Patent Publication Number: US-11657946-B2

Title: Common mode choke coil

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims benefit of priority to Japanese Patent Application No. 2019-202352, filed Nov. 7, 2019, the entire content of which is incorporated herein by reference. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a common mode choke coil. 
     Background Art 
     A common mode choke coil is known as one type of circuit noise filter. For example, International Publication No. 2015/029976 discloses a common mode choke coil that includes a body composed of an insulator, a plurality of coil conductors that are provided in the body and each consist of a spiral-shaped coil portion and an extension portion that is connected to the coil portion and extends in a straight line, a plurality of outer electrodes that are provided on a surface of the body, and a plurality of outer pads that connect the extension portions and the outer electrodes to each other. In each coil conductor, the angle formed between the coil portion and the extension portion at the contact point where the coil portion and the extension portion are connected to each other is set to be an obtuse angle. 
     In the common mode choke coil disclosed in International Publication No. 2015/029976, the angle formed between the coil portion and the extension portion in each coil conductor at the contact point where the coil portion and the extension portion are connected to each other is set to be an obtuse angle in order suppress degradation of inductance caused by some magnetic flux generated by the coil conductors being canceled out. However, the two coils in this common mode choke coil have significantly different path lengths from each other, and therefore there is a risk of the inductances of the two coils being greatly shifted from each other. Therefore, when such a common mode choke coil is incorporated into a circuit, among the lines corresponding to the individual coils, the signal-waveform sharpness of one line may be weakened as a result of the characteristic impedance between that signal line and ground (GND) being greatly shifted. In other words, the noise suppression function provided by the common mode choke coil may be reduced. 
     SUMMARY 
     Accordingly, the present disclosure provides a common mode choke coil that has an excellent noise suppression function. 
     A preferred embodiment of the present disclosure provides a common mode choke coil that includes an element body formed by stacking a plurality of insulating layers in a height direction; a first coil and a second coil that are built into the element body; a first outer electrode that is provided on a surface of the element body and is electrically connected to one end of the first coil; a second outer electrode that is provided on a surface of the element body at a position that faces the first outer electrode in a width direction that is perpendicular to the height direction and that is electrically connected to another end of the first coil; a third outer electrode that is provided on a surface of the element body and is electrically connected to one end of the second coil; and a fourth outer electrode that is provided on a surface of the element body at a position that faces the third outer electrode in the width direction and that is electrically connected to another end of the second coil. When L1 is an inductance of the first coil and L2 is an inductance of the second coil, 100×|L1−L2|/((L1+L2)/2)≤5 at 1 GHz. 
     According to the preferred embodiment of the present disclosure, a common mode choke coil having an excellent noise suppression function can be provided. 
     Other features, elements, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of preferred embodiments of the present disclosure with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic perspective view illustrating an example of a common mode choke coil of an embodiment of the present disclosure; 
         FIG.  2    is an exploded schematic plan view illustrating an example of the internal structure of an element body in  FIG.  1   ; 
         FIG.  3    is a schematic sectional view illustrating a cross section taken along line A 1 -A 2  in  FIG.  1   ; 
         FIG.  4    is a schematic sectional view illustrating a cross section taken along line B 1 -B 2  in  FIG.  1   ; 
         FIG.  5    is a schematic sectional view illustrating a cross section taken along line C 1 -C 2  in  FIG.  1   ; 
         FIG.  6    is a schematic diagram for describing a method for measuring the inductances of a first coil and a second coil; 
         FIG.  7    is a schematic diagram for describing the method for measuring the inductances of the first coil and the second coil; 
         FIG.  8    is an exploded schematic plan view illustrating the internal structure of an element body of a common mode choke coil of the related art; 
         FIG.  9    is an exploded schematic plan view illustrating another example of the internal structure of the element body in  FIG.  1   ; 
         FIG.  10    is a graph illustrating the inductance-frequency characteristics of a first coil and a second coil of a common mode choke coil of example 1; 
         FIG.  11    is a graph illustrating the inductance-frequency characteristics of a first coil and a second coil of a common mode choke coil of comparative example 1; 
         FIG.  12    is a graph illustrating the impedance-frequency characteristics of the first coil and the second coil of the common mode choke coil of example 1; and 
         FIG.  13    is a graph illustrating the impedance-frequency characteristics of the first coil and the second coil of the common mode choke coil of comparative example 1. 
     
    
    
     DETAILED DESCRIPTION 
     Hereafter, a common mode choke coil of an embodiment of the present disclosure will be described. Note that the present disclosure is not limited to the following configurations and may be modified as appropriate within a range that does not depart from the gist of the present disclosure. Furthermore, combinations of a plurality of the preferred configurations described below are also included in the scope of the present disclosure. 
     Common Mode Choke Coil 
       FIG.  1    is a schematic perspective view illustrating an example of a common mode choke coil of an embodiment of the present disclosure. 
     In this specification, a length direction, a width direction, and a height direction of the common mode choke coil are the directions respectively defined by arrows L, W, and T, as indicated in  FIG.  1    and so on. The length direction L, the width direction W, and the height direction T are perpendicular to each other. 
     As illustrated in  FIG.  1   , a common mode choke coil  1  includes an element body  10 , a first outer electrode  21 , a second outer electrode  22 , a third outer electrode  23 , and a fourth outer electrode  24 . In addition, although not illustrated in  FIG.  1   , the common mode choke coil  1  also includes a first coil and a second coil that are built into the element body  10 , as described later. 
