Coil components, circuit boards, electronic devices, and methods for manufacturing coil components

Abstract

To provide a coil component with good magnetic saturation characteristics.SOLUTION: A coil component according to an embodiment according to an embodiment includes a circulating portion made of a circulating conductor, and a magnetic base that includes a first magnetic portion formed by bonding first metal particles having a first average particle size, and a second magnetic portion formed by bonding second metal particles having a second average particle size to enclose the circulating portion, where the second particle size is larger than the first particle size, and contains at least a part of the first magnetic portion on the outer circumferential side with respect to the circulating portion.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a coil component, a circuit board, an electronic device, and a method for manufacturing a coil component.

Background Art

[0002] Coil components have different characteristics required depending on the application. When magnetic saturation characteristics are required, an Mn-Zn ferrite material is used as the magnetic material, and when miniaturization of the component size is attempted, a metal magnetic material is often used as the magnetic material.

[0003] As a typical coil component using a metal magnetic material, there is a coil component called a metal composite in which a composite magnetic material obtained by mixing Fe-based metal magnetic particles and a resin is used. This type of coil component has been miniaturized to, for example, a size of 2 mm as the outer dimension.

[0004] Coil components using a metal magnetic material are manufactured through a process of applying pressure to a composite magnetic material obtained by mixing metal magnetic particles and a resin to solidify it. Therefore, due to the presence of the resin or the arrangement and degree of deformation of the metal magnetic particles, the filling rate of the metal magnetic particles is limited. For this reason, coil components using a metal magnetic material have a lower relative permeability obtained as a magnetic material, and are more restricted in applications than coil components using a ferrite magnetic material. For example, in applications where high inductance characteristics are required, coil components using a metal magnetic material may not be suitable.

[0005] In coil components using a metal magnetic material, it is required to expand the applications by increasing the relative permeability. As one method for increasing the relative permeability, a technique for increasing the filling rate of the metal magnetic material by applying a high pressure has been proposed.

[0006] Furthermore, in order to obtain inductance characteristics in coil components using metallic magnetic materials, the influence of the magnetic material located inside the circular portion (circular part) of the conductor is significant, and it is known that increasing the area of ​​the inner magnetic material is effective.

[0007] For example, Patent Document 1 proposes a technique to adjust the size of the magnetic material by polishing or other methods, thereby making the area of ​​the magnetic material on the inside and outside of the coil approximately the same. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2013-183052 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] In recent years, it has become clear that when considering a magnetic material as a whole, the magnetic material located on the outer edge of the circumferential region is not being used effectively. This is because, while the outer shape of a typical magnetic material is a rectangular parallelepiped, the outer shape of the circumferential region is circular or elliptical, and the difference in these shapes results in uneven magnetic flux distribution in certain areas. In many cases, the corners of a rectangular magnetic material do not utilize their inherent magnetic properties. However, if the inner circumference is enlarged and the outer shape of the circumference is made similar to the outer shape of the magnetic material, the length of the conductor forming the circumference increases, resulting in higher resistance. In other words, simply enlarging the circumference does not improve the performance of the coil component. This situation, where the filling density is high, the core area increases, and miniaturization progresses, significantly affects the characteristics of the coil component. One particularly significant effect is that the magnetic flux becomes non-uniform on the outer edge of the circumference, causing localized concentration of magnetic flux. As a result, the coil component becomes more susceptible to magnetic saturation. Therefore, the present invention aims to provide a coil component with good magnetic saturation characteristics. [Means for solving the problem]

[0010] To solve the above problems, a coil component according to one aspect of the present invention comprises a circumferential portion made of a circumferential conductor, a magnetic substrate having a first magnetic portion in which first metal particles having an average particle size of a first particle size are bonded, and a second magnetic portion in which second metal particles having an average particle size of a second particle size are bonded, enclosing the circumferential portion, wherein the second particle size is larger than the first particle size, and at least a part of the first magnetic portion is included on the outer circumference side of the circumferential portion.

[0011] Furthermore, according to one embodiment of the present invention, the first magnetic portion is provided adjacent to the outer circumference of the circumferential portion. Furthermore, according to one embodiment of the present invention, the first magnetic portion is provided over the entire circumference of the circumferential portion.

[0012] Furthermore, according to one embodiment of the present invention, the first magnetic portion occupies more than half of the volume of the magnetic substrate on the outer circumference side of the circumferential portion. Furthermore, according to one embodiment of the present invention, the first magnetic portion is provided between the circumferential portion and the external electrode. Furthermore, according to one embodiment of the present invention, the longest side of the external shape is 1.0 mm or less. Furthermore, a circuit board according to one aspect of the present invention comprises any of the above-mentioned coil components and a substrate on which the above-mentioned coil components are mounted. Furthermore, an electronic device according to one aspect of the present invention includes the above-mentioned circuit board.

[0013] Furthermore, a method for manufacturing a coil component according to one aspect of the present invention is a method for manufacturing any of the above-mentioned coil components, comprising, in any order, the steps of: forming the first magnetic portion; forming the second magnetic portion; and encapsulating a circumferential portion consisting of a circumferential conductor within a magnetic substrate containing the first magnetic portion and the second magnetic portion.

[0014] Also, according to the manufacturing method of the coil component according to one aspect of the present invention, the portion on the outer peripheral side of the circumferential portion in the magnetic substrate is formed of one type of material. Also, according to the manufacturing method of the coil component according to one aspect of the present invention, the binder that binds the first metal particles and the binder that binds the second metal particles are of the same component. Also, according to the manufacturing method of the coil component according to one aspect of the present invention, the binding of the first metal particles in the first magnetic portion and the binding of the second metal particles in the second magnetic portion are performed in the same process.

Effect of the Invention

[0015] According to the present invention, a coil component having good magnetic saturation characteristics can be obtained.

