Patent Publication Number: US-6218925-B1

Title: Electronic components

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention elates to an electronic component comprising one or more coils buried in a chip. 
     2. Description of the Related Art 
     FIG. 2 shows a side sectional view of a laminated inductor as a conventional electronic component on this head. 
     In FIG. 2,  20  is a laminated inductor comprising a rectangular-parallelepiped-shaped chip  21  of a magnetic substance material, a spiral coil  22  buried in the chip  21 , and a pair of terminal electrodes  23  provided at the longitudinal ends of the chip  21 . The winding center line, i.e., longitudinal axis, Y of the coil  22  is orthogonal to a line joining the terminal electrodes  23  together (extending in the longitudinal direction of the chip), and the end of the coil  22  is guided out to the end surface of the chip where it is connected to the respective terminal electrode  23 . 
     To mount the laminated inductor  20  on a conductor pattern on a circuit board, two orientations are available in which the winding center line (Y) of the coil  22  is perpendicular to the mounting surface of the circuit board (Z) as shown in FIG.  3  and in which winding the center line (Y) of the coil  22  is parallel with the mounting surface of the circuit board (Z) as shown in FIG.  4 . 
     There is a difference in inductance between the mounting orientations in FIGS. 3 and 4 due to the different locational relationship between the coil  22  and the circuit board (Z) resulting in a difference in magnetic reluctance to magnetic fluxes outside the chip. In particular, in a laminated inductor using a chip material of a lower relative magnetic permeability, the difference in mounting orientation causes a significant difference in magnetic reluctance and thus a relatively large difference in inductance. 
     To solve such a problem, a laminated inductor has been proposed in which the orientation of the winding center line of the coil relative to the surface of the circuit board remains unchanged regardless of the mounting orientation (Japanese Patent Application Laid-Open No. 8-55726). 
     This laminated inductor is generally called a vertically laminated inductor wherein a laminated structure is formed in the direction of a line joining the terminal electrodes together as shown in FIGS. 5 to  7 . 
     A chip  31  in a vertically laminated inductor  30 , which is shown in FIGS. 5 to  7 , is formed by laminating a top-layer sheet (A) of a magnetic material, coil-layer sheets (B 1 ) to (B 4 ) of a magnetic material, and a bottom-layer sheet (C) of a magnetic material. A leadout conductor (Pa) is formed in the top layer-sheet (A) of a magnetic material in such a way as to overlap a via hole (h). Four types of approximately-U-shaped coil conductors (Pb 1 ) to (Pb 4 ) are formed in the coil-layer sheets (B 1 ) to (B 4 ) of a magnetic material in such a way that their ends overlap the via hole (h). In addition, a rectangular leadout conductor (Pc) is formed in the bottom-layer sheet (C) of a magnetic material in such a way as to overlap the via hole (h). Furthermore, terminal electrodes  33  are formed at the respective ends of the chip  31  in the lamination direction to constitute the vertically laminated inductor  30 . 
     The coil conductors (Pb 1 ) to (Pb 4 ) are connected together via the via hole (h) to form the coil  32 , and the respective ends of the coil  32  are connected to the terminal electrodes  33  via leadout conductors  34   a  and  34   b  consisting of leadout conductors (Pa) and (Pc) formed in the top- and bottom-layer sheets (A) and (C) of a magnetic material. 
     In the vertically laminated inductor  30  of the configuration shown in FIGS. 5 to  7 , when a current flows through the inductor, two fluxes are generated; one of them is parallel with the winding center line (Y) of the coil  32 , while the other rotates around the leadout conductors  34   a  and  34   b.  These magnetic fluxes form the inductance of the chip. 
     When, however, the laminated inductor  30  is mounted on the circuit board (Z), there is a difference in distance between the leadout conductor  34   a  or  34   b  and the circuit board (Z), between the mounting orientation shown in FIG.  8  and the mounting orientation shown in FIG. 9 in which the inductor is vertically revered. Consequently, there is a difference in magnetic reluctance to magnetic fluxes generated around the leadout conductors  34   a  and  34   b,  resulting in a difference in inductance depending on the mounting orientation. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an electronic component including a coil that avoids a difference in inductance depending on the mounting orientation. 
     The present invention provides an electronic component comprising a coil buried in a rectangular-parallelepiped-shaped chip and terminal electrodes located at the respective ends of the chip and connected to the respective ends of the coil, wherein the winding center line of the coil, i.e., the coil axis, is set on a straight line joining the central points of a pair of opposed end surfaces of the chip at which terminal electrodes are formed and wherein the winding locus of the coil as seen in the direction of the winding center line and leadout conductors each joining the end of the coil and the terminal electrode together are arranged at positions and/or in conditions such that when the electronic component is mounted on a circuit board, the winding locus of the coil and the distance between the leadout conductor and the circuit board remains unchanged at least despite the reversal of the electronic component. 
     In the electronic component of this configuration, the distances between the coil and the circuit board and between the leadout conductor and the circuit board remain unchanged whichever of the four surfaces of the chip different from its end surfaces is opposed to the circuit board, as long as, for example, a cross section of the chip perpendicular to the winding center line of the coil is square. Thus, the magnetic reluctance remains the same in each mounting orientation, thereby preventing the inductance provided by the coil and leadout conductors from being changed by the mounting orientation. Consequently, this electronic component precludes a difference in inductance depending on the mounting orientation. In addition, when the chip is shaped like a rectangular parallelepiped and the cross section of the chip perpendicular to the winding center line of the coil is not square, the distance between the leadout conductor and the circuit board remains unchanged despite the vertical reversal of the chip in mounting it on the circuit board. As a result, when the cross section of the chip perpendicular to the winding center line of the coil has a shape other than a square, the inductance remains unchanged despite the vertical reversal of the chip in mounting it on the circuit board. 
     Moreover, the present invention provides an electronic component wherein the inductance remains unchanged regardless of the mounting orientation even if the chip is shaped like a cylinder as described above. For example, the present invention provides an electronic component comprising a coil buried in a cylinder-shaped chip and terminal electrodes located at the respective ends of the chip and connected to the respective ends of the coil, wherein the winding center line of the coil is set on a straight line joining the central points of a pair of opposed end surfaces of the chip at which terminal electrodes are formed, wherein the distance between the winding locus of the coil as seen in the direction of the winding center line and the central point through which the winding center line of the coil passes remains constant in any cross section of the chip which the winding center line of the coil crosses perpendicularly, and wherein at either end of the chip, a leadout conductor joining the end of the coil and the terminal electrode together is located on the winding center line of the coil. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a laminated inductor according to a first embodiment of the present invention; 
     FIG. 2 is a side sectional view of a laminated inductor according to a conventional example; 
     FIG. 3 is a perspective of how a conventional laminated inductor is mounted; 
     FIG. 4 is a perspective of how a conventional laminated inductor is mounted; 
     FIG. 5 is a side sectional view of a vertically laminated inductor according to a conventional example; 
     FIG. 6 is a perspective view of a vertically laminated inductor according to a conventional example; 
     FIG. 7 is a exploded perspective view of a laminated structure of a vertically laminated inductor according to a conventional example; 
     FIG. 8 is a side sectional view of how a laminated inductor is mounted according to a conventional example; 
     FIG. 9 is a side sectional view of how a laminated inductor is mounted according to a conventional example; 
     FIG. 10 is an exploded perspective view of a laminated structure of the laminated inductor according to the first embodiment of the present invention; 
     FIG. 11 is a perspective view of a laminated inductor according to a second embodiment of the present invention; 
     FIG. 12 is an exploded perspective view of the laminated structure of the laminated inductor according to the second embodiment of the present invention; 
     FIGS. 13 a  to  13   f  show the winding locus of another coil according to the second embodiment of the present invention; 
     FIG. 14 is a perspective view showing a laminated inductor according to a third embodiment of the present invention; 
     FIG. 15 shows the winding locus of a coil according to the third embodiment of the present invention as seen in the direction of the winding center line of the coil; 
     FIG. 16 is a perspective view showing a laminated inductor according to a fourth embodiment of the present invention; 
     FIG. 17 is a perspective view showing a laminated inductor according to a fifth embodiment of the present invention; 
     FIG. 18 shows the winding locus of a coil according to the fifth embodiment of the present invention as seen in the direction of the winding center line of the coil; 
     FIG. 19 is an exploded perspective view showing the laminated structure of the laminated inductor according to the fifth embodiment of the present invention; 
     FIG. 20 is a perspective view showing a laminated inductor according to a sixth embodiment of the present invention; 
     FIG. 21 shows positions at which leadout conductors are formed according to the sixth embodiment of the present invention; 
     FIG. 22 is a perspective view showing a laminated inductor according to a seventh embodiment of the present invention; 
     FIG. 23 shows a position at which leadout conductors are formed according to the seventh embodiment of the present invention; 
     FIG. 24 is a perspective view showing a laminated inductor according to an eighth embodiment of the present invention; 
     FIG. 25 shows the winding locus of a coil according to the eighth embodiment of the present invention as seen in the direction of the winding center line of the coil; and 
