Coil component

Abstract

The coil component 10 of the present invention includes a unit body 12 and an external electrode 30. The unit body includes a coil conductor 16 formed by winding a wire covered with an insulating film and a magnetic body portion 14 containing metallic magnetic particles and resin. The metallic magnetic particles include first metallic magnetic particles 40 and second metallic magnetic particles 42. The particle size distribution of the metallic magnetic particles, calculated based on the equivalent circle diameter obtained from a cross-sectional image of the magnetic body portion 14, has at least two peaks and at least one bottom. The bottom with the lowest frequency and above is designated as the first metallic magnetic particle 40, and the bottom with a frequency lower than the lowest frequency is designated as the second metallic magnetic particle 42. The first metallic magnetic particle 40 includes a particle having a recess 40a that satisfies a predetermined condition in the cross-section. At least a portion of at least one second metallic magnetic particle 42 is disposed inside the recess 40a of the first metallic magnetic particle 40.

Description

Technical Field

[0001] This invention relates to coil components. Background Technology

[0002] As an existing coil component (reactor), its main body consists of a magnetic core and a coil. The magnetic core is made of a composite material composed of metallic magnetic particles and resin. Moreover, the composite material of the magnetic core is made of a soft magnetic composite material.

[0003] Existing soft magnetic composite materials suffer from low permeability and low inductance in reactors made from them. Furthermore, existing techniques, which involve mixing metallic magnetic particles with resin to form a specific shape, suffer from the following drawbacks: increased resin content relative to metallic magnetic particles leads to decreased permeability and density in the resulting soft magnetic composite material, and deterioration of DC overlap characteristics.

[0004] Therefore, the following technique is proposed: by adding a second particle with a smaller average particle size to a first particle with high sphericity and large average particle size, the gaps between particles can be filled, thereby increasing the density of the resulting soft magnetic composite material. This allows for a magnetic core formed from the soft magnetic composite material to have high permeability, which can improve the inductance of reactors using this core (see Patent Document 1).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2016-39331 Summary of the Invention

[0008] However, the soft magnetic composite material used in the core of the reactor disclosed in Reference 1 has a higher permeability due to the use of highly spherical particle size, such as 100μm to 200μm. On the other hand, there are concerns about the increased loss in the high-frequency region.

[0009] Therefore, the main objective of this invention is to provide a coil component that has high permeability and good high-frequency characteristics.

[0010] The coil component of the present invention is a coil component comprising a unit body and an external electrode. The unit body comprises a coil conductor formed by winding a wire and a magnetic body containing metallic magnetic particles and resin. The external electrode is electrically connected to the exposed surface of the coil conductor's lead-out portion on the surface of the unit body and is disposed on the surface of the unit body. The metallic magnetic particles include first metallic magnetic particles and second metallic magnetic particles. The particle size distribution of the metallic magnetic particles, calculated based on the equivalent circle diameter obtained from a cross-sectional image of the magnetic body, has at least two peaks and at least one bottom. Particles with a minimum frequency above the bottom are designated as first metallic magnetic particles, and particles with a minimum frequency below the bottom are designated as second metallic magnetic particles. The first metallic magnetic particles include particles having a concave portion in the cross-section that satisfies a predetermined condition, wherein the minimum distance between the front ends of the openings of the concave portion is set to L. 01 Let L be the longest distance among the line segments parallel to the line segment with the minimum distance between the concave portion of the cross-section of the first metallic magnetic particle and the front end of the opening. 02 At that time, L 02 >L 01 At least a portion of at least one second metallic magnetic particle is disposed inside the recess of the first metallic magnetic particle.

[0011] In the coil component of the present invention, the particle size distribution of the metallic magnetic particles, calculated from the equivalent circle diameter obtained from the cross-sectional image of the cross-section of the magnetic body portion, has at least two peaks and at least one bottom. It includes metallic magnetic particles with the bottom having the minimum frequency or higher designated as first metallic magnetic particles and the bottom having the minimum frequency or lower designated as second metallic magnetic particles. The first metallic magnetic particles include particles having a concave portion that satisfies a predetermined condition in the cross-section. At least a portion of at least one second metallic magnetic particle is disposed inside the concave portion of the first metallic magnetic particle having the concave portion. Therefore, the filling rate of the metallic magnetic particles in the magnetic body portion becomes higher, thereby improving the permeability of the coil component.

[0012] Furthermore, the coil component of the present invention includes a first metallic magnetic particle having a recess in its cross-section that satisfies a predetermined condition in the magnetic body portion containing metallic magnetic particles and resin. The predetermined condition is that the minimum distance between the front ends of the openings of the recess is set to L. 01 Let L be the longest distance among the line segments that are parallel to the line segment with the minimum distance between the front end of the opening and the line segment that is equivalent to a chord in the concave part of the cross section of the first metallic magnetic particle. 02 At that time, L 02 >L 01 Therefore, the surface area of ​​the first metal magnetic particle relative to the volume of the magnetic body can be increased, thus reducing eddy current losses in the high-frequency region, and the coil component can also be used at higher frequencies.

[0013] According to the present invention, a coil component with high permeability and good high-frequency characteristics can be provided.

[0014] The above-mentioned objects, other objects, features and advantages of the present invention will become even clearer from the following description of embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0015] Figure 1 This is a perspective view schematically illustrating an embodiment of the coil component of the present invention.

[0016] Figure 2 yes Figure 1 A perspective view of the magnetic body containing the coil conductor embedded in the coil component.

[0017] Figure 3 This refers to the coil component of the present invention. Figure 1 Section III-III of line III.

[0018] Figure 4 This refers to the coil component of the present invention. Figure 1 Section IV-IV of the line.

[0019] Figure 5 It is a graph showing the particle size distribution of the equivalent circular diameter of metallic magnetic particles in a magnetic body.

[0020] Figure 6 It means Figure 3 The diagram shows the filling state of each metallic magnetic particle in a portion of region R1, indicated by the dashed line.

[0021] Figure 7 This is a schematic cross-sectional view of the first metallic magnetic particle.

[0022] Figure 8 It is a diagram showing a state in which at least one part or all of a second metal magnetic particle is disposed inside the recess of the first metal magnetic particle in the cross section of the magnetic body.

[0023] Figure 9 It is a diagram showing a state in which a portion or all of a plurality of second metal magnetic particles are arranged inside the recess of the first metal magnetic particle in the cross section of the magnetic body.

[0024] Figure 10 It is a diagram showing a state in which at least a portion of the first metal magnetic particle and at least a portion or all of the second metal magnetic particle are arranged inside the recess of the first metal magnetic particle in the cross section of the magnetic body.

[0025] Figure 11It is the minimum distance L between the front ends of the opening and the recess of the first metallic magnetic particle in the cross-section of the magnetic body. 01 A graph comparing the particle size of a second metallic magnetic particle d2 with the particle size at which the peak of the highest frequency in the particle size distribution of the second metallic magnetic particle is located.

[0026] Figure 12 This is a diagram showing the outer perimeter L1 of the crescent-shaped first metallic magnetic particle in the cross-section of the magnetic body and the circumference L2 of the circle whose area is equivalent to that of the first metallic magnetic particle.

[0027] Figure 13 L represents the minimum distance L between the front ends of the recess and the opening of the first metallic magnetic particle in the cross-section of the magnetic body. 01 A diagram showing the perimeter Lc of the first metallic magnetic particle, excluding the inner side of the opening in the recess.

[0028] Figure 14 This is a diagram showing the area S0 of the region R0 inside the line segment that is the minimum distance from the front end of the opening of the first metallic magnetic particle in the cross section of the magnetic body, and the cross-sectional area Sc of the first metallic magnetic particle.

