Patent Publication Number: US-11657948-B2

Title: Wire-wound core, wire-wound core manufacturing method, and wire-wound-equipped electronic component

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims benefit of priority to Japanese Patent Application No. 2017-198306, filed Oct. 12, 2017, the entire content of which is incorporated herein by reference. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a wire-wound core, a wire-wound core manufacturing method, and a wire-wound-equipped electronic component including a wire-wound core and, more particularly, to improvements in a configuration of a terminal electrode disposed on the wire-wound core and in a terminal electrode formation method. 
     Background Art 
     For example, a technique described in Japanese Unexamined Patent Application Publication No. 2003-243226 aims to provide a wire-wound-type electronic component that makes mass production of a core easier, has small variations in inductance, and has stable fixation strength on a printed circuit board when being mounted on the printed circuit board and to provide a manufacturing method of such a wire-wound-type electronic component. To this end, a following configuration is described in Japanese Unexamined Patent Application Publication No. 2003-243226. 
     A core having a substantially quadrangular shape is obtained by cutting a sheet formed of a magnetic material or a non-magnetic material in length and width directions. Terminal electrodes are disposed on respective end portions of a bottom surface of the core. Recessed portions having a depth greater than a thickness of a wound wire are respectively formed by cutting on a portion of the bottom surface of the core between the terminal electrodes and on a top surface of the core. A part of a wound wire is accommodated in the recessed portions. In addition, ends of the wound wire are fixed to the respective terminal electrodes. 
     To increase the reliability of electrical connection and mechanical fixation of an electronic component including a core described above when the electronic component is mounted on a mount board, wider soldered areas of the terminal electrodes are more desirable. More specifically, the terminal electrodes are desirably formed not only on the bottom surface of the core to be oriented toward the mount board when the electronic component is mounted on the mount board but also on outer end surfaces that face respective outer sides of the core. 
     On the other hand, according to Japanese Unexamined Patent Application Publication No. 2003-243226, the terminal electrodes are formed on a sheet before each core is cut therefrom to increase mass productivity. More specifically, it is described in Japanese Unexamined Patent Application Publication No. 2003-243226 that the terminal electrodes are formed by stacking a conductor green sheet containing conductive power together with insulator green sheets (paragraphs 0044 to 0046), by applying and baking a conductor paste (paragraph 0067), or by using a copper-fixed sheet (paragraph 0069). 
     Since the terminal electrodes described in Japanese Unexamined Patent Application Publication No. 2003-243226 are formed on a sheet before each core is cut therefrom using one of the aforementioned methods, the terminal electrodes have a film shape that extends along only the bottom surface of the core. That is, since the outer end surfaces of the core are surfaces that appear by cutting the sheet, terminal electrodes that extend from the bottom surface to the outer end surfaces of the core cannot be formed using the method described in Japanese Unexamined Patent Application Publication No. 2003-243226 as long as the terminal electrodes are formed on the sheet before each core is cut therefrom. 
     Note that substantially the same advantage as that obtained by terminal electrodes that extend from the bottom surface to the outer end surfaces of the core may be obtained even with terminal electrodes that extend only along the bottom surface of the core if the thickness of the terminal electrodes is increased. However, there is a limit in terms of increasing the thickness of the terminal electrodes. In practice, it is almost impossible to expect substantially the same advantage as that obtained by the terminal electrodes extending from the bottom surface to the outer end surfaces of the core. In addition, an eddy current loss due to magnetic flux linkage increases as the thickness of the terminal electrodes increases, resulting in degradation of characteristics. 
     In addition, paragraph 0067 of Japanese Unexamined Patent Application Publication No. 2003-243226 describes that the terminal electrodes may be formed by applying and baking a conductor paste after each core is cut from the sheet. However, it is easily presumed that this method is inferior in terms of mass productivity and becomes more difficult to carry out as the size of the core decreases. 
     In addition, when a conductor paste is applied as described above, a dip method is usually used. In this case, since the conductor paste is applied to four lateral surfaces that are adjacent to the bottom surface of the core, that is, two lateral surfaces, an inner end surface, and an outer end surface, the height of the electrode portion that can be formed on the end surface is limited because the electrode portion formed on the inner end surface needs to have a height that does not touch the wound wire wound around a core portion such as the recessed portions of Japanese Unexamined Patent Application Publication No. 2003-243226. 
     The height of the electrode portion can be increased only on the outer end surface by diagonally dipping the core to the conductor paste. However, since end portions of the core need to be dipped separately in this case, mass productivity further decreases. 
     SUMMARY 
     Accordingly, this disclosure provides a wire-wound core manufacturing method that enables fabrication of a wire-wound core including terminal electrodes extending from a bottom surface to outer end surfaces at a high productivity also in the case where the size of the wire-wound core decreases and a wire-wound core fabricated using this method. 
     This disclosure also provides a wire-wound-equipped electronic component including the aforementioned wire-wound core. 
     According to preferred embodiments of the present disclosure, a wire-wound core includes a core portion having a longitudinal direction, a first flange portion disposed at a first end portion of the core portion in the longitudinal direction, a second flange portion disposed at a second end portion of the core portion in the longitudinal direction, a terminal electrode disposed at the first flange portion, and a terminal electrode disposed at the second flange portion. When a face to be oriented toward a mount board when the wire-wound core is mounted on the mount board is defined as a bottom surface and a face of the first flange portion that faces an outer side opposite to a side where the core portion is located is defined as an outer end surface, the outer end surface has a recessed portion that reaches the bottom surface of the first flange portion. 
     The terminal electrode disposed at the first flange portion includes a bottom surface electrode portion that is formed of a film conductor extending along the bottom surface of the first flange portion and an end surface electrode portion that is formed of a conductor filling the recessed portion and is in contact with the bottom surface electrode portion. Note that the end surface electrode portion that is continuous to the bottom surface electrode portion is not limited to the end surface electrode portion that is integrated with the bottom surface electrode portion and may be just in contact with the bottom surface electrode portion as a separate portion. 
     The above-described terminal electrode can be easily and efficiently formed on the wire-wound core if a manufacturing method described later is used. 
     In addition, when a face opposite to the bottom surface is defined as a top surface, the top surface of the core portion and the top surface of the first flange portion may be flush with each other or the top surface of the core portion may be lower than the top surface of the first flange portion. The state in which the top surface of the core portion is lower than the top surface of the first flange portion is, in other words, a state in which the top surface of the core portion is located closer to the mount board than the top surface of the first flange portion. 
     In addition, when a face opposite to the bottom surface is defined as a top surface and a face linking the bottom surface and the top surface to each other is defined as a lateral surface, the lateral surface of the core portion and the lateral surface of the first flange portion may be flush with each other or the lateral surface of the core portion may be lower than the lateral surface of the first flange portion. The state in which the lateral surface of the core portion is lower than the lateral surface of the first flange portion is, in other words, a state in which the lateral surface of the core portion is located closer to the central axis of the core portion than the lateral surface of the first flange portion. 
