JP2021052180A - Inductor - Google Patents

Abstract

To provide an inductor improved in heat dissipation characteristics.SOLUTION: An inductor includes: a substrate 10 having a mounting surface 10b facing a circuit board, the top surface 10a facing the mounting surface, and end surfaces each connecting the mounting surface 10b and the top surface 10a; an external electrode 21 attached on the mounting surface 10b of the substrate 10; an external electrode 22 attached on the mounting surface of the substrate apart from the external electrode 21 in a length direction perpendicular to the end surfaces; and an internal conductor which is provided in the substrate, and one end of which is electrically connected to the external electrode 21 while the other end of which is electrically connected to the external electrode 22, the internal conductor extending linearly from the external electrode 21 toward the external electrode 22 in a plan view viewed from a thickness direction perpendicular to the mounting surface 10b. In a front view viewed from a width direction W perpendicular to the thickness direction T and the length direction L, a distance (T1-T2) between the mounting surface and a position farthest from the mounting surface 10b on the axis A of the internal conductor is less than half of an interval T1 between the top surface and the mounting surface.SELECTED DRAWING: Figure 5

Description

The present invention relates to inductors.

As disclosed in Japanese Patent Application Laid-Open No. 10-144526 (Patent Document 1), a magnetic substrate made of a ferrite material, a rectangular parallelepiped-shaped inner conductor provided in the magnetic substrate, and one end and the other end of the inner conductor. Inductors having two external electrodes, each connected to, have been conventionally known. This internal conductor extends linearly from one external electrode to the other external electrode in a plan view.

Japanese Unexamined Patent Publication No. 10-144526

In recent years, as the current of equipment and circuits has been increasing mainly for electrical components, soft magnetic metal materials that are less likely to cause magnetic saturation even when a large current flows have come to be used as the material of the magnetic substrate of the inductor. ing. However, in a magnetic substrate made of a soft magnetic metal material, an eddy current is likely to be generated as compared with a magnetic substrate made of a ferrite material, and a temperature rise is likely to occur due to Joule heat generated by the eddy current.

Further, when a large current flows through the inductor, heat generation from the current path in the inductor increases. Most of the heat generated in the current path of the inductor is dissipated by heat conduction to the printed circuit board on which the inductor is mounted. However, when a large current flows through the inductor, the heat generated by the inductor may not be sufficiently dissipated only by heat dissipation by heat conduction to the printed circuit board.

An object of the present invention is to solve or alleviate at least a part of the above-mentioned problems. One of the more specific objects of the present invention is to improve the heat dissipation characteristics of the inductor. Other objects of the present invention will be made clear through the description throughout the specification.

The inductor according to one aspect of the present invention is attached to a substrate having a mounting surface facing the circuit board, an upper surface facing the mounting surface, and an end surface connecting the mounting surface and the upper surface, and the mounting surface of the substrate. A first external electrode is provided, a second external electrode is attached to the mounting surface of the substrate at a distance from the first external electrode in a length direction perpendicular to the end surface, and one end thereof is provided in the substrate. Is electrically connected to the first external electrode and the other end is electrically connected to the second external electrode, and is viewed from the first external electrode in a plan view from a thickness direction perpendicular to the mounting surface. It includes an internal conductor that extends linearly toward the second external electrode. In one aspect, the distance between the mounting surface and the position farthest from the mounting surface on the axis of the inner conductor in the front view seen from the width direction perpendicular to the thickness direction and the length direction is the said. It is less than half the distance between the top surface and the mounting surface.

In one aspect of the invention, the substrate is an upper region extending parallel to the mounting surface and the top surface and between the intermediate surface and the top surface by an intermediate surface equidistant from the mounting surface and the top surface. And the lower area. In one aspect of the invention, the internal conductor is
The whole is arranged in the lower area.

In one aspect of the present invention, the substrate is divided into a first region surrounded by the inner conductor and the mounting surface and a second region other than the first region in the front view, and the first region is described. The region is formed of a material having a higher saturation magnetic flux density than the second region.

In one aspect of the present invention, the first external electrode is attached to the substrate only on the mounting surface.

In one aspect of the present invention, the second external electrode is attached to the substrate only on the mounting surface.

In one aspect of the present invention, the inner conductor is formed of a conductive material having a higher electrical conductivity than the material of the first outer electrode.

In one aspect of the invention, the substrate comprises metal magnetic particles.

In one aspect of the present invention, the inner conductor has a first inner conductor pattern and a second inner conductor pattern arranged in the substrate at a distance from the inner conductor pattern, and the first inner conductor pattern. Each of the inner conductor patterns extends linearly from the first external electrode toward the second external electrode in a plan view viewed from a thickness direction perpendicular to the mounting surface, and one end is exposed from the mounting surface. Then, it is connected to the first external electrode and the other end is exposed from the mounting surface and connected to the second external electrode.

One embodiment of the present invention relates to a circuit board including any of the above inductors.

One embodiment of the present invention relates to an electronic device including the above circuit board.

According to the disclosure of the present specification, the heat dissipation characteristics of the inductor can be improved.

It is a perspective view of the inductor according to one Embodiment of this invention mounted on a circuit board. It is a front view of the inductor of FIG. It is a top view of the inductor of FIG. It is an exploded view of the inductor of FIG. FIG. 5 is a cross-sectional view taken along the line XX of the inductor of FIG. It is sectional drawing of the inductor according to another embodiment of this invention. It is sectional drawing of the inductor according to another embodiment of this invention. It is sectional drawing of the inductor according to another embodiment of this invention. It is sectional drawing of the inductor according to another embodiment of this invention. It is sectional drawing of the inductor according to another embodiment of this invention. It is sectional drawing of the inductor according to another embodiment of this invention. It is sectional drawing of the inductor according to another embodiment of this invention. It is sectional drawing of the inductor according to another embodiment of this invention. It is a front view of the inductor according to another embodiment of this invention.