[0029] Figure 15 It is a diagram showing a state in which at least a portion of at least one second metallic magnetic particle and at least a portion or all of at least one inorganic oxide particle are simultaneously disposed inside the recess of the first metallic magnetic particle in the cross section of the magnetic body.

[0030] Figure 16 This is a diagram showing the state in which an insulating film is formed on the first metallic magnetic particle.

[0031] Figure 17 It is an exploded perspective view showing the state in which coil conductors are installed in the first and second molded bodies during the manufacturing of the unit body.

[0032] Symbol Explanation

[0033] 10 coil components

[0034] 12 units

[0035] 12a First Main Face

[0036] 12b Second Main Face

[0037] 12c First Side

[0038] 12d second side

[0039] 12e First end face

[0040] 12f Second End Face

[0041] 14 Magnetic Body

[0042] 16 coil conductor

[0043] 18 winding sections

[0044] 20 hollow areas

[0045] 22a First Exit Section

[0046] 22b Second Exit

[0047] 24a First exposed part

[0048] 24b Second exposed part

[0049] 30 External Electrodes

[0050] 30a First External Electrode

[0051] 30b Second External Electrode

[0052] 32a First base electrode layer

[0053] 32b Second base electrode layer

[0054] 34a First Coating

[0055] 34b Second Coating

[0056] 36a First Ni plating

[0057] 36b Second Ni plating

[0058] 38a First Sn plating layer

[0059] 38b Second Sn plating

[0060] 40 First metallic magnetic particles

[0061] 40a recess

[0062] 40b opening

[0063] 42 Second metallic magnetic particles

[0064] 44 Inorganic Particles

[0065] 46 Insulating film

[0066] 50 First Molded Body

[0067] 52 bottom surface

[0068] 52a

[0069] 52b below

[0070] 54 scroll sections

[0071] 54a front end

[0072] 56a First side wall portion

[0073] 56b Second side side wall portion

[0074] 56c First end face side wall portion

[0075] 56d Second end face side wall portion

[0076] 58a First incision

[0077] 58b Second incision

[0078] 60 Second Molded Body

[0079] 60a First Main Face

[0080] 60b Second Main Face

[0081] x-direction of pressure (height direction)

[0082] y-width direction

[0083] z-length direction Detailed Implementation

[0084] 1. Coil component

[0085] Hereinafter, the coil component of an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0086] Figure 1 This is a perspective view schematically illustrating an embodiment of the coil component of the present invention. Figure 2 yes Figure 1 A perspective view of the magnetic body containing the coil conductor embedded in the coil component. Figure 3 This refers to the coil component of the present invention. Figure 1 Section III-III of line III. Figure 4 This refers to the coil component of the present invention. Figure 1 Section IV-IV of the line.

[0087] The coil component 10 has a cuboid unit 12 and an external electrode 30.

[0088] (a) Unit

[0089] The unit 12 has a magnetic body portion 14 and a coil conductor 16 embedded in the magnetic body portion 14. The unit 12 has a generally rectangular shape and has a first main surface 12a and a second main surface 12b opposite each other in the pressure direction x, a first side surface 12c and a second side surface 12d opposite each other in the width direction y orthogonal to the pressure direction x, and a first end surface 12e and a second end surface 12f opposite each other in the length direction z orthogonal to the pressure direction x and the width direction y. The size of the unit 12 is not particularly limited.

[0090] (b) Magnetic body section

[0091] The magnetic body 14 covers the coil conductor 16. The external shape of the magnetic body 14 is roughly the same as that of the unit body 12, and is approximately cuboid in shape. The magnetic body 14 is formed by heating and pressurizing the first molded body 50 and the second molded body 60, which will be described later, in a mold.

[0092] The magnetic body 14 contains multiple metallic magnetic particles and resin.

[0093] The resin is not particularly limited, but examples include thermosetting resins, epoxy resins, phenolic resins, polyester resins, polyimide resins, polyolefin resins, and other organic materials. The resin material can be just one type or two or more.

[0094] The metallic magnetic particles include a first metallic magnetic particle 40 and a second metallic magnetic particle 42.

[0095] The first metallic magnetic particle 40 and the second metallic magnetic particle 42 are not particularly limited, but examples include iron, cobalt, or nickel, or alloys containing one or more of these. Preferably, the first metallic magnetic particle and the second metallic magnetic particle are iron or iron alloys. The iron alloy is not particularly limited, but examples include Fe-Si, Fe-Si-Cr, Fe-Ni, Fe-Si-Al, etc. The first metallic magnetic particle and the second metallic magnetic particle can be only one type, or there can be two or more types.

[0096] The definitions of each metallic magnetic particle in the first metallic magnetic particle 40 and the second metallic magnetic particle 42 are as follows.

[0097] First, the median particle size (D50) of the average particle size of the metallic magnetic particles in the magnetic body 14 is calculated based on the cross-sectional image of the particles.

[0098] First, using the roundness measurement method described later, the coil component 10 is cross-sectioned through grinding, FIB, and section milling to expose the cross-section of the metallic magnetic particles, forming an exposed surface. After exposing the cross-section and forming the exposed surface, the exposed surface is observed using SEM at 500x to 5000x magnification. Using the image analysis software WinROOF2018, the equivalent circle diameter is calculated for more than 50 particles. For the equivalent circle diameter, a circle with the same area as the cross-sectional area of ​​each metallic magnetic particle is considered, and the diameter of this circle is taken as the equivalent circle diameter. Then, this equivalent circle diameter is calculated as the average particle size, i.e., the median particle size (D50), of each metallic magnetic particle. Figure 5 As shown, the particle size distribution of the equivalent circle diameter has at least two peaks and a base between these peaks. The base, located between the two peaks, is the point where the frequency reaches a minimum.

[0099] Then, the metallic magnetic particles above the bottom with the minimum frequency are designated as the first metallic magnetic particles 40, and those below the bottom with the minimum frequency are designated as the second metallic magnetic particles 42. In the particle size distribution, when there are only two peaks, the bottom between the peaks becomes the bottom with the minimum frequency.

[0100] The first metallic magnetic particle 40 is spherical in shape. Furthermore, the first metallic magnetic particle 40 includes particles having spherical recesses 40a within them that satisfy predetermined conditions. For example... Figure 6 and Figure 7 As shown, the cross-sectional shape of the first metallic magnetic particle 40 with the recess 40a is crescent-shaped. More specifically, the minimum distance between the front ends of the openings 40b of the recess 40a in the cross-section of the first metallic magnetic particle 40 is set as L. 01 Let L be the longest distance among the line segments that are parallel to the line segment that is the minimum distance between the concave portion 40a of the cross-section of the first metallic magnetic particle 40 and the front end of the opening portion 40b. 02 When L is satisfied 02 >L 01 .

[0101] By having such a recess 40a in the first metallic magnetic particle 40, the surface area of ​​the first metallic magnetic particle 40 relative to the volume can be increased compared to when the first metallic magnetic particle 40 is spherical. Therefore, the eddy current loss in the high-frequency region is reduced, and the coil component 10 can also be used at higher frequencies.

[0102] The peak of the maximum frequency in the particle size distribution of the first metallic magnetic particles 40 is preferably between 10 μm and 50 μm. Furthermore, when the peak of the maximum frequency of the first metallic magnetic particles 40 is 10 μm or more, the permeability of the coil component 10 can be improved. On the other hand, when the peak of the maximum frequency of the first metallic magnetic particles 40 exceeds 50 μm, the eddy current loss in the high-frequency region increases, and the characteristics in the high-frequency region decrease.

[0103] like Figure 6 As shown, the second metallic magnetic particle 42 is spherical in shape and has a circular cross-section.

