Coil component and method of manufacturing the same

Abstract

The present invention provides a coil component and a method for manufacturing the same. The magnetic body of the coil component includes, as soft magnetic alloy particles: a first particle whose alloy components are substantially composed of Fe, Si, and Cr; and a second particle whose alloy components contain Fe and Si and an element other than Si and Cr that is more easily oxidized than Fe. The average particle size of the second particle is smaller than the average particle size of the first particle. The first particle has an amorphous oxide film containing Si and Cr on its surface, and the second particle has a layer of crystalline oxide containing the element other than Si and Cr that is more easily oxidized than Fe on its surface. The crystalline oxide forms a joint extending between a plurality of the first particles. The coil component of the present invention has improved mechanical strength.

Description

Technical Field

[0001] The present invention relates to a coil component and a method for manufacturing the same. Background Art

[0002] In coil components, fundamental properties such as inductance are determined by the combination of the magnetic body and conductor. In particular, the magnetic material that constitutes the magnetic body significantly influences the coil component's properties, so the appropriate material is typically selected based on the coil component's structure and operating environment. For example, automotive coil components are required to operate at high voltages, so ferrite-based magnetic materials with superior dielectric strength are often used.

[0003] However, in recent years, metallic magnetic materials have begun to be used in place of ferrites in automotive coil components. This is because metallic magnetic materials are less susceptible to magnetic saturation than ferrites, allowing for miniaturization of coil components. In recent years, with the increasing electrification of automobiles, the number of electronic components used has tended to increase. On the other hand, due to the limited space available for electronic components and the substrates on which they are mounted, miniaturization of each electronic component is required. Therefore, in response to this demand, coil components made of metallic magnetic materials have begun to be used.

[0004] Metal magnetic materials have an advantage over ferrites in being less susceptible to magnetic saturation, but they lack electrical insulation. Consequently, magnetic bodies made of metal magnetic materials can become electrically conductive under high voltages. Magnetic bodies made of metal magnetic materials are composed of metal magnetic particles in contact with each other. Therefore, various methods focusing on electrically insulating the surfaces of metal magnetic particles have been studied as technologies to improve the electrical insulation properties of these magnetic bodies.

[0005] Furthermore, because automotive coil components are subject to vibration and temperature fluctuations, the magnetic bodies that comprise them also require high mechanical strength and durability. The mechanical strength and durability of magnetic bodies made of metallic magnetic materials are primarily achieved through the bonding of the metal magnetic particles. Therefore, it is known that this bonding is achieved while electrically insulating the surfaces of the metal magnetic particles.

[0006] For example, Patent Document 1 discloses a technology in which a molded body of soft magnetic alloy particles containing iron, silicon, and an element more easily oxidized than iron is heat-treated in the atmosphere to form an oxide layer composed of metal oxide on the surface of the particles, and the particles are bonded to each other via the oxide layer.

[0007] Patent Document 2 discloses a technique in which the surface of Fe-Si-Cr soft magnetic alloy powder particles is covered or attached with a Si compound such as TEOS or colloidal silica, and after forming, heat-treated in the atmosphere to bond the particles to each other via an oxide phase.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-249774

[0011] Patent Document 2: Japanese Patent Application Laid-Open No. 2015-126047 Summary of the Invention

[0012] Technical problem to be solved by the invention

[0013] According to the above-mentioned various technologies, a magnetic body and a coil component having excellent mechanical strength can be obtained. However, there is a demand for further improvement in the mechanical strength of the magnetic body and / or the coil component.

[0014] Therefore, an object of the present invention is to provide a coil component having improved mechanical strength.

[0015] Technical solutions to technical problems

[0016] The present inventors have conducted various studies to achieve the above-mentioned object, and have found that a coil component having the following features [1] to [4] exhibits high mechanical strength, thereby completing the present invention.

[0017] [1] The magnetic material is composed of two types of soft magnetic alloy particles, large and small.

[0018] [2] An amorphous oxide film containing Si is formed on the surface of soft magnetic alloy particles having a relatively large particle size.

[0019] [3] A crystalline oxide layer is formed on the surface of soft magnetic alloy particles having a small particle size.

[0020] [4] The crystalline oxide forms a junction extending between a plurality of soft magnetic alloy particles having a relatively large particle size.

[0021] That is, the first embodiment of the present invention for solving the above-mentioned technical problems is a coil component, which includes a magnetic body containing soft magnetic alloy particles and a conductor arranged inside or on the surface of the magnetic body, and the coil component is characterized in that: the above-mentioned magnetic body includes, as soft magnetic alloy particles: a first particle, whose alloy components are essentially composed of Fe, Si and Cr; and a second particle, whose alloy components contain Fe and Si and elements other than Si and Cr that are more easily oxidized than Fe, the average particle size of the above-mentioned second particles is smaller than the average particle size of the above-mentioned first particles, the above-mentioned first particles have an amorphous oxide film containing Si and Cr on their surfaces, the above-mentioned second particles have a layer of crystalline oxide containing elements other than Si and Cr that are more easily oxidized than Fe on their surfaces, and the above-mentioned crystalline oxide forms a junction extending to multiple above-mentioned first particles.

[0022] A second embodiment of the present invention is a method for manufacturing a coil component, the coil component including a magnetic body containing soft magnetic alloy particles and a conductor disposed within or on the surface of the magnetic body. The method for manufacturing the coil component is characterized by comprising:

[0023] (a) preparing a first powder and a second powder as soft magnetic alloy powders, wherein the alloy composition of the first powder consists essentially of Fe, Si, and Cr, and the second powder contains Fe and Si and an element other than Si and Cr that is more easily oxidized than Fe as alloy components, and has an average particle size smaller than that of the first powder;

[0024] (d) a step of mixing the first powder and the second powder to obtain a mixed powder;

[0025] (e) forming the mixed powder obtained in the above (d) to obtain a compact;

[0026] (f) a step of heat-treating the molded body obtained in the above (e) at a temperature of 500° C. to 900° C. in an atmosphere having an oxygen concentration of 10 ppm to 800 ppm to obtain a magnetic body; and

[0027] (g) performing at least one of the following steps (1) and (2): (1) in the above step (e), configuring a conductor or a precursor thereof inside or on the surface of the above-mentioned formed body; (2) after performing the above step (f), configuring a conductor on the surface of the above-mentioned magnetic body.

[0028] Furthermore, a third embodiment of the present invention is a circuit board on which the above-mentioned coil component is mounted.

[0029] Effects of the Invention

[0030] According to the present invention, a coil component having improved mechanical strength can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is an explanatory diagram of the microstructure of the magnetic body (the contact state of different types of particles) in the coil component according to one embodiment of the present invention.

[0032] Figure 2 This is an explanatory diagram showing a step of confirming that the insulating layer is amorphous in the present invention.

[0033] Figure 3 It is an explanatory diagram of the microstructure of the magnetic body (the contact state between the first particles) in the coil component according to one embodiment of the present invention.

[0034] Figure 4 This is an explanatory diagram showing a state in which first particles are joined to each other via a joining portion in a magnetic body in a coil component according to one embodiment of the present invention.

[0035] Figure 5 This is an explanatory diagram showing a state in which the gaps between particles are filled with a joint portion in a magnetic body in a coil component according to one embodiment of the present invention.