Hereinafter, various embodiments of the present invention will be described with reference to the drawings as appropriate. The components common to the plurality of drawings are designated by the same reference numerals throughout the plurality of drawings. It should be noted that each drawing is not always drawn to the correct scale for convenience of explanation.

The inductor 1 according to the embodiment of the present invention will be described with reference to FIGS. 1 to 5. First, the outline of the inductor 1 will be described with reference to FIGS. 1 to 3. FIG. 1 is a perspective view of an inductor 1 according to an embodiment of the present invention, FIG. 2 is a front view of the inductor 1, and FIG. 3 is a plan view of the inductor 1. As shown in the drawing, the inductor 1 is separated from the base 10, the internal conductor 25 provided in the base 10, the external electrode 21 provided on the surface of the base 10, and the external electrode 21 on the surface of the base 10. An external electrode 22 provided at a position is provided.

Each figure shows an L-axis, a W-axis, and a T-axis that are orthogonal to each other. In the present specification, the "length" direction, the "width" direction, and the "thickness" direction of the inductor 1 are the "L" direction and the "W" of FIG. 1, respectively, unless otherwise understood in the context. The direction and the "T" direction. According to the method of determining this direction, the external electrode 22 is arranged at a position separated from the external electrode 21 in the length direction (L direction).

The inductor 1 is used, for example, in a large current circuit through which a large current flows. The inductor 1 may be used in a signal circuit or a high frequency circuit. The inductor 1 may be used as a bead inductor for noise suppression.

The inductor 1 is mounted on the circuit board 2. Two lands 3a and 3b are provided on the mounting board of the circuit board 2. The external electrode 21 is arranged so as to face the land 3a when the inductor 1 is mounted on the circuit board 2, and the external electrode 22 is the land 3b of the circuit board 2 when the inductor 1 is mounted on the circuit board 2. It is arranged so that it can face each other. The inductor 1 may be mounted on the circuit board 2 by joining the external electrode 21 and the land 3a and the external electrode 22 and the land 3b with solder, respectively. Various electronic components other than the inductor 1 can be mounted on the circuit board 2. The circuit board 2 can be mounted on various electronic devices. Electronic devices on which the circuit board 2 can be mounted include smartphones, tablets, game consoles, automobile electrical components, and various other electronic devices. The inductor 1 may be an internal component embedded inside the mounting board of the circuit board 2.

The substrate 10 is formed of a magnetic material into a rectangular parallelepiped shape. In one embodiment of the present invention, the substrate 10 has a length dimension (dimension in the L direction) of 0.4 mm to 10 mm, a width dimension (dimension in the W direction) of 0.2 to 10 mm, and a height dimension (dimension in the T direction). Dimensions) are formed to be 0.2 to 10 mm. The present invention can be widely applied from relatively small inductors to relatively large inductors. The dimensions of the substrate 10 are not limited to those specifically described herein. In the present specification, the term "rectangular parallelepiped" or "rectangular parallelepiped shape" does not mean only "rectangular parallelepiped" in a mathematically strict sense.

The substrate 10 has a first main surface 10a, a second main surface 10b, a first end surface 10c, a second end surface 10d, a first side surface 10e, and a second side surface 10f. The outer surface of the substrate 10 is defined by these six surfaces. The first main surface 10a and the second main surface 10b face each other, the first end surface 10c and the second end surface 10d face each other, and the first side surface 10e and the second side surface 10f face each other. Facing each other. Each of the first end surface 10c and the second end surface 10d connects the first main surface 10a and the second main surface 10b, and also connects the first side surface 10e and the second side surface 10f. Since the first main surface 10a is on the upper side of the substrate 10 when the circuit board 2 is used as a reference, the first main surface 10a may be referred to as an "upper surface". Similarly, the second main surface 10b may be referred to as the "lower surface". Since the inductor 1 is arranged so that the second main surface 10b faces the circuit board 2, the second main surface 10b may be referred to as a "mounting surface" or a "mounting surface 10b". When referring to the vertical direction of the inductor 1, the vertical direction of FIG. 1 is used as a reference. The thickness direction of the inductor 1 or the substrate 10 can be perpendicular to at least one of the upper surface 10a and the mounting surface 10b. The length direction of the inductor 1 or the substrate 10 can be a direction perpendicular to at least one of the first end surface 10c and the second end surface 10d. The width direction of the inductor 1 or the substrate 10 can be a direction perpendicular to at least one of the first side surface 10e and the second side surface 10f. The width direction of the inductor 1 or the substrate 10 may be a direction perpendicular to the thickness direction and the length direction of the inductor 1 or the substrate 10.

In the illustrated embodiment, the external electrode 21 is provided so as to be in contact with the mounting surface 10b, the first end surface 10c, and the upper surface 10a of the substrate 10. The external electrode 22 is provided so as to be in contact with the mounting surface 10b, the second end surface 10d, and the upper surface 10a of the substrate 10. At least one of the external electrode 21 and the external electrode 22 may be provided on the substrate 10 so as to be in contact with only the mounting surface 10b. FIG. 15 shows an inductor 1 in which the external electrodes 21 and 22 are provided so as to be in contact with only the mounting surface 10b. The shapes and arrangements of the external electrodes 21 and 22 are not limited to those expressly described herein.