Brief Description of the Drawings

[0016] [Figure 1] It is a perspective view showing a coil component according to an embodiment of the present invention. [Figure 2] It is a cross-sectional view of the coil component shown in FIG. 1. [Figure 3] It is a view showing a coil component of a modified example. [Figure 4] It is a cross-sectional view of the magnetic substrate in the coil component shown in FIG. 1. [Figure 5] It is a schematic enlarged view showing the microscopic structure of the first magnetic portion. [Figure 6] It is a schematic enlarged view showing the microscopic structure of the second magnetic portion. [Figure 7] It is a view showing the first stage of the manufacturing process of the coil component. [Figure 8] It is a schematic enlarged view of region R1. [Figure 9] It is a view showing the second stage of the manufacturing process of the coil component. [Figure 10] It is a view showing the third stage of the manufacturing process of the coil component. [Figure 11] It is a schematic enlarged view of region R2. [Figure 12]This diagram shows the fourth stage of the coil component manufacturing process. [Figure 13] This figure shows the first step of the manufacturing process in the second embodiment. [Figure 14] This figure shows the second stage of the manufacturing process in the second embodiment. [Figure 15] This figure shows the third stage of the manufacturing process in the second embodiment. [Figure 16] This figure shows the fourth step of the manufacturing process in the second embodiment. [Figure 17] This figure shows the first step of the manufacturing process in the third embodiment. [Figure 18] This figure shows the second stage of the manufacturing process in the third embodiment. [Figure 19] This figure shows the third stage of the manufacturing process in the third embodiment. [Figure 20] This figure shows the fourth step of the manufacturing process in the third embodiment. [Figure 21] This figure shows the first step of the manufacturing process in the fourth embodiment. [Figure 22] This figure shows the second stage of the manufacturing process in the fourth embodiment. [Figure 23] This figure shows the third stage of the manufacturing process in the fourth embodiment. [Figure 24] This figure shows the first step of the manufacturing process in the fifth embodiment. [Figure 25] This figure shows the second stage of the manufacturing process in the fifth embodiment. [Figure 26] This figure shows the third stage of the manufacturing process in the fifth embodiment. [Figure 27] This figure shows the first step of the manufacturing process in the sixth embodiment. [Figure 28] This figure shows the second stage of the manufacturing process in the sixth embodiment. [Figure 29] This figure shows the third stage of the manufacturing process in the sixth embodiment. [Figure 30] This figure shows the fourth step of the manufacturing process in the sixth embodiment. [Figure 31]This figure shows the first step of the manufacturing process in the seventh embodiment. [Figure 32] This figure shows the second stage of the manufacturing process in the seventh embodiment. [Figure 33] This figure shows the third stage of the manufacturing process in the seventh embodiment. [Figure 34] This figure shows the fourth step of the manufacturing process in the seventh embodiment. [Figure 35] This figure shows the fifth step of the manufacturing process in the seventh embodiment. [Figure 36] This figure shows the sixth step of the manufacturing process in the seventh embodiment. [Figure 37] This figure shows the seventh step of the manufacturing process in the seventh embodiment. [Figure 38] This figure shows a modified example of the external electrode 12. [Modes for carrying out the invention]

[0017] The embodiments of the present invention will be described in detail below with reference to the attached drawings. Note that the following embodiments are not limiting to the present invention, and not all combinations of features described in the embodiments are necessarily essential to the configuration of the present invention. The configuration of the embodiments may be modified or changed as appropriate depending on the specifications and various conditions (operating conditions, operating environment, etc.) of the device to which the present invention is applied.

[0018] The technical scope of the present invention is defined by the claims and is not limited by the following individual embodiments. The drawings used in the following description may differ in scale and shape from the actual structure for the sake of clarity. Components shown in the previously described drawings may be referenced as appropriate in later descriptions of the drawings.

[0019] <Structure of coil components> Figure 1 is a perspective view showing a coil component according to one embodiment of the present invention. Figure 2 is a cross-sectional view of the coil component shown in Figure 1. Figure 2(A) shows a cross-section along line AA shown in Figure 1, and Figure 2(B) shows a cross-section along line BB shown in Figure 2(A). The coil component 1 is mounted on a substrate 2a. The substrate 2a is provided with, for example, two land portions 3. The coil component 1 has one magnetic substrate 11 and two external electrodes 12. The coil component 1 is mounted on the substrate 2a by soldering each external electrode 12 to the land portions 3. A circuit board 2 according to one embodiment of the present invention comprises the coil component 1 and a substrate 2a on which the coil component 1 is mounted. The circuit board 2 can be provided in various electronic devices. Examples of electronic devices equipped with the circuit board 2 include automotive electrical components, servers, board computers, and various other electronic devices. Coil component 1 may be an inductor, transformer, filter, reactor, or any other type of coil component. Coil component 1 may also be a coupled inductor, choke coil, or any other type of magnetically coupled coil component. Coil component 1 may be, for example, an inductor used in a DC / DC converter. The applications of coil component 1 are not limited to those expressed herein.

[0020] In this specification, unless otherwise understood in context, directions are described using the "L-axis," "W-axis," and "H-axis" directions of Figure 1 as reference, and are referred to as the "length," "width," and "height" directions, respectively. The "height" direction may also be referred to as the "thickness" direction.

[0021] The coil component 1 has a rectangular parallelepiped shape. Specifically, the coil component 1 has a first end face 1a and a second end face 1b at both ends in the length direction, a first main surface 1c (top surface 1c) and a second main surface 1d (bottom surface 1d) at both ends in the height direction, and a front surface 1e and a rear surface 1f at both ends in the width direction.

[0022] The first end face 1a, the second end face 1b, the first main face 1c, the second main face 1d, the front face 1e, and the rear face 1f of the coil component 1 may all be flat or curved surfaces. Furthermore, the eight corners and twelve edges of the coil component 1 may be rounded.

[0023] In this specification, even if the first end face 1a, the second end face 1b, the first main face 1c, the second main face 1d, the front face 1e, and part of the rear face 1f of the coil component 1 are curved, or if the corners or edges of the coil component 1 are rounded, such a shape may be referred to as a "rectangular parallelepiped shape." In other words, in this specification, "rectangular parallelepiped" or "rectangular parallelepiped shape" does not mean a "rectangular parallelepiped" in a mathematically strict sense.

