Patent Publication Number: US-9406428-B2

Title: Inductor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of priority to Japanese Patent Application No. 2014-023055 filed Feb. 10, 2014, the entire content of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present technical field relates to inductors and in particular relates to an inductor that includes a magnetic material and a non-magnetic material. 
     BACKGROUND 
     The multilayer inductor described in Japanese Unexamined Patent Application Publication No. 2007-317892 is a known example of an inductor of the related art. In this type of inductor (hereafter referred to as inductor of the related art), a coil is built into a multilayer body formed by stacking a plurality of insulator layers on top of one another. The coil is formed of a plurality of coil conductors and via conductors and has a substantially helical shape. When a current flows through the inductor of the related art, lines of magnetic force are concentrated around corners of the coil conductors located in end portions of the coil and magnetic saturation is liable to occur. As a result, a problem occurs in that the alternating current resistance is high. 
     SUMMARY 
     Accordingly, an object of the present disclosure is to provide an inductor that includes a magnetic material and a non-magnetic material and that is capable of suppressing an increase in alternating current resistance. 
     An inductor according to an embodiment of the present disclosure includes a body composed of a non-magnetic material and a magnetic material; and a helical-shaped coil located inside the body; an inner circumferential surface of the coil being covered by the non-magnetic material. In an orthogonal direction that is orthogonal to a central axis direction, which is a direction in which a central axis of the coil extends, and that is orthogonal to an advancement direction of a conductor that forms the coil, a sum of a width of the conductor and a width of the non-magnetic material covering an inner circumferential side of the conductor in a center portion of the coil in the central axis direction is larger than a sum of a width of the conductor and a width of the non-magnetic material covering an inner circumferential side of the conductor in an end portion of the coil on one side in the central axis direction. 
     In the inductor according to the embodiment of the present disclosure, the sum of the width of the conductor and the width of the non-magnetic material covering the inner circumferential side of the conductor that are located in the center portion of the coil is larger than the sum of the width of the conductor and the non-magnetic material covering the inner circumferential side of the conductor that are located in the end portion of the coil. Thus, the interval between the lines of magnetic force passing through the end portion of the coil is widened in a width direction of the conductor. Thus, concentration of the lines of magnetic force around corners of the conductor located in end portions of the coil can be suppressed and magnetic saturation can be more effectively suppressed. As a result, with the inductor according to an embodiment of the present disclosure, an increase in the alternating current resistance in an inductor including a magnetic material and a non-magnetic material can be suppressed. 
     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 of the exterior of an inductor according to an embodiment. 
         FIG. 2  is an exploded perspective view of a state where the inductor according to the embodiment has been divided into layers on which there are coil conductors and layers on which there are no coil conductors. 
         FIG. 3  is a sectional view taken along section  3 - 3  in  FIG. 1 . 
         FIG. 4  is a sectional view of the inductor during its manufacture. 
         FIG. 5  is a sectional view of the inductor during its manufacture. 
         FIG. 6  is a sectional view of the inductor during its manufacture. 
         FIG. 7  is a sectional view of the inductor during its manufacture. 
         FIG. 8  is a sectional view of the inductor during its manufacture. 
         FIG. 9  is a sectional view of the inductor during its manufacture. 
         FIG. 10  is a diagram obtained by adding lines of magnetic force to a sectional view of an inductor of the related art. 
         FIG. 11  is a diagram obtained by adding lines of magnetic force to a sectional view of the inductor according to the embodiment. 
         FIG. 12  is a sectional view of an inductor according to a first modification. 
         FIG. 13  is a sectional view of an inductor according to a second modification. 
         FIG. 14  is a sectional view of an inductor according to a third modification. 
         FIG. 15  is an exploded perspective view of an inductor according to a fourth modification. 
         FIG. 16  is a sectional view of an inductor according to a comparative example. 
     
    
    