     In addition, the outer end surface and an end surface of the end surface electrode portion that faces the outer side may be flush with each other. In addition, when a face opposite to the bottom surface is defined as a top surface, an end portion of the recessed portion on a top surface side may be a flat surface parallel to the top surface of the first flange portion. 
     When a face opposite to the bottom surface is defined as a top surface and a face linking the bottom surface and the top surface to each other is defined as a lateral surface, the bottom surface electrode portion may reach the lateral surface of the first flange portion and the end surface electrode portion may be located on an inner side than the lateral surface of the first flange portion. In addition, the wire-wound core may further include a plurality of terminal electrodes each being the terminal electrode disposed at the first flange portion, and the plurality of terminal electrodes may be arranged in a direction that is perpendicular to the longitudinal direction and is parallel to the bottom surface. 
     In addition, the wire-wound core may further include a passive element that is connected to the plurality of terminal electrodes and is included in the first flange portion. For example, in the case where the passive element is a capacitor, a filter having a good noise removal effect, such as a π filter or a T filter, can be implemented using this wire-wound core. In addition, when a perpendicular bisector plane of a central axis extending in the longitudinal direction of the core portion is defined as a symmetry plane, the terminal electrode disposed at the first flange portion and the terminal electrode disposed at the second flange portion may be symmetrical or asymmetrical about the symmetry plane. 
     A wire-wound core manufacturing method described later is applicable to the various embodiments described above, and the wire-wound core can be easily manufactured even if the size of the wire-wound core decreases. In addition, according to preferred embodiments of the present disclosure, a wire-wound-equipped electronic component includes the wire-wound core described above, and a wire that is wound around the core portion of the wire-wound core, the wire having ends electrically connected to the respective terminal electrodes. 
     Further, according to preferred embodiments of the present disclosure, a wire-wound core manufacturing method for manufacturing the wire-wound core described above, includes creating a mother block in which a plurality of first mother sheets and a plurality of second mother sheets are stacked in this order, the plurality of first mother sheets being formed of a non-conductive material, and the plurality of second mother sheets being formed of a non-conductive material and having a plurality of through-holes each of which serves as the recessed portion. The method further includes forming a first groove on the mother block from a second mother sheet side to form a face serving as the bottom surface of the core portion in the mother block; and dividing the mother block along a plurality of x-direction division planes perpendicular to the bottom surface and a plurality of y-direction division planes perpendicular to the bottom surface to locate each of the plurality of through-holes on a corresponding outer end surface side. 
     In addition, in the step of creating the mother block, a conductor serving as the end surface electrode portion may be disposed in each of the plurality of through-holes. In addition, the step of creating the mother block may include forming the plurality of first mother sheets by printing, and forming the plurality of second mother sheets on the plurality of first mother sheets by printing. 
     In addition, in the step of creating the mother block, a conductor film serving as the bottom surface electrode portion may be disposed on a bottom surface of the second mother sheet located on a bottommost side among the plurality of second mother sheets, and the conductor film may be divided by either the x-direction division planes or the y-direction division planes. In this case, the bottom surface electrode portion reaches the lateral surface of the first flange portion. 
     In addition, the wire-wound core manufacturing method may further include forming, when a face opposite to the bottom surface is defined as a top surface and a face linking the bottom surface and the top surface to each other is defined as a lateral surface, through-holes in the first mother sheets and the second mother sheets to make the lateral surface of the core portion lower than the lateral surface of the first flange portion. In addition, the wire-wound core manufacturing method may further include forming, when a face opposite to the bottom surface is defined as a top surface, a second groove on the mother block from a top surface side to make the top surface of the core portion lower than the top surface of the first flange portion. In addition, the wire-wound core manufacturing method may further include forming a pattern conductor of a passive element on at least one of the pluralities of first and second mother sheets. 
     The wire-wound core according to the preferred embodiments of this disclosure includes the terminal electrode extending from the bottom surface to the outer end surface of the first flange portion. Thus, the reliability of electrical connection and mechanical fixation in the mounted state is successfully increased. 
     With the wire-wound core manufacturing method according to the preferred embodiments of this disclosure, the wire-wound core is fabricated roughly by creating a mother block in which a plurality of mother sheets, some of which have through-holes, are stacked, by forming a groove on the mother block, and by dividing the mother block. 
     The recessed portion can be efficiently formed with a high preciseness by forming through-holes in each of the mother sheets constituting the mother block before obtaining the mother block and by dividing the mother block to locate each of the through-holes on the corresponding outer end surface side even if the size of the wire-wound core decreases. That is, the reduction in size of the wire-wound core can be well handled by disposing a conductor serving as the end surface electrode portion in this recessed portion, compared with the case where a wire-wound core having an end surface electrode portion is obtained by molding using a die, for example. In addition, the terminal electrode extending from the bottom surface to the outer end surface of the flange portion can be efficiently formed with a high preciseness. In addition, the core portion can be efficiently formed with a high preciseness by forming the groove on the mother block. 
     In addition, most of steps for obtaining the wire-wound core are finished before dividing the mother block. Thus, division of the mother block enables many wire-wound cores to be obtained simultaneously and thus implements high productivity. In addition, the number of wire-wound cores obtained from a single mother block increases as the size of wire-wound cores to be obtained decreases. Thus, a decrease in cost of the wire-wound cores is expected. 
     In addition, processing conditions of formation of the through-holes in the mother sheets, formation of the groove on the mother block, and division of the mother block are changeable by changing the respective processing programs. Thus, various design changes can be quickly handled since re-fabrication of a die is not necessary, for example. 
