JP2023102541A - Coil component and method of manufacturing coil component - Google Patents

Abstract

To provide a coil component that suppresses plating elongation and that inhibits a deterioration in magnetic characteristics, and a method of manufacturing the same.SOLUTION: A coil component 1 comprises: a substrate 10 that includes a plurality of first metallic magnetic particles; a coil conductor 25 that is provided within the substrate; an insulating composite material layer 30 that is formed on a surface of the substrate; and a plating layer. The coil conductor has an end surface that is exposed from the surface of the substrate. The plating layer is provided on the end surface of the coil conductor. The composite material layer, which is provided to surround the end surface of the coil conductor, includes a plurality of second metallic magnetic particles and glass.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to coil components and methods of manufacturing coil components.

Coil components are passive elements used in electronic equipment. Coil components are used, for example, to remove noise in power supply lines and signal lines. The coil component includes a base, a coil conductor provided inside the base such that an end face is exposed from the base, and an external electrode connected to the end face of the coil conductor.

Japanese Patent Laying-Open No. 2018-170429 (Patent Document 1) describes a coil component including a Ni-plated layer formed on an end surface of a coil conductor and an Au-plated layer covering the Ni-plated layer. The plating layer may be a Sn plating layer containing Sn.

A substrate composed of metal magnetic particles has lower insulating properties than a substrate composed of a ferrite material. For this reason, in a coil component having a base made of metal magnetic particles, there is a possibility that undesired plating elongation may occur on the surface of the base. In the technical field of coil components, plating elongation refers to a phenomenon in which plating extends beyond the area where external electrodes are installed. Plating elongation is undesirable because it causes a short circuit between the external electrodes of the coil component and a short circuit between the coil component and other electronic components.

The coil component of Patent Document 1 has a glass layer formed on the coil conductor along the outer edge of the plating layer, and this glass layer suppresses plating elongation. Further, Japanese Patent Laying-Open No. 2013-254917 (Patent Document 2) describes a coil component having an insulating oxide coating provided on the surface of a base. This insulating oxide is, for example, glass. In the coil component of Patent Document 2, this insulating oxide suppresses plating elongation.

JP 2018-170429 A JP 2013-254917 A

The glass layer is effective in suppressing plating elongation, but it causes deterioration of the magnetic properties of the coil component. For example, since glass is a non-magnetic material, the magnetic permeability of the coil component deteriorates when glass is included in the substrate. A coil component is desired in which the plating elongation is suppressed and the deterioration of the magnetic properties that occurs in exchange for the suppression of the plating elongation is suppressed.

One of the objects of the present invention is to provide a coil component in which plating elongation is suppressed and deterioration in magnetic properties is suppressed, and a method for manufacturing the same. Other objects of the present invention will become apparent throughout the specification. The invention disclosed in the present specification may solve problems that are understood from other than the description in the column "Problems to be Solved by the Invention".

A coil component according to one embodiment includes a base containing a plurality of first metal magnetic particles, a coil conductor provided inside the base and having an end face exposed from the surface of the base, an external electrode provided on the end face of the coil conductor, and an insulating composite material layer containing a plurality of second metal magnetic particles and glass. The external electrodes include plating layers. A composite material layer is provided on the surface of the base so as to surround the end face of the coil conductor.

In one embodiment, the percentage of glass in the composite layer is 0.5 vol% or more and 10 vol% or less.

In one embodiment, the atomic proportion of Si in the glass is 70 at % or more and 90 at % or less.

In one embodiment, the atomic ratio of Si in the first metal magnetic particles is 3 at % or more and 10 at % or less.

In one embodiment, the atomic ratio of Si in the second metal magnetic particles is 3 at % or more and 10 at % or less.

In one embodiment, the average particle size of the second metal magnetic particles is larger than the average particle size of the first metal magnetic particles.

In one embodiment, the substrate does not contain a glass component.

In one embodiment, the substrate does not contain a resin component.

In one embodiment, the composite layer is provided on the surface of the substrate so as not to cover the end face of the coil conductor.

In one embodiment, the substrate presents a cuboid shape. In one embodiment, the coil conductor is exposed from the first side of the substrate, and the composite layer is provided on the substrate to cover the entire first side.

In one embodiment, a composite layer is provided on the substrate to cover at least part of the first side and at least part of the second side connected to the first side.

In one embodiment, the composite layer has a thickness of 10 μm or greater.

In one embodiment, the plurality of second metal magnetic particles includes one second metal magnetic particle and another second metal magnetic particle. Other second metal magnetic particles are adjacent to one second metal magnetic particle. One second metal magnetic particle is bonded to another second metal magnetic particle with glass.

In one embodiment, an insulating film is provided on the surface of each of the one second metal magnetic particle and the other second metal magnetic particle, and the one second metal magnetic particle and the other second metal magnetic particle are bonded via their respective insulating films.

In one embodiment, the coil conductor is exposed from the first surface of the base, and some of the plurality of second metal magnetic particles are exposed from the first surface of the base.

A coil component according to one embodiment further includes a base electrode layer provided between the end surface of the coil conductor and the plating layer.

In one embodiment, the composite material layer is provided so as to surround the underlying electrode layer when viewed in a direction perpendicular to the first surface of the base.

One embodiment of the present invention relates to a method of manufacturing a coil component. A method for manufacturing a coil component according to an embodiment includes the steps of: forming an insulating insulating film on the surface of a structure having a plurality of first metal magnetic particles and having a conductor portion provided therein, and having a through hole at a position corresponding to an end face of the conductor portion, the insulating insulating film including a plurality of second metal magnetic particles and a plurality of glass particles and exposed from the structure to form a laminate; heat-treating the laminate;

In one embodiment, the insulating film is formed on the structure such that the through hole accommodates a portion of the conductor portion.

In one embodiment, the average particle diameter of the plurality of glass powders is half or less of the average particle diameter of the plurality of second metal magnetic particles.

According to the embodiments of the invention described in this specification, it is possible to provide a coil component in which plating elongation is suppressed and deterioration in magnetic properties is suppressed, and a method for manufacturing the same.

1 is a perspective view schematically showing a coil component according to one embodiment of the present invention; FIG. FIG. 2 is a cross-sectional view schematically showing a cross section of the coil component of FIG. 1 taken along line II. 2 is an enlarged cross-sectional view showing an enlarged cross-section of part of the coil component of FIG. 1; FIG. 4 is an enlarged cross-sectional view showing an enlarged area A of FIG. 3; FIG. FIG. 3 is a schematic diagram for explaining metal magnetic particles contained in a substrate; FIG. 3 is a schematic diagram for explaining metal magnetic particles contained in a composite material layer; FIG. 3 is a schematic diagram for explaining bonding between metal magnetic particles contained in a composite material layer. FIG. 3 is a schematic diagram for explaining bonding between metal magnetic particles contained in a composite material layer. FIG. 6 is an enlarged cross-sectional view showing an enlarged cross-section of part of a coil component according to another embodiment of the present invention; FIG. 6 is an enlarged cross-sectional view showing an enlarged cross-section of part of a coil component according to another embodiment of the present invention; FIG. 6 is an enlarged cross-sectional view showing an enlarged cross-section of part of a coil component according to another embodiment of the present invention; FIG. 5 is a schematic cross-sectional view showing a cross section of a coil component according to another embodiment of the present invention; FIG. 4 is a flowchart showing a manufacturing process of a coil component according to one embodiment of the present invention;

Various embodiments of the present invention will now be described with reference to the drawings as appropriate. Components that are common in multiple drawings are given the same reference numerals throughout the multiple drawings. Please note that each drawing is not necessarily drawn to an exact scale for convenience of explanation. The embodiments of the invention described below do not necessarily limit the claimed invention. The elements described in the following embodiments are not necessarily essential to the solution of the invention.