     The element body  10  is, for example, substantially shaped like a rectangular parallelepiped having six surfaces as illustrated in  FIG.  1   . The element body  10  has a first end surface  10   a  and a second end surface  10   b , which face each other in the length direction L, a first side surface  10   c  and a second side surface  10   d , which face each other in the width direction W, and a first main surface  10   e  and a second main surface  10   f , which face each other in the height direction T. The first main surface  10   e  or the second main surface  10   f  is used as a mounting surface when the common mode choke coil  1  is mounted on a substrate. 
     Corner portions and edge portions of the element body  10  are preferably rounded. “Corner portions” of the element body  10  are parts where three surfaces of the element body  10  intersect. “Edge portions” of the element body  10  are parts where two surfaces of the element body  10  intersect. 
     As described later, the element body  10  is formed by stacking a plurality of insulating layers in the height direction T. 
     The insulating layers constituting the element body  10  are preferably composed of a glass ceramic material. Thus, the radio-frequency characteristics of the common mode choke coil  1  are improved. 
     The glass ceramic material preferably includes a glass material containing at least K, B, and Si. 
     The glass material preferably contains K at 0.5 to 5 wt % expressed in terms of K 2 O, B at 10 to 25 wt % expressed in terms of B 2 O 3 , Si at 70 to 85 wt % expressed in terms of SiO 2 , and Al at 0 to 5 wt % expressed in terms of Al 2 O 3 . 
     The glass-ceramic material preferably contains SiO 2  (quartz) and Al 2 O 3  (alumina) as fillers in addition to the glass material described above. In this case, the glass ceramic material preferably contains the glass material at 60 to 66 wt %, SiO 2  at 34 to 37 wt % as a filler, and Al 2 O 3  at 0.5 to 4 wt % as a filler. The radio-frequency characteristics of the common mode choke coil  1  are improved as a result of the glass ceramic material including SiO 2  as a filler. Furthermore, the mechanical strength of the element body  10  is improved as a result of the glass ceramic material including Al 2 O 3  as a filler. 
     The first outer electrode  21  is provided on the surface of the element body  10 , more specifically, the first outer electrode  21  extends along part of each of the first side surface  10   c , the first main surface  10   e , and the second main surface  10   f.    
     The second outer electrode  22  is provided on the surface of the element body  10 , more specifically, the second outer electrode  22  extends along part of each of the second side surface  10   d , the first main surface  10   e , and the second main surface  10   f . In addition, the second outer electrode  22  is provided at a position facing the first outer electrode  21  in the width direction W. 
     The third outer electrode  23  is provided on the surface of the element body  10 , more specifically, the third outer electrode  23  extends along part of each of the first side surface  10   c , the first main surface  10   e , and the second main surface  10   f  at a position spaced apart from the first outer electrode  21 . 
     The fourth outer electrode  24  is provided on the surface of the element body  10 , more specifically, the fourth outer electrode  24  extends along part of each of the second side surface  10   d , the first main surface  10   e , and the second main surface  10   f  at a position spaced apart from the second outer electrode  22 . In addition, the fourth outer electrode  24  is provided at a position facing the third outer electrode  23  in the width direction W. 
     The first outer electrode  21 , the second outer electrode  22 , the third outer electrode  23 , and the fourth outer electrode  24  may each have a single-layer structure or a multilayer structure. 
     In the case where the first outer electrode  21 , the second outer electrode  22 , the third outer electrode  23 , and the fourth outer electrode  24  each have a single-layer structure, for example, Ag, Au, Cu, Pd, Ni, and Al or an alloy of any of these metals may be used as the material forming the outer electrodes. 
     In the case where the first outer electrode  21 , the second outer electrode  22 , the third outer electrode  23 , and the fourth outer electrode  24  each have a multilayer structure, each outer electrode may for example include a base electrode layer containing Ag, a Ni plating film, and a Sn plating film stacked in this order from the surface of the element body  10 . 
       FIG.  2    is an exploded schematic plan view illustrating an example of the internal structure of the element body in  FIG.  1   .  FIG.  3    is a schematic sectional view illustrating a cross section taken along line A 1 -A 2  in  FIG.  1   .  FIG.  4    is a schematic sectional view illustrating a cross section taken along line B 1 -B 2  in  FIG.  1   .  FIG.  5    is a schematic sectional view illustrating a cross section taken along line C 1 -C 2  in  FIG.  1   . 
     As illustrated in  FIGS.  2 ,  3 ,  4 , and  5   , the element body  10  is formed by stacking, in the height direction T, a plurality of insulating layers including an insulating layer  11   a , an insulating layer  11   b , an insulating layer  11   c , an insulating layer  11   d , and an insulating layer  11   e . The insulating layer  11   a  is located on the side of the element body  10  near the second main surface  10   f  and the insulating layer  11   e  is located on the side of the element body  10  near the first main surface  10   e . In  FIGS.  3 ,  4 , and  5   , the boundaries between these insulating layers are illustrated as dotted lines for the sake of explanation but the boundaries may not be clearly visible in reality. 
     The insulating layer  11   a , the insulating layer  11   b , the insulating layer  11   c , the insulating layer  11   d , and the insulating layer  11   e  are preferably formed of the same material. 