[0036] Figure 6 Schematic diagrams showing the appearance of coil components produced in Examples and Comparative Examples of the present invention.

[0037] Figure 7 It is a schematic diagram showing the state of support and load of the test piece in the three-point bending test performed in Examples and Comparative Examples of the present invention.

[0038] Description of Reference Numerals

[0039] 1 Coil components

[0040] 2 Magnetic body

[0041] 21 The first particle

[0042] 211 alloy part (first particle)

[0043] 212 Amorphous oxide film

[0044] 22 The second particle

[0045] 221 Alloy part (of the second particle)

[0046] 222 Crystalline oxide layer

[0047] 23 Joint

[0048] 3 External electrodes DETAILED DESCRIPTION

[0049] Hereinafter, with reference to the accompanying drawings, the structure and effects of the present invention will be described in conjunction with the technical ideas. However, the mechanism of action includes inferences, and whether or not they are correct does not limit the present invention. In addition, among the constituent elements of the following embodiments, constituent elements that are not recorded in the independent claims representing the highest concept can be described as arbitrary constituent elements. In addition, the description of the numerical range (the description of two numerical values ​​connected by "~") is intended to include the numerical values ​​recorded as the upper limit and the lower limit.

[0050] [Coil parts]

[0051] The coil component of the first embodiment of the present invention (hereinafter sometimes simply referred to as the "first embodiment") includes: a magnetic body containing soft magnetic alloy particles; and a conductor arranged inside or on the surface of the magnetic body. In the above-mentioned magnetic body, the soft magnetic alloy particles include: a first particle whose alloy components are essentially composed of Fe, Si and Cr; and a second particle whose alloy components contain Fe and Si and elements other than Si and Cr that are more easily oxidized than Fe. In addition, the average particle size of the above-mentioned second particles is smaller than the average particle size of the above-mentioned first particles. In addition, the above-mentioned first particles have an amorphous oxide film containing Si and Cr on their surfaces, and the above-mentioned second particles have a layer of crystalline oxide whose main component is elements other than Si and Cr that are more easily oxidized than Fe on their surfaces. In addition, the above-mentioned crystalline oxide forms a junction extending to a plurality of the above-mentioned first particles.

[0052] Hereinafter, the magnetic body and the conductor according to the first embodiment will be described in detail.

[0053] <About Magnetic Materials>

[0054] like Figure 1 As shown, the magnetic material of the first embodiment includes first particles 21 having an amorphous oxide film 212 on the surface, and second particles 22 having a crystalline oxide layer 222 on the surface and having an average particle size smaller than that of the first particles.

[0055] The first particle 21 comprises an alloy consisting essentially of Fe, Si, and Cr. "Essentially consisting" here means containing no other components besides unavoidable impurities. Furthermore, it comprises an amorphous oxide film 212 formed on its surface and an alloy portion 211 located within it. Because its average particle size is larger than that of the second particle (described later), and as will be described later, the amorphous oxide film 212 is thinner and the alloy portion 211 is relatively high in proportion, the first particle 21 primarily contributes to the magnetic properties of the magnetic body. The ratio of the alloy components in the first particle 21 is not particularly limited. However, since a higher Fe content leads to superior magnetic properties, it is preferable to maximize the Fe content within a range that achieves the desired electrical insulation and oxidation resistance. An appropriate Fe content is 30% by mass or greater, more preferably 50% by mass or greater, and even more preferably 70% by mass or greater. On the other hand, the Fe content is preferably 98% by mass or less. Furthermore, the Si content is preferably 1% by mass or greater to improve the electrical resistance of the alloy portion 211 and suppress the degradation of magnetic properties due to eddy currents. Furthermore, the Cr content is preferably 0.2 mass % or more from the viewpoint of suppressing oxidation of Fe in the alloy portion 211 and maintaining high magnetic properties.

[0056] The amorphous oxide film 212 on the surface of the first particle 21 contains Si, Cr, and O as constituent elements and is amorphous. Since the oxide film 212 is amorphous and contains Si, it can impart higher electrical insulation with a thinner thickness. In addition, since the oxide film 212 contains Cr, it can suppress the degradation of properties caused by oxidation of Fe in the alloy portion 211. While remaining amorphous, the amorphous oxide film 212 may also contain elements other than Si, Cr, and O, and their types and contents are not particularly limited. Therefore, as described below, when the amorphous oxide film 212 is formed by attaching a Si-containing substance to the surface of the first particle, a Si-containing substance containing elements other than Si and Cr may also be used. However, with regard to Fe, since the amorphous oxide film 212 crystallizes at relatively low concentrations, the electrical insulation of the magnetic body and / or coil component is greatly reduced, and therefore it is preferably not contained as much as possible.

[0057] Here, the fact that the oxide film 212 is amorphous is confirmed by the following steps. First, a thin-sheet sample cut from a magnetic body is observed using a high-resolution transmission electron microscope (HR-TEM). The oxide film identified by the difference in contrast (brightness) in the electron microscope image is Fourier transformed to obtain a reciprocal space pattern (see Figure 2(1)). In addition, if the reciprocal space pattern is a pattern obtained by nanobeam diffraction, a measurement device other than HR-TEM can also be used. Next, in the obtained reciprocal space pattern, the average value I of the signal intensity is calculated for each distance r from the beam incident position. r,avg That is, the signal strength I is measured at multiple points at equal distances r from the beam incident position. r , and average them. Then, based on the obtained I r,avg and r, to obtain the radial distribution function (refer to Figure 2 (2)). Next, in the radial distribution function, find the point r where the signal intensity becomes the maximum among the points other than r=0. p (Refer to Figure 2 (3)). Finally, the beam incident position is r p The signal intensity of each point at a distance of θ is plotted against the rotation angle θ, and the maximum intensity I among the signal intensities of each point is compared. rp,max and the minimum intensity I rp,min (Refer to Figure 2 (4)). And, when I rp,max The value is less than I rp,min When the value of is 1.5 times greater than that of , the observed oxide film is judged to be amorphous.

[0058] The second particles 22 contain Fe and Si as alloy components, as well as elements other than Si and Cr that are more easily oxidized than Fe (hereinafter sometimes referred to as "M" or "M element"). Furthermore, they include a crystalline oxide layer 222 formed on the surface and an alloy portion 221 located inside the second particle 22. In the second particle 22, the crystalline oxide layer 222 is formed thicker than the above-mentioned amorphous oxide film 212, and is firmly bonded to the adjacent soft magnetic alloy particles via this layer 222, thereby contributing to an improvement in the mechanical strength of the magnetic body. Generally, an increase in the thickness of the oxide layer formed on the surface of the soft magnetic alloy particle means a decrease in the proportion of the alloy portion, which has an adverse effect on the magnetic properties. However, in the first embodiment, the above-mentioned adverse effects are reduced by making the average particle size of the second particle 22 smaller than that of the above-mentioned first particle 21. There is no particular limitation on the proportion of the alloy components in the second particle 22. From the perspective of maintaining the magnetic properties, it is preferable to make the Fe content as high as possible within the range that can obtain the desired electrical insulation and oxidation resistance. The appropriate Fe content is 30% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more. On the other hand, the Fe content is preferably 98% by mass or less. Furthermore, the Si content is preferably 1% by mass or more from the perspective of increasing the electrical resistance of the alloy portion 221 and suppressing the degradation of magnetic properties due to eddy currents. Furthermore, the M element content is preferably 0.2% by mass or more from the perspective of suppressing oxidation of Fe in the alloy portion 221 and the resulting degradation of magnetic properties.

