Stacked coil array

Abstract

To provide a multilayer type coil array capable of suppressing reduction of an inductance value while suppressing the increase in DC resistance.SOLUTION: A multilayer type coil array includes an element assembly 10 including a magnetic layer, a first coil and a second coil, a first external electrode and a second external electrode connected to the first coil, a third external electrode and a fourth external electrode connected to the second coil, a first extraction conductor and a second extraction conductor connected to the first external electrode and the second external electrode, respectively, and a third extraction conductor 43 and a fourth extraction conductor 44 connected to the third external electrode and the fourth external electrode, respectively. Each of a first coil conductor layer 51 and a second coil conductor 52 includes an avoidance part 60 that is disposed inside or outside the first extraction conductor 41 in order to avoid the first extraction conductor 41, and a linear part 65 connected to the avoidance part.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a stacked coil array.

Background Art

[0002] Patent Document 1 discloses a stacked coil array for a DC-DC converter, which includes a body including a magnetic layer containing magnetic particles, a first coil and a second coil built in the body, and a first external electrode, a second external electrode, a third external electrode, and a fourth external electrode provided on the surface of the body and electrically connected to any one of the ends of the first coil and the second coil, respectively. A non-magnetic layer is provided between the first coil and the second coil. The first coil and the second coil are each formed by connecting a plurality of coil conductors in the stacking direction. An end drawn from the coil conductor closest to the second coil among the plurality of coil conductors of the first coil is connected to the first external electrode, and the other end of the first coil is connected to the second external electrode. An end drawn from the coil conductor closest to the first coil among the plurality of coil conductors of the second coil is connected to the third external electrode, and the other end of the second coil is connected to the fourth external electrode. The first external electrode and the third external electrode are connected to the output terminals of the switching elements of the DC-DC converter.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As shown in FIG. 1B of Patent Document 1, a lead conductor for connecting to an external electrode is provided at the end of the first coil or the second coil in the stacking direction (height direction T in FIG. 1B). In order to avoid such a lead conductor, the coil conductor constituting the first coil or the second coil needs to be arranged inside or outside the lead conductor in a plan view from the stacking direction.

[0005] However, when the coil conductor constituting the first coil or the second coil is arranged inside the lead conductor as in the example shown in FIG. 1B of Patent Document 1, the inner diameter area of the coil conductor is reduced by the coil conductor located in the portion avoiding the lead conductor (hereinafter also referred to as the avoidance portion), so that there is a problem that the inductance value is likely to decrease. Further, when the width of the coil conductor is narrowed in order to secure the inner diameter area of the coil conductor, there is a problem that the DC resistance (Rdc) increases.

[0006] On the other hand, although not described in Patent Document 1, when the coil conductor constituting the first coil or the second coil is arranged outside the lead conductor, the area of the substantial magnetic path is reduced by the thickness of the lead conductor, so that there is a problem that the inductance value is likely to decrease.

[0007] Note that the above problems are not limited to the laminated coil array for a DC-DC converter, but are common problems in laminated coil arrays.

[0008] The present invention has been made to solve the above problems, and an object thereof is to provide a laminated coil array capable of suppressing an increase in DC resistance and suppressing a reduction in inductance value.