A coil component 1 according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. FIG. 1 is a perspective view schematically showing the coil component 1, FIG. 2 is a schematic cross-sectional view of the coil component 1 taken along line II of FIG. 1, and FIG. 3 is an enlarged cross-sectional view showing a part of the cross section of FIG. As illustrated, the coil component 1 includes a base 10, a coil conductor 25 provided inside the base 10, an insulating composite material layer 30 provided on the surface of the base 10, an external electrode 21 provided on the surface of the composite material layer 30, and an external electrode 22 provided on the surface of the composite material layer 30 at a position spaced apart from the external electrode 21. The external electrode 21 is electrically connected to one end of the coil conductor 25 , and the external electrode 22 is electrically connected to the other end of the coil conductor 25 . Each of the external electrodes 21 and 22 includes a plating layer. Details of the plating layer will be described later.

The coil component 1 can be mounted on the mounting substrate 2a. Land portions 3a and 3b are provided on the mounting substrate 2a. The coil component 1 is mounted on the mounting substrate 2a by joining the external electrodes 21 and the land portions 3a and connecting the external electrodes 22 and the land portions 3b. A circuit board 2 according to one embodiment of the present invention includes a coil component 1 and a mounting board 2a on which the coil component 1 is mounted. 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, electrical components of automobiles, servers, and various other electronic devices. For clarity of illustration, the illustration of the mounting board 2a and the land portions 3a and 3b is omitted except in FIG.

The coil component 1 may be inductors, transformers, filters, reactors, inductor arrays, and various other coil components. The coil component 1 may be a coupled inductor, a choke coil, or various other magnetically coupled coil components. Coil component 1 may be, for example, an inductor used in a DC/DC converter. Applications of the coil component 1 are not limited to those specified in this specification.

The base 10 is made of a magnetic material and has a rectangular parallelepiped shape. In one embodiment of the present invention, the base 10 is configured such that the dimension in the L-axis direction (length dimension) is greater than the dimension in the W-axis direction (width dimension) and the dimension in the T-axis direction (height dimension). For example, the length dimension ranges from 1.0 mm to 6.0 mm, the width dimension ranges from 0.5 mm to 4.5 mm, and the height dimension ranges from 0.5 mm to 4.5 mm. The dimensions of substrate 10 are not limited to those specifically described herein. In this specification, the term "rectangular parallelepiped" or "rectangular parallelepiped shape" does not mean only "rectangular parallelepiped" in a mathematically strict sense. The dimensions and shape of the substrate 10 are not limited to those specified herein.

The base 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. Substrate 10 has its outer surface defined by these six faces. The first main surface 10a and the second main surface 10b form both ends in the height direction of the base 10, the first end surface 10c and the second end surface 10d form both ends in the length direction of the base 10, and the first side surface 10e and the second side surface 10f form both ends in the width direction of the base 10. As shown in FIG. 1, the first main surface 10a is on the upper side of the substrate 10, so the first main surface 10a is sometimes referred to as the "upper surface." Similarly, the second major surface 10b may be called a "lower surface" or a "bottom surface". Since the coil component 1 is arranged so that the second principal surface 10b faces the mounting substrate 2a, the second principal surface 10b is sometimes called a "mounting surface". The upper surface 10a and the lower surface 10b are separated by the height dimension of the base 10, the first end face 10c and the second end face 10d are separated by the length dimension of the base 10, and the first side face 10e and the second side face 10f are separated by the width dimension of the base body 10.

Substrate 10 is composed of a magnetic material containing a plurality of metal magnetic particles. The metal magnetic particles contained in the substrate 10 have an insulating film on their surfaces. This insulating film may be an oxide film containing an oxide obtained by oxidizing a metal element contained in the metal magnetic particles of the substrate 10 . Adjacent metal magnetic particles contained in the substrate 10 are bonded to each other via an insulating film formed on their surfaces. The substrate 10 may contain two or more types of metal magnetic particles having different average particle sizes.

In one embodiment, substrate 10 does not contain a resin component. If the base contains a resin component, the filling rate of the first metal magnetic particles in the base decreases, resulting in deterioration of the magnetic permeability of the base. Since the base 10 does not contain a resin component, it is possible to prevent the magnetic permeability of the base 10 from decreasing due to the resin component, thereby improving the magnetic permeability of the coil component 1 .

The substrate 10 in one embodiment does not contain a glass component in the center. If the substrate contains a glass component, the filling rate of the first metal magnetic particles in the substrate decreases, resulting in deterioration of the magnetic permeability of the substrate. Since the base 10 does not contain a glass component in the central portion, it is possible to prevent the magnetic permeability of the base 10 from decreasing due to the glass component, thereby improving the magnetic permeability of the coil component 1 . The central portion of the substrate that is free of glass components can be, for example, the central region 12 shown in FIG. The central region 12 is located between the upper and lower surfaces of the coil conductor 25 in the T-axis direction in the base 10, and indicates the region inside the outer peripheral surface of the later-described winding portion 25A of the coil conductor 25 in the LW plane.

When the substrate 10 does not contain a resin component and a glass component, adjacent metal magnetic particles contained in the substrate 10 are bonded to each other via an insulating film formed on their surfaces.

As shown in FIG. 2, the coil conductor 25 has a winding portion 25A wound around a coil axis Ax extending along the thickness direction (T-axis direction), a lead portion 25B extending from one end of the winding portion 25A to the lower surface 10b of the base 10, and a lead portion 25C extending from the other end of the winding portion 25A to the lower surface 10b of the base 10. As shown in FIG. 3, the coil conductor 25 is exposed from the base 10 only at the end face 25B1 of the lead portion 25B and the end face 25C1 of the lead portion 25C. Parts of the coil conductor 25 other than the end faces 25B1 and 25C1 are embedded in the base 10. As shown in FIG.

The winding portion 25A has a plurality of conductor patterns C11 to C16. The plurality of conductor patterns C11 to C16 extend along a planar direction perpendicular to the coil axis Ax and are separated from each other in the direction of the coil axis Ax. Each of the conductor patterns C11 to C16 is electrically connected to adjacent conductor patterns through vias (not shown). Thus, the winding portion 25A of the coil conductor 25 is composed of the conductor patterns C11 to C16 and vias. The conductor pattern C11 is electrically connected to the external electrode 22 via the lead portion 25C, and the conductor C16 is electrically connected to the external electrode 21 via the lead portion 25B.

In the illustrated embodiment, the composite layer 30 is provided on the lower surface 10b of the substrate 10 . The composite material layer 30 is provided on the base 10 so as to cover part or all of the lower surface 10b. In the illustrated embodiment, the composite layer 30 covers the entire lower surface 10b. As shown in FIG. 3, a through hole 30a is formed through the composite material layer 30 in the T-axis direction at a position facing the end surface 25B1 of the lead portion 25B in the composite material layer 30. As shown in FIG. Similarly, a through-hole 30b that penetrates the composite material layer 30 in the T-axis direction is provided at a position in the composite material layer 30 that faces the end surface 25C1 of the lead portion 25C.

In this way, the composite material layer 30 is provided on the lower surface 10b of the base 10 so as to surround the end surface 25B1 of the lead portion 25B and the end surface 25C1 of the lead portion 25C when the coil component 1 is viewed from the lower surface 10b side. The composite material layer 30 is interposed between the external electrodes 21 and 22 on the lower surface 10b. Since the composite layer 30 is insulating, the external electrodes 21 and 22 are electrically isolated from each other outside the substrate 10 . The illustrated composite layer 30 is an example. The composite material layer 30 may be provided only on a part of the lower surface 10b, or may be provided on a surface other than the lower surface 10b of the substrate 10. FIG.

