阅读说明：本技术 线圈部件 (Coil component ) 是由 荒木建一 石田启一 野口裕 于 2020-09-22 设计创作，主要内容包括：本发明提供耐湿性高的线圈部件。上述线圈部件具有具备线圈导体的大致长方体形状的第一磁性体部、和配置于第一磁性体部的至少上表面的第二磁性体部,第一磁性体部包含由金属磁性体构成的第一磁性粒子,第二磁性体部包含第二磁性粒子以及树脂,第二磁性体部中的树脂的含量比第一磁性体部中的树脂的含量多。(The invention provides a coil component with high moisture resistance. The coil component includes a first magnetic body portion having a substantially rectangular parallelepiped shape and including a coil conductor, and a second magnetic body portion disposed on at least an upper surface of the first magnetic body portion, the first magnetic body portion including first magnetic particles made of a metal magnetic body, the second magnetic body portion including second magnetic particles and a resin, a content of the resin in the second magnetic body portion being greater than a content of the resin in the first magnetic body portion.)

1. A coil component in which, among other things,

the coil component includes:

a first magnetic body portion having a substantially rectangular parallelepiped shape and including a coil conductor; and

a second magnetic body portion disposed on at least an upper surface of the first magnetic body portion,

the first magnetic body portion includes first magnetic particles made of a metal magnetic body, the second magnetic body portion includes second magnetic particles and a resin, and a content of the resin in the second magnetic body portion is greater than a content of the resin in the first magnetic body portion.

2. The coil component of claim 1,

the first magnetic particles have oxide films on surfaces thereof, and the first magnetic particles are bonded to each other via the oxide films.

3. The coil component of claim 1 or 2, wherein,

the first magnetic body portion has a laminated structure.

4. The coil component according to any one of claims 1 to 3, wherein,

the second magnetic particles are made of a metallic magnetic body.

5. The coil component according to any one of claims 1 to 4, wherein,

the coil conductor includes a plurality of coil conductor layers stacked in a winding axis direction of the coil conductor, and an insulating layer is disposed between the plurality of coil conductor layers.

6. The coil component of claim 5, wherein,

the insulating layer has a relative magnetic permeability lower than that of the first magnetic body portion.

7. The coil component according to any one of claims 1 to 6, wherein,

the second magnetic body portion is disposed on an upper surface of the first magnetic body portion and four side surfaces adjacent to the upper surface,

both ends of the coil conductor are drawn out to the lower surface of the first magnetic body.

8. The coil component of claim 7,

an insulating film is disposed on a lower surface of the first magnetic body portion.

9. The coil component of claim 8, wherein,

the insulating film contains a resin.

10. The coil component according to any one of claims 1 to 9, wherein,

the first magnetic body portion has four side surfaces parallel to a winding axis of the coil conductor,

the coil conductor is exposed on at least one of the four side surfaces.

11. The coil component according to any one of claims 1 to 10, wherein,

the first magnetic particles and the second magnetic particles differ in at least one of their average particle diameter and composition.

12. The coil component according to any one of claims 1 to 11, wherein,

the second magnetic body portion has a lower porosity than the first magnetic body portion.

13. The coil component according to any one of claims 1 to 12, wherein,

the second magnetic body portion has an average thickness of 10 to 200 μm on each surface of the first magnetic body portion on which the second magnetic body portion is disposed.

14. The coil component according to any one of claims 1 to 13, wherein,

the second magnetic particles are nanocrystalline particles.

15. The coil component according to any one of claims 1 to 13, wherein,

the second magnetic particles are amorphous magnetic particles.

16. The coil component according to any one of claims 1 to 15, wherein,

the second magnetic body portion further includes third magnetic particles having an average particle diameter different from that of the second magnetic particles.

17. The coil component according to any one of claims 1 to 16, wherein,

the first magnetic body portion further includes fourth magnetic particles having an average particle diameter different from that of the first magnetic particles.

18. The coil component according to any one of claims 1 to 17, wherein,

at least one of the first magnetic body portion and the second magnetic body portion includes flat-shaped magnetic particles.

Technical Field

The present invention relates to a coil component.

Background

Conventionally, sintered metal magnetic particles have been used as a magnetic material constituting an electronic component such as a coil component.

Patent document 1 discloses a composite material having a structure in which the surface of a substance a, which is a particulate metal or alloy, is almost covered with a coating film of a substance B having a higher resistance than the substance a, so that the particles of the substance a are hardly in contact with each other, and the ratio of the particle diameters of the substance a to the average particle diameter thereof is substantially in the range of 0.8 to 1.2, and the relative density is 97% or more. Patent document 1 describes that a composite sintered body having a high electrical resistance can be obtained with a thinner insulating layer by the composition of the composite material described herein.

Patent document 1: japanese laid-open patent publication No. 4-346204

The characteristics required for coil components include excellent moisture resistance.

Disclosure of Invention

The invention aims to provide a coil component with high moisture resistance.

As a result of extensive studies, the present inventors have found that, in a coil component including a first magnetic part including metal magnetic particles and a second magnetic part disposed on at least an upper surface of the first magnetic part and including magnetic particles and a resin, a coil component having high moisture resistance can be obtained by increasing the content of the resin in the second magnetic part to be larger than the content of the resin in the first magnetic part, and have completed the present invention.

According to an aspect of the present invention, there is provided a coil component,

the coil component includes:

a first magnetic body portion having a substantially rectangular parallelepiped shape and including a coil conductor; and

a second magnetic body portion disposed on at least an upper surface of the first magnetic body portion,

the first magnetic body portion includes first magnetic particles made of a metal magnetic body, the second magnetic body portion includes second magnetic particles and a resin, and a content of the resin in the second magnetic body portion is greater than a content of the resin in the first magnetic body portion.

According to the coil component of the present invention, moisture resistance can be improved.

Drawings

Fig. 1 is a schematic cross-sectional view of a coil component according to a first embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view of a coil component according to a second embodiment of the present invention.

Fig. 3 is a schematic cross-sectional view of a modified example of the coil component according to the second embodiment of the present invention.

Fig. 4 is a schematic view showing the direction of the magnetic field generated in the coil member.

Fig. 5 is a schematic diagram illustrating a method for manufacturing a coil component according to a first embodiment of the present invention.

Fig. 6 is a schematic diagram illustrating a method for manufacturing a coil component according to a first embodiment of the present invention.

Fig. 7 is a schematic diagram illustrating a method for manufacturing a coil component according to a first embodiment of the present invention.

Fig. 8 is a schematic diagram illustrating a method for manufacturing a coil component according to a first embodiment of the present invention.

Fig. 9 is a schematic diagram illustrating a method for manufacturing a coil component according to a first embodiment of the present invention.

Description of the reference numerals

1 … coil component; 10 … a first magnetic body; 11. 12, 13, 14, 15, 16, 17 … a first magnetic body layer; 20 … a second magnetic body; 30 … coil conductors; 31. 32, 33, 34, 35 … coil conductor layers; 36. 37 … via layer; 40 … an insulating film; 50 … outer electrode; 50a … first outer electrode; 50b … second external electrode (plating layer); 60 … an insulating layer; 100 … magnetic body.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the embodiments described below are for illustrative purposes, and the present invention is not limited to the embodiments described below.

The various numerical ranges set forth in this specification are also intended to include the lower limit as well as the upper limit as such. It is needless to say that the terms "above" and "below" are used, and the numerical value itself is also included unless otherwise specified. For example, if a numerical range of 1 to 10 is taken as an example, it should be interpreted as "1" including the lower limit value and "10" including the upper limit value.