Means for Solving the Problems

[0009] The stacked coil array of the present invention includes an element body including a magnetic layer, a first coil provided inside the element body and including a plurality of first coil conductor layers in a stacking direction, a second coil provided inside the element body at a position farther from a bottom surface of the element body in the stacking direction than the first coil and including a plurality of second coil conductor layers in the stacking direction, first and second external electrodes provided on the bottom surface of the element body and electrically connected to the first coil, third and fourth external electrodes provided on the bottom surface of the element body and electrically connected to the second coil, and a third external electrode provided inside the element body. the first coil conductor layer includes a first lead conductor connecting an end of the first coil conductor layer closest to the second coil to the first external electrode, a second lead conductor provided inside the element body and connecting the other end of the first coil to the second external electrode, a third lead conductor provided inside the element body and connecting an end of the second coil conductor layer closest to the first coil to the third external electrode, and a fourth lead conductor provided inside the element body and connecting the other end of the second coil to the fourth external electrode. The first coil conductor layer includes an avoidance portion disposed inside or outside the first lead conductor in a plan view from the stacking direction to avoid at least the first lead conductor, and a straight portion connected to the avoidance portion. The second coil conductor layer includes an avoidance portion that is arranged inside or outside the fourth lead conductor in a plan view from the stacking direction to avoid the fourth lead conductor, and a straight portion connected to the avoidance portion. The width of the first coil conductor layer located at at least one of the avoidance portions is narrower than the width of the first coil conductor layer located at the straight portion, or the width of the second coil conductor layer located at the avoidance portion is narrower than the width of the second coil conductor layer located at the straight portion, or the width of the first coil conductor layer located at at least one of the avoidance portions is narrower than the width of the first coil conductor layer located at the straight portion, and the width of the second coil conductor layer located at the avoidance portion is narrower than the width of the second coil conductor layer located at the straight portion. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a multilayer coil array that can suppress an increase in DC resistance and a decrease in inductance value. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view schematically showing an example of a multilayer coil array according to the present invention. [Diagram 2] FIG. 2 is a perspective view schematically showing an example of the internal structure of the multilayer coil array shown in FIG. [Figure 3] FIG. 3 is a perspective view of the internal structure shown in FIG. 2, in which the first coil, the first lead conductor, and the second lead conductor are extracted. [Figure 4] FIG. 4 is a perspective view of the internal structure shown in FIG. 2, in which the second coil, the third lead conductor, and the fourth lead conductor are extracted. [Figure 5] FIG. 5 is a plan view of the internal structure shown in FIG. 2 as seen from the bottom side of the element body. [Figure 6] FIG. 6 is a plan view for explaining a method for measuring the width of the first coil conductor layer 51 located in the avoidance portion 60 when the first coil conductor layer 51 is curved. [Figure 7A] Figure 7A is a graph showing the relationship between the average rate of increase in DC resistance (horizontal axis) and the average rate of increase in inductance value (vertical axis) when the width of the first coil conductor layer or the second coil conductor layer located in the avoidance portion is A, the width of the first coil conductor layer or the second coil conductor layer located in the straight portion is B, and the reference value is A=B=0.190. [Figure 7B] FIG. 7B is a graph showing the relationship between the average increase rate of DC resistance (horizontal axis) and the ratio of average inductance value to average DC resistance (vertical axis) when A=B=0.190 is used as the reference. [Figure 8] FIG. 8 is a plan view schematically showing a first modified example of the internal structure of the multilayer coil array of the present invention. [Figure 9] FIG. 9 is a plan view schematically showing a second modified example of the internal structure of the multilayer coil array of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, the laminated coil array of the present invention will be described. Note that the present invention is not limited to the following configuration and may be appropriately modified without departing from the gist of the present invention. Also, a combination of a plurality of the individual preferred configurations described below is also within the scope of the present invention.

[0013] The laminated coil array of the present invention is used, for example, in a DC-DC converter. The laminated coil array of the present invention can also be applied to uses other than DC-DC converters.

[0014] In this specification, terms indicating the relationship between elements (for example, "parallel", "orthogonal", etc.) and terms indicating the shape of elements do not mean only a strictly literal aspect, but also a substantially equivalent range, for example, a range including a difference of about several percent.

[0015] The drawings shown below are schematic diagrams, and their dimensions, scales of aspect ratios, etc. may be different from those of actual products.

[0016] FIG. 1 is a perspective view schematically showing an example of the laminated coil array of the present invention. FIG. 2 is a perspective view schematically showing an example of the internal structure of the laminated coil array shown in FIG. 1. Note that the shapes and arrangements of the laminated coil array and each component are not limited to the illustrated examples.

[0017] The laminated coil array 1 shown in FIGS. 1 and 2 includes a base body 10, a first coil 21, a second coil 22, a first external electrode 31, a second external electrode 32, a third external electrode 33, a fourth external electrode 34, a first lead conductor 41, a second lead conductor 42, a third lead conductor 43, and a fourth lead conductor 44.

[0018] The base body 10 has, for example, a rectangular parallelepiped shape or a substantially rectangular parallelepiped shape having six faces. The base body 10 may have rounded corners and edges. A corner is a portion where three faces of the base body 10 intersect, and an edge is a portion where two faces of the base body 10 intersect.

[0019] In FIGS. 1 and 2, the length direction, width direction, and height direction in the stacked coil array 1 and the element body 10 are shown as the L direction, W direction, and T direction, respectively. The length direction L, width direction W, and height direction T are orthogonal to each other. The mounting surface of the stacked coil array 1 is, for example, a surface (LW surface) parallel to the length direction L and the width direction W.

[0020] The element body 10 shown in FIG. 1 has a first main surface 11 and a second main surface 12 opposite to each other in the height direction T, a first end surface 13 and a second end surface 14 opposite to each other in the length direction L orthogonal to the height direction T, and a first side surface 15 and a second side surface 16 opposite to each other in the width direction W orthogonal to the length direction L and the height direction T. In the example shown in FIG. 1, the first main surface 11 of the element body 10 corresponds to the bottom surface of the element body 10.

[0021] The element body 10 includes a magnetic layer.

[0022] The element body 10 preferably has a laminated structure. Specifically, the element body 10 preferably includes a plurality of magnetic layers in the lamination direction (for example, the height direction T). Note that the boundaries of the respective layers of the laminated structure of the element body 10 do not have to be clearly visible.

[0023] When the element body 10 has a laminated structure, the degree of freedom in the design of the stacked coil array 1 increases. For example, when manufacturing the stacked coil array 1 including the first external electrode 31, the second external electrode 32, the third external electrode 33, and the fourth external electrode 34 on the bottom surface (the first main surface 11) of the element body 10, it becomes easy to draw out the first coil 21 and the second coil 22 to the bottom surface side.