[0024] In one embodiment of the present invention, the coil component 1 has a conductor 14 inside a magnetic substrate 11. The conductor 14 has a circumferential portion 14a that is routed inside the magnetic substrate 11 and an extended portion 14b that is drawn out from the circumferential portion 14a and connected to an external electrode 12.

[0025] The conductor 14 is formed from a wire having a metal wire such as Ag or Cu and an insulating coating provided on the surface of the metal wire. Alternatively, the conductor 14 is formed by covering a plated metal wire with an insulating coating. For example, if the number of turns in the circumferential portion 14a of the conductor 14 is one turn or more, and the lead-out portions 14b are provided at mutually opposing locations around the circumferential portion 14a, the number of turns will include less than one turn, such as 1.5 turns and 2.5 turns. In the example shown in Figure 2, the circumferential portion 14a consists of a wire that runs along the upper surface 1c and the bottom surface 1d of the coil component 1, forming a so-called horizontal winding structure.

[0026] As shown in Figure 2(B), the external electrode 12 is, for example, a so-called L-shaped electrode, formed in a portion extending from the bottom surface 1d to the first end surface 1a, and in a portion extending from the bottom surface 1d to the second end surface 1b. The external electrode 12 is formed from a metal such as Ag, Cu, Ti, Ni, or Sn, and for example, it is formed to a thickness of 1 to 5 μm. Alternatively, the external electrode 12 may be formed from a combination of multiple types of metal layers, with a total thickness of 5 to 10 μm. Furthermore, the external electrode 12 may be formed from a combination of metal layers that partially contain resin, with a total thickness of 10 to 20 μm.

[0027] The magnetic substrate 11 is formed from metal particles containing Fe, Ni, or Co. The magnetic substrate 11 may also contain resin, metal oxide, or ceramic material in addition to the metal particles. The metal particles forming the magnetic substrate 11 have soft magnetic properties and are also referred to as metallic magnetic particles. In addition to Fe, Ni, and Co, the metal particles may contain any of Si, Cr, Al, B, and P, or a combination of Si, Cr, Al, B, and P. The magnetic substrate 11 may also be formed from a combination of multiple types of metal particles.

[0028] Furthermore, the metal particles forming the magnetic substrate 11 are not particularly limited in shape, but are spherical or nearly spherical, with a particle size of, for example, 1 to 60 μm, and have a certain degree of particle size distribution. The metal particles may be insulated. If the magnetic substrate 11 contains other particles such as even smaller metal nanoparticles, metal oxides, or ceramic materials, the size of these other particles is 0.01 to 1 μm. When the magnetic substrate 11 contains other particles, these other particles contribute, for example, to reducing voids or supplementing mechanical strength, rather than enhancing the magnetic function.

[0029] The metal particles forming the magnetic substrate 11 are bound together by a binder such as a resin, metal oxide, or ceramic material. The magnetic substrate 11 contains 85 vol% or more of metal particles, and may contain 88 vol% or more, with the remainder being an insulating material other than metal particles. The magnetic substrate 11 may be a compacted powder in which metal particles are bonded together without a binder. The material of the magnetic substrate 11 is not limited to those expressed herein, and any known material can be used as the material of the magnetic substrate.

[0030] Coil component 1 has an external shape where one side is 4.0 mm or less, 2.0 mm or less, and 1.0 mm or less when viewed from the height direction H, and a height of 1.0 mm or less, 0.65 mm or less, and 0.5 mm or less. Furthermore, the external shape when viewed from the height direction H may be a square or a rectangle, and the height may be less than one side. In addition, if the external shape when viewed from the height direction H is a rectangle, the longer side is 3.0 mm or less, and 1.0 mm or less.

[0031] Here, we will describe a modified version of coil component 1. Figure 3 shows a modified example of coil component 1. The shape of the external electrode 12 of coil component 1 in Figure 3 is different from the shape of the external electrode 12 of coil component 1 in Figure 1. In the modified example, the coil component 1 has, for example, five-sided electrode type external electrodes 12 that cover both ends of the magnetic substrate 11 in the longitudinal direction L. The coil component 1 is mounted on the substrate 2a by soldering each external electrode 12 to the land portion 3. The circuit board 2 comprises the coil component 1 and the substrate 2a on which the coil component 1 is mounted.

[0032] Furthermore, the conductor 14 (not shown) inside the magnetic substrate 11 has a so-called vertical winding structure, which is wound around the first end face 1a and the second end face 1b of the coil component 1. The contribution of each part of the magnetic substrate 11 to the magnetic properties of the coil component 1 is mainly determined by its positional relationship with the peripheral portion 14a of the conductor 14. In other words, when parts of the magnetic substrate 11 are distinguished by their contribution to the magnetic properties, they are distinguished, for example, as the inner peripheral portion surrounded by the peripheral portion 14a or the outer peripheral portion surrounding the outside of the peripheral portion 14a, and this is the same whether the conductor 14 is wound horizontally or vertically. For this reason, the explanation below will continue with the example of horizontal winding shown in Figures 1 and 2.

[0033] <Structure of magnetic substrate> Figure 4 is a cross-sectional view of the magnetic substrate 11 in the coil component 1 shown in Figures 1 and 2. The cross-sectional view in Figure 4 shows the same cross-section as the cross-sectional view in Figure 2(B), but it is illustrated with a focus on the detailed structure of the magnetic substrate 11. The magnetic substrate 11 includes a first magnetic portion 11a and a second magnetic portion 11b, and encloses a circumferential portion 14a. In the example shown in Figure 4, the first magnetic portion 11a is provided on the outer circumference side of the circumferential portion 14a, and the second magnetic portion 11b is provided in a location other than the first magnetic portion 11a.