     FIG. 26 is an exploded perspective view showing the laminated structure of the laminated inductor according to the eighth embodiment of the present invention; 
     FIG. 27 is a perspective view showing a laminated inductor according to a ninth embodiment of the present invention; 
     FIG. 28 is a side sectional view showing a laminated inductor according to the ninth embodiment of the present invention; 
     FIG. 29 is an exploded perspective view showing the laminated structure according to the ninth embodiment of the present invention; 
     FIG. 30 shows the arrangement of a leadout conductor as seen in the direction of the center line of a coil according to the ninth embodiment of the present invention; 
     FIG. 31 shows another example of the leadout conductor according to the ninth embodiment of the present invention; 
     FIG. 32 is a side sectional view showing a laminated inductor according to a tenth embodiment of the present invention; 
     FIG. 33 shows another example for setting the length of a first leadout conductor according to the tenth embodiment of the present invention; 
     FIG. 34 is a side sectional view showing a laminated inductor according to an eleventh embodiment of the present invention; 
     FIG. 35 is a side sectional view showing a laminated inductor according to a twelfth embodiment of the present invention; 
     FIG. 36 is an exploded perspective view showing a laminated structure of a laminated inductor according to a thirteenth embodiment of the present invention; 
     FIG. 37 is a side sectional view showing a laminated inductor according to a fourteenth embodiment of the present invention; 
     FIG. 38 is a side sectional view showing a laminated inductor according to a fifteenth embodiment of the present invention; 
     FIG. 39 is a top sectional view showing the laminated inductor according to the fifteenth embodiment of the present invention; 
     FIG. 40 is an exploded perspective view showing the laminated structure of the laminated inductor according to a fifteenth embodiment of the present invention; 
     FIG. 41 is a side sectional view showing a laminated inductor according to a sixteenth embodiment of the present invention; 
     FIG. 42 describes how a gap is formed in a chip according to the sixteenth embodiment of the present invention; 
     FIG. 43 is a side sectional view showing a laminated inductor according to a seventeenth embodiment of the present invention; 
     FIG. 44 describes how the gap in the chip is impregnated with a synthetic resin according to the seventeenth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is described in detail with reference to the accompanying drawings. 
     FIG. 1 is a perspective view showing a laminated inductor  10  according to a first embodiment of the present invention, and FIG. 10 is an exploded perspective view showing the laminated structure of the laminated inductor  10 . In the figures,  11  is a rectangular parallelepiped chip of a magnetic or non-magnetic insulating material having a laminated structure,  12  is a coil consisting of internal conductors buried in the chip  11  and spirally connected together, and  13   a  and  13   b  are a pair of terminal electrodes provided at the respective ends of the chip  11  in the lamination direction of the laminated structure. 
     The coil  12  is formed in such a way that its winding center line (Y) is located on a straight line joining the centers of the end surfaces of the chip  11  forming the terminal electrodes  13   a  and  13   b.  The respective ends of the coil  12  are connected to the terminal electrodes  13   a  and  13   b  via leadout conductors  14   a  and  14   b  located on the winding center line (Y) of the coil  12 . 
     The chip  11  is formed by laminating one or more layers of a top-layer sheet  41  consisting of an rectangular insulating material sheet of a predetermined thickness; connection sheets  42  and  47 ; coil-layer sheets  43  to  46 ; and a bottom-layer sheet  48  as shown in FIG.  10 . 
     In the following description, the lamination direction of the sheets  41  to  48  is defined as the vertical direction so as to correspond to FIG.  10 . 
     The coil  12  is formed by laminating a plurality of rectangular coil-layer sheets  43  to  46  having in their top surface approximately-U-shaped internal coil conductors (Pb 1 ) to (Pb 4 ), respectively, having at one end the via hole (h) with a conductor filled therein. When the coil-layer sheets  43  to  46  are laminated, the via-hole end of each of the internal coil-conductors (Pb 1 ) to (Pb 4 ) is connected via the conductor in the via hole (h) to the other end of another internal coil conductor immediately above or below the first conductor so that the internal coil conductors (Pb 1 ) to (Pb 4 ) formed in the plurality of layers form the spiral coil  12 . 
     In addition, the coil  12  is formed in such a way that the winding locus of the coil as seen in the direction of the winding center line (Y) is point-symmetrical around the central point through which the winding center line (Y) passes. 
     In the following description, the via hole with a conductor filled therein is simply referred to as a “via hole”, and “connected to the via hole” and “connected via the via hole”mean “connected to the conductor filled in the via hole” and “connected via the conductor filled in the via hole”. 
     In addition, a connection sheet  42  having in its surface a connection conductor (Pa 1 ) with the via hole (h) formed at one end is laminated on the coil-layer sheet  43 , and this via hole (h) connects the connection conductor (Pa 1 ) and the internal coil conductor (Pb 1 ) together. 
     Furthermore, one or more top-layer sheets  41  with the leadout conductor (Pa) formed in the via hole (h) located at the center are laminated on the connection sheet  42 , and during lamination, the leadout conductor (Pa) is connected to the other end of the connection conductor (Pa 1 ). 
     In addition, a connection sheet  47  having in its surface a connection conductor (Pc 1 ) with the via hole (h) formed at one end is laminated under the coil-layer sheet  46 , and the other end of the connection conductor (Pc 1 ) and the internal coil conductor (Pb 4 ) are connected together via the via hole (h) formed in the coil-layer sheet  46  located over the connection conductor (Pc 1 ). 
     Furthermore, one or more bottom-layer sheets  48  with the leadout conductor (Pc) formed in the via hole (h) located at the center are laminated under the connection sheet  47 , and during lamination, the leadout conductor (Pc) is connected to one end of the connection conductor (Pc 1 ). 
     Thus, the plurality of leadout conductors (Pa) form the leadout conductor  14   a,  and the plurality of leadout conductors (Pc) form the leadout conductor  14   b.    
     Next, a method for fabricating this laminated inductor is described. 
     Before fabrication, the sheets  41  to  48  are prepared. 
     The coil-layer sheets  43  to  46  are formed by forming a via hole (h) at a predetermined position of each insulating green sheet mainly consisting of a BaO or TiO 2  ceramic material and then forming four types of U-shaped internal coil conductors (Pb 1 ) to (Pb 4 ) in the respective sheets in such a way that their ends overlap the via hole (h). In addition to the U shape, the internal coil conductors (Pb 1 ) to (Pb 4 ) may have a non-annular shape such as an L shape, as is well known. 
     The top- and bottom-layer sheets  41  and  48  are produced by forming the via hole (h) at the center of each of similar insulating green sheets, that is, at the position of the winding center line of the coil  12  and then forming the rectangular leadout conductors (Pa) and (Pc) in the sheets in such a way as to overlap the via hole (h). 
     The connection sheets  42  and  47  are produced by forming the via hole (h) at a predetermined position of each of similar insulating sheets and then forming the connection conductors (Pa 1 ) and (Pc 1 ) in such a way as to overlap both the internal coil conductors (Pb 1 ) to (Pb 4 ) and the leadout conductors (Pa) and (Pc), respectively. 
     The via hole (h) is formed by means of the irradiation of laser beams if the insulating green sheet is supported by a film. Alternatively, the via hole (h) is formed by means of die punching if the insulating green sheet is not supported by a film. 
     Then, the film (if any) is peeled off from each of the prepared sheets  41  to  48 , which are then laminated in the above order and compressed at a pressure about 500 kg/cm 2  to form a sheet laminated body. The number of the top- and bottom-layer sheets  41  and  48  used corresponds to the layer thickness, and the number of the coil-layer sheets  43  to  46  used corresponds to the number of coil windings. 
     Then, the sheet laminated body is baked at about 900° C. A method such as dipping is then used to apply a conductor paste to both lamination-wise ends of the chip  11  obtained by means of baking, and the paint is baked to form the terminal electrodes  13   a  and  13   b,  thereby obtaining the laminated inductor  10 . Then, the terminal electrodes  13   a  and  13   b  may be Sn—pb plated as required. 
     In the laminated inductor  10 , the chip  11  is shaped like a rectangular-parallelepiped, the winding center line (Y) of the coil  12  is set on a straight line joining the centers of the end surfaces of the chip where the terminal electrodes  13   a  and  13   b  are formed, and the leadout conductors  14   a  and  14   b  are located on the winding center line (Y). Thus, when the laminated inductor  10  is mounted on the circuit board in such a way that the surface of the circuit board is opposed to the top or bottom surface of the chip  11  in FIG. 1, the distances (the locational relationship) between the coil  12  and the circuit board and between the leadout conductors  14   a  and  14   b  and the circuit board remains unchanged in either case. Thus, the magnetic resistance to magnetic fluxes generated around the coil  12  and leadout conductors  14   a  and  14   b  is almost the same in each mounting orientation, thereby preventing the inductance from being changed. 
     In addition, when the laminated inductor  10  is mounted on the circuit board whichever of the four surfaces of the chip  11  different from its end surfaces in FIG. 1 is opposed to the surface of the circuit board, even if the chip  11  is vertically reversed in mounting on the circuit board, the distances (the locational relationship) between the coil  12  and the circuit board and between the leadout conductors  14   a  and  14   b  and the circuit board remain unchanged. Thus, the magnetic resistance to magnetic fluxes generated around the coil  12  and leadout conductors  14   a  and  14   b  is almost the same in each mounting orientation, thereby preventing the inductance from being changed. 
     Next, a second embodiment of the present invention is described. 
     FIG. 11 is a perspective view showing a laminated inductor according to a second embodiment of the present invention, and FIG. 12 is an exploded perspective view showing the laminated structure of the laminated inductor. In the figures, the same components as in the first embodiment has the same reference numerals, and their description is omitted. 