The substrate 10 is made of a magnetic material. The magnetic material for the substrate 10 may contain a plurality of metallic magnetic particles. The metal magnetic particles contained in the magnetic material for the substrate 10 include, for example, (1) metal particles such as Fe and Ni, (2) Fe-Si-Cr alloy, Fe-Si-Al alloy, Fe-Ni alloy and the like. Crystal alloy particles, (3) amorphous alloy particles such as Fe-Si-Cr-BC alloy, Fe-Si-Cr-B alloy, or (4) mixed particles in which these are mixed. The composition of the metallic magnetic particles contained in the core 10 is not limited to that described above. For example, the metal magnetic particles contained in the core 10 are Co-Nb-Zr alloy, Fe-Zr-Cu-B alloy, Fe-Si-B alloy, Fe-Co-Zr-Cu-B alloy, Ni-Si-. It may be a B alloy or a Fe-AL-Cr alloy. The Fe-based metal magnetic particles contained in the substrate 10 may contain 80 wt% or more of Fe. An insulating film may be formed on each surface of the metal magnetic particles. The insulating film may be an oxide film formed by oxidizing the above metal or alloy. The insulating film provided on each surface of the metal magnetic particles may be, for example, a silicon oxide film coated by the sol-gel method.

In one embodiment, the metallic magnetic particles have an average particle size of 1.5 to 20 μm. The average particle size of the metal magnetic particles contained in the substrate 10 may be smaller than 1.5 μm or larger than 20 μm. The substrate 10 may contain two or more types of metal magnetic particles having different average particle diameters from each other. For example, the metal magnetic particles for a composite magnetic material include a first metal magnetic particle having a first average particle size, and a second metal magnetic particle having a second average particle size smaller than the first average particle size. May include.

The substrate 10 may be formed of a composite magnetic material containing metal magnetic particles and a binder. When the substrate 10 is formed of a composite magnetic material, the binder contained in the composite magnetic material is, for example, a thermosetting resin having excellent insulating properties. Examples of the binder include epoxy resin, polyimide resin, polystyrene (PS) resin, high-density polyethylene (HDPE) resin, polyoxymethylene (POM) resin, polycarbonate (PC) resin, polyvinylidene fluoride (PVDF) resin, and phenol (Phenolic). ) Resin, polytetrafluoroethylene (PTFE) resin, or polybenzoxazole (PBO) resin can be used. Further, the binder may be an oxide film on the surface of each of the metal magnetic particles, or an oxide different from the oxide film. The metal magnetic particles may be bonded to each other by these oxides.

The inner conductor 25 is provided so as to electrically connect the outer electrode 21 and the outer electrode 22 in the substrate 10. The inner conductor 25 may have a plurality of inner conductor patterns, or may have only a single inner conductor pattern. In the illustrated embodiment, the inner conductor 25 has six inner conductor patterns 25a-25f. One end and the other end of the inner conductor pattern 25a are exposed from the mounting surface 10b toward the outside of the substrate 10, and are connected to the external electrode 21 at the one end and the external electrode 22 at the other end. .. The end face of the inner conductor 25 in contact with the outer electrode 21 faces the land 3a when the inductor 1 is mounted on the circuit board 2, and the end face of the inner conductor 25 in contact with the outer electrode 22 attaches the inductor 1 to the circuit board 2. It is provided so as to face the land 3b when mounting. The inner conductors 25b to 25f have the same or similar shape as the inner conductors 25a. The inner conductor patterns 25a to 25f are arranged apart from each other in the substrate 10. As described above, the internal conductors 25a to 25f are arranged in parallel between the external electrode 21 and the external electrode 22 in the substrate 10. Each of the inner conductor patterns 25a to 25f may be connected to an adjacent inner conductor pattern. For example, a part or the whole of the inner conductor pattern 25b may have at least one of the inner conductor pattern 25a and the inner conductor pattern 25c connected in the substrate 10.

As shown in FIG. 3, the inner conductor pattern 25a extends linearly from the outer electrode 21 toward the second outer electrode 22 in a plan view (from the viewpoint seen from the T axis). That is, the internal conductor pattern 25a does not have a portion that is arranged so as to face each other in the substrate 10 when viewed in a plan view. In the present specification, when the inner conductor pattern 25a does not have a portion in the substrate 10 that faces each other in a plan view, the inner conductor pattern 25a extends linearly from the outer electrode 21 toward the outer electrode 22. .. The inner conductor pattern 25a may be arranged on a straight line drawn from the outer electrode 21 toward the second outer electrode 22. Similar to the inner conductor patterns 25a, the inner conductor patterns 25b to 25f also extend linearly from the outer electrode 21 toward the second outer electrode 22 in a plan view (from the viewpoint seen from the T axis).

Next, with reference to FIG. 4, the laminated structure of the inductor 1 produced by the lamination process will be described. FIG. 4 shows an exploded view of the inductor 1. In FIG. 4, the external electrodes 21 and 22 are not shown for convenience of explanation. As shown in FIG. 4, the substrate 10 includes magnetic material layers 11a to 11f, a cover layer 12, and a cover layer 13. Each of the magnetic material layers 11a to 11f, the cover layer 12, and the cover layer 13 is made of a magnetic material. The substrate 10 is laminated in the order of the cover layer 12, the magnetic material layers 11a to 11f, and the cover layer 13 from the positive side to the negative side in the W-axis direction. The cover layers 12 and 13 may each have a plurality of magnetic material layers. The inductor 1 may be made by a method other than the lamination process. For example, the inductor 1 may be made by a thin film process or a compression molding process.