[ first embodiment ]

Fig. 1 is a schematic cross-sectional view of a coil component 1 according to a first embodiment of the present invention. The coil component 1 according to the first embodiment includes a first magnetic section 10 having a substantially rectangular parallelepiped shape and including a coil conductor 30, and a second magnetic section 20 disposed on at least an upper surface of the first magnetic section 10. In addition, in the present specification, "rectangular parallelepiped" includes a cube. In the present specification, the term "substantially rectangular parallelepiped" also includes a rectangular parallelepiped having a curvature at least at one of a corner portion and a ridge portion. In addition, a shape in which there is no region including at least a part of the ridge line portion is also included in "substantially rectangular parallelepiped". In the present specification, the first magnetic body portion 10 and the second magnetic body portion 20 are collectively referred to as "magnetic body portions" (denoted by reference numeral 100 in fig. 4).

The first magnetic body 10 includes first magnetic particles made of a metallic magnetic body. As described later, the first magnetic body 10 may further contain a resin. The second magnetic body portion 20 includes second magnetic particles and a resin. As will be described later, the second magnetic part 20 may further include third magnetic particles, and the first magnetic part 10 may further include fourth magnetic particles.

The content of the resin in the second magnetic body portion 20 is greater than the content of the resin in the first magnetic body portion 10. That is, in coil component 1 according to the present embodiment, at least one surface of first magnetic part 10 having a relatively small resin content is covered with second magnetic part 20 having a relatively large resin content. The coil component 1 according to the present embodiment has such a structure, and thus has high moisture resistance as described in detail below.

First, since second magnetic material portion 20 contains a larger amount of resin than first magnetic material portion 10, the amount of voids that can be present inside second magnetic material portion 20 is smaller than the amount of voids that can be present inside first magnetic material portion 10. In coil component 1 according to the present embodiment, at least the upper surface of first magnetic section 10 having a large number of voids is covered with second magnetic section 20 having a small number of voids. That is, at least the upper surface of the outer surfaces of the magnetic body portions is formed of the second magnetic body portion 20 having a small number of voids. Therefore, the amount of voids in the vicinity of the outer surface of the magnetic body portion can be reduced. As a result, it is possible to suppress the intrusion of moisture into the magnetic section through the air gap, and to improve the moisture resistance of the coil component 1.

In contrast, when the magnetic body is constituted by a sintered body obtained by firing only the magnetic particles at a high temperature, although the filling rate of the magnetic particles in the magnetic body can be increased, voids may be formed between the magnetic particles during firing, and as a result, many voids may be present in the vicinity of the outer surface of the magnetic body. When there are many voids near the outer surface of the magnetic body portion, moisture can enter the interior of the magnetic body portion through the voids. As a result, the moisture resistance of the coil component is lowered. On the other hand, in coil component 1 according to the present embodiment, even when first magnetic part 10 includes many voids, second magnetic part 20 is arranged on at least the upper surface of first magnetic part 10, so that intrusion of moisture into the interior of the magnetic part through the voids can be suppressed, and as a result, moisture resistance of coil component 1 can be improved.

In the coil component 1 according to the present embodiment, since the amount of the voids in the vicinity of the outer surface of the magnetic part is reduced as described above, it is possible to suppress the plating liquid from entering the inside of the magnetic part through the voids during the plating treatment described later. As a result, it is possible to suppress a decrease in voltage resistance and the occurrence of short-circuit failure due to the immersion of the plating solution, and it is possible to improve the voltage resistance of the coil component 1. Further, plating penetration can also be prevented.

In contrast, when the magnetic body portion is formed of only a sintered body obtained by firing magnetic particles at a high temperature, there is a possibility that many voids are present in the vicinity of the outer surface of the magnetic body portion as described above. When there are many voids near the outer surface of the magnetic part, the plating liquid may enter the magnetic part through the voids, and as a result, the withstand voltage of the coil component may be lowered. On the other hand, in the coil component 1 according to the present embodiment, even when the first magnetic part 10 includes many voids, the second magnetic part 20 is disposed on at least the upper surface of the first magnetic part 10, so that the plating liquid can be prevented from entering the inside of the magnetic part through the voids, and as a result, the withstand voltage of the coil component 1 can be improved.

In addition, the coil component 1 according to the present embodiment can have excellent magnetic characteristics. In the coil component 1 according to the present embodiment, the first magnetic part 10 contains a smaller amount of resin than the second magnetic part 20, and therefore the first magnetic particles can be filled with a high density. By providing the first magnetic material portion 10, the magnetic permeability of the first magnetic material portion 10 and the entire magnetic material portion can be improved. The amount of voids can be evaluated by the void ratio described later. Preferably, the first magnetic body 10 contains substantially no resin. When the first magnetic material portion 10 does not substantially contain resin, the first magnetic particles can be further densely filled in the first magnetic material portion 10, and as a result, the magnetic permeability of the first magnetic material portion 10 and the entire magnetic material portion can be further improved.

Further, depending on the type (composition) of the magnetic particles, there are particles whose magnetic permeability is reduced by performing heat treatment at a high temperature (for example, a high temperature such as about 600 ℃). When the magnetic particles made of such a material are heat-treated at a high temperature to form the magnetic portion, the dc bias characteristics of the obtained coil component 1 can be reduced. In contrast, the second magnetic material portion 20 can be formed without performing heat treatment (firing) at a high temperature because the resin content is relatively large. For example, the second magnetic body portion 20 can be formed by curing a resin. Therefore, as the second magnetic particles included in the second magnetic section 20, particles of a material whose magnetic permeability is easily lowered by heat, for example, a material having a high saturation magnetic flux density (Bs) such as pure iron and/or a nanocrystalline material, can be used. As described above, the second magnetic material portion 20 can be formed at a temperature much lower than the ordinary firing temperature, and therefore, even when a material whose magnetic permeability is likely to decrease due to heat is used, the decrease in magnetic permeability of the second magnetic particles can be suppressed. As described above, since the second magnetic material portion 20 does not require high-temperature firing that can cause a decrease in magnetic permeability, various materials can be appropriately selected as the second magnetic particles included in the second magnetic material portion 20 according to desired characteristics (magnetic characteristics and the like). Therefore, the characteristics of the coil component 1 can be easily adjusted, and the coil component 1 having excellent characteristics (direct current superposition characteristics) can be realized.

In the coil component 1 according to the present embodiment, the core outer peripheral portion (second magnetic part 20) having a relatively large resin content is molded on the first magnetic part 10 corresponding to the core portion, thereby improving moisture resistance and voltage resistance. Such a method can reduce the time required for production and can suppress the cost, as compared with a method in which the moisture resistance and the voltage resistance are improved by impregnating the core with a resin, for example.

(method of measuring resin content)

The content of the resin in the first magnetic part 10 and the second magnetic part 20 can be measured by the method described below. First, the coil component 1 is cut to form a cross section. The position and direction of cutting are appropriately set so that both the first magnetic material portion 10 and the second magnetic material portion 20 are exposed in cross section. For example, as described later, when the coil member 1 includes the external electrode 50 on the bottom surface, the coil member 1 is cut in a direction perpendicular to the bottom surface to form a cross section perpendicular to the bottom surface. The cross section is machined by ion milling. In the cross section after the machining, time-of-flight secondary ion mass spectrometry (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), or energy dispersive X-ray analysis (EDX) is performed for each of the first magnetic body portion 10 and the second magnetic body portion 20. When the cross section of the coil component 1 is analyzed, carbon (C) is detected in a region where resin exists due to the composition of the resin component, whereas C is hardly contained in a region where resin does not exist. Therefore, the content of the resin can be calculated based on the size of the area of the region where C is detected in the cross section of the coil member 1.