[0024] The magnetic layer includes magnetic particles made of a magnetic material. The magnetic particles may be particles of a metal magnetic material such as Fe, Co, Ni, and an alloy containing at least one of these (metal magnetic particles) or ferrite particles. The magnetic particles are preferably Fe particles or Fe alloy particles. As the Fe alloy, an Fe—Si based alloy, an Fe—Si—Cr based alloy, an Fe—Si—Al based alloy, an Fe—Si—B—P—Cu—C based alloy, an Fe—Si—B—Nb—Cu based alloy, etc. are preferable.

[0025] The surface of the metal magnetic particles made of the above metal magnetic material is preferably covered with an insulating film. When the surface of the metal magnetic particles is covered with an insulating film, the insulation between the metal magnetic particles can be enhanced. As a method for forming an insulating film on the surface of the metal magnetic particles, a sol-gel method, a mechanochemical method, or the like can be used. As the material constituting the insulating film, oxides such as P and Si are preferable. Further, the insulating film may be an oxide film formed by oxidizing the surface of the metal magnetic particles. The thickness of the insulating film is preferably 1 nm or more and 50 nm or less, more preferably 1 nm or more and 30 nm or less, and still more preferably 1 nm or more and 20 nm or less. For example, a cross section obtained by polishing a sample of the stacked coil array is photographed with a scanning electron microscope (SEM), and from the obtained SEM photograph, the thickness of the insulating film covering the surface of the metal magnetic particles can be measured.

[0026] The average particle diameter of the metal magnetic particles in the magnetic layer is preferably 1 μm or more and 30 μm or less, more preferably 1 μm or more and 20 μm or less, and still more preferably 1 μm or more and 10 μm or less. The average particle diameter of the metal magnetic particles in the magnetic layer can be measured by the procedure described below. Regarding a cross section obtained by cutting a sample of the stacked coil array, a plurality of regions (for example, 5 regions) (for example, 130 μm × 100 μm) are photographed with SEM, and the obtained SEM images are analyzed using image analysis software (for example, A-image-kun (registered trademark) manufactured by Asahi Kasei Engineering Co., Ltd.) to obtain the equivalent circle diameter of the metal magnetic particles. The average value of the obtained equivalent circle diameters is taken as the average value of the metal magnetic particles.

[0027] The base body 10 may include a non-magnetic layer between the first coil 21 and the second coil 22. By providing a non-magnetic layer between the first coil 21 and the second coil 22, the insulation between the first coil 21 and the second coil 22 can be enhanced, and a short circuit occurring between the two can be suppressed.

[0028] The non-magnetic layer may contain a glass ceramic material, a non-magnetic ferrite material, or the like as a non-magnetic material. The non-magnetic layer preferably contains a non-magnetic ferrite material as a non-magnetic material. The non-magnetic ferrite material may have a composition of 40 mol% to 49.5 mol% Fe calculated as Fe2O3, 6 mol% to 12 mol% Cu calculated as CuO, and the remainder ZnO. The non-magnetic material may optionally contain additives such as Mn3O4, Co3O4, SnO2, Bi2O3, and SiO2, and may also contain trace amounts of unavoidable impurities. The non-magnetic layer preferably contains Zn-Cu ferrite.

[0029] The thickness of the nonmagnetic layer can be measured using the procedure described below. A stacked coil array sample is placed vertically and the sample is hardened with resin, with the LT surface exposed. The sample is polished to a depth of approximately half in the W direction using a polishing machine, exposing a cross section parallel to the LT surface. After polishing, the polished surface is processed using ion milling (Ion Milling System IM4000, manufactured by Hitachi High-Tech Corporation) to remove any sagging of the internal conductor caused by polishing. The approximate center of the nonmagnetic layer in the polished sample is photographed using an SEM, and the thickness of the approximate center of the nonmagnetic layer is measured from the obtained SEM photograph. This is defined as the thickness of the nonmagnetic layer.

[0030] The element body 10 may include a nonmagnetic portion between the multiple first coil conductor layers 51 that make up the first coil 21, or between the multiple second coil conductor layers 52 that make up the second coil 22. In this case, the nonmagnetic portion is provided in at least one location between adjacent coil conductor layers of the first coil conductor layer 51 and the second coil conductor layer 52. By providing a nonmagnetic portion between adjacent coil conductor layers, it is possible to prevent leakage of magnetic flux.

[0031] The non-magnetic layer and the non-magnetic portion preferably have the same composition, for example, the non-magnetic layer and the non-magnetic portion preferably are made of Zn-Cu ferrite.

[0032] A first coil 21 and a second coil 22 are provided inside the element body 10. The first coil 21 and the second coil 22 are preferably magnetically coupled. Note that the element body 10 may be provided with two coils including only the first coil 21 and the second coil 22, or may be provided with three or more coils including the first coil 21 and the second coil 22.

[0033] The first coil 21 includes multiple first coil conductor layers 51 in the stacking direction (e.g., height direction T). Adjacent first coil conductor layers 51 are connected to each other through via conductors. The first coil 21 may include two first coil conductor layers 51 in the stacking direction, or may include three or more first coil conductor layers 51 in the stacking direction.