Internal conductor patterns 25a to 25f are provided on one surface of the magnetic material layers 11a to 11f, respectively. In the illustrated embodiment, the inner conductor patterns 25a to 25f are provided on the surface of the pair of surfaces intersecting the W-axis direction of the magnetic layers 11a to 11f on the negative side in the W-axis direction. The inner conductor patterns 25a to 25f are formed, for example, by printing a conductive paste made of a metal or alloy having excellent conductivity by a screen printing method. Of the surfaces of the magnetic layers 11a to 11f, the surface on which the internal conductor patterns 25a to 25f are formed is an example of the coil forming surface. As the material of this conductive paste, Ag, Pd, Cu, Al or an alloy thereof can be used. The inner conductor patterns 25a to 25f may be formed by a method other than the screen printing method, for example, a sputtering method, an inkjet method, or a known method other than these. In one embodiment, the internal conductor patterns 25a-25f are formed from a material having a higher electrical conductivity than the external electrode 21 and the external electrode 22.

Next, the internal conductor pattern 25a will be described with reference to FIG. FIG. 5 is a sectional view taken along line XX of the inductor 1. The XX-ray cross section of the inductor 1 shows a cross section of the substrate 10 cut at a cut surface parallel to the LT plane and passing through the inner conductor pattern 25a. It may be considered that FIG. 5 shows a view through which the substrate 10 is transmitted so that the internal conductor pattern 25a can be seen in the front view from the W-axis direction (that is, from the width direction). The description of the inner conductor pattern 25a also applies to the inner conductor patterns 25b-25f wherever possible in context. That is, in the following, the inner conductor patterns 25a to 25f will be described by taking the inner conductor pattern 25a as an example.

The substrate 10 extends parallel to the upper surface 10a and the mounting surface 10b, and is divided into an upper region and a lower region by an intermediate surface B equidistant from the upper surface 10a and the mounting surface 10b. That is, the substrate 10 is divided by the intermediate surface B into an upper region between the intermediate surface B and the upper surface 10a and a lower region between the intermediate surface B and the mounting surface 10b. As is clear from this definition, at any position included in the upper region, the distance from the top surface 10a is smaller than the distance from the mounting surface 10b, and at any position included in the lower region, the distance from the top surface 10a is. It is larger than the distance from the mounting surface 10b.

As shown, the internal conductor pattern 25a extends from the external electrode 21 to the external electrode 22 along the axis A extending from the external electrode 21 to the external electrode 22. The lower end of the inner conductor pattern 25a is exposed from the mounting surface 10b, and the first portion 25a1 extending from one end in the positive direction of the T axis and the positive direction of the L axis and the lower end thereof are exposed from the mounting surface 10b. It has a second portion 25a2 extending from one end in the positive direction of the T axis and the negative direction of the L axis, and a third portion 25a3 connecting the upper end of the first portion 25a1 and the upper end of the second portion 25a2. The lower end of the first portion 25a1 is connected to the external electrode 21, and the lower end of the second portion 25a2 is connected to the external electrode 22. In the illustrated embodiment, the third portion 25a3 extends parallel to the top surface 10a.

The inner conductor pattern 25a has an inner peripheral surface 25X extending parallel to the axis A from the outer electrode 21 to the outer electrode 22 between the axis A and the mounting surface 10b, and the outer electrode 21 to the outside between the axis A and the upper surface 10a. It has an outer peripheral surface 25Y extending parallel to the axis A to the electrode 22. The axis A of the inner conductor pattern 25a may be determined with reference to the inner peripheral surface 25X. For example, the axis A may be a set of points equidistant from the inner peripheral surface 25X. The axis A may be a set of midpoints of a line segment sandwiched between a point on the inner peripheral surface 25X, a normal at the point, and a point where the normal intersects the outer peripheral surface 25Y. The axis A substantially coincides with the direction in which the current flows in the inner conductor pattern 25a.

In one embodiment, the inner conductor pattern 25a has a distance between the mounting surface 10b and the position farthest from the mounting surface 10b on the axis A, which is more than half of the distance (T1) between the upper surface 10a and the mounting surface 10b. Is also configured and arranged so as to be small. In one embodiment, the internal conductor pattern 25a is configured and arranged such that the first portion 25a1, the second portion 25a2, and the third portion 25a3 are all included in the lower region of the substrate 10.

In one embodiment, the cross-sectional area of the cross section obtained by cutting the internal conductor pattern 25a along the direction perpendicular to the axis A (internal conductor cross-sectional area) is the mounting surface of the external electrode 21 in contact with the first end surface 10c. It is larger than the cross-sectional area (outer conductor cross-sectional area) cut along the direction parallel to 10b. In one embodiment, the cross-sectional area of the cross section obtained by cutting the internal conductor pattern 25a along the direction perpendicular to the axis A is such that the portion of the external electrode 22 in contact with the second end surface 10d is parallel to the mounting surface 10b. It is larger than the cross-sectional area cut along. When the cross-sectional area along the mounting surface 10b of the external electrode 21 is not constant, the average of the cross-sectional areas of the external electrodes 21 in each of the cross sections passing through the three points arranged at equal intervals in the T-axis direction is taken as the external electrode. It can be a cross-sectional area of 21. The same applies to the cross-sectional area of the external electrode 22.