     DETAILED DESCRIPTION 
     Hereafter, an inductor according to an embodiment and a manufacturing method of the inductor will be described. 
     Outline Configuration of Inductor 
     Hereafter, an outline configuration of the inductor according to the embodiment will be described while referring to  FIG. 1 . A stacking direction of an inductor  10  is defined as a z-axis direction, and a direction that extends along the long edges of the inductor and a direction that extends along the short edges when viewed in plan from the z-axis direction are respectively defined as an x-axis direction and a y-axis direction. In addition, a surface that is located on the positive side in the z-axis direction is referred to as an upper surface and a surface that is located on the negative side in the z-axis direction is referred to as a lower surface. The x axis, the y axis and the z axis are orthogonal to one another. 
     The inductor  10  includes a multilayer body (body)  20 , a coil  30  and outer electrodes  40   a  and  40   b . In addition, the inductor  10  has a substantially rectangular parallelepiped shape as illustrated in  FIG. 1 . 
     Configuration of Multilayer Body 
     The configuration of the multilayer body  20  will be described with reference to  FIG. 2 . The multilayer body  20  is formed by stacking insulator layers  22   a  to  22   k  on top of one another in order from the positive side in the z-axis direction. In addition, each of the insulator layers  22   a  to  22   k  has a substantially rectangular shape when viewed in plan from the z-axis direction. Examples of a material of the insulator layers  22   a  to  22   k  include magnetic materials (such as a magnetic-powder-containing resin) and non-magnetic materials (such as glass, alumina and composite materials thereof). 
     The insulator layer  22   a  is located in an end portion of the multilayer body  20  on the positive side in the z-axis direction as illustrated in  FIG. 2 . In addition, the insulator layer  22   a  is formed of a magnetic material. 
     The insulator layer  22   b  is located below the insulator layer  22   a . In addition, the insulator layer  22   b  is formed of a magnetic material layer  24   b  composed of a magnetic material and a non-magnetic material layer  26   b  composed of a non-magnetic material. The non-magnetic material layer  26   b  is a substantially band-shaped non-magnetic material layer provided parallel to an outer edge of the insulator layer  22   b  and has a substantially square annular shape when viewed in plan from the z-axis direction. In addition, when viewed in plan from the z-axis direction, the magnetic material layer  24   b  is provided around the periphery of the non-magnetic material layer  26   b  with a coil conductor  32   b , which will be described later, interposed therebetween and is also provided inside the substantially square annular shape of the non-magnetic material layer  26   b.    
     The insulator layer  22   c  is located below the insulator layer  22   b . In addition, the insulator layer  22   c  is formed of a magnetic material layer  24   c  composed of a magnetic material and a non-magnetic material layer  26   c  composed of a non-magnetic material. The non-magnetic material layer  26   c  is a substantially band-shaped non-magnetic material layer provided parallel to an outer edge of the insulator layer  22   c  and has a substantially square annular shape when viewed in plan from the z-axis direction. The magnetic material layer  24   c  is provided around the periphery of the non-magnetic material layer  26   c  and inside the substantially square annular shape of the non-magnetic material layer  26   c  when viewed in plan from the z-axis direction. 
     The insulator layer  22   d  is located below the insulator layer  22   c . In addition, the insulator layer  22   d  is formed of a magnetic material layer  24   d  composed of a magnetic material and a non-magnetic material layer  26   d  composed of a non-magnetic material. The non-magnetic material layer  26   d  is a substantially band-shaped non-magnetic material layer provided parallel to an outer edge of the insulator layer  22   d  and has a substantially square annular shape when viewed in plan from the z-axis direction. In addition, when viewed in plan from the z-axis direction, the magnetic material layer  24   d  is provided around the periphery of the non-magnetic material layer  26   d  with a coil conductor  32   d , which will be described later, interposed therebetween and is also provided inside the substantially square annular shape of the non-magnetic material layer  26   d.    
     The insulator layer  22   e  is located below the insulator layer  22   d . In addition, the insulator layer  22   e  is formed of a magnetic material layer  24   e  composed of a magnetic material and a non-magnetic material layer  26   e  composed of a non-magnetic material. The non-magnetic material layer  26   e  is a substantially band-shaped non-magnetic material layer provided parallel to an outer edge of the insulator layer  22   e  and has a substantially square annular shape when viewed in plan from the z-axis direction. The magnetic material layer  24   e  is provided around the periphery of the non-magnetic material layer  26   e  and inside the substantially square annular shape of the non-magnetic material layer  26   e  when viewed in plan from the z-axis direction. 
     The insulator layer  22   f  is located below the insulator layer  22   e . In addition, the insulator layer  22   f  is formed of a magnetic material layer  24   f  composed of a magnetic material and a non-magnetic material layer  26   f  composed of a non-magnetic material. The non-magnetic material layer  26   f  is a substantially band-shaped non-magnetic material layer provided parallel to an outer edge of the insulator layer  22   f  and has a substantially square annular shape when viewed in plan from the z-axis direction. In addition, when viewed in plan from the z-axis direction, the magnetic material layer  24   f  is provided around the periphery of the non-magnetic material layer  26   f  with a coil conductor  32   f , which will be described later, interposed therebetween and is also provided inside the substantially square annular shape of the non-magnetic material layer  26   f.    