Hereinafter, each element constituting the coil component 1 according to the present embodiment will be described in more detail.

(first magnetic body 10)

In the coil component 1, the first magnetic body portion 10 is disposed in the core portion of the coil conductor 30. The first magnetic body 10 includes first magnetic particles made of a metallic magnetic body. The first magnetic body 10 may further contain a resin. When the first magnetic body portion 10 contains a resin, the type of the resin is not particularly limited, and can be appropriately selected according to desired characteristics. The first magnetic part 10 may include 1 or more kinds of resins selected from, for example, epoxy-based resins, benzene resins, polyester resins, polyimide resins, polyolefin resins, Si-based resins, acrylic resins, polyvinyl butyral resins, cellulose resins, alkyd resins, and the like. When first magnetic body portion 10 contains a resin, the molecular weight of the resin contained in first magnetic body portion 10 is preferably larger than the molecular weight of the resin contained in second magnetic body portion 20.

(first magnetic particle)

The metal magnetic material constituting the first magnetic particles may be, for example, Fe (pure iron) or an alloy (FeSi, FeAl, fesicrcr, or the like). Preferably, the first magnetic particles are particles composed of FeSi. By using FeSi as a material constituting the first magnetic particles, the magnetic characteristics of the coil component 1 can be further improved.

The first magnetic body portion 10 may also contain an auxiliary agent that assists in forming an oxide film of the first magnetic particles. The auxiliary agent may also contain Zn (zinc) and/or Li (lithium), for example. When the auxiliary agent contains zinc, the zinc serves as a nucleus for forming the oxide film, and thus, as will be described later, formation of the oxide film on the surface of the first magnetic particles and bonding of the oxide films to each other (bonding of the first magnetic particles to each other via the oxide film) can be promoted when the first magnetic particles are fired. In the case where the first magnetic particles contain zinc, the oxide film of the first magnetic particles may contain zinc oxide.

The average particle diameter of the first magnetic particles is preferably 1 μm to 50 μm, more preferably 1 μm to 30 μm, and still more preferably 3 μm to 20 μm. The average particle diameter of the first magnetic particles can be measured by the method described below. First, in the measurement of the content of resin, the cross section of the coil component 1 is formed by the same method as the above-described method, and is processed by ion milling. The cross section after processing was observed by a Scanning Electron Microscope (SEM). The magnification of SEM is preferably about 500 times or more and 5000 times or less. The particle diameter (corresponding to the diameter of a circle) of the first magnetic particles can be measured from the obtained SEM image, and the average value of 100 or more first magnetic particles is defined as the average particle diameter of the first magnetic particles. The average particle diameter of the second magnetic particles, the third magnetic particles, the fourth magnetic particles, and the like, which will be described later, can also be measured by the same method as the above-described method. It is considered that the average particle diameter of the magnetic particles such as the first magnetic particles, the second magnetic particles, the third magnetic particles, and the fourth magnetic particles included in the finished coil component 1 is substantially the same as the average particle diameter of the magnetic particles of the raw material (that is, the magnetic particles used for producing the magnetic paste or the magnetic sheet described later). The average particle diameter of the magnetic particles of the raw material can be determined by measuring the volume-based median diameter D50 by a laser diffraction/scattering method.

Preferably, the first magnetic particles have an oxide film on the surface. In the case where the first magnetic particles have an oxide film, the first magnetic particles are preferably bonded to each other via the oxide film. In the present specification, the "oxide film" refers to a film made of an oxide, and may be a film made of, for example, a metal oxide or glass (e.g., Si-based glass). Since the oxide film has an electrical insulating property, when the first magnetic particles have an oxide film, the insulating property of the magnetic portion can be further improved, and the withstand voltage of the coil component 1 can be further improved. The oxide film may be formed by oxidizing a part of the metal element included in the first magnetic particle. Alternatively, the oxide film may be formed by coating the surface of the first magnetic particle with glass. The glass coating can be suitably carried out by a known method. If the oxide film is a glass film such as a phosphate glass-based glass film, the withstand voltage of the coil component 1 can be further improved. Therefore, it is more preferable that the first magnetic particles have a glass film as an oxide film. The thickness of the oxide film is preferably 3nm to 100nm, more preferably 8nm to 50nm, and still more preferably 10nm to 20 nm.

Preferably, the first magnetic body portion 10 further includes fourth magnetic particles having an average particle diameter different from that of the first magnetic particles. When the first magnetic material portion 10 contains two or more types of magnetic particles having different average particle diameters, the magnetic particles can be further filled into the first magnetic material portion 10 at a high density, and as a result, the magnetic permeability can be further improved. The magnetic material constituting the fourth magnetic particle is not particularly limited, and can be appropriately selected according to the desired characteristics. Among them, it is also preferable to be made of a metallic magnetic material. The fourth magnetic particles preferably have an average particle size smaller than that of the first magnetic particles, and are preferably made of any one of Fe (pure iron) and an Fe-containing alloy (FeSi alloy or the like). When the first magnetic material portion 10 includes the fourth magnetic particles, the content (volume conversion) of the first magnetic particles in the first magnetic material portion 10 is preferably larger than the content (volume conversion) of the fourth magnetic particles. The average particle diameter of the fourth magnetic particles is preferably 0.1 μm to 50 μm, more preferably 0.5 μm to 30 μm, and still more preferably 1 μm to 10 μm.

A void can exist inside the first magnetic body 10. As will be described later, the porosity of the second magnetic material portion 20 is preferably lower than the porosity of the first magnetic material portion 10.

Preferably, the first magnetic body 10 has a laminated structure. When the first magnetic section 10 has a laminated structure, the degree of freedom in designing the coil component 1 is increased. For example, in the case of manufacturing the coil component 1 having the external electrode 50 on the bottom surface, if the first magnetic section 10 has a laminated structure, there is an advantage that the coil conductor 30 can be easily drawn out to the bottom surface side.

(second magnetic body 20)

The second magnetic body 20 is disposed on at least an upper surface of the first magnetic body 10. The second magnetic body portion 20 has a structure in which individual magnetic particles or a combination of a plurality of magnetic particles are dispersed in a matrix of a resin. Preferably, the second magnetic material portion 20 is disposed so as to cover the entire upper surface of the first magnetic material portion 10, but the second magnetic material portion 20 may be provided only on a part of the upper surface of the first magnetic material portion 10 due to the disposition of other components such as the external electrode 50. The second magnetic material portions 20 are preferably arranged on four side surfaces adjacent to the upper surface of the first magnetic material portion 10 in addition to the upper surface. In this case, the second magnetic section 20 may be disposed only on a part of each of the four side surfaces, but is preferably disposed on the entire surface of each of the four side surfaces. The moisture resistance and voltage resistance of coil component 1 can be improved as the area of the region in which second magnetic part 20 is arranged (i.e., the region covered with second magnetic part 20) on the surface of first magnetic part 10 is larger. In addition, in the case where the coil component 1 includes the later-described insulating film 40, the moisture resistance and the voltage resistance of the coil component 1 can be improved as the area of the region in which either the second magnetic part 20 or the insulating film 40 is arranged (i.e., the region covered with either the second magnetic part 20 or the insulating film 40) on the surface of the first magnetic part 10 is larger. However, a part of the first magnetic part 10 may be exposed on the surface of the coil component 1 according to the present embodiment.