[0104] Furthermore, the peak of the maximum frequency in the particle size distribution of the second metallic magnetic particles 42 is preferably 0.2 μm to 10 μm. More preferably, it is 8 μm or less, and even more preferably 5 μm or less. By making the particle size of the second metallic magnetic particles 42 smaller than the average particle size of other metallic magnetic particles, the filling rate of metallic magnetic particles in the magnetic body portion 14 is increased, which can improve the magnetic permeability of the magnetic body portion 14 and improve the DC overlap characteristics. When the peak of the maximum frequency in the particle size distribution of the second metallic magnetic particles 42 is 10 μm or less, high filling of metallic magnetic particles can be achieved in the magnetic body portion 14. When the peak of the maximum frequency in the particle size distribution of the second metallic magnetic particles 42 is less than 0.2 μm, the fluidity during molding decreases, making high filling difficult.

[0105] The peak of the maximum frequency in the particle size distribution of the first metallic magnetic particle 40 is preferably greater than the peak of the maximum frequency in the particle size distribution of the second metallic magnetic particle 42. By including particles of different sizes, the filling rate is increased, which can improve the permeability of the magnetic body 14 and also improve the DC overlap characteristics.

[0106] The average roundness of the first metallic magnetic particle 40 having the recess 40a is preferably 0.89 or less.

[0107] It should be noted that the roundness of each metallic magnetic particle is calculated as follows.

[0108] That is, in the cross-section of each metallic magnetic particle, when the area of ​​the metallic magnetic particle is set as S and the perimeter as L, it is defined as 4πS / L. 2 The cross-section of the metallic magnetic particles refers to the exposed surface formed by exposing the unit body 12 of the coil component 10 through grinding, FIB (Focused Ion Beam), or cross-section polishing (CP), etc., and the cross-section of the metallic magnetic particles on this exposed surface. After exposing the cross-section of the unit body 12 to form the exposed surface, each metallic magnetic particle is observed using SEM (Scanning Electron Microscope) at 500x to 5000x magnification. Using the image analysis software WinROOF2018 (Mitani Shoji Co., Ltd.), the area S and perimeter L of more than 50 particles are measured, and the average roundness is calculated.

[0109] When the total content of the first metallic magnetic particles 40 and the second metallic magnetic particles 42 is converted into an area of ​​100%, the content of the first metallic magnetic particles 40 is preferably 40% to 85%. When the content of the first metallic magnetic particles 40 is 70% to 85%, the effective permeability of the coil component 10 can be improved.

[0110] When the total content of the first metallic magnetic particles 40 and the second metallic magnetic particles 42 is converted into area and set to 100%, the content of the second metallic magnetic particles 42 is preferably 15% to 60%. When the content of the second metallic magnetic particles 42 is 15% to 30%, the effective permeability of the coil component 10 can be improved.

[0111] Here, the content of each of the first metallic magnetic particles 40 and the second metallic magnetic particles 42 is calculated as follows.

[0112] That is, the cross-section of the magnetic body 14 is exposed, for example, in any 500μm region of the cross-section, the content of each metal magnetic particle is calculated based on the sum of the cross-sectional areas of each metal magnetic particle (let Sa be the sum of the cross-sectional areas S1 of the first metal magnetic particles 40, and Sb be the sum of the cross-sectional areas S2 of the second metal magnetic particles 42). The content of the first metal magnetic particle is Sa / (Sa+Sb), and the content of the second metal magnetic particle is Sb / (Sa+Sb).

[0113] The first metallic magnetic particle 40 and the second metallic magnetic particle 42 can have the same composition. By using the same composition, the flow of magnetic flux inside the magnetic body 14 becomes more uniform, and the overlap characteristic becomes higher.

[0114] It should be noted that the composition of metallic magnetic particles can be analyzed as follows.

[0115] That is, the composition of metallic magnetic particles can be analyzed using compositional analysis devices such as EDX (Energy Dispersive X-ray spectroscopy), XPS (X-ray Photoelectron Spectroscopy), and TOF-SIMS (Time of Flight Secondary Ion Mass Spectroscopy).

[0116] In the magnetic body portion 14, the resin content (converted to area) is preferably 5% to 25%. This increases the area ratio of each metallic magnetic particle contained in the magnetic body portion 14, thereby improving the magnetic permeability of the magnetic body portion 14. It should be noted that if the resin content is less than 5%, flowability cannot be ensured during molding, making high filling difficult.

[0117] Here, the resin content in the magnetic body 14 is calculated as follows.

[0118] That is, the cross-section of the magnetic body portion 14 is exposed, for example, in any 500 μm region of its cross-section, and the area of ​​the resin is calculated in the form of St, which is the area of ​​the resin relative to the area of ​​the arbitrary 500 μm region.

[0119] like Figure 8 (a) Figure 8 As shown in (b), in the cross-section of the magnetic body portion 14, at least a portion of at least one second metal magnetic particle 42 is disposed inside the recess 40a of the first metal magnetic particle 40. Since the second metal magnetic particle 42 enters the interior of the recess 40a of the first metal magnetic particle 40, the decrease in magnetic permeability of the magnetic body portion 14 caused by the recess 40a can be suppressed.

[0120] like Figure 8 (c) Figure 8 As shown in (d), in the cross-section of the magnetic body portion 14, it is preferable to arrange all of at least one second metal magnetic particle 42 inside the recess 40a of the first metal magnetic particle 40. Since the second metal magnetic particle 42 enters the recess 40a of the first metal magnetic particle 40, the magnetic permeability of the magnetic body portion 14 can be improved.

[0121] Furthermore, in the cross-section of the magnetic body portion 14, the proportion of first metal magnetic particles 40 having a recess 40a in which at least a portion of a second metal magnetic particle 42 is disposed within the recess 40a of the first metal magnetic particle 40 is 50% or more. Because the proportion of first metal magnetic particles 40 containing a second metal magnetic particle 42 disposed within the recess 40a of the first metal magnetic particle 40 is large, the magnetic permeability of the magnetic body portion 14 can be improved.

[0122] like Figure 9 As shown, in the cross-section of the magnetic body portion 14, when at least one second metallic magnetic particle 42 is completely inserted into the recess 40a of the first metallic magnetic particle 40, the content of the second metallic magnetic particle 42 inside the recess 40a is preferably 40% or more on average. Since the second metallic magnetic particle 42 is inserted into the recess 40a of the first metallic magnetic particle 40, the magnetic permeability of the magnetic body portion 14 can be improved.

[0123] It should be explained that, for example Figure 9As shown, the content of the second metallic magnetic particles 42 inside the recess 40a of the first metallic magnetic particles 40 is calculated in the opening 40b as the ratio of the total area of ​​the second metallic magnetic particles 42 located in the region R0 to the area of ​​the region R0 inside the line segment of the first metallic magnetic particles 40 that is the minimum distance between the front ends of the opening 40b.

[0124] like Figure 10 As shown, in the cross-section of the magnetic body portion 14, at least a portion of at least one other first metallic magnetic particle 402 and at least a portion of the second metallic magnetic particle 42 enter the interior of the recess 40a of the first metallic magnetic particle 401. The content of the other first metallic magnetic particles 402 and the second metallic magnetic particles 42 in the recess 40a of the first metallic magnetic particle 401 is preferably an average of 50% or more. Because the other first metallic magnetic particles 40 and the second metallic magnetic particles 42 enter the recess 40a of the first metallic magnetic particle 40, the magnetic permeability of the magnetic body portion 14 can be increased.

[0125] It should be explained that, for example Figure 10 As shown, the content of other first metallic magnetic particles 402 and second metallic magnetic particles 42 inside the recess 40a of the first metallic magnetic particle 401 is calculated in the opening 40b in the form of the ratio of the sum of the areas of the other first metallic magnetic particles 402 and second metallic magnetic particles 42 located in the region R0 to the area inside the region R0 of the line segment of the first metallic magnetic particle 401 that is the minimum distance between the front ends of the opening 40b.