     In the element body  10 , at least one insulating layer having no conductor portions such as coil conductors, extension electrodes, and via conductors may be stacked on at least either of the side of the insulating layer  11   a  near the second main surface  10   f  and the side of the insulating layer  11   e  near the first main surface  10   e . For example, in the element body  10 , an insulating layer  11   f  may be stacked on the side of the insulating layer  11   e  near the first main surface  10   e , as illustrated in  FIGS.  2 ,  3 ,  4 , and  5   . It is preferable that this additional insulating layer  11   f  be composed of the same material as the insulating layer  11   a , the insulating layer  11   b , the insulating layer  11   c , the insulating layer  11   d , and the insulating layer  11   e.    
     A first coil  31  and a second coil  32  are built into the element body  10 . 
     The first coil  31  is formed by stacking a plurality of coil conductors, including a first coil conductor and a second coil conductor, together with insulating layers in the height direction T and electrically connecting the coil conductors to each other. In addition, the second coil  32  is formed by stacking a plurality of coil conductors, including a third coil conductor and a fourth coil conductor, together with insulating layers in the height direction T and electrically connecting the coil conductors to each other. This is described in more detail below. 
     A second coil conductor  42  is provided on a main surface of the insulating layer  11   a . The second coil conductor  42  includes a second line portion  52  and a second land portion  62 . One end of the second line portion  52  is connected to a second extension electrode  72  that extends from the second outer electrode  22 . The other end of the second line portion  52  is connected to the second land portion  62 . 
     A fourth coil conductor  44  is provided on a main surface of the insulating layer  11   b . The fourth coil conductor  44  includes a fourth line portion  54  and a fourth land portion  64 . One end of the fourth line portion  54  is connected to a fourth extension electrode  74  that extends from the fourth outer electrode  24 . The other end of the fourth line portion  54  is connected to the fourth land portion  64 . 
     A land portion  65   a  is provided on the main surface of the insulating layer  11   b  at a position that is spaced apart from the fourth land portion  64 . In addition, a via conductor  81   a  that penetrates through the insulating layer  11   b  in the height direction T is provided at a position that overlaps the land portion  65   a.    
     A land portion  65   b  is provided on a main surface of the insulating layer  11   c . In addition, a via conductor  81   b  that penetrates through the insulating layer  11   c  in the height direction T is provided at a position that overlaps the land portion  65   b.    
     A land portion  65   c  is provided on the main surface of the insulating layer  11   c  at a position that is spaced apart from the land portion  65   b . In addition, a via conductor  81   c  that penetrates through the insulating layer  11   c  in the height direction T is provided at a position that overlaps the land portion  65   c.    
     A first coil conductor  41  is provided on a main surface of the insulating layer  11   d . The first coil conductor  41  includes a first line portion  51  and a first land portion  61 . One end of the first line portion  51  is connected to a first extension electrode  71  that extends from the first outer electrode  21 . The other end of the first line portion  51  is connected to the first land portion  61 . 
     A via conductor  81   e  that penetrates through the insulating layer  11   d  in the height direction T is provided at a position that overlaps the first land portion  61 . 
     A land portion  65   d  is provided on the main surface of the insulating layer  11   d  at a position that is spaced apart from the first land portion  61 . In addition, a via conductor  81   d  that penetrates through the insulating layer  11   d  in the height direction T is provided at a position that overlaps the land portion  65   d.    
     A third coil conductor  43  is provided on a main surface of the insulating layer  11   e . The third coil conductor  43  includes a third line portion  53  and a third land portion  63 . One end of the third line portion  53  is connected to a third extension electrode  73  that extends from the third outer electrode  23 . The other end of the third line portion  53  is connected to the third land portion  63 . 
     A via conductor  81   f  that penetrates through the insulating layer  11   e  in the height direction T is provided at a position that overlaps the third land portion  63 . 
     As described above, when the insulating layer  11   a , the insulating layer  11   b , the insulating layer  11   c , the insulating layer  11   d , and the insulating layer  11   e  having the conductor portions such as the coil conductors, extension electrodes, and the via conductors are sequentially stacked in the height direction T, the first land portion  61  of the first coil conductor  41  is electrically connected to the second land portion  62  of the second coil conductor  42  by the via conductor  81   e , the land portion  65   b , the via conductor  81   b , the land portion  65   a , and the via conductor  81   a  in this order, as illustrated in  FIGS.  2  and  3   . Thus, the first coil  31  is formed. Furthermore, the third land portion  63  of the third coil conductor  43  is electrically connected to the fourth land portion  64  of the fourth coil conductor  44  by the via conductor  81   f , the land portion  65   d , the via conductor  81   d , the land portion  65   c , and the via conductor  81   c  in this order. Thus, the second coil  32  is formed. 
     As illustrated in  FIGS.  2  and  4   , one end of the first coil  31  (one end of first line portion  51 ) is electrically connected to the first outer electrode  21  via the first extension electrode  71 . The other end of the first coil  31  (one end of second line portion  52 ) is electrically connected to the second outer electrode  22  via the second extension electrode  72 . 
     As illustrated in  FIGS.  2  and  5   , one end of the second coil  32  (one end of third line portion  53 ) is electrically connected to the third outer electrode  23  via the third extension electrode  73 . The other end of the second coil  32  (one end of fourth line portion  54 ) is electrically connected to the fourth outer electrode  24  via the fourth extension electrode  74 . 