     In addition, the second embodiment differs from the first embodiment in that the two leadout conductors are not located on the winding center line (Y) of the coil but symmetrically around the winding center line (Y). 
     That is, in a laminated inductor  50  in the second embodiment, leadout conductors  51   a,    51   b  and  52   a,    52   b  are formed at the respective ends of a chip  11  in such a manner that their ends are exposed on one of the diagonal lines in the end surface of the chip and at an equal distance from the central point through which the winding center line (Y) passes and that the conductors are parallel with the winding center line (Y), is as shown in FIG.  11 . 
     The leadout conductors  51   a,    51   b,    52   a,  and  52   b  can each be obtained by forming the via hole (h) and the leadout conductors (Pa) and (Pc) in the top- and bottom-layer sheets  41  and  48 , as in the leadout conductors  14   a  and  14   b  in the first embodiment. 
     In addition, connection conductors (Pd 1 ) and (Pd 2 ) shaped to connect the ends of the coil  12  to the leadout conductors  51   a,    51   b,    52   a,  and  52   b  are formed in connection sheets  42  and  47 . 
     The laminated inductor  50  according to the second embodiment can provide effects similar to those of the first embodiment. 
     That is, in the laminated inductor  50  in the second embodiment, the winding center line (Y) of the coil  12  is set in the direction of a line joining centers of the end surfaces of the chip together, the coil  12  is formed in such a way that the winding locus of the coil  12  as seen in the direction of the winding center line is point-symmetrical around the central point through which the winding center line (Y) passes, and the two leadout conductors  51   a  and  51   b  or  52   a  and  52   b  joining the end of the coil and the terminal electrode  13   a  and  13   b  together are located symmetrically around the winding center line (Y) of the coil  12 . Thus, if the inductor is vertically reversed when mounted on the circuit board, the distances between the coil  12  and the circuit board and between the leadout conductors  51   a  and  51   b  or  52   a  and  52   b  remain unchanged. Thus, the magnetic resistance remains the same in each mounting orientation, thereby preventing the inductance provided by the coil  12  and leadout conductors  51   a,    51   b,    52   a,  and  52   b  from being changed by the mounting orientation. 
     Although the second embodiment forms the leadout conductors  51   a,    51   b  and  52   a,    52   b  on the diagonal line on the respective end surface of the chip  11 , the present invention is not limited to this aspect. The above effects can be obtained as long as the leadout conductors are formed symmetrically around the winding center line (Y) of the coil  12 , and the positions at which the conductors are formed and the number of them may be determined as required. 
     In addition, although the first and second embodiments form the coil  12  in such a way that the winding locus of the coil  12  as seen in the direction of the winding center line (Y) of the coil  12  is rectangular, the present invention is not limited to this aspect. Similar effects can be obtained by forming the coil  12  in such a way that the winding locus of the coil as seen in the direction of the winding center line (Y) is point-symmetrical around the central point through which the winding center line (Y) passes. For example, the winding locus (Loc) of the coil  12  as seen in the direction of the winding center line (Y) must only be point-symmetrical around the central point (Yp) through which the winding center line (Y) passes, as shown in FIGS. 13 a  to  13   f,  and similar effects can be obtained even if the winding locus (Loc) is a slightly tilted rectangle, a square, a circle, an ellipse, or a lightly tilted ellipse. 
     Next, a third embodiment of the present invention is described. 
     FIG. 14 is a perspective view of a laminated inductor  60  according to a third embodiment, and FIG. 15 shows the winding locus of a coil as seen in the direction of the winding center line of the coil. 
     In the figures,  61  is a rectangular-parallelepiped chip of a magnetic or non-magnetic insulating material having a laminated structure,  62  is a coil consisting of internal conductors buried in the chip  61  and spirally connected together, and  63   a  and  63   b  are a pair of terminal electrodes provided at the respective longitudinal ends of the chip  61 , that is, the respective ends in the lamination direction of the laminated structure. In addition,  64   a  and  64   b  are leadout conductors that connect both ends of the coil  62  to the terminal electrodes  63   a  and  63   b,  respectively. 
     The winding center line (Y) of the coil  62  is set on a straight line joining the centers of the end surfaces of the chip  61 , and the leadout conductors  64   a  and  64   b  are located on the winding center line (Y). 
     The third embodiment is configured in almost the same manner as the laminated inductor  10  in the first embodiment and differs from it in that the coil  62  is formed in such a manner that the winding locus (Loc) of the coil  62  is parallel with one of the four sides (the bottom surface in FIG. 14) of the chip  61  different from its end surfaces and that the locus (Loc) is symmetrical around a straight line (X) orthogonal to the winding center line (Y) of the coil  62 . 
     That is, the winding locus (Loc) of the coil  62  shown in FIG. 15 constitutes an isosceles triangle having as a vertical bisector the straight line (X) passing through the central point (Yp). 
     In the laminated inductor  60  of this configuration, the winding center line (Y) of the coil  62  is set on the straight line joining the centers of the end surfaces of the chip on which the terminal electrodes  63   a  and  63   b  are formed. In addition, the coil  62  is formed in such a manner that the winding locus (Loc) of the coil  62  as seen in the direction of the winding center line (Y) is parallel with one of the sides of the chip different from its end surfaces and that the locus (Loc) is symmetrical around the straight line (X) orthogonal to the winding center line (Y). Moreover, the leadout conductors  64   a  and  64   b  joining the respective ends of the coil  62  and the terminal electrodes  63   a  and  63   b  are located on the winding center line (Y) of the coil  62 . Thus, when the laminated inductor  60  is mounted on the circuit board (Z), the distances between the coil  62  and the circuit board (Z) and between the leadout conductors  64   a  and  64   b  and the circuit board (Z) remain unchanged whichever of the front and rear surfaces of the chip that are the two sides (the top and bottom surfaces in FIG. 14) parallel with the straight line (X) orthogonal to the winding center line (Y) is opposed to the surface of the circuit board (Z). Accordingly, the magnetic resistance remains the same in each mounting orientation, thereby preventing the inductance provided by the coil  62  and leadout conductors  64   a  and  64   b  form being changed by the mounting orientation. 
     Next, a fourth embodiment of the present invention is described. 
     FIG. 16 is a perspective view showing a laminated inductor according to a fourth embodiment of the present invention. In the figures, the same components as in the third embodiment has the same reference numerals, and their description is omitted. 
     In addition, the fourth embodiment differs from the third embodiment in that the two leadout conductors are not located on the winding center line (Y) of the coil  62  but symmetrically around the winding center line (Y). 
     That is, in a laminated inductor  60 ′ in the fourth embodiment, leadout conductors  65   a,    65   b  and  66   a,    66   b  are formed at the respective ends of a chip  61  in such a manner that their ends are exposed on one of the diagonal lines in the end surface of the chip  61  and at an equal distance from the central point through which the winding center line (Y) passes and that the conductors are parallel with the winding center line (Y), is as shown in FIG.  16 . 
     The leadout conductor  65   a,    65   b,    66   a,  and  66   b  can be obtained by forming the via hole (h) and the leadout conductors (Pa) and (Pc) in the top- and bottom-layer sheets  41  and  48 , as described above. 
     In addition, of course, connection conductors shaped to connect the ends of the coil  62  to the leadout conductors  65   a,    65   b,    66   a,  and  66   b  are formed in connection sheets  42  and  47 . 
     The laminated inductor  60 ′ according to the fourth embodiment can provide effects similar to those of the third embodiment. 
     That is, in the laminated inductor  60 ′, the winding center line (Y) of the coil  62  is set on a straight line joining the centers of the end surfaces of the chip where terminal electrodes  63   a  and  63   b  are formed. In addition, the coil  62  is formed in such a manner that the winding locus (Loc) of the coil  62  is parallel with one of the sides of the chip  61  different from its end surfaces and that the locus is symmetrical around a straight line orthogonal to the winding center line (Y) of the coil  62 . Furthermore, the two leadout conductors  65   a  and  65   b  or  66   a  and  66   b  joining the end of the coil and the terminal electrode  63   a  or  63   b  together are located symmetrically around the winding center line (Y) of the coil  62 . Thus, when the laminated inductor  60 ′ is mounted on the circuit board, the distances between the coil  62  and the circuit board and between the leadout conductors  65   a,    65   b,    66   a,  and  66   b  and the circuit board remain unchanged whichever of the front and rear surfaces of the chip  61  that are the two sides parallel with the straight line orthogonal to the winding center line (Y) is opposed to the surface of the circuit board. Accordingly, the magnetic resistance remains the same in each mounting orientation, thereby preventing the inductance provided by the coil  62  and leadout conductors  65   a,    65   b,    66   a,  and  66   b  being changed by the mounting orientation. 
     Although the fourth embodiment forms the leadout conductors  65   a,    65   b  and  66   a,    66   b  on the diagonal line on the respective end surface of the chip  61 , the present invention is not limited to this aspect. The above effects can be obtained as long as the leadout conductors are formed symmetrically around the winding center line (Y) of the coil  62 , and the positions at which the conductors are formed and the number of them may be determined as required. 
     In addition, although the third and fourth embodiments form the coil  62  in such a way that the winding locus of the coil  62  as seen in the direction of the winding center line (Y) of the coil  62  is an isosceles triangle, the present invention is not limited to this aspect. 
     Similar effects can be obtained by forming the coil  62  in such a manner that the winding locus of the coil as seen in the direction of the winding center line (Y) is parallel with one of the sides of the chip  61  different from its end surfaces and that the locus is symmetrical around the straight line (X) orthogonal to the winding center line (Y). 