     The insulator layer  22   g  is located below the insulator layer  22   f . In addition, the insulator layer  22   g  is formed of a magnetic material layer  24   g  composed of a magnetic material and a non-magnetic material layer  26   g  composed of a non-magnetic material. The non-magnetic material layer  26   g  is a substantially band-shaped non-magnetic material layer provided parallel to an outer edge of the insulator layer  22   g  and has a substantially square annular shape when viewed in plan from the z-axis direction. The magnetic material layer  24   g  is provided around the periphery of the non-magnetic material layer  26   g  and inside the substantially square annular shape of the non-magnetic material layer  26   g  when viewed in plan from the z-axis direction. 
     The insulator layer  22   h  is located below the insulator layer  22   g . In addition, the insulator layer  22   h  is formed of a magnetic material layer  24   h  composed of a magnetic material and a non-magnetic material layer  26   h  composed of a non-magnetic material. The non-magnetic material layer  26   h  is a substantially band-shaped non-magnetic material layer provided parallel to an outer edge of the insulator layer  22   h  and has a substantially square annular shape when viewed in plan from the z-axis direction. In addition, when viewed in plan from the z-axis direction, the magnetic material layer  24   h  is provided around the periphery of the non-magnetic material layer  26   h  with a coil conductor  32   h , which will be described later, interposed therebetween and is also provided inside the substantially square annular shape of the non-magnetic material layer  26   h.    
     The insulator layer  22   i  is located below the insulator layer  22   h . In addition, the insulator layer  22   i  is formed of a magnetic material layer  24   i  composed of a magnetic material and a non-magnetic material layer  26   i  composed of a non-magnetic material. The non-magnetic material layer  26   i  is a substantially band-shaped non-magnetic material layer provided parallel to outer edges of the insulator layer  22   i  on both the positive and negative sides in the x-axis direction and parallel to an outer edge of the insulator layer  22   i  on the negative side in the y-axis direction, and has a substantially backward C shape when viewed in plan from the z-axis direction. The magnetic material layer  24   i  is provided in portions of the insulator layer  22   i  other than portions where the non-magnetic material layer  26   i  is provided. 
     The insulator layer  22   j  is located below the insulator layer  22   i . In addition, the insulator layer  22   j  is formed of a magnetic material layer  24   j  composed of a magnetic material and a non-magnetic material layer  26   j  composed of a non-magnetic material. The non-magnetic material layer  26   j  is a substantially band-shaped non-magnetic material layer provided parallel to outer edges of the insulator layer  22   j  on both the positive and negative sides in the x-axis direction and parallel to an outer edge of the insulator layer  22   j  on the negative side in the y-axis direction, and has a substantially backward C shape when viewed in plan from the z-axis direction. The magnetic material layer  24   j  is provided in portions of the insulator layer  22   j  other than portions where the non-magnetic material layer  26   j  and a coil conductor  32   j , which will be described later, are provided. 
     The insulator layer  22   k  is located in an end portion of the multilayer body  20  on the negative side in the z-axis direction. In addition, the insulator layer  22   k  is formed of a magnetic material. 
     Configuration of Outer Electrodes 
     The configuration of the outer electrodes  40   a  and  40   b  will be described with reference to  FIG. 1 . As illustrated in  FIG. 1 , the outer electrode  40   a  is provided so as to cover a surface of the multilayer body  20  on the positive side in the x-axis direction and part of each of the surfaces surrounding that surface. In addition, the outer electrode  40   b  is provided so as to cover a surface of the multilayer body  20  on the negative side in the x-axis direction and part of each of the surfaces surrounding that surface. The material of the outer electrodes  40   a  and  40   b  is a conductive material such as Au, Ag, Pd, Cu or Ni. 
     Configuration of Coil 
     The configuration of the coil  30  will be described with reference to  FIG. 2 . As illustrated in  FIG. 2 , the coil  30  is located inside the multilayer body  20  and is formed of the coil conductors (conductors)  32   b ,  32   d ,  32   f ,  32   h  and  32   j  and via conductors  34   b ,  34   d ,  34   f  and  34   h . In addition, the coil  30  has a substantially helical shape and a central axis of the helical shape is parallel to the z axis. In short, the coil  30  has a helical shape that loops around while advancing in the stacking direction. The material of the coil  30  is a conductive material such as Au, Ag, Pd, Cu or Ni. 