In one embodiment, the plating layers included in the external electrodes 21 and 22 are formed on the surface 30S of the composite material layer 30 by electroplating or electroless plating. The external electrode 21 may include two or more plating layers. For example, the external electrode 21 may have a Ni plating layer formed on the surface 30S of the composite material layer 30 and a Sn plating layer formed on the surface of the Ni plating layer. The external electrode 22 can be configured similarly to the external electrode 21 . In one embodiment, the external electrode 21 is connected to the coil conductor 25 at the end face 25B1 of the lead portion 25B, and the external electrode 22 is connected to the coil conductor 25 at the end face 25C1 of the lead portion 25C. The plated layer included in the external electrode 21 may be directly connected to the end surface 25B1 of the lead portion 25B, or may be connected via a base electrode layer included in the external electrode 21 . Similarly, the plated layer included in the external electrode 22 may be directly connected to the end surface 25C1 of the lead portion 25C, or may be connected via the base electrode layer included in the external electrode 22. FIG.

In one embodiment, the composite material layer 30 is provided on the surface of the substrate 10 so as not to cover the end faces 25B1, 25C1. That is, the composite material layer 30 may be arranged at a position spaced apart from the end surfaces 25B1 and 25C1. In one embodiment, the composite material layer 30 may be provided so as to surround the end surface 25B1 and the end surface 25C1 when viewed from the T-axis direction. If the positions of the end faces 25B1, 25C1 and the through-holes are not precisely aligned, part of the insulating composite material layer 30 covers the end faces 25B1, 25C1, causing an increase in electrical resistance between the coil conductor 25 and the external electrodes 21, 22. In one embodiment, the composite material layer 30 is provided on the base 10 away from the end surfaces 25B1 and 25C1 so that the composite material layer 30 does not cover the end surfaces 25B1 and 25C1.

Composite layer 30 includes metal magnetic particles and glass. The composite material layer 30 may be produced from a composite material sheet obtained by, for example, mixing metal magnetic particles and glass powder into a slurry prepared by adding a solvent to a resin to prepare a composite material paste, and forming the composite material into a sheet. Through holes are provided in the composite sheet. The through-holes may be filled with a conductive paste that serves as a part of the external electrodes 21 and 22 (for example, a base electrode layer or a plated layer) or a precursor of the lead portions 25B and 25C. A part of the external electrodes 21 and 22 (for example, a base electrode layer or a plating layer) may be provided on the surface of the composite material sheet opposite to the base 10 so as to cover the through holes. The composite sheet is provided on the surface of substrate 10 (or a precursor of substrate 10). The composite material layer 30 is obtained by heating the composite material sheet provided on the surface of the substrate 10 .

The metal magnetic particles contained in the composite material layer 30 may have an insulating film on their surfaces. This insulating film may be an oxide film containing an oxide obtained by oxidizing the metal element contained in the metal magnetic particles. Adjacent ones among the metal magnetic particles contained in the composite material layer 30 can be bonded to each other via the insulating film on the surface thereof. Also, the metal magnetic particles contained in the composite material layer 30 can be bonded to the metal magnetic particles contained in the substrate 10 via the insulating films formed on the respective surfaces. Composite material layer 30 may include two or more types of metal magnetic particles having different average particle sizes.

Composite material layer 30 is configured to exhibit excellent insulating properties by adjusting the content ratio of glass. Since the composite material layer 30 has excellent insulating properties, plating elongation of the plating layers included in the external electrodes 21 and 22 formed on the surface of the composite material layer 30 can be suppressed.

In order to suppress plating elongation, it has been proposed to incorporate a glass component into the base of the coil component or to form a glass layer (a layer made of glass containing no magnetic material) on the exposed surface of the coil conductor (see Patent Documents 1 and 2). However, since glass is a nonmagnetic material, if the glass layer suppresses the plating elongation, the glass layer deteriorates the magnetic properties of the coil component. In one embodiment of the present invention, the composite material layer 30 contains not only glass but also metal magnetic particles that exhibit magnetism. The magnetic permeability of the composite material layer 30 can be 50% or more, preferably 80% or more, of the magnetic permeability of the substrate 10 .

In one embodiment, the composite material layer 30 is provided on the entire lower surface 10b of the base 10 (however, the end surfaces 25B1 and 25C1 of the coil conductor 25 are not covered with the composite material layer 30). By covering the entire lower surface 10b of the substrate 10 with the insulating composite material layer 30, plating elongation can be suppressed more reliably. Further, even if the composite material layer 30 is provided on the entire lower surface 10 b of the base 10 , deterioration of the magnetic properties of the coil component 1 can be suppressed by the metal magnetic particles contained in the composite material layer 30 .

In one embodiment, composite layer 30 has a resistivity of 1.5×10 ⁹ Ω·cm or greater. In one embodiment, a specific resistance of 1.5×10 ⁹ Ω·cm or more can be achieved by setting the volume ratio of glass in the composite material layer 30 to 0.5 vol % or more and 10 vol % or less. Since glass has a high affinity with the metal magnetic particles having oxide films on their surfaces, the molten glass easily spreads along the surfaces of the metal magnetic particles in the composite material layer 30 when the composite material layer 30 is formed. Therefore, even if the glass contained in the composite material layer 30 is in a small amount of 0.5 vol% or more and 10 vol% or less, it can be ubiquitously distributed throughout the composite material layer 30 along the surfaces of the metal magnetic particles.

In one embodiment, the metallic magnetic particles of the composite layer 30 desirably contain Si. A silicon oxide film is likely to be formed on the surface of metal magnetic particles containing Si, and molten glass has a particularly high affinity for this silicon oxide film. Therefore, when the metal magnetic particles of the composite material layer 30 contain Si, the composite material layer 30 can more reliably achieve high insulation (for example, a specific resistance of 1.5×10 ⁹ Ω·cm or more). The metal magnetic particles of the composite material layer 30 can contain an element other than Si that forms an oxide having a high affinity with molten glass, such as Al. For example, oxides of amphoteric metals such as Zn, Sn and Pb have a high affinity with molten glass. Therefore, the metal magnetic particles of the composite layer 30 may contain at least one of Zn, Sn, and Pb.

By reducing the volume ratio of the glass in the composite material layer 30, the volume ratio of the metal magnetic particles in the composite material layer 30 can be increased accordingly. By setting the volume ratio of the glass in the composite material layer 30 to 0.5 vol% or more and 10 vol% or less, the volume ratio of the metal magnetic particles in the composite material layer 30 can be increased, thereby improving the magnetic permeability of the coil component. The magnetic permeability of the composite material layer 30 can be 50% or more, preferably 80% or more, of the magnetic permeability of the substrate 10 .

The glass included in composite layer 30 may be, for example, silica glass or borosilicate glass. Any glass containing Si can be used as the glass contained in the composite material layer 30 .