[0126] like Figure 11 As shown, in the cross-section of the magnetic body portion 14, when the particle size d2 is set to the peak of the maximum frequency in the particle size distribution of the second metallic magnetic particle 42, the minimum distance L between the front ends of the recess 40a and the opening 40b of the first metallic magnetic particle 40 is... 01 The average value preferably satisfies L 01 >d2. Since the opening 40b of the first metallic magnetic particle 40 is larger than the particle size at which the peak of the maximum frequency in the particle size distribution of the second metallic magnetic particle 42 is located, the second metallic magnetic particle 42 can easily enter the recess 40a, thereby improving the magnetic permeability of the magnetic body portion 14.

[0127] For the first metallic magnetic particle 40, such as Figure 12As shown, in the cross-section of the magnetic body portion 14, when the outer perimeter of the first metallic magnetic particle 40 having a crescent-shaped recess 40a is defined as L1, and the circumference of a circle with an area equivalent to the area of ​​the first metallic magnetic particle 40 is defined as L2, the average value of L1 / L2 is preferably 5.0 or less. When the average value of L1 / L2 is 5.0 or less, the eddy current loss in the high-frequency region is reduced, and the coil component 10 can be used at higher frequencies. It should be noted that when the average value of L1 / L2 exceeds 5.0, the recess 40a of the first metallic magnetic particle 40 becomes larger, making it difficult to flow during the thermoforming of the first molded body 50 and the second molded body 60, which are described later, constituting the magnetic body portion 14. Therefore, the filling rate of the metallic magnetic particles in the magnetic body portion 14 decreases, resulting in a decrease in the permeability and DC overlap characteristics of the coil component 10. Furthermore, the average value of L1 / L2 is more preferably 1.2 or more.

[0128] Here, the perimeter of the first metallic magnetic particle 40 is determined based on the cross-section of the magnetic body 14.

[0129] That is, the cross-section of the metallic magnetic particles refers to the exposed surface formed by exposing the center of the shaped body 12 containing the coil component 10, which is orthogonal to the length direction z of the unit body 12, through cross-sectional ion milling (or grinding, FIB processing, etc.), and the cross-section of the metallic magnetic particles on this exposed surface. After exposing the cross-section of the unit body 12 to form the exposed surface, the particles are observed using SEM at 500x to 5000x magnification. L1 and L2 are calculated using the image analysis software WinROOF2018. Then, L1 / L2 is calculated using more than 50 particles, and its average value is obtained, thereby calculating the cross-section of the metallic magnetic particles.

[0130] For the first metallic magnetic particle 40, such as Figure 13 As shown, in the cross-section of the magnetic body portion 14, the minimum distance between the front ends of the recess 40a and the opening 40b of the first metal magnetic particle 40 is set as L. 01 When the perimeter of the first metallic magnetic particle 40, excluding the inner side of the opening 40b of the recess 40a, is set as Lc, L 01 / (Lc+L 01 The average value of ) is preferably 0.03 to 0.4.

[0131] If L 01 / (Lc+L 01 If the average value of L is 0.03 or higher, the second metallic magnetic particles 42 can easily enter the interior of the recess 40a. Therefore, by increasing the filling density of metallic magnetic particles in the magnetic body portion 14, the permeability of the coil component 10 can be improved, and the DC overlap characteristics can also be improved. On the other hand, if L 01 / (Lc+L 01If the average value of the first metallic magnetic particles 40 exceeds 0.4, the first metallic magnetic particles 40 will have difficulty flowing, and the filling rate of metallic magnetic particles in the magnetic body 14 will become lower.

[0132] It should be noted that L 01 Lc is determined based on the cross-sectional image of the unit body 12 of the coil component 10.

[0133] Here, the L of the first metallic magnetic particle 40 01 Lc is calculated through the following steps.

[0134] The cross-section of the metallic magnetic particles refers to the exposed surface formed by exposing the cross-section of the unit body 12 containing the coil component 10, which is orthogonal to the longitudinal direction z of the unit body 12, through cross-sectional ion milling (or grinding, FIB processing, etc.). The cross-section of the metallic magnetic particles on this exposed surface is then observed using SEM at 500x to 5000x magnification. The L value is calculated using the image analysis software WinROOF2018. 01 And Lc. L 01 Lc is the shortest distance from the front end of the opening 40b of the first metallic magnetic particle 40, and Lc is the perimeter of the first metallic magnetic particle 40 excluding the inner side of the opening 40b. Then, L is calculated using more than 10 particles. 01 / (Lc+L 01 ), calculate their average value, and then calculate the result.

[0135] For the first metallic magnetic particle 40, such as Figure 14 As shown, in the cross-section of the magnetic body portion 14, when the area of ​​the region R0 inside the line segment of the first metal magnetic particle 40 that is the minimum distance between the front ends of the opening portion 40b is set as S0, and the cross-sectional area of ​​the first metal magnetic particle 40 having the recess 40a is set as Sc, the average value of S0 / (Sc+S0) is preferably 0.05 to 0.8.

[0136] If S0 / (Sc+S0) is 0.05 or higher, the second metallic magnetic particle 42 can easily enter the recess 40a of the first metallic magnetic particle 40, thereby increasing the permeability of the coil component 10. However, if S0 / (Sc+S0) exceeds 0.8, the first metallic magnetic particle 40 is easily deformed during the molding of the first molded body 50 and the second molded body 60, which will be described later, constituting the magnetic body portion 14, making it difficult to achieve high filling density of metallic magnetic particles in the magnetic body portion 14.

[0137] It should be noted that S0 and Sc are determined based on the cross-sectional image of the magnetic body 14.

[0138] Here, the S0 and Sc of the first metallic magnetic particle 40 can be calculated through the following steps.

[0139] The cross-section of a metallic magnetic particle refers to the cross-section of the unit body 12 containing the coil component 10, which is orthogonal to the longitudinal direction z of the unit body 12, exposed by cross-sectional ion milling (or grinding, FIB processing, etc.), forming an exposed surface, and the cross-section of the metallic magnetic particle on this exposed surface. After the cross-section of the unit body 12 is exposed to form the exposed surface, the particle is observed using SEM at 500x to 5000x magnification. S0 and Sc are calculated using the image analysis software WinROOF2018. S0 is the area R0 of the region R0 of the recess 40a inside the shortest distance line segment connecting the front end of the opening 40b of the first metallic magnetic particle 40, and Sc is the cross-sectional area of ​​the first metallic magnetic particle 40. Then, S0 / (Sc+S0) is calculated using more than 50 particles, and its average value is obtained, thus calculating the cross-section of the metallic magnetic particle 40.

[0140] The magnetic body 14 preferably further contains inorganic oxide particles 44.

[0141] Inorganic oxide particles 44 include, for example, silica fillers, ferrites, and glass.

[0142] The resistivity of inorganic oxide particles 44 is higher than that of metallic magnetic particles. Therefore, if the magnetic body 14 contains inorganic oxide particles 44, the voltage withstand capability of the coil component 10 can be improved.

[0143] The inorganic oxide particles 44 are preferably glass or non-magnetic ferrite. Because glass or non-magnetic ferrite has high magnetic reluctance, the overlap characteristics of the coil component 10 can be improved.

[0144] Furthermore, the inorganic oxide particles 44 are preferably magnetic ferrites. Since magnetic ferrites have high permeability, the permeability of the coil component 10 can be further improved.

[0145] For the first metallic magnetic particle 40, such as Figure 15 (a) Figure 15 As shown in (b), in the cross-section of the magnetic body portion 14, preferably at least a portion of at least one second metal magnetic particle 42 and at least a portion of at least one inorganic oxide particle 44 are simultaneously disposed inside the recess 40a of the first metal magnetic particle 40.