[0034] It is preferable that the thickness of each of the first coil conductor layers 51 is the same. It is also preferable that the thickness of the first coil conductor layer 51 is equal to the thickness of the second coil conductor layer 52, which will be described later.

[0035] The second coil 22 is provided at a position farther from the bottom surface (first main surface 11) of the element body 10 than the first coil 21.

[0036] The second coil 22 includes multiple second coil conductor layers 52 in the stacking direction (e.g., height direction T). Adjacent second coil conductor layers 52 are connected to each other through via conductors. The second coil 22 may include two second coil conductor layers 52 in the stacking direction, or may include three or more second coil conductor layers 52 in the stacking direction. The number of stacked second coil conductor layers 52 may be the same as or different from the number of stacked first coil conductor layers 51.

[0037] The thickness of each of the second coil conductor layers 52 is preferably the same.

[0038] The first external electrode 31 and the second external electrode 32 are provided on the bottom surface (first main surface 11) of the element body 10 and are electrically connected to the first coil 21. The third external electrode 33 and the fourth external electrode 34 are provided on the bottom surface (first main surface 11) of the element body 10 and are electrically connected to the second coil 22. In the multilayer coil array 1, the bottom surface (first main surface 11) of the element body 10 can be used as a mounting surface. That is, mounting on the bottom surface of the multilayer coil array 1 becomes possible.

[0039] The first external electrode 31 may be provided only on the first main surface 11 of the element body 10, or may be provided across the first main surface 11 of the element body 10 and at least one of the first end face 13 and the first side face 15.

[0040] The second external electrode 32 may be provided only on the first main surface 11 of the element body 10, or may be provided across the first main surface 11 of the element body 10 and at least one of the second end face 14 and the first side face 15.

[0041] The third external electrode 33 may be provided only on the first main surface 11 of the element body 10, or may be provided across the first main surface 11 of the element body 10 and at least one of the first end face 13 and the second side face 16.

[0042] The fourth external electrode 34 may be provided only on the first main surface 11 of the element body 10, or may be provided across the first main surface 11 of the element body 10 and at least one of the second end face 14 and the second side face 16.

[0043] The first external electrode 31, the second external electrode 32, the third external electrode 33, and the fourth external electrode 34 may each be made of a conductive material such as Ag. For example, the first external electrode 31, the second external electrode 32, the third external electrode 33, and the fourth external electrode 34 each include a base electrode layer containing Ag and one or more plating layers provided on the base electrode layer.

[0044] The thicknesses of the first external electrode 31, the second external electrode 32, the third external electrode 33, and the fourth external electrode 34 are each preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less.

[0045] The thickness of the external electrode such as the first external electrode 31 can be measured by the procedure described below. The sample is polished in the same manner as the method described above, and the portion of the external electrode is photographed with an SEM. In the obtained SEM photograph, one location at the approximate center of the external electrode is measured and defined as the thickness of the external electrode.

[0046] The first lead conductor 41, the second lead conductor 42, the third lead conductor 43, and the fourth lead conductor 44 are provided inside the base body 10.

[0047] The first lead conductor 41 connects the end of the first coil layer 51 of the first coil 21 that is closest to the second coil 22 among the ends of the first coil 21 and the first external electrode 31. The first lead conductor 41 preferably extends along the stacking direction (for example, the height direction T). The first lead conductor 41 may have a stacked structure.

[0048] The second lead conductor 42 connects the other end of the first coil 21 and the second external electrode 32. The second lead conductor 42 preferably extends along the stacking direction (for example, the height direction T). The second lead conductor 42 may have a stacked structure.

[0049] The third lead conductor 43 connects the end of the second coil layer 52 of the second coil 22 that is closest to the first coil 21 among the ends of the second coil 22 and the third external electrode 33. The third lead conductor 43 preferably extends along the stacking direction (for example, the height direction T). The third lead conductor 43 may have a stacked structure.

[0050] The fourth lead conductor 44 connects the other end of the second coil 22 and the fourth external electrode 34. The fourth lead conductor 44 preferably extends along the stacking direction (for example, the height direction T). The fourth lead conductor 44 may have a stacked structure.

[0051] FIG. 3 is a perspective view of extracting the first coil, the first lead conductor, and the second lead conductor from the internal structure shown in FIG. 2.

[0052] As shown in FIG. 3, the first coil conductor layer 51 includes an avoidance portion 60 disposed inside each of the first lead conductor 41, the third lead conductor 43, and the fourth lead conductor 44 in a plan view from the lamination direction (for example, the height direction T) to avoid the first lead conductor 41, the third lead conductor 43, and the fourth lead conductor 44, and a straight portion 65 connected to the avoidance portion 60.

[0053] Note that the avoidance portion 60 of the first coil conductor layer 51 may be disposed inside the first lead conductor 41 in a plan view from the lamination direction (for example, the height direction T) to avoid at least the first lead conductor 41. That is, the first coil conductor layer 51 may include at least the avoidance portion 60 for avoiding the first lead conductor 41, and may not include the avoidance portion 60 for avoiding at least one of the third lead conductor 43 and the fourth lead conductor 44.