The inner conductor pattern 25a is arranged at a position separated from the upper surface 10a by the upper margin D1. More specifically, the inner conductor pattern 25a is arranged so that the distance between the upper surface 10a of the substrate 10 and the outer peripheral surface 25Y of the inner conductor pattern 25a is the upper margin D1. In the illustrated embodiment, the internal conductor pattern 25a is configured and arranged so that the upper margin D1 is larger than half (T1 / 2) of the height direction dimension T1 of the substrate 10.

In one embodiment, in the internal conductor pattern 25a, the distance T2 between the axis A and the upper surface 10a of the substrate 10 is larger than half the distance between the upper surface 10a and the mounting surface 10b in the XX line cross section. It is configured and arranged so as to. In the illustrated embodiment, the distance between the upper surface 10a and the mounting surface 10b is equal to the height dimension T1 of the substrate 10. Therefore, in the illustrated example, the relationship of T2> T1 / 2 holds.

In the X-ray cross section (that is, in the front view seen from the W axis), the substrate 10 has a first region 10r1 and a first region 10r1 surrounded by the internal conductor pattern 25a and the mounting surface 10b by the internal conductor pattern 25a. It is partitioned into a second region 10r2 other than the above. More specifically, the first region 10r1 is the inner peripheral edge which is the line of intersection between the inner peripheral surface 25X and the XX line cross section, and the mounting surface 10b and the XX line when viewed from the W axis. It is an area surrounded by the bottom edge, which is the line of intersection with the cross section. The second region 10r2 is the intersection of the outer peripheral edge, which is the line of intersection between the outer peripheral surface 25Y and the XX line cross section, and the upper surface 10 atp first end surface 10c and the XX line cross section in the front view seen from the W axis. Area surrounded by the upper edge, which is a line, the right edge, which is the intersection of the first end face 10c and the X-ray cross section, and the left edge, which is the intersection of the second end face 10d and the XX line cross section. Is. The area of the first region 10r1 is smaller than that of the second region 10r2. Therefore, if the first region 10r1 and the second region 10r2 are made of the same magnetic material, magnetic saturation is likely to occur in the first region 10r1, which may cause deterioration of the DC superimposition characteristic of the inductor 1. Therefore, in one embodiment, the first region 10r1 may be formed of a magnetic material having a relatively high saturation magnetic flux density, and the second region 10r2 may be formed of a magnetic material having a saturation magnetic flux density lower than that of the first region 10r1. .. For example, the saturation magnetic flux of the first region 10r1 is increased by increasing the Fe content of the metal magnetic particles contained in the first region 10r1 to be larger than the Fe content of the metal magnetic particles contained in the second region 10r2. be able to.

The shape and arrangement of the inner conductor pattern 25a are not limited to those illustrated in FIG. The inner conductor pattern 25a can take various shapes and arrangements different from the shapes and arrangements exemplified in FIG. A modified example of the inner conductor pattern 25a will be described with reference to FIGS. 6 to 13.

In another embodiment of the present invention as a modification of the inner conductor pattern 25a, the inner conductor pattern 25a may have a curved surface, as shown in FIG. When the outer peripheral surface 25Y has an intersection where straight lines intersect, magnetic flux may be concentrated near the intersection. According to the internal conductor pattern 25a shown in FIG. 6, since there is no intersection where the straight lines intersect, it is possible to prevent the magnetic flux from concentrating in the vicinity of the intersection. As a result, the DC superimposition characteristic of the inductor 1 is further improved.

In another embodiment of the present invention as a modification of the inner conductor pattern 25a, the inner conductor pattern 25a is composed of only curved lines in a cross section of the inner peripheral surface 25X and the outer peripheral surface 25Y when viewed from the W axis direction. You may. For example, as shown in FIG. 7, the curve constituting the inner peripheral surface 25X and the outer peripheral surface 25Y is an elliptical partial elliptical arc whose long axis is parallel to the L axis or whose long axis coincides with the L axis. May be good. As shown in FIG. 8, the curve constituting the inner peripheral surface 25X and the outer peripheral surface 25Y may be an elliptical partial elliptical arc whose minor axis is parallel to the L axis or whose minor axis coincides with the L axis. As shown in FIGS. 7 and 8, when the inner conductor pattern 25a does not have a linear portion parallel to the upper surface 10a, the upper surface 10a of the outer peripheral surface 25Y of the inner conductor pattern 25a is the most. The distance between the close position and the upper surface 10a is defined as the upper margin D1. The curves forming the inner peripheral surface 25X and the outer peripheral surface 25Y may be a partial arc or an elliptical partial elliptical arc. By forming the inner peripheral surface 25X and the outer peripheral surface 25Y only with curved lines in the cross-sectional view seen from the W-axis direction, it is possible to prevent the magnetic flux from concentrating on a part of the region in the substrate 10, and as a result, the inductor 1 DC superimposition characteristics are improved. In particular, since the curves forming the inner peripheral surface 25X and the outer peripheral surface 25Y are elliptical partial elliptical arcs and partial arcs, in addition to preventing the concentration of magnetic flux, the DC resistance (Rdc) is lowered while ensuring the inductance value. It becomes possible.