     The coil conductor  32   b  is a line-shaped conductor that is provided so as to extend alongside the non-magnetic material layer  26   b . Therefore, the coil conductor  32   b  has a substantially square annular shape when viewed in plan from the z-axis direction. In addition, the coil conductor  32   b  contacts the non-magnetic material layer  26   b  on the inner circumferential side of the substantially square annular shape formed by the coil conductor  32   b . Furthermore, the upper surface of the coil conductor  32   b  contacts the insulator layer  22   a  and the lower surface of the coil conductor  32   b  contacts the non-magnetic material layer  26   c . Here, a sum w 1  of a width of the coil conductor  32   b  and a width of the non-magnetic material layer  26   b  located on the inner circumferential side of the coil conductor  32   b  is smaller than a width w 2  of the non-magnetic material layer  26   c . One end of the coil conductor  32   b  is exposed at the surface of the multilayer body  20  from an outer edge of the insulator layer  22   b  on the positive side in the x-axis direction and is connected to the outer electrode  40   a . The other end of the coil conductor  32   b  is connected to the via conductor  34   b , which penetrates through the insulator layer  22   c  in the z-axis direction, in the vicinity of a corner formed by an outer edge of the insulator layer  22   b  on the positive side in the x-axis direction and an outer edge of the insulator layer  22   b  on the positive side in the y-axis direction. 
     The coil conductor  32   d  is a line-shaped conductor that is provided so as to extend alongside the non-magnetic material layer  26   d . Therefore, the coil conductor  32   d  has a substantially square annular shape when viewed in plan from the z-axis direction. In addition, the coil conductor  32   d  contacts the non-magnetic material layer  26   d  on the inner circumferential side of the substantially square annular shape formed by the coil conductor  32   d . In addition, the upper surface of the coil conductor  32   d  contacts the non-magnetic material layer  26   c  and the lower surface of the coil conductor  32   d  contacts the non-magnetic material layer  26   e . Here, a sum w 3  of a width of the coil conductor  32   d  and a width of the non-magnetic material layer  26   d  located on the inner circumferential side of the coil conductor  32   d  is larger than the width w 2  of the non-magnetic material layer  26   c  and smaller than a width w 4  of the non-magnetic material layer  26   e . One end of the coil conductor  32   d  is connected to the via conductor  34   b  in the vicinity of a corner C 1  formed by an outer edge of the insulator layer  22   d  on the positive side in the x-axis direction and an outer edge of the insulator layer  22   d  on the positive side in the y-axis direction. In addition, the other end of the coil conductor  32   d  is located in the vicinity of the corner C 1  and a little further toward the center of the insulator layer  22   d  than the one end of the coil conductor  32   d , and furthermore is connected to the via conductor  34   d , which penetrates through the insulator layer  22   e  in the z-axis direction. 
     The coil conductor  32   f  is a line-shaped conductor that is provided so as to extend alongside the non-magnetic material layer  26   f . Therefore, the coil conductor  32   f  has a substantially square annular shape when viewed in plan from the z-axis direction. In addition, the coil conductor  32   f  contacts the non-magnetic material layer  26   f  on the inner circumferential side of the substantially square annular shape formed by the coil conductor  32   f . In addition, the upper surface of the coil conductor  32   f  contacts the non-magnetic material layer  26   e  and the lower surface of the coil conductor  32   f  contacts the non-magnetic material layer  26   g . Here, a sum w 5  of a width of the coil conductor  32   f  and a width of the non-magnetic material layer  26   f  located on the inner circumferential side of the coil conductor  32   f  is larger than the width w 4  of the non-magnetic material layer  26   e  and larger than a width w 6  of the non-magnetic material layer  26   g . One end of the coil conductor  32   f  is connected to the via conductor  34   d  in the vicinity of a corner C 2  formed by an outer edge of the insulator layer  22   f  on the positive side in the x-axis direction and an outer edge of the insulator layer  22   f  on the positive side in the y-axis direction. In addition, the other end of the coil conductor  32   f  is located in the vicinity of the corner C 2  and a little further toward the outer edge of the insulator layer  22   f  than the one end of the coil conductor  32   f , and furthermore is connected to the via conductor  34   f , which penetrates through the insulator layer  22   g  in the z-axis direction. 
     The coil conductor  32   h  is a line-shaped conductor that is provided so as to extend alongside the non-magnetic material layer  26   h . Therefore, the coil conductor  32   h  has a substantially square annular shape when viewed in plan from the z-axis direction. In addition, the coil conductor  32   h  contacts the non-magnetic material layer  26   h  on the inner circumferential side of the substantially square annular shape formed by the coil conductor  32   h . In addition, the upper surface of the coil conductor  32   h  contacts the non-magnetic material layer  26   g  and the lower surface of the coil conductor  32   h  contacts the non-magnetic material layer  26   i . Here, a sum w 7  of a width of the coil conductor  32   h  and a width of the non-magnetic material layer  26   h  located on the inner circumferential side of the coil conductor  32   h  is smaller than the width w 6  of the non-magnetic material layer  26   g  and larger than a width w 8  of the non-magnetic material layer  26   i . One end of the coil conductor  32   h  is connected to the via conductor  34   f  in the vicinity of a corner C 3  formed by an outer edge of the insulator layer  22   h  on the positive side in the x-axis direction and an outer edge of the insulator layer  22   h  on the positive side in the y-axis direction. In addition, the other end of the coil conductor  32   h  is located in the vicinity of the corner C 3  and a little further toward the center of the insulator layer  22   h  than the one end of the coil conductor  32   h , and furthermore is connected to the via conductor  34   h , which penetrates through the insulator layer  22   i  in the z-axis direction. 