(second magnetic particle)

The magnetic material constituting the second magnetic particles is not particularly limited, and can be appropriately selected according to desired characteristics. As described above, since the second magnetic part 20 does not require heat treatment at high temperature, the second magnetic particles may be particles made of a magnetic material whose magnetic permeability is easily lowered by heat. Since various magnetic materials can be selected as the second magnetic particles according to desired characteristics, characteristics (such as direct current superposition characteristics) of the coil component 1 can be easily adjusted. As a result, coil component 1 having excellent characteristics can be realized. Preferably, the second magnetic particles are composed of Fe (pure iron) or a nanocrystalline material. When pure iron is used as the magnetic material constituting the second magnetic particles, the saturation magnetic flux density Bs of pure iron is high, and therefore, the dc superimposition characteristics of the coil component 1 can be improved. When a nanocrystalline material is used as the magnetic material constituting the second magnetic particles, eddy current loss can be reduced, and as a result, the dc bias characteristics of the coil component 1 can be improved.

More specifically, the second magnetic particles may be made of 1 or more kinds of magnetic materials selected from ceramic magnetic materials (ferrite, etc.) and metal magnetic materials (Fe (pure iron), alloys of FeSi, FeAl, fesicrcr, etc.), and the like. Among them, the second magnetic particles are also preferably made of a metallic magnetic body. The use of the second magnetic particles made of a metallic magnetic material can further improve the dc bias characteristics of the coil component 1. The second magnetic particles are more preferably made of pure iron, and still more preferably made of pure iron. In the case where the second magnetic particles are made of a metallic magnetic material, the second magnetic particles may be any of amorphous metal particles, nanocrystalline particles, or crystalline particles.

The average particle diameter of the second magnetic particles is preferably 1 μm to 50 μm, more preferably 1 μm to 30 μm, and still more preferably 3 μm to 20 μm.

It is preferable that the first magnetic particles and the second magnetic particles differ in at least one of average particle diameter and composition. By selecting the second magnetic particles having a different average particle diameter and/or composition from the first magnetic particles, the magnetic permeability of the magnetic portion can be easily improved, and the dc bias characteristic of the coil component 1 can be more easily improved.

The composition of the first magnetic particles and the second magnetic particles can be measured by the method described below. First, in the measurement of the content of the resin, the cross section of the coil component 1 is formed by the same method as the above-described method, and is processed by ion milling. In the obtained cross section, the first magnetic particle and the second magnetic particle are analyzed by XPS, EDX, or TOF-SIMS, respectively, to determine the components contained in the first magnetic particle and the second magnetic particle, respectively. The composition of the third magnetic particles, the fourth magnetic particles, and the like described below can also be measured by the same method as the above-described method.

Preferably, the second magnetic particles are nanocrystalline particles. In the present specification, "nanocrystal particle" refers to a particle composed of a nanocrystal material. The "nanocrystalline material" refers to a material in which crystal grains having an average grain size of several nm to several tens of nm are dispersed in an amorphous phase, or a polycrystal composed of crystal grains having an average grain size of several nm to several tens of nm. When the second magnetic particles are nanocrystalline particles, eddy current loss can be reduced, and as a result, the dc bias characteristics of the coil component 1 can be improved. The nanocrystalline particles are preferably particles made of a nanocrystalline material of, for example, pure iron and/or FeSi.

As another method, it is preferable that the second magnetic particles are amorphous magnetic particles. When the second magnetic particles are amorphous magnetic particles, the iron loss is small, and the efficiency is high.

Preferably, the second magnetic particles have an oxide film on the surface. When the second magnetic particles have an oxide film, the insulating property of the magnetic portion can be further improved, and the withstand voltage of the coil component 1 can be further improved. The oxide film of the second magnetic particles may be a film of, for example, a metal oxide or glass (e.g., Si-based glass). The oxide film of the second magnetic particles is preferably a glass film (a film of Si-based glass, P-based glass (phosphate glass-based, etc.) or Bi-based glass, etc.). The thickness of the oxide film is preferably 3nm to 100nm, more preferably 8nm to 50nm, and still more preferably 10nm to 20 nm.

(resin)

The kind of resin included in the second magnetic body portion 20 is not particularly limited, and can be appropriately selected according to the desired characteristics. The second magnetic part 20 may include, for example, 1 or more kinds of resins selected from epoxy-based resins, benzene resins, polyester resins, polyimide resins, polyolefin resins, Si-based resins, acrylic resins, polyvinyl butyral resins, cellulose resins, alkyd resins, and the like. The content of the resin in the second magnetic body portion 20 is greater than the content of the resin in the first magnetic body portion 10. The content of the resin in the second magnetic part 20 is larger than that in the first magnetic part 10, and thus, as described above, the coil component 1 having high moisture resistance and high withstand voltage and having excellent magnetic characteristics can be realized.

Preferably, the second magnetic body portion further includes third magnetic particles having an average particle diameter different from that of the second magnetic particles. When the second magnetic material portion 20 contains two or more types of magnetic particles having different average particle diameters, the second magnetic material portion 20 can be further filled with magnetic particles at a higher density, and as a result, the magnetic permeability can be further improved. The magnetic material constituting the third magnetic particles is not particularly limited, and can be appropriately selected according to desired characteristics. The magnetic member may be made of a metal magnetic material. The third magnetic particles preferably have an average particle size smaller than that of the second magnetic particles, and are preferably made of any one of Fe (pure iron) and an alloy containing Fe (FeSi alloy or the like). When the second magnetic material portion 20 contains the third magnetic particles, the content (volume conversion) of the second magnetic particles in the second magnetic material portion 20 is preferably larger than the content (volume conversion) of the third magnetic particles. The average particle diameter of the third magnetic particles is preferably 0.1 μm to 50 μm, more preferably 0.5 μm to 30 μm, and still more preferably 1 μm to 10 μm.

At least one of the first magnetic body portion 10 and the second magnetic body portion 20 preferably includes flat magnetic particles. In the present specification, the term "flat shape" refers to a shape having an aspect ratio (a/b) defined by the ratio of the major axis a to the minor axis b of the magnetic particle of 10 to 150. When the first magnetic material portion 10 and/or the second magnetic material portion 20 contain flat magnetic particles, the flat magnetic particles are preferably oriented such that the flat surfaces of the magnetic particles are along the direction of the magnetic field generated inside the coil component 1. As an example, the direction of the magnetic field in the magnetic section 100 of the coil component 1 is indicated by an arrow in fig. 4. When the flat magnetic particles are oriented such that the flat surfaces thereof are along the direction of the magnetic field, the magnetic permeability of the magnetic body portion can be greatly improved, and the coil component 1 having extremely excellent magnetic characteristics can be obtained.

In case the first magnetic body 10 comprises flat shaped magnetic particles, the first magnetic particles and/or the fourth magnetic particles may be flat shaped or may comprise flat shaped magnetic particles in addition to the first magnetic particles and, if present, the fourth magnetic particles. Similarly, in the case where the second magnetic body portion 20 contains magnetic particles having a flat shape, the second magnetic particles and/or the third magnetic particles may have a flat shape, or may contain magnetic particles having a flat shape in addition to the second magnetic particles and, if present, the third magnetic particles. The flat magnetic particles may be contained in only one of the first magnetic material portion 10 and the second magnetic material portion 20, or may be contained in both the first magnetic material portion 10 and the second magnetic material portion 20.