[0059] Examples of the M element as the alloy component of the second particles include Al, Zr, Ti, Mn, and Ni. Of these, Al or Mn is preferred because the mechanical strength of the oxide is high and the crystalline oxide layer 222 and the bonding portion 23 described later can be strengthened.

[0060] The crystalline oxide layer 222 on the surface of the second particle 22 is composed mainly of the above-mentioned M element. Here, the so-called main component in this specification refers to the component with the largest content ratio under the mass standard. The crystalline oxide layer 222 is firmly bonded to the adjacent soft magnetic alloy particles as described above, and contributes to the improvement of the mechanical strength of the magnetic body. The above-mentioned crystalline oxide layer 222 is preferably single crystal from the perspective of obtaining a higher strength magnetic body. Here, the fact that the crystalline oxide layer 222 is single crystal is confirmed by the following steps.

[0061] First, a thin slice sample with a thickness of 50 to 100 nm was removed from the center of the coil component using a focused ion beam (FIB) instrument. The magnetic portion was then observed directly using a scanning transmission electron microscope (STEM) equipped with an annular dark-field detector and an energy-dispersive X-ray spectroscopy (EDS) detector. Next, the alloy portion located within the soft magnetic alloy particle was identified based on differences in contrast (brightness) in the electron microscope image. Within this portion, the composition of a 200 nm x 200 nm region was calculated using the ZAF method using EDS, and this was used as the composition of the alloy portion. The STEM-EDS measurement conditions were an accelerating voltage of 200 kV, an electron beam diameter of 1.0 nm, and a measurement time set such that the cumulative signal intensity within the range of 6.22 keV to 6.58 keV at each point in the alloy portion reached 25 counts or more. If the resulting alloy portion composition contained the element M, the soft magnetic alloy particle containing this alloy portion was determined to be the second particle. Next, in the electron microscope image, a portion located near the surface of the soft magnetic alloy particle identified as the second particle, where the contrast differs from that of the alloy portion, is identified as a crystalline oxide layer. An electron diffraction pattern is measured for this layer. If the diffraction pattern exhibits a two-dimensional dot array mesh pattern (lattice-like spots), the layer is identified as a single crystal.

[0062] Furthermore, the above-described method for determining the composition of the alloy portion can also be used to determine the composition of the amorphous oxide film 212 and the crystalline oxide layer 222 .

[0063] The second particles 22 have an average particle size smaller than that of the first particles 21. Thus, even if the layer 222 of the crystalline oxide is formed thickly on the surface, the adverse effects on the magnetic properties can be suppressed. The ratio of the average particle size of the second particles 22 to the average particle size of the first particles 21 is preferably 0.02 to 0.5. By making this ratio greater than 0.02, the bonding strength between the particles can be improved. On the other hand, by making this ratio less than 0.5, the adverse effects on the magnetic properties can be suppressed. As the average particle size of each particle, for example, the first particle can be 5 μm to 20 μm, and the second particle can be 0.1 μm to 2 μm. Here, the average particle size of each particle is calculated by the following steps.

[0064] First, the magnetic body of the coil component is ground to obtain a cross-section (ground surface). Next, the ground surface is observed using a scanning electron microscope. In order to selectively obtain electron information near the surface of the ground surface, the acceleration voltage during observation is limited to about 2kV. In addition, in order to easily distinguish the metal magnetic particle part and the oxide film part between the particles, backscattered electron images are used for observation and the obtained images are saved. The magnification at this time is set to about 2000 times to 5000 times. Next, the observed part is subjected to surface analysis by EDS, and based on the difference in the elements contained, it is determined whether each particle is the first particle or the second particle. Next, based on the metal magnetic particles in the saved image, the major and minor diameters are measured, and the average value is used as the particle size of the metal magnetic particles. Finally, based on the particle size of each particle obtained and the above-mentioned judgment results, the average value is calculated for the first particle and the second particle respectively, and used as the average particle size of the first particle and the average particle size of the second particle, respectively.

[0065] In the magnetic body of the first embodiment, as Figure 3 As shown in FIG. 2 , the oxide of the M element that forms the above-mentioned crystalline oxide layer 222 leaves the second particle 22 and reaches the contact portion between the above-mentioned first particles 21, forming a joint 23 that extends between the plurality of first particles 21. Since the contact portions between the first particles 21 are in contact with each other due to the amorphous oxide film 212, it is difficult to obtain a high joint strength. However, the above-mentioned joint 23 can be used to strengthen the above-mentioned contact portion, thereby improving the joint strength and obtaining a magnetic body with high mechanical strength. The above-mentioned joint 23 can also be as Figure 4 As shown, the first particles 21 are arranged so as to be bonded to each other via the bonding portion 23. Here, the first particles 21 being bonded to each other via the bonding portion 23 means that adjacent first particles 21 are not in direct contact with each other via the bonding portion 23.

[0066] In addition, the above-mentioned joint 23 is as follows Figure 5 As shown, it is preferable to fill the gaps between the soft magnetic alloy particles 21 and 22. This can reduce the porosity of the magnetic body and further improve the mechanical strength.

[0067] The magnetic material of the first embodiment may contain soft magnetic metal particles, various fillers, and the like in addition to the first and second particles as long as desired properties are obtained.

[0068] <About Conductors>

[0069] The material, shape, and configuration of the conductor are not particularly limited and can be appropriately determined based on the desired characteristics. As an example of the material, silver or copper, or alloys thereof, can be exemplified. In addition, as an example of the shape, a straight line, a zigzag shape (meandering), a planar coil shape, a spiral shape, etc. can be exemplified. In addition, as an example of the configuration, a configuration in which a coated wire is wound around a magnetic body, a configuration in which conductors of various shapes are embedded within a magnetic body, etc. can be exemplified.

[0070] [Method for manufacturing coil component]

[0071] A method for manufacturing a coil component according to a second embodiment of the present invention (hereinafter, sometimes simply referred to as “the second embodiment”) includes the following processes and / or operations.

[0072] (a) As soft magnetic alloy powder, prepare: a first powder whose alloy components are essentially composed of Fe, Si and Cr; and a second powder whose alloy components contain Fe and Si and an element other than Si and Cr that is more easily oxidized than Fe (M element) and has an average particle size smaller than that of the above-mentioned first particles.

[0073] (d) The first powder and the second powder are mixed to obtain a mixed powder.

[0074] (e) The mixed powder obtained in the above (d) is compacted to obtain a compact.

[0075] (f) The compact obtained in the above (e) is heat-treated at a temperature of 500° C. to 900° C. in an atmosphere having an oxygen concentration of 10 ppm to 800 ppm to obtain a magnetic body.

[0076] (g) performing at least one of the following (1) and (2): (1) in the above (e), configuring a conductor or a precursor thereof inside or on the surface of the above-mentioned formed body; (2) after performing the above (f), configuring a conductor on the surface of the above-mentioned magnetic body.