     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 perspective view illustrating an external appearance of a wire-wound-equipped electronic component including a wire-wound core according to a first embodiment of this disclosure with a face to be oriented toward a mount board facing upward; 
         FIG.  2    is a perspective view illustrating an unprocessed mother sheet prepared for fabrication of the wire-wound core illustrated in  FIG.  1   ; 
         FIG.  3    is a perspective view illustrating a state in which a plurality of through-holes are formed in the unprocessed mother sheet illustrated in  FIG.  2   ; 
         FIG.  4    is a perspective view illustrating a staking order of first to third mother sheets that are stacked to obtain a mother block; 
         FIG.  5    is a perspective view illustrating the mother block obtained by stacking the first to third mother sheets illustrated in  FIG.  4   ; 
         FIG.  6    is a perspective view illustrating a state in which first grooves are formed on the mother block illustrated in  FIG.  5   ; 
         FIG.  7    is a perspective view illustrating a state in which the mother block illustrated in  FIG.  6    is divided along x-direction division planes; 
         FIG.  8    is a perspective view illustrating a state in which the mother block illustrated in  FIG.  7    is further divided along y-direction division planes; 
         FIG.  9    is a partially enlarged sectional view of the mother block illustrated in  FIG.  7    taken along line VIII-VIII in  FIG.  7   ; 
         FIG.  10    is a perspective view illustrating an external appearance of a wire-wound core according to a second embodiment of this disclosure with a face to be oriented toward a mount board facing upward; 
         FIG.  11    describes a step of manufacturing the wire-wound core illustrated in  FIG.  10    and is a perspective view illustrating a state in which second grooves as well as the first grooves are formed on the mother block illustrated in  FIG.  6   ; 
         FIG.  12    is a perspective view illustrating an external appearance of a wire-wound core according to a third embodiment of this disclosure with a face to be oriented toward a mount board facing upward; 
         FIG.  13    describes a step of manufacturing the wire-wound core illustrated in  FIG.  12    and is a diagram corresponding to  FIG.  4   ; 
         FIG.  14    is a perspective view illustrating an external appearance of a wire-wound core according to a fourth embodiment of this disclosure with a face to be oriented toward a mount board facing upward; 
         FIG.  15    is a perspective view illustrating a state in which through-holes are formed in an unprocessed mother sheet prepared for fabrication of the wire-wound core illustrated in  FIG.  14   ; 
         FIG.  16    is a perspective view illustrating a second mother sheet in which first conductors are disposed in respective first through-holes corresponding to the through-holes illustrated in  FIG.  15   ; 
         FIG.  17    is a perspective view illustrating a third mother sheet corresponding to the second mother sheet illustrated in  FIG.  16    on which conductor films are disposed; 
         FIG.  18    is a perspective view illustrating an external appearance of a wire-wound core according to a fifth embodiment of this disclosure with a face to be oriented toward a mount board facing upward; 
         FIG.  19    is a plan view illustrating a portion of a mother block created to fabricate the wire-wound core illustrated in  FIG.  18   ; 
         FIG.  20    is a perspective view illustrating an external appearance of a wire-wound core according to a sixth embodiment of this disclosure with a face to be oriented toward a mount board facing upward; 
         FIGS.  21 A and  21 B  are partially enlarged views of the wire-wound core illustrated in  FIG.  20   , specifically,  FIG.  21 A  is a sectional view taken along line A-A in  FIG.  20   , and  FIG.  21 B  is a sectional view taken along line B-B in  FIG.  20   ; 
         FIGS.  22 A and  22 B  are plan views illustrating portions of two types of the second mother sheets prepared for fabrication of the wire-wound core illustrated in  FIG.  20   , specifically,  FIG.  22 A  illustrates the second mother sheet that provides a section taken along line C-C in  FIG.  21 A , and  FIG.  22 B  illustrates the second mother sheet that provides a section taken along line D-D in  FIG.  21 B ; 
         FIG.  23    is an equivalent circuit diagram of a π filter that can be implemented using the wire-wound core illustrated in  FIG.  20   ; 
         FIG.  24    is an equivalent circuit diagram of a T filter that can be implemented using a modification of the wire-wound core illustrated in  FIG.  20   ; and 
         FIG.  25    is an equivalent circuit diagram of an L filter that can be implemented using another modification of the wire-wound core illustrated in  FIG.  20   . 
     
    
    
     DETAILED DESCRIPTION 
     First Embodiment 
     A wire-wound-equipped electronic component  2  including a wire-wound core  1  according to a first embodiment of this disclosure will be described first with reference to  FIG.  1   .  FIG.  1    illustrates the wire-wound-equipped electronic component  2  with a bottom surface thereof to be oriented toward a mount board facing upward. The wire-wound-equipped electronic component  2  illustrated in  FIG.  1    constitutes a coil component having a single coil, for example. 
     The wire-wound core  1  included in the wire-wound-equipped electronic component  2  includes a core portion  4  where a wound wire  3  is disposed, a first flange portion  5 , a second flange portion  6 , a first terminal electrode  17 , and a second terminal electrode  18 . The core portion  4  has a longitudinal direction. The first flange portion  5  and the second flange portion  6  are respectively located at a first end portion and a second end portion that are opposite to each other in the longitudinal direction of the core portion  4 . 
     The wire-wound core  1  is formed of a non-conductive material, more specifically, a non-magnetic material such as alumina, a magnetic material such as ferrite, glass, or a resin. The wire-wound core  1  is preferably formed of a ceramic material such as alumina or ferrite or of glass in the case where the wire-wound core  1  is fabricated using a manufacturing method described later. 
     A section of each of the core portion  4 , the first flange portion  5 , and the second flange portion  6  taken along a plane that is perpendicular to the longitudinal direction of the core portion  4  has a substantially quadrangular shape. Thus, when a face to be oriented toward a mount board M when the wire-wound core  1  is mounted is defined as a bottom surface, the core portion  4  includes a core-portion bottom surface  7  which is the bottom surface of the core portion  4 , a core-portion top surface  8  which is the top surface located on the side opposite to the core-portion bottom surface  7 , a first core-portion lateral surface  9 , and a second core-portion lateral surface  10 . The first core-portion lateral surface  9  and the second core-portion lateral surface  10  are lateral surfaces linking the core-portion bottom surface  7  and the core-portion top surface  8 , and extend in the linking direction and face opposite lateral directions. 
     In each of the first flange portion  5  and the second flange portion  6 , a face that is located on a side opposite to the core portion  4  side and that faces outward is defined as an outer end surface  16 . More specifically, each of the first flange portion  5  and the second flange portion  6  includes a flange-portion bottom surface  11 , a flange-portion top surface  12 , a first flange-portion lateral surface  13 , a second flange-portion lateral surface  14 , an inner end surface  15 , and the outer end surface  16 . The flange-portion bottom surface  11  is oriented toward the mount board M as a bottom surface when the wire-wound core  1  is mounted and is located closer to the mount board M than the core-portion bottom surface  7 . The flange-portion top surface  12  is a top surface located on a side opposite to the flange-portion bottom surface  11 . The first flange-portion lateral surface  13  and the second flange-portion lateral surface  14  extend as lateral surfaces in a direction perpendicular to the mount board M, link the flange-portion bottom surface  11  and the flange-portion top surface  12  to each other, and face opposite lateral directions. The inner end surface  15  is one of end portions of the core portion  4  that faces the core portion  4 . The outer end surface  16  faces outward opposite to the inner end surface  15 . The outer end surface  16  has a recessed portion  21  that reaches the flange-portion bottom surface  11 . 
     Although not illustrated, ridge portions and corner portions on the external shape of the wire-wound core  1  are preferably R-chamfered. Thus, the aforementioned quadrangular shapes of the sections of the core portion  4 , the first flange portion  5 , and the second flange portion  6  include such R-chamfered shapes, C-chamfered shapes, and shapes having a slightly uneven surface or a curved surface. 
     The first flange portion  5  and the second flange portion  6  respectively have the first terminal electrode  17  and the second terminal electrode  18 . Each of the first terminal electrode  17  and the second terminal electrode  18  includes a bottom surface electrode portion  19  formed along the flange-portion bottom surface  11  and an end surface electrode portion  20  formed along the outer end surface  16 . The bottom surface electrode portion  19  is formed of a film conductor extending along the flange-portion bottom surface  11 . The end surface electrode portion  20  is formed of a conductor that fills the recessed portion  21  and is in contact with the bottom surface electrode portion  19 . 
     Although not illustrated in  FIG.  1   , the end surface electrode portion  20  formed along the outer end surface  16  of the first flange portion  5  has substantially the same shape as the end surface electrode portion  20  formed along the outer end surface  16  of the second flange portion  6 . The first terminal electrode  17  and the second terminal electrode  18  are formed of a conductor that contains a metal such as silver, gold, copper, or nickel as a conductive component, for example. 