     The coil axes of the first coil  31  and the second coil  32  extend in the height direction T through the centers of the cross-sectional shape of the coils in a sectional view in the height direction T. 
     In a sectional view in the height direction T, the first coil  31  and the second coil  32  may have outer shapes consisting of substantially straight line portions and curved line portions as illustrated in  FIG.  2    or may instead have substantially circular or polygonal outer shapes. 
     In a sectional view in the height direction T, the first land portion  61 , the second land portion  62 , the third land portion  63 , the fourth land portion  64 , the land portion  65   a , the land portion  65   b , the land portion  65   c , and the land portion  65   d  may have substantially circular shapes as illustrated in  FIG.  2    or may have substantially polygonal shapes. 
     For example, Ag, Au, Cu, Pd, Ni, Al, or an alloy of any of these metals may be used as the material forming the first line portion  51 , the second line portion  52 , the third line portion  53 , the fourth line portion  54 , the first land portion  61 , the second land portion  62 , the third land portion  63 , the fourth land portion  64 , the land portion  65   a , the land portion  65   b , the land portion  65   c , the land portion  65   d , the first extension electrode  71 , the second extension electrode  72 , the third extension electrode  73 , the fourth extension electrode  74 , the via conductor  81   a , the via conductor  81   b , the via conductor  81   c , the via conductor  81   d , the via conductor  81   e , and the via conductor  81   f.    
     In the common mode choke coil  1 , when L1 is the inductance of the first coil  31  and L2 is the inductance of the second coil  32 , 100×|L1−L2|/((L1+L2)/2)≤5 at 1 GHz. “100×|L1−L2|/((L1+L2)/2)” expresses the degree of deviation between the inductance of the first coil  31  and the inductance of the second coil  32 . The common mode choke coil  1  having an excellent noise suppression function particularly in a radio-frequency band can be realized by setting the degree of deviation between the inductances to be less than or equal to 5%. 
     In the common mode choke coil  1 , at 1 GHz, it is preferable that 100×|L1−L2|/((L1+L2)/2)≤4 and it is particularly preferable that 100×|L1−L2|/((L1+L2)/2)=0, i.e., L1=L2. 
     In the common mode choke coil  1 , at 100 MHz, it is preferable that 100×|L1−L2|/((L1+L2)/2)≤3, it is more preferable that 100×|L1−L2|/((L1+L2)/2)≤1, and it is particularly preferable that 100×|L1−L2|/((L1+L2)/2)=0, i.e., L1=L2. 
     L1 and L2 may lie in a range from 1 nH to 10 nH. The effect of the deviation between the inductance of the first coil  31  and the inductance of the second coil  32  on the noise suppression function tends to be more pronounced when the inductances of the first coil  31  and the second coil  32  are small. In contrast, the noise suppression function of the common mode choke coil  1  is excellent even when the inductances of the first coil  31  and the second coil  32  are small. 
     The inductances of the first coil  31  and the second coil  32  are measured in the following way.  FIGS.  6  and  7    are schematic diagrams for describing a method for measuring the inductances of the first coil and the second coil. 
     First, as illustrated in  FIG.  6   , the first outer electrode  21 , which is electrically connected to one end of the first coil  31 , is connected to an input terminal (IN) of a network analyzer and the second outer electrode  22 , which is electrically connected to the other end of the first coil  31 , is connected to an output terminal (OUT) of the network analyzer. In addition, as illustrated in  FIG.  6   , the third outer electrode  23 , which is electrically connected to one end of the second coil  32 , and the fourth outer electrode  24 , which is electrically connected to the other end of the second coil  32 , are each connected to a 50Ω termination resistor. The inductance of the first coil  31  is measured with the common mode choke coil  1  connected to the network analyzer in this way. 
     Next, as illustrated in  FIG.  7   , the third outer electrode  23 , which is electrically connected to one end of the second coil  32 , is connected to the input terminal (IN) of the network analyzer and the fourth outer electrode  24 , which is electrically connected to the other end of the second coil  32 , is connected to the output terminal (OUT) of the network analyzer. In addition, as illustrated in  FIG.  7   , the first outer electrode  21 , which is electrically connected to one end of the first coil  31 , and the second outer electrode  22 , which is electrically connected to the other end of the first coil  31 , are each connected to a 50Ω termination resistor. The inductance of the second coil  32  is measured with the common mode choke coil  1  connected to the network analyzer in this way. 
     For example, the network analyzer “E5071C” manufactured by Keysight Technologies is used as the network analyzer. 
     In the common mode choke coil  1 , it is preferable that 100×(R1−R2)/R1≤3 when R1≥R2 and that 100×(R2−R1)/R2≤3 when R2≥R1, where R1 is the path length of the first coil  31  and R2 is the path length of the second coil  32 . “100×(R1−R2)/R1” and “100×(R2−R1)/R2” express the degree of deviation between the path length of the first coil  31  and the path length of the second coil  32 . The degree of deviation between the inductance of the first coil  31  and the inductance of the second coil  32  becomes sufficiently small and as a result the noise suppression function of the common mode choke coil  1  is markedly improved by making the degree of path length deviation less than or equal to 3%. 