[0077] Below, the above-mentioned necessary processing operations and a part of the optional processing operations performed thereon are described in detail. In addition, in the second embodiment, it is of course possible to perform processing operations other than the processing operations described in detail below, which are well known to those skilled in the art.

[0078] <About Processing Operation (a)>

[0079] In the second embodiment, the soft magnetic alloy powders used include: a first powder whose alloy components consist essentially of Fe, Si, and Cr; and a second powder whose alloy components contain Fe, Si, and the element M, and whose average particle size is smaller than that of the first particles. This is based on the following indirect knowledge obtained by the inventors during the process of completing the present invention: that among soft magnetic alloy particles containing Fe, Si, and an element other than Si that is more easily oxidized than Fe, particles containing only Cr as an element other than Si that is more easily oxidized than Fe exhibit higher electrical insulation properties and can form a thinner oxide layer when heat-treated in a low-oxygen atmosphere, compared to particles containing other elements. Taking this knowledge into consideration, along with the fact that the properties of large-diameter particles have a greater influence on the magnetic properties of a magnetic body than those of small-diameter particles, the inventors have devised a method for obtaining a magnetic body that maintains its magnetic properties while maintaining high strength by making the Fe-Si-Cr-based soft magnetic alloy particles, which have advantageous magnetic properties from the perspective of forming an oxide layer with high electrical insulation and a small thickness, large-diameter particles, and small-diameter particles, which have advantageous mechanical strength from the perspective of forming an oxide layer with less high electrical insulation but a large thickness. The soft magnetic alloy powder composed of each particle is described in detail below.

[0080] Fe, which is a common alloying component in the first and second powders, is a component that contributes to the magnetic properties of the soft magnetic alloy particles constituting each powder. Therefore, it is preferred that in any powder, the Fe content is as high as possible within the range in which the desired oxide can be formed on the surface of the soft magnetic alloy particles by the heat treatment described later. The preferred Fe content is 30% by mass or more, more preferably 50% by mass or more, and further preferably 70% by mass or more. On the other hand, when the Fe content becomes too much, under the influence of its oxidation, there is the possibility that the desired oxide cannot be formed on the surface of the soft magnetic alloy particles constituting each powder. Therefore, it is preferred that the Fe content is 98% by mass or less.

[0081] Si, a common alloying component in the first and second powders, contributes to the electrical insulation properties of the soft magnetic alloy particles constituting each powder. Furthermore, in the first powder, it forms the main component of the amorphous oxide film having high electrical insulation properties formed on the surface of the soft magnetic alloy particles by the heat treatment described later. From the perspective of imparting desired electrical insulation properties to the soft magnetic alloy particles and forming an amorphous oxide film on the entire surface of the soft magnetic alloy particles (first particles) constituting the first powder, the Si content in each powder is preferably 1% by mass or more, more preferably 1.5% by mass or more, and even more preferably 2% by mass or more. On the other hand, from the perspective of maintaining the magnetic properties of the soft magnetic alloy particles constituting each powder, the Si content is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 5% by mass or less.

[0082] Cr, an essential component of the first powder, has the effect of suppressing the oxidation of Fe in the soft magnetic alloy particles and the resulting reduction in magnetic properties. On this basis, the Cr in the soft magnetic alloy particles diffuses to the surface of the particles through the heat treatment described below, forming an amorphous oxide film together with the above-mentioned Si. This can inhibit the diffusion of oxygen to the alloy portion located inside the particles, and suppress the oxidation of Fe and the crystallization of the amorphous oxide film caused by the diffusion, thereby improving the stability of the amorphous oxide film. From the perspective of fully exerting the above-mentioned effects, the Cr content in the first particles is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more. On the other hand, from the perspective of increasing the Fe content in the soft magnetic alloy particles and suppressing the segregation of Cr in the particles to obtain excellent magnetic properties, the Cr content in the first particles is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 2% by mass or less.

[0083] The M element, an essential component of the second powder, has the same effect as the Cr mentioned above in suppressing the oxidation of Fe in the soft magnetic alloy particles and the resulting reduction in magnetic properties. On this basis, the M element in the soft magnetic alloy particles diffuses to the surface of the particles through the heat treatment described below and forms a layer of crystalline oxide. This layer is thicker than the amorphous oxide film mentioned above. Therefore, compared to the bonding performed by the amorphous oxide film, the bonding strength with adjacent soft magnetic alloy particles is improved, and the volume of the voids between the particles is reduced, thereby improving the mechanical strength of the magnetic body.

[0084] Examples of the M element include Al, Zr, Ti, Mn, and Ni. Of these, Al or Mn is preferred because the oxide formed by heat treatment has high mechanical strength and can increase the strength of the joints between the soft magnetic alloy particles.

[0085] As the second powder, a powder having a smaller average particle size than that of the first powder is used. Thus, even when a thick layer of crystalline oxide is formed on the surface of the soft magnetic alloy particles by the heat treatment described later, the adverse effects on the magnetic properties can be suppressed. Preferably, the ratio of the average particle size of the second powder to the average particle size of the first powder is 0.02 to 0.5. By making this ratio greater than 0.02, the effect of increasing the bonding strength between the particles by the formation of the crystalline oxide layer can be fully exerted. On the other hand, by making this ratio less than 0.5, the adverse effects on the magnetic properties can be suppressed. As the average particle size of each powder, for example, the first powder can be 5 μm to 20 μm, and the second powder can be 0.1 μm to 2 μm. This average particle size can be measured, for example, using a particle size distribution measuring device using a laser diffraction / scattering method.

[0086] <About Processing Operation (d)>

[0087] In the treatment operation (d), the first powder and the second powder are mixed to obtain a mixed powder. In this case, soft magnetic metal powders, various fillers, etc. other than the first and second powders may be mixed as long as a magnetic body having desired properties can be obtained.

[0088] The first powder and the second powder can be mixed by any method commonly used for mixing powders, for example, a method using various mixers such as a ribbon blender or a V-type blender, or a method using a ball mill.

[0089] <About Processing Operation (e)>

[0090] In the processing operation (e), the mixed powder obtained in the above (d) is compacted to obtain a compact.

[0091] The forming method is not particularly limited, and for example, the mixed powder and resin are mixed and supplied to a forming die such as a mold, and the resin is cured by applying pressure such as a mold press. Alternatively, a method of laminating and pressing green sheets containing the mixed powder may be employed.

[0092] When a compact is obtained by compression molding using a mold or the like, the compression molding conditions can be appropriately determined depending on the types of the mixed powder and the resin to be mixed therewith, their mixing ratio, and the like.

[0093] The resin mixed with the mixed powder is not particularly limited as long as it is a resin that can bond the soft magnetic alloy particles constituting the mixed powder to each other to form and retain their shape, and volatilizes carbon components and the like without leaving any residue by the heat treatment (f) described later. As an example, acrylic resins, butyral resins, and vinyl resins having a decomposition temperature of 500°C or less can be cited. In addition, lubricants represented by stearic acid or its salts, phosphoric acid or its salts, and boric acid and its salts can be used together with or instead of the resin. The amount of resin and / or lubricant added can be appropriately determined in consideration of formability and shape retention, and for example, it can be 0.1 to 5 parts by mass relative to 100 parts by mass of the soft magnetic alloy powder.