     The coil conductor  32   j  is a line-shaped conductor that is provided so as to extend alongside the non-magnetic material layer  26   j . Therefore, the coil conductor  32   j  has a substantially backward C shape when viewed in plan from the z-axis direction. In addition, the coil conductor  32   j  contacts the non-magnetic material layer  26   j  on the inner circumferential side of the substantially backward C shape formed by the coil conductor  32   j . In addition, the upper surface of the coil conductor  32   j  contacts the non-magnetic material layer  26   i  and the lower surface of the coil conductor  32   j  contacts the insulator layer  22   k . Here, a sum w 9  of a width of the coil conductor  32   j  and a width of the non-magnetic material layer  26   j  located on the inner circumferential side of the coil conductor  32   j  is smaller than the width w 8  of the non-magnetic material layer  26   i . One end of the coil conductor  32   j  is connected to the via conductor  34   h  in the vicinity of a corner formed by an outer edge of the insulator layer  22   j  on the positive side in the x-axis direction and an outer edge of the insulator layer  22   j  on the positive side in the y-axis direction. Furthermore, the other end of the coil conductor  32   j  is exposed at the surface of the multilayer body  20  from the outer edge of the insulator layer  22   j  on the negative side in the x-axis direction and is connected to the outer electrode  40   b.    
     In the thus-configured inductor  10 , the inner circumferential surface of the coil  30  is covered by the non-magnetic material layers  26   b  to  26   j , which form circular arcs when viewed from a direction that is orthogonal to the z-axis direction, as illustrated in  FIG. 3 . In addition, the sum w 5  of the width of the coil conductor  32   f  and the width of the non-magnetic material layer  26   f  covering the inner circumferential side of the coil conductor  32   f  that are located in a center portion of the coil  30  in the z-axis direction (central axis direction) is larger than the sum w 1  of the width of the coil conductor  32   b  and the width of the non-magnetic material layer  26   b  covering the inner circumferential side of the coil conductor  32   b  that are located in an end portion of the coil  30  on the positive side in the z-axis direction (one side in central axis direction). 
     Manufacturing Method 
     A method of manufacturing the inductor according to the embodiment will be described with reference to  FIG. 1  and  FIGS. 4 to 13 . Hereafter, a manufacturing method in which a single inductor is the target will be described, but in reality a single inductor would be obtained by manufacturing and then cutting into individual pieces a mother multilayer body in which a plurality of multilayer bodies are connected to one another and then forming the outer electrodes on the individual inductors. 
     First, a magnetic material paste obtained by mixing a ferrite powder, which is a magnetic material, with an organic component such as a binder into a paste is applied onto a holding substrate such as an alumina substrate using a printing method and then dried to form the insulator layer  22   k  illustrated in  FIG. 4 . 
     Next, a conductive paste having Ag, Pd, Cu, Ni or the like as a main component is applied onto the insulator layer  22   k  using a printing method and then dried to form the coil conductor  32   j  illustrated in  FIG. 5 . 
     In addition, a non-magnetic material paste formed of borosilicate glass and a ceramic filler is applied so as to cover the upper surface and the inner circumferential side of the coil conductor  32   j  using a printing method and then dried to form the non-magnetic material layers  26   i  and  26   j  as illustrated in  FIG. 6 . In order to allow formation of the via conductor  34   h , the non-magnetic material paste is not applied to the upper surface of one end of the coil conductor  32   j.    
     After formation of the non-magnetic material layers  26   i  and  26   j , as illustrated in  FIG. 7 , a magnetic material paste is applied to parts of the insulator layer  22   k  on which the non-magnetic material layer  26   j  and the coil conductor  32   j  have not been formed using a printing method and then dried, in order to form the magnetic material layers  24   i  and  24   j . Thus, formation of the insulator layers  22   i  and  22   j  is completed. After formation of the insulator layers  22   i  and  22   j , a conductive paste is applied using a printing method to fill the via hole in order to form the via conductor  34   h.    
     After that, steps similar to the steps for forming the coil conductor  32   j , the non-magnetic material layers  26   i  and  26   j , the magnetic material layers  24   i  and  24   j  and the via conductor  34   h  are repeated. However, non-magnetic material paste is applied so that the non-magnetic material layer  26   f  located in a center portion in the z-axis direction maximally juts out on the inner circumferential side of the coil  30 . In this way, the insulator layers  22   c  to  22   h , the coil conductors  32   b ,  32   d ,  32   f  and  32   h  and the via conductors  34   b ,  34   d  and  34   f  are formed. 