[0146] For the first metallic magnetic particle 40, such as Figure 15 (c) Figure 15 As shown in (d), in the cross-section of the magnetic body portion 14, more preferably, at least a portion of at least one second metallic magnetic particle 42 and all of at least one inorganic oxide particle 44 simultaneously enter the recess 40a of the first metallic magnetic particle 40.

[0147] The surfaces of the first metallic magnetic particle 40 and the second metallic magnetic particle 42 can be covered with an insulating film. By covering the surface of each metallic magnetic particle with an insulating film, the internal resistance of the magnetic body 14 can be increased. In addition, since the insulating film ensures the insulation of the surface of the metallic magnetic particles, short circuit defects between the coil conductor 16 and the external electrode 30 can be suppressed.

[0148] It should be explained that, for example Figure 16 As shown, preferably, an insulating film 46 is formed on the outer surface of the first metallic magnetic particle 40, and at least a portion of the inner surface of the recess 40a of the first metallic magnetic particle 40 is not formed with the insulating film 46. It should be noted that it is more preferable that the insulating film 46 is not formed on the entire inner side of the recess 40a. Since there is no insulating film 46 on the inner side of the recess 40a of the first metallic magnetic particle 40, the proportion of magnetic body area is increased, thereby improving the effective magnetic permeability of the magnetic body portion 14.

[0149] Materials for insulating films include silicon oxides, phosphate-based glasses, and bismuth-based glasses.

[0150] The thickness of the insulating film is not particularly limited, but it is preferably 5 nm to 500 nm, more preferably 5 nm to 100 nm, and even more preferably 10 nm to 100 nm. By further increasing the thickness of the insulating film, it is expected that the voltage withstand capability and DC overlap characteristics of the magnetic body portion 14 will be improved. In addition, by further reducing the thickness of the insulating film, the amount of metallic magnetic particles in the magnetic body portion 14 can be increased, thereby increasing the permeability of the magnetic body portion 14.

[0151] (c) Coil conductor

[0152] The coil conductor 16 has: a winding portion 18 formed by winding a wire containing a conductive material into a coil shape, a first lead-out portion 22a extending to one side of the winding portion 18, and a second lead-out portion 22b extending to the other side of the winding portion 18. A hollow region 20 is formed in the center of the winding portion 18.

[0153] The winding section 18 is formed by winding it into two sections. The coil conductor 16 is formed by winding a flat wire into an α-wound shape.

[0154] A first lead-out portion 22a protrudes from the first end face 12e of the unit body 12 to form a first exposed portion 24a, and a second lead-out portion 22b protrudes from the second end face 12f of the unit body 12 to form a second exposed portion 24b. In the first exposed portion 24a, the exposed surface of the first lead-out portion 22a is formed to intersect the extending direction of the first lead-out portion 22a. Similarly, in the second exposed portion 24b, the exposed surface of the second lead-out portion 22b is formed to intersect the extending direction of the second lead-out portion 22b.

[0155] The coil conductor 16 is composed of metal wire, leads, or other conductive wires. The conductive material of the coil conductor 16 is not particularly limited, but may be, for example, a metallic composition consisting of Ag, Au, Cu, Ni, Sn, or alloys thereof. Copper is preferably used as the conductive material. There may be only one conductive material, or there may be two or more conductive materials.

[0156] The surface of the wire constituting the coil conductor 16 is covered with an insulating material to form an insulating film. By covering the wire constituting the coil conductor 16 with an insulating material, the insulation between the wound coil conductors 16 and between the coil conductors 16 and the magnetic body portion 14 can be made more reliable.

[0157] It should be noted that no insulating film is formed on the first exposed portion 24a and the second exposed portion 24b of the wire constituting the coil conductor 16.

[0158] The insulating material used as the insulating film is not particularly limited, but examples include polyurethane resin, polyester resin, epoxy resin, polyamide-imide resin, and polyimide resin. Preferably, polyamide-imide resin is used as the insulating film.

[0159] The thickness of the insulating film is preferably 2μm to 10μm.

[0160] Furthermore, no insulating film is disposed in the exposed portions (exposed surfaces) of the end faces 12e and 12f of the unit body 12 of the first exposed portion 24a and the second exposed portion 24b of the coil conductor 16. As a result, the coil conductor 16 can be directly electrically connected to the first base electrode layer 32a and the second base electrode layer 32b, thereby reducing the resistance between the coil conductor 16 and the first base electrode layer 32a and the second base electrode layer 32b.

[0161] (d) External electrode

[0162] External electrodes 30 are disposed on the first end face 12e side and the second end face 12f side of the unit body 12. The external electrodes 30 have a first external electrode 30a and a second external electrode 30b.

[0163] The first external electrode 30a is disposed on the surface of the first end face 12e of the unit body 12. It should be noted that the first external electrode 30a can be formed to extend from the first end face 12e and cover a portion of each of the first main face 12a, the second main face 12b, the first side face 12c, and the second side face 12d; or it can be formed to extend from the first end face 12e toward the second main face 12b and cover a portion of each of the first end face 12e and the second main face 12b. In this case, the first external electrode 30a is directly electrically connected to the first exposed portion 24a of the coil conductor 16 and electrically connected to the first lead-out portion 22a.

[0164] The second external electrode 30b is disposed on the surface of the second end face 12f of the unit body 12. It should be noted that the second external electrode 30b can be formed to extend from the second end face 12f and cover a portion of each of the first main face 12a, the second main face 12b, the first side face 12c, and the second side face 12d, or it can be formed to extend from the second end face 12f toward the second main face 12b and cover a portion of each of the second end face 12f and the second main face 12b. In this case, the second external electrode 30b is directly electrically connected to the second exposed portion 24b of the coil conductor 16 and electrically connected to the second lead-out portion 22b.

[0165] The thickness of the first external electrode 30a and the second external electrode 30b is not particularly limited, but can be, for example, 1 μm to 50 μm, preferably 5 μm to 20 μm.

[0166] The first external electrode 30a includes a first base electrode layer 32a and a first plating layer 34a disposed on the surface of the first base electrode layer 32a. Similarly, the second external electrode 30b includes a second base electrode layer 32b and a second plating layer 34b disposed on the surface of the second base electrode layer 32b.

[0167] The first base electrode layer 32a is disposed on the surface of the first end face 12e of the unit body 12. Therefore, the first base electrode layer 32a is in direct contact with the first exposed portion 24a of the coil conductor 16. It should be noted that the first base electrode layer 32a may be formed to extend from the first end face 12e and cover a portion of each of the first main face 12a, the second main face 12b, the first side face 12c, and the second side face 12d, or it may be formed to extend from the first end face 12e and cover a portion of each of the first end face 12e and the second main face 12b.

[0168] Furthermore, the second base electrode layer 32b is disposed on the surface of the second end face 12f of the unit body 12. Therefore, the second base electrode layer 32b is in direct contact with the second exposed portion 24b of the coil conductor 16. It should be noted that the second base electrode layer 32b can be formed to extend from the second end face 12f and cover a portion of each of the first main face 12a, the second main face 12b, the first side face 12c, and the second side face 12d, or it can be formed to extend from the second end face 12f and cover a portion of each of the second end face 12f and the second main face 12b.

[0169] The first base electrode layer 32a and the second base electrode layer 32b can be formed from resin electrode layers. The resin electrode layer comprises a resin component and a metal component. The resin component of the resin electrode layer comprises at least one selected from polyurethane resin, epoxy resin, phenolic resin, acrylic resin, silicone resin, polyimide resin, polyamide-imide resin, polyamide resin, etc. The metal component of the resin electrode layer may, for example, comprise at least one selected from Cu, Ni, Ag, Pd, Ag-Pd alloy, Au, etc. The resin electrode layer can be multilayered. The resin electrode layer can be formed by impregnating a conductive paste comprising resin and metal components onto the unit body 12 and then thermally curing it.