     Next, a fifth embodiment of the present invention is described. 
     FIG. 17 is a perspective view of a laminated inductor  70  according to a fifth embodiment, FIG. 18 shows the winding locus of a coil as seen in the direction of the winding center line of the coil, and FIG. 19 is an exploded perspective view showing the laminated structure of the inductor. 
     In these figures,  71  is a rectangular-parallelepiped-shaped chip of a magnetic or non-magnetic insulating material having a laminated structure, and  72  is a coil consisting of internal conductors buried in the chip  71  and spirally connected together. Reference numerals  73   a  and  73   b  designate a pair of terminal electrodes provided at the respective longitudinal ends of the chip  71 , that is, the respective ends in the lamination direction of the laminated structure of the chip  71 . 
     An end surface  71   a  of the chip  71  on which the terminal electrode  73   a  or  73   b  is formed constitutes a square. In addition, the coil  72  is formed in such a way that its winding center line Y is located on a straight line joining together the centers of the end surfaces  71   a  of the chip  71  forming the terminal electrodes  73  and  73   b  and that the winding locus of the coil  72  as seen in the direction of the winding center line (Y) is line-symmetrical around each of the two diagonal lines of the end surface  71   a  of the chip  71 . Furthermore, the respective ends of the coil  72  are connected to the terminal electrodes  73   a  and  73   b  via leadout conductors  74   a  and  74   b  located on the winding center line (Y) of the coil  72 . 
     The coil  72  is formed by laminating a plurality of square coil-layer sheets  83  to  86  having in their top surface U-shaped internal coil conductors (Pe 1 ) to (Pe 4 ), respectively, having at one end the via hole (h) with a conductor filled therein. When the coil-layer sheets  83  to  86  are laminated, the via-hole end of each of the internal coil-conductors (Pe 1 ) to (Pe 4 ) is connected via the conductor in the via hole (h) to the other end of another internal coil conductor immediately above or below the first conductor so that the internal coil conductors (Pe 1 ) to (Pe 4 ) formed in the plurality of layers form the spiral coil  72 . 
     In addition, according to the fifth embodiment, the coil  72  is formed in such a manner that the winding locus of the coil  72  as seen in the direction of the winding center line (Y) of the coil  72  constitutes a square having diagonal lines overlapping the two corresponding diagonal lines in the end surface  71   a  of the chip  71 . 
     A square connection sheet  82  having in its surface a connection conductor (Pf 1 ) with the via hole (h) formed therein is laminated on the coil-layer sheet  83 , and this via hole (h) connects the connection conductor (Pf 1 ) and the internal coil conductor (Pe 1 ) together. 
     Furthermore, one or more square top-layer sheets  81  with the leadout conductor (Pa) formed in the via hole (h) located as described above are laminated on the connection sheet  82 , and during lamination, the leadout conductor (Pa) is connected to the connection conductor (Pf 1 ). 
     In addition, a connection sheet  87  having in its surface a square connection conductor (Pf 2 ) with the via hole (h) formed therein is laminated under the coil-layer sheet  86 , and the connection conductor (Pf 2 ) and the internal coil conductor (Pe 4 ) are connected together via the via hole (h) formed in the coil-layer sheet  86  located over the conductor (Pf 2 ). 
     Furthermore, one or more square bottom-layer sheets  88  with the leadout conductor (Pc) formed in the via hole (h) located as described above are laminated under the connection sheet  87 , and during lamination, the leadout conductor (Pc) is connected to the connection conductor (Pf 2 ). 
     Thus, the plurality of leadout conductors (Pa) for the leadout conductor  74   a,  and the plurality of leadout conductors (Pc) form the leadout conductor  74   b.    
     In the laminated inductor  70  of the above configuration, the coil  72  is formed in such a way that the cross section of the chip perpendicular to the winding center line (Y) of the coil  72  is a square and that the winding locus of the coil  72  as seen in the direction of the winding center line (Y) is line-symmetrical around each of the two diagonal lines of the end surface of the chip  71 . Thus, when the chip  71  is mounted on the circuit board, the distances (the locational relationship) between the coil  72  and the circuit board and between the leadout conductors  74   a  and  74   b  and the circuit board remain unchanged whichever of the top and bottom surfaces and sides of the chip  71  is opposed to the surface of the circuit board. Accordingly, the magnetic resistance and inductance of the laminated inductor  70  remains the same whichever mounting orientation is selected. 
     Next, a sixth embodiment of the present invention is described. 
     FIG. 20 is a perspective view showing a laminated inductor according to the sixth embodiment of the present invention, and FIG.  21  shows positions at which leadout conductors are formed. In the figures, the same components as in the fifth embodiment has the same reference numerals, and their description is omitted. 
     In addition, the sixth embodiment differs form the fifth embodiment in that the two leadout conductors are not located on the winding center line (Y) of the coil  72  but are located at the respective ends of the chip  71  on the diagonal line in the end surface thereof and symmetrically around the winding center line (Y) of the coil  72 . 
     That is, in a laminated inductor  70 ′ in the sixth embodiment, leadout conductors  75   a ,  75   b  and  75   c ,  75   d  are formed at the respective ends of a chip  71  such a manner that their ends are exposed on one of the diagonal lines in the end surface of the chip  71  and at an equal distance (D) from the central point (Yp) through which the winding center line (Y) passes and that the conductors are parallel with the winding center line (Y), as shown in the figure. 
     The leadout conductors  75   a ,  75   b ,  75   c , and  75   d  can each be obtained by forming the via hole (h) and the leadout conductors in the top- and bottom-layer sheets  81  and  88 , as in the leadout conductors  74   a  and  74   b  in the fifth embodiment. 
     In addition, connection conductors shaped to connect the ends of the coil  72  to the leadout conductors  75   a ,  75   b ,  75   c , and  75   d  are formed in the connection sheets  82  and  87 . 
     The laminated inductor  70 ′ according to the sixth embodiment can provide effects similar to those of the fifth embodiment. 
     In the laminated inductor  70 ′ of the above configuration, the coil  72  is formed in such a way that the cross section of the chip perpendicular to the winding center line (Y) of the coil  72  is a square and that the winding locus of the coil  72  as seen in the direction of the winding center line is line-symmetrical around each of any two crossing straight lines perpendicularly crossing the winding center line (Y) of the coil  72 . Furthermore, at least two of the leadout conductors  75   a  and  75   d  are located on the diagonal line in the cross section of the chip and symmetrically around the winding center line of the coil  72 . Thus, even if multiple mounting orientations are possible in which the inductor is mounted on the circuit board, the distances between the coil  72  and the circuit board and between the leadout conductors  75   a  to  75   d  and the circuit board are always the same. Consequently, the distances between the coil  72  and the circuit board and between the leadout conductors  75   a  to  75   d  and the circuit board remain unchanged regardless of the multiple mounting orientations, that is, whichever of the four sides of the chip different from the end surfaces is opposed to the surface of the circuit board. Accordingly, the magnetic resistance remains the same in each mounting orientation, thereby preventing the inductance provided by the coil  72  and leadout conductors  75   a  to  75   d  from being changed by the mounting orientation. 
     Next, a seventh embodiment of the present invention is described. 
     FIG. 22 is a perspective view showing a laminated inductor  70 ″ according to the seventh embodiment of the present invention, and FIG. 23 shows positions at which leadout conductors are formed. In the figures, the same components as in the fifth embodiment has the same reference numerals, and their description is omitted. 
     In addition, the seventh embodiment differs from the fifth embodiment in that the leadout conductors are not located on the winding center line (Y) of the coil  72  but at the respective ends of the chip at four different positions that are 90°-rotation-symmetrical about the winding center line of the coil  72 . 
     That is, in a laminated inductor  70 ″ in the seventh embodiment, leadout conductors  76   a  to  76   a  and  76   e  to  76   h  are formed at the respective ends of a chip  71  in such a manner that their ends are exposed on any two crossing straight lines (X 1 ) and (X 2 ) crossing the winding center line (Y) in the end surface of the chip and at an equal distance (D) from the central point (Yp) through which the winding center line (Y) passes and that the conductors are parallel with the winding center line (Y), as shown in the figure. 
     The conductors  76   a  and  76   h  can each be obtained by forming the via hole and the leadout conductors in the top- and bottom-layer sheets  81  and  88 , as in the leadout conductors  74   a  and  74   b  in the fifth embodiment. 
     In addition, connection conductors shaped to connect the ends of the coil  72  to the leadout conductors  76   a  to  76   h  are formed in connection sheets  82  and  87 . 
     The laminated inductor  70 ″ according to the seventh embodiment can provide effects similar to those of the fifth embodiment. 
     Although the fifth to seventh embodiments form the coil  72  in such a way that the winding locus (Loc) of the coil  72  as seen in the direction of the winding center line (Y) of the coil  72  is a square having diagonal lines overlapping the two corresponding diagonal lines in the end surface  71   a  of the chip  71 , the present invention is not limited to this aspect. Similar effects can be obtained by forming the coil  72  in such a manner that the winding locus of the coil  72  as seen in the direction of the winding center line (Y) is parallel with the cross section of the chip and that the locus is also line-symmetrical about each of any two crossing straight lines crossing the winding center line (Y) of the coil  72 . 
     Next, an eighth embodiment of the present invention is described. 
     FIG. 24 is a perspective view of a laminated inductor  90  according to the eighth embodiment, FIG. 25 shows the winding locus of a coil as seen in the direction of the winding center line of the coil, and FIG. 26 is an exploded perspective view showing the laminated structure of the inductor. 
