal metal attachments applicable to the disclosure are not limited to those shown in the drawings. For example, in addition to the flange upper surface, the protrusion may also be formed in the mounting portion  114  and the groove may be formed in the flange lower surface  16 A. Further, a chamfered portion  16 H may be provided on the flange lower surface  16 A, an upper surface groove  161  for alignment may be provided in the flange upper surface  16 B, the protrusion  122  may be provided on the upper surface contact portion  112 A of the terminal metal attachment, and the fitting portion  115  may be formed by bending the tip of the mounting portion  114 . 
     A junction mechanism in which the winding wire  32  is connected to the junction surface  136  of the terminal metal attachment  130 ′ will be described with reference to  FIGS. 11 a  to 11 c   .  FIGS. 11 a  and 11 c    are enlarged views of the terminal metal attachment  130 ′, and  FIG. 11 b    is a sectional view of  FIG. 11 a    along the line # C-# C. Referring to  FIG. 11 b   , the clamping piece  138  is formed by folding a flat plate member that stands from one side of the junction surface  136  toward the junction surface  136  along the folding line L 6 . 
     The clamping piece  138  includes a receiving portion  138 A, a constricting portion  138 B, and a tip portion  138 C stated in the order closer to the folding line L 6 . The receiving portion  138 A, the constricting portion  138 B, and the tip portion  138 C are separated from the junction surface by the distance “da”, the distance “db”, and the distance “dc”, respectively. The clamping piece  138  is formed such that the distance “da” is larger than both of the distance “db” and the distance “dc”. It is preferable that the clamping piece  138  be formed such that the distance “da” is larger than the diameter of the winding wire  32 . Thereby, it is possible to clamp the winding wire  32  without damaging the winding wire  32 . 
     In one embodiment of the disclosure, the clamping piece  138  is formed such that the distance “db” is smaller than the distance da and the distance “dc”, and smaller than the diameter of the winding wire  32 . In this way, it is possible to prevent the winding wire  32  that has been inserted through the receiving portion  138 A from being displaced from the receiving portion  138 A. The distance dc between the tip portion  138 C and the junction surface  136  is set to be smaller than the distance da and larger than the distance db. 
     In one embodiment of the disclosure, the clamping piece  138  is configured such that the folding line L 6  is arranged collinearly with a virtual line VL 1  (see  FIG. 5 ) that connects the winding start position P 11  and the clamping point P 13 . Thus, the lead portion  32 B can be clamped over the entire width of the receiving portion  138 A of the clamping piece  138 , so that it is possible to hold the lead portion  32 B stably. 
     The tip end of the winding wire  32  exposed from the clamping piece  138  is disposed at a position overlapping with the wide portion  140 B of the fastening portion  140  while the lead portion  32 B is temporarily fixed to the clamping piece  138 . Similarly to the clamping portion  138 , the fastening portion  140  is also formed by folding a flat plate member that stands upright from one side of the junction surface  136  toward the junction surface  136 . The tip of the winding wire  32  is disposed so as to overlap with the fastening portion  140  and the fastening portion  140  is then melted using a YAG laser. The melted portion swells and its width shrinks, and a connecting portion  140 C that has a rounded shape is formed. 
     The terminal metal attachments  110 ,  110 ′,  130  are also configured similarly to the terminal metal attachments  130 ′ described above. 
     Arrangement of the windings provided in a common mode filter according to another embodiment of the disclosure will be now described with reference to  FIG. 13 .  FIG. 13  is a schematic view of the common mode filter according to the other embodiment showing the arrangement of windings as viewed from the left side surface. The common mode filter in the embodiment shown in  FIG. 13  has a winding core  14 ′ having a circular cross section. The center of the winding core  14 ′ is represented by C 1 ′. The common mode filter  100 ′ shown in  FIG. 13  has the winding core  14 ′ that has a different shape from the common mode filter  100  in  FIG. 6 . Since the shape of the winding core is different, it is natural that the positions of the winding start position P 11 ′ and the winding start position P 31 ′ shown in  FIG. 13  are different from the winding start position P 11  and the winding start position P 31  shown in  FIG. 6 . 