     The path length of the first coil  31  means the total length of the wiring line connected between the first extension electrode  71  and the second extension electrode  72 , more specifically, the length of the line passing through the first line portion  51 , the first land portion  61 , the via conductor  81   e , the land portion  65   b , the via conductor  81   b , the land portion  65   a , the via conductor  81   a , the second land portion  62 , and the second line portion  52 . The path length of the second coil  32  means the total length of the wiring line connected between the third extension electrode  73  and the fourth extension electrode  74 , more specifically, the length of the line passing through the third line portion  53 , the third land portion  63 , the via conductor  81   f , the land portion  65   d , the via conductor  81   d , the land portion  65   c , the via conductor  81   c , the fourth land portion  64 , and the fourth line portion  54 . 
     The path length of the first coil  31  and the path length of the second coil  32  are determined in the following manner. First, the common mode choke coil  1  (element body  10 ) is ground down so as to expose an LW cross section that is parallel to the length direction L and the width direction W. Then, the length of the line passing through the center of the width of each line portion and each land portion is measured for each LW section, as illustrated in  FIG.  2   , using a microscope. In addition, the common mode choke coil  1  (element body  10 ) is ground down so as to expose an LT cross section that is parallel to the length direction L and the height direction T. Then, the dimension of each via conductor in the height direction T is measured using the microscope in the LT cross section as illustrated in  FIG.  3   . The dimension of each via conductor in the height direction T may be measured in a WT cross section that is parallel to the width direction W and the height direction T. The path length of the first coil  31  and the path length of the second coil  32  are determined by adding together all of the thus-obtained measured values for the first coil  31  and the second coil  32 . 
     In the common mode choke coil  1 , it is desirable to reduce the difference between the path length of the first coil  31  and the path length of the second coil  32 , as described above, from the viewpoint of reducing the deviation between the inductance of the first coil  31  and the inductance of the second coil  32 . A specific example of a method for reducing the difference between the path length of the first coil  31  and the path length of the second coil  32  will be described below. 
     First, description will be given of a common mode choke coil of the related art, which will be compared with the present disclosure.  FIG.  8    is an exploded schematic plan view illustrating the internal structure of an element body of the common mode choke coil of the related art. As illustrated in  FIG.  8   , in the common mode choke coil of the related art, the length of the first line portion  51  and the length of the second line portion  52  are each considerably shorter than those in the configuration illustrated in  FIG.  2   , and this results in the path length of the first coil  31  being considerably shorter than the path length of the second coil  32 . In other respects, the common mode choke coil of the related art illustrated in  FIG.  8    is similar to the example of a common mode choke coil of the embodiment of the present disclosure illustrated in  FIG.  2   . 
     In contrast to the common mode choke coil of the related art illustrated in  FIG.  8   , in the example common mode choke coil of the embodiment of the present disclosure illustrated in  FIG.  2   , a path adjusting portion  91   a  (part surrounded by dotted lines) is provided for the first line portion  51  and a path adjusting portion  91   b  (part surrounded by dotted lines) is provided for the second line portion  52 , i.e., the path length of the first coil  31  is increased. Thus, in the example common mode choke coil of the embodiment of the present disclosure illustrated in  FIG.  2   , the difference between the path length of the first coil  31  and the path length of the second coil  32  is reduced. 
     In the example common mode choke coil of the embodiment of the present disclosure illustrated in  FIG.  2   , as a result of the first line portion  51  being provided with the path adjusting portion  91   a  and the second line portion  52  being provided with the path adjusting portion  91   b , the manner in which the first line portion  51  is routed to the first land portion  61  and the manner in which the second line portion  52  is routed to the second land portion  62  are changed compared with the common mode choke coil of the related art illustrated in  FIG.  8   . 
     More specifically, in the example common mode choke coil of the embodiment of the present disclosure illustrated in  FIG.  2   , the other end of the first line portion  51  is connected to the first land portion  61  from a side near the first extension electrode  71  in the width direction W and the other end of the second line portion  52  is connected to the second land portion  62  from a side near the second extension electrode  72  in the width direction W. In addition, looking at the second coil  32 , the other end of the third line portion  53  is connected to the third land portion  63  from a side near the third extension electrode  73  in the width direction W and the other end of the fourth line portion  54  is connected to the fourth land portion  64  from a side near the fourth extension electrode  74  in the width direction W. 
     In contrast, in the common mode choke coil of the related art illustrated in  FIG.  8   , the other end of the first line portion  51  is connected to the first land portion  61  from the opposite side from where the first extension electrode  71  is located in the width direction W and the other end of the second line portion  52  is connected to the second land portion  62  from the opposite side from where the second extension electrode  72  is located in the width direction W. 
     As illustrated in  FIG.  2   , the path adjusting portion  91   a  and the path adjusting portion  91   b  are preferably shaped so as to generally follow the circumferential shape of the first coil  31 , but may instead have a meandering shape. 
     The path adjusting portions are provided in the first coil  31  in the example common mode choke coil of the embodiment of the present disclosure illustrated in  FIG.  2   , but such path adjusting portions may instead be provided in the second coil  32  in the case where the path length of the second coil  32  is considerably shorter than the path length of the first coil  31  in the common mode choke coil of the related art. 
     A method of reducing the difference between the path length of the first coil  31  and the path length of the second coil  32  by providing path adjusting portions has been described, but the following method may also be used. 