     After formation of the coil conductor  32   b , as illustrated in  FIG. 8 , the non-magnetic material paste is applied so as to cover the inner circumferential side of the coil conductor  32   b  using a printing method and then dried, to form the non-magnetic material layer  26   b . After formation of the non-magnetic material layer  26   b , as illustrated in  FIG. 9 , the magnetic material paste is applied to parts of the insulator layer  22   c  on which the non-magnetic material layer  26   b  and the coil conductor  32   b  have not been formed using a printing method and then dried, in order to form the magnetic material layer  24   b . In this way, the insulator layer  22   b  is formed. In addition, the magnetic material paste is applied to the entirety of the upper surface of the insulator layer  22   b  using a printing method to form the insulator layer  22   a , and thereby formation of an unfired mother multilayer body is completed. 
     Next, the unfired mother multilayer body is cut into individual multilayer bodies  20  of certain dimensions using a dicing saw and a plurality of unfired multilayer bodies  20  are thus obtained. 
     Each unfired multilayer body  20  is subjected to a de-binder treatment and firing. The de-binder treatment is for example performed under conditions of 400° C. for 2 hours in a low oxygen atmosphere. The firing is for example performed under conditions of 2.5 hours at 870° C. to 900° C. 
     A fired multilayer body  20  is obtained through the above-described process. The multilayer body  20  is chamfered by being subjected to barrel finishing. After that, an electrode paste composed of a conductive material having Ag as a main component is applied to surfaces of the multilayer body  20 . The applied electrode paste is baked under conditions of a temperature of around 800° C. for around 1 hour. In this way, silver electrodes are formed that will become the outer electrodes  40   a  and  40   b.    
     Finally, formation of the outer electrodes  40   a  and  40   b  is completed by performing Ni plating and Sn plating on the surfaces of the silver electrodes. Manufacture of the inductor  10  illustrated in  FIG. 1  is completed through the above-described processes. 
     Effects 
     Next the effects of the present disclosure will be described with reference to  FIG. 3 ,  FIG. 10  and  FIG. 11 . In the inductor  10 , magnetic saturation can be suppressed. Specifically, in an inductor  500  of the related art in which the inner circumferential surface of a coil is not covered by a non-magnetic material layer as illustrated in  FIG. 10 , when a current flows, lines of magnetic force H 500  are concentrated around corners of coil conductors located in end portions of a coil  530  of the inductor  500  and magnetic saturation is likely to occur. However, in the inductor  10 , as illustrated in  FIG. 3 , the sum w 5  of the width of the coil conductor  32   f  and the width of the non-magnetic material layer  26   f  covering the inner circumferential side of the coil conductor  32   f  that are located in a center portion of the coil  30  in the z-axis direction (central axis direction) is larger than the sum w 1  of the width of the coil conductor  32   b  and the width of the non-magnetic material layer  26   b  covering the inner circumferential side of the coil conductor  32   b  that are located in the end portion of the coil  30  on the positive side in the z-axis direction (one side in central axis direction). Thus, in the inductor  10 , lines of magnetic force H 10  generated when a current flows form shapes close to an ellipse, and therefore the interval between the lines of magnetic force H 10  becomes wider in the width direction of the conductors as illustrated in  FIG. 11 . As a result, in the inductor  10 , concentration of lines of magnetic force around corners of conductors located in the end portions of the coil  30 , particularly on the inner circumferential side of the coil  30  can be suppressed and magnetic saturation can be suppressed. 
     First Modification 
     A first modification will be described with reference to  FIG. 12 . An inductor  10 A according to the first modification and the inductor  10  differ from each other in terms of the shape of the non-magnetic material layers  26   b  to  26   j  that cover the inner circumferential surface of the coil  30 . In the inductor  10 A, as illustrated in  FIG. 12 , the non-magnetic material layers  26   b  to  26   j , which cover the inner circumferential surface of the coil  30 , cover the inner circumferential surface of the coil  30  in such a way as to form a triangular shape with a center portion in the z-axis direction being an apex when viewed from a direction orthogonal to the z-axis direction. Also in the thus-configured inductor  10 A, concentration of lines of magnetic force around corners of conductors located in end portions of the coil can be suppressed and magnetic saturation can be suppressed. The rest of the configuration of the inductor  10 A is the same as that of the inductor  10 . Therefore, other than the shape of the non-magnetic material layers  26   b  to  26   j  covering the inner circumferential surface of the coil  30 , description of the inductor  10 A is the same as that of the inductor  10 . 
     Second Modification 
     A second modification will be described with reference to  FIG. 13 . An inductor  10 B according to the second modification and the inductor  10  differ from each other in terms of the shape of the non-magnetic material layers  26   b  to  26   j  that cover the inner circumferential surface of the coil  30 . In the inductor  10 B, as illustrated in  FIG. 13 , when viewed in a direction orthogonal to the z-axis direction, both end portions of inner circumferential outer edges of the non-magnetic material layers  26   b  to  26   j , which cover the inner circumferential surface of the coil  30  form a substantially circular arc shape and the center portions that connect the end portions to each other both have a shape that is substantially parallel to the z-axis direction. Also in the thus-configured inductor  10 B, concentration of lines of magnetic force around corners of conductors located in end portions of the coil can be suppressed and magnetic saturation can be suppressed. The rest of the configuration of the inductor  10 B is the same as that of the inductor  10 . Therefore, other than the shape of the non-magnetic material layers  26   b  to  26   j  covering the inner circumferential surface of the coil  30 , description of the inductor  10 B is the same as that of the inductor  10 . 