In another embodiment of the present invention as a modification of the inner conductor pattern 25a, as shown in FIGS. 9 and 10, the first portion 25a1 and the second portion 25a2 of the inner conductor pattern 25a are formed with a T-axis. It may extend in parallel directions. In these embodiments, the side margin D2, which is the distance between the first portion 25a1 and the first end surface 10c of the substrate 10, is smaller than the upper margin D1. In the illustrated embodiment, the distance between the second portion 25a2 and the first end face 10c of the substrate 10 is equal to the side margin D2. The distance between the second portion 25a2 and the second end surface 10d of the substrate 10 may be larger or smaller than the side margin D2. The internal conductor pattern 25a shown in FIG. 9 has a first protruding portion 25a4 projecting from the lower end portion of the first portion 25a1 toward the first end surface 10c, and a second end surface 10d from the lower end portion of the third portion 25a3. It has a second protruding portion 25a5 that protrudes toward the direction. The first protruding portion 25a4 and the second protruding portion 25a5 reduce the area of the inner conductor pattern 25a in the region between the first portion 25a1 and the first end surface 10c, but in this region, a current flows through the inner conductor pattern 25a. Since the magnetic saturation occurs immediately after the first time, even if the area of the region is reduced, the influence on the DC superimposition characteristic is small. Therefore, the first protruding portion 25a4 and the second protruding portion 25a5 increase the contact area between the internal conductor pattern 25a and the external electrodes 21 and 22 without substantially adversely affecting the DC superimposition characteristics, and electrically connect the two. You can connect securely. Further, by increasing the contact area between the internal conductor pattern 25a and the external electrodes 21 and 22, the heat in the inductor 1 can be more efficiently dissipated from the external electrodes 21 and 22 via the lands 3a and 3b). it can. As shown in FIG. 10, the internal conductor pattern 25a does not have the first protruding portion 25a4 and the second protruding portion 25a5, and may be configured to be exposed only from the mounting surface 10b. In another embodiment, the side margin D2 may be zero.

In another embodiment of the present invention as a modification of the inner conductor pattern 25a, FIGS. 11 to 13 show a further modification of the inner conductor pattern 25a. In FIGS. 11 to 13, the external electrodes 21 and 22 are omitted for simplification of the illustration. FIG. 11 shows a modified example of the internal conductor pattern 25a shown in FIG. The inner conductor pattern 25a of FIG. 11 is arranged between the inner virtual ellipse C1 and the outer virtual ellipse C2. The virtual ellipse C1 is centered on the midpoint in the L-axis direction of the side corresponding to the mounting surface 10b in the XX-line cross section, and has a minor axis having a length of G4 / 2 extending in the T-axis direction and L1 extending in the L-axis direction. It has a major axis with a length of / 2. L1 is the dimension of the substrate 10 in the L-axis direction, and is smaller than twice the dimension in the height direction of the substrate 10. That is, the relationship of L1 <2T1 is established. G4 is greater than 0, preferably less than T1 / 4. As a result, the internal conductor pattern 25a can be arranged in the vicinity of the mounting surface 10b, so that the heat dissipation efficiency can be improved. G4 is preferably larger than T1 / 8 in order to acquire inductance and suppress magnetic saturation in the first region 10r1. In addition to the geometric arrangement of the internal conductor pattern 25a, the first region 10r1 is formed of a magnetic material having a relatively high saturation magnetic flux density, and the second region 10r2 is a magnetic material having a lower saturation magnetic flux density than the first region 10r1. By forming from, it is possible to further suppress the intensive magnetic saturation in the first region 10r1. The outer virtual ellipse C2 is concentric with the virtual ellipse C1 and has a minor axis of T1 / 2 length extending in the T-axis direction and a major axis of L1 length.

FIG. 12 shows a modified example of the internal conductor pattern 25a shown in FIG. The inner conductor pattern 25a of FIG. 12 is arranged between the virtual circle C11 and the virtual circle C12. The inner conductor pattern 25a shown in FIG. 12 has a shape obtained by extending the inner conductor pattern 25a shown in FIG. 11 in the L-axis direction. In the embodiment of FIG. 12, the virtual ellipse C1 has a minor axis having a length of G4 / 2 extending in the T-axis direction and a long axis having a length of T1 extending in the L-axis direction centered on the midpoint in the L-axis direction. Has. L1 is equal to twice the height dimension of the substrate 10. That is, the relationship of L1 = 2T1 is established. The outer virtual ellipse C2 is concentric with the virtual ellipse C1 and has a minor axis of T1 / 2 length extending in the T-axis direction and a major axis of L1 length.

FIG. 13 shows a modified example of the internal conductor pattern 25a shown in FIG. The inner conductor pattern 25a of FIG. 13 is arranged between the inner virtual line C21 and the outer virtual line C22. In the embodiment of FIG. 13, the virtual line C21 and the virtual line C22 are composed of a curve at both ends and a straight line segment connecting the curves. One curve of the virtual line C21 and the virtual line C22 extends from the position of the first end surface 10c in the L-axis direction by the length of T1 in the L-axis direction, and the other curve extends from the position of the first end surface 10c in the L-axis direction by the length of T1. It extends by the length of T1 in the L-axis direction from the position of. The straight line segment of the virtual line C21 and the virtual line C22 has a length obtained by dividing L1 by 2T1.

According to the embodiment shown in FIGS. 11 to 13, the curves forming the inner peripheral surface 25X and the outer peripheral surface 25Y are elliptical partial elliptical arcs and partial arcs, in addition to preventing the concentration of magnetic flux. It is possible to reduce the direct current resistance (Rdc) while ensuring the inductance value.

Subsequently, an exemplary manufacturing method of the inductor 1 according to the embodiment of the present invention will be described. The inductor 1 can be manufactured, for example, by a lamination process. Hereinafter, an example of a method for manufacturing the inductor 1 by the lamination process will be described. For this explanation, FIG. 4 is appropriately referred to.