[0170] Furthermore, the first base electrode layer 32a and the second base electrode layer 32b can each be formed as plated electrodes. The first base electrode layer 32a and the second base electrode layer 32b can be formed by electroplating or by electroless plating.

[0171] Furthermore, the main components of the metal materials constituting the first base electrode layer 32a and the second base electrode layer 32b are preferably the same as the main components of the metal material constituting the coil conductor 16. This results in a stronger metal bond between the coil conductor 16 and the first base electrode layer 32a and the second base electrode layer 32b, thus increasing the bonding strength and reducing DC resistance.

[0172] The average thickness of the first base electrode layer 32a and the second base electrode layer 32b is, for example, 10 μm.

[0173] The first plating layer 34a is configured to cover the first base electrode layer 32a. Specifically, the first plating layer 34a is configured to cover the first base electrode layer 32a disposed on the first end face 12e, and may be configured to cover the surface of the first base electrode layer 32a extending from the first end face 12e and disposed on the first main face 12a, the second main face 12b, the first side face 12c and the second side face 12d, or may be configured to cover a portion of the first base electrode layer 32a that extends from the first end face 12e and covers each portion of the second main face 12b.

[0174] The second plating layer 34b is configured to cover the second base electrode layer 32b. Specifically, the second plating layer 34b is configured to cover the second base electrode layer 32b disposed on the second end face 12f. It can be configured to cover the surface of the second base electrode layer 32b extending from the second end face 12f and disposed on the first main face 12a, the second main face 12b, the first side face 12c, and the second side face 12d. Alternatively, it can be configured to cover a portion of the second base electrode layer 32b that extends from the second end face 12f and covers each portion of the second main face 12b.

[0175] The metal material used for the first plating layer 34a and the second plating layer 34b may include, for example, at least one selected from Cu, Ni, Ag, Sn, Pd, Ag-Pd alloy, or Au.

[0176] The first coating 34a and the second coating 34b can be formed as multiple layers.

[0177] The first plating layer 34a is a double-layer structure consisting of a first Ni plating layer 36a and a first Sn plating layer 38a formed on the surface of the first Ni plating layer 36a. The second plating layer 34b is a double-layer structure consisting of a second Ni plating layer 36b and a second Sn plating layer 38b formed on the surface of the second Ni plating layer 36b.

[0178] The average thickness of the first Ni coating 36a and the second Ni coating 36b is, for example, 5 μm.

[0179] In addition, the average thickness of the first Sn coating 38a and the second Sn coating 38b is, for example, 10 μm.

[0180] It should be noted that the first external electrode 30a and the second external electrode 30b can be configured as follows.

[0181] For example, the first base electrode layer 32a and the second base electrode layer 32b can be Ag-containing resin electrodes, or they can be composed of an Ag sputtered layer, a Cu sputtered layer, or a Ti sputtered layer formed by sputtering. It should be noted that when the first base electrode layer 32a and the second base electrode layer 32b are composed of Ag-containing resin electrodes, they may contain glass frit. Furthermore, when the first base electrode layer 32a and the second base electrode layer 32b are formed by sputtering layers, a Cu sputtered layer can be formed on the Ti sputtered layer.

[0182] In addition, the outermost layer of the first plating layer 34a and the second plating layer 34b may consist only of Sn plating layers 38a and 38b.

[0183] Alternatively, an Ag plating layer and a Ni plating layer can be formed on the unit body 12 without forming the first base electrode layer 32a and the second base electrode layer 32b.

[0184] If the length z-axis dimension of the coil component 10 is set as L, then L is preferably 1.0 mm to 12.0 mm. If the width y-axis dimension of the coil component 10 is set as W, then W is preferably 0.5 mm to 12.0 mm. If the pressure x-axis dimension of the coil component 10 is set as T, then it is preferably 0.5 mm to 6.0 mm.

[0185] according to Figure 1The coil component 10 shown has a particle size distribution of metal magnetic particles calculated from the equivalent circle diameter obtained from the cross-sectional image of the cross-section of the magnetic body 14. It has at least two peaks and at least one bottom. It includes metal magnetic particles with the bottom having the minimum frequency and above designated as first metal magnetic particles 40 and the bottom having the minimum frequency and below designated as second metal magnetic particles 42. The first metal magnetic particles 40 include particles having a recess 40a that satisfies a predetermined condition in the cross-section. At least a portion of at least one second metal magnetic particle 42 is disposed inside the recess 40a of the first metal magnetic particle 40 having the recess 40a. Therefore, the filling rate of metal magnetic particles in the magnetic body is increased, thereby improving the permeability of the coil component.

[0186] In addition, according to Figure 1 The coil component 10 shown includes a first metal magnetic particle 40 having a recess 40a in its cross-section that satisfies a predetermined condition in the magnetic body portion 14 containing metal magnetic particles and resin. The predetermined condition is that the minimum distance between the front ends of the openings 40b of the recess 40a is set to L. 01 Let L be the longest distance among the line segments that are parallel to the line segment that is the minimum distance between the concave portion 40a of the cross-section of the first metallic magnetic particle 40 and the front end of the opening portion 40b. 02 At that time, L 02 >L 01 Therefore, the surface area of ​​the first metal magnetic particle 40 relative to the volume of the magnetic body 14 can be increased, thus reducing eddy current losses in the high-frequency region, and the coil component can also be used at higher frequencies.

[0187] 2. Manufacturing method of coil components

[0188] Next, the manufacturing method of the coil component will be explained.

[0189] The manufacturing method of the coil component includes (a) a process of manufacturing granulated powder, (b) a process of manufacturing a first molded body and a second molded body, (c) a process of manufacturing a unit body, and (d) a process of forming an external electrode.

[0190] (a) Process of manufacturing granulated powder

[0191] The manufactured granulated powder is a composite material containing metallic magnetic particles A, metallic magnetic particles B, resin, and solvent.

[0192] (Preparation of metallic magnetic particles)

[0193] First, prepare metallic magnetic particles A and B.

[0194] (Metallic magnetic particle A)

[0195] For example, Fe-based soft magnetic material powders such as α-Fe, Fe-Si, Fe-Si-Cr, Fe-Si-Al, Fe-Ni, and Fe-Co can be used as the metallic magnetic particle A. Furthermore, regarding the material morphology of the metallic magnetic particle, amorphous materials with good soft magnetic properties are preferred, but there are no particular limitations; crystalline materials are also acceptable.

[0196] The average particle size of the metallic magnetic particles A is preferably 10 μm to 50 μm. It should be noted that the average particle size is, for example, the median particle size (D50). It should also be noted that if the average particle size of the metallic magnetic particles B exceeds 50 μm, the eddy current loss in the high-frequency region increases, and the characteristics in the high-frequency region decrease.

[0197] Metallic magnetic particles A include particles with concave portions.

[0198] In order to form a recess in the metallic magnetic particle A, the following treatment is performed.

[0199] That is, for the prepared magnetic material powder, metallic magnetic particles A are produced by gas atomization or water atomization. Here, by increasing the spray volume of gas or water or increasing the spray pressure, it is possible to promote the formation of voids, increase the size of voids, or control the sphericity. Generally, when attempting to form concave areas in metallic magnetic particles by atomization, the shape of the particles deviates from a true sphere, and the overall average sphericity of the produced particles increases. In this embodiment, metallic magnetic particles A are produced by water atomization. In addition, the appearance of the produced metallic magnetic particles can be selected, and the ratio of voids to void-free particles can be adjusted.

[0200] It should be noted that the method for producing metallic magnetic particles with concave portions is not limited to atomization; other methods may also be used.