[0034] Figure 5 is a schematic enlarged view showing the microscopic structure of the first magnetic part 11a, and Figure 6 is a schematic enlarged view showing the microscopic structure of the second magnetic part 11b. The first magnetic portion 11a has a structure in which first metal particles 11c are bonded to each other. The first metal particles 11c have a particle size distribution, and the average particle size in this particle size distribution is 1 to 10 μm. The average particle size of the first metal particles 11c will be referred to as the first particle size below.

[0035] The second magnetic portion 11b has a structure in which second metal particles 11d are bonded to each other. The second metal particles 11d have a particle size distribution, and the average particle size in this particle size distribution is 5 to 20 μm. The average particle size of the second metal particles 11d will be referred to as the second particle size below. Since the second particle size is larger than the first particle size, the first magnetic part 11a has higher magnetic saturation characteristics compared to the second magnetic part 11b, and the second magnetic part 11b has higher relative permeability compared to the first magnetic part 11a.

[0036] The average particle size of the metal particles can be determined, for example, by a laser diffraction particle size distribution analyzer. Alternatively, the average particle size of the metal particles may be determined by observing the cross-section of the magnetic substrate 11 with an optical microscope, measuring particles larger than 1 μm, and calculating from the measurement results.

[0037] As shown in Figure 4, by providing the first magnetic part 11a on the outer circumference side of the circumferential part 14a, the magnetic saturation characteristics of the coil component 1 are improved. This improvement in magnetic saturation characteristics allows for a reduction in the area of ​​the magnetic substrate 11 on the outer circumference side of the circumferential part 14a, when viewed in a plane perpendicular to the coil axis of the circumferential part 14a, thus enabling miniaturization of the coil component 1. Furthermore, by having both the first magnetic part 11a and the second magnetic part 11b in the magnetic substrate 11, both improved magnetic saturation characteristics and the maintenance of high relative permeability are achieved, improving the performance of the coil component 1. In other words, the performance of the coil component 1 is maintained, thus enabling miniaturization of the coil component 1. At least a portion of the first magnetic part 11a needs to be provided on the outer circumference side of the circumferential part 14a; the other portion of the first magnetic part 11a may be provided on the inner circumference side of the circumferential part 14a.

[0038] The first magnetic portion 11a is preferably provided adjacent to the outer circumference of the circumferential portion 14a, as shown in Figure 4. Here, the outer circumference of the circumferential portion 14a means the area outside the circumferential portion 14a within the upper and lower range that appears to overlap with the circumferential portion 14a when viewed from the inside of the circumferential portion 14a. Furthermore, "adjacent" means that there is no other magnetic material between the circumferential portion 14a and the first magnetic portion 11a. Specifically, this includes cases where the circumferential portion 14a and the first magnetic portion 11a are in direct contact, or where they are in contact via an insulator. Since the area adjacent to the outer circumference of the circumferential portion 14a is an area where magnetic fields easily pass through, providing the first magnetic portion 11a at this location improves the magnetic saturation characteristics of the coil component 1.

[0039] It is desirable that the first magnetic portion 11a be provided on the outer circumference of the circumferential portion 14a, extending over its entire circumference. In other words, the first magnetic portion 11a is provided over the entire surface of the circumferential portion 14a when viewed from the inner circumference to the outer circumference. To put it another way, the first magnetic portion 11a is provided surrounding the outer circumference of the circumferential portion 14a. By providing the first magnetic portion 11a over its entire circumference, the magnetic saturation characteristics are maintained over the entire circumference, further improving the magnetic saturation characteristics of the coil component 1.

[0040] On the outer circumference of the circumferential portion 14a, it is desirable that the proportion of the first magnetic portion 11a be 50% or more. Here, "proportion of 50% or more" means, for example, that the first magnetic portion 11a accounts for 50% or more of the volume of the magnetic substrate 11 on the outer circumference of the circumferential portion, with the volume of the magnetic substrate 11 on the outer circumference being 100%. By having the proportion of the first magnetic portion 11a be 50% or more, the magnetic saturation characteristics of the coil component 1 are maintained.

[0041] Regarding the portion of the magnetic substrate 11 on the outer circumference side of the circumferential portion 14a, it is desirable to provide the first magnetic portion 11a between the circumferential portion 14a and the external electrode 12, as this increases the insulation between the circumferential portion 14a and the external electrode 12. Providing it between the circumferential portion 14a and the external electrode 12 means that the first magnetic portion 11a exists between the parts of the external electrode 12 and the circumferential portion 14a that are connected by the shortest distance. For example, if the external electrode 12 is provided on end faces 1a and 1b, the first magnetic portion 11a exists in the region enclosed by the line connecting the entire outer circumference of the external electrode 12 and the circumferential portion 14a by the shortest distance, covering the entire circumferential portion 14a within this region.

[0042] Furthermore, among the portions of the magnetic substrate 11 located on the outer circumference of the circumferential portion 14a, the portion with the thinnest thickness in the direction of approaching or receding from the circumferential portion 14a (for example, the portion shown in Figure 4) is the portion that has the greatest influence on the magnetic properties of the coil component 1. For this reason, it is particularly desirable that the arrangement of the first magnetic portion 11a described above be realized at the portion of the magnetic substrate 11 with the thinnest thickness. The portion of the magnetic substrate 11 with the thinnest thickness is, for example, 0.1 mm or less, and even 0.05 mm or less.

[0043] The magnetic substrate 11 may have a third magnetic part (not shown) in addition to the first magnetic part 11a and the second magnetic part 11b. The magnetic material of the third magnetic part may be a magnetic material with the same components as the first magnetic part 11a, a magnetic material with the same components as the second magnetic part 11b, or a magnetic material with different components from both the first magnetic part 11a and the second magnetic part 11b.

[0044] <Manufacturing method for coil components> The following describes the manufacturing method of the coil component 1, focusing on the process of manufacturing the magnetic substrate 11. The magnetic substrate 11 is made from a molded body formed by compression molding or warm molding of a composite material in which metal particles and resin are mixed to form the first magnetic part 11a and the second magnetic part 11b, respectively. Hereinafter, the formation by compression molding or warm molding will simply be referred to as "molding". The pressure during molding of the magnetic substrate 11 is 10 MPa to 1 GPa, and the temperature is 10 to 200°C.