Si contained in the glass of the composite material layer 30 bonds with Si contained in the first metal magnetic particles of the substrate 10 via oxygen. The bond between the Si contained in the glass of the composite material layer 30 and the Si contained in the first metal magnetic particles of the base 10 through oxygen strengthens the bond between the composite material layer 30 and the base 10 . When the Si content in the glass of the composite material layer 30 is insufficient, the bonding via oxygen between the Si contained in the glass of the composite material layer 30 and the Si contained in the first metal magnetic particles of the substrate 10 decreases, and the bonding strength of the composite material layer 30 to the substrate 10 decreases. On the other hand, glass containing excessive Si is difficult to sinter. If the glass contained in the composite material layer 30 is not sufficiently sintered, the composite material layer 30 or a portion thereof is likely to separate from the substrate 10 due to insufficient strength of the glass. According to one embodiment of the present invention, by setting the atomic ratio of Si in the glass to 70 at % or more and 90 at % or less, it is possible to sufficiently secure bonding via oxygen between Si contained in the glass of the composite material layer 30 and Si contained in the first metal magnetic particles of the base 10, prevent the glass in the composite material layer 30 from becoming difficult to sinter, and suppress peeling of the composite material layer 30 or a portion thereof from the base 10.

The first metal magnetic particles preferably contain a sufficient amount of Si in order to sufficiently ensure the strength of the bonding via oxygen between the Si contained in the glass of the composite material layer 30 and the Si contained in the first metal magnetic particles of the base 10. On the other hand, if the atomic ratio of Si in the first metal magnetic particles becomes excessive, the atomic ratio of Fe in the first metal magnetic particles decreases, so the magnetism developed by the first metal magnetic particles weakens, and as a result, the magnetic permeability of the coil component 1 decreases. In one embodiment, by setting the atomic ratio of Si in the first metal magnetic particles of the base 10 to 3 at % or more and 10 at % or less, it is possible to sufficiently secure the bonding between the Si contained in the glass of the composite material layer 30 and the Si contained in the first metal magnetic particles of the base 10 via oxygen, and realize a coil component with high magnetic permeability.

It is desirable that the second metal magnetic particles contained in the composite material layer 30 also contain Si in an appropriate atomic ratio. If the atomic proportion of Si in the second metal magnetic particles is insufficient, the bonding between the Si contained in the second metal magnetic particles and the Si contained in the glass in the composite material layer 30 through oxygen decreases, and the strength of the composite material layer 30 decreases. On the other hand, if the atomic ratio of Si in the second metal magnetic particles is excessive, the magnetism exhibited by the second metal magnetic particles is weakened, leading to a decrease in magnetic permeability of the coil component 1 . According to one embodiment of the present invention, by setting the atomic ratio of Si in the second metal magnetic particles to 3 at % or more and 10 at % or less, it is possible to sufficiently ensure the strength of the composite material layer 30 and realize the coil component 1 with high magnetic permeability.

In one embodiment, the thickness T1 of the composite layer 30 is greater than or equal to 10 μm. The thickness T1 of the composite material layer 30 may be 10 μm or more and 50 μm or less. The thickness T1 of the composite material layer 30 may be thicker than the thickness T2 of the external electrode 22 . The thickness of the external electrode 21 may be the same as the thickness T2 of the external electrode 22 . By increasing the thickness of the composite material layer 30, when the external electrodes 21 and 22 are provided along the lower surface 10b as shown in FIG. In addition, since the insulating composite material layer 30 contains metal magnetic particles, even if the thickness T1 of the composite material layer 30 is large (for example, even if it is 10 μm or more), deterioration of the magnetic properties of the coil component 1 can be suppressed.

Next, with further reference to FIG. 4, bonding between the base 10 and the composite material layer 30 will be described. 4 is an enlarged cross-sectional view showing an enlarged area A of FIG. 3. FIG. A region A in FIG. 3 is a region spanning the substrate 10 and the composite material layer 30 .

As shown in FIG. 4, the base 10 contains a plurality of first metal magnetic particles 11 . As shown in FIG. 5a, the first metal magnetic particle 11 has a metal portion 11a exhibiting magnetism and an insulating film 11b covering the surface of the metal portion 11a. The metal portion 11a is made of a soft magnetic metal material.

Composite material layer 30 includes a plurality of second metal magnetic particles 31 and glass 32 . As shown in FIG. 5b, the second metal magnetic particle 31 has a metal portion 31a exhibiting magnetism and an insulating film 31b covering the surface of the metal portion 31a. The metal portion 31a is made of a soft magnetic metal material. A portion of the second metal magnetic particles 31 are exposed to the outside on the surface 30S of the composite material layer 30 . Therefore, the surface 30</b>S of the composite material layer 30 has unevenness caused by the second metal magnetic particles 31 .

In one embodiment, the soft magnetic metal material for metal portion 11a and metal portion 31a contains Fe and Si. As the soft magnetic metal material for the metal portion 11a and the metal portion 31a, for example, Fe--Si--Cr, Fe--Si--Al, Fe--Si--Cr--BC, Fe--Si--B--Cr, Fe--Si--BP--Cu, or a mixed material thereof can be used. Soft magnetic metal materials for the metal portion 11a and the metal portion 31a are not limited to those described above. For example, the soft magnetic metal material for the metal portion 11a and the metal portion 31a can contain Zr, Nb, or other elements in addition to the above elements. The atomic ratio of Si in the metal portion 11a and the metal portion 31a can be 3 at % or more and 10 at % or less. The composition of the metal portion 11a may be the same as or different from the composition of the metal portion 31a.

The insulating film 11b can contain an oxide obtained by oxidizing the element contained in the metal portion 11a. The insulating film 11b can contain, for example, silicon oxide (SiO2), which is an oxide of Si. Similarly, the insulating film 31b can contain an oxide obtained by oxidizing an element contained in the metal portion 31a, and can contain silicon oxide (SiO2), which is an oxide of Si.

Adjacent ones among the first metal magnetic particles 11 contained in the substrate 10 are bonded to each other in the insulating film 11b. Near the boundary between the substrate 10 and the composite material layer 30, the first metal magnetic particles 11 contained in the substrate 10 and the second metal magnetic particles 31 contained in the composite material layer 30 are bonded to each other at their respective insulating films 11b and 31b. The bonding between the first metal magnetic particles 11 and the second metal magnetic particles 31 can suppress the separation of the composite material layer 30 from the substrate 10 .

Adjacent ones of the second metal magnetic particles 31 contained in the composite layer 30 may be bonded to each other in the insulating film 31b, as shown in FIG. 6a. When adjacent metal magnetic particles 32 are bonded to each other at the insulating film 31b, glass 32 may be filled in the region around the bonding position. Adjacent ones of the second metal magnetic particles 31 may be bonded via glass 32, as shown in FIG. 6b. Since the second metal magnetic particles 31 contain Si or an element other than Si that forms an oxide that has a high affinity with molten glass, they can be strongly bonded to the glass 32 . In FIG. 6 b , adjacent second metal magnetic particles 31 are separated from each other, but are joined together by glass 32 . Some of the many second metal magnetic particles 31 contained in the composite material layer 30 may be bonded to the adjacent second metal magnetic particles 31 at their respective insulating films 31b, and the rest may be bonded to the adjacent second metal magnetic particles 31 via the glass 32. The glass 32 fills the gaps between the second metal magnetic particles 31 . Glass 32 is ubiquitous throughout composite layer 30 .

In one embodiment, the average particle size of the first metal magnetic particles 11 is 1 μm to 30 μm. The average particle size of the first metal magnetic particles 11 can be determined as follows. That is, the substrate 10 is cut along the T-axis direction to expose the cross section, and the cross section is photographed with a scanning electron microscope (SEM) at a magnification of 2,000 to 5,000 times to obtain an SEM image.