       FIG.  9    is an exploded schematic plan view illustrating another example of the internal structure of the element body in  FIG.  1   . In this other example of the common mode choke coil of the embodiment of the present disclosure illustrated in  FIG.  9   , the coil diameter of the second coil  32  is reduced without changing the number of turns of the second coil  32 , in other words, the path length of the second coil  32  is made shorter compared with the common mode choke coil of the related art illustrated in  FIG.  8   . Thus, in this other example of the common mode choke coil of the embodiment of the present disclosure illustrated in  FIG.  9   , the difference between the path length of the first coil  31  and the path length of the second coil  32  is reduced. 
     In this other example of the common mode choke coil of the embodiment of the present disclosure illustrated in  FIG.  9   , the coil diameter of the second coil  32  is smaller than the coil diameter of the first coil  31 . On the other hand, the coil diameter of the first coil  31  may be made smaller than that of the second coil  32  without changing the number of turns of the first coil  31  in the case where the path length of the second coil  32  is considerably shorter than the path length of the first coil  31  in the common mode choke coil of the related art. In summary, one coil diameter out of the coil diameter of the first coil  31  and the coil diameter of the second coil  32  may be made smaller than the other coil diameter. 
     The coil diameters (outer diameters) of the first coil  31  and the second coil  32  mean the diameters of area equivalent circles of the cross-sectional shapes (outer shapes) of the coils in a sectional view in the height direction T. 
     The number of turns of the first coil  31  and the number of turns of the second coil  32  may be less than or equal to five turns. The effect of the deviation between the inductance of the first coil  31  and the inductance of the second coil  32  on the noise suppression function tends to be more pronounced when the number of turns of the first coil  31  and the second coil  32  is small. In contrast, the common mode choke coil  1  has an excellent noise suppression function even when the number of turns of the first coil  31  and the second coil  32  is small Note that the number of turns of the first coil  31  and the number of turns of the second coil  32  may be greater than or equal to five turns. 
     It is preferable that the width of the first line portion  51 , the width of the second line portion  52 , the width of the third line portion  53 , and the width of the fourth line portion  54  in a sectional view in the height direction T be identical from the viewpoint of reducing the deviation between the inductance of the first coil  31  and the inductance of the second coil  32 . 
     In the common mode choke coil  1 , at 1 GHz, it is preferable that 100×|Z1−Z2|/((Z1+Z2)/2)≤5, it is more preferable that 100×|Z1−Z2|/((Z1+Z2)/2)≤4, and it is particularly preferable that 100×|Z1−Z2|/((Z1+Z2)/2)=0, i.e., Z1=Z2, where Z1 is the impedance of the first coil  31  and Z2 is the impedance of the second coil  32 . “100×|Z1−Z2|/((Z1+Z2)/2)” expresses the degree of deviation between the impedance of the first coil  31  and the impedance of the second coil  32 . By reducing this impedance deviation to be less than or equal to 5%, the noise suppression function of the common mode choke coil  1  becomes especially excellent, particularly in a radio-frequency band. 
     In the common mode choke coil  1 , at 100 MHz, it is preferable that 100×|Z1−Z2|/((Z1+Z2)/2)≤3, it is more preferable that 100×|Z1−Z2|/((Z1+Z2)/2)≤1, and it is particularly preferable that 100×|Z1−Z2|/((Z1+Z2)/2)=0, i.e., Z1=Z2. 
     The impedances of the first coil  31  and the second coil  32  are measured in the same manner as in the inductance measurement method described with reference to  FIGS.  6  and  7   . 
     Method of Manufacturing Common Mode Choke Coil 
     Next, an example of a method of manufacturing the common mode choke coil of the embodiment of the present disclosure will be described. 
     Preparation of Glass Ceramic Material 
     K 2 O, B 2 O 3 , SiO 2 , Al 2 O 3 , and so forth are mixed in a prescribed ratio. The resulting mixture is then melted by being subjected to firing. The resulting melted mixture is then quenched to produce a glass material. Next, a glass ceramic material is prepared by adding SiO 2  (quartz), Al 2 O 3  (alumina), and so forth to the glass material as fillers. 
     Preparation of Glass Ceramic Sheets 
     A ceramic slurry is prepared by adding an organic binder such as polyvinyl butyral resin, an organic solvent such as ethanol or toluene, a plasticizer, and so forth to the glass ceramic material and mixing the materials. The ceramic slurry is then molded into a substantially sheet-like shape using a doctor blade method or the like and then punched to form prescribed shapes, thereby forming glass ceramic sheets. 
     Formation of Conductor Patterns 
     Coil-conductor conductor patterns corresponding to the coil conductors illustrated in  FIG.  2   , extension-electrode conductor patterns corresponding to the extension electrodes illustrated in  FIG.  2   , and via-conductor conductor patterns corresponding to the via conductors illustrated in  FIG.  2    are formed on and in the individual glass ceramic sheets by screen printing or the like using a conductive paste such as Ag paste. When forming the via-conductor conductor patterns, via holes are formed in advance by irradiating prescribed portions of the glass ceramic sheets with a laser and then filling the via holes with a conductive paste. 
     Manufacture of Multilayer Block 
     The glass ceramic sheets on and in which conductor patterns have been formed are stacked in the order illustrated in  FIG.  2   . A prescribed number of glass ceramic sheets on and in which no conductor patterns have been formed may be stacked on the top and the bottom of the thus-formed multilayer body. After that, the resulting multilayer body is subjected to pressure bonding using a warm isostatic pressing (WIP) process or the like to produce a multilayer block. 