[0045] In the manufacturing of the magnetic substrate 11, the molding of the molded body may involve a combination of pressure and heat. The combination of pressure and heat makes it possible to mold at relatively low pressures of 10 to 100 MPa. Examples of molding methods that combine pressure and heat include sheet molding and transfer molding. In the molding of the molded body in the manufacturing of the magnetic substrate 11, composite materials for the first magnetic part 11a and the second magnetic part 11b are prepared by a particle size formulation method in which multiple types of metal particles with different particle sizes are combined, thereby obtaining the first magnetic part 11a and the second magnetic part 11b having the desired particle size. That is, a first composite material containing first metal particles 11c with an average particle size of the first particle size and a second composite material containing second metal particles 11d with an average particle size of the second particle size are prepared by particle size formulation. The first composite material is used for molding the first magnetic part 11a, and the second composite material is used for molding the second magnetic part 11b. In the molding of the first composite material and the second composite material, it is desirable that the binder, such as resin, has the same component. By having the same component binder, the first magnetic part 11a and the second magnetic part 11b are combined and bonded more reliably than when the components are different.

[0046] Alternatively, in the molding of the molded body during the manufacture of the magnetic substrate 11, a first magnetic part 11a and a second magnetic part 11b having the desired particle size can also be obtained by a flow control method that adjusts the molding thickness and the size of the metal particles, for example. That is, during molding, the flow is restricted for the larger metal particles in areas with a small molding thickness, so the proportion of larger metal particles in the areas with a small molding thickness is reduced. Specifically, the first magnetic part 11a is molded to a thickness of less than three times the average particle size of the metal particles contained in the composite material, and the second magnetic part 11b is molded to a thickness of three times or more the average particle size.

[0047] The specific manufacturing process for coil component 1 will be explained below, with reference to the diagram. Figures 7 to 12 illustrate the manufacturing process of coil component 1. Figures 7, 9, and 10 show a top view (A) and a cross-sectional view (B) along the CC line in the top view (A). Figure 8 shows a schematic enlarged view of region R1 shown in Figure 7, and Figure 11 shows a schematic enlarged view of region R2 shown in Figure 10. Figure 12 shows a cross-sectional view corresponding to the cross-sectional view shown in Figure 2(B). In one example of a specific manufacturing process for the coil component 1, the magnetic substrate 11 is formed in two parts: a bottom portion 111 on the bottom surface 1d side of the coil component 1, and an upper portion 112 on the top surface 1c side of the coil component 1.

[0048] For example, as shown in Figure 7, the bottom portion 111 is formed first. The bottom portion 111 has a bottom plate portion 111a that extends along the bottom surface 1d of the coil component 1, and a projection portion 111b that protrudes in an elliptical shape from the bottom plate portion 111a toward the upper surface 1c of the coil component 1. The elliptical shape of the projection portion 111b is such that the surrounding portion 14a of the conductor 14 fits perfectly inside.

[0049] The bottom portion 111 is formed by filling a mold corresponding to the shapes of the bottom plate portion 111a and the protruding portion 111b with the composite material. For example, when the bottom portion 111 is formed by a flow control method, the metal particles contained in the composite material are second metal particles 11d with an average particle size of the second particle size, and the bottom plate portion 111a becomes a second magnetic portion 11b to which the second metal particles 11d are bonded.

[0050] On the other hand, the thickness d1 (Figure 8) of the protrusion 111b is formed to be less than three times the second particle size, and the flow of larger particles among the second metal particles 11d is restricted. In other words, in the mold portion corresponding to the protrusion 111b with thickness d1, small-particle metal particles flow in without restriction, while the flow of large-particle metal particles is restricted. As a result, the particle size distribution of the metal particles forming the protrusion 111b changes from the particle size distribution of the second metal particles 11d, and the protrusion 111b becomes a first magnetic portion 11a to which first metal particles 11c with an average particle size smaller than the second particle size are bonded. In the molding of the bottom portion 111, the bonding of metal particles in the first magnetic portion 11a and the bonding of metal particles in the second magnetic portion 11b are performed in the same process (for example, a pressurizing process). As a result, the first magnetic portion 11a and the second magnetic portion 11b are reliably integrated.

[0051] In forming the bottom portion 111, the bonding of the first metal particles 11c and the second metal particles 11d may be achieved by heat treatment. Bonding of the metal particles by heat treatment increases the strength of the bottom portion 111 and strengthens the bond between the bottom plate portion 111a and the protruding portion 111b (i.e., the bond between the first magnetic portion 11a and the second magnetic portion 11b). As shown in Figure 9, the conductor 14 is positioned inside the elliptical projection 111b of the molded body at the bottom 111. For convenience, in the following descriptions, only the circumferential portion 14a may be shown as a representative of the conductor 14. With the arrangement of the conductor 14 shown in Figure 9, the projection 111b is in contact with the outer circumference of the circumferential portion 14a and surrounds the entire circumference of the circumferential portion 14a.

[0052] Subsequently, as shown in Figure 10, the upper part 112 is formed on the bottom part 111 and the conductor 14 to obtain a molded body 110 that is integrated with the conductor 14. This molded body 110 becomes the magnetic substrate 11. The upper part 112 has an upper plate portion 112a that extends along the upper surface 1c of the coil component 1, and a core portion 112b and an outer edge portion 112c that protrude from the upper plate portion 112a toward the bottom surface 1d. The core portion 112b protrudes from the upper plate portion 112a on the inner circumference side of the circumferential portion 14a, and the outer edge portion 112c protrudes from the upper plate portion 112a on the outer circumference side of the circumferential portion 14a.