     Also in the common mode filter  100 ′ shown in  FIG. 13 , the winding start position P 11 ′ and the winding start position P 31 ′ are arranged symmetrically to each other with respect to the center C 1 ′ of the winding core  14 . The clamping piece  118  and the clamping piece  138  are arranged symmetrically to each other with respect to the center C 1 ′ of the winding core  14 . Although not shown in the drawing, in the common mode filter  100 ′ of  FIG. 13 , the winding ending position and the winding ending position are arranged symmetrically to each other with respect to the center C 1 ′ of the winding core  14 ′. 
     Even if the cross-sectional shape of the winding core is different, by arranging the corresponding winding start positions, the corresponding winding end positions and the securing portions symmetrically with respect to the center of the winding core, it is possible to equalize the length of the lead portion  32 A of the winding wire  32  and the length of the lead portion  34 A of the winding wire  34  and it is possible to equalize the length of the lead portion  32 B of the winding wire  32  and the length of the lead portion  34 B of the winding wire  34 . Also in the common mode filter  100 ′ shown in  FIG. 13 , since the winding portion  32 C and the winding portion  34 C are wound by the same number of turns in the same circumferential direction as are in the common mode filter  100 . Therefore, in the common mode filter  100 ′, by arranging the corresponding winding start positions, the corresponding winding end positions, and the clamping pieces symmetrically with respect to the center of the winding core, it is possible to equalize the length of the winding wire  32  and the length of the winding wire  34 . 
     Another example of the junction mechanism in which the winding wire  32  is connected to the junction surface of the terminal metal attachment will be described with reference to  FIG. 14 .  FIG. 14  is an enlarged view of a terminal metal attachment  230  according to an embodiment of the disclosure. This terminal metal attachment  230  is applied to the common mode filter  100  in place of the terminal metal attachment  130 ′ shown in  FIG. 11 . 
     The terminal metal attachment  230  includes a junction surface  236 , a clamping piece  238 , and a fastening portion  240 . The clamping piece  238  is formed by folding a flat plate member that stands from one side of the junction surface  236  toward the junction surface  236  along the folding line L 6 ′. This folding line L 6 ′ is inclined at a larger angle with the axial direction of the winding core  14  compared to the folding line L 6  in  FIG. 11A . The junction surface  236  shown in  FIG. 14  is inclined at a larger angle with the axial direction of the winding core  14  compared to the junction surface  136  in  FIG. 11A . 
     According to such a configuration, when the lead portion  32 B enters into the terminal metal attachment  230  at the same angle as  FIG. 11A , the bent line L 6 ′ is inclined with respect to the lead portion  32 B. When the lead portion  32 B is attached to the terminal metal attachment  230 , the lead portion  32 B is firstly arranged to extend along the bending line L 6 ′, and then the clamping piece  238  is folded along the folding line L 6 ′. In this way, the lead portion  32 B is temporarily fasten to the junction surface  236  as illustrated in  FIG. 14 . At this point, the lead portion  32 B is bent at a bent portion P 5 . The bent portion P 5  is located at a position corresponding to the clamping point closest to the winding end position of the winding wire  32  in the clamping piece  238 . 
     According to such an arrangement, even when a force is applied to the winding wire  32  in a direction in which the winding wire  32  comes off from the clamping piece  238 , the bent portion of the lead portion  32 B is caught by the clamping piece  238 , which prevents the winding wire  32  from coming off. 
     The dimensions, materials, and arrangements of the various constituent components described in this specification are not limited to those explicitly described in the embodiments, and the various constituent components can be modified to have arbitrary dimensions, materials, and arrangements within the scope of the present invention. The elements other than those explicitly described herein can be added to the described embodiments; and part of the elements described for the embodiments can be omitted. For example, the terminal electrodes  40 ,  42 ,  44 ,  46  may be formed by baking Ag paste on the corresponding flanges  16 ,  22  and sequentially performing Ni plating and Sn plating on the surface of the baked Ag paste.