[0201] Furthermore, the outer surface of the metallic magnetic particle A is coated with an insulating film. Here, when forming the insulating film using mechanical methods, the metallic magnetic particles and insulating material powder can be fed into a rotating container, and particle composite formation can be achieved through mechanochemical treatment, thereby forming an insulating film on the surface of the magnetic powder. It should be noted that it is preferable not to form an insulating film inside the recesses of the metallic magnetic particle A. Not forming an insulating film inside the recesses of the metallic magnetic particle A can improve the effective permeability of the coil component.

[0202] As a material for the aforementioned metallic magnetic particles A with recesses, for example, Fe-Si-Cr alloy particles with an average particle size of 26 μm and coated with an insulating film of 10 nm thickness made of zinc phosphate glass are prepared. It should be noted that the Fe-Si-Cr alloy particles contain 90.8 wt% Fe, 6.7 wt% Si, and 2.5 wt% Cr.

[0203] (Metallic magnetic particle B)

[0204] For example, Fe-based soft magnetic material powders such as α-Fe, Fe-Si, Fe-Si-Cr, Fe-Si-Al, Fe-Ni, and Fe-Co can be used as the metallic magnetic particles B. Furthermore, regarding the material morphology of the metallic magnetic particles, amorphous materials with good soft magnetic properties are preferred, but there are no particular limitations; crystalline materials are also acceptable.

[0205] Metallic magnetic particles B are produced by gas atomization and water atomization.

[0206] The average particle size of the metallic magnetic particles B is preferably 0.2 μm to 10 μm. More preferably, the average particle size of the metallic magnetic particles B is 8 μm or less, and even more preferably 5 μm or less. It should be noted that the average particle size is, for example, the median particle size (D50). If the average particle size of the metallic magnetic particles B is less than 0.2 μm, the flowability during molding decreases, making high filling difficult.

[0207] Furthermore, the surface of the metallic magnetic particles B is coated with an insulating film. Here, in the case of forming the insulating film by mechanical means, the metallic magnetic particles and insulating material powder can be fed into a rotating container, and particle composite can be performed by mechanochemical treatment, thereby forming an insulating film on the surface of the magnetic powder.

[0208] As a material for the aforementioned metallic magnetic particles B, for example, Fe-Si-Cr alloy particles with an average particle size of 4 μm and coated with an insulating film of 10 nm thickness made of zinc phosphate glass are prepared. It should be noted that the Fe-Si-Cr alloy particles contain 90.8 wt% Fe, 6.7 wt% Si, and 2.5 wt% Cr.

[0209] It should be noted that the average particle size of each metallic magnetic particle was determined by the following method.

[0210] First, the average particle size of each metallic magnetic particle before granulation, i.e., the median particle size (D50), can be determined using a particle size distribution measuring device such as a laser diffraction apparatus. Here, the median particle size (D50) refers to the average particle size D50 (equivalent to the particle size at a cumulative percentage of 50% of the volume).

[0211] (resin)

[0212] Resin materials contained in composite materials include, for example, thermosetting resins, epoxy resins, phenolic resins, polyester resins, polyimide resins, polyolefin resins, and other organic materials. There may be only one type of resin material, or there may be two or more types.

[0213] In this embodiment, epoxy resin is used as the thermosetting resin.

[0214] A lower resin content can improve the effective magnetic permeability of the coil component 10, which is therefore preferred. Specifically, it is particularly preferred (in terms of area) to be 25% or less. On the other hand, when it is less than 5%, flowability cannot be ensured during molding, making high filling difficult, so it is preferred to be 5% or more.

[0215] It should be noted that in this embodiment, the granulation powder is mixed and shaped according to the following volume ratio.

[0216] That is, let the ratio of metallic magnetic particles A: metallic magnetic particles B: resin be 56:19:25.

[0217] (solvent)

[0218] Additionally, acetone is prepared as a solvent.

[0219] (Manufacturing of granulated powder)

[0220] Next, using the prepared metallic magnetic particles A, metallic magnetic particles B, resin material, and solvent, granulated powder is manufactured.

[0221] First, magnetic metal particles A and magnetic metal particles B are mixed and stirred in a stirring container. The mixing ratio of the magnetic metal particles is magnetic metal particle A: magnetic metal particle B = 75:25 by weight.

[0222] It should be noted that the higher the ratio of the particle size of magnetic metal particles A to magnetic metal particles B (average particle size of magnetic metal particles A / average particle size of magnetic metal particles B), the higher the filling rate of magnetic metal particles in the coil component, which can improve the permeability. In addition, it can improve the DC overlap characteristics.

[0223] Next, the prepared resin and solvent are added to the metal magnetic particles A and B that are being mixed and stirred in the mixing container.

[0224] It should be noted that the amount of resin added is 3.0 wt% of the total weight of magnetic metal particles A and magnetic metal particles B, and the amount of solvent added is 1.0 wt% of the total weight of magnetic metal particles A and magnetic metal particles B.

[0225] Next, the metal magnetic particles A, metal magnetic particles B, resin and solvent added to the mixing container are stirred and dried.

[0226] Then, using a vibrating screen, coarse particles are removed from the composite material of stirred metallic magnetic particles A, metallic magnetic particles B, resin, and solvent to obtain granulated powder.

[0227] It should be noted that by changing the mixing ratio of each metallic magnetic particle, the mixing and stirring time, and L... 01The value of / d2, etc., can be adjusted to adjust the proportion of other first and second metal magnetic particles arranged inside the recess of the first metal magnetic particle.

[0228] (b) The process of manufacturing the first molded body and the second molded body

[0229] Next, the obtained granulated powder is used to manufacture the first molded body 50 and the second molded body 60.

[0230] Here, the structure of the first molded body 50 will be explained first.

[0231] like Figure 17 As shown, the first molded body 50 includes a plate-shaped bottom part 52, a columnar roll part 54 disposed on the upper surface 52a of the bottom part 52, and a first side side wall part 56a, a second side side wall part 56b, a first end side wall part 56c and a second end side wall part 56d surrounding the roll part 54 and disposed on the upper surface 52a of the bottom part 52.

[0232] The first side wall portion 56a and the second side wall portion 56b are disposed opposite each other in the width direction y on the upper surface 52a of the bottom portion 52, and the first end face side wall portion 56c and the second end face side wall portion 56d are disposed opposite each other in the length direction z on the upper surface 52a of the bottom portion 52.

[0233] A first cutout 58a is provided on the first end face sidewall portion 56c. A second cutout 58b is provided on the second end face sidewall portion 56d.

[0234] The cross-section of the scroll portion 54, which is approximately perpendicular to the central axis A, is elliptical or approximately elliptical. For example... Figure 17 As shown, the spool portion 54 can gradually taper away from the bottom portion 52. That is, the front end portion 54a of the spool portion 54 can be thinner than the root portion connected to the bottom portion 52.

[0235] Next, the structure of the second molded body 60 will be described.

[0236] like Figure 17 As shown, the second molded body 60 is a plate-shaped component with a first main surface 60a and a second main surface 60b that are approximately rectangular.

[0237] The first molded body 50 and the second molded body 60 described above are manufactured as follows.

[0238] First, the granulated powder produced in the granulation process is molded using a mold that becomes the first molding body. At this time, the temperature is set to room temperature, and a pressure of 50 MPa is applied. Next, the produced granulated powder is molded using a mold that becomes the second molding body. At this time, the temperature is set to room temperature, and a pressure of 50 MPa is applied.

[0239] The first and second molded bodies manufactured as described above are further subjected to a temperature of 100°C for 10 seconds for temporary curing.

[0240] As described above, the first molded body 50 and the second molded body 60 are manufactured.

[0241] (c) Process of manufacturing unit

[0242] Next, using the first molded body 50 and the second molded body 60, a unit body 12 with the coil conductor 16 embedded is manufactured.

[0243] like Figure 17 As shown, the upper surface 52a of the bottom part 52 of the first molded body 50 is positioned opposite a main surface 60a (or 60b) of the second molded body 60, and a coil conductor 16 is inserted between the first molded body 50 and the second molded body 60. Then, the first molded body 50 and the second molded body 60 are joined together with the coil conductor 16 sandwiched between them.