[0053] For example, a mold having the shape of the upper surface 1c side of the upper part 112 is placed over the bottom part 111 and the conductor 14, and the composite material is filled into the mold to form the upper part 112. In forming the upper part 112, no particular thickness limit is set, and it is formed to a sufficient thickness of at least three times the thickness of the second grain size. That is, even in the thinnest region R2 of the upper part 112, the thickness d2 is at least three times the second grain size. Therefore, as shown in Figure 11, the entire upper part 112, including the thinnest part of the outer edge 112c, becomes the second magnetic part 11b to which the second metal particles 11d are bonded. In this way, by forming the magnetic substrate 11, which includes the first magnetic part 11a and the second magnetic part 11b, from the same composite material (i.e., one type of material), the number of types of metal particles used in the composite material is minimized, and cost increases are suppressed.

[0054] In the example described above, the bottom 111 and the top 112 are molded from the same composite material, but the bottom 111 and the top 112 may be molded from different composite materials. For example, the bottom 111 may be molded from a composite material containing first metal particles 11c, and the top 112 may be molded from a composite material containing second metal particles 11d. In this case, the entire bottom 111 becomes the first magnetic part 11a, and the top 112 becomes the second magnetic part 11b. In this case, the first magnetic portion 11a may be formed to be thicker than the second magnetic portion 11b on the outer circumference of the circumferential portion 14a, and the first magnetic portion 11a may occupy more than half of the thickness of the magnetic substrate 11 on the outer circumference of the circumferential portion 14a.

[0055] The molded body 110, which forms the magnetic substrate 11 and is integrated with the conductor 14, may be subjected to further heat treatment. Heat treatment strengthens the bond between the bottom portion 111 and the upper portion 112, improving the integration between the conductor 14 and the magnetic substrate 11. After a magnetic substrate 11 integrated with the conductor 14 is obtained, as shown in Figure 12, an external electrode 12 is formed on the outer surface of the magnetic substrate 11 to obtain a coil component 1. The external electrode 12 is made of the above-mentioned material such as Ag or Cu, and is formed on the surface of the magnetic substrate 11 by methods such as paste printing, film formation by sputtering or plating, or adhesion of metal foil. Alternatively, a portion of the external electrode 12 may be provided before heat treatment of the magnetic substrate 11.

[0056] According to the manufacturing process shown in Figures 7 to 12, a magnetic substrate 11 having a first magnetic part 11a and a second magnetic part 11b is obtained by molding, and integration with the conductor 14 is also achieved by molding. Therefore, integration is reliably achieved without adding any assembly processes.

[0057] The molded body 110 of the magnetic substrate 11 can be further improved in terms of mechanical strength by heat treatment. Furthermore, any part of the magnetic substrate 11, conductor 14, and external electrode 12 may be processed after formation. For example, a part of the lead portion 14b of the conductor 14 may be processed and exposed from the surface of the magnetic substrate 11. Alternatively, for example, the surface of the magnetic substrate 11 may be processed to create the formation surface for the external electrode 12. In addition, according to the manufacturing process shown in Figures 7 to 12, the arrangement and dimensions of the first magnetic part 11a and the second magnetic part 11b can be easily changed.

[0058] <Other Embodiments> The following description focuses on the differences between other embodiments of coil component 1 and the manufacturing processes shown in Figures 7 to 12. Figures 13 to 16 show the manufacturing process of the coil component 1 in the second embodiment. Each of Figures 13 to 15 shows a top view (A) and a cross-sectional view (B) showing a cross-section along the CC line in the top view (A). Figure 16 shows a cross-sectional view corresponding to the cross-sectional view in Figure 12. In the second embodiment, the bottom portion 111 of the magnetic substrate 11 has elliptical projections 111b protruding from the bottom plate portion 111a on both the outer and inner sides of the circumferential portion 14a. Both the outer and inner projections 111b have a thickness of, for example, less than three times the second particle size, and constitute the first magnetic portion 11a. In other words, in the second embodiment, the first magnetic portion 11a is provided on both the outer and inner sides of the circumferential portion 14a.

[0059] In the second embodiment, as shown in Figure 14, the conductor 14 is positioned on the molded body of the bottom portion 111 such that the circumferential portion 14a fits between the outer and inner circumferential portions 14a. Then, as shown in Figure 15, the upper portion 112 is molded on the bottom portion 111 and the conductor 14 to obtain a molded body 110 that is integrated with the conductor 14 and becomes a magnetic substrate 11. In the second embodiment, as in the first embodiment, the upper portion 112 has an upper plate portion 112a, a core portion 112b, and an outer edge portion 112c. In the second embodiment, the core portion 112b is located further inward from the protruding portion 111b located on the inner circumferential side of the circumferential portion 14a. In the second embodiment as well, the upper part 112 has no thickness limit, and its thickness, including the thinnest part, is more than three times the second particle size. Therefore, the entire upper part 112 becomes the second magnetic part 11b.

[0060] In the second embodiment as well, an external electrode 12 is formed on the outer surface of a magnetic substrate 11 integrally molded with a conductor 14, as shown in Figure 16, to obtain a coil component 1. In the second embodiment as well, the coil component 1 has high magnetic saturation characteristics and high inductance characteristics, and miniaturization is possible while maintaining the performance of the coil component 1.

[0061] Figures 17 to 20 show the manufacturing process of the coil component 1 in the third embodiment. Each of Figures 17 to 19 shows a top view (A) and a cross-sectional view (B) showing a cross-section along the CC line in the top view (A). Figure 20 shows a cross-sectional view corresponding to the cross-sectional view in Figure 12.

[0062] In the third embodiment, the bottom portion 111 of the magnetic substrate 11 has an elliptical projection 111b protruding from the bottom plate portion 111a, as well as a core portion 111c protruding to the inner circumference side of the circumferential portion 14a. In the third embodiment as well, the projection 111b has a thickness of, for example, less than three times the second particle size, and becomes the first magnetic portion 11a. On the other hand, the core portion 111c becomes the second magnetic portion 11b.