     The wound wire  3  is formed of a copper wire coated with a resin insulator of polyurethane or polyimide, for example. The wound wire  3  is helically wound around the core portion  4 . A first end  3   a  of the wound wire  3  is connected to the first terminal electrode  17 , and a second end  3   b  opposite to the first end  3   a  of the wound wire  3  is connected to the second terminal electrode  18 . For example, heat-pressure crimping is used to connect the wound wire  3  to the first terminal electrode  17  and the second terminal electrode  18 . 
     As described above, the flange-portion bottom surface  11  is located closer to the mount board M than the core-portion bottom surface  7 . In other words, the flange-portion bottom surface  11  is located at a higher position than the core-portion bottom surface  7 . Thus, the wound wire  3  is successfully configured not to protrude to outside of the first flange portion  5  and the second flange portion  6  on the mount board M side. Thus, the wound wire  3  is successfully protected from stress applied from the mount board M side. In addition, a predetermined distance or more can be provided between the wound wire  3  and solder applied to the first terminal electrode  17  and the second terminal electrode  18  when the wire-wound core  1  is mounted. Consequently, an undesirable influence of adhesion of the solder to the wound wire  3  on the wound wire  3  is successfully avoided. 
     A manufacturing method of the wire-wound core  1  illustrated in  FIG.  1    will be described next with reference to  FIGS.  2  to  9   . 
     First, as illustrated in  FIG.  2   , an unfired mother sheet  25  is prepared, which is obtained by shaping a slurry containing a non-conductive material, for example, a ceramic material such as alumina or ferrite, into a sheet. At this stage, the mother sheet  25  is not processed at all. 
     Then, as illustrated in  FIG.  3   , through-holes  26  are formed at portions of the mother sheet  25 . The through-holes  26  provide the recessed portions  21  in which respective conductors serving as the end surface electrode portions  20  of the first terminal electrode  17  and the second terminal electrode  18  described above are disposed. The plurality of through-holes  26  are arranged to form rows and columns in a plane direction of the mother sheet  25 . The through-holes  26  have, for example, a shape of quadrangular openings and are formed by using die-cut processing or laser processing on the mother sheet  25 . 
     Then, a step of stacking the mother sheets is performed.  FIG.  4    illustrates, in a stacking order, first mother sheets  25   a , second mother sheets  25   b , and a third mother sheet  25   c  that are stacked to obtain a mother block  27  illustrated in  FIG.  5   . 
     Referring to  FIG.  4   , each of the first mother sheets  25   a  is the mother sheet  25  illustrated in  FIG.  2   . The first mother sheets  25   a  have no through-holes  26 . A predetermined number of first mother sheets  25   a  are consecutively stacked. 
     A plurality of first through-holes  26   a  are formed in each of the second mother sheets  25   b  that are stacked on the first mother sheets  25   a . First conductors  28   a  are disposed in the respective first through-holes  26   a . For example, the first conductor  28   a  is formed of a conductive paste with which each of the first through-holes  26   a  is filled by printing. For example, a conductive paste containing a metal, such as silver, gold, copper, or nickel as a conductive component is used as the conductive paste. The conductive paste having substantially the same composition is used as each conductive paste to be recited in the following description. 
     Each of the second mother sheets  25   b  is created using the mother sheet  25  illustrated in  FIG.  3   . The through-holes  26  of the mother sheet  25  illustrated in  FIG.  3    are used as the first through-holes  26   a  of the second mother sheet  25   b . The first through-holes  26   a  serve as the respective recessed portions  21  that define the respective end surface electrode portions  20  of the first terminal electrode  17  and the second terminal electrode  18 . The first conductors  28   a  serve as the respective end surface electrode portions  20 . A predetermined number of second mother sheets  25   b  are consecutively stacked. 
     Note that the first through-holes  26   a  of the second mother sheets  25   b  may be formed collectively in the plurality of mother sheets  25  after the plurality of mother sheets  25  illustrated in  FIG.  2    are stacked together. In addition, the plurality of first through-holes  26   a  that are regularly arranged in the plurality of second mother sheets  25   b  that are stacked together may be collectively filled with the conductive paste that serves as the first conductors  28   a.    
     The third mother sheet  25   c  is stacked on the second mother sheets  25   b  with a first principal surface  29  of the third mother sheet  25   c  being oriented outward. The third mother sheet  25  has a plurality of conductor films  30  formed in a strip pattern on the first principal surface  29 . The third mother sheet  25   c  is equivalent to the second mother sheet  25   b  that has the conductor films  30  on the bottom surface side and that is to be located on the bottommost side. That is, second through-holes  26   b  are formed in the third mother sheet  25   c  as illustrated by removing a portion of the conductor film  30  located on the right end in  FIG.  4    and second conductors  28   b  are disposed in the respective second through-holes  26   b.    
     For example, the second conductors  28   b  are formed of a conductive paste with which the respective second through-holes  26   b  are filled by printing just like the first conductors  28   a . In addition, the conductor films  30  are formed by printing a conductive paste, for example. Note that filling of the second through-holes  26   b  with the conductive paste serving as the second conductors  28   b  is preferably performed simultaneously with printing of the conductive paste forming the conductor films  30 . 
     Through the above-described stacking step, the mother block  27  illustrated in FIG.  5  is created. The mother block  27  is pressed in the stacking direction if necessary. 
     Then, as illustrated in  FIG.  6   , a step of forming a plurality of first grooves  31  on the mother block  27  from the second mother sheet  25   b  side, that is, from the first principal surface  29  side of the third mother sheet  25   c , is performed to form faces that serve as the core-portion bottom surfaces  7  (see  FIG.  1   ) of the core portions  4  in the mother block  27 . The first grooves  31  are formed in respective regions between the plurality of conductor films  30  formed in a stripe pattern. The first grooves  31  are formed by cutting processing using a dicer, for example. The diameter of the core portions  4  is appropriately changeable by changing the depth of the first grooves  31 . This can contribute to an improvement in the preciseness of the dimensions of the core portion  4 . 
     Then, as illustrated in  FIGS.  7  and  8   , the mother block  27  is divided along a plurality of x-direction division planes  32  and a plurality of y-direction division planes  33  that are perpendicular to the bottom surface of the mother block  27  to locate the plurality of first through-holes  26   a  on the respective outer end surface  16  sides and to obtain the plurality of wire-wound cores  1 . In this embodiment, the mother block  27  is divided along the x-direction division planes  32  first as illustrated in  FIG.  7   . Then, the mother block  27  is divided along the y-direction division planes  33  as illustrated in  FIG.  8   . As indicated by this step, locating the first through-holes  26   a  on the respective outer end surface  16  sides refers to dividing the mother block  27  so that each of the first through-holes  26   a  is located at the outer end of the resultant second mother sheets  25   b  regardless of the presence or absence of the first conductor  28   a.    