     In these figures,  91  is a cylindrical chip of a magnetic or non-magnetic insulating material having a laminated structure, and  92  is a coil consisting of internal conductors buried in the chip  91  and spirally connected together. Reference numerals  93   a  and  93   b  designate a pair of terminal electrodes provided at the respective longitudinal ends of the chip  91 , that is, the respective ends in the lamination direction of the laminated structure of the chip. 
     The end surface  91   a  of the chip on which the terminal electrode  93   a  or  93   b  is formed is circular, and the coil  92  is formed in such a way that its winding center line (Y) is located on a straight line joining together the centers of the end surfaces  91   a  of the chip forming the terminal electrodes  93   a  and  93   b  and that the winding locus (Loc) of the coil as seen in the direction of the winding center line (Y) constitutes in any cross section of the chip a circle having as its center the central point (Yp) through which the winding center line (Y) passes. That is, the coil  92  is formed in such a manner that the winding locus (Loc) as seen in the direction of the winding center line (Y) of the coil  92  is located at an equal distance from the winding center line (Y). 
     Moreover, the respective ends of the coil  92  are connected to the terminal electrodes  93   a  and  93   b  via leadout conductors  94   a  and  94   b  located on the winding center line (Y) of the coil  92 . 
     The coil  92  is formed by laminating a plurality of circular coil-layer sheets  103  and  104  having in their top surface circular internal coil conductors (Pg 1 ) and (Pg 2 ), respectively, having at one end the via hole (h) with a conductor filled therein. When the coil-layer sheets  103  and  104  are laminated, the via-hole end of the internal coil-conductor (Pg 1 ) or (Pg 2 ) is connected via the conductor in the via hole (h) to the other end of the other internal coil conductor over the first conductor so that the internal coil conductors (Pg 1 ) and (Pg 2 ) formed in the plurality of layers form the spiral coil  92 . 
     A circular connection sheet  102  having in its surface a connection conductor (Ph 1 ) with the via hole (h) formed therein is laminated on the coil-layer sheet  103 , and this via hole (h) connects the connection conductor (Ph 1 ) and the internal coil conductor (Ph 1 ) together. 
     Furthermore, one or more circular top-layer sheets  101  with the leadout conductor (Pa) formed in the via hole (h) located at the center are laminated on the connection sheet  102 , and during lamination, the leadout conductor (Pa) is connected to the connection conductor (Ph 1 ). 
     In addition, a connection sheet  105  having in its surface a circular connection conductor (Ph 2 ) with the via hole (h) formed therein is laminated under the coil-layer sheet  104 , and the connection conductor (Ph 2 ) and the internal coil conductor (Pg 2 ) are connected together via the via hole (h) formed in the coil-layer sheet  104  located over the conductor (Ph 2 ). 
     Furthermore, one or more circular bottom-layer sheets  106  with the leadout conductor (Pc) formed in the via hole (h) located at the center are laminated under the connection sheet  105 , and during lamination, the leadout conductor (Pc) is connected to the connection conductor (Ph 2 ). 
     Thus, the plurality of leadout conductors (pa) form the leadout conductor  94   a,  and the plurality of leadout conductors (Pc) form the leadout conductor  94   b.    
     According to the laminated inductor  90  consisting of the above configuration, the winding center line (Y) of the coil  92  is formed in the direction of a line joining the centers of the end surfaces  91   a  of the chip where the terminal electrodes  93   a  and  93   b  are formed, the coil  92  is formed in such a way that the distance between the winding locus (Loc) of the coil  92  as seen in the direction of the winding center line (Y) and the central point through which the winding center line (Y) passes remains constant, and the leadout conductors  94   a  and  94   b  connecting the coil  92  to the terminal electrodes  93   a  and  93   b  are located on the winding center line (Y) of the coil  92 . Consequently, when the inductor is mounted on the circuit board, the distances between the coil  92  and the circuit board and between the leadout conductors  94   a  and  94   b  and the circuit board remain unchanged regardless of the manner in which it is mounted as long as the winding center line (Y) of the coil is parallel with the surface of the circuit board. As a result, the magnetic resistance remains the same in each mounting orientation, thereby preventing the inductance provided by the coil  92  and leadout conductors  94   a  and  94   b  from being changed by the mounting orientation. 
     Next, a ninth embodiment of this invention is described. 
     FIG. 27 is a perspective view showing a laminated inductor  110  in the ninth embodiment, FIG. 28 is a side sectional view of FIG. 27, FIG. 29 is an exploded perspective view showing the laminated structure of FIG. 27, and FIG. 30 shows the arrangement of a leadout conductor as seen in the direction of the winding center line of the coil. In the figures, the same components as in the first embodiment have the same reference numerals and their description is omitted. The ninth embodiment differs from the first embodiment in that both ends of a coil  112  are set symmetrical around the center of the chip  11  and in that leadout conductors connecting the respective ends of the coil  112  to terminal electrodes  13   a  and  13   b  are also formed symmetrically around the center of the chip  11 . 
     That is, in the ninth embodiment, the respective ends of the coil  112  are located on the winding locus of the coil as seen in the direction of the winding center line (Y) and symmetrically around the center of the chip  11 . 
     In addition, the leadout conductors connecting the respective ends of the coil  112  to the terminal electrodes  13   a  and  13   b  are composed of first leadout conductors  114   a  and  114   b,  first connection conductors  115   a  and  115   b,  and connection conductors (second connection conductors)  116   a  and  116   b.    
     The first leadout conductors  114   a  and  114   b  are located on the winding center line (Y). One end of each of the first leadout conductors  114   a  and  114   b  is connected to the connection conductor  116   a  and  116   b,  while the other end is exposed from the end surface of the chip  11  and connected to the terminal electrode  13   a  and  13   b.    
     The first connection conductors  115   a  and  115   b  are located parallel with the winding center line (Y). One end of each of the first connection conductors  115   a  and  115   b  is connected to the end of the coil  112 , while the other end is connected to the connection conductor  116   a  or  116   b.    
     The connection conductors  116   a  and  116   b  are each L-shaped and are perpendicular to the winding center line (Y) of the coil  112 . In addition, the connection conductors  116   a  and  116   b  are located symmetrically around the central point of the chip  11 . 
     As shown in FIG. 29, the chip  11  is formed by laminating one or more layers of a first to a third upper-layer sheets  121 A to  121 C, coil layer sheets  122  to  126 , and a first to a third-lower layer sheets  127 A to  127 C, wherein each sheet consists of a rectangular insulating material sheet of a predetermined thickness. 
     In the following description, the laminating direction of the sheets of the sheets  121  to  127  is assumed to be the vertical direction so as to correspond to FIG.  29 . 
     The coil  112  is formed by laminating a plurality of rectangular coil layer sheets  122  to  126  having formed thereon approximately U-shaped internal coil conductors Pj 1  to Pj 5  each having a via hole (h) with a conductor filled therein at one end. When the coil layer sheets  122  to  126  are laminated, one end of each internal coil conductor Pj 1  to Pj 5  is connected to the other end of the vertically adjacent one through the conductors in the via hole (h) so that the internal coil conductors Pj 1  to Pj 5  formed in multiple layers form the spiral coil  112 . 
     In addition, the coil  112  is formed is formed in such a way that the winding locus of the coil as seen in the direction of the winding center line (Y) is point-symmetrical around the central point through which the winding center line (Y) passes. 
     In addition, one or more layers of the third upper-layer sheets  121 C each having a connection conductor Pk 1  formed in the via hole (h) are laminated on the coil layer sheet  122 , and during lamination, the connection conductor Pk 1  is connected to the internal coil conductor Pj 1  and the connection conductor  116   a.    
     In addition, the second upper-layer sheet  121 B having in its surface a connection conductor  116   a  having the via hole (h) formed at one end is laminated on the third upper-layer sheet  121 C. These via holes (h) connect the second upper-layer sheet  121 B to the connection conductor Pk 1  of the third upper-layer sheet  121 C. 
     Furthermore, one or more first upper-layer sheets  121 A each having a leadout conductor Pk 2  in the central via hole (h) are formed on a second upper-layer sheet  121 B, and during lamination, the leadout conductor Pk 2  is connected to the other end of the connection conductor  116   a.    
     In addition, one or more layers of the first lower-layer sheets  127 A each having a connection conductor Pl 1  formed in the via hole (h) are laminated under the coil layer sheet  126 , and during lamination, the connection conductor Pl 1  is connected to the internal coil conductor Pj 5  and the connection conductor  116   b.    
     In addition, the second lower-layer sheet  127 B having in its surface a connection conductor  116   b  having the via hole (h) formed at one end is laminated under the first lower-layer sheet  127 A, and the via hole (h) formed in the first lower-layer sheet  127 A located over the second lower-layer sheet  127 B connects the second lower-layer sheet  127 B to the connection conductor Pl 1 . 
     Furthermore, one or more third lower-layer sheets  127 C each having a leadout conductor Pl 2  in the central via hole (h) are formed under the second lower-layer sheet  127 B, and during lamination, the leadout conductor Pl 2  is connected to the other end of the connection conductor  116   b.    
     Thus, the plurality of leadout conductors Pk 1  form a one-end-side first leadout conductor  115   a,  while the plurality of leadout conductors Pl 1  form the other-end-side first leadout conductor  115   b.  In addition, the plurality of leadout conductors Pk 2  form a one-end-side first leadout conductor  114   a,  while the plurality of leadout conductors Pl 2  form the other-end-side first leadout conductor  114   b.  Furthermore, the respective ends of the coil  112  are located on the winding locus of the coil as seen in the direction of the winding center line (Y) and symmetrically around the center of the chip  11 . 