[0094] When the green sheets are stacked and pressed together to obtain a formed body, a method can be adopted in which the green sheets are stacked using a suction conveyor or the like and then hot-pressed using a molding press. When a plurality of coil components are obtained from the pressed stack, the stack can be divided using a cutting machine such as a shearing machine or a laser cutter.

[0095] In this case, the green sheet is typically manufactured by applying a slurry comprising soft magnetic alloy powder and a binder to the surface of a base film such as a plastic film by a coating machine such as a doctor blade or a die coater and drying it. As the binder used, there is no particular limitation as long as it is a binder that can shape the soft magnetic alloy powder into a sheet and can maintain its shape, and can remove carbon components and the like without residue by heating. As an example, polyvinyl acetal resins based on polyvinyl butyral can be exemplified. The solvent used to modulate the above-mentioned slurry is also not particularly limited, and glycol ethers based on butyl carbitol can be used. The content of each component in the above-mentioned slurry can be appropriately adjusted according to the forming method of the green sheet to be adopted or the thickness of the green sheet to be modulated.

[0096] <About Processing Operation (f)>

[0097] In the treatment operation (f), the molded body obtained by the above (e) is heat-treated at a temperature of 500°C to 900°C in an atmosphere with an oxygen concentration of 10ppm to 800ppm to obtain a magnetic body. As a result, the resin (binder) in the molded body is volatilized and removed, and crystalline oxides are generated on the surface of the soft magnetic alloy particles (second particles) constituting the second powder, thereby bonding the soft magnetic alloy particles to each other. The heat treatment for volatilizing and removing the resin (binder) in the molded body can also be performed independently before the treatment operation (f). In this case, it is preferred that the oxygen concentration in the heat treatment atmosphere be set to 10ppm or more, and in order to suppress the oxidation of Fe, the heat treatment temperature be set to 400°C or less.

[0098] The oxygen concentration in the heat treatment atmosphere is set to 10ppm to 800ppm. By setting the oxygen concentration in the heat treatment atmosphere to 10ppm or more, the surface of the soft magnetic alloy particles constituting the soft magnetic alloy powder can be oxidized, the particles are electrically insulated from each other, and the particles are bonded to each other via oxides. From the perspective of promoting the oxidation of the M element in the soft magnetic alloy particles (second particles) constituting the second powder and generating a sufficient amount of crystalline oxide to firmly bond the soft magnetic alloy particles to each other, it is preferred that the above-mentioned oxygen concentration be 100ppm or more, more preferably 200ppm or more. On the other hand, by setting the oxygen concentration in the heat treatment atmosphere to 800ppm or less, the oxidation of Fe in the soft magnetic alloy particles (first particles) constituting the first powder and the resulting formation of crystalline oxides on the surface of the particles can be suppressed. It is preferred that the above-mentioned oxygen concentration be 500ppm or less, more preferably 300ppm or less.

[0099] The heat treatment temperature is set to 500°C to 900°C. By setting the heat treatment temperature to 500°C or higher, the surface of the soft magnetic alloy particles constituting the soft magnetic alloy powder can be oxidized, the particles can be electrically insulated from each other, and the particles can be bonded to each other via oxides. The above-mentioned heat treatment temperature is preferably 550°C or higher, and more preferably 600°C or higher. On the other hand, by setting the heat treatment temperature to 900°C or lower, the oxidation of Fe in the soft magnetic alloy particles (first particles) constituting the first powder and the resulting formation of crystalline oxides on the surface of the particles can be suppressed. The above-mentioned heat treatment temperature is preferably 850°C or lower, and more preferably 800°C or lower.

[0100] The heat treatment time may be any time sufficient to allow the crystalline oxide formed on the surface of the second particles to grow and reach the contact portion between the first particles. As an example, it can be 30 minutes or longer, preferably 1 hour or longer. On the other hand, in order to prevent the formation of a crystalline oxide film on the surface of the first particles and to complete the heat treatment in a short time to improve productivity, the heat treatment time can be 5 hours or shorter, preferably 3 hours or shorter.

[0101] Here, the oxidation of Fe in the soft magnetic alloy particles (first particles) constituting the first powder and the generation of the crystalline oxide on the particle surface caused thereby can be suppressed by reducing at least one of the oxygen concentration in the heat treatment atmosphere or the heat treatment temperature or shortening the heat treatment time. Therefore, for example, when it is necessary to improve the oxygen concentration in the heat treatment atmosphere, when it is desired to suppress the generation of the crystalline oxide as much as possible, the heat treatment temperature can be set to be lower or the heat treatment time can be set to be shorter. In addition, when it is necessary to improve the heat treatment temperature, the oxygen concentration in the heat treatment atmosphere can be set to be lower or the heat treatment time can be set to be shorter. In addition, when it is necessary to make the heat treatment time longer, the oxygen concentration in the heat treatment atmosphere can be set to be lower or the heat treatment temperature can be set to be lower.

[0102] <About Processing Operation (g)>

[0103] In processing operation (g), a conductor or a precursor thereof is placed. Here, a conductor is a component that remains as a conductor within the coil component, while a precursor of a conductor is a component that contains a binder resin, etc., in addition to the conductive material that becomes a conductor within the coil component, and is then transformed into a conductor through heat treatment. There are two methods for placing the conductor or its precursor, as described below.

[0104] (1) In the above (e), a conductor or a precursor thereof is arranged inside or on the surface of the above-mentioned molded body.

[0105] When a compact is obtained by press molding, a method can be adopted in which a mold pre-placed with a conductor or its precursor is filled with a mixed powder of a soft magnetic alloy and then press molded.

[0106] When the formed body is obtained by laminating and pressing the green sheets, a method can be adopted in which a conductor precursor is placed on the green sheets by printing a conductor paste, etc., and then laminating and pressing the green sheets. This allows the conductor or its precursor to be placed inside or on the surface of the laminate.

[0107] As the conductor paste to be used, a conductor paste containing a conductor powder and an organic vehicle can be exemplified. As the conductor powder, powders of silver, copper, or alloys thereof can be used. The particle size of the conductor powder is not particularly limited. For example, the average particle size (median diameter (D)) calculated from the particle size distribution measured on a volume basis can be used. 50)) is a powder of 1μm to 10μm. The composition of the organic vehicle can be determined by considering the compatibility with the binder contained in the raw sheet. As an example, a polyvinyl acetal resin such as polyvinyl butyral (PVB) can be dissolved and / or swelled in a glycol ether solvent such as butyl carbitol. The ratio of the conductor powder and the organic vehicle in the conductor paste can be appropriately adjusted according to the viscosity of the paste suitable for the printer to be used or the film thickness of the conductor pattern to be formed.

[0108] In either case, the configured conductor precursor is formed into a conductor by the subsequent processing operation (f).

[0109] (2) After performing the above step (f), a conductor is arranged on the surface of the magnetic body.

[0110] In this case, the conductor can be arranged by winding a coated wire around the obtained magnetic body, or by arranging a conductor precursor on the surface of the magnetic body by printing a conductor paste or the like and then baking it in a heating device such as a firing furnace.

[0111] <About Processing Operation (b)>

[0112] In the second embodiment, before the treatment operation (d), a treatment operation (treatment operation (b)) of attaching a Si-containing substance to the surface of each particle (first particle) constituting the first powder prepared in the treatment operation (a) may be performed.