     As a result of the above-described division along the x-direction division planes  32  and the y-direction division planes  33 , the conductor films  30  are divided. Consequently, the conductor films  30  become the bottom surface electrode portions  19  of the first terminal electrode  17  and the second terminal electrode  18  of the individual wire-wound cores  1 .  FIG.  9   , which is a sectional view taken along line VIII-VIII in  FIG.  7   , illustrates how the conductor films  30  are divided as a result of division along the y-direction division planes  33 . 
     In addition,  FIG.  9    illustrates how the first conductors  28   a  and the second conductor  28   b  respectively in the first through-holes  26   a  and the second through-hole  26   b  are divided as a result of division along the y-direction division planes  33 . As a result of this division, the first conductors  28   a  and the second conductor  28   b  become the end surface electrode portions  20  of the first terminal electrode  17  and the second terminal electrode  18  of each wire-wound core  1 . 
     The bottom surface electrode portions  19  and the end surface electrode portions  20  of the first terminal electrode  17  and the second terminal electrode  18  of each wire-wound core  1  are formed by the division described above. In such a case, when a width direction denotes a direction in which the first flange-portion lateral surface  13  and the second flange-portion lateral surface  14  face each other, each of the bottom surface electrode portions  19  is disposed all over the width direction of the flange-portion bottom surface  11  and reaches the first flange-portion lateral surface  13  and the second flange-portion lateral surface  14  as illustrated in  FIG.  1   . In addition, each of the end surface electrode portions  20  is disposed at a central portion excluding both end portions of the corresponding outer end surface  16  in the width direction and is located on the inner side of the first flange-portion lateral surface  13  and the second flange-portion lateral surface  14  as illustrated in  FIG.  1   . Note that the width direction is a direction that is perpendicular to the longitudinal direction of the core portion  4  and is parallel to the bottom surface to be oriented toward the mount board M when the wire-wound core  1  is mounted. 
     Note that either the division along the x-direction division planes  32  or the division along the y-axis direction division planes  33  may be performed first. 
     The wire-wound core  1  obtained in the above-described manner is fired. Consequently, the unfired mother sheets  25   a  to  25   c  containing a ceramic material such as alumina or ferrite are sintered, and the first terminal electrode  17  and the second terminal electrode  18  formed of the conductive paste are also sintered. Although the mother block  27  is divided usually by cutting, another method may be used in which grooves for fold-cutting are formed in advance and the mother block  27  is cut by folding along the grooves after being fired. 
     The wire-wound core  1  has following structural characteristics as a result of the manufacturing method described above. 
     First, both the outer end surface  16  of the first flange portion  5  and an outside-facing face (face that is exposed from the outer end surface  16 ) of the end surface electrode portion  20  of the first terminal electrode  17  are flat surfaces and are flush with each other. In addition, both the outer end surface  16  of the second flange portion  6  and an outside-facing face (face that is exposed from the outer end surface  16 ) of the end surface electrode portion  20  of the second terminal electrode  18  are flat surfaces and are flush with each other. This is because both the outer end surface  16  and the face of the end surface electrode portion  20  exposed from the outer end surface  16  are faces that appear as a result of division of the mother block  27  along the corresponding y-direction division plane  33  as is apparent from  FIG.  9   . 
     Note that plating such as Ni-plating or Sn-plating is applied to the first terminal electrode  17  and the second terminal electrode  18  if necessary. When such plating is applied, the faces of the end surface electrode portions  20  of the first terminal electrode  17  and the second terminal electrode  18  that are exposed from the outer end surfaces  16  protrude relative to the respective outer end surfaces  16  of the first flange portion  5  and the second flange portion  6  because of the presence of the plating film. Thus, when plating is applied, the state in which the outer end surface  16  and the outside-facing face of the end surface electrode portion  20  are flush with each other indicates that the outer end surface  16  and the face of the end surface electrode portion  20  exposed from the outer end surface  16  are flush with each other when they are compared with each other without the plating film. 
     In addition, the end portion of the recessed portion  21  on the flange-portion top surface  12  side is a flat surface parallel to the flange-portion top surface  12 . This is because the bottom surface that defines the first through-hole  26   a  located at the end portion of the recessed portion  21  on the flange-portion top surface  12  side is provided by a flat principal surface of the first mother sheet  25   a  as is apparent from  FIG.  4   . 
     The first to third mother sheets  25   a  to  25   c  are formed of a slurry containing ceramic power such as alumina or ferrite in the first embodiment described above. Instead of this configuration, the first to third mother sheets  25   a  to  25   c  may be formed of a slurry containing glass power having a lower dielectric constant and the wire-wound core  1  formed of glass may be obtained by heating the first to third mother sheets  25   a  to  25   c . With this configuration, a distributed capacitance of the wire-wound core  1  can be reduced, and high-frequency characteristics of the wire-wound-equipped electronic component  2  illustrated in  FIG.  1    that serves as an inductor can be improved. 
     Second Embodiment 
     A wire-wound core  1   a  according to a second embodiment of this disclosure will be described next with reference to  FIG.  10   . In  FIG.  10    and the subsequent figures, components equivalent to those illustrated in  FIGS.  1  to  9    are denoted by the same or substantially the same reference signs to omit a duplicate description. 
     In the first embodiment described above, the core-portion top surface  8  of the wire-wound core  1  and the flange-portion top surfaces  12  are flush with each other. In contrast, in the second embodiment, the core-portion top surface  8  of the wire-wound core  1   a  is lower than the flange-portion top surfaces  12 . That is, the core-portion top surface  8  is located closer to the mount board M than the flange-portion top surfaces  12 . With such a configuration, the wound wire  3  (see  FIG.  1   ) is successfully configured not to protrude to outside of the first flange portion  5  and the second flange portion  6  on the core-portion top surface  8  side. Thus, the wound wire  3  is successfully protected from stress applied from the core-portion top surface  8  side. 
     The wire-wound core  1   a  according to the second embodiment can be fabricated by modifying part of the above-described manufacturing method of the wire-wound core  1  according to the first embodiment in the following manner. Specifically, as illustrated in  FIG.  11   , a step of forming second grooves  34  on the mother block  27  from a top surface side opposite to the first principal surface  29  side of the third mother sheet  25   c  (see  FIG.  4   ) is further performed to expose a face that serves as the core-portion top surface  8  in the mother block  27 . Briefly, as illustrated in  FIG.  11   , the second grooves  34  as well as the first grooves  31  are formed on the mother block  27  illustrated in  FIG.  6   . 
     Note that either the first grooves  31  or the second grooves  34  may be formed first. In addition, the first grooves  31  and the second grooves  34  may have the same or substantially the same depth or different depths. 
     The core-portion top surface  8  of the resultant wire-wound core  1   a  is provided by the bottom surface of the second groove  34 . Thus, the diameter of the core portion  4  is appropriately changeable by changing not only the depth of the first groove  31  but also the depth of the second groove  34 . This can contribute to an improvement in the preciseness of the dimensions of the core portion  4 . 
     Third Embodiment 
     A wire-wound core  1   b  according to a third embodiment of this disclosure will be described next with reference to  FIG.  12   . 
     In the third embodiment, the core-portion top surface  8  of the wire-wound core  1   b  is lower than the flange-portion top surfaces  12  as in the second embodiment described above. With this configuration, the wound wire  3  (see  FIG.  1   ) is successfully configured not to protrude to outside of the first flange portion  5  and the second flange portion  6  on the core-portion top surface  8  side. 