     The connection conductors  116   a  and  116   b  constitute a second connection conductor. In addition, a second leadout conductor is composed of the first connection conductors  115   a  and  115   b  and the connection conductors (second connection conductors)  116   a  and  116   b.    
     In the above laminated inductor  110 , the chip  11  is rectangular parallelopiped, the winding center line (Y) of the coil  112  is set on the straight line joining together the centers of the end surfaces of chip on which the terminal electrodes  13   a  and  13   b  are formed, respectively, and both ends of the coil  112  are set symmetrical around the center of the chip  11 . Furthermore, the first leadout conductors  114   a  and  114   b,  first connection conductors  115   a  and  115   b,  and connection conductors (second connection conductors)  116   a  and  116   b  which all connect the respective end of the coil  112  to the terminal electrodes  13   a  and  13   b,  are located symmetrically around the center of the chip  11 . Thus, when the laminated inductor  110  is mounted on the circuit board in such a way that the top or bottom surface of the chip  11  in FIG. 27 is opposed to the surface of the circuit board, the positional relationship between the circuit board and the coil  112 , first leadout conductors  114   a  and  114   b,  first connection conductors  115   a  and  115   b,  and connection conductors (second connection conductors)  116   a  and  116   b  remains unchanged in the entire chip whichever surface of the chip is opposed to the circuit board. That is, the positional relationship between the coil  112  and the circuit board remains the same even if the inverted laminated inductor  110  is mounted on the circuit board. The positional relationship between the circuit board and the first leadout conductor  114   a,  first connection conductor  115   a,  and connection conductor (second connection conductor)  116   a  all on one side of the coil  112  and the positional relationship between the circuit board and the first leadout conductor  114   b,  first connection conductor  115   b,  and connection conductor (second connection conductor)  116   b  all on the other side are inverted when the vertically inverted laminated inductor  110  is mounted on the circuit board. In the entire laminated inductor  110 , however, the general positional relationship can be assumed to remain unchanged. 
     Thus, almost uniform magnetic resistance is effected on magnetic fluxes generated around the coil  112 , first leadout conductors  114   a  and  114   b,  first connection conductors  115   a  and  115   b,  and connection conductors (second connection conductors)  116   a  and  116   b,  thereby preventing the inductance from varying. 
     In addition, if the laminated inductor  110  is mounted on the circuit board in such a way that one of the sides of the chip  11  in FIG. 27 other than its end surfaces is opposed to the surface of the circuit board, the general positional relationship between the circuit board and the coil  112 , first leadout conductors  114   a  and  114   b,  first connection conductors  115   a  and  115   b,  and connection conductors (second connection conductors)  116   a  and  116   b  remains unchanged whichever surface is opposed to the surface of the circuit board. Accordingly, almost uniform magnetic resistance is effected on magnetic fluxes generated around the coil  112 , first leadout conductors  114   a  and  114   b,  first connection conductors  115   a  and  115   b,  and connection conductors (second connection conductors)  116   a  and  116   b,  thereby preventing the inductance from varying. 
     Furthermore, the connection conductors  116   a  and  116   b  may be L-shaped and located on the winding locus of the coil  112  to increase the inductance of the coil  112 . 
     The positions and shapes of the first leadout conductors  114   a  and  114   b,  first connection conductors  115   a  and  115   b,  and connection conductors (second connection conductors)  116   a  and  116   b  are not limited to those described above, and similar effects can be obtained as long as these components are symmetrical about the center of the chip  11 . 
     Similar effects can also be obtained even if the chip  11  is shaped like a regular square pole, that is, formed to have a square cross section perpendicular to the winding center line of the coil  112 . In this case, each of the sheets  121  to  127  forming the chip  11  may be shaped like a square. Furthermore, by arranging the first connection conductors  115   a  and  115   b  on a diagonal line in a cross section of the coil  112  perpendicular to the winding center line and the connection conductors  116   a  and  116   b  on a diagonal line as shown in FIG. 31, similar effects can be obtained even if not only vertically inverted but also rotated inductor is mounted on the circuit board. 
     Next, a tenth embodiment of this invention is described. 
     FIG. 32 is a side sectional view showing a laminated inductor  131  according to the tenth embodiment. In this figure, the same components as in the ninth embodiment have the same reference numerals and their description is omitted. The tenth embodiment differs from the ninth embodiment in that the length L 1  of the first connection conductors  115   a  and  115   b  is set larger than the length L 2  of the first leadout conductors  114   a  and  114   b.    
     This configuration allows the first leadout conductors  114   a  and  114   b  and the connection conductors  116   a  and  116   b  to be separated from the center of the magnetic fluxes generated by the coil  112 . This can in turn reduce the loss of magnetic fields caused by the effect of the first leadout conductors  114   a  and  114   b  and connection conductors  116   a  and  116   b,  thereby increasing “Q” of the inductor. 
     By setting the length L 2  of the first leadout conductors  114   a  and  114   b  smaller than the length L 3  of the terminal electrodes  13   a  and  13   b  formed on surfaces of the chip  11  other than its end surfaces as shown in FIG. 33, the loss of magnetic fields caused by the effect of the first leadout conductors  114   a  and  114   b  and connection conductors  116   a  and  116   b  can be reduced. 
     Next, an eleventh embodiment of this invention is described. 
     FIG. 34 is a side sectional view showing a laminated inductor  132  according to the eleventh embodiment. In this figure, the same components as in the ninth embodiment have the same reference numerals and their description is omitted. The eleventh embodiment differs from the ninth embodiment in that the length L 1  of the first connection conductors  115   a  and  115   b  is set smaller than the length L 2  of the first leadout conductors  114   a  and  114   b.    
     This configuration increases the gap between the first connection conductors  115   a  and  115   b  and the terminal electrodes  13   a  and  13   b  formed in a portion of the chip  11  other than its end surfaces to reduce the floating electrostatic capacity generated therebetween, thereby increasing the resonant frequency of the inductor. To increase this effect, the length L 2  of the first leadout conductors  114   a  and  114   b  is preferably set larger than the length L 3  of the terminal electrodes  13   a  and  13   b  formed in a surface of the chip  11  other than its end surfaces. 
     Next, a twelfth embodiment of this invention is described. 
     FIG. 35 is a side sectional view showing a laminated inductor  133  according to the twelfth embodiment. In this figure, the same components as in the ninth embodiment have the same reference numerals and their description is omitted. According to the twelfth embodiment, the length L 2  of the first leadout conductors  114   a  and  114   b  is set the same as the length l 3  of the terminal electrode formed in a surface of the chip  11  other than its end surfaces. By setting the length l 2  of the first leadout conductors  114   a  and  114   b  in this manner, the floating electrostatic capacity can be prevented from occurring between the first connection conductors  115   a  and  115   b  and the terminal electrodes  13   a  and  13   b  while the loss of magnetic fields caused by the effect of the first leadout conductors  14   a  and  14   b  and connection conductors (second connection conductor)  116   a  and  116   b  can be reduced. This configuration is particularly effective when the number of windings of the coil  112  is small. 
     Next, a thirteenth embodiment of this invention is described. 
     FIG. 36 is an exploded perspective view showing the laminated structure of a laminated inductor  134  according to a thirteenth embodiment. In this figure, the same components as in the ninth embodiment have the same reference numerals and their description is omitted. The thirteenth embodiment differs from the ninth embodiment in that two coil conductors Pj 1 , two coil conductors Pj 2 , two coil conductors Pj 3 , two coil conductors Pj 4 , two coil conductors Pj 5 , and two coil conductors Pj 6  forming the coil  112  are laminated so as to be connected in parallel, thereby reducing the electric resistance of the coil  112 . 
     Next, a fourteenth embodiment of this invention is described. 
     FIG. 37 is a side sectional view showing a laminated inductor  135  according to a fourteenth embodiment. In this figure, the same components as in the ninth embodiment have the same reference numerals and their description is omitted. The fourteenth embodiment differs from the ninth embodiment in that the thickness of the first leadout conductors  114   a  and  114   b  is set larger than that of the first connection conductors  115   a  and  115   b.  That is, the diameter of the via holes (h) formed in the leadout conductors Pk 2  and Pl 2  forming the first leadout conductors  114   a  and  114   b  is set larger than that of the via holes (h) formed in the connection conductors Pk 1  and Pl 1  forming the first connection conductors  115   a  and  115   b.  This configuration increases the area of the exposed portion of the first leadout conductors  114   a  and  114   b  at the end surfaces of the chip  11  compared to the prior art, thereby improving the connectivity between the first leadout conductors  114   a  and  114   b  and the terminal electrodes  13   a  and  13   b.    
     Next, a fifteenth embodiment of this invention is described. 
     FIG. 38 is a side sectional view showing a laminated inductor  136  according to a fifteenth embodiment, and FIG. 39 is its top sectional view. In these figures, the same components as in the ninth embodiment have the same reference numerals and their description is omitted. The fifteenth embodiment differs from the ninth embodiment in that the second connection conductor  117   a  and  117   b  connecting the first leadout conductors  114   a  and  114   b  and the first connection conductors  115   a  and  115   b  together are formed in such a way as to gradually approach the winding center line (Y) and first leadout conductors  114   a  and  114   b.  That is, as shown in FIG. 40, the second connection conductors  117   a  and  117   b  are formed by using the via holes (h) to couple the connection conductors Pk 3  and Pl 3  formed in the plurality of second upper-layer sheet insulating body layers in such a way as to be arranged like steps. This configuration allows the second connection conductors  117   a  and  117   b  to be arranged approximately in a line crossing the first leadout conductors at a larger angle (obtuse angle). 