[0244] More specifically, firstly, the first molded body 50 is housed in the cavity of the mold used for unit molding.

[0245] Next, the coil conductor 16 is positioned between the first molded body 50 and the second molded body 60, with the spool portion 54 of the first molded body 50 disposed within the hollow region 20 of the winding portion 18. At this time, the coil conductor 16 is positioned such that its first lead-out portion 22a extends from the first cut portion 58a of the first molded body 50, and its second lead-out portion 22b extends from the second cut portion 58b of the first molded body 50. It should be noted that an insulating film is formed on the surface of the coil conductor 16.

[0246] Then, the second molded body 60 is placed so as to cover the first molded body 50 on which the coil conductor 16 is disposed.

[0247] Next, with the second molded body 60 placed on the first molded body 50, the temperature is raised to 200°C. Then, while heated, thermoforming is performed by applying pressure of 10 MPa for 120 seconds.

[0248] As described above, manufacture unit 12.

[0249] (d) The process of forming the external electrode

[0250] Next, a first external electrode 30a is formed on the first end face 12e of the unit body 12, and a second external electrode 30b is formed on the second end face 12f.

[0251] Next, an Ag-containing conductive paste is applied to the first end face 12e and the second end face 12f of the unit 12 to form the base electrode layer. When a resin electrode layer is formed as the base electrode layer, a conductive paste containing resin components and metal is applied by, for example, impregnation, followed by thermosetting to form the base electrode layer. The thermosetting temperature is preferably 120°C to 200°C.

[0252] Next, a plating layer is formed on the surface of the base electrode layer. More specifically, a Ni plating layer and a Sn plating layer are formed on the base electrode layer to form the outer electrode 30. Thus, the first exposed portion 24a of the coil conductor 16 is electrically connected to the first outer electrode 30a, and the second exposed portion 24b of the coil conductor 16 is electrically connected to the second outer electrode 30b. This plating process can be performed using electroless plating.

[0253] As described above, coil component 10 is manufactured.

[0254] It should be noted that, as described above, the embodiments of the present invention are disclosed in the foregoing description, but the present invention is not limited thereto.

[0255] That is, without departing from the technical concept and purpose of the present invention, various changes can be made to the above-described embodiments in terms of structure, shape, material, quantity, position or configuration, and these changes are included in the present invention.

Claims

1. A coil component comprising: The unit cell comprises a coil conductor formed by winding a wire and a magnetic body containing metallic magnetic particles and resin. An external electrode is electrically connected to the exposed surface of the lead-out portion of the coil conductor that is exposed on the surface of the unit body and is disposed on the surface of the unit body; in, The metallic magnetic particles include a first metallic magnetic particle and a second metallic magnetic particle. The particle size distribution of the metallic magnetic particles, calculated based on the equivalent circle diameter obtained from a cross-sectional image of the magnetic body, has at least two peaks and at least one bottom. Particles with frequencies above the bottom (which has the lowest frequency) are designated as the first metallic magnetic particles, and particles with frequencies lower than the bottom (which has the lowest frequency) are designated as the second metallic magnetic particles. The first metallic magnetic particle includes particles having a concave portion in the cross-section that satisfies specified conditions. The specified condition is that the minimum distance between the front ends of the openings of the recess is set to L. 01 Let L be the longest distance among the line segments that are parallel to the line segment that is the minimum distance between the front end of the opening and the line segment that is equivalent to a chord in the concave portion of the cross section of the first metallic magnetic particle. 02 At that time, L 02 >L 01 ; The recess of the first metallic magnetic particle is provided with at least a portion of the second metallic magnetic particle.

2. The coil component according to claim 1, wherein, The recess of the first metallic magnetic particle contains at least one entire portion of the second metallic magnetic particle.

3. The coil component according to claim 1 or 2, wherein, In the cross-section of the magnetic body portion, the proportion of the number of first metal magnetic particles having the recess in which at least a portion of the second metal magnetic particles are disposed inside the recess of the first metal magnetic particle is 50% or more.

4. The coil component according to any one of claims 1 to 3, wherein, In the cross-section of the magnetic body portion, when at least one of the second metal magnetic particles is disposed inside the recess of the first metal magnetic particle, the content of the second metal magnetic particles inside the recess is on average 40% or more.

5. The coil component according to any one of claims 1 to 4, wherein, In the cross-section of the magnetic body portion, at least a portion of another first metal magnetic particle and at least a portion of a second metal magnetic particle are disposed inside the recess of the first metal magnetic particle, and the average content of the other first metal magnetic particle and the second metal magnetic particle in the recess of the first metal magnetic particle is 50% or more.

6. The coil component according to any one of claims 1 to 5, wherein, The peak of the maximum frequency in the particle size distribution of the first metallic magnetic particle is 10 μm to 50 μm.

7. The coil component according to any one of claims 1 to 6, wherein, The peak of the maximum frequency in the particle size distribution of the second metallic magnetic particles is 0.2 μm to 10 μm.

8. The coil component according to any one of claims 1 to 7, wherein, The first metallic magnetic particle and the second metallic magnetic particle have the same composition.

9. The coil component according to any one of claims 1 to 8, wherein, An insulating film is formed on the outer surface of the first metallic magnetic particle, while at least a portion of the inner surface of the recess of the first metallic magnetic particle is not formed with an insulating film.

10. The coil component according to any one of claims 1 to 9, wherein, In the cross-section of the magnetic body portion, the resin content is 5% to 25% when converted to area.

11. The coil component according to any one of claims 1 to 10, wherein, When the total content of the first and second metallic magnetic particles is converted into area and set to 100%, the content of the first metallic magnetic particles is 40% to 85%, and the content of the second metallic magnetic particles is 15% to 60%.

12. The coil component according to any one of claims 1 to 11, wherein, In the cross-section of the magnetic body portion, when the outer perimeter of the first metallic magnetic particle having the concave portion is set as L1, and the circumference of the circle, which is converted into an area equivalent to a circle, is set as L2, the average value of L1 / L2 is 5.0 or less.

13. The coil component according to any one of claims 1 to 12, wherein, In the cross-section of the magnetic body portion, the minimum distance between the front ends of the openings of the recesses of the first metal magnetic particles is set as L. 01 When the perimeter of the first metallic magnetic particle, excluding the inner side of the opening of the recess, is set as Lc, L 01 / (Lc+L 01 The average value is 0.03 to 0.

4.

14. The coil component according to any one of claims 1 to 13, wherein, In the cross-section of the magnetic body, when the particle size at the location of the peak of the maximum frequency in the particle size distribution of the second metallic magnetic particle is set as d2, the minimum distance L between the front ends of the openings of the recesses of the first metallic magnetic particles is... 01 The average value satisfies L 01 >d2.

15. The coil component according to any one of claims 1 to 14, wherein, In the cross-section of the magnetic body, when the area inside the region of the line segment with the minimum distance between the front ends of the opening portion of the first metal magnetic particle that forms the concave portion is set as S0, and the cross-sectional area of ​​the first metal magnetic particle having the concave portion is set as Sc, the average value of S0 / (Sc+S0) is 0.05 to 0.

8.

16. The coil component according to any one of claims 1 to 15, wherein, The magnetic body further contains inorganic oxide particles.

17. The coil component according to claim 16, wherein, In the cross-section of the magnetic body portion, at least a portion of the second metal magnetic particle and at least a portion of the inorganic oxide particle are simultaneously disposed in the recess of the first metal magnetic particle.

18. The coil component according to claim 16 or 17, wherein, The inorganic oxide particles are glass.

19. The coil component according to claim 16 or 17, wherein, The inorganic oxide particles are ferrites.

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