[0113] In the treatment operation (b), the Si-containing substance adheres to the surface of the soft magnetic alloy particles (first particles) constituting the first powder, thereby facilitating the formation of an amorphous film with a uniform thickness on the surface of the first particles.

[0114] Examples of the Si-containing substance include silane coupling agents based on tetraethoxysilane (TEOS), silica particles based on colloidal silica, etc. The amount of the Si-containing substance used can be appropriately determined depending on its type and the particle size of the soft magnetic alloy particles.

[0115] As a method for attaching the Si-containing substance to the surface of the soft magnetic alloy particles (first particles) constituting the first powder, examples include spraying the particles with the Si-containing substance in a liquid state or impregnating the particles and then drying. Furthermore, if the Si-containing substance is in particulate form, examples include dry mixing or contacting (spraying or impregnating) with a slurry in which the Si-containing substance is dispersed, followed by drying. Alternatively, coating using a sol-gel method using a silane coupling agent may be employed.

[0116] <About Processing Operation (c1)>

[0117] In the case of performing the treatment operation (b) above, the first powder after the treatment operation is heat-treated at a temperature of 100°C to 700°C in an inert gas atmosphere, or is heat-treated at a temperature of 100°C to 300°C in an atmosphere with an oxygen concentration of less than 100 ppm (treatment operation (c1)). Here, the inert gas refers to N2 or a rare gas. As a result, the Si-containing substance attached to the surface of the alloy particles (first particles) constituting the first powder forms an amorphous film containing Si and O, and the mechanical strength of the formed film and the adhesion strength to the metal particles are improved. The film acts as an insulating layer in the magnetic body in the coil component, electrically insulating the soft magnetic alloy particles.

[0118] The heat treatment temperature is preferably set to 100°C or higher. This can promote the formation of the above-mentioned amorphous film. In addition, the mechanical strength and adhesion strength of the formed film to the metal particles are improved. However, when the heat treatment temperature is too high, the oxidation of the soft magnetic metal powder or the crystallization of the amorphous film becomes significant, and the characteristics of the obtained magnetic body are reduced. Therefore, in the heat treatment in an oxygen-containing atmosphere of less than 100 ppm, the heat treatment temperature is preferably set to 300°C or lower. On the other hand, in the heat treatment in an inert atmosphere, since oxidation of the soft magnetic metal powder hardly occurs, the upper limit of the heat treatment temperature can be set to 700°C.

[0119] The holding time at the heat treatment temperature is not particularly limited. However, from the perspective of sufficiently forming an amorphous thin film and sufficiently improving the mechanical strength and adhesion strength of the formed thin film to the metal particles, it is preferably 30 minutes or longer, more preferably 50 minutes or longer. On the other hand, from the perspective of suppressing the formation of a crystalline film and completing the heat treatment in a short time to increase the formation rate, the heat treatment time is preferably 2 hours or shorter, more preferably 1.5 hours or shorter.

[0120] <About Processing Operation (c2)(1)>

[0121] In addition, in the second embodiment, the above-mentioned treatment operation (c1) can be replaced by heat treatment (treatment operation (c2)) of the first powder with Si-containing substance attached to the surface at a temperature of 300°C to 900°C in an atmosphere with an oxygen concentration of 3ppm to 100ppm. As a result, Si or Cr in the alloy particles (first particles) constituting the first powder diffuses to the surface of the particles and is oxidized on the surface. At this time, since an amorphous oxide film is formed on the surface of the first particles, it interacts with the amorphous film derived from the Si-containing substance to form an amorphous film of sufficient thickness. The film acts as an insulating layer in the magnetic body in the coil component, electrically insulating the first particle formed with the film from other adjacent alloy particles. Therefore, a magnetic body and / or coil component with excellent insulation and low loss during driving can be obtained.

[0122] By setting the oxygen concentration in the heat treatment atmosphere to 3 ppm or more and the heat treatment temperature to 300°C or more, the reaction between Si and Cr as alloy components and oxygen can be promoted. As a result, the surface of the soft magnetic alloy particles (first particles) constituting the first powder can be covered with an amorphous film with high electrical insulation. On the other hand, by setting the oxygen concentration in the heat treatment atmosphere to 100 ppm or less and the heat treatment temperature to 900°C or less, the excessive oxidation of Fe in the first particles and the resulting formation of crystalline oxides on the particle surface can be suppressed. As a result, the reduction in magnetic properties and electrical insulation can be suppressed. It is preferred that the above-mentioned oxygen concentration be 5 ppm or more. In addition, it is preferred that the above-mentioned oxygen concentration be 50 ppm or less, more preferably 30 ppm or less, and even more preferably 10 ppm or less. On the other hand, it is preferred that the above-mentioned heat treatment temperature be 350°C or more, more preferably 400°C or more. In addition, it is preferred that the above-mentioned heat treatment temperature be 850°C or less, more preferably 800°C or less.

[0123] The holding time at the heat treatment temperature is not particularly limited. From the perspective of forming an amorphous film of sufficient thickness, it is preferably 30 minutes or longer, more preferably 1 hour or longer. On the other hand, from the perspective of suppressing the formation of a crystalline film and completing the heat treatment in a short time to improve productivity, the heat treatment time is preferably 5 hours or shorter, more preferably 3 hours or shorter.

[0124] Here, the excessive oxidation of Fe in the first particle and the resulting formation of crystalline oxides on the surface of the first particle can be suppressed by reducing at least one of the oxygen concentration in the heat treatment atmosphere or the heat treatment temperature, or by shortening the heat treatment time. Therefore, for example, when it is necessary to increase the oxygen concentration in the heat treatment atmosphere, if it is desired to suppress the oxidation of Fe as much as possible, the heat treatment temperature can be set lower or the heat treatment time can be set shorter. In addition, when it is necessary to increase the heat treatment temperature, the oxygen concentration in the heat treatment atmosphere can be set lower or the heat treatment time can be set shorter. In addition, when it is necessary to extend the heat treatment time, the oxygen concentration in the heat treatment atmosphere can be set lower or the heat treatment temperature can be set lower.

[0125] <About Processing Operation (c2)(2)>

[0126] The above-mentioned treatment operation (c2) can also be performed on the first powder that has not been subjected to the above-mentioned treatment operation (b). As a result, an amorphous oxide film containing Si, Cr and O can be formed with a uniform thickness on the surface of the soft magnetic alloy particles (first particles) constituting the first powder. The film acts as an insulating layer in the magnetic body in the coil component, electrically insulating the soft magnetic alloy particles. Therefore, a magnetic body and / or coil component with uniform thickness of the insulating layer and excellent magnetic properties can be obtained. In addition, in this case, the thickness of the insulating layer can be made thinner than that of the case where the above-mentioned treatment operation (b) is performed, so the proportion of the alloy part inside the first particle can be increased, and a magnetic body and / or coil component with more excellent magnetic properties can be obtained.

[0127] According to the second embodiment described above, a magnetic body can be obtained in which large-sized soft magnetic alloy particles having a highly electrically insulating amorphous oxide film formed on their surfaces are joined to smaller soft magnetic alloy particles via a crystalline oxide having high mechanical strength. This improves the mechanical strength of the coil component having this magnetic body.