[0063] In the third embodiment, as shown in Figure 18, the conductor 14 is positioned on the molded body of the bottom portion 111 such that the circumferential portion 14a fits between the protruding portion 111b and the core portion 111c. Then, as shown in Figure 19, the upper portion 112 is molded on the bottom portion 111 and the conductor 14 to obtain a molded body 110 which is an integral part of the conductor 14 and becomes a magnetic substrate 11. In the third embodiment, the upper portion 112 has an upper plate portion 112a and an outer edge portion 112c, and does not have a core portion. In the third embodiment as well, there is no limit to the thickness of the upper portion 112, and the thickness, including the thinnest part, is three times or more the second particle size. Therefore, the entire upper portion 112 becomes the second magnetic portion 11b.

[0064] In the third embodiment as well, an external electrode 12 is formed on the outer surface of a magnetic substrate 11 integrally molded with the conductor 14, as shown in Figure 20, to obtain the coil component 1. In the third embodiment as well, the coil component 1 has high magnetic saturation characteristics and high inductance characteristics, and miniaturization is possible while maintaining the performance of the coil component 1.

[0065] Figures 21 to 23 show the manufacturing process of the coil component 1 in the fourth embodiment. Each of Figures 21 to 23 shows a top view (A) and a cross-sectional view (B) showing a cross-section along the CC line in the top view (A). In the fourth embodiment, a coil component 1 having a structure similar to that of the third embodiment is manufactured using a different manufacturing process than that of the third embodiment.

[0066] In the fourth embodiment, as shown in Figure 21, a mold 40 for forming the bottom portion 111 is prepared and the conductor 14 is placed inside the mold 40. Then, as shown in Figure 22, the bottom portion 111 having a bottom plate portion 111a, a protruding portion 111b, and a core portion 111c is formed. During this forming, the thickness of the protruding portion 111b is set by the gap between the mold 40 and the circumferential portion 14a. Note that the bottom portion 111 is shown in an inverted state with the bottom surface 1d facing upwards.

[0067] In the fourth embodiment, the bottom portion 111 is molded with the conductor 14 inside the mold 40, resulting in a higher degree of integration between the bottom portion 111 and the conductor 14 compared to the third embodiment. The molded body, with the bottom portion 111 and the conductor 14 integrated, is removed from the mold 40 and inverted. Subsequently, as shown in Figure 23, an upper part 112 similar to that of the third embodiment is molded onto the molded body in which the bottom part 111 and the conductor 14 are integrated, thereby obtaining a molded body 110 that becomes a magnetic substrate 11, integrated with the conductor 14. In the fourth embodiment, an external electrode 12 is also formed to obtain a coil component 1 (not shown).

[0068] In the manufacturing process of the fourth embodiment, a coil component 1 with the same structure as in the third embodiment can be manufactured. Furthermore, in the fourth embodiment, the integration between the conductor 14 and the magnetic substrate 11 is higher compared to the third embodiment.

[0069] Figures 24 to 26 show the manufacturing process of the coil component 1 in the fifth embodiment. Each of Figures 24 to 26 shows a top view (A) and a cross-sectional view (B) showing a cross-section along the CC line in the top view (A). In the fourth embodiment, a coil component 1 having a structure similar to that of the first embodiment is manufactured using a different manufacturing process than that of the first embodiment. In the fifth embodiment, as shown in Figure 24, the upper part 112 is formed first. The upper part 112 is formed by filling a mold corresponding to the shapes of the upper plate portion 112a, the core portion 112b, and the outer edge portion 112c with the composite material. Note that the upper part 112 is shown in an inverted state with the upper surface 1c facing downwards.

[0070] In the fifth embodiment, the conductor 14 is positioned on the molded upper part 112 as shown in Figure 25. That is, the core portion 112b of the upper part 112 is inserted inside the circumferential portion 14a of the conductor 14, and the conductor 14 is housed in the molded upper part 112. Then, as shown in Figure 26, the bottom portion 111 is molded on the upper part 112 and the conductor 14, and a molded body 110 which becomes a magnetic substrate 11, integrated with the conductor 14, is obtained. In the fifth embodiment, the thickness of the protrusion 111b is set by the gap between the outer edge portion 112c of the upper part 112 and the circumferential portion 14a. Also in the fifth embodiment, an external electrode 12 is formed to obtain a coil component 1 (not shown).

[0071] In the manufacturing process of the fifth embodiment, a coil component 1 with the same structure as in the first embodiment can be manufactured. According to the manufacturing process of the fifth embodiment, the adhesion between the protruding portion 111b which becomes the first magnetic portion 11a and the peripheral portion 14a of the conductor 14 is high, and the magnetic properties of the coil component 1 are stable.

[0072] Figures 27 to 30 show the manufacturing process of the coil component 1 in the sixth embodiment. Figures 27 to 29 each show a top view (A) and a cross-sectional view (B) showing a cross-section along the CC line in the top view (A). Figure 30 shows a cross-sectional view corresponding to the cross-sectional view in Figure 12. In the sixth embodiment, as shown in Figure 27, the upper part 112 is formed first. The upper part 112 in the sixth embodiment has an upper plate portion 112a and a core portion 112b. Then, as shown in Figure 28, the conductor 14 is placed on the molded body of the upper part 112. That is, the core portion 112b of the upper part 112 is inserted inside the peripheral portion 14a of the conductor 14, and the conductor 14 is placed on the molded body of the upper part 112.

[0073] In the sixth embodiment, as shown in Figure 29, the bottom portion 111 is molded on the upper portion 112 on which the conductor 14 is arranged, to obtain a molded body 110 which is a magnetic substrate 11 integrated with the conductor 14. In the sixth embodiment, the upper portion 112 is molded from the second composite material, and the bottom portion 111 is molded from the first composite material. As a result, the entire bottom portion 111 becomes the first magnetic portion 11a, and the entire outer circumference of the circumferential portion 14a becomes the first magnetic portion 11a, so high magnetic saturation characteristics can be obtained. In the sixth embodiment, as shown in Figure 30, an external electrode 12 is formed on the outer surface of the magnetic substrate 11 which is integrally molded with the conductor 14 to obtain the coil component 1.