[0054] FIG. 4 is a perspective view of extracting the second coil, the third lead conductor, and the fourth lead conductor from the internal structure shown in FIG. 2.

[0055] As shown in FIG. 4, the second coil conductor layer 52 includes an avoidance portion 60 disposed inside the fourth lead conductor 44 in a plan view from the lamination direction (for example, the height direction T) to avoid the fourth lead conductor 44, and a straight portion 65 connected to the avoidance portion 60.

[0056] In this specification, the avoidance portion 60 means the side of the first coil conductor layer 51 or the second coil conductor layer 52 closest to the lead conductor such as the first lead conductor 41. The side located in the avoidance portion 60 may be linear or curved. Further, the avoidance portion 60 may be composed of two or more line segments.

[0057] FIG. 5 is a plan view of the internal structure shown in FIG. 2 as viewed from the bottom surface side of the element body.

[0058] In the example shown in FIG. 5, the width of the first coil conductor layer 51 located in the avoidance portion 60 (the length indicated by A in FIG. 5) is narrower than the width of the first coil conductor layer 51 located in the straight portion 65 (the length indicated by B in FIG. 5).

[0059] Rather than narrowing the overall width of the first coil conductor layer 51, by narrowing the width of the first coil conductor layer 51 located in the avoidance portion 60, an increase in DC resistance can be suppressed. Further, by narrowing the width of the first coil conductor layer 51 located in the avoidance portion 60, a reduction in the inner diameter area of the first coil conductor layer 51 can be suppressed, so that a reduction in the inductance value can be suppressed.

[0060] It is sufficient that the width of the first coil conductor layer 51 located in at least one avoidance portion 60 is narrower than the width of the first coil conductor layer 51 located in the straight portion 65, but it is preferable that the widths of the first coil conductor layers 51 located in all three avoidance portions 60 are narrower than the width of the first coil conductor layer 51 located in the straight portion 65.

[0061] Similarly, the width of the second coil conductor layer 52 located in the avoidance portion 60 may be narrower than the width of the second coil conductor layer 52 located in the straight portion 65.

[0062] To summarize the above, it is sufficient that the width of the first coil conductor layer 51 located at at least one avoidance portion 60 is narrower than the width of the first coil conductor layer 51 located at the straight portion 65, or the width of the second coil conductor layer 52 located at the avoidance portion 60 is narrower than the width of the second coil conductor layer 52 located at the straight portion 65, or the width of the first coil conductor layer 51 located at at least one avoidance portion 60 is narrower than the width of the first coil conductor layer 51 located at the straight portion 65 and the width of the second coil conductor layer 52 located at the avoidance portion 60 is narrower than the width of the second coil conductor layer 52 located at the straight portion 65. Among these, it is preferable that the width of the first coil conductor layer 51 located at all three avoidance portions 60 is narrower than the width of the first coil conductor layer 51 located at the straight portion 65 and the width of the second coil conductor layer 52 located at the avoidance portion 60 is narrower than the width of the second coil conductor layer 52 located at the straight portion 65. Note that in the first coil conductor layer 51, the width of the straight portion 65 does not have to be constant depending on the measurement position. In that case, the narrowest position of the straight portion 65 is taken as the measurement target. Similarly, in the second coil conductor layer 52, the width of the straight portion 65 does not have to be constant depending on the measurement position. In that case, the narrowest position of the straight portion 65 is taken as the measurement target.

[0063] FIG. 6 is a plan view for explaining a method of measuring the width when the first coil conductor layer 51 located at the avoidance portion 60 is curved. When the first coil conductor layer 51 located at the avoidance portion 60 is linear or the avoidance portion 60 is composed of two or more line segments, the narrowest position of the first coil conductor layer 51 located at the avoidance portion 60 is taken as the measurement target.

[0064] Find the midpoint P1 of the outer periphery of the avoidance portion 60 of the first coil conductor layer 51, and draw a tangent line L1 from the midpoint P1 to the outer periphery. Draw a perpendicular line L2 from the midpoint P1 to the tangent line L1. Find the intersection point P2 of the inner periphery of the avoidance portion 60 of the first coil conductor layer 51 and the perpendicular line L2. Define the length of the line segment connecting P1 and P2 as the width of the first coil conductor layer 51 located at the avoidance portion 60. The width of the second coil conductor layer 52 located at the avoidance portion 60 can also be measured by the same method.

[0065] The stacked coil array 1 shown in FIG. 1 can be manufactured by, for example, the method described in Japanese Patent Application Laid-Open No. 2020-61415, etc., except for changing the widths of the first coil conductor layer 51 and the second coil conductor layer 52. Note that a plurality of stacked coil arrays may be manufactured by integrally molding and then separating a laminate corresponding to the plurality of stacked coil arrays.