A gap may exist inside the first magnetic body portion 10 and the second magnetic body portion 20. The amount of voids present inside the magnetic body portion can be evaluated by the void ratio obtained by the following method. First, in the measurement of the content of resin, the cross section of the coil component 1 is formed by the same method as the above-described method, and is processed by ion milling. The processed cross section was observed by SEM. The magnification of SEM is preferably about 500 times or more and 5000 times or less. The area of the voids present between the magnetic particles (the region where neither the magnetic particles nor the resin is present) in the obtained SEM image is determined using image analysis software or the like. The void ratio is defined as a ratio of the area of the voids to the area of the entire SEM image. The porosity of the second magnetic material portion 20 is preferably lower than the porosity of the first magnetic material portion 10. In the case where the porosity of the second magnetic part 20 covering at least the upper surface of the first magnetic part 10 is relatively low, the intrusion of water into the coil component 1 and the intrusion of the plating liquid can be further effectively suppressed. The porosity of second magnetic material portion 20 is preferably 5% or less, more preferably 3% or less, still more preferably 1% or less, and most preferably substantially no voids (that is, the porosity is 0%).

The average thickness of the second magnetic material portion 20 is preferably 10 μm to 200 μm on each surface of the first magnetic material portion 10 on which the second magnetic material portion 20 is disposed. Since the second magnetic material portion 20 contains a larger amount of resin than the first magnetic material portion 10, the second magnetic material portion 20 tends to be more difficult to break than the first magnetic material portion 10. By disposing the second magnetic material portion 20 so as to cover at least the upper surface of the first magnetic material portion 10 and further by setting the average thickness of the second magnetic material portion 20 to 10 μm or more, it is possible to prevent cracks (cracks) from occurring in the coil component 1. This effect is particularly remarkable when the first magnetic material portion 10 is present outside the winding portion of the coil conductor 30, as shown in fig. 9, for example. The first magnetic material portion 10 tends to be easily broken at a portion outside the coil conductor 30. In this case, if the average thickness of the second magnetic material portion 20 is 10 μm or more, the occurrence of cracks in the first magnetic material portion 10 existing outside the coil conductor 30 can be effectively prevented. Further, when the average thickness of the second magnetic part 20 is 10 μm or more, the penetration of moisture into the coil component 1 and the penetration of the plating solution can be further effectively suppressed, and the moisture resistance and the voltage resistance of the coil component 1 can be further improved. When the average thickness of the second magnetic part 20 is 200 μm or less, the volume of the first magnetic part 10 in the entire coil component 1 can be relatively increased. Since the first magnetic section 10 contains a relatively small amount of resin (or contains substantially no resin) and is filled with magnetic particles at a high density, the magnetic characteristics of the coil component 1 can be further improved if the volume of the first magnetic section 10 is relatively large. The average thickness of the second magnetic material portion 20 is more preferably 10 μm to 100 μm on each surface of the first magnetic material portion 10 on which the second magnetic material portion 20 is disposed.

When the second magnetic material portions 20 are disposed on the upper surface and the surfaces other than the upper surface (for example, four side surfaces adjacent to the upper surface) of the first magnetic material portion 10, the average thicknesses of the second magnetic material portions 20 in the respective surfaces of the first magnetic material portion 10 may be the same or may be different from each other. When the second magnetic material portions 20 are arranged on the upper surface of the first magnetic material portion 10 and the surfaces other than the upper surface (for example, four side surfaces adjacent to the upper surface), the average thickness of the second magnetic material portions 20 in the upper surface of the first magnetic material portion 10 is larger than the average thickness of the second magnetic material portions 20 in the surfaces other than the upper surface.

The average thickness of the second magnetic material portion 20 can be measured by the procedure described below. First, the coil member 1 is cut in a direction perpendicular to the surface of the first magnetic material portion 10 on which the second magnetic material portion 20 to be measured is disposed, thereby forming a cross section. The cross section of the coil component 1 is formed by the same method as the above method used for measuring the content of the resin, and is processed by ion milling. The cross section after the processing is observed by SEM, the thickness of the second magnetic body portion 20 is measured at a plurality of places, and the average value thereof can be set as the average thickness of the second magnetic body portion 20.

It is preferable that a part of the component constituting the second magnetic body portion 20 is immersed in the inside of the first magnetic body portion 10. Due to the porosity of the first magnetic part 10, the pressing conditions in the manufacturing process of the coil component 1 described later, the viscosity of the resin included in the second magnetic part 20, and the like, a part of the component (resin component or the like) constituting the second magnetic part 20 may penetrate into the first magnetic part 10. In this case, the adhesion performance between the first magnetic part 10 and the second magnetic part 20 can be improved, and as a result, the moisture resistance and the withstand voltage of the coil component 1 can be further improved.

(coil conductor 30)

The coil conductor 30 is provided inside the first magnetic body 10. The coil conductor 30 may include a plurality of coil conductor layers laminated in the winding axis direction of the coil conductor 30. Both ends of the coil conductor 30 are drawn out to the outer surface of the magnetic body and electrically connected to the external electrode 50.

Both ends of the coil conductor 30 are preferably led out to the lower surface of the magnetic body. For example, as shown in fig. 1, when the second magnetic material portion 20 is disposed on the upper surface of the first magnetic material portion 10 and four side surfaces adjacent to the upper surface, both ends of the coil conductor 30 are preferably drawn out to the lower surface of the first magnetic material portion 10. In this way, when both ends of the coil conductor 30 are drawn out to the lower surface of the magnetic portion, the external electrode 50 can be disposed only on the bottom surface of the magnetic portion. When the external electrode 50 of the coil component 1 is such a bottom electrode, short-circuiting between adjacent coil components 1 can be suppressed. Further, if the external electrode 50 is a bottom electrode, the size of the external electrode can be reduced. As a result, the volume of the magnetic portion of the entire coil component 1 can be relatively increased, and therefore the magnetic characteristics of the coil component 1 can be further improved. Further, the coil component 1 may be required to be mounted on the bottom surface. In this case, it may be advantageous if the external electrode 50 is a bottom surface electrode.

The coil conductor 30 is completely embedded in the first magnetic material portion 10 except for the lead portion connected to the external electrode 50, but as shown in fig. 1, a part of the coil conductor 30 may be exposed on the surface of the first magnetic material portion 10 (the interface between the first magnetic material portion 10 and the second magnetic material portion 20). For example, as shown in fig. 1, when the first magnetic material portion 10 has four side surfaces parallel to the winding axis of the coil conductor 30, the coil conductor 30 is preferably exposed on at least one of the four side surfaces of the first magnetic material portion 10. In this case, the inner diameter of the winding portion of the coil conductor 30 can be increased, and as a result, the magnetic characteristics (inductance, dc superimposition characteristics, and the like) of the coil component 1 can be further improved. Further, the second magnetic material portion 20, which tends to be less likely to break than the first magnetic material portion 10, and the coil conductor 30 are in direct contact with each other, so that the occurrence of cracks (cracks) due to impact can be prevented. In coil component 1 shown in fig. 1, coil conductors 30 are exposed on four side surfaces of first magnetic section 10. As shown in fig. 1, the coil conductor 30 is preferably exposed on the upper surface of the first magnetic material portion 10. The coil conductor 30 is preferably made of a metal conductor such as Ag or Cu. The coil conductor 30 may also comprise glass. When the coil conductor 30 and the external electrode 50 are formed by simultaneous firing as described later, if glass is included in the coil conductor 30 and the external electrode 50, the bonding strength between the coil conductor 30 and the external electrode 50 can be improved.