     Manufacture of Element Body 
     Individual chips are manufactured by cutting the multilayer block into pieces of a prescribed size by using a dicer or the like. After that, the individual chips are fired, whereby the glass ceramic sheets become the insulating layers and the coil-conductor conductor patterns, the extension-electrode conductor patterns, and the via-conductor conductor patterns become the coil conductors, the extension electrodes, and the via conductors. As a result, the element body having the first coil and the second coil built thereinto as illustrated in  FIG.  2    is manufactured. The first extension electrode, which is connected to one end of the first coil, and the third extension electrode, which is connected to one end of the second coil, are exposed at the first side surface of the element body. The second extension electrode, which is connected to the other end of the first coil, and the fourth extension electrode, which is connected to the other end of the second coil, are exposed at the second side surface of the element body. 
     The corner portions and edge portions of the element body may be rounded by performing barrel polishing, for example. 
     Formation of Outer Electrodes 
     A conductive paste containing Ag and glass frit is applied to at least four locations on both side surfaces of the element body where the extension electrodes are exposed. Then, base electrode layers are formed by baking the thus-formed films. Next, a Ni plating film and a Sn plating film are sequentially formed on each base electrode layer by performing electrolytic plating. As a result, the first outer electrode, the second outer electrode, the third outer electrode, and the fourth outer electrode are formed as illustrated in  FIG.  1   . 
     The common mode choke coil of the embodiment of the present disclosure as exemplified in  FIGS.  1 ,  2   , and so on is manufactured as described above. 
     EXAMPLE 
     Hereafter, an example that discloses the common mode choke coil of the embodiment of the present disclosure in a more specific manner is described. The present disclosure is not limited to just the following example. 
     Example 1 
     A common mode choke coil of example 1 was manufactured using the following method. 
     Preparation of Glass Ceramic Material 
     K 2 O, B 2 O 3 , SiO 2 , and Al 2 O 3  were weighed in a prescribed ratio and mixed inside a platinum crucible. Then, the resulting mixture was melted by firing the mixture at a temperature in the range from 1500° C. to 1600° C. After that, the resulting melted mixture was quenched to produce a glass material. 
     Next, glass powder was prepared by pulverizing the glass material so that the average particle diameter D 50  was in a range from 1 μm to 3 μm. In addition, quartz powder and alumina powder with an average particle diameter D 50  in a range from 0.5 μm to 2.0 μm were prepared as fillers. Here, the average particle diameter D 50  is a particle diameter corresponding to a volume basis cumulative percentage of 50%. A glass ceramic material was then prepared by adding the quartz powder and the alumina powder to the glass powder as fillers. 
     Preparation of Glass Ceramic Sheets 
     A ceramic slurry was prepared by adding an organic binder such as polyvinyl butyral resin, an organic solvent such as ethanol or toluene, a plasticizer, and a PSZ medium to a ball mill together with the glass ceramic material and mixing the materials. Then, the ceramic slurry was molded into a substantially sheet-like shape with a thickness in a range from 20 μm to 30 μm using a doctor blade method or the like and then punched to form substantially rectangular shapes, thereby forming glass ceramic sheets. 
     Formation of Conductor Patterns 
     Coil-conductor conductor patterns corresponding to the coil conductors illustrated in  FIG.  2   , extension-electrode conductor patterns corresponding to the extension electrodes illustrated in  FIG.  2   , and via-conductor conductor patterns corresponding to the via conductors illustrated in  FIG.  2    were formed on and in the individual glass ceramic sheets by screen printing or the like using a conductive paste such as a Ag paste. When forming the via-conductor conductor patterns, via holes were formed in advance by irradiating prescribed portions of the glass ceramic sheets with a laser and then filling the via holes with a conductive paste. 
     Manufacture of Multilayer Block 
     The glass ceramic sheets on and in which conductor patterns had been formed were stacked in the order illustrated in  FIG.  2   . A prescribed number of glass ceramic sheets on and in which no conductor patterns had been formed were stacked on the top and the bottom of the thus-formed multilayer body. After that, the resulting multilayer body was subjected to pressure bonding using a warm isostatic pressing process or the like to produce a multilayer block. The pressure bonding conditions were a temperature of 80° C. and a pressure of 100 MPa. 
     Manufacture of Element Body 
     The multilayer block was cut into pieces of a prescribed size using a dicer or the like, thereby manufacturing individual chips. After that, the individual chips were fired at 880° C. for 1.5 hours, whereby the glass ceramic sheets became the insulating layers and the coil-conductor conductor patterns, the extension-electrode conductor patterns, and the via-conductor conductor patterns became the coil conductors, the extension electrodes, and the via conductors. As a result, the element body having the first coil and the second coil built thereinto as illustrated in  FIG.  2    was manufactured. The first extension electrode, which is connected to one end of the first coil, and the third extension electrode, which is connected to one end of the second coil, were exposed at the first side surface of the element body. The second extension electrode, which is connected to the other end of the first coil, and the fourth extension electrode, which is connected to the other end of the second coil, were exposed at the second side surface of the element body. 