     In the second embodiment described above, the first core-portion lateral surface  9  of the wire-wound core  1   a  is flush with the first flange-portion lateral surfaces  13  and the second core-portion lateral surface  10  of the wire-wound core  1   a  is flush with the second flange-portion lateral surfaces  14 . In contrast, in the third embodiment, the first core-portion lateral surface  9  and the second core-portion lateral surface  10  of the wire-wound core  1   b  are lower than the first flange-portion lateral surface  13  and the second flange-portion lateral surface  14 , respectively. In other words, in the third embodiment, the first core-portion lateral surface  9  and the second core-portion lateral surface  10  are closer to a central axis of the core portion  4  than the first flange-portion lateral surface  13  and the second flange-portion lateral surface  14 , respectively. Briefly, the first core-portion lateral surface  9  and the second core-portion lateral surface  10  are located on the inner side than the first flange-portion lateral surface  13  and the second flange-portion lateral surface  14 , respectively. With such a configuration, the wound wire  3  is successfully configured not to protrude to outside of the first flange portion  5  and the second flange portion  6  also on the first core-portion lateral surface  9  side and the second core-portion lateral surface  10  side. 
     Thus, according to the third embodiment, the wound wire  3  is successfully protected from stress applied from the core-portion top surface  8  side and stress applied from the first core-portion lateral surface  9  side and the second core-portion lateral surface  10  side. 
     To make the first core-portion lateral surface  9  and the second core-portion lateral surface  10  lower than the first flange-portion lateral surfaces  13  and the second flange-portion lateral surfaces  14 , respectively, third through-holes  35  are formed in all the first to third mother sheets  25   a  to  25   c  as illustrated in  FIG.  13    during fabrication of the wire-wound core  1   b  according to the third embodiment. The third through-holes  35  are located to stretch over the respective x-direction division planes  32  (see  FIG.  7   ). The third through-holes  35  may be formed in advance in the first to third mother sheets  25   a  to  25   c  before stacking, or may be collectively formed in all the first to third mother sheets  25   a  to  25   c  of the mother block  27  obtained by stacking the first to third mother sheets  25   a  to  25   c . The diameter of the core portion  4  is appropriately changeable by changing the shape and the dimensions of the third through-holes  35 . 
     In addition, the step illustrated in  FIG.  11    that is adopted in the second embodiment, specifically, the step of forming the second grooves  34  on the mother block  27  to expose a face that serves as the core-portion top surface  8  in the mother block  27  is also performed in the case of manufacturing the wire-wound core  1   b  according to the third embodiment. 
     The other steps are performed as in the first embodiment. 
     An embodiment in which the first core-portion lateral surface  9  and the second core-portion lateral surface  10  are lower than the first flange-portion lateral surfaces  13  and the second flange-portion lateral surfaces  14 , respectively, but the core-portion top surface  8  and the flange-portion top surfaces  12  are flush with each other may be conceivable as a modification of the third embodiment. 
     Fourth Embodiment 
     A wire-wound core  1   c  according to a fourth embodiment of this disclosure will be described next with reference to  FIG.  14   . 
     In the first to third embodiments described above, a single first terminal electrode  17  is disposed at the first flange portion  5  and a single second terminal electrode  18  is disposed at the second flange portion  6 . In contrast, in the fourth embodiment, two first terminal electrodes  17   a  and  17   b  are disposed at the first flange portion  5  in the width direction, and two second terminal electrodes  18   a  and  18   b  are disposed at the second flange portion  6  in the width direction. 
     Each of the first terminal electrodes  17   a  and  17   b  and the second terminal electrodes  18   a  and  18   b  includes the bottom surface electrode portion  19  formed of a film conductor that extends along the flange-portion bottom surface  11  and the end surface electrode portion  20  that is continuous to the bottom surface electrode portion  19  and is formed of a conductor filling the recessed portion  21  that is formed to reach the flange-portion bottom surface  11  on the outer end surface  16 . Note that the end surface electrode portion  20  that is continuous to the bottom surface electrode portion  19  may be integrated with the bottom surface electrode portion  19  or may be just in contact with the bottom surface electrode portion  19 . 
     The wire-wound core  1   c  according to the fourth embodiment is advantageously used in a wire-wound-equipped electronic component such as a coil component including two wound wires and four terminal electrodes, for example, a common-mode choke coil or a transformer. For example, in the case of a common-mode choke coil, two wires are wound around the core portion  4  in the same direction. A first end of a first wound wire, among the two wires, is connected to the first terminal electrode  17   a , and a second end of the first wound wire is connected to the second terminal electrode  18   a . In addition, a first end of a second wound wire, among the two wires, is connected to the first terminal electrode  17   b , and a second end of the second wound wire is connected to the second terminal electrode  18   b.    
     The wire-wound core  1   c  according to the fourth embodiment can be fabricated by changing part of the manufacturing method of the wire-wound core  1  according to the first embodiment described above in the following manner. 
     Specifically, a mother sheet  37  illustrated in  FIG.  15    is used in place of the mother sheet  25  having the through-holes  26  illustrated in  FIG.  3   .  FIG.  15    illustrates a portion of the mother sheet  37  in an enlarged manner. A plurality of through-holes  38  are formed in the mother sheet  37 . In  FIG.  15   , the x-direction division planes  32  and the y-direction division planes  33  are denoted by alternate long and short dashed lines. Two through-holes  38  are disposed in each region between the two adjacent x-direction division planes  32  along the corresponding y-direction division plane  33  to stretch over the corresponding y-direction division plane  33 . Each of the through-holes  38  provides the recessed portion  21  in which a conductor that serves as the end surface electrode portion  20  of a corresponding one of the first terminal electrodes  17   a  and  17   b  and the second terminal electrodes  18   a  and  18   b  is disposed. 
     In the fourth embodiment, second mother sheets  37   b  illustrated in  FIG.  16    and a third mother sheet  37   c  illustrated in  FIG.  17    are respectively used in place of the second mother sheets  25   b  and the third mother sheet  25   c  illustrated in  FIG.  4    in the first embodiment when the mother sheets  37  are stacked. Each of the second mother sheet  37   b  illustrated in  FIG.  16    and the third mother sheet  37   c  illustrated in  FIG.  17    is created using the mother sheet  37  illustrated in  FIG.  15   . 
     In the second mother sheet  37   b  illustrated in  FIG.  16   , the through-holes  38  of the mother sheet  37  illustrated in  FIG.  15    are used as first through-holes  38   a  and first conductors  39   a  are disposed in the respective first through-holes  38   a . For example, the first conductors  39   a  are formed of a conductive paste with which the first through-holes  38   a  are filled by printing. 
     The third mother sheet  37   c  illustrated in  FIG.  17    has a plurality of conductor films  41  on a first principal surface  40  thereof. In the third mother sheet  37   c  illustrated in  FIG.  17   , the through-holes  38  of the mother sheet  37  illustrated in  FIG.  15    are used as second through-holes  38   b  and second conductors  39   b  are disposed in the respective second through-holes  38   b  as illustrated by removing a portion of the conductor film  41  located on the right-lowermost side in  FIG.  17   . Each of the conductor films  41  is disposed at a position to cover the corresponding second conductor  39   b  disposed in the corresponding second through-hole  38   b.    