In one embodiment, the average particle size of the second metal magnetic particles 31 is 1 μm to 30 μm. The average particle size of the second metal magnetic particles 31 may be larger than the average particle size of the first metal magnetic particles 11 . When forming a plating layer on the surface to be plated, the smoother the layer to be plated, the more easily the plating elongation occurs. If the unevenness of the surface to be plated becomes large, it becomes difficult for the current to flow between the adjacent protrusions across the recesses during the plating process, so that the plating is difficult to be formed between the protrusions. In this way, by increasing the unevenness of the surface to be plated, plating elongation is suppressed. As the average particle diameter of the second metal magnetic particles 31 increases, the unevenness of the surface 30S of the composite material layer 30 increases, so that the formation of plating on the surface of the composite material layer 30 can be prevented. The average particle size of the second metal magnetic particles 31 can be determined in the same manner as the average particle size of the first metal magnetic particles 11 .

Although the boundary between the substrate 10 and the composite material layer 30 is clearly shown in FIG. 4, the boundary between the substrate 10 and the composite material layer 30 may not be visible. When the boundary between the substrate 10 and the composite material layer 30 cannot be visually recognized, the area where the glass exists between the metal magnetic particles (the area where the metal magnetic particles and the glass are mixed) can be regarded as the composite material layer 30, and the area where the glass does not exist can be regarded as the substrate 10.

Next, another embodiment will be described with reference to FIG. FIG. 7 is an enlarged cross-sectional view showing an enlarged cross-section of part of a coil component according to another embodiment. In the embodiment shown in FIG. 7, the through hole 30b of the composite material layer 30 is formed so that its diameter is larger than the diameter of the end face 25C1 of the lead portion 25C. An end face 25C1 of the lead portion 25C is exposed from the base 10, and the composite material layer 30 is provided so as to surround the end face 25C1. Thereby, the composite material layer 30 can be separated from the end face 25C1 of the lead portion 25C. Therefore, it is possible to prevent the DC resistance of the coil conductor 25 from increasing due to the composite material layer 30 covering the end face 25C1. Although not shown, the through hole 30a of the composite material layer 30 may be formed so that its diameter is larger than the diameter of the end face 25B1 of the lead portion 25B.

Next, another embodiment will be described with reference to FIG. FIG. 8 is an enlarged cross-sectional view showing an enlarged cross-section of part of a coil component according to another embodiment. In the embodiment shown in FIG. 8, the tip of the lead-out portion 25C of the coil conductor 25 protrudes from the base 10, and the projecting portion 25C2 is accommodated in the through hole 30b of the composite material layer 30. When the composite material layer 30 is formed from the composite material sheet, the composite material sheet is pressure-molded together with the precursor of the base 10, so that the through-holes of the composite material sheet are filled with the conductive paste serving as the precursor of the lead portions 25C, and the conductive paste filled in the through-holes becomes the projecting portions 25C2. That is, when the composite material layer 30 is formed from the composite material sheet, pressure molding is performed together with the precursor of the base 10, so that the through-holes of the composite material sheet are filled with the conductive paste serving as the precursor of the lead-out portion 25C.

In one embodiment, a composite sheet may be formed with a precursor of portions of the external electrodes 21 , 22 , and the precursor of portions of the external electrodes 21 , 22 may be pressure molded with the composite sheet and the substrate 10 precursor. As a result, precursors for portions of the external electrodes 21 and 22 (for example, base electrode layers) connected to the precursors for the lead portions 25B and 25C can be formed. A part of the precursor of the external electrodes 21 and 22 can be formed by applying a conductive paste to a composite magnetic material sheet and baking the applied conductive paste to the composite material sheet. A portion of the precursor of the external electrodes 21, 22 may be filled in through-holes formed in the composite sheet.

Next, with reference to FIG. 9, an embodiment in which the external electrodes 21 and 22 include base electrode layers will be described. FIG. 9 is an enlarged cross-sectional view showing an enlarged cross-section of part of a coil component according to another embodiment. In the embodiment shown in FIG. 9, the external electrode 22 has a base electrode layer 22a and a plating layer 22b. The base electrode layer 22a is provided on the surface 30S of the composite material layer 30, and the plating layer 22b is provided on the surface of the base electrode layer 22a. The base electrode layer 22a is formed, for example, by applying a paste-like conductive material (for example, silver) to the surface 30S of the composite material layer 30 and drying the applied conductive material. The base electrode layer 22 a may be provided so as to close the through holes 30 b of the composite material layer 30 . The base electrode layer 22a may be applied to the end face 25C1 of the lead portion 25C. A portion of the underlying electrode layer 22 a extends along the lower surface of the composite material layer 30 .

In one embodiment, the precursor of the base electrode layer 22a is formed, for example, by coating a composite material sheet, which is a precursor of the composite magnetic layer 30, with a conductive paste so as to cover the through-holes of the composite material sheet. The composite material sheet on which the precursor of the base electrode layer 22a is formed may be pressure-molded together with the precursor of the substrate 10. FIG.

The plating layer 22b is formed on the surface of the underlying electrode layer 22a by, for example, electroplating. The plating layer 22b extends along the conductive base electrode layer 22a to the edge of the base electrode layer 22a. In one embodiment, composite material layer 30 is provided to surround underlying electrode layer 22a. That is, the base electrode layer 22a is surrounded by the composite material layer 30 when viewed from the T-axis direction. In other words, when viewed from the T-axis direction, at least a portion of the composite material layer 30 is arranged outside the outer edge of the base electrode layer 22a. In the illustrated embodiment, part of the composite material layer 30 is arranged at positions on the plus side and the minus side in the L-axis direction relative to both ends of the base electrode layer 22a in the L-axis direction. A part of the composite material layer 30 may be arranged at positions on the positive side and the negative side in the W-axis direction relative to both ends of the base electrode layer 22a in the W-axis direction. Since the insulating composite material layer 30 is arranged outside the base electrode layer 22a, the plated layer 22b extends to the edge of the base electrode layer 22a, but does not extend further outward.

The plated layer 22b and the coil conductor 25 can be electrically connected more reliably by the base electrode layer 22a.

Although not shown, the external electrode 21 may also have a base electrode layer provided between the plating layer and the composite material layer 30 . The description regarding the base electrode layer 22 a also applies to the base electrode layer included in the external electrode 21 .

Next, another embodiment will be described with reference to FIG. FIG. 10 is a cross-sectional view schematically showing a cross section of a coil component according to another embodiment. The coil component 1 shown in FIG. 10 comprises a composite material layer 130 . The composite material layer 130 is provided on the lower surface 10b, the first end surface 10c, and the second end surface 10 of the substrate 10. As shown in FIG. In the illustrated embodiment, the composite material layer 130 is provided on the substrate 10 so as to cover the entire lower surface 10b of the substrate 10, a portion of the first end surface 10c, and a portion of the second end surface 10d.

Composite layer 130, like composite layer 30, includes metal magnetic particles and glass. Even when the external electrodes 21 and 22 extend to the boundary of the lower surface 10b with the first end surface 10c and the boundary with the second end surface 10d, respectively, the composite material layer 130 can prevent the occurrence of plating elongation extending to the first end surface 10c and the second end surface 10d. Moreover, even if the composite material layer 130 is provided not only on the lower surface 10b of the base 10 but also on the first end surface 10c and the second end surface 10d of the base 10, deterioration of the magnetic properties of the coil component 1 can be suppressed. In addition, peeling from the composite material layer 130 or a part thereof from not only the lower surface 10b of the main body of the base body 10 but also the first end surface 10c and the second end surface 10d is suppressed.

Next, an example of a method for manufacturing the coil component 1 will be described with reference to FIG. 11 . First, in step S11, a laminate is produced in which a composite material sheet serving as the composite material layer 30 is formed on the surface of the structure in which the conductor portion serving as the coil conductor 25 is embedded. A structure included in this laminate can be produced by, for example, a sheet lamination method. In the following examples, structures are made by sheet lamination.