[0066] FIG. 7A is a graph showing the relationship between the average increase rate of the DC resistance (horizontal axis) and the average increase rate of the inductance value (vertical axis) when the width of the first coil conductor layer or the second coil conductor layer located in the avoidance portion is A, the width of the first coil conductor layer or the second coil conductor layer located in the straight portion is B, and the reference is when A = B = 0.190. FIG. 7B is a graph showing the relationship between the average increase rate of the DC resistance (horizontal axis) and the ratio of the average of the inductance value to the average of the DC resistance (vertical axis) when the reference is when A = B = 0.190.

[0067] FIGS. 7A and 7B show the simulation results of a stacked coil array having the same internal structure as FIG. 2. Specifically, it shows the simulation results when, in all layers, the values of A and B in all avoidance portions 60 are changed to the values shown in Table 1. As shown in Table 1, in the comparative example, the overall width of the coil conductor layer is narrowed, whereas in the example, the width of the coil conductor layer located in the avoidance portion is narrowed. Note that FIGS. 7A and 7B also show a straight line obtained by linearly approximating the results of the comparative example and a curve obtained by fourth-order approximating the results of the example.

[0068] Note that the average of the DC resistances (average of Rdc) is the average value of the DC resistance of the first coil and the DC resistance of the second coil. The average increase rate of the DC resistance (average increase rate of Rdc) is the increase rate with respect to the average of the DC resistances (0%) at A = B = 0.190 which is the reference.

[0069] Similarly, the average inductance value (L average) is the average value of the inductance value of the first coil and the inductance value of the second coil. The increase rate of the average inductance value (increase rate of L average) is the increase rate with respect to the average inductance value (0%) at the reference A = B = 0.190.

[0070]

Table 1

[0071] From FIGS. 7A, 7B and Table 1, instead of narrowing the entire width of the first coil conductor layer 51 or the second coil conductor layer 52 (i.e., setting A / B = 1), by narrowing the width of the first coil conductor layer 51 or the second coil conductor layer 52 located in the avoidance portion 60 (i.e., setting A / B < 1), it can be confirmed that while an increase in the DC resistance (Rdc) is suppressed, a reduction in the inductance value (L) is suppressed. For example, the ratio of A / B is preferably 0.474 or more and 0.895 or less, and more preferably 0.579 or more.

[0072] The stacked coil array of the present invention is not limited to the above-described embodiment, and various applications and modifications can be made within the scope of the present invention regarding the configuration of the stacked coil array, manufacturing conditions, and the like.

[0073] FIG. 8 is a plan view schematically showing a first modification of the internal structure of the stacked coil array of the present invention.

[0074] In the example shown in FIG. 8, in a plan view from the stacking direction (for example, the height direction T), at least one of the first lead conductor 41, the second lead conductor 42, the third lead conductor 43, and the fourth lead conductor 44 is located on the outer edge side of the element 10 rather than the straight portions 65 of the first coil conductor layer 51 and the second coil conductor layer 52.

[0075] By disposing the lead conductors such as the first lead conductor 41 outside the outer edge of the base body 10 rather than the straight portion 65, further reduction in the inner diameter area of the first coil conductor layer 51 and the second coil conductor layer 52 can be suppressed, and further reduction in the inductance value can be suppressed.

[0076] As shown in FIG. 8, in a plan view from the stacking direction (for example, the height direction T), it is preferable that all of the first lead conductor 41, the second lead conductor 42, the third lead conductor 43, and the fourth lead conductor 44 are located outside the outer edge of the base body 10 rather than the straight portion 65 of the first coil conductor layer 51 and the straight portion 65 of the second coil conductor layer 52.

[0077] FIG. 9 is a plan view schematically showing a second modification of the internal structure of the stacked coil array of the present invention.

[0078] In the example shown in FIG. 9, the avoidance portion 60 of the first coil conductor layer 51 is disposed outside the first lead conductor 41 in a plan view from the stacking direction in order to avoid at least the first lead conductor 41, and the avoidance portion 60 of the second coil conductor layer 52 is disposed outside the fourth lead conductor 44 in a plan view from the stacking direction in order to avoid the fourth lead conductor 44.

[0079] By disposing the avoidance portion 60 of the first coil conductor layer 51 or the second coil conductor layer 52 outside the lead conductors such as the first lead conductor 41, the inner diameter area of the first coil conductor layer 51 and the second coil conductor layer 52 can be ensured. Further, by narrowing the width of the first coil conductor layer 51 or the second coil conductor layer 52 located in the avoidance portion 60, reduction in the area of the base body 10 outside the first coil 21 and the second coil 22 can be suppressed, and reduction in the inductance value can be suppressed.

[0080] As shown in FIG. 9, the avoidance portion 60 of the first coil conductor layer 51 may be disposed outside each of the first lead conductor 41, the third lead conductor 43, and the fourth lead conductor 44 in a plan view from the stacking direction in order to avoid the first lead conductor 41, the third lead conductor 43, and the fourth lead conductor 44. In that case, it is preferable that the width of the first coil conductor layer 51 located at all three avoidance portions 60 is narrower than the width of the first coil conductor layer 51 located at the straight portion 65, and the width of the second coil conductor layer 52 located at the avoidance portion 60 is narrower than the width of the second coil conductor layer 52 located at the straight portion 65.