     Third Modification 
     A third modification will be described with reference to  FIG. 14 . An inductor  10 C according to the third modification and the inductor  10  differ from each other in terms of the shape of the non-magnetic material layers  26   b  to  26   j  that cover the inner circumferential surface of the coil and in that a non-magnetic material layer  26   k  is newly added. In the inductor  10 C, as illustrated in  FIG. 14 , the non-magnetic material layers  26   b  to  26   j , which cover the inner circumferential surface of the coil  30 , cover the inner circumferential surface of the coil  30  in such a way as to form a triangular shape with a center portion in the z-axis direction being an apex when viewed from a direction orthogonal to the z-axis direction. In addition to this, the non-magnetic material layer  26   k  is provided in the vicinity of a center portion of the coil  30  so as to be substantially parallel to a plane orthogonal to the z-axis direction. Also in the thus-configured inductor  10 C, concentration of lines of magnetic force around corners of conductors located in end portions of the coil can be suppressed and magnetic saturation can be suppressed. As a result of providing the non-magnetic material layer  26   k , magnetic saturation on the inner circumferential side of the coil  30  can be further suppressed. The rest of the configuration of the inductor  10 C is the same as that of the inductor  10 . Therefore, other than the shape of the non-magnetic material layers  26   b  to  26   j  covering the inner circumferential surface of the coil  30  and the new addition of the non-magnetic material layer  26   k , description of the inductor  10 C is the same as that of the inductor  10 . 
     Fourth Modification 
     A fourth modification will be described with reference to  FIG. 15 . An inductor  10 D according to the fourth modification and the inductor  10  differ from each other in terms of the shape of the non-magnetic material layers  26   b  to  26   j  that cover the inner circumferential surface of the coil  30  and in that an outer circumferential surface of the coil  30  is also covered by the non-magnetic material layers  26   b  to  26   j . In the inductor  10 D, as illustrated in  FIG. 15 , the non-magnetic material layers  26   b  to  26   j  cover the inner circumferential surface of the coil  30  in such a way as to form a triangular shape with a center portion in the z-axis direction being an apex when viewed from a direction orthogonal to the z-axis direction. In addition to this, in the inductor  10 D, the non-magnetic material layers  26   b  to  26   j  cover the outer circumferential surface in such a way as to form a triangular shape with a center portion in the z-axis direction being an apex. In the thus-configured inductor  10 D, as a result of the outer circumferential surface also being covered by the non-magnetic material layers in addition to the inner circumferential surface of the coil  30 , the lines of magnetic force generated when a current flows are spread out even more in the width direction of the conductors than in the inductor  10 . Thus, concentration of lines of magnetic force around corners of conductors located in end portions of the coil can be further suppressed and magnetic saturation can be even more effectively suppressed. The rest of the configuration of the inductor  10 D is the same as that of the inductor  10 . Therefore, other than the shapes of the non-magnetic material layers  26   b  to  26   j  covering the inner circumferential surface of the coil  30  and the fact that the outer circumferential surface of the coil  30  is also covered by the non-magnetic material layers  26   b  to  26   j , the description of the inductor  10 D is the same as that of the inductor  10 . 
     The inventors of the present application performed experiments in order to confirm the above-described effects. In the experiments, a sample S 1  corresponding to the inductor of the related art, a sample S 2  corresponding to an inductor  600  obtained by providing non-magnetic material layers that form outer edges parallel to the z-axis direction at the inner circumferential surface in the inductor of the related art as illustrated in  FIG. 16 , a sample S 3  that corresponds to the inductor  10 , a sample S 4  that corresponds to the inductor  10 A, a sample S 5  that corresponds to the inductor  10 B, a sample S 6  that corresponds to the inductor  10 C and a sample S 7  that corresponds to the inductor  10 D were used. There were 8 coil conductors in each of the samples and the dimensions of the samples were about 1.6 mm×0.8 mm×0.8 mm. In addition, a line width of the coil conductors was about 140 μm and the thickness was about 50 μm. In addition, the interval between the coil conductors was about 10 μm and a side gap was about 100 μm. The width of portions of the non-magnetic material layers, which were provided so as to cover the inner circumferential surface of the coil in each of the samples, having the largest width was about 20 μm. 
     In the experiments, in order to investigate an alternating current resistance Rac in each of the samples, a peak pulse current I p-p , a direct current Idc, a loss P and a direct current resistance Rdc were measured for each of the samples at each frequency. The alternating current resistance Rac was obtained by substituting the measured values into the following expression.
 