First, a magnetic sheet containing metal magnetic powder is prepared in order to fabricate a structure in which a conductor portion to be the coil conductor 25 is embedded. A magnetic sheet can be obtained, for example, by applying a metal magnetic paste to the surface of a plastic base film, drying it, and cutting the dried metal magnetic paste into a predetermined size. The metal magnetic paste is prepared, for example, by adding an appropriate amount of solvent to a resin material containing metal magnetic powder to be the metal magnetic particles 11 . Metal magnetic powder is a powder composed of a soft magnetic metal material containing Fe and Si. An insulating film may be formed in advance on the surface of the metal magnetic powder. Known resin materials such as polyvinyl butyral (PVB) resin, epoxy resin, and silicon resin can be used as the resin material for the metal magnetic paste.

Next, through holes for forming vias are formed at predetermined positions of the plurality of magnetic sheets. Next, a conductor precursor pattern is formed on each magnetic sheet by applying a conductive paste by screen printing or the like to the surface of each of the plurality of magnetic sheets in which the through holes are formed. This conductive paste contains a conductive material having excellent conductivity, such as Ag, Pd, Cu, Al, or alloys thereof. Conductor Precursor Patterns Formed on Magnetic Sheets Conductor precursor patterns have shapes corresponding to any of the conductor patterns C11 to C16. When the conductive paste is applied to the magnetic sheet, the conductive paste is embedded in the through-holes of the magnetic sheet, and the conductive paste embedded in the through-holes serves as a via precursor. A part of the via precursor becomes the lead portions 25B and 25C after the heat treatment.

Next, a composite material sheet to be the composite material layer 30 is prepared. A composite material sheet can be obtained, for example, by applying a composite material paste to the surface of a plastic base film, drying the composite material paste, and cutting the dried composite material paste into a predetermined size. The composite material paste is prepared, for example, by adding an appropriate amount of solvent to a resin material containing metal magnetic powder to be the metal magnetic particles 11 and glass powder to be the glass 32 . The metal magnetic powder contained in the composite material paste is powder composed of a soft magnetic metal material containing Fe and Si. The composition of the metal magnetic powder contained in the composite material paste may be the same as or different from the composition of the metal magnetic powder contained in the magnetic sheet. The average particle size of the metal magnetic powder contained in the composite material paste may be larger than the average particle size of the metal magnetic powder contained in the magnetic sheet. The glass powder is, for example, silica glass powder, borosilicate glass powder, or other known glass powder. In one embodiment, the average particle size of the glass powder is smaller than the average particle size of the metal magnetic powder contained in the composite material paste. The average particle size of the glass powder is, for example, 1/4 to 1/2 of the average particle size of the metal magnetic powder contained in the composite material paste. Known resin materials such as polyvinyl butyral (PVB) resin, epoxy resin, and silicon resin can be used as the resin material for the composite material paste. Through holes are formed in the composite material sheet at positions corresponding to the lead portions 25B and 25C. The through holes may be filled with a conductive paste that serves as a precursor of the lead portions 25B and 25C (for example, the projecting portion 25C2). This conductive paste may be the same as the conductive paste embedded in the through-holes of the magnetic sheet. The through holes may not be filled with this conductive paste. The opening of the through hole may be formed in the same shape as the end surfaces 25B1 and 25C1 of the lead portions 25B and 25C, or may be formed larger than the end surfaces 25B1 and 25C1. When the external electrodes 21 and 22 have a base electrode layer, a precursor pattern of the base electrode layer of the external electrodes 21 and 22 can be formed on the composite magnetic material sheet by applying a conductive paste by screen printing or the like to the surface including the through holes of the composite material sheet in which the through holes are formed. This conductive paste contains a conductive material having excellent conductivity, such as Ag, Pd, Cu, Al, Ni, or alloys thereof. The precursor patterns of the base electrode layers of the external electrodes 21 and 22 become the base electrode layers that are part of the external electrodes 21 and 22 after the heat treatment. When the conductive paste is applied to the composite material sheet, the conductive paste may be embedded in the through-holes of the composite material sheet, and the conductive paste embedded in the through-holes may serve as a via precursor. A part of the via precursor becomes the lead portions 25B and 25C after the heat treatment.

Next, the magnetic sheet having the conductor precursor pattern prepared as described above, the magnetic sheet having no conductor precursor pattern formed thereon and serving as the cover layer, and the composite material sheet are laminated, and the laminated sheets are thermally compressed to obtain a mother laminate. The magnetic sheets on which conductor precursor patterns are formed are laminated such that each conductor precursor pattern formed on each magnetic sheet is connected to an adjacent conductor precursor pattern via a via precursor. The composite material sheet is laminated on the lower surface of the magnetic sheet that serves as the cover layer. The composite material sheet is laminated with the magnetic material sheet so that the through-holes and via precursors corresponding to the lead-out portions 25B and 25C are aligned. Next, chip laminates are obtained by separating the mother laminate into individual pieces using a cutting machine such as a dicing machine or a laser processing machine.

In step S11, the structure in which the conductor portion to be the coil conductor 25 is embedded may be manufactured by a method known to those skilled in the art other than the sheet lamination method, such as compression molding, slurry build, or thin film process.

Next, in step S12, the chip stack is degreased, and the degreased chip stack is heat-treated. The heat treatment to the chip laminated body is performed, for example, at 400° C. to 950° C. for 20 minutes to 120 minutes. The heat treatment may be performed in air. The heat treatment may be performed in a low-oxygen atmosphere.

By this heat treatment, the conductor precursor pattern and the via precursor are sintered to form the coil conductor 25 . Further, the heat treatment removes the resin and the solvent from the magnetic sheet, and sinters the metal magnetic powder contained in the magnetic sheet to form the metal magnetic particles 11 to form the substrate 10 .

In the heat treatment of step S12, the resin and solvent are further eliminated from the composite material sheet, the metal magnetic powder contained in the composite material sheet is sintered to form metal magnetic particles 31, and the glass powder melts and flows into the gaps between the adjacent metal magnetic particles 31 to form the glass 32 between the metal magnetic particles 31, thereby forming the composite material layer 30. When the average particle size of the glass powder in the composite material sheet is smaller than the average particle size of the metal magnetic powder, the glass powder tends to be arranged between the metal magnetic powders in the composite material sheet. Therefore, when the average particle size of the glass powder in the composite material sheet is smaller than the average particle size of the metal magnetic powder, the glass 32 does not aggregate in a part of the composite material layer 30 and tends to be omnipresent in the composite material layer 30 .

When the composite material sheet is provided with the precursor of the underlying electrode layers of the external electrodes 21 and 22, the precursor of the underlying electrode layers of the external electrodes 21 and 22 becomes the underlying electrode layers of the external electrodes 21 and 22 in step S12.

The heat treatment may be performed in two stages. In the first heat treatment of the first stage, heat treatment is performed at a temperature below the softening temperature of the glass powder contained in the composite material sheet to form an oxide film on the surface of the magnetic material sheet and the metal magnetic powder contained in the composite material sheet. For example, when the glass powder is borosilicate glass powder, the first heat treatment may be performed at a temperature lower than 820° C., which is the softening point of borosilicate glass (for example, 400° C. to 700° C.). By this first heat treatment, the resin and solvent disappear from each sheet, and the metal magnetic particles 11 can be bonded together, the metal magnetic particles 31 can be bonded together, and the metal magnetic particles 11 and 31 can be bonded. In the second heat treatment in the second stage, the chip stack after the first heat treatment is heated at a temperature higher than the softening temperature of the glass powder (for example, at 850° C. to 950° C. described above). By the second heat treatment, the glass portion melts and moves to the gaps between adjacent metal magnetic particles 31 . If the heat treatment is performed in one step, the formation of an oxide film on the surface of the metal magnetic powder contained in the composite material sheet, the bonding of the metal magnetic particles 31 via this oxide film, and the melting of the glass can occur in parallel. If the glass 32 is interposed between the metal magnetic particles 31, it may cause the strength of the composite material layer 30 to decrease. By performing the heat treatment in two stages as described above, melting of the glass occurs after the metal magnetic particles 31 are bonded to each other, so that the metal magnetic particles 31 can be bonded to each other.