(insulating film 40)

As shown in fig. 1, the coil component 1 may include an insulating film 40. In the coil component 1, the insulating film 40 is preferably disposed on the lower surface of the first magnetic body portion 10. In the present specification, the term "insulating film" refers to a layer having higher insulation (i.e., higher resistance) than the first magnetic material portion 10 in a broad sense, and refers to a layer having a volume resistivity of 10 in a narrow sense⁶A layer of Ω cm or more. The presence of the insulating film 40 can further effectively suppress the intrusion of water into the coil component 1 and the intrusion of the plating solution. As a result, the coil part can be further improvedThe moisture resistance and voltage resistance of the element 1. In addition, as shown in fig. 1, when the external electrodes 50 are disposed on the bottom surface, there is a possibility that a short circuit may occur between the external electrodes 50. In this case, by disposing the insulating film 40 on the lower surface (bottom surface) of the first magnetic material portion 10, the insulation between the external electrodes 50 can be improved, and the withstand voltage can be further improved. As shown in fig. 1, the entire surface of the first magnetic section 10 of the coil component 1 is preferably covered with the second magnetic section 20, the insulating film 40, or the external electrode 50. With this configuration, the immersion of water into the coil component 1 and the immersion of the plating solution can be most effectively suppressed. However, in the coil component 1 according to the present embodiment, the insulating film 40 is not an essential structure, and the effects of the present invention can be obtained even when the insulating film 40 is not provided.

When the insulating film 40 is disposed on the lower surface of the first magnetic material portion 10 (i.e., the surface facing the upper surface of the first magnetic material portion 10 on which the second magnetic material portion 20 is disposed), the insulating film 40 preferably does not extend on the upper surface of the second magnetic material portion 20.

The insulating film 40 preferably contains resin. In the case where the insulating film 40 contains a resin, the insulating film 40 can be easily formed by a method such as screen printing or dip coating. The composition of the resin contained in the insulating film 40 is not particularly limited, and for example, it preferably contains 1 or more kinds of resins selected from epoxy-based resins, urethane resins, polyester resins, polyamide-imide resins, Si-based resins, and acrylic resins.

(external electrode 50)

The shape and position of the external electrode 50 are not particularly limited, and the shape and position of the external electrode 50 can be selected according to the application and the like. Preferably, the external electrode 50 is a bottom electrode disposed on the bottom surface (lower surface) of the magnetic portion as shown in fig. 1. When the external electrode 50 is disposed only on the bottom surface of the magnetic portion, the size of the external electrode 50 can be reduced. As a result, the volume of the magnetic portion of the entire coil component 1 can be relatively increased, and therefore the magnetic characteristics of the coil component 1 can be further improved. Further, the coil component 1 may be required to be mounted on the bottom surface. In this case, it may be advantageous if the external electrode 50 is a bottom surface electrode. As shown in fig. 1, the external electrode 50 may have a structure in which a first external electrode 50a as a base electrode is covered with a second external electrode 50b as a plating layer. As will be described later, the external electrode 50 may be formed of a layer (indicated by reference numeral 50a as a first external electrode in fig. 1) made of the same material as the coil conductor 30 and a second external electrode 50b as a plating layer, but the external electrode 50 may be formed of only 1 or more second external electrodes 50b as plating layers. In this case, the external electrode 50 is formed such that the end of the coil conductor 30 drawn out to the surface of the magnetic body is electrically connected to the external electrode 50. In addition, instead of the second external electrode 50b as a plating layer, a layer of the external electrode 50 may be formed by sputtering or dip coating.

When the external electrode 50 has a layer made of the same material as the coil conductor 30, for example, the first external electrode 50a is preferably made of a metal conductor such as Ag, Cu, Ni, or Sn. The first external electrode 50a may further include glass. When the coil conductor 30 and the first external electrode 50a are formed by simultaneous firing, if glass is included in the coil conductor 30 and the first external electrode 50a, the bonding strength between the coil conductor 30 and the first external electrode 50a can be improved, and the mechanical strength of the first external electrode 50a can be improved.

[ second embodiment ]

Next, the coil component 1 according to the second embodiment will be described below with reference to fig. 2. The coil component 1 according to the second embodiment has the same configuration as the coil component 1 according to the first embodiment, except that the coil component 1 further includes the insulating layer 60. Therefore, the following description mainly describes the details of the insulating layer 60, and descriptions of other structures are omitted. The coil component 1 according to the second embodiment can improve moisture resistance, as with the coil component 1 according to the first embodiment. The coil component 1 according to the second embodiment can have high moisture resistance and excellent magnetic characteristics.

(insulating layer 60)

In the coil component 1 shown in fig. 2, the coil conductor 30 includes a plurality of coil conductor layers laminated in the winding axis direction of the coil conductor 30, and the insulating layer 60 is disposed between the plurality of coil conductor layers. In the present specification, the term "insulating layer" refers to a layer having higher insulation (i.e., higher resistance) than the coil conductor 30 in a broad sense, and refers to a layer having a volume resistivity of 10 in a narrow sense⁶A layer of Ω cm or more. By disposing the insulating layer 60 between the coil conductor layers, it is possible to prevent short-circuiting between the coil conductor layers, and to improve the reliability of the coil component 1. In the coil component 1 shown in fig. 2, the insulating layer 60 is disposed only at a position overlapping with the coil conductor layer in a plan view. However, the arrangement of the insulating layer 60 is not limited to the case shown in fig. 2, and the insulating layer 60 may be arranged at a position not overlapping with the coil conductor layer in a plan view. Preferably, the insulating layer 60 is disposed between adjacent coil conductor layers as shown in fig. 2, and the short-circuit prevention effect can be further improved by such a configuration. However, the insulating layer 60 may be disposed only at one position in the region between the adjacent coil conductor layers. With this configuration, the effect of preventing short-circuiting between the coil conductor layers can be obtained. In the coil component 1 shown in fig. 2, the insulating layer 60 is also disposed on the side surface of the lead portion of the coil conductor 30. The effect of preventing short-circuiting can be further improved by disposing the insulating layer 60 on the side surface of the lead portion.

The insulating layer 60 may be made of a magnetic material or may be made of a non-magnetic material. The volume resistivity of the insulating layer 60 is preferably higher than the volume resistivity of the first magnetic body 10. Therefore, the insulating layer 60 is preferably made of a material having a higher volume resistivity than the material of the first magnetic body portion 10. The insulating layer 60 may contain, for example, metal magnetic particles having a small particle diameter (average particle diameter of about 0.1 μm or more and 5 μm or less). The smaller the particle diameter of the metal magnetic particle, the higher the insulation. Therefore, the insulating layer 60 can be formed using metal magnetic particles having a small particle diameter. The metal magnetic particles preferably have an insulating coating on the surface thereof.

The relative permeability of the insulating layer 60 is preferably lower than the relative permeability of the first magnetic body portion 10. In this case, the dc superimposition characteristic of the coil component 1 can be further improved. More preferably, the insulating layer 60 is a non-magnetic ceramic layer. When the insulating layer 60 is a non-magnetic ceramic layer, the dc bias characteristic of the coil component 1 can be further improved. The non-magnetic ceramic layer may also contain, for example, a non-magnetic ferrite.

Fig. 3 shows a modification of the coil component 1 according to the second embodiment. In the coil component 1 shown in fig. 3, the insulating layer 60 is also provided at a position not overlapping the coil conductor 30 in a plan view. With this configuration, the occurrence of short-circuiting between the coil conductor layers can be further effectively suppressed.

[ method for producing coil component ]

A method for manufacturing a coil component according to the present invention will be described below with reference to fig. 5 to 9, taking the coil component 1 according to the first embodiment as an example. However, the method described below is merely an example, and the method for manufacturing the coil component according to the present invention is not limited to the method described below.