[0074] Figures 31 to 37 show the manufacturing process of the coil component 1 in the seventh embodiment. Each of Figures 31 to 34 shows a top view (A) and a cross-sectional view (B) showing a cross-section along the CC line in the top view (A). In the seventh embodiment, the conductor 14 and the magnetic substrate 11 are formed by a lamination method. For example, as shown in Figure 31, first, a magnetic sheet 115 made of the second composite material is prepared. Then, as shown in Figure 32, a planar conductor pattern 141 for forming the conductor 14 is created on the surface of the magnetic sheet 115 by printing, for example (screen printing, inkjet printing, gravure printing). Methods other than printing, such as plating, vapor deposition, or paste transfer, may be used to form the conductor pattern 141.

[0075] Furthermore, holes (not shown) are made in the magnetic sheet 115 for forming connecting conductors that connect the conductor patterns 141 between sheets, and these holes are filled with a conductor material. The connecting conductors are made, for example, by printing or filling. The printing of the connecting conductors may be performed simultaneously with the printing of the conductor patterns 141 or separately. Methods other than printing, such as plating, vapor deposition, or paste transfer, may also be used to form the connecting conductors.

[0076] Next, regarding the magnetic sheet 115 on which the conductor pattern 141 is formed, as shown in Figure 33, the inner circumference of the conductor pattern 141 is filled with the second composite material to form the core portion 116. Also, as shown in Figure 34, the outer circumference of the conductor pattern 141 is filled with the first composite material to form the outer edge portion 117. Therefore, in the seventh embodiment, the magnetic sheet 115 and the core portion 116 become the second magnetic portion 11b, and the outer edge portion 117 becomes the first magnetic portion 11a.

[0077] Multiple layers of the "single layer" structure obtained through the process shown in Figures 31 to 34 are prepared. However, as shown in Figure 35, for example, the shape of the conductor pattern 141 in each layer is different so that the conductor pattern 141 is connected in a spiral. Then, as shown in Figure 36, these multiple layers are stacked on top of each other, and other magnetic sheets 118 are stacked on top of and below, and then compressed to obtain a laminate 150.

[0078] Then, the resulting laminate 150 is subjected to heat treatment to obtain a magnetic substrate 11 containing the conductor 14. In the heat treatment of the laminate 150, the resin may be removed by thermal decomposition at a temperature of 600 to 850°C, and an oxide may be formed on the surface of the metal magnetic particles.

[0079] Subsequently, as shown in Figure 37, an external electrode 12 connected to the conductor 14 is formed on the outer surface of the laminate 150 (magnetic substrate 11) to obtain the coil component 1. It is desirable that a magnetic layer 119 made of the first composite material is provided between the conductor pattern 141 and the external electrode 12 in the laminate 150 (magnetic substrate 11). The magnetic layer 119 made of the first composite material becomes the first magnetic part 11a and contributes to improving the insulation between the conductor pattern 141 and the external electrode 12.

[0080] Figure 38 shows a modified example of the external electrode 12. The external electrodes 12 formed on the outer surface of the laminate 150 (magnetic substrate 11) may be external electrodes 12 that reach above and below the laminate 150 (magnetic substrate 11). When such external electrodes 12 are provided, it is desirable that the magnetic layer 119 made of the first composite material be provided above and below the conductor pattern 141. [Explanation of symbols]

[0081] 1. Coil component 2 Circuit boards 2a board 3 Land Section 11 Magnetic substrate 11a 1st magnetic part 11b Second magnetic part 11c 1st metal particle 11d Second metal particles 110 Molded body 111 Bottom 112 Top 111a Bottom plate part 111b Protrusion 111c core 112a Upper plate section 112b Core 112c Outer edge 115 Magnetic Sheet 116 Core 117 Outer edge 118 Magnetic Sheets 119 Magnetic layer 12 External electrode 14 Conductors 14a Loop section 14b Drawer part 141 Conductor Pattern 150-layer structure

Claims

1. A circular section consisting of a conductor, A magnetic substrate having a first magnetic portion formed by bonding first metal particles having an average particle size of a first particle size, and a second magnetic portion formed by bonding second metal particles having an average particle size of a second particle size, and enclosing the circumferential portion, wherein the second particle size is larger than the first particle size, and at least a part of the first magnetic portion is included on the outer circumference side of the circumferential portion, Equipped with, A coil component characterized in that the first magnetic portion is provided over the entire circumference adjacent to the outer periphery of the circumferential portion, which is a part of the periphery of the circumferential portion, and the second magnetic portion is provided in a location other than the first magnetic portion, including the outer periphery of the first magnetic portion provided on the outer periphery of the circumferential portion.

2. The coil component according to claim 1, characterized in that the first magnetic portion occupies more than half of the volume of the magnetic substrate on the outer circumference side of the circumferential portion.

3. The coil component according to claim 1 or 2, characterized in that the first magnetic portion is provided between the circumferential portion and the external electrode.

4. The coil component according to any one of claims 1 to 3, characterized in that the longest side of the external shape is 1.0 mm or less.

5. A coil component according to any one of claims 1 to 4, A circuit board characterized by comprising a substrate on which the coil component is mounted.

6. An electronic device characterized by comprising the circuit board described in claim 5.

7. A manufacturing method for producing a coil component according to any one of claims 1 to 4, The process of forming the molded body of the first magnetic part, A step of forming the molded body of the aforementioned two magnetic parts, A process for creating a magnetic substrate in which a circumferential portion consisting of a circumferential conductor is enclosed within the molded bodies of the first magnetic portion and the second magnetic portion, A method for manufacturing a coil component, characterized by having the elements in any order.

8. The method for manufacturing a coil component according to claim 7, characterized in that the portion of the magnetic substrate on the outer periphery side of the circumferential portion is formed of a single type of material.

9. A method for manufacturing a coil component according to claim 7 or 8, characterized in that the binder for bonding the first metal particles and the binder for bonding the second metal particles have the same component.

10. The method for manufacturing a coil component according to claim 9, characterized in that the bonding of the first metal particles in the first magnetic part and the bonding of the second metal particles in the second magnetic part are performed in the same process.

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