Next, in step S<b>13 , external electrodes 21 and 22 are formed on the surface of composite material layer 30 . The plating layers included in the external electrodes 21 and 22 may be formed by an electrolytic plating method or an electroless plating method. The external electrodes 21 and 22 extend along the surface of the composite material layer 30 and are formed to fill the through holes 30a and 30b. A base electrode layer (for example, base electrode layer 22a) may be formed by applying a conductive paste to the surface of composite material layer 30 and through holes 30a and 30b, and a plating layer (for example, plated layer 22b) may be formed on the surface of base electrode layer 22a. In order to form this base electrode layer, a precursor of the base electrode layer may be formed in advance in steps S11 and S12. In steps S11 and S12, the precursor of the underlying electrode layer may be formed so as to be connected to the ends of the precursor of the lead portions 25B and 25C. Thus, by connecting the precursor of the base electrode layer to the precursor of the lead portions 25B and 25C in steps S11 and S12 in advance, the connectivity between the lead portions 25B and 25C and the external electrodes 21 and 22 can be improved.

In order to verify the influence of the glass volume ratio in the composite material layer 30 on the occurrence of plating elongation, seven types of samples were produced as follows. These seven types of samples were produced by a sheet lamination method according to the manufacturing method shown in FIG. Specifically, first, a plurality of magnetic sheets were produced using metal magnetic powder (Fe--Si--Cr crystalline alloy). The composition of the metal magnetic powder was Fe: 93 wt%, Si: 5%, and Cr: 2 wt%. A conductor precursor pattern and a via precursor were formed on each magnetic sheet by forming through holes in the magnetic sheets and applying a conductive paste containing silver to the magnetic sheets having the through holes.

Also, a composite material sheet was produced using metal magnetic powder (Fe—Si—Cr crystalline alloy, Fe: 93 wt %, Si: 5%, Cr: 2 wt %) and glass powder (borosilicate glass powder). Moreover, the atomic ratio of Si in the glass powder was set to 80 at %. The mixing ratio of the metal magnetic powder and the glass powder in the composite material sheet was as described in the column of "Glass Material Volume Ratio" in Table 1 below. That is, seven types of composite material sheets were produced by mixing metal magnetic powder and glass powder at the mixing ratios shown in Table 1. Through holes were formed in the composite material sheet at positions corresponding to the lead portions 25B and 25C. This magnetic sheet and one of the seven types of composite material sheets were laminated and thermocompressed to produce a laminate. For each of the seven types of composite material sheets, laminates were produced in the same manner to obtain seven types of laminates with different glass ratios in the composite material sheets.

Next, each of the seven types of laminates was heated at 900° C. for 60 minutes to obtain a substrate having a coil conductor 25 inside and a composite material layer formed on the surface. Next, a conductive paste produced by adding a resin and a solvent to Ag particles was applied to the surface of the composite material layer so as to fill each of the two through-holes of the composite material layer, and this conductive paste was baked on the composite material layer at 600 ° C. to form a base electrode layer. Next, a plated layer containing Ni was formed on the surface of the base electrode layer by electroplating, thereby forming an external electrode including the base electrode layer and the plated layer.

As described above, 1020 pieces each of seven types of coil components (Samples 1 to 7) were produced. The inductance of 10 pieces of each of samples 1 to 7 was measured using a commercially available impedance analyzer, and the measured impedance was converted to magnetic permeability. For each of Samples 1 to 7, the average magnetic permeability determined from 10 samples is listed in the "Permeability" column in Table 1 below.

In addition, 10 samples for specific resistance measurement were selected from each of samples 1 to 7, an electrode for specific resistance measurement was applied to the surface of each of the selected samples, and a commercially available resistance meter was used to measure the specific resistance of the composite material layer for each sample to which the electrode was applied. For each of Samples 1-7, the average resistivity obtained from the 10 samples is listed in the "Resistivity" column in Table 1 below.

In addition, for the remaining 1000 samples of each of samples 1 to 7, the composite material layer was observed from the side surface (from the W axis direction in FIG. 1) with an optical microscope, and the composite material layer was peeled from the substrate over a length of 20 μm or more.

In addition, the surface of each of the 1000 samples on which the composite material layer was formed was observed with an optical microscope to confirm the presence or absence of plating elongation. In this observation, it was determined that unwanted plating elongation occurred when the plating elongation was 30 μm or more. For each of Samples 1 to 7, the rate at which plating elongation occurred is shown in the column of "Plating elongation occurrence rate" in Table 1 below.

From the measurement results shown in Table 1, it was confirmed that when the volume ratio of the glass contained in the insulating composite material layer was 0.5 vol% or more, almost no plating elongation occurred on the surface of the insulating composite material layer. Moreover, it was confirmed that a high magnetic permeability of 20 or more can be realized when the volume ratio of the glass contained in the insulating composite material layer is 10 vol % or less. Furthermore, it was confirmed that the insulating composite material layer could be strongly bonded to the substrate when the glass volume ratio in the insulating composite material layer was in the range of 0.5 vol % to 10 vol %.

Next, four types of samples, Samples 8 to 11, were produced as follows. In producing Samples 8 to 11, the volume ratio of the glass powder in the composite material sheet was set to 5 vol %. The atomic ratio of Si in the metal magnetic powder (Fe--Si--Cr crystalline alloy) used in the magnetic sheet was set as shown in the column of "Si ratio in metal magnetic powder" in Table 2 below. That is, four types of magnetic sheets were produced using metal magnetic powder containing Si in the atomic proportions shown in Table 2. The materials of the magnetic sheet and the composite material sheet other than these were the same as those of Samples 1-7. A laminate was produced by laminating one of these four kinds of magnetic material sheets and a composite material sheet and bonding them by thermocompression. For each of the four types of magnetic sheets, laminates were produced in the same manner to obtain four types of laminates having different Si atomic ratios in the metal magnetic powder contained in the magnetic sheets. Next, each of the four types of laminates was heat-treated in the same manner as Samples 1 to 7, and the heat-treated laminates were subjected to the same methods as Samples 1 to 7 to form a base electrode layer and a plating layer to form external electrodes. As described above, four types of coil components (Samples 8 to 11) were produced. 1020 pieces of each of samples 8 to 11 were produced. For each of Samples 8 to 11, magnetic permeability, specific resistance, rate of peeling, and rate of elongation of plating were measured in the same manner as Samples 1 to 7. The measurement results are as follows.

From the measurement results shown in Table 2, it was confirmed that the insulating composite material layer hardly separated from the substrate when the atomic ratio of Si in the metal magnetic powder contained in the magnetic sheet was 3 at% or more. On the other hand, from sample 8, when the atomic ratio of Si in the metal magnetic powder contained in the magnetic sheet was 2 at %, peeling occurred at a rate of 20 ppm. When the atomic ratio of Si in the metal magnetic powder contained in the magnetic sheet is low, the insulating composite material layer is likely to separate from the substrate. This is probably because when the atomic ratio of Si in the metal magnetic powder contained in the magnetic sheet (i.e., the atomic ratio of Si in the first metal magnetic particles 11 of the substrate) is insufficient, the bonding between the Si contained in the first metal magnetic particles of the substrate and the Si contained in the glass of the insulating composite material layer decreases through oxygen, and the bonding strength of the insulating composite material layer to the substrate deteriorates. Further, from the measurement results in Table 2, it was confirmed that a high magnetic permeability of 20 or more can be realized when the atomic ratio of Si in the metal magnetic powder contained in the magnetic sheet is 10 atomic % or less. Furthermore, it was confirmed that plating elongation hardly occurs when the atomic ratio of Si in the metal magnetic powder contained in the magnetic sheet is 3 at % or more and 10 at % or less.