     Next, the corner portions and edge portions of the element body were rounded by placing the element body in a rotary barrel machine along with a medium and performing barrel polishing. 
     Formation of Outer Electrodes 
     A conductive paste containing Ag and glass frit was applied to at least four locations on both side surfaces of the element body where the extension electrodes were exposed. Then, base electrode layers were formed by baking the resulting films at 810° C. for 1 minute. The thickness of the base electrode layers was 5 μm. Next, a Ni plating film and a Sn plating film were sequentially formed on each base electrode layer by performing electrolytic plating. The thickness of each Ni plating film and Sn plating film was 3 μm. As a result, the first outer electrode, the second outer electrode, the third outer electrode, and the fourth outer electrode were formed as illustrated in  FIG.  1   . 
     The common mode choke coil of example 1 was manufactured as described above. The size of the common mode choke coil of example 1 was 0.6 mm in the length direction, 0.5 mm in the width direction, and 0.3 mm in the height direction. 
     Comparative Example 1 
     A common mode choke coil of comparative example 1 was manufactured in the same manner as the common mode choke coil of example 1 except that the element body in which the first coil and the second coil were built in as illustrated in  FIG.  8    was manufactured. 
     Evaluation 
     Evaluation of the common mode choke coils of example 1 and comparative example 1 was performed as described below. 
     Inductance 
     The inductances of the first coils and the second coils of the common mode choke coils were measured using the above-described method and the frequency characteristics were evaluated.  FIG.  10    is a graph illustrating the inductance-frequency characteristics of the first coil and the second coil of the common mode choke coil of example 1.  FIG.  11    is a graph illustrating the inductance-frequency characteristics of the first coil and the second coil of the common mode choke coil of comparative example 1. 
     Next, when L1 and L2 represent the measured values of the inductances of the first coil and the second coil and the degree of deviation between these inductances was evaluated by calculating 100×|L1−L2|/((L1+L2)/2). This evaluation was carried under conditions of frequencies of 1 GHz and 100 MHz. The obtained results are illustrated in Table 1. 
     Impedance 
     The impedances of the first coils and the second coils of the common mode choke coils were measured using the above-described method and the frequency characteristics were evaluated.  FIG.  12    is a graph illustrating the impedance-frequency characteristics of the first coil and the second coil of the common mode choke coil of example 1.  FIG.  13    is a graph illustrating the impedance-frequency characteristics of the first coil and the second coil of the common mode choke coil of comparative example 1. 
     Next, Z1 and Z2 represent the measured values of the impedances of the first coil and the second coil and the degree of deviation between these impedances was evaluated by calculating 100×|Z1−Z2|/((Z1+Z2)/2). This evaluation was carried under conditions of frequencies of 1 GHz and 100 MHz. The obtained results are illustrated in Table 1. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Example 1 
                 Comparative Example 1 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 Frequency 
                 First 
                 Second 
                 Deviation 
                 First 
                 Second 
                 Deviation 
               
               
                   
                 (Hz) 
                 Coil 
                 Coil 
                 (%) 
                 Coil 
                 Coil 
                 (%) 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Inductance 
                 100 
                 MHz 
                 8.74 
                 8.65 
                 1.0 
                 7.46 
                 6.55 
                 13.0 
               
               
                 (nH) 
                 1 
                 GHz 
                 7.84 
                 7.56 
                 3.6 
                 6.64 
                 5.59 
                 17.2 
               
               
                 Impedance 
                 100 
                 MHz 
                 5.71 
                 5.66 
                 0.9 
                 4.73 
                 4.15 
                 13.1 
               
               
                 (Ω) 
                 1 
                 GHz 
                 51.3 
                 49.7 
                 3.2 
                 43.1 
                 36.6 
                 16.3 
               
               
                   
               
            
           
         
       
     
     As illustrated in Table 1, the degree of deviation between the inductance of the first coil and the inductance of the second coil was smaller in the common-mode choke coil of example 1 than in the common-mode choke coil of comparative example 1. In addition, as illustrated in  FIGS.  10  and  11   , the common mode choke coil of example 1 exhibited frequency characteristics in which the inductance of the first coil and the inductance of the second coil were closer to each other than in the common mode choke coil of comparative example 1. 
     As illustrated in Table 1, the degree of deviation between the impedance of the first coil and the impedance of the second coil was smaller in the common-mode choke coil of example 1 than in the common-mode choke coil of comparative example 1. In addition, as illustrated in  FIGS.  12  and  13   , the common mode choke coil of example 1 exhibited frequency characteristics in which the impedance of the first coil and the impedance of the second coil were closer to each other than in the common mode choke coil of comparative example 1. 
     Path Length 
     The path lengths of the first and second coils of the common mode choke coils were measured using the method described above and the respective measured values were represented by R1 and R2. The degree of deviation between these path lengths was evaluated by calculating 100×(R1−R2)/R1 when R1≥R2 and 100×(R2−R1)/R2 when R2≥R1. As a result, the degree of deviation between the path length of the first coil and the path length of the second coil was 2.1% in the common mode choke coil of example 1 and 6.4% in the common mode choke coil of comparative example 1. 
     From the above evaluation results, it was found that the common mode choke coil of example 1 had a superior noise suppression function than the common mode choke coil of comparative example 1. 
     While preferred embodiments of the disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the disclosure. The scope of the disclosure, therefore, is to be determined solely by the following claims.