(preparation of magnetic paste)

A magnetic paste for forming the first magnetic body portion 10 is prepared. The first magnetic particles, the resin, and the solvent were kneaded to prepare a magnetic paste. The first magnetic particles are described in detail above. As the first magnetic particles, for example, magnetic particles having a D50 of 10 μm can be used. In addition, as the first magnetic particles, magnetic particles in which an oxide film such as a phosphate glass oxide film is formed in advance may be used. As the resin used for the magnetic paste, for example, 1 or more kinds of resins selected from a polyvinyl butyral resin, an acrylic resin, an epoxy resin, a cellulose resin, an alkyd resin, and the like can be used. Examples of the solvent used for the magnetic paste include ethanol, toluene, xylene, terpineol, dihydroterpineol, butyl carbitol acetate, and/or ester alcohol. The contents of the magnetic particles (including the first magnetic particles, the fourth magnetic particles, and the like in some cases), the resin, and the solvent in the magnetic paste are preferably 50 wt% to 95 wt%, 1 wt% to 20 wt%, and 5 wt% to 30 wt%, respectively, based on the weight of the entire magnetic paste.

(production of magnetic sheet)

Magnetic sheets for forming the second magnetic body portion 20 are prepared. The paste for producing a magnetic sheet, which is obtained by kneading the second magnetic particles, the resin, and the solvent, is formed into a sheet, and the sheet is dried to produce a magnetic sheet. The second magnetic particles are described in detail above. As the second magnetic particles, for example, magnetic particles having a D50 of 20 μm can be used. As the second magnetic particles, magnetic particles in which an oxide film such as a phosphate glass oxide film is formed in advance may be used. As an example, a combination of first magnetic particles on which a glass-based oxide film is not formed in advance and second magnetic particles on which a glass-based oxide film (such as a phosphate glass-based oxide film) is formed in advance can be used. In this case, the thickness of the oxide film of the second magnetic particles may be, for example, 10 nm. As the resin used for the paste for producing the magnetic sheet, for example, 1 or more resins selected from epoxy-based resins, benzene resins, polyester resins, polyimide resins, polyolefin resins, Si-based resins, and acrylic resins can be used. Examples of the solvent used for the paste for producing the magnetic sheet include MEK (methyl ethyl ketone), N-Dimethylformamide (DMF), PGM (propylene glycol monomethyl ether), PMA (propylene glycol monomethyl ether acetate), DPM (dipropylene glycol monomethyl ether), and/or DPMA (dipropylene glycol monomethyl ether acetate). The resin used for the magnetic paste and the resin used for the paste for producing the magnetic sheet may have the same composition or different compositions. The solvent used for the magnetic paste and the solvent used for the paste for producing the magnetic sheet may have the same composition or different compositions. The content of the magnetic particles, the resin, and the solvent is preferably 50 wt% to 90 wt%, 1 wt% to 20 wt%, and 5 wt% to 30 wt%, respectively, based on the weight of the entire paste used to produce the magnetic sheet. Further, commercially available magnetic sheets may be used as the magnetic sheets.

(preparation of conductor paste)

A conductor paste for forming the coil conductor 30 and, as the case may be, the first outer electrode 50a is prepared. The conductive paste is prepared by kneading particles of a metal conductor such as Ag or Cu, a binder, and a solvent. The conductor paste may also contain glass. When the coil conductor 30 and the first external electrode 50a are formed by simultaneous firing using the same conductor paste as described later, if glass is included in the conductor paste, the bonding strength between the coil conductor 30 and the first external electrode 50a can be improved.

(preparation of insulating paste)

An insulating paste for forming the insulating film 40 is prepared. Preferably, the insulating paste contains 1 or more resins selected from the group consisting of epoxy-based resins, Si-based resins, polyimide-based resins, polyamide-imide-based resins, fluorine-based resins, and acrylic resins.

(formation of first magnetic body 10)

As shown in fig. 5, the first magnetic layers 11, 12, 13, 14, 15, 16, 17, the coil conductor layers 31, 32, 33, 34, 35, and the via layers 36, 37 are stacked to form a stacked body. First, a base material on which the first magnetic body layer and the coil conductor layer are laminated is prepared. The substrate may be, for example, a release-treated PET film or a flat metal mold. A first magnetic layer 11 is formed by applying a magnetic paste on the base material by screen printing or the like, and dried in an oven at about 150 ℃ (fig. 5 (a)).

A conductor paste is applied to the dried first magnetic layer 11 by screen printing or the like to form the coil conductor layer 31, which is dried in an oven at about 150 ℃. Next, a magnetic paste is applied to a portion where the coil conductor layer 31 is not formed to form the first magnetic layer 12, and the first magnetic layer is dried in an oven at about 150 ℃ (fig. 5 (b)).

Next, a conductor paste is applied to the first magnetic layer 12 and the coil conductor layer 31 to form the coil conductor layer 32 and the via hole layer 36, and dried in an oven. The first magnetic layer 13 is formed by applying a magnetic paste to a portion where the coil conductor layer 32 and the via layer 36 are not formed, and is dried in an oven ((c) of fig. 5).

By the same steps as those described above, the coil conductor layers 33, 34, 35, the via hole layers 36, 37, and the first magnetic layers 14, 15, 16, 17 are formed in this order as shown in fig. 5 (d) to 5 (g), and dried in an oven. Finally, as shown in fig. 5 (h), a conductor paste is applied on the first magnetic layer 17 and the via layers 36, 37 to form a first external electrode 50a, which is dried in an oven. Thus, a laminate was obtained.

In the example shown in fig. 5, the total of 7 first magnetic layers and the total of 5 coil conductor layers are stacked, but the number of stacked first magnetic layers and coil conductor layers and the shape of the coil pattern are not limited to those shown in fig. 5, and a linear shape or the like can be appropriately designed according to desired characteristics or the like. The number of laminated coil conductor layers may be, for example, about 1 to 50 layers. In addition, in fig. 5, a step of forming a first magnetic body layer, a coil conductor layer, and a via layer corresponding to one first magnetic body portion 10 is shown, but actually, the first magnetic body layer, the coil conductor layer, and the via layer corresponding to a plurality of first magnetic body portions 10 are formed at the same time. As another method, the coil conductor layer may be formed by photolithography or an additive method.

The laminate thus obtained is pressed and cut into a size corresponding to the first magnetic material portion 10. In this case, the coil conductor layer may or may not be exposed on the surface of the laminate formed by cutting.

The cut laminate was barrel-ground to form a curve at the corner of the laminate.

The rolled laminate is heated at a temperature of about 400 ℃ to degrease the binder contained in the laminate.

The degreased laminate is fired at a temperature of about 700 ℃ in an atmospheric atmosphere to obtain a first magnetic body portion 10 including the coil conductor 30 (fig. 6). During firing, oxide films can be formed on the surfaces of the first magnetic particles, and the oxide films can be bonded to each other. The thickness of the oxide film formed may be, for example, 10 nm. In the examples shown in fig. 5 to 9, the coil conductor 30 and the first external electrode 50a are fired simultaneously.

The size of the resulting first magnetic body portion 10 may be, for example, L (length): 1.4mm × W (width): 0.6mm × T (thickness): 0.7 mm. In the examples shown in fig. 5 to 9, both ends of the coil conductor 30 are drawn out to the bottom surface of the first magnetic section 10 (fig. 6).