[0081] The following content is disclosed in this specification.

[0082] <1> A body including a magnetic layer, A first coil provided inside the body and including a plurality of first coil conductor layers in a stacking direction, A second coil provided inside the body at a position farther from the bottom surface of the body than the first coil in the stacking direction and including a plurality of second coil conductor layers in the stacking direction, A first external electrode and a second external electrode provided on the bottom surface of the body and electrically connected to the first coil, A third external electrode and a fourth external electrode provided on the bottom surface of the body and electrically connected to the second coil, A first lead conductor provided inside the body and connecting an end portion of the first coil conductor layer closest to the second coil among the end portions of the first coil and the first external electrode, A second lead conductor provided inside the body and connecting the other end portion of the first coil and the second external electrode, A third lead conductor provided inside the body and connecting an end portion of the second coil conductor layer closest to the first coil among the end portions of the second coil and the third external electrode, A fourth lead conductor provided inside the body and connecting the other end portion of the second coil and the fourth external electrode, the first coil conductor layer includes at least an avoidance portion disposed inside or outside the first lead conductor in a plan view from the stacking direction to avoid the first lead conductor, and a straight portion connected to the avoidance portion; the second coil conductor layer includes an avoidance portion disposed inside or outside the fourth lead conductor in a plan view from the stacking direction to avoid the fourth lead conductor, and a straight portion connected to the avoidance portion, A stacked coil array in which the width of the first coil conductor layer located in at least one of the avoidance portions is narrower than the width of the first coil conductor layer located in the straight portion, or the width of the second coil conductor layer located in the avoidance portion is narrower than the width of the second coil conductor layer located in the straight portion, or the width of the first coil conductor layer located in at least one of the avoidance portions is narrower than the width of the first coil conductor layer located in the straight portion, and the width of the second coil conductor layer located in the avoidance portion is narrower than the width of the second coil conductor layer located in the straight portion.

[0083] <2> the avoidance portion of the first coil conductor layer is disposed inside the first lead conductor in a plan view from the stacking direction so as to avoid at least the first lead conductor; the avoidance portion of the second coil conductor layer is disposed inside the fourth lead conductor in a plan view from the stacking direction so as to avoid the fourth lead conductor. <1> The stacked coil array according to claim 1.

[0084] <3> the avoidance portion of the first coil conductor layer is arranged inside the first lead conductor, the third lead conductor, and the fourth lead conductor in a plan view from the stacking direction in order to avoid the first lead conductor, the third lead conductor, and the fourth lead conductor; the width of the first coil conductor layer located in all three of the avoidance portions is narrower than the width of the first coil conductor layer located in the straight portion, and the width of the second coil conductor layer located in the avoidance portions is narrower than the width of the second coil conductor layer located in the straight portion; <2> The stacked coil array according to claim 1.

[0085] <4> when viewed from above in the stacking direction, at least one of the first lead conductor, the second lead conductor, the third lead conductor, and the fourth lead conductor is located closer to the outer edge of the element body than the straight line portion of the first coil conductor layer and the straight line portion of the second coil conductor layer; <2> or <3> The stacked coil array according to claim 1.

[0086] <5> the avoidance portion of the first coil conductor layer is disposed outside the first lead conductor in a plan view from the stacking direction so as to avoid at least the first lead conductor; the avoidance portion of the second coil conductor layer is disposed outside the fourth lead conductor in a plan view from the stacking direction in order to avoid the fourth lead conductor. <1> The stacked coil array according to claim 1.

[0087] <6> the avoidance portion of the first coil conductor layer is arranged outside the first lead conductor, the third lead conductor, and the fourth lead conductor in a plan view from the stacking direction in order to avoid the first lead conductor, the third lead conductor, and the fourth lead conductor, the width of the first coil conductor layer located in all three of the avoidance portions is narrower than the width of the first coil conductor layer located in the straight portion, and the width of the second coil conductor layer located in the avoidance portions is narrower than the width of the second coil conductor layer located in the straight portion; <5> The stacked coil array according to claim 1.

[0088] <7> When the width of the first coil conductor layer or the second coil conductor layer located in the avoidance portion is A and the width of the first coil conductor layer or the second coil conductor layer located in the straight portion is B, the ratio of A / B in all avoidance portions in all layers is 0.474 or more and 0.895 or less. <1> ~ <6> 10. The stacked coil array according to claim 9, wherein the first and second coils are stacked in a direction perpendicular to the plane of the substrate.

[0089] <8> The stacked coil array according to <7>, wherein the ratio of A / B is 0.579 or more.

[0090] <9> The stacked coil array according to any one of <1> to <8>, which is used in a DC-DC converter.