Next, four types of samples, Samples 12 to 15, were produced as follows. In producing samples 12 to 15, the volume ratio of the glass powder in the composite material sheet was set to 5 vol %. The atomic ratio of Si in the glass powder (borosilicate glass powder) contained in the composite material sheet was set as shown in the column of "Si ratio in glass powder" in Table 3 below. That is, four types of composite material sheets were produced using the glass powder containing Si at the atomic ratio shown in Table 3. The materials of the magnetic sheet and the composite material sheet other than these were the same as those of Samples 1-7. A laminate was produced by laminating a magnetic material sheet and one of four types of composite material sheets and thermocompression bonding them. For each of the four types of composite material sheets, laminates were produced in the same manner to obtain four types of laminates having different Si atomic ratios in the glass powder contained in the composite material sheets. Next, each of the four types of laminates was heat-treated in the same manner as Samples 1 to 7, and the heat-treated laminates were subjected to the same methods as Samples 1 to 7 to form a base electrode layer and a plating layer to form external electrodes. As described above, four types of coil components (Samples 12 to 15) were produced. xx pieces of each of samples 12 to 15 were produced. For each of Samples 12 to 15, magnetic permeability, specific resistance, rate of peeling occurrence, and rate of plating elongation were measured in the same manner as Samples 1 to 7. The measurement results are as follows.

From the measurement results shown in Table 3, it was confirmed that the composite material layer hardly separated from the substrate when the atomic ratio of Si in the metal magnetic powder contained in the magnetic sheet was 70 at % or more and 90 at % or less. On the other hand, from sample 12, when the atomic ratio of Si in the glass powder was 65 at %, peeling occurred at a rate of 42 ppm. When the atomic ratio of Si in the glass powder (that is, the atomic ratio of Si in the glass 32) is low, the composite material layer is likely to separate from the substrate. This is considered to be because when the atomic ratio of Si in the glass in the insulating composite material layer becomes low, the bonding strength of the insulating composite material layer to the substrate decreases due to the reduced bonding between the Si contained in the glass and the Si contained in the first metal magnetic particles of the substrate through oxygen. In addition, when the atomic ratio of Si in the glass powder is high, the composite material layer tends to peel off from the substrate. It is considered that the glass containing excessive Si is difficult to sinter and has low strength, and if the glass contained in the composite material layer is not sufficiently sintered, the insulating composite material layer or a part thereof tends to peel off from the substrate due to insufficient strength of the glass.

The dimensions, materials, and arrangement of each component described in the various embodiments above are not limited to those explicitly described in each embodiment, and each such component can be modified to have any dimension, material, and arrangement that may fall within the scope of the present invention.

Components not explicitly described in this specification may be added to each of the embodiments described above, and some of the components described in each embodiment may be omitted.

The notations such as “first”, “second”, “third” in this specification etc. are attached to identify the constituent elements, and do not necessarily limit the number, order, or content thereof. Also, numbers for identifying components are used for each context, and numbers used in one context do not necessarily indicate the same configuration in other contexts. Also, it does not preclude a component identified by a certain number from having the function of a component identified by another number.

Reference Signs List 1 coil component 10 substrate 21, 22 external electrode 22a base electrode layer 22b plating layer 11 first metal magnetic particle 25 coil conductor 30, 130 composite material layer 31 second metal magnetic particle 32 glass Ax coil shaft

Claims (20)

a substrate comprising a plurality of first metal magnetic particles;
a coil conductor provided inside the base and having an end face exposed from the surface of the base;
an external electrode including a plating layer and provided on the end face;
an insulating composite material layer provided on the surface of the base so as to surround the end face of the coil conductor and containing a plurality of second metal magnetic particles and glass;
Coil component with The proportion of the glass in the composite material layer is 0.5 vol% or more and 10 vol% or less.
The coil component according to claim 1. The atomic ratio of Si in the glass is 70 at% or more and 90 at% or less.
The coil component according to claim 1 or 2. The atomic ratio of Si in the first metal magnetic particles is 3 at % or more and 10 at % or less.
The coil component according to any one of claims 1 to 3. The atomic ratio of Si in the second metal magnetic particles is 3 at % or more and 10 at % or less.
The coil component according to any one of claims 1 to 4. The coil component according to any one of claims 1 to 5, wherein said second metal magnetic particles have an average particle size larger than that of said first metal magnetic particles. The substrate does not contain a glass component,
The coil component according to any one of claims 1 to 6. The base does not contain a resin component,
The coil component according to any one of claims 1 to 7. The composite material layer is provided on the surface of the base so as not to cover the end face of the coil conductor.
The coil component according to any one of claims 1 to 8. The base has a rectangular parallelepiped shape,
The coil conductor is exposed from the first surface of the base,
The composite material layer is provided on the base so as to cover the entire first surface.
The coil component according to any one of claims 1 to 9. The base has a rectangular parallelepiped shape,
The coil conductor is exposed from the first surface of the base,
The composite material layer is provided on the base so as to cover at least part of the first surface and at least part of the second surface connected to the first surface.
The coil component according to any one of claims 1 to 10. the composite layer has a thickness of 10 μm or more;
The coil component according to any one of claims 1 to 11. one second metal magnetic particle among the plurality of second metal magnetic particles is bonded to another second metal magnetic particle among the plurality of second metal magnetic particles adjacent to the one second metal magnetic particle by the glass;
The coil component according to any one of claims 1 to 12. The plurality of second metal magnetic particles includes one second metal magnetic particle and another second metal magnetic particle adjacent to the one second metal magnetic particle,
an insulating film is provided on each surface of the one second metal magnetic particle and the another second metal magnetic particle,
The one second metal magnetic particle and the other second metal magnetic particle are bonded via respective insulating films,
The coil component according to any one of claims 1 to 13. The base has a rectangular parallelepiped shape,
The coil conductor is exposed from the first surface of the base,
a portion of the plurality of second metal magnetic particles are exposed from the first surface of the base;
The coil component according to any one of claims 1 to 14. further comprising a base electrode layer provided between the end surface of the coil conductor and the plating layer;
A coil component according to any one of claims 1 to 15. The coil conductor is exposed from the first surface of the base,
The composite material layer is provided so as to surround the underlying electrode layer when viewed in a direction perpendicular to the first surface.
The coil component according to claim 16. forming an insulating insulating film containing a plurality of second metal magnetic particles and a plurality of glass particles and having through holes at positions corresponding to the end surfaces of the conductor portion exposed from the structure, on the surface of the structure including the plurality of first metal magnetic particles and having the conductor portion provided therein to form a laminate;
a step of subjecting the laminate to a heat treatment;
forming an external electrode including a plating layer on the end surface of the conductor portion exposed from the surface of the structure;
A method of manufacturing a coil component comprising: The insulating film is formed in the structure so that the through hole accommodates a part of the conductor.
A method for manufacturing a coil component according to claim 19. The average particle diameter of the plurality of glass powders is not more than half the average particle diameter of the plurality of second metal magnetic particles.
A method for manufacturing a coil component according to claim 18 or 19.

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