 Rac =( P−Rdc×Idc   2 )/( I   p-p /2√{square root over (3)}) 2  
 
     Values of alternating current resistance obtained as results of the experiments are illustrated in Table 1 and taking the alternating current resistance of sample S 1  as 100%, ratios of the alternating current resistances of samples S 2  to S 7  with respect to this value are illustrated in Table 2. 
     
       
         
           
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Alternating Current Resistance (Ω) 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Fre- 
                 Sam- 
                   
                   
                   
                   
                   
                   
               
               
                 quency 
                 ple 
                 Sample 
                 Sample 
                 Sample 
                 Sample 
                 Sample 
                 Sample 
               
               
                 (MHz) 
                 S1 
                 S2 
                 S3 
                 S4 
                 S5 
                 S6 
                 S7 
               
               
                   
               
               
                 2 
                 0.196 
                 0.209 
                 0.169 
                 0.164 
                 0.167 
                 0.185 
                 0.163 
               
               
                 4 
                 0.414 
                 0.409 
                 0.398 
                 0.386 
                 0.396 
                 0.374 
                 0.379 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
             
               
                   
                 TABLE 2 
               
             
            
               
                   
                   
               
               
                   
                 Alternating Current Resistance Ratio (%) 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Fre- 
                 Sam- 
                   
                   
                   
                   
                   
                   
               
               
                 quency 
                 ple 
                 Sample 
                 Sample 
                 Sample 
                 Sample 
                 Sample 
                 Sample 
               
               
                 (MHz) 
                 S1 
                 S2 
                 S3 
                 S4 
                 S5 
                 S6 
                 S7 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 2 
                 — 
                 106 
                 86 
                 84 
                 85 
                 94 
                 83 
               
               
                 4 
                 — 
                 99 
                 96 
                 93 
                 96 
                 90 
                 92 
               
               
                   
               
            
           
         
       
     
     In the results of the experiments, it is clear that the alternating current resistances Rac of the samples S 3  to S 7  at the measured frequencies (2 MHz and 4 MHz) are lower than those of samples S 1  and S 2 . This indicates that concentration of lines of magnetic force around corners of conductors located in end portions of the coil is suppressed and that as a result magnetic saturation is suppressed in the samples S 3  to S 7 , which correspond to the embodiment and modifications. 
     Other Embodiments 
     The inductor according to the present disclosure is not limited to the inductor of the embodiment and can be modified within the scope of the gist of the disclosure. For example, the number of turns and the number of layers of the coil, the shape of the insulator layers and so forth may be appropriately chosen. In addition, the embodiment and modifications may be combined with one another. 
     As has been described above, the present disclosure is of use in inductors and is excellent in that an increase in alternating current resistance in an inductor including a magnetic material and a non-magnetic material can be suppressed. 
     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.