Explanation of Signs

[0091] 1 Stacked coil array 10 Element body 11 First main surface (bottom surface) 12 Second main surface 13 First end face 14 Second end face 15 First side surface 16 Second side surface 21 First coil 22 Second coil 31 First external electrode 32 Second external electrode 33 Third external electrode 34 Fourth external electrode 41 First lead conductor 42 Second lead conductor 43 Third lead conductor 44 Fourth lead conductor 51 First coil conductor layer 52 Second coil conductor layer 60 Avoidance portion 65 Straight portion A Width of the first coil conductor layer or the second coil conductor layer located in the avoidance portion B Width of the first coil conductor layer or the second coil conductor layer located in the straight portion L Length direction T Height direction W Width direction

Claims

1. A base body including a magnetic layer, A first coil provided inside the base body and including a plurality of first coil conductor layers in a stacking direction, A second coil provided inside the base body at a position farther from the bottom surface of the base body than the first coil in the stacking direction and including a plurality of second coil conductor layers in the stacking direction, A first external electrode and a second external electrode provided on the bottom surface of the base body and electrically connected to the first coil, A third external electrode and a fourth external electrode provided on the bottom surface of the base body and electrically connected to the second coil, A first lead conductor provided inside the base body and connecting an end portion of the first coil, which is the end portion of the first coil conductor layer closest to the second coil, and the first external electrode, A second lead conductor provided inside the base body and connecting the other end portion of the first coil and the second external electrode, A third lead conductor provided inside the base body and connecting an end portion of the second coil, which is the end portion of the second coil conductor layer closest to the first coil, and the third external electrode, A fourth lead conductor provided inside the base body and connecting the other end portion of the second coil and the fourth external electrode, and comprising, The first coil conductor layer includes an avoidance portion disposed inside or outside the first lead conductor in a plan view from the stacking direction to avoid at least the first lead conductor, and a straight portion connected to the avoidance portion, The second coil conductor layer includes an avoidance portion disposed inside or outside the fourth lead conductor in a plan view from the stacking direction to avoid the fourth lead conductor, and a straight portion connected to the avoidance portion, The width of the narrowest position of the first coil conductor layer located at at least one of the avoidance portions is narrower than the width of the narrowest position of the first coil conductor layer located at the straight portion, or the width of the narrowest position of the second coil conductor layer located at the avoidance portion is narrower than the width of the narrowest position of the second coil conductor layer located at the straight portion, or the width of the narrowest position of the first coil conductor layer located at at least one of the avoidance portions is narrower than the width of the narrowest position of the first coil conductor layer located at the straight portion, and the width of the narrowest position of the second coil conductor layer located at the avoidance portion is narrower than the width of the narrowest position of the second coil conductor layer located at the straight portion, a stacked coil array.

2. The avoidance portion of the first coil conductor layer is disposed inside the first lead conductor in a plan view from the lamination direction in order to avoid at least the first lead conductor. The avoidance portion of the second coil conductor layer is disposed inside the fourth lead conductor in a plan view from the lamination direction in order to avoid the fourth lead conductor. The laminated coil array according to claim 1. **Claim 3** The avoidance portion of the first coil conductor layer is disposed inside each of the first lead conductor, the third lead conductor, and the fourth lead conductor in a plan view from the lamination direction in order to avoid the first lead conductor, the third lead conductor, and the fourth lead conductor. The width of the narrowest position of the first coil conductor layer located at all three avoidance portions is narrower than the width of the narrowest position of the first coil conductor layer located at the straight portion, and the width of the narrowest position of the second coil conductor layer located at the avoidance portion is narrower than the width of the narrowest position of the second coil conductor layer located at the straight portion. The laminated coil array according to claim 2. **Claim 4** In a plan view from the lamination direction, at least one of the first lead conductor, the second lead conductor, the third lead conductor, and the fourth lead conductor is located on the outer edge side of the element body rather than the straight portion of the first coil conductor layer and the straight portion of the second coil conductor layer. The laminated coil array according to claim 2. **Claim 5** The avoidance portion of the first coil conductor layer is disposed outside the first lead conductor in a plan view from the lamination direction in order to avoid at least the first lead conductor. The avoidance portion of the second coil conductor layer is disposed outside the fourth lead conductor in a plan view from the lamination direction in order to avoid the fourth lead conductor. The laminated coil array according to claim 1. **Claim 6** The avoidance portion of the first coil conductor layer is disposed outside each of the first lead conductor, the third lead conductor, and the fourth lead conductor in a plan view from the lamination direction in order to avoid the first lead conductor, the third lead conductor, and the fourth lead conductor. The width of the narrowest position of the first coil conductor layer located at all three of the avoidance portions is narrower than the width of the narrowest position of the first coil conductor layer located at the straight portion, and the width of the narrowest position of the second coil conductor layer located at the avoidance portion is narrower than the width of the narrowest position of the second coil conductor layer located at the straight portion. The stacked coil array according to claim 5.

7. When the width of the narrowest position of the first coil conductor layer or the second coil conductor layer located at the avoidance portion is A, and the width of the narrowest position of the first coil conductor layer or the second coil conductor layer located at the straight portion is B, in all layers, the ratio of A / B at all avoidance portions is 0.474 or more and 0.895 or less. The stacked coil array according to any one of claims 2 to 6.

8. The stacked coil array according to claim 7, wherein the ratio of A / B is 0.579 or more.

9. The stacked coil array according to claim 1, 2 or 5, which is used in a DC-DC converter.

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