     The following effects can be obtained by forming the second connection conductor  117   a  and  117   b  connecting the first connection conductors  115   a  and  115   b  and the first leadout conductors  114   a  and  114   b  together in such a way as to gradually approach the winding center line (Y) and first leadout conductors  114   a  and  114   b.  The second connection conductors  117   a  and  117   b  are formed so as to correspond to the gradual attenuation of the field strength, so the floating electrostatic capacity can be prevented from occurring between the second connection conductors and the terminal electrodes while reducing the loss of magnetic fields. This is particularly effective if the terminal electrodes  13   a  and  13   b  cover the coil  112  due to the compactification of electronic components or a large number of windings of the coil  112 . 
     Next, a sixteenth embodiment of this invention is described. 
     FIG. 41 is a side sectional view showing a laminated inductor  137  according to a sixteenth embodiment. In this figure, the same components as in the ninth embodiment have the same reference numerals and their description is omitted. The sixteenth embodiment differs from the ninth embodiment in that a gap  141  is formed between the insulating bodies (magnetic substances) and internal conductors constituting the chip  11 . The internal conductors constitute the coil  112 , the first leadout conductors  114   a  and  114   b,  the first connection conductors  115   a  and  115   b,  and the connection conductors (second connection conductors)  116   a  and  116   b.    
     If the gap  141  is formed between the magnetic substances and internal conductors constituting the chip  11  and even if the magnetic substances or internal conductors constituting the chip  11  are expanded or contracted due to external magnetic fields, the internal strain caused by the difference in contraction rate between the magnetic substances and the internal conductors does not occur, thereby reducing the variation of the inductance value caused by external fields to improve reliability. 
     This embodiment formed the gap  141  between the magnetic substances and internal conductors constituting the chip  11 , in the following manner. 
     First, 49.0 mol % of Fe 2 O 3 , 35.0 mol % of NiO, 10.0 mol % of ZnO, and 6.0 mol % of CuO were each weighted, and these compounds were mixed with water using a ball mill to obtain a mixture. 
     Next, the mixture was dried and temporarily burned in the air at 800° C. for one hour to form an incompletely burned substance (ferrite). The incompletely burned substance was placed in the ball mill, where it is crushed for 15 hours while water is being added thereto. The slurry obtained was spray-dried using a spray dryer to obtain powders of the incompletely burned substance (ferrite powders). The specific surface area of the ferrite powders was 2.8 m 2 /g. 
     Then, the ferrite powders and a binder mainly consisting of polyvinylbutyral were mixed in the ball mill to form a slurry. 
     Then, the slurry was defoamed using a deaerator and was coated on a polyester film using the doctor blade method. After drying, the film was cut into predetermined sizes and a through-hole is formed at a predetermined position of each piece to obtain magnetic substance sheets of thickness about 50 μm. 
     In addition, 70 wt. % of Ag powders (spherical grains, average grain size: 0.3 μm), 9 wt. % of ethylcellulose, 19 wt. % of butylcarbitol, and 2 wt. % of thickner were kneaded to produce Ag paste for internal conductor patterns. 
     Next, the conductor patterns consisting of the Ag paste were each printed on the incompletely burned magnetic substance sheet using the screen printing method. 
     Then, after the conductive patterns were dried, the magnetic substance sheets were laminated and pressurized at a pressure of 500 kg/cm 2  so as to be joined and integrated together. The sheets were then cut into dices to form a large number of laminate chips. 
     Then, the laminate chips were heated to burn and remove the binder, and were subsequently burned at 900° C. for one hours. 
     Then, the Ag paste is coated on one of the end surfaces of the laminate chip from which the terminal of the outermost conductor pattern was led out, and was burned in the air at 700° C. to form a large number of laminated inductors  137  each with a terminal electrode formed and connected to the terminal of the conductor pattern. 
     In this manufacturing method, the specific surface are of the magnetic substance powders that are a material of the magnetic substance sheets is preferably between 1.0 and 10.0 m 2 /g, and the specific surface area of the conductive powders that are a material of the conductive patterns is preferably between 0.5 and 5.0 m 2 /g. 
     The specific surface area of the magnetic substance powders should be between 1.0 and 10.0 m 2 /g because below 1.0 m 2 /g, the magnetic substance powders cannot be sintered even if they are burned at 1,000° C. or lower and because beyond 10.0 m 2 /g, a large amount of time and labor is required to manufacture powders to increase costs. 
     In addition, the specific surface area of the conductive powders should be 0.5 m 2 /g or more because if the specific surface area of the magnetic substance powders is 1.0 m 2 /g or more, contraction sufficient to form the gap  141  between the magnetic substance powders and the conductive powders cannot be obtained unless the specific surface area of the conductor powders is larger than or equal to this value. 
     The specific surface area of the conductive powders should be 5.0 m 2 /g or less because if the specific surface area of the magnetic substance powders is 10.0 m 2 /g or less, contraction sufficient to form the gap  141  between the magnetic substance powders and the conductive powders can be obtained if the specific surface are of the conductor powders is smaller than or equal to this value. 
     In addition, this manufacturing method enables the continuous gap to be formed almost uniformly in the magnetic substances constituting the chip  11 , as shown in FIG.  42 . 
     According to the above manufacturing method, of the large number of laminated inductors  137  each with the gap  141  formed between the magnetic substance bodies and internal conductors constituting the chip  11 , several tens are sampled and impregnated with an epoxy resin by means of pressurization. The inductors are heated to thermally set the epoxy resin. The resin is then broken and its broken surface is observed to confirm the gap  141 . 
     The method for forming the gap between the magnetic substances and internal conductors forming the chip  11  includes methods for changing the amounts of contraction of these materials, their specific surface areas, or their grain sizes, a method for containing in the magnetic substance sheet the decomposed resin that may otherwise be evaporated and disappear during burning, and a method for changing the burning conditions. 
     In addition, since the leadout conductor section connecting the coil  112  to the terminal electrodes  13   a  and  13   b,  in particular, the second leadout conductor consisting of the first connection conductors  115   a  and  115   b  and the connection conductors  116   a  and  116   b  is most likely to be broken due to the internal strain, the gap is preferably formed at least around the second leadout conductor. 
     Next, a seventeenth embodiment of this invention is described. 
     FIG. 43 is a side sectional view showing a laminated inductor  138  according to a seventeenth embodiment. In this figure, the same components as in the sixteenth embodiment have the same reference numerals and in their description is omitted. The seventeenth embodiment differs from the sixteenth embodiment in that a gap is formed between the magnetic substances and between the magnetic substances and internal conductors constituting the chip  11 , followed by the impregnation of the gap with a synthetic resin  142 , and in that the terminal electrodes  13   a  and  13   b  are formed of porous conductors so that the pores in the terminal electrodes  13   a  and  13   b  are impregnated with the synthetic resin. The internal conductors constitute the coil  112 , the first leadout conductors  114   a  and  114   b,  the first connection conductors  115   a  and  115   b,  and the connection conductors (second connection conductors)  116   a  and  116   b.  The above synthetic resin may be silicone, epoxy, or phenol resin, but may be a different resin. 
     In the laminated inductor  137  manufactured using the manufacturing method described in the sixteenth embodiment, the gap is formed between the magnetic substances and internal conductors constituting the chip  11  and is also formed between the magnetic substances and inside the terminal electrodes  13   a  and  13   b  constituting the chip  11 , as shown in FIG.  44 . The following effects can be obtained by impregnating the gap with the synthetic resin. When the gap between the magnetic substances and internal conductors constituting the chip  11  is impregnated with the synthetic resin  142 , the internal conductors, which have been partly floating in the chip  11  due to the gap, are fixed and precluded from vibrating despite an external impact or a rapidly varying electromagnetic force, thereby preventing the metal of the internal conductors from being fatigued, which improves reliability of the electronic components. 
     In addition, as shown in FIG. 44, when the gap  11  between the magnetic substances  143  constituting the chip  11  is impregnated with the synthetic resin  142 , the binding strength of the chip  11  in the laminating direction is increased to restrain the chip  11  from being peeled off along the gap in order to improve reliability. 
     In addition, since the terminal electrodes  13   a  and  13   b  are formed of a porous material in which the internal gap consists of a continuous pore, the chip  11  can be impregnated with the synthetic resin through the terminal electrodes  13   a  and  13   b.  This configuration enables the gap in the chip  11  to be impregnated with the synthetic resin easily. 
     Moreover, since the terminal electrodes  13   a  and  13   b  are formed of a porous material in which the internal gap consists of a continuous pore, the synthetic resin contained in the terminal electrodes  13   a  and  13   b  continues with the synthetic resin contained in the chip  11  to improve the mechanical strength of the terminal electrodes  13   a  and  13   b  in binding with the chip  11 . 
     To manufacture the laminated inductor  138 , the laminated inductor  137  described in the sixteenth embodiment is formed first. At this point, the Ag paste for the terminal electrodes  13   a  and  13   b  has the following composition. 
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 Ag powders (spherical grains; average grain 
                 70 wt. % 
               