First, a plurality of unfired magnetic sheet made of a magnetic material is prepared. The unfired magnetic sheet becomes the magnetic layers 11a to 11f and the cover layers 12 and 13 after firing. The unfired magnetic sheet is formed, for example, from a composite magnetic material containing a binder and a plurality of metal magnetic particles. Next, by printing a conductive paste on each surface of the unfired magnetic sheet, an unfired conductor pattern that becomes an internal conductor pattern 25a to 25f after firing is formed.

Next, the unfired magnetic sheet on which the unfired conductor pattern is formed is laminated to obtain an intermediate laminate. A plurality of unfired magnetic sheets to be the cover layer 12 are laminated on one end in the laminating direction of the intermediate laminate, and a plurality of unfired magnetic sheets to be the cover layer 13 are laminated on the other end to form an unfired laminate. obtain.

Next, the unfired chip laminate is obtained by individualizing the unfired laminate using a cutting machine such as a dicing machine or a laser processing machine. Next, the unfired chip laminate is degreased and the degreased unfired chip laminate is fired to obtain a fired chip laminate. Next, the fired chip laminate is subjected to a polishing process such as barrel polishing.

Next, the external electrode 21 and the external electrode 22 are formed on the surface of the chip laminate. The external electrode 21 and the external electrode 22 are formed, for example, by applying a conductive paste to the surface corresponding to the mounting surface 10b of the chip laminate to form a base electrode, and forming a plating layer on the surface of the base electrode. Will be done. The plating layer has, for example, a two-layer structure consisting of a nickel plating layer containing nickel and a tin plating layer containing tin. If necessary, at least one of a solder barrier layer and a solder wet layer may be formed on the external electrode 21 and the external electrode 22. From the above, the inductor 1 is obtained.

Some of the steps included in the above manufacturing method can be omitted as appropriate. In the method of manufacturing the inductor 1, steps not explicitly described herein can be performed as needed. A part of each step included in the above-mentioned method for manufacturing the inductor 1 can be executed by changing the order at any time without departing from the spirit of the present invention. If possible, some of the steps included in the above-mentioned method for manufacturing the inductor 1 can be performed simultaneously or in parallel.

Next, the action and effect according to the above embodiment will be described. According to the inductor 1 according to the above embodiment, in front view, the distance between the mounting surface 10b and the position farthest from the mounting surface 10b on the axis A of the internal conductor 25 (for example, the internal conductor pattern 25a) is the upper surface. Since it is smaller than half of the distance between the 10a and the mounting surface 10 (for example, the height T1 of the base 10), the Joule heat generated in the inner conductor 25 is more efficiently dissipated from the mounting surface 10b of the base 10. be able to. When the entire inner conductor is arranged in the lower region below the virtual line B of the substrate 10, heat can be dissipated from the mounting surface 10b more efficiently. Most of the Joule heat generated in the inner conductor 25 is transferred from the inner conductor 25 to another member constituting the circuit board 2 via the lands 3a and 3b by heat conduction, but heat dissipation by this heat conduction alone is sufficient. It may not be possible to dissipate all the Joule heat generated by the inner conductor 25. Therefore, the distance (T1-T2) between the axis A of the inner conductor 25 and the mounting surface 10b is made smaller than half of the distance between the upper surface 10a and the mounting surface 10b (for example, the height T1 of the substrate 10). By arranging the internal conductor 25 in the circuit board 25, the Joule heat generated by the coil conductor 25 can be efficiently conducted from the mounting surface 10b of the substrate 10 to the circuit board 2.

According to the above embodiment, since the entire inner conductor 25 is arranged in the lower region below the virtual line B of the substrate 10, the inner conductor passes through the upper region of the substrate 10 as compared with the case where the inner conductor passes through the upper region of the substrate 10. The length of the inner conductor in the substrate 10 can be shortened. As a result, the DC resistance of the inner conductor can be reduced, so that the Joule heat generated from the inner conductor 25 can be reduced.

According to the above embodiment, the internal conductor 25 extending linearly in a plan view is exposed from the mounting surface 10b to the outside of the substrate 10 and is connected to the external electrodes 21 and 22. Therefore, the current flowing from the land 3a to the inner conductor 25 via the outer electrode 21 passes through the inner conductor 25 and flows to the land 3b via the outer electrode 22. As described above, the current flowing through the inductor 1 is a small distance between the land 3a and one end of the internal conductor 25 and between the land 3b and the other end of the internal conductor 25 (in the T-axis direction of the external electrodes 21 and 22). It flows through the external electrodes 21 and 22 by a distance (distance corresponding to the thickness). Generally, the outer electrode of an inductor is made of a material that has a lower electrical conductivity than the inner conductor. Further, the portion of the external electrode in contact with the end surface (the surface connecting the mounting surface and the upper surface) of the substrate has a cross-sectional area smaller than that of the internal conductor. Therefore, when the inner conductor is exposed from the end face of the substrate like a conventional inductor in which the inner conductor extends linearly, the current passes through the outer electrode in the section from the exposed position of the inner conductor to the land. Since the distance from the exposed position of the internal conductor to the land on the end surface of the substrate is longer than the distance from the mounting surface of the substrate to the land, the external electrode interposed in the section from the exposed position of the internal conductor to the land is the DC resistance of the inductor. It becomes an increase factor of. In the inductor 1 according to the embodiment of the present invention, since the inner conductor 25 is exposed from the mounting surface 10b of the base 10, the current passing through the inductor 1 is between the land 3a and one end of the inner conductor 25 and the land 3b. It passes through the external electrodes 21 and 22 by a short distance between the and the internal conductor 25. As described above, according to the inductor 1, since the ratio of the external electrodes 21 and 22 to the current path is smaller than that of the conventional inductor, the DC resistance can be reduced as compared with the conventional inductor.