The first magnetic body 10 may also contain a resin. The resin contained in the first magnetic body 10 may be derived from the resin contained in the magnetic paste. At least a part of the resin contained in the magnetic paste may be lost by decomposition or the like during firing, but a part of the resin contained in the magnetic paste may remain in the first magnetic body portion 10. However, it is preferable that the first magnetic body 10 contains substantially no resin.

The first magnetic body portion 10 after firing may be impregnated with a resin. By impregnating the first magnetic body portion 10 with resin, at least a part of the gap existing in the first magnetic body portion 10 is filled with resin. As a result, the number of voids present in the first magnetic material portion 10 is further reduced, and the penetration of moisture and plating liquid into the first magnetic material portion 10 can be further suppressed. Therefore, plating adhesion and reliability failure in the coil component 1 can be further suppressed. The resin impregnated in the first magnetic part 10 may be, for example, 1 or more resins selected from epoxy-based resins, benzene resins, polyester resins, polyimide resins, polyolefin resins, Si-based resins, acrylic resins, polyvinyl butyral resins, cellulose resins, and alkyd resins.

A plurality of first magnetic material portions 10 are aligned and fixed on an adhesive sheet or the like. Magnetic sheets are arranged on the upper surfaces of the plurality of first magnetic material portions 10 arranged in this order, and a second magnetic material portion 20 is formed by pressing (punching). Alternatively, instead of the magnetic sheet, a magnetic paste prepared by another method may be applied, dried, and pressed to form the second magnetic body portion 20. As another method, the first magnetic material portion 10 may be disposed in a die that is one turn larger than the first magnetic material portion 10, and the second magnetic material portion 20 may be formed by disposing a magnetic sheet on the upper surface of the first magnetic material portion 10 and pressing the magnetic sheet. As another method, a granulated powder may be prepared by mixing magnetic particles (second magnetic particles or the like) and a resin, and the second magnetic body portion 20 may be formed by charging the granulated powder into a metal mold in which the first magnetic body portion 10 is disposed and molding the same. When the second magnetic body portion 20 is formed using a metal mold, a cutting step described later is not required.

The first magnetic body portion 10 having the second magnetic body portion 20 disposed on the surface thereof is heated at a temperature of about 200 ℃ to cure the resin. Next, the coil component 1 is cut into a size corresponding to the size of each coil component 1, and the coil component 1 in which the second magnetic sections 20 are arranged on the upper surface of the first magnetic section 10 and four side surfaces adjacent to the upper surface is obtained (fig. 7). In fig. 7, the second magnetic body portion 20 disposed on the upper surface of the first magnetic body portion 10 is formed across four side surfaces adjacent to the upper surface.

Next, an insulating paste is applied to the lower surface of the coil member 1 by screen printing or the like to form an insulating film 40 (fig. 8). The insulating film 40 may be formed by electrodeposition coating, dipping paint, or the like.

Next, a second external electrode 50b as a plating layer is formed over the first external electrode 50a (fig. 9). At this time, the second magnetic material portion 20 is disposed on the upper surface of the first magnetic material portion 10 and four side surfaces adjacent to the upper surface, and the insulating film 40 is disposed on the lower surface of the first magnetic material portion 10 (that is, the entire surface of the first magnetic material portion 10 is covered with either the second magnetic material portion 20 or the insulating film 40), thereby suppressing the plating solution from entering the inside of the magnetic material portion. Instead of the second external electrode 50b as the plating layer, a layer of the external electrode 50 may be formed by sputtering, dipping paint, or the like. Through the above steps, the coil component 1 can be manufactured.

The coil component 1 thus obtained is excellent in moisture resistance and voltage resistance, and has excellent magnetic characteristics. The size of the coil component 1 is not particularly limited, and may be, for example, L (length): 1.6mm × W (width): 0.8mm × T (thickness): 0.8 mm.

The above-described manufacturing method relates to the manufacturing method of the coil component 1 according to the first embodiment, but the coil component 1 according to the second embodiment can also be manufactured by the above-described manufacturing method. For example, the coil component 1 according to the second embodiment can be manufactured by laminating the insulating layers 60 between the coil conductor layers 31, 32, 33, 34, and 35 shown in fig. 5.

The present invention includes the following embodiments, but is not limited to these embodiments.

(embodiment 1) a coil component comprising:

a first magnetic body portion having a substantially rectangular parallelepiped shape and including a coil conductor; and

a second magnetic body portion disposed on at least an upper surface of the first magnetic body portion,

the first magnetic body portion includes first magnetic particles made of a metal magnetic body, the second magnetic body portion includes second magnetic particles and a resin, and a content of the resin in the second magnetic body portion is greater than a content of the resin in the first magnetic body portion.

(embodiment 2) according to the coil component described in embodiment 1,

the first magnetic particles have oxide films on surfaces thereof, and the first magnetic particles are bonded to each other via the oxide films.

(embodiment 3) the coil component according to the embodiment 1 or 2,

the first magnetic body portion has a laminated structure.

(embodiment 4) the coil component according to any one of the embodiments 1 to 3,

the second magnetic particles are made of a metallic magnetic body.

(embodiment 5) the coil component according to any one of embodiments 1 to 4,

the coil conductor includes a plurality of coil conductor layers stacked in a winding axis direction of the coil conductor, and an insulating layer is disposed between the plurality of coil conductor layers.

(embodiment 6) according to the coil component described in embodiment 5,

the insulating layer has a relative magnetic permeability lower than that of the first magnetic body portion.

(embodiment 7) the coil component according to any one of the embodiments 1 to 6,

the second magnetic body portion is disposed on the upper surface of the first magnetic body portion and four side surfaces adjacent to the upper surface,

both ends of the coil conductor are drawn out to the lower surface of the first magnetic body portion.

(embodiment 8) according to the coil component described in embodiment 7,

an insulating film is disposed on a lower surface of the first magnetic body portion.

(embodiment 9) according to the coil component described in embodiment 8,

the insulating film contains a resin.

(embodiment 10) the coil component according to any one of the embodiments 1 to 9,

the first magnetic body portion has four side surfaces parallel with respect to a winding axis of the coil conductor,

the coil conductor is exposed on at least one of the four side surfaces.

(embodiment 11) the coil component according to any one of the embodiments 1 to 10,

the first magnetic particles and the second magnetic particles differ in at least one of their average particle diameter and composition.

(embodiment 12) the coil component according to any one of embodiments 1 to 11,

the second magnetic body portion has a lower porosity than the first magnetic body portion.

(embodiment 13) the coil component according to any one of embodiments 1 to 12,

the average thickness of the second magnetic body portion is 10 [ mu ] m or more and 200 [ mu ] m or less on each surface of the first magnetic body portion on which the second magnetic body portion is arranged.

(embodiment 14) the coil component according to any one of the embodiments 1 to 13,

the second magnetic particles are nanocrystalline particles.

(embodiment 15) the coil component according to any one of the embodiments 1 to 13,

the second magnetic particles are amorphous magnetic particles.

(embodiment 16) the coil component according to any one of the embodiments 1 to 15,

the second magnetic body portion further includes third magnetic particles having an average particle diameter different from that of the second magnetic particles.

(embodiment 17) the coil component according to any one of embodiments 1 to 16,

the first magnetic body portion further includes fourth magnetic particles having an average particle diameter different from that of the first magnetic particles.

(embodiment 18) the coil component according to any one of the embodiments 1 to 17,

at least one of the first magnetic body portion and the second magnetic body portion includes flat-shaped magnetic particles.

The coil component according to the present invention has high moisture resistance, and therefore can be used for electronic devices and the like requiring high reliability.