[0128] [Circuit Board]

[0129] A circuit board according to a third embodiment of the present invention (hereinafter sometimes simply referred to as “the third embodiment”) is a circuit board on which the coil component according to the first embodiment is mounted.

[0130] The structure of the circuit board is not limited, and a structure suitable for the purpose may be adopted.

[0131] In the third embodiment, the coil component of the first embodiment is used to form a circuit board that is not easily damaged even when subjected to vibration or impact.

[0132] (Example)

[0133] Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[0134] [Example 1]

[0135] <Production of Coil Components and Test Magnetic Materials>

[0136] First, as the first powder, a soft magnetic alloy powder containing 94.5 wt% Fe, 2.0 wt% Si, and 3.5 wt% Cr, with the remainder being inevitable impurities, and having an average particle size of 4 μm, was prepared. Separately, as the second powder, a soft magnetic alloy powder containing 97.0 wt% Fe, 2.0 wt% Si, and 1.0 wt% Al, with the remainder being inevitable impurities, and having an average particle size of 2 μm, was prepared. The first powder was then heat-treated at 700°C for one hour in an atmosphere with an oxygen concentration of 7 ppm. Next, 90 parts by mass of the heat-treated first powder was mixed with 10 parts by mass of the second powder, a polyvinyl butyral (PVB)-based binder resin, and a dispersion medium to prepare a slurry. This slurry was then formed into sheets using an automatic coating machine, yielding green sheets. Next, Ag paste was printed onto the green sheets to form the precursors of the internal conductors. The green sheets were then stacked, press-bonded, and singulated to form a compact. Next, the molded body was heat treated at 800°C for 1 hour in an atmosphere with an oxygen concentration of 800 ppm to obtain a magnetic body having an internal conductor. Finally, external electrodes connected to the internal conductor were formed to obtain a magnetic body having an internal conductor. Figure 6 The coil component has the shape shown in FIG.

[0137] The green sheets without internal electrode precursors were stacked, pressed, and processed into disk-shaped compacts, which were then heat-treated under the above-mentioned conditions to obtain disk-shaped test magnetic bodies with a diameter of 7 mm and a thickness of 0.5 to 0.8 mm.

[0138] The green sheets without internal electrode precursors were stacked and pressed together to form a rectangular compact. Heat treatment was performed under the above conditions to obtain a rectangular test magnetic body with a length of 50 mm, a width of 5 mm, and a thickness of 4 mm.

[0139] <Measurement of Average Particle Size of Soft Magnetic Alloy Particles>

[0140] The average particle sizes of the first and second particles of the soft magnetic alloy in the obtained coil component were measured by the above-mentioned method. The first particles had an average particle size of 4 μm, and the second particles had an average particle size of 2 μm.

[0141] <Confirmation of the Structure and Composition of Oxide Film and Oxide Layer>

[0142] The structure and composition of the oxide film and oxide layer formed on the surface of the soft magnetic alloy particles in the magnetic body were confirmed using the above-mentioned method for the obtained coil component. As a result, it was determined that an amorphous oxide film containing Si and Cr was formed on the surface of the first particle. In addition, it was determined that a layer of crystalline oxide (Al2O3) with Al as the main component was formed on the surface of the second particle. Furthermore, it was confirmed that the same oxide as that on the surface of the second particle was formed at the contact portion between the first particles, extending between the multiple first particles in contact.

[0143] <Measurement of Magnetic Permeability>

[0144] The relative magnetic permeability of the obtained coil component was measured at a frequency of 10 MHz using an LCR meter (4285A manufactured by Agilent Technologies). The relative magnetic permeability obtained was 32.

[0145] <Evaluation of Electrical Insulation>

[0146] The electrical insulation properties of the coil component were evaluated using the volume resistivity and dielectric breakdown voltage of the disk-shaped test magnetic body.

[0147] An Au film was formed by sputtering on the entire both surfaces of the disk-shaped test magnetic body described above to prepare an evaluation sample.

[0148] The volume resistivity of the resulting evaluation sample was measured according to JIS-K6911. The Au films formed on both surfaces of the sample served as electrodes. A voltage was applied between the electrodes to achieve an electric field strength of 60 V / cm. The resistance value was measured, and the volume resistivity was calculated based on the resistance value. The volume resistivity of the evaluation sample was 500 Ω·cm.

[0149] The dielectric breakdown voltage of the obtained evaluation sample was measured by applying a voltage between the Au films formed on both sides of the sample as electrodes and measuring the current value. The applied voltage was gradually increased and the current value was measured. The current density calculated from the current value was 0.01A / cm 2 The electric field strength calculated from the voltage at that time was taken as the breakdown voltage. The insulation breakdown voltage of the evaluation sample was 6.2 kV / cm.

[0150] <Evaluation of Mechanical Strength>

[0151] The mechanical strength of the coil component was evaluated by a three-point bending test of the aforementioned rectangular parallelepiped test magnetic body (test piece).

[0152] For the above test piece Figure 7The fracture stress σ is calculated by the following (Equation 1) based on the maximum load W when the fracture occurs and considering the bending moment M and the second moment of area I. b The above test was carried out on 10 test pieces, and the fracture stress σ b The average value is taken as the breaking stress of the magnetic body of Example 1. The breaking stress obtained is 17 kgf / mm 2 .

[0153]

[0154] [Example 2]

[0155] <Production of Coil Components and Test Magnetic Materials>

[0156] A coil component and a test magnetic body of Example 2 were produced in the same manner as in Example 1 except for the following points.

[0157] Before mixing with the second powder, binder resin, and dispersion medium, the first powder was dispersed in a mixed solution of ethanol and aqueous ammonia. A treatment solution containing tetraethoxysilane (TEOS), ethanol, and water was mixed and stirred. The first powder was then separated by filtration and dried. The treated first powder was then mixed with the second powder, binder resin, and dispersion medium. The molded body was heat-treated at 800°C for one hour in an atmosphere with an oxygen concentration of 800 ppm.

[0158] <Confirmation of the Structure and Composition of Oxide Film and Oxide Layer>

[0159] For the obtained coil component, the structure and composition of the oxide film and oxide layer formed on the surface of the soft magnetic alloy particles in the magnetic body were confirmed using the same method as in Example 1, and it was confirmed that an oxide film and oxide layer having the same structure and composition as in Example 1 were formed.

[0160] <Evaluation of Coil Components and Test Magnetic Materials>

[0161] The properties of the resulting coil component and test magnetic body were measured in the same manner as in Example 1. The relative magnetic permeability of the coil component was 30, the resistivity of the evaluation sample was 510 Ω·cm, the dielectric breakdown voltage was 5.6 kV / cm, and the three-point bending fracture stress of the magnetic body was 16 kgf / mm. 2 .

[0162] [Example 3]

[0163] <Production of Coil Components and Test Magnetic Materials>

[0164] The coil component and test magnetic body of Example 3 were produced in the same manner as in Example 1 except that the first powder was mixed with the second powder, a binder resin, and a dispersion medium to prepare a slurry without heat treatment.

[0165] <Confirmation of the Structure and Composition of Oxide Film and Oxide Layer>

[0166] For the obtained coil component, the structure and composition of the oxide film and oxide layer formed on the surface of the soft magnetic alloy particles in the magnetic body were confirmed using the same method as in Example 1, and it was confirmed that an oxide film and oxide layer having the same structure and composition as in Example 1 were formed.