     For example, the second conductors  39   b  are formed of a conductive paste with which the second through-holes  38   b  are filled by printing, just like the first conductors  39   a . In addition, the conductor films  41  are formed by printing a conductive paste, for example. Note that filling of the second through-holes  38   b  with the conductive paste serving as the second conductors  39   b  is preferably performed simultaneously with printing of the conductive paste forming the conductor films  41 . 
     A mother block is obtained by using the second mother sheets  37   b  and the third mother sheet  37   c  described above in place of the second mother sheets  25   b  and the third mother sheet  25   c  illustrated in  FIG.  4   , respectively, and by stacking the first mother sheets  25   a , the second mother sheets  37   b , and the third mother sheet  37   c  together. Then, substantially the same steps as those of the first embodiment are performed. Consequently, the wire-wound core  1   c  illustrated in  FIG.  14    is obtained. 
     In the wire-wound core  1   c , the bottom surface electrode portions  19  of the first terminal electrodes  17   a  and  17   b  and the second terminal electrodes  18   a  and  18   b  are provided by division of the conductor films  41  described above. In addition, the end surface electrode portions  20  are provided by the first conductors  39   a  and the second conductors  39   b  filling the recessed portions  21 , which are obtained by cutting the first through-holes  38   a  and the second through-holes  38   b.    
     If a plurality of terminal electrodes disposed at a single flange portion are formed only by applying a conductive paste, a complex application process is needed because the terminal electrodes have a fine structure and a space between the terminal electrodes is narrow. However, when the method described above is used, a plurality of terminal electrodes can be easily formed even if the plurality of terminal electrodes have a fine structure and are arranged with a narrow space therebetween. 
     Fifth Embodiment 
     A wire-wound core  1   d  according to a fifth embodiment of this disclosure will be described next with reference to  FIG.  18   . 
     In the first to fourth embodiments described above, when a perpendicular bisector plane of the central axis extending in the longitudinal direction of the core portion  4  serves as a symmetry plane, the first terminal electrode  17  or the first terminal electrodes  17   a  and  17   b  disposed at the first flange portion  5  and the second terminal electrode  18  or the second terminal electrodes  18   a  and  18   b  disposed at the second flange portion  6  are symmetrical about the symmetry plane. In contrast, in the fifth embodiment, first terminal electrodes  17   c  and  17   d  disposed at the first flange portion  5  and second terminal electrodes  18   c ,  18   d , and  18   e  disposed at the second flange portion  6  are asymmetrical about the symmetry plane. 
     More specifically, in the fifth embodiment, the two first terminal electrodes  17   c  and  17   d  are disposed at the first flange portion  5  in the width direction, and the three second terminal electrodes  18   c ,  18   d , and  18   e  are disposed at the second flange portion  6  in the width direction. In addition, the first terminal electrode  17   d  disposed at the first flange portion  5  has a width-direction dimension larger than the first terminal electrode  17   c.    
     Since the wide terminal electrode  17   d  of the wire-wound core  1   d  according to the fifth embodiment successfully provides a sufficient area for connecting ends of two or more wires thereto, the wire-wound core  1   d  can advantageously constitute a coil component such as a pulse transformer including a center tap, for example. 
     The wire-wound core  1   d  according to the fifth embodiment can be fabricated by modifying part of the manufacturing method of the wire-wound core  1   c  according to the fourth embodiment described above in the following manner. 
       FIG.  19    is a plan view illustrating a portion of a mother block  43  created to fabricate the wire-wound core  1   d  according to the fifth embodiment. In  FIG.  19   , the x-direction division planes  32  and the y-direction division planes  33  are denoted by alternate long and short dash lines. On the first principal surface  40  of the third mother sheet  37   c  located on one end of the mother block  43  in the stacking direction, conductor films  41   a  and  41   b  that serve as the bottom surface electrode portions  19  of the first terminal electrodes  17   c  and  17   d  disposed at the first flange portion  5  and conductor films  41   c ,  41   d , and  41   e  that serve as the bottom surface electrode portions  19  of the second terminal electrodes  18   c ,  18   d , and  18   e  disposed at the second flange portion  6  are disposed along the respective y-direction division planes  33  to stretch over the respective y-direction division planes  33 . In  FIG.  19   , the through-holes  26  for the recessed portions  21  that define the end surface electrode portions  20  of the first terminal electrodes  17   c  and  17   d  and the through-hole  26  for the recessed portions  21  that define the end surface electrode portions  20  of the second terminal electrodes  18   c ,  18   d , and  18   e  disposed at the second flange portion  6  are denoted by dash lines. 
     As is apparent from  FIG.  19   , the number, the positions, dimensions, and/or shapes of conductor films for the bottom surface electrodes portions of the terminal electrodes can be modified variously from the configuration of the terminal electrodes by changing the number, positions, dimensions, and/or shapes of through-holes for the recessed portions that define the end surface electrode portions. 
     Sixth Embodiment 
     A wire-wound core  1   e  according to a sixth embodiment of this disclosure will be described next with reference to  FIG.  20   . 
     The wire-wound core  1   e  according to the sixth embodiment has substantially the same external appearance as the wire-wound core  1   c  according to the fourth embodiment illustrated in  FIG.  14   . Thus, the same or substantially the same reference signs as those denoting the components illustrated in  FIG.  14    are used in  FIG.  20   . 
     The wire-wound core  1   e  according to the sixth embodiment includes passive elements at the first flange portion  5  and the second flange portion  6 .  FIGS.  21 A and  21 B  are partially enlarged views of the wire-wound core  1   e . Specifically,  FIG.  21 A  is a sectional view taken along line A-A in  FIG.  20   , and  FIG.  21 B  is a sectional view taken along line B-B in  FIG.  20   . 
     In the sixth embodiment, the wire-wound core  1   e  includes capacitors as the passive elements. As illustrated in  FIGS.  21 A and  21 B , first capacitor electrodes  45  and  46  opposing each other are disposed at the first flange portion  5 , and second capacitor electrodes  47  and  48  opposing each other are disposed at the second flange portion  6 . 
     The end surface electrode portions  20  of the first terminal electrodes  17   a  and  17   b  and the second terminal electrodes  18   a  and  18   b  also contribute to electrical connections of the first and second capacitor electrodes  45  to  48 . More specifically, the first capacitor electrodes  45  and  46  are electrically connected to the first terminal electrodes  17   a  and  17   b , respectively. The second capacitor electrodes  47  and  48  are electrically connected to the second terminal electrodes  18   a  and  18   b , respectively. Thus, electrostatic capacity due to the first capacitor electrodes  45  and  46  opposing each other is formed between the first terminal electrodes  17   a  and  17   b . Likewise, electrostatic capacity due to the second capacitor electrodes  47  and  48  opposing each other is formed between the second terminal electrodes  18   a  and  18   b.    