               
                   
                 size: 0.5 μm) 
               
               
                   
                 Glass frit (ZnO—B 2 O 3 —SiO 2 ) 
                  4 wt. % 
               
               
                   
                 Etylcellulose 
                  9 wt. % 
               
               
                   
                 Mixture of butylcarbitolacetate and 
                 13 wt. % 
               
               
                   
                 ethylcarbitol (1:1) 
               
               
                   
                   
               
            
           
         
       
     
     The use of the Ag paste of the above composition makes the terminal electrodes  13   a  and  13   b  porous and allows the pores in the terminal electrodes  13   a  and  13   b  to connect the surfaces of the terminal electrodes  13   a  and  13   b  to the surface of the chip  11 . 
     Subsequently, a silicone resin liquid, which as been diluted with toluene, is placed in a container, and the laminated inductor  137  with the gaps formed therein is placed in the silicone resin liquid. The container is then placed in a pressure-reduced container to reduce the pressure down to 30 Torr using a vacuum pump. The container is left as it is approximately for 10 minutes. This processing allows the gap between the magnetic substances and between the magnetic substances and internal conductors to be impregnated with the silicone resin. 
     Then, the laminated inductor is unloaded from the container and is heated at 200° C. for one hour to harden the silicone resin contained in the gap. 
     Next, the laminated inductor is placed in a rotary barrel to remove the silicone resin from the surfaces of the terminal electrodes  13   a  and  13   b.  The surface of the terminal electrodes  13   a  and  13   b  are electroplated to complete the laminated inductor  138 . 
     The synthetic resin is generally susceptible to heat, so the synthetic resin cannot be applied until after the baking of the terminal electrodes  13   a  and  13   b.  Due to the terminal electrodes  13   a  and  13   b  formed of the porous conductive material, however, the above manufacturing method enables the entire chip  11  to be impregnated with the synthetic resin even after the terminals  13   a  and  13   b  have been formed. 
     Since the leadout conductor section connecting the coil  112  to the terminal electrodes  13   a  and  13   b,  in particular, the second leadout conductor consisting of the first connection conductors  115   a  and  115   b  and the connection conductors  116   a  and  116   b  is most likely to be broken due to the internal strain, the gap is preferably formed at least around the second leadout conductor to be impregnated with the resin. 
     Although the first to seventeenth embodiments have been described by referencing the laminated inductor as an example of a laminated electronic component, the present invention is not limited to this aspect. Of course, similar effects can be obtained from compote electronic components as long they have a coil in a chip of a laminated structure. 
     In addition, the present invention can be implemented in many other forms without deviating from its sprits and major features. Thus, the above embodiments are only illustrative in any sense and should not be construed to be limitative. The scope of the present invention is indicated by the claims and is not bound by the specification. Moreover, all variatiosn and changes belonging to the uniform scope of the claims fall within the scope of the present invention.