[0167] <Evaluation of Coil Components and Test Magnetic Materials>

[0168] The properties of the resulting coil component and test magnetic body were measured in the same manner as in Example 1. The relative magnetic permeability of the coil component was 34, the resistivity of the evaluation sample was 470 Ω·cm, the dielectric breakdown voltage was 5.2 kV / cm, and the three-point bending fracture stress of the magnetic body was 17 kgf / mm. 2 .

[0169] [Comparative Example 1]

[0170] <Production of Coil Components and Test Magnetic Materials>

[0171] A coil component and a test magnetic body of Comparative Example 1 were produced by the same method as in Example 3 except that the second powder was not used and only the first powder was used as the soft magnetic alloy powder.

[0172] <Confirmation of the Structure and Composition of Oxide Film and Oxide Layer>

[0173] For the obtained coil component, the structure and composition of the oxide film and oxide layer formed on the surface of the soft magnetic alloy particles in the magnetic body were confirmed using the same method as in Example 1, and the presence of crystalline oxides could be confirmed on the surface of the soft magnetic alloy particles and in the contact areas between the particles.

[0174] <Evaluation of Coil Components and Test Magnetic Materials>

[0175] The properties of the resulting coil component and test magnetic body were measured in the same manner as in Example 1. The relative magnetic permeability of the coil component was 28, the resistivity of the evaluation sample was 10 Ω·cm, the dielectric breakdown voltage was 0.92 kV / cm, and the three-point bending fracture stress of the magnetic body was 7 kgf / mm. 2 .

[0176] [Comparative Example 2]

[0177] <Production of Coil Components and Test Magnetic Materials>

[0178] A coil component and a test magnetic body of Comparative Example 2 were produced by the same method as in Example 3 except that the first powder was not used and only the second powder was used as the soft magnetic alloy powder.

[0179] <Confirmation of the Structure and Composition of Oxide Film and Oxide Layer>

[0180] The structure and composition of the oxide film and oxide layer formed on the surface of the soft magnetic alloy particles in the magnetic body were confirmed for the obtained coil component using the same method as in Example 1. No amorphous oxide film was confirmed on the surface of the soft magnetic alloy particles.

[0181] <Evaluation of Coil Components and Test Magnetic Materials>

[0182] The properties of the resulting coil component and test magnetic body were measured in the same manner as in Example 1. The relative magnetic permeability of the coil component was 22, the resistivity of the evaluation sample was 20 Ω·cm, the dielectric breakdown voltage was 1.0 kV / cm, and the three-point bending fracture stress of the magnetic body was 9 kgf / mm. 2 .

[0183] The above results are summarized in Table 1.

[0184] Table 1

[0185]

[0186] Comparison of the Examples and Comparative Examples reveals that a coil component comprising a magnetic body comprising a first soft magnetic alloy particle and a second particle having a smaller average particle diameter, wherein the particles are bonded via an oxide film and / or oxide layer having a specific structure, exhibits higher mechanical strength than a coil component not comprising a magnetic body having such a structure. Furthermore, such a structure increases magnetic permeability, resulting in a coil component having superior magnetic properties. Furthermore, such a structure increases resistivity and dielectric breakdown voltage, resulting in a coil component having superior electrical insulation properties.

[0187] Possibility of industrial application

[0188] According to the present invention, a coil component with improved mechanical strength can be provided. The coil component of the present invention is not easily damaged even when subjected to vibration or impact, and is therefore suitable for applications such as automobiles. In addition, according to a preferred embodiment of the present invention, a coil component with improved magnetic properties can be provided, and thus the present invention is also useful in terms of enabling miniaturization of components. Furthermore, according to a preferred embodiment of the present invention, a coil component with improved electrical insulation can be provided, and is therefore suitable for applications such as automobiles that apply high voltage.

Claims

1. A coil component comprising a magnetic body containing soft magnetic alloy particles and a conductor disposed inside or on the surface of the magnetic body, wherein: In the magnetic body, As soft magnetic alloy particles, including: The first particle, whose alloy composition is substantially composed of Fe, Si and Cr; and the second particle, whose alloy composition contains Fe and Si and an element other than Si and Cr that is more easily oxidized than Fe, The average particle size of the second particles is smaller than the average particle size of the first particles. The first particle has an amorphous oxide film containing Si and Cr on its surface. The second particles have a layer on their surfaces containing a crystalline oxide of an element other than Si and Cr that is more easily oxidized than Fe, and The crystalline oxide is separated from the second grains and forms a junction extending between the plurality of first grains at a contact portion or a gap between the first grains.

2. The coil component according to claim 1, wherein: The mass ratio of Fe in the soft magnetic alloy particles is 30 to 98%.

3. The coil component according to claim 1 or 2, wherein: The crystalline oxide is a single crystal.

4. The coil component according to claim 1 or 2, wherein: The element other than Si and Cr that is more easily oxidized than Fe is Al or Mn.

5. The coil component according to claim 1 or 2, wherein: The joints fill the gaps between the soft magnetic alloy particles.

6. A method for manufacturing a coil component, comprising a magnetic body containing soft magnetic alloy particles and a conductor disposed inside or on the surface of the magnetic body, the method comprising: (a) preparing a first powder and a second powder as soft magnetic alloy powders, wherein the alloy components of the first powder are substantially composed of Fe, Si, and Cr, and the second powder contains Fe and Si and an element other than Si and Cr that is more easily oxidized than Fe as alloy components, and has an average particle size smaller than that of the first powder; (d) mixing the first powder and the second powder to obtain a mixed powder; (e) forming the mixed powder obtained in (d) to obtain a formed body; (f) a step of heat-treating the molded body obtained in the above (e) at a temperature of 500° C. to 900° C. in an atmosphere having an oxygen concentration of 10 ppm to 800 ppm to obtain a magnetic body; and (g) performing at least one of the following steps (1) and (2): (1) in step (e), disposing a conductor or a precursor thereof inside or on the surface of the formed body; (2) After performing the step (f), a conductor is arranged on the surface of the magnetic body.

7. The method for manufacturing a coil component according to claim 6, wherein: Before the step (d), the following steps are also performed: (b) A step of attaching a Si-containing substance to the surface of each particle constituting the first powder.

8. The method for manufacturing a coil component according to claim 7, wherein: The first powder subjected to the treatment (b) is further subjected to the following steps: (c1) A step of performing heat treatment at a temperature of 100° C. to 700° C. in an inert gas atmosphere, or at a temperature of 100° C. to 300° C. in an atmosphere having an oxygen concentration of 100 ppm or less.

9. The method for manufacturing a coil component according to claim 7, wherein: The first powder subjected to the treatment (b) is further subjected to the following steps: (c2) A step of performing heat treatment at a temperature of 300° C. to 900° C. in an atmosphere having an oxygen concentration of 3 ppm to 100 ppm.

10. The method for manufacturing a coil component according to claim 6, wherein: Before the step (d), the following steps are also performed: (c2) A step of heat-treating the first powder prepared in the above (a) at a temperature of 300° C. to 900° C. in an atmosphere having an oxygen concentration of 3 ppm to 100 ppm.

11. A circuit board, characterized in that: The coil component according to any one of claims 1 to 5 is mounted thereon.

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