       FIGS.  22 A and  22 B  are plan views of portions of two kinds of second mother sheets  49   a  and  49   b  prepared for fabrication of the wire-wound core  1   e . Specifically,  FIG.  22 A  illustrates the second mother sheet  49   a  that provides a section taken along line C-C in  FIG.  21 A , and  FIG.  22 B  illustrates the second mother sheet  49   b  that provides a section taken along line D-D in  FIG.  21 B . 
     In  FIGS.  22 A and  22 B , the x-direction division planes  32  and the y-direction division planes  33  are denoted by alternate long and short dashed lines. The portion illustrated in  FIGS.  22 A and  22 B  will be described. Pattern conductors  51  and  52  that respectively serve as the first capacitor electrode  45  and the second capacitor electrode  47  when the second mother sheet  49   a  is divided at the y-direction division planes  33  are disposed on the second mother sheet  49   a  illustrated in  FIG.  22 A . Pattern conductors  53  and  54  that respectively serve as the first capacitor electrode  46  and the second capacitor electrode  48  when the second mother sheet  49   b  is divided at the y-direction division planes  33  are disposed on the second mother sheet  49   b  illustrated in  FIG.  22 B . 
     As illustrated in  FIG.  22 A , the pattern conductor  51  is connected to the conductor  39   a  that provides the end surface electrode portion  20  of the first terminal electrode  17   a , and the pattern conductor  52  is connected to the conductor  39   a  that provides the end surface electrode portions  20  of the first terminal electrode  17   a  and the second terminal electrode  18   a . As illustrated in  FIG.  22 B , the pattern conductor  53  is connected to the conductor  39   a  that provides the end surface electrode portion  20  of the first terminal electrode  17   b , and the pattern conductor  54  is connected to the conductor  39   a  that provides the end surface electrode portions  20  of the first terminal electrode  17   b  and the second terminal electrode  18   b.    
     Thus, the wire-wound core  1   e  according to the sixth embodiment can be obtained by replacing at least some of the second mother sheets  37   b  with the second mother sheets  49   a  and  49   b  in the manufacturing method of the wire-wound core  1   c  according to the fourth embodiment described above. 
     The wire-wound core  1   e  according to the sixth embodiment can constitute a filter having a good noise removal effect, such as a π filter  55  whose equivalent circuit is illustrated in  FIG.  23   . 
     To obtain the π filter  55  illustrated in  FIG.  23   , the wound wire disposed at the core portion  4  of the wire-wound core  1   e  implements an inductor L 1 , a first end of the wound wire is connected to the first terminal electrode  17   a , and a second end of the wound wire is connected to the second terminal electrode  18   a . Consequently, the π filter  55  is obtained in which the inductor L 1  is connected between the first terminal electrode  17   a  and the second terminal electrode  18   a , a capacitor C 1  is connected between the first terminal electrodes  17   a  and  17   b , and a capacitor C 2  is connected between the second terminal electrodes  18   a  and  18   b  as illustrated in  FIG.  23   . 
     In addition, if the wire-wound core  1   e  according to the sixth embodiment is slightly modified, filters such as a T filter  56  and an L filter  57  whose equivalent circuits are respectively illustrated in  FIGS.  24  and  25    can be obtained. 
     To obtain the T filter  56  illustrated in  FIG.  24   , one set of capacitor electrodes, for example, the first capacitor electrodes  45  and  46  of the wire-wound core  1   e  is omitted. Two wound wires are disposed at the core portion  4 . A first end of a first wound wire, among the two wound wires, is connected to the first terminal electrode  17   a , and a second end of the first wound wire is connected to the second terminal electrode  18   a . A first end of a second wound wire, among the two wound wires, is connected to the first terminal electrode  17   b , and a second end of the second wound wire is connected to the second terminal electrode  18   a . Consequently, the T filter  56  is obtained in which an inductor L 2  is connected between the first terminal electrode  17   a  and the second terminal electrode  18   a , an inductor L 3  is connected between the first terminal electrode  17   b  and the second terminal electrode  18   a , and a capacitor C 3  is connected between the second terminal electrodes  18   a  and  18   b.    
     To obtain the L filter  57  illustrated in  FIG.  25   , one set of capacitor electrodes, for example, the first capacitor electrodes  45  and  46  of the wire-wound core  1   e  is omitted. In addition, for example, the first terminal electrode  17   b  may be omitted. The wound wire disposed at the core portion  4  implements an inductor L 4 , a first end of the wound wire is connected to the first terminal electrode  17   a , and a second end of the wound wire is connected to the second terminal electrode  18   a . Consequently, the L filter  57  is obtained in which the inductor L 4  is connected between the first terminal electrode  17   a  and the second terminal electrode  18   a  and a capacitor C 4  is connected between the second terminal electrodes  18   a  and  18   b.    
     In the wire-wound core  1   e  described above, the passive elements included in the wire-wound core  1   e  and connected between the two first terminal electrodes  17   a  and  17   b  disposed at the first flange portion  5  and between the two second terminal electrodes  18   a  and  18   b  disposed at the second flange portion  6  are capacitors. However, the passive elements may be elements having another function, for example, resistance elements. 
     OTHER EMBODIMENTS 
     While this disclosure has been described above in relation to the illustrated embodiments, various other embodiments are possible within the scope of this disclosure. 
     For example, as for the staking order of the mother sheets, instead of stacking the first mother sheets  25   a , the second mother sheets  25   b , and the third mother sheet  25   c  in this order from the bottom as illustrated in  FIG.  4   , the opposite stacking order may be adopted. 
     In addition, instead of using the method for staking a plurality of mother sheets formed in a sheet shape in advance as described above, a method for repeatedly performing printing to obtain a stacked state of a plurality of mother sheets may be used to create the mother block  27 . Specifically, a method may be used which includes forming first mother sheets by printing; forming, by printing, a stack of a predetermined number of second mother sheets in which the plurality of first through-holes are formed and the first conductors are disposed in the respective first through-holes; and forming, by printing, a third mother sheet in which the plurality of second through-holes are formed and the second conductors are disposed in the respective second through-holes and that have the first principal surface on which the conductor films are formed. In the method, the forming the first mother sheets, the forming the second mother sheets, and the forming the third mother sheet are performed on any of mother sheets already formed. 
     In addition, when the wire-wound core includes a plurality of terminal electrodes, not all the terminal electrodes need to have the characteristic configuration of this disclosure. In other words, there may be a terminal electrode not having the characteristic configuration of this disclosure. Thus, for example, only the terminal electrode disposed at one of the flange portions may have the characteristic configuration of this disclosure. 
     In addition, the film conductors that constitute the bottom surface electrode portions of the terminal electrodes are formed using a conductive paste in the embodiments described above. However, the conductors may be formed using another material, for example, a plating film or a metal leaf. 
     In addition, the conductors serving as the end surface electrode portions of the terminal electrodes are formed using a conductive paste in the embodiments described above. However, the conductors may be formed using another material, for example, a conductive metal piece filling the recessed portion. 
     While some of different embodiments have been described above, the configurations of the different embodiments may be partially replaced or combined to carry out this disclosure. 
     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.