If the Fe content in the Fe-based metal magnetic particles contained in the substrate 10 is 80 wt% or more, the inductor 1 is used in an application in which ^{a current value of 0.15 A / mm 3 or more per unit volume is required.} obtain. If the Fe content in the metal magnetic particles contained in the substrate 10 is 85 wt% or more, the inductor 1 can be used in applications where ^{a current value of 0.2 A / mm 3 or more per unit volume is required.} If Fe in the metal magnetic particles contained in the substrate 10 is 90 wt% or more, the inductor 1 can be used in an application in which ^{a current value of 0.25 A / mm 3 or more per unit volume is required.} As described above, since magnetic saturation is suppressed in the substrate 10 of the inductor 1 according to one or more embodiments of the present invention, a large current can be passed through the internal conductor 25. For example, when the inductance L of the inductor 1 is made smaller than 300 nH, the current value per unit volume ^{can be 0.15 A / mm 3} or more. Further, when the inductance L of the inductor 1 is made smaller than 150 nH, the current value per unit volume ^{can be set to 0.2 A / mm 3} or more. Further, when the inductance L of the inductor 1 is made smaller than 75 nH, the current value per unit volume ^{can be set to 0.25 A / mm 3} or more. In the inductor 1 including the substrate 10 containing metal magnetic particles having a Fe content of 80 wt% or more, heat generation due to current application is small. Further, it can be used for high frequency applications, for example, a frequency of 5 MHz or higher.

When the inductor 1 is mounted on the circuit board 2, the end face of the inner conductor 25 in contact with the outer electrode 21 and the land 3a of the circuit board 2 face each other, and the end face of the inner conductor 25 in contact with the outer electrode 22 and the circuit board 2 By facing the lands 3b, not only the heat generation of the inductor 1 can be suppressed, but also the heat generation in the region between the inductor 1 and the lands 3a and 3b can be suppressed. Even if the external electrodes 21 and 22 between the inductor 1 and the lands 3a and 3b are formed of a material having low electrical conductivity, heat generation in the external electrodes 21 and 22 when a current is applied can be suppressed.

According to the above embodiment, since at least one of the external electrode 21 and the external electrode 22 is provided so as to be in contact with only the mounting surface 10b, the external electrode is provided on the first end surface 10c and the second end surface 10d of the substrate 10. 21 and 22 are not in contact. Thereby, when the dimension of the inductor 1 in the L-axis direction is determined, the dimension of the substrate 10 in the L-axis direction can be increased by the width of the external electrodes 21 and 22.

The dimensions, materials, and arrangement of each component described herein are not limited to those expressly described in the embodiments, and each component may be included within the scope of the present invention. Can be transformed to have the dimensions, materials, and arrangement of. In addition, components not explicitly described in the present specification may be added to the described embodiments, or some of the components described in the respective embodiments may be omitted.

1 Inductor 2 Circuit board 3a, 3b Land 10 Base 10a Top surface 10b Mounting surface 10r1 First area 10r2 Second area 21, 22 External electrode 25 Internal conductor 25a to 25f Internal conductor pattern

Claims (10)

A substrate having a mounting surface facing the circuit board, an upper surface facing the mounting surface, and an end surface connecting the mounting surface and the upper surface.
A first external electrode attached to the mounting surface of the substrate,
A second external electrode attached to the mounting surface of the substrate at a distance from the first external electrode in a length direction perpendicular to the end surface.
A flat surface provided in the substrate, one end of which is electrically connected to the first external electrode and the other end of which is electrically connected to the second external electrode, as viewed from a thickness direction perpendicular to the mounting surface. Visually, an internal conductor extending linearly from the first external electrode toward the second external electrode,
With
In the front view seen from the width direction perpendicular to the thickness direction and the length direction, the distance between the mounting surface and the position farthest from the mounting surface on the axis of the inner conductor is the distance between the upper surface and the mounting. Less than half the distance from the surface,
Inductor. The substrate extends in parallel with the mounting surface and the upper surface, and has an upper region between the intermediate surface and the upper surface by an intermediate surface equidistant from the mounting surface and the upper surface, and the intermediate surface and the mounting. Divided into a lower area between the faces
The entire inner conductor is arranged in the lower region.
The inductor according to claim 1. In the front view, the substrate is divided into a first region surrounded by the inner conductor and the mounting surface, and a second region other than the first region.
The first region is formed of a material having a higher saturation magnetic flux density than the second region.
The inductor according to claim 1 or 2. The inductor according to any one of claims 1 to 3, wherein the first external electrode is attached to the substrate only on the mounting surface. The inductor according to any one of claims 1 to 3, wherein the second external electrode is attached to the substrate only on the mounting surface. The inner conductor is formed of a conductive material having a higher electrical conductivity than the material of the first outer electrode.
The inductor according to any one of claims 1 to 3. The substrate contains metallic magnetic particles.
The inductor according to any one of claims 1 to 7. The inner conductor has a first inner conductor pattern and a second inner conductor pattern arranged in the substrate at a distance from the inner conductor pattern.
Each of the first inner conductor pattern and the inner conductor pattern extends linearly from the first outer electrode toward the second outer electrode in a plan view viewed from a thickness direction perpendicular to the mounting surface, and one end thereof is It is exposed from the mounting surface and connected to the first external electrode, and the other end is exposed from the mounting surface and connected to the second external electrode.
The inductor according to any one of claims 1 to 7. A circuit board comprising the inductor according to any one of claims 1 to 8. An electronic device including the circuit board according to claim 9.

Images